HomeMy WebLinkAbout20140309.tiff EXHIBIT L
Drainage Report
Sterling Energy Centennial Gas Plant Drainage Narrative
I. Introduction
This narrative will discuss the existing and proposed drainage at the proposed Centennial Gas
Plant to be constructed in the Southeast Quarter of the Southwest Quarter of Section 25,
Township 9 North, Range 61 West of the 6th Principal Meridian in rural Weld County, Colorado
by Sterling Energy Investments LLC (Sterling). The attached Vicinity Map shows the general
location of the project. This narrative includes a brief description of the site, and the proposed
grading, water quality detention facility, and analysis methods to be used.
The proposed Centennial Gas Plant will consist of an office structure, warehouse structure,
skids, flare, and other smaller equipment such as tanks, pipe supports, transformers, and small
storage areas as shown in the attached conceptual plot plan. The center of the site surrounding
the proposed facilities will be covered with gravel to provide a stable driving surface to access
all of the facilities. A gravel access road will be constructed along the west and north boundary
of the site and a septic system is also planned for the facility.
II. Site Description
The site is currently comprised of open range with native grasses. The site topography slopes
gently downward to the northeast. The maximum elevation is about 4,963 feet in the southwest
corner of the site and the minimum elevation is about 4,939 feet in the northeast corner of the
site. The soil at the site is comprised of the Olney Fine Sandy Loam. Runoff will flow overland
to the southeast for about 14 miles before it flows into Wildcat Creek at the southern edge of
Weld County, which then flows into the South Platte River.
III. Engineering Methodology
Based on the preliminary site plan, we anticipate that site grading will generally consist of
minimal cuts and fills, other than cuts required for foundation and floor slab subgrade
preparation. In general, the site will be graded to keep runoff from the graveled area separated
from the grassed area and off-site runoff. Runoff from the graveled area will not be allowed to
flow onto the grassed area and runoff from the grassed area will not be allowed to flow onto the
graveled area. By doing this, the proposed water quality treatment facility, an extended
detention basin, will only treat runoff from the gravel, but its size will be minimized.
The extended detention basin will be located at the northern edge of the site, where the existing
topography is the lowest. Because the existing topography is very flat on the north side of the
site, it will be difficult to design a facility that will provide sufficient storage and be able to drain
properly. To alleviate these problems, the graveled area on the north side of the site will
probably be raised several feet, and to balance cut fill, there will be a small amount of
excavation on the south side so the cut and fill can be balanced.
We will estimate the runoff from the graveled area, and because it is less than 160 acres, we
will use the Rational Method. The runoff rate will be estimated according to Urban Drainage
and Flood Control District's Urban Storm Drainage Criteria Manual (UDFCD DCM) procedures
and Weld County's addendum to the procedures. No storm sewers, inlets, open channels, or
culverts are expected to be used at the site.
The site will be graded so that runoff from the graveled area will flow into a proposed extended
detention basin to enhance the water quality. The extended detention basin will be designed
according to UDFCD DCM guidelines and Weld County's addendum to the procedures. The
extended detention basin will detain the water quality capture volume for 40 hours and the
emergency spillway will be designed to pass the 100-year flow. The extended detention basin
embankment will be at a 3:1 slope or flatter with a minimum top width of 12 feet.
IV. Summary
Only a portion of the proposed Centennial Gas Plant site will have gravel placed on it, and
runoff from the gravel will be collected and detained in an extended detention basin to enhance
the runoff from the graveled area before it is released to its natural flow path. The flow will be
estimated according to the UDFCD DCM guidelines and the Weld County addendum, and the
extended detention basin and its appurtenances will also be designed according to the UDFCD
DCM and Weld County guidelines. Off-site flow and runoff from the undisturbed grassland on-
site will flow as it has historically and will be routed around the proposed extended detention
basin.
_ iv
Project Location
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PROJECT NO. 124721 FIGURE
DRAWN: 1/30/2013 Centennial Gas Plant
Vicinity Map
KL EINFEL DER DRAWN BY. B.Carlin
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1
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GasPlantSiteMap.mxd
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DRAINAGE REPORT
PROPOSED CENTENNIAL GAS PLANT
VICINITY OF COUNTY ROAD 89 AND
COUNTY ROAD 100
WELD COUNTY, COLORADO
A Report Prepared for:
Gordon W. Stevenson
Executive Vice President— Operations
Sterling Energy
One Tabor Center
1200 17th Street, Suite 2850
Denver, CO
Prepared by:
Bruce Curtis, P.E., Ph.D.
Principal Professional
Kleinfelder Project Number 124271-7
Kleinfelder West
4815 List Drive, Unit 115
Colorado Springs, CO 80919
Phone: (719) 632-3593
Fax: (719) 632-2648
Copyright 2013 Kleinfelder
All Rights Reserved
ONLY THE CLIENT OR ITS DESIGNATED REPRESENTATIVES MAY USE THIS DOCUMENT AND ONLY FOR THE SPECIFIC
PROJECT FOR WHICH THIS REPORT WAS PREPARED.
124271-7/CSP13R0465 October 25, 2013
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October 25, 2013
Heidi Hansen, P.E., CFM
Weld County Public Works
1111 H Street
Greeley, CO 80632
Subject: Drainage Report for Use by Special Review
Proposed Centennial Gas Plant
Vicinity of County Road 89 and County Road 100
Weld County, Colorado
Ms. Hansen:
Please find attached the drainage report presenting the results of our drainage analysis and
drawing preparations for the proposed Centennial Gas Plant to be located in rural northeast
Weld County, Colorado. The report contains the engineer's certification, a description of the
project location, the drainage basins, the criteria used in our analyses and design, the drainage
facility design, and our conclusions. In addition, the appendices include the hydrologic and
hydraulic calculations, drainage basin maps, a maintenance plan, the Use by Special Review
(USR) checklist that we used to guide us in this submittal, and the design drawings. This
drainage report is presented for your review as part of a USR submittal.
If you have any questions regarding this report or need additional information, please contact
our office at (303) 781-8211.
Respectfully submitted,
KLEINFELDER WEST, INC.
Bruce Curtis, P.E., Ph.D.
Principal Professional
BAC/VKA
Enclosures
124271-7/CSP13R0465 Page i of Hi October 25, 2013
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4815 List Drive, Unit 115,Colorado Springs, CO 80919-3340 pl 719.632.3593 tl 719.632.2648
KLElAIFELDER
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Engineer's Certification:
I hereby certify that this report for the drainage design of Sterling Energy— Centennial Gas Plan
was prepared by me (or under my direct supervision) in accordance with the provisions of the
Weld County storm drainage criteria for the owners thereof.
/ ...........
O� R •4O :
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. S/ ALENG..'
Bruce Curtis, P.E., Ph.D.
Name Seal
124271-7/CSP13R0465 Page ii of iii October 25, 2013
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TABLE OF CONTENTS
PAGE
Cover Letter
Engineer's Certification
1 INTRODUCTION 1
1.1 LOCATION 1
1.2 DESCRIPTION OF PROPERTY 1
2 DRAINAGE BASINS AND SUB-BASINS 2
2.1 MAJOR BASIN DESCRIPTION 2
2.2 SUB-BASIN DESCRIPTION 2
3 DRAINAGE DESIGN CRITERIA 3
3.1 DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS 3
3.2 HYDROLOGICAL CRITERIA 3
3.3 HYDRAULIC CRITERIA 4
4 DRAINAGE FACILITY DESIGN 6
4.1 GENERAL CONCEPT 6
4.2 SPECIFIC DETAILS 6
5 CONCLUSIONS 7
5.1 COMPLIANCE WITH WELD COUNTY CODE 7
5.2 DRAINAGE CONCEPT 7
6 REFERENCES 8
FIGURES
Figure 1 —Vicinity Map
Figure 2 — Drainage Basin Boundary Map
Construction Drawings in pockets at end of report
APPENDICES
A Hydrologic Computations
B Hydraulic Computations
C USR Checklist
D Maintenance Plan
124271-7/CSP13R0465 Page iii of iii October 25, 2013
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1 INTRODUCTION
1.1 LOCATION
The proposed Centennial Gas Plant will be constructed in the Southeast Quarter of the
Southwest Quarter of Section 25, Township 9 North, Range 61 West of the 6th Principal
Meridian in rural Weld County, Colorado by Sterling Energy Investments LLC (Sterling). The
site is directly north of County Road 100 and about 3.5 miles east of County Road 89. The
attached Vicinity Map shows the general location of the project.
There are no open channels, lakes, streams, irrigation facilities or any other water resource
facilities in the vicinity of the project. Runoff will flow overland to the northeast for about 14
miles before it flows into Wildcat Creek at the southern edge of Weld County, which then flows
into the South Platte River. The site is not located near any developments, and it is not located
in any municipality.
1.2 DESCRIPTION OF PROPERTY
The site is approximately 41 acres. The site is currently comprised of open range with native
grasses. The site topography slopes gently downward to the northeast. The maximum
elevation is about 4,963 feet in the southwest corner of the site and the minimum elevation is
about 4,939 feet in the northeast corner of the site. The soil at the site is comprised of the
Olney Fine Sandy Loam.
There are no major open channels on the site and the property is owned by Sterling Energy.
The proposed Centennial Gas Plant will consist of an office structure, compressor building,
skids, flare, and other smaller equipment such as tanks, pipe supports, transformers, and small
storage areas as shown in the attached conceptual plot plan. The center of the site
surrounding the proposed facilities will be covered with gravel to provide a stable driving surface
to access all of the facilities. A septic system is also planned for the facility.
There are no irrigation facilities in the vicinity and the groundwater depth is deep and not an
issue for site development.
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2 DRAINAGE BASINS AND SUB-BASINS
2.1 MAJOR BASIN DESCRIPTION
There are no Weld County Master Drainage Plans for this area. The watershed is very flat with
no defined channels. Runoff flows generally to the northeast for about 14 miles before it flows
into Wildcat Creek at the southern edge of Weld County, which then flows into the South Platte
River. No FEMA—defined floodplains or floodways affect the property. On-site contours are
provided on the attached construction drawings at 1-foot contour intervals. Off-site contours
are shown on Figure 2 (Off-site Drainage Basin Boundaries) were obtained from a US
Geological Survey(USGS) quadrangle (quad) map with a contour interval of 10 feet.
2.2 SUB-BASIN DESCRIPTION
Historically, runoff has flowed overland to the northeast across the property and this drainage
pattern will not be altered for the proposed site plan. Off-site flow also flows to the northeast
towards the property. Historically, County Road 100 has intercepted the vast majority of the off-
site runoff from the south side of County Road 100 in roadside ditches. The ditches have the
capacity to capture and convey 45.4 cubic feet per second (cfs), and the peak 100-year storm
generates a peak flow of 46.4 cfs, so about 1 cfs overtops the road and flows onto the property
during a 100-year event. The capacity of the roadside ditch on the north side of County Road
100 will be increased slightly so no flow from the south side of the County Road 100 flows onto
the site in the future.
A small amount of off-site flow north of County Road 100 will also onto the site. This overland
runoff will continue to flow as it has historically across the site. A small earthen berm will be
constructed on the site, to prevent this runoff from crossing over the graveled area, so that it will
not need to be detained and treated in the proposed detention basin.
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3 DRAINAGE DESIGN CRITERIA
3.1 DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS
No previous drainage studies were performed for the site. There are few constraints for the
site. The existing grade is relatively flat, and there are no existing structures, utilities, or
irrigation facilities on the site. County Road 100 lies on the south side of the site and its ditches
intercept runoff from the south and convey it along the road past the site. Two entrances will be
constructed across the south ditch and 15-inch corrugated metal pipe (CMP) culverts will be
placed to convey flow beneath the entrances.
3.2 HYDROLOGICAL CRITERIA
Precipitation data for the site was obtained from the NOAA website
(http://hdsc.nws.noaa.qov/hdsc/pfds/pfds map cont.html?bkmrk=co). The rainfall depths are
provided in the calculations for off-site and on-site runoff included in Appendix A. Precipitation
and runoff were generated for the 2-year, 5-year, 10-year, 25-year, 50-year, and 100-year
storm events. Only the 10-year (for culvert flow and releases from the detention basin) and the
100-year recurrence intervals (emergency spillway)were used in the design.
The Weld County Engineering and Construction Criteria (April 2012) was used to estimate off-
site and on-site runoff for the facility. Because the total drainage area is less than 160 acres,
the Rational Method was used to estimate runoff. County Road 100 forms the southern
boundary of the site and because the runoff generally flows north, the roadside ditch intercepts
runoff. Because of the small size of the site and off-site drainage area, no routing was
necessary. The time of concentration was estimated according to the Weld County Criteria and
the Urban Drainage and Flood Control District (UDFCD) criteria. The 100-year peak flow
entering the detention basin will be about 27 cfs, and the peak release from the detention basin,
based on the historic 10-year event, will be about 5 cfs. A complete set of the results are
provided in the off-site and on-site flow calculations supplied in Appendix A.
The Urban Drainage and Flood Control District's (UDFCD) detention basin sizing worksheet
(UD-Detention_v2.33.xls) was used to estimate the required detention volume. Because the
drainage basin is small (less than 80 acres), the Modified FAA method in the spreadsheet was
used to estimate the required detention volume. The detention basin is located in the northeast
portion of the site where runoff has historically flowed and will outlet to the northeast corner
where the existing elevation is the lowest. The site will be graded so that all runoff from
graveled or impervious surfaces will enter the detention basin. The Initial Surcharge Volume
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should be a minimum of 4 inches deep and have a minimum volume of 0.3% of the WQCV. It
is the available storage volume that begins at the water surface elevation of the micropool and
extends upward to a grade break within the basin.
The Urban Drainage and Flood Control District's (UDFCD) Best Management Practice (BMP)
design worksheet (UD-BMP_v3.02.xls) was used to estimate the required water quality
detention volume. The Extended Detention Basin (EDB) BMP was selected to enhance the
water quality of the runoff because the site has greater than 5 acres of equivalent impervious
area; the watershed is less than 640 acres; and the depth to ground water is deep. Also, there
is no baseflow, and the EDB can be incorporated into the detention basin.
Off-site flow from the south will be captured by the roadside ditches and conveyed around the
site as it has historically. Off-site flow from the west will flow as it has historically and will be
prevented from entering the site by place a small berm adjacent to the graveled area.
3.3 HYDRAULIC CRITERIA
The conveyance capacity of the roadside ditch on the south side of County Road 100 is about
42 cfs and the capacity of the ditch on the north side is about 3 cfs. Because of the simplicity of
the channel and the lack of obstructions, Manning's Equation was used to estimate channel
capacity. The calculations are provided in Appendix A and were calculated as part of the
hydrologic analysis to estimate runoff flowing onto the site.
The detention basin outlet is an 11-inch orifice in the outlet structure. The detention basin will
store the 100-year volume of 1.80 acre-feet at an elevation of 4942.8 feet. The top of the
detention basin embankment is at an elevation of 4944.0 feet for a freeboard of 1.2 feet. Water
that exceeds this elevation will spill into the top of the outlet structure and flow out through an
18-inch diameter pipe. The construction drawings included in the pockets in this report have
details of the outlet structure. The stage-storage curve and table are found in the Detention
basin calculation in Appendix B along with the other detention basin calculations.
The water quality outlet design is based off of the UDFCD's procedures. The outlet consists of
a well screen for a trash rack and three 1-inch diameter orifices for the outlet control. The
calculations for designing the water quality outlet are found in Appendix B and the details of the
water quality outlet design are shown in the construction drawings.
124271-7/CSP13R0465 Page 4 of 8 October 25, 2013
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The culvert from the outlet structure is a 27-inch diameter reinforced concrete pipe (RCP) with a
slope of 0.8%. A 27-inch pipe has sufficient capacity to pass 26.8 cfs (100-year inflow) and
thus serve as the emergency "spillway" from the detention basin. Calculations are provided in
Appendix B. The flow in the north roadside ditch should be negligible and no analysis was
performed to design the size of the entrance road culverts. The minimum size was chosen.
There are no storm sewers or inlets on the site. Gravel will be placed on the only parts of the
site that will have traffic and be disturbed and all runoff flows into the detention basin where a
portion of the Water Quality Capture Volume (WQCV) is set aside for capturing sediment. The
Weld County criteria or the UDFCD criteria was used for all calculations on this design.
•
•
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4 DRAINAGE FACILITY DESIGN
4.1 GENERAL CONCEPT
On-site runoff generally flows to the northeast and into the detention basin. Offsite runoff flows
how it has historically. Flow from the south is capture by the roadside ditches and routed east
along the road and runoff from the west flows as sheet flow and is prevented from entering the
graveled area by a small berm.
Tables, charts, and drawings are found in the appendices. Figures are also found in the
appendices but two figures (Vicinity Map and Off-site Drainage Basin Boundaries) are located
in Figures section of the report. There are no hydraulic structures associated with this project
except for the outlet structure culvert.
4.2 SPECIFIC DETAILS
Because of the flat slope of the detention basin, maintenance equipment can access the bottom
of the basin and the outlet structure from the graveled area. The outlet structure can also be
access from the 10-foot wide berm around the detention basin. No permits are required for this
project. A maintenance plan is provided in Appendix D.
124271-7/CSP13R0465 Page 6 of 8 October 25, 2013
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5 CONCLUSIONS
5.1 COMPLIANCE WITH WELD COUNTY CODE
The design will meet Weld County code. We are asking for a variance of the release rate from
the detention basin for the historic 5-year flow to the historic 10-year flow. We were told that
the County plans on doing this in the future and to go ahead and design it that way for our
project.
Because the existing topography is extremely flat near the proposed detention basin (<0.2%), it
is not possible to provide the detention basin and trickle channel with a 1% slope and provide
the necessary detention and outflow requirements from the detention basin. We are requesting
a variance from the County for the required basin and channel slopes. Because of the small
drainage area and sandy soil, ponding water and wetland growth should not be a problem.
5.2 DRAINAGE CONCEPT
The facilities will capture and release runoff at a rate that should be non-erosive. The outlet is
designed to spread outflow from the detention pond evenly so that it leaves the site as sheet
flow and does not cause damage downstream. There are not channels to release outflow into.
There is no Master Drainage Plan for this area and there are no irrigation facilities in the vicinity.
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6 REFERENCES
Weld County, Weld County Engineering and Construction Criteria, April 2012.
Urban Drainage and Flood Control District, Urban Storm Drainage Criteria Manual, Volume 1,
June 2001.
Urban Drainage and Flood Control District, Urban Storm Drainage Criteria Manual, Volume 2,
June 2001.
Urban Drainage and Flood Control District, Urban Storm Drainage Criteria Manual, Volume 3,
November 2010.
National Oceanic and Atmospheric Administration, website
(http://hdsc.nws.noaa.eov/hdsc/pfds/pfds map cont.html?bkmrk=co
124271-7/CSP13R0465 Page 8 of 8 October 25, 2013
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FIGURES
124271-7/CSP13R0465 October 25, 2013
Copyright 2013 Kleinfelder
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DRAWN: 10/23Y2013' Centennial Gas Plant
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PROJECT NO. 124721 FIGURE
�/ DRAWN: 10/24/2013 Centennial Gas Plant
Off-site Drainage Basin Boundaries
KLE/NFEL DER DRAWN BY: L Hocked2
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FILE NAME: Weld County,Colorado
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APPENDIX A
HYDROLOGIC COMPUTATIONS
124271-7/CSP13R0465 October 25, 2013
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roM r,.o ,bNbs
Sterling Energy—
PROJECT: Centennial Gas Plant PROJECT NO.: 124271
SUBJECT: Off-site Runoff Calculations BY: Bruce Curtis DATE: 9/12/13
REVIEWED BY: • Axi4a'L DATE:•kW tsti
PURPOSE:
Perform runoff calculations to estimate flow entering roadside ditch and runoff needing to be
captured by the proposed detention basin.
GIVEN:
1. Sub-watershed 1 area=46.1 acres
2. Sub-watershed 2 area=30.0 acres
3. Sub-watershed 3 area=37.8 acres
4. Existing Land Use/Vegetation=Grass
5. North and south roadside ditch dimensions were measured on a site visit and will be
drawn in the worksheet.
6. Site location: Let.40.715036°;Long.-104.156812°
7. Precipitation data obtained from NOAA website at above coordinates:
hlto://hdsc.nws.noaa.gov/hdsc/ofds/pfds map cont.hlmt?bkmrk=co
8. Percent Imperviousness—Existing Conditions =0%
ASSUMPTIONS:
1. The entire drainage area is Hydrologic Soil Group B.
2. Manning's n value for roadside ditch is 0.03(mainly did with same grass).
ANALYSIS:
The Weld County Engineering and Construction Criteria(April 2012)was used to estimate off-site
and on-site runoff for the facility. Because the total drainage area is less than 160 acres,the
Rational Method was used to estimate runoff. County Road 100 forms the southern boundary of
the site and because the runoff generally flows north, the roadside ditch intercepts runoff. The
runoff In combination with the estimated roadside ditch capacity calculation will estimate whether
flow overtops the road and flows onto the Centennial Gas Plant site. The time of concentration Is
estimated for existing conditions and for conditions where the runoff over tops the road and flows
through the site to the detention basin. The time of concentration is not estimated to design the
roadside ditches.
Manning's equation will be used to estimate the capacity of the roadside ditch. There are ditches
on both sides of the road.
General Steps:
1. Estimate Off-site flow from South onto Site
a. Calculate time of concentration.
b. Estimate Rainfall Intensity, I.
c. Estimate the Runoff Coefficient,C.
d. Estimate peak flow entering roadside ditch during 2-year through 100-year storm
events.
2. Estimate capacity of roadside ditch.
3. If runoff exceeds ditch capacity,then design roadside ditch enlargement to capture
excess runoffs.
The calculation sheets provide the actual analyses.
Page 1 of 1
�' -\ SHEET _ OF
KLEINFELOER
PROJECT NO. //J.z'/ry21/
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PROJECT NO. 124721 .. ' FIGURE
DRAWN: 91172019 v centennial Gas Plant
KLE/NFELOERDRAWR!BY: BCarlin 1 alsCl"l!]LtNBp ,. ,f
Bright People.Right Solutions. CHECKED BY: N.Peace -
wenkte Molder corn FILENAME: WhId County.Colorado -.
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PROJECT NO. 124721 FIGURE ~
DRAWN: 1/302013 Centennial Gas Plant
DRAWN BY; B.Cadin Soils Map
KL E/NFEL OER CHECKED BY: N.Peace 2
Bright People.Right Solutions.
nww.kkmtekfarcom FILE NAME: Nth County,Colorado
oasPlanISolls.mxd
RUNOFF DRAINAGE CRITERIA MANUAL(V. 1)
L= length of overland flow(500 ft maximum for non-urban land uses,300 ft maximum for urban f 6
land uses)
S=average basin slope(ft/fl)
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.
, r
2.4.2 •O.aeilsud Travel Time. For catchments with overland and channelized flow, the time of
Cl; :,•
concentration needs to be considered In combination with the overland travel time,4,which Is calculated
using the hydraulic properties of the swale,ditch,or channel. For preliminary work,the overland travel
time,r„can be estimated with the help of Figure RO-1 or the following equation(Guo 1999):
V=C,,SNos (RO-4)
In which:
V=velocity(ft/sec)
C,.=conveyance coefficient(from Table RO-2)
S„.=watercourse slope(ft/ft)
TABLE RO-2
Conveyance Coefficient,Cr
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, rr,is then the sum of the initial flow time,r;,and the travel time,r„as per
Equation RO-2. , - t
r. C
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,r,)in an urbanized catchment should nol
exceed the time of concentration calculated using Equation RO-5.
t`=- 180 + I 0 (RO-5)
.
RO.6 05/2001
Urban Drainage and Flood Control District
DRAINAGE CRITERIA MANUAL(V.1) RUNOFF
TABLE RO.3
Recommended Percentage Imperviousness Values
Land Use or Percentage
Surface Characteristics 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 45
(when land use not defined)
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.
Based In part on the data collected by the District since 1969,an empirical relationship between C and
the percentage Imperviousness for various storm return periods was developed. Thus,values for C can
be determined using the following equations(Urbonas,Guo and Tucker 1990).
C,, =KA + f.3lf' —1,4412 +1.1351—0.12)for CA≥0,otherwise CA-0 (RO-6)
CCD =K.D +0.858i' —0.78612 +0.774i+0.04) (RO-7)
CB =(CA +CCD)/2
in which:
i=%imperviousness/100 expressed as a decimal(see Table RO-3)
06/2001 RO-9
Urban Drainage and Flood Control District
DRAINAGE CRITERIA MANUAL(V. 1) RUNOFF
TABLE R0-5
Runoff Coefficients,C
Percentage
Imperviousness Type C and D NRCS Hydrologic Soil Groups
2-yr 5-yr I 10-yr 25-yr 50-yr 100-yr
0% 0.04 0.15 . 0.25 0.37 044 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 0.32 043 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 0.33 040 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% 0.37 043 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 CIAO 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
06/2001 RO-11
Urban Drainage and Flood Control District
Precipitation Frequency Data Server Page 1 of 4
NOAA Atlas 14,Volume H,Version 2 ,-.,.4.
4 Location name:Briggsdate,Colorado,U Coordinates: S' r
nates:40.7150,-104.1568
II
'QJ- Elevation:4940ft'
• •sauna:Go9pk Mops •,..,,,
POINT PRECIPITATION FREQUENCY ESTIMATES
Sala Parka.Deborah Madb.Sandra PavIOvt Idv&Hay Md,att St laurem CMTrypakk Oak
UmWt Micham YAM,Georfery Benno
NOM.Natimal Maier Servke.Slyer Spiv.Marylon
pF tabular I pF graphical i Maps 8 aerialg
PF tabular
PDS-based point precipitation frequency estimates with 90%confidence Intervals(in inches)1 _
Duration Average recurrence Interval(years)
• 1 2 6 10 26 60 I 100 200 600 1000
6-min 0.268 I 0.313 l 0.412 - 0.502 0.638 I 0.752 0.675 1.01 1.20 1.35
10.201-0.3331(0.24-4404)1(0.319-0532) 10.385-0.650)(0.490.0.656)$0.551-1.03) 10.619-1.22) 0.685-1.44) (0.782-175) (0655-198)
10-min 0.378 0.458 0.803 0,734 0.934 1.10 1.26 1.48 1.76 1.99
(0.294-0.487)(0.356-0591),10.467-0778) (0566-09521 (0.703.1.27) (0807-1.51) 10.907-1.79) (1.00-2.11) 1115-256) (125-2.901
15-min 0,461 0.559 0.735 0.596 . ' 1.14 1.34 1.56 180 2,14 2.42
(0359-0504)(0.435-0.721) (0.559-09491 (0.690-1.16)'(0857-1.551 (0984-1841 11.11-2.18) (1,22-2571 It40.3.121 1133-3.54)
30-min 0.624 0.755 0.992 1.21 1.53 1.80 2.09 2.40 2.85 3.21
• (0455-0803)(0.588-0.974)(0.769-1.28) 10.930-1371 (1.15-2071 (1.32-2.46) (1.45.291).(1.63-343) 1136.4151 (203-4.70)
60•min 0.768 i 0.928 1.22 1.49 1.90 2.25 2.62 3.03 3.62 4,09
10.593-0989(1(0.722-1.201 40944-1.58) (1.15-193) (1.43-258) 41.65-308) (1.86-3.66) (2.06-433) (236-528) (259.6.00)
2.84 0.913 1.10 1,45 1.77 2.27 2.69 3.15 3.66 .' 4.39 ' 4.98
1 (0.718-1.16) 10065-1.401 (1.13-1851 (1.38-2.271 (1.73-3.06) (2.00-365) (226.436) (2.52-5.18) (2.90-634) (3.19-7.22)
1 3•hr 0.991 1.19 1.56 1.91 2.45 2.93 3.44 4.01 4.83 5.51
i1,, (0.784-1 25) (0.940-1.511 (1.23-1.98) (1.49-2431 (1.89-3.301 (219-3.951 12.49-4.74) (2.78-5,64) (3.22-5 95) (355-7.94)
6-hr 1.14 1.36 1.77 2.16 HI 2.75 3.25 3.86 4.49 5.40 6.15
40914-1.43) (1.09-1.701. (1.41-2.22) (171-2,72) 12.15-3.66) (246-438) (282.525) (3.14.6241 1364-7.671 (4.01.8.76)
12-hr 1.33 I 1.55 2.03 2.40 7.07 3.59 4.16 4.77 5.64 6.34 -
(1.07-1.64) I(1.28-1.951. (1.64.212) . (196-7041 (2.40-4.00) (2 74-4.71) (3.06-5.57) (3.37-5.53) (383-7891 (418-8.921
24•hr 1.56 1.82 2.29 2.72 3.35 3.89 4,46 8.05 5.98 .6.67
(128-1,91) (149-2.23) (1.87-2611 (2.20-3 34) (2.65-4.31) (330-5 041 (332-5.901 (3634.67) (4.10-8.25) (4.45.9,29)
2-day 1.77 2,08 2.60 3.06 3.73 4.27 4.84 5.45 6.29 6.96
(1.47-215), (1.72-2511 (2.14-3.15) 1211-3.72) 11297-4.70) (3.32-5.44) (3.64-630) (3 B3-7.251 (437-8.58) 1470-9.58)
3-day 0.61-2.321
2.24 2.77 3.23 3.90 4.45 5.03 5.64 6.49 7.17
1161.2321 (1,86-2591 1229-3331 (266.3901 (3t3-4.691 (3,49-5 631 (381-650) (4.10-7A6) (454.8.79) (407.9.79)
4•dey 2.06 2.37 2,91 3.37 4.05 4,60 5.18 5.79 6.64 ' 7.32
(1.73-2.47) (1.98-2.94) ' (2.42-3.46) (2.80-4.061 (3.27-505) 1362-5791 (3.94.6.68) (4.23-7.52) (4.67-894) 1500-994)
7•tlay 2.36 2.72 3.31 3,52 433 5,09 5.65 6.24 7.04 7.65
(1.99.2.76) (229-3.22) (2.79-3.93) (3.19-4.55) (3.67-555) ,(4.03-631) (4.33-7.17) (4.59-5.101 (499-9.35):(528-10.3)
10-day 2.63 3.02 3.67 4.21 4.95 5.52 6.09 6.57 7.43 8.01
. (2.23.309) , (2 57-335) _13.1(•4.341 (3.55-4 99) (403-8011 (4.40-6.79) (4.69-7 55L (4.93-8.56) (529-979) 15.56-107)
20•day 3.46 3.93 4.58 5,29 ' 6.11 6.74 7.35 715 8.74 9.32 '
(2.98402) (338.4.57) (4,01-545) (4.51-6191 (603-7321 (5.42-617) (5.72-9.101 (595-10,1) (629-1141 (635-123)
30-0ay 416 4.70 5.55 6.24 7.18 754 8.50 9.14 9.96 10,6
(3.81-481) (407-543) (4,79-5431 (536-7.25) (5.92-849) (5.35.9.42) (565.104) (688-1151 (7.22-128)-(7.46-1391
45-day
5.04 5.70 6.73 754 830 9.37 10,1 10.8 11.6 12.2
1440-5.78) (4.97-6.541 ' (585-7.74) 16 52-8 701 (715-10.1) (183-11.21 (7.96-1231 (8.16-13.41 (8.45-14.5) 1872-159)
fi0•day 5.77 6.56 7.78 833 9,93 10.6 11.6 12.3 13.1 13.7
1506-6.581 5.75-7A9 5.00.8901 (7.58-10.0) (525-1161 .81-127) (9,14-13.9) (933-1521 (9.60-15.51 (981-17.71
1 Predpfalkn frequency(PF)estimates In MD table am based on frequency analysts of partial duraton settee(PDS).
Numbers In parenThesh are PF estmotea at IGwer end upper bounds of 0)a 9095 canlidence Interval The probability that predp0alkn frequency estimates(fat
a Oven duraoion end avenue reeute==mob r>4 be create(Man the upper'Wind(or less Ilion Ne lawerbound)'Is 5%.E411malee a1 upper bounds ere
not ditched eBaMsiprabobfe Mash*pmelette on(P)A1)esrmalea and may be Maher thoneonenty vaild PMP values,
Please refer to NOMA11as 14 document(or more Information
Rack ID Tao
PF graphical
http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat--110.7150&lon=-104.1568&dat... 9/12/2013
KLEINFEGOE!?
mom AtQI Noe s Mw
Sterling Energy—
PROJECT: Centennial Gas Plant PROJECT NO.: 124271
SUBJECT: On-site Runoff Calculations BY: Bruce Curtis DATE: 9/12/13
REVIEWED BY: /-GLuv tt L.$Jt#t?R DATE: :LE/t 3}'l3'
PURPOSE:
Perform runoff calculations to estimate peak flow needing to be captured and released by the
proposed detention basin.
GIVEN:
1. Sub-watershed 4 area=21.8 acres
2. Existing Land Use/Vegetation=Grass
3. Site location: Lat.40.715036°;Long.-104.156812°
4. Precipitation data obtained from NOAA website at above coordinates:
htto://hdsc.nws,noaa.00v/hdsc/pfds/pfds map cont.html?bkmrk=co
ASSUMPTIONS:
1. The entire drainage area is Hydrologic Soil Group B.
2. Structures shown on the map but not included In the impervious area calculations are
suspended on supports or racks and therefore the land beneath them is pervious.
3. No precipitation runoff leaves the Secondary containment berm.
ANALYSIS:
The Weld County Engineering and Construction Criteria(April 2012)was used to estimate off-site
and on-site runoff for the facility. Because the total drainage area is less than 160 acres,the
Rational Method was used to estimate runoff. The proposed detention basin will be placed at the
lowest elevation of the site in the northeast corner. County Road 100 forms the southern
boundary of the site and because the runoff generally flows north, the roadside ditch intercepts all
runoff from the 100-year storm event, as shown In a previous calculation,and no off-site runoff
from the south flows onto the site. A small berm will be placed just west of the graveled area to
prevent off-site flow from the west and runoff from the undisturbed area on the west side of the
site from entering the detention basin. On the east side of the site, some minor grading and the
natural topography will prevent off-site flow from entering the detention basin. The site will be
graded so that all runoff from graveled or impervious surfaces will enter the detention basin.
General Steps:
1. Estimate peak runoff needing to be captured by detention basin during 2-year through
100-year storm events.
a. Calculate time of concentration.
b. Estimate Rainfall Intensity, I.
c. Estimate the Runoff Coefficient,C.
d. Estimate the peak flow needing to be captured by detention basin.
2. Estimate the peak flow to be released by detention basin.
a. Calculate time of concentration.
b. Estimate Rainfall Intensity, I.
c. Estimate the Runoff Coefficient, C.
d. Estimate the peak flow needing to be captured by detention basin.
The calculation sheets provide the actual analyses.
Page 1 of 1
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C.Composite Runoff Coefficient Calculation
1.Area Calculations
a.Impervious Area
Impervious
Area
Structure (acres)
Office 0.023
Warehouse 0.055
Compressor Building 0.138
Inlet Filtration 0.002
Amine Skid(2) 0.037
TEG Skid(2) 0.019
Thermal Oxidizer 0.006
FG Skid 0.006
Genset 0.037
Transformers 0.002
IA Building 0.005
MCC 0.010
Refrigeration Compressor(2) 0.014
Unlabeled Compressors(3) 0.029
Unlabeled Tank 0.001
Regeneration Gas Heater(2) 0.028
Hot Oil Heater(2) 0.017
Hot Oil Skid(2) 0.007
KO Pump 0.001
Flare 0.001
Total Impervious Area 0.437
b.Graveled Area
Graveled
Area
Location (acres)
Entrance Road 0.652
Work Area 13.800
Total Graveled Area 14.452
c.No Runoff
Secondary Containment Berm Area=50 x 120= 0.138 acres
No precipitation runoff leaves the Secondary containment berm.
`..twit&,ytJ;t4 L.
d.Other Structures (AP-314 I%
The remainder of the structures shown on the map are assumed to be suspended on supports or racks and therefore
the land beneath them Is pervious.
a Drainage Area
Toal Drainage Area= 21.800 acres
Drainage area measured from AutoCAD.
2. Runoff Coefficients
a.Runoff Coefficients(from UDFCD DCM)
H5G B HSG C&D
100-Year 100-Year
Percent Runoff Runoff
Land Use Imperviousness Coefficient Coefficient
Roofs(includes all structures) 90 0.81 0.83
Gravel 40 0.5 0.58
Undeveloped Area 2 0.36 0.51
3. Composite Runoff Coefficient Calculation
Area Runoff Imperviousness
Land Use (acres) Coef. (%)
Roofs 0.437 0.81 90
Gravel(minus the secondary containment area) 14.314 0.5 40
Undeveloped(Type B Soil) 7.049 0.36 2
Composite Values 0.46✓ 28.7
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 I 0.43 0.48 0.55 0.58 0.62
60% 0.41 I 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 0.60 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 I 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% 0.18 025 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 0.36 042 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
06/2001 RO-11
Urban Drainage and Flood Control District
Precipitation Frequency Data Server Page 1 of 4
NOAA Atlas 14,Volume 8,Version 2
Location name:Bdggsdale,Colorado,US 4/ ,r '
Coordinates:40.7150,-104.1568 •Elevation:4940fr , .
'saarn'Gao9B Maps f
POINT PRECIPITATION FREQUENCY ESTIMATES
&u9+Pere.Deborah Mann.Sandra Pem(vlc,Muni Pay.Michael 51 Laurent.Carl Trypoht Odle
Unruh.Mdmel Yerle.Ge:Bery 8omin '
NOM.NalbnalYAather Servte.We,6prng,Morylyd
PF labular I PE graphical I Marys & aerials
PF tabular.
' PDS-based point precipitation frequency estimates with 90%confidence Intervals(in Inches)1 I
Qu�Pgh Average rocurrvnco Interval(years)
f 1 1 2 I 6 10 25 50 100 1 200 500 . 1000 •
5-min 0.258 0.313 0.412 0,502 0.638 0152 0.975 1.01 1,20 1.35
(0201-0 3331 (0243-0.404) 10.319-0532)(0.386-0.650) 10.480-0.868191651-1.031 10 619-1.22 (0685-1.44)(0.782-1.75)40856-1.991
10-min 0.378 0.458 0.603 0.734 0.934 1.10 1.28 • 1.48 1.76 1,98
402944.4871 10 356-0.591}(0.467-0.778) (0.566.0.052) (0.703-1271 (0.007-1.51) 40907-1.791 (1.00-2.111 _(1.15-2.56) (1.25-2.90)
16-min 0.461 0.569 0.735 0.896 1.14 -7:3-,r-Mb 1.89 2.14 2.42
,359-0.594) 0435-0721 (0.569-0.949} (0.690-1.16) (0357-1.55).40.984-1.841 11.114218) (1.22.257) (1_40-3.121 (153-354) '
0.624 0.756 0.992 1.21 1.53 1.80 2,08 i 2.40 . 2.86 3.21
30-min
10.485-0.6031(0568-0.9741 (0.769-1.28) (0.930-1.57) (1.15-2.07) -(1.32.2.46) (1.48-291))(1.63-3.43) (1.86-4.151 12.03-4.70)
60-min 0.768 0.928 1.22 - 1.49 1.90 2.25 2.62 3.03 3.62 4.09 ‹.-
--->). 10598-0.989) (0722-1.201 (0.944-158) (1.15-1.93) 11.43-2.59) (1.65-3.06) (1.86-3.661 (2.06-4.33) (236-5.28) (2.59-6 00)
2-hr 0.913 • 1.10 1.45 1.77 2.27 2.69 3.15 3.66 4.39 4.98
10.718.1.16) 10865-1.40) (1.13.1.85) (1.38-2271 11.73-346) (2.00-3.65) (2.264.381 (252-5.18) (2.90-&34) 13.19-7.22)
3-hr 0.991 1.19 1.56 1.91 2.45 2.93 3.44 4.01 4.83 5.51
10.784-1.251 (0940-1.51) (123-1.98) (1.49-2.431 (1.89-3.301 12.19-3.951 (2.49-4.74) (2.78.5.64) (322-6.95) (3.55-7.04)
6-hr 1.14 1.36 1.77 2.16 2.76 3.28 3.86 4.49 6.40 6.15
10.914-413) (1.09-1.70) I.(141-2221 11.71-2.721 42.15-356) (2.48-438) 12.82-525) (3.14-6.24) 1364-7.67) (4.01-8 76)
12-hr 1.33 1.58 203 2.44 3.07 3.69 4,16 4.77 5.64 6.34
. (1.07-1.64) (1.29-1.951 .(1.64-252) 41.96.3.04) (2,40-400) 12.74-4.71) 1306-5.57) (337-6.53) (383-7.89) (4.18-8 92)
24-hr 1.56 1.82 2.29 2.72 3.35 3.69 4.46 5.08 5.96 6,67
129-1.91) (1,49-223) I (1.87-2.91) 12.20-3.34) 1265.431) 13.00-504) 1332-590) (353-&87) (4.10-9251 (4.45-9.29)
1.77 - 2.08 ' 2.60 3.06 3/3 4.27 ' 4.64 5.45 6.29 6.96
2-day
(147-2.15) (1.72-2 513 (2.14-3.15) (251-3 72) 12.97-4.70) (332.544) 1364-630) 1393-7.26) (437-8581 (470-9.59)
1.93 ' 2.24 2.77 3.23 3,90 4.45 ' £03 5.64 6.49 7.17
3-day (161-2.32) ' 1186-2.991 1229-3.33) 4256-3.90) p.13.4.69) 1349-5.63) 13.61-6.501 (4.10-7.48) (4.64-a.79) (487-9.791
4•day 2.06 2.37 2.91 3.37 4.05 4.60 5.16 5.79 • 5.64 7.32
(1.73-247) (198-2.641 (242.3.48) 12.80.4.06) (327-5.05) (362.5.79) (3.94.6.661 (4.23-7.82) 14.67-8.941 (500-9.94)
7-day 2.36 2.72 3.31 3.82 4.63 5.09 5.65 6.24 7.04 7.66
1199-2.79) (229-3.221 (279-3.93) 13.19-4.55) 13.67-5.55) (4.03-6.31) (4,33-7.17)_{4.59.8.10)1 (4.99-9,35) (528-10.3)
10•day 2.63 3.02 3.67 4.21 4.96 5.52 ' 6.09 6.67 7.43 8.01
(2.23-3.09) 12.57-3.56) (311.434) 13.55-4.99) (4.03-6.01) (4.40-6,79) (4.69-7.65) (4.93-858) 1529-9.79) (5.56-10.7)
20-day 3.46 3.93 4.66 5.29 6.11 6.74 7.35 7.95 8.74 9.32
12.98-402) (3.38-4.57) 1401-5461 (4.51-6,191 (5.03-7.321 1542-8.171 1612-9.10) (5.95-10.11 1629-11.4) 16.55-123)
30-day (3.61-4.81)
4.70 5.55 6.24 7.16 7.84 6.50 9.14 9.96 10.6
(361-4.81) (4.07-5431. .(479.6.431 15.36-7.25) (5,92-8,49) (635.9421 16.66-10.41 16.68-11.51 (7.22-1281 (.48.13.91
46-0ay 5.04 , 6.70 6.73 7.54 6.60 9.37 10.1 10.8 ' 11.6 12.2
p40-576) 14.97-6541 45.85-7.74) 16,52-9.701 17.15-10.1) 17.63-112) 17.96-12.3) 18.16-13.41 (8.48-14.81 (8,72-158)
60-day 5.77 6.56 7.78 8/3 9.93 10.8 11.6 12.3 13.1 13.7
1506-6.58) 1575-7.49) (6.60-8 90) (7.58-100) (8.2B-11.61 18.81-127) (9.14-13.9) 19.33-1521 (9.60-16.6) 19,81-177)
r Predptlatun frequency 4PF)estimates In this fable ere based on frequency analysis of partial duration sodas(PDS).
Numbers In patonlhe9ssare PF estimates Wawaend upper bounds of the 90%confidence tn(orval The probability Oral predphnOen frequency e*dmolas(for
a given duration and overdgn recurrence interval)will ba greater than the upper bound(orlon than It a lower bound)4.5%.Eal)nates at upper bounds are
not checked against probable max'h unt preerpaauon(PMP)esvnoles and may be hIghdrtnen arrrenuy vend PMP valuer.
Please refer to NOAH Mina 14 document for more Infonru0on.
Back to Top
PF graphical
http://hdsc.nws.noaa.gov/hdsc/pfds/pfds jrintpage.html?tat=40.7150&Ion=-104.1568&dat... 9/12/2013
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.
( r II
2.4.2 -Overland Travel Time. For catchments with overland and channelized flow, the lime of
c/, :f•
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, r„can be estimated with the help of Figure RO-1 or the following equation (Guo 1999):
=C„Sw" (RO-4)
in which:
Y=velocity(ft/sec)
C,.=conveyance coefficient(from Table RO-2)
S,,.=watercourse slope(f/ft)
-E{ :. .
V TABLE RO-2
Conveyance Coefficient, C,
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, 4, is then the sum of the Initial flow time,q,and the travel time,t„as per
•
Equation RO-2. C T. ' t
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,r,)in an urbanized catchment should not
exceed the time of concentration calculated using Equation RO-5.
_
1` 180 + 10 (RO-5)
RO.6 06/2001
Urban Drainage and Flood Control District
DRAINAGE CRITERIA MANUAL(V. 1) RUNOFF
TABLE RO-3
Recommended Percentage Imperviousness Values
Land Use or Percentage
Surface.Characteristics Imperviousness.
Business:
Commercial areas 95
Neighborhood areas 85
Residential:
Single-family •
Multi-unit(detached) 60
Multi-unit(attached) 75
Half-acre tot Or larger •
Apartments 80
Industrial:
Light areas BO
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 45
(when land use not defined)
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.
Based in part on the data collected by the District since 1969,an empirical relationship between C and
the percentage imperviousness for various storm return periods was developed. Thus,values for C can
be determined using the following equations(Urbonas, Guo and Tucker 1990).
C4 =K4 + (1.31/3 —1.44i2 + 1.1351—0.12) for CA≥O.otherwise CA a 0 (RO-6)
CCD =KCO +(0.858i' 0.786i= +0.7741+0.04) (RO-7)
Ce =(CA +Cc0V2
in which:
i= % imperviousness/100 expressed as a decimal(see Table RO-3)
0612001 RO-9
Urban Drainage and Flood Control District
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APPENDIX B
HYDRAULIC COMPUTATIONS
124271-7/CSP13R0465 October 25, 2013
Copyright 2013 Kleinfelder
KLE/NFELDER
�ro+r rw.`.wn bow.
Sterling Energy—
PROJECT: Centennial Gas Plant PROJECT NO.: 124271
SUBJECT: Detention Basin Size BY: Bruce Curtis DATE: . 10/3/13
Calculations REVIEWED BY: /n.hc.(.4(/ti,i,.•.r DATE: /v(23/f;.
PURPOSE:
Perform calculations to size the detention basin volume and configuration.
GIVEN:
1. Undeveloped Imperviousness=2%from UDFCD DCM
2. Proposed Imperviousness=28.7% from On-Site Runoff Calculation
3. Sub-watershed 4 area =21.8 acres
4. Existing Land UseNegetation =Grass
5. Site location: Lat.40.715036°;Long. -104.156812°
6. Hydrologic Soil Group=B from NRCS map provided In Off-Site Runoff Calculation
7. Time of Concentration= 1 hour from On-Site Runoff Calculation
8. Allowable Unit release rate for a 10-year storm event=0.23 from UDFCD OCM (Default
value chosen)In correspondence with Weld County we were told that the County will
soon be changing their release rate to the 10-year storm under existing conditions rather
than the 5-year storm event currently listed in the Weld County Engineering and
Construction Criteria manual. We are asking for a variance to allow the use of the 10-
year storm event for a release rate from the detention basin.
9. 10-Year, 1-hour precipitation depth=1.49 inches from the On-site Runoff Calculation
10. 100-Year, 1-hour precipitation depth =2.62 inches from the On-site Runoff Calculation
ASSUMPTIONS:
1. Include a low flow outlet for approximately the 2-year existing flow. This is not required
by the County but will allow the facility to drain quicker.
2. The low flow outlet will be set at the top of the WOCV elevation.
3. Because the existing topography is extremely flat near the proposed detention basin
(<0.2%), it is not possible to provide the detention basin and trickle channel with a 1%
slope and provide the necessary detention and outflow requirements from the detention
basin. It is assumed that the County will grant a variance for the required basin and
channel slopes. Because of the small drainage area and sandy soil,ponding water and
wetland growth should not be a problem.
4. Detention basin length should be about 2 times the width.
ANALYSIS:
The Urban Drainage and Flood Control District's(UDFCD)detention basin sizing worksheet(UD-
Detention_v2.33.xls)was used to estimate the required detention volume. Because the drainage
basin Is small(less than 80 acres),the Modified FAA method in the spreadsheet was used to
estimate the required detention volume. To balance the site grading,the proposed detention
basin will be placed In the northeast corner of the site where the topography is slightly higher to
generate more cut to be used as fill elsewhere on the site. The detention basin will outlet to the
northeast corner where the existing elevation is the lowest. The site will be graded so that all
runoff from graveled or impervious surfaces will enter the detention basin.
The Initial Surcharge Volume should be a minimum of 4 inches deep and have a minimum
volume of 0.3%of the WQCV. It is the available storage volume that begins at the water surface
elevation of the micropool and extends upward to a grade break within the basin.
Page 1 of 2
KLEINFELDER
/wmnw%aY+wreo.
Sterling Energy—
PROJECT: Centennial Gas Plant PROJECT NO.: 124271
SUBJECT: Detention Basin Size BY: Bruce Curtis DATE: 1013/13
Calculations REVIEWED BY: / n,no.(-4L trifrt DATE: to(2.3I
General Steps:
1. Estimate the volume of the detention basin required to capture the 100-year runoff from
the site after development and release flow from the detention basin at the 10-year
undeveloped flow rate.
2. Estimate the minimum detention basin footprint and depth to provide the required
storage. The actual detention basin size and depth will be greater than this to provide for
uncertainties in future design changes or construction irregularities.
3. Develop storage vs elevation table and curve.
4. Develop outflow vs elevation table and curve.
The calculation sheets provide the actual analyses.
Page 2 of 2
��� SHEET / OF /
KLE/NFEL DER
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UDFCO DET Nmp BASI.VOLUM• TMA Yet FAA Y.lO 01MgVtlw.hOMl. bT4
UOFI:OOETENnON BASIN W WhE ESTIMATING WORKBOOK Version 3.]J,RNe4ed Aupuf]2813
V6M.N0n_.233 a.,Mn1FMPIA
IM/2a126 W om
DETENTION VOLUME BY THE MODIFIED FAA METHOD 1
I
?mice'::
Basin ID:
Inflow and Outflow Volumes vs.Rainfall Duration
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UDFCD DETENTION BASIN VOLUME ESTIMATING WCRABOON Version 2.33,Released Appal 2013
1160.•M,.l Mgt law/al FAA ItI7C0I15 Of PM
DISCHARGE FROM DETENTION BASIN
Low Flow Pipe Diameter= 18 inches
Elevation of Low Flow Pipe Invert= 4940 feet
Entrance Type= Square Edge with Headwall
Low Flow Orifice Diameter= 6 inches
Orifice Coeffiient= 0.6
Elevation of Center Point of Orifice= 4941.98 feet
Length of weir= 4 feet
Weir Coefficient= 3.00 Calculated from Equation in Chow
Elevation of Top of Weir= 4942.51 feet
THEORETICAL HEAD THEORETICAL HEAD
HEAD FLOW ABOVE FLOW ABOVE FLOW
ABOVE THROUGH ORIFICE THROUGH LOWFLOW TOP OF OVER TOTAL
ELEVATION PIPE INVERT PIPE CENTER ORIFICE OUTFLOW WEIR WEIR OUTFLOW
(feet) (feet) (cfs) (feet) (cfs) (cfs) (feet) (cfs) (cfs)
4940 0 0.0 0 0:0 0.0 0.0 0.0 0.0
4940.5 0.5 6.0 0 0.0 0.0 0.0 0.0 0.0
4941 1 8.5 0 0.0 0.0 0.0 0.0 0.0
4941.45 1.45 10.2 0 0.0 0.0 0.0 0.0 0.0
4942 2 12.0 0.02 0.1 0.1 0.0 0.0 0.1
4942.5 2.5 13.5 0.52 0.7 0.7 0.0 0.0 0.7
4943 3 14.7 1.02 1.0 1.0 0.5 4.1 5.1
4943.5 3.5 15.9 1.52 1.2 1.2 1.0 11.8 13.0
4944 4 17.0 2.02 1.3 1.3 1.5 21.8 23.2
DetentionbasinDesign.xls 10/23/2013
Release-Weir
8:06 PM
STORAGE IN DETENTION BASIN
ELEVATION INCREMENTAL CUMULATIVE
ELEVATION AREA AREA INCREMENT VOLUME VOLUME
(feet) (sq.feet) (acres) (feet) (acre-feet) (acre-feet)
4940.67 5000 0.11 0.00
0.33 0.04
4941 6400 0.15 0.04
0.5 0.14
4941.5 20000 0.46 0.19
0.5 0.40
4942 53046 1.22 0.59
0.5 0.70
4942.5 70000 1.61 - 1.30
0.5 0.85
4943 77466 1.78 2.14
DetentionBasinDesign.xls 10/23/2013
Storage 8:07 PM
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Sterling Energy—
PROJECT: Centennial Gas Plant PROJECT NO.: 124271
SUBJECT: Water Quality Feature Size BY: Bruce Curtis DATE: 1O/3/13
and Outlet Calculations REVIEWED BY: I-.L.N gNif re- DATE: to/2-31/3
PURPOSE:
Perform calculations to size the water quality portion of the detention basin volume and the water
quality outlet.
GIVEN:
1. Proposed Imperviousness=28.7% from On-Site Runoff Calculation
2. Sub-watershed 4 area=21.8 acres
3.
ASSUMPTIONS:
1. The UDFCD recommends that because of the small size of the drainage area, the Water
Quality Capture Volume(WQCV)should be estimated and used in the design and not the
Excess Urban Runoff Volume(EURV),even though the water quality volume is part of
the detention storage.
2. Because of the small size of the subwatershed a forebay will not be utilized.
3. Because the existing topography is extremely flat near the proposed detention basin
(<0.2%), It is not possible to provide the detention basin and trickle channel with a 1%
slope and provide the necessary detention and outflow requirements from the detention
basin. It is assumed that the County will grant a variance for the required basin and
channel slopes. Because of the small drainage area and sandy soil,ponding water and
wetland growth should not be a problem.
4. Depth of micropool will be 2.5 feet
5. Surface area of micropool will be at least 10 sq.ft.
6. Assume initial water quality depth Is 1 foot.
7. The Initial Surcharge Volume should be a minimum of 4 inches deep and have a
minimum volume of 0.3% of the WQCV.
ANALYSIS:
The Urban Drainage and Flood Control District's (UDFCD)Best Management Practice(BMP)
design worksheet(UD-BMP_v3.02.xls)was used to estimate the required detention volume. The
Extended Detention Basin(EDB)BMP was selected to enhance the water quality of the runoff
because the site has greater than 5 acres of equivalent impervious area, the watershed is less
than 640 acres,and the depth to ground water is deep. Also, there is no baseflow and the EDB
can be incorporated into the detention basin.
General Steps:
1. Estimate Water Quality Capture Volume(WQCV)and the design volume(1.2'WQCV).
2. Design the micropool and outlet structure
a. Using storage vs elevation curve,estimate storage elevation that will provide
WQCV.
b. Input depth of WQCV(H)into spreadsheet and spreadsheet will"design"outlet
requirements. H is the difference in elevation between the WQCV storage
elevation and the top elevation of the micropool (or lowest water quality outlet
orifice elevation).
3. Design Initial surcharge volume
a. Input depth and spreadsheet estimates volume
Page 1 of 2
ICLE//NFELOER
k .....
Sterling Energy—
PROJECT: Centennial Gas Plant PROJECT NO.: 124271
SUBJECT: Water Quality Feature Size BY: Bruce Curtis DATE: 10/3/13
and Outlet Calculations REVIEWED BY: L L.4/4\4144 . DATE: ie(2-3//S
4. Design trash rack
a. Spreadsheet designs(rash rack
The calculation sheets provide(he actual analyses.
Page 2 or 2
"",':3' 1� �L ..-..Ya7u+ ...c. r a ,.4.r vw.. ',ri'.a '$ _...•.n S-'�l
f Design Procedure Form Extended Detention Basin(EDB) ,
— —' — — —Sh0atl of
Designer. Bruce Curtis 1
Company: xlalnfdder
Bela: October B,2013
Project Starring Engrg)...Centennial Gas Plant
Location: "Wald County,CO
i.Basin SIc age Vduma
A)EHeHive MpeMasness of TridderyAree,1. - I.= 28.7 % :u„
yy B)TlhularyAme's imperviousness Patin 11.Id 100) I=tP6ee28741acl f-
E- 5_
C)Contributing Wataehed Area Ares• 21.800 so 1y;
0)For Watersheds Outside of Ha Denver Region.Depth of Avorsga de= h (
When 1y� Wm Peahen Slam €c,.
E)Design Caltepl Deese One
(Stied EIAtV when also(Halpin frllood control) f ®Wei Caepy Caanwe Vlore(WQMO !'cid
ODi:egg Nat wlrvwrc(gum)
Fj Design Volume(1.2 WOCV)Based on 44c 0ur Iran lime Vosiny=�ea2i8G9 l ac41 Y7-`
(WWaa,•(1A•(091'P.1.19'Ir.0.7s•1/12•Arne•1.2)
eF. G)For Walarshode Oueido of the 0onver Rogan. Varna.aw l-. 2"' 1 ncfi .
Water Dually Cagan Vakane(WOCV)Design Wo ne
Wwocv oats=Nit Voand0.A3))
Hl User Input d Water Ovally Capture Volume(WOCV)Design Volume Vasrwiuvw• acM
F':
Vo
(Orgy If tlBacnl WOW Design Wane is desired)
OozCc—
ky I)Predominant Weilershed BRCS Soil Group )
OA
®B ti
QC/0
4 r 17.22.212.2d%::222221 Si
id
2.Bain Snape:Lenglhto Nldt ROW L:W= 2.0 :1
(A basin earth to width raga of al leas(2:1 wit Improve Tss mductiai.) _
E
$J 3.Basin Side Slopes
A)Basin Maximum Side Slopes Z= 4.00 Uri S?
(Horizonte)distance per unit vodka,4:1 ce Bailer preforms!)
42
4.Net
A)Desoto moans of providing energy dissipation al concentrated
.y` Neavbcalicns:
—ate -- -:e:,.. .4•,•4.;a.µ gr. c. sF
UO.BMP_v3.02 gig,EDB 10/812013.1'12 PM
1-,s ' ,c,.T'..-77 ,.,'YS'R _,e-�..z....,.a; ==. rtr..i"" r., r r a.w ar, -G -,:W-v-niv.�' 3.v T.
Design Procedure Form: Extended Detention Basin(EDE) - - ir
_.._
ShOM2oral+`
Designer: Bruce Curtis
Company: Kleintelder _
Date: October 5,2013
Prefect: Shrimp Energy•Cenlerudal Gas Plant
-
mutton: Wald County,CO
J,
5.Porvbay ;.
A)Mnlmum FcrobeyVduma "-•:, V,a=�`efl1 q pg'1�5T epf .
(Vru,= 3% dine WucV).. „tart'._
5,
B}Actual Forebey Volume '� Pa h. ac11 r„-•^
`
C)Forebay Depth �.• Dr• h f� b''�
(Dr' 18 Inch maximum) �"\ r f,s r ''.'.d
D}ReedyDacharge • - 1. ..-r .r.
3
II Undetolne0100-yea'Peak Discharge .! eA
'n
Gl Fonbay Discharge Design Row 0. ';:S chi
14
(Or=0.02'O,W)
E)Farebay Discharge Design ` 1''
3'•" OrAsc Dse
O6e1,,von ��•.Rt ow too er,Wlfor berm wl pipe} tJ'
OWRI with Rect.Npds \ `tit tt
O welnaiVttddl Weir \•
F)Discharge Ftpe S1 (mnfmun&Inches) Calculated De•0235144M0269 In "
G)Rectangular Notch Width Calculated Wx•wiscomma In
Ogle one ' ;-.PAOIIDE ACTR)SrSTEhfLONOIIUOhiAL
6.TricVe Chame) • SLOPE FROM FONECAY TO MCROPOOL
OC ,� ^ WRHNDMEANDERINO.RWMPANO tit
A)Typo dTdWe Channel -1'^ ®Se &ean SOIL RIPRAPLINEDCHANNELS ARE
HOT RBCOMMENOEO. ��
5.
MINIMUM DEPTH OF t.6 FEET 1 .
9 Seca dTdckle Channel S r
00100',,-fi lit '
'rv,...e...� .
7 MCNpcd and DUDal Structure
A)Devils of Mdopod(2.54eol nank,um) O .• 28 8
EllSlrtace Area Of Matmood(1Olf*mirrmuml Ao• 110 agit Yt
C)Outlet Toe
r Osase OI,e
e Crake Pate rr
C1Odrr ptscn0ey t...3.1
I:
Ptq
)e
0)Depth dDesign Velum:,(EHRVa12 WOCV)Basee co the Design H. 1.32 leaf IA
ei
Concept Chosen Under I.E.
E)Vdmne to Drain Over Prescribed lime WCICV•F51316158=43 eat
K
F)Drain Time Ta• 40 hours
(M'n To for WOC l=40 holm Mae;fOr EURV•72 hours)
Recommended Recomded!Want=Outlet Area per fox.(AJ A.• 0012=? I square Inches d
el)Orifice Dmenslans: F.i
I)Circular Ori TYce Diameter or Ds• 12 inchm
I) Numbed Columns A,• 1-4W514 number
J)Actual Design Outlet Ame per fox(A) A,•P,s1221117er'T..3'-S9squato Whet s d {r4'
K)Numb ROM RI) Err, 3':�T-ASTnumber " .
2
L)Totet Outlet Area(k) A W:3:1+?�?T square Inches
tfr
-:.:.:�_^'? .y*>t-: t,?lM1:Ssv>_$,N�><T:2.1::c'xc1'y.s-rc'rm:r-1i- .:.n:. ,r .
UD-BMP v3 22 xis,EDS 10/812013,1,12 PM
a '.l: ':._.Cx-'tr^�.. -. .c^:c•^.tf�'�:: d ..�.�.�..' %, „z � +', . sxv-i» "' " .�m".F?'"� rr
) � .._._ Design Procedure Farm: Extended Detenllon Basin(EDB) — Tr"
sSheet or x1
Designer: Brun Culla
Company: Klein(elder •
13 Date: October IL 3013
Prolecl: Siwllno Energy•Centennial Cu Sent
Location: Weld County,CO
8,Mal Surcherye Volume
A)Depth of Initial Surcharge Vtlime On• 4.0 h
4 (Minimum recommended depth 04 Inches)
fta
B)Minim=Mal Surcharge Valuma Va•INSW35.835438 w ti -`.
(Mrimlm volume of 0.3%of the WQCVIif
C)Ir3lal Surcharge Provided Above Moopool V••p wn 'LI
3" aemeOne ..
e.Trash Pack
di ®am+br(up to 2"aYnem) l'.
d A)Type of Wale-Chary Drake Used Oge:ta,vlar(Thk '
h) rter B)waterauoray screen Open Ares:At•345(ear)'An A,•WWI irengal squat.Inches 53
1 C) For 2•,a Smaller,gram agpp(pp(See red Sheet T•12):
it
0 Wirth of Water Quality Screen end Commie Opm5g(Wm.,) Wes••Ert(2LS05312hcties
ti'
f:
'ppg lit Height of Water OueMy 5creen(Hm) lam a {3d 3fllnrhes
Chrte au
H)Type ol Screen,Describe II'Other ® nn was Bu with 60%Lpmura•A
7 Oowe(emwe): lu
a
9 39
tat
4.,
. 1 w':�iue
Mos QC ,d,
• ... �0 Akm*vae AManmp 9l Snla(a Moil)
CI MY,(oerate): $
I
19:9:
:a
E S-1
[
a
<:-a...n.•uv ar 4s.�:.. -rvK'a<+,^-.,.aS�.RS-i, -�...rw.r ry .-y - .._ x�aA3_. . u,,.gY� Vr..a+%t
UO•BMP v3.02 xis,EDB 10/812013,1:12PM
ii Design Procedure Form: Extended Detention Basin(EDB) i
- •Sheol 4 014 4-
Designer, Douce Cud6
{ Congany Klelnrilder
A..
Dale: October e,3du
y holm!: Sliding Energy•Cenlennlal Gas Plant
,� Loallon: Weld County,CO
4 g I.
10 Overflow Embankment
4
1 A)Describe embankmem preletlbn/a ie0year end greeter ovenopping: Np1a. FMw grimier burl 100}ver vAl Oowmnto cutlet elambite. ... b also b:
Ino ests4b8 a Pm epVdWmMl deMeVealn. _. x,
Dl Sbped Overflow Embankment Za• 4.00 R111 Cf
J7 (Horizontal dslance per Wlvadeo1.4:I a Palle Figured) ).
t
7 {crow Era- - 9:
11.Vegeladoa
3 ®nok0rkins
A
j 14 Access
t,
AI Oacrib4 SmMarwnl Removal Procedures
.
Notes - _. i;
li
k -
n.., -..,:,..-.r X -'.z,:g;75i- x.-.-' ...:u"lF:n.. =fig!»,,,.- r�M<:5 r .-iTr.=rr-r,:T?rsp-n
�l arrw,x5'.4s3•T.vvP`"e'e-.TTr'-^�'^Eew.^,'R"!rTavitvlu tar.. _
UD•DMP_3 03.xls•EDB 10/8/2013.1:12 PM
I KLE NFELOER
Sterling Energy—
PROJECT: Centennial Gas Plant PROJECT NO.: 124271
SUBJECT: Outlet Culvert Calculations BY: Bruce Curtis DATE: 10/23/13
REVIEWED BY: / j .R' . DATE: (o/2Y//3
PURPOSE:
Perform calculations to size the culvert from the outlet structure.
GIVEN:
1. Upstream invert elevation =4940.0 feet
2. Downstream Invert elevation =4939.0 feet
3. Culvert length = 125 feet
ASSUMPTIONS:
1. Use a 24-inch diameter RCP
27
ANALYSIS: 2.7
The FHWA nomographs were used to estimate the capacity of the 2f--inch RCP.
General Steps:
1. Estimate the water surface elevation necessary to pass the 100-year peak inflow. If the
capacity at the top of the detention basin embankment(4944.0 feet)Is equal to or greater
than the 100-year inflow(26.8 cfs)then the pipe can serve as the emergency spillway.
The calculation sheets provide the actual analyses.
Page 1 of 1
HYDROLOGIC CRITERIA AND DRAINAGE DESIGN MANUAL
•
CULVERT RATING rn
s
i I I II
Jzu` av°�ocn . ' IVII NQ co o
o r ti
F- c a> Q Sc f HEADWATER N ComrnoL a Hill
'�
O
h m ELEVATION
O
co o .F 0 o •jog oil liii !
CS
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z °MIIIIII
a W1.
ii I 6 di
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Y x44 Lt. 13g ° 31441 I I I I I
Z tpriS 'C IIIIIIi
CC
r o Q
° rt1j-' I_ (1111I1111 ie
�. = , •. ` � HIHIJ
3
• • Ill a� sI1
n1U iI IiIIII cc{ J c Ft
NJ
fn = =�O m9� Hi Int4
HA Lei C
0o• .3 O
Iti_ m ! n n
t f Q �� Q NAY rI HId Q y t
~ •
, h a � U. cc
w
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Oa. 3 Ili J W '(V a Cc !N� Intrim1 R ;Ong
= J
i
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I
REFERENCE:
STANDARD FORM 7
CHART 1O
7160 —10,000
—168 ,—.6,000 EXAMPLE (1) (2) (3)
156 —6 000 0.42 Iloamloam(3A feel)
-
,
—5
•000
0.120 afs
—144 _ —°•
- —4,000 yt s )16 — 6. _ - 5.
— 132 - 0 fool -
4.
-3,000 11) 2.6 ea —5' —4.
—120 _ RI 2.1 TA - -
106 _ 2,000 13) 2.2 7.7 ----4. 3 -
_ 7 c0 I.Sol - - _3.
96 -.1,000 ^3. - -
— —BOO _
—84
— —r—600 ///`'--__ — 2. —2_
-400 / ;_ z. =f,73
i.— 72 400 C _ . _
Y .
S — 300 .6+% _ —L5 — 1.5
co
2 N - K ' _
m -60 p -200 W. l.6
a —54 ¢r/ - a - _
cc W — 46 ��ia _ 100 2 - - -
— 80
J a — 2
42 u = 60 w J- — 1.0 1.0
a W —50 o
c a _ SCALE ENTRANCE —1O _
co 40 TYPE •
in
II_ — 36 —.9
W _. 111 Silvan ides silk — .9
33 A..enll 0 — .9 -
a — - a
a - 20 (2) ..r Goma end rite
— 30 Was') x
13) Gr..ee se. —.6
— 10
—
— 24 �° — .7 —.1
— 6 To o.seal.(2)or 0)project '_
21 _ 5 Aerlxonl.02 Is seals
Melba - -
—4 use strata)InclinedI4e Mre,e
o.Ai 0 su Ie.,ir
_ 3 Was oo.bi. —.6 --.6
— 18 _
-
2 -
-15 -
- �.5
—1.0
— 12 HEADWATER DEPTH FOR
HEADWATER SCALES 253 CONCRETE PIPE CULVERTS
BUREAU OF N�lIC 110.03 Nr119U REVISED 1.14Y1964 WITH INLET CONTROL
181
O
CHART 5
r 2000
i W - SIIII Sew -
—1000 z X SOWER= OUTLET CULVERT FLOWING FULL --3
0 a
-600 -120 Tor eu14 iro
n on r11 rulinun wmm l, NW e, -.6
• IMIMe1 lMFIMC iw WE Irwln e1K111n -
-600 —106
-300 -96 • N,%�-LO
-400 --64 —' _
-300
-72 / -
-.66 /13 H�
H ^200 -60 NIP y"4, a '.
W -34 / . x "
U - ci
_ -49=T-- r 00
34;Z
O o
• a
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I? ^00� F.
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a ^60 I
en `33 AOO 500 ^6
c —30 F -
W -30-40 b0O •# : .-6
r
4, o —
O 'N -10
v
24
-20 -21
-16 -20
-10 -13
-6
-6 -12
-3
-4
HEAD FOR
CONCRETE PIPE CULVERTS
FLOWING FULL
SURMA 0r 10LC 00401 JAN. If43 n t 0.0 I2
185
O CHART 4
3 �■■�■■
1 ■� � 3'� de CANNOT EXCEED TOP OF PIPE
1.51
OEM. ■■■„■■■■�.■®�■■■■■
0
O ID 20 30 40 SO 60 70 60 90 100
-2-4,8 DISGHARGE-Q-GFS
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i 7
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OF PIPE x
a 2 'Dto Ia6 ' 1_ I I 5
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P 0 100 200 300 400 500 600 700 600 900 1000 u
et DISCHARGE-O-GFS I-
6
V a
14
6 Q7 do CANNOT EXCEED TOP OF PIPE
- [4 9'DIA
0 . 1000 2000 3000 4000
DISCHARGE-O-CFS
BUREAU OF PUBLIC ROADS
JAN.1964 CRITICAL DEPTH
CIRCULAR PIPE
184
KLE/NFELOER
ua+inroeymu..w
�1
Sterling Energy—
PROJECT: Centennial Gas Plant PROJECT NO.: 124271
SUBJECT: Culvert Outlet Protection . BY: Bruce Curtis DATE: 10/9/13
Calculations REVIEWED BY: LIA-Co L ,4dr7vf- DATE ',.' 't=3 1T
PURPOSE:
Design Culvert Outlet Protection.
GIVEN:
1. Peak flow=5 cfs z7
2. Outlet pipe diameter=l Vinches
ASSUMPTIONS:
1. The tailwater depth is unknown.
2. Assume the allowable water velocity Is 5.5 fps to prevent erosion.
3. No precipitation runoff leaves the Secondary containment berm.
ANALYSIS:
The Urban Drainage and Flood Control District's Drainage Criteria Manual was used to design
the energy dissipation basin for the culverdutlet from the detention basin. Because there is no
channel near the site,the energy dissipation basin will be designed to discharge flow overland as
sheet flow, as It has historically,and at non-erosive velocities.
General Steps:
1. Determine if UDFCD procedures and figures are valid for these conditions.
2. Estimate the minimum riprap size.
3. Estimate the minimum basin length.
The calculation sheets provide the actual analyses.
•
Page 1 of 1
SHEET ( OF I-
KLEINEELDER
�/enyme�c x;gnrsam;a . PROJECT NO. / 211 2 h7/
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ENG-08 REV 05/08
SHEET 2- OF
KLE/NFELDER
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PROJECT NO.
PROJECT REVIEWED BY DATE
SUBJECT BY DATE
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ENG-08 REV 05/08
DRAINAGE CRITERIA MANUAL (V. 1) MAJOR DRAINAGE
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Use Do instead of D whenever flow is supercritical in the barrel.
** Use Type L for a distance of 3D downstream .
FIGURE MD-21
Riprap Erosion Protection at Circular Conduit Outlet Valid for Q/D25≤6.0
•
06/2001 MD-109
Urban Drainage and Flood Control District
DRAINAGE CRITERIA MANUAL (V. 1) MAJOR DRAINAGE
G = Expansion Angle
8
7
6. 6
6 1
ri o Q
a :171
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O .1 .2 .3 .4 .5 .6 .7 .8
TAILWATER DEPTH/ CONDUIT HEIGHT, Yf /D
FIGURE MD-23
Expansion Factor for Circular Conduits
06/2001 MD-111
Urban Drainage and Flood Control District
APPENDIX C
USR CHECKLIST
124271-7/CSP13R0465 October 25, 2013
Copyright 2013 Kleinfelder
Case Name:
Case Number: Date:
Weld County Public Works
Use by Special Review (USR) and Site Plan Review (SPR)
Drainage Report Outline
The following checklist is to be utilized as guidance, and may not be all inclusive. Other concerns
not included in this checklist may arise during the review process.
NOTE: A HARDCOPY OF THE DRAINAGE REPORT AND CONSTRUCTION DRAWINGS MUST BE
SUBMITTED TO PUBLIC WORKS FOR REVIEW.
Not
Comment Headings Included Included
N/A
All reports shall be typed on 8-1/2"x 11" paper and bound. Drawings
(24"x 36")shall be included. The drawings shall be bound within the
report or included within a pocket attached inside the back cover of the
report. The report shall be a stand-alone document and therefore all
important reference material,supporting documents,and calculations
shall be copied and included within the report appendix. The report shall
include a cover letter presenting the drainage design for review and shall
be prepared or supervised by an engineer licensed in Colorado. Only
original documents sealed in ink will be accepted. The sealed report
shall contain a certification sheet as follows:
"I hereby certify that this report for the drainage design of(Insert Name of
Project)was prepared by me(or under my direct supervision)in
accordance with the provisions of the Weld County storm drainage
criteria for the owners thereof."
The Drainage Report is stamped,signed,and dated by a registered P.E. �.
licensed to practice in the State of Colorado.
All submitted construction plan sheets are stamped,signed,and dated by
a registered P.E. licensed to practice in the State of Colorado.
The following items at a minimum should be discussed in the Drainage Report narrative and should
be supported with maps and calculations in the Appendix. Include a copy of this checklist with the
Drainage Report submittal.
I. General Location and Description
A. Location
1. Township, Range, Section,%-Section. k
2. Local streets within and adjacent to the development. \(
3 Major open channels, lakes, streams, irrigation and other water resource
facilities within and adjacent to proposed project site. �(
4 Names of surrounding developments including jurisdiction
(municipalities). 7�
B. Description of Property \/
1. Area in acres. �
2. Ground cover and soil types. X�
3. Major open channels and property ownership.
4. General project description.
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Case Name:
Case Number: Date:
6 Irrigation facilities and facility ownership information within 200 ft. of
property. �(
6. Groundwater characteristics(where applicable). X
II. Drainage Basins and Sub-Basins V
A. Major Basin Description
1. Reference to Weld County Master Drainage Plan(s)where applicable.
2. Major basin drainage characteristics.
3 Identification of all FEMA-defined 100-year floodplains and floodways \/
affecting the property. (<
4 On-site 8,offsite contours at minimum 2-ft vertical intervals are to be
included on the Drainage Report drawings. J�
B. Sub-Basin Description
1 Historic drainage patterns on the subject property and adjacent
properties.
Off-site drainage flow patterns and impacts on the subject property
2. (minimum 200 ft outside property boundary, or until no further off-site
contributing flow area is encountered).
III. Drainage Design Criteria l(
A. Development Criteria Reference and Constraints �(
Discussion of previous drainage studies (i.e. project master plans)for the 1^
1. subject property that influence or are influenced by the proposed \7/
drainage design for the site.
Discussion of site constraints such as slopes, streets, utilities, existing
2. structures, irrigation ditches,and the site plan impacts on the proposed
drainage plan.
B. Hydrological Criteria K'
1 Identify design rainfall amounts and source of design storm depth
information, NOAA Atlas, UD&FCD maps, etc.
2 Identify design storm recurrence intervals. Reference the appropriate '
information in the Appendix. 7
Identify runoff calculation method(s)and any computer models. Include
3 summaries of the routing and accumulation of flows at all identified
design points for minor and major storm runoff. Reference the results in
the Appendix.
4 Identify detention discharge and storage calculation methods and
computer models. Reference the results in the Appendix.
5 Discuss of off-site flows will be routed around the proposed site or over C
the spillway for the 100-yr developed condition. n
C. Hydraulic Criteria x
Identify conveyance capacities from County references and any computer `�
models. 1`
Identify detention outlet type. Include a summary of the 100-year water
2 surface elevation,spillway/overflow facility. Reference the appendix for
the calculations. Include summaries of the detention storage sizing and
provide a stage-storage table/curve identifying water quality storage, 100-
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Case Name:
Case Number: Date: •
yr detention pond storage,and 1 ft of freeboard. Reference the
calculations in the Appendix.
3 Identify water quality outlet configuration. Reference the calculations in
the Appendix.
4 Identify culverts including diameter, type, and lope. Reference the
calculations in the Appendix. �C
•
Identify storm sewer inlets, manholes, etc. Reference the calculations in
5
the Appendix.
6. Discussion of permanent erosion control features.
Discussion and justification of criteria or calculation methods (for water
7. quality,check dams,drop structures, rundowns, etc.) used that are not
presented in Weld County CODE.
IV. Drainage Facility Design
A. General Concept
1. Discussion of concept and typical on-site drainage patterns. X
2 Discussion of compliance with off-site runoff considerations and �/
constraints. 1.\
3 Discussion of the content of all tables, charts,figures, or drawings in the
report.
4 Discussion of anticipated hydraulic structures (channels,pipes,
rundowns,etc.).
B. Specific Details �(
1 Discussion of maintenance access and aspects of the design. Include a
maintenance plan.
2 Provide copies of CDPHE, CAFO, DRMS,or State Engineers permit
applications where applicable.
V. Conclusions
A. Compliance with the Weld County CODE X
1. Statement of whether or not the design will meet Weld County Code. X
B. Drainage concept ‘z
1. Effectiveness of drainage design to control damage from storm runoff.
Influence of proposed development on any applicable Weld County
2. Master Drainage Plan recommendations.
Identification of and intent to obtain written approval of affected irrigation
3 company or other property owner(s). Weld County may require that the \/
applicant provide evidence that offsite impacted jurisdictions have been
notified of the proposed plans. _
4 Reference all criteria and technical resources utilized.
•
The Appendices should include at a minimum the following information. The Drainage Report should
be a standalone document and needs to include copies of all pertinent references used in the
generation of the Drainage Report.
VI. Appendices `X
A. Hydrologic Computations
Page 3 of 5
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Case Name:
Case Number: Date:
1 Vicinity Map showing location of the site in relation to surrounding area.
Show the approximate boundaries of the site.
2 FIRMette showing location of the site in relation to the FEMA mapped
floodplains/floodways. Show the approximate boundaries of the site.
3 Soil Survey Information/Map showing soil types and soil hydrologic
groups for the project site.
4 Rainfall Maps with the project location identified. Maps can be from ,
UDFCD or NOAA as applicable. �[
5. Land use assumptions regarding adjacent properties.
6 Initial and major storm runoff computations at specific design points. (5-
yr, 10-yr, and 100-yr)
7. Historic and fully developed runoff computations at specific design points. X
6 Computer model input and output. Include model files and/or
spreadsheets on a CD-ROM to be attached to the Drainage Report.
B. Hydraulic Computations
Culvert sizing. Provide computations showing slope, pipe size, material, 4) /J&tm-.i, E(2 L ho.- 5�
1. invert elevations, 100-year energy grade line(EGL1oa), and hydraulic X 0,C hi-cr// h+ e. ce 1-eIt'
profile. 04-
2. Storm inlet sizing. F 3nJ
3.
Swale or channel sizing. The calculations need to show stability
calculations for unvegetated and vegetated conditions. V
4 Riprap or other revetment design. The calculations need to include
design for bedding and qeo-fabric.
5 Pond area/volume capacity and outlet sizing. Show calculations for the
100-year water surface elevations and overflow facilities. 7�
6. Orifice plate, spillway,and pond outlet sizing.
7. Include computations for permanent erosion control features.
8. Any computer model input and output. Include model files and/or �p
spreadsheets on a CD-ROM to be attached to the Drainage Report.
C. 24 x 36 Maps X
Historic Drainage Basin Map. Show drainage basin boundaries (on-site \ / 8..C4 v F 7+u�i��51zt
pro5+
1. and off-site),2 ft on-site and off-site drainage boundaries, design points, aQ syh aiX 1 f d
historic flow path,flow path length, and flow path slope.
Fully Developed Drainage Basin Map. Show drainage basin boundaries &ecavm off iourl� Sri
(on-site and off-site), 2 ft on-site and off-site drainage boundaries, design p v-oV+ e/ 0 n
2 points, developed flow path, flow path length, and flow path slope. Show \/ q). X (
drainage easement including metes and bounds description around all l
drainage related features. Show any other drainage easements that may
exist on the project site.
Construction Drawings showing location, sizing, and details for all storm
3. sewers, open channels, culverts,cross-pans, and other appurtenances. Ni(
Include cross sections of swales and open channels.
Construction Drawings showing location of detention facilities and outlet
4. works. Include the 100-year water surface elevations,overflow facilities, \�
and labels for pond volume and discharge.
Grading Plan showing existing and proposed contours. Identify the
5 lowest opening elevation of buildings showing that they are above the
100-year water surface elevations of channels, swales, streets, ponds, or
other drainage facilities.
Erosion and Sediment Control Plan showing all BMPs to be utilized on-
6. site. Include typical installation details, installation notes, and
maintenance notes for all BMPs to be utilized on the project site.
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Case Name:
Case Number: Date:
Detail sheets for pond outlet, orifice plate,trash rack, spillway
7.
configuration, riprap, culverts, channels, etc.
All culverts are to be identified and profiled in the Construction Drawings E GC ar /-IG L eca o'c,2-
8. with slope, pipe size, material, invert elevations, 100-year energy grade \/ a, 5c."n(/ g/a a uce J� yft
line(EGL100),and hydraulic profile. l� ocgt p.1. Cti c 5 4 re-
On all Construction Drawings show the location of all existing and X pro v''
g' proposed utilities and identify the utility as existing or proposed.
10. The elevations of manhole and inlet inverts are identified and profiled.
11. Miscellaneous hydraulic structures/features are shown on the
Construction Drawings.
•
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M:1CIay\Development Checklists\USR-SPR Drainage Report Checklist.docx
APPENDIX D
MAINTENANCE PLAN
124271-7/CSP13R0465 October 25, 2013
Copyright 2013 Kleinfelder
Maintenance Plan for Extended Detention Basin (EDB)
This maintenance plan is based on the maintenance plan published in Volume 3 of UDFCD's Drainage
Criteria Manual. EDBs have low to moderate maintenance requirements on a routine basis, but may
require significant maintenance once every 15 to 25 years. Maintenance frequency depends on the
amount of construction activity within the tributary watershed,the erosion control measures implemented,
the size of the watershed,and the design of the facility.
Inspection
Inspect the EDB at least twice annually, observing the amount of sediment in the micro pool and checking
for debris at the outlet structure.
Debris and Litter Removal
Remove debris and litter from the detention area as required to minimize clogging of the outlet.
Mowing and Plant Care
When starting from seed, mow native/drought tolerant grasses only when required to deter weeds during
the first three years. Following this period,mowing of native/drought tolerant grass may stop or be
reduced to maintain a height of no less than 6 inches(higher mowing heights are associated with deeper
roots and greater drought tolerance). In general, mowing should be done as needed to maintain
appropriate height and control weeds.
Mosquito Control
Although the provided design implements practices specifically developed to deter mosquito breeding,
some level of mosquito control may be necessary if the BMP is located in close proximity to outdoor
amenities. The most effective mosquito control programs include weekly inspection for signs of mosquito
breeding with treatment provided when breeding is found. These inspections can be performed by a
mosquito control service and typically start in mid-May and extend to mid-September. Treatment should
be targeted toward mosquito larvae. Mosquitoes are more difficult to control when they are adults. This
typically requires neighborhood fogging with an insecticide. The use of larvicidal briquettes or"dunks"
may be appropriate. These are typically effective for about one month and perform best when the basin
has a hard bottom (e.g., concrete lined micropool).
Irrigation Scheduling and Maintenance
Adjust irrigation throughout the growing season to provide the proper irrigation application rate to
maintain healthy vegetation. Less irrigation is typically needed in early summer and fall, with more
irrigation needed during July and August.Native grass and other drought tolerant plantings should not
require irrigation after establishment. Check for broken sprinkler heads and repair them, as needed.
Completely drain the irrigation system before the first winter freeze each year.Upon reactivation of the
irrigation system in the spring, inspect all components and replace damaged parts,as needed.
Sediment Removal from the Trickle Channel and Micropool
Remove sediment from the trickle channel annually. Sediment removal from the micropool is required
about once every one to four years, and should occur when the depth of the pool has been reduced to
approximately 18 inches. Small micropools may be vacuumed and larger pools may need to be pumped in
order to remove all sediment from the micropool bottom. Removing sediment from the micropool will
benefit mosquito control. Ensure that the sediment is disposed of properly and not placed elsewhere in
the basin.
Sediment Removal from the Basin Bottom
Remove sediment from the bottom of the basin when accumulated sediment occupies about 20%of the
water quality design volume or when sediment accumulation results in poor drainage within the basin.
The required frequency may be every 15 to 25 years or more frequently in basins where construction
activities are occurring.
Erosion and Structural Repairs
Repair basin inlets, outlets,trickle channels, and all other structural components required for the basin to
operate as intended. Repair and vegetate eroded areas as needed following inspection.
Hello