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March 16 , 1990 Foe
Wes Potter, Director CQTORn�\3
Weld County Health Department LL ri
1516 Hospital Road
Greeley, CO 80631
RE: City of Longmont sludge composting facilities ( #440013 )
Dear Wes:
The materials accompanying this letter are the application for a
Certificate of Designation for a solid waste processing facility. The
City wishes to compost the waste sludge from its wastewater treatment
plant at a site adjacent to the our existing landfill, and requires a
CD to allow this use of the property. The CD application is for a
waste processing facility only; no disposal of any material will take
place on the site. As we have discussed with you, a complete
description of the project, including the facilities plan, the
engineering reports and the plan of operation are included to provide
information on the project for you, the commissioners, the State and
the public. We have also included several journal articles, excerpts
from design texts and our composting research results to acquaint all
the reviewing parties with the concept of aerated static pile
composting of sludge.
Bids on the project have been opened and, pending EPA approval of the
construction contracts, we are ready to proceed. We would like to
begin construction in late spring of this year, if possible. We would
be happy to provide any further information or assistance which would
assist you or the State in your review. If you have any questions or
comments on the enclosed information, or need additional material,
please call Calvin Youngberg of my staff at 651-8399 .
Sincerely,,
CITY OF LONGMONT
Steven Miller, Director
Water/Wastewater Utilities
SM/cy
Enc.
901350
cc: Steve Orzinski, CDH
Rod Allison, Weld County Planning PL0813
Neal Renfroe
WATER/WASTEWATER UTILITIES
1100 SOUTH SHERMAN STREET, LONGMONT,COLORADO 80501 (303) 651-8376
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CITY OF LONGMONT
WASTEWATER SOLIDS HANDLING FACILITIES
APPLICATION FOR WELD COUNTY CERTIFICATE OF DESIGNATION
The following information is presented to comply with the Colorado
Department of Health' s Solid Waste Disposal Site or Facility
Application Guidance Document. Since the Certificate of Designation
is being requested for a sludge composting (processing) facility only,
and no disposal of any waste material on the site is proposed, much of
the Guidance does not apply. A general description of the facility is
presented below, after which the specific requirements of the Guidance
are addressed.
History and Description of Proposed Facilities
In 1987 , the City of Longmont completed an $8 million expansion of its
wastewater treatment plant. Missing from this expansion were
facilities to handle waste sludge ( "solids" ) . A decision on solids
handling was delayed because the Environmental Protection Agency (EPA)
and the City were involved in a joint research project to evaluate
innovative sludge treatment methods. When the final research data on
these methods had been collected, the City initiated a study to
compare the innovative sludge treatment and disposal methods with
other alternatives. This Solids Management Study, which was prepared
by Black and Veatch Engineers, was completed in late 1987 . The
findings of the study were that aerated static pile composting of
sludge and land application of the composted material were the most
cost-effective and environmentally sound alternatives for wastewater
solids handling. The study met all Federal requirements for
facilities planning defined in the Clean Water Act so that the City
could apply for Federal funding to construct the recommended sludge
treatment facilities . The study was approved by both the Colorado
Department of Health and EPA in 1988 and design of the facilities was
begun later that year.
As part of the preliminary design work, some of the original study
assumptions and costs were re-evaluated and refined. Several minor
changes were then made to the original study and issued as an Addendum
in 1989 . These changes are discussed in more detail in the following
paragraph. The Addendum was approved by the State and EPA in 1989 . A
construction grant was also applied for and awarded in 1989. Bids on
the project were opened in January and February of 1990 and award of
construction contracts is currently pending EPA review of the bidding
documents. Since funding has been made available for the project,
construction depends on Weld County approval of rezoning of the site
on which the facilities are to be located and granting of a
Certificate of Designation for a solid waste processing operation.
Construction of the project is scheduled to begin in the late spring
of 1990 . A copy of the Solids Management Study and the Addendum are
enclosed for your information. The records of newspaper articles and
public hearings are contained in the appendices to the study.
�C1`1?4
Application for Weld County Certificate of Designation
City of Longmont Wastewater Solids Handling Facilities
Page 2
One of the changes addressed in the Addendum to the Solids Management
Study is location of the composting facilities. The original study
recommended locating the composting operation on the City landfill
property. However, investigations of the soil and fill depths at the
landfill found that the site was unsuitable for the type of structures
that were needed. In order to avoid the delays involved in re-opening
the study and revising the environmental assessment, other sites in
close proximity to the original were examined. The land immediately
north of the landfill was found to be available and has been purchased
by the City. The specific piece of property is known as the
Baldridge/Richardson PUD, which is located next to Highway 119
adjacent to the City' s existing landfill. A map of the PUD which
shows the proposed purchase is enclosed as part of the CD application.
We have been working with the owner of the property and have
demonstrated to his satisfaction that the composting project will be
in harmony with the proposed land uses on the remainder of his PUD.
However, since the land is currently zoned for industrial and
commercial uses, it must be rezoned to agricultural in order to allow
the proposed use. The owner has agreed that the purchase of the land
is subject to approval of rezoning by Weld County. The rezoning
request has been submitted to the Weld County Planning Department for
review.
A brief physical description of the composting project may also be
helpful to you in your review, and is presented here as a supplement
to the information contained in the CD application. The project will
include new facilities located both at the wastewater plant and at the
composting site. The initial step in the composting process will be
dewatering of waste sludge at the City' s wastewater plant. The
dewatered sludge will then be trucked to the composting project site.
At that location, it will be mixed with an amendment such as finished
compost, composted organic material or wood chips and placed into five
foot high piles for composting. Both the mixing and composting/curing
buildings will be completely enclosed to insure the correct conditions
for composting and proper control of all processes. The composting
process will be controlled and accelerated by forced aeration supplied
to the piles via blowers and perforated pipe. This initial composting
period will last for 28-30 days. Finished compost will then be placed
in curing piles and aerated at a lower rate for 30-60 days. Both
composting and curing will be operated using microprocessor control of
aeration rates to guarantee rapid stabilization of the sludge. The
final product will be disposed of on the City' s currently approved
land application sites in Boulder County or used as a revegetation
amendment on the existing landfill, which will close in 1990 .
Odor control and mitigation of odor problems has been a major factor
in both planning and design of the project. The facilities contain
several features which address odor concerns. First, the site for the j
composting facilities was chosen in part because it experiences
weather and wind patterns that are favorable for dispersion and
dilution. Second, both the mixing and composting operations will take
place in fully enclosed buildings with forced ventilation. Since
mixing the dewatered sludge with amendment will be the primary source
of any odors in the project, the mixing building air will be
Or O I?'°
Application for Weld County Certificate of Designation
City of Longmont Wastewater Solids Handling Facilities
Page 3
separately vented through an organic/soil scrubber. To deal with any
odors generated in the composting process, the composting/curing
building will contain large, roof-mounted updraft fans to provide high
ventilation rates and disperse any odors into the atmosphere even
during stable weather conditions . One of the primary directives in
the design of the facilities was to make them compatible with the
existing and proposed land uses in the area.
CERTIFICATE OF DESIGNATION APPLICATION - LONGMONT WASTEWATER SLUDGE
COMPOSTING FACILITIES
The following application information follows the requirements
outlined in the the Solid Waste Disposal Site or Facility Application
Guidance Document.
1. Topography.
A topographic map of the facilities site is shown on sheet 6C-2 of the
attached plans. The highest elevation on the property will be 4920
ft. The lowest is at the bottom of the stormwater runoff detention
pond at 4905 ft. The surface slope of the site is very gradual from
Southwest to Northeast, varying only from 4920 ft. to 4908 ft. over a
distance of 800 ft. (approximately 1. 5% or less) .
2 . Flood plains.
There are no flood plains on the site. The St. Vrain River 100-year
flood plain lies approximately 250 feet to the Southeast of the
Southeast corner of the site. The river is, however, 120 feet below
the level of the property and the site slopes away from it. Neither
the River nor its floodplain will be impacted by the project.
3 . Aquifer recharge.
There will be no aquifer recharge on the site. The composting process
itself will utilize a mixture of dewatered sludge and amendment that
will average 50% solids by weight. All of the composting area will be
under a building roof and protected from precipitation. The
composting and mixing building floors will be paved with asphalt or
concrete. There will be no leachate from the composting process to
impact groundwater. Site runoff associated with precipitation will be
channeled to an evaporation pond which will be lined with impervious
material. Roof runoff will be separately collected in its own storm
sewer system and discharged to the St. Vrain River. Sheets 6C-2
through 6C-5 of the attached plans show the runoff control methods to
be used on the project.
4 . Groundwater Travel Distance.
Not applicable. There will be no disposal of waste on the site and no
contamination of groundwater. The runoff control methods described in
3 . , above, will deal with any site runoff due to precipitation. The
soils report which is attached shows the only groundwater that was
found was 60 feet below the surface level of the site.
rea7:" I
Application for Weld County Certificate of Designation
City of Longmont Wastewater Solids Handling Facilities
Page 4
5 . Isolate Wastes.
Not applicable. No wastes will be disposed on the site. The material
being composted will be retained in the process for approximately 80
days. Volume reduction of the compost will determine the actual
curing/storage time.
6 . Aquifer Beneficial Use.
Not applicable. No aquifers will be impacted by the project. There
is no use of groundwater on or anywhere around the site.
7 . Groundwater Protection.
The only part of the project that deals with groundwater protection is
the containment/evaporation pond for site runoff. The pond has been
designed to completely contain a 24-hour, 100-year storm event, in
accordance with Section 4 . 2. 2 of the state Solid Waste Regulations.
The pond is shown on pages 6-C-1 and 6-C-2 of the attached plans.
Design information is as follows:
Design Storm: 4 . 5 inches in 24 hours
Impervious area: 5 . 04 acres
No infiltration or evaporation was assumed.
Pond volume: 782 , 400 gallons @ 4 ft. depth (pond is 6 ft. deep)
8. Surface water diversion structures.
The site runoff will controlled by graded swales around the buildings
and curbing around paved areas to collect and channel the runoff to
the containment/ evaporation pond described above. The plans and
cross-sections for runoff diversion channels are shown on pages 6-C-2
of the attached plans .
9. Geologic Hazards.
There are no known or identified geologic hazards on the site.
10 . Monitoring Wells.
Not applicable. Since no disposal will take place on the site, no
groundwater contamination will occur.
11. Adequate Cover.
Not applicable; applies to landfills.
12 . Final Cover.
Not applicable.
13 . Water.
Water for construction purposes (soil compaction and dust control)
will be obtained from the City' s water system and hauled to the site.
14. Site description.
The attached design report and plan of operation contain a site
description. The mailing address for the facilities will be:
City of Longmont
Water/Wastewater Utilities Division
1100 S. Sherman
Longmont, CO 80501
15. Area of site.
The total land area of the site is 11 .0 acres. No disposal will take
place on the site.
Application for Weld County Certificate of Designation
City of Longmont Wastewater Solids Handling Facilities
Page 5
16 . Waste stream.
The wastes that will be accepted for treatment by the facilities will
be waste sludge generated by the City of Longmont ' s municipal
wastewater treatment plant. The project is dedicated to the City' s
sludge, and no other waste streams will be allowed or accepted. It is
possible that at startup there will be a need for composted organic
material for use as an amendment; in this event, only composted animal
or farm waste would be accepted. After startup, the composting
operation is designed to utilize recycled finished compost as the
amendment. The attached engineering report outlines the proposed
composting process.
17. Service Area.
The facilities will serve the citizens of the City of Longmont.
Access to the site is directly off of Highway 119 , three miles east of
the City.
18 . Geologic data.
Most of the information requested for this item is for landfill/
disposal purposes. The composting facilities will not involve any
disposal or impact on geology. For construction and environmental
assessment purposes, information on general geology and a soils report
prepared by Empire Laboratories, Inc. , are attached.
19. Geologic Hazards.
No geologic hazards have been identified on the site.
20 . Surface waters .
The only surface water within two miles of the site is the St. Vrain
River, which is approximately 250 feet Southeast of the property. The
site is 120 feet above the river and slopes to the Northeast. Since
there will be no disposal on the site and no leachate of any kind,
there will be no impact on the surface water.
21 . Aquifer information.
Not applicable. The groundwater level on the site was found to be at
least 60 feet below the surface when the soil borings for the attached
soils report were taken. The project will not impact the groundwater
aquifer in any way.
22 . Domestic wells.
No domestic wells exist within one mile of the site. Potable water in
the area is provided by the Left Hand Water Company.
23 . Hydrologic properties of aquifer.
Not applicable. There will be no disposal of material and no impact
on groundwater quality associated with the facilities .
24 . Flood plains. IPOc7
See Number 2 . , above.
25 . Potential impacts to surface and groundwater.
There will be no impacts to surface or groundwater due to these
facilities. There will be no disposal or fill areas on the site. The
building runoff which will be separately channeled to St. Vrain Creek
will consist of roof drainage only.
Application for Weld County Certificate of Designation
City of Longmont Wastewater Solids Handling Facilities
Page 6
26. Groundwater quality.
Not applicable.
27. Engineering data.
There will be no cover or liner material involved in this project,
since it is for sludge processing and treatment, not disposal. Maps
for the site are shown on page 6-C-1 of the attached plans. No
monitoring wells are proposed for the site since there will be no
impact on groundwater.
28 . Operational data.
The City of Longmont will be operating the sludge composting
facilities. The City has been operating a wastewater treatment plant
at its present location and treating/disposing of waste sludge since
the early 1950 ' s. The current methods of anaerobic digestion and land
application have been in place since 1983 . Sludge is currently
applied to over 2000 acres of land approved by the Colorado Department
of Health under the State beneficial use regulations. The City, in
conjunction with the University of Colorado, has been involved in
numerous sludge composting research projects since 1984. These
projects, a summary of which is attached, formed the basis for design
of the proposed composting facilities.
If the facilities are found to be in noncompliance, the City will take
responsibility for correcting any problems. Specific persons who will
be responsible are:
Steven Miller
Director of Water/Wastewater Utilities
1100 S. Sherman
Longmont, CO 80501
Geoff Dolan
City Manager
City of Longmont
3rd and Kimbark
Longmont, CO 80501
The composting operation will be 5 days per week (Monday-Friday) , 8
hours per day. Initially, 4 operators will be assigned to the
facilities; at full capacity, 5 will be needed. The attached Plan of
Operation outlines the operation philosophy, staffing needs, and
budget for the facilities.
The attached design report describes the waste volumes to be treated
at the facilities . Initial volumes will be 4 dry tons/day, with
ultimate (year 2010 ) capacity rated at 8. 5 dry tons/day. Waste sludge
will be taken directly from the thickeners and dewatered to between
23% and 25% solids; this equates to 4300 gallons/day initially and
9300 gallons per day at capacity. A sludge quality summary based on
the City' s monitoring records is also part of the design report.
Record-keeping proposed for the composting operation is defined in the
attached Plan of Operation. All incoming sludge will be monitored for
quantity and quality as required by State and Federal sludge
{ycOn17 e
Application for Weld County Certificate of Designation
City of Longmont Wastewater Solids Handling Facilities
Page 7
regulations. As a minimum, the finished compost must meet the
requirements of the Colorado Department of Health with respect to
stability, pathogen reduction and metals content; testing and record
keeping have been established in accordance with these requirements,
which were established for land application of sludge for beneficial
use.
29. Disposal Cells.
Not applicable.
30. Cover Application.
Not applicable.
31. Fencing.
The fence around the site will be 4-strand barbed wire. A diagram of
the fence is shown on page 6-C-2 of the attached plans. No other
barriers are planned, because there will be no blowing or drifting
material on the site; all mixing and composting operations will take
place in enclosed buildings.
33 . Nuisance conditions.
Nuisance conditions associated with the project may include odors
generated from the mixing and composting operations. Mitigation of
the odors from the mixing building will be through the use of a
soil/compost scrubber. All of the building' s air will be routed
through the scrubber. Odors from the composting piles will be
minimized through proper operation of the process. Forced aeration of
the piles will be used, with temperature feedback control of the
aeration rate. Each pile will have its own dedicated blower and
control system. This will insure that the piles remain aerobic and at
the proper temperatures for composting. Operational management of
this kind at other composting facilities has been shown to be
effective in preventing odors. In addition, the composting building
has been designed with positive ventilation for dispersion/dilution of
the building air. Upblast fans with a total throughput of 220 ,000 cfm
will be located on the compost building roof. These fans will help to
dilute any odor problems, even in stagnant atmospheric conditions.
The site for the facilities was also analyzed for meteorological
conditions. Wind conditions are favorable for dispersion of any odors
and the site is above and away from the St. Vrain River corridor which
is prone to temperature inversions. Both the natural and constructed
features described above are expected to mitigate any odor problems.
If odors prove to be a problem in the future, the ventilation systems
in the buildings at the site can be easily modified to accept
scrubbers.
Other problems, such as disease vectors, dust, etc. are not expected
to be a problem. The finished compost stored on the site will be used
as amendment for new compost or disposed of on approved agricultural
land. It will not be stored long enough to attract any vectors.
Active compost piles are at high enough temperatures to eliminate
pathogens and any bacterial vectors. Dust in the composting process
will be controlled by maintaining pile moisture content and covering
each pile with a layer of finished material. Since all operations are
enclosed, the chances of any dust or nuisance escaping from the site
are very small. If any fugitive dust problems occur, the City, will
Cr it* ry.?'"
I
Application for Weld County Certificate of Designation
City of Longmont Wastewater Solids Handling Facilities
Page 8
provide control measures using water trucks or water from the
irrigation system to wet down the problem areas. The dust can then be
removed by using appropriate attachments on the skidsteers that are
part of the composting site equipment. If needed, City street
sweepers could also be used to control dust.
34. Windblown debris.
Not applicable; no disposal on site.
35 . Conceptual plans.
An emergency response plan is a requirement of the Federal grant which
was used to fund the composting facilities. The plan will be included
in the O&M manual for the project, which will be completed and
approved by the State and EPA before startup. Emergency procedures
will include notification requirements, steps that can be taken to
remedy any problems, and an outline of responsibilities and chain of
command in an emergency. Typical emergency conditions will include
flood, power outage, fire, equipment malfunction or breakdown, etc.
None of these situations is expected to be critical due to the
location and design of the facilities as well as the stable nature of
the composting process.
Response to nuisance complaints, including investigation of problems
and contact with the public, will be the responsibility of the Solids
Handling Operations Supervisor. The ultimate responsibility for
correction of nuisances, however, will lie with the Director of
Water/Wastewater Utilities. A staffing plan and chain of command is
shown in the attached Plan of Operation.
Water will only be needed for dust control and washing of equipment.
This will be obtained from the Left Hand Water Company and from the
St. Vrain River. The latter will also be used to irrigate the
landscaping on the site. A joint effort between the City' s Water
Quality Division and Solid Waste Division is under way to develop a
pump station for bringing irrigation water to the site. Other than
site irrigation, minimal amounts of water are expected to be needed
for operations on the site ( less than 1000 gallons/day) .
36 . Closure.
Not applicable. The facilities do not include disposal sites which
would require closure. If the facilities ' useful life is over after
the 20-year design period, other uses may be found for the site and
the buildings. It is probable that the life of the project will be
longer than that initially envisioned, however.
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Solids Management Study'
City of Longmont, Colorado
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FACILITY PLAN SUPPLEMENT
SOLIDS MANAGEMENT PLAN
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SOLIDS MANAGEMENT PLAN
TABLE OF CONTENTS
Page
SUMMARY OF FINDINGS AND RECOMMENDATIONS
A. FINDINGS a
B. RECOMMENDATIONS b
INTRODUCTION
A. BACKGROUND i
B. PURPOSE AND SCOPE i
CHAPTER 1 - CURRENT SITUATION
A. DESCRIPTION AND PERFORMANCE OF EXISTING SYSTEM 1-1
1. WASTEWATER TREATMENT 1-1
2. SLUDGE AND SOLIDS HANDLING FACILITIES 1-1 '
a. Preliminary Treatment 1-1
b. Primary Clarifiers 1-4
c. Final Clarifiers 1-4
d. Gravity Sludge Thickener 1-5
e. Anaerobic Digesters 1-5
f. Belt Filter Press 1-6
g. Static Pile Composting 1-7
h. Sludge Oxidation 1-7
i. Land Application 1-9
j. Landfill 1-9
B. INDUSTRIAL WASTEWATER PRETREATMENT PROGRAM 1-9
1. BACKGROUND 1-9
2. ORGANIC WASTE DISCHARGES 1-10
3. PRIORITY POLLUTANT DISCHARGES 1-11
C. WASTE FLOW AND LOADS 1-15
1. WASTEWATER FLOWS 1-15
2. WASTE LOADS 1-15
TC-1
Page
CHAPTER 1 - CURRENT SITUATION (Continued)
D. QUANTITY OF SLUDGE 1-18
E. SLUDGE QUALITY 1-19
1. QUALITY PARAMETERS AND CLASSIFICATION 1-19
F. BENEFICIAL USE AND SOLID WASTE REGULATIONS 1-21
1. BENEFICIAL USE OF SLUDGE BY CLASSIFICATION 1-21
a. Grade I Sludge 1-21
b. Grade II Sludge 1-21
c. Grade III Sludge 1-21
d. Grade IV Sludge 1-23
2. STABILIZATION OF SLUDGE 1-23
a. Aerobic Digestion 1-23
b. Anaerobic Digestion 1-24
c. Composting 1-24
3. PROCESS TO FURTHER REDUCE PATHOGENS 1-24
G. BACKGROUND ENVIRONMENT 1-24
1. LAND APPLICATION SITES 1-25
2. COMPOSTING SITE 1-25
3. SLUDGE OXIDATION IN A VERTICAL TUBE
REACTOR 1-25
CHAPTER 2 - FUTURE SITUATION
A. POPULATION FORECAST 2-1
B. WASTE FLOW AND LOADS 2-2
C. TREATMENT FACILITY STAGING 2-2
D. QUANTITY OF SLUDGE 2-3
E. QUALITY OF SLUDGE 2-4
CHAPTER 3 - SLUDGE MANAGEMENT ALTERNATIVES
A. LAND APPLICATION 3-2
B. COMPOSTING 3-5
C. CO-COMPOSTING 3-19
D. SLUDGE OXIDATION IN A VERTICAL TUBE
REACTOR 3-19
TC-2
•
Page
CHAPTER 3 - SLUDGE MANAGEMENT ALTERNATIVES (Continued)
E. ENVIRONMENT ASPECTS OF THE PROPOSED 3_22
ALTERNATIVES
1. LAND APPLICATION 3-22
2. COMPOSTING 3-24
3. CO-COMPOSTING 3-26
4. SLUDGE OXIDATION IN A VERTICAL TUBE REACTOR 3-26
CHAPTER 4 - ALTERNATIVE ANALYSIS
A. INTRODUCTION . 4-1
B. COST OF ALTERNATIVES 4-1
C. PRESENT WORTH ANALYSIS 4-1
1. LAND APPLICATION OF DIGESTED SLUDGE
AT AGRONOMIC RATES 4-3
2. COMPOSTING OF RAW SLUDGE 4-4
3. SLUDGE OXIDATION IN A VERTICAL TUBE
REACTOR 4-4
D. OTHER CONSIDERATIONS 4-5
1. ENERGY CONSUMPTIONS 4-5
2. RELIABILITY 4-5
3. FLEXIBILITY 4-6
4. EXPANDABILITY 4-6
5. OPERATIONAL COMPLEXITY • 4-7
6. LAND AREA REQUIREMENTS 4-7
7. POTENTIAL REGULATORY IMPACT 4-7
8. POTENTIAL LIABILITY TO LONGMONT 4-8
9. ODOR POTENTIAL 4-8
10. ENVIRONMENTAL IMPACTS 4-9
E. ALTERNATIVE RANKING 4-17
•
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TC-3
Page
CHAPTER 5 - RECOMMENDED SLUDGE MANAGEMENT PLAN
A. INTRODUCTION 5-1
B. FACILITY STAGING 5-2
C. OPERATIONAL MODIFICATIONS 5-3
D. UTILITY MANAGEMENT 5-3
E. LOCAL FUNDING 5-4
F. ENVIRONMENTAL SUMMARY 5-6
LIST OF APPENDICES
APPENDIX A LIST OF ABBREVIATIONS
APPENDIX B BACKGROUND ENVIRONMENT
APPENDIX C HISTORICAL WASTEWATER LOADINGS
APPENDIX D LAND APPLICATION AREA REQUIREMENTS
APPENDIX E ALTERNATIVE CAPITAL AND OPERATION
AND MAINTENANCE COSTS
APPENDIX F PUBLIC PARTICIPATION
LIST OF TABLES
Page
TABLE 1 INVENTORY OF SLUDGE AND SOLIDS
HANDLING FACILITIES 1-2
_ TABLE 2 INDUSTRIAL DISCHARGE LIMITATIONS
FOR SELECTED HEAVY METALS 1-12
TABLE 1-3 LIMITATION OF INFLUENT METALS
CONCENTRATIONS BASED ON CONTROLLING
CATEGORIES 1-14
TABLE 1-4 AVERAGE ANNUAL WASTE FLOW AND LOADS
FOR 1982-1986 1-16
(}1 ?
TC-4
LIST OF TABLES
(Continued)
Page
TABLE 1-5 MAXIMUM INFLUENT WASTE LOAD RATIOS
FOR 1982-1986 1-17
TABLE 1-6 CURRENT ANNUAL AVERAGE RAW SLUDGE
PRODUCTION 1-18
TABLE 1-7 MAXIMUM CONCENTRATION OF ELEMENTS
OR COMPOUNDS FOR CLASSIFICATION OF
SLUDGES 1-20
TABLE 1-8 CITY OF LONGMONT, DIGESTED SLUDGE
ELEMENT OR COMPOUND CONCENTRATION 1-22
TABLE 2-1 POPULATION PROJECTION FOR LONGMONT'S
SERVICE AREA 2-1
TABLE 2-2 PROJECTED ANNUAL AVERAGE WASTE FLOWS
AND LOADS 2-2
TABLE 2-3 PROJECTED ANNUAL AVERAGE RAW SLUDGE
PRODUCTION 2-3
TABLE 2-4 PROJECTED MAXIMUM MONTH RAW SLUDGE
PRODUCTION 2-4
TABLE 3-1 AGRICULTURAL LAND REQUIREMENTS 3-4
TABLE 3-2 PRELIMINARY DESIGN CRITERIA
LAND APPLICATION AT AGRONOMIC RATES, •
2.4 PERCENT TOTAL SOLIDS, CITY-
OPERATED, ALTERNATIVE A-1 3-6
TABLE 3-3 PRELIMINARY DESIGN CRITERIA
LAND APPLICATION AT AGRONOMIC RATES,
3.5 PERCENT TOTAL SOLIDS, CITY-
_ OPERATED, ALTERNATIVE A-2 3-7
TABLE 3-4 PRELIMINARY DESIGN CRITERIA
LAND APPLICATION AT AGRONOMIC RATES,
2.4 PERCENT TOTAL SOLIDS, CONTRACT
HAUL, ALTERNATIVE A-3 3-8
C)C32 ?A.
TC-5
LIST OF TABLES
(Continued)
Page
TABLE 3-5 PRELIMINARY DESIGN CRITERIA
LAND APPLICATION AT AGRONOMIC RATES,
3.5 PERCENT TOTAL SOLIDS, CONTRACT
HAUL, ALTERNATIVE A-4 3-9
TABLE 3-6 PRELIMINARY DESIGN CRITERIA
AERATED STATIC PILE COMPOSTING
OF RAW SLUDGE WITHOUT AMENDMENT,
ALTERNATIVE B-1 3-13
TABLE 3-7 PRELIMINARY DESIGN CRITERIA
AERATED STATIC PILE COMPOSTTNG
OF RAW SLUDGE WITH AMENDMENT,
ALTERNATIVE B-2 3-15
TABLE 3-8 PRELIMINARY DESIGN CRITERIA
AERATED WINDROW COMPOSTING OF
RAW SLUDGE WITH AMENDMENT,
ALTERNATIVE B-3 3-17
TABLE 3-9 PRELIMINARY DESIGN CRITERIA
SLUDGE OXIDATION IN A VERTICAL
TUBE REACTOR, ALTERNATIVE C-1 3-21
TABLE 4-1 CITY OF LONGMONT, SLUDGE MANAGEMENT
ALTERNATIVES COST SUMMARY 4-2
TABLE 4-2 RANKING OF RELATIVE ENVIRONMENTAL
EFFECTS 4-11
TABLE 4-3 RATING OF RELATIVE ENVIRONMENTAL
EFFECTS 4-12
TABLE 4-4 ALTERNATIVE RANKING 4-14
lisr,?as
TC-6
LIST OF FIGURES
Following
Page
FIGURE 1-1 UNIT PROCESSES CAPACITY 1-1
FIGURE 3-1 DAILY MATERIALS FLOW
AERATED STATIC PILE COMPOSTING
OF RAW SLUDGE WITHOUT AMENDMENT 3-11
FIGURE 3-2 DAILY MATERIAL FLOW
AERATED STATIC PILE COMPOSTING
OF RAW SLUDGE WITH AMENDMENT 3-11
FIGURE 3-3 DAILY MATERIAL FLOW
AERATED WINDROW COMPOSTING
OF RAW SLUDGE WITH AMENDMENT 3-11
FIGURE 5-1 DAILY MATERIAL FLOW
AERATED STATIC PILE COMPOSTING
OR RAW SLUDGE WITHOUT AMENDMENT 5-1
C' e t.2 A
TC-7
SUMMARY OF FINDINGS AND RECOMMENDATIONS
A. FINDINGS
While the City currently has a successful contract hauling and
digested sludge disposal program, Longmont has decided to supplement
its current Wastewater Facility Plan to incorporate a long-term solids
management program. The plan has been developed to serve the projected
population and anticipated average annual sludge generation presented
below:
POPULATION AND ANNUAL AVERAGE
SLUDGE GENERATION PROJECTIONS
Primary Sludge Secondary Sludge Total Sludge
Year Population Production Production Production
(dry ton/day) (dry ton/day) (dry ton/day)
1990 68,400 3.6 3.2 6.8
2000 79,900 4.2 3.8 8.0
2010 89,700 4.5 4.0 8.5
Three major technologies were evaluated in this plan: land applica-
tion, composting, and sludge oxidation.
From these three primary technologies, the following eight alterna-
tives were developed to determine the best overall solids management plan
for Longmont:
• City-operated land application of digested sludge at a
2.4 percent total solids concentration.
• City-operated land application of digested sludge at a
3.5 percent total solids concentration.
• City-contracted land application of digested sludge at a
2.4 percent total solids concentration.
• City-contracted land application of digested sludge at a
3.5 percent total solids concentration.
• Aerated static pile composting of raw sludge.
• Aerated static pile composting of raw sludge with amendment
addition.
• Aerated windrow composting of raw sludge with amendment addition.
• Sludge oxidation in a vertical tube reactor.
The necessary sludge storage, processing, and staffing requirements
were included for all the alternatives to allow the option to be operated
as a separate facility, not dependent on the current staff of the waste-
water treatment facility.
B. RECOMMENDATIONS
Based on a detailed present worth cost analysis and a summary ranking
of the alternatives, construction of an offsite composting facility is the
recommended plan. Aerated static pile composting of raw sludge with
non-aerated windrow curing will provide, the City with a cost-effective,
environmentally sound sludge management program. The total project
cost, including capital cost, the purchase of equipment, and engineering
services, is estimated to be $4,008,000. Staging the purchase of a second
front-end loader will reduce this to $3,858,000.
The capital cost is based on the construction of a facility to compost
the sludge quantities expected during the design year. While the facili-
ties will be built to serve the design year population, grant funding will
be available only for those facilities required to serve the current
population. Using the ratio of current population to design year
population, approximately 65 percent of the capital cost, or $2,508,000,
is eligible for grant funding. Since composting provides a product which
will be used beneficially, it is anticipated that 75 percent funding will
be available. At this funding level, the grant amount will be approxi-
mately $1,881,000. The remaining capital cost, $1,977,000, will be
provided by the City of Longmont. Funds are currently available in the
wastewater utility reserves for the Longmont portion of the capital costs.
The actual grant amount and City share will be dependent upon actual
construction costs and the determination of current capacity requirements.
To aid in the determination of eligible costs, it is recommended that the
construction contract be bid on a unit price basis.
q -- ..d
b
The operation and maintenance costs of the composting facility will
impact the residents of Longmont at a level of $0.38 per person per month.
This amount has been estimated based on the anticipated operation and
maintenance costs and projected population for the year 2000. While
increasing the cost of service, the City of Longmont believes that the new
facilities can be operated without an increase in the current rate
structure.
The reader is referred to Chapter 5, RECOMMENDED SLUDGE MANAGEMENT
PLAN, for additional details regarding the proposed facilities.
C"Z?
c
INTRODUCTION
A. BACKGROUND
The City of Longmont initiated the development of a solids management
plan to provide a long-range program for the management of the sludge
generated at the wastewater treatment facility. The criteria set by the
City dictated that the plan be environmentally sound, flexible, reliable,
cost-effective, publicly-acceptable, and implementable. Since the plan is
intended to supplement the City's current Wastewater Facility Plan, it has
been prepared to meet the requirements of the United States Environmental
Protection Agency (EPA) construction grants program.
B. PURPOSE AND SCOPE
The Solids Management Plan has included detailed evaluation of three
major technologies: land application of digested sludge, composting of raw
sludge, and raw sludge oxidation in a vertical .tube reactor. To evaluate
these three major technologies, a total of eight alternatives were
analyzed. The eight alternatives are as follow:
• City-operated land application of digested sludge at a
2.4 percent total solids concentration.
• City-operated land application of digested sludge at a
3.5 percent total solids concentration.
• City-contracted land application of digested sludge at a
2.4 percent total solids concentration.
• City-contracted land application of digested sludge at a
3.5 percent total solids concentration.
• Aerated static pile composting with non-aerated windrow curing of
raw sludge without amendment addition.
• Aerated static pile composting with non-aerated windrow curing of
raw sludge with amendment addition.
• Aerated windrow composting of raw sludge with amendment addition.
• Sludge oxidation in a vertical tube reactor.
('e .n ".
i
In addition to evaluating these alternatives, the City utility staff
is currently cooperating with the Community Development Department staff
who are analyzing the feasibility of co-composting. If preprocessing of
solid waste is deemed cost-effective, the wastewater utility staff has
expressed a willingness to use the material as a composting amendment. If
additional facilities are required to store and process the solid waste,
the City would fund these facilities from sources outside the wastewater
utility.
The evaluation included a detailed present worth analysis together
with the ranking of alternatives based on non-monetary criteria such as
environmental impact, reliability, operational complexity, and others.
Following the evaluation, the recommended plan was identified and
developed. In order to project future sludge production, identify
alternatives and sites, perform the evaluation, and develop a recommended
plan, a solids management group was formed. The group included members
from the City's utility engineering and operations staff, representatives
of the University of Colorado at Boulder, and the City's consultants.
Regularly-scheduled workshops were held to streamline report develop-
ment and meet the completion date required by the Colorado Department of
Health for obtaining a position on the fundable portion of the Fiscal Year
1988 priority list. The workshops provided a forum for all members of the
group to offer input and work together so that the report would address all
the major issues of concern to the City of Longmont.
rkennst.01,
ii
CHAPTER 1
CURRENT SITUATION
A. DESCRIPTION AND PERFORMANCE OF EXISTING SYSTEMS
1. WASTEWATER TREATMENT. The Longmont Wastewater Treatment Facility
was originally designed to treat 8.2 million gallons of sewage per day
(mgd). The expanded capacity of the facility is currently about 11.6 mgd.
The plant was designed for annual average five-day biochemical oxygen
demand (BOD) and total suspended solids (TSS) loadings of 15,840 pounds per
day (lbs/day) and 12,960 lbs/day, respectively.
Primary treatment at the site consists of mechanical screening and
aerated grit removal, followed by primary clarification. Secondary
treatment begins with first-stage trickling filters. Following the
first-stage trickling filters, the flow is split and the wastewater
receives further treatment in either the second-stage trickling filter or
the rotating biological contactors. The trickling filter effluent then
flows through the solids contact tank, final clarifiers, and chlorine
contact basin where it joins the rotating biological contactor effluent
prior to discharge into the St. Vrain Creek.
Plant performance records have been reviewed for the period from 1982
through 1986 and are attached to this report as Appendix C. The data
indicate that the facility has consistently met the effluent limitations
contained in the City's National Pollutant Discharge Elimination System
(NPDES) permit.
2. SLUDGE AND SOLIDS HANDLING FACILITIES. This section provides a
description of the sludge handling facilities at the Longmont WWTP.
Included is a discussion of the performance potential for each of the major
unit processes, a graphical depiction of which is presented on Figure 1-1.
The design criteria for each of the sludge and solids handling facilities
are presented in Table 1-1.
a. Preliminary Treatment. Preliminary treatment consists of two bar
screens, two aerated grit basins, and a comminutor. The bar screens are
mechanically cleaned, and the screenings are dropped to a belt conveyor.
A hand-cleaned bar screen is available to accommodate bypass flow when
necessary. All screenings are transported by truck to a landfill.
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TABLE 1-1
INVENTORY OF SLUDGE AND
SOLIDS HANDLING FACILITIES
Item Description
Mechanical Bar Screens
Number of Units 2
Screen Width, ft 4
Clear Spacing, in. 1
Hand-Cleanad Bar Baran
Number of Units 1
Screen Width, ft 4
Clear Spacing, in. 3/4
Grit Chamber
Number of Units 2
Type Aerated
Capacity, mud 21.4
Grit Pumps
Number of Units 2
Type Centrifugal, constant spead
Capacity, each 800 gpm at 45 ft TIN
Primary Clarifiers
Number of Unita 3
Dimensions 1 at 85 ft diameter, 8,-9" SSD;
1 at 80 ft diameter, 7,-8" SSD;
1 at 70 ft diameter, 8•-2" SND
Total Surface Area, eq ft 14,550
Primary Sludge Pumps
Number of Units 3
Typs Centrifugal
Capacity 2 constant spead at 240 gpm
at 43 ft TAI;
1 variable speed at 300 gpm
at 12 ft TDH
Final Clarifier
Number of Units 2
Dimensions, each 120 ft diameter, 17,-4" SWD, with
40 ft diameter flocculation cone
Total Surfaes Area, sq ft 22,620
Secondary Sludge Wasting Pump
Number of Units 2
Type Centrifugal, variable speed
Capacity, each 500 gpm at 16 ft TAI
Scum Pumps
Number of Units 1
Typo Positive displacement,
constant speed
Capacity 75 gpm at 125 ft TAI
1-2 n, h^?n
TABLE 1-1
INVENTORY OF SLUDGE AND
SOLIDS HANDLING FACILITIES
(Continued)
Item Description
Screw Pumps
Number of Unto 2
Type 60-inch diameter spiral
Capacity, each, mqd 15.7
Reaeration Basin Pumps
Humber of Units 3
Type Centrifugal variable speed
Capacity, each 2,780 cps at 62 ft TDH
Sludge Thickener ,
Number of Units 1 .
Diameter, ft 35
Side Water Depth, ft 10
Cons Section Height, ft 3
Thickened Sludge Pumps
Number of Units 2
TYPe Positive displacement, lobe rotor
Capacity, each, gpm 220
Anaerobic Digesters
Number of Units 2
Operational Status 1 heated, with floating cover;
1 net heated, with fixed cover
Diameter, ft 45
Side titter Depth, ft 27
Cone Section Height, ft 6
Digested Sludge Transfer Pump
Number of Wits 1
Type Double piston, positive
displacement
Capacity 150 gpm at 125 ft TDH
Belt Filter Press
Number of Wits 1
Type Cantilever
Simi, meter 1,2
Capacity, gal/min 100
Cake Solids, percent 30 to 60
1-3
Grit removal is accomplished with aerated grit chambers, grit washers,
cyclone degritters, and grit screw collectors. The grit removal system has
a rated design capacity of 21.4 mgd. The grit is hauled with the
screenings to a landfill.
b. Primary Clarifiers. Secondary sludge is wasted to the headworks
and combines with the incoming sewage just prior to the equalization basin.
The combined wastewater stream is settled in three primary clarifiers of
different sizes. The total surface area of the clarifiers is 14,555 square
feet (sq ft).
The present operating strategy for the primary clarifiers is to
minimize the sludge blanket in any of the basins. As a consequence, a
relatively thin sludge (less than 2,000 mg/1) is pumped from the clarifiers
to the gravity thickener. This operational strategy has been adopted as a
means of keeping the contents of the gravity thickener "fresh".
As seen on Figure 1-1, the primary clarifiers have been rated as
having the capacity to handle plant flows up to 11.6 mgd. This rating
was based on a surface overflow rate of 800 gpd/sq ft, with all three
clarifiers on-line. Beyond this flow rate, it was projected that the
performance of the clarifiers could be expected to deteriorate.
c. Final Clarifiers. Secondary sludge produced by the trickling
filter/solids contact process is removed from the wastewater stream in the
two final clarifiers. Underflow from the final clarifiers is pumped to the
reaeration basin, where it is either "wasted" to the headworks or returned
to the solids contact process. As with the primary clarifiers, the current
operating strategy is to avoid carrying a sludge blanket in the final
clarifiers. The clarifiers are 120 feet in diameter and have a 40-foot
diameter center well. The center wells serve as flocculation zones for
the biological sludge and are, therefore, gently mixed.
The potential capacity of the final clarifiers was projected using a
surface overflow rate of 600 gpd/sq ft. This loading resulted in a rating
of 12.1 mgd, as illustrated on Figure 1-1. The clarifiers have a total
surface area of 22,600 sq ft, of which 2,500 sq ft represents the surface
gOC?4
1-4
area of the center wells. Since quiescent conditions are required for
proper clarification, the center well surface area was not included in
the calculations for determining surface overflow capacity.
d. Gravity Sludge Thickener. Combined primary and secondary sludge
is pumped from the three primary clarifiers to the gravity thickener. The
current operating strategy for the thickener is to carry a 3- to 4-foot
sludge blanket. If the blanket is much deeper than this, odor problems may
develop during the summer months. However, if the depth of blanket is less
than 3 feet, the sludge rake does not move a uniform sludge to the hopper.
Thickened sludge is pumped to either the anaerobic digesters or to the belt
filter press for further processing.
The capacity rating for the gravity thickener was projected based on a •
solids loading of 15 lbs/day/sq ft. Given 960 sq ft of thickener surface
area, a solids loading of 14,400 lbs/day could be processed. The weir
plates of the thickener are badly rusted and poorly attached. This
condition must be corrected for the potential capacity to be realized.
e. Anaerobic Digesters. A portion of the gravity thickened sludge
is pumped to anaerobic digesters for stabilization. The Longmont WWTP has
two anaerobic digesters of equal size and currently operates them in
series. One of the digesters has a floating cover, whereas the other has a
fixed cover. The capacity of the present heat exchanger is only sufficient
to heat one of the two units; therefore, one of the digesters is primarily
used for storage. No supernating of the digested sludge is practiced.
The high-rate digesters are fitted with oversized mixing/recirculation
systems and have a demonstrated capability of achieving adequate stabiliza-
tion when operated at a hydraulic retention time (HRT) of 15 days and a
temperature of 95 F. Therefore, in projecting the potential capacity of
the digesters, a minimum HRT of 15 days was used. Capacity of only the
heated digester was used in the evaluation.
The maximum operating volume of the heated digester is 333,000 gallons.
For this volume, a HRT of 15 days dictates a thickened sludge feed capacity
of 22,200 gpd. Thickened sludge production averaged 17,800 gpd at a plant
flow of 7.87 mgd during the period of May 1, 1986 to March 31, 1987.
nir tr? .a
1-5
Assuming similar plant influent characteristics in the future, a rated
capacity for the anaerobic digester of 9.8 mgd was projected by
proportioning. As an option, the rated capacity of the digesters could be
effectively doubled by providing additional heat exchanger capacity for
the second digester.
f. Belt Filter Press. The City's 1.2-meter belt filter press is
currently used as a backup to the anaerobic digesters and as a dewatering
process for the pilot-scale composting project. It can be fitted with
either fabric or steel belts and is capable of producing a cake with a
total solids concentration of 30 percent. The performance of the belt
press has been found to be dependent upon the quantity and type of polymer
added and the loading rate and concentration of feed sludge.
The belt filter press was rated by the manufacturer at 2,000 lbs/hr
throughput (100 gpm at 4 percent total solids). Although a lower loading
should be used for design of new facilities, the 2,000 lbs/hr rating was
used in projecting the potential capacity of the existing press. For the
purposes of projection, press operation was assumed to be eight hours per
day, five days per week. At a rated capacity of 2,000 lbs/hr, the press
could dewater 80,000 pounds of thickened sludge per week, or 11,430 lbs/day
for a seven-day average.
This rating assumes that it would be possible to deliver 24 hours of
sludge production to the belt press within an eight-hour period. This is
not possible currently since thickener performance deteriorates if sludge
is held to match this schedule. Additional sludge storage facilities would
be required to optimize the capacity of the belt press without changing the
operational parameters. As an option, it may be possible to retrofit one or
both of the digesters to serve as storage facilities, since full use of the
belt press would negate the need for anaerobic digestion. If this is done,
it will be necessary to correct the groundwater infiltration problem
experienced in the digesters when they are operated at a liquid depth of
less than 15 feet.
1-6
g. Static Pile Composting. Raw sludge composting at the Longmont
WWTP is presently operating at a pilot-scale. Thickened sludge is pumped
to the belt filter press one or two days per month for dewatering. The
dewatered sludge cake is combined with recycled compost in a one to one
ratio to form new compost pile core material. An equal amount of recycled
compost is then added as cover material to minimize odors.
Positive aeration is provided for 10 minutes of every 30 minutes
during the first 14 days of the composting cycle. The pile temperature is
monitored to achieve a minimum pile temperature of 40 C for five days of
the composting cycle. Once these conditions are met, operation is switched
to a 14-day drying cycle. During this period, positive aeration is
provided for 30 minutes of every hour. Since the composting project is
pilot-scale, a potential capacity rating has not been projected.
h. Sludge Oxidation in Vertical Tube Reactor. In the vertical tube
reactor (VTR) process, oxygen is combined with sludge and pumped into an
annular space created by the concentric tubes. The static head of the
mile-deep column of liquid sludge creates the required high pressure for
the process. The high pressure, in conjunction with dissolved oxygen and
the heat of reaction, results in wet air oxidation of the sludge.
Oxidation begins when the temperature in the reactor reaches approxi-
mately 180 C. When temperatures of approximately 204 C to 280 C are
attained, autogenic oxidation of the sludge is reported to occur. Once
autogenic oxidation begins, the heat exchanger used initially to warm the
sludge may be reversed to recover heat from the process. The oxidized
sludge stream is returned to the surface through the outer annular space.
Presently, the VTR facility at the Longmont WWTP is not in operation.
The facility was operated intermittently for approximately 18 months during
1984-1985 as a demonstration project.
- The Longmont WWTP average sludge production averaged 5 to 6 dry tons
per day during the demonstration. Initially, the facility was operated by
mixing air with the raw sludge prior to pumping it into the reactor. The
results indicated an inadequate supply of oxygen was available to produce
the level of COD reduction originally predicted. By switching to a pure
oxygen enrichment system, COD loadings were increased while obtaining the
C 0 1:-2 A
1-7 f
predicted COD reductions. It was also determined that a minimum of 10 to
11 dry tons per day of sludge was required for the process to operate
autogenously.
The sludge quantity produced by the Longmont WWTP was insufficient
to maintain the operation at the desired capacity with the increased COD
loading capability. Additional sludge from surrounding municipalities was
hauled to the Longmont site to increase the loading rate. Throughout the
demonstration, the raw sludge quantity treated ranged from 5 dry tons per
day to 30 dry tons per day.
Odor control was not a significant problem at the Longmont facility,
except during startup periods when low process temperatures resulted in
inadequate oxidation of some odorous organic compounds. Once the process
was established, odors were not noticeable.
Effluent from the VTR was pumped to a settling basin equipped with
plate separators where the ash was separated from the effluent. Chemical
analyses of the ash showed low metals concentrations, and it was not
considered a hazardous waste. The settled ash slurry was pumped at
approximately 5 to 6 percent total solids to onsite storage basins or into
tanker trucks and hauled to a privately-owned disposal site. The liquid
effluent was returned to the wastewater treatment plant at the trickling
filters. Although the BOD loading on the plant was increased by 20 to
25 percent, plant operation was not significantly impacted. Slightly
higher COD and ammonia levels were noticed in the plant effluent, but no
increase was observed that led to a violation of NPDES discharge permit.
The major maintenance item for the Longmont VTR facility was the
reactor interior where inorganic solids formed a scale that was removed
periodically with an acid wash. The reactor capacity was reduced if this
scale was not removed.
Performance of the VTR process was measured by the reduction of COD
in the sludge. The COD reduction goal was approximately 80 percent. The
measured COD reduction ranged from 60 to 66 percent when air was used as an
oxygen source in the Longmont facility. Use of pure oxygen resulted in COD
reductions of approximately 80 percent.
r � ' ".
1-8
Due to the demonstration nature of the VTR facility, it was opera-
tional about 67 percent of the time. This represented a greater amount
of downtime than would be expected for a fully operational plant. Some of
the causes of downtime included equipment maintenance, descaling of the
reactor, reactor fouling by organic materials, and lack of sufficient sludge
for processing.
i. Land Application. Anaerobically digested sludge is land applied
at a total solids concentration of 2.4 percent by a private contractor.
The liquid sludge is hauled by tanker truck to the application sites where
it is surface applied. Crops that are commonly grown on the sludge-amended
soil include wheat and corn. The sludge is applied at an agronomic rate
that meets the crop nitrogen requirements.
j . Landfill. The landfill operation serves as a backup to the land
application program and the pilot-scale composting program. Lime
stabilized raw sludge that has been dewatered by the belt filter press is
landfilled when land application or composting is not feasible. The sludge
cake is trucked to the landfill using City-owned and operated equipment.
B. INDUSTRIAL WASTEWATER PRETREATMENT PROGRAM
1. BACKGROUND. The City of Longmont has developed a pretreatment
program to control the impact of industrial waste discharges. The program
enables the City to prevent the introduction of pollutants into the
municipal wastewater treatment that could either: (1) interfere with the
plant performance, (2) pass through the various unit processes untreated
and enter into the receiving stream, or (3) cause interference with sludge
use or disposal.
A list has been compiled of all businesses in the City that fall within
any of the industrial categories that are subject to the United States
- Envrionmental Protection Agency (EPA) Categorical Pretreatment Standards.
The individual businesses on this list are sent an industrial wastewater
pretreatment questionnaire that requests information pertaining to items
such as the water usage, products manufactured, and the types of pollutants
CS-7"\
1-9
that might be found in the waste discharge. As a result of this ongoing
industrial wastewater survey, businesses have been characterized as
follows:
• Non-Significant Industrial Users. These industries are con-
sidered to have little potential for discharging wastes
detrimental to the wastewater treatment plant.
• Significant Industrial Users. These industries are considered
to have the potential for discharging wastes detrimental to the
wastewater treatment plant. These wastes are considered to be
detrimental because of either an excessive concentration of
organics (BOD5 or suspended solids) or the presence of priority
pollutants.
• Commercial Users. These businesses have the potential of dis-
charging either BOD5 or suspended solids in excess of the City's
surcharge limits. They are typically businesses that handle
foods (i.e. , restaurants, grocery stores, and convenience
stores).
2. ORGANIC WASTE DISCHARGES. The City has estahlished industrial
waste surcharge limits and surcharge rates as a means of controlling
excessive BOD5 and suspended solids discharges. The surcharge limit is
300 mg/1 for BOD5 and 330 mg/1 for suspended solids. A surcharge is
assessed in addition to the normal sewer rates and use charges at discharge
levels above these values.
Longmont Foods, a turkey processing plant, has been responsible for a
significant portion of the historic organic load to the wastewater treat-
ment plant. The BOD5 load from Longmont Foods represented 39 percent of
the wastewater treatment plant total BOD load in 1982. Longmont Foods
installed a primary pretreatment system in the summer of 1983 and reduced
their BOD5 contribution to 25 percent of the total wastewater treatment
plant load for that year. The primary components of the pretreatment
system consist of screening, pH neutralization, and dissolved air
flotation.
Proper operation of the pretreatment system was expected to reduce the
Longmont Foods BOD5 load to 10 percent of the wastewater treatment plant
total. Although these levels have not been achieved on a consistent basis,
RTenro n
1-10
the Longmont Foods BOD5 contribution has averaged only 15 percent of the
treatment plant total since April 1986. The total BOD5 contribution from
other Longmont businesses is 3 to 5 percent of the treatment plant total,
with the load from no other single business considered to be significant.
3. PRIORITY POLLUTANT DISCHARGES. To date, the City of Longmont
has only established discharge limitations for the heavy metal priority
pollutants. Presently, no industry in the City discharges organic priority
pollutants at a concentration or mass loading that is considered to be
detrimental to either the wastewater treatment plant or stream quality.
The City will establish limitations for that category of priority pollu-
tants if and when the discharge of organic chemicals becomes a significant
problem.
The City's major sources of heavy metal discharges are electroplating
industries. Centerline Circuits, a manufacturer of printed circuit boards,
is responsible for two-thirds of the total waste flow from metal-
discharging industries. In establishing the permit limitations for the
discharge of heavy metals, Longmont used the levels set forth for the
electroplating point source category in the General Pretreatment Regula-
tions in the Clean Water Act of 1977. The daily maximum and average
maximum concentrations for selected heavy metals are presented in
Table 1-2.
The City elected to apply the limitations for electroplating
industries to all industrial dischargers of heavy metals. These limita-
tions provided considerable leniency to non-electroplating industries,
since the permissible concentration levels are higher than for any other
industrial category.
Once these limitations had been established, the City used three
criteria to ensure that heavy metal mass loadings were not detrimental to
— the wastewater treatment plant or its receiving stream. One criterion was
that the level of pollutant should not result in a violation of the Stream
Water Quality Standards. Although criterion was that heavy metal concen-
trations should be low enough that the treatment plant sludge meets the
Grade II category for the disposal of sludge on agricultural lands, as
defined by the State of Colorado Domestic Sewage Sludge Regulations. The
1-11 r
TABLE 1-2
INDUSTRIAL DISCHARGE LIMITATIONS
FOR SELECTED HEAVY METALS
Daily Average
Pollutant Maximum_ Maximum
(mg/1) (mg/1)
Cadmium 1.2 0.7
Chromium 7.0 4.0
Copper 4.5 2.7
Lead 0.6 0.4
Nickel 4.1 2.6
Zinc 4.2 2.6
0,^ M
1-12
third criterion was that the level of pollutant should not cause an inter-
ference with the performance of any unit process at the wastewater
treatment plant.
In reviewing the plant data, the Pretreatment Division could not
identify any occasions when process performance was limited by the presence
of heavy metals. Therefore, the two categories by which metal loadings to
the treatment plant were assessed were their impact on stream water quality
and land application of sludge. The Pretreatment Division determined the
maximum permissible metal loadings for obtaining compliance in each
category by using EPA formulae and methods. The category which required
the lowest influent concentration of a given metal was considered to be
the controlling category. Table 1-3 presents a list of the controlling
category for each of six heavy metals and the maximum permissible influent
concentration for that metal and category.
Heavy metal loadings associated with the discharge of domestic
waste were estimated by assuming that weekend flows were essentially
non-industrial. The metal loadings so determined were taken to be the
constant, baseline load. Industrial metal loadings were conservatively
estimated by assuming that each metal-discharging industry would discharge
at the maximum concentration allowed by their existing permit. By adding
the industrial metal loads to the baseline loads, and dividing by the plant
flow, it was found that the influent concentration of each heavy metal
should be less than the maximum permissible concentration set forth in
Table 1-3. On the basis of these calculations, it was decided that the
present industrial discharge limitations were satisfactory and required no
adjustments.
Several industries are presently meeting their permit with ease and
could perhaps meet more stringent limitations. However, the Pretreatment
Division has adopted a "good neighbor" policy in that they do not request
lower permit levels as long as the controlling categories (land applica-
tion and stream water quality) are met with the existing limitations in
effect. Most industries have installed or upgraded their pretreatment
nee 7',
1-13
TABLE 1-3
LIMITATION OF INFLUENT METAL CONCENTRATIONS
BASED ON CONTROLLING CATEGORIES
Maximum
Permissible
Metal Concentration Controlling Categories
(mg/1)
Cadmium 0.0056 Land Application and
Stream Water Quality
Chromium 0.48 Stream Water Quality
Copper 0.18 Land Application
Lead 0.24 Land Application
Nickel 0.23 Land Application
Zinc 0.50 Land Application
• k .
1-14
systems since the discharge limitations went into effect. As a result,
the wastewater treatment plant has seen a gradual improvement in influent,
effluent, and sludge metal concentrations.
C. WASTE FLOW AND LOADS
1. WASTEWATER FLOWS. The annual average wastewater flows for 1982
through 1986 are presented in Table 1-4. A review of the data shows a
22 percent increase from 1982 to 1983, which had the highest recorded
average flow for the period. Flows were virtually the same during 1984
and 1985, 7.40 mgd and 7.37 mgd, respectively, and increased slightly to
7.54 mgd in 1986.
2. WASTE LOADS. The principal design waste loads are BOD5 and
TSS. Table 1-4 summarizes the annual average raw wastewater BOD5 and TSS
loadings from 1982 through 1986. The loadings are presented in both dry
tons per day (tons/day) and pounds per million gallons (lbs/mg) of influent
flow. A review of the data presented in Table 1-4 indicates that both the
BOD5 and TSS loading rates, expressed as lbs/mg, dropped between 1983 and
1984. The reductions were approximately 15 percent for both BOD5 and
TSS. It is believed that this reduction can be attributed to the pretreat-
ment program implemented by the City. Following this reduction, the BOD5
and TSS loads averaged 1,460 and 1,150 lbs/mg, respectively, for the period
1984 through 1986.
In addition to determining the annual average waste loads, plant data
were utilized to estimate waste load peaking factors. Each monthly average
waste load was divided by the annual average to estimate the peaking
factor. This analysis was performed for each month from 1982 through 1986
for both BOD5 and TSS. All monthly/annual average load ratios are
presented in Appendix C. The maximum influent waste load ratios for each
year are presented in Table 1-5. A review of the information presented in
Table 1-5 indicates that the peak influent waste load ratios are 1.29 and
1.53 for BOD5 and TSS, respectively. The average of the maximum for the
five years of data are 1.22 for BOD5 and 1.30 for TSS.
1-15
TABLE 1-4
AVERAGE ANNUAL WASTE FLOW
AND LOADS FOR 1982-1986
Year Flow Raw Influent BOD5 Raw Influent TSS •
(mgd) (tons/day) (lbs/mg) (tons/day) (lbs/mg)
1982 6.37 5.50 1,750 4.33 1,380
1983 7.79 6.60 1,720 5.16 1,350
1984 7.40 5.29 1,460 4.19 1,140
1985 7.37 5.37 1,480 4.40 1,210
1986 7.54 5.37 1,440 4.10 1,110
F C' 774,
1-16
TABLE 1-5
MAXIMUM INFLUENT WASTE LOAD
RATIOS FOR 1982-1986
Maximum Influent
Waste Load Ratios*
Year BOD5 TSS
1982 1.19 (Mar) 1.53 (Feb)
1983 1.29 (Jan) 1.38 (Jan)
1984 1.19 (Apr) 1.21 (Feb)
1985 1.16 (Mar) 1.13 (Apr)
1986 1.28 (Oct) 1.23 (Apr)
*Ratio of monthly average load to annual average load.
Pre-71;
1-17
D. QUANTITY OF SLUDGE
As discussed in Section C, the average flows and waste loads to the
treatment facility have been compiled for the period from 1982 through
1986. During this period, there were no records of the amount of sludge
discharged from the gravity thickener and entering either the digester, the
Dewatering Building, or the VTR sludge oxidation unit.
The sludge collected within the treatment plant for the period was
estimated from records maintained for contract hauling, sludge dewatering,
and VTR operation. It has been estimated from these records that the
annual average total raw sludge production under the current operating
conditions is 1.08 pounds per pound of BODS removed across the entire
plant. The annual average secondary sludge generation is estimated to be
0.72 pound of secondary sludge per pound of BODS removed in the secondary
system.
Using the sludge generation rates described above and the waste loads
currently being experienced at the treatment facility, the average annual
raw sludge generation for 1987 is 5.9 dry tons per day. The production
rate is divided between primary and secondary sludge as shown in Table 1-6.
TABLE 1-6
CURRENT ANNUAL AVERAGE RAW SLUDGE PRODUCTION
Primary Sludge Secondary Sludge Total Sludge
Year Production Production Production
(dry tons/day) (dry tons/day) (dry tons/day)
1987 3.1 2.8 5.9
Further discussion of the sludge production criteria can be found in
Chapter 2, FUTURE SITUATION.
e O^?'\
1-18
E. SLUDGE QUALITY
1. QUALITY PARAMETERS AND CLASSIFICATION. The quality of a sludge
is measured by its physical and chemical composition. Nutrient, metal,
and toxic organic concentrations within the sludge are often determining
factors which dictate the final use or disposal option. The extent to
which these parameters impact the environment determines the acceptable
method(s) of reuse and disposal.
Low heavy metal concentrations are desirable for all disposal alter-
natives, while nutrient concentrations can be beneficial or detrimental,
depending upon the disposal method chosen. A sludge with low nutrient
concentrations is unattractive as a fertilizer, while sludges with very
high nutrient concentrations can contribute to groundwater quality
degradation associated with leaching of nitrogen.
The Colorado Department of Health (CDH), along with the EPA, has
adopted regulations and guidelines addressing sludge quality. The current
EPA regulations limit the maximum cumulative loading of cadmium to the soil
and dictate groundwater quality criteria that must be maintained. The CDH
has prepared criteria to classify sludge, which allows for beneficial use
dependent upon its classification. The CDH criteria for classification of
sludge are shown in Table 1-7. Note that each value listed is the maximum
allowable concentration, and if any one constituent is over the limit, the
sludge is graded accordingly. Sludges with concentrations higher than
those indicated for the Grade III classification are classified Grade IV.
The CDH criteria further state that:
"The classification of sludge generated by a given producer
shall be determined by the results of a six-month average of
all analyses of that sludge performed by the producer and/or
the Department."
The City of Longmont 1986 sludge characteristics have been reported on a
monthly basis and include both six-month and annual averages. The informa-
tion for 1985 and 1984, however, includes only annual averages. For the
purpose of this discussion, annual averages will be used.
1-19
TABLE 1-7
MAXIMUM CONCENTRATION OF ELEMENTS OR
COMPOUNDS FOR CLASSIFICATION OF SLUDGES
Grade Cd(1) Cu(1) Pb(1) Ni(1) Zn(1) PCB(2)
I 25 625 1,000 250 1,250 3
II 70 1,650 2,500 650 3,325 10
III 125 3,125 5,000 1,250 6,250 10
(1)Expressed as dry weight basis (milligram of element per kilogram
of sludge).
(2)Expressed as wet weight basis (parts per million).
,CYCY77 s%
1-20
Table 1-8 shows the heavy metal data for 1984 through 1986, which
indicates that the quality of the sludge has steadily improved since
implementation of the pretreatment program. Comparing the concentrations
to the CDH classification criteria indicates that the City's sludge has
improved from Grade III in 1984 to Grade II in 1986, with copper the
determining element in all cases. The Industrial Pretreatment Program
instituted by the City has reduced copper concentrations from
2,130 mg/kg in 1984 to 630 mg/kg in 1986, while the remaining elements
have been below the maximum concentration for Grade I sludge in all three
years. Through July 1987, the City of Longmont sludge has continually
met the Grade I criteria for the year.
F. BENEFICIAL USE AND SOLID WASTE REGULATIONS
1. BENEFICIAL USE OF SLUDGE BY CLASSIFICATION. The sludge classifi-
cation is extremely important since it dictates the acceptable beneficial
uses of the sludge. The following paragraphs summarize the uses allowed
for each classification of stabilized sludge. Note that some form of
stabilization must be performed prior to using the sludge, and a discussion
of stabilization techniques will follow the beneficial use descriptions.
a. Grade I Sludge. Dewatered, Grade I sludge solids between 16 and
40 percent, that has been stored for a one-year period or has undergone a
Process to Further Reduce Pathogens (PFRP), may be applied to any land for
any beneficial use. All other Grade I sludge may be applied only to
agricultural or disturbed lands. The CDH defines disturbed land as that
from which vegetation, topsoil, or overburden has been removed.
b. Grade II Sludge. Grade II sludge may be applied only to agri-
cultural or disturbed lands.
c. Grade III Sludge. Grade III sludge may be applied only to dis-
turbed lands or agricultural lands on which no food chain crops will be
planted. Following the application of a Grade III sludge, cultivation of
a food chain crop is forbidden for a three-year period. The CDH defines
food chain crops as those crops grown for human consumption or feed for
animals whose products are consumed by humans.
nc
1-21
TABLE 1-8
CITY OF LONGMONT
DIGESTED SLUDGE ELEMENT OR COMPOUND CONCENTRATIONS
(1) (1) (1) (1) (1) (2) Limiting
Year Cd Cu Pb Ni Zn PCB Grade Element
1984 4 2,130 430 140 720 N/A III Cu
1985 12 1,840 390 220 810 N/A III Cu
1986 11 630 180 39 1,150 N/A II Cu
(1)Expressed as dry weight basis (milligram of element per kilogram
of sludge).
(2)Expressed as weight basis (parts per million).
ne CT?
1-22
d. Grade IV Sludge. Grade IV sludge may not be used for a bene-
ficial purpose and must be disposed of as a solid waste in accordance with
the requirements of the Solid Wastes Disposal Sites and Facilities Act,
C.R.S. 1973, 30-20-101 et seq. , as amended.
2. STABILIZATION OF SLUDGE. As stated previously, any sludge
applied to the land for beneficial use must be stabilized. The CDH has set
minimum stabilization criteria for aerobic digestion, anaerobic digestion,
and composting. The criteria for each stabilization method have been
summarized as follows.
a. Aerobic Digestion. Sludge receiving aerobic digestion will be
considered stabilized if it meets any of the following criteria:
(1) Volatile solids reduction is 38 percent or greater.
(2) The oxygen uptake rate of undiluted sludge is either:
(a) mg 02/hr/gm volatile suspended solids (VSS) , dependent
upon temperature, as follows:
Less than or equal to to 2.0 mg 02/hr/gm VSS at
greater than 20 C.
Less than or equal to 1.3 mg 02/hr/gm VSS at 18-20 C.
Less than or equal to 1.0 mg 02/hr/gm VSS at 15-18 C.
Less than or equal to 0.7 mg 02/hr/gm VSS at 0-15 C.
(b) mg 02/1/hr, as follows:
Less than or equal to 10 mg 02/1/hr at 20 C.
(3) Digested sludge volatile solids content is less than 65 percent.
(4) Mean Cell Residence Time (sludge age) from an aeration system(s)
is at least 20 days.
n e C^'p
1-23
b. Anaerobic Digestion. Sludge receiving anaerobic digestion will
be considered stabilized if it meets any of the following criteria:
(1) Volatile solids reduction is 38 percent or greater.
(2) Volatile acids content is less than 500 mg/1.
(3) Digested sludge volatile solids content is less than 65 percent.
c. Composting. Sludge that has received some form of composting
will be considered stabilized if it meets any of the following criteria:
(1) Volatile solids reduction is 38 percent or greater.
(2) Volatile solids content is less than 65 percent
(3) Sludge total composting and curing time is a minimum of 80 days.
(4) Sludge is maintained at minimum operating conditions of 40 C for
five days. For four hours during this period, the temperature
shall exceed 55 C.
3. PROCESSES TO FURTHER REDUCE PATHOGENS. In addition to stabili-
zation, Grade I sludges that are to be distributed for use on any land for
any beneficial purpose must undergo a PFRP. The EPA lists the criteria for
a number of pathogen reduction processes in Appendix II of their Criteria
for Classification of Solid Waste Disposal Facilities and Practices,
CFR 40, Part 257. The processes described by the EPA include composting,
heat drying, heat treatment, thermophilic aerobic digestion, beta ray
irradiation, gamma ray irradiation, and pasteurization.
G. BACKGROUND ENVIRONMENT
An assessment has been prepared to describe the impact the proposed
alternatives will have on the existing Longmont environment. Sites for
land application, composting, and sludge oxidation in a vertical tube
reactor have been evaluated.
'C ?h.
1-24
1. LAND APPLICATION SITES. Nine locations have been identified as
prospective sites for the land application of digested sludge. The sites
were selected based on the following criteria:
• Sites within a 5-mile radius of the WWTP, and
• Sites currently permitted or within the permitting process for
the land application of sludge during 1987, or
• Sites currently engaged in dryland farming operations that might
be suitable for future land application sites, or
• Previous land application sites, compiled from year 1983.
2. COMPOSTING SITE. The remote composting site evaluated is
located approximately 3.5 miles east of the treatment plant at the existing
landfill site. The 50-acre site is bordered by the St. Vrain Creek on the
south and east. This site has been chosen for the following reasons:
• Proximity to the treatment plant.
• Site is currently owned by the City of Longmont.
• The remote site should reduce potential odor concerns.
• Compost generated initially can be utilized for site reclamation.
3. SLUDGE OXIDATION IN A VERTICAL TUBE REACTOR. The VerTech system
would remain at the existing WWTP location. The environmental assessment
describes any affect the system's resultant ash may have on the
environment.
The reader is referred to Appendix B for additional information con-
cerning Longmont's background environment.
1-25
CHAPTER 2
FUTURE SITUATION
A. POPULATION FORECAST
The current population projection developed by the Denver Regional
Council of Governments (DRCOG) for the Longmont service area is presented
in Table 2-1.
TABLE 2-1
POPULATION PROJECTION
FOR LONGMONT'S SERVICE AREA
Year Population
1985 52,000
1990 68,400
2000 79,900
2010 85,700
Longmont's population projection was recently updated by DRCOG follow-
ing the issuance of the May 1983 Executive Summary Addendum to the February
1975 Sewage Facilities Report. The addendum was prepared to modify the
report to comply with a previously revised 1995 projected population of
72,000.
To check the variation between the population projection contained in
the addendum with that used in this plan, the 1990 and 2000 values listed
above were interpolated to estimate a 1995 population of 74,150. This is
approximately 3 percent greater than the 1995 population presented in the
Executive Summary Addendum. This small increase in projected population
will not have a significant effect on the implementation of this plan.
It is anticipated that the solids management alternative developed in
this plan will be implemented by the year 1990. Using 1990 as the base
year, the projected population increase is approximately 25 percent during
the 20-year planning period.
0k nr.—^0 n
2-1
B. WASTE FLOWS AND LOADS
Historical wastewater flows and loads from 1982 through 1986 are
tabulated in Appendix C. Projected flows and organic loads are based on
the populations listed in Table 2-1 and the historical average per capita
flow, BOD, and TSS generation rates presented in Appendix C. Table 2-2
summarizes the waste flow and load projections used in this study.
TABLE 2-2
PROJECTED ANNUAL AVERAGE
WASTE FLOWS AND LOADS
Year Flow BOD TSS
(mgd) (tons/day) (tons/day)
1990 10.2 7.6 6.0
2000 11.6 8.9 7.0
2010 12.3 9.6 7.6
C. TREATMENT FACILITY STAGING
While Table 2-2 projects a flow of 12.3 mgd in 2010, the existing
wastewater treatment facility capacity is approximately 11.6 mgd. Thus,
there may be a shortfall of plant capacity between the years 2000 and 2010.
However, since any such shortfall would be within 6 percent of the current
rated capacity, no major liquid stream plant expansions are proposed during
the study period.
As shown on Figure 1-1, a number of the unit processes for solids
processing do not have adequate capacity for the entire planning period.
Therefore, where required for alternative development, appropriate
expansions to existing sludge facilities are included in the evaluation.
iniCr 7.a
2-2
D. QUANTITY OF SLUDGE
Future sludge production was estimated using the projected BOD
loadings and the sludge generation rates tabulated from plant operating
data for the period 1982 through 1986. During this period, the mean sludge
generation rates were determined to be as follow:
• Average Primary Clarifier Efficiency: 60 percent for TSS and
35 percent for BOD.
• Average Secondary Sludge Production: 0.72 lb secondary sludge/lb
secondary BOD removed.
Based on the sludge generation rates listed above and the waste
loadings projected in Table 2-2, the annual average raw sludge production
has been estimated over the planning period and is summarized in Table 2-3.
TABLE 2-3
PROJECTED ANNUAL AVERAGE
RAW SLUDGE PRODUCTION
Primary Sludge Secondary Sludge Total Sludge
Year Production Production Production
(dry ton/day) (dry ton/day) (dry ton/day)
1990 3.6 3.2 6.8
2000 4.2 3.8 8.0
2010 4.5 4.0 8.5
In addition to the annual average raw sludge production, the maximum
month raw sludge production has been estimated. This was accomplished by
compiling 60 ratios of monthly average to annual average BOD for the years
1982 through 1986 and determining the ratio that 95 percent of the months
were below. This analysis showed that maximum month BOD loads are about
1.25 times greater than the annual average. Using this data and the annual
average raw sludge generation rates listed above, the maximum month raw
sludge production has been projected and is presented in Table 2-4.
r,C CS?
2-3
TABLE 2-4
PROJECTED MAXIMUM MONTH
RAW SLUDGE PRODUCTION
Primary Sludge Secondary Sludge Total Sludge
Year Production Production Production
(dry ton/day) (dry ton/day) (dry ton/day)
1990 4.5 4.0 8.5
2000 5.2 4.8 10.0
2010 5.6 5.0 10.6
E. QUALITY OF SLUDGE
Longmont's sludge quality and Industrial Pretreatment Program have
been discussed in Chapter 1. The quality of Longmont's digested sludge has
steadily improved from 1984 through 1986, as shown in Table 1-8. As stated
in Chapter 1, copper is the only element reported with a concentration
exceeding that acceptable for a Grade I classification. The City is
currently working with a number of industries to improve pretreatment and
anticipates reporting a Grade I quality sludge by the end of 1987.
While striving to obtain and maintain a Grade I wastewater sludge,
at this time, the City of Longmont does not intend to supply stabilized
sludge for public distribution that has also been treated by a process to
further reduce pathogens (PFRP). As will be discussed, the City intends to
develop a large enough agricultural and disturbed land reclamation market
to distribute its stabilized sludge in liquid, dewatered, or composted
form. This will allow for beneficial use of the sludge while maintaining
flexibility within Longmont's pretreatment and solids management programs.
ne en.?
n
2-4
CHAPTER 3
SLUDGE MANAGEMENT ALTERNATIVES
Future sludge management alternatives available to the City of
Longmont for the sludge generated at the wastewater treatment plant are
discussed in the sections that follow. Longmont is a city with strong ties
to agriculture. As such, the alternatives evaluated, with the exception of
two, propose to reuse the sludge for agricultural purposes. The four basic
technologies identified for sludge disposal are as follows:
• Land application of anaerobically digested sludge at agronomic
rates.
• Composting of raw sludge using the aerated static pile or aerated
windrow methods.
• Co-composting of raw sludge with processed solid waste.
• Sludge oxidation in a vertical tube reactor.
Using these four technologies, eight sludge management alternatives have
been evaluated.
These technologies and subsequent alternatives were selected following
an initial screening process to eliminate those alternatives that show no
apparent benefit to the City. The main criteria used in the initial
screening include cost, potential for beneficial reuse, potential regula-
tory impacts, and compatibility with current operational practice.
Alternatives eliminated during the initial screening include:
Land Application
• Dedicated land disposal.
• Land application of dewatered sludge.
Composting
• In-vessel composting systems.
• Composting of digested sludge.
Volume Reduction
• Incineration.
• Zimpro wet air oxidation.
Landfill
• Landfill of dewatered sludge.
The purpose of this chapter is to develop the preliminary design
criteria for the alternatives. The criteria include the design and
operational parameters for each process along with facility and trans-
portation requirements.
A. LAND APPLICATION
Land application of anaerobically digested sludge at agronomic rates
is the method of sludge management currently being practiced by Longmont.
Presently, raw sludge is gravity thickened prior to anaerobic digestion.
The digested sludge is then transported in liquid form for application to
agricultural land. The amount of sludge applied to the fields is dependent
upon the type of crops to be grown and their nitrogen requirements.
The first four alternatives evaluated were variations of the
technology for land application at agronomic rates. The items that will
vary among the alternatives are the total solids concentration of the
sludge following anaerobic digestion and the method of operation. Both
City-owned and operated, and privately-owned and operated alternatives
were evaluated.
Using these two variations, the first four alternatives are as
follows:
• Alternative A-1. City-operated land application of anaerobi-
cally digested sludge with a total solids concentration of
2.4 percent.
• Alternative A-2. City-operated land application of anaerobi-
cally digested sludge with a total solids concentration of
3.5 percent.
3-2
• Alternative A-3. Contract hauling and land application of
anaerobically digested sludge with a total solids concentration
of 2.4 percent.
• Alternative A-4. Contract hauling and land application of
anaerobically digested sludge with a total solids concentration
of 3.5 percent.
The first step in developing the preliminary design criteria for the
land application alternatives was to evaluate the sludge application rates
and the agricultural land requirements. The Colorado Domestic Sewage
Sludge Regulations limit the annual sludge application rate by crop
nitrogen requirements and the cadmium application rate. Since the Longmont
WWTP has low cadmium concentrations, the annual application rate will be
dependent on the crop nitrogen requirements.
Both corn and wheat are crops commonly grown in the Longmont area that
are suitable for sludge application. Corn grown for silage has the highest
nitrogen requirement of these crops; therefore, the highest sludge applica-
tion rate would be to land on which silage corn is to be grown. Table 3-1
shows the annual application rate and the area requirements for each of
the crops evaluated.
Since the quantity of sludge to be applied in each of the land
application alternatives is the same, the area required for each of the
alternatives is the same. Table 3-1 shows that the agricultural land
requirements would range from 1,030 acres to 3,430 acres, depending on
the crop to be grown. The land area requirements have been calculated
assuming subsurface injection of liquid sludge. Surface spreading, as
presently permitted in Boulder County, would reduce these requirements by
10 to 20 percent. The allowable reduction would result from the volatili-
zation of ammonia. The land area calculations are attached as Appendix D.
The Colorado Domestic Sewage Sludge Regulations also limit the cumu-
lative sludge application at a site based on the cumulative loading of
cadmium, copper, lead, nickel, and zinc. A review of the Longmont sludge
quality indicates that copper would limit site life. If an application
rate of 2.4 dry tons per acre per year is utilized, and an average copper
eN c*.}ry 7
is
3-3
TABLE 3-1
AGRICULTURAL LAND REQUIREMENTS
Sludge Area
2122 Application Rate Required
(dry tons/acre/yr) (acres/yr)
Corn (silage) 3.0 1,030
Corn (grain) 2.6 1,210
Wheat (irrigated) 2.4 1,290
Wheat (dry land) 0.9 3,430
Barley (irrigated) 2.1 1,470
3-4
concentration of 625 mg/kg is assumed in the sludge, the estimated site
life would be 35 years. This estimated site life is also based on a soil
pH of 7.8 and a cation exchange capacity (CEC) of 15 meq/100 g.
After establishing the application rates and area requirements, the
next step was to establish the operational parameters and the facility and
transportation requirements. These criteria are shown for the alternatives
in Tables 3-2 through 3-5.
For Alternatives A-1 and A-3, raw primary and secondary sludge would
be thickened in the existing gravity thickener prior to anaerobic
digestion. The digested sludge would be land applied at a total solids
concentration of 2.4 percent.
In Alternatives A-2 and A-4, the raw sludge would be thickened by
centrifugation prior to anaerobic digestion. The digested sludge for these
alternatives would have a total solids concentration of 3.5 percent, and
would also be land applied.
For each of the land application alternatives, the anaerobic digestion
system would be upgraded to accommodate the design sludge quantity and to
provide approximately 14 days sludge storage. In addition, each alterna-
tive would require upgrading of the sludge loading station.
Alternatives A-1 and A-2 would require that the City of Longmont
purchase tanker trucks and application vehicles. In Alternatives A-3 and
A-4, the contractor would be responsible for hauling and applying the
sludge.
B. COMPOSTING
Aerobic composting is a method of sludge stabilization in which sludge
organics are decomposed by microbiological organisms in the presence of
oxygen. The end product of sludge composting is a stabilized humus-like
- material that can be used as a soil amendment. Composting is an aerobic
process that is impacted by several operational parameters. These include
the oxygen concentration within the compost pile, and the temperature,
moisture, and volatile solids content of the compost. Each of these
parameters affects the viability of the aerobic organisms responsible for
decomposition of the sludge solids.
�,
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7,
3-5
TABLE 3-2
PRELIMINARY DESIGN CRITERIA
LAND APPLICATION AT AGRONOMIC RATES
ALTERNATIVE A-1
Design Capacity, dry ton/day
Annual Average 8.5
Maximum Month 10.6
Additional Digester Capacity
Volume, gal 737,000
Storage Capacity, days 14
Operation Requirements
Days Per Week 5
Shifts Per Day 1
Production Hours Per Shift 7
Staffing Per Shift 11
Handling Criteria
One-way Distance to Site, miles 20
Average Speed, mph 20
Truck Capacity, gal 7,000
Number of Trucks 6
Land Application Equipment
Applicator Capacity, gal 4,000
Number of Applicators 2
re 0-7
3-6
TABLE 3-3
PRELIMINARY DESIGN CRITERIA
LAND APPLICATION AT AGRONOMIC RATES
ALTERNATIVE A-2
Design Capacity, dry ton/day
Annual Average 8.5
Maximum Month 10.6
Centrifuge Equipment Capacity
Size, each, gpm
200
Number Required 2
Additional Digester Capacity
Volume, gal 505,000
Storage Capacity, days 14
Operation Requirements
Days Per Week 5
Shifts Per Day 1
Production Hours Per Shift 7
Staffing Per Shift 10
Handling Criteria
One-way Distance to Site, miles 20
Average Speed, mph 20
Truck Capacity, gal 7,000
Number of Trucks 4
Land Application Equipment
Applicator Capacity, gal 4,000
Number of Applicators 2
err,:rfr
3-7
TABLE 3-4
PRELIMINARY DESIGN CRITERIA
LAND APPLICATION AT AGRONOMIC RATES
ALTERNATIVE A-3
Design Capacity, dry ton/day
Annual Average 8.5
Maximum Month 10.6
Additional Digester Capacity
Volume, gal 737,000
Storage Capacity, days 14
Operation Requirements
Days Per Week 5
Shifts Per Day 1
Production Hours Per Shift 7
Staffing Per Shift 2
Ccr:'\?
3-8
TABLE 3-5
PRELIMINARY DESIGN CRITERIA
LAND APPLICATION AT AGRONOMIC RATES
ALTERNATIVE A-4
Design Capacity, dry ton/day
Annual Average 8.5
Maximum Month 10.6
Centrifuge Equipment Capacity
Size, each, gpm
200
Number Required 1
Additional Digester Capacity
Volume, gal 505,000
Storage Capacity, days 14
Operation Requirements
Days Per Week 5
Shifts Per Day 1
Production Hours Per Shift 7
Staffing Per Shift 2
3-9
There are a number of engineered systems available for composting
municipal sludge. These systems are often divided into two categories:
open and in-vessel composting systems.
Open systems include aerated static pile and windrow systems. Open
systems are usually exposed to the atmosphere, but can be housed to reduce
the detrimental effects of precipitation. Open systems usually require
more area than comparably sized in-vessel systems, but have lower capital
costs.
In-vessel systems compost sludge in self-contained reactors or
vessels. There are two basic types of reactors: horizontal and vertical
flow systems. The main difference in these systems is the method used for
moving compost through the vessel. In-vessel systems can be further
classified according to the method used for maintaining aerobic conditions
within the compost. All in-vessel systems use forced aeration, while some
systems also use mechanical mixing in combination with forced aeration.
During the evaluation of composting, both aerated static pile and
windrow composting methods were evaluated. In-vessel systems were not
considered because of the high capital cost of these systems and because
sufficient low cost land should be available for the implementation of an
open composting system. Each alternative was evaluated for composting raw
sludge having a total solids concentration of 22 percent. All active
composting and curing would be performed under cover. Following is a
summary of the composting alternatives evaluated:
• Alternative B-1. Aerated static pile composting of raw sludge
without amendment, and with non-aerated windrow curing.
• Alternative B-2. Aerated static pile composting of raw sludge
and amendment, with non-aerated windrow curing.
• Alternative B-3. Aerated windrow composting of raw sludge with
amendment.
To obtain the total solids concentration necessary for composting, raw
sludge would be dewatered using belt filter presses. The existing belt
filter press facility would be upgraded to accommodate one additional
2.2-meter unit. The dewatered cake would be loaded into dump trucks and
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3-10
hauled to the compost facility, which would be located offsite. Once the
sludge is received at the compost facility, the method of handling the
sludge would be dependent on the method of composting selected.
In Alternative B-1, the sludge cake would be mixed with recycled
compost by a windrow mixing machine. The initial compost mixture would
then be placed in piles over a permanent aeration system. The piles would
not be mixed during the 21-day active composting period. During active
composting, air would be supplied to the compost pile. Following active
composting, the compost would be cured in a non-aerated windrow for
approximately 30 days. The curing windrow would be mixed periodically
to facilitate drying. Figure 3-1 shows the materials flow for
Alternative B-1.
The composting process used in Alternative B-2 is the same as that
used for Alternative B-1 except that an amendment, such as wood chips,
would be mixed with the sludge cake and recycled compost. The wood chips
would help to improve porosity of the compost and the structural integrity
of the pile, which would allow the formation of a taller static pile.
A taller static pile would reduce the area requirements for composting.
Figure 3-2 shows the materials flow for Alternative B-2. The wood used
would be of sufficient size to allow screening. For the purpose of this
evaluation, it is anticipated that 70 percent of the wood chips would be
reclaimed.
In the windrow composting system, Alternative B-3 a bed of wood chips
would be placed over a permanent aeration system. Sludge cake would then
be spread over the wood chip. An auger machine would be used initially for
mixing the sludge and wood chips. A windrow mixer would be used following
the auger to shape the pile and to mix the compost at periodic intervals.
Figure 3-3 shows the materials flow for Alternative B-3.
Unlike the aerated static pile method, windrow composting does not
usually require a curing step. Active composting would occur during the
first 15 days of the 24-day composting period, while compost drying would
occur during the last nine days of the period. Air would be drawn through
the windrow during active composting (negative aeration) , and air would be
forced through the windrow during the drying process (positive aeration).
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The preliminary design criteria for each of the alternatives are shown
in Tables 3-6 through 3-8. The criteria include storage, transportation,
equipment, and labor requirements.
The area required for all of the compost alternatives will be depen-
dent on the site. Preliminary estimates indicate that less than 5 acres
would be required for a compost facility.
_ One of the ancillary processes required for the composting alterna-
tives is odor control. The City indicated that the site of its existing
landfill would be the probable location of any compost facility. Since
this site is remotely located, it is anticipated that odors released during
composting of raw sludge would have minimal impact on the public. There-
fore, the air drawn through the compost piles would .be exhausted to an
odor scrubber consisting of only finished compost.
Another requirement of composting is the collection and disposal
of leachate and condensate. With the probable location of the compost
facility remote from the treatment plant, it would not be feasible to
return the collected leachate/condensate to the plant through a wastewater
collection system. Transport of the leachate/condensate to the treatment
plant using tank trucks would be feasible, but would be a costly
alternative. Therefore, the leachate/condensate will likely be collected
and disposed in an onsite evaporation pond. The possibility also exists
that this liquid can be land applied during the summer if suitable cropland
can be found close to the composting site.
Storm water runoff from the composting site would also be collected
and transported to the evaporation pond. Precipitation landing on the roof
of the structures would be collected through a gutter system and trans-
ported through downspouts away from the facility. This will minimize the
size of the evaporation pond or irrigation facility.
3-12
TABLE 3-6
PRELIMINARY DESIGN CRITERIA
AERATED STATIC PILE COMPOSTING
OF RAW SLUDGE WITHOUT AMENDMENT
ALTERNATIVE B-1
_ Design Capacity, dry ton/day
Annual Average 8.5
Maximum Month 10.6
Raw Sludge Storage
Solids Concentration, percent 5.5
Storage Requirement, days 5
Storage Volume Required, gal 185,000
Dewatered Sludge, percent
Minimum Solids Concentration 22
Volatile Solids Concentration 75
Operation Requirements
Days Per Week 5
Shifts Per Day 1
Production Hours Per Shift 7
Staffing Per Shift 7
Hauling Criteria
One-Way Distance, miles 5
Average Speed, mph 20
Truck Capacity, cu yd 12
Number of Trucks 2
Mixing Equipment
Type Windrow mixer
Number 1
Active Composting Area
Number of Static Piles 4
Pile Height, ft 5
Pile Residence Time (average), days 21
Building Area Requirement (net), sq ft 78,400
3-13 ni e n 2 A
TABLE 3-6
PRELIMINARY DESIGN CRITERIA
AERATED STATIC PILE COMPOSTING
OF RAW SLUDGE WITHOUT AMENDMENT
ALTERNATIVE B-1
(Continued)
Blower Operation
Peak Continuous
Intermittent
Average (timer or
temperature
control)
Blower Requirements 8 at 2,100
scfm/blower
Curing/Drying Area
Residence Time (average), days 30
Pile Height, ft 15
Building Area Requirement (net), sq ft 13,000
Finished Compost Storage
Storage Required (average), days 60
Pile Height, ft 15
Building Area Requirement (net), sq ft 7,000
ret,??.
3-14
TABLE 3-7
PRELIMINARY DESIGN CRITERIA
AERATED STATIC PILE COMPOSTING
OF RAW SLUDGE WITH AMENDMENT
ALTERNATIVE B-2
Design Capacity, dry ton/day
Annual Average 8.5
Maximum Month 10.6
Raw Sludge Storage
Solids Concentration, percent 5.5
Storage Requirement, days 5
Storage Volume Required, gal 185,000
Dewatered Sludge, percent
Minimum Solids Concentration 22
Volatile Solids Concentration 75
Operation Requirements
Days Per Week 5
Shifts Per Day 1
Production Hours Per Shift 7
Staffing Per Shift 7
Hauling Criteria
One-Way Distance, miles 5
Average Speed, mph 20
Mixing Equipment
Type Windrow mixer
Number 1
Active Composting Area
Number of Static Piles 4
Pile Height, ft 12
Pile Residence Time (average), days 21
Building Area Requirement (net), sq ft 32,400
n t) '•:,•q,
3-15
TABLE 3-7
PRELIMINARY DESIGN CRITERIA
AERATED STATIC PILE COMPOSTING
OF RAW SLUDGE WITH AMENDMENT
ALTERNATIVE B-2
(Continued)
Blower Operation
Peak Continuous
Average Intermittent
(timer or
temperature
control)
Blower Requirements 8 at 2,100
scfm/blower
Curing/Drying Area
Residence Time (average), days 30
Pile Height, ft 15
Building Area Requirement (net) , sq ft 13,000
Finished Compost Amendment Storage
Storage Required (average), days 60
Pile Height, ft 15
Building Area Requirement (net), sq ft 12,000
3-16
TABLE 3-8
PRELIMINARY DESIGN CRITERIA
AERATED WINDROW COMPOSTING
OF RAW SLUDGE WITH AMENDMENT
ALTERNATIVE B-3
r- Design Capacity, dry ton/day
Annual Average
8.5
Maximum Month 10.6
Raw Sludge Storage
Solids Concentration, percent 5.5
Storage Requirement, days 5
Storage Volume Required, gal 185,000
Dewatered Sludge, percent
Minimum Solids Concentration 22
Volatile Solids Concentration 75
Operation Requirements
Days Per Week 5
Shifts Per Day 1
Production Hours Per Shift 7
Staffing Per Shift 6
Hauling Criteria
One-Way Distance, miles 5
Average Speed, mph 20
Windrow Composting
Windrow Residence Time (average), days 24
Number of Windrows 24
Windrow Height, ft 5
Windrow Width, ft
4
Top
Base
16
Windrow Length, ft 76
Building Area Required (net), sq ft 65,300
3-17
TABLE 3-8
PRELIMINARY DESIGN CRITERIA
AERATED WINDROW COMPOSTING
OF RAW SLUDGE WITH AMENDMENT
ALTERNATIVE B-3
(Continued)
Blower Operation
Continuous
Peak
Intermittent
Average (timer or
temperature
control)
Blower Requirements 12 @ 1,200
scfm/blower
Finished Compost/Amendment Storage
Storage Required (average), days 60
Pile Height, ft 15
Building Area Required, sq ft 12,000
r' r-. e ? A
3-18
C. CO-COMPOSTING
Co-composting is the aerobic, microbiological stabilization of sewage
sludge combined with municipal solid waste. As in sludge composting,
co-composting produces a humus-like product that can be used as a soil
amendment.
Co-composting has been used primarily as a conditioning and disposal
method for solid waste. In this process, raw sludge is added to municipal
refuse to increase the moisture and volatile solids content of the refuse.
The quantity of material that can be co-composted is dependent on the
quantity of refuse to be composted. The systems available for
co-composting are the same as those previously described for sludge
• composting.
Solid waste must be processed to remove ferrous and non-ferrous
metals, glass, hard plastics, and other nonbiodegradable materials prior
to being mixed with sludge. The fraction remaining for co-composting is
composed of paper, light plastics, and small portions of glass and metal
that were not removed.
The solid waste will also require size reduction prior to or after the
separation process, depending on the separation methods used. The purpose
of reducing the size of the refuse is to improve the rate of biodegradation
of the material.
If the preprocessing of solid waste is determined to be cost-effective
based on the anticipated extension of landfill life, the wastewater utility
staff has agreed to consider the use of refuse as an amendment in compost-
ing operations. The additional facilities required for the storage and
processing of solid waste with sludge would be financed by the City through
some mechanism other than the wastewater utility funds.
_ D. SLUDGE OXIDATION IN A VERTICAL TUBE REACTOR
VerTech Treatment Systems has proposed to modify the existing VTR
facility to process raw sludge quantities ranging from 3 to 10 dry tons per
day. The primary modifications that have been proposed include the
following:
3-19
• Remove the existing 10-inch reactor and repair the reactor
casing.
• Install a new reactor.
• Overhaul surface equipment and control systems.
• Add a mechanical ash dewatering system.
Alternative C-1 is the processing of Longmont's raw sludge in the
modified VTR facility. Preliminary design criteria were developed for this
alternative and are shown in Table 3-9. The criteria include the require-
ments for sludge storage, sludge processing, ash transportation, and ash
landfilling.
In this process, raw sludge would be pumped to the VTR facility at a
total solids concentration of approximately 5.5 percent. Oxygen would be
mixed with the sludge by adding pure oxygen and air to the sludge stream.
Effluent from the reactor would be discharged to the existing plate
separator where the ash and liquid effluent would be separated prior to
further dewatering of the ash.
The ancillary facilities required for this alternative include raw
sludge storage, ash dewatering and disposal, liquid effluent treatment, and
acid storage and treatment. The raw sludge storage requirement will be
dependent on the system downtime since the VTR facility would operate
continuously. Reactor descaling would likely be required every to 10 to
15 days, which would result in the reactor being down for approximately
15 hours every two weeks. In addition, if the reactor must be removed for
repairs, the facility could be inoperable for a significantly longer
period. For this reason, a minimum of five days storage capacity has been
provided in the preliminary design criteria.
Following dewatering, ash generated by the process would be disposed
in a privately-owned landfill. Analyses of the ash produced during the
demonstration project indicated that it would not be a hazardous material.
Mechanical dewatering of ash collected during operation of the demonstra-
tion facility indicated that total solids concentration ranging from 40 to
75 percent were attainable.
TABLE 3-9
PRELIMINARY DESIGN CRITERIA
SLUDGE OXIDATION IN A VERTICAL TUBE REACTOR
ALTERNATIVE C-1
Design Capacity, dry ton/day
Annual Average 9.5
Maximum Month 10.6
•
Raw Sludge Storage
Solids Concentration, percent 5.5
Storage Requirement, days 5
Storage Volume Required, gal 195,000
Operation Requirements
Days Per Week 7
Shifts Per Day 3
Production Hours Per Shift 7
Staffing Per Shift 1
VTR Operations
Electrical Power Requirements, kW/year 622,000
Oxygen Requirements, tons/day 6.0
Ash Landfilling
Ash Quantity, cu yd/day 3.5
One-way Distance, miles 20
Truck Capacity, cu yd 30
Number of Trucks 1
3-21 � ci7.1,
Liquid effluent from the solids separation processes would be returned
to the treatment plant headworks. It is estimated that the BOD concentra-
tion of the effluent would be approximately 20 percent of the VTR feed
concentration. The volume of effluent to be treated would be approximately
equal to the volume of the sludge processed in the reactor. By returning
the effluent to the plant headworks, the quantity of sludge produced may be
increased. The additional sludge quantity was estimated at 1.8 dry tons
per day for the design year 2010 sludge generation.
The acid required for descaling should be stored onsite since
descaling would be a regular maintenance procedure. Storage should be
provided for a one-month supply of acid. Additional storage may be
required for the used acid, which ultimately must be treated and disposed
offsite.
E. ENVIRONMENTAL ASPECTS OF THE PROPOSED ALTERNATIVES
1. LAND APPLICATION. The fundamental objective of land application
of stabilized wastewater treatment plant sludge solids is to apply the
sludge in such a manner that the soils can assimilate the solids and
prevent the offsite movement of any deleterious byproducts to adjacent
lands, into a flowing stream, or into the underlying groundwater. There-
fore, the selection of a suitable site is paramount to a successful
program. Site selection must be based on several basic interrelated
parameters: landscape features, soil parent material including geologic
characteristics, and properties of the soil. Ideally, the appropriate
landscape features of the site should include a closed or modified closed
drainage system and slopes of less than 4 percent. Soil parent material
should include medium-textured material; have a high pH and/or free
carbonates (calcareous); and bedrock and unconsolidated substrata should
_ be free of coarse conducting layers or conduits, and should always be at
least 3-4 feet below the soil surface. Soils should have high surface
infiltration capacity and moderate subsoil permeability, a thickness of
at least 3 feet without restrictive layers, be well or moderately well
3-22 ,00772 °‘
drained, have moderate to high available water capacity, have a pH ranging
from 6.5 to 8.2, and have medium to high levels of organic matter in the
surface horizon.
The constituents and characteristics of the sludge to be applied are
also to be considered. If the above criteria are met for site selection,
then future use of the land must also be appraised. All of the sites in
this study are presently being used for agricultural purposes. For the
program to be successful, the owners or operators of the sites must be
assured that uninterrupted use of their land will be maintained. The heavy
metal, nutrient, and persistent organic concentrations must correspond to
the agronomic application rates if such assurance is to be given.
The odor aspect of land application of sludge can be significant.
Sludge will cause odor problems where residents are in close proximity to
the disposal site. This can be mitigated by subsoil injection of the
sludge or incorporation of surface applied sludge. Proper stabilization or
digestion of sludge prior to application also greatly lessens the odor
impacts.
Noise associated with land application of sludge will be generated by
the machinery involved. Tractors or truck applicators will be used in the
disposal method. The noise generated will be no greater than that
generated by ordinary farm equipment.
The visual aspects of land application will be short-term and no more
objectionable than normal farming practices.
Vector production will be minimized by incorporation of subsoil
injection of the sludge. Surface applied sludge will quickly dry, flake,
and self-incorporate into the upper soil layers.
All sludge to be land applied must be treated by a "process to sig-
nificantly reduce pathogens". Aerobic and anaerobic digestion, composting,
or other types of stabilization will adequately accomplish this reduction.
Public access to land receiving sludge applications must be controlled for
at least 12 months, and grazing by animals whose products are consumed by
humans must be prevented for at least one month after application.
3-23 41017.47,45
Pathogenic microorganisms such as bacteria, viruses, protozoa, and
parasitic worms are found in raw sewage. Sludge stabilization processes
destroy most of the pathogens. Some of the most common bacterial pathogens
associated with sewage are Salmonella, Shigella, Vilorio, and
Campylobacter. Major pathogenic viruses include Poliovirus,
Coxsackieviruses, Echoviruses, and Hepatitis virus. Common parasites
T include Entamoeba histolytica, Giarda lamblia, and Balantidium coli.
Intestinal Ascaris can also be transmitted by close contact with sewage.
Fungi spores of Aspergillus fumigates are frequently found in dust near
compost operations where wood chips are used as an amendment.
In land application of sludge, pathogens survive for a period of time
following application. Temperature is an important factor in this
survival. In the case of bacteria, and probably viruses, the die-off rate
is approximately doubled with each 10 degree rise in temperature between
5C and 30C.
Land application of digested sludges has shown little impact on
bacterial contamination of groundwater, provided that the groundwater
table is not too high and the soil is well drained.
Rainfall, temperature, evaporation, and wind are important environ-
mental factors for the land application of sludge. The Longmont area is
warm and arid and is very suitable for this sludge disposal practice.
2. AERATED STATIC PILE OR AERATED WINDROW COMPOSTING OF RAW SLUDGE.
Composting is a process of sludge stabilization by aerobic microbial
decomposition. This alternative would involve the transport of dewatered
raw sludge from the wastewater treatment plant to the City of Longmont
landfill site for composting. A new composting facility requires
approximately one acre of relatively flat land for each 4 dry tons of
sludge processed, to provide the area sufficient for pathogen reduction
requirements. Additional land would be required for curing, storage, and
screening.
Composting is a desirable alternative for sludge disposal because it
is generally more publicly acceptable than other methods. It will generate
a product with reduced odor potential that is easily stored and has greatly
decreased levels of persistent organics and pathogens.
3-24 _,.rC ,?,m
Because all of the compost activity occurs above ground and most
operations take place on asphalted pads, soils and geology of the site do
not normally restrict its use. They are, however, important environmental
aspects in that the site must be well drained and adequately bermed to
reduce the effect on surrounding properties or watercourses by wet weather
runoff.
Raw sludge can be malodorous. Its transport and use in a composting
operation may cause temporary odor problems. In the standard procedure for
composting, raw sludge is mixed with recycled compost or other amendment
soon after delivery, thus reducing the odor potential. Use of negative
aeration, drawing air through the pile, and exhausting the air through a
finished compost pile also helps to control odors. •
Noise will be a potential factor in any composting operation. Pile
mixing equipment and blower operation will periodically cause greater than
normal noise.
Vector production via composting at the City landfill site will not
significantly impact the area. The fungus Aspergillus fumigatus has been
shown to be associated with compost operations when wood chips are used as
an amendment. Studies have shown, however, that the higher spore concen-
trations are restricted to the immediate composting area and should not
pose any public health threat to the surrounding area.
Dust production during delivery, mixing, and handling of compost could
be a problem to surrounding residents and workers at the site. This will
be temporary, and long-term reduction can be accomplished by_ paving the
access road and instituting a housekeeping program, including the use of
water or other chemicals to reduce dust generation. Workers at the compost
site should avoid inhaling dust by wearing protective masks when mixing the
piles or moving the finished compost.
_ Leachate and runoff from the composting site must be controlled to
prevent environmental impacts. Since the active composting, curing, and
storage areas would be covered, most of the runoff from the site would be
uncontaminated roof drainage, and this water can be conveyed directly to
surface streams. Smaller amounts of leachate, blower condensate, and
surface runoff will also be generated, and these discharges have typically
3-25 fz :^ y!r
higher BOD, heavy metal, and suspended solids concentrations. Precautions
must be taken to prevent the discharge of such flows to adjacent
watercourses.
3. CO-COMPOSTING OF RAW SLUDGE WITH PROCESSED SOLID WASTE. The use
of processed municipal solid waste as an amendment and organic substrate
for compost operations has been practiced in a number of locations.
Biological oxidation is the most important aspect of the composting process
and the reduction of solid waste volume is the benefit of co-composting in
that landfill life can be extended.
Raw sludge will be transported to the Longmont landfill site and mixed
with processed municipal solid waste. Odor generated from this truck
transport will be temporary. Also, air discharged by blowers in the
compost area will be vented through finished compost to reduce the odor
impacts.
4. SLUDGE OXIDATION IN A VERTICAL TUBE REACTOR. This process
involves the deep well oxidation of sludge under pressure and at high
temperature. Sludge at 5.5 percent solids is pumped through a long
vertical pipe extending a mile below ground, generating an ashed material
in an aqueous matrix. This material is then dewatered to produce a highly
stabilized ash residual.
There are virtually no adverse environmental aspects associated with
this method other than temporary odor production at the treatment plant
site.
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3-26
CHAPTER 4
ALTERNATIVE ANALYSIS
A. INTRODUCTION
In this chapter, a comparative analysis of the alternatives described
in Chapter 3 will be presented. The analysis included a comparison of both
r monetary and non-monetary considerations. The non-monetary considerations
include factors such as energy dependency, reliability, flexibility,
expandability, operational complexity, potential regulatory impact, and
potential liability to the City. The first portion of the chapter will
compare the present worth of the alternatives. The second portion will
•
compare the non-monetary aspects of the alternatives.
B. COST OF ALTERNATIVES
To compare the total present worth of the alternatives, estimated
capital costs were determined along with the anticipated operation and
maintenance costs for the year 2000. The year 2000 average annual sludge
production, 8.0 dry tons per day, was chosen to estimate annual average
operation and maintenance costs during the planning period. Using a
20-year cost evaluation period and the current EPA discount rate of
8-7/8 percent, the annual average operation and maintenance costs were
then converted to a present worth value. The anticipated costs for the
alternatives are presented in Tables E-1 through E-16 in Appendix E.
Equipment replacement costs have been included in the operation and
maintenance tables. For this analysis, it has been assumed that any heavy
equipment, sludge transport, and sludge application vehicles would be
replaced after 10 years of service and would have no salvage value.
C. PRESENT WORTH ANALYSIS
Table 4-1 summarizes the total present worth of the eight
alternatives. The present worth was calculated by adding the capital cost,
present worth of the operation, maintenance and equipment replacement
costs, and subtracting the present worth of the estimated remaining, or
salvage value.
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4-1
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The remaining value of the alternatives has been estimated to be
25 percent of the cost of the permanent structures that are constructed.
The permanent structures include such items as the proposed dewatering
building and composting structures. The equipment within the buildings
and pavement around the structures have not been included.
The present worth costs were calculated using a 20-year planning
period and a discount rate of 8-7/8 percent. Current labor and utility
costs were increased 15 percent to represent the costs for labor, fuel,
and electricity in 1990, the anticipated year of project startup.
In addition to the total present worth, Table 4-1 presents the unit
cost of each alternative and its relative cost when compared to the lowest
cost alternative. The present worth of the alternatives ranges from
$6,753,000 for City-operated land application of digested sludge at
2.4 percent total solids to $8,334,000 for sludge oxidation in a vertical
tube reactor. The difference in present worth costs between the most
cost-effective and least cost-effective alternatives is approximately
23 percent.
The differences in total present worth will be discussed for each of
the four sludge management technologies.
1. LAND APPLICATION OF DIGESTED SLUDGE AT AGRONOMIC RATES. Four
land application alternatives were evaluated to address questions of (1)
whether a City-controlled land application program would be more cost-
effective than contract hauling for an operation the size of the City
of Longmont, and (2) whether additional thickening prior to digestion to
increase the digested sludge solids concentration would be a cost-effective
measure.
Based on price quotes received from contract hauling firms, it appears
cost-effective for Longmont to implement their own land application
program. Contract hauling firms were asked to estimate their charge to the
City, on a cost per gallon basis, for a "turnkey" land application program.
The turnkey operation assumes no City involvement outside the limits of the
treatment facility.
4-3
Using the average costs received, $0.0289 per gallon for 2.4 percent
total solids, and $0.0321 per gallon for 3.5 percent total solids, it does
not appear cost-effective for Longmont to enter into a contract hauling
agreement for the land application of sludge.
The reduced land application operation and maintenance costs asso-
ciated with an increase of digested sludge total solids concentration
r do not offset the increased capital cost of the additional thickening
equipment. By increasing the total solids concentration of the digested
sludge and reducing the volume, the land application costs could be
reduced. However, the additional capital and operation and maintenance
costs associated with the required thickening more than offset the
potential savings and, in the case of the City-operated system, increase
the disposal cost by approximately 9 percent.
2. COMPOSTING OF RAW SLUDGE. Three composting alternatives have
been evaluated: aerated static pile composting without amendment, aerated
static pile composting with amendment, and aerated windrow composting with
amendment. A review of Table 4-1 shows that the difference in present
worth between these alternatives is approximately 2 percent, well within
the accuracy limits of the analysis. Based on this information, it is
concluded that each of composting alternatives can be operated for
essentially the same cost.
3. SLUDGE OXIDATION IN A VERTICAL TUBE REACTOR. VerTech Treatment
Systems provided information regarding the use of this wet oxidation system
as a sludge treatment process. Following oxidation, the ash would be
dewatered and landfilled. Using the information provided by VerTech and
criteria used in the development of other alternatives, a present worth of
$8,334,000 was estimated. As stated previously, this is the highest
present worth of all the alternatives, approximately 23 percent greater
than the most cost-effective alternative.
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4-4 ..y 7q
D. OTHER CONSIDERATIONS
A number of criteria other than cost were analyzed in the development
of the Solids Management Plan. A plan must be more than just cost-
effective to provide the City of Longmont with a satisfactory long-term
solution for its solids management. The alternatives were compared against
the following criteria to determine the best solution for the City of
Longmont:
• Energy consumption.
• Reliability.
• Flexibility.
• Expandability.
• Operational complexity.
• Land area requirements.
• Potential regulatory impact.
• Potential liability to Longmont.
• Odor potential.
• Environmental impacts.
A discussion of each of the criteria is provided in the following
paragraphs.
1. ENERGY CONSUMPTION. The alternative with the lowest total annual
energy consumption is land application of liquid sludge at 3.5 percent
total solids. Land application of liquid sludge at 2.4 percent total
solids was the second most energy-efficient alternative.
Following land application, the composting alternatives were the least
dependent upon energy. Sludge oxidation in a vertical tube reactor was the
most energy-dependent, with estimated annual energy costs approximately
180 percent higher than land application at 3.5 percent solids.
2. RELIABILITY. The composting alternatives are considered to be
the most reliable of the alternatives analyzed. Composting, as evaluated
in this plan, would not be weather-dependent. The composting operations
would take place under cover, which would provide protection from
precipitation. The composting alternatives, while using heavy equipment,
are not considered to be highly mechanized. In addition, the composting
alternatives are less likely than the land application alternatives to be
impacted by future development adjacent to Longmont.
The City-operated land application alternative is the next most
reliable alternative, although it is dependent upon weather and farming
schedules. The City-operated program has been ranked at a higher level of
reliability than contract hauling since the City-operated alternative is
not dependent on a contract with an outside organization.
Theoretically, the sludge oxidation alternative should be a reliable
sludge processing alternative. However, due to the lack of data demon-
strating continuous operation, the VerTech System was given the same
ranking as contracted land application.
3. FLEXIBILITY. Each of the alternatives evaluated for use at
Longmont would provide a flexible method for disposal or reuse of sludge.
However, composting was considered to provide the highest level of flexi-
bility of all the alternatives. Variations in sludge production could be
accommodated in the composting facility by modifying detention times and
recycle volumes. The land application alternatives are also flexible and
could be modified to incorporate changes in sludge quantity or nutrient
concentrations.
The VerTech sludge oxidation facility would also offer flexibility to
the City at loading rates below the system capacity of 10 dry tons per day.
The VerTech System is the best alternative evaluated for treating sludge of
a poor quality. It is not anticipated, however, that Longmont's sludge
will be contaminated and not suited to beneficial reuse. As discussed in
Chapter 1, the City's pretreatment program has facilitated an increase in
the quality of the sludge such that it is nearly a Grade I classification.
4. EXPANDABILITY. Composting of raw sludge and land application of
digested sludge would be readily expandable. The land application alter-
natives would be the easiest to expand up to the point of requiring an
additional digester. Construction of a third digester on the current
plant site would be difficult.
4-6 .n,C6'71•?
Expansion of the composting facilities would have minimal impact at
the treatment facility, but would involve the construction of additional
composting area at the offsite location. The existing 1.2-meter belt
filter press may have to be replaced with a larger unit, depending upon
the amount of expansion. If a second 2.2 meter were installed, the City's
dewatering capability would be expanded to approximately 15 dry tons per
day, which is nearly double the projected annual average sludge production.
Expansion of the VerTech Treatment System beyond 10 dry tons per day
would involve the construction of a second vertical tube reactor. For this
reason, this technology has been given the lowest ranking for
expandability.
5. OPERATIONAL COMPLEXITY. The VerTech sludge oxidation alternative
would be the most complex to operate. The soil sampling, groundwater
monitoring requirements, and coordination with farmers make the land
application the next most complex alternative. Composting is the least
complex of the alternatives evaluated.
6. LAND AREA REQUIREMENTS. The VerTech sludge oxidation system
would require the smallest total area at approximately one acre.
Composting is the next most space-efficient alternative, requiring
approximately 5 acres.
Land application of sludge at agronomic rates requires the largest
total land area. As discussed in Chapter 3, the land area requirements
range from 1,000 to over 3,000 acres, depending upon the crop grown. The
cooperation of farmers and ranchers around the City of Longmont has been
good historically. However, population growth, changes in regulations, and
increased development may decrease the area available for application.
7. POTENTIAL REGULATORY IMPACT. The alternative most susceptible to
regulatory changes is land application. The State of Colorado is currently
modifying the regulations regarding land application. The cost of a land
application program could increase substantially if the modifications
require an increase in haul distance or eliminate one or more of the crops
that can be grown on a land application site.
4-7 car 072 s
The ash generated by the VerTech Treatment System has successfully
passed the current EP toxicity test. Although the ash has not been
subjected to the TCLP test, it is anticipated that ash could be landfilled
for the duration of the study period.
The compost generated would most likely be classified Grade II and
would have undergone a process to further reduce pathogens (PFRP). The
City currently anticipates generating an adequate market within the
agricultural community to recycle all of the product. It is anticipated
that minor changes to the regulations will have limited impact on the
process.
8. POTENTIAL LIABILITY TO LONGMONT. The City of Longmont is
responsible for the safe processing and disposal or reuse of their sludge.
For this reason, the City maintains some liability no matter which
alternative is implemented.
As discussed previously, the ash resulting from the oxidation of
sludge has passed the EP toxicity test and should not pose a threat to a
landfilling operation. The entire VerTech System, however, has not been
continuously demonstrated in full-scale operation at any location. If the
City purchases the system and cannot successfully operate it in the manner
projected by VerTech, the cost of processing sludge could become extremely
high.
Land application at agronomic rates involves a minimal liability
associated with potential adverse environmental impacts. The main risk
to Longmont with this alternative is related to the required number of
vehicles on the road.
As with digested sludge land application, the spreading of finished
compost on agricultural and disturbed land poses a minimal negative
environmental impact. The transport of a dewatered sludge and finished
_ compost will require fewer vehicles, thereby reducing the likelihood of
vehicle mishaps.
9. ODOR POTENTIAL. Composting of raw sludge has the highest odor
potential of all the alternatives evaluated. Sludge solids will emit odors
in a composting configuration until the compost becomes fully aerobic.
With proper operation, however, the odors will be minimal except during
v`^-7h
4-8
periods of pile construction and startup. The siting of the composting
facility is critical in minimizing odor impacts. Land application of
digested sludge can be performed with limited release of odors, and the
VerTech System also generates little odor when operated properly.
10. ENVIRONMENTAL IMPACTS. In evaluating the environmental impacts
of the four alternatives, the following parameters were considered:
• Recycling of sludge nutrients.
• Dust generation.
• Exhaust emissions.
• Noise production.
• Odor potential.
• Road traffic.
• Spill potential.
• Groundwater impacts.
• Surface water impacts.
• Soil impacts.
• Community resources.
• WWTP operation enhancement.
• Reliability.
Land application involves the handling of digested sludge at solids
concentrations of 2.4 percent or 3.5 percent. These solids will be trucked
by tanker or "nurse" vehicle to sites where the sludge will be transferred
to a surface spreader or to a subsurface injector vehicle for ultimate land
application.
The second alternative involves the dewatering of raw sludge at the
WWTP to 20-25 percent solids. This material will be trucked to the
Longmont landfill site where it will be composted. The types of composting
methods evaluated include aerated static pile and aerated windrow systems.
The compost operation will take place on an asphalted pad covered by a
metal building with three sides enclosed. The pad will be bermed to
facilitate the capture of any runoff from the composting and storage areas.
All roof leaders will drain off the pad area. The finished compost will
be either distributed at the site, trucked to reuse sites for application,
or landfilled.
4-9
The third alternative involves the trucking of dewatered raw sludge to
the Longmont landfill site where it will be mixed with processed municipal
solid waste and co-composted. The ultiamte disposal of the compost product
will likely be achieved through landfilling.
The fourth alternative is the sludge oxidation method. This involves
the transfer of thickened raw sludge to the VTR facility adjacent to the
WWTP. The sludge will be pumped under pressure into the tubular reactor
where an autogenic oxidation reaction takes place to convert the organic
material in the sludge into water, carbon dioxide, and inorganic ash. This
material will be pumped to the surface and dewatered to approximately
70 percent solids. The ash will be trucked to a landfill for ultimate
disposal. Any free liquid from the dewatering process will be returned to
the WWTP for processing.
In the following ranking analysis of these alternatives, the alterna-
tive having the most beneficial/least adverse environmental impacts has
been given a low ranking number. Conversely, the alternative with the
least beneficial/most adverse environmental impacts has been given a high
ranking number. All rankings have been done relative to each other for
each specific parameter (see Table 4-2).
The rating analysis employs a system in which each parameter is
weighted in importance relative to all others. Each alternative rating is
computed using the rankings in relationship to these weights. The alter-
native with the highest rating is considered the most beneficial as it
relates to environmental impacts. The next highest would be the next most
beneficial, etc. (see Table 4-3).
The first item of consideration in the ranking is the recycling of the
sludge nutrients. Land application will introduce the greatest amount of
nutrients to the soil, giving this alternative the best ranking. Only a
portion of the sludge nutrient resources will be retained for recycle with
the composting and co-composting alternatives. The oxidation process will
develop a product which will only be landfilled, thus recycling none of the
nutrient resources.
nr eq?"k,
4-10
TABLE 4-2
RANKING OF RELATIVE ENVIRONMENTAL EFFECTS
Lend Sludge
Parameter Application Composting Co-Composting Oxidation
Recycle Sludge Nutrients 1 3 3 4
Duet Generation - Treatment 1 2 3 1
Dust Generation - Disposal 4 3 2 1
Exhaust - Treatment 1 2 2 4
Exhaust - Disposal 4 2 2 2
Noise - Treatment 2 3 2 2
Noise - Disposal 4 2 2 1
Odor - Treatment 2 3 4 3
Odor - Disposal 3 2 3 1
Spill Potential - Treatment 3 3 3 1
Spill Potential - Disposal 4 2 2 1
Road Traffic 4 3 3 2
Groundwater Impacts 3 2 3 1
Surface Water Impacts 3 3 3 2
Soil Impacts 3 2 4 1
Aesthetics 4 2 3 1
Recycle Resources 3 3 5 3
Enhance WWTP 4 3 3 3
Reliability 4 2 2 4
1 e Most beneficial, least adverse
5 e Least beneficial, most adverse
0142.?.
4-11
TABLE 4-3
RATING OF RELATIVE ENVIRONMENTAL EFFECTS
Land Sludge
Parameter Weight Application Composting Co-Composting Oxidation
Recycle Sludge Nutrients 10 3.8 2.3 2.3 1.5
Dust Generation - Treatment 5 1.5 1.2 0.9 1.5
Dust Generation — Disposal 5 0.7 1.1 1.4 1.8
Exhaust - Treatment 5 1.7 1.3 1.3 0.7
Exhaust — Disposal 10 1.4 2.9 2.9 2.9
Noise — Treatment 5 1.3 1.0 1.3 1.3
Noise — Disposal 5 0.7 1.3 1.3 1.7
Odor - Treatment 10 3.3 2.5 1.7 2.5
Odor — Disposal 10 2.0 2.7 2.0 3.3
Spill Potential — Treatment 5 1.1 1.1 1.1 1.8
Spill Potential — Disposal 15 2.0 4.0 4.0 5.0
Road Traffic 10 1.7 2.5 2.5 3.3
Groundwater Impacts 15 3.0 4.0 3.0 5.0
Surface Water Impacts 15 3.5 3.5 3.5 4.6
Soil Impacts 15 3.2 4.3 2.1 5.4
Aesthetics 20 2.9 5.7 4.3 7.1
Recycle Resources 10 3.0 3.0 1.0 3.0
Enhance WWTP 10 1.8 2.7 2.7 2.7
Reliability 15 2.5 5.0 5.0 2.5
Totals 195 41.0 52.0 44.3 57.6
NOTE: The Environmental Effects Rating has been prepared to illustrate the relative
environmental impacts of the alternatives evaluated. In Table 4-3, the higher rating
indicates a lower detrimental impact to the environment.
”c e,r:..,fit
4-12
The ranking of alternatives with respect to dust generation is based
on a consideration of treatment site methodology, vehicle miles, and the
type of roads used for sludge transport. Dust will be generated by
turning, handling, and loading in the composting operation. This ranking
considered dust generated at the treatment sites and in the transportation
corridor to and including the disposal sites. At the treatment site, the
land application and sludge oxidation alternatives would generate the least
amount of dust because the sludge would be in liquid form. The composting
and co-composting alternatives are ranked higher because they would
generate dust during the compost operation, with negligible amounts being
generated during transport from the WWTP to the landfill. The rankings for
dust generated at the disposal site show the land application alternative
to be high because of the gravel roads on which the tanker trucks must
drive to reach the application sites. Since the solids quantities are
reduced in the composting alternative, the composting and co-composting
alternatives were given lower rankings. Sludge oxidation was ranked the
lowest due to the relatively innocuous method of landfilling the smaller
amount of dewatered ash as the ultimate disposal practice.
The land application alternative will generate the least amount of
exhaust emission at the WWTP with sludge oxidation generating the most,
especially during times of loss of autogenicity in the vertical tube
reactor. The only exhaust generated by the composting and co-composting
alternatives would be during transport to the landfill site. At the
disposal sites, land application ranks higher than the rest due to the road
miles driven in reaching the sites. Composting is next in rank because at
the compost site gas- or diesel-driven machinery will be used to mix, turn,
move, and load the compost during the process. Also, some road miles will
be driven delivering the compost to the ultimate disposal sites. Sludge
oxidation and composting were given the same ranking because there will be
some road miles driven delivering the final material from the reactor to
the landfill. Co-composting is also equal in rank because the onsite
handling of the compost is the only exhaust generating activity associated
with this disposal method.
4-13
In assessing the noise impacts at the treatment site, composting ranks
higher than the rest due to the somewhat higher noise level associated with
the use of mixing and turning equipment.
Offsite noise generated by land application vehicles delivering and
applying the sludge to the land application sites cause this ranking to be
the highest. Composting and co-composting rank next because there will be
some offsite road noise not associated with the sludge oxidation method.
Since the sludge applied in the land application alternative is
digested, it will not impart as objectionable an odor at the WWTP as the
other alternatives. The raw sludge ingredient and the use of processed
municipal solid waste in co-composting give this alternative the highest
odor potential ranking. Composting and sludge oxidation are equal and
relatively high also due to the use and handling of raw sludge. The odor
released at the disposal sites in the land application alternative could be
noticed temporarily during applcation. The ranking of co-composting is
equal to that of land application because the odor of compost with
municipal solid waste may be objectionable to some people. Composting
ranks next lowest because of the stability of the process and the raw
products used. The sludge oxidation alternative destroys most odor causing
organics in the sludge and, therefore, should be the least odorous.
The ranking of alternatives with respect to road traffic was based on
the relative number of road miles anticipated for trucks or tankers trans-
porting the variety of materials. Land application ranks high because
the land application sites are spread throughout the area. Composting and
co-composting also rank high because the material will have to be moved
twice, once from the WWTP to the landfill and again to the ultimate
disposal sites. Sludge oxidation ranks the lowest because it has the
smallest volume of materials to be moved and the lowest number of miles
to be driven.
The potential for spills at the treatment site is highest with the
land application alternative due to the low percent solids to be handled.
Composting and co-composting are equal in rank because the percent solids
of the material at the WWTP will also be low, but must be dewatered to a
4-14
concentration of 20-25 percent, adding to the potential for spill. Sludge
oxidation ranks the lowest because the spill potential is minimized by
moving the sludge to the reactor through pipelines.
At the disposal sites, land application ranks highest because the
potential for spills to occur enroute to the land application site is
high due to the number of sites involved and the miles traveled. Compost-
ing and co-composting rank next because spills could occur enroute to the
landfill, and compost spills could occur enroute to the ultimate disposal
site. Sludge oxidation ranks lowest because potential for spills to occur
near the reactor site and enroute to the landfill will be minimal.
The ranking of groundwater impacts takes into account the potential
for subsurface water contamination by leachate from land application and
landfill sites. The sludge will contain heavy metals which will be con-
centrated in the sludge/compost residues prior to ultimate disposal. Land
application ranks highest due to the increased possibility of groundwater
contamination by application of liquid sludge. Hydraulic connections
between the plow plate and groundwater table could increase this potential.
The compost alternatives rank moderately high to medium because of the
possibility of ultimate use as a soil amendment adding to the contamination
potential for groundwater. Co-composting would be a bit higher in rank due
to the use of solid waste as the amendment. Sludge oxidation ranks lowest
because the possibilty of groundwater contamination is minimal during
treatment and in ultimate landfill disposal.
The alternatives were ranked on surface water impacts based on
proximity to surface watercourses and runoff potential. Land application
ranks medium because of the possibility of surface water contamination due
to runoff to drainage ditches in close proximity to many of the proposed
land application sites. Sites were chosen to minimize this potential;
however, severe weather could produce a problem. Composting and
co-composting are considered equal due to the same considerations presented
above. Sludge oxidation is the lowest because of the proposed ultimate
disposal method of landfilling the dewatered ash.
4-15
r ',,.,
Co-composting ranks highest in the area of soil impacts due to the
potential of heavy metal contamination at the ultimate disposal site. Land
application ranks next because the practice of land application of sludge
tends to seal the soil surface regardless of the soil texture. Composting
has a better ranking because it will increase porosity and add nutrients as
a soil additive. Sludge oxidation ranks best because the impacts to soils
will be minimal.
Land application was given a higher rank on overall aesthetics due to
the presence of trucks and applications over a greater period of time than
the compost or sludge oxidation operations. A well-run sludge management
program is one that the public does not notice is actually in operation.
In determining the impacts of the recycling of resources, an analysis
was made of the overall use and generation of resources by the
alternatives. Co-composting ranked the highest because there is virtually
no return of resources as the end product will be landfilled. Sludge
oxidation could use less energy and potentially generate steam for use.
Composting and land application can return some of the sludge resources to
the earth, while expending a moderate amount of resources.
The VWTP impact involves the potential benefit to overall facility
operation. Land application ranks highest because sludge will have to be
digested, adding a treatment operation to the process not found in
composting, co-composting, or sludge oxidation.
The alternatives were ranked as to their relative reliability. Land
application ranks high because the operation is weather-dependent. The
land application program is subject to facility upsets that affect the
quality of the sludge and its acceptability for application. Sludge
oxidation also ranks high due to some operational problems during the
demonstration phase and uncertainties inherent in new technologies.
Composting is a proven method of sludge treatment. Putting the operation
under roof greatly enhances the reliability of this alternative.
4-16 net/T:)it
E. ALTERNATIVE RANKING
The matrix presented as Table 4-4 ranks each of the alternatives
based on the criteria presented in Sections C and D of this chapter. The
ranking has been developed so that the lowest number indicates the highest
ranking. As an example, sludge oxidation in a vertical tube reactor had
the lowest total land area requirement and has been ranked 1 for this
criterion on Table 4-4. Composting of raw sludge has the greatest odor
potential of all the alternatives and has been ranked 4 for this criterion.
In instances where the alternatives were similar for a certain
criterion, the same ranking was given to each. For certain criteria, there
was no superior alternative, so a 1 ranking was not used. Conversely, the
fourth ranking was only used for alternative technologies that were clearly
the worst in a certain category.
A review of the rankings indicates that composting of raw sludge is
the most advantageous long-term solids management plan for the City of
Longmont. The present worth value of composting, however, is approximately
5 percent higher than the most cost-effective alternative. However, at
the level of detail presented in this plan, it is difficult to estimate the
capital and operation and maintenance costs to within 5 percent. A number
of factors such as population changes, or the introduction of a new
industry to Longmont could affect these costs. The main objective of the
present worth analysis is to see how the alternatives compare to each other
given the same circumstances.
Considering all factors, composting of sludge is the most economical
and advantageous, long-term technology available to Longmont, and is
recommended for implementation.
4-17
TABLE 4-4
ALTERNATIVE RANKING
Technology
City-Operated City-Contracted Sludge Oxidation
Land Land Composting in a Vartical
Criteria Application Application of Raw Sludge Tube Reactor
3 2 4
Present worth Value 1
Reliability 2 3 1 3
Flexibility 2 2 1 3
2 2 1 4
Expendability
Operational Complexity 2 2 1 4
Land Area Reguirements 4 4 2 1
Regulatory Impacts 4 4 2 2
Liability 3 4 2 3
Odor Potential 2 2 4 1
Environmental Impacts 3 3 2 1
TOTAL 24 29 18 26
4-18 cy O2: ?/^,
CHAPTER 5
RECOMMENDED SLUDGE MANAGEMENT PLAN
A. INTRODUCTION
The evaluation of all considerations indicates that the City should
use composting for long-term sludge management even though the estimate of
costs shows composting to be slightly more expensive than land application.
Composting was determined to be the most desirable alternative due to its
reliability, flexibility, expandability, low operational complexity, small
area requirements, and its environmental acceptability. For further
information regarding the evaluation of these considerations, refer to
Chapter 4. •
During the evaluation of alternatives, three methods of composting
were evaluated. These methods included the following:
• Aerated static pile composting without amendment, followed by
non-aerated windrow curing.
• Aerated static pile composting with amendment, followed by
non-aerated windrow curing.
• Aerated windrow composting with amendment.
Since the costs for each of these composting alternatives are not signifi-
cantly different, the City has indicated a desire to use the alternative
that would expand their current aerated static pile composting operation,
which does not use amendment.
The recommended composting plan would compost dewatered, raw sludge
that has a total solids concentration of 22 percent. The compost would be
aerated during the active composting period. Following an active compost-
ing period of 21 days, the compost would be cured in a non-aerated windrow
for an additional 30 days. A windrow mixing machine would be used to mix
the compost periodically, which would facilitate drying of the compost.
Both composting and curing processes would be covered to minimize the
detrimental effects of precipitation. Figure 5-1 shows the material flow
diagram for the desired composting operation.
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Of the three composting alternatives evaluated, aerated static pile
composting without amendment would require the largest area of the three
composting alternatives due to the limitation on pile height. Without
amendment in the compost, the static pile could not be constructed higher
than 5 feet due to the low porosity of the initial mixture. Amendment
could be incorporated readily within the recommended plan if the City were
to decide to add amendment after further evaluation of the pilot composting
program.
B. FACILITY STAGING
Once the recommended sludge management plan was developed, the need
for staged implementation of the plan was investigated. Staged implemen-
tation must be performed to qualify for federal funds if the expected
population increase over the design period is equal to or greater than
30 percent. A review of population estimates, as reported by DRCOG,
indicates that the expected population increase 1s less than 30 percent.
Therefore, the City is not required to stage construction of the compost
facility to obtain federal support.
Although staging of construction is not required, the City could stage
its purchase of front-end loaders. Two front-end loaders were included
to provide firm capacity in the design year; however, during the first
several years of operation, one front-end loader would not be fully
utilized. Therefore, the City could delay the purchase of an additional
front-end loader until the time when the first one is fully utilized.
Since composting probably could not be implemented until the year
1990, the City will require an interim sludge management program. It is
recommended that the City continue the existing contract land application
program while investigating the feasibility of oxidizing sludge using
the modified VTR facility. If VerTech is willing to enter into a short-
term contract and sludge oxidation is shown to be more cost-effective
than contract land application, then the City could use sludge oxidation
as an interim sludge disposal measure.
5-2
In addition, until full-scale composting can be implemented, the City
should continue to operate its pilot-scale composting program. The
pilot-scale program can be used to verify further the operational
requirements for the full-scale composting program.
C. OPERATIONAL MODIFICATIONS
Implementation of the recommended composting program would result in
several modifications to the existing sludge management program. These
modifications would include expansion of the dewatering system, discon-
tinuation of digestion, and the cessation of contract land application
activities.
The existing dewatering system would be upgraded and expanded to
include an additional 2.2 meter belt filter press. A new dewatering
facility would be constructed to house the existing belt filter press and
the new press. A truck loading station would be incorporated with the
dewatering facility.
Since raw sludge would be composted in the proposed plan, the existing
anaerobic digesters would be shut down. However, the digesters would be
maintained in operating condition to serve as a backup method for sludge
stabilization. The digesters could also be used for sludge storage, if
required.
The existing contract hauling and land application program would be
eliminated once composting is implemented. This should not present any
problems to the City since there is no long-term contract with the current
hauling firm.
D. UTILITY MANAGEMENT
The existing sludge handling program is administered by City personnel
responsible for wastewater treatment. The City should establish a sludge
management group whose sole responsibility would be operation of the sludge
management facilities in order to successfully implement the proposed
composting program. A separate sludge management group would focus
attention on the production of a quality compost that should be readily
marketable.
el(,0:7? ,
5-3
E. LOCAL FUNDING
The federal government has established support programs designed to
aid municipalities in the construction of water and wastewater treatment
facilities. Generally, the federal government will provide funds for
55 percent of the capital cost of the project for satisfying current
demands. However, since the proposed composting facility is considered
to be an innovative/alternative technology, the composting plant would be
eligible for additional funding amounting to 20 percent of the capital cost
to address current facility requirements.
Table E-9 within Appendix E shows the estimated total capital cost for
the recommended composting program to be $3,485,000. When engineering and
administration costs of 15 percent are added to this amount, the total .
project costs become $4,008,000. Staging the purchase of a second
front-end loader will reduce this to $3,858,000.
The capital cost is based on the construction of a facility to compost
the sludge quantities expected during the design year. While the
facilities will be built to serve the design year population, grant funding
will be available only for those facilities required to serve the current
population. Using the ratio of current population to design year popula-
tion, approximately 65 percent of the capital cost, or $2,508,000, is
eligible for grant funding. Since composting provides a product which will
be used beneficially, it is anticipated that 75 percent funding will be
available. At this funding level, the grant amount will be approximately
$1,881,000. The remaining capital cost, $1,977,000, will be provided by the
City of Longmont. Funds are currently available in the wastewater utility
reserves for the Longmont portion of the capital costs.
The actual grant amount and City share will be dependent upon actual
construction cost and the determination of current capacity requirements.
_ To aid in the determination of eligible costs, it is recommended that the
construction contract be bid on a unit price basis.
The operation and maintenance costs of the composting facility will
impact the residents of Longmont at a level of $0.38 per person per month.
This amount has been estimated based on the anticipated operation and
maintenance costs and projected population for the year 2000. While
5-4 `'..
increasing the cost of service, the City of Longmont believes that the
new facilities can be operated without an increase in the current rate
structure.
F. ENVIRONMENTAL SUMMARY
The final environmental rating of the alternatives based on the
rankings in Tables 4-2 and 4-3 showed the sludge oxidation method to have
the highest, most environmentally beneficial score. Costs and concerns
about long-term reliability associated with sludge oxidation, however, lead
to a decision for composting as the recommended alternative.
Composting raw sewage sludge offers an environmentally sound alterna-
tive for the management of WWTP solid residues. Sludge collected in a WWTP
contains organic and inorganic constituents which will compost readily
with the addition of bulking materials and external air. Volatile solids
reduction takes place by microbial decomposition with the generation of
heat and water vapor. After curing, the compost can be used as future
bulking material or distributed to the public to recycle the nutrients
inherent in the raw material. This recycling aspect is environmentally
beneficial to the City of Longmont and the surrounding end users.
The proposed design will include a covered compost area. A berm and
sealed asphalt base will also be provided. This will protect the surround-
ing area from runoff or leachate percolation. By enclosing three sides of
the building, the City of Longmont will ensure that year-round operation
can take place, adding to the reliability of the project.
The siting of the project is proposed for the Longmont landfill
located in Weld County. The site is environmentally suited for this type
of operation. Noise, dust, and exhaust production will not be appreciably
different from the current landfilling operation being practiced on the
site. The other sites described earlier in relation to land application
would also be suitable for the location of a compost operation. Some of
these sites might actually be perferable to the landfill site from the
standpoint that there may be some potential difficulty in stabilizing the
5-5
fill material as a base for the new facilities. However, a positive aspect
to locating the compost operation at the Longmont landfill is the
relatively short, direct route sludge trucks would take from the WWTP.
In summary, the following items make composting the recommended plan:
• Use of raw undigested sludge.
• Reliability of the composting operation.
• Recycling of nutrients.
• Proven technology.
• Previous successful City of Longmont experience.
• Adequate sites for location of composting operations.
t f' ? As
5-6
APPENDIX A
LIST OF ABBREVIATIONS
APPENDIX A
LIST OF ABBREVIATIONS
ave average
BODS biochemical oxygen demand measured at 20° Centigrade
after five days of incubation
Btu British thermal unit
C Centigrade
CDR Colorado Department of Health
CDPS Colorado Discharge Permit System
cfs cubic feet per second
COD chemical oxygen demand
CHAS complete miz activated sludge
DWS dry weight solids
ENRrBCI Engineering News Record-Building Cost Index
EPA Environmental Protection Agency
g Farenheit
ft feet
ft2 square feet
ft3 cubic feet
fps feet per second
gpcd gallons per capita per day
gpd gallons per day
gpd/ft gallons per day per lineal foot
gpd/ft2 gallons per day per square foot
gpm gallons per minute
hp horsepower
I&A innovative and alternative
I/I infiltration/inflow
kW kilowatts
lbs pounds
maz maximtM
mis milliliters
mgd million gallons per day
mg/kg milligrams per kilogram
mg/1 milligrams per liter
N nitrogen
NPDES National Pollutant Discharge Elimination System
0&M operation and maintenance
p phosphorus
pg hydrogen ion concentrations
ppcd pounds per capita per day
ppd pounds per day
psi pounds per square inch
Q7-10 seven-day, 10-year low flaw
RAS return activated sludge
RBC rotating biological contactors
rpm revolutions per minute
SSES Sewer System Evaluation Survey
sem standard cubic feet per minute
TDS total dissolved solids
temp temperature
TIN total E,eldahl nitrogen
TSS total suspended solids
VS volatile solids
WAS waste activated sludge
WWTP wastewater treatment plant
WQCC Water Quality Control Commission
WQCD Water Quality Control Division
A-2 e, ,r•: ,,, A
APPENDIX B
BACKGROUND ENVIRONMENTAL ASSESSMENT DATA
A. INTRODUCTION
This section describes the existing environment that would be affected
by the proposed project. Such a description provides a baseline for
comparing the expected future environmental effects of project alternatives.
Potential sites are identified in the Longmont area on which the
proposed project can be located. The sludge management alternatives to
be considered are: land application, composting, and below-ground aqueous-
phase oxidation. See Figure B-1 for proposed locations.
1. LAND APPLICATION SITES. Nine locations have been identified as
prospective sites for the land application of digested sludge. The sites
were selected based on the following criteria:
o Sites within a 5 mile radius of the Wastewater Treatment Facility
(WWTF), and
o Sites currently permitted or within the permitting process for
the land application of sludge during 1987, or
o Sites currently engaged in dryland farming operation that may
be suitable for future land application sites, or
o Previous land application sites, compiled from year 1983.
a . Site #1, SSSL, 515, T3N, R69W.
(1) Physiography and Topography. This 160 acre site is located
approximately 4.5 miles from the Longmont WWTF in northern Boulder County
and is situated southeast of Terry Lake due north of the City of Longmont.
It is part of the Colorado Piedmont Section of the Great Plains Physio—
graphic Province. There is no impounded or moving water on this site.
The land surface is relatively flat with a peak elevation of 5150 feet
M.S.L., gently sloping 1% to 5130 feet M.S.L. on the east, 5120 feet
M.S.L. on the west and north, and 5110 ft M.S.L. at the south at a slope
of 2.5%. The most outstanding feature of the area is the abrupt wall—
, } ' "3"'
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FIGURE B-I
GENERAL SITES LAYOUT
like mountain front forming the boundary between the Front Range and the
Piedmont Area. The narrow foothills area is characterized by a series of
folded and faulted sedimentary strata. It is currently in dryland wheat
strip farming.
(2) Geology. Geologic formations of the area range in age from the
Precambrian to Recent. They consist of Precambrian metamorphic and
igneous rocks; sedimentary rocks of Paleozoic and Mesozoic age; a few
small bodies of igneous intrusive rock of Tertiary age; and unconsolidated
surficial deposits of Quaternary age. The Pierre Shale sedimentary
formation crops out just to the east of the foothills area and throughout
the northeast part of the area. The Quaternary deposits in the area are
of 4 principle kinds: alluvial, slope-wash colluvium, eolian silt and
sand, and talus and landslide deposits.1
This site is evidenced by eolium (windblown clay, silt (loess) , sand
and granules) from the upper Holocene to Bull Lake Glaciation. It is
light brown to reddish brown to olive-gray deposits appearing mainly as a
blanket of loess as much as 15 feet thick but generally less than 3 feet
thick.2
This rolling upland unit is located in the Upland Subsection of the
Piedmont Section of the Great Plains Province. It is described as an
area which is underlain by shale and sandstone bedrock in part coal-bearing.
The bedrock is generally nearly flat lying and locally faulted and3folded.
It is close or at the surface along some incised drainage courses.
(3) Soils.1 The Nunn—Heldt Association is the soil association
present in this site. It is generally identified as nearly level to
moderately sloping, deep soils on terraces and uplands. The soils of
this site formed from clay parent materials slope from 0-9%. This associ-
ation makes up about 20% of the area including this site. It is about
55% Nunn soils and about 15% Heldt soils. Ascalon, Colby, Gaynor, Kim,
Kutch, Longmont, Renohill, Valmont and Weld make up the remaining 30%.
TABLE, B-1
1,4
SOIL PROPERTIES
LONGMONT, CO AREA
Depth to
Seasonal Depth Avail. H2O
High Depth to From Perme-
Slope H2O Table Bedrock Surface ability Drainage Aprox. Capacity (in. Reaction
Soil Type (X) ft.) (ft. (ft.) Texture (in./hr.) Class CEC (820/in. Soil) (PH)
CoB 1-3 5 - 60 0-60 SICL 0.6-2.0 W 15 0.19-0.21 7.4-8.4
3-5 5 60 0-60 SICL 0.6-2.0 W 15 0.19-0.21 7.4-8.4
u_, 0-3 5 60 0-60 SICL 0.2-0.6 W 15 0.19-0.21 7.4-9.0
Ct 5-9 5 60 0-60 SICL 0.6-2.0 W 15 0.19-0.21 7.4-8.4
Gall 1-3 5 20-40 0-30 SICL 0.2-0.6 W 15 0.14-0.16 7.9-8.4
30 SHALE
GaD 3-9 5 60 0-30 SICL 0.2-0.6 W 10-15 0.14-0.16 7.9-8.4
30 SHALE
Heil 0-3 5 60 0-20 C 0.06-0.2 MW 15 0.14-0.16 7.4-8.4
20-60 CL 0.2-0.6 MW 15 0.15-0.17 7.4-8.4
HeC 3-5 5 60 0-20 C 0.06-0.2 MW 15 0.14-0.16 7.4-8.4
20-60 CL 0.2-0.6 MW 15 0.15-0.17 7.4-8.4
NuA 0-1 5 60 0-10 CL 0.2-0.6 W 15 0.17-0.21 6.6-7.8
10-23 C 0.06-0.6 W 15 0.14-0.16 7.4-8.4
23-60 CL 0.2-0.6 W 15 0.190.21 7.4-8.4
NuB 1-3 5 60 0-10 CL 0.2-0.6 W 15 0.17-0.21 6.6-7.8
10-23 C 0.06-0.6 W 15 0.14-0.16 7.4-8.4
23-60 CL 0.2-0.6 W 15 0.19-0.21 7.4-8.4
SgE 3-20 5 10-20 0-13 L 0.6-2.0 W 10-15 0.16-0.18 7.4-8.4
WeB I-3 5 60 12136 CL L 0.066006 W 515 0.1400116 6.6-7.3
36-60 L 0.2-2.0 W 15 0.16-0.20 7.4-8.4
WIA 0-1 5 60 0-6 L 0.6-2.0 W 15 0.16-0.18 6.6-7.3
6-12 C 0.06-0.2 W 15 0.14-0.16 6.6-7.3
12-60 L 0.6-2.0 W 15 0.16-0.18 7.4-8.4
W1B 1-3 5 60 0-60 L 0.6.2.0 W 15 0.16-0.18 6.6-7.3
6-12 C 0.06-0.2 W 15 0.14-0.16 6.6-7.3
12-60 L 0.6-2.0 W 15 0.16-0.18 7.4-8.4
WoC 3-5 5 60 0-6 L 0.6-2.0 W 15 0.16-0.18 6.6-7.3
6-12 C 0.06-0.2 W 15 0.14-0.16 6.6-7.3
12-60 L 0.6-2.0 W 15 0.16-0.18 7.4-8.4
Aquols --- 0.5-1.0 60 0-48 ---
48-60 SA 20 P 10-15 0.04-0.06 7.4-8.4
Aquents --- 0.5-1.0 60 0-48 --
48-60 SA 20 P 10-15 0.04-0.06 7.4-8.4
Cascajo 5-20 6 60 0-9 GSAL 2.0-6.0 E 5-10 0.07-0.09 7.4-8.4
9-31 GSAL 6.0-20.0 E 5-10 0.05-0.08 7.4-8.4
31-60 GSAL 6.0-20.0 E 5-10 0.05-0.06 7.4-8.4
Wiley 3-5 6 60 0111 10
60 SICL 0.6-2.0 W 1515 0.19-0.21 7.9-8.4
- Sandy
- Sandy Loam
SICL - Silty Clay Loam
C - Clay
CL - Clay Loam
L - Loam
GSAL - Gravelly Sandy Loam
SIL - Silty Loam
W - Well-Drained
MW - Moderately Well-drained
P - Poorly Drained
E - Excessively Drained C?CC':7:"?,4
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7 NIWOT-LOVELAND-CALKINi 6 FIGURE B•2
GENERAL SOIL TYPES
The Nunn soils are nearly level to moderately sloped and have a
surface layer of clay loam or sandy clay loam and a subsoil of clay. The
Heldt soils are nearly level to gently sloping and have a surface layer
and subsoil of clay.
The soil types present at this site include: CoC (Colby-silty clay
loam), Ct (Colby-Gaynor Association), GaB (Gaynor-silty loam), HeB (Heldt
clay), HeC (Heldt-clay) , and NuB (Nunn-sandy clay loam) . See Table B-1
for soils data. See Figure B-2 for a depiction of the general soil
associations of the area.
Colby Series
This series is made up of deep, well-drained soils. The soils
formed on upland slopes in loamy, uniform wind-deposited material.
Slopes are 1 to 9% and the elevations are 4900 ft M.S.L. to 5500 ft
M.S.L. In a representative profile the surface layer is brown silty clay
loam about 12 inches thick. Underlying this is pale brown and light
yellowish-brown silty clay loam and clay loam about 48 inches thick.
Soil reaction is moderately alkaline. The soil is strongly calcerous
throughout the profile and contains soft lime segregations below a depth
of 43 inches. Colby soils have moderate permeability and the available
water capacity is high.
Gaynor Series
This series is made up of moderately deep, well drained soils.
These soils formed on uplands in loamy alluvial and wind-laid materials.
Slopes are 1-9% and elevations are 4900 ft M.S.L. to 5500 ft M.S.L. In a
representative profile the surface layer is light olive-brown, silty clay
loam about 6 inches thick. Below this is a light olive-brown silty clay
loam about 4 inches thick with an underlying material of light yellowish-
brown silty clay loam about 20 inches thick. Under this is soft calcareous
silty shale. The soil reaction is moderately alkaline. This soil has
moderately slow permeability and the available water capacity is moderate.
Heldt Series
This series is made up of deep, moderately well drained soils formed
as terraces and uplands in loamy alluvium weathered from sedimentary
rock. The slopes are 0-5% and elevations range from 4900 ft M.S.L. to
5500 ft M.S.L. In a representative profile the surface layer is grayish-
brown clay about 8 inches thick. The upper 12 inches of subsoil is
strongly calcareous, light olive-brown clay. The lower 16 inches are
strongly calcareous, light yellowish-brown clay loam. The substratum is
strongly calcareous light yellowish-brown clay loam to a depth of 60 inches
or more. The soil reaction is moderately alkaline with slow permeability.
The available water capacity is high.
Nunn Series
This series is made up of deep, well drained soils formed on terraces
and valley side slopes in loamy alluvium. The slopes range from 0-9% and
elevations of 4900 ft M.S.L. to 5500 ft M.S.L. In a representative
profile the surface layer is grayish-brown clay loam about 10 inches
thick. The subsoil is brown and very pale brown clay that grades to clay
loam about 20 inches thick. It is noncalca reous in the upper part but
contains soft lime segregation in the lower part. The substratum is
strongly calcareous, very pale brown clay loam extending to a depth of
60 inches or more. In the surface layer the soil reaction is neutral.
In the upper part of the subsoil it is mildly alkaline grading to moder-
ately alkaline in the lower part. These soils have a slow to moderately
slow permeability and the available water capacity is high.
(4) Water
(a) Ground Water. Ground water information is based on United
States Geological Survey (USGS) investigations taken during the test year
1976-1977. This site lies within an area where localized water-table
aquifers occur in colluvial, landslide, and windblown deposits and in
consolidated sedimentary rocks where rocks near land surface are fractured
and weathered. The aquifers may not be saturated year-round, however,
the depth to water table generally ranges from 5-20 feet with a seasonal
water table depth generally less than 10 feet. The depth to water table
results of wells tested during the test years in the area north and east
of the City of Longmont showed a range of 3 to 12 feet below the surface.
(See Figure B-3) .
The area to the northeast of Longmont lies within a region where the
T dissolved solids concentration in ground water is generally greater than
500 mg/1. See Table B-2 for ground water chemical constituents of the
area.
Probable well yields from the northeast Longmont area show generally
less than 50 gpm. Yields cannot be sustained throughout, the year from
wells in the Gun Barrel Hill area because of unconsolidated alluvial
deposits which are drained for part of the year.
In a study conducted by the USGS comparing depth to water table data
for the late 1950's to the ]ate 1970's results showed that in a well
located in consolidated sedimentary rock the depth to water table increased
by 20%; from 16.1 to 20 feet. This indicates that a wide-spread ground
`,rater depletion is possibly occuring.
5
(b) Surface Water. Surface water resources near this site include
Terry Lake northwest, Divide and Walker Reservoirs northeast, Rough and
Ready Ditch southwest, Calkins (Union Reservoir) southeast, and the St.
Vrain Creek which flows south of site about 4.5 miles away. The site is
not within the 100 year flood plain of the St. Vrain. (See Figure B-4) .
The City of Longmont is supplied by drinking water which originates
in the mountains west of the city at Button Rock Reservoir as well as
other sources. A series of aqueducts and pipelines bring the water to a
filtration plant on S.R.66 west of Hygiene, Colorado where it is treated
and stored prior to flowing to the City.
The following are factors which do and will continue to affect the
quality of the St. Vrain Creek:
o Agricultural Retention flow - 5 large ditches empty to creek.
o Stormwater Runoff - 20% of the City of Longmont's sewer system
is combined.
[e� r 2 Ari
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FIGURE 8-3
DEPTH TO GROUNDWATER
TABLE B-2
SUMMARY OF SELECTED CHEMICAL CONSTITUENTS
OF WELL WATER FROM LONGMONT, CO AREA
SAMPLED IN CONSOLIDATED ROCK AND WINDBLOWN DEPOSITS5
# Exceeding
- Parameter Units Standard Range # Samples Standard
Dissolved Solids mg/1 500 a 223 - 3903 19 13
Dissolved Arsenic ug/1 50 b 1 - 1 15 0
Dissolved Chloride mg/1 250 a 1.2 - 370 69 2
Dissolved Fluoride mg/1 1.8 b 0.4 - 3.3 16 2
Dissolved Iron ug/1 300 a 1 - 2200 17 2
Dissolved Manganese ug/1 50 a 1 - 410 16 3
Dissolved Magnesium mg/1 125 a 14 - 320 19 5
Dissolved Nitrate/ mg/1 10 b 0.02 - 40 68 12
Nitrite as N
Dissolved Selenium ug/1 10 b 1 - 160 15 2
Dissolved Sulfate mg/1 250 a 21 - 2600 19 11
Hardness of CaCO3 mg/1 None 120 - 2200 19 --
a - Recommended State Standards for Public Water Supplies (Colorado Dept.
of Health - 1971), with the exception of Magnesium, standards are the
same as recommended Federal Standards established for the Public
Water Supplies (U.S. EPA - 1977) . No Federal Magnesium standard.
b - Primary (Mandatory) State Standards for Drinking Water Supply - same
as Mandatory Federal Standards established for Drinking Water Supplies
(U.S. EPA - 1976) . Standard for Fluoride is based on annual average
of maximum daily air temperature in study area.
TERRY L I �(DM" REB.
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FIGURE B-4
FLOOD PLAIN-100 YEAR
o Landfill leachate - the landfill is located in Weld County
adjacent to the creek.
o Septic hauler disposal - unknown amounts of septage is covertly
and illegally dumped.
o Lime pile runoff.
o Mining and dewatering from gravel operations.
o Cement manufacturing.
o City of Longmont WWTF effluent.
6
The land application of sludge will not adversely affect the quality
of the St. Vrain Creek. Precautions will be taken to assure safe and
clean transport of the sludge to the disposal site. Sites will be chosen
where runoff will be minimized.
(5) Air
(a) Climate. This site along with the entire Longmont area has a
high plains, continental climate with wide variation in temperature
throughout the year. Four different sources influence Longmont's weather.
These include arctic air from Canada and Alaska; warm, moist air from the
Gulf of Mexico; warm dry air from Mexico and the southwestern deserts;
and Pacific Ocean air modified by its transit over the mountains to the
west. The majority of weather systems come from the west and lose most
of their moisture before reaching the area accounting for a low annual
precipitation of 13.0 inches, moderate average relative humidity of 52%,
and sunshine 70% of the time. The average yearly temperature is 48.8°F.
Daytime average summer (April through September) relative humidity is
36%. Daytime average winter (October through March) relative humidity is
44%. Generally, early morning humidity ranges from 55-60% in summer, and
from 60-70% in the winter.7 The length of the growing season is 140 days
with the average date of first killing frost being September 28. The
average date of the last killing frost is May 11.1 The mean number of
days per year when the maximum temperature fails to reach 32° is 22.6
days. Table B-3 shows climatic data for the Longmont area.
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Winter conditions can hinder the land application of sludge, creating
a necessity for storage or alternative treatment and disposal method—
ologies.
The prevailing winds of the area are from the south with an mean
speed of 8-9 miles per hour, with peak gusts of over 50 miles per hour.
This would tend to favor northeast land disposal sites.?
(b) Air Quality. This site is located in an area of relatively good
air quality. The major source of air pollution is wind—borne dust (particles)
from roads, agricultural activity, and industry in and around the City of
Longmont. The USEPA has established the National Ambient Air Quality
Standards (NAAQS) for 6 pollutants: carbon monoxide, ozone, nitrogen
dioxide, sulfur dioxide, particulate matter and lead. The current standards
and 1985 air quality results are presented in Table B-4.
Primary standards are intended to protect public health; whereas, 3
secondary standards are intended to protect public welfare. The 100 ug/m
annual geometric mean observed value for total suspended particulates not
only exceeds the EPA standards but also exceeds the State of Colorado
standards of 45 ug/m3,9
The following factors adversely affect the quality of air in the
City of Longmont:
0 2 coal burning foundaries.
o Odor from the turkey processing plant.
Because of the prevailing south wind and the locations of the proposed
land application sites, the air quality of the City will not be adversely
affected by the proposed disposal method.
(6) Biotic Components.
(a) Terrestrial Ecosystems. The entire Longmont area, can be
divided into various ecosystems or vegetational classes: plains grass—
land, plains streamside, lakes and marshes and agricultural land. The
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types of wildlife habitat include: openland habitat, wetland habitat,
and the rangeland habitat. The openland habitat consists of cropland,
pasture, meadows, and areas overgrown with grasses, herbs, shrubs, and
vines. The wetland habitat consists of open, marshy or swampy, shallow
water areas where water-tolerant plants grow. The rangelend habitat
consists of wild herbaceous plants and shrubs. This site is agricultural
in nature with dryland wheat strip (Triticum aestivum) farming. Examples
of other farming crops which can occur in the area include corn, sugar
beets, and other garden vegetables.4 See Table B-5.
Small arms of wetland vegetation are located in the Longmont area.
Tree species which could be present in these arms include Boxelder (Acer
negundo) and plains Cottonwood (Populus sargentii) . Shrubs and herbs
could include Tamanisk (Tamarix .pentandra) , Carrizo (Common Reed) (Phragmites
communis) , Water Crowfoot (Ranunculus aquatilis) , Pondweed (Potamogeton
spp.), Rush (Juncus spp.), Sedge (Ca rex spp.), Spike rush (Eleocharis
macrostachya) , Watermilfoil (Myriophyllum spice tum) , and Willow-herb,
northern (Epilobium slandulosum) .
Other trees which could be found along the creeks and ditches include:
Boxelder (Acer negundo) , Cottonwood, broad leaf (Populus sargentii), and
Russian Olive (Elm gnus angustifolia) . Understory shrubs could include
Hawthorn (Crategus spp.) and Willow (Salix spp) .10 There are no threatened
or endangered species of trees on this site or in the immediate area of
Longmont.
Due to the proximity of impounded water and the terrestrial habitats
described above, a variety of birds can be found.
Birds that are considered abundant in the area are the Canada goose
(Branta canadensis) , Redhead (Aythya americana), Horned Lark (Eremophila
alpestris) , Clift swallow (Petrochelidon pyrrhonota), Black-billed Magpie
(Pica pica) , American Robin (Turdus migratorius) , Starling (Sturnus
vulgaris) , House Sparrow (Passer domesticus) , Western Meadowlark (Sturnella
ric A
neglecta) , Redwinged Blackbird, (Agelaius phoeniceus) , Lark sparrow
(Chondestes srammacus), and Ring—billed Gull (Lanus delawarensis) .11 See
Table B-6 for a description of the threatened and/or endangered bird
species in the area.
Reptiles and amphibians common or abundant in the area are the Great
T Plains Toad (Bufo cognatus), Woodhouse's Toad (Bufo woodhousei), Boreal
Chorus Frog (Pseudacris triseriata maculate) , Leopard Frog (Rana pipiens) ,
Barred Tiger Salamander (Ambystoma tigrinum mavortium) , Blotched Tiger
Salamander (Ambystoma tigrinum melanostictum) , Arizona Tiger Salamander
(Ambystoma tigrinum nebulosum) , Red-Lipped Plateau Lizard (Sceloporus
undulatus erythrocheilus) , and Prairie Six-lined Racerunner (Cnemidophorus
sexlineatus) .12 There are no threatened or endangered reptile or amphibian
species within the area.
Mammals in the Longmont area which are considered abundant in the
wild are: Desert cottontail (Sylvilagus audubonii), White-tailed jackrabbit
(Lepus townsendii) , Golden-mantled ground squirrel (Spermophilus lateralis) ,
Black-tailed prairie dog (Cynomys ludovicianus), Ord's kangaroo rat
(Dipodomys ordii) , Western harvest mouse (Reithrodontomys megalotis) ,
Deer mouse (Peromyscus maniculatus) and Montaine vole (Microtus montanus) .13
See Table B-6 for a description of threatened and/or endangered mammal
species within the area.
(b) Aquatic Ecosystems. The aquatic ecosystems in the area include
the river and ditch streamsides as well as the lakes and marsh lands.
The St. Vrain Creek flows west to east through the area and supports a
variety of plant and animal life.
Fish species common to waters in the area are: Central stoneroller
(Campostroma aromalum), Common carp (Cyprines carpio) , Bigmouth shiner
(Notropis dorsalis) , Red shiner (Notropis lutrensis) , Sand shiner (Notropis
stramineus), Fathead minnow (Pimephales promelas), Longnose dace (Rhinichthys
cataractae) , Cheer Chub (Semotilus atromaculatus) , Longnose sucker (Catostamus
catostamus), White sucker (Catostamas commersoni) , Plains Killifish
flitF n:17 �;
(Fundulus zebrinus) , and Green sunfish (Lepomis cyanellus) .14 See Table B-6
for a description of the threatened and/or endangered fish species in the
area.
Benthic samplings in St. Vrain Creek revealed a variety of midges
(Chironomidae), beetles (Baetidae) , caddis flies (Hydropsychidae), aquatic
earthworms (Lumbircidae) , and round worms (Nematode) among other insect
larvae and snails.15
(c) Threatened and Endangered Species. There are a number of plant
and animal species in the State of Colorado which are either threatened
or endangered with regard to extirpation. Affected plant species within
the Larimer, Boulder, and Weld Counties area include: greenleaf bluebells
(Mertensia virdis var. cane) , Guara (Guara neomexicana spp. coloradensis) ,
Whitlow-work (Drabs exunguiculata) , and Icegrass (Phippsia algida) . 6
The affected animal species within the tri-county area include:
White pelican (Peleca nus erythrorhynchos), Peregrine falcon (Falco peregrinus) ,
Greenback cutthroat trout (Salmo clarki stomias) , Johnny darter (Etheostoma
nigrum), and Plains orangethroat darter (Etheostama spectabile pulchellum) .
A listing of other threatened and endangered species within the State of
Colorado and specifically within northeast Colorado are in Table B-6.17
See Figure B-5 for an illustration of the present ranges of the threatened
and endangered species of the area.
The critical wildlife habitats in the area are Rabbit Mountain,
Lagerman Reservoir (+ wetlands), Lefthand Creek Cottonwood groves (+ wetlands),
Gaynor Ickes (+ wetlands) , Panama Reservoir (+ wetlands) , and B-J Acres
Ranch,18 These areas will not be affected by the land application of
sludge. See Figure B-6 for locations of these critical wildlife habitats.
(7) Socioeconomic Factors. This site is located one half mile north
of a partially developed residential area. It is bordered on the east by
U.S. Road 287 which is designated an "Open Corridor" of Boulder County
Open Space. It is bordered by a light-duty road on the south and there
reer,a
TERM lAR[ cs.-DIVIDE RES.
RABBIT
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MUNICIPAL
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in WHITE PELICAN ! 4::;;::::2rj
FIGURE 8-5
PRESENT RANGES OF
THREATENED OR
ENDANGERED WILDLIFE
. TERRY LANE JDIVIOE NEB.
S
RABBII `
T11 ....
+
CRITICAL
ny WILDLIFE
s HABITAT
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AGERMAN RES -
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CRITICAL /
WILDLIFE HABITAT _ I/
GAYNOR t
LEFT NAND CREEK LANE
COTTCNWO0O Fiw Fy{ -
GROVES Y/
h PANAMA ES NO.I , ?
CRITICAL LOUPE
HABITA
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ACRES
BOULDER a RANCH
RESFVOIR
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FIGURE B•6
CRITICAL WILDLIFE
HABITATS
is an unimproved dirt road on the west of the site which leads to a few
residences offsite. The site is currently used for agriculture, a use
compatible for the land application of sludge.
The site is located within an area designated as Significant Agri-
- cultural land of National Importance. Prime significant farmlands have
adequate and dependable water supplies, favorable temperatures, and a
growing season, good soil characteristics, protection from floods, slight
slope, and historically good yields. On this site the following are not
present or proposed: county trails, road or expressway expansion, or
transit expansion. A bike lane is proposed along the asst boundry. The
site is not within any critical wildlife habitats, natural landmark area,
or natural area, and it is not an archeologically or historically sensitive
area. The prominent cultural resource of site is the scenic mountain
vista seen to the west. 18 With any land application of sludge this
resource will be maintained.
b. Site #2, NH1/4, 513, T3N, R69N.
(1) Physiography and Topography. This 60 acre site is approxi—
mately 5 miles from the Longmont WWTF in northern Boulder County and is
situated east of Divide and Walker Reservoirs and northeast of the City
of Longmont. It is part of the Colorado Piedmont Section of the Great
Plains Physiographic Province. There is no impounded water on this site,
however, the Supply and Highland Ditches run through the southwestern
corner. The surface gently slopes 3% northeast to southwest from 5210 ft
M.S.L. to 5110 ft M.S.L. There are no other outstanding physiographic
features to this site besides the Front Range described in a.(1) . It is
currently in dryland farming.
(2) Geology. This site is evidenced by eolium (described in a. (2))
as well as the upper transition member of the Pierre Shale. The deposits
are Cretaceous in age and are described as a friable sandstone, soft
shaly sandstone containing thin—bedded sandy shale and large calcareous
sandstone concretions. This member can be up to 2000 ft thick.2
See a. (2) for a discussion of the upland unit.
(3) Soils. This site contains mostly the Weld-Colby Association
with the Nunn-Heldt Association in the southwest corner. See a. (3) for a
discussion of the Nunn-Heldt Association. Weld-Colby Association is
identified as nearly level to sloping, deep soils on uploads. The soils
are farmed in uniform windblown materials. This association makes up
about 10% of the area including this site. It is 35% Weld soils and
about 35% Colby soils. AscaLan, Gaynor, Manvel, Nunn and Otero soils
make up the remaining 30%. Soil types present are: CoB (Colby-silty
clay loam) , CoC (Colby-silty clay loam) , SgE (Shingle-Gaynor Complex) ,
W1B (Weld loam) and WoB (Weld-Colby Complex) .
Weld soils are nearly level with a surface layer of loam, fine sandy
loam, a loamy sand that is 6 to 14 meters thick. The subsoil is clay or
heavy clay loam.
Colby soils are mainly greatly sloping to sloping. They have a
surface layer and underlying layer of silty clay loam. See Table B-1
for soils data.
Shingle Series
This series is made up of shallow, well-drained soils formed on
upland hills and ridges in calcareous loamy residuum weathered from shale
or sandstone. Slopes range from 3-25 percent and elevations are 4900 ft
M.S.L. to 5500 ft M.S.L. In a representative profile the surface layer
is strongly calcareous, pale-brown loam about 4 inches thick with the
next 3 inches being a light yellowish brown loam. The underlying material,
about 6 inches thick, is strongly calcareous, brownish-yellow loam with
weathered shale and sandstone underlying. In the surface layer the soil
reaction is mildly alkaline, with increasing depth it becomes moderately
alkaline. These soils have moderate permeability with low available
water capacity.
Weld Series
This series is made up of deep, well-drained soils formed on smooth
uplands, mainly in loamy wind-laid parent material. The slopes range
from 0-5% with elevations of 4900 ft M.S.L. to 5500 ft M.S.L. In a
representative profile the surface layer is brown loam about 6 inches
thick with a 6 inch subsoil of brown clay that grades to a strongly
calcareous, pale brown clay loam. The substatrum is strongly calcareous,
pale brown loam that extends to a depth of 60 inches or more. In the
surface layer the soil reaction is neutral becoming alkaline with
increasing depth. The soils have slow permeability with high available
water capacity. 1
Colby Series - See a. (3) for a discussion.
(4) Water - See a. (4) for a representative discussion.
(5) Air - See a. (5) for a representative discussion.
(6) Biotic Components - See a. (6) for a representative discussion.
(7) Socioeconomic Factors. This site is not within a geological
hazard area. It is not archeologically or historically sensitive, nor is
it within a critical wildlife or plant habitat, natural landmark, or
natural area. This area is not a significant agricultural land, nor are
there any open space constraints, proposed county trails, proposed roads
or expressways, or any proposed bikeways. 18
c. Site #3, NE36, 522, T3N, R69W.
(1) Physiography and Topography. This 140 acre site is approxi—
mately 4 miles from the Longmont WWTF in northern Boulder County and is
situated southwest of Walker Reservoir and southeast of Terry Lake, north
of the City of Longmont. It is part of the Colorado Piedmont Section of
the Great Plains Physiographic Province. There is no impounded or flowing
water on this site. The surface gently slopes 1.5% northwest at 5130 ft
M.S.L. to southeast 5085 ft M.S.L. The site is broken up into 7-8 farm
plots.
(2) Geology - See a. (2) for a representative discussion.
(3) Soils. This site contains the Nunn-Heldt soil association.
See a. (3) for a further discussion of the Nunn-Heldt Association. The types
of soils present are: CoB (Colby Silty Clay loam), Ct (Colby Gaynor
Association) , GaD (Gaynor Silty Clay loam) , NuB (Nunn sandy clay loam)
and WoB (Weld-Colby Complex). See Table B-1 for soils data. See a.(2)
for a discussion of the Colby, Gaynor and Nunn Series and b.(2) for a
discussion of the Weld Series. l
(4) Water - See a. (4) for a representative discussion.
(5) Air - See a. (5) for a representative discussion.
(6) Biotic Components - See a. (6) for a representative discussion.
(7) Socioeconomic Factors. This site is not within a geologic
hazard area. It is not archeologically or historically sensitive, nor is
it within a critical wildlife or plant habitat, natural landmark, or
natural area. The site is designated nationally significant agricultural
land, and it is bounded on the west by a designated U.S. 287, an open corridor.
There are no proposed county trails, roads or expressways. There is a
bikelane proposed along U.S. 287. 18
d. Site 114, N'/2, 523, T3N, R69W.
(1) Physiography and Topography. This 310 acre site is approximately
4 miles from the Longmont WWTF in northern Boulder County and is situated
south of Walker Reservoir. It is part of the Colorado Piedmont Section
of the Great Plains Physiographic Province. There is no impoundment
water on this site. There is however, a drainage ditch in the southeast
section of the site. The surface gently slopes 1-22 from a peak southwest
at 5110 ft M.S.L. and east to 5055 ft M.S.L. There is not other out—
standing physiographic feature other than those described in a. (1). The
site is broken up into numerous farm plots.
(2) Geology - See a. (2) for discussion.
(3) Soils. This site contains the Nunn-Heldt soil association.
See a. (3) for further discussion of the Nunn-Heldt Association. The type of
soils present are: CoB (Colby Silty Clay loam) , CoC (Colby Silty Clay
loam) , NuA (Nunn clay loam) , NuB (Nunn Clay loam), and GaB (Gaynor silty
clay loam). See Table B-1 for soils data. See a. (3) for a discussion of
the Colby, Gaynor, and Nunn Series.1
(4) Water - See a. (4) for a representative discussion.
(5) Air - See a. (5) for a representative discussion.
(6) Biotic Components - See a.(6) for a representative discussion.
(7) Socioeconomic Factors. This site is not within a geologic
hazard area, nor is it an archeologically or historically sensitive area.
It is not within a critical wildlife or plant habitat, natural landmark,
or natural area. This site is designated nationally significant agri-
cultural land. There are no open space constraints, proposed county
trails or roads, or proposed bikeways associated with this site.18
e. Site #5, NF)L, 526, T3N, R69W.
(1) Physiography and Topography. This 160 acre site is approxi—
mately 3 miles from the Longmont WWTF and is situated northwest of
Calkins Lake (Union Reservoir) and northeast of the City of Longmont. It
is part of the Colorado Piedmont Section of the Great Plains Physiographic
Province. There is no impounded water on this site, however, the head
waters of the Spring Gulch Ditch originate near the middle. The surface
barely slopes 1% northwest at 5040 ft M.S.L. to southeast at 5012 ft
M.S.L. The site consists of a few farms with residences at the north
boundary along SR 66.
(2) Geology - See a. (2) for a representative discussion.
(3) Soils. This site contains the Nunn-Heldt soil association.
See a. (3) for a further discussion of the Nunn-Heldt Association. The types
of soils present are: NuA (Nunn clay loam), NuB (Nunn clay loam), CoB
(Colby Silty Clay loam), and CsB (Colby Silty Clay loam, wet) . See Table
B-1 for soil data. See a.(3) for a discussion of the Colby and Nunn
Series.l
(4) Water - See a. (4) for a representative discussion.
(5) Air - See a. (5) for a representative discussion.
(6) Biotic Components - See a.(6) for a representative discussion.
(7) Socioeconomic Factors. This site is not within an archeologically
or historically sensitive area, nor is it within a wildlife or plant
critical habitat. It is designated a significant agricultural land.
There are no open corridor constraints associated with this site. There
are no proposed county trails, roads or expressways planned for this
site. 18
f. Site #6, Nil, 525, T3N, R69W.
(1) Physiography and Topography. This 370 acre site is approxi—
mately 3 miles from the Longmont WWTF and is situated northwest of Calkins
Lake (Union Reservoir) and northeast of the City of Longmont. It is part
of the Colorado Piedmont Section of the Great Plains Physiographic Province.
There is no impounded water on this site; however, Spring Gulch Ditch
passes through at the extreme southwest comer. There is also some wet
weather standing water on the north property line. The surface gently
slopes 1-2% northwest at 5035 ft M.S.L. to the southeast at 4995 ft
M.S.L. The site consists of dairy farm plots 25-50 acres each. There
are residences along SR 66 on the north boundary for which a setback must
be applied.
(In
(2) Geology - See a. (2) for a representative discussion.
(3) Soils. This soil contains the Nunn-Heldt soil association.
See a.(3) for a further discussion of the Nunn-Heldt Association. The
types of soils present are: CoB (Colby Silty Clay loam), CoC (Colby
Silty Clay loam) , CsB (Colby Silty Clay loam, wet) , GaB (Gaynor Silty
Clay loam) , GaD (Raynor Silty Clay loam), NuA (Nunn Clay loam), NuB (Nunn
Clay loam) , and W1A (Weld Loam) . See Table B-1 for soil data. See a. (3)
for a discussion of Colby, Nunn, and Gaynor Series. See b. (3) for a
discussion of the Weld Series.1
(4) Water - See a. (4) for a representative discussion.
(5) Air - See a. (5) for a representative discussion.
(6) Biotic Components - See a. (6) for a representative discussion.
(7) Socioeconomic Factors. This site is not within an archeologi-
cally or historically sensitive area, nor is it within a wildlife or
plant critical habitat. It is not designated a significant agricultural
land. There are no open corridor constraints associated with this site.
There are no proposed county trails, roads or expressways planned for
this site. There is an existing bike path on SR 66 to the North and a
proposed bike lane on County Line Road to the east.18
g. Site #7, S41/4, 56, T2N, R69W.
(1) Physiography and Topography. This site is within the boundaries
of the Longmont Municipal Airport property. There is approximately 140A
of usable land. It is situated 3 miles west of the Longmont WWTF, south
of St. Vrain Creek. It is part of the Colorado Piedmont Section of the
Great Plains Physiographic Province. There is no impounded water on the
site, however, there are drainage and irrigation supply ditches on the
west border, near the south border and at the North border. The surface
is nearly level with a 0.6% slope from 5053 ft M.S.L. west to 5028 ft
("). C,n
M.S.L. east. The site is currently being farmed in corn and is the
location of the airport facility. A marshy area is located at the northwest
boundary along the west ditch, 5120 ft M.S.L. on the west and north and
5110 ft M.S.L. on the south at a slope of 2.55.
(2) Geology. See a. (2) for a representative discussion. This
transitional lowland unit is located in the Lowland Subsection of the
Piedmont Section of the Great Plains Province. It is described as an
area probably underlain mainly by terrace or upland gravels, covered in
part by windblown material.2
(3) Soils. This site contains the Nunn-Heldt soil association.
See a. (3) for further discussion of the Nunn-Heldt Association. The soil
type at this site is NuA (Nunn clay loam) . See Table B-1 for soil data.
See a. (3) for a discussion of the Nunn Series.
1
(4) Water - See a.(4) for a representative discussion.
(5) Air - See a. (5) for a representative discussion.
(6) Biotic Components - See a. (6) for a representative discussion.
(7) Socioeconomic Factors. This site, the Longmont Municipal
Airport, is of importance to the growth and development of the area. The
land within the boundaries which are not associated with the operation of
the airport are currently farmed by lease arrangement. Economic development
will continue around the airport as the City continues to expand. The
fact that the City owns the land and with an airport authority has complete
control of the activity on the land makes this site a good candidate for
an emergency land application site. In the event that one or more of the
other sites is unavailable for application due to permit problems or time
constraints, this site can always be available. The same agronomic rates
for application can be applied on this site as on the other sites.
ri r.
The only proposed amendments to the area will be expansions of the
airport operations.
h. Site #8, 55, TIN, R69W.
(1) Physiography and Topography. This 640 Acre site is approximately
5 miles south of the Longmont WWTP. It is part of the Colorado Piedmont
r Section of the Great Plains Physiographic Province. There is no impounded
water within the site with a drainage ditch from Gun Barrel Hill through
the south Section 9 of the site to Boulder Creek. The surface in the
north two—thirds of the site slopes 3.5% from 5390 ft M.S.L. to 5205 ft
M.S.L.
(2) Geology - See a. (2) for a representative discussion. The majority
of the site is light brown to reddish brown in olive gray deposits appear
mainly as a blanket of Loess as much as 15 ft thick but generally less
than 3 ft thick. The small area on the top of Gun Barrel Hill is a
pre-rocky flats alluvium which is brown to white cemented ground and sand
3-6 feet thick.
This is a flat-topped upland unit located in the Upland Subsection
of the Piedmont Section of the Great Plains Province. It is described as
gravel deposits as much as 15-20 ft thick on flat-topped uplands. Locally,
the upper part of the gravel is clayey and calcareous and commonly has a
thick strongly developed soil profile. The bedrock shale and sandstone
below the gravel may be exposed in bordering slopes or covered by colluvium
or windblown silt or sand.2
(3) Soils. This site contains the Weld-Colby soil association.
See b.(3) for a further discussion of this association. Soils present are:
Ct (Colby-Gaynor association) , WeB (Weld fine sandy loam) , WoB (Weld-Colby
Complex), and WoC (Weld-Colby Complex). Ascalon soils are found in the
SW corner but because of slope constraints these will not be described or
used as land application soils.1 See Table B-1 for soils data.
(4) Water - See a.(4) for representative discussion.
flee-tn.
(5) Air - See a. (5) for representative discussion.
(6) Biotic Components - See a. (6) for representative discussion.
(7) Socioeconomic Factors. This site is not within a geologic
hazard area, nor is it archeologically or historically sensitive. It is
not within a designated wildlife or plant critical habitat. This site
contains significant agricultural lands of statewide importance. This
section has also been designated as Proposed County Open Space or that
land which should be left intentionally free from future development.
There are no proposed county tracks, roads or expressways planned for the
site. A bike lane is proposed to the east on North 95th Street.18
i. Site #9, 54, TIN, R69W.
(1) Physiography and Topography. This site is approximately 5
miles from the Longmont WWTF. It is 640 acres in area and is situated
south of the City of Longmont. It is part of the Colorado Piedmont
Section of the Great Plains Physiographic Province. There is no impounded
water on this site, however a drainage ditch does travel west to east
through the north half of the site and the Whiterock Ditch is at the east
boundary. The surface slopes 2% from west to east, 5222 ft M.S.L, to
5110 ft M.S.L. The most outstanding physiographic feature of the site is
the abrupt wall-like mountain front forming the boundary between the
Front Range and the Piedmont or plains. The narrow foothills area along
the western margin of the Piedmont is characterized by a series of folded
and faulted sedimentary strata.
(2) Geology. See a. (2) for a representative discussion. The majority
of the site is light brown to reddish brown in olive gray deposits appearing
mainly as a blanket of loess as much as 15 ft thick but generally less
than 3 ft thick.
This is a flat-topped upland unit located in the upland subsection
of the Piedmont Section of the Great Plains Province. It is described as
,r:('e ") A
gravel deposits as much as 15-20 ft thick on flat-topped uplands. Locally,
the upper part of the gravel is clayey and calcareous and commonly has a
thick strongly developed soil profile. The bedrock shale and sandstone
below the gravel may be exposed in bordering slopes or covered by colluvium
or windblown silt or sand.2
(3) Soils. This site contains the Weld-Colby soil association.
See b.(3) for a further discussion of their association. Soils present are:
WeB (Weld-fine sandy loam) , WoB (Weld-Colby Complex) and WoC (Weld-Colby
Complex) . See Table B-1 for soils data.1
(4) Water - See a. (4) for representative discussion.
(5) Air - See a. (5) for representative discussion.
(6) Biotic Components — See a. (6) for representative discussion.
(7) Socioeconomic Factors. This site is not within a geologic
hazard area, nor is it archeologically or historically sensitive. It is
not within a designated wildlife or plant critical habitat. This site
contains significant agricultural lands of state—wide and national importance.
It is not constrained by county open space regulations. There are no
proposed county trails, roads or expressways planned for. the site. A
bike lane is proposed to the west of North 95th Street.18
2. COMPOSTING SITE
a. Site #10, S1, NE'1, 58, T2N, R68W - Longmont City Landfill Site.
(1) Physiography and Topography. This site is approximately 3.5
miles due East of the Longmont WWTF in western Weld County. It is about
50 acres in area and is bounded on the south and east by the St. Vrain
Creek. This site is part of the Colorado Piedmont Section of the Great
Plains Physiographic Province. The slope slopes abruptly with convulsions
along the bottom land of the creek. There are areas on the site where
the slopes exceed 10%. Elevations range from 4960 ft M.S.L. to 4860 ft
r o^ A.,
M.S.L. The site is currently being used as the Longmont City landfill.
The estimated useful life of the landfill is 2-3 years.
(2) Geology. This site's geology is comparable to that of sites
a. and b. in that it is evidenced by eolium as well as Pierre shale
_ deposits. It also contains a Post—Piney Creek Alluvium from the upper
Holocene, a deposit of the Quaternary Age. This deposit is adjacent to
the St. Vrain Creek. It is a dark—gray humic, sandy to gravelly alluvium,
containing scattered plant remains. This underlies flood plains and
major streams and terraces less than 10 ft above the stream level and is from
5 to 15 feet thick.
This bottomland unit is located in the Lowland Subsection of the
Colorado Piedmont Section of the Great Plains Province. It is further
described as alluvium with some windblown sediment.2
(3) Soils. The soils of this site are of two association: Aquolls-
Aquents-Bankard Association and Wiley-Colby-Weld Association. The majority
of this landfill site is located on the Aquolls-Aquents-Bankard type with
the Wiley-Colby-Weld occuring at the North of the site.
The Aquolls-Aquents-Bankard Association is identified as deep, level
and nearly level, poorly drained and somewhat excessively drained loamy
soils and sandy loans formed in alluvium. It is about 35% Aquolls, 20%
Aquents, 20% Bankard soils, and 25% is soils of minor extent. Aquolls
and Aquents form an intermingled complex pattern along the outer limits
of the bottom land, or flood plain. Bankard soils are adjacent to the
streams. Aquolls and Aquents are poorly drained, whereas Bankards are
somewhat excessively drained.
The Wiley-Colby-Weld Association is identified as deep, nearly level
to moderately sloping, well-drained silt loams and lcams formed in
calcareous eloian deposits. It is about 30% Wiley, 30% Colby, 15% Weld,
and 25% in soils of minor extent. Wiley and Colby soils form an inter—
n( (^? ,,
r
mingled complex pattern on the steeper side slopes. Weld soils are along
the narrow ridgetops and on the nearly level sides slopes. Wiley soils
have a silt loam surface layer and a silty clay loam subsoil.
Wiley Series
This series are plain soils and slopes from 0-5%. The top 11 inches
is a pale brown silt loam which is mildly alkaline. The next 13 inches
is a pale brown silty clay loam, calcareous and moderately alkaline. The
next 10 inches is also pale brown silty clay loam. The lower 26 inches
is very pale brown silty clay loam, calcareous, and moderately alkaline.4
See a. (3) for a discussion of the Colby Series and b.(3) for a discussion
of the Weld Series. See Table B-1 for soils data.
(4) Water - See a.(4) for a representative discussion.
(5) Air - See a. (5) for a representative discussion.
(6) Biotic Components - See a. (6) for a representative discussion.
(7) Socioeconomic Factors. The Longmont City Landfill is currently
in operation on this site. It is estimated that the site will be useful
for the landfilling of MSW for another 2-3 years. Landfills in general
are located in areas where there are few potentially effected residential
or commercial developments. The expansion of this landfill site can be
accomplished relatively easily because of the sparce population of the
area. It would, however, be recommended that a new site be chosen which
is not in as close proximity to a navigable stream as the current site
is.
The operation of a co—composting process at this site could extend
the life of the landfill due to the volume reduction experienced.
r. G "
There are no other socioeconomic constraints associated with this
site.
3. ADDITIONAL SITES OF THE AREA. In the event that the combined
area of the sites available is not adequate, additional lands should be
T targeted as potential sites. These lands could include:
o Site 0 11 SE'x, S23, T3N, R69W - 160 acres.
o Site 11 12 VIII, S24, T3N, R69W - 320 acres.
These sites offer the same potential as other sites in the area.
- ,.
REFERENCES
1. Soil Survey of Boulder County Area, Colorado, United States Department
of Agriculture, Soil Conservation Service, January 1975.
2. R. Colton, Geologic Map of the Boulder-Fort Collins-Greeley Area,
Colorado, Map I-866-G, 1978.
3. E.S. Crosby, Landforms in the Boulder-Fort Collins-Greeley Area,
Front Range Urban Corridor, Colorado, Map I-855-H, 1978.
4. Soil Survey of Weld County, Colorado-Southern Part, United States
Department of Agriculture, Soil Conservation Service, September 1980.
5. D.H. Miller and P.A. Schneider, Well Yields and Chemical Quality of
Water from Water-Table Aquifers in the Boulder-Fort Collins-Greeley
Area, Front Range Urban Corridor, Colorado, Map I-855-J, 1978.
6. Calvin Youngberg, Engineer, City of Longmont, Colorado, personal
communication to R.S. Peoples, Black S Veatch, April 14, 1987.
7. Meteorological Data for 1985, National Climatic Data Center, Asheville,
N.C.
8. Climatological Data, Colorado, National Oceanic and Atmospheric
Administration, Vol. 90-1985, Vol. 91-1986.
9. Colorado Air Quality Data Report, State of Colorado, Department of
Health, Air Pollution Control Division, Technical Services Program,
1985.
10. J.W. Mart and D.G. Steward, Vegetation Map of the Colorado Springs-
Castle Rock Area, Front Range Urban Corridor, 1979.
11. H.E. Kingery and W.D. Graul, eds. , Colorado Bird Distribution Latilong
Study, The Colorado Field Ornithologists, 1978.
12. David Langlois, ed. , Colorado Reptile and Amphibian Distribution Latilong,
Study, 1978.
13. Steven J. Bissell, ed. , Colorado Mammal Distribution Latilong Study,
1978.
14. K.D. Fausch and Lynn H. Schrader, "Use of the Index of Biotic
Integrity to Evaluate the Effects of Habitat, Flow, and Water
Quality on Fish Communities in Three Colorado Front Range Rivers,"
Department of Fishery and Wildlife Biology, Colorado State University,
1986.
15. "1985 Annual Report, St. Vrain Creek, Biosurvey Results, prepared
for City of Longmont," Colorado State University, 1985.
16. "An Illustrated Guide to the Proposed Threatened and Endangered
Plant Species in Colorado," Ecology Consultants, Inc., Fort Collins,
Colorado, April 1978.
_ 17. "Essential Habitat for Threatened or Endangered Wildlife in Colorado,"
Wildlife Management Section, Division of Wildlife, Department of
Natural Resources, State of Colorad, 1978.
18. "Boulder County Comprehensive Plan, Goals, Policies, and Maps,"
Boulder County Board of County Commissioners, Adopted, March 12,
1987.
TABLE B-5
FARMING CROPS
LONGMONT, CO AREA
Common Name Scientific Name
Corn Zea mays
Kentucky bluegrass Poa pratensis
Beans Phaseolus spp.
Beets Beta vulgaris
Cabbage Brassica oleracea
Cauliflower Brassica spp.
Carrot Daucus carota
Celery Apium graveoleus
Lettuce Lactuca sativa
Onion Allium ceps
Pumpkin & Squash Cucurbia spp.
Radish Raphanus sativus
Rhubarb Rheum rhapanticum
Spinach Spinacia oleracea
Tomato Lycopersicum esculentum
Turnip Brassica spp.
!" 07 3 �,.
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TABLE B-7
BIRDS OF NORTHCENTRAL COLORADO
The following listing includes bird species which are breeding or
_ non-breeding year-round or nesting season residents. They are also, to
the extent of distribution, abundant or common (at least 1/acre as
breeders) :
White Pelican Pelecanus erythrorhynchos
Canada Goose Branta canadensis
Mallard Anas platyrhynchos
American Wigeon Maraca americana
Redhead Aythya americana
American Coot Fulica americana
Killdeer Charadrius vociferus
Rock Dove Columba livia
Mourning Dove Zenaidura macroura
Great Horned Owl ' Bubo virginianus
White-throated Swift Aeronautes saxatalis
Broad-tailed Humming Bird Selasphorus platycercus
Common Flicker Colaptes safer
Red-headed Woodpecker Melanerpes erythrocephalus
Horned Lark Eremophilia alpestris
Violet-green Swallow Tachycineta thalassina
Tree Swallow Iridoprocne bicolor
Barn Swallow Hirundo rustics
Cliff Swallow Petrochelidon pyrrhonota
Black-billed Magpie Pica pica
American Robin Turdus Migratorius
Hermit Thrush Hylocichla guttata
Starling Sturnus vulgaris
Virginia 's Warbler Vermivora virginiae
Yellow Warbler Dendroica petechia
Black-throated Gray Warbler Dendroica nigrescens
Common Yellowthroat Geothlypis trichas
Wilson's Warbler Wilsonia pusilla
Western Meadowlark Sturnella neglecta
Yellow-headed Blackbird Banthocephalus xanthocephalus
Red-winged Blackbird Agelaius phoeniceus
Brewer's Blackbird Euphagus cyanocephalus
Common Grackle Quiscalus quiscula
House Finch Carpodacus mexicanus
Vesper Sparrow Pooecetes grammineus r '
Lark Sparrow Chondestes grammacus "
Gray-headed Junco Junco caniceps
Chipping Sparrow Spizella passerina C", '
Brewer's Sparrow Spizella breweri
White-crowned Sparrow Zonotrichia lencophrys
TABLE B-8
FISH SPECIES OF THE SOUTH PLATTE RIVER BASIN
Common Name Scientific Name
Clupeidae
gizzard shad Dorosoma cepedianum
Salmonidae
kokanee Oncorhynchus nerka
mountain whitefish Pros opium williamsoni
greenback cutthroat trout Salmo clarki stomias
rainbow trout Salmo sairdneri
brown trout Salmo trutta
brook trout Salvelinus fontinalis
Artie grayling Thymallus arcticus
Esocidae
northern pike Es ox lucius
Cyprinidae
central stoner oller Campostoma anomalum
goldfish Carassius aura tus
lake chub Couesius plumbeus
common carp Cyprinus carpio
brassy minnow Hybognathus hankinsoni
plains minnow Hybognathus placitus
hornyhead chub Nocomis biguttatus
• golden shiner Notemigonus crysoleucas
common shiner Notropis cornutus
bigmouth shiner Notropis dorsalis
blacknose shiner Notropis heterolepis
red shiner Notropis lutrensis
sand shiner Notropis stramineus
suckermouth minnow Phena cob ius mirabilis
northern redbelly dace Phoxinus eos
finescale dace Phoxinus neogaeus
fathead minnow Pimephales promalas
longnose dace Rhinichthys cataractae
creek chub Semotilus a t roma cu la tus
TABLE B-8 (Continued)
FISH SPECIES OF THE SOUTH PLATTE RIVER BASIN
Common Name Scientific Name
Catostomidae
river ra rpsucker Carpiodes carpio
longnose sucher Catostomus catostomus
white sucker Catostomus commersoni
Ic to lurida e
black bullhead Ictalurus melas
brown bullhead Ictalurus nebulosus
channel catfish Ictalurus punctatus
stonecat Noturus flavus
Cyprinodontidae
plains topminnow Fundulus sciadicus
plains killfish Fundulus zebrinus
Casterosteidae
brook stickleback Culaea inconstans
Percichthyidae
white bass Morone chrysops
striped bass Morone saxatilis
Centrarchidae
green sunfish Lepomis cyanellus
pumpkinseed Lepomis gibbosus
orangespotted sunfish Lepomis humilis
bluegill Lepomis macrochirus
_ smallmouth bass Micropterus dolomieui
Largemouth bass Micropterus salmoides
white crappie Pomoxis annularis
black crappie Pomoxis nigromaculatus
Percidae
Iowa darter Etheostoma exile
Johnny darter Etheostoma nigrum f'
yellow perch Peres flavescens �:-
walleye Stizostedion vitreum (oq
Scia enida a C
freshwater drum Aplodinotus grunniens
APPENDIX C
WASTEWATER TREATMENT PLANT LOADINGS 1982-1986
LCNGIE T COLORADO
SOLIDS MANAGEMENT STUDY
BLACK 6 VEATCH PROJECT NUMBER 13803.120
MARCH 20,1987
MONTHLY AVERAGE BOD LOADINGS 1982
AVERAGE INFLUENT EFFLUENT BOD BOD INFLUENT INFLUENT
MONTH FLOW BOD BOD REMOVED REMOVED BOD BOD
(mgd) (tons/day) (tons/day) (tons/day) (percent) (lbs/mg) RATIO
(m0/yr)
JANUARY 5.62 5.41 1.08 4.34 80.1 1,926.5 1.10
FEBRUARY 5.40 4.81 0.70 4.11 85.4 1,781.5 1.02
MARCH 5.39 5.60 0.68 4.92 87.9 2,076.6 1.19
APRIL 5.40 5.38 0.54 4.84 90.0 1,993.3 1.14
MAY 6.69 5.16 0.75 4.41 85.4 1,542.9 0.88
JOVE 7.02 6.12 1.02 5.10 83.3 1,743.0 1.00
JULY 7.59 7.37 0.75 6.62 89.8 1,943.2 1.11
AUGUST 7.84 5.39 0.79 4.61 85.4 1,376.1 0.79
SEPTEMBER 7.40 5.28 0.71 4.57 86.5 1,426.1 0.82
OCTOBER 6.88 5.14 0.51 4.63 90.1 1,492.9 0.85
NOVEMBER 5.90 5.56 0.59 4.97 89.4 1,884.9 1.08
DECEMBER 5.31 4.75 0.65 4.10 86.3 1,789.6 1.02
AVERAGE 6.37 5.50 0.73 4.77 86.6 1,748.1 1.00
c.'7,F4'
CI vl ,, ,.
LEWGMONT COLORADO
SOLIDS MANAGEMENT STUDY
BLACK S VEATCH PROJECT NLMBER 13803.120
MARCH 20,1987
MONTHLY AVERAGE TSS LOADINGS 1982
AVERAGE INFLUENT EFFLUENT TSS TSS INFLUENT INFLUENT
MONTH FLEW TSS TSS REMOVED REMOVED TSS TSS
(mgd) (tons/day) (tons/day) (tons/day) (percent) (lbs/mg) RATIO
(mo/yr)
JPNUARY 5.62 3.96 0.87• 3.09 78.1 1,409.4 1.02
FEBRUARY 5.40 5.70 0.65 5.05 88.6 2,111.1 1.53
MARCH 5.39 3.73 0.68 3.06 81.9 1,384.0 1.00
APRIL 5.40 4.01 0.65 3.36 83.7 1,484.4 1.07
MAY 6.69 4.45 0.80 3.65 82.0 1,330.3 0.96
J(NE 7.02 4.54 0.70 3.84 84.6 1,292.0 0.93
JULY 7.59 3.93 0.65 3.28 83.4 1,034.3 0.75
AUGUST 7.84 4.48 0.92 3.57 79.6 1,142.9 0.83
SEPTEMBER 7.40 5.10 0.87 4.24 83.0 1,378.4 1.00
OCTOBER 6.88 4.15 0.75 3.40 81.9 1,206.4 0.87
NOVEMBER 5.90 3.74 0.70 3.04 81.3 1,266.1 0.92
DECEMBER 5.31 4.15 0.60 3.55 85.5 1,563.1 1.13
AVERAGE 6.37 4.33 0.74 3.59 82.8 1,383.5 1.00
F"
C(CTS`f .
LCNGMENT COLORADO
SOLIDS MANAGEMENT STUDY
BLACK & VEATCH PROJECT NLMBER 13803.120
MARCH 20,1987
MONTHLY AVERAGE BOD LOADINGS 1983
AVERAGE INFLUENT EFFLUENT ROD BOD INFLUENT INFLUENT
MONTH FLCN BOD BOD REMOVED REMOVED BOD BOO
(mgd) (tons/day) (tons/day) (tons/day) (percent) (lbs/mg) RATIO
(mo/yr)
JANUARY 5.40 6.01 0.74 5.27 87.6 2,226.9 1.29
FEBRUARY 5.29 5.56 0.62 4.94 88.9 2,101.7 1.22
MARCH 7.25 6.68 0.76 5.91 88.6 1,841.5 1.07
APRIL 7.28 6.28 0.82 5.46 87.0 1,726.4 1.00
MAY 8.58 8.19 1.04 7.16 87.3 1,909.9 1.11
JIMJE 8.69 8.00 1.08 6.91 86.4 1,840.2 1.07
JULY 9.37 7.70 1.33 6.37 82.7 1,643.0 0.95
AUGUST 9.21 7.18 0.96 6.22 86.6 1,559.6 0.91
SEPTEMBER 8.72 6.18 0.98 5.20 84.1 1,417.8 0.82
OCTOBER 7.86 5.51 0.82 4.69 85.1 1,401.1 0.81
NOVEMBER 7.8.5 5.76 ' 0.82 4.94 85.8 1,467.9 0.85
DECEMBER 7.95 6.13 1.19 4.94 80.5 1,542.9 0.90
AVERAGE 7.79 6.60 0.93 5.67 85.9 1,723.2 1.00
cl:?-
LCNGMONT COLORADO
SOLIDS MANAGEMENT STUDY
BLACK & VEATCH PROJECT NUMBER 13803.120
MARCH 20,1987
MONTHLY AVERAGE TSS LOADINGS 1983
AVERAGE INFLUENT EFFLUENT TSS TSS INFLUENT INFLUENT
MONTH FLOW TSS TSS REMOVED REMOVED TSS TSS
(mgd) (tons/day) 'tons/day) (tons/day) (percent) (lbs/mg) RATIO
(mo/yr)
JANUARY 5.40 5.02 0.59 4.44 ' 88.4 1,859.8 1.38
FEBRUARY 5.29 4.15 0.57 3.57 86.2 1,567.9 1.16
MARCH 7.25 5.06 0.85 4.21 83.1 1,395.9 1.04
APRIL 7.28 4.86 0.76 4.10 84.4 1,334.3 ' 0.99
MAY 8.58 5.33 0.93 4.40 82.6 1,242.7 0.92
J(NE 8.69 6.13 0.78 5.34 87.2 1,410.2 1.05
JULY 9.37 6.10 0.90 5.20 85.3 1,301.1 0.97
AUGUST 9.21 6.45 0.96 5.49 85.1 1,401.1 1.04
SEPTEMBER 8.72 5.16 0.98 4.18 81.0 1,184.3 0.88
OCTOBER 7.86 4.69 0.92 3.77 80.4 1,192.6 0.89
NOVEMBER 7.85 4.32 0.92 3.40 78.8 1,100.9 0.82
DECEMBER 7.95 4.67 1.13 3.55 75.9 1,176.0 0.87
AVERAGE 7.79 5.16 0.86 4.30 83.2 1,347.2 1.00
, err) (9'ek
L0NGMONT COLORADO
SOLIDS MANAGEMENT STUDY
BLACK S VEATCH PROJECT NUMBER 13803.120
MARCH 20,1987
MONTHLY AVERAGE BOD LOADINGS 1984
AVERAGE INFLUENT EFFLUENT BOO BOD INFLUENT INFLUENT
MCNTH FLOW BOD BOD REMOVED REMOVED BOD BOO
(mgd) (tons/day) (tons/day) (tons/day) (percent) (Ibs/mg) RATIO
(mo/yr)
JANUARY 6.86 5.92 0.89 5.03 85.0 1,725.9 1.18
FEBRUARY 6.31 5.38 0.68 4.70 87.4 1,705.2 1.17
MARCH 6.12 5.22 0.64 4.58 87.3 1,705.2 1.17
APRIL 6.79 5.88 0.78 5.10 86.8 1,732.0 1.19
MAY 6.96 5.30 0.73 4.57 86.1 1,523.3 1.05
JUNE 7.28 4.80 0.71 4.09 85.2 1,319.5 0.91
JULY 8.71 5.48 0.77 4.72 86.0 1,258.7 0.86
AUGUST 9.13 5.41 0.94 4.47 82.6 1,184.7 0.81
SEPTEMBER 8.33 4.67 0.79 3.88 83.1 1,121.0 0.77
OCTOBER 8.41 5.05 0.78 4.27 84.7 1,200.8 0.82
NOVEMBER 7.20 5.34 0.81 4.53 84.8 1,483.3 1.02
DECEMBER 6.67 5.06 0.69 4.38 86.4 1,518.4 1.04
AVERAGE 7.40 5.29 0.77 4.53 85.5 1,456.5 1.00
LONEMCNT COLORADO
SOLIDS MANAGEMENT STUDY
BLACK & VEATCH PROJECT NUMBER 13803.120
MARCH 20,1987
MONTHLY AVERAGE TSS LOADINGS 1984
AVERAGE INFLUENT EFFLUENT TSS TSS INFLUENT INFLUENT
MONTH FLON TSS TSS REMOVED REMOVED TSS TSS
(mgd) (tons/day) (tons/day) (tons/day) (percent) (lbs/mg) RATIO
(mo/yr)
JANUARY 6.86 4.47 0.89 3.58 80.0 1,304.2 1.14
FEBRUARY 6.31 4.38 0.74 3.64 83.2 1,387.3 1.21
MARCH 6.12 3.45 0.66 2.79 80.8 1,128.9 0.99
APRIL 6.79 3.86 0.81 3.05 79.1 1,136.5 0.99
MAY 6.96 3.94 0.70 3.24 82.3 1,132.2 0.99
JUNE 7.28 3.71 0.77 2.94 79.3 1,017.9 0.89
JULY 8.71 4.42 0.78 3.64 82.4 1,015.6 0.89
AUGUST 9.13 4.64 0.99 3.66 78.8 1,016.8 0.89
SEPTEMBER 8.33 3.92 0.82 3.11 79.2 941.5 0.82
OCTOBER 8.41 4.90 0.91 3.98 81.4 1,164.7 1.02
NOVEMBER 7.20 4.29 0.84 3.45 80.5 1,192.2 1.04
DECEMBER 6.67 4.28 0.77 3.51 82.1 1,283.2 1.12
AVERAGE 7.40 4.19 0.81 3.38 80.7 1,143.4 1.00
€v t^2 Al
LONGMCNT COLORADO
SOLIDS MANAGEMENT STUDY
BLACK & VEATCH PROJECT NUMBER 13803.120
MARCH 20,1987
MENTHLY AVERAGE BOD LOADINGS 1985
AVERAGE INFLUENT EFFLUENT BOD BOO INFLUENT INFLUENT
MONTH FLAN BOD BOD REMOVED REMOVED BOD BOD
(m9d) (tons/day) (tons/day) (tons/day) (percent) (16s/m9) RATIO
(mo/yr)
JANUARY 6.25 4.90 0.63 4.27 87.1 1,569.3 1.06
FEBRUARY 6.15 5.21 0.63 4.57 87.8 1,693.3 1.14
MARCH 6.17 5.30 0.68 4.62 87.2 1,719.4 1.16
APRIL 6.55 5.09 0.83 4.27 83.8 1,555.3 1.05
MAY 7.34 5.32 1.18 4.14 77.7 1,449.2 0.98
JLNE 7.90 5.13 0.83 4.30 83.8 1,297.8 0.88
JURY 8.97 6.05 0.98 5.07 83.8 1,348.5 0.91
AUGUST 9.99 6.94 1.50 5.44 78.4 1,389.2 0.94
SEPTEMBER 7.71 5.13 0.96 4.18 81.3 1,331.9 0.90
OCTOBER 8.31 4.83 0.76 4.07 84.3 1,163.3 0.79
NOVEMBER 6.95 5.35 0.73 4.62 86.3 1,539.6 1.04
DECEMBER 6.17 5.23 0.63 4.60 88.0 1,693.7 1.14
AVERAGE 7.37 5.37 0.86 4.51 84.1 1,479.2 1.00
LONBICNT COLORADO
SOLIDS MANAGEMENT STUDY
BLACK & VEATCH PROJECT NUMBER 13803.120
MARCH 20,1987
MONTHLY AVERAGE TSS LOADINGS 1985
AVERAGE INFLUENT EFFLUENT TSS TSS INFLUENT INFLUENT
MONTH FLW TSS TSS REMOVED REMOVED TSS TSS
(mgd) (tons/day) (tons/day) (tons/day) (percent) (lbs/m9) RATIO
(mo/yr)
JANUARY 6.25 3.84 0.74 3.09 80.6 1,227.2 1.02
FEBRUARY 6.15 3.94 0.71 3.23 82.0 1,282.1 1.06
MARCH 6.17 4.08 0.76 3.32 81.3 1,322.9 1.10
APRIL 6.55 4.46 0.75 3.71 83.2 1,362.1 1.13
MAY 7.34 4.76 0.81 3.96 83.0 1,298.1 1.08
MC 7.90 4.40 0.85 3.55 80.8 1,112.9 0.92
JULY 8.97 4.83 0.88 3.95 81.8 1,076.4 0.89
AUGUST 9.99 5.50 0.91 4.58 83.4 1,100.3 0.91
SEPTEMBER 7.71 4.23 0.80 3.44 81.2 1,097.9 0.91
OCTOBER 8.31 4.60 0.94 3.66 79.6 1,107.8 0.92
NOVEMBER 6.95 4.37 0.84 3.53 80.8 1,256.5 1.04
DECEMBER 6.17 3.83 0.77 3.06 79.8 1,242.3 1.03
AVERAGE 7.37 4.40 0.81 3.59 81.5 1,207.2 1.00
rift .• >.4
LCNGMCNT COLORADO
SOLIDS MPNAGEMENr STUDY
BLACK & VEATCH PROJECT NLMBER 13803.120
MARCH 20,1987
MCNiHLY AVERAGE BOD LOADINGS 1986
AVERAGE INFLUENT EFFLUENT BOD BOD INFLUENT INFLUENT
MONTH FLOH BOD ROD REMOVED REMOVED BOD BOD
(mgd) (tons/day) (tons/day) (tons/day) (percent) (lbs/mg) RATIO
(mo/yr)
•
JANUARY 6.17 4.95 0.52 4.43 89.5 1,604.5 1.11
FEBRUARY 5.86 5.17 0.50 4.66 90.2 1,762.6 1.22
MARCH 5.69 4.26 0.39 3.86 90.7 1,495.5 1.04
APRIL 7.33 4.84 0.62 4.21 87.1 1,320.0 0.92
MAY 7.35 4.98 0.52 4.46 89.5 1,355.3 0.94
JLNE 7.56 4.56 0.53 4.03 88.4 1,206.1 0.84
JULY 8.61 3.58 0.53 3.05 85.3 831.2 0.58
AUGUST 8.79 5.25 1.00 4.25 80.9 1,194.6 0.83
SEPTEMBER 8.73 5.89 1.11 4.77 81.1 1,349.0 0.94
OCTOBER 8.18 7.53 1.06 6.47 85.9 1,841.8 1.28
NOVEMBER 8.45 6.38 0.84 5.53 86.8 1,509.8 1.05
DECEMBER 7.78 7.09 0.68 6.41 90.4 1,824.2 1.27
AVERAGE 7.54 5.37 0.69 4.68 87.2 1,441.2 1.00
nt CT?is
LONEMENT COLORADO
SOLIDS MANAGEMENT STUDY
BLACK S VEATCH PROJECT NU18ER 13803.120
MARCH 20,1987
MONTHLY AVERAGE TSS LOADINGS 1986
AVERAGE INFLUENT EFFLUENT TSS TSS INFLUENT INFLUENT
MONTH FLOW TSS TSS REMOVED REMOVED TSS RATIO
( A
I0
(mgd) (tons/day) (tons/day) (tons/day) (percent) (lbs/mg)
JAVIARY 6.17 3.93 0.69 3.23 82.3 1,273.5 1.15
FEBRUARY 5.86 3.66 0.70 2.96 80.9 1,248.5 1.13
MARCH 5.69 3.67 0.59 3.08 84.0 1,288.2 1.16
APRIL 7.33 4.98 0.67 4.31 86.5 1,358.5 1.23
MAY 7,35 4.16 0.34 3.82 91.9 1,131.8 1.02
AXE 7.56 3.97 0.27 3.70 93.2 1,049.6 0.95
JULY 8,61 4.38 0.35 4.02 91.9 1,016.3 0.92
AUGUST 8,79 3.90 0.31 3.60 92.1 888.2 0.80
SEPTEMBER 8,73 3.84 0.29 3.55 92.4 881.1 0.80
OCTOBER 8.18 4.48 0.38 4.10 91.5 1,096.9 0.99
MEMBER 8.45 4.34 0.38 3.96 91.2 1,028.5 0.93
DECEMBER 7.78 3.93 0.30 3.63 92.3 1,011.3 0.91
AVERAGE 7.54 4.10 0.44 3.66 89.2 1,106.0 1.00
ern
APPENDIX D
LAND APPLICATION LAND AREA REQUIREMENTS
nre77m
CALCULATICN OF SLUDGE LOADING RATES BASED ON 1/2
IRRIGATED IBaT NITROGEN REQUIREMENTS
(70 bu/ac)
LONTNCNT COLORADO
APRIL 28,1587
* STEP 1 - DEFINITICN OF TERMS
No = Available Organic Nitrogen (16/dt)
NH3 = Available Ammonia Nitrogen (1b/dt)
NO3 = Available Nitrate Nitrogen (16/dt)
N = Total Available Nitrogen (lb/dt)
SI = Residual Nitrogen (16/ac)
AR = Application Rate of Sludge (dt/ac)
Cd = Cadmiun Concentration in the Sludge (mg/kg)
Pb = Lead Concentration in the Sludge (mg/kg)
Zn = Zinc Concentration in the Sludge (mg/kg)
Cu = Copper Concentration in the Sludge (mg/kg)
Ni = Nickel Concentration in the Sludge (mg/kg)
* STEP 2 - INPUT CATA
Organic N Concentration = 32,500 mg/kg
Ammonia N Concentration = 40,300 mg/kg
Nitrate N Concentration = 100 mg/kg
Volatilization Factor = 1.0
Cenitrification Factor = 0.6
Crop N Requirement = 160 16/ac
Sludge Cd Concentration = 11.0 mg/kg
Sludge Pb Concentration = 1: .0 mg/kg
Sludge Zn Concentration = 900.0 mg/kg
Sludge Cu Concentration = 625.0 mg/kg
Sludge Ni Concentration = 50.0 mg/kg
Maximum Annual Cd Conc. = 0.25 lb/ac/yr
Maximum Cumulative Cd Conc. = 5.0 lb/ac
Maximum Cumulative Pb Conc. = 500 lb/ac
Maximum Cumulative Zn Conc. = 250 16/ac
Maximum Cumulative Cu Conc. = 125 lb/ac
Maximum Cumulative Ni Conc. = 50 lb/ac
Daily Sludge Production = 8.5 dt/day
* STEP 3 - CALCULATE TOTAL AVAILABLE NITROGEN
No = 13.0 lb/dt
NH3 = 80.6 lb/dt
NO3 = 0.2 lb/dt
N = 56.3 lb/dt
# Available Nitrogen has been calculated by totaling
No, NH3, and N03 and multiplying by the Denitrification factor
* STEP 4 - CALCULATE APPLICATION RATES*
Year 1 AR = 2.8 dt/ac
Year 2 AR = 2.6 dt/ac
Year 3 AR = 2.5 dt/ac
Year 4 AR = 2.4 dt/ac
Year 5 AR = 2.4 dt/ac
# Calculated rates differ from year to year due to varying rates of
organic nitrogen mineralization.
CALCULATION OF SLUDGE LOADING RATES BASED ON 2/2
IRRIGATED WHEAT NITROGEN REQUIREMENTS
(70 bu/ac)
LONGM(NT COLORADO
APRIL 28,1987
* STEP 5 - CALCULATE SITE LIFE AND/OR LIMITING APPLICATION RATE
Maximum Maximum
Sludge Metals Cumulative Annual Site
Conc. Loading# Metals@ Metals Life
Element (lb/dt) (ib/ac/yr) (Ib/ac)(lb/ac/yr) (yrs)
Cd 0.02 0.1 5.0 0.25 80
Pb 0.36 1.0 500 - 489
Zn 1.80 5.1 250 - 49
Cu 1.25 3.6 125 - 35
Ni 0.10 0.3 50 - 176
# Dependent on CEC value. Obtain values from EPA Process Design
Manual, Land Application of Municipal Sludge, EPA-625/1-83-016
# Based on the sludge application rate calculated for the first year
* STEP 6 - CALCULATE AREA REQUIREMENTS
AREA = [SLUDGE QUANTITY(DTPD) * 365 DAYS/YEAR] / APPLICATION RATE
AREA = 1,286 acres
CALCULATICN OF SLUDGE LOADING RATES BASED ON 1/2
BARLEY NITROGEN REQUIREMENTS
(90 bu/ac)
LCNEMCNT COLORADO
APRIL 28,1987
* STEP 1 - DEFINITION OF TEAMS
No = Available Organic Nitrogen (lb/dt)
NH3 = Available Ammonia Nitrogen (lb/dt)
N03 = Available Nitrate Nitrogen (lb/dt)
N = Total Available Nitrogen (lb/dt)
RN = Residual Nitrogen (lb/ac)
AR = Application Rate of Sludge (dt/ac)
Cd = Cadoiun Concentration in the Sludge (mg/kg)
Pb = Lead Concentration in the Sludge (mg/kg)
Zn = Zinc Concentration in the Sludge (mg/kg)
Cu = Copper Concentration in the Sludge (mg/kg)
Ni = Nickel Concentration in the Sludge (mg/kg)
* STEP 2 - INPUr DATA
Organic N Concentration = 32,500 mg/kg
Ansonia N Concentration = 40,300 mg/kg
Nitrate N Concentration = 100 mg/kg
Volatilization'Factor = 1.0
Denitrification Factor = 0.6
Crop N Requirmoent = 140 lb/ac
Sludge Cd Concentration = 11.0 mg/kg
Sludge Pb Concentration = 180.0 mg/kg
Sludge Zn Concentration = 900.0 mg/kg
Sludge Cu Concentration = 625.0 mg/kg
Sludge Ni Concentration = 50.0 mg/kg
Maximum Annual Cd Conc. = 0.25 lb/ac/yr
Maximum Cumulative Cd Conc. = 5.0 lb/ac
Maximum Cumulative Pb Conc. = 500 16/ac
Maximum Cumulative Zn Conc. = 250 lb/ac
Maximum Cumulative Cu Conc. = 125 lb/ac
Maximum Cumulative Ni Conc. = 50 lb/ac
Daily Sludge Production = 8.5 dt/day
* STEP 3 - CALCULATE TOTAL AVAILABLE NITROGEN
No = 13.0 lb/dt
NH3 = 80.6 lb/dt
N03 = 0.2 lb/dt
N = 56.3 lb/dt
# Available Nitrogen has been calculated by totaling
No, NH3, and N03 and multiplying by the Denitrification factor
* STEP 4 - CALCULATE APPLICATICN RATES*
Year 1 AR = 2.5 dt/ac
Year 2 AR = 2.3 dt/ac
Year 3 AR = 2.2 dt/ac
Year 4 AR = 2.1 dt/ac
on .,
Year 5 AR = 2.1 dt/ac < A 0.a^..•: n
• Calculated rates differ from year to year due to varying rates of
organic nitrogen mineralization.
CALCULATION OF SLUDGE LOADING RATES BASED ON 2/2
BARLEY NITROGEN REQUIREMENTS
(90 bu/ac)
LONEMONT COLORADO
APRIL 28,1987
* STEP 5 - CALCULATE SITE LIFE AND/OR LIMITING APPLICATICN RATE
Maximum Maximum
Sludge Metals Cumulative Annual Site
Conc. Loading* Metals# Metals Life
Elument (1b/dt) (lb/ac/yr) (lb/ac)(lb/ac/yr) (yrs)
Cd 0.02 0.1 5.0 0.25 91
Pb 0.36 0.9 500 - 558
Zn 1.80 4.5 250 - 56
Cu 1.25 3.1 125 - 40
Ni 0.10 0.2 50 - 201
# Dependent on CEC value. Obtain values from EPA Process Design
Manual, Land Application of Municipal Sludge, EPA-625/1-83-016
# Based on the sludge application rate calculated for the first year
* STEP 6 - CALCULATE AREA REQUIREMENTS
AREA = [SLUDGE QUANTITY(DTPD) * 365 DAYS/YEAR1 / APPLICATION RATE
AREA = 1,470 acres
CALCULATION OF SLUDGE LOADING RATES BASED ON 1/2
DRY LAND WHEAT NITROGEN REQUIREMENTS
(25 bu/ac)
L NGMENT COLORADO
APRIL 28,1987
* STEP 1 - DEFINITIDN OF TERMS
No = Available Organic Nitrogen (lb/dt)
NH3 = Available Ammonia Nitrogen (lb/dt)
NO3 = Available Nitrate Nitrogen (lb/dt)
N = Total Available Nitrogen (lb/dt)
RN = Residual Nitrogen (1b/ac)
AR = Application Rate of Sludge (dt/ac)
Cd = Cadmiun Concentration in the Sludge (mg/kg)
Pb = Lead Concentration is the Sludge (mg/kg)
Zn = Zinc Concentration in the Sludge (mg/kg)
Cu = Capper Concentration in the Sludge (mg/kg)
Ni = Nickel Concentration in the Sludge (mg/kg)
* STEP 2 - INPUT DATA
Organic N Concentration = 32,500 mg/kg
Ammonia N Concentration = 40,300 mg/kg
Nitrate N Concentration = 100 mg/kg
Volatilization Factor = 1.0
Denitrification Factor = 0.6
Crop N Requirement = 60 lb/ac
Sludge Cd Concentration = 11.0 mg/kg
Sludge Pb Concentration = 180.0 mg/kg
Sludge Zn Concentration = 900.0 mg/kg
Sludge Cu Concentration = 625.0 mg/kg
Sludge Ni Concentration = 50.0 mg/kg
Maximum Annual Cd Conc. = 0.25 lb/ac/yr
Maximum Cumulative Cd Conc. = 5.0 lb/ac
Maximum Cumulative Pb Conc. = 500 16/ac
Maximum Cumulative Zn Conc. = 250 lb/ac
Maximum Cumulative Cu Conc. = 125 lb/ac
Maximum Cumulative Ni Conc. = 50 lb/ac
Daily Sludge Production = 8.5 dt/day
* STEP 3 - CALCULATE TOTAL AVAILABLE NITROGEN
No = 13.0 lb/dt
NH3 = 80.6 lb/dt
NO3 = 0.2 lb/dt
N = 56.3 lb/dt
# Available Nitrogen has been calculated by totaling
No, NH3, and NO3 and multiplying by .the Denitrification factor
* STEP 4 - CALCULATE APPLICATION RATES#
Year 1 AR = 1.1 dt/ac
Year 2 AR = 1.0 dt/ac
Year 3 AR = 0.9 dt/ac
Year 4 AR = 0.9 dt/ac net `'^7
Year 5 AR = 0.9 dt/ac
# Calculated rates differ from year to year due to varying rates of
organic nitrogen mineralization.
CALCULATION OF SLUDGE LOADING RATES BASED ON 2/2
DRY LAND WHEAT NITROGEN REQUIREMENTS
(25 bu/ac)
L NEMCNlT COLORADO
APRIL 28,1987
* STEP 5 - CALCULATE SITE LIFE AND/OR LIMITING APPLICATION RATE
Maximum Maximum
Sludge Metals Cumulative Annual Site
Conc. Loading* Metals@ Metals Life
Element (lb/dt) (16/ac/yr) (16/ac)(lb/ac/yr) (yrs)
Cd 0.02 0.0 5.0 0.25 213
Pb 0.36 0.4 500 - 1303
Zn 1.80 1.9 250 - 130
Cu 1.25 1.3 125 - 94
Ni 0.10 0.1 50 - 469
@ Dependent on CEC value. Obtain values from EPA Process Design
Manual, Land Application of Municipal Sludge, EPA-625/1-83-016
@ Based on the sludge application rate calculated for the first year
* STEP 6 - CALCULATE AREA REQUIREMENTS
AREA = [SLUDGE QUANTITY(DTPD) * 365 DAYS/YEAR] / APPLICATION RATE
AREA = 3,430 acres
CALCULATION OF SLUDGE LOADING RATES BASED ON 1/2
CORN NITROGEN REQUIREMENTS
GRAIN CORN (140 bu/ac)
LCNGMONT COLORADO
APRIL 28,1987
* STEP 1 - DEFINITION OF TERMS
No = Available Organic Nitrogen (lb/dt)
NH3 = Available Ammonia Nitrogen (lb/dt)
NO3 = Available Nitrate Nitrogen (lb/dt)
N = Total Available Nitrogen (16/dt)
RN = Residual Nitrogen (1b/ac)
AR = Application Rate of Sludge (dt/ac)
Cd = Cadaiun Concentration in the Sludge (mg/kg)
Pb = Lead Concentration in the Sludge (mg/kg)
Zn = Zinc Concentration in the Sludge (mg/kg)
Cu = Copper Concentration in the Sludge (mg/kg)
Ni = Nickel Concentration in the Sludge (mg/kg)
* STEP 2 — INPUT DATA
Organic N Concentration = 32,500 mg/kg
Ammonia N Concentration = 40,300 mg/kg
Nitrate N Concentration = 100 mg/kg.
Volatilization Factor = 1.0
Denitrification Factor = 0.6
Crop N Requirement = 170 lb/ac
Sludge Cd Concentration = 11.0 mg/kg
Sludge Pb Concentration = 180.0 mg/kg
Sludge Zn Concentration = 900.0 mg/kg
Sludge Cu Concentration = 625.0 mg/kg
Sludge Ni Concentration = 50.0 mg/kg
Maximum Annual Cd Conc. = 0.25 lb/ac/yr
Maximum Cumulative Cd Canc. = 5.0 lb/ac
Maximum Cumulative Pb Conc. = 500 lb/ac
Maximum Cumulative Zn Conc. = 250 lb/ac
Maximum Cumulative Cu Conc. = 125 lb/ac
Maximum Cumulative Ni Conc. = 50 lb/ac
Daily Sludge Production = 8.5 dt/day
* STEP 3 - CALCULATE TOTAL AVAILABLE NITROGEN
No = 13.0 lb/dt
NH3 = 80.6 lb/dt
NO3 = 0.2 lb/dt
N = 56.3 lb/dt
# Available Nitrogen has been calculated by totaling
No, NH3, and NO3 and multiplying by the Denitrification factor
* STEP 4 - CALCULATE APPLICATION RATES#
Year 1 AR = 3.0 dt/ac
Year 2 AR = 2.7 dt/ac
Year 3 AR = 2.6 dt/ac
Year 4 AR = 2.6 dt/ac
Year 5 AR = 2.6 dt/ac
# Calculated rates differ from year to year due to varying rates of
organic nitrogen mineralization.
•
CALCULATION OF SLUDGE LORDING RATES BASED ON 2/2
CORN NITROGEN REQUIREMENfS
GRAIN CORN (140 bu/ac)
LONGMENT COLORADO
APRIL 28,1987
* STEP 5 - CALCULATE SITE LIFE AND/OR LIMITING APPLICATION RATE
Maximum Maximum
Sludge Metals Cumulative Annual Site
Conc. Loading# Metals@ Metals Life
Elanent (lb/dt) (lb/arlyr) (lb/ac)(lb/ac/yr) (yrs)
Cd 0.02 0.1 5.0 0.25 75
Pb 0.36 1.1 500 - 460
Zn 1.80 5.4 250 - 46
Cu 1.25 3.8 125 - 33
Ni 0.10 0.3 50 - 166
@ Dependent on CEC value. Obtain values from EPA Process Design
Manual, Land Application of Municipal Sludge, EPA-625/1-83-016
# Based on the sludge application rate calculated for the first year
* STEP 6 - CALCULATE AREA REQUIREMENTS
AREA = [SLUDGE QUANTITY(DTPD) * 365 DAYS/YEARI / APPLICATIEN RATE
AREA = 1,211 acres
+('0:';',7
CALCULATICN OF SLUDGE LOADING RATES BASED ON 1/2
CORN NITROGEN REQUIREMENTS
SILAGE CORN
LCN6MONT COLORADO
APRIL 28,1987
* STEP 1 - DEFINITIQI OF TERMS
No = Available Organic Nitrogen (lb/dt)
NH3 = Available Ammonia Nitrogen (lb/dt)
NO3 = Available Nitrate Nitrogen (lb/dt)
N = Total Available Nitrogen (lb/dt)
RN = Residual Nitrogen (lb/ac)
AR = Application Rate of Sludge (dt/ac)
Cd = Cadmiun Concentration in the Sludge (mg/kg)
Pb = Lead Concentration in the Sludge (mg/kg)
Zn = Zinc Concentration in the Sludge (mg/kg)
Cu = Copper Concentration in the Sludge (mg/kg)
Ni = Nickel Concentration in the Sludge (mg/kg)
* STEP 2 - INPUr DATA
Organic N Concentration = 32,500 mg/kg
Ammonia N Concentration = 40,300 mg/kg
Nitrate N Concentration = 100 mg/kg
Volatilization Factor = 1.0
Denitrification Factor = 0.6
Crop N Requirement = 200 lb/ac
Sludge Cd Concentration = 11.0 mg/kg
Sludge Pb Concentration = 180.0 mg/kg
Sludge Zn Concentration = 900.0 mg/kg
Sludge Cu Concentration = 625.0 mg/kg
Sludge Ni Concentration = 50.0 mg/kg
Maximum Annual Cd Conc. = 0.25 lb/ac/yr
Maximum Cumulative Cd Conc. = 5.0 lb/ac
Maximum Cumulative Pb Conc. = 500 lb/ac
Maximum Cumulative Zn Conc. = 250 lb/ac
Maximum Cumulative Cu Conc. = 125 lb/ac
Maximum Cumulative Ni Conc. = 50 16/ac
Daily Sludge Production = • 8.5 dt/day
* STEP 3 - CALCULATE TOTAL AVAILABLE NITROGEN
No = 13.0 lb/dt
NH3 = 80.6 lb/dt
NO3 = 0.2 lb/dt
N = 56.3 lb/dt
# Available Nitrogen has been calculated by totaling
No, NH3, and NO3 and multiplying by the Denitrification factor
* STEP 4 - CALCULATE APPLICATION PATES#
Year 1 AR = 3.6 dt/ac
Year 2 AR = 3.2 dt/ac
Year 3 AR = 3.1 dt/ac
Year 4 AR = 3.0 dt/ac
Year 5 AR = 3.0 dt/ac `
# Calculated rates differ from year to year due to varying rates of
organic nitrogen mineralization.
CALCULATION OF SLUE LOADING RATES BASED ON 2/2
COIN! NITROGEN REQUIREMENTS
SILAGE CORN
LONGMONT COLORADO
APRIL 28,1987
* STEP 5 - CALCULATE SITE LIFE AND/OR LIMITING APPLICATION RATE
Maximum Maximum
Sludge Metals Cumulative Annual Site
Conc. Loading# Metals@ Metals Life
Element (lb/dt) (1b/ac/yr) (16/ac)(1b/ac/yr) (yrs)
Cd Y 0.02 0.1 5.0 0.25 64
Pb 0.36 1.3 500 - 391
Zn 1.80 6.4 250 - 39
Cu 1.25 4.4 125 - 28
Ni 0.10 0.4 50 - 141
@ Dependent on CEC value. Obtain values from EPA Process Design
Manual, Land Application of Municipal Sludge, EPA-625/1-83-016
# Based on the sludge application rate calculated for the first year
* STEP 6 - CALCULATE AREA REQUIREMENTS
•
AREA = (SLUDGE QUN4TITY(DTPD) * 365 DAYS/YEAR] / APPLICATION RATE
AREA = 1,029 acres
APPENDIX E
ALTERNATIVE CAPITAL AND
OPERATION AND MAINTENANCE COSTS
THE 16 TABLES THAT FOLLOW PRESENT THE CAPITAL
COSTS ALONG WITH THE AVERAGE YEARLY OPERATION
AND MAINTENANCE COSTS FOR EACH OF THE EIGHT
SLUDGE MANAGEMENT ALTERNATIVES DESCRIBED •IN
CHAPTER 3.
{
TABLE E-1
CAPITAL COST
LAND APPLICATION OP DIGESTED SLUDGE AT AGRONOMIC RATES
2.4 PERCENT TOTAL SOLIDS CONCENTRATION
20-MILE HAUL DISTANCE
CITY-OPERATED
CAPITAL COST
Sludge Digestion
SO-feet Diameter Digester, lump sus $ 800,000
Sludge Leading Station
Grading and Drainage Improvements, lump sum 20,000
Loading Station Improvements, lump sum 150,000
Paving, 10,000 sq yd at $14/aq yd 140,000
Sludge Transport/Injection Vehicles
Muse Trucks, 7,000 gal each, 6 at $120,000 each 720,000
Application Vehicles, 4,000 gal each, 2 at $145,000 each 290,000
SUBTOTAL $2,120,000
Contingencies at 20 Percent 420,000
,TOTAL CAPITA. COST, $2,540,000
TABLE E-2
OPERATION AND MAINTENANCE COSTS
LAND APPLICATION OF DIGESTED SLUDGE AT AGRONOMIC RATES
2.4 PERCENT TOTAL SOLIDS CONCENTRATION
20-MILE HAUL DISTANCE
CITY-OPERATED
REPLACNTENT COSTS
Equipment Replacement
Sludge Transport and Injection Vehicles Replaced
at 30 Years with No Salvage Value
Nuree Trucks, 6 at $120,000 each $ 720,000
Application Vehicles, 2 at $145,000 each 290,000
TOTAL REPLACEMENT COST $1,010,000
OPERATION AND MAINTENANCE COSTS
Labor
Operators, 9 at $32,400 per year $ 291,600
Mechanic, 1 at $32,400 per year 32,400
Supervisor, 1 at $38,400 per year 38,400
TOTAL LABOR COSTS $ 362,400
Fuel
22,000 Gal Per Year at $0.64 Per Gal $ 14,100
Maintenance
Sludge Transport Vehicles $ 8,000
Sludge Application Vehicles 13,000
Digesters 15,000
TOTAL MAINTENANCE COSTS $ 36,000
TOTAL OPERATION AND MAINTENANCE COSTS $ 412,500
TABLE E-3
CAPITAL COST
LAND APPLICATION OF DIGESTED SLUMS AT AGRONOMIC BATES
3.5 PERCENT TOTAL SOLIDS CONCENTRATION
20-NILE HAUL DISTANCE
CITY-OPERATED
CAPITAL COST
Centrifuge Thickening of Raw Sludge
Thickening Building, 750 eq ft at 120/sq ft $ 90,000
Centrifuges, 2 at 5275,000 each 550,000
Polymer System, lump sum 80,000
Sludge Digestion
50-Foot Diameter Digester, lump sum 800,000
Sludge Loading Station
Grading and Drainage Improvements, lump sum 20,000
Loading Station Improvements, lump sum 150,000
Paving, 10,000 eq yd at $14/sq yd 140,000
Sludge Transport/Injection Vehciles
Nurse Trucks, 7,000 gal each, 4 et $120,000 each 480,000
Application Vehicles, 4,000 gal each, 2 at 5145,000 each 290,000
SUBTOTAL $2,600,000
Contingencies at 20 Percent 520,000
TOTAL CAPITAL COST $3,120,000
,ne :,.�
TABLE E-4
OPERATION AND MAINTENANCE COSTS
LAND APPLICATION OF DIGESTED SLUDGE AT AGRONOMIC RATES
3.5 PERCENT TOTAL SOLIDS CONCENTRATION
T-. 20-MILE HAUL DISTANCE
CITY—OPERATED
REPLACEMENT COSTS
Equipment Replacement
Sludge Transport and Injection Vehicles Replaced
at 10 Years with No Salvage Value
Nurse Trucks, 4 at $120,000 each $ 480,000
Application Vehicles, 2 at $145,000 each 290,000
TOTAL REPLACEMENT COST $ 770,000
OPERATION AND MAINTENANCE COSTS
Labor
Operators, 8 at $32,400 per year $ 259,200
Mechanic, 1 at $32,400 per year 32,400
Supervisor, 1 at $38,400 per year 38,400
TOTAL TABOR COSTS $ 330,000
Fuel
15,200 Gal Per Year at $0.64 Per Gal $ 10,000
Power
56,000 kWh at $0.06 Per kWh $ 3,400
Chemicals
Polymer, 14,600 lb at $3 per lb $ 43,800
Maintenance
Sludge Transport Vehicles $ 4,000
Sludge Application Vehicles 9,000
Digesters 15,000
Centrifuge 13,000
TOTAL MAINTENANCE COSTS $ 41,000
TOTAL OPERATION AND MAINTENANCE COSTS $ 428,200
"Tr C ?Mk
TABLE 6-5
CAPITAL COST
LAND APPLICATION OF DIGESTED SLUDGE AT AGRONOMIC RATES
2.4 PERCENT TOTAL SOLIDS CONCENTRATION
CONTRACT HAUL
CAPITAL COST
Sludge Digestion
50-Foot Diameter Digester, lump sus $ 800,000
Sludge Loading Station
Grading and Drainage Improvements, lump Sum 20,000
loading Station Improvements, lump sum 150,000
Paving, 10,000 sq yd at $14/sq yd 140,000
SUBTOTAL $1,110,000
Contingencies at 20 Percent 222,000
TOTAL CAPITAL COST $1,332,000
J\,.C82
TABLE 6-6
OPERATION AND MAINTENANCE COSTS
LAND APPLICATION OF DIGESTED SLUDGE AT AGRONOMIC RATES
2.4 PERCENT TOTAL SOLIDS CONCENTRATION
CONTRACT HAUL
OPERATION AND MAINTENANCE COSTS
Labor
Operators, 2 at $32,400 per year $ 64,800
Supervisor, 1 et $38,400 per year 38,400
TOTAL. LABOR COSTS $ 103,200
Maintenance
Digesters $ 15,000
Contract Hauling
18,000,000 Gal at $0.0269 Per Gal $ 523,000
TOTAL, OPERATION AND MAINTENANCE COSTS $ 641,200
4- 1Q
TABLE 6-7
CAPITAL COST
LAND APPLICATION OP DIGESTED SLUDGE AT AGRONOMIC BATES
3.5 PERCENT TOTAL SOLIDS CONCENTRATION
CONTRACT HAUL
CAPITAL COST
Centrifuge Thickening of Raw Sludge
Thickening Building, 750 sq ft at 120/sq ft $ 90,000
Centrifuges, 2 at $275,000 each 550,000
Polymer System, lump sum 80,000
Sludge Digestion
50-Foot Diameter Digester, lump sum $ 800,000
Sludge Loading Station
Grading and Drainage Improvements, lump sum 20,000
Loading Station Improvements, lump sum 150,000
Paving, 10,000 sq yd at $14/sq yd 140,000
SUBTOTAL $1,830,000
Contingencies at 20 Percent 366,000
TOTAL CAPITAL COST $2,196,000
4-? = Ajt
TABLE E-8
OPERATION AND mhzer EBANCE COSTS
LAND APPLICATION OF DIGESTED SLUDGE AT AGRONOMIC FATES
3.5 PERCENT TOTAL SOLIDS CONCENTRATION
CONTRACT HAUL
OPERATION AND MAINTENANCE COSTS
Labor
Operators, 2 at $32,400 per year $ 64,800
Supervisor, 1 at $38,400 per year 38,400
TOTAL LABOR COSTS $ 103,200
Power
56,000 kWh at $0.06 per kWh $ 3.400
Chemicals
Polymer, 14,600 lb at $3 Per lb $ 43,800
Maintenance
Digesters $ 15,000
Centrifuge 13,000
Contract Hauling
12,400,000 Gal at $0.0321 Per Gal $ 398,000
TOTAL OPERATION AND MAINTENANCE COSTS $ 576,400
Or(7;82
11U3LE P.-9
CAPITAL COST
AERATED STATIC PILE COMPOSTING OF RAW SLUDGE
5-FOOT PILE HEIGHT
CAPITAL COST
Sludge Dwatering
Grading and Drainage Improvements, lump sum $ 5,000
Dewatering Building, 3,000 sq ft at $120/sq ft 360,000
One 2.2-Meter Belt Press at $220,000, Plus
Installation at 20 Percent 264,000
Relocate Existing Belt Filter Proms 50,000
Polymer System, lump sus 180,000
Sludge Transport Vehicles
Dump Trucks, 2 at $75,000 each 150,000
Aerated Static Pile Composting Facility
Grading and Drainage Impcovements, lump sum 36,000
Paving, 31,000 sq yd at $14/sq yd 434,000
Composting Building, 78,400 sq ft at $5.20/sq ft 408,000
Aeration Blowers, 8 at $4,200 each I! - 33,600
Aeration Piping, lump sum 225,000
Future Oder Control System Piping, lump sum 10,000
Electrical and Instrumentation Including
Lightning Protection, lump sum 110,000
Gond/onset* Evaporation Pond, lump sum 60,000
Compost Curing Building, 13,000 sq ft at $5.20/sq ft 68,000
Finished Compost Storage Building
Grading and Drainage Improvements, lump sus 5,000
Paving, 700 sq yd at $14/sq yd 9,800
Finished Compost Storage Building, 7,000 sq ft at $5.20/sq ft 36,000
Composting Equipment
Front-End Loaders, 2 at $150,000 each 300,000
Windrow Mixing Machine, 1 at $160,000 160,000
SUBTOTAL $2,904,400
Contingencies at 20 Percont 581,000
TOTAL CAPITAL COST $3,485,000
•
8C Cso
TABLE E-10
OPERATION AND MAINTENANCE COSTS
AERATED STATIC PILE COMPOSTING OF RAN SLUDGE
5-FO0T PILE HEIGHT
REPLACEMENT COSTS
Equipment Replacement
Sludge Handling Equipment Replaced et
10 Years with No Salvage Value
Dump Truckee 2 at $75,000 each $ 150,000
windrow Mixing Machine, 1 at $160,000 160,000
Front-End Loaders, 2 at $150,000 each 300,000
TOTAL REPLACEMENT COST $ 610,000
OPERATION AND MAINTENANCE COSTS
Labor
•
Operators, 5 at $32,400 per year $ 162,000
Mechanic, 1 at $32,400 per year 32,400
Supervisor, 1 at $38,400 per year 38,400
TOTAL LABOR COSTS $ 232,800
Fuel
7,300 Gal Per Year at $0.64 Per Gal $ 4,700
Power
284,000 kWh at $0.06 Per kWh $ 17,000
Chemicals
Polymer, 35,000 Lb at $3 per lb $ 105,000
Maintenance
Sludge Transport Vehicles $ 4,000
Composting Equipment 9,000
TOTAL MAINTENANCE COSTS $ 13,000
TOTAL OPERATION AND MAINTENANCE COSTS $ 372,500
cir c' ni
�tp_i
TABLE E-11
CAPITAL COST
AERATED STATIC PILE COMPOSTING OF RAN SLUDGE
12-FOOT PILE HEIGHT
WITH AM0 MMENP ADDITION
..- CAPITAL COST
Sludge Dewatering
Grading and Drainage Improvements, lump sue $ 5,000
Dewatering Building, 3,000 sq ft at $120/sq ft 360,000
One 2.2-Meter Belt Press at $220,000, Plus
Installation at 20 Percent 264,000
Relocate Existing Belt Filter Press 33,000
Polymer System, lump sum 180,000
Sludge Transport Vehicles
Dump Trucks, 2 at $75,000 each 150,000
Aerated Static Pile Composting Facility
Grading and Drainage Improvements, lump sum 15,000
Paving, 31,000 sq yd at $14/sq yd 434,000
Composting Building, 32,400 sq ft at $5.20/sq ft 169,000
Aeration Blowers, 8 at $4,200 each 33,600
Aeration Piping, lump sum 100,000
Future Odor Control System Piping, lump sum 10,000
Electrical and Instrumentation Including
Lightning Protection, lump sum 110,000
Condensate Evaporation Pond, lump sum 21,000
Compost Curing Building, 13,000 sq ft at $5.20/sq ft 68,000
Finished Compost Screening
Grading and Drainage Improvements, lump nu 4,000
Paving, 400 sq yd at $14/sq yd 5,600
•
Screening Equipment, lump sum 3,000
Finished Compost Storage Building
Grading and Drainage Improvements, lump sum 5,000
Paving, 1,500 sq yd at $14/sq yd 21,000
Finished Compost Storage Building, 12,000 sq ft at $5.20/sq ft 62,000
Composting Equipment
Front-End Loaders, 2 at $150,000 each 300,000
Windrow Mixing Machine, 1 at $160,000 160,000
SUBDDI'A. $2,513,200
Contingencies at 20 Percent 503,000
TOTAL CAPITA, COST $3,016,200
TABLE E-12
OPERATION AND MAINTENANCE COSTS
AERATED STATIC PILE COMPOSTING or RAN SLUDGE
12-FOOT PILE HEIGHT
WITH AHEM= ADDITION
REPIACE:MT COSTS
Equipment Replacement
Sludge Handling Equipment Replaced at
10 Years with No Salvage Value
Dump Trucks, 2 at $75,000 each $ 150,000
windrow Mixing Machine, 1 at $160,000 160,000
Front-End Loaders, 2 at $150,000 each 300,000
Screening Equipment 3,000
TOTAL REP[. O:ME T COST 5 613,000
OPERATION AND MAINTENANCE COSTS
Labor
Operators, 6 at $32,400 per year $ 194,400
Mechanic, 1 at $32,400 per year 32,400
Supervisor, 1 at $38,400 per year 38,400
TOTAL LABOR COSTS $ 265,200
Fuel
7,300 Gal Per Year at $0.64 Per Gal $ 4,700
Power
284,000 kWh at $0.06 Per kWh $ 17,000
Chemicals
Polymer, 35,000 lb at $3 per lb $ 105,000
Amendment
4,000 cu yd at $6 Per cu yd $ 24,000
Maintenance
Sludge Transport Vehicles $ 4,000
Composting Equipment 9,000
TOTAL MAINTENANCE CASTS $ 13,000
TOTAL OPERATION AND MAINTENANCE COSTS $ 396,500
'ea.74
TABLE 6-13
CAPITAL COST
AERATED WINDROW COMPOSTING OF RAW SLUDGE
WITH AMENDMENT ADDITION
CAPITAL COST
Sludge Dewatering
Grading and Drainage Improvements, lump sum $ 5,000
Dewatering Building, 3,000 sq ft at $120/sq ft 360,000
One 2.2-Meter Belt Press et $220,000, plus
Installation at 20 Percent 264,000
Relocate Existing Belt Filter Press 50,000
Polymer Feed System, lump sus 180,000
Sludge Transport Vehicles
Dump Trucks, 2 at $75,000 each 150,000
Aerated Windrow Composting Facility
Grading and Drainage Improvements, lump sus 30,000
Paving, 22,000 aq yd et $14/sq yd 294,000
Composting Building, 65,300 sq ft at $5.20/sq ft 340,000
Aeration Blowers, 12 at $3,500 each 42,000
Aeration Piping, lump sus 200,000
Future Odor Control System Piping, lump sum 10,000
Electrical and Instrumentation Including
Lightning Protection, lump sum 110,000
Condensate Evaporation Pond, lump sum 21,000
Finished Compost/Amendment Storage Building
Grading and Drainage Improvements, lump sum 5,000
Paving, 1,500 sq yd at $14/sq yd 21,000
Finished Compost Storage Building, 12,000 sq ft at $5.20/sq ft 62,000
Composting Equipment
front—End Loaders, 2 at $150,000 each 300,000
Mixing Auger, 1 at $165,000 165,000
Windrow Mixing Machine, 1 at $160,000 160,000
SUBTOTAL $2,769,000
Contingencies at 20 Percent 554,000
TOTAL CAPITAL COST $3,323,000
TABLE E-14
OPERATION AND MAINTENANCE COSTS
AERATED WINDROW COMPOSTING OF NAM SLUDGE
WITH AMENDMENT ADDITION
REPLACEMENT COSTS
Equipment Replacement
Sludge Handling Equipment Replaced at
10 Years with No Salvage Value
Dump Trucks, 2 at $75,000 each $ 150,000
Front—End Loaders, 2 at $150,000 each 300,000
Mixing Auger, 1 at $165,000 165,000
Windrow Mixing Machine, 1 at $160,000 160,000
TOTAL REPLACEMENT COST $ 775,000
OPERATION AND MAINTENANCE COSTS
Labor
Operators, 4 at $32,400 per year $ 129,600
Mechanic, L at $32,400 per year 32,400
Suparvisor, 1 at S38,400 per year 38,400
TOTAL LABOR COSTS $ 200,400
Fuel
6,000 Gal Per Year at $0.64 Per Gal $ 4,000
Power
266,000 kWh at $0.06 Per kWh $ 16,000
Chemicals
Polymer, 35,000 lb at $3 per lb $ 105,000
Amendment
10,000 cu yd at $6 Per cu yd $ 60,000
Maintenance
Sludge Transport Vehicles $ 4,000
Composting Equipment 9,000
TOTAL MAINTENANCE COSTS $ 13,000
TOTAL OPERATION AND MAINTENANCE COSTS $ 398,400
•
.� .;_}
TABLE E-15
CAPITAL COST
CITY-OPERATED
SLUDGE OXIDATION IN A
VERTICAL TUBE REACTOR
CAPITAL COST
Vertech Equipment
Vertech Equipment (from Vertsch proposal), lump sum $2,912,000
Ash Transport Vehicles
Front-End Loader, 1 at $150,000 150,000
Dump Truck, 1 at $75,000 75,000
SUBTOTAL $3,137,000
Contingencies at 20 Percent 627,000
TOTAL CAPITAL COST $3,764,000
TABLE 6-16
OPERATION AND MAINTENANCE COSTS
CITY-OPERATED
SLUDGE OXIDATION IN A
VERTICAL TUBE REACTOR
REPLACEMENT COSTS
Equipment Replacement
Front—End Loader, 1 at $150,000 $ 150,000
Dump Truck, 1 at $75,000 75,000
TOTAL REPLACEMENT COST $ 225,000
OPERATION AND MAINTENANCE COSTS
Labor
Operators, 5 at $32,400 per year $ 162,000
Mechanic, 1 at $32,400 per year 32,400
Supervisor, 1 at $38,400 per year 38,400
TOTAL LABOR COSTS $ 232,800
fuel
1,500 Gal Per Year at $0.64 Per Gal $ 1,000
VTR Supplemental Fuel (Vertech proposal) 4,400
Power
622,000 kWh (Vertech proposal) at $0.06 Per kWh $ 37,300
Chemicals
Mid Mesh, $7/dry ton (Vertech proposal) $ 20,400
Oxygen, $53/dry ton (Vertech proposal) 155,000
Landfill of Ash
Tipping lees $ 5,500
Maintenance
AM Transport Vehicles $ 6,000
Vertical Tube Reactor and Support Systems,
$11/dry ton (Vertech proposal) 32,100
TOTAL OPERATION AND MAINTEZANCE COSTS $ 494,500
SC or 1
or
APPENDIX F
PUBLIC PARTICIPATION
ve C.84?Fg
APPENDIX F
PUBLIC PARTICIPATION
This appendix will review efforts made to solicit and incorporate public
comments into the City of Longmont's Solids Management Study. The
presentation ofthe public participation aspects of this study will be
presented in the same chronological order in which they occurred.
Organization of this appendix is as follows:
Page
Affidavit of Publication F-1
June 29, 1987 Article in the
Longmont Times Call F-3 •
July 1, 1987 Article in the
Longmont Times Call F-6
Public Bearing Attendance
Record, July 8, 1987 F-7
Public Bearing Minutes,
July 8, 1987 F-8
July 9, 1987 Article in the
Longmont Times Call F-10
.(2.cs24
AFFIDAVIT OF PUBLICATION JUL 141981
;hi
•
State of Colorado
County of Boulder
I, J. RC Hofmann ,do
NOTICE OF PUBLIC HEARING
i nnl swear that the LONGMONT DAILY TIMES CALL is a ChrT of LONOMoar i
Y wASTEWATERTREATMENT
FACILITIES PLAN
daily newspaper printed, in whole or in part, and published in SOLIDS MANAGEMENT PLANT
the City AIM M
Longmont, County of Boulder, State of Colorado, and TO WHOM IT MAIMS NCERN:ENT . .
which has enteral CIICU18t10II therein and in PLEASE NOTE THAT a public hearing will be
4 parts of Boulder and held at 7:70 P.M.on the Nh Car of July.1967 In
CouWeld Counties; that said newspaper has been continuously and Mei a a ThirdAvenue, Long�moont, Coloic Center rado.
uninterruptedly published for The public hearing is being held pursuant to TM*
pt period of more than siz months ParRegulais en 35 a the 7p, d Car of Femora
next prior to the first publication of the annexed legal notice of . THE PURPOSE of the public Mooring is to"-
advertisement, that said newspaper has been admitted to the Man amenublic review and comment to Me say's
Management eat • FacHNIont la tlw CSell-
ll-
United States mails as second-class matter under the provisions •
W�•hr Ttanmad aneUNNstion The mo-
provim0 fivesMoor treatment
PIN d M•val of
waste
Memo-
of the Act of March 3 1879,or an amendments thereof,and that Mne for tr.amaeaile waste a war audw
any plant Future
by the'CNps wctIon astewater Mea It ire•1lnenlf
said newspaper is a daily news phase F y t e cSoli s Manag the'Pan.will be
Partially papa y paper duly qualified for carton y f funded
sales grant from thee".asp al
pOW89W hasCons • Ras from 1M.Farm
publishing legal notices and advertisements within the meaning swap.�.Cannteticnm Greco��- .
of the laws of the State of Colorado;that copies of each number of roThe'gild`Management public hearin Plan will b Isi a"te°
P Iwwnd the plane h hearing
rusk istmony
-r attend ttM Plan.
ia. hNerxlp arse plug iMlmsnv
said newspaper, in which said notice of advertisement was regarding the Plan.
published, were transmitted by mail or carrier to each of the M�d docCopies umeents Mho Solids
bey available torte examine
BIIhBCIlbBrs of said news q tiro by the public otitis City of Lagmant Service •
paper, according to the accustomed Centen 1100 o mSae�mnwat'etrcda�mont,
CPI* i
mode of business in this office. trsl.Division dining manna' warkinp Maws.IS
AJs.la r P.M.),bopianlnp AN U.19M..
rublblNd In the Deily Times Call,.Lonrnad,
That the annexed legal notice or advertisement was published cant Join s,17,w,M,1967 . .
in the regular and entire editions of said daily newspaper:co e
imaxkwaexkioxitkeossaexiimpcmicaactuameak for the period of
4 consecutive insertions; and that the first publication of
said notice was in the issue of said newspaper dated
June 5 , 19 8,ind that the last publication of said
notice was in the issue of said newspaper dated
June 26 19 87 -
ti
n ral Manager
-inscribed and sworn to before me this 2 6th
. of June / ,19 87
Notary Public;
seTARJ- - My Commission Expires
October 6, 1989
717 • 4th Avenue
FEES 58-q4 a Longmont
urn% condo 80501
(rIC , �S Ad, 1.
F-1
a 1111.' LA11. 1 1111L'O"Las.LL
. Phones Times-Call Publishing Co.
303/776-2244 Post Office Box 299 Invoice
Metro 717 Fourth Avenue 8 Terry Street
444-3636 Longmont, Colorado 80501 No. C 14675
TO .City of Longmont MUE6-11-87
Civic Center P.O4,O02 2
Longmont, Co. 80501
Alice Hamon
DATE DESCRIPTION PRICE AMOUNT
$
June 5, 12,19,26, 1987
Hearing Wastewater Treatment
38 lines x 1 column 1st insertion .50 19.00
2nd,3r,4th insertions .35ea 39.90
58.90
Required affidavits for legol advertising will be mailed offer the last doy of publication.
/G y00�I`lo—V8/of_ �a
•
ask. 4s��y,r9
F-2
ant: 1W
. 1 c - iiitiLpvir .
1 al a: : oni affil. .
..f,11/4044010 i�l�j �� . .
i .'J-a�i i i. i
. 11ta n 1j $
� �111111"" e
2 ;atit�l i iG ix
a.:: tlil _
1 24 f•3 'p ply
•,• ;III 1 � day
i ;_. ig,
�' a
:. .. 14:24.1„
�. „ is tg, Jiltit
tis e �.� i ail .
1 'is Ili y
�. ilifill-iti rip ,
iil
- �. 1
i fil;)fil fif
M ills *Ml CeoIII1011%11 !if
-;'-i • 11 :mile' i ii
' 11111111 a
=ra $l' riEl 3ala� a
� Aibi illi t; it I
tra � $
�s.s PI
711. BMil�� $ 1 is il ill ii 11 '
= filii illlltill 2!_, I 8
- :I 1111; ;
F-3
CITY COUNCIL COMMUNICATION
June 30 , 1987
The Water Quality Division and Black and Veatch Engineers have
completed a study of treatment and disposal options for waste
sludge produced by the City' s wastewater treatment plant. This
study , known as the "Solids Management Plan, " completes the
planning work needed to proceed with the final portion of the
current wastewater plant expansion. The original planning study
( facilities plan) for the wastewater plant, which was completed in
1982 , did not address long-term options for sludge disposal . The
major reason for this was the construction of the Vertical Tube
Reactor (VTR) process in 1982 . VTR was developed as a joint
project between Vertec Inc. , the Environmental Protection Agency
and the City. Since this process was experimental and innovative,
actual operational experience was needed so that it could be
compared with other sludge treatment options . Since that time, an
evaluation of the VTR process has been completed. However, since
VTR was only operational for a short period of time in 1984 and
1985 the primary method of solids handling during the last five
years has been digestion of sludge followed by disposal on
agricultural land. A long-term land disposal program was not
developed because of the lack of comparison with other
alternatives . The Solids Management Plan provides such a
comparison .
City engineering and operations staff, in conjunction with Black
and Veatch and representatives of the University of Colorado,
initially developed a list of all conceivable treatment and
disposal options . After a thorough screening of these options ,
City staff decided which were appropriate to the City' s situation
and these were designated for further study. The Solids
Management Plan contains an evaluation of these sludge treatment
and disposal methods which examines their cost-effectiveness ,
reliability, long-term applicability and environmental impact .
The attached "Summary of Findings and Recommendations" includes a
discussion of the alternatives and a brief discussion of the
evaluation process used in the Solids Management Plan. The
evaluated alternatives include VTR, composting and land disposal ,
all of which the City has had experience with over the last five
years . VTR, although low in environmental impacts , proved to be
the most costly and least reliable process . Land application of
digested sludge was the least costly alternative, but its
applicability over the long term was judged to be questionable
because of the changing nature of state and federal regulations .
Composting of the sludge with disposal of the composted product on
agricultural land was found to be the most desirable alternative .
The use of composting for treatment also allows for possible co-
composting with municipal refuse in the future. It is proposed
that the composting facilities be constructed on the property
currently being used as the City landfill .
F-4 ,202
Since solids treatment facilities will be built with a federal
grant, the study must be approved by both the State Health
Department and Environmental Protection Agency. It is currently
being reviewed by the State. If a grant is offered after the
start of the Federal fiscal year (October 1 ) , design of the
facilities will be completed by spring of 1988 and construction is
scheduled to start in summer or fall of that year. The
construction period is estimated to last between 1 and 1-1/2
years, therefore the facilities will probably not be in place and
operational until the spring of 1990. Until then, land
application will probably continue to be used for sludge disposal ,
although an interim arrangement with Vertec for privatization of
sludge treatment is being actively pursued.
Construction and operation of the composting facilities will not
require any increase in sewer charges for City residents , since
the costs of the plant expansion, including solids handling , were
included in previous rate increases.
F-5
....--w
ni(a.,._
Sludge ,c-,6_ ,35-.c-- ...?./.
.?.
COIl1Yf� st In the meantime, he said, the I
pOS Yliig olwningty g the"Verrttiiccal Tube Re with the mo-
discussed tor" - an experimental device at
the wastewater treatment plant
By JOHN FRYAR that also can reduce sludge to wa-
ter and ash — to reduce Long-
Times Call Staff Writer mont's sludge volumes until the
The proposal to build a 83.8 mil- , composting firm might facility
be allowed y. The
lion facility for composting Long- han-
dle sludge and non-toxic industrial
mont's sewage sludge is in a"very �
preliminary" stage, the city coun- . ' wastes from private businesses
cil was told Tuesday night by Ar- and other communities in that
den Wallum, director of the • VTR,since Longmont does not pro-.
municipal utilities deparltaent's duce enough sludge by itself to
water quality control division keep the equipment going full-
While the council is not yet being time.
- asked to take.action on the plan, -i Councilman John Caldwell asked
Councilman Bill Swenson and seve- j Walkup to submit more detailed :
ral of his council colleagues ex- information from an analysis by
pressed interest during Tuesday the city staff and a consulting engi-
night's study session on a possible neering firm abed Longmont's op-
side benefit to establishment of a tions for disposing cif its sewage
composting process — the use of sludge.
. such a facility to compost organic As part of the process of getting
solid waste picked up in Long- the necessary state and federal ap-
mont's residential trash collect- proves prior to applying'for a
tions,along with the sewage sludge grant for the wastewater treat-
generated by the wastewater treat- ment plant's "solids management
ment plant. plan"for the treatment and dispo--.
Such composting of trash and sal of waste sludge, a public hear-
garbage — after metals, plastics, ing has been scheduled for 7:30
glass and other non-biodegradable p.m. July 8, in Courtroom 2 of the
. items are separated out — could Civic Center Complex, Third Ave- •
help the city achieve a goal of re- nue and Emery Street
during its dependence on limited A more detailed presentation
landfill space for disposing of solid about the-composting plan and
waste. Longmont's other-options for deal-
• • Wallum said it has been esti- j ing with sewage solids is to be
mated that composting could re- made at that hearing.Copies of the
duce the volume of such organic ( solids management plan are avail-
solid waste by 75 percent. able for public examination at the
He also said,however, that even water quality division offices in the
- if a$1.86 million federal grant can city's Service Center'building,1180
be obtained to help pay for the pro-
posed I S. Sherman St
sludge composting facility,it , - ------ -
could be three to five years from
now before the process is in opera-
lion:
ZO /v6 /nPA 7/ --
., ,it_e_ y % 79(5 7 -
�� U
594
F-6 -
ATTENDANCE RECORD
LONGMONT, COLORADO
SOLIDS MANAGEMENT PLAN
JULY 8, 1987
PUBLIC BEARING
Name Address
Mark Maxwell Black & Veatch/Aurora, Colorado
Dan Linstedt Black & Veatch/Aurora, Colorado
Mark Lang Black & Veatch/Aurora, Colorado
Arden Wallum •
ACity of Longmont/Longmont, Colorado
Calvin Youngberg City of Longmont/Longmont, Colorado
Grant Grover City of Longmont/Longmont, Colorado
Debbie English Colorado Department of Health/Denver, Colorado
John Chase Colorado Department of Health/Denver, Colorado
William Schwoyer VerTech Treatment Systems/Denver, Colorado
Larry Jaycox VerTech Treatment Systems/Denver, Colorado
Greg Jordan E.C.O. Products Company/Longmont, Colorado
John Jordan E.C.O. Products Company/Longmont, Colorado
R. J. Crowley Local/Boulder, Colorado
Jeffrey D. Thomas Longmont Times Call/Longmont, Colorado
0rvL S
1
JUL 161987.E j
BLACK g, VEA1O.41 CITY OF LONGMONT
SOLIDS MANAGEMENT STUDY
QUESTIONS AND COMMENTS AT PUBLIC HEARING OF JULY 8 , 1987
The following is a summary of the questions and comments received
at the public hearing for the solids management study ( facilities
plan addendum) on July 8, 1987 . The responses that were provided
by the City and Black and Veatch are also summarized.
1 . John Jordan asked if the $0 . 36 per user costs were in
addition to existing charges and taxes and in addition to what
the City pays to match the grant.
The City and B&V explained that the $0 . 36 was for O&M costs
only and that this did not apply to the capital costs (which are
the only costs covered by grant funding) . In other words , no
debt service is included in the $0 . 36 per user which was
presented in the plan.
2 . John Jordan asked for a breakdown of the capital and O&M
costs of the alternatives .
He was provided with a summary of these costs and a copy of
the solids management study.
3 . John Jordan commented on the odors generated by the
composting operation especially during mixing/remixing . As an
example, he cited the operation in Loveland which mixed sludge
with manure for compost. He asked what the City intended to do
about the possible odors .
The City and B&V explained that odors were generally caused
by moisture problems in the compost mix and that control of
moisture content in the sludge would minimize the problems . It
was also explained that the facility would be enclosed on three
sides and covered to minimize the effects of weather on the
compost operation. B&V also pointed out that the proposed
operation was for static pile, not windrow composting, thereby
minimizing the necessity for remixing and physically aerating the
piles .
4 . Jordan asked why the regulatory aspects of compost were not
rated the same as those for land application (re : the alternative
rankings in the study) , since the compost is also proposed to be
disposed of on land.
T 5 . The City responded that the end product of composting is not
impacted as much by the changing nature of the regulations
because of the different options for disposal (land application,
landfilling, etc. ) and because of the large reductions in volume
of solids to be disposed. B&V explained that even though
composting would concentrate some constituents , such as metals ,
the composted product would still be eligible for use on land.
In addition, the composting process is rated as a PFRP (Process
to Further Reduce Pathogens ) and also removes much of the
• nitrogen in the sludge, thereby increasing the disposal options
for the compost.
vrelt>p
As-
F-8
Public Hearing Comments
Page 2
6 . John Jordan noted that the ash from the VTR process , which
was hauled by him when VTR was operational , was difficult to
dispose of since most disposal sites would not accept it.
Bill Schwoyer (Vertech) noted that they have arrangements
with a brick manufacturer to take the ash.
7 . Bill Schwoyer (Vertech ) asked how odor control at the site
would be managed.
B&V responded that if odor control was needed, air in the
initial mixing and aeration area of the composting building would
be vented to a wet scrubber using both basic and acid solutions .
The recycle stream from the scrubber would probably be trucked
back to the treatment plant. It was also noted that odor control
was not included in the costs because of the remote location of
the site and the feeling that proper process control would
minimize any problems .
8 . Jordan asked how large the composting area was going to be
and what kind of structure was envisioned.
B&V responded that the total site would be 5 acres , with the
area to be covered by buildings approximately . 3 acres of the
total . The buildings would be metal , treated appropriately to
prevent corrosion.
.(Vet2 4
F-9
,
/`I 2 L
Timm &E, leortma, ly 9, X967
Hearing focuses �
on compost plan !4
By JEFF THOMAS ceive four out of four points for 1
Timin Call Staff Writer its odor problems in.a ranking 1111
What should Longmont do with scheme of the options considered
by the Waste Water
eight tons of sludge that is pro- E bei
ng desisirraa on le
jected to be produced daily fromran t°g the least desirable
the city's wastewater treatment whichwould ing, Bus y u
be located at the
facility by the year 2800? • current city landfill site,signiH-
According to a presentation by qtly outranked the other op-
Black and Veach, an engi- lions in areas of reliability,
neering firm consulting for the flexibility, qty and op a
city on a 20-year Solid Waste erational complexity. j
Management Plan, the sludge Cal Youngberg, an engineer
can be: shipped either by the with the Waste Water Division,
city or private contractors for said odor problems will be cut
land application; composted in down by a three-sided building
an aerated"He", or shat down surrounding the project and oth,
e ��Pr'es- scrubbing"o oxidize imder er sus — such as an "sin.
sure. machine—could be
The ;3.8 �n t put is place if the odor problem
compost
t plan grew too severe.
was endowed by
Water Division and the consul- ager f� �� ea� said
Cant engineers at a public hear- the company expects as much as
ing Wednesday night. However GO pent of the cost of initial
one local resident said the com- capital casts of the project could
lost plan will produce a more be grant eligible.
odorous problem than other ap- Operational costs of the com-
tions• post facility, L.instedt said,
"It's by far one of the most would be 38 cents per resident—
smelliest operations I've ever a most Youngberg said has al.
experienced," said John Jordon ready been figured into the cur.
of WM Lamplighter Drive. Jon. rent user rates,
don has bean transporting The Longmont Qty Council is
sludge for the city since 1974,he expected to consider the project
said. in about a month, Youngberg
The compost operation did re- said,
•
ti c-
a..i r .ly. q .
F-10
SOLIDS MANAGEMENT STUDY
CITY OF LONGMONT
Addendum
Prepared by
City of Longmont Water Quality Division
June, 1989
FM',A
TABLE OF CONTENTS
Title Page
I . BACKGROUND 3
II . SUMMARY OF FINDINGS 4
III. CHANGES TO SOLIDS MANAGEMENT PLAN 5
IV. ENVIRONMENTAL ASSESSMENT 12
V. COST ESTIMATES 13
VI . FINANCIAL IMPACT 18
VII . SUMMARY AND CONCLUSIONS 19
APPENDIX A 20
APPENDIX B 21
LIST OF FIGURES
Title Page
Figure 1 - Project Site Location 7
Figure 2 - Location of Thickener 9
LIST OF TABLES
Title Page
Table 1 - Comparison of Building Construction Costs 5
Table 2 - Design Criteria for New Thickener 8
Table 3 - Composting Operation Design Criteria 11
Table 4 - Capital Cost Summary, Aerated Static Pile 14
Table 5 - Operation and Maintenance Cost Summary 16
Table 6 - Solids Management Alternatives Cost Summary 17
�� ro
-2-
I . BACKGROUND
I
The Solids Management Study for the City of Longmont was approved
by the State Health Department and EPA in 1988. The study, which
was prepared by Black & Veatch Engineers, recommended
construction of sludge composting facilities at the City' s
existing landfill site. Following approval of the study, another
consultant, Camp, Dresser and McKee, was hired to complete the
design portion of the project. The first design task, referred
to as "predesign," was an evaluation of some of the
recommendations in the Solids Management Study in order to more
closely define the scope of the solids handling project. The
predesign effort used a workshop approach to assess the
applicability and costs of these recommendations. The consultant
and City engineering and operations staff were all equally
involved in the workshops. The specific items that were re-
evaluated are as follows:
1 . Transporting sludge to the composting site via pipeline vs.
transport by truck (the latter was originally recommended in the
Solids Management Study) .
2 . In-plant thickening, dewatering and storage capabilities.
3 . Sizing and type of mixing and aeration equipment for sludge
composting.
4. Sizing and configuration of buildings at the composting
site.
5 . Assessment of odor control alternatives for composting site.
6 . Change in location of the project because of problems with
probable settlement and methane production at the landfill,
making it an unsuitable building site.
This Addendum presents the conclusions of the predesign
evaluation and the proposed modifications to the Solids
Management Study.
to
-3-
II . SUMMARY OF FINDINGS
The predesign effort resulted in the following conclusions :
1. Transport of sludge to the composting site via truck was
confirmed to be the most cost-effective and flexible method. No
change to the recommendations of the Solids Management Study is
necessary.
2. An additional sludge thickener at the WWTP was found to be
necessary for reasons of storage volume and reliability of
thickening operations. The belt press was re-sized to reflect
projected sludge quantities and equipment life. Polymer usage
was reviewed and adjusted based on actual operational experience
at the wastewater plant.
3 . The equipment used in the composting operation was revised
to be more applicable to the type of operation that is proposed.
Batch-type, mixing equipment was found to be more appropriate and
less costly than the windrow mixer originally proposed in the
Solids Management Study. The design of the sludge aeration
system was also refined with respect to blower sizing and the
type of aeration piping to be used. However, the basic
recommendations of the Solids Management Study were not modified.
4 . The sizing of of the composting, mixing and curing buildings
at the composting site was revised based on more specific
composting design criteria than what was available in the
original Solids Management Study. An operations building was
also added, since it was not included in the Solids Management
Study and is necessary for operations personnel at the site.
5 . Odor control alternatives were evaluated and, as in the
Solids Management Study, dispersion and dilution were chosen as
the preferred methods. The mixing building, where a major
portion of the odors will probably be generated, will be vented
through a low-cost finished compost/soil scrubber pile. As the
study recommended, provisions will be made for venting the
buildings through chemical scrubbers or other odor control
facilities if it becomes necessary to do so in the future.
6 . A site adjacent to the landfill, which does not contain
trash fill or other problem materials, was identified as a
possible site for the composting facilities . Purchase of the
site was recommended.
Costs of these changes were incorporated into the project cost
estimates and the cost-effectiveness analysis in the Solids
Management Study was revised. There was essentially no change in
the cost of composting relative to other alternatives evaluated
in the Study. Environmental and financial impacts were also re-
analyzed and found to be the same as in the original Solids
Management Study. Therefore, it was confirmed that aerated
static pile composting was still the most cost-effective and
environmentally acceptable solids handling alternative.
III . CHANGES TO SOLIDS MANAGEMENT PLAN
The predesign effort resulted in several recommended changes to
the facilities plan. Essentially, they are all refinements of
the project as - originally proposed, and do not change the
relative cost-effectiveness of composting or any other aspects of
the original alternative evaluation, including environmental
impacts. The changes and the resulting revised cost estimates
are discussed in the following sections.
A. Project site relocation
During the preparation of the Solids Management Study the City' s
solid waste division was asked to provide information about which
areas at the City landfill would be usable for the sludge
composting. facilities. Based on the available records of fill
material, which were sketchy for the areas in question, the solid
waste division recommended keeping any structures as close to the
North boundary of the landfill as possible. In March of 1989,
soil borings were taken at the proposed site on the landfill.
The results of these borings are contained in Appendix A. Trash
depths under the ,proposed locations of the composting structures
ranged from 10 feet to over 40 feet. Based on these results,
cost estimates were prepared for corrective measures which would
be needed to allow construction of the composting facilities on
the landfill. Table 1 shows the results of the cost estimates
and a comparison with "standard" construction costs at a site off
the landfill. For purposes of these estimates, the cost of an
off-landfill site was estimated at $11,000 per acre, based on
property values in the area east of the landfill. The composting
facilities will require 11 acres to provide buffer zones and
comply with other land use considerations.
TABLE 1
Comparison of Building Construction Costs
Building Cost Building Cost
Buildings/Facilities On Landfill Off Landfill
Composting/curing bldgs. $908 ,00O $596 ,000
Mixing/storage bldgs. $229 ,000 $181 , 000
Sitework $224,000 $272 , 000
Land cost 11 . 0 acres @ -0- $121 ,000
$11 , 000/acre
Totals $1 , 361 , 000 $1 , 170 ,000
The higher values for construction on the landfill stem from the
need for caissons to support the buildings, additional grading
and excavation and gas collection/ venting systems to treat
methane and other off-gases. The costs are for construction
only, and do not include future costs for re-grading and re-
paving associated with settlement of the land at the site. Since 1
the landfill will probably settle as much as 100 over the next 20
years , these costs could be significant.
-5-
Because of the cost difference noted in Table 1 and the future
settlement and environmental problems associated with
construction on the landfill, it is recommended that the
composting facilities be constructed at a site other than the
landfill. However, a new site needs to be close to the original
in order to avoid avoid any additional environmental impacts.
Proximity to the landfill is also required to accommodate the
planned disposal of compost at the landfill and minimize disposal-
related transportation costs. A review of property in the area
found that the land adjacent to the North landfill boundary is
available. Construction on this property would move the
composting facilities approximately 500 feet to the North of
their original location. The locations of the original site and
the proposed site are shown in Figure 1.
The new site presents several implementation problems. First, if
Federal funds are to be used for purchase of the land, an
appraisal to determine fair market value is required. Second,
proper zoning, as well as a Certificate of Designation for a
waste processing facility, need to be obtained from Weld County.
Although the property is currently zoned for light
industrial/commercial use, Weld County officials have indicated
that there would be no problem with rezoning the property for use
as a composting facility. They have also stated that the
Certificate of Designation for the existing landfill could be
modified to include a sludge processing facility and that it
could be extended to the new property following rezoning.
B. Thickening, dewatering and sludge storage at WWTP
One of the original findings of the Solids Management Study was
that the existing thickener at the wastewater plant did not have
sufficient capacity for the projected sludge loadings . Also, the
sludge removal rate required to feed the belt presses in an 8-
hour shift was found to be 152 gallons per minute, which is too
high for proper operation of the thickener (over 65 gallons per
minute causes the sludge blanket to be pulled out and dilution of
sludge) . The Solids Management Study recommended additional
piping to the digesters and belt presses or separate sludge
storage tanks to solve this problem. However, the Study failed
to include any facilities or costs associated with these
recommendations. The Study' s evaluation of the thickener also
did not account for the lack of unit process redundancy.
During predesign, several thickener operation options were
analyzed, including one of those mentioned in the Solids
Management Study, the use of storage tanks for buffering the
sludge drawoff from the thickener. Storage tanks were ruled out
since the existing thickener has inadequate solids capacity to
handle design year loadings and could not produce adequately
thickened sludge for later dewatering by the belt presses . This
indicated that a second thickener was necessary. An additional
reason for a new thickener was provided by its ability to serve
as a sludge storage tank. Since the assumptions for operation
of the composting project were based on an 8 hour day and 5-day-
per-week operation, sludge must be stored in the plant over
-6- VArGSA CJ1
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Figure 1
Project Site Location
- "C;C g•� "9fR •
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weekends, which can last up to three days. Two thickeners would
provide adequate sludge storage, allow the belt presses to be fed
at a rate of less than 65 gpm and still provide for retention of
waste sludge over weekends. Lack of redundancy in a critical
part of the sludge treatment operation is an additional reason
for a second thickener. The existing thickener is the only unit
of its type at the plant. Gravity thickening to 6% solids is
essential to provide proper solids concentrations to both the
digester and the belt press. If the thickener were to go out of
service for any length of time, even a few days, it would not be
possible to dewater sludge to an adequate concentration for
composting. Although unthickened sludge could be routed to the
digesters, several days' production would reduce their treatment
capacity and cause operational upsets. Dewatering the sludge to
the necessary 23$-25% after partial digestion would also be
difficult. Two thickeners are also necessary to provide capacity
for future sludge loads and allow the use of either thickener as
a backup unit to prevent operational upsets.
For the above reasons, the addition of a second thickener
identical to the existing unit is recommended. The design
criteria for the thickener and the available storage volumes and
underflow rates are shown in Table 2.
TABLE 2
Design Criteria for New Thickener
Design year ( 2010 ) sludge production = 8 . 5 dry tons/day
Solids loading at design year ( 2010) = 22 ,800 lb/day
Solids loading capacity = 14,400 lb/day
Maximum sludge withdrawal rate = 65 gpm
Sludge storage required = 138,000 gallons ( 3 days
production)
Storage available per thickener ( 4 ft. blanket) = 29 ,000
gallons
Storage available per thickener ( 8 ft. blanket) = 58 , 000
gallons
Thickener diameter = 35 feet
Thickener depth = 10 feet
A new pump station will be constructed next to the new thickener
and will be tied into the existing belt press feed piping. The
locations of the new thickener and pump station are shown in
Figure 2 . Costs for the thickener are reflected in the cost-
effectiveness analysis and cost estimates in Part V.
Belt press size was also evaluated during predesign. The Solids
Management study recommended a new 2 . 2 meter press to supplement
the City' s existing 1 . 2 meter unit. Sludge production in the
year 2010 would require belt presses capable of handling 152
gallons per minute. A single 2 . 2 meter press has the capacity
for this amount. The Solids Management Study called for the City
to purchase a new 2 . 2 meter press in the future when sludge
-8- °I1.191944
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Figure 2 •
Location of New Thickener at WWTP
F,24
production was high enough to justify it. However, the actual
rate of increase in sludge production is unknown and a 2 . 2 meter
press may provide extra capacity that is not currently needed.
Running a larger press below its design loading rate is also
inefficient. Based on these reasons, a new 1.2 meter press is
recommended. The use of two 1. 2 meter machines will provide a
capacity of 160 gallons per minute, which is essentially the
projected 2010 loading rate. If one press is out of service, a
1 . 2 meter unit can be loaded at approximately 110 gallons per
minute for short periods of time and perform acceptably. In
conjunction with the storage provided in the thickeners, belt
press capacity should be adequate until a replacement is needed
in the future. Costs for the 1. 2 meter belt press are included
in the cost analysis in Part V.
Polymer usage for dewatering sludge was also reviewed. Operation
of the City' s existing belt press as well as demonstrations of
other manufacturers ' units at the WWTP have shown that, with
proper polymer mixing, polymer usage is approximately 3-5 lb. per
dry ton of sludge. Chemical costs were revised to reflect this
figure and are included in the costs analysis in Part V.
C. Compost Operation and Unit Process Sizing
Both the size of the proposed composting building and the type
and size of the unit processes to be used in composting were
examined during predesign. The recommended changes are a
refinement of the original concept proposed in the Solids
Management Study. Positive aeration was chosen as the most
applicable aeration method. After reviewing several aeration
methods, it was decided that aeration piping that can be laid out
and connected in place and varied to match the compost pile
configuration would provide the most operational flexibility.
Blower size was also re-evaluated based on recent information on
positive aeration. Many of the problems with composting systems
around the country, such as odors and inability to achieve
stability criteria, have been shown to stem from inadequate
aeration. Research by Rutgers University, as well as the City' s
own pilot operation, show that an acceptable aeration rate is
135 cfm per dry ton of sludge. Since there will be 24 active
composting piles at any given time and each will be controlled by
temperature feedback, 24 blowers are required. The curing piles
will also be aerated, although at a much lower rate.
Mixing of sludge and amendment was also evaluated. The original
Solids Management Study recommended a "Scarab" type of windrow
mixer. Static pile systems, however, do not need to be turned
and mixed on a regular basis , so this type of mixer is
unnecessary. It has also proved to be a costly and maintenance-
intensive unit in other projects. After reviewing several
different mixer types, in-place "box" mixers were chosen. These
can be filled with sludge and amendment with a small loader; the
total cost of mixers and loader is less than the "Scarab"
originally proposed. The in-place mixers have an additional
advantage in that they are equipped with load cells which allow
for direct measurement of sludge and amendment as they are mixed.
-10- �ip1
•1Ce ?,4S
Other recommendations for the composting buildings and equipment
remain as in the Solids Management Study. The design criteria
for the compost operation are shown in Table 3 . Capital and O&M
costs for the revised composting operation are contained in Part
V.
TABLE 3
Composting Operation Design Criteria
Unit Size/Capacity
Composting/curing building 229 ft. x 335 ft.
20 ft. high
Compost aeration blowers 24 x 5 H.P.
1148 cfm/blower
Curing aeration blowers 8 x 2 H.P.
30 cfm/blower
Polyethylene aeration piping. 6-inch diameter
3 x 90 feet/pile
3000 feet total
Mixing building 80 ft. x 35 ft.
20 ft. high
Mixing equipment 2 x 18 . 5 cu. yd.
60 H.P. mixer
D. OPERATIONS BUILDING
The Solids Management Study did not include any accommodations
for the operators at the compost site. This appears to have been
an oversight. The site is three miles from the wastewater plant
in a rural area. Many pieces of equipment, including the loaders
and the aeration blowers, will have to be maintained on site. In
addition, the operators will be constructing the aeration piping,
loading the mixers, building the piles and performing operational
testing, and setting and controlling the blower operation. It is
apparent that the operators will not have time or be able to use
the wastewater treatment plant facilities, and that an operations
building is necessary. A metal, two-story building is proposed
which contains a locker room and shower, a small operator ' s lab,
a break room, a supervisor ' s office and a shop/vehicle work bay.
The building area would be approximately 3000 sq. ft. The
estimated cost of the building is $130 , 000 , and is included in
the revised capital costs shown in Part V.
IV. ENVIRONMENTAL ASSESSMENT
The changes outlined in Part III . are, for the most part,
refinements of the original plan as proposed in the Solids
Management Study. Although the facility location is different
(by 500 feet) , the new site is within the same area analyzed in
the Study. Environmental impacts associated with the new
location are therefore identical to those described in the
Study. Since odor was identified as an impact of concern, the
City decided to review and augment the work originally done on
odor dispersion. An analysis of wind direction and speed was
performed as part of the predesign activities. This analysis,
which is contained in Appendix B, shows that the predominant
winds at both the original and new sites are from the west and
northwest, with daily movement from the southwest during the
warmer months. Vertical dispersion will also be enhanced by the
use of large updraft fans in the composting and curing building.
These facts, coupled with the location of the project site,
reinforce the conclusion of the Solids Management Study that
dispersion is the most applicable primary odor control strategy.
None of the otherienvironmental factors, including the subjective
ranking of alternatives, is affected by the changes in the
project described in Part III. Therefore, the environmental
assessment in the Solids Management Study still applies and no
modifications are necessary.
P� T -
-12- '.l ,a
V. COST ESTIMATES
The revised capital cost estimates for both the in-plant
modifications and the composting facilities are shown in Table
4 . Operation and Maintenance costs are shown in Table 5. A
revised present worth comparison of alternatives, based on Table
4-1 in the original Solids Management Study, is shown in Table
6. The present worth analysis shows that the cost of the changes
outlined in this Addendum has not altered the relative cost-
effectiveness of the aerated static pile alternative. It remains
the alternative chosen by the City for reasons of cost, ability
to meet future regulatory requirements and operational
flexibility.
-13- ern
ct>4
TABLE 4
Capital Cost Summary
Aerated Static Pile Composting
5-foot pile height
Item Capital Cost
In-Plant Improvements
Sludge Dewatering
Dewatering Building $306,000
New 1. 2 meter belt press 180,000
Relocate existing 1. 2 meter press 15,000
Liquid sludge loading facility 5 ,000
Polymer system 105 ,000
Installation 188,000
New Thickener
Thickener tank and equipment 81,000
Thickener pump station 122,000
Installation 63 ,000
Site Improvements
Demolition 5 ,000
Paving 25 , 000
Relocate waste gas burner 15, 000
Yard piping 90, 000
Electrical improvements 50, 000
In-Plant Sub-Total $1, 250 , 000
Composting Facilities
Land, 11 . 0 acres @ $11, 000/acre $121 ,000
Static Pile Composting Facility
Composting/Curing Building, 76 ,715 sq. ft. 254,000
Mixing/Storage Building, 7 ,800 sq. ft. 191,000
Paving, 11, 250 sq. yd. 93 , 000
Compost aeration blowers, 24 @ $7 ,000 168 ,000
Compost curing blowers, 8 @ $5 ,000 40 ,000
Roof ventilation fans , 9 @ $5 ,000 45 ,000
Aeration piping 75 , 000
Electrical and control systems 220 , 000
Composting Equipment
Dump Trucks, 1 @ $45, 000 45 , 000
Loader, 1 @ $175, 000 175 , 000
Large skidsteer, 1 @ $54 , 000 54 , 000
Small skidsteer, 1 @ $18 ,000 18 ,000
In-place box mixers , 2 @ $80,000 160 , 000
-14- ET'0F:7,4
TABLE 4
(Continued)
Capital Cost Summary
Aerated Static Pile Composting
5-foot pile height
Item Capital Cost
Sitework and Improvements
Grading and Drainage Improvements 155,000
Landscaping 23,000
Paving 66,000
Access road reconstruction 57,000
Fencing 10,000
Sanitary Sewer 75,000
Jack and Bore (Highway crossing) 35,000
Utility Service Connections 12,000
Operations Building
Building, 3 ,000 sq. ft. 130,000
Electrical 5, 000
Water system and storage tanks 32,000
Furnishings 18,000
Weather Station 10,00O
Composting Facilities Sub-Total $2 , 287,000
Total, In-plant and composting $3 , 537 ,000
15 o Contingency 530, 550
GRAND TOTAL $4 ,067 , 550
IC.NneS24
-15-
TABLE 5
Operation and Maintenance Cost Summary
Aerated Static Pile Composting
5-foot pile height
Item O&M Cost
Replacement Costs (Sludge handling equipment
replaced at 10 years, no salvage value)
Dump Trucks, 1 @ $45,000 $ 45,000
Loader 175,000
Large skidsteer 54,000
Small skidsteer 18,000
Total Replacement Cost $292,000
Operation Costs
Labor, 4 operators @ $32, 400/yr. $129 , 600
Labor, 1 mechanic @ $32,400/yr. 32,400
Labor, 1 Supervisor @ $38,400/yr. 38,400
Fuel, 7, 300 gals/yr. @ $0.64/gal. 4,700
Power, 706, 275 kwh/yr. @ $0.06/kwh 43 ,000
Polymer, 15 , 500 lb. @ $3 .00/lb. 46 , 500
Maintenance Costs
Loaders and dump trucks 4,000
Composting equipment 9 ,000
Total O&M costs $307 , 600
rAnCi3 i
-16-
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VI . FINANCIAL IMPACT
As noted in the Solids Management Study, the addition of the
sludge composting operation is not expected to have any effect on
the City of Longmont' s rates or charges to customers. Operators
for the new facilities will be taken from the existing staff
positions, therefore salary expenses are already included in the
existing plant budget. There are sufficient funds in the
wastewater operating fund to cover all other O&M expenses
incurred by this project. The City passed its sewer use
ordinance in 1983 and raised user rates enough to fund future
sludge treatment and disposal operations.
The local matching share for the capital cost portion of the
project will be provided by borrowing against operating revenues.
This was also done during the previous plant expansion ( 1985-
1987) . The City has analyzed these revenues and determined that
they are adequate to fund the local share.
Therefore, the solids handling project will have no additional
financial impact on the users of Longmont' s wastewater system.
. !a
r {
-18- �,. ,
VII . SUMMARY AND CONCLUSIONS
The City of Longmont and Black & Veatch Engineers completed a
Solids Management Study in 1987, which was approved by the State
and EPA in 1988. Portions of the solids handling project
described in that Study were re-evaluated during the initial part
of the project' s design phase. In-plant equipment needs were
examined, resulting in the recommended construction of a new
thickener and reduction in size of the belt press. Design
assumptions for the composting part of the project were revised
to account for recent developments in composting operation.
Building sizes were reduced and the size and number of blowers
were modified accordingly. Potential problems with construction
on the City' s existing landfill resulted in a change in the
location of the composting facilities. Finally, an operations „
building was added at the composting site to provide the
operators with work space, a locker room, offices and an
operations lab.
Capital and O&M costs were developed for the recommended changes
and a present worth analysis was performed to compare the revised
project to the other alternatives originally evaluated in the
Solids Management Study. The changes in the project reduced the
present worth of aerated static pile composting from $7 , 141,890
to $6,990 ,683 . Costs for the other alternatives remained
unchanged. The lower cost for static pile composting did not
alter its relative position in the comparison; within the
accuracy of cost estimating at this point, it is still equal to
the least cost alternative.
There were no additional environmental factors or financial
impacts due to the changes in the recommended project. The
assessment of these items in the Solids Management Study remains
unchanged.
.:f � _ ;
-19-
APPENDIX A
, Soil borings at landfill
-20-
- Empire Laboratories, Inc. CORPORATE OFFICE
P.O.Box 503•(303)484-0359
GEOTECHNICAL ENGINEERING 8 MATERIALS TESTING 301 Na Howes• Fon Collins,Colorado 80522
March 16 , 1989
City of Longmont
Water & Sewer Department
1100 S . Sherman hwR u0 MS
Longmont, CO 80501
Attention: Mr. Cal Youngberg
RE: Composting Facility
r
Longmont, Colorado
Gentlemen:
Enclosed please find a test boring location plan, key to borings
and log of borings from the drilling performed at the original
.location of the proposed composting facility as per your request .
If you have any questions, please contact us .
Very truly yours ,
EMPIRE LABORATORIES, INC.
Li pCL‘b
Edward J . Paas , P . E.
Longmont Branch Manager
Colorado Registration #15776
cc : Camp , Dresser & McKee
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'P Branch Offices
W
- fl0.On: i 0859 RO.80.t 135 PO.Box 1744 PO.Boa Sfi 59
�f /= Colorado Boom's.CO90935 Longmont,CO 80502 Greeley.GO606J2 Cheyenne,`/✓1'8200]
,y 7 Ut9I 59 PLn0 (]03)]]6-]921 13031350460 00]1632.9224
.1.��!/ Memberol Consulting Engineers Council
TEST BORING LOCATION PLAN
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EMPIRE LABORATORIES, INC.
LOG OF BORINGS
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EMPIRE LABORATORIES, INC.
LOG Of BORINGS
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EMPIRE LABORATORIES, INC.
1
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1 SHELBY TUBE SAMPLE
STANDARD PENETRATION DRIVE SAMPLER
WATER TABLE 0.0 hrs AFTER DRILLING
C HOLE CAVED
5/12 Indicates that 5 blows of a 140 pound hammer falling 30 inches was required to penetrate 12 inches.
V t92(9'L
EMPIRE LABORATORIES-INC.
LOG OF BORINGS
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90 14/12
13 12
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_ 85 _ / 20/12
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EMPIRE LABORATORIES, INC.
LOG Of BORINGS
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EMPIRE LABORATORIES, INC.
LOG Of BORINGS
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EMPIRE LABORATORIES, HNC
APPENDIX B
Odor dispersion/prevailing wind analysis
Dre, l>
-21-
MEMORANDUM
TO: Cal Youngberg, City of Longmont
Roger Hartman
Design Files
FROM: Brian Janonis
SUBJECT: Compost .Odor Sources & Control
DATE: October 18, 1988
Odor management techniques can be characterized in ways.
The WPCF Manual of Practice No. 22 considers source control,
chemical addition, incineration and other thermal processes,
precipitation, condensation, dispersion/dilution, filtration and
containment as practical techniques for controlling .odors in was
tewater. facilities. For the purposes of this report, odor
management techniques will be divided in three areas of activity.
1. Reduction df odorous compounds or odor precursors at the
source.
2. Deodorization and treatment.
3. Dilution and dispersion.
A. Sources
Sources of odors at the compost facility will include the follow-
ing areas:
Sludge trucks
Mixing area
Composting building
The site
The sludge trucks will haul raw sludge from the wastewater treat-
ment plant to the compost facility. Care should be taken to
clean them and to cover the box.
The most odorous part of the pilot program was the mixing. Care
should be taken to minimize the time raw sludge is kept at the
mixing area and mixing should be done when atmospheric conditions
are the most favorable.
The compost building will have the largest area of odorous
material on the site. Here it is important to provide conditions
to maximize the rate of aerobic decomposition. Aerobic decom-
position yields predominantly CO2, H2O and stabilized organic
residue; anaerobic conditions yield strong unpleasant odorous
compounds. Good aerobic conditions in compost include adequate
aeration, temperature, free air space, a uniform mix and good
( moisture conditions.
The site itself can be a source of odors if adequate drainage and
good housekeeping is not performed. erilreru
B. Deodorization
Deodorization is the neutralization, chemical conversion or cap-
ture of odorous compounds. Chemical conversion includes flame,
thermal, and catalytic combustion, chemical reaction and chemical
oxidation. Odorant capture can be by wet scrubbing, adsorption
and absorption.
Combustion techniques include flame, thermal, and catalytic
combustion. Complete combustion is generally considered to be
the best way to deodorize:foul-smelling gases (1). In thermal
oxidation, odorous gases are preheated and passed into a combus-
tion chamber. Thermal oxidation is generally done in the range
of 1200 to 1600 degrees F and requires a minimum residence time
of 0.3 seconds.
Flame oxidation is most effective for controlling high concentra-
tions of odorous gases in low volumes. The odorous gas must have
a fuel content to be flared although supplemental fuel, such as
natural gas, may be used to stabilize or maintain the flame.
This method is commonly considered wasteful ofits fuel value.
The City is currently using this method to deodorize digester
gas.
Catalytic oxidation occurs in the range of 600 to 800 degrees F
and involves the use of precious metals as catalyst. The
catalyst is easily fouled by heavy metals so the gases must be
controlled. The most common example of this technique is the
catalytic converter found on all of today's automobiles.
Wet scrubbers can deodorize by chemical conversion or odorant
capture. Two stage wet scrubbers were found to be effective when
piloted at MSDD No. 1. The first stage is generally a low pH
acid scrubber to remove ammonia in its soluble state. The second
stage is generally a chemical scrubber to oxidize organic
compounds.
Wet scrubbers can add up to one-third of the construction cost to
a compost facility. The addition of wet scrubbers to the Fort
Collins facility are estimated to cost between $476,000 to
$594,000 Annual operating costs are estimated to be $62,000. A
significant cost associated with scrubbers is sidestream
treatment, especially of ammonia.
C. Dilution and Dispersion
Dilution of any source of odor, even from a scrubber discharge is
important in reducing odor detection. Factors such as height of
discharge, distance to nearest receptor and atmospheric condi-
tions are all important factors.
The landfill site is surrounded by agricultural land on all sides
with the Saint Vrain River along the south and east boundaries.
The nearest receptors of odor in all directions are shown belciwrite.,
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Direction Nearest Receptor Distance
North-Northeast Residence 1500 feet
East Farm/Residence 4000 feet
South Residence 4800 feet
Southwest Farm/Residence 4000 feet
West Farm/Residence 4800 feet
Atmospheric conditions such as temperature inversions create
problem conditions. These are conditions dictated by nature..
During these time,. a fan might be the only means of providing
dilution. Important atmospheric conditions that influence the
dispersion of odors are as follows:
- Wind -determines direction and speed of horizontal
odor transport and dispersion.
- Atmospheric
Stability -determines the rate of vertical odor disper-
sion and mixing.
- Mixing
Height -determines vertical extent to which odors may
be mixed.
(, 1 . Climate
Historical climatic data has been compiled for Longmont. Monthly
temperatures for Longmont are shown in Table 1.
Precipitation is usually generated from cold fronts from the
Northwest associated with moisture pushed into the area from the
Gulf of Mexico by low pressure systems. Local thunder storms
produce some additional summer precipitation. Annual average
precipitation for Longmont is about 12.0 inches per year.
Precipitation data is shown in Table 2.
Winds in the area exhibit diurnal wind directions generally out
of the Southeast during the daytime and out of the North -
Northwest during the nighttime. Winds from the Northwest occur
in a higher frequency than those from the Southeast. Predominant
winds generally follow the drainage pattern of the Saint Vrain
River.
The summers are characterized by warm sunny days and light
breezes, with morning temperatures in the 50's. Afternoon tem-
peratures typically reach into the low 90's. Late afternoon con-
vective activity is common with showers or thunderstorms occuring
frequently during the summer months. Precipitation is generally
light, but can occasionally be quite heavy with accompanying hail
and strong gusty winds in more intense thunderstorms.
Clr
i✓ ;t.; ".
Winters are much cooler, with average temperatures generallyP3, 'i
ranging from the 20's to 40' s. Extremely cold periods with tem-
peratures below zero may also occur and persist for several days -
at a time.
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r 2. Wind
The National Center for Atmospheric Research maintains a measure-
ment station at the Longmont airport west of the City under the
Prototype Regional Observing and Forecasting System (PROFS). Raw
data for 1981 was obtained from the Colorado State Climotologist
and reduced to windrose format. Exhibit 1 shows total wind by
direction. Equally predominant winds come from the Northwest and
West-Northwest which follows the Saint Vrain drainage in the area
of the station. The Saint Vrain flows from the West-Northwest in
this area. Many of these winds are high velocity.
The West-Northwest wind is typical of nighttime downslope .
drainage of cooler air. The East-Southeast wind is typical. of -
daytime upslope flow. The strongest winds from the western sec-
tors are associates with large-scale weather systems.
The nighttime surface drainage flows cause conditions of low dis
persion which have been observed by City staff. Early morning
downslope flow tends to be out of the north and west, following
the Saint Vrain River.
Low velocity winds move odors in a plug flow fashion with very
little dispersion. Exhibit 2 is a windrose for winds less than 3
knots. Again the predominant wind is from the Northwest.
J The worst wind conditions is low velocity wind under very stable
l atmospheric conditions. Most stable atmospheric conditions occur
before dawn. Exhibit 3 is a windrose for less than 3 knots at
midnight. Again the predominant wind is from the West-Northwest.
The landfill is located along the Saint Vrain Creek where the
creek runs from the southwest to the northeast. It is reasonable
to anticipate a low velocity along this drainage from the
southwest.
3. Stability. and Mixing Height
Atmospheric stability is determined by the temperature lapse
rate. As air moves upward, the pressure decreases and the air
will expand which causes it to cool_ This is called the
adiabatic lapse rate. The relation of the temperature gradient
to the adiabatic lapse rate determines the degree of dispersion
(stability) as shown in Exhibit 4.
Temperature gradients less than the adiabatic lapse rate are tur-
bulent and have a high degree of dispersion. Positive tempera-
ture gradients (temperature inversions) are very stable and cause
the odorous air to move with very little dispersion. Odors tend
to disperse rapidly in unstable conditions and disperse very
slowly in stable conditions.
No stability data could be found for Longmont. However stability
data for three sites along the Front Range are shown in Table 3. a
TABLE 3
Stability Class Frequencies in the Longmont Region
Frequency of Occurrence (z)
Stability Class Rawhide Anheuser-Busch Denver
A. Extremely Unstable 48.3 23.7 1.3
B. Unstable 18.9 6.5 8.3
C. Slight Unstable 6.7 6.2 14.0
D. Neutral 3.5 26.2 40.6
E. Stable 14.2 15.7 19.2
F. Very Stable 8.4 21.6 16.5
TABLE 4
Diurnal and Seasonal Variability of Mixing Height
Based on Observations at Denver, Colorado
. .Season Morning Afternoon
Winter 300m 1,400m
Spring 500m 3,000m
Summer 300m 3,600m
Autumn 200m 2, 100m
C4 1S
The Rawhide data show an unusually high percentage of unstable
conditions. The Denver data would appear to be more repre-
sentative of the conditions to be found at the landfill.
The mixing height is also important in assessing odor dispersion
potential. Table 4 shows diurnal and seasonal variations.
Generally, vertical mixing is best in the afternoon. Summer has
the best afternoon dispersion characteristics. The worst verti-
cal mixing occurs in the winter.
Temperature inversions are common in the region and are generally
worse in the winter. Winter inversions can last for several days .
and cause very stable conditions.
•
There are two recognized methods to deal with odors during stable
atmospheric conditions. One is to install artificial barriers
such as walls and the other is to disperse odorous concentrations
with a fan.
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