HomeMy WebLinkAboutWINDSONG AT ROCK CREEK - PDP - PDP150024 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTPDP DRAINAGE REPORT
FOR
WINDSONG AT ROCK CREEK
Prepared For:
VISTA POINTE DEVELOPMENT CO., LLC
C/O Lenity Architecture
3150 Kettle Court SE
Salem, Oregon 97301
November 11, 2015
Project No. 39727.00
Prepared By:
JR Engineering, LLC
2900 South College Avenue, Suite 3D
Fort Collins, CO 80525
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TABLE OF CONTENTS
Engineer’s Certification Block ........................................................................................................... iii
VICINITY MAP ................................................................................................................................... iv
GENERAL DESCRIPTION AND LOCATION ............................................................................................ 1
LOCATION ..................................................................................................................................... 1
DESCRIPTION OF PROPERTY .......................................................................................................... 1
FLOODPLAIN SUBMITTAL REQUIREMENTS ..................................................................................... 2
DRAINAGE BASINS AND SUB-BASINS ................................................................................................. 3
MAJOR BASINS AND SUB-BASINS ................................................................................................... 3
SUB-BASIN DESCRIPTION ............................................................................................................... 4
EXISTING OFFSITE DRAINAGE BASINS ............................................................................................ 4
EXISTING ONSITE DRAINAGE BASINS ............................................................................................. 5
PROPOSED SUB-BASINS DESCRIPTIONS ......................................................................................... 6
DRAINAGE DESIGN CRITERIA ........................................................................................................... 16
REGULATIONS ............................................................................................................................. 16
MINIMIZATION OF THE DCIA ....................................................................................................... 16
DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS ........................................................... 16
HYDROLOGIC CRITERIA ................................................................................................................ 16
HYDRAULIC CRITERIA ................................................................................................................... 17
FLOODPLAIN REGULATIONS COMPLIANCE ................................................................................... 17
MODIFICATIONS OF CRITERA ....................................................................................................... 17
DRAINAGE FACILITY DESIGN ............................................................................................................ 18
GENERAL CONCEPT ..................................................................................................................... 18
WATER QUALITY/ DETENTION FACILITIES .................................................................................... 18
LOW IMPACT DEVELOPMENT ...................................................................................................... 18
CONCLUSIONS ................................................................................................................................. 19
COMPLIANCE WITH STANDARDS ................................................................................................. 19
DRAINAGE CONCEPT ................................................................................................................... 19
REFERENCES .................................................................................................................................... 20
APPENDIX
Appendix A – Figures
Appendix B – Hydrologic Calculations
Appendix C – Hydraulic Calculations
Appendix D – Water Quality/Detention Calculations
Appendix E – Maps
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Engineer’s Certification Block
I hereby certify that this Project Development Plan Drainage Report for Windsong at Rock Creek was
prepared by me (or under my direct supervision) for JR Engineering, LLC and the owners thereof and
meets or exceeds the criteria of the City of Fort Collins Stormwater Design Standards.
Timothy J. Halopoff, PE
Registered Professional Engineer
State of Colorado No. 37953
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VICINITY MAP
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GENERAL DESCRIPTION AND LOCATION
LOCATION
Windsong at Rock Creek is located in the southeast quarter of Section 4, Township 6 North, Range 68
West of the 6th Principal Meridian in the City of Fort Collins, Larimer County, Colorado. More
specifically, the Windsong site is a 3.334 acre property that is currently undeveloped and is being used
for agricultural purposes. The site is zoned HC, Harmony Corridor, and will support a memory care
facility and associated amenities once developed.
The Windsong at Rock Creek site is bounded on the south by Rock Creek Drive, on the west by
Ziegler Road, and on the north and east by unplatted land. Further to the east of the site lies
Technology Parkway, and further to the north of the site lies existing right-of-way for Precision Drive,
although the roadway has not been constructed between Technology Parkway and Ziegler Road.
Surrounding developments include Harvest Park west of Ziegler Road, Fossil Ridge High School south of
Rock Creek Drive, Harmony Technology Park Filing 3 east of Technology Parkway and
Brookfield/Morningside to the east of Filing 3, and Harmony Technology Park Filing 1 north of Precision
Drive.
The site is only encumbered by a 15-foot utility easement on the west side, paralleling Zielger Road.
The site is located in the McClellands drainage basin and there are no major drainageways adjacent to
the site.
DESCRIPTION OF PROPERTY
The Windsong at Rock Creek site is 3.334 acres at the northeast corner of Ziegler Road and Rock
Creek Drive. The existing site generally slopes from the southwest to the northeast with slopes ranging
between 0.70% and 3.5%. The property is generally covered with sparse native grasses. The site
currently drains to the east. Runoff sheet flows off the east side of the property and a portion of the
runoff flows to the west after the berm along the far west of the property.
The Windsong site’s soils consist of loamy soil, predominately Nunn clay loam. Nunn clay loam belongs
to hydrologic soils Group C. Group C soils have a slow infiltration rate when thoroughly wet. These
consist chiefly of soils having a layer that impedes the downward movement of water or soils of
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moderately fine texture or fine texture. These soils have a slow rate of water transmission. The slopes
of the Nunn clay loam ranges from 0-3 percent. Supporting figures can be found in the Appendix, page
A-1.
An existing irrigation ditch is located on the west end of the site paralleling Ziegler Road. According to
the Mainstreet Health & Wellness Suites final plat by Edmonds Land Surveying, Inc., recorded May 22,
2015, this irrigation easement has been granted to the Poudre School District. This private irrigation
ditch, per the approved Mainstreet Health & Wellness Suites Final Drainage and Erosion Control Report
by Aspen Engineering, dated February 18, 2015, is being abandoned in place through the entire Harmony
Technology Park. As such, the irrigation ditch will be abandoned in place with the proposed Windsong
at Rock Creek Development.
The proposed use of the site is a memory care assisted living facility. The proposed concept includes
one main building with two patios, two internal courtyards, garden plaza with walkways, and parking lots
within the perimeter of the site. The proposed main building is 38,131 total square feet.
FLOODPLAIN SUBMITTAL REQUIREMENTS
The site is shown on FEMA FIRM panel 08069C0994F, dated December 19, 2006. The site lies within
Zone X, areas which are determined to be outside the 0.2% annual chance floodplain. The “City of Fort
Collins Floodplain Review Checklist for 50% Submittals” checklist is not applicable for this PDP Drainage
Report. The FIRM panel is included in Appendix A.
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DRAINAGE BASINS AND SUB-BASINS
MAJOR BASINS AND SUB-BASINS
The proposed Windsong Fort Collins site is located in the McClellands major basin. The McClellands
Basin encompasses approximately 3.4 square miles in southeast Fort Collins. The storm runoff from the
basin originates northeast of College Avenue and Harmony Road and drains southeast through the
Oakridge, Willow Springs, Stetson Creek and Harvest Park developments. A single major drainageway,
McClellands Creek, conveys flow from the upper end of the basin to the downstream discharge point
along the Fossil Creek Reservoir Inlet Ditch. The majority of the basin is either developed, or is being
developed, with residential and commercial land areas. There are no major drainageways located within
or immediately adjacent to the site.
The McClellands Basin was developed in accordance with its original master plan and storm drainage
criteria; therefore, many of the recommended improvements were completed. However, there are still
some localized flooding problems. The recommended plan of improvements includes pond enlargement,
spillway construction, and inlet additions. Once these improvements are completed, the existing facilities
would be up to current drainage standards. The “McClellands Creek Basin Selected Plan – Water
Quality Improvements Drainage Master Plan Update”, prepared by ICON Engineering, Inc., shows the
proposed water quality improvements which includes retrofitting the existing Miramont, Oak Ridge,
Willow Springs, Preston Jr. High, and the Harmony Crossing Ponds to accommodate the required water
quality volumes. As well, stream restoration and habitat improvements are proposed along the
McClellands Creek. The Drainage Master Plan update is currently underway and is to portray these
proposed improvements to the McClellands Basin.
The site is located at the east part of the basin outside the McClelland’s Creek Floodplain shown in the
“McClelland’s Creek Master Drainage Plan Update” by Icon Engineering. The site is located south of an
area with existing flood control and east of an area with both existing water quality and flood control.
The site itself is located in an area with neither flood control or water quality. Improvements identified
in the previous approved Drainage Reports include the design of five detention ponds within the
Oak/Cottonwood Farm development prepared by RBD, Inc. Engineering Consultants in May 1992 and
revised in March 1995 [2]. The construction of Lot 1, Lot 2, Boardwalk Crossing, Filing 2 located north
of West Harmony Road and west of South College Avenue has been designed to have the runoff be
routed to the system in Boardwalk Drive and was designed in 1996 by Stewart & Associated, Inc [3].
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Regional Detention Pond 278 and 247 located west of Pleasant Valley Lake and east of Seneca Street
were designed by Sear-Brown Group in October 2000 [4]. Six detention ponds were designed for the
development north of Ketcher road and west of Strauss Cabin Road by Northern Engineering in
December 2010 [5].
SUB-BASIN DESCRIPTION
Windsong is governed by the City’s Reasonable Use policy, in which the proposed drainage basins will
need to follow the generally accepted principle of releasing the 100-year developed condition flow rate
at the same location and magnitude as the 2-year pre-development condition flow rate. There are offsite
areas that flow across the proposed development site. The existing drainage basins within the site flow
to the either East of the site or North of the site. Referring to the “Existing Drainage Plan”, included in
the Appendix, the following describes the existing condition drainage basins.
EXISTING OFFSITE DRAINAGE BASINS
The site has two existing offsite drainage sub-basins that flow onto the site, entering in two separate
locations. The existing offsite land use is classified as farming/agricultural, but for the analysis, the land
use will be assumed to have a 45% imperviousness (for undefined land use) to be provide a conservative
approximation of the offsite flows entering the Windsong site. The conservative imperviousness will
account for any changes or fluctuations of the surface characteristics north of the site. In the ultimate
condition, the offsite flows will be collected and conveyed to a separate storm system within the
respective developments and these developed flows will no longer enter the Windsong site.
SUB-BASIN (OF1)
Sub-basin OF2 consists of 2.30 acres north of the site and is assumed to drain in a southeasterly
direction onto the subject property. Based on the surveyed surface characteristics north of the
site and the Google topography, the slopes are assumed to match the surveyed area north of
site and will continue to drain in the southeast direction. In the existing condition, runoff from
this portion of the farm field (assumed 45% impervious) is conveyed through the Windsong site.
In the future, the land north of the site is planned to be developed and the offsite runoff will be
directed away from the Windsong property. It is assumed that the slopes are consistent with
the slopes just north of the site, with a range from 0.5% to 1.0%.
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EXISTING ONSITE DRAINAGE BASINS
The site has three existing onsite drainage basins approximately delineated by a high point at the middle
and southern end of the site with sub-basin EX1 on the north half and EX2 on the southern half. Sub-
basin EX2 and sub-basin EX3 border the roadway. Sub-basin EX2 drains to the south and then east
along the curb. Sub-basin EX3 runoff drains to the west and then north along the curb.
SUB-BASIN (EX1)
Sub-basin EX1 consists of a 2.99 acre area of undeveloped farm land with native grasses covering
the majority of the ground and is assumed to be 2% impervious for historic flow analysis. Runoff
from the north farm land (Sub-basins OF1 and OF2) enters the site along the northern
boundary and joins on-site flows. Runoff generally flows southeasterly across basin EX-1, at
slopes ranging from 0.50% to 1.0%. There is an existing low point east of the site that causes
the onsite and offsite runoffs to converge in northern half of the basin and then drain east off
the site. The offsite runoff flows southeast, converges in the northern half, and then flows east
off the site. The sub-basin onsite runoff from the south flows northeast towards the same low
point outside the site.
Towards the southern end of the sub-basin, there is a ridge that directs runoff on the southern
end of the ridge to drain south towards the roadway. An existing berm along the northern
section of the roadway redirects a portion of the runoff back east off the site.
All flows within the sub-basin EX1 exit the site at the east boundary.
SUB-BASIN (EX2)
Sub-basin EX2 consists of a 0.17 acre area of undeveloped farm land with native grasses covering
the majority of the ground and is assumed to be 2% impervious for historic flow analysis. Sub-
basin EX2 borders the north side of the existing Rock Creek Drive roadway. Runoff that that
drains south of the ridge on the southern side of the site, flows over the existing berm and into
the roadway curb. The curb then directs the flows to the east. Runoff north of the berm
generally flows southeasterly towards the roadway, at slopes ranging from 0.50% to 0.8%.
Across the berm the slopes range from 6.0%-10.0% and along the curb the slope is ranges from
0.40% to 1.30%.
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SUB-BASIN (EX3)
Sub-basin EX7 consists of a 0.19 acre area of undeveloped farm land with native grasses covering
the majority of the ground and is assumed to be 2% impervious for historic flow analysis. Sub-
basin EX7 borders the east side of the existing Ziegler Road roadway and west of the existing
concrete channel. The runoff drains west of the existing concrete channel and east of the
roadway curb. The stormwater converges to the bottom of the slope that lies in between the
curb and channel before being routed north of the site. The slope ranges from 0.05% to 7.0%.
Along the southwest side of the site and within the sub-basin, the runoff flows west towards the
existing Zeigler Drive roadway and then the curb directs the flows east. The slopes range from
2.5% to 3.0%. All flows within the sub-basin EX2 exit the site at the at the south end and flow
east along the existing roadway curb.
PROPOSED SUB-BASINS DESCRIPTIONS
No offsite flows will enter the site once it is developed, as concurrent development is expected to take
place for the filing north of the Windsong site. Offsite flows will be accounted for with onsite water
quality and detention in their respective filings.
SUB-BASIN A1
Sub-basin A1consists of 0.39 acres and is located at the northwest corner of the subject
property. Sheet flow from the northwest side of the proposed building and parking lot will
travel north to a parking lot curb. A perforated underdrain pipe will be placed approximately
two feet from the curb flowline and is to collect the runoff from the building and parking lot.
Once the runoff drains into the perforated pipe, it will route the runoff to the stormwater
system on the east side of the site. In situations in which the perforated pipe is at full capacity,
the flows will bypass the underdrain and will be routed to a concrete drain pad which will be set
at the low point in the curb. The runoff will outfall at the concrete pad and into the bioswale to
the north which will then travel east to the FES. The flow will be piped and then routed east
and then south through the storm sewer to outfall into the WQ Detention Pond A. The east
side of the berm along the northwest corner of the site will direct the sheet flows to collect on
the parking lot and sheet flow towards the low point in the curb.
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The slope of the initial flow across the parking lot is ranges from 2.0 % to 2.10% and across the
pavers the slope is 0.75%. The longitudinal slope of the sidewalks ranges from 0.5% to 4.5%.
The imperviousness of the asphalt and pavers is set at 100% and the imperviousness of the
concrete curb and sidewalks/walkways is set at 90%. The imperviousness of the roof of the
building will be set at 90%. All areas outside the parking lot, building and sidewalks are assumed
to be lawn with an imperviousness set at 5%.
SUB-BASIN A2
Sub-basin A2 consists of 0.50 acres and is located at the northeast corner of the subject
property, adjacent to sub-basin A1. Sheet flow from the north-center and northeast side of the
proposed building and parking lot travels north to a parking lot curb. A perforated underdrain
pipe will be placed approximately two feet from the curb flowline for the full stretch of the curb
and is to collect the initial sheet flow from the building and parking lot. Once the runoff drains
into the perforated pipe, the stormwater will be routed to the stormwater system on the east
side of the site. In situations in which the perforated pipe is at full capacity, the flows will bypass
the underdrain and will be routed to a concrete drain pad which will be set at the low point in
the east corner of the curb. There will be two concrete pads along the curb, one to the west of
the trash enclosure and the second at the midpoint of the curb on the east side of the trash
enclosure. The runoff will outfall at the concrete pads and into the second bioswale to the
north. The bioswale beings at the first concrete drain pad and directs the flows east through
the swale and outfalls to the proposed grated manhole at the north east corner. The flow will
be piped through the storm sewer system to outfall into WQ Detention Pond A. The west side
of the berm along the northeast corner of the site will direct the sheet flows to collect on the
parking lot or swale.
The slope of the initial flow across the parking lot is ranges from 1.90 % to 3.0% and across the
pavers the slope is 0.75%. The longitudinal slope of the sidewalks ranges from 0.5% to 7.5%.
The imperviousness of the asphalt and pavers is set at 100% and the imperviousness of the
concrete curb and sidewalks/walkways is set at 90%. The imperviousness of the roof of the
building will be set at 90%. All areas outside the parking lot, building and sidewalks are assumed
to be lawn with an imperviousness set at 5%.
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SUB-BASIN A3
Sub-basin A3 consists of 0.01 acres and is located at the northeast corner of the building within
the subject property. Runoff from the berm along the patio and south of the sidewalk drains
into the proposed grated manhole. The piped flows connect to the storm sewer pipe through
sub-basin A8 with a wye fitting and are routed south to WQ Detention Pond A before exiting
the site. The slope towards the grated manhole ranges from 5.0 % to 25.0%. All areas outside
the parking lot, building and sidewalks are assumed to be lawn with an imperviousness set at 5%.
SUB-BASIN A4
Sub-basin A4 consists of 0.18 acres and is located on the west side of the building within the
subject property. The basin consists of the building patio and the swale directing flow to the
north. Runoff from the west side of the building will flow from the roof and into the concrete
patio or grated manhole north of the patio. In the patio area, the runoff will enter the four
proposed grated manholes with the piped flows routed east. The swale west of the patio berm
collects the runoff from the berms on the east and west side of the swale and directs the flows
north to the proposed grated manhole outside of the patio. The piped flows will then travel
south and combine with the piped flows from within the patio. The piped flows travel east and
connect to the proposed storm sewer system on the east side of the building patio (sub-basin
A8) with a tee fitting. The storm sewer system directs the runoff south to WQ Detention Pond
A before exiting the site.
The slope of the initial flow across the concrete courtyard lot ranges from 1.00 % to 2.0%. The
imperviousness of the concrete is set at 90%. The imperviousness of the roof of the building
will be set at 90%. All areas outside the parking lot, building and sidewalks are assumed to be
lawn with an imperviousness set at 5%.
SUB-BASIN A5
Sub-basin A5 consists of 0.24 acres and encompasses the west-half of the building within the
subject property. Runoff from the west half of the building will flow from the roof and into the
concrete courtyard. The runoff will enter two proposed grated manholes with the piped flows
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routed east. The runoff in sub-basin A5 combines with the piped flows from sub-basin A4. The
piped flows travel east and connect to the proposed storm sewer system on the east side of the
building patio (sub-basin A8) with a tee fitting. The storm sewer system directs the runoff south
to WQ Detention Pond A before exiting the site.
The slope of the initial flow across the concrete courtyard lot ranges from 1.00 % to 2.0%. The
imperviousness of the concrete is set at 90%. The imperviousness of the roof of the building
will be set at 90%.
SUB-BASIN A6
Sub-basin A6 consists of 0.24 acres and encompasses the east-half of the building within the
subject property. Runoff from the east half of the building will flow from the roof and into the
concrete courtyard. The runoff will enter two proposed grated manholes with the piped flows
routed east. The runoff in sub-basin A6 combines with the piped flows from sub-basin A4 and
A5. The piped flows travel east and connect to the proposed storm sewer system on the east
side of the building patio (sub-basin A8) with a tee fitting. The storm sewer system directs the
runoff south to WQ Detention Pond A before exiting the site.
The slope of the initial flow across the concrete courtyard lot ranges from 1.00 % to 2.0%. The
imperviousness of the concrete is set at 90%. The imperviousness of the roof of the building
will be set at 90%.
SUB-BASIN A7
Sub-basin A7 consists of 0.10 acres and is located on the east side of the building within the
subject property. The basin consists of only the building patio. Runoff from the east side of the
building will flow from the roof into the concrete patio and enter the four proposed grated
manholes with the piped flows routed east. The runoff in sub-basin A7 combines with the piped
flows from sub-basin A4 to A6. The piped flows travel east and connect to the proposed storm
sewer system on the east side of the building patio (sub-basin A8) with a tee fitting. The storm
sewer system directs the runoff south to WQ Detention Pond A before exiting the site.
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The slope of the initial flow across the concrete courtyard lot ranges from 1.00 % to 2.0%. The
imperviousness of the concrete is set at 90%. The imperviousness of the roof of the building
will be set at 90%. All areas outside the parking lot, building and sidewalks are assumed to be
lawn with an imperviousness set at 5%.
SUB-BASIN A8
Sub-basin A8 consists of 0.13 acres and is located on the east side of the building and patio
within the subject property. Runoff from the southeast side of the building patio berm will be
routed to the proposed grated manhole at the southeast corner of the building. The ridge along
the east side of the sub-basin is set higher than the sidewalk, directing the runoff on the east
side of the ridge to flow to the private roadway. The runoff within the sub-basin outfall into the
grated manhole and the piped flows travel south to the WQ Detention Pond A prior to exiting
the site.
The slope of the initial flow across the lawns range from 2.0 % to 25% and across the patio the
slope is ranges from 1.0% to 2.0%. The imperviousness of the concrete patio is set at 90% and
the imperviousness of the roof of the building will also be set at 90%. All areas outside the
building and patio are assumed to be lawn with an imperviousness set at 5%.
SUB-BASIN A9
Sub-basin A9 consists of 0.09 acres and is located on the south side of the building within the
subject property. The sub-basin includes a proposed grated manhole and swale. Runoff from
the building sheet falls into the swale and is routed west towards the proposed grated manhole.
The piped flows are routed south through the sub-basin A10 proposed grated manhole and A11
inlet prior to outfalling into WQ Detention Pond A. The slope towards the grated manhole
ranges from 8.0 % to 20.0% with the swale slope at a 2.0%. All areas outside the parking lot,
building and sidewalks are assumed to be lawn with an imperviousness set at 5%.
SUB-BASIN A10
Sub-basin A10 consists of 0.02 acres and is located in the middle of the south parking lot within
the subject property. Runoff from the sidewalk to the west of the basin sheet falls to the
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proposed grated manhole at the center of the sub-basin. The piped flows are routed east
through the sub-basin A11 proposed inlet prior to outfalling into WQ Detention Pond A. The
sub-basin runoff is combined with sub-basin A10 piped flows. The slope towards the grated
manhole ranges from 2.0 % to 15.0%. The imperviousness of the concrete patio is set at 90%
and all areas outside the parking lot, building and sidewalks are assumed to be lawn with an
imperviousness set at 5%.
SUB-BASIN A11
Sub-basin A11consists of 0.12 acres and is located north of the south property entrance of the
subject property. A ridge will stretch from the west side of the property entrance and north to
the sub-basin B5 curb, causing the parking lot to be broken up into two sub-basins. The two
sub-basins will be located on the east and west side of the parking lot, with sub-basin A11 on
the east side. The runoff from the property entrance travels northeast and the runoff on the
east side of the building entrance travels southeast to the inlet prior to outfalling into WQ
Detention Pond A. The piped flows at the inlet will combine with runoff from sub-basins B1 to
B5 and A9 to A10.
The slope of the initial flow across the parking lot is ranges from 0.05 % to 2.8% and the slope
across the sidewalks/pathways ranges from 1.0% to 4.0%. The imperviousness of the asphalt is
set at 100% and the imperviousness of the concrete curb and sidewalks/walkways is set at 90%.
The imperviousness of the roof of the building will be set at 90%.
SUB-BASIN A12
Sub-basin A12 consists of 0.29 acres and is located at the southeast corner of the property and
consists of the WQ Detention Pond A. The pond will collect runoff from sub-basins A1 to A11
and B1 to B5 prior to exiting the site. In a major storm situation, the stormwater in the pond
can back up into WQ Pond B, which is tributary to Pond A. The sub-basin itself includes the
pond and the parking lot to the north of the pond. A proposed concrete pad will be placed at
the low point in the curb, causing the runoff in the parking lot to sheet flow and drain into the
pond. At the east side of the pond, a Water Quality outfall structure is proposed to outfall the
stormwater to the existing storm sewer system to the east of the site.
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The slope of the sheet flow across the parking lot ranges from 0.75 % to 2.0% and the slope
across the bottom of the pond is approximately 2.0%. The imperviousness of the asphalt is set
at 100% and the imperviousness of the concrete curb and sidewalks/walkways is set at 90%.
The imperviousness of the roof of the building will be set at 90% and all areas outside the
parking lot, building and sidewalks are assumed to be lawn with an imperviousness set at 5%.
SUB-BASIN B1
Sub-basin B1 consists of 0.04 acres and is located at the southwest side of the building patio
within the subject property. The sub-basin consists of a proposed grated manhole and swale.
Runoff from the berm along the patio and the berm on the east side of the sidewalk, collects
into the swale and is routed to the proposed grated manhole. The manhole also collects the
runoff from building and the second berm east of the sidewalk. The piped flows outfall into WQ
Detention Pond B (tributary to WQ Detention Pond A), where the runoff is then routed to
WQ Detention Pond A. The slope of the swale is approximately 2.0% and the slope from the
building and berms ranges from 10.0 % to 20.0%. All areas outside the parking lot, building and
sidewalks are assumed to be lawn with an imperviousness set at 5%.
SUB-BASIN B2
Sub-basin B2 consists of 0.21 acres and is located at the southwest corner of the property and
consists of the WQ Detention Pond B. The pond is tributary to WQ Detention Pond A and
will outfall into Pond A prior to exiting the site. In a major storm situation, the stormwater in
the Pond A can back up into Pond B and allows the ponds to be considered one WQ detention
pond. The sub-basin itself includes the pond and the land on the north and east side of the
berms. Within the pond itself, there will be a proposed trickle channel connecting the two FES
on the northwest and southeast sides. The runoff within the basin will outfall into the Pond B
trickle channel and will combine with sub-basin B1 piped flows.
The slope of the bottom of the pond ranges from 2.0% to 5.0% and the slope of the trickle
channel is approximately 0.50%. The side slope of the pond is approximately 25%. The
imperviousness of the concrete sidewalks/walkways is set at 90% and all areas outside the
parking lot, building and sidewalks are assumed to be lawn with an imperviousness set at 5%.
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SUB-BASIN B3
Sub-basin B3 consists of 0.08 acres and is located on the south side of the building within the
subject property. The sub-basin includes a proposed grated manhole and swale. Runoff from
the building sheet falls into the swale and is routed east towards the proposed grated manhole.
The piped flows are routed south through the sub-basin B4 proposed inlet to the A11 proposed
inlet prior to outfalling into WQ Detention Pond A. The slope towards the grated manhole
ranges from 4.0 % to 10.0% with the swale slope ranges from 2.0% to 3.0%. All areas outside
the parking lot, building and sidewalks are assumed to be lawn with an imperviousness set at 5%.
SUB-BASIN B4
Sub-basin B4 consists of 0.14 acres and is located north of the south property entrance of the
subject property. A ridge will stretch from the west side of the property entrance and north to
the sub-basin B5 curb, causing the parking lot to be broken up into two sub-basins. The two
sub-basins will be located on the east and west side of the parking lot, with sub-basin B4 on the
west side. The runoff from the property entrance travels northwest and the runoff on the west
side of the building entrance travels southwest to the inlet prior to outfalling into WQ
Detention Pond A. The piped flows at the inlet will combine with runoff from sub-basins B1 to
B3. The WQ Detention Pond B east ridge is set higher than the sidewalk, directing the runoff
on the east side of the ridge to flow to the parking lot.
The slope of the initial flow across the parking lot is ranges from 2.0 % to 3.0% and the slope
across the sidewalks/pathways ranges from 0.5% to 4.0%. The imperviousness of the asphalt is
set at 100% and the imperviousness of the concrete curb and sidewalks/walkways is set at 90%.
The imperviousness of the roof of the building will be set at 90%.
SUB-BASIN B5
Sub-basin B5 consists of 0.02 acres and is located in the middle of the south parking lot within
the subject property. The lawn within the basin sheet flows to the proposed grated manhole at
the center. The piped flows are routed east through the sub-basin A11 proposed inlet prior to
outfalling into WQ Detention Pond A. The sub-basin runoff is combined with sub-basins B1 to
Windsong at Rock Creek November 2015
PDP Drainage Report
14
B4 piped flows. The slope towards the grated manhole ranges from 1.0 % to 10.0%. All areas
outside the parking lot, building and sidewalks are assumed to be lawn with an imperviousness
set at 5%.
SUB-BASIN C1
Sub-basin C1 consists of 0.06 acres and is located on the west side of the subject property. The
flows are routed offsite and will flow down to the existing curb along Ziegler Road. The existing
curb will then direct the runoff north of the site. The slope of the flow from the sidewalk is
approximately 2.0% and the slope down from the proposed berms is approximately 25%. The
imperviousness of the concrete sidewalks/walkways is set at 90% and all areas outside the
parking lot, building and sidewalks are assumed to be lawn with an imperviousness set at 5%.
SUB-BASIN C2
Sub-basin C2 consists of 0.13 acres and is located on the west side of the subject property. The
flows are routed offsite and will flow down to the existing curb along Ziegler Road. The existing
curb will then direct the runoff south of the site. The slope of the flow from the sidewalk is
approximately 2.0% and the slope down from the proposed berms is approximately 25%. The
runoff at the south entrance flows to the existing curb and is directed east. The imperviousness
of the concrete sidewalks/walkways is set at 90% and all areas outside the parking lot, building
and sidewalks are assumed to be lawn with an imperviousness set at 5%.
SUB-BASIN C3
Sub-basin C3 consists of 0.10 acres and is located on the south side of the subject property.
The flows are directed offsite and will flow down to the existing curb along Rock Creek Drive
roadway. The existing curb will then direct the runoff east of the site. The slope of the flow
from the sidewalk ranges from 2.0% to 8.50% and the slope down from the proposed berms is
approximately 25%. The runoff at the south entrance flows to the existing curb and is directed
east. The imperviousness of the concrete curb and sidewalks/walkways is set at 90% and all
areas outside the parking lot, building and sidewalks are assumed to be lawn with an
imperviousness set at 5%.
Windsong at Rock Creek November 2015
PDP Drainage Report
15
SUB-BASIN C4
Sub-basin C4 consists of 0.09 acres and is located on the south side of the subject property.
The flows are directed offsite and will flow down to the existing curb along Rock Creek Drive
roadway. The existing curb will then direct the runoff east of the site. The slope of the flow
from the sidewalk is approximately 2.0%. The imperviousness of the asphalt is set at 100% and
the imperviousness of the concrete sidewalks/walkways is set at 90%. All areas outside the
parking lot, building and sidewalks are assumed to be lawn with an imperviousness set at 5%.
SUB-BASIN C5
Sub-basin C5 consists of 0.05 acres and is located on the south side of the subject property.
The flows are directed offsite and will flow down to the existing curb along Rock Creek Drive
roadway. The proposed private roadway creates sheet flow south of the high point in the and
causes the runoff to flow to the proposed concrete pan. The existing curb will then direct the
runoff east of the site. The slope of the flow from the sidewalk is approximately 2.0% and the
slope of the roadway is approximately 3.0%. The imperviousness of the asphalt is set at 100%
and the imperviousness of the concrete sidewalks/walkways is set at 90%. All areas outside the
parking lot, building and sidewalks are assumed to be lawn with an imperviousness set at 5%.
SUB-BASIN C6
Sub-basin C6 consists of 0.37 acres and is located on the east side of the subject property. The
sub-basin includes the private roadway. The runoff sheet flows east to the roadway and then is
routed to the concrete pad at the low point at the middle of the curb. The runoff is drained
offsite at the east side of the property. The slope of the roadway cross slope is approximately
2.0% with a longitudinal slope ranging from 0.5% to 2.0%. The cross slope of the sidewalk and
lawns are approximately 2.0% and the slope from the berm is approximately 25%. The
imperviousness of the asphalt is set at 100% and the imperviousness of the concrete
sidewalks/walkways is set at 90%. All areas outside the parking lot, building and sidewalks are
assumed to be lawn with an imperviousness set at 5%.
Windsong at Rock Creek November 2015
PDP Drainage Report
16
DRAINAGE DESIGN CRITERIA
REGULATIONS
This report was prepared to meet or exceed the City of Fort Collins stormwater criteria. The City of
Fort Collins Storm Drainage Design Criteria and Construction Manual (with all current 2011
Revisions)(FCSDDCCM) and the Urban Drainage Flood Control District’s (UDFCD) Drainage Criteria
Manual (USDCM) Volumes 1, 2 and 3 were referenced as guidelines for this design.
MINIMIZATION OF THE DCIA
Volume reduction is an important part of the Four Step Process and is fundamental to effective
stormwater management. Per City criteria, a minimum of 50 percent of new impervious surface area
must be treated by a Low-Impact Development (LID) best management practice (BMP). The proposed
LID BMPs will have the effect of slowing runoff through the site lot and increasing infiltration and rainfall
interception by encouraging infiltration and careful selection of vegetative cover. The improvements will
decrease the runoff coefficient from the site and are expected to have no adverse impact on the timing,
quantity, or quality of stormwater runoff. Site-specific LID BMPs are discussed in the following sections
of this report and an illustrative LID/Surface Map is provided in Appendix E.
DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS
The master drainage report for the Windsong at Rock Creek site is the Final Drainage and Erosion Control
Study for Harmony Technology Park Site Master Plan, Fort Collins, Colorado, prepared by Stantec Consulting
Inc., and dated May 21, 2008.
HYDROLOGIC CRITERIA
The rational method was performed to calculate the peak runoff rates for each basin. Weighted percent
imperviousness and weighted runoff coefficients were calculated for each basin using USDCM Tables
RO-3 and RO-5 based on Natural Resources Conservation Service (NRCS) Type C hydrologic soil
classification and surface characteristics of each basin. The time of concentration was calculated using
USDCM Equation RO-3 and the intensity was calculated using the corresponding storm rainfall depth
and USDCM Equation RA-3. To more closely match the City of Fort Collins IDF Curve, Coefficient 3 of
the UDFCD’s intensity formula was adjusted to 0.7867. The City of Fort Collins area has 2-year, 1-hour
rainfall depth of 0.82 inches and a 100-year, 1-hour rainfall depth of 2.86 inches. These depths do
Windsong at Rock Creek November 2015
PDP Drainage Report
17
account for the 1997 adjusted rainfall depths. The 2-hour 100-year rainfall total is 3.67 inches, based on
the rainfall frequencies adopted by the City of Fort Collins.
HYDRAULIC CRITERIA
This report demonstrates that the proposed stormwater retention and future detention concept is able
to reduce the 100-year developed condition flows to the 2-year historical release rates; thereby
satisfying the City’s Reasonable Use requirements. The Rational Formula-based Federal Aviation
Administration (FAA) method is used to size the detention pond in accordance with City criteria, as the
tributary area is less than 20 acres in size. The resulting storage volume is increased by a factor of
twenty (20) percent to better match the result that would be obtained from SWMM modeling, per City
criteria. The entire water quality capture volume is added to the minor and factored major detention
volumes. An overflow spillway is required at the 100-year water surface elevation, set to flow at no
more than six inches of depth at the peak pond inflow rate, and one foot of freeboard is provided from
the spillway crest to the top of pond.
The ultimate Windsong at Rock Creek storm drainage system will be designed to convey the minor and
major storm events through the property with the proposed inlets, storm sewer pipes, and swales for
the flows being calculated by this report. Per the requirements provided by the City of Fort Collins
Storm Drainage Design Criteria and Construction Manual, all inlets and storm pipes will be designed to
convey the 100-year storm flows. During the major storm event, the developed condition 100-year
storm, the accumulated water depth in the ponds will be held to a maximum level in the ponds of one-
foot below all building finished floor elevations. This drainage report demonstrates that the flow rate
released downstream is less than would historically be experienced, and that the effects of erosion and
sediment transport are lessened through increased infiltration the source.
FLOODPLAIN REGULATIONS COMPLIANCE
The Windsong at Rock Creek site is not located in a regulatory floodplain.
MODIFICATIONS OF CRITERA
No modifications to City criteria are proposed herein. No variances from City criteria are sought with
this PDP Drianage Report.
Windsong at Rock Creek November 2015
PDP Drainage Report
18
DRAINAGE FACILITY DESIGN
GENERAL CONCEPT
The proposed improvements to the Windsong site will result in developed condition runoff being
conveyed around the proposed building and to the east via storm sewer and surface flow. Low-impact
development best management practices are proposed to improve the quality of runoff and aid in
reducing peak flows. Specifically, permeable pavement systems are proposed for portions of the parking
lot and drive aisle, and grass lined bio-swales are on the north and west sides of the site to improve
water quality.
Runoff from the site is captured in inlets located in the parking lot and in open areas adjacent to the
building, as well as in the patio courtyard areas. Runoff is conveyed in storm sewers in south and
easterly directions to the proposed pond at the south end of the site. Secondly, surface overflow paths
have been provided, such that the 100-year storm flows remain at least one foot below the finished
floor elevation in a fully clogged inlet condition.
WATER QUALITY/ DETENTION FACILITIES
There currently exists no storm drain outfall that allows the site flows to reach the existing storm drain
system at Rock Creek Drive and Technology Parkway. Outfall concepts are currently being investigated
in collaboration with adjacent landowners, although a specific concept has not been advanced.
Therefore, an extended detention basin has been proposed in lieu of any regional detention located near
Rock Creek Drive and Technology Parkway. The onsite detention pond will provide water quality
treatment and storm peak attenuation, and will release at the 2-year historic discharge to a proposed
outfall pipe on the south end of the Harmony Park site. See Appendix C
LOW IMPACT DEVELOPMENT
A minimum of 50 percent of new impervious surface area is treated by a Low-Impact Development
(LID) best management practice (BMP) in accordance with City criteria. The BMPs proposed for the
Windsong site include permeable interlocking concrete pavers, grass swales, and an extended detention
basin for water quality treatment. Of the total 2.03 acres of impervious area, 1.85 acres of the site is
treated by LIDs. Also, the minimum threshold of permeable pavers for new parking is met, with a total
of 67 percent of new parking placed on permeable pavers.
Windsong at Rock Creek November 2015
PDP Drainage Report
19
CONCLUSIONS
COMPLIANCE WITH STANDARDS
The hydrologic and water quality calculations were performed using the required methods as outlined in
the City of Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria
Manual. The proposed drainage improvements meet or exceed the City’s requirements. This PDP
Drainage Report and the complimenting drainage plans and LID plans propose appropriate grading,
permanent landscaping, LID BMPs, and onsite facilities (e.g. storm sewer, inlets, retention/detention
facilities) that are shown in their preliminary configuration and will be designed in the Final Drainage
Report for Windsong at Rock Creek with supporting calculations. This report exhibits that both the
storm water systems meet or exceed the requirements set forth in the City of Fort Collins “Storm
Drainage Criteria Manual and Construction Standards” and addenda.
DRAINAGE CONCEPT
The proposed concept for the development of the Windsong at Rock Creek site involves surface flows
and piping of developed conditions flows to a proposed onsite water quality pond. LID site
enhancements will treat the site runoff at the source before allowing the runoff to be conveyed to the
proposed retention pond. Offsite flows from the north will be conveyed through the site and directly
released at the, quality and rate as historically passed through the site. The existing conditions drainage
patterns are maintained in the proposed and future conditions. The proposed improvements will have
no adverse impacts on the flow rate, character, or quality of runoff leaving the site.
Windsong at Rock Creek November 2015
PDP Drainage Report
20
REFERENCES
East Harmony Portion of McClellands Basin 100-Year Master Plan, Icon Inc., August 1999.
Final Drainage and Erosion Control Study for Harmony Technology Park Site Master Plan, Fort Collins,
Colorado; Stantec Consulting Inc., May 21, 2008.
Hydrologic Group Rating for Larimer County Area, Colorado; USDA-Natural Resources Conservation
Service, National Cooperative Soil Survey, July 21, 2010.
Storm Drainage Criteria Manual and Construction Standards; City of Fort Collins Storm Water Utility,
City of Fort Collins, Colorado, January 1997.
Urban Storm Drainage Criteria Manual (Volumes 1, 2, and 3); Urban Drainage and Flood Control
District, June 2001.
Windsong at Rock Creek November 2015
PDP Drainage Report
21
APPENDICES
APPENDIX A – FIGURES
;-2(732+ %8 63'/
'6))/ 7-8)
;-2(732+ %8
63'/ '6))/
7-8)
APPENDIX B – HYDROLOGIC CALCULATIONS
Subdivision: Windsong Project Name: Windsong
Location: Fort Collins Project No.:
Calculated By: KAU
Checked By: 0
Date: 9/23/15
EX1 2.99 100 0.00 0.00 90 0.00 0.00 2 2.99 2.00 90 0.00 0.00 2.00
EX2 0.17 100 0.00 0.00 90 0.00 0.00 2 0.17 2.00 90 0.00 0.00 2.00
EX3 0.19 100 0.00 0.00 90 0.00 0.00 2 0.19 2.00 90 0.00 0.00 2.00
OF1 2.30 100 0.00 0.00 90 0.00 0.00 2 2.30 2.00 90 0.00 0.00 2.00
TOTAL 5.64 2.00
Area (ac) Weighted % Imp. % Imp. Area (ac) Weighted
% Imp.
COMPOSITE % IMPERVIOUS CALCULATIONS
39727.00
Basins Total
Weighted %
Basin ID Total Area (ac) % Imp. Area (ac) Imp.
Weighted
% Imp. % Imp. Area (ac)
Weighted
% Imp. % Imp.
Paved Roads (w/ Pavers) Concrete Walks/Pavement Undeveloped Area (Historic Flow Analysis) Roofs
Page 5 of 34 11/6/2015
X:\1520000.all\1528001\Excel\US Highway 85\Drainage\2015-11-4_Drainage Calcs.xlsm
Subdivision: Windsong Project Name: Windsong
Location: Fort Collins Project No.:
Calculated By: KAU
Checked By: 0
Date: 9/23/15
FINAL
BASIN D.A. Hydrologic Impervious C100 C
5 L S Ti
L S Cv VEL. Tt COMP. T
c TOTAL Urbanized Tc
Tc
ID (AC) Soils Group (%) (FT) (%) (MIN) (FT) (%) (FPS) (MIN) (MIN) LENGTH(FT) (MIN) (MIN)
EX1 2.99 C 2.00 0.51 0.16 390 0.7 38.1 0 0.5 20.0 1.4 0.0 38.1 390.0 12.2 12.2
EX2 0.17 C 2.00 0.51 0.16 218 0.5 32.6 146 0.5 20.0 1.4 1.7 34.3 364.0 12.0 12.0
EX3 0.19 C 2.00 0.51 0.16 17 2.4 5.3 0 0.5 20.0 1.4 0.0 5.3 17.0 10.1 5.3
OF1 2.30 C 2.00 0.51 0.16 604 0.6 50.0 0 0.5 20.0 1.4 0.0 50.0 604.0 13.4 13.4
NOTES:
Ti = (0.395*(1.1 - C
5)*(L)^0.5)/((S)^0.33), S in ft/ft
Tt=L/60V (Velocity From Fig. 501)
Velocity V=Cv*S^0.5, S in ft/ft
Tc Check = 10+L/180
For Urbanized basins a minimum Tc of 5.0 minutes is required.
For non-urbanized basins a minimum Tc of 10.0 minutes is required
For C & D Soils C-5 = (-0.10i+0.11)+(0.8585i^3-.786i^2+0.774i+0.04)
For C & D Soils C-100 = (-0.39i+0.46)+(0.8585i^3-.786i^2+0.774i+0.04)
Cv
2.5
5
7
10
15
20
Tillage/field
Short pasture and lawns
Nearly bare ground
Grassed waterway
Paved areas and shallow paved swales
Heavy Meadow
STANDARD FORM SF-2
TIME OF CONCENTRATION
39727.00
SUB-BASIN INITIAL/OVERLAND TRAVEL TIME Tc CHECK
DATA (Ti) (T
t) (URBANIZED BASINS)
Type of Land Surface
Page 6 of 34 11/6/2015 X:\1520000.all\1528001\Excel\US Highway 85\Drainage\2015-11-4_Drainage Calcs.xlsm
Project Name: Windsong
Subdivision: Windsong Project No.:
Location: Fort Collins Calculated By: KAU
Design Storm: Checked By: 0
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff.
Tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Slope (%)
Street Flow (cfs)
Design Flow (cfs)
Slope (%)
Pipe Size (inches)
Length (ft)
Velocity (fps)
Tt (min)
REMARKS
1 OF1 2.30 0.16 13.4 0.37 1.96 0.7
EX1 2.99 0.16 12.2 0.49 2.05 1.0
2 EX2 0.17 0.16 12.0 0.03 2.06 0.1
3 EX3 0.19 0.16 5.3 0.03 2.74 0.1 12.2 0.55 2.05 1.1
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
39727.00
2-Year
9/23/15
S:\Engineers\Scott Brown\2010-08-20 - Final Drainage Calcs-Template.xls Page 7 of 34 11/6/2015
Subdivision: Windsong Project Name: Windsong
Location: Fort Collins Project No.:
Calculated By: KAU
Checked By: 0
Date: 9/23/15
A1 0.39 100 0.13 32.70 90 0.04 9.30 5 0.13 1.70 90 0.09 20.90 64.60
A2 0.50 100 0.21 42.10 90 0.06 10.50 5 0.14 1.40 90 0.09 17.10 71.10
A3 0.08 100 0.04 45.10 90 0.02 20.30 5 0.03 1.60 90 0.00 0.00 67.00
A4 0.18 100 0.00 0.00 90 0.06 27.50 5 0.07 1.80 90 0.06 29.90 59.20
A5 0.24 100 0.00 0.00 90 0.06 20.50 5 0.00 0.00 90 0.19 69.50 90.00
A6 0.24 100 0.00 0.00 90 0.06 20.50 5 0.00 0.00 90 0.19 69.50 90.00
A7 0.10 100 0.00 0.00 90 0.04 39.20 5 0.00 0.00 90 0.06 50.80 90.00
A8 0.19 100 0.00 0.00 90 0.00 0.00 5 0.19 4.90 90 0.00 1.90 6.80
A9 0.09 100 0.00 4.10 90 0.00 2.90 5 0.02 1.00 90 0.06 64.50 72.50
A10 0.02 100 0.00 20.90 90 0.00 15.20 5 0.01 3.10 90 0.00 0.00 39.20
A11 0.12 100 0.05 42.90 90 0.03 23.90 5 0.01 0.60 90 0.02 16.80 84.20
A12 0.29 100 0.11 36.40 90 0.03 8.00 5 0.16 2.70 90 0.00 0.00 47.10
B1 0.04 100 0.00 0.00 90 0.00 0.00 5 0.04 4.50 90 0.00 9.20 13.70
B2 0.21 100 0.00 0.00 90 0.02 8.30 5 0.19 4.50 90 0.00 0.00 12.80
B3 0.08 100 0.00 0.00 90 0.00 0.00 5 0.02 1.50 90 0.06 63.60 65.10
B4 0.14 100 0.04 26.80 90 0.04 24.70 5 0.03 1.00 90 0.04 22.90 75.40
B5 0.02 100 0.00 14.60 90 0.00 1.40 5 0.02 4.20 90 0.00 0.00 20.20
C1 0.06 100 0.00 0.00 90 0.01 20.70 5 0.04 3.80 90 0.00 0.00 24.50
C2 0.13 100 0.00 0.00 90 0.03 22.60 5 0.10 3.70 90 0.00 0.00 26.30
C3 0.10 100 0.00 0.00 90 0.03 29.70 5 0.06 3.30 90 0.00 0.00 33.00
C4 0.09 100 0.00 0.00 90 0.02 17.70 5 0.07 4.00 90 0.00 0.00 21.70
C5 0.05 100 0.01 33.10 90 0.02 46.40 5 0.01 0.80 90 0.00 0.00 80.30
C6 0.22 100 0.15 68.30 90 0.06 25.60 5 0.01 0.20 90 0.00 0.00 94.10
TOTAL 3.575 52.25
% Imp. Area (ac) Weighted
% Imp.
Paved Roads (w/ Pavers) Lawns/Agricultural Flow Analysis
COMPOSITE % IMPERVIOUS CALCULATIONS
Weighted
% Imp.
Concrete Walks/Pavement
% Imp. Area (ac) Weighted
% Imp. % Imp. Area (ac)
39727.00
Weighted % Imp.
Basins Total
Weighted %
Basin ID Total Area (ac) % Imp. Area (ac) Imp.
Roofs
X:\3970000.all\3972700\Excel\Drainage\2015-11-4_Drainage Calcs.xlsm Page 1 of 1 11/17/2015
Subdivision: Windsong Project Name: Windsong
Location: Fort Collins Project No.:
Calculated By: KAU
Checked By: 0
Date: 9/23/15
FINAL
BASIN D.A. Hydrologic Impervious C100 C
5 L S Ti
L S Cv VEL. Tt COMP. T
c TOTAL Urbanized Tc
Tc
ID (AC) Soils Group (%) (FT) (%) (MIN) (FT) (%) (FPS) (MIN) (MIN) LENGTH(FT) (MIN) (MIN)
A1 0.39 C 64.60 0.65 0.49 95 8.3 5.4 74 0.6 20.0 1.5 0.8 6.2 169.0 10.9 6.2
A2 0.50 C 71.10 0.68 0.54 45 1.9 5.5 148 0.5 20.0 1.4 1.7 7.3 193.0 11.1 7.3
A3 0.08 C 67.00 0.66 0.51 20 25.0 1.7 25 0.5 20.0 1.4 0.3 2.0 45.0 10.3 5.0
A4 0.18 C 59.20 0.63 0.45 11 16.3 1.6 152 1.6 20.0 2.5 1.0 2.6 163.0 10.9 5.0
A5 0.24 C 90.00 0.83 0.75 0 13.0 0.0 117 0.5 20.0 1.4 1.4 1.4 117.0 10.7 5.0
A6 0.24 C 90.00 0.83 0.75 0 13.0 0.0 121 0.5 20.0 1.4 1.4 1.4 121.0 10.7 5.0
A7 0.10 C 90.00 0.83 0.75 45 20.0 1.6 75 1.0 20.0 2.0 0.6 2.2 120.0 10.7 5.0
A8 0.19 C 6.80 0.52 0.19 5 16.0 1.5 3 0.0 20.0 0.0 0.0 1.5 7.6 10.0 5.0
A9 0.09 C 72.50 0.69 0.55 5 8.0 1.1 65 2.0 20.0 2.8 0.4 1.5 70.0 10.4 5.0
A10 0.02 C 39.20 0.58 0.35 25 4.2 4.3 0 0.0 20.0 0.0 0.0 4.3 25.0 10.1 5.0
A11 0.12 C 84.20 0.78 0.67 48 2.3 4.1 38 0.5 20.0 1.4 0.4 4.5 86.0 10.5 5.0
A12 0.29 C 47.10 0.60 0.38 40 8.5 4.1 17 2.3 20.0 3.0 0.1 4.2 57.0 10.3 5.0
B1 0.04 C 13.70 0.54 0.23 11 16.3 2.1 62 2.0 20.0 2.8 0.4 2.5 73.0 10.4 5.0
B2 0.21 C 12.80 0.54 0.23 46 5.4 6.2 90 1.2 20.0 2.2 0.7 6.9 136.0 10.8 6.9
B3 0.08 C 65.10 0.65 0.49 9 4.5 2.0 81 2.8 20.0 3.3 0.4 2.4 90.0 10.5 5.0
B4 0.14 C 75.40 0.71 0.58 44 2.9 4.4 28 2.3 20.0 3.0 0.2 4.6 72.0 10.4 5.0
B5 0.02 C 20.20 0.55 0.26 41 2.7 7.1 0 0.0 20.0 0.0 0.0 7.1 41.0 10.2 7.1
C1 0.06 C 24.50 0.56 0.28 16 2.0 4.8 0 2.0 20.0 2.8 0.0 4.8 16.0 10.1 5.0
C2 0.13 C 26.30 0.56 0.29 52 7.3 5.5 0 2.0 20.0 2.8 0.0 5.5 52.0 10.3 5.5
C3 0.10 C 33.00 0.57 0.32 14 2.2 4.1 60 0.5 20.0 1.4 0.7 4.8 74.0 10.4 5.0
C4 0.09 C 21.70 0.56 0.27 13 2.6 4.0 0 0.5 20.0 1.4 0.0 4.0 13.0 10.1 5.0
C5 0.05 C 80.30 0.75 0.63 35 25.0 1.7 30 2.0 20.0 2.8 0.2 1.9 65.0 10.4 5.0
C6 0.22 C 94.10 0.88 0.80 22 2.6 1.9 0 0.5 20.0 1.4 0.0 1.9 22.0 10.1 5.0
NOTES: Cv
Ti = (0.395*(1.1 - C
5)*(L)^0.5)/((S)^0.33), S in ft/ft 2.5
Tt=L/60V (Velocity From Fig. 501) 5
Velocity V=Cv*S^0.5, S in ft/ft 7
Tc Check = 10+L/180 10
For Urbanized basins a minimum Tc of 5.0 minutes is required. 15
For non-urbanized basins a minimum Tc of 10.0 minutes is required 20
For C & D Soils C-5 = (-0.10i+0.11)+(0.8585i^3-.786i^2+0.774i+0.04)
For C & D Soils C-100 = (-0.39i+0.46)+(0.8585i^3-.786i^2+0.774i+0.04)
Nearly bare ground
Grassed waterway
Paved areas and shallow paved swales
Type of Land Surface
Heavy Meadow
Tillage/field
Short pasture and lawns
STANDARD FORM SF-2
TIME OF CONCENTRATION
SUB-BASIN Tc CHECK
39727.00
DATA (URBANIZED BASINS)
INITIAL/OVERLAND
(Ti)
TRAVEL TIME
Project Name: Windsong
Subdivision: Windsong Project No.:
Location: Fort Collins Calculated By: KAU
Design Storm: Checked By: 0
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff.
Tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Slope (%)
Street Flow (cfs)
Design Flow (cfs)
Slope (%)
Pipe Size (inches)
Length (ft)
Velocity (fps)
Tt (min)
REMARKS
Runoff from northwest pavement will drain out of a concrete
concrete drain pad and into a bioswale. The flow is directed to
FES A1 routed to the Grated Manhole A2 by a swale
1 0.39 0.49 6.2 0.19 2.61 0.5 (in cases the perfoated pipe is at maximum capacity)
Runoff from the northeast pavement will drain out of a
concrete drain pad and into a bioswale routed for Grated
Manhole A2. Piped flows from A1 and runoff from the
northeast pavement enter the Grated Manhole A2 and then
directed south to sub-bsain A8 (in cases the perfoated pipe is at
2 A2 0.50 0.54 7.3 0.27 2.49 0.7 7.3 0.46 2.49 1.1 maximum capacity)
Runoff from the crowned private road will drina into the inlet
3 A3 0.08 0.51 5.0 0.04 2.78 0.1 and outfall into A8
Runoff from the roof will drain to the 4 Grated Manholes
4 A4 0.18 0.45 5.0 0.08 2.78 0.2 within the patio area
Runoff from the roof and piped flows from sub-basin A4 will drain into
the courtyward to the grated manholes, the stormwater will then be
5 A5 0.24 0.75 5.0 0.18 2.78 0.5 5.0 0.26 2.78 0.7 routed to the storm sewer tee section in sub-basin A8
Runoff from the roof will drain into the courtyard to the grated
manholes, the stormwater will be combined with piped flows from A5
6 A6 0.24 0.75 5.0 0.18 2.78 0.5 5.0 0.44 2.78 1.2 and will be routed to the tee section in cub-basin A8
Runoff from the roof will drain to the 4 grated manholes within the
7 A7 0.10 0.75 5.0 0.07 2.78 0.2 5.0 0.51 2.78 1.4 patio area and combined with piped flows from sub-basins A4 and A5
Runoff from the patio berm and piped flows from A1 to A7 enter
sub-basin A8 and then to Pond A, the runoff will be filtered into
the soil beneeath the manhole. In cases when the manhole is at
full capacity, the stromwater will be routed to the A12 Basin.
8 A8 0.19 0.19 5.0 0.04 2.78 0.1 7.3 1.05 2.49 2.6 A swale south of the building will also direct the flow to A8
A swale will direct the flow from the building and into the
9 A9 0.09 0.55 5.0 0.05 2.78 0.1 Grated Manhole A9
Runoff in sub-basin A10 collects in the grated manhole and is
10 A10 0.02 0.35 5.0 0.01 2.78 0.0 5.0 0.06 2.78 0.2 combined with sub-basin A9 piped flows
The swale adjacent to the west patio berm is to collect runoff from
Project Name: Windsong
Subdivision: Windsong Project No.:
Location: Fort Collins Calculated By: KAU
Design Storm: Checked By: 0
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff.
Tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Slope (%)
Street Flow (cfs)
Design Flow (cfs)
Slope (%)
Pipe Size (inches)
Length (ft)
Velocity (fps)
Tt (min)
REMARKS
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN (MINOR STORM)
(RATIONAL METHOD PROCEDURE)
39727.00
2-Year
9/23/15
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
Pond Basin A12 collects A1 to A11 and B1 to B5 piped flows
12 A12 0.29 0.38 5.0 0.11 2.78 0.3 7.3 1.49 2.49 3.7 and outfalls to the outlet structure routing the flows east
18 C1 0.06 0.28 5.0 0.02 2.78 0.1 Runoff flows to Ziegler Raod and directed (North) off site
Runoff flows to Ziegler Raod and directed (south) to
C2 0.13 0.29 5.5 0.04 2.71 0.1 Rock Creek Drive and then directed east
Runoff flows to south to Rock Creek Drive and then
C3 0.10 0.32 5.0 0.03 2.78 0.1 5.5 0.07 2.71 0.2 directed east
Runoff flows to south to Rock Creek Drive and then
C4 0.09 0.27 5.0 0.02 2.78 0.1 5.5 0.09 2.71 0.2 directed east
Runoff flows south to the concrete pan on Rock Creek Drive
19 C5 0.05 0.63 5.0 0.03 2.78 0.1 5.5 0.30 2.71 0.1 and then directed east
Runoff along the private street will enter the concrete pad at the
low point on the east side of the street. The stormwater will
20 C6 0.22 0.80 5.0 0.18 2.78 0.5 outfall off the site
X:\3970000.all\3972700\Excel\Drainage\2015-11-4_Drainage Calcs.xlsm Page 2 of 2 11/17/2015
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN (MAJOR STORM)
(RATIONAL METHOD PROCEDURE)
Project Name: Windsong
Subdivision: Windsong Project No.:
Location: Fort Collins Calculated By: KAU
Design Storm: Checked By: 0
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff.
Tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Slope (%)
Street Flow (cfs)
Design Flow (cfs)
Slope (%)
Pipe Size (inches)
Length (ft)
Velocity (fps)
Tt (min)
REMARKS
Runoff from northwest pavement will drain out of a concrete
concrete drain pad and into a bioswale. The flow is directed to
FES A1 routed to the Grated Manhole A2 by a swale
1 A1 0.39 0.65 6.2 0.25 9.12 2.3 3.2 0.5 12 (in cases the perfoated pipe is at maximum capacity)
Runoff from the northeast pavement will drain out of a
concrete drain pad and into a bioswale routed for Grated
Manhole A2. Piped flows from A1 and runoff from the
northeast pavement enter the Grated Manhole A2 and then
directed south to sub-bsain A8 (in cases the perfoated pipe is at
2 A2 0.50 0.68 7.3 0.34 8.69 3.0 7.3 0.59 8.69 5.1 7.9 0.5 18 maximum capacity)
Runoff from the crowned private road will drina into the inlet
3 A3 0.08 0.66 5.0 0.06 9.70 0.6 2.7 0.5 12 and outfall into A8
Runoff from the roof will drain to the 4 Grated Manholes
4 A4 0.18 0.63 5.0 0.11 9.70 1.1 4.5 1.0 12 within the patio area
Runoff from the roof and piped flows from sub-basin A4 will drain into
the courtyward to the grated manholes, the stormwater will then be
5 A5 0.24 0.83 5.0 0.20 9.70 1.9 5.0 0.31 9.70 3.0 3.2 0.5 12 routed to the storm sewer tee section in sub-basin A8
Runoff from the roof will drain into the courtyard to the grated
manholes, the stormwater will be combined with piped flows from A5
6 A6 0.24 0.83 5.0 0.20 9.70 1.9 5.0 0.51 9.70 4.9 5.8 0.5 15 and will be routed to the tee section in cub-basin A8
Runoff from the roof will drain to the 4 grated manholes within the
7 A7 0.10 0.83 5.0 0.08 9.70 0.8 5.0 0.59 9.70 5.7 8.1 1.0 15 patio area and combined with piped flows from sub-basins A4 and A5
Runoff from the patio berm and piped flows from A1 to A7 enter
sub-basin A8 and then to Pond A, the runoff will be filtered into
the soil beneeath the manhole. In cases when the manhole is at
full capacity, the stromwater will be routed to the A12 Basin.
8 A8 0.19 0.52 5.0 0.10 9.70 1.0 7.3 1.34 8.69 11.6 11.9 0.5 21 A swale south of the building will also direct the flow to A8
A swale will direct the flow from the building and into the
9 A9 0.09 0.69 5.0 0.06 9.70 0.6 3.2 0.5 12 Grated Manhole A9
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN (MAJOR STORM)
(RATIONAL METHOD PROCEDURE)
Project Name: Windsong
Subdivision: Windsong Project No.:
Location: Fort Collins Calculated By: KAU
Design Storm: Checked By: 0
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff.
Tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Slope (%)
Street Flow (cfs)
Design Flow (cfs)
Slope (%)
Pipe Size (inches)
Length (ft)
Velocity (fps)
Tt (min)
REMARKS
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
39727.00
100-Year
9/23/15
Pond Basin A12 collects A1 to A11 and B1 to B5 piped flows
12 A12 0.29 0.60 5.0 0.17 9.70 1.6 7.3 1.86 8.69 16.2 17.1 0.5 24 and outfalls to the outlet structure routing the flows east
18 C1 0.06 0.28 5.0 0.02 9.70 0.2 Runoff flows to Ziegler Raod and directed (North) off site
Runoff flows to Ziegler Raod and directed (south) to
C2 0.13 0.29 5.5 0.04 9.44 0.4 Rock Creek Drive and then directed east
Runoff flows to south to Rock Creek Drive and then
C3 0.10 0.32 5.0 0.03 9.70 0.3 5.5 0.07 9.44 0.7 directed east
Runoff flows to south to Rock Creek Drive and then
C4 0.09 0.27 5.0 0.02 9.70 0.2 5.5 0.09 9.44 0.9 directed east
Runoff flows south to the concrete pan on Rock Creek Drive
19 C5 0.05 0.63 5.0 0.03 9.70 0.3 5.5 0.30 9.44 0.3 and then directed east
Runoff along the private street will enter the concrete pad at the
low point on the east side of the street. The stormwater will
20 C6 0.22 0.80 5.0 0.18 9.70 1.7 outfall off the site
X:\3970000.all\3972700\Excel\Drainage\2015-11-4_Drainage Calcs.xlsm Page 2 of 2 11/17/2015
APPENDIX C – HYDRAULIC CALCULATIONS
APPENDIX D – WATER QUALITY/DETENTION CALCULATIONS
Subdivision: Windsong Project Name: Windsong
Location: Fort Collins Project No.: 39727.00
Calculated By: KAU
Checked By: 0
Date: 9/23/15
Water Quality Pond A
Basin Area % Imp
A1 0.3872 64.6
A2 0.4969 71.1
A3 0.0126 5
A4 0.1818 59.2
A5 0.2414 90
A6 0.2415 90
A7 0.0989 90
A8 0.1257 7.7
A9 0.0887 72.5
A10 0.0172 39.2
A11 0.1157 84.2
A12 0.2903 47.1
B1 0.0422 20.2
B2 0.2138 12.8
B3 0.0829 65.1
B4 0.1437 75.4
B5 0.0198 20.2
Total 2.8003 62.6
Detention Pond Tributary Areas
X:\3970000.all\3972700\Excel\Drainage\2015-11-4_Drainage Calcs.xlsm Page 15 of 32 11/10/2015
Subdivision:
Project Name:
Project No.:
Calculated By:
Date:
Water Quality/Detention Volume Requirements
Required Volume
(ac-ft)
[1] WQCV 0.073
[2] 1.2*WQCV 0.088
[3] 2-Year 0.039
[4] 100-Year 0.460
[5] 20% of 100-Year 0.092
[6] TOTAL POND VOLUME 0.640
Design Volumes for Stage-Storage Tables
Required Volume
(ac-ft)
[7] Design WQCV 0.088
[8] Design 2-Year Vol 0.127
[9] Design 100-Year Vol 0.640
[1] Water Quality Capture Volume from UD-Detention WQCV tab
[2] Design Volume from UD-Detention WQCV tab
[3] 2-Year required storage volume from UD-Detention FAA tab
[4] 100-Year required storage volume from UD-Detention FAA tab
[5] 20% of 100-Year required storage volume from UD-Detention FAA tab per City criteria
[6] Total Required Volume: Row [2]+ Row [4]+ Row [5]
[7] Design WQCV: Same as Row [2]
[8] Design 2-Year Vol: Row [2]+Row[3]
[9] Design 100-Year Vol: Row [2]+ Row [4]+ Row [5]
Harmony Technology Park
Windsong at Rock Creek
39727.00
TAB
11/5/2015
Project:
Basin ID:
Design Information (Input): Design Information (Input):
Catchment Drainage Imperviousness Ia = 62.60 percent Catchment Drainage Imperviousness I
a = 62.60 percent
Catchment Drainage Area A = 2.800 acres Catchment Drainage Area A = 2.800 acres
Predevelopment NRCS Soil Group Type = C A, B, C, or D Predevelopment NRCS Soil Group Type = C A, B, C, or D
Return Period for Detention Control T = 2 years (2, 5, 10, 25, 50, or 100) Return Period for Detention Control T = 100 years (2, 5, 10, 25, 50, or 100)
Time of Concentration of Watershed Tc = 11 minutes Time of Concentration of Watershed Tc = 11 minutes
Allowable Unit Release Rate q = 0.33 cfs/acre Allowable Unit Release Rate q = 0.33 cfs/acre
One-hour Precipitation P1 = 0.82 inches One-hour Precipitation P
1 = 2.86 inches
Design Rainfall IDF Formula i = C1* P1
/(C2+Tc
)^C3 Design Rainfall IDF Formula i = C1
* P1/(C2
+Tc)^C3
Coefficient One C1 = 28.50 Coefficient One C
1 = 28.50
Coefficient Two C2 = 10 Coefficient Two C
2 = 10
Coefficient Three C3 = 0.789 Coefficient Three C
3 = 0.789
Determination of Average Outflow from the Basin (Calculated): Determination of Average Outflow from the Basin (Calculated):
Runoff Coefficient C = 0.43 Runoff Coefficient C = 0.64
Inflow Peak Runoff Qp-in = 2.59 cfs Inflow Peak Runoff Qp-in = 13.43 cfs
Allowable Peak Outflow Rate Qp-out = 0.92 cfs Allowable Peak Outflow Rate Qp-out = 0.92 cfs
Mod. FAA Minor Storage Volume = 1,679 cubic feet Mod. FAA Major Storage Volume = 20,043 cubic feet
Mod. FAA Minor Storage Volume = 0.039 acre-ft Mod. FAA Major Storage Volume = 0.460 acre-ft
15 <- Enter Rainfall Duration Incremental Increase Value Here (e.g. 5 for 5-Minutes)
Rainfall Rainfall Inflow Adjustment Average Outflow Storage Rainfall Rainfall Inflow Adjustment Average Outflow Storage
Duration Intensity Volume Factor Outflow Volume Volume Duration Intensity Volume Factor Outflow Volume Volume
minutes inches / hr acre-feet "m" cfs acre-feet acre-feet minutes inches / hr acre-feet "m" cfs acre-feet acre-feet
(input) (output) (output) (output) (output) (output) (output) (input) (output) (output) (output) (output) (output) (output)
0 0.00 0.000 0.00 0.00 0.000 0.000 0 0.00 0.000 0.00 0.00 0.000 0.000
15 1.84 0.046 0.85 0.79 0.016 0.030 15 6.43 0.238 0.85 0.79 0.016 0.222
30 1.27 0.063 0.68 0.62 0.026 0.038 30 4.44 0.329 0.68 0.62 0.026 0.303
45 0.99 0.074 0.62 0.57 0.035 0.039 45 3.45 0.383 0.62 0.57 0.035 0.348
60 0.82 0.081 0.59 0.54 0.045 0.037 60 2.85 0.423 0.59 0.54 0.045 0.378
75 0.70 0.087 0.57 0.53 0.054 0.033 75 2.45 0.453 0.57 0.53 0.054 0.399
90 0.62 0.092 0.56 0.52 0.064 0.028 90 2.15 0.479 0.56 0.52 0.064 0.415
105 0.55 0.096 0.55 0.51 0.073 0.023 105 1.93 0.500 0.55 0.51 0.073 0.427
120 0.50 0.100 0.54 0.50 0.083 0.017 120 1.75 0.519 0.54 0.50 0.083 0.436
135 0.46 0.103 0.54 0.50 0.092 0.011 135 1.61 0.535 0.54 0.50 0.092 0.443
150 0.43 0.106 0.54 0.49 0.102 0.004 150 1.49 0.550 0.54 0.49 0.102 0.448
165 0.40 0.109 0.53 0.49 0.112 -0.003 165 1.39 0.564 0.53 0.49 0.112 0.453
180 0.37 0.111 0.53 0.49 0.121 -0.010 180 1.30 0.577 0.53 0.49 0.121 0.456
195 0.35 0.113 0.53 0.49 0.131 -0.017 195 1.22 0.588 0.53 0.49 0.131 0.458
210 0.33 0.115 0.53 0.48 0.140 -0.025 210 1.16 0.599 0.53 0.48 0.140 0.459
225 0.31 0.117 0.52 0.48 0.150 -0.032 225 1.10 0.610 0.52 0.48 0.150 0.460
240 0.30 0.119 0.52 0.48 0.159 -0.040 240 1.05 0.619 0.52 0.48 0.159 0.460
255 0.29 0.121 0.52 0.48 0.169 -0.048 255 1.00 0.628 0.52 0.48 0.169 0.460
270 0.27 0.123 0.52 0.48 0.178 -0.055 270 0.96 0.637 0.52 0.48 0.178 0.459
285 0.26 0.124 0.52 0.48 0.188 -0.063 285 0.92 0.645 0.52 0.48 0.188 0.458
300 0.25 0.126 0.52 0.48 0.197 -0.071 300 0.88 0.653 0.52 0.48 0.197 0.456
315 0.24 0.127 0.52 0.48 0.207 -0.080 315 0.85 0.661 0.52 0.48 0.207 0.454
330 0.24 0.129 0.52 0.48 0.216 -0.088 330 0.82 0.668 0.52 0.48 0.216 0.452
345 0.23 0.130 0.52 0.48 0.226 -0.096 345 0.79 0.675 0.52 0.48 0.226 0.449
360 0.22 0.131 0.51 0.47 0.235 -0.104 360 0.77 0.682 0.51 0.47 0.235 0.446
375 0.21 0.133 0.51 0.47 0.245 -0.112 375 0.74 0.688 0.51 0.47 0.245 0.443
Project:
Basin ID:
UDFCD DETENTION BASIN VOLUME ESTIMATING WORKBOOK Version 2.35, Released January 2015
DETENTION VOLUME BY THE MODIFIED FAA METHOD
Windsong at Rock Creek
Water Quality/Detention Pond A
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 100 200 300 400 500 600 700 800 900 1000
Volume (acre-feet)
Duration (Minutes)
Inflow and Outflow Volumes vs. Rainfall Duration
Minor Storm Inflow Volume Minor Storm Outflow Volume Minor Storm Storage Volume Major Storm Inflow Volume Major Storm Outflow Volume Major Storm Storage Volume
UD-Detention - Pond A.xls, Modified FAA 11/10/2015, 4:55 PM
Project:
Basin ID:
WQCV Design Volume (Input):
Catchment Imperviousness, Ia = 62.6 percent
Catchment Area, A = 2.80 acres Diameter of holes, D = 0.656 inches
Depth at WQCV outlet above lowest perforation, H = 1.00 feet Number of holes per row, N = 1
Vertical distance between rows, h = 4.00 inches OR
Number of rows, NL = 3.00
Orifice discharge coefficient, Co = 0.70 Height of slot, H = inches
Slope of Basin Trickle Channel, S = 0.005 ft / ft Width of slot, W = inches
Time to Drain the Pond = 40 hours
Watershed Design Information (Input): 1
Percent Soil Type A = %
Percent Soil Type B = %
Percent Soil Type C/D = 100 %
Outlet Design Information (Output):
Water Quality Capture Volume, WQCV = 0.315 watershed inches
Water Quality Capture Volume (WQCV) = 0.073 acre-feet 0.00
Design Volume (WQCV / 12 * Area * 1.2) Vol = 0.088 acre-feet
Outlet area per row, Ao = 0.30 square inches
Total opening area at each row based on user-input above, Ao = 0.34 square inches
Total opening area at each row based on user-input above, Ao = 0.002 square feet
3
Row 1 Row 2 Row 3 Row 4 Row 5 Row 6 Row 7 Row 8 Row 9 Row 10 Row 11 Row 12 Row 13 Row 14 Row 15 Row 16 Row 17 Row 18 Row 19 Row 20 Row 21 Row 22 Row 23 Row 23 6
4915.27 4915.60 4915.94 Flow
4915.00 0.0000 0.0000 0.0000 0.00
4915.50 0.0063 0.0000 0.0000 0.01
4916.00 0.0113 0.0083 0.0032 0.02
4916.50 0.0146 0.0125 0.0099 0.04
4917.00 0.0173 0.0156 0.0136 0.05
4917.50 0.0197 0.0182 0.0165 0.05
4918.00 0.0218 0.0204 0.0189 0.06
4918.50 0.0237 0.0225 0.0211 0.07
4919.00 0.0255 0.0243 0.0231 0.07
4919.50 0.0271 0.0260 0.0249 0.08
4920.00 0.0287 0.0277 0.0266 0.08
4920.50 0.0302 0.0292 0.0282 0.09
4921.00 0.0316 0.0306 0.0297 0.09
#N/A
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Worksheet Protected
Project:
Basin ID:
STAGE-DISCHARGE SIZING OF THE WATER QUALITY CAPTURE VOLUME (WQCV) OUTLET
Windsong at Rock Creek
Water Quality/Detention Pond A
4914.00
4915.00
4916.00
4917.00
4918.00
4919.00
4920.00
4921.00
4922.00
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
Stage (feet, elev.)
Discharge (cfs)
STAGE-DISCHARGE CURVE FOR THE WQCV OUTLET STRUCTURE
UD-Detention - Pond A.xls, WQCV 11/10/2015, 4:57 PM
Subdivision Windsong Project Name: Windsong
Location Fort Collins Project No. 39727.00
By: KAU
Volume=1/3 x Depth x (A+B+(A*B)^0.5) Checked By: 0
A - Upper Surface Date: 9/23/15
B - Lower Surface
Pond SW Corner
Stage Stage
Stage Surface Area Stage Volume Cumulative Volume Cumulative Volume
Elevation (square feet) (cubic feet) (cubic feet) (acre feet)
0.00 4915.50 111 0 0 0.00
0.50 4916.00 467 134 134 0.00
1.00 4916.50 1,676 505 639 0.01
1.50 4917.00 2,992 1,151 1,790 0.04
2.00 4917.50 3,932 1,726 3,516 0.08
2.50 4918.00 4,579 2,126 5,642 0.13
3.00 4918.50 5,116 2,423 8,065 0.19
3.50 4919.00 8,196 3,298 11,363 0.26
4.00 4919.50 6,468 3,657 15,020 0.34
4.50 4920.00 10,676 4,242 19,262 0.44
5.00 4920.50 10,417 5,273 24,535 0.56
5.50 4921.00 6,149 4,095 28,630 0.66
6.00 4921.50 4,848 2,743 31,373 0.72
6.50 4922.00 4,976 2,456 33,829 0.78
Volume Water Surface Elevation
Water Quality 0.09 4918.18
2-Year Detention 0.13 4918.38
100-Year Detention 0.64 4921.02
WATER QUALITY POND A VOLUME CALCULATIONS
Volume (acre feet)
X:\3970000.all\3972700\Excel\Drainage\2015-11-4_Drainage Calcs.xlsm Page 18 of 32 11/10/2015
Project:
Basin ID:
X
1
#1 Vertical #2 Vertical
Sizing the Restrictor Plate for Circular Vertical Orifices or Pipes (Input) Orifice Orifice
Water Surface Elevation at Design Depth Elev: WS = 4,921.00 feet
Pipe/Vertical Orifice Entrance Invert Elevation Elev: Invert = 4,915.00 feet
Required Peak Flow through Orifice at Design Depth Q = 0.92 cfs
Pipe/Vertical Orifice Diameter (inches) Dia = 18.0 inches
Orifice Coefficient Co = 0.63
Full-flow Capacity (Calculated)
Full-flow area Af = 1.77 sq ft
Half Central Angle in Radians Theta = 3.14 rad
Full-flow capacity Qf = 19.8 cfs
Percent of Design Flow = 2145%
Calculation of Orifice Flow Condition
Half Central Angle (0<Theta<3.1416) Theta = 0.61 rad
Flow area Ao = 0.08 sq ft
Top width of Orifice (inches) To = 10.31 inches
Height from Invert of Orifice to Bottom of Plate (feet) Yo = 0.14 feet
Elevation of Bottom of Plate Elev Plate Bottom Edge = 4,915.41 feet
Resultant Peak Flow Through Orifice at Design Depth Qo = 0.9 cfs
Width of Equivalent Rectangular Vertical Orifice Equivalent Width = 0.57 feet
Centroid Elevation of Equivalent Rectangular Vertical Orifice Equiv. Centroid El. = 4,915.07 feet
Windsong at Rock Creek
Water Quality/Detention Pond A
RESTRICTOR PLATE SIZING FOR CIRCULAR VERTICAL ORIFICES
UD-Detention - Pond A.xls, Restrictor Plate 11/10/2015, 5:00 PM
APPENDIX E – MAPS
WINDSONG AT ROCK CREEK
PERMEABLE PAVEMENT AREA EXHIBIT
LID IMPLEMENTATION PLAN
Know what's
Surface Material Area (SF) % of Total
Pervious Interlocking
Concrete Pavers (PICP)
21,723 66%
Impervious Asphalt
Pavement
11,085 34%
Total 32,808 100%
Parking Areas
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
CityDate Engineer
WaterDate & Wastewater Utility
StormwaterDate Utility
ParksDate & Recreation
TrafficDate Engineer Date
EnvironmentalDate Planner
Date
Larimer County, Colorado
UTILITY PLAN APPROVAL
LarimerDate County Engineer
WINDSONG AT ROCK CREEK
IMPERVIOUS AREA TREATMENT PLAN
Know what's
Total Site Area 3.34 AC
New Impervious Area 2.03 AC
Required Minimum Impervious Area to be
Treated
1.02 AC
LID Treated Area #1 0.13 AC
LID Treated Area #2 0.26 AC
Area Treated by LID Basin 3.24 AC
Building Roofs Treated by LID BMP's 0.88 AC
Sidewalks Treated by LID BMP's 0.18 AC
Patios Treated by LID BMP's 0.20 AC
Permeable Interlocking Concrete Pavers 0.20 AC
Impervious Area Not Treated 0.18 AC
Total Impervious Area Treated 1.85 AC
50% On-Site Treatment by LID Requirement
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
CityDate Engineer
WaterDate & Wastewater Utility
StormwaterDate Utility
ParksDate & Recreation
TrafficDate Engineer Date
EnvironmentalDate Planner
Date
Larimer County, Colorado
UTILITY PLAN APPROVAL
LarimerDate County Engineer
LID TREATED
AREA #1
LID TREATED
AREA #2
LID TREATED
AREA #2
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
CityDate Engineer
WaterDate & Wastewater Utility
StormwaterDate Utility
ParksDate & Recreation
TrafficDate Engineer Date
EnvironmentalDate Planner
Date
Larimer County, Colorado
UTILITY PLAN APPROVAL
LarimerDate County Engineer
DESIGN BASIN D.A. Impervious C100 C5
POINT ID (AC) (%)
1 OF1 2.30 2.00 0.51 0.16
EX1 2.99 2.00 0.51 0.16
2 EX2 0.17 2.00 0.51 0.16
3 EX3 0.19 2.00 0.51 0.16
SUB-BASIN
DATA
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
CityDate Engineer
WaterDate & Wastewater Utility
StormwaterDate Utility
ParksDate & Recreation
TrafficDate Engineer Date
EnvironmentalDate Planner
Date
Larimer County, Colorado
UTILITY PLAN APPROVAL
LarimerDate County Engineer
DESIGN BASIN D.A. Hydrologic Impervious C100 C5
POINT ID (AC) Soils Group (%)
1 A1 0.39 C 64.60 0.65 0.49
2 A2 0.50 C 71.10 0.68 0.54
3 A3 0.08 C 67.00 0.66 0.51
4 A4 0.18 C 59.20 0.63 0.45
5 A5 0.24 C 90.00 0.83 0.75
6 A6 0.24 C 90.00 0.83 0.75
7 A7 0.10 C 90.00 0.83 0.75
8 A8 0.19 C 6.80 0.52 0.19
9 A9 0.09 C 72.50 0.69 0.55
10 A10 0.02 C 39.20 0.58 0.35
11 A11 0.12 C 84.20 0.78 0.67
12 A12 0.29 C 47.10 0.60 0.38
13 B1 0.04 C 13.70 0.54 0.23
14 B2 0.21 C 12.80 0.54 0.23
15 B3 0.08 C 65.10 0.65 0.49
16 B4 0.14 C 75.40 0.71 0.58
17 B5 0.02 C 20.20 0.55 0.26
18 C1 0.06 C 24.50 0.56 0.28
C2 0.13 C 26.30 0.56 0.29
C3 0.10 C 33.00 0.57 0.32
C4 0.09 C 21.70 0.56 0.27
19 C5 0.05 C 80.30 0.75 0.63
20 C6 0.22 C 94.10 0.88 0.80
SUB-BASIN
DATA
WQ DETENTION
POND B
WQ DETENTION
POND A
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
CityDate Engineer
WaterDate & Wastewater Utility
StormwaterDate Utility
ParksDate & Recreation
TrafficDate Engineer Date
EnvironmentalDate Planner
Date
Larimer County, Colorado
UTILITY PLAN APPROVAL
LarimerDate County Engineer
#N/A
#N/A
#N/A
#N/A
#N/A
#N/A
#N/A
#N/A
#N/A
Override
Area
Row 1
Override
Area
Row 2
Override
Area
Row 3
Override
Area
Row 4
Override
Area
Row 5
Override
Area
Row 6
Override
Area
Row 7
Override
Area
Row 8
Override
Area
Row 9
Override
Area
Row 10
Override
Area
Row 11
Override
Area
Row 12
Override
Area
Row 13
Override
Area
Row 14
Override
Area
Row 15
Override
Area
Row 16
Override
Area
Row 17
Override
Area
Row 18
Override
Area
Row 19
Override
Area
Row 20
Override
Area
Row 21
Override
Area
Row 22
Override
Area
Row 23
Override
Area
Row 24
Central Elevations of Rows of Holes in feet
Collection Capacity for Each Row of Holes in cfs
STAGE-DISCHARGE SIZING OF THE WATER QUALITY CAPTURE VOLUME (WQCV) OUTLET
Windsong at Rock Creek
Water Quality/Detention Pond A
UD-Detention - Pond A.xls, WQCV 11/10/2015, 4:57 PM
390 0.21 0.134 0.51 0.47 0.254 -0.121 390 0.72 0.695 0.51 0.47 0.254 0.440
405 0.20 0.135 0.51 0.47 0.264 -0.129 405 0.70 0.701 0.51 0.47 0.264 0.437
420 0.20 0.136 0.51 0.47 0.274 -0.137 420 0.68 0.706 0.51 0.47 0.274 0.433
435 0.19 0.137 0.51 0.47 0.283 -0.146 435 0.66 0.712 0.51 0.47 0.283 0.429
450 0.19 0.138 0.51 0.47 0.293 -0.154 450 0.65 0.718 0.51 0.47 0.293 0.425
465 0.18 0.139 0.51 0.47 0.302 -0.163 465 0.63 0.723 0.51 0.47 0.302 0.421
480 0.18 0.140 0.51 0.47 0.312 -0.171 480 0.61 0.728 0.51 0.47 0.312 0.417
495 0.17 0.141 0.51 0.47 0.321 -0.180 495 0.60 0.733 0.51 0.47 0.321 0.412
510 0.17 0.142 0.51 0.47 0.331 -0.188 510 0.59 0.738 0.51 0.47 0.331 0.408
525 0.16 0.143 0.51 0.47 0.340 -0.197 525 0.57 0.743 0.51 0.47 0.340 0.403
540 0.16 0.144 0.51 0.47 0.350 -0.206 540 0.56 0.748 0.51 0.47 0.350 0.398
555 0.16 0.145 0.51 0.47 0.359 -0.214 555 0.55 0.753 0.51 0.47 0.359 0.393
570 0.15 0.146 0.51 0.47 0.369 -0.223 570 0.54 0.757 0.51 0.47 0.369 0.388
585 0.15 0.147 0.51 0.47 0.378 -0.232 585 0.53 0.762 0.51 0.47 0.378 0.383
600 0.15 0.148 0.51 0.47 0.388 -0.240 600 0.52 0.766 0.51 0.47 0.388 0.378
615 0.15 0.148 0.51 0.47 0.397 -0.249 615 0.51 0.770 0.51 0.47 0.397 0.373
630 0.14 0.149 0.51 0.47 0.407 -0.258 630 0.50 0.774 0.51 0.47 0.407 0.367
645 0.14 0.150 0.51 0.47 0.416 -0.266 645 0.49 0.778 0.51 0.47 0.416 0.362
660 0.14 0.151 0.51 0.47 0.426 -0.275 660 0.48 0.782 0.51 0.47 0.426 0.356
675 0.14 0.151 0.51 0.47 0.435 -0.284 675 0.47 0.786 0.51 0.47 0.435 0.351
690 0.13 0.152 0.51 0.47 0.445 -0.293 690 0.46 0.790 0.51 0.47 0.445 0.345
705 0.13 0.153 0.51 0.47 0.455 -0.302 705 0.46 0.794 0.51 0.47 0.455 0.339
720 0.13 0.154 0.51 0.47 0.464 -0.310 720 0.45 0.798 0.51 0.47 0.464 0.334
735 0.13 0.154 0.51 0.47 0.474 -0.319 735 0.44 0.801 0.51 0.47 0.474 0.328
750 0.12 0.155 0.51 0.47 0.483 -0.328 750 0.43 0.805 0.51 0.47 0.483 0.322
765 0.12 0.156 0.51 0.47 0.493 -0.337 765 0.43 0.808 0.51 0.47 0.493 0.316
780 0.12 0.156 0.51 0.47 0.502 -0.346 780 0.42 0.812 0.51 0.47 0.502 0.310
795 0.12 0.157 0.51 0.47 0.512 -0.355 795 0.42 0.815 0.51 0.47 0.512 0.304
810 0.12 0.158 0.51 0.47 0.521 -0.363 810 0.41 0.819 0.51 0.47 0.521 0.298
825 0.12 0.158 0.51 0.47 0.531 -0.372 825 0.40 0.822 0.51 0.47 0.531 0.291
840 0.11 0.159 0.51 0.47 0.540 -0.381 840 0.40 0.825 0.51 0.47 0.540 0.285
855 0.11 0.160 0.51 0.47 0.550 -0.390 855 0.39 0.829 0.51 0.47 0.550 0.279
870 0.11 0.160 0.51 0.47 0.559 -0.399 870 0.39 0.832 0.51 0.47 0.559 0.272
885 0.11 0.161 0.51 0.47 0.569 -0.408 885 0.38 0.835 0.51 0.47 0.569 0.266
900 0.11 0.161 0.51 0.47 0.578 -0.417 900 0.38 0.838 0.51 0.47 0.578 0.260
Mod. FAA Minor Storage Volume (cubic ft.) = 1,679 Mod. FAA Major Storage Volume (cubic ft.) = 20,043
Mod. FAA Minor Storage Volume (acre-ft.) = 0.0386 Mod. FAA Major Storage Volume (acre-ft.) = 0.4601
Determination of MAJOR Detention Volume Using Modified FAA Method
(For catchments less than 160 acres only. For larger catchments, use hydrograph routing method)
(NOTE: for catchments larger than 90 acres, CUHP hydrograph and routing are recommended)
UDFCD DETENTION BASIN VOLUME ESTIMATING WORKBOOK Version 2.35, Released January 2015
Determination of MINOR Detention Volume Using Modified FAA Method
DETENTION VOLUME BY THE MODIFIED FAA METHOD
Windsong at Rock Creek
Water Quality/Detention Pond A
UD-Detention - Pond A.xls, Modified FAA 11/10/2015, 4:55 PM
Runoff in sub-basin A10 collects in the grated manhole and is
10 A10 0.02 0.58 5.0 0.01 9.70 0.1 5.0 0.07 9.70 0.7 2.7 0.5 12 combined with sub-basin A9 piped flows
The swale adjacent to the west patio berm is to collect runoff from
13 B1 0.04 0.23 5.0 0.01 9.70 0.1 3.2 0.5 12 the berm and route the flows to the grated manhole B1
Pond Basin B2 collects the sub-basin runoff
14 B2 0.21 0.23 6.9 0.05 8.84 0.4 6.9 0.06 8.84 0.5 2.8 0.5 12 and B1 piped flows
A swale will direct the flow from the building and into the
15 B3 0.08 0.49 5.0 0.04 9.70 0.4 3.2 0.5 12 Grated Manhole A3
The Sump Inlet collects sub-basin B4 runoff as well as piped flows from
16 B4 0.14 0.58 5.0 0.08 9.70 0.8 6.9 0.18 8.84 1.6 2.7 0.5 12 Pond Basin B2 and piped flows from sub-basin B3
Runoff in sub-basin B5 collects in the grated manhole and is
17 B5 0.02 0.26 7.1 0.01 8.77 0.1 7.1 0.19 8.77 1.7 2.7 0.5 12 combined with sub-basin B1 to B4 piped flows
The Sump Inlet collects sub-basin A11 runoff combined with A9 to
11 A11 0.12 0.78 5.0 0.09 9.70 0.9 7.1 0.35 8.77 3.1 4.9 0.5 15 A10 piped flows as well as B1-B4 piped flows
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
39727.00
100-Year
9/23/15
X:\3970000.all\3972700\Excel\Drainage\2015-11-4_Drainage Calcs.xlsm Page 1 of 2 11/17/2015
13 B1 0.04 0.23 5.0 0.01 2.78 0.0 the berm and route the flows to the grated manhole B1
Pond Basin B2 collects the sub-basin runoff
14 B2 0.21 0.23 6.9 0.05 2.53 0.1 6.9 0.06 2.53 0.2 and B1 piped flows
A swale will direct the flow from the building and into the
15 B3 0.08 0.49 5.0 0.04 2.78 0.1 Grated Manhole A3
The Sump Inlet collects sub-basin B4 runoff as well as piped flows from
16 B4 0.14 0.58 5.0 0.08 2.78 0.2 6.9 0.18 2.53 0.5 Pond Basin B2 and piped flows from sub-basin B3
Runoff in sub-basin B5 collects in the grated manhole and is
17 B5 0.02 0.26 7.1 0.01 2.51 0.0 7.1 0.19 2.51 0.5 combined with sub-basin B1 to B4 piped flows
The Sump Inlet collects sub-basin A11 runoff combined with A9 to
11 A11 0.12 0.67 5.0 0.08 2.78 0.2 7.1 0.33 2.51 0.8 A10 piped flows as well as B1-B4 piped flows
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN (MINOR STORM)
(RATIONAL METHOD PROCEDURE)
A1
39727.00
2-Year
9/23/15
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
X:\3970000.all\3972700\Excel\Drainage\2015-11-4_Drainage Calcs.xlsm Page 1 of 2 11/17/2015
(Tt)
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