HomeMy WebLinkAboutVILLAGE ON HORSETOOTH (AFFORDABLE HOUSING) - PDP - PDP160025 - REPORTS - DRAINAGE REPORTPRELIMINARY DRAINAGE AND
EROSION CONTROL REPORT
FOR
VILLAGE ON HORSETOOTH
AT
1506 W. HORSETOOTH ROAD
FORT COLLINS, CO 80526
PREPARED FOR
FORT COLLINS HOUSING AUTHORITY
Fort Collins, CO 80521
SEPTEMBER 20, 2016
Fort Collins Housing Authority - Village on Horsetooth
ENGINEER’S STATEMENT:
“I hereby certify that this report (plan) for the Preliminary Drainage Design for the Fort Collins
Housing Authority Village on Horsetooth was prepared by me (or under my direct supervision) in
accordance with the provisions of the City of Fort Collins Standards for the Responsible Parties
thereof. I understand that the City of Fort Collins does not and shall not assume liability for
drainage facilities designed by others.”
______________________________
Charles R. Hager, IV, P.E.
Registered Professional Engineer
State of Colorado No. 37146
Fort Collins Housing Authority - Village on Horsetooth
PRELIMINARY DRAINAGE AND EROSION CONTROL REPORT
FOR
FORT COLLINS HOUSING AUTHORITY
VILLAGE ON HORSETOOTH
JVA, Inc.
25 Old Town Square, Suite 200
Fort Collins, CO 80524
phone: 970-225-9099
JVA Project No. 2595c
SEPTEMBER 20, 2016
Fort Collins Housing Authority - Village on Horsetooth
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TABLE OF CONTENTS
SITE LOCATION AND DESCRIPTION ......................................................................................... 5
DRAINAGE BASINS AND HISTORIC RUNOFF ............................................................................. 6
HISTORIC DRAINAGE ......................................................................................................... 6
DRAINAGE DESIGN CRITERIA ................................................................................................ 6
HYDROLOGIC METHOD AND DESIGN STORM FREQUENCIES ................................................... 6
HYDRAULIC CRITERIA ........................................................................................................ 6
VARIANCES FROM THE CRITERIA ............................................................................................ 7
DRAINAGE FACILITY DESIGN ................................................................................................. 7
GENERAL CONCEPT ......................................................................................................... 7
PROPOSED DEVELOPED SUBBASINS .................................................................................... 7
PROPOSED DETENTION POND AND LID ............................................................................ 10
HISTORIC/DEVELOPED BASIN COMPARISON ..................................................................... 10
STORMWATER POLLUTION PREVENTION/EROSION CONTROL .................................................. 11
TEMPORARY EROSION CONTROL ..................................................................................... 11
PERMANENT EROSION CONTROL ..................................................................................... 11
STORMWATER MANAGEMENT CONTROLS ............................................................................ 11
SEQUENCE OF CONSTRUCTION ACTIVITIES ............................................................................ 14
CONCLUSIONS .................................................................................................................. 15
REFERENCES ...................................................................................................................... 16
LIST OF TABLES
TABLE 1. HISTORIC BASIN PROPERTIES AND FLOWS ..................................................................... 6
TABLE 2. DEVELOPED BASIN PROPERTIES AND FLOWS COEFFICIENTS ............................................. 9
Fort Collins Housing Authority - Village on Horsetooth
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APPENDICES
Appendix A – Figures
Appendix B – Hydraulic/Hydrologic Computations
Appendix C – Referenced Documents
Fort Collins Housing Authority - Village on Horsetooth
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SITE LOCATION AND DESCRIPTION
The Village on Horsetooth (site) is being developed by the Fort Collins Housing Authority and is
located in Southeast Quarter of Section 27, Township 7 North, Range 69 West of the 6th
Principal
Meridian, in Larimer County, Fort Collins, Colorado. Refer to Appendix A, Figure 1, for the site
vicinity map. Horsetooth Road (Horsetooth) to the south, Pleasant Valley and Lake Canal (Canal)
to the east, and residential subdivisions to the north and west border the property. There is open
space and residential housing to the west. The site is located in the Foothills Stormwater Basin.
The Foothill basin drains west to east through open channels and storm sewer that discharges into
the Fossil Creek Reservoir Inlet Ditch. The Foothills Basin Master Plan Water Quality Conceptual
Alternatives Map, provided by the City of Fort Collins, shows that the site is required to provide
flood control and water quality; the map is attached in Appendix C.
The current site is approximately 7.96 acres of partially developed land with an existing house and
horse stable, arena and grazing open space area with a total percent impervious of 16.0%. The site
historically generally drains to the east towards and into the Canal via overland flow with slopes
ranging from 0.2% to 8.0%. The north half of Horsetooth bordering the site drains to the north
onto the site and into the Canal. From the geotechnical report dated July 19, 2016, the soil is
mainly sandy clay and clayey sand with no bedrock encountered in the borings. Ground water was
located 19 to 22 feet below ground surface and did not drastically change several days after
drilling. A soil map created using the USDA Natural Resources Conservation Service Web Soil
Survey identifies the site’s soil as Altvan-Satanta Loams, which is in the hydrologic soil group B
with infiltration rates ranging from 0.6 to 2 inches/hour. Further investigation of the soils
infiltration rate in the locations of the detention pond and low impact development (LID) ponds
will be completed. A summary of the conclusions of the geotechnical report and the web soil
survey results are provided in Appendix C.
According to the FEMA Flood Insurance Rate Map Panel Number 08069C0986G dated
05/02/2012, the site is located outside of the 100-year floodplain area. The map panel is attached
in Appendix C.
The proposed site construction includes the demolition of the existing home, horse stables and
arena, gravel roadway and the construction of 9 new multi-unit residential buildings and clubhouse
building with surrounding asphalt parking areas, playground and grass fields, sidewalks, water
quality controls and detention pond. The site development will increase the overall percent
impervious to 48.2%. The proposed development cannot drain or discharge into the Canal and
must tie into the City of Fort Collins (City) storm sewer system located in Horsetooth or flow onto
Horsetooth, which eventually drains to Fossil Creek Reservoir Inlet Ditch. Storm valley gutters,
area inlets, under drains, curb cuts, chases, channels and culverts are located throughout the site to
capture and convey runoff to the LIDs and detention pond.
The main purpose of this study is to analyze the existing and developed drainage patterns in order
to convey stormwater into the Horsetooth storm sewer system without causing adverse effects to
the site and surrounding and downstream properties. The proposed scope of work will include
new storm piping, valley gutters, area drains, inlets, curb cuts, and site grading to accommodate
three bioretention ponds, a detention pond, and piping to the existing Horsetooth storm system.
Fort Collins Housing Authority - Village on Horsetooth
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An outlet structure and pipe with a restrictor plate will be installed in the pond to control the 100-
year storm outflow rate to the calculated 2-year historical runoff rate. WQCV will be attained in
the bioretention ponds. A spillway is located along the southeast edge of the pond and will direct
flow onto Horsetooth if the outlet structure is ever clogged or not performing correctly.
DRAINAGE BASINS AND HISTORIC RUNOFF
HISTORIC DRAINAGE
The site historically drains to the east towards and into the Pleasant Valley and Lake Canal via
overland flow with slopes ranging from 0.2% to 8.0%. Runoff from the north half of Horsetooth
bordering the site drains north onto the site and into the Canal. The site consists of a gravel
roadway, house, horse stables, arena, and grazing area which have an overall percent impervious
of 16.0%. The peak 2-year and 100-year runoff rates are 2.21 cfs and 28.78 cfs, respectively.
The historic drainage is outlined below. Design flow calculations and the historical drainage map
are provided in Appendix A.
Table 1. Historic Basin Properties and Flows
Drainage
Basin
Design
Point
Area
(acre)
%
Impervious
Q-2
(cfs)
Q-100
(cfs)
Runoff
Coefficient
H1 1 7.96 16.0% 2.21 28.78 0.53
Total 7.96 16.0% 2.21 28.78 0.53
DRAINAGE DESIGN CRITERIA
HYDROLOGIC METHOD AND DESIGN STORM FREQUENCIES
The drainage for the site was designed to meet or exceed the City of Fort Collin’s Standards and
Specifications, including the Stormwater Criterial Manual which incorporates most of the Urban
Drainage and Flood Control District Criteria Manual (USDCM). The site’s basin percent
impervious values were calculated using impervious values from Table 6-3 in the USDCM. For
the Modified FAA calculations, the values for the 2-year and 100-year event rainfall intensity
duration for 0 to 60 minutes were taken from Table RA-7 in the City of Fort Collins’ Stormwater
Criteria Manual. Equation 5.30 from the USDCM was used to calculate intensities for the 60 to
180 minute time steps. The runoff coefficients were calculated using USDCM’s Table 6-4
equations.
HYDRAULIC CRITERIA
The proposed drainage facility has been designed to comply with the City of Fort Collins
Stormwater Criteria Manual, the Foothills Basin Master Plan design, and UDFCD’s Drainage
Criteria Manual. The Foothills Basin Master Plan requires best management practices to have
both flood control and water quality. Sizing for inlets and pipes have not been completed at this
Fort Collins Housing Authority - Village on Horsetooth
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time, but UD-Inlet Version 3.14, Manning’s Equation, Hydraflow, and Flowmaster will be utilized
as needed for calculations. Preliminary drainage plans are included in the construction documents.
The pond volume was calculated using the modified FAA method and includes the 100-year runoff
volume but none of the WQCV because that volume is being captured and treated separately in
the site’s three bioretention ponds. The City’s stormwater criteria manual. Pond volume, WQCV,
bioretention sizing, and runoff calculations are attached in Appendix B.
VARIANCES FROM THE CRITERIA
As per the City’s comments dated May 9, 2016, the site is required to discharge the 100-year event
at the historical 2-year rate. There is a micropool in the detention basin outlet structure to allow
the bioretention underdrains to tie into the structure. There are no forebays in the pond since all
concentrated flows entering the detention pond pass through one of the three bioretention ponds.
Riprap aprons will act as velocity dissipaters for the concentrated runoff entering the bioretention
ponds.
DRAINAGE FACILITY DESIGN
GENERAL CONCEPT
As per the Foothills Basin Master Plan design, the site was graded in an attempt to capture all site
runoff to be treated and detained in the three bioretention ponds and the extended detention basin
located along the east side of the site. The detention pond has an outlet structure that ties into the
City’s existing storm sewer system on the south side of Horsetooth. The shallow elevation of this
connection restricts the bottom elevation of the detention pond. A very small portion of the site,
11.3%, was not able to be captured and treated onsite. This offsite flow will either drain onto
Horsetooth Road and follow existing drainage pathways to the east or drain to the east into the
Canal. The open space area in the center of the site will capture the runoff from the playground,
sidewalk, and open space through the uses of area inlets which tie into the proposed storm system
and discharges into LID Pond 3. Six of the roof drains will connect into the same system along
with the south portion of the site. Furthermore, the east portion of the parking lot sheet flows into
LID Pond 3. The west side of the site and three roofs will drain to the north into LID Pond 1. LID
Pond 1 is hydraulically connected to LID Pond 2 by a culvert set 1.5 feet above the bottom of the
pond. A portion of the parking lot to the north and east and one roof drain into LID Pond 2. All
onsite runoff, besides the detention pond, will be directed to one of the three LID ponds. There
are overflows in the ponds to allow for larger storm events to discharge into the detention pond.
Also, the bioretention ponds will have an underdrain system that is connected through the three
ponds and ties into the outlet structure micropool. The parking lot will act as part of the detention
pond for larger storm events, but will have no greater than one foot of ponding at the deepest point.
Vertical curb and gutter will be installed along Horsetooth road to convey flows east along the
road, similar to what is occurring to the west and east along Horsetooth.
PROPOSED DEVELOPED SUBBASINS
The site was delineated into seventeen subbasins, A1-A7, B1-B3, and R1-R10. Basins A1-A7 and
R1-R10 will be captured and treated in the bioretention ponds and detention pond. Basin B1-B3
are the offsite basins and will not be have treatment before leaving the site either to Horsetooth
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Road or the Canal. Basin A1, A2 and A6 all contain a bioretention pond for LID treatment. Basins
A3, A4 and A5 collect runoff into inlets and the proposed storm system that discharges into LID
Pond 3. Basins A7 contains the detention pond. Roof basins R3-R5 and R8-R10 will either
connect into the storm system or sheet flow into the parking lot and be transported to the LID Pond
3. Roof basins R1, R6, and R7 will be piped or sheet flow into LID Pond 1. Roof basin R2 will
be piped into LID Pond 2. The developed drainage map is provided in Appendix A.
SUBBASIN DESCRIPTIONS:
• Subbasin A1 contains the most of the west portion of the sites and half of the north area.
This includes parking lot, sidewalk and landscaped areas. Flow is directed into the parking
lot and a valley gutter the runs to the north and has a valley grate as well as a curb cut to
direct flow into LID Pond 1. LID Pond 1 is a bioretention pond with underdrain. A culvert
connects Basin A1 to Basin A2.This area flows around to the east and through a culvert
underneath the emergency access to Basin A6.
• Subbasin A2 contains half of the north portion of the site and a little of the east portion.
This includes landscaped, parking lot, sidewalk areas, and LID Pond 2. Runoff is directed
across the parking lot to the curb and gutter and a curb cut into the bioretention pond. Once
the pond is at capacity, flow then discharges into the detention pond.
• Subbasin A3 contains the west portion of the sites south and west areas. This includes
parking lot, landscaped and sidewalk areas. The basin drains onto the parking lot and into
the valley gutter and curb and gutter to a sumped inlet. The inlet discharges into LID Pond
3.
• Subbasin A4 contains the east portion of the sites south area. This includes sidewalk,
landscape, and parking lot areas. The basin drains onto the parking lot and into the valley
gutter and curb and gutter to a sumped inlet. The inlet discharges into LID Pond 3.
• Subbasin A5 contains the open space area in the center of the site. This includes picnic
areas, the playground, sidewalk and grass area. Flow is directed to the center of the open
space where there are two area drains to collect flow into the storm system that discharges
into the LID Pond 3.
• Subbasin A6 contains most of the east portion of the parking lot area and LID Pond 3.
Flow is directed to the east and is captured in the curb in gutter that has two curb cuts into
the bioretention pond. The basin also includes landscaped and sidewalk areas. Once the
bioretention pond is at capacity flow from basin A6 will discharge into the detention pond.
• Subbasin A7 contains the detention pond and the concrete walk along the east edge of the
pond. All A basins and R basins drain into the pond before being discharged into the
Horsetooth storm system.
• Subbasin B1 contains the south portion of the site that drains offsite. This includes
landscaped area, sidewalk and the entrance into the property. Runoff will sheet flow across
the landscaped areas and road onto Horsetooth Road and be directed to the east along the
curb and gutter.
• Subbasin B2 contains the north portion of the site that drains offsite. This area exists
because of the detention basins berm. Flow is directed to the north into a swale running
west to east that discharges into the Canal. Very minor flow, 0.60 cfs for the 100-year
event, will enter the Canal.
Fort Collins Housing Authority - Village on Horsetooth
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• Subbasin B3 contains the east side of the dentention ponds embankment. Flow from the
embankment will be directed to the east into the Canal. The 100-year peak flow is 1.44
cfs.
• Roof Subbasins R1, R6, and R7 will be surface discharge into basin A1 or piped into the
basins bioretention pond.
• Roof Subbasin R2 will be piped into the bioretention pond in basin A2.
• Roof Subbasins R3, R4, R5, R8, R9 and R10 will all eventually be discharged into basin
A6’s bioretention pond. Roof Subbasins R3, R4, R5 will be piped into the sites storm
system. Roof Subbasins R8, R9, and R10 will either be piped into the storm system or
surface discharged into basins A3 or A4 where the flow will then be captured in inlets and
piped to the bioretention pond.
Table 2. Developed Basin Properties and Flows Coefficients
Drainage
Basin
Design
Point
Area
(acre)
%
Impervious
Q-2
(cfs)
Q-100
(cfs)
Runoff
Coeff's
C100
A1 1 1.10 60.3% 1.46 7.09 0.75
A2 2 0.55 49.7% 0.57 3.15 0.70
A3 3 0.67 68.5% 0.97 4.39 0.79
A4 4 0.27 71.2% 0.44 1.96 0.80
A5 5 1.38 21.7% 0.57 5.72 0.56
A6 6 0.88 66.4% 1.31 6.01 0.78
A7 7 0.85 8.1% 0.14 3.23 0.49
B1 8 0.45 11.9% 0.10 1.76 0.51
B2 9 0.13 5.0% 0.02 0.60 0.48
B3 10 0.31 2.0% 0.02 1.44 0.46
R1 11 0.16 90.0% 0.38 1.47 0.90
R2 12 0.16 90.0% 0.37 1.45 0.90
R3 13 0.16 90.0% 0.38 1.47 0.90
R4 14 0.11 90.0% 0.25 0.98 0.90
R5 15 0.07 90.0% 0.16 0.61 0.90
R6 16 0.10 90.0% 0.23 0.90 0.90
R7 17 0.16 90.0% 0.37 1.45 0.90
R8 18 0.16 90.0% 0.38 1.47 0.90
R9 19 0.16 90.0% 0.37 1.45 0.90
R10 20 0.10 90.0% 0.23 0.90 0.90
Site Total 7.96 48.2% 8.70 47.52 0.69
Total to Pond 7.05 53.4% 8.56 43.71 0.72
Total Offsite (B Basins) 0.90 7.5% 0.14 3.80 0.49
Total To LID Pond 1 1.53 68.7% 2.43 10.91 0.79
Total To LID Pond 2 0.71 59.0% 0.94 4.60 0.74
Total To LID Pond 3 3.97 56.2% 5.05 24.97 0.73
Fort Collins Housing Authority - Village on Horsetooth
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PROPOSED DETENTION POND AND LID
As per the City’s requirement, the 100-year runoff volume is captured in the detention pond and
has an outflow rate equal to the historical 2-year flow rate of 2.21 cfs. This is accomplished
through the installation of a restrictor plate on the 15 inch RCP outlet pipe. Only a small portion
of the sites area, 11.3%, was not designed to drain onsite into the detention pond and bioretention
ponds. A total of 99.16% of the modified and added impervious surface is captured and treated in
one of the bioretention ponds. The bottom of the pond is at an elevation of 5105.29 feet and is
5.20 feet deep with a total volume of 4.39 acre-ft. The detention pond emergency overflow
spillway is located on the southern edge of the pond at an elevation of 5109.50 ft and will discharge
to Horsetooth Road if the outlet structure of the pond is ever clogged or malfunctioning. The
spillway will be designed to be able to discharge the peak 100-year runoff rate of 43.71 cfs with 9
inches of head. For the 100-year storm event, the pond will have a maximum water surface
elevation of 5109.02 ft, which is a pond volume of approximately 1.33 acre-feet. There is a
difference of 0.48 ft between the 100-year water surface elevation and spillway elevation because
of the tie in elevation along Horsetooth. The top of pond was designed at 5110.50 ft to allow for
1 foot of freeboard above the spillway bottom. Access to the pond and outlet can be achieved by
entering the pond from parking lot and driving along the pond bottom.
Three bioretention ponds, labeled LID Pond 1, 2, and 3, were designed for water quality control.
The WQCV is a total of 5,277 cf. All three ponds have a depth of 1.5 feet for site drainage
purposes. The ponds will include 18 inches or amended soil, 6 inches of squeegee, and 12 inches
of gravel with an underdrain in the gravel section. Both LID Pond 1 and 2 have sufficient bottom
surface areas to treat the required WQCV entering the ponds. LID Pond 1 is required to treat 1,417
cf of WQCV. The pond has a bottom area of 3,347 sqft and will only have approximately 945 sqft
of amended soil and underdrain system along the center of the pond. LID Pond 2 is required to
treat 571 cf of WQCV. The pond has a bottom area of 2,111 sqft and will only have approximately
380 sqft of amended soil and underdrain system along the center of the pond. LID Pond 3 is
required to treat 3,081 cf of WQCV. The pond has a bottom surface area of 1,731 sqft. Therefore,
the amended soil area needs to be included up to an elevation of 5106.69 ft, which is 0.69 ft above
the bottom of the pond. The total ponded area in all three ponds is 17,632 cf, which is much larger
than the required WQCV. The underdrain pipe will have a very shallow slope and will tie into the
outlet structure at a lower elevation than the outlet pipe creating a sump situation. The head from
the higher elevations of the pond bottoms will force the underdrain to empty into the outlet
structure and overflow into the outlet pipe.
HISTORIC/DEVELOPED BASIN COMPARISON
The site contains one historical basin that drains to the east into the Pleasant Valley and Lake
Canal. The developed site still drains primarily to the east, but instead of draining into the Canal,
the runoff is collected and discharged into the Horsetooth storm sewer system. A very small
portion of the site 11.3% drains offsite. This includes the east and north sides of detention ponds
embankment, 0.45 acres and 2.05 cfs, which will drain into the Canal. There is also a portion of
the site, 0.45 acres and 1.76 cfs, which will drain south onto Horsetooth. The existing site has a
peak 100-year runoff rate of 28.78 cfs. As required by the City, the detention pond has a discharge
rate of 2.21 cfs into the Horsetooth system, which is equivalent to the historical 2-year peak runoff
rate. In the event that the detention ponds outlet pipe is clogged, the pond’s overflow spillway
will safely convey flow onto Horsetooth at a peak rate of 43.71 cfs. The site’s three LID ponds
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will treat 99.16% of the sites WQCV, with only 0.98% of the impervious area draining offsite.
The LID ponds will have amended soils with an underdrain system to promote infiltration.
STORMWATER POLLUTION PREVENTION/EROSION CONTROL
TEMPORARY EROSION CONTROL
A temporary erosion control plan is to be implemented for the site during construction. Temporary
erosion control measures include, but are not limited to, slope and swale protection provided by
the use of erosion control wattles/sediment control logs, inlet protection, vehicle tracking control
at access points to the site. All temporary erosion control measures are to be removed after they
are deemed unnecessary. Refer to the Erosion Control Plan and Details for the Village on
Horsetooth for additional detailed information.
PERMANENT EROSION CONTROL
Chapter 2 of the Urban Drainage and Flood Control District’s Urban Storm Drainage Criteria
Manual Volume 3 (USDCM) provides guidelines for the selection of appropriate permanent
structural BMPs for a site that is to be developed or redeveloped. The Village on Horsetooth is
best characterized as a “conventional redevelopment” with over 1 acre of impervious area on the
project site. The BMP decision tree for such sites is provided in Figure 2-2 of the USDCM. As
previously stated, the site and surrounding vicinity is comprised of hydrologic soil group Type B
soils, per the NRCS soil survey, with a depth to bedrock of greater than 5 feet.
Permanent erosion control measures include, but are not limited to, the constructed detention
ponds, riprap pads placed for culvert and flared end section outlet protection, seeding and mulch
placed to enable and established vegetative growth, etc. Long-term maintenance of these erosion
control measures shall be the responsibility of the owner of the property. A general erosion control
plan has been provided in the construction documents.
STORMWATER MANAGEMENT CONTROLS
The Stormwater Management Plan (SWMP) administrator is to be determined.
According to the CDPHE Stormwater Fact Sheet – Construction, construction activities produce
many different kinds of pollutants which may cause stormwater contamination problems. The main
pollutant of concern at construction sites is sediment. Grading activities remove grass, rocks,
pavement, and other protective ground covers, resulting in the exposure of underlying soil to the
elements. The soil is then easily picked up by wind and/or washed away by rain or snowmelt.
In addition, construction activities often require the use of toxic or hazardous materials such as
fuel, fertilizers, pesticides, and herbicides, and building materials such as asphalt, sealants, and
concrete, which may also pollute stormwater. These materials can be harmful to humans, plants,
and aquatic life.
There are no known potential pollution sources. However, this condition should be confirmed by
the owner/operator or SWMP administrator. Other pollution sources that could be present include:
runoff from vehicle washing, vehicle maintenance and/or fueling, There are no known existing
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non-stormwater components of discharge (i.e., springs, landscape irrigation return flow, etc.), or
any anticipated during construction.
1. All Disturbed and Stored Soil:
The total disturbed area will be approximately 8.3 acres. Soil stockpiles should be kept
below the locally mandated maximum height of 10 feet and surrounded with sediment
control devices. If the storage of these soils occurs over a period greater than 30 days,
then consider temporarily seeding the soil to minimize soil loss to wind and water
erosion.
2. Vehicle Tracking of Sediments:
The majority of the existing site is unpaved. A temporary stabilized stone pad (Vehicle
Tracking Control pad, VTC) will be provided at points of ingress and egress onto the
unpaved area. The VTC is designed to reduce the amount of mud transported onto the
public roads by construction traffic. If the site is extraordinarily muddy, then consider
designating an area to wash construction vehicles before they leave the site and enter
the public right-of-way. A BMP such as this is a good way to avoid the costs associated
with street cleaning or accidentally discharging large amounts of sediment into other
storm drain systems.
When in doubt, choose methods that prevent pollution rather than ones that force
clean-up at the downstream end just before the stormwater enters the receiving
waters. In other words, the most efficient construction site BMPs are those that
prevent erosion from happening.
3. Inlet Protection (IP): gravel inlet protection will be used on all inlets to prevent
sediment and debris from entering the storm drain system.
4. Street sweeping will be conducted as necessary to remove sediment tracked on to
pavement and adjacent streets.
5. Management of Contaminated Soils:
There are no known contaminated soils on site. If contaminated soils are found, the
contractor shall report to the SWMP administrator.
6. Loading and Unloading Operations:
Loading/unloading activities will occur within the paved area of the site or a
temporary gravel staging area will be provided.
7. Outdoor Storage Activities:
Materials storage, waste disposal, and vehicle maintenance and fueling can occur
within an enclosed and secure area.
8. Vehicle and Equipment Maintenance and Fueling:
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Materials should be stored and handled in covered areas to prevent contact with
stormwater, and chemicals should be stored within berms or secondary containment
devices to prevent leaks and spills from entering stormwater runoff.
Spill Management
In general, spill prevention and response should include the following:
a) Notification procedures to be used in the event of an accident. At the very
least, the SWMP Administrator should be notified. Depending on the nature
of the spill and the material involved, the Colorado Department of Health,
downstream water users, or other agencies may also need to be notified.
b) Instructions for clean-up procedures.
c) Provisions for absorbents are to be made available for use in fuel areas, and
for containers to be available for used absorbents.
d) Procedures for properly washing out concrete trucks and other equipment in a
manner and location so that the materials and wash water cannot discharge
from the site, and never into a storm drain system or stream.
9. Significant Dust or Particulate Generating Processes:
Disturbed areas not yet ready to be seeded, landscaped, paved, or otherwise stabilized
shall be watered, or ripped as necessary to preclude visible dust emissions. Contractor
shall make every effort to minimize particulate emissions from vehicles performing the
work, including but not limited to regular maintenance of construction equipment.
10. Routine Maintenance Activates Involving Fertilizer, Pesticides, Detergents, Fuels,
Solvents, Oils, Etc:
Materials should be stored and handled in covered areas to prevent contact with
stormwater, and chemicals should be stored within berms or secondary containment
devices to prevent leaks and spills from entering stormwater runoff.
11. On-site Waste Management Practices (Waste Piles, Liquid Wastes, Dumpsters, etc):
Materials storage, waste disposal, and vehicle maintenance and fueling can occur
within an enclosed and secure area. The area can be enclosed with temporary fencing
and accessed through a gate with a lock.
12. Concrete Truck/Equipment Washing:
A concrete washout facility will be provided onsite. Properly wash out concrete trucks
and other equipment in a manner and location (a minimum of 50 feet away from any
inlet structures) so that the materials and wash water cannot discharge from the site,
and never into a storm drain system or stream.
13. Dedicated Asphalt and Concrete Batch Plants:
There will be no dedicated batch plant on site.
14. Non-Industrial Waste Source Such as Workers Trash And Portable Toilets:
Fort Collins Housing Authority - Village on Horsetooth
Page 14 of 16
Garbage cans shall be located at break areas and portable toilets shall be provided if
onsite bathroom facilities cannot be used. Locate dumpsters and portable toilets away
from drainage courses (minimum 50 feet from any inlet structures) and stake down
toilets to prevent tipping.
15. Other Areas or Procedures where Potential Spills can Occur:
Records of spills, leaks, or overflows that result in the discharge of pollutants must be
documented and maintained. Record all spills that are responded to, even if they do
not result in a discharge of pollutants. Information that should be recorded for all
occurrences includes the time and date, weather conditions, reasons for the spill, etc.
Some spills may need to be reported to immediately. Specifically, a release of any
chemical, oil, petroleum product, sewage, etc., which may enter waters of the State of
Colorado (which include surface water, ground water and dry gullies or storm sewers
leading to surface water) must be reported. More guidance is available on the web at
www.colorado.gov. The Division’s toll-free 24-hour number for environmental
hazards and chemical spills and releases is 1-877-518-5608.
SEQUENCE OF CONSTRUCTION ACTIVITIES
Construction Start Date (This is the day you expect to begin disturbing soils, including grubbing,
stockpiling, excavating, demolition, and grading activities): January 2017
Final Stabilization Date (this is when the site is finally stabilized. This means that all disturbed
areas have been either built on, paved, or a uniform vegetative cover reaching over 70% of the
initial vegetative density has been established.) Even if you are doing one part of the project, the
estimated completion date must be for the overall project: June 2018
Construction Sequencing: (Detailed construction sequencing to be determined by the contractor)
1. Installation of temporary erosion and sediment control measures.
This includes all sediment control logs, and inlet protection where land disturbing activities
will occur.
2. Sequence of all land disturbing activity.
Overlot grading in preparation for pouring of new sidewalks and building foundations will
occur early in the construction schedule. Additional land disturbance will occur around the
site for utility installation and the construction of the new driveway approach and sidewalk.
3. Drainage facility construction.
Construction of the detention pond, storm inlets and piping will occur early in the schedule.
4. Sediment basins, temporary channel stabilization.
Sediment control logs or erosion control blankets will be installed on the banks of the
vegetated detention pond and swale on the east side of the site.
5. Seeding
All disturbed areas will be seeded upon completing of finish grading. Refer to the landscape
plans for detailed planting and seeding schedule.
6. Mulching.
Fort Collins Housing Authority - Village on Horsetooth
Page 15 of 16
Spread straw mulch uniformly over seeded areas at a rate of 90 lbs per 1000 square feet of
ground. No more than 25% of the ground should be visible. Crimp or pinch mulch into
soil 2-4 inches by using either a mulch anchoring tool, a farm disk operating on the contour
of the slope, or by cleating with bulldozer tracks operating up and down the slopes (to
prevent tracks from forming gullies).
7. Required maintenance activities (e.g. after-storm checks of all BMPs, etc.).
All temporary sediment control BMPs shall be inspected after each rain event to ensure
proper protection and to determine if cleaning is necessary. Final cleaning of all storm
facilities shall be provided upon final stabilization of site.
CONCLUSIONS
This Preliminary Drainage and Erosion Control Report for the Fort Collins Housing Authority
Village on Horsetooth has been prepared to comply with the stormwater criteria set by the UDFCD
and the City of Fort Collins.
The proposed drainage system presented in this report is designed to convey the 100-year peak
stormwater runoff through the site to the proposed detention pond. Through calculations and
review of the proposed storm drain system, there appears to be adequate capacity to convey the
proposed flows. This report also proposes best management practices for erosion control,
permanent landscaping, riprap, and on-site construction facilities.
It can therefore be concluded that development of the detention pond complies with all of the
stormwater jurisdictional criteria and will not adversely affect the existing streets, storm drain
system and/or detention/water quality facilities.
Fort Collins Housing Authority - Village on Horsetooth
Page 16 of 16
REFERENCES
1. Urban Storm Drainage Criteria Manual (Volumes 1, 2, and 3), Urban Drainage and Flood
Control District, June 2001, January 2016.
2. City of Fort Collins Stormwater Criteria Manual, City of Fort Collins, December 2013.
3. “Geotechnical Investigation FCHA Village At Horsetooth 1506 West Horsetooth Road
Fort Collins, Colorado”, CTL Thompson Incorporated, Dated July 19, 2016.
4. City of Fort Collins Foothills Basin Master Plan, Retrieved from http://www.fcgov.com/
utilities/what-we-do/stormwater/drainage-basins/foothills-basin on August 8, 2016.
APPENDIX A – FIGURES
SHEET NUMBER
C JVA, INC
DATE:
JOB NUMBER:
CHECKED BY:
DRAWN BY:
DESIGNED BY:
NO. DATE DRAWN DESIGNED REVISION / ISSUE DESCRIPTION
JVA, Incorporated 25 Old Town Square
Suite 200 Fort Collins, CO 80524
E-mail: info@jvajva.com
Phone: 970.225.9099 Fax: 970.225.6963
CONSULTING ENGINEERS
FCHA - VILLAGE ON HORSETOOTH
2595c
09/20/2016
HISTORIC DRAINAGE MAP
LAT
LAT
CRH
FIG 2
SHEET NUMBER
C JVA, INC
DATE:
JOB NUMBER:
CHECKED BY:
DRAWN BY:
DESIGNED BY:
NO. DATE DRAWN DESIGNED REVISION / ISSUE DESCRIPTION
JVA, Incorporated 25 Old Town Square
Suite 200 Fort Collins, CO 80524
E-mail: info@jvajva.com
Phone: 970.225.9099 Fax: 970.225.6963
CONSULTING ENGINEERS
VILLAGE ON HORSETOOTH
2595c
09/20/2016
DEVELOPED DRAINAGE MAP
LAT
LAT
CRH
FIG 3
APPENDIX B – HYDRAULIC/HYDROLOGIC
COMPUTATIONS
JVA Incorporated JVA Office:
25 Old Town Square, S 200 Fort Collins
Fort Collins, CO 80524
Ph: (970) 225 9099
Version 2016_XT: 6/30/2016
Project Information:
Job Name: Village On Horsetooth
Job Number: 2595c
Date: 9/20/2016
Designed by: LAT
Municipality : Fort_Collins Soil Type: B
Runoff Calculations:
Minor Design Storm: 2 year
Major Design Storm: 100 year
Detention Calculations:
Minor Storm Detention: 2 year plus 0 % WQCV
Major Storm Detention: 100 year plus 0 % WQCV
Detention Volume by: ≤5ac FAA >5ac FAA+20% Enter WQCV : 1,417 cf
(GB, PP, PLD, SFB, EDB,etc.)
Allowable Release Rates (if applicable):
Max release rate 1 cfs / acre? No Site Area: 7.96 acres
Enter Offsite flows to bypass site (these will be added to the allowable release rates)
Q2 = 0.00 cfs (bypass flows) Q2allow= 2.21 cfs
Q100 = 0.00 cfs (bypass flows) Q100allow = 2.21 cfs
Rainfall Data Information:
Enter City, Town, or County: Fort_Collins
Frequency of Design
Event
Do you need to Calc P1? No
2 yr 0.82 in
5 yr 1.14 in
10 yr 1.40 in
100 yr 2.86 in
Runoff Coefficient Calculations:
Use UDFCD Equations? Yes
Intensity Duration Values:
I-D-F FortCollinsIDF
One Hour Point Rainfall P1
2595c - Rational Calculations 9182016.xlsx INTRO Page 1 of 1
JVA Incorporated Job Name: Village On Horsetooth
25 Old Town Square, S 200 Job Number: 2595c
Fort Collins, CO 80524 Date: 9/20/16
Ph: (970) 225 9099 By: LAT
Village On Horsetooth
Historic Runoff Coefficient & Time of Concentration Calculations
Location: Fort_Collins
Minor Design Storm: 2
Major Design Storm: 100
Soil Type: B
Basin Design Data
I (%) = 100% 90% 90% 40% 25% 25% 2% 2% I (%) tc Comp
tc
Final
Basin
Name
Design
Point
Apaved
streets
(sf)
Adrives/co
nc (sf)
Aroof
(sf)
Agravel
(sf)
Aplygnd
(sf)
Aart. turf
(sf)
Alscape (B
soil)
(sf)
Alscape
(C/D soil)
(sf)
ATotal
(sf)
ATotal
(ac)
Imp
(%)
C2 C5 C10 C100
Upper
most
Length
(ft)
Slope
(%)
ti
(min)
Length
(ft)
Slope
(%)
Type of Land Surface K
Velocity
(fps)
tt
JVA Incorporated Job Name: Village On Horsetooth
25 Old Town Square, S 200 Job Number: 2595c
Fort Collins, CO 80524 Date: 9/20/16
Ph: (970) 225 9099 By: LAT
Village On Horsetooth
Composite Runoff Coefficient Calculations
Location: Fort_Collins
Minor Design Storm: 2
Major Design Storm: 100
Soil Type: B
C Value calculated from UDFCDCM Chapter 6
Basin Design Data
I (%) = 100% 90% 90% 40% 25% 25% 2% 2% I (%)
Basin
Name
Design
Point
Apaved
streets
(sf)
Adrives/c
onc (sf)
Aroof
(sf)
Agravel
(sf)
Aplygnd
(sf)
Aart. turf
(sf)
Alscape (B
soil)
(sf)
Alscape
(C/D soil)
(sf)
ATotal
(sf)
ATotal
(ac)
Imp
(%)
C2 C5 C10 C100
A1 1 19,060 10,428 18,268 47,760 1.10 60.3% 0.54 0.56 0.61 0.75
A2 2 6,554 5,593 11,621 23,768 0.55 49.7% 0.44 0.46 0.53 0.70
A3 3 12,305 8,228 8,480 29,013 0.67 68.5% 0.61 0.64 0.68 0.79
A4 4 5,356 3,381 3,148 11,885 0.27 71.2% 0.63 0.66 0.70 0.80
A5 5 11,570 4,297 44,084 59,951 1.38 21.7% 0.19 0.20 0.30 0.56
A6 6 17,136 8,997 12,246 38,379 0.88 66.4% 0.59 0.62 0.66 0.78
A7 7 2,584 34,520 37,104 0.85 8.1% 0.07 0.08 0.19 0.49
B1 8 721 1,432 17,647 19,800 0.45 11.9% 0.11 0.11 0.22 0.51
B2 9 200 5,665 5,865 0.13 5.0% 0.04 0.05 0.17 0.48
B3 10 13,613 13,613 0.31 2.0% 0.02 0.02 0.14 0.46
R1 11 7,180 7,180 0.16 90.0% 0.80 0.84 0.85 0.90
R2 12 7,081 7,081 0.16 90.0% 0.80 0.84 0.85 0.90
R3 13 7,180 7,180 0.16 90.0% 0.80 0.84 0.85 0.90
R4 14 4,814 4,814 0.11 90.0% 0.80 0.84 0.85 0.90
R5 15 2,973 2,973 0.07 90.0% 0.80 0.84 0.85 0.90
R6 16 4,426 4,426 0.10 90.0% 0.80 0.84 0.85 0.90
R7 17 7,081 7,081 0.16 90.0% 0.80 0.84 0.85 0.90
JVA Incorporated Job Name: Village On Horsetooth
25 Old Town Square, S 200 Job Number: 2595c
Fort Collins, CO 80524 Date: 9/20/16
Ph: (970) 225 9099 By: LAT
Village On Horsetooth
Composite Runoff Coefficient Calculations
Location: Fort_Collins
Minor Design Storm: 2
Major Design Storm: 100
Soil Type: B
C Value calculated from UDFCDCM Chapter 6
Basin Design Data
I (%) = 100% 90% 90% 40% 25% 25% 2% 2% I (%)
Basin
Name
Design
Point
Apaved
streets
(sf)
Adrives/c
onc (sf)
Aroof
(sf)
Agravel
(sf)
Aplygnd
(sf)
Aart. turf
(sf)
Alscape (B
soil)
(sf)
Alscape
(C/D soil)
(sf)
ATotal
(sf)
ATotal
(ac)
Imp
(%)
C2 C5 C10 C100
Runoff Coeff's
19,060 10,428 18,687 0 0 0 18,268 0 66,443 1.53 68.7% 0.61 0.64 0.68 0.79
6,554 5,593 7,081 0 0 0 11,621 0 30,849 0.71 59.0% 0.52 0.55 0.60 0.74
34,797 32,176 33,654 4,297 0 0 67,958 0 172,882 3.97 56.2% 0.50 0.52 0.58 0.73
721 1,632 0 0 0 0 36,925 0 39,278 0.90 7.5% 0.07 0.07 0.19 0.49
60,411 50,781 59,422 4,297 0 0 132,367 0 307,278 7.05 53.4% 0.47 0.50 0.56 0.72
SITE
% Imperv
Total Area
(ft2)
Area of
Imperv
(ft2)
Total
Area
(ft2)
7.5% 39,278 2,928 346,556
JVA Incorporated Job Name: Village On Horsetooth
25 Old Town Square, S 200 Job Number: 2595c
Fort Collins, CO 80524 Date: 9/20/2016
Ph: (970) 225 9099 By: LAT
Village On Horsetooth
Water Quality Capture Volume (WQCV) Calculations (UDFCD Volume 3 Chapter 3)
Location: Fort_Collins
Major Design Storm: 100
Soil Type: B
WQCV=a((0.91I3)-(1.19I2)+(0.78I))
Where:
WQCV = Water Quality Capture Volume (watershed inches)
a = Drain Time Coefficient (see table below )
I = Imperviousness (%/100)
Drainage Time (hrs) Coefficient, a
12 0.8 Rain Garden =12hours
24 0.9
40 1.00
LID POND 1 LID POND 2 LID POND 3
a= 0.80 a= 0.80 a= 0.80
I= 0.687 %/100 I= 0.590 %/100 I= 0.562 %/100
WQCV= 0.213 watershed inches WQCV= 0.185 watershed inches WQCV= 0.178 watershed inches
Vrequired=1.2*(WQCV/12)*A*43560 Vrequired=1.2*(WQCV/12)*A*43560 Vrequired=1.2*(WQCV/12)*A*43560
WQCV= 0.213 watershed inches WQCV= 0.185 watershed inches WQCV= 0.178 watershed inches
A = 1.53 acre A = 0.71 acre A = 3.97 acre
Vrequired = 1417 cf Vrequired = 571 cf Vrequired = 3081 cf
Vrequired = 0.033 acre-ft Vrequired = 0.013 acre-ft Vrequired = 0.071 acre-ft
WQCV ONSITE (ALL A BASIN AND R BASIN)
a= 0.80
I= 0.534 %/100
WQCV= 0.172 watershed inches
Vrequired=1.2*(WQCV/12)*A*43560
WQCV= 0.172 watershed inches
A = 7.05 acre
Vrequired = 5277 cf
Vrequired = 0.121 acre-ft
JVA Incorporated Job Name: Village On Horsetooth
25 Old Town Square, S 200 Job Number: 2595c
Fort Collins, CO 80524 Date: 9/20/2016
Ph: (970) 225 9099 By: LAT
Village On Horsetooth
Bioretention Ponds LID Underdrain Design (UDFCD Volume 3 Chapter 4)
Location: Fort_Collins
Onsite Required WQCV 5,277
Soil Type: B
LID Pond 1 WEIGHTED INCREMENTAL CUMMULATIVE
Required WQCV= 1,417 cf ELEVATION DEPTH (D) AREA (A1) AVG AREA (A2) VOLUME VOLUME
Bottom Area= 3,347 sf ft ft ft
2
ft
2
ft
3
ft
3
Total Height of LID= 1.50 ft 5107.0 3,347 0
Provided Volume= 7,570 cf 5108.0 1.0 5,398 4,373 4,332 4,332
Area of Amended Soil= 945 sf 5108.5 0.5 7,617 6,508 3,238 7,570
Top of Pond
5108.50 1.50 7,570 cf 0.174 ac-ft
LID Pond 2
Required WQCV= 571 cf WEIGHTED INCREMENTAL CUMMULATIVE
Bottom Area= 2,111 sf ELEVATION DEPTH (D) AREA (A1) AVG AREA (A2) VOLUME VOLUME
Total Height of LID= 1.50 ft ft ft ft
2
ft
2
ft
3
ft
3
Provided Volume= 5,536 cf 5107.0 2,111 0
Area of Amended Soil= 381 sf 5108.0 1.0 4,084 3,098 3,044 3,044
5108.5 0.5 5,944 5,014 2,492 5,536
Top of Pond
5108.50 1.50 5,536 cf 0.127 ac-ft
LID Pond 3
Required WQCV= 3,081 cf WEIGHTED INCREMENTAL CUMMULATIVE
Bottom Area= 1,731 sf ELEVATION DEPTH (D) AREA (A1) AVG AREA (A2) VOLUME VOLUME
Total Height of LID= 1.50 ft ft ft ft
2
ft
2
ft
3
ft
3
Provided Volume= 4,526 cf 5106.0 1,731 0
Area of Amended Soil= 2,054 sf* 5106.25 0.25 2,148 1,940 484 484
*bottom area plus part of side slope 5106.5 0.3 2,574 2,153 589 1,073
5107.0 0.5 3,448 2,590 1,500 2,574
5107.5 0.5 4,381 3,915 1,953 4,526
Top of Pond
5107.50 1.50 4,526 cf 0.104 ac-ft
* Uses Prismoidal Formula
Total Site LID Volume 17,632 cf
JVA Incorporated Job Name: Village On Horsetooth
25 Old Town Square, S 200 Job Number: 2595c
Fort Collins, CO 80524 Date: 9/20/16
Ph: (970) 225 9099 By: LAT
Village On Horsetooth
Time of Concentration Calculations
Location: Fort_Collins
Minor Design Storm: 2
Major Design Storm: 100
Soil Type: B
Sub-Basin Data tc
Comp
tc
Final
Basin
Name
Design
Point
ATotal
(ac)
C5
Upper
most
Length
(ft)
Slope
(%)
ti
(min)
Length
(ft)
Slope (%) Type of Land Surface Cv
Velocity
(fps)
tt
(min)
Time of
Conc
ti
+ tt
= tc
Total
Length
(ft)
tc
=(L/180)+
10 (min)
Min
tc
A1 1 1.10 0.56 49 4.3% 4.3 372 1.0%
Paved areas & shallow
paved swales
20 2.0 3.1 7.4 421 12.3 7.4
A2 2 0.55 0.46 55 2.7% 6.2 178 0.9% Grassed waterway 15 1.4 2.1 8.3 233 11.3 8.3
A3 3 0.67 0.64 90 1.8% 6.6 134 0.6%
Paved areas & shallow
paved swales
20 1.5 1.5 8.1 224 11.2 8.1
A4 4 0.27 0.66 78 1.3% 6.5 29 2.2%
Paved areas & shallow
JVA Incorporated Job Name: Village On Horsetooth
25 Old Town Square, S 200 Job Number: 2595c
Fort Collins, CO 80524 Date: 9/20/16
Ph: (970) 225 9099 By: LAT
Village On Horsetooth Developed Storm Runoff Calculations
Design Storm : 2 Year Point Hour Rainfall (P
1) : 0.82
Basin Name
Design Point
Area (ac)
Runoff Coeff
tc (min)
C*A (ac)
I (in/hr)
Q (cfs)
Total tc (min)
ΣC*A (ac)
I (in/hr)
Q (cfs)
Inlet Type
Q intercepted
Q carryover
Q bypass
Pipe Size (in)
or equivalent
Pipe Material
Slope (%)
Pipe Flow
(cfs)
Max Pipe
Capacity (cfs)
Length (ft)
Velocity (fps)
tt (min)
Total Time
(min)
Notes
A1 1 1.10 0.54 7.40 0.59 2.47 1.46 7.40 0.59 2.47 1.46
A2 2 0.55 0.44 8.30 0.24 2.37 0.57 8.30 0.24 2.37 0.57
A3 3 0.67 0.61 8.10 0.41 2.39 0.97 8.10 0.41 2.39 0.97
A4 4 0.27 0.63 6.70 0.17 2.57 0.44 6.70 0.17 2.57 0.44
A5 5 1.38 0.19 11.00 0.27 2.13 0.57 11.00 0.27 2.13 0.57
A6 6 0.88 0.59 7.10 0.52 2.51 1.31 7.10 0.52 2.51 1.31
A7 7 0.85 0.07 10.10 0.06 2.20 0.14 10.10 0.06 2.20 0.14
B1 8 0.45 0.11 10.60 0.05 2.16 0.10 10.60 0.05 2.16 0.10
B2 9 0.13 0.04 5.90 0.01 2.69 0.02 5.90 0.01 2.69 0.02
B3 10 0.31 0.02 5.00 0.01 2.85 0.02 5.00 0.01 2.85 0.02
R1 11 0.16 0.80 5.00 0.13 2.85 0.38 5.00 0.13 2.85 0.38
R2 12 0.16 0.80 5.00 0.13 2.85 0.37 5.00 0.13 2.85 0.37
R3 13 0.16 0.80 5.00 0.13 2.85 0.38 5.00 0.13 2.85 0.38
R4 14 0.11 0.80 5.00 0.09 2.85 0.25 5.00 0.09 2.85 0.25
R5 15 0.07 0.80 5.00 0.05 2.85 0.16 5.00 0.05 2.85 0.16
R6 16 0.10 0.80 5.00 0.08 2.85 0.23 5.00 0.08 2.85 0.23
R7 17 0.16 0.80 5.00 0.13 2.85 0.37 5.00 0.13 2.85 0.37
R8 18 0.16 0.80 5.00 0.13 2.85 0.38 5.00 0.13 2.85 0.38
R9 19 0.16 0.80 5.00 0.13 2.85 0.37 5.00 0.13 2.85 0.37
R10 20 0.10 0.80 5.00 0.08 2.85 0.23 5.00 0.08 2.85 0.23
Total to Pond 8.56
Total Site 8.70
Total Offsite 0.14
JVA Incorporated Job Name: Village On Horsetooth
25 Old Town Square, S 200 Job Number: 2595c
Fort Collins, CO 80524 Date: 9/20/16
Ph: (970) 225 9099 By: LAT
Village On Horsetooth Developed Storm Runoff Calculations
Design Storm : 100 Year Point Hour Rainfall (P
1) : 2.86
Basin Name
Design Point
Area (ac)
Runoff Coeff
tc (min)
C*A (ac)
I (in/hr)
Q (cfs)
Total tc (min)
ΣC*A (ac)
I (in/hr)
Q (cfs)
Inlet Type
Q intercepted
Q carryover
Q bypass
Pipe Size (in)
or equivalent
Pipe Material
Slope (%)
Pipe Flow
(cfs)
Max Pipe
Capacity (cfs)
Length (ft)
Velocity (fps)
tt (min)
Total Time
(min)
Notes
A1 1 1.10 0.75 7.40 0.82 8.63 7.09 7.40 0.82 8.63 7.09
A2 2 0.55 0.70 8.30 0.38 8.28 3.15 8.30 0.38 8.28 3.15
A3 3 0.67 0.79 8.10 0.53 8.35 4.39 8.10 0.53 8.35 4.39
A4 4 0.27 0.80 6.70 0.22 8.95 1.96 6.70 0.22 8.95 1.96
A5 5 1.38 0.56 11.00 0.77 7.42 5.72 11.00 0.77 7.42 5.72
A6 6 0.88 0.78 7.10 0.69 8.76 6.01 7.10 0.69 8.76 6.01
A7 7 0.85 0.49 10.10 0.42 7.69 3.23 10.10 0.42 7.69 3.23
B1 8 0.45 0.51 10.60 0.23 7.54 1.76 10.60 0.23 7.54 1.76
B2 9 0.13 0.48 5.90 0.06 9.37 0.60 5.90 0.06 9.37 0.60
B3 10 0.31 0.46 5.00 0.14 9.95 1.44 5.00 0.14 9.95 1.44
R1 11 0.16 0.90 5.00 0.15 9.95 1.47 5.00 0.15 9.95 1.47
R2 12 0.16 0.90 5.00 0.15 9.95 1.45 5.00 0.15 9.95 1.45
R3 13 0.16 0.90 5.00 0.15 9.95 1.47 5.00 0.15 9.95 1.47
R4 14 0.11 0.90 5.00 0.10 9.95 0.98 5.00 0.10 9.95 0.98
R5 15 0.07 0.90 5.00 0.06 9.95 0.61 5.00 0.06 9.95 0.61
R6 16 0.10 0.90 5.00 0.09 9.95 0.90 5.00 0.09 9.95 0.90
R7 17 0.16 0.90 5.00 0.15 9.95 1.45 5.00 0.15 9.95 1.45
R8 18 0.16 0.90 5.00 0.15 9.95 1.47 5.00 0.15 9.95 1.47
R9 19 0.16 0.90 5.00 0.15 9.95 1.45 5.00 0.15 9.95 1.45
R10 20 0.10 0.90 5.00 0.09 9.95 0.90 5.00 0.09 9.95 0.90
Total to Pond 43.71
Total Site 47.52
Total Offsite 3.80
JVA Incorporated Job Name: Village On Horsetooth
25 Old Town Square, S 200 Job Number: 2595c
Fort Collins, CO 80524 Date: 9/20/16
Ph: (970) 225 9099 By: LAT
Village On Horsetooth
Detention Pond Volume Calculations: FAA Procedure
Based on FAA Procedure, per Federal Aviation Agency "Airport Drainage" Manual
Drainage Basin A
Design Storm 2 year
Composite "C" Factor 0.56
Time of Concentration Tc 11.00 min (Max Tc)
Basin Size 7.05 acre
Release Rate Calculations
Allowable Release Rate for Site 2.21 cfs (Historic Flows for Basin H1)
Less Undetained Offsite Flows - 0.00 cfs
Allowable Release Rate for Pond 2.21 cfs
Rainfall Intensity Calculations
Point Hour Rainfall (P1) : 0.82 C1= 28.5
Rainfall Intensity: FortCollinsIDF C2= 10
I= C1*P1/(C2+T0)^C3 C3= 0.789
Volume Calculations
Inflow Volume = C * I * A * time (sec)
Outflow Volume = Alowable Release Rate * time (sec)
Storage Volume = Inflow Volume - Outflow Volume
Time
t
(min)
Intensity
I
(in/hr)
Inflow
Vin
(ft3)
Outflow
Adjustment
Factor m
Average
Outflow
(cfs)
Outflow
Vout
(ft3)
Storage
Vstor
(ft3)
5.0 2.85 3,361 1.00 2.21 662 2,699
10.0 2.21 5,212 1.00 2.21 1,324 3,888
15.0 1.87 6,615 0.87 1.91 1,721 4,895
20.0 1.61 7,594 0.78 1.71 2,052 5,542
25.0 1.43 8,431 0.72 1.59 2,383 6,049
30.0 1.30 9,198 0.68 1.51 2,713 6,484
35.0 1.17 9,674 0.66 1.45 3,044 6,630
40.0 1.07 10,113 0.64 1.41 3,375 6,737
45.0 0.99 10,528 0.62 1.37 3,706 6,822
50.0 0.92 10,872 0.61 1.35 4,037 6,835
55.0 0.87 11,298 0.60 1.32 4,368 6,930
60.0 0.82 11,603 0.59 1.31 4,699 6,904
65.0 0.77 11,878 0.58 1.29 5,030 6,849 Intensity Equation
70.0 0.74 12,157 0.58 1.28 5,361 6,796
75.0 0.70 12,417 0.57 1.26 5,692 6,725
JVA Incorporated Job Name: Village On Horsetooth
25 Old Town Square, S 200 Job Number: 2595c
Fort Collins, CO 80524 Date: 9/20/16
Ph: (970) 225 9099 By: LAT
Village On Horsetooth
Detention Pond Volume Calculations: FAA Procedure
Based on FAA Procedure, per Federal Aviation Agency "Airport Drainage" Manual
Drainage Basin A
Design Storm 100 year
Composite "C" Factor 0.72
Time of Concentration Tc 11.00 min (Max Tc)
Basin Size 7.05 acre
Release Rate Calculations
Allowable Release Rate for Site 2.21 cfs (Historic Flows for Basin H1)
Less Undetained Offsite Flows - 0.00 cfs
Allowable Release Rate for Pond 2.21 cfs
Rainfall Intensity Calculations
Point Hour Rainfall (P1) : 2.86 C1= 28.5
Rainfall Intensity: FortCollinsIDF C2= 10
I= C1*P1/(C2+T0)^C3 C3= 0.789
Volume Calculations
Inflow Volume = C * I * A * time (sec)
Outflow Volume = Alowable Release Rate * time (sec)
Storage Volume = Inflow Volume - Outflow Volume
Time
t
(min)
Intensity
I
(in/hr)
Inflow
Vin
(ft3)
Outflow
Adjustment
Factor m
Average
Outflow
(cfs)
Outflow
Vout
(ft3)
Storage
Vstor
(ft3)
5.0 9.95 15,065 1.00 2.21 662 14,403
10.0 7.72 23,377 1.00 2.21 1,324 22,054
15.0 6.52 29,615 0.87 1.91 1,721 27,895
20.0 5.60 33,915 0.78 1.71 2,052 31,864
25.0 4.98 37,701 0.72 1.59 2,383 35,318
30.0 4.52 41,062 0.68 1.51 2,713 38,348
35.0 4.09 43,327 0.66 1.45 3,044 40,283
40.0 3.75 45,374 0.64 1.41 3,375 41,999
45.0 3.47 47,217 0.62 1.37 3,706 43,510
50.0 3.23 48,965 0.61 1.35 4,037 44,928
55.0 3.03 50,531 0.60 1.32 4,368 46,163
60.0 2.86 51,963 0.59 1.31 4,699 47,264
65.0 2.70 53,196 0.58 1.29 5,030 48,166 Intensity Equation
70.0 2.57 54,444 0.58 1.28 5,361 49,083
75.0 2.45 55,608 0.57 1.26 5,692 49,917
JVA Incorporated Job Name: Village On Horsetooth
25 Old Town Square, S 200 Job Number: 2595c
Fort Collins, CO 80524 Date: 9/20/16
Ph: (970) 225 9099 By: LAT
POND VOLUME CALCULATIONS - STAGE / STORAGE
Pond Volume = Prismoidal Formula
Volume Equation = (A1+A2+SQRT(A1*A2)*D/3
WEIGHTED INCREMENTAL CUMMULATIVE
ELEVATION DEPTH (D) AREA (A1) AVG AREA (A2) VOLUME VOLUME
ft ft ft
2
ft
2
ft
3
ft
3
5105.3 20 0
5105.5 0.2 92 56 10 10
5106.0 0.5 2,404 1,248 494 505
5106.5 0.5 4,003 3,204 1,585 2,090
5107.0 0.5 9,779 6,891 3,340 5,429
5107.5 0.5 12,731 11,255 5,611 11,041
5108.0 0.5 25,773 19,252 9,436 20,477
5108.5 0.5 30,327 28,050 14,010 34,487
5109.0 0.5 61,442 45,885 22,489 56,976
5109.5 0.5 79,226 70,334 35,073 92,049
5110.0 0.5 100,595 89,911 44,849 136,898
5110.5 0.5 116,970 108,783 54,340 191,238
Top of Pond
5110.50 5.20 191,238 cf 4.390 ac-ft
Required
Volume (ft
3
)
Required
Volume (ac-ft)
Water Surface
Elevation Water Depth
V2 + 0% WQCV 6,930 cf 0.159 ac-ft 5107.13 ft 1.83 ft
V100 + 0% WQCV 58,109 cf 1.334 ac-ft 5109.02 ft 3.72 ft
V2 + 0% WQCV V100 + 0% WQCV
Vol Elev Vol Elev
5429.33 5107.00 56975.79 5109.00
6929.79 5107.13 58109.31 5109.02
11040.63 5107.50 92048.73 5109.50
Stage / Storage Input Table
TOTAL VOLUME
Pond Volume Summary Table
Volume Interpolation Calculations
2595c - Rational Calculations 9182016.xlsx Vol Pond Page 1 of 2
JVA Incorporated Job Name: Village On Horsetooth
25 Old Town Square, S 200 Job Number: 2595c
Fort Collins, CO 80524 Date: 9/20/16
Ph: (970) 225 9099 By: LAT
0
Top of Pond
191,238 cf
5110.50
V2 + 0% WQCV
6,930 cf
5107.13 ft
V100 + 0% WQCV
58,109 cf
5109.02 ft
5105.0
5105.5
5106.0
5106.5
5107.0
5107.5
5108.0
5108.5
5109.0
5109.5
5110.0
5110.5
5111.0
0 50,000 100,000 150,000 200,000 250,000
WATER SURFACE ELEVATION
(FEET ABOVE MSL)
POND VOLUME (CF)
STAGE VS. STORAGE
Water Quality Detention Pond
2595c - Rational Calculations 9182016.xlsx Vol Pond Page 2 of 2
JVA Incorporated Job Name: Village On Horsetooth
25 Old Town Square, S 200 Job Number: 2595c
Fort Collins, CO 80524 Date: 9/20/16
Ph: (970) 225 9099 By: LAT
ORIFICE PLATE AT OUTLET PIPE WORKSHEET
Orifice Plate using Headwater above opening and
Q=cA(2gH)^.5 C= 0.65 QMAJOR
allowable release rate: 2.21 cfs
Summary of Available Pipe Releases 100-yr Water Surface Elev: 5109.02 ft
Pipe Dia Area Head H Q Inv Elev at Outlet Struct: 5105.20 ft
Outfall Pipe at centroid avail out Outlet Pipe at Structure: 15 in
(in) (sf) (ft) (cfs)
12 0.79 3.32 7.46
15 1.23 3.19 11.43
18 1.77 3.07 16.13
24 3.14 2.82 27.49
30 4.91 2.57 41.00
36 7.07 2.32 56.09
Q=cA(2gH)^.5 C= 0.65
Iteration process
Q 2.21 cfs
c 0.65
Hhead
3.19 ft
Needed Area 0.24 sf
Using Area- determine
Ao 0.24 sf
Apipe 1.23 sf
theta 4.188 rad
Ao-calced 0.24 sf
m -0.31 ft distance above(+) or below(-) center
H 0.31 ft Height above pipe invert
+
JVA Incorporated Job Name: CSU Medical Center
25 Old Town Square Job Number: 2487c
Fort Collins, CO 80524 Date: 9/20/16
Ph: 970.225.9099 By: LAT
Fax: 970.225.6923
CSU Medical Center
Emergency Overflow Spillway Calculations
Broad-Crested Weir Equation-Trapezoidal Shape
where: Q = Discharge (cfs)
C = Weir Coeffecient
L = Weir Length (ft)
H = Average Weir Head (ft)
H:V =Side Slope
Calculations
Knowns: 4.00
0.75
3.087
5609.50
43.71
18.80
19.00
1.00
5610.5
27.00
Berm Width 6.0
Side Slopes (H:V)
Desired Spillway Head
Weir Coefficient
Spillway Elevation
100-yr Pond Inflow
Calculated Spillway
Use Spillway Length
Spillway Depth
(including 6" freeboard)
Top of Berm Elevation
Top of Berm Length
2
5
2
3
H
V
H
QCLH C
= +
2595c - Rational Calculations 9182016.xlsx Page 1 of 1 8/28/06
APPENDIX C – REFERENCED DOCUMENTS
400 North Link Lane | Fort Collins, Colorado 80524
Telephone: 970-206-9455 Fax: 970-206-9441
GEOTECHNICAL INVESTIGATION
FCHA VILLAGE AT HORSETOOTH
1506 WEST HORESTOOTH ROAD
FORT COLLINS, COLORADO
FORT COLLINS HOUSING AUTHORITY
1715 West Mountain Avenue
Fort Collins, Colorado 80521
Attention: Kristin Fritz, AICP
Project No. FC07464-120
July 19, 2016
FORT COLLINS HOUSING AUTHORITY
VILLAGE AT HORSETOOTH
CTL | T PROJECT NO. FC07464-120
1
SCOPE
This report presents the results of our Geotechnical Investigation for the
proposed FCHA Village at Horsetooth in Fort Collins, Colorado. The purpose of
the investigation was to evaluate the subsurface conditions and provide founda-
tion recommendations and geotechnical design criteria for the project.
The report was prepared from data developed during field exploration, la-
boratory testing, engineering analysis and experience with similar conditions.
The report includes a description of subsurface conditions found in our explorato-
ry borings and discussions of site development as influenced by geotechnical
considerations. Our opinions and recommendations regarding design criteria
and construction details for site development, foundations, floor systems, slabs-
on-grade, lateral earth loads, pavements and drainage are provided. If the pro-
posed construction changes, we should be requested to review our recommen-
dations. Our conclusions are summarized in the following paragraphs.
SUMMARY OF CONCLUSIONS
1. Soils encountered in our borings consisted of interlayered sandy
clay and clayey sand to the depths explored. Based on laboratory
testing, the soils are generally non-expansive to low-swelling. No
bedrock was encountered in our borings.
2. Groundwater was encountered at depths of 19 to 23 feet during
drilling and was measured several days after drilling at depths of 19
to 22 feet. Existing groundwater levels are not expected to signifi-
cantly affect the proposed construction.
3. We believe the proposed structures can be constructed on a
spread footing foundation placed on natural, undisturbed soil and/or
properly compacted fill. Foundation design and construction rec-
ommendations are presented in this report.
FORT COLLINS HOUSING AUTHORITY
VILLAGE AT HORSETOOTH
CTL | T PROJECT NO. FC07464-120
2
4. We believe slab-on-grade floors are appropriate for this site. Some
movement of slab-on-grade floors should be anticipated. We ex-
pect movements will be minor, on the order of 1 inch or less. If
movement cannot be tolerated, structural floors should be consid-
ered.
5. Pavement subgrade at this site will generally consist of A-4 and A-
2-4 materials according to AASHTO criteria, with expected poor to
good subgrade support. Recommended section thicknesses and
pavement materials are provided in this report.
SITE CONDITIONS AND PROPOSED CONSTRUCTION
The area of proposed development is on the north side of Horsetooth
Road east of Big Ben Drive in Fort Collins, Colorado. An existing residence with
horse stalls and associated pasture areas were located on site at the time of our
investigation. The ground surface is generally flat; vegetation consisted of natural
grasses, weeds and trees. A ditch runs along the eastern boundary of the proper-
ty.
We understand that the proposed construction will consist of nine apart-
ment buildings having 96 units, a club house, and associated paved parking are-
as and access drives. No below grade areas are planned.
INVESTIGATION
Subsurface conditions were investigated by drilling thirteen exploratory
borings to depths of approximately 20 to 30 feet. Our representative observed
drilling operations, logged the soil found in the borings, and obtained samples.
Groundwater measurements were taken during and several days after drilling.
Summary logs of the borings, including results of field penetration resistance
tests, are presented on Figures 2 and 3.
Soil Map—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/11/2016
Page 1 of 3
4487500 4487530 4487560 4487590 4487620 4487650 4487680 4487710
4487500 4487530 4487560 4487590 4487620 4487650 4487680 4487710
490980 491010 491040 491070 491100 491130 491160 491190 491220 491250 491280 491310
490980 491010 491040 491070 491100 491130 491160 491190 491220 491250 491280 491310
40° 32' 24'' N
105° 6' 23'' W
40° 32' 24'' N
105° 6' 8'' W
40° 32' 17'' N
105° 6' 23'' W
40° 32' 17'' N
105° 6' 8'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 50 100 200 300
Feet
0 20 40 80 120
Meters
Map Scale: 1:1,610 if printed on A landscape (11" x 8.5") sheet.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at 1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil line
placement. The maps do not show the small areas of contrasting
soils that could have been shown at a more detailed scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more accurate
calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as of
Map Unit Legend
Larimer County Area, Colorado (CO644)
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
3 Altvan-Satanta loams, 0 to 3
percent slopes
8.2 100.0%
Totals for Area of Interest 8.2 100.0%
Soil Map—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/11/2016
Page 3 of 3
Larimer County Area, Colorado
3—Altvan-Satanta loams, 0 to 3 percent slopes
Map Unit Setting
National map unit symbol: jpw2
Elevation: 5,200 to 6,200 feet
Mean annual precipitation: 13 to 15 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 135 to 150 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Altvan and similar soils: 45 percent
Satanta and similar soils: 30 percent
Minor components: 25 percent
Estimates are based on observations, descriptions, and transects of the
mapunit.
Description of Altvan
Setting
Landform: Benches, terraces
Landform position (three-dimensional): Side slope, tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Mixed alluvium
Typical profile
H1 - 0 to 10 inches: loam
H2 - 10 to 18 inches: clay loam, loam, sandy clay loam
H2 - 10 to 18 inches: loam, fine sandy loam, silt loam
H2 - 10 to 18 inches: gravelly sand, gravelly coarse sand, coarse
sand
H3 - 18 to 30 inches:
H3 - 18 to 30 inches:
H3 - 18 to 30 inches:
H4 - 30 to 60 inches:
H4 - 30 to 60 inches:
H4 - 30 to 60 inches:
Properties and qualities
Slope: 0 to 3 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat):
Moderately high to high (0.60 to 2.00 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 10 percent
Map Unit Description: Altvan-Satanta loams, 0 to 3 percent slopes---Larimer County Area,
Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/11/2016
Page 1 of 3
Available water storage in profile: Very high (about 13.2 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: B
Description of Satanta
Setting
Landform: Structural benches, terraces
Landform position (three-dimensional): Side slope, tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Mixed alluvium and/or eolian deposits
Typical profile
H1 - 0 to 9 inches: loam
H2 - 9 to 18 inches: loam, clay loam, sandy clay loam
H2 - 9 to 18 inches: loam, clay loam, fine sandy loam
H2 - 9 to 18 inches:
H3 - 18 to 60 inches:
H3 - 18 to 60 inches:
H3 - 18 to 60 inches:
Properties and qualities
Slope: 0 to 1 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat):
Moderately high to high (0.60 to 2.00 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 10 percent
Available water storage in profile: Very high (about 27.4 inches)
Interpretive groups
Land capability classification (irrigated): 1
Land capability classification (nonirrigated): 3c
Hydrologic Soil Group: B
Minor Components
Nunn
Percent of map unit: 10 percent
Larim
Percent of map unit: 10 percent
Map Unit Description: Altvan-Satanta loams, 0 to 3 percent slopes---Larimer County Area,
Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/11/2016
Page 2 of 3
Stoneham
Percent of map unit: 5 percent
Data Source Information
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 10, Sep 22, 2015
Map Unit Description: Altvan-Satanta loams, 0 to 3 percent slopes---Larimer County Area,
Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/11/2016
Page 3 of 3
Village On Horsetooth - Wetlands Map
Source: DS,Airbus USDA, Esri, USGS, DigitalGlobe, AEX, Getmapping, GeoEye, Earthstar Aerogrid, Geographics, IGN, IGP, swisstopo, CNES/and
Estuarine and Marine Deepwater
Estuarine and Marine Wetland
Freshwater Emergent Wetland
Freshwater Forested/Shrub Wetland
Freshwater Pond
Lake
Other
Riverine
August 11, 2016
0 0.130325 0.065 0.mi
0 0.05 0.1 0.2 km
1:4,058
This page National was produced Wetlands by the Inventory NWI mapper (NWI)
This Service map is is not for responsible general reference for the accuracy only. The or US currentness Fish and Wildlife of the
base be used data in shown accordance on this with map. the All layer wetlands metadata related found data on should the
Wetlands Mapper web site.
#*
#*
#*
#*
#*
W PROSPECT RD
W DRAKE RD
W HARMONY RD
W HORSETOOTH RD
S TAFT HILL RD
S SHIELDS ST
S COLLEGE AVE
S LEMAY AVE
S TIMBERLINE RD
ZIEGLER RD
P l
e
a
s
a
n
t
V
a
l
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e
y
a
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d
L
a
k
e
Ca
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a l
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w
M
er
c
er
D
i
t
ch
Larime
r
Co
u
nty
C
anal
N
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Larimer
C
ount
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a l
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i
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C
han
n
el
Dixon
C
a
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o
n Lateral
Foothills
Mall Boltz
MS
TiCmhbuerrclihne
Fort HCSollins
EleBmeaetntiteary
SEhleempaerndtsaoryn
S TIMBERLINE RD
E LEMAY AVE
E PROSPECT RD
UP RAILROAD
Warren
Troutman
SCteawsaert
Westfield
FOOTHILLS Water Quality Master Concepetual Plan BASIN Alternatives
Fort ● Retrofit Collins Existing High School Pond to Pond
accommodate Volume Water Quality
Collindale ●Pond Retrofit Existing PUD Pond to
accommodate Volume Water Quality
Warren ● Water Lake Quality Treatment
provided Lake in Existing Warren
Southmoor ● Retrofit Existing Village Pond Pond to
accommodate Volume Water Quality
Lake ● Water Sherwood Quality Treatment
provided Sherwood in Existing Lake
Parkwood ● Retrofit Existing East Pond Pond to
accommodate Volume Water Quality
Proposed Restoration Stream
Improvement
0 500000 1,000 2,[
Feet
NAIP Image - 2009
Proposed BMP Basin Type
Foothills Basin Boundary
Flood Control Only
Water Quality Only
Flood Control and Water Quality
Proposed Improvements
None
Proposed Proposed WaterConceptual Quality Alternatives
Undeveloped Area
Water
Stream - Canal
Parks
Proposed andRestoration Habitat Stream Improvements
#* Proposed Water Quality Pond
SITE
the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 10, Sep 22, 2015
Soil map units are labeled (as space allows) for map scales 1:50,000
or larger.
Date(s) aerial images were photographed: Apr 22, 2011—Apr 28,
2011
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor shifting
of map unit boundaries may be evident.
Soil Map—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/11/2016
Page 2 of 3
−
=
2
* cos
2
sin
2
2 θ θ
π
π θ
A o A pipe r r
=
2
cos θ
m r
H = r + m
2595c - Rational Calculations 9182016.xlsx Major Orifice Page 1 of 1
80.0 2.34 56,700 0.57 1.25 6,022 50,677
85.0 2.24 57,728 0.56 1.25 6,353 51,374
90.0 2.15 58,699 0.56 1.24 6,684 52,015
95.0 2.07 59,620 0.56 1.23 7,015 52,605
100.0 2.00 60,497 0.56 1.22 7,346 53,151
105.0 1.93 61,332 0.55 1.22 7,677 53,655
110.0 1.87 62,131 0.55 1.21 8,008 54,123
115.0 1.81 62,896 0.55 1.21 8,339 54,558
120.0 1.75 63,631 0.55 1.20 8,670 54,961
125.0 1.70 64,338 0.54 1.20 9,001 55,337
130.0 1.65 65,019 0.54 1.20 9,332 55,687
135.0 1.61 65,676 0.54 1.19 9,662 56,013
140.0 1.56 66,310 0.54 1.19 9,993 56,317
145.0 1.52 66,925 0.54 1.19 10,324 56,600
150.0 1.49 67,520 0.54 1.18 10,655 56,865
155.0 1.45 68,097 0.54 1.18 10,986 57,111
160.0 1.42 68,657 0.53 1.18 11,317 57,340
165.0 1.39 69,202 0.53 1.18 11,648 57,554
170.0 1.35 69,731 0.53 1.17 11,979 57,753
175.0 1.33 70,247 0.53 1.17 12,310 57,938
180.0 1.30 70,750 0.53 1.17 12,641 58,109 Max from FoCo CM
Maximum Volume (ft3) 58,109
0% WQCV 0 ft3
Required 100Yr Volume 58,109 ft3
Detention Storage Calculations
2595c - Rational Calculations 9182016.xlsx Modified FAA-100-yr Page 1 of 1
80.0 0.67 12,661 0.57 1.25 6,022 6,638
85.0 0.64 12,890 0.56 1.25 6,353 6,537
90.0 0.62 13,107 0.56 1.24 6,684 6,423
95.0 0.59 13,313 0.56 1.23 7,015 6,298
100.0 0.57 13,509 0.56 1.22 7,346 6,163
105.0 0.55 13,695 0.55 1.22 7,677 6,018
110.0 0.53 13,874 0.55 1.21 8,008 5,866
115.0 0.52 14,044 0.55 1.21 8,339 5,706
120.0 0.50 14,209 0.55 1.20 8,670 5,539
125.0 0.49 14,366 0.54 1.20 9,001 5,366
130.0 0.47 14,518 0.54 1.20 9,332 5,187
135.0 0.46 14,665 0.54 1.19 9,662 5,003
140.0 0.45 14,807 0.54 1.19 9,993 4,813
145.0 0.44 14,944 0.54 1.19 10,324 4,620
150.0 0.43 15,077 0.54 1.18 10,655 4,422
155.0 0.42 15,206 0.54 1.18 10,986 4,220
160.0 0.41 15,331 0.53 1.18 11,317 4,014
165.0 0.40 15,452 0.53 1.18 11,648 3,805
170.0 0.39 15,571 0.53 1.17 11,979 3,592
175.0 0.38 15,686 0.53 1.17 12,310 3,376
180.0 0.37 15,798 0.53 1.17 12,641 3,158 Max from FoCo CM
Maximum Volume (ft3) 6,930
0% WQCV 0 ft3
Required 2Yr Volume 6,930 ft3
Detention Storage Calculations
2595c - Rational Calculations 9182016.xlsx Modified FAA-2-yr Page 1 of 1
Direct Runoff Total Runoff Inlets Pipe Pipe/Swale Travel Time
2595c - Rational Calculations 9182016.xlsx Q100 Page 1 of 1
Direct Runoff Total Runoff Inlets Pipe Pipe/Swale Travel Time
2595c - Rational Calculations 9182016.xlsx Q Minor Page 1 of 1
paved swales
20 3.0 0.2 6.7 107 10.6 6.7
A5 5 1.38 0.20 183 2.1% 17.3 Grassed waterway 15 0.0 0.0 17.3 183 11.0 11.0
A6 6 0.88 0.62 55 1.5% 5.8 214 1.8%
Paved areas & shallow
paved swales
20 2.7 1.3 7.1 269 11.5 7.1
A7 7 0.85 0.08 34 5.2% 6.3 343 1.0% Grassed waterway 15 1.5 3.8 10.1 377 12.1 10.1
B1 8 0.45 0.11 115 0.8% 21.0
Paved areas & shallow
paved swales
20 0.0 0.0 21.0 115 10.6 10.6
B2 9 0.13 0.05 15 11.9% 3.3 231 1.0% Grassed waterway 15 1.5 2.6 5.9 246 11.4 5.9
B3 10 0.31 0.02 25 14.6% 4.1 Grassed waterway 15 0.0 0.0 4.1 25 10.1 5.0
R1 11 0.16 0.84 60 2.0% 3.0
Paved areas & shallow
paved swales
20 0.0 0.0 3.0 60 10.3 5.0
R2 12 0.16 0.84 60 2.0% 3.0
Paved areas & shallow
paved swales
20 0.0 0.0 3.0 60 10.3 5.0
R3 13 0.16 0.84 45 2.0% 2.6
Paved areas & shallow
paved swales
20 0.0 0.0 2.6 45 10.3 5.0
R4 14 0.11 0.84 60 2.0% 3.0
Paved areas & shallow
paved swales
20 0.0 0.0 3.0 60 10.3 5.0
R5 15 0.07 0.84 60 2.0% 3.0
Paved areas & shallow
paved swales
20 0.0 0.0 3.0 60 10.3 5.0
R6 16 0.10 0.84 60 2.0% 3.0
Paved areas & shallow
paved swales
20 0.0 0.0 3.0 60 10.3 5.0
R7 17 0.16 0.84 60 2.0% 3.0
Paved areas & shallow
paved swales
20 0.0 0.0 3.0 60 10.3 5.0
R8 18 0.16 0.84 60 2.0% 3.0
Paved areas & shallow
paved swales
20 0.0 0.0 3.0 60 10.3 5.0
R9 19 0.16 0.84 60 2.0% 3.0
Paved areas & shallow
paved swales
20 0.0 0.0 3.0 60 10.3 5.0
R10 20 0.10 0.84 60 2.0% 3.0
Paved areas & shallow
paved swales
20 0.0 0.0 3.0 60 10.3 5.0
Initial Overland Time (ti
)
Travel Time (tt
)
tt
=Length/(Velocity x 60)
tc Urbanized Check
ON
2595c - Rational Calculations 9182016.xlsx Developed Tc Page 1 of 1
Percent of WQCV LID
Treated
334%
TOTAL VOLUME
TOTAL VOLUME
TOTAL VOLUME
0.84% % of Impervious Area not being detain. B Basin Area of Impervious / Total Site Area
99.16% % of Total Sites Impervious Area being detain.
11.3% Total Site Area not being sent to Detention Pond. B Basin Area / Total Site Area
Total To LID Pond 1
(A1, R1, R6, R7)
B Basin
Total To LID Pond 3
(A3, A4, A5, A6, R3,
R4, R5, R8, R9, R10)
Total To LID Pond 2
(A2, R2)
Tota; to Pond
(All A and All R)
Total Offsite
(B1, B2, B3)
2595c - Rational Calculations 9182016.xlsx Developed C Page 2 of 2
R8 18 7,180 7,180 0.16 90.0% 0.80 0.84 0.85 0.90
R9 19 7,081 7,081 0.16 90.0% 0.80 0.84 0.85 0.90
R10 20 4,426 4,426 0.10 90.0% 0.80 0.84 0.85 0.90
61,132 52,413 59,422 4,297 0 0 169,292 0 346,556 7.96 48.2% 0.43 0.45 0.52 0.69
Runoff Coeff's
Total Site
2595c - Rational Calculations 9182016.xlsx Developed C Page 1 of 2
(min)
Time of
Conc
ti + tt = tc
Total
Length
(ft)
tc=(L/180)+
10 (min.)
Min
tc
H1 1 17,418 530 8,896 61,172 258,545 346,561 7.96 16.0% 0.14 0.15 0.25 0.53 500 1.3% 35.5 143 0.8%
Paved areas & shallow
paved swales
20 1.8 1.3 36.9 643 13.6 13.6
TOTAL SITE 17,418 530 8,896 61,172 0 0 258,545 0 346,561 7.96 16.0% 0.14 0.15 0.25 0.53
Basin
Name
Design
Point
Time of
Conc
(tc)
C2 C5 C10 C100 2 5 10 100 ATotal (sf)
ATotal
(ac)
Q2 Q5 Q10 Q100
H1 1 13.6 0.14 0.15 0.25 0.53 1.94 0.00 3.33 6.79 346,561 7.96 2.21 0.00 6.75 28.78
TOTAL SITE 346,561 7.96 2.21 0.00 6.75 28.78
Initial Overland Time (ti)
Travel Time (tt) tt=Length/(Velocity
x 60)
tc Urbanized Check
ON
Runoff Coeff's Rainfall Intensities (in/hr) Area Flow Rates (cfs)
Runoff Coeff's
2595c - Rational Calculations 9182016.xlsx Historic Page 1 of 1