HomeMy WebLinkAbout20131592.tiffPRELIMINARY DRAINAGE REPORT
FOR
KEOTA OIL AND GAS PROCESSING FACILITY
WELD COUNTY, COLORADO
Prepared for:
Noble Energy
1625 Broadway, Suite 2200
Denver, CO 80202
Prepared by:
Tetra Tech, Inc.
1900 South Sunset Street, Suite 1-F
Longmont, Colorado 80501
Tetra Tech Job No. 133-35719-13005
February 2013
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TETRA TECH
TETRA TECH
February 22, 2013
Heidi Hansen
Weld County — Public Works
1111 H Street
Greeley, CO 80631
Re: Preliminary Drainage Report for Keota Oil and Gas Processing Facility
Tetra Tech Job No. 133-35719-13005
Dear Ms. Hansen:
On behalf of Noble Energy, we are submitting this Preliminary Drainage Report for the Keota Oil
and Gas Processing Facility. Proposed development includes a natural gas processing facility,
storage area and gas plant staging area, a future central processing facility, a LNG (liquefied natural
gas) plant, and a power substation. Oil and gas from Noble's well sites throughout the northern Weld
County area will be piped to this facility for treatment, processing and distribution. The enclosed
report provides information on the subject property's historic drainage patterns, and evaluates the
preliminary drainage design for the proposed facility.
A retention basin is proposed for a portion of this site's developed stormwater runoff. The concept
of retention is discussed in detail in this report. In accordance with Weld County Code, a variance
request letter for retention is included as an appendix to this report.
If there are any questions or comments concerning this report, please feel free to contact us.
Sincerely,
TETRA TECH
Josherman, P.E.
Project Civil Engineer
Enclosures
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TETRA TECH
ENGINEER'S CERTIFICATION
I hereby certify that this report for the preliminary drainage design of the Keota Oil and Gas
Processing Facility was prepared by me (or under my direct supervision) in accordance with the
provisions of the Weld County Storm Drainage Criteria fo - � ;licants of the property thereof.
'4�
Joshua 'tS�4»„'''�
Registered ' . ional Engineer
State of Colorado No. 43891
TABLE OF CONTENTS
Page
1.0 INTRODUCTION I
2.0 GENERAL LOCATION AND DESCRIPTION 1
2.1 Location 1
2.2 Proposed Development 1
3.0 DRAINAGE BASINS AND SUBBASINS 2
3.1 Major Basin Description 2
3.2 Historic Drainage Patterns 3
3.3 Off -Site Drainage Patterns 3
4.0 DRAINAGE DESIGN CRITERIA 3
5.0 DRAINAGE FACILITY DESIGN 4
5.1 General Concept 4
5.2 On -Site Drainage 5
5.3 Off -Site Drainage 6
5.4 Water Quality 6
6.0 CONCLUSIONS 7
7.0 REFERENCES 7
-i-
List of Appendices
Appendix A: Mapping
Vicinity Map
FEMA Flood Insurance Rate Map
Appendix B: Hydrology Computations
Appendix B-1: Soils Report
Appendix B-2: Rainfall Data
Appendix B-3: Historic Runoff Calculations
Appendix B-4: Off -site Runoff Calculations
Appendix B-5: Developed Runoff Calculations
Appendix C: Hydraulic Computations
Appendix C-1: Culvert Calculations
Appendix C-2: Drainage Channel Calculations
Appendix C-3: WQCV Calculations
Appendix C-4: Detention Pond Calculations
Appendix C-5: Retention Pond Calculations
Appendix D: Variance Letter
Appendix E: Drainage Plans
Off -Site Drainage Plan D-100
Historic Drainage Plan D-200
Preliminary Developed Drainage Plan D-201
1.0 INTRODUCTION
The purpose of this report is to identify and define preliminary solutions to storm drainage runoff.
With development of a green field site, one can expect an increase in impervious cover and,
therefore, an increase in peak storm water runoff. This report examines the undeveloped flow
patterns of off -site and on -site drainage basins and proposed storm water facilities designed to
mitigate the downstream impact of increased storm water runoff. The contents of this report are
prepared, at a minimum, in accordance with the Weld County Code for a Preliminary Drainage
Report.
2.0 GENERAL LOCATION AND DESCRIPTION
2.1 Location
The Keota Oil and Gas Processing Facility site is located approximately 5 miles east and 7 miles
north of the town of Briggsdale, Colorado on the east side of Weld County Road (WCR) 89. More
specifically, the subject property is located in the north half of the northwest quarter of Section 21,
Township 9 North, Range 61 West of the 6`h P.M., Weld County, Colorado. A vicinity map has been
provided in Appendix A.
2.2 Proposed Development
Noble Energy is proposing a natural gas processing facility, storage area and gas plant staging area, a
future central processing facility, a LNG (liquefied natural gas) plant, and a power substation;
development will occur on an 80 acre parcel located 7 miles north of State Highway 14 on the east
side of WCR 89. Noble Energy intends to purchase the subject property which is currently owned by
the Quarter Circle Lazy H Ranch; the property is currently undeveloped and consists of agricultural
rangeland. Surrounding land use adjacent to the subject parcel is primarily rangeland for livestock
grazing; a natural playa lake is located directly adjacent to and partially encumbers the property's
east boundary. A natural gas pipeline transverses northwest to southeast just north of the project site
and an overhead electric line also transverses northwest to southeast just south of the project site.
Natural gas from Noble's well sites throughout the northern Weld County area will be piped to this
facility for treatment. Gas is treated to remove carbon dioxide and water, processed to recover
natural gas liquids (NGL), and create a sellable gas stream for use by consumers. Gas and produced
liquids will be transported via pipelines.
Another function of the Keota Facility is to stabilize condensate. Stabilization will occur for
condensate from this facility and Noble's Lilli Gas Processing Facility. The Lilli facility is located
on WCR 96 west of WCR 129 and condensate will be trucked to the Keota site. Condensate steam
will be stored in atmospheric tanks until sold and trucked off -site.
A Liquified Natural Gas (LNG) plant and storage is also proposed on the property. Residue gas from
the Gas Processing Facility will be piped on -site to the LNG plant where it will be chilled to -275° F
and turned into a liquid. The LNG will be placed into vacuum insulated storage tanks for loading
into trucks for delivery to another site for use by vehicles.
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Noble is also proposing a future Central Processing Facility (CPF) on the site. Noble Energy would
construct the facility to serve wells in the vicinity of the Keota site. The wells would convey oil,
water and gas to the Keota CPF via pipeline to be further separated. Gas will be directed to the gas
plant, water separated out of the oil will be taken off -site for disposal at an independent approved
facility, and the oil will be sold and likely piped off -site.
Noble Energy may also sublease a portion of the facility as part of the process of getting the end
product delivered to customers. The first area will be leased to Southern Star for a residue gas meter.
The second area will be leased to OPPL or a similar company for a NGL meter. Both meters will be
connected to pipelines to convey the product offsite.
Development for the Keota Facility will be a phased approach. The first phase of development is
described above. The second phase of improvements includes: a central processing facility (CPF); a
storage area; and a staging area. Items stored in the storage and staging area will be new material.
Timing for future phases of development is unknown and is dependent on market conditions.
Access to the site will be located off WCR 89. There are two proposed access points from WCR 89
to the facility. All traffic will be directed to enter the site at the northern most entrance. A guard
house is proposed at this entrance. Trucks will then be directed to the appropriate location on the site
and leave from the south access point. There will be informational signs at the entrances to direct
traffic. Site improvements will include: access roads; miscellaneous buildings; oil and gas
equipment; and other support structures.
3.0 DRAINAGE BASINS AND SUBBASINS
3.1 Major Basin Description
The subject property is located in rural Weld County and is surrounded by undeveloped agricultural
rangeland. The project site lies in a FEMA designated area, Zone D: "no analysis of flood hazards
has been conducted." A Flood Insurance Rate Map (FIRM), Community Panel No. 0802660400C, is
provided in Appendix A.
The site is located outside any applicable Weld County or adjacent Master Drainage Plans. A minor
ridge line, running north -south, bisects the western half of the subject property. The site is located
within the Jackson Draw watershed; Jackson Draw is a tributary to Crow Creek. The western one -
quarter of the property generally sheet flows to the southwest towards WCR 89 and ultimately
Jackson Draw. The eastern three-quarters of the property generally sheet flows to the east toward a
natural playa lake. A playa lake can be defined as a basin with no outlet which periodically fills with
water to form a temporary lake.
According to the Soil Survey of Weld County, Colorado, Northern Part [1], site soils are primarily
sandy loams, clay barns and barns. Loam soils are generally well drained and slopes are between 0
and 6 percent. A detailed soil survey report has been provided in Appendix B-1.
PRELIMINARY DRAINAGE REPORT
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3.2 Historic Drainage Patterns
A minor ridge line divides the site into two historic sub -basins: Basin HI and Basin H2. Basin H 1
consists of the eastern one -quarter of the property; runoff from this basin generally sheet flows to the
southwest towards WCR 89. Basin H2 consists of the western three-quarters of the property and has
been further subdivided into two sub -basins; runoff from Basin H2 generally sheet flows to the east
toward a natural playa lake. A Historic Drainage Plan is enclosed with this report.
Historic runoff coefficients are calculated for each site soil type. The site rainfall depth information
has been obtained using the Rainfall Depth -Duration -Frequency charts provided by the Urban Storm
Drainage Criteria Manual, Volume 1, Ch. 4, as shown in Appendix B-2. Historic runoff coefficients
and peak flows for the 5 -year storm event have been provided in Table 1:
Table 1: Historic 5-yr Runoff Summary
Runoff Peak Flow, Corresponding
Basin ID Acres Coefficient, 5-yr 5-yr (cfs) POA
HI 20.70 0.10 3.89 HI
H2a 37.08 0.11 2.53 H2a
H2b 22.51 0.14 3.76 H2b
Detailed historic drainage calculations are provided in Appendix B-3.
3.3 Off -Site Drainage Patterns
Off -site drainage basin, 01, is approximately 259 acres and this runoff from north of the subject
property is generally routed across the northeastern corner of the project site as storm water drains to
the playa lake which is adjacent to the eastern project boundary. This offsite basin, O1, is merely a
sub -basin of an approximately 880 acre drainage area that contributes to the playa lake. Please see
the Off -site Drainage Plan that is enclosed with this report. Off -site drainage calculations are
provided in Appendix B-4.
4.0 DRAINAGE DESIGN CRITERIA
This report is prepared in compliance with the Urban Storm Drainage Criteria Manual, Volumes 1, 2
and 3; Weld County Code; and the Weld County Storm Drainage Criteria Addendum to the Urban
Storm Drainage Criteria Manuals Volumes 1, 2, and 3 [4]. Based on this criterion, a 100 -year storm
is used as the major storm when evaluating existing and proposed drainage facilities. Rainfall data
for the 6 -hour and 24 -hour storm event was collected using the NOAA Atlas 2, Precipitation -
Frequency Atlas of the Western United States, Volume III -Colorado [5], and then converted to 1 -hour
rainfall data using Urban Drainage and Flood Control District's (UDFCD's) UD-RainZone v1.01 a
spreadsheet.
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For basins less than 90 acres in area, which includes the on -site basins, the Rational Method is used
in stormwater runoff calculations. For the off -site drainage basin, which is greater than 160 acres, the
SCS Curve Number method was used for runoff evaluations using U.S. Army Corps of Engineers
HEC-HMS software. Runoff coefficients are weighted based on soil types and the historic and
proposed land cover encountered at the site.
Pipe Sizing: Site storm infrastructure capacities have been evaluated using Manning's Equation.
The access drive culvert is sized for the 10-yr storm event to convey existing drainage from WCR 89,
as well as to provide site access, during a major storm event. Additionally, outlet pipes from
detention ponds are sized for a maximum release rate of the 5 -year historic flow with the use of an
orifice plate. Erosion control devices will be provided at all culvert and swale outlets to protect
against downstream erosion. Preliminary pipe calculations have been provided in Appendix C-1.
Drainage Channel Sizing: A drainage channel is proposed along the northeast side of the facility to
route off -site flows through the subject property. This channel is sized for the 100 -year storm event
using Manning's Equation. Detailed channel calculations have been provided in Appendix C-2.
Detention Pond Sizing: The detention pond volumes have been determined using the UDFCD's
Detention Design — UD-Detention v2.2. Detention ponds are designed to detain the 100 -year
developed storm event with 1 -foot of freeboard for on -site flows and water quality capture. An
emergency spillway, trapezoidal weir, is proposed to convey the 100 -year flow rate at a 6 -inch depth.
Two detention ponds are proposed for the site. Detention Pond A-1 will be constructed immediately
and Detention Pond A-2 will be constructed as needed for future phases. Detailed detention pond
calculations have been provided in Appendix C-4.
Retention Pond Sizing: The proposed retention pond volume, 1.5 times the volume of runoff
generated by the 24 -hour, 100 -year storm, will be provided in accordance with the Weld County
Code. Retention volume will be achieved by excavating, within the project boundary, to create the
required volume. This additional volume will be created within the existing playa lake. The
watershed time of concentration will be used for the project's release rate to meet Weld County Code
and Colorado Water Law requirements for a drain time of less than 72 hours. Detailed retention
pond calculations have been provided in Appendix C-5.
It is understood that a variance request is required for approval of a retention pond. A copy of this
variance request is provided in Appendix D.
5.0 DRAINAGE FACILITY DESIGN
5.1 General Concept
The developed condition of the site mirrors the historical condition and stormwater runoff is divided
into two major drainage basins: Basin A and Basin B. Basin A is further subdivided into three sub -
basins and Basin B is subdivided into five sub -basins.
PRELIMINARY DRAINAGE REPORT
KEOTA OIL AND GAS PROCESSING FACILITY
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Basin A will flow west into corresponding detention ponds and be discharged to the roadside ditch
along WCR 89; the 100 -year developed storm event will be released at the 5 -year historic rate. Basin
B will discharge to the east; water quality ponds will reduce sediment from runoff prior to releasing
flows into the retention pond/playa lake.
5.2 On -site Drainage
Drainage Basin Al consists of Phase I facility improvements including both access drives. Basin Al
will be routed through Detention Pond Al, and will be released to the roadside ditch along WCR 89.
Drainage Basin A2 consists of an electrical substation and future facility improvements; Basin A2
will be routed through Detention Pond A2 where flows will be released to the roadside ditch along
WCR 89. Basin A3 consists of undeveloped property and will be released off -site under historic
drainage conditions.
Drainage Basin Bl consists of Phase 1 facility improvements. Basin B2 consists of future facility
improvements. Basins B1 and B2 will convey stormwater runoff to the east through a water quality
basin prior to releasing flows into the retention pond/playa lake. It is noted that the existing playa
lake does not have a natural spillway and that the probability for stormwater to be released via
surface flow from the playa lake basin is virtually zero. Basin B3 and Basin B4 consist of
undeveloped property and will be released off -site under historic drainage conditions.
Table 2 provides the peak flow rates for on -site Drainage Basins A and B. Developed runoff from
Basin Al and A2 is routed through detention ponds and flows will be attenuated to the 5 -year historic
rate. Basin B1 and B2 will be routed to the retention pond/playa lake where 1.5 times the peak
runoff will be retained.
Table 2: Onsite 100 -year Runoff Summary
Basin ID Acres
Runoff Coefficient, C Peak Flow, Q
100-yr (cfs)
Notes
A 1 6.57 0.46 18.97 Discharge to Pond Al
A2 6.59 0.38 16.21 Discharge to Pond A2
A3 2.98 0.35 3.38 Undeveloped
B1 16.98 0.45 43.24 Discharge to Retention Pond
B2 34.62 0.44 79.46 Discharge to Retention Pond
B3 7.68 0.43 8.29 Undeveloped
B4 3.98 0.48 6.10 Undeveloped
Detailed developed drainage calculations have been provided in Appendix B-5.
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FEBRUARY 2013
5.3 Off -site Drainage
Off -site drainage basin, Basin O1, will be conveyed through northeast corner of the project site via a
drainage channel. The channel is sized to convey the historic 100 -year runoff. Detailed calculations
have been provided in Appendix C-2.
5.4 Water Quality
The proposed water quality feature for the site is water quality capture ponds. Water quality capture
volume (WQCV) for Basin A will be located within the detention ponds. Separate water quality
ponds are provided for Basin B. Water quality volumes are sized in accordance with the Urban
Storm Drainage Criteria Manual, Volume 1-3 and the water quality features were designed to handle
the runoff from the whole developed portion of the site.
The site's developed runoff flows are designed to route through the water quality features. Per Urban
Storm Drainage Standards, 120% of the water quality volume will be provided. The proposed water
quality volume drain time is 40 -hours. A plate with water quality perforations is proposed as a water
quality orifice for the pond.
The WQCV is included in the detention pond volumes for Basin A. A standalone water quality pond
in Basin B is sized to include 120 percent of the water quality volume. One -foot of freeboard is
provided for each detention and water quality pond. WQCV calculations are presented in Appendix
C-3. A storage volume summary is provided below in Table 3.
Table 3: Storage Volume Summary
Pond Storage
Basin Al
(ac -ft)
Basin A2 Basin B
(ac -ft) (ac -ft)
Detention 0.70 0.64 n/a
Retention n/a n/a 10.2
Water Quality Capture 0.07 0.04 0.43
Notes:
1. One -ft. (1.0') of freeboard will be provided for detention and retention pond volumes.
2. WQCV included in detention pond volumes for Basin Al and A2.
3. WQCV for Basin B to be provided separately from retention pond.
PRELIMINARY DRAINAGE REPORT
KEOTA OIL AND GAS PROCESSING FACILITY
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FEBRUARY 2013
6.0 CONCLUSIONS
This report is prepared in compliance with the Weld County Code and the Weld County Storm
Drainage Criteria Addendum to the Urban Storm Drainage Criteria Manuals Volumes 1, 2 and 3.
The proposed drainage system for the Keota Oil and Gas Processing Facility will provide detention
for developed drainage basins, Basin A, and retention for developed drainage basins, Basin B.
Detention ponds for Basin A will capture the 100 -year developed runoff and release at the historic 5 -
year rate, thus the drainage will not adversely affect the existing drainage patterns of the site or areas
surrounding the site. Retention pond volumes for Basin B will be provided on -site within the
existing playa lake. Water quality capture volumes will be provided for all developed flows in an
effort to mitigate water quality impacts from stormwater runoff.
Upon Weld County's review and comment of this report, a Final Drainage Report will be completed,
including a more detailed analysis and construction drawings that will provide drainage channel and
culvert cross sections, detention pond profile and section, outlet structure and orifice plate details,
riprap sizing, operations and maintenance instructions for the proposed stormwater drainage facility,
and spot grading elevations at all inverts and key hydraulic points.
7.0 REFERENCES
1. United States Department of Agriculture Soil Conservation Service in cooperation with
Colorado Agricultural Experiment Station. Soil Survey of Weld County, Colorado,
Southern Part, September 1980.
2. Urban Drainage and Flood Control District. Urban Storm Drainage Criteria Manual,
Volume 1-3, June 2001.
3. Weld County Code. Weld County, Colorado, September 6, 2008.
4. Weld County Storm Drainage Criteria Addendum to the Urban Storm Drainage Criteria
Manuals Volumes 1, 2, and 3. Weld County Public Works Department, October 2006.
5. NOAA Atlas 2, Precipitation -Frequency Atlas of the Western United States, Volume III -
Colorado. U.S. Department of Commerce, 1973.
PRELIMINARY DRAINAGE REPORT
KEOTA OIL AND GAS PROCESSING FACILITY
-7-
FEBRUARY 2013
APPENDIX A - MAPPING
VICINITY MAP
FEMA FLOOD INSURANCE RATE MAP
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TETRA TECH
www.tetratech.com
1900 S Sunset Street, Suite 1-F
Longmont, Colorado 80501
PH: 303.772.5282 FAX: 303.772.7039
KEOTA GAS PROCESSING FACILITY
WELD COUNTY, COLORADO
VICINITY MAP
Project No.: 133-35719-13005
Date: 1/8/2013
Designed By: JJA
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APPENDIX B - HYDROLOGY COMPUTATIONS
APPENDIX B-1 SOILS REPORT
APPENDIX B-2 RAINFALL DATA
APPENDIX B-3 HISTORIC RUNOFF CALCULATIONS
APPENDIX B-4 OFF -SITE RUNOFF CALCULATIONS
APPENDIX B-5 DEVELOPED RUNOFF CALCULATIONS
APPENDIX B-1
SOILS REPORT
USDA United States
Department of
Agriculture
4 NRCS
Natural
Resources
Conservation
Service
A product of the National
Cooperative Soil Survey,
a joint effort of the United
States Department of
Agriculture and other
Federal agencies, State
agencies including the
Agricultural Experiment
Stations, and local
participants
Custom Soil Resource
Report for
Weld County,
Colorado, Northern
Part
Keota Gas Processing Facility
January 8. 2013
Preface
Soil surveys contain information that affects land use planning in survey areas. They
highlight soil limitations that affect various land uses and provide information about
the properties of the soils in the survey areas. Soil surveys are designed for many
different users, including farmers, ranchers, foresters, agronomists, urban planners,
community officials, engineers, developers, builders, and home buyers. Also,
conservationists, teachers, students, and specialists in recreation, waste disposal,
and pollution control can use the surveys to help them understand, protect, or enhance
the environment.
Various land use regulations of Federal, State, and local governments may impose
special restrictions on land use or land treatment. Soil surveys identify soil properties
that are used in making various land use or land treatment decisions. The information
is intended to help the land users identify and reduce the effects of soil limitations on
various land uses. The landowner or user is responsible for identifying and complying
with existing laws and regulations.
Although soil survey information can be used for general farm, local, and wider area
planning, onsite investigation is needed to supplement this information in some cases.
Examples include soil quality assessments (http://soils.usda.gov/sqi/) and certain
conservation and engineering applications. For more detailed information, contact
your local USDA Service Center (http://offices.sc.egov.usda.gov/locator/app?
agency=nrcs) or your NRCS State Soil Scientist (http://soils.usda.gov/contact/
state_offices/).
Great differences in soil properties can occur within short distances. Some soils are
seasonally wet or subject to flooding. Some are too unstable to be used as a
foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic
tank absorption fields. A high water table makes a soil poorly suited to basements or
underground installations.
The National Cooperative Soil Survey is a joint effort of the United States Department
of Agriculture and other Federal agencies, State agencies including the Agricultural
Experiment Stations, and local agencies. The Natural Resources Conservation
Service (NRCS) has leadership for the Federal part of the National Cooperative Soil
Survey.
Information about soils is updated periodically. Updated information is available
through the NRCS Soil Data Mart Web site or the NRCS Web Soil Survey. The Soil
Data Mart is the data storage site for the official soil survey information.
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs
and activities on the basis of race, color, national origin, age, disability, and where
applicable, sex, marital status, familial status, parental status, religion, sexual
orientation, genetic information, political beliefs, reprisal, or because all or a part of an
individual's income is derived from any public assistance program. (Not all prohibited
bases apply to all programs.) Persons with disabilities who require alternative means
2
for communication of program information (Braille, large print, audiotape, etc.) should
contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a
complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400
Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272
(voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and
employer.
3
Contents
Preface 2
How Soil Surveys Are Made 5
Soil Map 7
Soil Map 8
Legend 9
Map Unit Legend 10
Map Unit Descriptions 10
Weld County, Colorado, Northern Part 12
4 —Ascalon fine sandy loam, 0 to 6 percent slopes 12
10—Avar-Manzanola complex, 0 to 3 percent slopes 13
36—Manzanola clay loam, 0 to 3 percent slopes 14
40 —Nunn loam, 0 to 6 percent slopes 15
44 —Olney fine sandy loam, 0 to 6 percent slopes 16
54—Platner loam, 0 to 3 percent slopes 17
References 19
4
How Soil Surveys Are Made
Soil surveys are made to provide information about the soils and miscellaneous areas
in a specific area. They include a description of the soils and miscellaneous areas and
their location on the landscape and tables that show soil properties and limitations
affecting various uses. Soil scientists observed the steepness, length, and shape of
the slopes; the general pattern of drainage; the kinds of crops and native plants; and
the kinds of bedrock. They observed and described many soil profiles. A soil profile is
the sequence of natural layers, or horizons, in a soil. The profile extends from the
surface down into the unconsolidated material in which the soil formed or from the
surface down to bedrock. The unconsolidated material is devoid of roots and other
living organisms and has not been changed by other biological activity.
Currently, soils are mapped according to the boundaries of major land resource areas
(MLRAs). MLRAs are geographically associated land resource units that share
common characteristics related to physiography, geology, climate, water resources,
soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically
consist of parts of one or more MLRA.
The soils and miscellaneous areas in a survey area occur in an orderly pattern that is
related to the geology, landforms, relief, climate, and natural vegetation of the area.
Each kind of soil and miscellaneous area is associated with a particular kind of
landform or with a segment of the landform. By observing the soils and miscellaneous
areas in the survey area and relating their position to specific segments of the
landform, a soil scientist develops a concept, or model, of how they were formed. Thus,
during mapping, this model enables the soil scientist to predict with a considerable
degree of accuracy the kind of soil or miscellaneous area at a specific location on the
landscape.
Commonly, individual soils on the landscape merge into one another as their
characteristics gradually change. To construct an accurate soil map, however, soil
scientists must determine the boundaries between the soils. They can observe only
a limited number of soil profiles. Nevertheless, these observations, supplemented by
an understanding of the soil -vegetation -landscape relationship, are sufficient to verify
predictions of the kinds of soil in an area and to determine the boundaries.
Soil scientists recorded the characteristics of the soil profiles that they studied. They
noted soil color, texture, size and shape of soil aggregates, kind and amount of rock
fragments, distribution of plant roots, reaction, and other features that enable them to
identify soils. After describing the soils in the survey area and determining their
properties, the soil scientists assigned the soils to taxonomic classes (units).
Taxonomic classes are concepts. Each taxonomic dass has a set of soil
characteristics with precisely defined limits. The classes are used as a basis for
comparison to classify soils systematically. Soil taxonomy, the system of taxonomic
classification used in the United States, is based mainly on the kind and character of
soil properties and the arrangement of horizons within the profile. After the soil
scientists classified and named the soils in the survey area, they compared the
5
Custom Soil Resource Report
individual soils with similar soils in the same taxonomic class in other areas so that
they could confirm data and assemble additional data based on experience and
research.
The objective of soil mapping is not to delineate pure map unit components; the
objective is to separate the landscape into landforms or landform segments that have
similar use and management requirements. Each map unit is defined by a unique
combination of soil components and/or miscellaneous areas in predictable
proportions. Some components may be highly contrasting to the other components of
the map unit. The presence of minor components in a map unit in no way diminishes
the usefulness or accuracy of the data. The delineation of such landforms and
landform segments on the map provides sufficient information for the development of
resource plans. If intensive use of small areas is planned, onsite investigation is
needed to define and locate the soils and miscellaneous areas.
Soil scientists make many field observations in the process of producing a soil map.
The frequency of observation is dependent upon several factors, including scale of
mapping, intensity of mapping, design of map units, complexity of the landscape, and
experience of the soil scientist. Observations are made to test and refine the soil -
landscape model and predictions and to verify the classification of the soils at specific
locations. Once the soil -landscape model is refined, a significantly smaller number of
measurements of individual soil properties are made and recorded. These
measurements may include field measurements, such as those for color, depth to
bedrock, and texture, and laboratory measurements, such as those for content of
sand, silt, clay, salt, and other components. Properties of each soil typically vary from
one point to another across the landscape.
Observations for map unit components are aggregated to develop ranges of
characteristics for the components. The aggregated values are presented. Direct
measurements do not exist for every property presented for every map unit
component. Values for some properties are estimated from combinations of other
properties.
While a soil survey is in progress, samples of some of the soils in the area generally
are collected for laboratory analyses and for engineering tests. Soil scientists interpret
the data from these analyses and tests as well as the field -observed characteristics
and the soil properties to determine the expected behavior of the soils under different
uses. Interpretations for all of the soils are field tested through observation of the soils
in different uses and under different levels of management. Some interpretations are
modified to fit local conditions, and some new interpretations are developed to meet
local needs. Data are assembled from other sources, such as research information,
production records, and field experience of specialists. For example, data on crop
yields under defined levels of management are assembled from farm records and from
field or plot experiments on the same kinds of soil.
Predictions about soil behavior are based not only on soil properties but also on such
variables as climate and biological activity. Soil conditions are predictable over long
periods of time, but they are not predictable from year to year. For example, soil
scientists can predict with a fairly high degree of accuracy that a given soil will have
a high water table within certain depths in most years, but they cannot predict that a
high water table will always be at a specific level in the soil on a specific date.
After soil scientists located and identified the significant natural bodies of soil in the
survey area, they drew the boundaries of these bodies on aerial photographs and
identified each as a specific map unit. Aerial photographs show trees, buildings, fields,
roads, and rivers, all of which help in locating boundaries accurately.
6
Soil Map
The soil map section includes the soil map for the defined area of interest, a list of soil
map units on the map and extent of each map unit, and cartographic symbols
displayed on the map. Also presented are various metadata about data used to
produce the map, and a description of each soil map unit.
7
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MAP INFORMATION
MAP LEGEND
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Map Unit Legend
Weld County, Colorado, Northern Part (CO617)
Map Unit Symbol I
Map Unit Name
I Acres in AOI
Percent of AOI
4
10
Ascalon fine sandy loam, 0 to 6 percent
slopes
Avar-Manzanola complex, 0 to 3 percent
slopes
52.53
22.77
65.4%
28.4%
36
Manzanola clay loam, 0 to 3 percent slopes
1.9
2.3%
40
Nunn loam, 0 to 6 percent slopes
0.4
0.5%
44
Olney fine sandy loam, 0 to 6 percent slopes
0.9
1.1%
54
Platner loam, 0 to 3 percent slopes
1.8
2.3%
Totals for Area of Interest
80.3
100.0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the soils
or miscellaneous areas in the survey area. The map unit descriptions, along with the
maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas. A map unit is identified and named
according to the taxonomic classification of the dominant soils. Within a taxonomic
class there are precisely defined limits forthe properties of the soils. On the landscape,
however, the soils are natural phenomena, and they have the characteristic variability
of all natural phenomena. Thus, the range of some observed properties may extend
beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic
class rarely, if ever, can be mapped without including areas of other taxonomic
classes. Consequently, every map unit is made up of the soils or miscellaneous areas
for which it is named and some minor components that belong to taxonomic classes
other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
noncontrasting, or similar, components. They may or may not be mentioned in a
particular map unit description. Other minor components, however, have properties
and behavioral characteristics divergent enough to affect use or to require different
management. These are called contrasting, or dissimilar, components. They generally
are in small areas and could not be mapped separately because of the scale used.
Some small areas of strongly contrasting soils or miscellaneous areas are identified
by a special symbol on the maps. If included in the database for a given area, the
contrasting minor components are identified in the map unit descriptions along with
some characteristics of each. A few areas of minor components may not have been
observed, and consequently they are not mentioned in the descriptions, especially
where the pattern was so complex that it was impractical to make enough observations
to identify all the soils and miscellaneous areas on the landscape.
10
Custom Soil Resource Report
The presence of minor components in a map unit in no way diminishes the usefulness
or accuracy of the data. The objective of mapping is not to delineate pure taxonomic
classes but rather to separate the landscape into landforms or landform segments that
have similar use and management requirements. The delineation of such segments
on the map provides sufficient information for the development of resource plans. If
intensive use of small areas is planned, however, onsite investigation is needed to
define and locate the soils and miscellaneous areas.
An identifying symbol precedes the map unit name in the map unit descriptions. Each
description includes general facts about the unit and gives important soil properties
and qualities.
Soils that have profiles that are almost alike make up a soil series. Except for
differences in texture of the surface layer, all the soils of a series have major horizons
that are similar in composition, thickness, and arrangement.
Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity,
degree of erosion, and other characteristics that affect their use. On the basis of such
differences, a soil series is divided into soil phases. Most of the areas shown on the
detailed soil maps are phases of soil series. The name of a soil phase commonly
indicates a feature that affects use or management. For example, Alpha silt loam, 0
to 2 percent slopes, is a phase of the Alpha series.
Some map units are made up of two or more major soils or miscellaneous areas.
These map units are complexes, associations, or undifferentiated groups.
A complex consists of two or more soils or miscellaneous areas in such an intricate
pattern or in such small areas that they cannot be shown separately on the maps. The
pattern and proportion of the soils or miscellaneous areas are somewhat similar in all
areas. Alpha -Beta complex, 0 to 6 percent slopes, is an example.
An association is made up of two or more geographically associated soils or
miscellaneous areas that are shown as one unit on the maps. Because of present or
anticipated uses of the map units in the survey area, it was not considered practical
or necessary to map the soils or miscellaneous areas separately. The pattern and
relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha -
Beta association, 0 to 2 percent slopes, is an example.
An undifferentiated group is made up of two or more soils or miscellaneous areas that
could be mapped individually but are mapped as one unit because similar
interpretations can be made for use and management. The pattern and proportion of
the soils or miscellaneous areas in a mapped area are not uniform. An area can be
made up of only one of the major soils or miscellaneous areas, or it can be made up
of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.
Some surveys include miscellaneous areas. Such areas have little or no soil material
and support little or no vegetation. Rock outcrop is an example.
11
Custom Soil Resource Report
Weld County, Colorado, Northern Part
4 —Ascalon fine sandy loam, 0 to 6 percent slopes
Map Unit Setting
Elevation: 4,500 to 6,500 feet
Mean annual precipitation: 13 to 17 inches
Mean annual air temperature: 46 to 57 degrees F
Frost -free period: 130 to 160 days
Map Unit Composition
Ascalon and similar soils: 85 percent
Minor components: 15 percent
Description of Ascalon
Setting
Landform: Plains
Down -slope shape: Linear
Across -slope shape: Linear
Parent material: Calcareous loamy alluvium
Properties and qualities
Slope: 0 to 6 percent
Depth to restrictive feature. More than 80 inches
Drainage class: Well drained
Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high
(0.60 to 2.00 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum content: 10 percent
Maximum salinity: Nonsaline (0.0 to 2.0 mmhos/cm)
Available water capacity: Moderate (about 6.9 inches)
Interpretive groups
Farmland classification: Farmland of statewide importance
Land capability classification (irrigated): 3e
Land capability (nonirrigated): 3e
Hydrologic Soil Group: B
Ecological site: Loamy Plains (R067BY002CO)
Typical profile
0 to 8 inches: Fine sandy loam
8 to 22 inches: Sandy clay loam
22 to 60 inches: Sandy loam
Minor Components
Olney
Percent of map unit: 8 percent
Otero
Percent of map unit: 7 percent
12
Custom Soil Resource Report
10—Avar-Manzanola complex, 0 to 3 percent slopes
Map Unit Setting
Elevation: 4,400 to 5,600 feet
Mean annual precipitation: 11 to 15 inches
Mean annual air temperature: 46 to 52 degrees F
Frost -free period: 130 to 180 days
Map Unit Composition
Avar and similar soils: 45 percent
Manzanola and similar soils: 40 percent
Minor components: 15 percent
Description of Avar
Setting
Landform: Swales
Down -slope shape: Linear
Across -slope shape: Linear
Parent material: Calcareous loamy alluvium
Properties and qualities
Slope: 0 to 3 percent
Depth to restrictive feature: More than 80 inches
Drainage class: Well drained
Capacity of the most limiting layer to transmit water (Ksat): Moderately low to
moderately high (0.06 to 0.60 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum content: 15 percent
Maximum salinity: Very slightly saline to strongly saline (4.0 to 32.0 mmhos/cm)
Sodium adsorption ratio, maximum: 250.0
Available water capacity: Moderate (about 6.6 inches)
Interpretive groups
Farmland classification: Not prime farmland
Land capability (nonirrigated): 7s
Hydrologic Soil Group: D
Ecological site: Salt Flat (R067XY033CO)
Typical profile
0 to 3 inches: Fine sandy loam
3 to 8 inches: Clay loam
8 to 60 inches: Sandy clay loam
Description of Manzanola
Setting
Landform: Swales
13
Custom Soil Resource Report
Down -slope shape: Linear
Across -slope shape: Linear
Parent material: Calcareous clayey alluvium
Properties and qualities
Slope: 0 to 3 percent
Depth to restrictive feature: More than 80 inches
Drainage class: Well drained
Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately
high (0.00 to 0.20 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum content: 5 percent
Gypsum, maximum content: 3 percent
Maximum salinity: Nonsaline to slightly saline (0.0 to 8.0 mmhos/cm)
Sodium adsorption ratio, maximum: 15.0
Available water capacity: High (about 9.6 inches)
Interpretive groups
Farmland classification: Not prime farmland
Land capability (nonirrigated): 4e
Hydrologic Soil Group: C
Ecological site: Clayey Plains (R067BY042CO)
Typical profile
0 to 3 inches: Clay loam
3 to 18 inches: Clay
18 to 48 inches: Clay
48 to 60 inches: Clay loam
Minor Components
Heldt
Percent of map unit: 8 percent
Mollic halaquepts
Percent of map unit: 7 percent
Landforin: Swales
36—Manzanola clay loam, 0 to 3 percent slopes
Map Unit Setting
Elevation: 4,400 to 5,600 feet
Mean annual precipitation: 11 to 15 inches
Mean annual air temperature: 46 to 52 degrees F
Frost -free period: 140 to 180 days
Map Unit Composition
Manzanola and similar soils: 85 percent
Custom Soil Resource Report
Minor components: 15 percent
Description of Manzanola
Setting
Landform: Stream terraces, swales, plains
Down -slope shape: Linear
Across -slope shape: Linear
Parent material: Calcareous clayey alluvium
Properties and qualities
Slope: 0 to 3 percent
Depth to restrictive feature: More than 80 inches
Drainage class: Well drained
Capacity of the most limiting layer to transmit water (Ksat): Moderately low to
moderately high (0.06 to 0.20 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum content: 5 percent
Gypsum, maximum content: 3 percent
Maximum salinity: Nonsaline to slightly saline (0.0 to 8.0 mmhos/cm)
Sodium adsorption ratio, maximum: 15.0
Available water capacity: High (about 9.6 inches)
Interpretive groups
Farmland classification: Farmland of statewide importance
Land capability (nonirrigated): 4e
Hydrologic Soil Group: C
Ecological site: Clayey Plains (R067BY042CO)
Typical profile
0 to 3 inches: Clay loam
3 to 25 inches: Clay
25 to 48 inches: Clay
48 to 60 inches: Clay loam
Minor Components
Avar
Percent of map unit: 15 percent
40 —Nunn loam, 0 to 6 percent slopes
Map Unit Setting
Elevation: 4,500 to 6,700 feet
Mean annual precipitation: 12 to 18 inches
Mean annual air temperature: 46 to 54 degrees F
Frost -free period: 115 to 180 days
15
Custom Soil Resource Report
Map Unit Composition
Nunn and similar soils: 85 percent
Minor components: 15 percent
Description of Nunn
Setting
Landform: Stream terraces, plains
Down -slope shape: Linear
Across -slope shape: Linear
Parent material: Calcareous loamy alluvium
Properties and qualities
Slope: 0 to 6 percent
Depth to restrictive feature: More than 80 inches
Drainage class: Well drained
Capacity of the most limiting layer to transmit water (Ksat): Moderately low to
moderately high (0.06 to 0.20 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum content: 15 percent
Maximum salinity: Nonsaline (0.0 to 2.0 mmhos/cm)
Available water capacity: Moderate (about 9.0 inches)
Interpretive groups
Farmland classification: Prime farmland if irrigated
Land capability (nonirrigated): 4c
Hydrologic Soil Group: C
Ecological site: Loamy Plains (R067BY002CO)
Typical profile
0 to 7 inches: Loam
7 to 23 inches: Clay loam
23 to 60 inches: Clay loam
60 to 64 inches: Sandy clay loam
Minor Components
Manzanola
Percent of map unit: 8 percent
Avar
Percent of map unit: 7 percent
44 —Olney fine sandy loam, 0 to 6 percent slopes
Map Unit Setting
Elevation: 3,500 to 5,800 feet
Mean annual precipitation: 11 to 15 inches
Mean annual air temperature: 46 to 54 degrees F
16
Custom Soil Resource Report
Frost -free period: 125 to 175 days
Map Unit Composition
Olney and similar soils: 85 percent
Minor components: 15 percent
Description of Olney
Setting
Landform: Plains
Down -slope shape: Linear
Across -slope shape: Linear
Parent material: Calcareous loamy alluvium
Properties and qualities
Slope: 0 to 6 percent
Depth to restrictive feature: More than 80 inches
Drainage class: Well drained
Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high
(0.57 to 2.00 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum content: 15 percent
Maximum salinity: Nonsaline (0.0 to 2.0 mmhos/cm)
Available water capacity: Moderate (about 8.1 inches)
Interpretive groups
Farmland classification: Farmland of statewide importance
Land capability (nonirrigated): 4c
Hydrologic Soil Group: B
Ecological site: Loamy Plains (R067BY002CO)
Typical profile
0 to 6 inches: Fine sandy loam
6 to 18 inches: Sandy clay loam
18 to 60 inches: Sandy loam
60 to 64 inches: Sandy loam
Minor Components
Stoneham
Percent of map unit: 9 percent
Ascalon
Percent of map unit: 6 percent
54—Platner loam, 0 to 3 percent slopes
Map Unit Setting
Elevation: 4,500 to 5,900 feet
Mean annual precipitation: 17 to 19 inches
17
Custom Soil Resource Report
Mean annual air temperature: 46 to 52 degrees F
Frost -free period: 140 to 165 days
Map Unit Composition
Platner and similar soils: 80 percent
Minor components: 20 percent
Description of Platner
Setting
Landform: Stream terraces, plains
Down -slope shape: Linear
Across -slope shape: Linear
Parent material: Calcareous loamy alluvium
Properties and qualities
Slope: 0 to 3 percent
Depth to restrictive feature: More than 80 inches
Drainage class: Well drained
Capacity of the most limiting layer to transmit water (Ksat): Moderately low to
moderately high (0.06 to 0.20 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum content: 10 percent
Maximum salinity: Nonsaline (0.0 to 2.0 mmhos/cm)
Available water capacity: Moderate (about 8.9 inches)
Interpretive groups
Farmland classification: Prime farmland if irrigated
Land capability classification (irrigated): 2e
Land capability (nonirrigated): 3e
Hydrologic Soil Group: C
Ecological site: Loamy Plains (R067BY002CO)
Typical profile
0 to 4 inches: Loam
4 to 24 inches: Clay
24 to 60 inches: Sandy loam
Minor Components
Ascalon
Percent of map unit: 8 percent
Manzanola
Percent of map unit: 6 percent
Nunn
Percent of map unit: 6 percent
18
References
American Association of State Highway and Transportation Officials (AASHTO). 2004.
Standard specifications for transportation materials and methods of sampling and
testing. 24th edition.
American Society for Testing and Materials (ASTM). 2005. Standard classification of
soils for engineering purposes. ASTM Standard D2487-00.
Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of
wetlands and deep -water habitats of the United States. U.S. Fish and Wildlife Service
FWS/OBS-79/31.
Federal Register. July 13, 1994. Changes in hydric soils of the United States.
Federal Register. September 18, 2002. Hydric soils of the United States.
Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils
in the United States.
National Research Council. 1995. Wetlands: Characteristics and boundaries.
Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S.
Department of Agriculture Handbook 18. http://soils.usda.gov/
Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making
and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service,
U.S. Department of Agriculture Handbook 436. http://soils.usda.gov/
Soil Survey Staff. 2006. Keys to soil taxonomy. 10th edition. U.S. Department of
Agriculture, Natural Resources Conservation Service. http://soils.usda.gov/
Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and
Delaware Department of Natural Resources and Environmental Control, Wetlands
Section.
United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of
Engineers wetlands delineation manual. Waterways Experiment Station Technical
Report Y-87-1.
United States Department of Agriculture, Natural Resources Conservation Service.
National forestry manual. http://soils.usda.gov/
United States Department of Agriculture, Natural Resources Conservation Service.
National range and pasture handbook. http://www.glti.nrcs.usda.gov/
United States Department of Agriculture, Natural Resources Conservation Service.
National soil survey handbook, title 430 -VI. http://soils.usda.gov/
United States Department of Agriculture, Natural Resources Conservation Service.
2006. Land resource regions and major land resource areas of the United States, the
Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296.
http://soils.usda.gov/
19
Custom Soil Resource Report
United States Department of Agriculture, Soil Conservation Service. 1961. Land
capability classification. U.S. Department of Agriculture Handbook 210.
20
0
2
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GIS NIXO'KEO
NOBLE ENERGY, INC. Project No.: 133-35719-13005
WCR-106
Soils Legend
Map Unit No : Map Unit Name
4, Ascalon line sandy loam, 0 to 6 percent slopes
l 10; Avar-Manzanola complex, 0 to 3 percent slopes
40: Nunn loam, 0 to 6 percent slopes
44; Olney fine sandy loam, 0 to 6 percent slopes
45; Olney fine sandy loam, 6 to 9 percent slopes
154; Platner loam, 0 to 3 percent slopes
TETRA TECH
www.tetratech.com
1900 S. Sunset Street. Ste. 1-F
Longmont, Colorado 80501
Q `4. PHONE: (303) 772-5282 FAX (303) 772-7039
KEOTA GAS PROCESSING FACILITY
PRELIMINARY DRAINAGE REPORT
OFFSITE SOILS MAP
Date: JAN 11, 2013
Designed By: JJA
Figure No.
1
Map Unit Legend
Weld County, Colorado, Northern Part (CO617)
Map Unit Symbol
Map Unit Name
Hydrologic Soils Group
Area in AOI
Percent of AOI
4
Ascalon fine sandy loam, 0 to 6 percent slopes
B
7.98
2.9%
10
Avar-Manzanola complex, 0 to 3 percent slopes
D
6.02
2.2%
40
Nunn loam, 0 to 6 percent slopes
C
167.61
61.5%
44
Olney fine sandy loam, 0 to 6 percent slopes
B
77.22
28.3%
45
Olney fine sandy loam, 6 to 9 percent slopes
B
8.60
3.2%
54
Platner loam, 0 to 3 percent slopes
C
5.12
1.9%
Totals for Area of Interest
272.55
100.0%
APPENDIX B-2
RAINFALL DATA
IDF TABLE FOR ZONE ONE IN THE STATE OF COLORADO
Zone 1: South Platte, Republican, Arkansas, and Cimarron River Basins
Project: Noble Energy, Keota Oil and Gas Processing Facility
Enter the elevation at the center of the watershed: Elev = 4.960 (input)
1. Rainfall Depth -Duration -Frequency Table
Enter the 6 -hour and 24 -hour rainfall depths from the NOAA Atlas 2 Volume III in rightmost blue columns
Return
Period
Rainfall Depth in Inches at Time Duration
5 -rain
10 -min
15 -min
30 -ruin
1 -hr
2 -hr I
3 -hr
6 -hr
24 -hr
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
output
output
output
output
output
output
output
input
input
2-yr
0.29
0.45
0.57
0.79
1.00
1.13
1.23
1.39
1.75
5-yr
0.41
0.64
0.81
1.13
1.43
1.57
1.68
1.86
2.20
10-yr
0.49
0.77
0.97
1.35
1.70
1.86
1.98
2.16
2.58
25-yr
0.60
0.93
1.17
1.63
2.06
2.27
2.44
2.69
3.01
50-yr
0.69
1.08
1.36
1.89
2.39
2.57
2.71
2.92
3.34
100-yr
0 78
1.22
1 54
2 13
2 70
2.87
3.00
3 20
3 74
Note: Refer to NOAA Atlas 2 Volume Ill isopluvial maps for 6 -hr and 24 -hr rainfall depths.
2. Rainfall Intensity -Duration -Frequency Table
Return
Period
Rainfall Intensity in Inches Per Hour at Time Duration
5 -min
10 -min
15 -min
30 -min
1 -hr
2 -hr
3 -hr
6 -hr
24 -hr
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
output
output
output
output
output
output
output
output
output
2-yr
3.48
2.70
2.28
1.58
1.00
0.57
0.41
0.23
0.07
5-yr
4.96
3.85
3.25
2.25
1.43
0.79
0.56
0.31
0.09
10-yr
5 93
4.60
3.89
2.69
1.70
0.93
0.66
0.36
0.11
25-yr
7.16
5.56
4.69
3.25
2.06
1.14
0.81
0.45
0.13
50-yr
8.32
6.45
5.45
3.78
2.39
1.29
0.90
0.49
0.14
100-yr
9.40
7.30
6.16
4.27
2.70
1.44
1.00
0.53
0.16
Rain Zone 133 35719 13005.xls, Z-1 2/22/2013, 11:50 AM
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10-yr 25-yr
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100-yr
Rain Zone 133 35719 13005.xls, Z-1 2/22/2013, 11:50 AM
APPENDIX B-3
HISTORIC RUNOFF CALCULATIONS
Tetra Tech, Inc.
OA
= •�
d• 4
o
a`v
en O
Cti
V N
C .v
at
E
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E
G
Gravel Road
Y
I -hour Point Rainfall Depth
Runoff Coefficients, C
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1. Refer to Table RO-3 for Site Imperviousness
2. Refer to Table RO-S for Runoff Coefficients. C
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P:\357I9\ 133-35719- I3005\Docs\Reports \Prelim Drainage Report \Cales\Runoff Calculations_Kcota.xls
DRAINAGE CRITERIA MANUAL (V. 1) RUNOFF
2.4 Time of Concentration
One of the basic assumptions underlying the Rational Method is that runoff is a function of the average
rainfall rate during the time required for water to flow from the most remote part of the drainage area
under consideration to the design point. However, in practice, the time of concentration can be an
empirical value that results in reasonable and acceptable peak flow calculations. The time of
concentration relationships recommended in this Manual are based in part on the rainfall -runoff data
collected in the Denver metropolitan area and are designed to work with the runoff coefficients also
recommended in this Manual. As a result, these recommendations need to be used with a great deal of
caution whenever working in areas that may differ significantly from the climate or topography found in
the Denver region.
For urban areas, the time of concentration, tc, consists of an initial time or overland flow time, t„ plus the
travel time, t,, in the storm sewer, paved gutter, roadside drainage ditch, or drainage channel. For non -
urban areas, the time of concentration consists of an overland flow time, r,, plus the time of travel in a
defined form, such as a swale, channel, or drainageway. The travel portion, t,, of the time of
concentration can be estimated from the hydraulic properties of the storm sewer, gutter, swale, ditch, or
drainageway. initial time, on the other hand, will vary with surface slope, depression storage, surface
cover, antecedent rainfall, and infiltration capacity of the soil, as well as distance of surface flow. The
time of concentration is represented by Equation R0-2 for both urban and non -urban areas:
1� =1, +1$
in which:
t, = time of concentration (minutes)
t, = initial or overland flow time (minutes)
t, = travel time in the ditch, channel, gutter, storm sewer, etc. (minutes)
2.4.1 Initial Flow Time
The initial or overland flow time, t,, may be calculated using equation RO-3:
_ 0.395(1.1-05
1, S0."
in which:
t, = initial or overland flow time (minutes)
C5 = runoff coefficient for 5 -year frequency (from Table RO-5)
(RO-2)
(RO-3)
2007-01 RO-5
Urban Drainage and Flood Control District
RUNOFF DRAINAGE CRITERIA MANUAL (V. 1)
L = length of overland flow (500 ft maximum for non -urban land uses, 300 ft maximum for urban
land uses)
S = average basin slope (ft/ft)
Equation RO-3 is adequate for distances up to 500 feet. Note that, in some urban watersheds, the
overland flow time may be very small because flows quickly channelize.
2.4.2 Overland Travel Time
For catchments with overland and channelized flow, the time of concentration needs to be considered in
combination with the overland travel time, t,, which is calculated using the hydraulic properties of the
swale, ditch, or channel. For preliminary work, the overland travel time, t,, can be estimated with the help
of Figure RO-1 or the following equation (Guo 1999):
Y= C,,S,,.os
in which:
V = velocity (ft/sec)
C,. = conveyance coefficient (from Table RO-2)
S,,. = watercourse slope (ft/ft)
Table RO-2—Conveyance Coefficient, C,.
(RO-4)
Type of Land Surface
Conveyance Coefficient, C,.
Heavy meadow
2.5
Tillage/field
5
Short pasture and lawns
7
Nearly bare ground
10
Grassed waterway
15
Paved areas and shallow paved swales
20
The time of concentration, t,, is then the sum of the initial flow time, r„ and the travel time, t,, as per
Equation RO-2.
2.4.3 First Design Point Time of Concentration in Urban Catchments
Using this procedure, the time of concentration at the first design point (i.e., initial flow time, t,) in an
urbanized catchment should not exceed the time of concentration calculated using Equation RO-5.
L
I` 180 +10
in which:
(RO-5)
t, = maximum time of concentration at the first design point in an urban watershed (minutes)
RO-6
2007-01
Urban Drainage and Flood Control District
DRAINAGE CRITERIA MANUAL (V. 1) RUNOFF
Table RO-3—Recommended Percentage Imperviousness Values
Land Use or
Surface Characteristics
Percentage
Imperviousness
Business:
Commercial areas
95
Neighborhood areas
85
Residential:
Single-family
*
Multi -unit (detached)
60
Multi -unit (attached)
75
Half -acre lot or larger
Apartments
80
Industrial:
Light areas
80
Heavy areas
90
Parks, cemeteries
5
Playgrounds
10
Schools
50
Railroad yard areas
15
Undeveloped Areas:
Historic flow analysis
2
Greenbelts, agricultural
2
Off -site flow analysis
(when land use not defined)
45
Streets:
Paved
100
Gravel (packed)
40
Drive and walks
90
Roofs
90
Lawns, sandy soil
0
Lawns, clayey soil
0
* See Figures RO-3 through RO-5 for percentage imperviousness.
CA = KA + (1.31i3 —1.44i2 +1.135i — 0.12) for CA ≥ 0, otherwise CA= 0 (RO-6)
Co) = Ka, + (0.858i3 - 0.786i2 + 0.774i + 0.04) (RO-7)
CB = (CA + Ca)/2
2007-01
Urban Drainage and Flood Control District
RO-9
DRAINAGE CRITERIA MANUAL (V. 1)
RUNOFF
Table RO-5-- Runoff Coefficients, C
Percentage
Imperviousness
Type C and D NRCS Hydrologic Soil Groups
2-yr
5-yr
10-yr
25-yr
50-yr
100-yr
0%
0.04
0.15
0.25
0.37
0.44
0.50
5%
0.08
0.18
0.28
0.39
0.46
0.52
10%
0.11
0.21
0.30
0.41
0.47
0.53
15%
0.14
0.24
0.32
0.43
0.49
0.54
20%
0.17
0.26
0.34
0.44
0.50
0.55
25%
0.20
0.28
0.36
0.46
0.51
0.56
30%
0.22
0.30
0.38
0.47
0.52
0.57
35%
0.25
0.33
0.40
0.48
0.53
0.57
40%
0.28
0.35
0.42
0.50
0.54
0.58
45%
0.31
0.37
0.44
0.51
0.55
0.59
50%
0.34
0.40
0.46
0.53
0.57
0.60
55%
0.37
0.43
0.48
0.55
0.58
0.62
60%
0.41
0.46
0.51
0.57
0.60
0.63
65%
0.45
0.49
0.54
0.59
0.62
0.65
70%
0.49
0.53
0.57
0.62
0.65
0.68
75%
0.54
0.58
0.62
0.66
0.68
0.71
80%
0.60
0.63
0.66
0.70
0.72
0.74
85%
0.66
0.68
0.71
0.75
0.77
0.79
90%
0.73
0.75
0.77
0.80
0.82
0.83
95%
0.80
0.82
0.84
0.87
0.88
0.89
100%
0.89
0.90 (
0.92
0.94
0.95
0.96
TYPE B NRCS HYDROLOGIC SOILS GROUP
0%
0.02
0.08
0.15
0.25
0.30
0.35
5%
0.04
0.10
0.19
0.28
0.33
0.38
10%
0.06
0.14
0.22
0.31
0.36
0.40
15%
0.08
0.17
0.25
0.33
0.38
0.42
20%
0.12
0.20
0.27
0.35
0.40
0.44
25%
0.15
0.22
0.30
0.37
0.41
0.46
30%
0.18
0.25
0.32
0.39
0.43
0.47
35%
0.20
0.27
0.34
0.41
0.44
0.48
40%
0.23
0.30
0.36
0.42
0.46
0.50
45%
0.26
0.32
0.38
0.44
0.48
0.51
50%
0.29
0.35
0.40
0.46
0.49
0.52
55%
0.33
0.38
0.43
0.48
0.51
0.54
60%
0.37
0.41
0.46
0.51
0.54
0.56
65%
0.41
0.45
0.49
0.54
0.57
0.59
70%
0.45
0.49
0.53
0.58
0.60
0.62
75%
0.51
0.54
0.58
0.62
0.64
0.66
80%
0.57
0.59
0.63
0.66
0.68
0.70
85%
0.63
0.66
0.69
0.72
0.73
0.75
90%
0.71
0.73
0.75
0.78
0.80
0.81
95%
0.79
0.81
0.83
0.85
0.87
0.88
100%
0.89
0.90
0.92
0.94
0.95
0.96
2007-01
Urban Drainage and Flood Control District
RO-11
RUNOFF
DRAINAGE CRITERIA MANUAL (V. 1)
TABLE RO-5 (Continued) —Runoff Coefficients, C
Percentage
Imperviousness
Type A NRCS Hydrologic Soils Group
2-yr
5-yr
10-yr
25-yr
50-yr
100-yr
0%
0.00
0.00
0.05
0.12
0.16
0.20
5%
0.00
0.02
0.10
0.16
0.20
0.24
10%
0.00
0.06
0.14
0.20
0.24
0.28
15%
0.02
0.10
0.17
0.23
0.27
0.30
20%
0.06
0.13
0.20
0.26
0.30
0.33
25%
0.09
0.16
0.23
0.29
0.32
0.35
30%
0.13
0.19
0.25
0.31
0.34
0.37
35%
0.16
0.22
0.28
0.33
0.36
0.39
40%
0.19
0.25
0.30
0.35
0.38
0.41
45%
0.22
0.27
0.33
0.37
0.40
0.43
50%
0.25
0.30
0.35
0.40
0.42
0.45
55%
0.29
0.33
0.38
0.42
0.45
0.47
60%
0.33
0.37
0.41
0.45
0.47
0.50
65%
0.37
0.41
0.45
0.49
0.51
0.53
70%
0.42
0.45
0.49
0.53
0.54
0.56
75%
0.47
0.50
0.54
0.57
0.59
0.61
80%
0.54
0.56
0.60
0.63
0.64
0.66
85%
0.61
0.63
0.66
0.69
0.70
0.72
90%
0.69
0.71
0.73
0.76
0.77
0.79
95%
0.78
0.80
0.82
0.84
0.85
0.86
100%
0.89
0.90
0.92
0.94
0.95
0.96
RO-12
2007-01
Urban Drainage and Flood Control District
APPENDIX B-4
OFF -SITE RUNOFF CALCULATIONS
Project: Keota Facility Simulation Run: 100-yr
Start of Run: 01Jun2013, 06:00 Basin Model: O1
End of Run: 02Jun2013, 06:00 Meteorologic Model: 100-yr
Compute Time: 22Feb2013, 12:38:27 Control Specifications: Control 1
Hydrologic
Element
Drainage Area
(MI2)
Peak DischargeTime
(CFS)
of Peak
Volume
(AC -FT)
Off Site Basin, 01
0.426
216.2
01Jun2013, 07:58
21.6
Project: Keota Facility
Simulation Run: 100-yr Subbasin: Off Site Basin, O1
Start of Run:
End of Run:
Compute Time:
Computed Results
01Jun2013, 06:00
02Jun2013, 06:00
22Feb2013, 12:38:27
Basin Model:
Meteorologic Model:
Control Specifications:
Volume Units: AC -FT
01
100-yr
Control 1
Peak Discharge :
Total Precipitation :
Total Loss :
Total Excess :
216.2 (CFS)
65.1 (AC -FT)
43.5 (AC -FT)
21.6 (AC -FT)
Date/Time of Peak Discharge :
Total Direct Runoff :
Total Baseflow :
Discharge :
01Jun2013, 07:58
21.6 (AC -FT)
0.0 (AC -FT)
21.6 (AC -FT)
Subbasin "Off Site Basin, O1" Results for Run "100-yr"
I I 1 1 1
O O O CA 0 O CO OO
O CV
O O O O O O O
(u!) Uldo
O
O
N
O
to
O
O
(sdu) Mold
O
O
O
O
O
co
O
O
O
O
O
O
a
r -
N
O
02Jun201 3
Run:100-yr Element:OFF SITE BASIN, O1 Result. Precipitation Loss
--- Run:100-yr Element:OFF SITE BASIN, O1 Result Baseflow
O p
O -
a
U
� 7
a O
(.0) N
67 N
C
O v
O N O O
Z Z
Q Q
CO CO
W
H H
C U
LL LL
O O O
O C C
O d N
EE
U N
La -1
O O
O O
O C C
O J J
0
CY CY
O O 0
� I
Keota Oil and Gas Processing Facility
Off Site Runoff Calculations
2 Yr
1.75
24 -hour Point Rainfall Depth
5 Yr 10 Yr
2.20 2.58
100 Yr
3.74
Site Imperviousness
Roof/Tank Gravel Road Undeveloped
90
40
2
Map Unit No Mapunit Name
Hydrologic Soils
group
Area (acres)
4 Ascalon fine sandy loam, 0 to 6 percent slopes
10 Avar-Manzanola complex, 0 to 3 percent slopes
40 Nunn loam, 0 to 6 percent slopes
44 Olney fine sandy loam, 0 to 6 percent slopes
45 Olney fine sandy loam, 6 to 9 percent slopes
54 Platner loam, 0 to 3 percent slopes
B
D
C
B
B
C
7.98
6.02
167.61
77.22
8.60
5.12
272.55
Total =
Cover
Hydrologic
Conditions
A
SCS Curve Number, CN
D
B
C
Pasture,
Poor
68
79
86
89
grassland, or
Fair
49
69
79
84
range
Good
39
61
/4
80
0.426 square miles
Basin
Area
Basin Area (acres)
Soil Type D
Gravel Road
Basin Imneniousness (acresl
I',
CN
Soil Type B Soil Type C
Roof Tank Undeveloped
01
272.55
93.80
172.73
6.02
1.77
0
270.78
2.2
75.7
Basin
(ft)
5
(ft/ft)
Tsheet
Time of Concentration, Tc (mini
Tshallow Tchannel
Tc
Lag Time [min)
Tlag
01
5,725 0.016
35 44
0 79
48
Eguatiuns:
Tc = Tsheet + Tshallow + Tchannel
Tsheet = (0.007•(N•L)^0.5)/(P2^0.5 • S^0.8)
N - overland flow roughness coefficient per Table 14
L = flow length, ft. (30 - 300)
P2 = 2 -year, 24 -hour rainfall depth. inches
S = average watercourse slope. ft/ft
Tshallow = L / V
L = flow length, ft.
V = 16.1345 • S^03 (for an unpaved surface)
S = average watercourse slope
Tchannel =L/1/
L - flow length. ft.
V - (C•R^.67•S^0.5)/n
C - conversion constant. 1.49
R - hydraulic radius
S = average watercourse slope
a manning's roughness coefficient
P:\35719\133-35719-13005\Dots\Reports\Prelim Drainage Report\Calcs\
Offsite Soils and Calcs.xlsx
1 of 1 Tetra Tech, Inc.
Chapter 6 Modeling Direct Runoff
LL
t�, =CC,( )NS
(35)
where S = overall slope of longest watercourse from point of concentration to the
boundary of drainage basin; and N = an exponent, commonly taken as 0.33.
Others have proposed estimating tp as a function of tc , the watershed time of
concentration (Cudworth, 1989; USACE, 1987). Time of concentration is the time of
flow from the most hydraulically remote point in the watershed to the watershed
outlet, and may be estimated with simple models of the hydraulic processes, as
described here in the section on the SCS UH model. Various studies estimate tp as
50-75% of tc.
SCS Unit Hydrograph Model
The Soil Conservation Service (SCS) proposed a parametric UH model; this model is
included in the program. The model is based upon averages of UH derived from
gaged rainfall and runoff for a large number of small agricultural watersheds
throughout the US. SCS Technical Report 55 (1986) and the National Engineering
Handbook (1971) describe the UH in detail.
Basic Concepts and Equations
At the heart of the SCS UH model is a dimensionless, single -peaked UH. This
dimensionless UH, which is shown in ZZ, expresses the UH discharge, Ur, as a ratio
to the UH peak discharge, Up, for any time t, a fraction of Tp, the time to UH peak.
Research by the SCS suggests that the UH peak and time of UH peak are related by:
Up,=C A
Tp
(36)
in which A = watershed area; and C = conversion constant (2.08 in SI and 484 in
foot-pound system). The time of peak (also known as the time of rise) is related to
the duration of the unit of excess precipitation as:
At
Tp=z+1/ag
(37)
in which at= the excess precipitation duration (which is also the computational
interval in the run); and fag= the basin lag, defined as the time difference between the
center of mass of rainfall excess and the peak of the UH. [Note that for adequate
definition of the ordinates on the rising limb of the SCS UH, a computational interval,
�f , that is less than 29% of t,ag must be used (USACE, 1998).]
When the lag time is specified, the program solves Equation 37 to find the time of UH
peak, and Equation 36 to find the UH peak. With U,, and Tp known, the UH can be
found from the dimensionless form, which is built into the program, by multiplication.
Estimating the Model Parameters
The SCS UH lag can be estimated via calibration, using procedures described in
Chapter 9, for gaged headwater subwatersheds.
55
Chapter 6 Modeling Direct Runoff
For ungaged watersheds, the SCS suggests that the UH lag time may be related to
time of concentration, tc, as:
flag =0.6tc. (38)
Time of concentration is a quasi -physically based parameter that can be estimated
as:
t c = t.chvet + t shallow + t channel
(39)
where tsheet= sum of travel time in sheet flow segments over the watershed land
surface; tshallaw= sum of travel time in shallow flow segments, down streets, in gutters,
or in shallow rills and rivulets; and tchannel = sum of travel time in channel segments.
Identify open channels where cross section information is available. Obtain cross
sections from field surveys, maps, or aerial photographs. For these channels,
estimate velocity by Manning's equation:
CR2/3sv2
V -
77
(40)
where V = average velocity; R = the hydraulic radius (defined as the ratio of channel
cross-section area to wetted perimeter); S = slope of the energy grade line (often
approximated as channel bed slope); and C = conversion constant (1.00 for SI and
1.49 for foot-pound system.) Values of n, which is commonly known as Manning's
roughness coefficient, can be estimated from textbook tables, such as that in
Chaudhry (1993). Once velocity is thus estimated, channel travel time is computed
as:
L
tchannel = Y
where L = channel length.
(41 )
Sheet flow is flow over the watershed land surface, before water reaches a channel.
Distances are short —on the order of 10-100 meters (30-300 feet). The SCS
suggests that sheet -flow travel time can be estimated as:
0.007(NL)08
(sheer — (P )0.5 s0.4
(42)
in which N = an overland -flow roughness coefficient; L = flow length; P2 = 2 -year, 24 -
hour rainfall depth, in inches; and S = slope of hydraulic grade line, which may be
approximated by the land slope. (This estimate is based upon an approximate
solution of the kinematic wave equations, which are described later in this chapter.)
Table 14 shows values of N for various surfaces.
Sheet flow usually turns to shallow concentrated flow after 100 meters. The average
velocity for shallow concentrated flow can be estimated as:
V=
16.1345 J for unpaved sulfate
20.3282 J for paved surface
(43)
56
Chapter 6 Modeling Direct Runoff
From this, the travel time can be estimated with Equation 41.
Table 14. Overland -flow roughness coefficients for sheet -flow modeling (USACE,
1998)
Surface Description N
Smooth surfaces (concrete, asphalt, gravel, or bare soil) 0.011
Fallow (no residue) 0.05
Cultivated soils:
Residue cover 5 20% 0.06
Residue cover > 20% 0.17
Grass:
Short grass prairie 0.15
Dense grasses, including species such as weeping love grass, 0.24
bluegrass, buffalo grass, blue grass, and native grass mixtures
Bermudagrass 0.41
Range 0.13
Woods'
Light underbrush 0.40
Dense underbrush 0.80
Notes:
1 When selecting N, consider cover to a height of about 0.1 ft. This is the only part of the
plant cover that will obstruct sheet flow.
Clark Unit Hydrograph Model
Clark's model derives a watershed UH by explicitly representing two critical
processes in the transformation of excess precipitation to runoff:
• Translation or movement of the excess from its origin throughout the
drainage to the watershed outlet.
• Attenuation or reduction of the magnitude of the discharge as the
excess is stored throughout the watershed.
Basic Concepts and Equations
Short-term storage of water throughout a watershed —in the soil, on the surface, and
in the channels —plays an important role in the transformation of precipitation excess
to runoff. The linear reservoir model is a common representation of the effects of this
storage. That model begins with the continuity equation:
dS
—=I, —O,
;it
(44)
in which dS/dt = time rate of change of water in storage at time t, It = average inflow
to storage at time t, and Ot = outflow from storage at time t.
With the linear reservoir model, storage at time t is related to outflow as:
S, = RO, (45 )
57
Appendix A CN Tables
SCS TR-55 Table 2-2a — Runoff curve numbers for urban areas'
Cover description Curve numbers for hydrologic
soil group
Cover type and hydrologic condition
Average percent A BCD
impervious area -
Fully developed urban areas
Open space (lawns, parks, golf courses, cemeteries,
etc,)':
Poor condition (grass cover < 50%) 68 79 86 89
Fair condition (grass cover 50% to 75%) 49 69 79 84
Good condition (grass cover > 75%) 39 61 74 80
Impervious areas:
Paved parking lots, roofs, driveways, etc.
(excluding right-of-way) 98 98 98 98
Streets and roads:
Paved; curbs and storm sewers (excluding
right-of-way) 98 98 98 98
Paved; open ditches (including right-of-way) 83 89 92 93
Gravel (including right-of-way) 76 85 89 91
Dirt (including right-of-way) 72 82 87 89
Western desert urban areas:
Natural desert landscaping (pervious areas only)4 63 77 85 88
Artificial desert landscaping (impervious weed
barrier, desert shrub with 1- to 2 -inch sand
or gravel mulch and basin borders) 96 96 96 96
Urban districts:
Commercial and business 85 89 92 94 95
Industrial 72 81 88 91 93
Residential districts by average lot size
1/8 acre or less (town houses) 65 77 85 90 92
1/4 acre 38 61 75 83 87
1/3 acre 30 57 72 81 86
1/2 acre 25 54 70 80 85
1 acre 20 51 68 79 84
2 acre 12 46 65 77 82
Developing urban areas
Newly graded areas (pervious areas only,
no vegetation)s 77 86 91 94
Idle lands (CN's are determined using cover types
similar to those in table 2-2c
Average runoff condition. and 1, = 0.2S.
2 The average percent impervious area shown was used to develop the composite CN's. Other assumptions are as follows: impervious areas
are directly connected to the drainage system, impervious areas have a CN of 98, and pervious areas are considered equivalent to open
space in good hydrologic condition. CN's for other combinations of conditions may be computed using figure 2-3 or 2-4.
CH's shown are equivalent to those of pasture. Composite CN's may be computed for other combinations of open space cover type.
Composite CN's for natural desert landscaping should be computed using figures 2-3 or 2-4 based on the impervious area percentage (CN
= 98) and the pervious area CN. The pervious area CN's are assumed equivalent to desert shrub in poor hydrologic condition.
Composite CN's to use for the design of temporary measures during grading and construction should be computed using figure 2-3 or 2-4,
based on the degree of development (imperviousness area percentage) and the CN's for the newly graded pervious areas.
115
Chapter 3
Time of Concentration and
Travel Time
Travel time ( T1) is the time it takes water to travel
from one location to another in a watershed. Tt is a
component of time of concentration ( Ta ), which is
the time for runoff to travel from the hydraulically
most distant point of the watershed to a point of
interest within the watershed. 'I', is computed by
summing all the travel times for consecutive compo-
nents of the drainage conveyance system.
Tc influences the shape and peak of the runoff
hydrograph. Urbanization usually decreases Tc,
thereby increasing the peak discharge. But T, can be
increased as a result of (a) ponding behind small or
inadequate drainage systems, including storm drain
inlets and road culverts, or (b) reduction of land slope
through grading.
Factors affecting time of concen-
tration and travel time
Surface roughness
One of the most significant effects of urban develop-
ment on flow velocity is less retardance to flow. That
is, undeveloped areas with very slow and shallow
overland flow through vegetation become modified by
urban development: the flow is then delivered to
streets, gutters, and storm sewers that transport runoff
downstream more rapidly. Travel time through the
watershed is generally decreased.
Channel shape and flow patterns
In small non -urban watersheds, much of the travel
time results from overland flow in upstream areas.
Typically, urbanization reduces overland flow lengths
by conveying storm runoff into a channel as soon as
possible. Since channel designs have efficient hydrau-
lic characteristics, runoff flow velocity increases and
travel time decreases.
Slope
Slopes may be increased or decreased by urbanization,
depending on the extent of site grading or the extent
to which storm sewers and street ditches are used in
the design of the water management system. Slope will
tend to increase when channels are straightened and
decrease when overland flow is directed through
storm sewers, street gutters, and diversions.
Computation of travel time and
time of concentration
Water moves through a watershed as sheet flow,
shallow concentrated flow, open channel flow, or
some combination of these. The type that occurs is a
function of the conveyance system and is best deter-
mined by field inspection.
Travel time (Ti) is the ratio of flow length to flow
velocity:
T_
t 3600V
where:
[eq. 3-1]
Tt = travel time (hr)
L = flow length (ft)
V = average velocity (ft/s)
3600 = conversion factor from seconds to hours.
Time of concentration ( Tv ) is the sum of 'ft values for
the various consecutive flow segments:
T� = Ttr +Tt2 +...Ttm
where:
Te = time of concentration (hr)
m = number of flow segments
[eq. 3-2]
(210-VI-TR-55, Second Ed., June 1986) 3-1
Chapter 3
Time of Concentration and Travel Time Technical Release 55
Urban Hydrology for Small Watersheds
Figure 3-1 Average velocities for estimating travel time for shallow concentrated flow
Watercourse slope (ft/ft)
Average velocity (ft/sec)
3-2 (210-V1 TR-55, Second Ed., June 1986)
Chapter 3
Time of Concentration and Travel Time
Technical Release 55
Urban Hydrology for Small Watersheds
Sheet flow
Sheet flow is flow over plane surfaces. It usually
occurs in the headwater of streams. With sheet flow,
the friction value (Manning's n) is an effective rough-
ness coefficient that includes the effect of raindrop
impact; drag over the plane surface; obstacles such as
litter, crop ridges, and rocks; and erosion and trans-
portation of sediment. These n values are for very
shallow flow depths of about 0.1 foot or so. Table 3-1
gives Manning's n values for sheet flow for various
surface conditions.
Table 3-1 Roughness coefficients (Manning's n) for
sheet flow
Surface description n l/
Smooth surfaces (concrete, asphalt,
gravel, or bare soil) 0.011
Fallow (no residue) 0.05
Cultivated soils:
Residue cover ≤20% 0.06
Residue cover >20% 0.17
Grass:
Short grass prairie 0.15
Dense grasses 2i 0.24
Bermudagrass . 0.41
Range (natural) 0.13
Woods:2
Light underbrush 0.40
Dense underbrush 0.80
The n values are a composite of information compiled by Engman
(I986).
2 Includes species such as weeping lovegrass, bluegrass, buffalo
grass, blue grama grass, and native grass mixtures.
3 When selecting n , consider cover to a height of about 0.1 ft. This
is the only part of the plant cover that will obstruct sheet flow.
For sheet flow of less than 300 feet, use Manning's
kinematic solution (Overtop and Meadows 1976) to
compute Tt:
0
T _ .007(nL)o.s
t ( )°5s0.4
2
where:
[eq. 3-3]
Tt = travel time (hr),
n = Manning's roughness coefficient (table 3-1)
L = flow length (ft)
P2 = 2 -year, 24 -hour rainfall (in)
s = slope of hydraulic grade line
(land slope, ft/ft)
This simplified form of the Manning's kinematic solu-
tion is based on the following: (1) shallow steady
uniform flow, (2) constant intensity of rainfall excess
(that part of a rain available for runoff), (3) rainfall
duration of 24 hours, and (4) minor effect of infiltra-
tion on travel time. Rainfall depth can be obtained
from appendix B.
Shallow concentrated flow
After a maximum of 300 feet, sheet flow usually be-
comes shallow concentrated flow. The average veloc-
ity for this flow can be determined from figure 3-1, in
which average velocity is a function of watercourse
slope and type of channel. For slopes less than 0.005
ft/ft, use equations given in appendix F for figure 3-1.
Tillage can affect the direction of shallow concen-
trated flow. Flow may not always be directly down the
watershed slope if tillage runs across the slope.
After determining average velocity in figure 3-1, use
equation 3-1 to estimate travel time for the shallow
concentrated flow segment.
Open channels
Open channels are assumed to begin where surveyed
cross section information has been obtained, where
channels are visible on aerial photographs, or where
blue lines (indicating streams) appear on United States
Geological Survey (USGS) quadrangle sheets.
Manning's equation or water surface profile informa-
tion can be used to estimate average flow velocity.
Average flow velocity is usually determined for bank -
full elevation.
(210-VI-TR-55, Second Ed., June 1986) 3-3
Chapter 3
Time of Concentration and Travel Time Technical Release 55
Urban Hydrology for Small Watersheds
Manning's equation is:
2
V_1.49r3s2
n
where:
[eq. 3-4]
V = average velocity (ft/s)
r = hydraulic radius (ft) and is equal to a/p«.
a = cross sectional flow area (ft2)
p,Y = wetted perimeter (ft)
s = slope of the hydraulic grade line (channel
slope, ft/ft)
n = Manning's roughness coefficient for open
channel flow.
Manning's n values for open channel flow can be
obtained from standard textbooks such as Chow
(1959) or Linsley et al. (1982). After average velocity is
computed using equation 3-4, Ti for the channel seg-
ment can be estimated using equation 3-1.
Reservoirs or lakes
Sometimes it is necessary to estimate the velocity of
flow through a reservoir or lake at the outlet of a
watershed. This travel time is normally very small and
can be assumed as zero.
Limitations
• Manning's kinematic solution should not be used
for sheet flow longer than 300 feet. Equation 3-3
was developed for use with the four standard
rainfall intensity -duration relationships.
• In watersheds with storm sewers, carefully identify
the appropriate hydraulic flow path to estimate T,
Storm sewers generally handle only a small portion
of a large event. The rest of the peak flow travels
by streets, lawns, and so on, to the outlet. Consult a
standard hydraulics textbook to determine average
velocity in pipes for either pressure or nonpressure
flow.
• The minimum TT used in TR-55 is 0.1 hour.
• A culvert or bridge can act as a reservoir outlet if
there is significant storage behind it. The proce-
dures in TR-55 can be used to determine the peak
flow upstream of the culvert. Detailed storage
routing procedures should be used to determine
the outflow through the culvert.
Example 3-1
The sketch below shows a watershed in Dyer County,
northwestern Tennessee. The problem is to compute
're at the outlet of the watershed (point D). The 2 -year
24 -hour rainfall depth is 3.6 inches. All three types of
flow occur from the hydraulically most distant point
(A) to the point of interest (D). To compute T, first
determine Ti for each segment from the following
information:
Segment AB: Sheet flow; dense grass; slope (s) = 0.01
ft/ft; and length (L) = 100 ft. Segment BC: Shallow
concentrated flow; unpaved; s = 0.01 ft/ft; and
L = 1,400 ft. Segment CD: Channel flow; Manning's
n = .05; flow area (a) = 27 ft2; wetted perimeter
(p„) = 28.2 ft; s = 0.005 ft/ft; and L = 7,300 ft.
See figure 3-2 for the computations made on
worksheet 3.
3-4 (210-VI-TR-55, Second Ed., June 1986)
APPENDIX B-5
DEVELOPED RUNOFF CALCULATIONS
Tetra Tech, Inc.
L.•
Lim
H
61 Jet
• o
• L
on 0
Q =
rJa
C
z
O C`
O
V
0 O
Y
El
I -hr Point Rainfall Myth
o
O
O
L.V r
t
G..--
,
i.
N
'0 n h T4 moo
Y M T K Y
O O G C O C C
PI C N N N N
J 0 O O O O O
- 0 r1 - - - _
0 0 0 0 0 0 c
° O O'^ O O O
O G O O O O O
Ravin lumen iouwncss facres)
Gravel Road Roof Tank Undeveloped 1 %
.0 O Q ,d O O 0 O
Od N 7y OG ri ei 6 77
v, O P 00 V. V 8 Y
Y .O N- gt n 4 6
.'-e! 0 19 - 8 8
0 0 c ri - 0 O
- O O rSI'. ° 8 8
- 0 0 r, - 0 0 G
0
AA88g°'3,9
F
N
U
1'
_
4
C 0 0— 4 M N
c
8 0 8 `
••••090,9.—
T '' C 00 000
N co. co O: 'R N 8 Y T
W '0 r1 '� M r O r G S
D C
pa -
C W R
0) ti4 I"
U
}
y O
C _
- ..
NN
00 Op.
9 M Y t� 00 b
O O O. r O h P n
;-"z vi G .D 0 Of - g
,� pp. 4
�4 i N � � A C
t N O G ^I - O h
n
'0 O Q 0000 ly N O
=00a.•ico_
i
O
r.1
M V, N 0 N N N
'G .O M V. N M
O- O.. M .O O
4 Y fl ... ...i - 1
r'...,1
,OM,1 00 M 1`
M N - -
M f N- O� C N
N N_ N - O -
_
_
----,0000000
_
Mp P+ 00 .O .00
. ? .p
_ — V' 1 N .0 4
I I e
e
i n h
0 0 0 8 0 0 0
_ p •- O O .O O
`
_
�, M 4 S
!! .. ;TS om3
U
.14
o
• 2
in C
a
et at
I- F
O O
0C
ri
l
Tt. undeveloped - Ti + TI
0
APPENDIX C - HYDRAULIC COMPUTATIONS
APPENDIX C-1: CULVERT CALCULATIONS
APPENDIX C-2: DRAINAGE CHANNEL CALCULATIONS
APPENDIX C-3: WQCV CALCULATIONS
APPENDIX C-4: DETENTION POND CALCULATIONS
APPENDIX C-5: RETENTION POND CALCULATIONS
APPENDIX C-1
CULVERT CALCULATIONS
Tetra Tech. Inc.
Site _Imperviousness
Gravel Road Undeveloped
7
ri
I -hour Point Rainfall Depth
}
8
O O
h o
N N
O O
8 8
N
O O
j
on
0
▪ O
N
8
▪ 6
O
o r
c
'l.
88
O C
00
C O
00
Basin Flotcs U lcfst
.72
.1
✓ C
E
6• a O O
O O
8
I. Refer to Table RO-3 for Site Imperviousness
2. Refer to Table RO-5 for Runof1Coefficients. C
P:\35719\I33-35719-I3005\Docs\Reports\Prelim Drainage Report \Calcs\Runoff Calculations_Keota.xls
Culvert Report
Hydraflow Express Extension for AutoCAD® Civil 3D® 2009 by Autodesk, Inc.
Cir Culvert
Invert Elev Dn (ft)
Pipe Length (ft)
Slope (%)
Invert Elev Up (ft)
Rise (in)
Shape
Span (in)
No. Barrels
n -Value
Inlet Edge
Coeff. K,M,c,Y,k
= 4956.50
= 100.00
= 2.00
= 4958.50
= 15.0
= Cir
= 15.0
= 1
= 0.013
= Projecting
= 0.0045, 2, 0.0317, 0.69, 0.5
Embankment
Top Elevation (ft) = 4960.00
Top Width (ft) = 26.00
Crest Width (ft) = 20.00
Bev (MI
4%1.00
4960.00
495900
4958.00
4957.00
4956.00
4955.00
<Name)
Friday, Feb 22 2013
Calculations
Qmin (cfs) = 5.00
Qmax (cfs) = 15.00
Tailwater Elev (ft) = (dc+D)/2
Highlighted
Qtotal (cfs)
Qpipe (cfs)
Qovertop (cfs)
Veloc Dn (ft/s)
Veloc Up (ft/s)
HGL Dn (ft)
HGL Up (ft)
Hw Elev (ft)
Hw/D (ft)
Flow Regime
= 5.00
= 5.00
= 0.00
= 4.44
= 5.22
= 4957.58
= 4959.41
= 4959.91
= 1.13
= Inlet Control
30
40
HGL
50
60
Embank
10
90 100 110 120
H.. Depth (i0
250
inlet _ vtivi.
10 20
G [that
130 140
Reach Oll
150
050
-050
1.50
250
3.50
Q
Total
Veloc
Pipe Over
(cfs) (cfs)
5.00
6.00
7.00
8.00
9.00
10.00
11.00
12.00
5.00
5.63
5.80
5.94
6.07
6.18
6.29
6.34
13.00 6.42
14.00
6.54
Dn
(ft/s)
Up
(ft/s)
Depth
Dn
(in)
0.00
0.37
1.20
2.06
2.93
3.82
4.71
5.66
4.44
4.89
5.02
5.13
5.23
5.30
5.38
5.42
6.58 5.48
7.46
5.57
5.22 12.96
5.54 13.29
5.63 13.37
5.71 13.42
5.78 13.49
5.83 13.55
5.90 13.59
5.93 13.61
5.96 13.65
6.04 13.69
15.00 6.54 8.46 5.57 6.03 13.69
Hydraflow Express - Culvert Report - 02/22/13 1
Depth
Up
Dn
(in) (ft)
10.92
11.57
11.73
11.85
11.98
12.09
12.18
12.21
4957.58
4957.61
4957.61
4957.62
4957.62
4957.63
4957.63
4957.63
12.30 4957.64
12.39
12.39
4957.64
4957.64
Up
(ft)
HGL
Hw
(ft)
Hw/D
4959.41
4959.46
4959.48
4959.49
4959.50
4959.51
4959.52
4959.52
4959.53
4959.53
4959.53
4959.91
4960.04
4960.07
4960.10
4960.13
4960.16
4960.18
4960.20
1.13
1.23
1.26
1.28
1.30
1.32
1.35
1.36
4960.22 1.37
4960.25
4960.25
1.40
1.40
Hydraflow Express - Culvert Report - 02/22/13 2
Culvert Report
Hydraflow Express Extension for AutoCAD® Civil 3D® 2009 by Autodesk, Inc.
Driveway Culvert - South
Invert Elev Dn (ft)
Pipe Length (ft)
Slope (%)
Invert Elev Up (ft)
Rise (in)
Shape
Span (in)
No. Barrels
n -Value
Inlet Edge
Coeff. K,M,c,Y,k
= 4955.00
= 100.00
= 1.00
= 4956.00
= 15.0
= Cir
= 15.0
= 1
= 0.013
= Projecting
= 0.0045, 2, 0.0317, 0.69, 0.5
Embankment
Top Elevation (ft) = 4959.00
Top Width (ft) = 26.00
Crest Width (ft) = 20.00
Ebv (nl
4960.00
4959.00
4958.00
4957.00
4956.00
495500
4954.00
30
40
HGL
50
60
Enteric
70 80 90
100 110 120
Driveway Culvert - South
Friday, Feb 22 2013
Calculations
Qmin (cfs) = 5.00
Qmax (cfs) = 15.00
Tailwater Elev (ft) = (dc+D)/2
Highlighted
Qtotal (cfs)
Qpipe (cfs)
Qovertop (cfs)
Veloc Dn (ft/s)
Veloc Up (ft/s)
HGL Dn (ft)
HGL Up (ft)
Hw Elev (ft)
Hw/D (ft)
Flow Regime
= 5.00
= 5.00
= 0.00
= 4.44
= 5.22
= 4956.08
= 4956.91
= 4957.41
= 1.13
= Inlet Control
H.. Depth (ii)
400
Inky cachet
0
10 20
G Curvet
130 140
Reach (0(
3.00
2.00
1.00
0.00
1 CO
200
Q
Total
Veloc
Pipe Over
(cfs) (cfs)
Dn
(ft/s)
Up
(ft/s)
Depth
Dn
(in)
5.00
6.00
7.00
8.00
9.00
10.00
11.00
12.00
5.00
6.00
7.00
8.00
9.00
10.00
10.08
10.11
13.00 10.20
14.00
10.25
0.00
0.00
0.00
0.00
0.00
0.00
0.92
1.89
4.44
5.17
5.91
6.66
7.42
8.21
8.27
8.30
2.80 8.37
3.75
8.41
5.22 12.96
5.74 13.46
5.72 13.87
6.52 14.20
7.33 14.44
8.15 14.61
8.21 14.63
8.24 14.63
8.32 14.64
8.36 14.65
15.00 10.29 4.71 8.44 8.39 14.65
Hydraflow Express - Driveway Culvert - South - 02/22/13 1
Depth
Up
Dn
(in) (ft)
Up
(ft)
HGL
Hw
(ft)
Hw/D
10.92
11.91
14.78
15.00
15.00
15.00
15.00
15.00
4956.08
4956.12
4956.16
4956.18
4956.20
4956.22
4956.22
4956.22
15.00 4956.22
15.00
15.00
4956.22
4956.22
4956.91
4956.99
4957.23
4957.64
4958.04
4958.49
4958.53
4958.55
4958.59
4958.62
4958.63
4957.41
4957.61
4957.89
4958.20
4958.56
4959.01
4959.06
4959.08
1.13
1.29
1.51
1.76
2.05
2.41
2.44
2.46
4959.13 2.50
4959.16
4959.18
2.53
2.54
Hydraflow Express - Driveway Culvert - South - 02/22/13 2
APPENDIX C-2
DRAINAGE CHANNEL CALCULATIONS
Drainage Channel for Offsite Flows
Project Description
Friction Method
Solve For
Input Data
Roughness Coefficient
Channel Slope
Left Side Slope
Right Side Slope
Bottom Width
Discharge
Results
Normal Depth
Flow Area
Wetted Perimeter
Hydraulic Radius
Top Width
Critical Depth
Critical Slope
Velocity
Velocity Head
Specific Energy
Froude Number
Flow Type
GVF Input Data
Downstream Depth
Length
Number Of Steps
GVF Output Data
Upstream Depth
Profile Description
Profile Headloss
Downstream Velocity
Upstream Velocity
Normal Depth
Critical Depth
Channel Slope
Manning Formula
Normal Depth
Supercritical
0.030
0.01500 ft/ft
10.00 ft/ft (H:V)
20.00 ft/ft (H:V)
10.00 ft
222.60 ft3/s
1.37 ft
41.94 ft2
51.25 ft
0.82 ft
51.15 ft
1.39 ft
0.01399 ft/ft
5.31 ft/s
0.44 ft
1.81 ft
1.03
0.00 ft
0.00 ft
0
0.00 ft
0.00 ft
Infinity ft/s
Infinity ft/s
1.37 ft
1.39 ft
0.01500 ft/ft
Bentley Systems, Inc. Haestad Methods SotktidieQEl awMaster V8i (SELECTseries 1) [08.11.01.03)
2/22/201312:48:10 PM 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 1 of 2
Drainage Channel for Offsite Flows
GVF Output Data
Critical Slope 0.01399 ft/ft
Bentley Systems, Inc. Haestad Methods SoOBidiepliawMaster V8i (SELECTseries 1) [08.11.01.03)
2/22/201312:48:10 PM 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 2 of 2
Cross Section for Drainage Channel for Offsite Flows
Project Description
Friction Method
Solve For
Input Data
Roughness Coefficient
Channel Slope
Normal Depth
Left Side Slope
Right Side Slope
Bottom Width
Discharge
Cross Section Image
N
Manning Formula
Normal Depth
0.030
0.01500 ft/ft
1.37 ft
10.00 ft/ft (H:V)
20.00 ft/ft(H:V)
10.00 ft
222.60 ft3/s
F-1D.00ft H
1.37 ft
1
V:10 N
H: 1
Bentley Systems, Inc. Haestad Methods SoOBidieplNwMaster V8i (SELECTseries 1) [08.11.01.03]
2/22/201312:49:12 PM 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 1 of 1
APPENDIX C-3
WCQV CALCULATIONS
Keota Oil and Gas Processing Facility
WQCV Calculations
Basin ID
Contributing Area
(acres)
Imperviousness, I
(%)
WQCV
Design Volume
(ac -ft)
Al
6.57
17.5
0.105
0.07
A2
6.59
8.6
0.059
0.04
BI+B2
51.59
12.9
0.083
0.43
Equations:
WQCV = a (0.91I3 - 1.19I2+0781)
a = 1 (for 40 hr drain time)
Design Volume = (WQCV/12) * Area * 1.2
P:\35719\133-35719-13005\Docs\Reports\Prelim Drainage Report\Calcs\
Runoff Calculations Keota_xls Page 1 of 1
Tetra Tech, Inc.
Keota Oil and Gas Processing Facility
WQCV Pond - Basin B
Contour Contour Depth Incremental Cumulative Cumulative
Elevation Area Volume Volume Volume
(SQ FT) (FT) (CU FT) (CU FT) (AC FT)
4,949.60 587 0 0 0 0.00
4,949.80 4,440 0.2 503 503 0.01
4,950.00 11,136 0.2 1,558 2,060 0.05
4,950.20 20,630 0.2 3,177 5,237 0.12
4,950.40 32,755 0.2 5,338 10,575 0.24
4,950.60 47,080 0.2 7,984 18,559 0.43
4,950.80 63,578 0.2 11,066 29,625 0.68
4,951.00 82,241 0.2 14,582 44,206 1.01
4,951.20 102,869 0.2 18,511 62,717 1.44
4,951.40 128,161 0.2 23,103 85,820 1.97
4,951.60 169,135 0.2 29,730 115,550 2.65
4,951.80 222,614 0.2 39,175 154,725 3.55
4,952.00 273,062 0.2 49,568 204,292 4.69
4,952.20 285,346 0.2 55,841 260,133 5.97
4,952.40 299,032 0.2 58,438 318,571 7.31
WQCV (0.43 ac -ft)
Wier Crest Elev.
Page 1 of 1 Tetra Tech, Inc.
STAGE -DISCHARGE SIZING OF THE WATER QUALITY CAPTURE VOLUME (WQCV) OUTLET
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STAGE -DISCHARGE SIZING OF THE WATER QUALITY CAPTURE VOLUME (WQCV) OUTLET
STAGE -DISCHARGE CURVE FOR THE WQCV OUTLET STRUCTURE
A A N A
N f f PI 7 N N
(nap '1 al)a6e3S
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APPENDIX C-4
DETENTION POND CALCULATIONS
Keota Oil and Gas Processing Facility
Detention Pond Al Volume
Contour Contour Depth Incremental Cumulative Cumulative
Elevation Area Volume Volume Volume
(SQ FT) (FT) (CU FT) (CU FT) (AC FT)
4,955.20 577 0 0 0 0.00
4,955.40 2,679 0.2 326 326 0.01
4,955.60 6,195 0.2 887 1,213 0.03
4,955.80 11,120 0.2 1,732 2,945 0.07
4,956.00 17,388 0.2 2,851 5,795 0.13
4,956.20 24,772 0.2 4,216 10,011 0.23
4,956.40 32,519 0.2 5,729 15,741 0.36
4,956.60 40,385 0.2 7,290 23,031 0.53
4,956.80 48,394 0.2 8,878 31,909 0.73
4,957.00 56,521 0.2 10,491 42,400 0.97
4,957.20 64,786 0.2 12,131 54,531 1.25
4,957.40 72,588 0.2 13,737 68,268 1.57
4,957.60 80,324 0.2 15,291 83,560 1.92
4,957.80 86,851 0.2 16,718 100,277 2.30
4,958.00 92,082 0.2 17,893 118,170 2.71
4,958.20 96,006 0.2 18,809 136,979 3.14
WQCV (0.07 ac -ft)
10-yr WSE (0.18 ac -ft)
100-yr WSE (0.70 ac -ft)
Page 1 of 1 Tetra Tech, Inc.
DETENTION VOLUME BY THE MODIFIED FAA METHOD
Project: Keota Gas Processing Facility
Basin ID: Basin A-1
(For catchments less than 180 acres only. For larger catchments, use hydrograph routing method)
(NOTE: for catchments larger than 90 acres, CUHP hydrograph and routing are recommended)
Determination of MINOR Detention Volume Using Modified FAA Method
Determination of MAJOR Detention Volume Using Modified FAA Method
Deetan Information in tit :
I,=
A =
Typo a
T =
Tc =
q =
Pr •
C, =
C, •
C, =
percent
acres
A. B. C. or D
years t2. 5. 10, 25, 50. or 100)
minutes
cfsracre
inches
Design Information In tit :
I.
A •
Type •
T •
To •
G •
Pt •
C, •
C, •
Cr •
1750
percent
acres
A. B. C. cc D
hunt (2. 5.10. 25. 50. or 1001
minutes
dative
inches
Catchment Drainage Imperviousness
Catchment Dramege Are•
Predevelopment NRCS Soil Group
Return Period for Detention Control
Time of Concentration of Watershed
Allowable Unit RNaesa Rate
One -hour Pracrprratan
Design Rslntell IDF Formula 1 = Cj. P,!(C,+T,j•C,
CcePo ent One
Coefficient Two
Coefficient Three
17.50
Catchment Drainage Imperviousness
Catchment Drainage Area
Predevelopment NRCS Sod Group
Return Penod for Datenrwn Control
Time of Concantraoon of Watershed
Allowable Unn Release Rale
One -hour Precipitation
Design Rainfall 'OF Formula I =.C,' P,I(C,+T,•C,
Coefficient Om
Coefficient Two
Coefficient Three
6.57
8.570
B
B
10
100
14
14
0.19
0.19
1.70
2.70
28.50
28.50
10
10
0.789
0.788
Determination of Average Outflow from the Basin Calculated):
cfs
de
cubic feet
•5r045
Mr 5 -Minutes)
Determination of Avoracte Outflow from the Basin tCalculatedl:
cis
cis
cubic feel
a0a40
Runoff Coefficient
meow Peek Runoff
Allocable Peak
C =
Op -in •
Oudlow Rate Op -out =
Mod. FAA Minor Storage Volume •
Mod. FAA Minor Storage Volume =
c- Enter Rainfall Duration Incremental Inueese Value
0.26
Runoff Coefficient C •
Inflow Peek Runoff Op -in •
Allocable Peak Outfit, Rate Op -out it
Mod. FAA Major Storage Volume •
Mod. FAA Mater Storage Volume =
0.43
6.70
17.60
1.23
1.25
7,960
30.660
0.183
0.704
6
Here (e.g. 5
Rainfall
Duration
minutes
lnputl
Rainfall
Intensity
Indies! hr
(output)
Inflow
Volume
acre -feel
(Output)
Adjustment
Fedor
(output)
Average
Outflow
cis
(output)
Outflow
Volume
eve -taut
(output)
o.oiage
Volume
acre-feet
(output)
Rainfall
Duration
minutes
(nputl
Rainfall
Intensity
inches r hr
loutputI
Inflow
Volume
ecre.f.t
loutputl
Adjustment
Factor
'm'
(oWptrt)
Average
Outflow
cM
(Output)
Outlaw
Volume
acre-feet
)output'
Storage
Volume
acre -feat
loulputl
30
2.64
0.188
0.74
0.91
0.038
0.749
30
4.19
0 489
0.74
0.92
0.038
0.451
36
2.40
0.188
0.70
0.87
0.042
0.168
36
3.82
0520
0.70
0.88
0.042
0.478
40
2.21
0.208
0.88
0.64
0.048
0.182
40
3.61
0 547
0.48
035
0.047
0.500
45
2.05
0.217
0.68
0.81
0.060
0.187
46
328
0.571
0.16
0.82
0161
0120
50
1.92
0.225
0.0
0.79
0.065
0.171
50
314
0.592
0.64
010
0.065
0.537
55
1.80
0233
0.63
0.78
0.050
0.174
55
2.88
0.611
083
0.70
0.069
0.662
60
1.70
0299
0.62
0.76
0.063
0.176
so
2.69
0829
0.62
0.77
0.064
0.566
65
1.61
0.240
0.81
0.75
0.067
0.178
45
2.55
0.645
0.41
0.76
0.088
0.577
70
1.63
0261
0.90
0.74
0.072
0.190
10
2.42
0.660
0.60
0.75
0.072
0.588
75
1.46
0257
039
0.73
0176
0.181
75
2.31
0.875
089
0.74
0077
0.668
80
1.39
0262
0.50
0.73
0.080
0.142
so
221
0188
0.59
0.73
0.061
0.607
55
1.33
0.267
0.58
0.72
0.084
0.182
96
2.12
0.700
0.58
0.73
0.065
0.815
B0
1.28
0.271
0.59
0.71
0.088
0.153
90
2.03
0.712
0.56
0.72
0.080
0.623
95
923
0.275
0.57
0.71
0.003
0.183
95
1.96
0.723
0.57
0.72
0.084
0.829
100
1.19
02f9
037
0.70
0.097
0.182
fog
1.09
0.734
037
0.71
0.098
0.636
105
1.16
0.283
0.57
0.70
0.101
0.182
105
1.82
0.744
037
0.71
0.102
0.642
110
1.11
0.267
0.56
0.70
0.108
0.151
110
1.78
0.754
0.56
0.70
0.107
0.647
115
1.07
0.290
0.56
0.9
0.110
0.181
116
1.71
0.703
0.566
070
0.111
0.662
120
1.04
0284
0.66
0.69
0.114
0.180
120
1.65
0.772
018
0.70
0.116
0157
125
1.01
0297
0.56
0.69
0.118
0.179
125
1.00
0.781
0.56
0.70
0120
0361
130
0.98
0.300
0.55
0.68
0.123
0.178
130
1.56
0.789
0.55
069
0.124
0066
195
065
5.303
0.56
0.68
0.127
0.176
136
1.62
0.797
0.56
0.65
0.128
0165
140
0.93
0.306
0.55
0.69
0.131
0.175
140
1.48
0804
0.55
0.68
0.199
0172
145
0.91
0.309
0.65
0.55
0.135
0.174
145
1.44
0.812
0.55
0.09
0.131
0.675
160
088
0312
0.56
0.68
0140
0.172
160
1.40
0.819
085
0.08
0.141
0.678
155
086
0.315
0.55
0.67
0.144
0.171
155
1.37
0.828
0.65
0.68
0.115
0.881
160
034
0.317
0.54
0.67
0.118
0.169
160
1.34
0.833
014
0.68
0.150
0.853
195
0.82
0.320
0.54
0.67
0.152
0.167
165
1.31
0840
0.54
0.68
0.154
0.685
170
031
0 322
034
0.67
0.157
0.166
170
1.26
0 848
0.54
0.58
0.155
0.655
175
0.79
0.324
0.84
0.67
0.161
0.164
175
1.26
0852
034
0.67
0.163
0.650
180
0.77
0 327
034
0.87
0.185
0182
180
1.23
0.858
034
0.87
0-167
0.891
105
0.75
0.329
0.54
0.88
0.169
0.100
155
1.20
0.884
014
0.57
0.171
0.693
190
0.74
0 331
034
088
0.174
0.158
150
1.15
0.970
034
0.67
0.178
0196
195
0.73
0.333
034
086
0.178
0.168
195
1.15
0.878
031
0.07
0.180
0.96
200
0.71
0 338
0.54
0.68
0.182
0.153
200
1.13
0.881
031
0.87
0.184
0.97
205
0.70
0 338
033
080
0.198
0.151
205
1.11
0.887
013
0.57
0,19
0.66
210
039
0.340
0.53
068
0.151
0.149
210
1.09
0.892
0.53
0.57
0.16
0.90
215
0.9
0 342
0.53
0.9
0.195
0.147
215
1.07
0.97
0.63
0.67
0.197
0.700
220
0.66
0.343
0.53
0.9
0.16
0.144
220
1.06
0.902
0.53
0.56
0.201
0.701
225
0.55
0.345
033
0.68
0203
0.142
225
114
0.507
033
0.9
0206
0.702
230
0.64
0 347
OS3
0.6
0.208
0.140
230
1.02
0.912
0.53
0.6
0.210
0.702
235
0.63
0.349
0.53
035
0.212
0.137
235
1.00
0.917
033
0.66
0.214
0.703
240
012
0.351
013
0.85
0.216
0.136
240
0.99
0.922
0.53
0.6
0.219
0.703
245
0.61
0.353
033
0.65
0.220
0132
245
097
0.926
0.53
0.06
0.223
0.703
250
0.10
0.354
033
0.55
0.225
0.130
250
016
0.931
0.53
035
0.227
0.704
256
0.59
0.356
0.63
OM
0229
0.127
255
094
0.935
0.53
0.66
0231
0.704
266
0.55
0 958
0.53
015
0.233
0.125
280
093
0.940
0.53
0.66
0238
0.704
266
0.61
0.359
033
0.66
0.237
0.122
255
092
0.044
033
0.66
0210
0.704
270
0.57
0.361
083
0.55
0242
0.119
270
090
0.949
033
0.66
0244
0.704
275
054
0.363
053
0.65
0.246
0117
276
0.9
0.952
0.53
0.66
0.249
0.704
29
0.55
0 364
033
0.85
0250
0.114
26
086
0.950
0.53
0.9
0253
0.703
286
0.55
0.386
0.62
055
0254
0.111
285
0.87
0.60
032
0.66
0267
0.703
200
0.54
0 367
0.62
0.65
0.259
0.100
26
085
0.964
0.52
0.66
0.252
0.707
26
0.63
0.389
012
0.65
0 263
0.105
295
0.94
016
0.52
0.66
0206
0.702
300
052
0.370
052
0.56
0.287
0.100
300
083
0.972
0.52
065
0270
0.702
306
0.52
0.372
032
0.65
0.271
0.100
306
032
0.976
032
0.66
0274
0.702
310
0.51
0.373
032
0.55
0,276
0,097
310
0.81
0.56
052
0.9
0.279
0.701
315
0.51
0.374
0.62
0.66
0280
0096
315
0.80
0.983
0.62
0.66
0283
0.700
920
0.50
0.378
0.62
0.64
0284
0082
920
0.79
0.987
0.52
065
0287
0.700
325
0.49
0.377
0.52
0.84
0.288
0.089
325
0.78
0.991
0.52
0.65
0.292
0.899
330
0.49
0.379
052
0.64
0.293
0.088
330
0/7
0.994
052
0.85
0.298
0.898
Mod. FAA Minor Storage Volume (cubic 11.1 • 7,950 Mod. FAA Major Storage Volume (cubic n.) •
Mad. FAA Minor Storage Volume lacre•n.) a 0.1825 Mod. FAA Major Storage Volume (acre -n.) a
UDFCD DETENTION BASIN VOLUME ESTIMATING WORKBOOK Version 2 31. Released August 2012
30,660
0.7039
UD-Detention v2.31 Besrn 41. es. Modified FAA
212212013. 1:08 PM
DETENTION VOLUME BY THE MODIFIED FAA METHOD
Project: Keota Gas Processing Facility
Basin ID: Basin A•1
Inflow and Outflow Volumes vs. Rainfall Duration
Volume (acre-feet)
1.2
1
0.8
0.6
0.4
0.2
0
• •••.•
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100
150 200
Duration (Minutes)
250
300
Ye. II,FN..va.,. —ot—..b. n,Vohilv. Mow Stem SW,..e.n.. j Stem,�.V �M.,a.I Otettb..... ,a.m.%.a,.v....
350
UDFCD DETENTION BASIN VOLUME ESTIMATING WORKBOOK Version 2 31. Released August 2012
UD-Detention v2.31 Beem AI de Modified FAA
21222013. 1:0a PM
STAGE -DISCHARGE SIZING OF THE WATER QUALITY CAPTURE VOLUME (WQCV) OUTLET
TimetoD ,nt
o1
8
EEO -
0 0
0000
0000
OOO01
8
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0000
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0 0
0000
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Calculation of Colkction Cao+citr:
wLL
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STAGE -DISCHARGE SIZING OF THE WATER QUALITY CAPTURE VOLUME (WQCV) OUTLET
co
STAGE -DISCHARGE CURVE FOR THE WQCV OUTLET STRUCTURE
A A A
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(-nap'1 al) a6e3S
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W
N
RESTRICTOR PLATE SIZING FOR CIRCULAR VERTICAL ORIFICES
Project: Keota Facility
Basin ID: Basin Al
Sizing the Restrictor Plate for Circular Vertical Orifices or Pipes (input(
Water Surface Elevation at Design Depth
Pipe/Vertical Orifice Entrance Invert Elevation
Required Peak Flow through Orifice at Design Depth
PipeNertical Orifice Diameter (inches)
Orifice Coefficient
Full -flow Capacity (Calculated(
Full -flow area
Half Central Angle in Radians
Full -flow capacity
Calculation of Orifice Flow Condition
Half Central Angle (0<Theta<3.1416)
Flow area
Top width of Orifice (inches)
Height from Invert of Orifice to Bottom of Plate (feet)
Elevation of Bottom of Plate
Resultant Peak Flow Through Orifice at Design Depth
Width of Equivalent Rectangular Vertical Orifice
Elev. WS =
Elev: Invert =
0=
Dia =
C, =
Af=
Theta
Of=
Percent of Design Flow =
Theta =
A. _
T= _
y= _
Elev Plate Bottom Edge
a.=
#1 Vertical
Orifice
#2 Vertical
Orifice
4.956.80
4.955.20
1.23
12.0
0.60
0.79
3.14
4.0
323%
1.20
0.21
11.16
0.32
4.955.52
1.2
feet
feet
cfs
inches
all
rad
ofa
rad
sq ft
Inches
feet
feet
cfs
Equivalent Width • 0.66 feet
UD-Detention_v2 31_Basin Al xis. Restrictor Plate 2/22/2013. 1 09 PM
Client:
TETRA TECH • Professional Engineers •
rvo+0` Job No Sheet of I
Description: D+' 4 4 '� Designed By: " Date' � 2?
E iNg'ir P (AA "7, t 1 f V)Ct v!
J J Checked By: Date
gaso
ID 0^ r- e Je,I
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1,1_ 1 1.1q 1_171 I 4/ I- -- (6' 067"k
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Keota Oil and Gas Processing Facility
Detention Pond A2 Volume
Contour Contour Depth Incremental Cumulative Cumulative
Elevation Area Volume Volume Volume
(SQ FT) (FT) (CU FT) (CU FT) (AC FT)
4,955.60 2,433 0.0 0 0 0.00
4,955.80 6,565 0.2 900 900 0.02
4,956.00 12,856 0.2 1,942 2,842 0.07
4,956.20 22,044 0.2 3,490 6,332 0.15
4,956.40 34,166 0.2 5,621 11,953 0.27
4,956.60 47,024 0.2 8,119 20,072 0.46
4,956.80 57,481 0.2 10,450 30,522 0.70
4,957.00 64,348 0.2 12,183 42,705 0.98
4,957.20 67,062 0.2 13,141 55,846 1.28
4,957.40 69,682 0.2 13,674 69,521 1.60
4,957.60 72,625 0.2 14,231 83,751 1.92
4,957.80 75,879 0.2 14,850 98,602 2.26
4,958.00 79,637 0.2 15,552 114,153 2.62
WQCV (0.04 ac -ft)
10-yr WSE (0.13 ac -ft)
100-yr WSE (0.64 ac -ft)
Page 1 of 1 Tetra Tech, Inc.
DETENTION VOLUME BY THE MODIFIED FAA METHOD
Project: Keota Gas Processing Facility
Basin ID: Basin A-2
(For catchments less than 160 acres only. For larger catchments, use hydrograph routing method)
(NOTE: for catchments larger than 90 acres, CUHP hydrograph and routing are recommended)
Determination of MINOR Detention Volume Using Modified FAA Method
Determination of MAJOR Detention Volume Using Modified FAA Method
Destgn Information In tit :
I, =
A =
Typo a
T =
To =
q =
P, •
Cr =
C).
Cr =
percent
acres
A, B. C, Of D
years (2. 5. 10, 25, 50. or 1001
minutes
claimcra
inches
Desian Information In tit :
I.=
A =
Type •
T =il
It •
q =
Pr •
Cr •
es •
Cs=
8.60
percent
acres
A. B. C, or D
holm (2. 5, 10. 25, 50, or 100)
minutes
Cfa'....
inches
Catchment Drainage Imperviousness
Catchment Drainage Ara•
Predevelopmant NRCS Soil Group
Return Period for Detention Control
Time of Concentration of Watershed
Allowable O. Release Rate
One -hour Precipitation
Design Rainfall IOF Formula I a De P,f(Cr+T,j•C,
Coefficient Ono
Coefficient Two
Coeffkienf Three
8.60
Catchment Drainage Imperviousness
Catchment Drainage Area
Prede.opmenl NRCS Sad Group
Return Penod for Detention Control
Time of Concentration of Watershed
Allowable Una Release Rale
One -hour Precipitation
Design Rainfall IOF Formula I = C; P,/(C,+Ta-C,
Coefficient O.
Coefficient Two
Coefficient Three
6.59
8.590
B
a
10
100
13
13
0.19
0.19
1.70
2.70
28.50
28.50
10
10
0.7899
0.789
Determination of Average Outflow from the Basin Calculated):
cfa
efe
cubic feet
acre -R
for 5.Minules)
Determination of Average Outflow from the Basin (Calculated):
da
de
cubit feet
.60.40
Runoff Coefficient
inflow Peak Runoff
Allowable Peak
C =
Op -in =
Outflow Rate Op -out =
Mod. FAA Minor Storage Volume =
Mod. FAA Minor Storage Volume =
0. Enter Rainfall Duration Incremental Increase Value
0.21
Runoff Coefficient C 0
Inflow Peak Runoff Op -in =
Allowable Peak Outfit... Rate Op -out =
Mod. FAA Major Storage Volume a
Mod. FAA Major Storage Volume =
040
5.57
16.86
1.24
1.25
5.790
27.939
0.133
0.641
6
Here (e.g. 5
Unfelt
Duration
minutes
lkiputl
Rainfall
Intensity
Indies /Iv
longed)
Slow
Volume
acre-feet
ou (put)
Adjustment
Fedor
'm'
(maso(masonloutpd)
Avoreg*
Outflow
die
Outflow
Volume
acre-feet
(output)
Storage
7,unne
a ie•.uP .
i output:
Rainfall
Osrefion
minuses
.input)
Rainfall
Intensity
inches i hi.
(outputI
inflow
Volume
re -teat
loutputl
Adpntrnent
Factor
'm'
lostptf
Average
Outflow
die
(output)
OulOow
Volume
.crateot
lou1pu11
Storage
Volume
re -feet
(oufputl
30
2.64
0.151
0.72
0.90
0.037
0.114
30
4.19
0.456
0.72
0.91
0.097
0.419
36
2.40
0.100
0.69
0.96
0.041
0.119
36
3.82
0.485
0.68
0.67
0.042
0.443
40
2.21
0.169
0.67
0.83
0.048
0.123
40
3.61
0 510
0.87
034
0.046
0.464
46
2.05
0.178
0.85
0.80
0.050
0.128
45
328
0.532
0.66
0.81
0.060
0.482
50
1.82
0.583
0.83
0.79
0.054
0.129
50
904
0.552
0.65
0.70
0.065
0.498
55
1.80
0.189
0.52
0.77
0.058
0.130
56
2.88
0.670
0.62
0.78
0.068
0.511
60
1.70
0.194
0.51
0.76
0.003
0.131
80
2.69
OW
0.81
077
0.063
0.624
65
1.61
0.199
0.80
0.75
0.067
0.132
65
2.55
0.602
0.40
0.75
0088
0.536
70
1.53
0.204
0.00
0.74
0.071
0.133
re
2.42
0 610
060
075
0.072
0.614
75
1.46
0,206
039
073
0075
0.133
75
2.31
0.629
0.59
0.74
0.076
0.555
80
1.39
0.212
0.56
0.72
0.080
0.133
60
221
0 642
0.56
0.73
0.081
0.561
06
1.33
0216
0.58
0.72
0.064
0.132
86
2.12
0 653
0.58
0.72
0.085
0.508
BO
1.28
0.220
0.67
0.71
0688
0.131
90
2.03
0.664
0.57
0.72
0.089
0.676
95
1.23
0.223
0.57
0.71
0692
0.191
95
1.98
0 675
0.67
0.71
0.093
0.681
100
1.10
0228
0.57
0.70
0.097
0.130
fog
1.69
0 685
0.67
0.71
0.098
0.667
106
1.16
0229
0.68
0.70
0.101
0.129
105
1.82
0694
0.66
0.71
0102
0.692
110
1.11
0232
0.56
0.09
0.106
0.127
110
1.78
0.703
0.96
0.70
0.106
0.507
115
1.07
0.235
0.56
0.88
0.109
0.126
116
1.71
0 712
066
070
0.111
0.801
120
1.04
0238
0.66
0.69
0.114
0.124
120
1.65
0.720
0.66
0.70
0.116
0.606
125
1.01
0.241
0.55
0.69
0.118
0.123
125
1.80
0.728
0.55
0.89
0119
0.809
130
0.99
0243
0.66
0.66
0.122
0.121
130
1.56
0.736
035
0.69
0.124
0.612
135
0.95
0245
0.55
0.68
0.127
0.119
136
1.62
0.743
0.55
0.69
0.128
0.615
140
0.93
0248
0.55
0.68
0.131
0.117
140
1.48
0.751
0.55
0.69
0.132
0.616
145
0.91
0.250
055
0.08
0.135
0.115
145
1.44
0.756
0.60
0.68
0.137
0.621
160
038
0.253
054
0.67
0.139
0.113
160
1.40
0.764
034
0.68
0.141
0.623
155
0.06
0255
0.54
0.67
0.144
0111
165
1.37
0.771
0.54
0.09
0145
0.626
160
0.64
0.257
0.54
0.67
0.146
0,108
100
1.34
0.777
031
0.88
0.150
0.628
165
0.82
0.259
0.54
0.67
0.152
0.107
165
1.31
0.783
0.54
0.68
0154
0.829
170
0.81
0.261
054
0.67
0.156
0106
170
1.26
0.769
0.54
0.58
0.158
0.631
176
0.79
0203
054
0.67
0.161
0.102
175
1.26
0.796
034
0.67
0.162
0633
180
077
0.285
034
0.87
0.185
0.100
180
1.23
0.801
0.54
0.87
0.187
0.834
185
0.76
0.287
0.54
0.88
0.169
0.007
185
1.20
0.806
054
0.67
0.171
0635
190
0.74
0.268
054
066
0.173
0.085
150
1.16
0.812
054
0.87
0.176
0.636
195
0.73
0.270
053
0.68
0.178
0.092
195
1.15
0.817
053
8.07
0.180
0.637
200
0.71
0.272
053
0.08
0.182
0.090
200
1.13
0.822
033
0.67
0.184
0.659
205
0.70
0273
0.53
098
0.186
0.087
205
1.11
0.927
033
0.87
0,188
0.639
210
0.69
0276
0.63
0.68
0.191
0.085
210
1.00
0.832
033
067
0.193
0.640
216
008
0.277
0.53
0.86
0.195
0.082
215
1.07
0.837
0.63
0.67
0.197
0.840
220
098
0.278
0.63
0.86
0.189
0.079
220
1.06
0.842
033
0.06
0.201
0.641
226
0.05
0.280
0.53
0.68
0.203
0077
225
104
0.847
0.53
0.90
0.206
0.641
230
0.64
0.281
053
0.88
0.208
0.074
230
1.02
0.851
0.53
0.66
0.210
0.641
235
0.63
0.283
033
0.65
0212
0071
235
1.00
0856
033
066
0214
0641
240
022
0.284
033
0.85
0.218
0008
240
0.99
0.288
0.63
0.86
0219
0641
245
0.61
0286
033
0.65
0.220
0065
245
097
0.864
0.53
006
0.223
0.641
250
0.00
0287
053
035
0.225
0.062
250
0.86
0.888
0.53
0.88
0.227
0541
265
0.59
0298
0.63
095
0.229
0.060
265
094
0.873
0.63
0.89
0231
0.641
280
0.58
0.290
053
0.65
0.233
0.057
280
093
0.877
0.53
0.66
0.238
0.641
266
060
0.291
063
096
0.237
0.064
265
092
0.881
053
096
0240
0641
270
057
0.292
052
O86
0.242
0061
270
090
0985
0.52
066
0244
0.640
275
0.56
0.294
052
0.65
0146
0048
275
0.88
0.089
0522
0.66
0.249
0940
280
0.65
0.295
062
095
0250
0.045
280
090
0.892
0.52
0.66
0253
0.639
286
0.55
0296
032
0.65
0264
0042
285
0.87
0.896
0.52
0.88
0267
0839
290
0.64
0297
062
0.85
0.259
0.039
290
0.88
0 900
0.52
0.85
0.282
0 838
296
0.63
0.299
062
0,55
0.263
0.038
295
0.84
0903
032
0.88
0206
0 638
300
052
0.300
052
0.86
0287
0.033
300
093
0.907
032
0.88
0.270
0 637
0.638
306
0.52
0.301
032
0.65
0.272
0.029
306
0.42
0 911
0.52
0.88
0275
310
0.51
0.302
0.52
095
0,276
0026
310
0.81
0.914
0.52
0.65
0.279
0 635
315
0.51
0.303
032
0.06
0280
0.023
315
0.80
0918_
0.52
096
0.283
0.634
0.834_
320
0.50
0.304
0.62
0555
0284
0020
920
0.79
0.921
0.52
0.88
0 288
326
0.49
0.306
0.52
0.64
0.289
0.017
325
0.78
0 924
0.52
0.86
0.292
0.833
330
0.49
0.307
0.52
0.84
0.293
0.014
330
0.77
0.928
0.52
0.85
0298
0.832
Mod. FAA Minor Storage Volume (cubic ft.) • 5,780 Mod. FAA Malor Storage Volume (cubic n.) a 27,939
Mod. FAA Minor Storage Volume (acre•n.f a 0.1327 mod. FAA Maior Storage Volume (acre -n.) = 0.8414
UDFCD DETENTION BASIN VOLUME ESTIMATING WORKBOOK Version 2 31. Released August 2012
UD OeMo en_v2.31 6ede A2 rev.rds, Modified FAA
2f22/2013. 1:10 PM
DETENTION VOLUME BY THE MODIFIED FAA METHOD
Project: Keota Gas Processing Facility
Benin ID: Basin A-2
Volume (acre-feet)
0 0 0 0 0 0 0 0 0
0 -. N f.1 A (3, o, •--4 W 6
Inflow and Outflow Volumes vs. Rainfall Duration
•
•
•
OOOOOOOOOOOOOOOOOOO
000000000
000000000)0000000p000ppp0p0p0
0000
000 0000
0p0p000
0 50 100 150 200 250
Duration (Minutes)
300
350
-..-..-, %Wel ..M..v,M,. --..b. •,a,,,.. W.I. Mro.WM,.Ma..,....I.. Smymm.vw..V Ka, Sba.morw.Vahan*
ry SIV.msm.0g.v.m..
UDFCD DETENTION BASIN VOLUME ESTIMATING WORKBOOK Version 2 31. Released August 2012
UD OM sntien_v2.3I Beam A2 rev.* Modified FAA
2'222013. 1'.10 PM
RESTRICTOR PLATE SIZING FOR CIRCULAR VERTICAL ORIFICES
Project: Keota Facility
Basin ID: Basin A2
Sizing the Restrictor Plate for Circular Vertical Orifices or Pipes (input(
Water Surface Elevation at Design Depth
Pipe/Vertical Orifice Entrance Invert Elevation
Required Peak Flow through Orifice at Design Depth
PipeNertical Orifice Diameter (inches)
Orifice Coefficient
Full -flow Capacity (Calculated(
Full -flow area
Half Central Angle in Radians
Full -flow capacity
Calculation of Orifice Flow Condition
Half Central Angle (0<Theta<3.1416)
Flow area
Top width of Orifice (inches)
Height from Invert of Orifice to Bottom of Plate (feet)
Elevation of Bottom of Plate
Resultant Peak Flow Through Orifice at Design Depth
Width of Equivalent Rectangular Vertical Orifice
Elev. WS =
Elev: Invert =
o=
Dia =
C, =
Al
Theta =
of=
Percent of Design Flow =
Theta =
Eb =
T.=
Vo =
Elev Plate Bottom Edge =
a.=
#1 Vertical
Orifice
#2 Vertical
Orifice
4.957.20
4.955.60
1.2
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UD-Detention_v2 31_Basin A2_rev.xis. Restrictor Plate 2/22/2013. 1 16 PM
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APPENDIX C-5
RETENTION POND CALCULATIONS
Project: Keota Retention Simulation Run: 100 -Year Developed
Start of Run: 01Jun2013, 12:00 Basin Model: Basin B
End of Run: 02Jun2013, 12:00 Meteorologic Model: 100-yr Developed
Compute Time: 22Feb2013, 13:20:35 Control Specifications: Control 1
Hydrologic
Element
Drainage Area
(M12)
Peak DischargeTime
(CFS)
of Peak
Volume
(AC -FT)
Subbasin-B2
0.054094
70.2
02Jun2013, 00:20
4.2
Subbasin-B1
0.026531
41.5
02Jun2013. 00:15
2.4
Project: Keota Retention
Simulation Run: 100 -Year Developed Subbasin: Subbasin-B2
Start of Run:
End of Run:
Compute Time:
Computed Results
01Jun2013, 12:00
02Jun2013, 12:00
22Feb2013, 13:20:35
Basin Model:
Meteorologic Model:
Control Specifications:
Volume Units: AC -FT
Basin B
100-yr Developed
Control 1
Peak Discharge :
Total Precipitation :
Total Loss :
Total Excess :
70.2 (CFS)
10.8 (AC -FT)
6.6 (AC -FT)
4.2 (AC -FT)
Date/Time of Peak Discharge :
Total Direct Runoff :
Total Baseflow :
Discharge :
02Jun2013, 00:20
4.2 (AC -FT)
0.0 (AC -FT)
4.2 (AC -FT)
Project: Keota Retention
Simulation Run: 100 -Year Developed Subbasin: Subbasin-B1
Start of Run:
End of Run:
Compute Time:
Computed Results
01Jun2013, 12:00
02Jun2013, 12:00
22Feb2013, 13:20:35
Basin Model:
Meteorologic Model:
Control Specifications:
Volume Units: AC -FT
Basin B
100-yr Developed
Control 1
Peak Discharge :
Total Precipitation :
Total Loss :
Total Excess :
41.5 (CFS)
5.3 (AC -FT)
2.9 (AC -FT)
2.4 (AC -FT)
Date/Time of Peak Discharge :
Total Direct Runoff :
Total Baseflow :
Discharge :
02Jun2013, 00:15
2.4 (AC -FT)
0.0 (AC -FT)
2.4 (AC -FT)
Keota Gas Processing Facility
Basin B Calculations
2 Yr
24 -hour Point Rainfall Depth
5 Yr 10 Yr 100 Yr
1.75
2.20
2.58 3.74
Site Imperviousness
Roof/Tank Gravel Road Undeveloped
90
40
2
Cover
Hydrologic
Conditions
A
SCS Curve Number. CN
D
B
C
Pasture,
Poor
68
79
86
89
grassland, or
Fair
49
69
79
84
range
Good
39
61
74
80
Industrial
76
85
89
91
Basin
Area
Basin Area (acres).
Soil Type D
Gravel Road
Basin Imperviousness (acres)
I °o
CN
Soil Type B Soil Type C
RoofTank
Undeveloped
81
16.98
14.88
0.40
1.70
2.50
2.67
11.81
21.4
70.1
B2
34.62
19.38
1.04
14.19
1.76
1.88
30.98
8.7
71.1
Basin
L
(ft)
S
(ft/ft)
Time of Concentration, Tc
(min)
Lag Time
(min)
81
1,430
0.007
17.9
10.7
B2
1,950
0.009
20.8
12.5
Notes:
1. Refer to Developed Runoff Calculations for Time of Concentration calculations
P:\35719\133-35719-13005\Dots\Reports\Prelim Drainage Report\Calcs\
Basin B_SCS CN.xisx
1 of 1 Tetra Tech, Inc.
APPENDIX D - VARIANCE LETTER
O
TETRA TECH
February 22, 2013
County Engineer
Weld County Public Works
1111 H Street
Greeley, CO 80632
RE: Variance Request for Noble Energy's Keota Oil and Gas Processing Facility
Dear County Engineer:
Noble Energy is proposing a gas processing facility in rural Weld County. Development will occur on an
80 acre parcel located 7 miles north of State Highway 14 on the east side of Weld County Road (WCR)
89. More specifically, the property is the N'/z of the NW'/4 of Section 21, Township 9 North, Range 61
West. A Use by Special Review (USR) Permit application and accompanying Preliminary Drainage
Report are being submitted under separate cover in conjunction with this Variance Request.
The intent of this letter is to request a variance from Weld County Code, Chapters 5.1 and 5.11, with
regard to stormwater detention requirements. It is understood that the intent of the Weld County Code is
to reduce impacts of development on neighboring downstream properties by requiring stormwater
detention and thereby reducing peak runoff from said development; however, the subject property is
affected by unique circumstances that limits the feasibility for detention.
The subject property is surrounded by undeveloped agricultural rangeland. A ridge line, running north -
south, bisects the western half of the subject property. The eastern three-quarters of the property
generally sheet flows to the east toward a natural playa lake. A playa lake can be defined as a basin with
no outlet which periodically fills with water to form a temporary lake. The playa lake is located directly
adjacent to and partially encumbers the project's east boundary.
An 885 acre basin, more or less, defines the playa lake. The bottom of the playa lake is located directly
adjacent to the project site near elevation 4936. The elevation near the eastern property line is near 4940.
The last closed contour within the sub -basin is near elevation 4958. The playa lake basin does not have a
natural spillway and the probability for stormwater to be released via surface flow is virtually zero.
Detaining the 100 -year developed storm event and releasing at the 5 -year historic release rate for the
eastern three quarters of the development requires approximately 5.5 acre-feet of storage. Providing a
detention pond near the east property boundary would require construction of a berm within the playa
lake and could have negative impacts by reducing the storage volume of the lake. Detention upstream
from the east property boundary is not feasible since this would limit the developable footprint for the
subject property and thereby limit the economic feasibility of the entire project.
Tetra Tech, Inc.
9(10 c cur:se•. S:reei. 5Jcie
Tel .-50'3-772 52e2 Fax 303.7?27zr3g •A'W6 iea•sieC;r•cOM
0
TETRA TECH
The proposed alternative to detention is to provide retention. The required retention volume will be
achieved by expanding the existing playa lake within the project boundary. A volume of 1.5 times the 24 -
hour, 100 -year storm event plus one foot of freeboard will be provided in accordance with Weld County
Code. The time of concentration for the developed watershed will be used for the project's release rate to
meet Weld County Code and Colorado Water Law requirements for a drain time less than 72 hours. A
permanent water quality detention basin will be constructed upstream of the retention area to mitigate
water quality impacts to the playa lake.
This proposed alternative for retention considers the features and functions of the existing natural
drainage system and will mitigate the impact of developed runoff to the existing playa lake and adjacent
properties. Furthermore, Noble Energy will secure a letter from the adjacent property owner, Quarter
Circle Lazy H Ranch, Inc., for approval of this additional stormwater flow into the playa lake. It is
understood that this variance request is specific to this project's unique constraints and is not precedent
setting.
Please refer to the USR Permit application and Preliminary Drainage Report for additional, detailed
information regarding the proposed Keota Oil and Gas Processing Facility and preliminary drainage
calculations.
Thank you for your consideration and please contact me at josh.sherman@tetratech.com or 303-485-7565
if you have any questions or need any additional information.
Sincerely,
TETRA TECH
Jos Kerman, P.E.
Project Civil Engineer
jas
P:135719\133-35719-13005\ProjMgmt\Correspondence\Weld County Variance Letter Pam.docx
2
APPENDIX E - DRAINAGE PLANS
OFF SITE DRAINAGE PLAN D-100
HISTORIC DRAINAGE PLAN D-200
PRELIMINARY DEVELOPED DRAINAGE PLAN D-300
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