HomeMy WebLinkAboutKECHTER TOWNHOMES - FDP210002 - - DRAINAGE REPORT
FINAL DRAINAGE REPORT
AND EROSION CONTROL REPORT
February 17, 2021
Kechter Townhomes
Fort Collins, Colorado
Prepared for:
TWG
Ryan Kelly, Acquisitions Director
1301 East Washington Street, Suite 100
Indianapolis, IN 46202
317-559-7009
Prepared by:
301 N. Howes Street, Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158
www.northernengineering.com
Project Number: 1664-003
This Drainage Report is consciously provided as a PDF.
Please consider the environment before printing this document in its entirety. When a
hard copy is absolutely necessary, we recommend double-sided printing.
301 N. Howes Street, Suite 100, Fort Collins, CO 80521 970.221.4158 www.northernengineering.com
February 17, 2021
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Final Drainage and Erosion Control Report for
Kechter Townhomes
Dear Staff:
Northern Engineering is pleased to submit this Final Drainage and Erosion Control Report for your
review. This report accompanies the Final Development Plan submittal for the proposed Kechter
Townhomes development.
This report has been prepared in accordance to Fort Collins Stormwater Criteria Manual (FCSCM), and
serves to document the stormwater impacts associated with the proposed project. We understand that
review by the City is to assure general compliance with standardized criteria contained in the FCSCM.
If you should have any questions as you review this report, please feel free to contact us.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
Deborah Spaustat, PE
Design Engineer
Kechter Townhomes
Final Drainage Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND EXISTING SITE INFORMATION ................................................................ 1
A. Location ............................................................................................................................................. 1
B. Description of Property ..................................................................................................................... 1
C. Existing Sub-Basin Description .......................................................................................................... 2
II. Master Drainage Basin Information ................................................................................................. 3
III. Floodplain ........................................................................................................................................ 3
IV. Project Description .......................................................................................................................... 3
A. Overall Description............................................................................................................................ 3
B. Sub-Basin Description ....................................................................................................................... 4
V. PROPOSED DRAINAGE FACILITIES .................................................................................................... 5
A. Detention Basin and Outlet Design ................................................................................................... 5
B. Existing Storm Sewer in Kechter Road .............................................................................................. 6
C. WQCV design .................................................................................................................................... 6
D. LID Systems and design ..................................................................................................................... 7
E. Maintenance Access ......................................................................................................................... 8
F. Drainage Easements ......................................................................................................................... 8
VI. DRAINAGE DESIGN CRITERIA ........................................................................................................... 8
A. Regulations........................................................................................................................................ 8
G. Four Step Process .............................................................................................................................. 8
H. Development Criteria Reference and Constraints ............................................................................ 9
I. Hydrological Criteria ......................................................................................................................... 9
J. Hydraulic Criteria ............................................................................................................................ 10
K. Detention Calculation Method ....................................................................................................... 10
L. Floodplain Regulations Compliance ................................................................................................ 10
M. Modifications of Criteria ............................................................................................................. 10
VII. CONCLUSIONS ................................................................................................................................ 11
A. Compliance with Standards ............................................................................................................ 11
N. Drainage Concept ............................................................................................................................ 11
References .................................................................................................................................................. 12
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Final Drainage Report
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
B.1 – Detention Ponds
B.2 – Water Quality
B.3 – Storm Sewers
B.4 – Inlets
B.5 – Swales
APPENDIX C – Erosion Control Report
APPENDIX D – LID Exhibit
APPENDIX F – References
LIST OF FIGURES:
Figure 1 – Aerial Photograph ........................................................................................................................ 2
Figure 2 – Existing Floodplains ...................................................................................................................... 3
Figure 3– Proposed Site Plan ........................................................................................................................ 4
MAP POCKET:
DR1 - Drainage Exhibit
Kechter Townhomes
Final Drainage Report 1
I. GENERAL LOCATION AND EXISTING SITE INFORMATION
A. Location
Vicinity Map
A tract located in the southwest quarter of Section 4, Township 6 North, Range 68 West of the 6th Prime
Meridian, City of Fort Collins, County of Larimer, State of Colorado.
The project site is 4.68-acres located at 3620 Kechter Road approximately one mile west of the Kechter
Road/I-25 interchange. The site is situated between the Twin Silo Community Park to the west and
Observatory Village to the east with Radiant Park located directly south across Kechter Road.
The project is located in the McClellands Creek drainage basin in the Master Drainage Study. The direct
outfall for stormwater from the site is the existing stormwater system in Kechter Road, which discharges
to the Muskrat Ditch on the south side of Kechter Road in Radiant Park.
B. Description of Property
1. The project site is located in the Low Density Mixed-Use Neighborhood District. Currently the lot is
mostly undeveloped containing one single family home and several outbuildings. No stormwater
infrastructure exists onsite.
According to the United States Department of Agriculture (USDA) Natural Resources Conservation
Service (NRCS) Soil Survey the project site consists of Nunn clay loam and Fort Collins loam, which fall
Kechter Townhomes
Final Drainage Report 2
into Hydrologic Soil Group C.
Figure 1 – Aerial Photograph
The existing site is generally comprised of undeveloped land with natural grasses and vegetation. A
house, gravel drive, and out-buildings exist on the site.
This site will employ water quality features and runoff reduction facilities including rain gardens,
minimization of directed connected areas of imperviousness, and an extended detention basin.
An irrigation ditch runs outside of the property along the north and east boundary lines to Kechter Road.
There is an existing stormwater system in Kechter Road that was designed and installed as part of the
Willow Brook development (Observatory Neighborhood). The system comprises storm manholes and
18” RCP pipe.
The Final Drainage Report for Willow Brook shows this storm sewer as the point of discharge for
detention pond E with a 100-year release rate of 4.55-cfs. The Developed Drainage Plan in the report
shows the discharge rate at 4.3-cfs. The analysis of the storm sewer for the current project uses 4.55-cfs
to be conservative.
C. Existing Sub-Basin Description
1. Historically the property drains in four directions, as shown in the Existing Drainage Exhibit. The
southwest quarter of the site (basin A) sheet flows offsite to the pond in Twin Silo Park. The north
half of the site (basin B) drains to a low spot in the center of the field and either infiltrates into the
ground or evaporates. Basin C at the south east corner of the site sheet flows to Kechter Road and a
small basin D sheet flows to the existing irrigation ditch adjacent to the site.
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Final Drainage Report 3
A full analysis of the existing hydrology was not conducted since the detention requirements are based
on the McLellend Basin master plan and not historical release rates.
A full-size copy of the Existing Drainage Exhibit and Proposed Drainage Exhibit can be found in the Map
Pocket at the end of this report.
II. Master Drainage Basin Information
1. Kechter Townhomes is located within the McClellands Basin, which encompasses 3.4 square miles in
Southeast Fort Collins. McClellands Creek conveys flow from upper end of the basin northeast of
College Avenue and Harmony road to down to its point of discharge to the Fossil Creek Reservoir
Inlet Ditch.
There are no recommended improvements in the master plan for the Kechter Townhomes site. Onsite
detention is being provided per the McClellands Basin master plan’s requirement of 0.2-cfs per acre for
the minor storm event and 0.5-cfs per acre for the major storm event.
III. Floodplain
1. The subject property is not located in a FEMA or City regulatory floodplain.
Figure 2 – Existing Floodplains
IV. Project Description
A. Overall Description
1. The project is proposing to create an affordable housing neighborhood with 60 townhomes and a
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Final Drainage Report 4
public loop road on a 4.68-acre parcel of land off of Kechter Road. Vehicular connections to the
adjacent Observatory Neighborhood will be made at Eclipse Lane and Quasar Way.
2. Two raingardens will treat 58% of the newly created impervious areas and an extended detention
basin will provide additional water quality treatment and detain runoff to allowable release rates as
allowed in the McClelland Basin Master Plan.
3. The site will discharge from the extended detention basin (EDB) to the existing stormwater system
in Kechter Road.
4. All runoff from the site will be diverted to the extended detention basin. No runoff will be allowed
to flow directly to the irrigation ditch or adjacent properties.
Figure 3– Proposed Site Plan
B. Sub-Basin Description
1. The site is broken into nine sub-basins that drain to one of three locations.
Runoff from sub-basins A.1 and A.2 flows to Rain Garden A located in the southwest corner of the site.
Runoff in sub-basin A.1 is collected in a grass swale and flows south along the property line to the rain
garden. The swale has the capacity to convey 33% more flow than the major storm event. See appendix
B.5.
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Final Drainage Report 5
A gutter pan conveys runoff from sub-basin A.2 south to a double chase drain under the sidewalk at the
low point of the road where it enters the rain garden. The outlet of rain garden A discharges flow to the
extended detention sub-basin in C.5.
Runoff from sub-basin B.1 is collected in a gutter pan and flows south to a chase drain under the
sidewalk that discharges to rain garden B. Flow from sub-basin B.2 is collected in a storm system to the
east of the buildings that outlets to rain garden B. The outlet of rain garden B discharges flow to the
extended detention basin in C.5.
Runoff from sub-basins C.1 is collected in a gutter pan and conveyed south to an inlet installed inline on
the discharge pipe from rain garden A. Bypass flow is then collected in a double combination inlet at the
low point and discharged to the extended detention basin. Flow in sub-basin C.2 is collected in a storm
system in the central open space and conveyed south to the extended detention basin. Runoff in sub-
basins C.3 and C.4 is collected in gutter pans and inlets that then combines with runoff from basin C.2
before discharging tot the extended detention basin. The outfall of the EDB is the existing 18” RCP
stormwater system in Kecther Road. This storm system ultimately discharges to the Muskrat Ditch.
Table 1 summarizes the hydrologic characteristics of each subbasin and the total site.
Table 1 – Proposed Basin Hydrology Summary
Basin ID
Basin
Area
(acres)
Composite
% Imperv. C2 C100 Tc
(min)
Q2
(cfs)
Q100
(cfs)
A.1 0.49 43% 0.54 0.68 5.0 0.75 3.29
A.2 0.85 78% 0.79 0.99 5.0 1.91 8.34
B.1 0.75 81% 0.81 1.00 5.0 1.74 7.47
B.2 0.41 46% 0.56 0.70 5.0 0.66 2.89
C.1 0.62 83% 0.83 1.00 5.0 1.46 6.18
C.2 0.35 64% 0.69 0.86 5.0 0.68 2.97
C.3 0.52 78% 0.79 0.99 5.0 1.16 5.08
C.4 0.07 81% 0.82 1.00 5.0 0.15 0.66
C.5 0.63 2% 0.25 0.31 5.0 0.45 1.95
Total
Site 4.68 61% 0.67 0.84 5 8.98 39.17
V. PROPOSED DRAINAGE FACILITIES
A. Detention Basin and Outlet Design
1. The Extended Detention Basin was designed to limit release rates to the site to 0.2-cfs/acres for the
minor storm event and 0.5cf/acres for the major event.
The major storm event release rate was calculated to be 2.34-cfs based on the total onsite area of 4.68-
acres. This results in a required detention volume of 35,316 ft3, or 0.811-acre-ft.
The total volume provided in the extended detention basin in C.5 is 41,129 ft3, or 0.94-acre-ft. Table 2
summarizes the onsite detention:
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Final Drainage Report 6
Table 2: Extended Detention Basin Summary
Area of
Site
(acres)
Allowable
Q2 (cfs)
Allowable
Q100(cfs)
EURV
(ft3)
Water Quality
Capture
Volume (ft3)
Total
Volume
Required
(ft3)
Total
Volume
Provided
(ft3)
4.68 0.94 2.34 11,895 4,866 35,316 36,028
A detail of the EDB outlet structure is included on sheet D6. The major storm attenuation is controlled
by a 6” circular orifice plate on the 15” outlet pipe.
B. Freeboard and Spillway
1. The FCSWDM requires that the design provide 1’ foot of freeboard above the major storm WSEL.
This project is only able to provide 0.70’ of freeboard above the major storm WSEL due to vertical
limitations set by the existing storm sewer in Kechter Road and horizontal limitations from the
existing trees that are being preserved for habitat.
2. All minimum opening elevations of the proposed buildings are set at least 12” above the major
storm WSEL of 4896.65.
3. An emergency spillway for the EDB is not provided. Inlets D.1 and E.1 have grate elevations set at
4896.9 and 4897.0. The highest elevation of the pond is 4897.4 meaning the inlets would surcharge
before the pond overtops and water will exit down Kechter Road.
4. Additionally, the development has one alternate vehicular access routes for use if the entrance to
Wheelhouse Way is impassible.
C. Existing Storm Sewer in Kechter Road
1. The existing storm sewer in Kechter road was modeled in Storm and Sanitary Analysis using as-built
data from the existing conditions survey for pipe sizes and inverts and the proposed connection
from the extended detention basin in C.5.
The 100-year flow from the existing detention pond C was assumed to be 4.55-cfs and the flow from the
current project was assumed to be 2.34-cfs.
The existing storm sewer has the capacity to convey the increase in flow from the current project.
The results of the hydraulic model are included in the appendices.
D. Proposed Storm Sewer on-site
1. There are two main, private, storm sewer systems that collect runoff and convey it to the rain
gardens and EDB.
2. Storm sewer A consists of 12” HDPE pipe and nyloplast area drains and runs north to south along
the east property line before discharging to rain garden B. It has the capacity to convey the minor
and major storm event without surcharging. It was evaluated with water surface elevation in the
rain garden set to just above the WQCV elevation.
3. Storm sewer B is located in the central open space between buildings and also has the capacity to
convey the minor storm event without surcharging when the EDB WSEL is at the 10-year elevation.
However, when the EDB is at the 100-year elevation the backwater from the pond causes the HGL
and EGL to exceed the inlet grate elevation and the most downstream pipe to surcharge.
4. Storm sewer D conveys water from rain garden A to the EDB as well as collects runoff from basin C.1
in a single curb inlet, E.2.
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Final Drainage Report 7
5. Storm Sewer E collects bypass runoff from Inlet E.2 in double curb Inlet E.1, which us located at the
low point of the road.
6. Both storm sewer D and storm sewer E are heavily influenced by the water surface elevation in the
EDB. While both systems have the capacity to convey the minor storm event when the WSEL of the
pond is at or below the 10-year elevation, the backwater at the 100-year elevation governs both
systems during any runoff event and the inlets will surcharge.
7. Storm sewer, inlet, chase drain and swale capacity calculations are included in Appendix B.
E. WQCV design
1. The water quality capture volume for the extended basin was based on a 40-hour drain time.
The flow control plate in the outlet structure will consist of three rows of 1-1/16” diameter orifices set
at 10” vertical spacing.
A detail for the EDB outlet structure including the orifice plate is included on sheet D6.
F. LID Systems and design
1. The LID for this project will be provided by two rain gardens, which will treat 58.1% of the newly
created impervious area.
The rain garden required volumes were based on a 12-hour drain time. Table 3 summarizes the rain
gardens:
Table 3: Rain Garden Summary
Basin
Area
(acre)
%
Imperv
Volume
(ft3)
Min Flat
Area
(ft2)
Contributing
Basins
Rain Garden A 1.33 65 1,185 757 A.1 & A.2
Rain Garden B 1.16 68 1,086 693 B.1 & B.2
The raingardens will have underdrains connected to an ADS inlet. The underdrains will have orifice
plates on their outlets that will restrict flow to attain the 12-hour drain time.
The grate of the ADS inlet will be set the WSEL for the WQCV to convey flows in excess of the WQCV
directly to the EDB.
Storm events in excess of the 100-year event, or in the event the EDB outlet is clogged, will result
backwater storage in rain garden A.
Table 4 Summarizes the LID Project Requirements:
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Table 4: LID Project Requirements
Project Summary
Total Impervious Area 123,221 sf
Target Treatment Percentage 50%
Minimum Area to be Treated by LID
measures 61,610 sf
Rain Garden A
Impervious Treatment Area 37,459 sf
Rain Garden B
Impervious Treatment Area 34,318 sf
Total Treatment Area 71,777 sf
Offsite Treatment Area 210 sf
Onsite Treatment Area 71,567 sf
Percent Total Project Area Treated 58.1%
Basins A.2 includes 210-ft2 of offsite impervious area from Kechter Road that will be treated in Rain
Garden A. While the Rain Garden is designed to include this area, the calculations for required and
provided treatment of imperviousness areas omit it.
G. Maintenance Access
1. The EDB and both rain gardens can be accessed directly from the Right-of-Way and easements on
lots 4 and 5, block 3 for maintenance.
H. Drainage Easements
1. Tracts B, C and D are drainage easements for the rain gardens and extended detention basin.
2. There is a 6’ drainage and utility easement adjacent to the west, north and east property lines.
3. There is a 14’ drainage easement centered on storm sewer B in the central open space.
VI. DRAINAGE DESIGN CRITERIA
A. Regulations
1. There are no optional provisions outside of the FCSCM proposed with the Kechter project.
The project site has not been a part of any known previous drainage study, however, the Final Drainage
Report for Willow Brook, July 27, 2001, was referred to for the capacity analysis of the offsite receiving
storm system in Kechter Road.
I. Four Step Process
The overall stormwater management strategy employed with the Kechter Townhomes project
utilizes the “Four Step Process” to minimize adverse impacts of urbanization on receiving
waters. The following is a description of how the proposed development has incorporated
each step.
Step 1 – Employ Runoff Reduction Practices
Several techniques have been utilized with the proposed development to facilitate the
reduction of runoff peaks, volumes, and pollutant loads as the site is developed from the
current use by implementing multiple Low Impact Development (LID) strategies including:
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Final Drainage Report 9
Providing vegetated open areas throughout the site to reduce the overall impervious area
and to minimize directly connected impervious areas (MDCIA).
Routing flows, to the extent feasible, through rain gardens to provide additional
infiltration.
Providing on-site detention to increase time of concentration, promote infiltration and
reduce loads on existing storm infrastructure.
Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with Slow
Release
The efforts taken in Step 1 will facilitate the reduction of runoff; however, this development
will still generate stormwater runoff that will require additional BMPs and water quality. A
majority of stormwater runoff from the site will ultimately be intercepted and treated in
proposed rain gardens and an extended detention basin. Water quality for areas not routed
through the rain gardens will be provided within the extended detention basin volume.
Step 3 – Stabilize Drainageways
This property discharges detained stormwater to an existing storm sewer system in Kechter
Road. The project does not directly impact any drainageways.
Step 4 – Implement Site Specific and Other Source Control BMPs.
The proposed project will improve upon site specific source controls compared to historic
conditions:
Trash receptacles within home will allow for the disposal of solid waste.
Rain Gardens and extended detention basins to provide for water treatment prior to flows
being released to existing drainageways and storm infrastructure.
Standard Operating Procedures (SOPs) for BMP maintenance of Rain Gardens, Detention
ponds, and associated drainage infrastructure to remove sediment accumulation regularly.
J. Development Criteria Reference and Constraints
1. The proposed site is a part of the McClelland Drainage Basin, which requires onsite detention with a
0.2-cfs.ac release rate for the 10-year storm and a 0.5-cfs/acre release rate for the 100-year storm.
City of Fort Collins standard water quality requirements include treatment of 50% of the site runoff to
be treated using the standard water quality treatment as described in the Fort Collins Stormwater
Manual, Volume 3-Best Management Practices.
This site is subject to the LID requirements per the City of Fort Collins. Please see the LID Exhibit located
in the Appendix for calculations concerning LID treatment. For residential neighborhoods with public
streets, the City requires 50% of new or modified impervious areas to be treated with LID methods.
K. Hydrological Criteria
1. The Rational Method was used to compute stormwater runoff using runoff coefficients from Table
3.2-2 of the FCSCM.
2. Storm intensities based on time of concentration were interpolated from The City of Fort Collins
Rainfall Intensity-Duration-Frequency Curves shown in Figure 3.4-1 and Table 3.4-1 of the FCSCM.
Required detention storage was calculated using The Modified Federal Aviation Administration (FAA)
Procedure.
The 2-year storm event and the 100-year storm event were used as the minor and major design storms.
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Final Drainage Report 10
No other assumptions or calculation methods have been used with this development that are not
referenced by current City of Fort Collins criteria.
L. Hydraulic Criteria
1. All drainage facilities proposed with the Kechter Townhomes project are designed in accordance
with criteria outlined in the FCSCM.
Street capacity – inlets are located so that there is no overtopping of the curb during the minor storm
event and with a maximum depth of flow of 12’ in the gutter during the major storm event.
Cross-pan – the maximum depth allowed in the cross-pan is 6” for the minor storm event and 18” for
the major storm event .
Storm sewer – the minimum storm sewer size in the ROW is 15”. Storm sewers should not surcharge
during the minor storm event and must comply with street encroachment criteria during the major
storm event.
M. Detention Calculation Method
1. Onsite detention is required to restrict the 10-year storm release rate to 0.2-cfs/ac and the 100-year
storm release rate to 0.5-cfs/acre.
The Modified FAA Procedure was used to calculate the required detention volume based on the area of
the site as outlined in the FCSCM.
The volume of the pond was calculated using FCSCM Equation 6-4 for conical stage storage volume
approximation.
N. Floodplain Regulations Compliance
1. The subject property is located outside of all FEMA regulated and local floodplains and is not subject
to any floodplain regulations.
O. Modifications of Criteria
1. Several modifications of drainage criteria are requested:
1.1. Less than 1’ of freeboard above the 100-year water surface elevation in the extended detention
basin.
1.2. Surcharging of directly adjacent storm sewer pipes during the 2-year storm event when the
WSEL of the EDB is at the 100-year level. Specifically:
· Pipes 27, 28 and 29 in storm sewer system B will surcharge and the maximum EGL will be
above the grate elevation at inlet B-1. Surcharging occurs during 50-year event but EGL is
more than 12” below grate elevations.
· Pipes 41 and 44 in storm sewer system D will surcharge and the maximum EGL will be
above the grate elevation at inlet D-1. Surcharging occurs during 25-year event but EGL is
more than 12” below grate elevation.
· Pipe 39 in storm sewer system E will surcharge and the maximum EGL will be above the
grate elevation at inlet E-1. Surcharging occurs during 10-year event but EGL is more than
12” below grate elevation.
If overflow from the inlets occurs due to the WSEL in the EDB, it will pond in the gutter to an
elevation of approximately 4867.3 where it will then enter the cross-pan and gutter system in
Kechter Road. The depth of flow at the gutter line will be less than the limit of 12” and the
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Final Drainage Report 11
depth of flow at the crown will be less than the 6” limit.
1.3. Surcharging of Inlets B.1, D.1 and E.1 during the 100-year storm event due to backwater
resulting from the 100-year WSEL in the EDB. Overflow from the inlets will pond in the gutter
to an elevation of approximately 4867.3 where it will then enter the cross-pan and gutter
system in Kechter Road. The depth of flow at the gutter line will be less than the limit of 12”
and the depth of flow at the crown will be less than the 6” limit.
1.4. No emergency spillway for the EDP due to the inlets in Wheelhouse Way surcharging before the
WSEL overtops the pond.
2. All of these criteria modifications are related to the vertical and horizontal limitations imposed on
the EDB by existing storm sewer in Kechter Road and the preservation area adjacent to the pond.
VII. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with the Kechter Townhomes project complies with the City of Fort
Collins’ Stormwater Criteria Manual.
2. The drainage design proposed with the Kechter Townhomes project complies with the City of Fort
Collins’ Master Drainage Plan for the McLelland Basin.
There are no regulatory floodplains associated with the development.
The drainage plan and stormwater management measures proposed with the development are
compliant with all applicable State and Federal regulations governing stormwater discharge.
The site achieves LID treatment for 58.1% of total impervious areas. This is 8.1% above the
requirements set forth by the City of Fort Collins for Low Impact Development (LID). Please see LID
Exhibit located in the Appendix.
P. Drainage Concept
1. The drainage design for Kechter Townhomes effectively captures runoff from the entire site and
safely conveys it via curb & gutter, swales, and storm sewer to two rain gardens and an extended
detention basin.
2. Project LID requirements to treat a minimum of 50% of the newly created or modified impervious
areas is exceeded by 8.1%
3. Detention to achieve allowable release rates is provided by an extended detention basin, which also
provides water quality treatment.
4. 100% of the site is treated for water quality either by rain gardens and/or the extended detention
basin.
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Final Drainage Report 12
References
1. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No. 174,
2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code.
2. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and
Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007.
3. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation
Service, United States Department of Agriculture.
4. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District,
Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008.
5. Final Drainage Report for Willow Brook, TST Inc., Consulting Engineers, July 27, 2001.
APPENDIX A
HYDROLOGIC COMPUTATIONS
Project:Calculations By:Date:A.1 A.1 0.495 5 0.54 0.68 2.85 9.95 0.75 3.29A.2 A.2 0.855 5 0.79 0.99 2.85 9.95 1.91 8.34B.1B.10.755 5 0.81 1.00 2.85 9.95 1.74 7.47B.2B.20.415 5 0.56 0.70 2.85 9.95 0.66 2.89C.1C.10.625 5 0.83 1.00 2.85 9.95 1.46 6.18C.2C.20.355 5 0.69 0.86 2.85 9.95 0.68 2.97C.3C.30.525 5 0.79 0.99 2.85 9.95 1.16 5.08C.4C.40.075 5 0.82 1.00 2.85 9.95 0.15 0.66C.5C.50.635 5 0.25 0.31 2.85 9.95 0.45 1.95Total 4.685 5 0.67 0.84 2.85 9.95 8.98 39.17DPA A.1,A.2 1.335 5 0.70 0.88 2.85 9.95 2.67 11.63DPB B.1,B.2 1.165 5 0.72 0.90 2.85 9.95 2.40 10.48DPCC.1, C.2, C.3, C.4, C.52.185 5 0.63 0.79 2.85 9.95 3.91 17.05DESIGN PONTSFebruary 17, 2021Area, A(acres)Intensity,i2(in/hr)100-yr Tc(min)D. SpaustatKetcher TownhomesPROPOSED RUNOFF COMPUTATIONSC100DesignPointFlow,Q100(cfs)Flow,Q2(cfs)2-yrTc(min)C2Intensity, i100(in/hr)Sub-Basin(s)Rational Method Equation:Rainfall Intensity:Rainfall Intensity taken from the Fort Collins Stormwater Criteria Manual (FCSCM), Tables RA-7 and RA-8()()()AiCCQf=
CHARACTER OF SURFACE: RunoffCoefficient1PercentageImpervious1Project:Streets, Parking Lots, Roofs, Alleys, and Drives:Calculations By:Asphalt …………………........................... ..................................................................................0.95100%Date:Concrete ………………............................ ..................................................................................0.95 100%Gravel (packed) ………............................ ..................................................................................0.50 40%Roofs…………………............................. ..................................................................................0.95 90%Pavers…………………............................ ..................................................................................0.50 40%Recycled Asphalt........................... ..................................................................................0.80 80%Lawns and LandscapingPlaygrounds25%Sandy SoilFlat <2% …………............................. ..................................................................................0.10 2%Average 2% to 7%........................... ..................................................................................0.15 2%Steep >7% …………........................... ..................................................................................0.20 2%Clayey SoilFlat <2% …………............................. ..................................................................................0.20 2%Average 2% to 7%........................... ..................................................................................0.25 2%Steep >7% …………........................... ..................................................................................0.352%2-year Cf = 1.00 10-year Cf = 1.00USDA SOIL TYPE: CSub-Basin IDSub-Basin Area(sq. ft.)Sub-Basin Area(ac.)Area of Asphalt & Concrete(ac.)Area of Roofs(ac.)Area of Pavers(ac.)Area ofLandscaping(ac)2-yearComposite RunoffCoefficient10-yearComposite RunoffCoefficient100-yearComposite Runoff CoefficientComposite% Imperv.A.121,1820.49 0.204 0.000 0.000 0.282 0.54 0.54 0.68 43%A.236,9290.85 0.656 0.000 0.000 0.192 0.79 0.79 0.99 78%B.132,7080.75 0.603 0.000 0.000 0.148 0.81 0.81 1.00 81%B.217,9980.41 0.185 0.000 0.000 0.228 0.56 0.56 0.70 46%C.127,0450.62 0.512 0.000 0.000 0.109 0.83 0.83 1.00 83%C.215,0840.35 0.217 0.000 0.000 0.129 0.69 0.69 0.86 64%C.322,5160.52 0.398 0.000 0.000 0.119 0.79 0.79 0.99 78%C.42,8740.07 0.053 0.000 0.000 0.013 0.82 0.82 1.00 81%C.527,3500.63 0.000 0.000 0.000 0.628 0.25 0.25 0.31 2%Total Site203,6864.68 2.829 0.000 0.000 1.847 0.67 0.67 0.84 61%DPA 58,110 1.33 0.860 0.000 0.000 0.474 0.70 0.70 0.88 65%DPB 50,706 1.16 0.788 0.000 0.000 0.376 0.72 0.72 0.90 68%DPC94,8692.181.1810.0000.0000.9970.630.630.7955%Total Treated108,8172.501.6480.00000.850Offsite Treated343.620.010.0080.00000.000Total Onsite Treated108,4732.491.6400.00000.850DESIGN POINTSPROPOSED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONSKetcher TownhomesD. SpaustatFebruary 17, 20211) Runoff coefficients are taken from the Fort Collins Stormwater Criteria Manaual, Table 4.1-3and Table 3.2-2.100-year Cf = 1.25Composite Runoff Coefficient with Adjustment
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 DETENTION POND
B.2 WATER QUALITY
B.3 STORM SEWER
B.4 INLETS
B.5 SWALES
APPENDIX B.1
DETENTION POND
Project No.BD-20-051
D.Spaustat
Pond No :Extended Detention Basin
1
100-yr
0.84
Area (A)=4.68 acres 35316 ft3
Max Release Rate =2.34 cfs 0.811 ac-ft
Time Time
100-yr
Intensity Q100
Inflow
(Runoff)
Volume
Outflow
(Release)
Volume
Storage
Detention
Volume
(mins) (secs) (in/hr) (cfs)
(ft3) (ft
3) (ft
3)
5 300 9.950 39.17 11750 701.4 11048.8
10 600 7.720 30.39 18233 1402.8 16830.7
15 900 6.520 25.67 23099 2104.2 20994.7
20 1200 5.600 22.04 26453 2805.6 23647.1
25 1500 4.980 19.60 29405 3507.0 25898.0
30 1800 4.520 17.79 32027 4208.4 27818.2
35 2100 4.080 16.06 33727 4909.8 28817.4
40 2400 3.740 14.72 35333 5611.2 29722.0
45 2700 3.460 13.62 36774 6312.6 30461.4
50 3000 3.230 12.71 38144 7014.0 31129.8
55 3300 3.030 11.93 39360 7715.4 31644.8
60 3600 2.860 11.26 40529 8416.8 32112.5
65 3900 2.720 10.71 41757 9118.2 32639.3
70 4200 2.590 10.20 42820 9819.6 33000.7
75 4500 2.480 9.76 43930 10521.0 33409.4
80 4800 2.380 9.37 44970 11222.4 33747.2
85 5100 2.290 9.01 45973 11923.8 34049.6
90 5400 2.210 8.70 46977 12625.2 34352.0
95 5700 2.130 8.38 47792 13326.6 34465.4
100 6000 2.060 8.11 48654 14028.0 34626.1
105 6300 2.000 7.87 49599 14729.4 34869.4
110 6600 1.940 7.64 50402 15430.8 34971.0
115 6900 1.890 7.44 51335 16132.2 35202.6
120 7200 1.840 7.24 52150 16833.5 35316.0
125 7500 1.790 7.05 52846 17534.9 35311.4
130 7800 1.740 6.85 53425 18236.3 35188.6
135 8100 1.690 6.65 53886 18937.7 34947.8
140 8400 1.640 6.46 54228 19639.1 34588.8
145 8700 1.590 6.26 54452 20340.5 34111.8
150 9000 1.540 6.06 54559 21041.9 33516.7
155 9300 1.490 5.87 54547 21743.3 32803.5
DETENTION POND CALCULATION; FAA METHOD
Project Name :Ketcher Housing
Date :February 17, 2021
1.35
Design Point
Design Storm Required Detention Volume
Developed "C" =
Project Location :Fort Collins
Input Variables Results
Calculations By:
Stage
(ft)Elevation
Incremental
Depth
(ft)
Area
(ft2)
Volume
(ft3)
Cumulative
Volume
(ft3)
Cumulative
Volume
(acre-ft)
0.00 4,891.25 0.0 0.00 0 0 0.00
0.05 4,891.30 0.1 18.14 0 0 0.00
0.15 4,891.40 0.1 263.01 12 12 0.00
0.25 4,891.50 0.1 614.28 43 55 0.00
0.35 4,891.60 0.1 1,295.59 93 148 0.00
0.45 4,891.70 0.1 2,158.00 171 319 0.01
0.55 4,891.80 0.1 3,075.00 260 579 0.01
0.65 4,891.90 0.1 3,852.32 346 925 0.02
0.75 4,892.00 0.1 4,353.62 410 1,335 0.03
0.85 4,892.10 0.1 4,831.17 459 1,794 0.04
0.95 4,892.20 0.1 5,281.79 505 2,299 0.05
1.05 4,892.30 0.1 5,722.03 550 2,849 0.07
1.15 4,892.40 0.1 6,069.11 589 3,439 0.08
1.25 4,892.50 0.1 6,242.36 616 4,054 0.09
1.35 4,892.60 0.1 6,320.53 628 4,683 0.11
1.45 4,892.70 0.1 6,371.67 635 5,317 0.12 WQCV WSEL
1.55 4,892.80 0.1 6,406.37 639 5,956 0.14
1.65 4,892.90 0.1 6,424.72 642 6,598 0.15
1.75 4,893.00 0.1 6,434.90 643 7,241 0.17
1.85 4,893.10 0.1 6,444.96 644 7,885 0.18
1.95 4,893.20 0.1 6,455.07 645 8,530 0.20
2.05 4,893.30 0.1 6,465.24 646 9,176 0.21
2.15 4,893.40 0.1 6,475.45 647 9,823 0.23
2.25 4,893.50 0.1 6,485.67 648 10,471 0.24
2.35 4,893.60 0.1 6,495.87 649 11,120 0.26
2.45 4,893.70 0.1 6,506.05 650 11,770 0.27
2.55 4,893.80 0.1 6,516.21 651 12,421 0.29 EURV WSEL
2.65 4,893.90 0.1 7,769.09 713 13,134 0.30
2.75 4,894.00 0.1 7,777.85 777 13,912 0.32
2.85 4,894.10 0.1 7,786.60 778 14,690 0.34
2.95 4,894.20 0.1 7,795.28 779 15,469 0.36
3.05 4,894.30 0.1 7,803.88 780 16,249 0.37
3.15 4,894.40 0.1 7,812.40 781 17,030 0.39
3.25 4,894.50 0.1 7,820.96 782 17,811 0.41
3.35 4,894.60 0.1 7,829.73 783 18,594 0.43
3.45 4,894.70 0.1 7,838.40 783 19,377 0.44
3.55 4,894.80 0.1 7,846.98 784 20,162 0.46
3.65 4,894.90 0.1 7,855.46 785 20,947 0.48
3.75 4,895.00 0.1 7,863.96 786 21,733 0.50
3.85 4,895.10 0.1 7,872.66 787 22,520 0.52
3.95 4,895.20 0.1 7,881.42 788 23,307 0.54
4.05 4,895.30 0.1 7,890.07 789 24,096 0.55
4.15 4,895.40 0.1 7,898.59 789 24,885 0.57
4.25 4,895.50 0.1 7,907.05 790 25,676 0.59
4.35 4,895.60 0.1 7,915.62 791 26,467 0.61
4.45 4,895.70 0.1 7,924.31 792 27,259 0.63
4.55 4,895.80 0.1 7,933.10 793 28,052 0.64
4.65 4,895.90 0.1 7,941.78 794 28,845 0.66
4.75 4,896.00 0.1 7,950.36 795 29,640 0.68
4.85 4,896.10 0.1 7,958.94 795 30,435 0.70
4.95 4,896.20 0.1 7,967.52 796 31,232 0.72
5.05 4,896.30 0.1 7,976.12 797 32,029 0.74
5.15 4,896.40 0.1 7,984.74 798 32,827 0.75
5.25 4,896.50 0.1 7,993.37 799 33,626 0.77
5.35 4,896.60 0.1 8,002.02 800 34,426 0.79
5.45 4,896.70 0.1 8,010.69 801 35,226 0.81
5.55 4,896.80 0.1 8,019.39 802 36,028 0.83 100-Year WSEL
5.65 4,896.90 0.1 8,028.11 802 36,830 0.85
5.75 4,897.00 0.1 8,241.12 813 37,644 0.86
5.85 4,897.10 0.1 8,469.79 836 38,479 0.88
5.95 4,897.20 0.1 8,707.65 859 39,338 0.90
6.05 4,897.30 0.1 8,954.78 883 40,221 0.92
6.15 4,897.40 0.1 9,211.00 908 41,129 0.94
DETENTION POND CALCULATION; FAA METHOD
Project Name :
Project No.
Date :
Project Location :
Calculations By:
Detention Basin Volume- Conic Volume Approximation
Pond No :
Ketcher Housing
December 22, 2020
BD-20-051
D.Spaustat
Fort Collins
Pond 1
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Qa = 2.34 cfs
C = 0.604
Qa = Allowable Release Rate (cfs)Eh = 4896.70 ft
C = Discharge Coefficients (unitless)Ei = 4890.42 ft
Aa = Area Allowed of Opening (ft2)
g = Gravity (32.2 ft/s2)0.19 ft2
Eh = High Water Surface Elevation (ft)27.74 in2
Ei = Elevation of Outlet Invert (ft)
D0 = Diameter of orifice (in.)
0.50 ft
6 in
n =0.012
Q =46.79 cfs
S0 0.50 ft/ ft
Dr=Minimum diameter of pipe (in)
n = mannings roughness factor
Q = 120% of the undetained 100-year flow (cfs)1.22 ft
S0 = longitudinal slope of the pipe (ft/ft)14.69 in
Nominal Diameter
Material n
CMP 0.024
HDPE 0.020
RCP 0.012
Typical Manning's n
Values Use 15 in
Aa =
EDB
D0 =
Dr =
Kechter Townhomes February 17, 2021
1664-003 D. Spaustat
EDB Outlet Pipe/Detention Orifice Sizing
()ihEEgCAQ-=2
APPENDIX B.2
WATER QUALITY
WATER QUALITY CAPTURE VOLUME DESIGN CALCULATIONS
40-Hour Detention (Extended Detention Basin)
Project: 1664-003
By: DCS
Date: 2/17/2021
EDB
REQUIRED STORAGE:
BASIN AREA =4.68 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT =61 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO =0.6129 <-- CALCULATED
WQCV (watershed inches) =0.24 <-- CALCULATED from USDCM Vol.3, Equation 3-1
VWQCV (ft3) =4,899 <-- CALCULATED from USDCM Vol.3, Equation B-1
EURVc/d (watershed inches) =0.71 <-- CALCULATED from MHFD Volume 3, Equation 12-3
VEURV (ft3) =12,003
Project:
Basin ID:
s
Depth Increment = 0.10 ft
Watershed Information Top of Micropool -- 0.00 -- -- -- 0 0.000
Selected BMP Type =EDB -- 0.05 -- -- -- 18 0.000 0 0.000
Watershed Area = 4.68 acres -- 0.15 -- -- -- 263 0.006 12 0.000
Watershed Length = 560 ft -- 0.25 -- -- -- 614 0.014 58 0.001
Watershed Length to Centroid = 320 ft -- 0.35 -- -- -- 1,296 0.030 154 0.004
Watershed Slope = 0.010 ft/ft -- 0.45 -- -- -- 2,158 0.050 305 0.007
Watershed Imperviousness = 61.00% percent -- 0.55 -- -- -- 3,075 0.071 588 0.014
Percentage Hydrologic Soil Group A = 0.0% percent -- 0.65 -- -- -- 3,852 0.088 896 0.021
Percentage Hydrologic Soil Group B = 0.0% percent -- 0.75 -- -- -- 4,354 0.100 1,345 0.031
Percentage Hydrologic Soil Groups C/D = 100.0% percent -- 0.85 -- -- -- 4,831 0.111 1,804 0.041
Target WQCV Drain Time = 40.0 hours -- 0.95 -- -- -- 5,282 0.121 2,257 0.052
Location for 1-hr Rainfall Depths = User Input -- 1.05 -- -- -- 5,722 0.131 2,860 0.066
-- 1.15 -- -- -- 6,069 0.139 3,389 0.078
-- 1.25 -- -- -- 6,242 0.143 4,065 0.093
Optional User Overrides -- 1.35 -- -- -- 6,321 0.145 4,693 0.108
Water Quality Capture Volume (WQCV) =0.112 acre-feet 0.112 acre-feet -- 1.45 -- -- -- 6,372 0.146 5,264 0.121
Excess Urban Runoff Volume (EURV) =0.276 acre-feet 0.276 acre-feet -- 1.55 -- -- -- 6,406 0.147 5,967 0.137
2-yr Runoff Volume (P1 = 0.88 in.) = 0.190 acre-feet 0.88 inches -- 1.65 -- -- -- 6,425 0.147 6,544 0.150
5-yr Runoff Volume (P1 = 1.16 in.) = 0.280 acre-feet 1.16 inches -- 1.75 -- -- -- 6,435 0.148 7,251 0.166
10-yr Runoff Volume (P1 = 1.47 in.) = 0.393 acre-feet 1.47 inches -- 1.85 -- -- -- 6,445 0.148 7,895 0.181
25-yr Runoff Volume (P1 = 1.99 in.) = 0.606 acre-feet 1.99 inches -- 1.95 -- -- -- 6,455 0.148 8,476 0.195
50-yr Runoff Volume (P1 = 2.49 in.) = 0.805 acre-feet 2.49 inches -- 2.05 -- -- -- 6,465 0.148 9,186 0.211
100-yr Runoff Volume (P1 = 3.05 in.) = 1.040 acre-feet 3.05 inches -- 2.15 -- -- -- 6,475 0.149 9,768 0.224
500-yr Runoff Volume (P1 = 4.68 in.) = 1.709 acre-feet 4.68 inches -- 2.25 -- -- -- 6,486 0.149 10,481 0.241
Approximate 2-yr Detention Volume = 0.181 acre-feet -- 2.35 -- -- -- 6,496 0.149 11,130 0.256
Approximate 5-yr Detention Volume = 0.271 acre-feet -- 2.45 -- -- -- 6,506 0.149 11,715 0.269
Approximate 10-yr Detention Volume = 0.336 acre-feet -- 2.55 -- -- -- 6,516 0.150 12,432 0.285
Approximate 25-yr Detention Volume = 0.426 acre-feet -- 2.65 -- -- -- 7,769 0.178 13,069 0.300
Approximate 50-yr Detention Volume = 0.489 acre-feet -- 2.75 -- -- -- 7,778 0.179 13,923 0.320
Approximate 100-yr Detention Volume = 0.590 acre-feet -- 2.85 -- -- -- 7,787 0.179 14,701 0.337
-- 2.95 -- -- -- 7,795 0.179 15,403 0.354
Define Zones and Basin Geometry -- 3.05 -- -- -- 7,804 0.179 16,260 0.373
Zone 1 Volume (WQCV) = 0.112 acre-feet -- 3.15 -- -- -- 7,812 0.179 16,963 0.389
Zone 2 Volume (EURV - Zone 1) = 0.164 acre-feet -- 3.25 -- -- -- 7,821 0.180 17,823 0.409
Zone 3 Volume (100-year - Zones 1 & 2) = 0.314 acre-feet -- 3.35 -- -- -- 7,830 0.180 18,605 0.427
Total Detention Basin Volume = 0.590 acre-feet -- 3.45 -- -- -- 7,838 0.180 19,310 0.443
Initial Surcharge Volume (ISV) = user ft 3 -- 3.55 -- -- -- 7,847 0.180 20,173 0.463
Initial Surcharge Depth (ISD) = user ft -- 3.65 -- -- -- 7,855 0.180 20,880 0.479
Total Available Detention Depth (Htotal) = user ft -- 3.75 -- -- -- 7,864 0.181 21,744 0.499
Depth of Trickle Channel (HTC) =user ft -- 3.85 -- -- -- 7,873 0.181 22,531 0.517
Slope of Trickle Channel (STC) = user ft/ft -- 3.95 -- -- -- 7,881 0.181 23,240 0.534
Slopes of Main Basin Sides (Smain) = user H:V -- 4.05 -- -- -- 7,890 0.181 24,107 0.553
Basin Length-to-Width Ratio (RL/W) = user -- 4.15 -- -- -- 7,899 0.181 24,818 0.570
-- 4.25 -- -- -- 7,907 0.182 25,687 0.590
Initial Surcharge Area (AISV) =user ft 2 -- 4.35 -- -- -- 7,916 0.182 26,478 0.608
Surcharge Volume Length (LISV) =user ft -- 4.45 -- -- -- 7,924 0.182 27,191 0.624
Surcharge Volume Width (WISV) =user ft -- 4.55 -- -- -- 7,933 0.182 28,063 0.644
Depth of Basin Floor (HFLOOR) =user ft -- 4.65 -- -- -- 7,942 0.182 28,777 0.661
Length of Basin Floor (LFLOOR) =user ft -- 4.75 -- -- -- 7,950 0.183 29,651 0.681
Width of Basin Floor (WFLOOR) =user ft -- 4.85 -- -- -- 7,959 0.183 30,447 0.699
Area of Basin Floor (AFLOOR) =user ft 2 -- 4.95 -- -- -- 7,968 0.183 31,163 0.715
Volume of Basin Floor (VFLOOR) =user ft 3 -- 5.05 -- -- -- 7,976 0.183 32,040 0.736
Depth of Main Basin (HMAIN) =user ft -- 5.15 -- -- -- 7,985 0.183 32,759 0.752
Length of Main Basin (LMAIN) =user ft -- 5.25 -- -- -- 7,993 0.184 33,637 0.772
Width of Main Basin (WMAIN) =user ft -- 5.35 -- -- -- 8,002 0.184 34,437 0.791
Area of Main Basin (AMAIN) =user ft 2 -- 5.45 -- -- -- 8,011 0.184 35,158 0.807
Volume of Main Basin (VMAIN) =user ft 3 -- 5.55 -- -- -- 8,019 0.184 36,039 0.827
Calculated Total Basin Volume (Vtotal) =user acre-feet -- 5.65 -- -- -- 8,028 0.184 36,761 0.844
-- 5.75 -- -- -- 8,241 0.189 37,655 0.864
-- 5.85 -- -- -- 8,470 0.194 38,491 0.884
-- 5.95 -- -- -- 8,708 0.200 39,262 0.901
-- 6.05 -- -- -- 8,955 0.206 40,233 0.924
-- 6.15 -- -- -- 9,211 0.211 41,049 0.942
-- -- -- --
After providing required inputs above including 1-hour rainfall
depths, click 'Run CUHP' to generate runoff hydrographs using
the embedded Colorado Urban Hydrograph Procedure.
Volume
(ft 3)
Volume
(ac-ft)
Area
(acre)
DETENTION BASIN STAGE-STORAGE TABLE BUILDER
Optional
Override
Area (ft 2)
Length
(ft)
Optional
Override
Stage (ft)
Stage
(ft)
Stage - Storage
Description
Area
(ft 2)
Width
(ft)
Kechter Townhomes EDB
C.5
MHFD-Detention, Version 4.03 (May 2020)
Example Zone Configuration (Retention Pond)
MHFD-Detention-EDB, Basin 2/15/2021, 9:17 AM
1 User Defined Stage-Area Booleans for Message
1 Equal Stage-Area Inputs Watershed L:W
1 CountA Watershed Lc:L
Watershed Slope
0 Calc_S_TC Booleans for CUHP
1 CUHP Inputs Complete
0.55 H_FLOOR 1 CUHP Results Calculated
L_FLOOR_OTHER
0.00 ISV 0.00 ISV
0.00 Floor 0.00 Floor
1.38 Zone 1 (WQCV) 1.38 Zone 1 (WQCV)
2.49 Zone 2 (EURV) 2.49 Zone 2 (EURV)
4.26 Zone 3 (100-year)4.26 Zone 3 (100-year)
DETENTION BASIN STAGE-STORAGE TABLE BUILDER
MHFD-Detention, Version 4.03 (May 2020)
0.000
0.240
0.480
0.720
0.960
0.000
0.055
0.110
0.165
0.220
0.00 2.00 4.00 6.00 8.00 Volume (ac-ft)Area (acres)Stage (ft.)
Area (acres)Volume (ac-ft)
0
2400
4800
7200
9600
0
5
10
15
20
0.00 2.00 4.00 6.00 8.00 Area (sq.ft.)Length, Width (ft.)Stage (ft)
Length (ft)Width (ft)Area (sq.ft.)
MHFD-Detention-EDB, Basin 2/15/2021, 9:17 AM
Project:
Basin ID:
Estimated Estimated
Stage (ft) Volume (ac-ft) Outlet Type
Zone 1 (WQCV) 1.38 0.112 Orifice Plate
Zone 2 (EURV) 2.49 0.164 Orifice Plate
Zone 3 (100-year) 4.26 0.314 Weir&Pipe (Circular)
Total (all zones) 0.590
User Input: Orifice at Underdrain Outlet (typically used to drain WQCV in a Filtration BMP)Calculated Parameters for Underdrain
Underdrain Orifice Invert Depth = ft (distance below the filtration media surface) Underdrain Orifice Area =ft2
Underdrain Orifice Diameter = inches Underdrain Orifice Centroid = feet
User Input: Orifice Plate with one or more orifices or Elliptical Slot Weir (typically used to drain WQCV and/or EURV in a sedimentation BMP)Calculated Parameters for Plate
Invert of Lowest Orifice = 0.00 ft (relative to basin bottom at Stage = 0 ft) WQ Orifice Area per Row = 6.111E-03 ft2
Depth at top of Zone using Orifice Plate = 2.49 ft (relative to basin bottom at Stage = 0 ft) Elliptical Half-Width = N/A feet
Orifice Plate: Orifice Vertical Spacing = 10.00 inches Elliptical Slot Centroid = N/A feet
Orifice Plate: Orifice Area per Row = 0.88 sq. inches (diameter = 1-1/16 inches) Elliptical Slot Area = N/A ft2
User Input: Stage and Total Area of Each Orifice Row (numbered from lowest to highest)
Row 1 (required) Row 2 (optional) Row 3 (optional) Row 4 (optional) Row 5 (optional) Row 6 (optional) Row 7 (optional) Row 8 (optional)
Stage of Orifice Centroid (ft) 0.00 0.83 1.66
Orifice Area (sq. inches) 0.88 0.88 0.88
Row 9 (optional) Row 10 (optional) Row 11 (optional) Row 12 (optional) Row 13 (optional) Row 14 (optional) Row 15 (optional) Row 16 (optional)
Stage of Orifice Centroid (ft)
Orifice Area (sq. inches)
User Input: Vertical Orifice (Circular or Rectangular)Calculated Parameters for Vertical Orifice
Not Selected Not Selected Not Selected Not Selected
Invert of Vertical Orifice = N/A N/A ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Area =N/A N/A ft2
Depth at top of Zone using Vertical Orifice = N/A N/A ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Centroid = N/A N/A feet
Vertical Orifice Diameter = N/A N/A inches 1
User Input: Overflow Weir (Dropbox with Flat or Sloped Grate and Outlet Pipe OR Rectangular/Trapezoidal Weir (and No Outlet Pipe) Calculated Parameters for Overflow Weir
grate Zone 3 Weir Not Selected Zone 3 Weir Not Selected
Overflow Weir Front Edge Height, Ho = 2.49 N/A ft (relative to basin bottom at Stage = 0 ft)Height of Grate Upper Edge, Ht =3.12 N/A feet
Overflow Weir Front Edge Length = 1.00 N/A feet Overflow Weir Slope Length = 2.58 N/A feet
Overflow Weir Grate Slope = 4.00 N/A H:V Grate Open Area / 100-yr Orifice Area = 9.19 N/A
Horiz. Length of Weir Sides = 2.50 N/A feet Overflow Grate Open Area w/o Debris = 1.80 N/A ft2
Overflow Grate Open Area % = 70% N/A %, grate open area/total area Overflow Grate Open Area w/ Debris = 1.80 N/A ft2
Debris Clogging % = 0% N/A %
User Input: Outlet Pipe w/ Flow Restriction Plate (Circular Orifice, Restrictor Plate, or Rectangular Orifice)Calculated Parameters for Outlet Pipe w/ Flow Restriction Plate
Zone 3 Circular Not Selected Zone 3 Circular Not Selected
Depth to Invert of Outlet Pipe = 0.83 N/A ft (distance below basin bottom at Stage = 0 ft)Outlet Orifice Area = 0.20 N/A ft2
Circular Orifice Diameter = 6.00 N/A inches Outlet Orifice Centroid = 0.25 N/A feet
Half-Central Angle of Restrictor Plate on Pipe = N/A N/A radians
User Input: Emergency Spillway (Rectangular or Trapezoidal)Calculated Parameters for Spillway
Spillway Invert Stage= 5.40 ft (relative to basin bottom at Stage = 0 ft) Spillway Design Flow Depth= 0.76 feet
Spillway Crest Length = 6.00 feet Stage at Top of Freeboard = 7.16 feet
Spillway End Slopes = 4.00 H:V Basin Area at Top of Freeboard = 0.21 acres
Freeboard above Max Water Surface = 1.00 feet Basin Volume at Top of Freeboard = 0.94 acre-ft
Max Ponding Depth of Target Storage Volume =5.37 feet Discharge at Top of Freeboard =18.82 cfs
Routed Hydrograph Results
Design Storm Return Period =WQCV EURV 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year 500 Year
One-Hour Rainfall Depth (in) =N/A N/A 0.88 1.16 1.47 1.99 2.49 3.05 4.68
CUHP Runoff Volume (acre-ft) =0.112 0.276 0.190 0.280 0.393 0.606 0.805 1.040 1.709
Inflow Hydrograph Volume (acre-ft) =N/A N/A 0.190 0.280 0.393 0.606 0.805 1.040 1.709
CUHP Predevelopment Peak Q (cfs) =N/A N/A 0.1 0.6 1.6 4.0 5.9 8.3 14.5
OPTIONAL Override Predevelopment Peak Q (cfs) =N/A N/A 0.9 2.3
Predevelopment Unit Peak Flow, q (cfs/acre) =N/A N/A 0.20 0.14 0.35 0.85 1.26 0.50 3.09
Peak Inflow Q (cfs) =N/A N/A 3.0 4.5 6.3 9.9 13.1 17.0 27.5
Peak Outflow Q (cfs) =0.1 0.1 0.1 0.1 0.9 1.9 2.1 2.3 15.7
Ratio Peak Outflow to Predevelopment Q =N/A N/A N/A 0.2 0.6 0.5 0.4 1.0 1.1
Structure Controlling Flow =Plate Overflow Weir 1 Plate Plate Overflow Weir 1 Outlet Plate 1 Outlet Plate 1 Outlet Plate 1 Spillway
Max Velocity through Grate 1 (fps) =N/A N/A N/A N/A 0.4 1.0 1.1 1.2 1.2
Max Velocity through Grate 2 (fps) =N/A N/A N/A N/A N/A N/A N/A N/A N/A
Time to Drain 97% of Inflow Volume (hours) =39 60 52 61 62 59 57 55 47
Time to Drain 99% of Inflow Volume (hours) =40 64 54 65 67 66 66 65 62
Maximum Ponding Depth (ft) =1.38 2.49 1.83 2.40 2.75 3.43 4.25 5.37 6.07
Area at Maximum Ponding Depth (acres) =0.15 0.15 0.15 0.15 0.18 0.18 0.18 0.18 0.21
Maximum Volume Stored (acre-ft) =0.112 0.276 0.177 0.263 0.320 0.440 0.590 0.792 0.926
DETENTION BASIN OUTLET STRUCTURE DESIGN
MHFD-Detention, Version 4.03 (May 2020)
Kechter Townhomes EDB
C.5
The user can override the default CUHP hydrographs and runoff volumes by entering new values in the Inflow Hydrographs table (Columns W through AF).
Example Zone Configuration (Retention Pond)
MHFD-Detention-EDB, Outlet Structure 2/15/2021, 9:15 AM
COUNTA for Basin Tab =1 Ao Dia WQ Plate Type Vert Orifice 1Vert Orifice 2
Count_Underdrain = 0 0.11(diameter = 3/8 inch)2 1 1
Count_WQPlate = 1 0.14(diameter = 7/16 inch)
Count_VertOrifice1 = 0 0.18(diameter = 1/2 inch)Outlet Plate 1 Outlet Plate 2 Drain Time Message Boolean
Count_VertOrifice2 = 0 0.24(diameter = 9/16 inch)2 1 5yr, <72hr 0
Count_Weir1 = 1 0.29(diameter = 5/8 inch)>5yr, <120hr 0
Count_Weir2 = 0 0.36(diameter = 11/16 inch)Max Depth Row
Count_OutletPipe1 = 1 0.42(diameter = 3/4 inch)WQCV 139 Watershed Constraint Check
Count_OutletPipe2 = 0 0.50(diameter = 13/16 inch)2 Year 184 Slope 0.010
COUNTA_2 (Standard FSD Setup)= 1 0.58(diameter = 7/8 inch)EURV 250 Shape 1.54
Hidden Parameters & Calculations 0.67(diameter = 15/16 inch)5 Year 241
MaxPondDepth_Error? FALSE 0.76 (diameter = 1 inch)10 Year 276 Spillway Depth
Cd_Broad-Crested Weir 3.00 0.86(diameter = 1-1/16 inches)25 Year 344 0.76
WQ Plate Flow at 100yr depth = 0.19 0.97(diameter = 1-1/8 inches)50 Year 426
CLOG #1=70%1.08(diameter = 1-3/16 inches)100 Year 538 1 Z1_Boolean
Cdw #1 =0.89 1.20(diameter = 1-1/4 inches)500 Year 608 1 Z2_Boolean
Cdo #1 =0.69 1.32(diameter = 1-5/16 inches)Zone3_Pulldown Message 1 Z3_Boolean
Overflow Weir #1 Angle =0.245 1.45(diameter = 1-3/8 inches)1 Opening Message
CLOG #2=0%1.59(diameter = 1-7/16 inches)Draintime Running
Cdw #2 =#VALUE! 1.73(diameter = 1-1/2 inches)Outlet Boolean Outlet Rank Total (1 to 4)
Cdo #2 =#VALUE! 1.88(diameter = 1-9/16 inches)Vertical Orifice 1 0 0 1
Overflow Weir #2 Angle =#VALUE!2.03(diameter = 1-5/8 inches)Vertical Orifice 2 0 0 Boolean
Underdrain Q at 100yr depth = 0.00 2.20(diameter = 1-11/16 inches)Overflow Weir 1 1 1 0 Max Depth
VertOrifice1 Q at 100yr depth = 0.00 2.36(diameter = 1-3/4 inches)Overflow Weir 2 0 0 0 500yr Depth
VertOrifice2 Q at 100yr depth = 0.00 2.54(diameter = 1-13/16 inches)Outlet Pipe 1 1 1 1 Freeboard
2.72(diameter = 1-7/8 inches)Outlet Pipe 2 0 0 1 Spillway
Count_User_Hydrographs 0 2.90(diameter = 1-15/16 inches)0 Spillway Length
CountA_3 (EURV & 100yr) =1 3.09(diameter = 2 inches)FALSE Time Interval
CountA_4 (100yr Only) = 1 3.29(use rectangular openings)Button Visibility Boolean
COUNTA_5 (FSD Weir Only)= 0 0 WQCV Underdrain
COUNTA_6 (EURV Weir Only)= 1 1 WQCV Plate
0 EURV-WQCV Plate
Outlet1_Pulldown_Boolean 0 EURV-WQCV VertOriice
Outlet2_Pulldown_Boolean 1 Outlet 90% Qpeak
Outlet3_Pulldown_Boolean 0 Outlet Undetained
0 Weir Only 90% Qpeak
0 Five Year Ratio Plate
0 Five Year Ratio VertOrifice
EURV_draintime_user
Spillway Options
Offset
Overlapping
S-A-V-D Chart Axis Default X-axis Left Y-Axis Right Y-Axis
minimum bound 0.00 0 0
maximum bound 8.00 50,000 20
S-A-V-D Chart Axis Override X-axis Left Y-Axis Right Y-Axis
minimum bound
maximum bound
DETENTION BASIN OUTLET STRUCTURE DESIGN
MHFD-Detention, Version 4.00 (December 2019)
0
5
10
15
20
25
30
0.1 1 10FLOW [cfs]TIME [hr]
500YR IN
500YR OUT
100YR IN
100YR OUT
50YR IN
50YR OUT
25YR IN
25YR OUT
10YR IN
10YR OUT
5YR IN
5YR OUT
2YR IN
2YR OUT
EURV IN
EURV OUT
WQCV IN
WQCV OUT
0
1
2
3
4
5
6
7
0.1 1 10 100PONDING DEPTH [ft]DRAIN TIME [hr]
500YR
100YR
50YR
25YR
10YR
5YR
2YR
EURV
WQCV
0
2
4
6
8
10
12
14
16
18
20
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
45,000
50,000
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 OUTFLOW [cfs]AREA [ft^2], VOLUME [ft^3]PONDING DEPTH [ft]
User Area [ft^2]
Interpolated Area [ft^2]
Summary Area [ft^2]
Volume [ft^3]
Summary Volume [ft^3]
Outflow [cfs]
Summary Outflow [cfs]
MHFD-Detention-EDB, Outlet Structure 2/15/2021, 9:15 AM
WATER QUALITY CAPTURE VOLUME DESIGN CALCULATIONS12-Hour Detention (Rain Garden)Project: 1664-003By: DCSDate: 2/17/2021BASIN AREA =1.33<-- INPUT from impervious calcsBASIN AREA =1.16<-- INPUT from impervious calcsBASIN IMPERVIOUSNESS PERCENT =65<-- INPUT from impervious calcsBASIN IMPERVIOUSNESS PERCENT =68<-- INPUT from impervious calcsBASIN IMPERVIOUSNESS RATIO =0.6517<-- CALCULATEDBASIN IMPERVIOUSNESS RATIO =0.6833<-- CALCULATEDWQCV (watershed inches) =0.20<-- CALCULATED from USDCM Vol.3, Equation 3-1WQCV (watershed inches) =0.21<-- CALCULATED from USDCM Vol.3, Equation 3-1V (ft3) =1,185<-- CALCULATED from USDCM Vol.3, Equation B-1V (ft3) =1,086<-- CALCULATED from USDCM Vol.3, Equation B-1Af, Minimum Flat Filter Area (ft2) = 757<-- CALCULATED from USCDM Vol.3, Equation B-2Af, Minimum Flat Filter Area (ft2)693<-- CALCULATED from USCDM Vol.3, Equation B-2Pond Bottom Elev (ft) = 4,894.00Pond Bottom Elev (ft)4,896.30Underdrain invert at outlet (ft) =4,892.50Underdrain invert at outlet (ft)4,893.04Distance to center of orifice (ft) =1.54Distance to center of orifice (ft)3.29Orifice Diameter (in) =0.84 (7/8")Orifice Diameter (in)0.69 (3/4")Q100 (cfs) =11.6Q100 (cfs) =10D (in)18D (in)18Ao (ft2)1.77Ao (ft2)1.77Co0.67Co0.67d100 (ft)1.50d100 (ft)1.18REQUIRED STORAGE & SAND FILTER SIZE:REQUIRED STORAGE & SAND FILTER SIZE:RAIN GARDEN ARAIN GARDEN B
Project No.BD-20-051
D.Spaustat
Pond No :RGA
Detention Basin Volume- Conic Volume Approximation
Elevation
Increment
al Depth
(ft)
Area
(ft2)
Volume
(ft3)
Cumulative
Volume
(ft3)
Cumulative
Volume (acre-
ft)
4,894.00 0.0 848.7 0 0 0.00
4,894.10 0.1 892.66 87 87 0.00
4,894.20 0.1 937.45 91 179 0.00
4,894.30 0.1 983.07 96 275 0.01
4,894.40 0.1 1029.52 101 375 0.01
4,894.50 0.1 1076.81 105 481 0.01
4,894.60 0.1 1124.92 110 591 0.01
4,894.70 0.1 1173.86 115 706 0.02
4,894.80 0.1 1223.63 120 825 0.02
4,894.90 0.1 1274.23 125 950 0.02
4,895.00 0.1 1325.66 130 1,080 0.02
4,895.10 0.1 1395.92 136 1,216 0.03 WQCV WSEL
4,895.20 0.1 1460.48 143 1,359 0.03
4,895.30 0.1 1528.43 149 1,509 0.03
4,895.40 0.1 1602.55 157 1,665 0.04
4,895.50 0.1 1684.94 164 1,829 0.04
Calculations By:
RAIN GARDEN POND VOLUME
Project Name :Ketcher Housing
Date :February 17, 2021
Project Location :Fort Collins
Project No.BD-20-051
D.Spaustat
Pond No :RGB
Detention Basin Volume- Conic Volume Approximation
Elevation
Increment
al Depth
(ft)
Area
(ft2)
Volume
(ft3)
Cumulativ
e Volume
(ft3)
Cumulativ
e Volume
(acre-ft)
4,896.30 0.0 868.62 0 0 0.00
4,896.40 0.1 917.6 89 89 0.00
4,896.50 0.1 967.55 94 184 0.00
4,896.60 0.1 1018.47 99 283 0.01
4,896.70 0.1 1070.38 104 387 0.01
4,896.80 0.1 1123.26 110 497 0.01
4,896.90 0.1 1177.11 115 612 0.01
4,897.00 0.1 1231.94 120 732 0.02
4,897.10 0.1 1287.75 126 858 0.02
4,897.20 0.1 1344.54 132 990 0.02
4,897.30 0.1 1404.65 137 1,127 0.03 WQCV WSEL
4,897.40 0.1 1468.44 144 1,271 0.03
4,897.50 0.1 1533.66 150 1,421 0.03
4,897.60 0.1 1600.32 157 1,578 0.04
4,897.70 0.1 1668.41 163 1,741 0.04
4,897.80 0.1 1737.93 170 1,912 0.04
4,897.90 0.1 1808.89 177 2,089 0.05
4,898.00 0.1 1881.28 184 2,273 0.05
4,898.10 0.1 1955.11 192 2,465 0.06
4,898.20 0.1 2030.37 199 2,664 0.06
4,898.30 0.1 2107.06 207 2,871 0.07
4,898.40 0.1 2185.19 215 3,086 0.07
4,898.50 0.1 2264.75 222 3,308 0.08
4,898.60 0.1 2345.75 231 3,539 0.08
4,898.70 0.1 2428.18 239 3,778 0.09
4,898.80 0.1 2512.05 247 4,025 0.09
4,898.90 0.1 2597.34 255 4,280 0.10
4,899.00 0.1 2684.08 264 4,544 0.10
4,899.10 0.1 2772.24 273 4,817 0.11
4,899.20 0.1 2861.84 282 5,099 0.12
4,899.30 0.1 2952.88 291 5,389 0.12
4,899.40 0.1 3045.35 300 5,689 0.13
4,899.50 0.1 3139.25 309 5,998 0.14
4,899.60 0.1 3234.59 319 6,317 0.15
RAIN GARDEN POND VOLUME
Project Name :Ketcher Housing
Date :February 17, 2021
Project Location :Fort Collins
Calculations By:
APPENDIX B.3
STORM SEWERS
APPENDIX B.4
INLETS
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK =0.0 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb)SBACK =ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020)nBACK =
Height of Curb at Gutter Flow Line HCURB =4.75 inches
Distance from Curb Face to Street Crown TCROWN =15.0 ft
Gutter Width W =2.58 ft
Street Transverse Slope SX =0.030 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft)SW =0.098 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO =0.000 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020)nSTREET =0.012
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX =15.0 15.0
ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX =4.8 12.0
inches
Check boxes are not applicable in SUMP conditions
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow =SUMP SUMP cfs
Version 4.05 Released March 2017
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Kechter Townhomes
Inlet E.1
1664-003 UD-Inlet_v4.05, Inlet E.1 2/15/2021, 10:51 AM
Design Information (Input)MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from above)alocal =2.00 2.00 inches
Number of Unit Inlets (Grate or Curb Opening)No = 2 2
Water Depth at Flowline (outside of local depression)Ponding Depth = 4.8 7.5 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo (G) =3.00 3.00 feet
Width of a Unit Grate Wo =1.73 1.73 feet
Area Opening Ratio for a Grate (typical values 0.15-0.90)Aratio =0.43 0.43
Clogging Factor for a Single Grate (typical value 0.50 - 0.70)Cf (G) =0.50 0.50
Grate Weir Coefficient (typical value 2.15 - 3.60)Cw (G) =3.30 3.30
Grate Orifice Coefficient (typical value 0.60 - 0.80)Co (G) =0.60 0.60
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo (C) =3.00 3.00 feet
Warning 1 Height of Vertical Curb Opening in Inches Hvert =3.88 3.88 inches
Height of Curb Orifice Throat in Inches Hthroat =5.25 5.25 inches
Angle of Throat (see USDCM Figure ST-5)Theta = 0.00 0.00 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet)Wp =2.58 2.58 feet
Clogging Factor for a Single Curb Opening (typical value 0.10)Cf (C) =0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.7)Cw (C) =3.70 3.70
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70)Co (C) =0.66 0.66
Low Head Performance Reduction (Calculated)MINOR MAJOR
Depth for Grate Midwidth dGrate =0.422 0.651 ft
Depth for Curb Opening Weir Equation dCurb =0.14 0.37 ft
Combination Inlet Performance Reduction Factor for Long Inlets RFCombination =0.56 0.88
Curb Opening Performance Reduction Factor for Long Inlets RFCurb =1.00 1.00
Grated Inlet Performance Reduction Factor for Long Inlets RFGrate =0.56 0.88
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition)Qa =2.3 8.6 cfs
Inlet Capacity IS GOOD for Minor and Major Storms(>Q PEAK)Q PEAK REQUIRED =0.7 5.6 cfs
Warning 1: Dimension entered is not a typical dimension for inlet type specified.
CDOT/Denver 13 Combination
INLET IN A SUMP OR SAG LOCATION
Version 4.05 Released March 2017
H-VertH-Curb
W
Lo (C)
Lo (G)
Wo
WP
CDOT/Denver 13 Combination
Override
1664-003 UD-Inlet_v4.05, Inlet E.1 2/15/2021, 10:51 AM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK =0.0 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb)SBACK =ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020)nBACK =
Height of Curb at Gutter Flow Line HCURB =4.75 inches
Distance from Curb Face to Street Crown TCROWN =15.0 ft
Gutter Width W =2.58 ft
Street Transverse Slope SX =0.030 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft)SW =0.098 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO =0.013 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020)nSTREET =0.012
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX =15.0 15.0
ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX =4.8 12.0
inches
Allow Flow Depth at Street Crown (leave blank for no)check = yes
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow =5.2 96.0 cfs
Version 4.05 Released March 2017
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Kechter Townhomes
Inlet E.2
Minor storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
Major storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
1664-003 UD-Inlet_v4.05, Inlet E.2 2/15/2021, 10:51 AM
Design Information (Input)MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a')aLOCAL =2.0 2.0 inches
Total Number of Units in the Inlet (Grate or Curb Opening)No = 1 1
Length of a Single Unit Inlet (Grate or Curb Opening)Lo =3.00 3.00 ft
Width of a Unit Grate (cannot be greater than W, Gutter Width) Wo =1.73 1.73 ft
Clogging Factor for a Single Unit Grate (typical min. value = 0.5)Cf-G =0.50 0.50
Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1)Cf-C =0.10 0.10
Street Hydraulics: OK - Q < Allowable Street Capacity'MINOR MAJOR
Total Inlet Interception Capacity Q = 1.2 3.4 cfs
Total Inlet Carry-Over Flow (flow bypassing inlet)Qb =0.7 5.6 cfs
Capture Percentage = Qa/Qo =C% = 64 38 %
INLET ON A CONTINUOUS GRADE
Version 4.05 Released March 2017
CDOT/Denver 13 CombinationCDOT/Denver 13 Combination
1664-003 UD-Inlet_v4.05, Inlet E.2 2/15/2021, 10:51 AM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK =0.0 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb)SBACK =ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020)nBACK =
Height of Curb at Gutter Flow Line HCURB =4.75 inches
Distance from Curb Face to Street Crown TCROWN =15.0 ft
Gutter Width W =2.58 ft
Street Transverse Slope SX =0.030 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft)SW =0.098 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO =0.007 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020)nSTREET =0.012
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX =15.0 15.0
ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX =4.8 12.0
inches
Allow Flow Depth at Street Crown (leave blank for no)check = yes
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow =3.9 71.9 cfs
Version 4.05 Released March 2017
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Kechter Townhomes
Inlet B.1
Minor storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
Major storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
1664-003 UD-Inlet_v4.05, Inlet B.1 2/15/2021, 10:51 AM
Design Information (Input)MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a')aLOCAL =2.0 2.0 inches
Total Number of Units in the Inlet (Grate or Curb Opening)No = 1 1
Length of a Single Unit Inlet (Grate or Curb Opening)Lo =3.00 3.00 ft
Width of a Unit Grate (cannot be greater than W, Gutter Width) Wo =1.73 1.73 ft
Clogging Factor for a Single Unit Grate (typical min. value = 0.5)Cf-G =0.50 0.50
Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1)Cf-C =0.10 0.10
Street Hydraulics: OK - Q < Allowable Street Capacity'MINOR MAJOR
Total Inlet Interception Capacity Q = 0.1 0.6 cfs
Total Inlet Carry-Over Flow (flow bypassing inlet)Qb =0.0 0.1 cfs
Capture Percentage = Qa/Qo =C% = 79 84 %
INLET ON A CONTINUOUS GRADE
Version 4.05 Released March 2017
CDOT/Denver 13 CombinationCDOT/Denver 13 Combination
1664-003 UD-Inlet_v4.05, Inlet B.1 2/15/2021, 10:51 AM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK =0.0 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb)SBACK =ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020)nBACK =
Height of Curb at Gutter Flow Line HCURB =4.75 inches
Distance from Curb Face to Street Crown TCROWN =15.0 ft
Gutter Width W =2.58 ft
Street Transverse Slope SX =0.030 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft)SW =0.098 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO =0.007 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020)nSTREET =0.012
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX =15.0 15.0
ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX =4.8 12.0
inches
Allow Flow Depth at Street Crown (leave blank for no)check = yes
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow =4.0 73.9 cfs
Version 4.05 Released March 2017
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Kechter Townhomes
Inlet B.2
Minor storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
Major storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
1664-003 UD-Inlet_v4.05, Inlet B.2 2/15/2021, 10:50 AM
Design Information (Input)MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a')aLOCAL =2.0 2.0 inches
Total Number of Units in the Inlet (Grate or Curb Opening)No = 1 1
Length of a Single Unit Inlet (Grate or Curb Opening)Lo =3.00 3.00 ft
Width of a Unit Grate (cannot be greater than W, Gutter Width) Wo =1.73 1.73 ft
Clogging Factor for a Single Unit Grate (typical min. value = 0.5)Cf-G =0.50 0.50
Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1)Cf-C =N/A N/A
Street Hydraulics: OK - Q < Allowable Street Capacity'MINOR MAJOR
Total Inlet Interception Capacity Q = 0.8 2.3 cfs
Total Inlet Carry-Over Flow (flow bypassing inlet)Qb =0.3 2.8 cfs
Capture Percentage = Qa/Qo =C% = 70 45 %
INLET ON A CONTINUOUS GRADE
Version 4.05 Released March 2017
CDOT/Denver 13 Valley GrateCDOT/Denver 13 Valley Grate
1664-003 UD-Inlet_v4.05, Inlet B.2 2/15/2021, 10:50 AM
HY-8 Culvert Analysis Report - Chase A.2
Crossing Discharge Data
Discharge Selection Method: Specify Minimum, Design, and Maximum Flow
Minimum Flow: 0.5 cfs
Design Flow: 1.91 cfs
Maximum Flow: 8.34 cfs
Table 1 - Summary of Culvert Flows at Crossing: Chase A.2
Headwater Elevation (ft) Total Discharge (cfs) Culvert 1 Discharge
(cfs)
Roadway Discharge
(cfs) Iterations
4897.15 0.50 0.50 0.00 1
4897.27 1.28 1.28 0.00 1
4897.34 1.91 1.91 0.00 1
4897.43 2.85 2.71 0.12 12
4897.47 3.64 3.00 0.61 7
4897.50 4.42 3.13 1.26 5
4897.52 5.20 3.10 2.07 4
4897.54 5.99 2.87 3.10 4
4897.56 6.77 2.62 4.14 4
4897.58 7.56 2.35 5.17 3
4897.60 8.34 2.03 6.29 3
4897.39 2.32 2.32 0.00 Overtopping
Table 2 - Culvert Summary Table: Culvert 1
********************************************************************************
Straight Culvert
Inlet Elevation (invert): 4897.01 ft, Outlet Elevation (invert): 4896.99 ft
Culvert Length: 4.50 ft, Culvert Slope: 0.0044
*******************************************************************************
Total
Discha
rge
(cfs)
Culvert
Discha
rge
(cfs)
Headw
ater
Elevati
on (ft)
Inlet
Contro
l Depth
(ft)
Outlet
Contro
l Depth
(ft)
Flow
Typ
e
Norma
l Depth
(ft)
Critical
Depth
(ft)
Outlet
Depth
(ft)
Tailwat
er
Depth
(ft)
Outlet
Velocit
y (ft/s)
Tailwat
er
Velocit
y (ft/s)
0.50 0.50 4897.1
5 0.134 0.144 2-M
2c 0.129 0.079 0.079 0.107 1.589 2.335
1.28 1.28 4897.2
7 0.249 0.261 2-M
2c 0.235 0.147 0.147 0.194 2.177 3.303
1.91 1.91 4897.3
4 0.325 0.338 7-M
2c 0.305 0.192 0.192 0.251 2.487 3.800
2.85 2.71 4897.4
3 0.424 0.424 7-M
2c 0.333 0.243 0.243 0.327 2.797 4.356
3.64 3.00 4897.4
7 0.462 0.462 7-M
2c 0.333 0.259 0.259 0.385 2.891 4.719
4.42 3.13 4897.5
0 0.481 0.489 7-M
2t 0.333 0.267 0.273 0.440 2.866 5.024
5.20 3.10 4897.5
2 0.476 0.512 7-M
2t 0.333 0.265 0.325 0.492 2.379 5.288
5.99 2.87 4897.5
4 0.444 0.536 4-FF
f 0.333 0.252 0.333 0.543 2.150 5.518
6.77 2.62 4897.5
6 0.412 0.556 4-FF
f 0.333 0.237 0.333 0.591 1.968 5.726
7.56 2.35 4897.5
8 0.377 0.573 4-FF
f 0.333 0.220 0.333 0.639 1.760 5.912
8.34 2.03 4897.6
0 0.339 0.589 4-FF
f 0.317 0.200 0.333 0.686 1.520 6.080
Water Surface Profile Plot for Culvert: Culvert 1
Site Data - Culvert 1
Site Data Option: Culvert Invert Data
Inlet Station: 21.88 ft
Inlet Elevation: 4896.84 ft
Outlet Station: 26.38 ft
Outlet Elevation: 4896.82 ft
Number of Barrels: 2
Culvert Data Summary - Culvert 1
Barrel Shape: Concrete Box
Barrel Span: 2.00 ft
Barrel Rise: 0.50 ft
Barrel Material: Concrete
Embedment: 2.00 in
Barrel Manning's n: 0.0240 (top and sides)
Manning's n: 0.0240 (bottom)
Culvert Type: Straight
Inlet Configuration: Square Edge (90º) Headwall
Inlet Depression: None
Roadway Data for Crossing: Chase A.2
Roadway Profile Shape: Irregular Roadway Shape (coordinates)
Irregular Roadway Cross-Section:
Coord No. Station (ft) Elevation (ft)
0 0.57 4897.49
1 19.46 4897.39
2 55.16 4897.64
Roadway Surface: Paved
Roadway Top Width: 4.50 ft
HY-8 Culvert Analysis Report – Chase B.1
Crossing Discharge Data
Discharge Selection Method: Specify Minimum, Design, and Maximum Flow
Minimum Flow: 0.5 cfs
Design Flow: 1.74 cfs
Maximum Flow: 7.47 cfs
Table 1 - Summary of Culvert Flows at Crossing: Chase B.1
Headwater Elevation (ft) Total Discharge (cfs) Culvert 1 Discharge
(cfs)
Roadway Discharge
(cfs) Iterations
4899.43 0.50 0.50 0.00 1
4899.60 1.20 1.20 0.00 1
4899.70 1.74 1.67 0.05 17
4899.76 2.59 1.99 0.59 8
4899.79 3.29 2.14 1.13 5
4899.81 3.98 2.25 1.71 4
4899.83 4.68 2.31 2.36 4
4899.85 5.38 2.36 2.99 3
4899.86 6.08 2.41 3.65 3
4899.88 6.77 2.44 4.31 3
4899.89 7.47 2.48 4.97 3
4899.66 1.48 1.48 0.00 Overtopping
Table 2 - Culvert Summary Table: Culvert 1
********************************************************************************
Straight Culvert
Inlet Elevation (invert): 4899.19 ft, Outlet Elevation (invert): 4899.16 ft
Culvert Length: 12.04 ft, Culvert Slope: 0.0022
********************************************************************************
Total
Discha
rge
(cfs)
Culvert
Discha
rge
(cfs)
Headw
ater
Elevati
on (ft)
Inlet
Contro
l Depth
(ft)
Outlet
Contro
l Depth
(ft)
Flow
Typ
e
Norma
l Depth
(ft)
Critical
Depth
(ft)
Outlet
Depth
(ft)
Tailwat
er
Depth
(ft)
Outlet
Velocit
y (ft/s)
Tailwat
er
Velocit
y (ft/s)
0.50 0.50 4899.4
3 0.214 0.242 2-M
2c 0.249 0.125 0.125 0.026 2.004 9.584
1.20 1.20 4899.6
0 0.378 0.415 2-M
2c 0.446 0.223 0.223 0.044 2.681 13.466
1.74 1.67 4899.7
0 0.472 0.512 7-M
2c 0.500 0.279 0.279 0.056 2.998 15.593
2.59 1.99 4899.7
6 0.534 0.571 7-M
2c 0.500 0.313 0.313 0.071 3.176 18.170
3.29 2.14 4899.7
9 0.563 0.599 7-M
2c 0.500 0.329 0.329 0.083 3.254 19.926
3.98 2.25 4899.8
1 0.585 0.621 7-M
2c 0.500 0.340 0.340 0.093 3.309 21.425
4.68 2.31 4899.8
3 0.598 0.641 7-M
2c 0.500 0.346 0.346 0.103 3.339 22.778
5.38 2.36 4899.8
5 0.609 0.658 7-M
2c 0.500 0.351 0.351 0.112 3.363 23.997
6.08 2.41 4899.8
6 0.618 0.674 7-M
2c 0.500 0.356 0.356 0.121 3.384 25.103
6.77 2.44 4899.8
8 0.626 0.689 7-M
2c 0.500 0.359 0.359 0.129 3.401 26.154
7.47 2.48 4899.8
9 0.634 0.703 7-M
2c 0.500 0.363 0.363 0.138 3.420 27.098
Water Surface Profile Plot for Culvert: Culvert 1
Site Data - Culvert 1
Site Data Option: Culvert Invert Data
Inlet Station: 14.33 ft
Inlet Elevation: 4899.19 ft
Outlet Station: 26.37 ft
Outlet Elevation: 4899.16 ft
Number of Barrels: 1
Culvert Data Summary - Culvert 1
Barrel Shape: Concrete Box
Barrel Span: 2.00 ft
Barrel Rise: 0.50 ft
Barrel Material: Concrete
Embedment: 0.00 in
Barrel Manning's n: 0.0240
Culvert Type: Straight
Inlet Configuration: Square Edge (90º) Headwall
Inlet Depression: None
Roadway Data for Crossing: Chase B.1
Roadway Profile Shape: Irregular Roadway Shape (coordinates)
Irregular Roadway Cross-Section:
Coord No. Station (ft) Elevation (ft)
0 0.15 4899.84
1 14.23 4899.75
2 30.39 4899.66
Roadway Surface: Paved
Roadway Top Width: 4.50 ft
APPENDIX B.5
SWALES
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Friday, Feb 12 2021
Swale A
Triangular
Side Slopes (z:1) = 5.50, 3.25
Total Depth (ft) = 0.64
Invert Elev (ft) = 4895.00
Slope (%) = 1.35
N-Value = 0.030
Calculations
Compute by: Known Q
Known Q (cfs) = 4.38
Highlighted
Depth (ft) = 0.63
Q (cfs) = 4.380
Area (sqft) = 1.74
Velocity (ft/s) = 2.52
Wetted Perim (ft) = 5.66
Crit Depth, Yc (ft) = 0.58
Top Width (ft) = 5.51
EGL (ft) = 0.73
0 1 2 3 4 5 6 7 8
Elev (ft)Depth (ft)Section
4894.75 -0.25
4895.00 0.00
4895.25 0.25
4895.50 0.50
4895.75 0.75
4896.00 1.00
Reach (ft)
APPENDIX C
EROSION CONTROL REPORT
Mountain’s Edge
Preliminary Erosion Control Report
A comprehensive Erosion and Sediment Control Plan (along with associated details) will be included with
the final construction drawings. It should be noted, however, that any such Erosion and Sediment
Control Plan serves only as a general guide to the Contractor. Staging and/or phasing of the BMPs
depicted, and additional or different BMPs from those included may be necessary during construction,
or as required by the authorities having jurisdiction.
It shall be the responsibility of the Contractor to ensure erosion control measures are properly
maintained and followed. The Erosion and Sediment Control Plan is intended to be a living document,
constantly adapting to site conditions and needs. The Contractor shall update the location of BMPs as
they are installed, removed or modified in conjunction with construction activities. It is imperative to
appropriately reflect the current site conditions at all times.
The Erosion and Sediment Control Plan shall address both temporary measures to be implemented
during construction, as well as permanent erosion control protection. Best Management Practices from
the Volume 3, Chapter 7 – Construction BMPs will be utilized. Measures may include, but are not limited
to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways and inlet
protection at existing and proposed storm inlets. Vehicle tracking control pads, spill containment and
clean‐up procedures, designated concrete washout areas, dumpsters, and job site restrooms shall also
be provided by the Contractor.
Grading and Erosion Control Notes can be found on Sheet CS2 of the Utility Plans. The Utility Plans at
final design will also contain a full‐size Erosion Control Plan as well as a separate sheet dedicated to
Erosion Control Details. In addition to this report and the referenced plan sheets, the Contractor shall
be aware of, and adhere to, the applicable requirements outlined in any existing Development
Agreement(s) of record, as well as the Development Agreement, to be recorded prior to issuance of the
Development Construction Permit. Also, the Site Contractor for this project will be required to secure a
Stormwater Construction General Permit from the Colorado Department of Public Health and
Environment (CDPHE), Water Quality Control Division – Stormwater Program, before commencing any
earth disturbing activities. Prior to securing said permit, the Site Contractor shall develop a
comprehensive StormWater Management Plan (SWMP) pursuant to CDPHE requirements and
guidelines. The SWMP will further describe and document the ongoing activities, inspections, and
maintenance of construction BMPs.
APPENDIX D
LID EXHIBIT
GAS
CONTROL
IRR
CONTROL
IRR
CONTROL
IRR
CONTROL
IRR
S
VAULT
ELEC
W FE
S
D
S
SS
HY DCONTROL
IRR
CONTROL
IRR
CONTROL
IRR
D
E
VAULT
ELEC
T
VAULT
ELECCXGTTE EWW W W W W
WT T T
E
E E E
E XXXXXXXXXXXXXXE E EX G G G G G
GWST ST ST ST ST ST ST ST ST ST ST ST STSTSS SS SS SS SS SS SS
SS
SSSSSS SS
SSXX X X X
X X X X X
XXXXXXXXXELEC
WWTTTTEEEEEEEETE
TEEEEEEEEE
E ETT T
EEEEEEEEEEEEEEEEEEEEEEEE
E EEEE
EEEEEEEEEEEEEEETE EEE EEE
EE
EC
ECLIPSE LANE
CACTUSCURVE)CACTUS
CURVEWHEELHOUSEWAYQUASAR WAYLOGGERS
LANE
PARCEL X
WILLOW BROOK
PARCEL W
WILLOW BROOK
PARCEL NO.
8604000904
PARCEL NO.
8604000904
B
A
ECLIPSE LANE
CACTUSCURVE)QUASAR WAYA.2
0.85 AC
C.1
0.62 AC
C.2
0.35 AC
C.3
0.52 AC
C.5
0.63 AC
C.4
0.07 AC
A.1
0.49 AC
B.2
0.41 AC
B.1
0.75 AC
EXTENDED DETENTION BASIN
REQUIRED VOL=35,316 CF
PROVIDED VOL=41,129 CF
CHASE DRAIN
A.2
STORM SEWER D
POND OUTLET
STORM SYSTEM
W/ INLINE DRAINS
PROPOSED SWALE
PROPOSED SWALE
PROPOSED SWALE
STORM SEWER A
RAIN GARDEN
OUTLET
PROPOSED CULVERT
(IRRIGATION DITCH)
CURB & GUTTER (TYP.)
CURB INLET E.1
STORM SEWER A
STORM SEWER B
RAIN
GARDEN B
6' DRAINAGE &
UTILITY EASEMENT
6' DRAINAGE &
UTILITY EASEMENT
6' DRAINAGE &
UTILITY EASEMENT
TRACT D
DRAINAGE EASMENT
RAIN GARDEN A
TRACT C
DRAINAGE EASEMENT
TRACT B
DRAINAGE EASMENT
CURB INLET B.1
CURB INLET B.2
CHASE DRAIN
B.1
CURB INLET D.1
12" RCP
12" RCP
14' DRAINAGE EASEMENT
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
before you dig.Call
R
NORTH
LID PROJECT SUMMARY
A
1.62 AC
LEGEND:
PROPOSED CONTOUR
PROPOSED STORM SEWER
PROPOSED SWALE
EXISTING CONTOUR
PROPOSED CURB & GUTTER
PROPERTY BOUNDARY
PROPOSED INLET
DRAINAGE BASIN LABEL
DRAINAGE BASIN BOUNDARY
NOTES:
1.REFER TO THE FINAL DRAINAGE REPORT FOR WILLOW BROOK, JULY 27, 2001 BY
TST, INC. CONSULTING ENGINEERS FOR ADDITIONAL INFORMATION.
UDPROPOSED UNDERDRAIN
BENCHMARK
PROJECT DATUM: NAVD88
BENCHMARK #1:
City of Fort Collins Benchmark 2-03
Location: South side Kechter Road approximately 0.6 miles west of Strauss Cabin Road on the
east end of the south parapet wall of the bridge over the Dixon Canyon Lateral.
Elevation= 4898.14 (NAVD88)
BENCHMARK #2:
City of Fort Collins Benchmark 13-13
Location: On the west side of Strauss Cabin Road, approximately 90-ft south of Kechter Road,
on the northwest corner of a storm inlet.
Elevation= 4887.05 (NAVD88)
Please note: This plan set is using NAVD88 for a vertical datum. Surrounding developments
have used NGVD29 Unadjusted Datum (prior City of Fort Collins Datum) for their vertical
datums.
If NGVD29 Unadjusted Datum (prior City of Fort Collins Datum) is required for any purpose, the
following equation should be used: NGVD29 Unadjusted Datum (prior City of Fort Collins
Datum) = NAVD88 - 3.18'
Basis of Bearings
South line of the Southeast Quarter of Section 4-6-68 as bearing South 88°11'39" East.
SheetKECHTER TOWNHOMESThese drawings areinstruments of serviceprovided by NorthernEngineering Services, Inc.and are not to be used forany type of constructionunless signed and sealedby a ProfessionalEngineer in the employ ofNorthern EngineeringServices, Inc.NOT FOR CONSTRUCTIONREVIEW SETof 1
LID (LID) EXHIBITLOW IMPACT DEVELOPMENT 1
LID BASIN/TREATMENT SUMMARY
LID A
1.33
LID B
1.16
LID BASIN LABEL
DRAINAGE BASIN BOUNDARY
LID B
0.97
APPENDIX F
REFERENCES
Hydrologic Soil Group—Larimer County Area, Colorado
(Ketcher Townhomes)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
6/25/2020
Page 1 of 444836004483800448400044842004484400448460044848004483600448380044840004484200448440044846004484800498300498500498700498900499100499300499500499700499900500100
498300 498500 498700 498900 499100 499300 499500 499700 499900 500100
40° 30' 51'' N 105° 1' 18'' W40° 30' 51'' N104° 59' 52'' W40° 30' 8'' N
105° 1' 18'' W40° 30' 8'' N
104° 59' 52'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 450 900 1800 2700
Feet
0 100 200 400 600
Meters
Map Scale: 1:9,340 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
35 Fort Collins loam, 0 to 3
percent slopes
C 83.8 29.7%
36 Fort Collins loam, 3 to 5
percent slopes
C 28.4 10.1%
73 Nunn clay loam, 0 to 1
percent slopes
C 6.0 2.1%
74 Nunn clay loam, 1 to 3
percent slopes
C 143.8 51.0%
76 Nunn clay loam, wet, 1
to 3 percent slopes
C 17.0 6.0%
103 Stoneham loam, 5 to 9
percent slopes
B 3.1 1.1%
Totals for Area of Interest 282.0 100.0%
Hydrologic Soil Group—Larimer County Area, Colorado Ketcher Townhomes
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
6/25/2020
Page 3 of 4
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.4 Intensity-Duration-Frequency Curves for Rational Method
Page 8
Table 3.4-1. IDF Table for Rational Method
Duration
(min)
Intensity
2-year
(in/hr)
Intensity
10-year
(in/hr)
Intensity
100-year
(in/hr)
Duration
(min)
Intensity
2-year
(in/hr)
Intensity
10-year
(in/hr)
Intensity
100-year
(in/hr)
5 2.85 4.87 9.95
39 1.09 1.86 3.8
6 2.67 4.56 9.31
40 1.07 1.83 3.74
7 2.52 4.31 8.80
41 1.05 1.80 3.68
8 2.40 4.10 8.38
42 1.04 1.77 3.62
9 2.30 3.93 8.03
43 1.02 1.74 3.56
10 2.21 3.78 7.72
44 1.01 1.72 3.51
11 2.13 3.63 7.42
45 0.99 1.69 3.46
12 2.05 3.50 7.16
46 0.98 1.67 3.41
13 1.98 3.39 6.92
47 0.96 1.64 3.36
14 1.92 3.29 6.71
48 0.95 1.62 3.31
15 1.87 3.19 6.52
49 0.94 1.6 3.27
16 1.81 3.08 6.30
50 0.92 1.58 3.23
17 1.75 2.99 6.10
51 0.91 1.56 3.18
18 1.70 2.90 5.92
52 0.9 1.54 3.14
19 1.65 2.82 5.75
53 0.89 1.52 3.10
20 1.61 2.74 5.60
54 0.88 1.50 3.07
21 1.56 2.67 5.46
55 0.87 1.48 3.03
22 1.53 2.61 5.32
56 0.86 1.47 2.99
23 1.49 2.55 5.20
57 0.85 1.45 2.96
24 1.46 2.49 5.09
58 0.84 1.43 2.92
25 1.43 2.44 4.98
59 0.83 1.42 2.89
26 1.4 2.39 4.87
60 0.82 1.4 2.86
27 1.37 2.34 4.78
65 0.78 1.32 2.71
28 1.34 2.29 4.69
70 0.73 1.25 2.59
29 1.32 2.25 4.60
75 0.70 1.19 2.48
30 1.30 2.21 4.52
80 0.66 1.14 2.38
31 1.27 2.16 4.42
85 0.64 1.09 2.29
32 1.24 2.12 4.33
90 0.61 1.05 2.21
33 1.22 2.08 4.24
95 0.58 1.01 2.13
34 1.19 2.04 4.16
100 0.56 0.97 2.06
35 1.17 2.00 4.08
105 0.54 0.94 2.00
36 1.15 1.96 4.01
110 0.52 0.91 1.94
37 1.16 1.93 3.93
115 0.51 0.88 1.88
38 1.11 1.89 3.87
120 0.49 0.86 1.84
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.4 Intensity-Duration-Frequency Curves for Rational Method
Page 9
Figure 3.4-1. Rainfall IDF Curve – Fort Collins
MAP POCKET
DR1 – OVERALL DRAINAGE EXHIBIT
GAS
CONTROL
IRR
CONTROL
IRR
CONTROL
IRR
CONTROL
IRR
S
VAULT
ELEC
W FE
S
D
S
SS
HY DCONTROL
IRR
CONTROL
IRR
CONTROL
IRR
D
E
VAULT
ELEC
T
VAULT
ELECCXGTTE EWW W W W W
WT T T
E
E E E
E XXXXXXXXXXXXXXE E EX G G G G G
GWST ST ST ST ST ST ST ST ST ST ST ST STSTSS SS SS SS SS SS SS
SS
SSSSSS SS
SSXX X X X
X X X X X
XXXXXXXXXELEC
WWEXTENDED DETENTION BASIN
REQUIRED VOL=35,316 CF
PROVIDED VOL=36,028 CF
CHASE DRAIN
A.2
STORM SEWER D
POND OUTLET
STORM SYSTEM
W/ INLINE DRAINS
PROPOSED SWALE
PROPOSED SWALE
PROPOSED SWALE
STORM SEWER A
RAIN GARDEN
OUTLET
ECLIPSE LANE
CACTUSCURVE)QUASAR WAYPROPOSED CULVERT
(IRRIGATION DITCH)
PARCEL X
WILLOW BROOK
PARCEL W
WILLOW BROOK
PARCEL R
WILLOW BROOK
POUDRE R-1 SCHOOL DISTRICT
PARCEL NO. 8604000904
CURB & GUTTER (TYP.)EX DRIPLINE CANOPY
(AREA UNDEERNEATH TO
REMAIN UNDISTURBED)
TAPER TOP WALL
TAPER TOP WALL
EX DRIPLINE CANOPY
(AREA UNDEERNEATH TO
REMAIN UNDISTURBED)
CURB INLET E.1
STORM SEWER A
STORM SEWER B
A.2
0.85 AC
C.1
0.62 AC
C.2
0.35 AC
C.3
0.52 AC
C.5
0.63 AC
C.4
0.07 AC
A.1
0.49 AC
RAIN
GARDEN B
6' DRAINAGE &
UTILITY EASEMENT
6' DRAINAGE &
UTILITY EASEMENT
6' DRAINAGE &
UTILITY EASEMENT
TRACT D
DRAINAGE EASMENT
RAIN GARDEN A
TRACT C
DRAINAGE EASEMENT
TRACT B
DRAINAGE EASMENT
A
B
C
B.2
0.41 AC
B.1
0.75 AC
CURB INLET B.1
CURB INLET B.2
CHASE DRAIN
B.1
CURB INLET D.1
12" RCP
12" RCP
14' DRAINAGE EASEMENT
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
HYDROLOGY SUMMARY
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
before you dig.Call
R
NORTH
LID SUMMARY
EXTENDED DETENTION BASIN SUMMARY
A
1.62 AC
LEGEND:
PROPOSED CONTOUR
PROPOSED STORM SEWER
PROPOSED SWALE
EXISTING CONTOUR
PROPOSED CURB & GUTTER
PROPERTY BOUNDARY
PROPOSED INLET
ADESIGN POINT
FLOW ARROW
DRAINAGE BASIN LABEL
DRAINAGE BASIN BOUNDARY
PROPOSED SWALE SECTION
11
NOTES:
1.REFER TO THE FINAL DRAINAGE REPORT FOR WILLOW BROOK, JULY 27, 2001 BY
TST, INC. CONSULTING ENGINEERS FOR ADDITIONAL INFORMATION.
UDPROPOSED UNDERDRAIN
BENCHMARK
PROJECT DATUM: NAVD88
BENCHMARK #1:
City of Fort Collins Benchmark 2-03
Location: South side Kechter Road approximately 0.6 miles west of Strauss Cabin Road on the
east end of the south parapet wall of the bridge over the Dixon Canyon Lateral.
Elevation= 4898.14 (NAVD88)
BENCHMARK #2:
City of Fort Collins Benchmark 13-13
Location: On the west side of Strauss Cabin Road, approximately 90-ft south of Kechter Road,
on the northwest corner of a storm inlet.
Elevation= 4887.05 (NAVD88)
Please note: This plan set is using NAVD88 for a vertical datum. Surrounding developments
have used NGVD29 Unadjusted Datum (prior City of Fort Collins Datum) for their vertical
datums.
If NGVD29 Unadjusted Datum (prior City of Fort Collins Datum) is required for any purpose, the
following equation should be used: NGVD29 Unadjusted Datum (prior City of Fort Collins
Datum) = NAVD88 - 3.18'
Basis of Bearings
South line of the Southeast Quarter of Section 4-6-68 as bearing South 88°11'39" East.
EXISTING NATURAL HABITAT BUFFER ZONE
PROPOSED NATURAL HABITAT BUFFER ZONE
EXISTING WETLAND
SheetKECHTER TOWNHOMESThese drawings areinstruments of serviceprovided by NorthernEngineering Services, Inc.and are not to be used forany type of constructionunless signed and sealedby a ProfessionalEngineer in the employ ofNorthern EngineeringServices, Inc.NOT FOR CONSTRUCTIONREVIEW SETof 36
DR1 DRAINAGE EXHIBIT36
DESIGN POINT SUMMARY