HomeMy WebLinkAboutENCLAVE AT REDWOOD - FDP220014 - DOCUMENT MARKUPS - ROUND 2 - DRAINAGE REPORT
PRELIMINARY DRAINAGE REPORT
FOR
ENCLAVE AT REDWOOD
Fort Collins, CO 80524
Date: August 18, 2021
Revised: October 19, 2021
December 22, 2021
Prepared for:
9555 South Kingston Court
Denver, CO 80112
Phone: 303‐488‐0061
Prepared by:
Mark A. West, P.E., C.F.M.
1120 Lincoln Street, Suite 1000
Denver, CO 80203
Ph.: 303‐623‐6300, Fax: 303‐623‐6311
Harris Kocher Smith Project No. 201013
Enclave at Redwood
Table of Contents
December 22, 2021
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ................................................................................................... 4
A. Site Location ....................................................................................................................................... 4
B. Description of Property ...................................................................................................................... 4
II. MASTER DRAINAGE BASIN DESCRIPTION .................................................................................................. 5
A. Floodplain........................................................................................................................................... 5
B. Master Drainage Basin ....................................................................................................................... 5
III. DRAINAGE DESIGN CRITERIA ................................................................................................................. 6
A. Regulations and Previous Studies ...................................................................................................... 6
B. Four‐Step Process .............................................................................................................................. 6
C. Hydrologic Design Criteria ................................................................................................................. 7
D. Hydraulic Design Criteria .................................................................................................................... 8
E. Variances ............................................................................................................................................ 9
F. Erosion Control .................................................................................................................................. 9
IV. PROPOSED DRAINAGE SYSTEMS ............................................................................................................ 9
A. General Concept ................................................................................................................................ 9
B. Proposed Basins ............................................................................................................................... 10
C. Specific Details ................................................................................................................................. 12
V. CONCLUSIONS ......................................................................................................................................... 16
A. Compliance with Standards ............................................................................................................. 16
B. Drainage Concept ............................................................................................................................. 16
VI. REFERENCES ......................................................................................................................................... 17
VII. APPENDICES ......................................................................................................................................... 18
Appendix A – Vicinity Map, FIRM, Geotechnical Engineering Report ....................................................... A
Appendix B ‐ Portions from Relevant Previous Studies ............................................................................ B
Appendix C – Subcatchment Hydrology .................................................................................................... C
Appendix D – Detention Storage Sizing ..................................................................................................... D
Appendix E – SWMM Model and Results .................................................................................................. E
Appendix F – Low Impact Development ................................................................................................... F
Appendix G – Drainage Map ..................................................................................................................... G
Enclave at Redwood
Engineer Certification
December 22, 2021
Engineer Certification
I hereby attest that this report for the preliminary drainage design for the Enclave at Redwood was
prepared by me or under my direct supervision, in accordance with the provisions of the Fort
Collins Stormwater Criteria Manual. I understand that the City of Fort Collins does not and will not
assume liability for drainage facilities designed by others.
__________________________________ _______________________
Mark A. West, P.E., C.F.M. Date
State Of Colorado Registration No. 38561
On Behalf of Harris Kocher Smith
Enclave at Redwood
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December 22, 2021
I. GENERAL LOCATION AND DESCRIPTION
a. Site Location
The proposed Enclave at Redwood development (hereinafter referred to as “Site”) is located in the
southeast ¼ of Section 1, Township 7 north, Range 69 west of the sixth Principal Meridian, City of Fort
Collins, County of Larimer, State of Colorado. The Site is bounded by Redwood Street to the west and
East Suniga Road to the south. A small portion of the Site exists south of East Suniga Road. Adjacent
developments include the Meadows at Redwood PUD Phase 1 (Redwood Meadows) to the west,
Northfield to the east and southeast, and Evergreen Park 3rd (Evergreen) to the north. Lake Canal exists
as an irrigation ditch adjacent to the Site to the east and southeast, and Redwood Channel lies adjacent
to the Site to the north. The Site will connect to Redwood St to the southwest, Lupine Dr in Redwood
Meadows to the west, Steeley Dr in Northfield to the southeast, and Collamer Dr in Northfield to the
east. See Appendix A for the Vicinity Map. The Site exists entirely within the Dry Creek master drainage
basin.
b. Description of Property
The Site is approximately 29.66 acres of undeveloped land. The undeveloped land is made up of various
native trees and grasses. The Site generally slopes from west to east at grades between roughly 0.3%
and 1% towards Lake Canal. Lake Canal is an irrigation ditch and discharging stormwater from the
developed Site to this ditch will require approval from the ditch ownership. Redwood Pond is an existing
regional pond to the northwest of the Site, it historically outfalls east into the Redwood Channel
drainage ditch that exists north of the Site. The proposed development of the Site will feature mutli‐
family housing, public and private roadways, walks, parks, a clubhouse with pool, landscaped areas, four
on‐Site detention facilities and low‐impact‐development systems.
Cole Garner Geotechnical has prepared a Geotechnical Engineering Report for Enclave at Redwood
Residential Development on August 11, 2021. This report details existing soils information for the Site.
Ten borings were drilled on‐Site to examine subsurface conditions in February of 2021. Groundwater
was encountered in all borings at the time of drilling and approximately two weeks after drilling at
depths ranging from 8 to 12 feet below existing Site grades. In order to account for seasonal
groundwater fluctuations, Cole Garner measured groundwater levels in the aforementioned borings
again in September of 2021. It was found that three of the ten borings saw no change in groundwater
elevation, six of the ten borings saw a rise in groundwater of less than 1.5 feet, and one of the borings
saw a rise in groundwater of 4 feet. The drainage design of the Site will consider the readings from
September to be the more accurate reading indicative of the wet season. Due to shallow groundwater
concerns, construction dewatering may be required. All drainage facilities will be located at least 24
inches above groundwater. Please see Appendix A for relevant portions of the Geotechnical Engineering
Report and a table of the groundwater readings taken in September of 2021.
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II. MASTER DRAINAGE BASIN DESCRIPTION
A. Floodplain
The Site is shown on the Federal Emergency Agency’s (FEMA) Flood Insurance Rate Map (FIRM)
Community Panel Numbers 08069C0977G and 08069C0981G, effective June 17, 2008. Lake Canal is
partially located within Zone X (0.2% annual chance flood hazard) and therefore the Site is partially
within this zone. Because the development of the Site will not involve altering of Lake Canal, no
floodplain modifications are necessary. Please refer to Appendix A for more details.
a. Master Drainage Basin
The Site exists in the Dry Creek Master Drainage Basin, but according to the City of Fort Collins, the Dry
Creek Master Drainage Plan is outdated and not specific to the Site. The North East College Corridor
Outfall Design Report prepared by Ayres Associates in August 2009 (NECCO) will be utilized to impose
drainage conditions on the Site instead of the Dry Creek Master Drainage Plan. Please see Appendix B
for relevant portions from the NECCO report. This report details the design and construction of a
regional pond that conveys a large amount of runoff from the Dry Creek basin in a new storm main
beneath E Suniga St running from west to east. This report also contains design plans to revise the
existing Redwood Pond’s grading and change its outfall location from the Redwood Channel drainage
ditch north of the Site to the NECCO storm main beneath E Suniga St south of the Site. The Redwood
Pond changes detailed in the NECCO report have not been constructed, and therefore the A2 lateral
outlined in the NECCO report has not been constructed either. The Site will require design and
construction of the proposed Redwood Pond outlet structure and the A2 lateral storm line that are
detailed in the NECCO report. No other proposed changes to the Redwood Pond will be constructed as
part of this development, as the Site contributes no runoff to the Redwood Pond. The A2 lateral storm
line will connect to an existing stub from the NECCO main and will act as the ultimate outfall of the
developed Site.
The basins from the NECCO report that were analyzed for this report include basins 113, 213, 313, 413,
and 812. The Site exists in basins 113, 313, and 413. Basin 413 will remain undeveloped and thus the A3
lateral detailed in the NECCO report will not be constructed, and runoff from this basin will continue to
follow historic patterns and release into Lake Canal undetained and untreated. The NECCO report calls
for future on‐Site detention for basins 113 and 313, which will each require a 100‐year release rate of
0.2 cubic‐feet‐per‐second (CFS) per acre. Basin 213 consists of the Redwood Meadows development and
would require water quality treatment but no detention if redeveloped in the future. The Site will
provide inlets at various points between the border of the Redwood Meadows development and the
Site boundary in order to capture all runoff from basin 213 and route it to the A2 lateral storm line.
Basin 812 consists of the Redwood Pond, which the NECCO report details as requiring regrading and
redesign to allow for a 100‐year detention volume of 7.70 acre‐feet (ac‐ft) and an additional 2.16 ac‐ft of
storage for water quality. The redesign would entail adding additional pond facilities such as trickle
channels and forebays, as well as plugging the existing outlet, but leaving the existing berm and
overflow spillway. As stated above, because the Site will not contribute runoff to the Redwood Pond,
only the outlet structure and storm lateral A2 will be designed and constructed as part of this
development. Please see Section IV of this report for more information on the proposed redesign of the
Redwood Pond. The on‐Site detention facilities will meet the release rate constraint of 0.2 CFS/acre
imposed by the NECCO Report.
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Also provided for the development of drainage for the Site was an existing conditions SWMM model
featuring the constructed NECCO storm main under E Suniga St and the regional pond designed in the
NECCO Report. This SWMM model was updated for the preliminary drainage analysis.
Historic drainage analysis of the Site shows that the entirety of the Site (29.66 acres) discharges into
Lake Canal existing along the Site boundary running from the southeast to the northeast. The existing
Site has an imperviousness of 2% and an approximate 100‐year runoff of 14 CFS, all of which discharges
into Lake Canal. Any stormwater discharging from the developed Site into Lake Canal will require
approval from the ditch ownership. The Site will contribute some undetained and untreated runoff to
Lake Canal due to the Site’s existing drainage patterns. Please see Section IV of this report for
approximate 100‐year runoff values discharging to Lake Canal from the developed Site. Please note the
approximate runoff stated here and in Section IV is calculated using SWMM’s hydrologic calculator,
more accurate runoff calculations using the Rational Method will be included in a later version of this
report.
III. DRAINAGE DESIGN CRITERIA
A. Regulations and Previous Studies
The principal design criteria used for this report was the Fort Collins Stormwater Criteria Manual, revised
December 2018 (FCSCM). In addition, Mile High Flood District’s (MHFD) Urban Storm Drainage Criteria
Manual, Volumes 1‐3 revised August 2018, September 2017, and January 2021 respectively, were used
(USDCM). The NECCO report from above also provides a certain level of drainage criteria for the Site
that must be met.
a. Four‐Step Process
b. Step 1: Employ Runoff Reduction Practices
The Site will feature numerous open areas dedicated for low‐impact‐development (LID), parks, and
above ground detention. Wherever possible, vegetated swales will be used to convey runoff to area
inlets and roof drains will be used to convey flow to these swales, directly to LID implements, or to
storm sewer structures.
c. Step 2: Implement BMPs That Provide a WQCV with Slow Release
There are four LID systems incorporated on‐Site, all of them being isolator rows for underground
infiltration. These implements are utilized to treat over 75% of newly added impervious are with the
development of the Site per the FCSCM. A majority of the remainder of the Site’s impervious areas will
be treated in the above ground on‐Site detention pond.
d. Step 3: Stabilize Streams
The Site will be far upstream of Dry Creek and the NECCO report has already considered developed
release rates from the Site entering Dry Creek. There will be no need to provide stream stabilization of
Dry Creek with the development of the Site.
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e. Step 4: Implement Site Specific and Other Source Control BMPs
Because the Site is not a new development or redevelopment of an industrial or commercial zone this
step is not applicable to the Site.
f. Hydrologic Design Criteria
Design Frequencies – For the Site, the minor storm will be the 2‐year and the major storm will be the
100‐year. For detention volume and release rates, the WQCV and 100‐year storm events have been
analyzed.
Rainfall Data ‐ Fort Collins varies by runoff calculation method. For the purpose of this preliminary
drainage report, only SWMM was used in calculating runoff. Below is Table 4.1‐4 which presents rainfall
intensity values for use in SWMM modelling.
Hydrologic Computation Method – As stated above, only EPA SWMM 5.1 was used to calculate runoff
for this preliminary drainage design. As of now the basins tributary to each of the ponds have not been
broken into smaller sub‐basins for the purpose of inlet calculations. For future iterations of this report,
the rational method will be utilized to size inlets and storm drains. SWMM uses basin imperviousness,
slope, area, and width along with several default parameters to calculate runoff. SWMM inputs can be
found in Appendix E as well as Section IV of this report. The rational method uses weighted “C”
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December 22, 2021
coefficients based upon surface type and a time of concentration to determine runoff. Fort Collins
rational method IDF table and “C” coefficient table can be found in Appendix C along with SWMM
subcatchment default parameters and imperviousness by surface type tables. A summary of SWMM
results for each subcatchment can be found in Appendix C as well. The rational method “C” coefficient
and water quality event rainfall intensities were utilized in the Modified FAA Procedure to calculate the
WQCV for the isolator rows. It should be noted that imperviousness values used were rounded up from
exact calculated values for this preliminary drainage design.
Detention Volume Computation Method – For project sizes greater than 20 acres, SWMM is required for
detention calculation. SWMM storage nodes are used to represent the ponds and require storage curves
(depth‐area), SWMM then computes a volume based on these tables. SWMM outlet links are used to
represent a ponds outlet structure and require rating curves (depth‐release). SWMM can also utilize
orifice, weir, or conduit links for a pond’s outlet structure. A mix of these different links were utilized for
the Site’s SWMM modelling. More discussion on pond modelling in the Site SWMM model can be found
in Section IV of this report, and all calculations relating to detention ponds and facilities can be found in
Appendix D. The FCSCM requires that the WQCV be added to the 100‐year storage volume as opposed
to being included in said volume, thus the WQCV has been included in the SWMM model’s storage
nodes as an initial water depth value. Please see below for more information on computation of the
WQCV. See Appendix E for SWMM output results of storage nodes.
Water Quality Control Volume Calculation – The only LID systems implemented on‐Site are isolator rows
featuring underground infiltration. Three of these systems are included as part of an underground
detention chamber system, and one other features isolator row chambers solely. For these isolator row
systems, a spreadsheet received from Advanced Drainage Systems (ADS) was used to determine the
number of chambers needed based on product choice, chamber volume, and required WQCV. For the
sizing of these systems, two different WQCV values are compared to determine which results in a higher
number of required chambers. The first is 120% of the WQCV based on a 12‐hour drain time, which can
be calculated using UD‐BMP’s rain garden tab and multiplying that value by 1.2. The second is the WQCV
calculated from the modified FAA procedure, which uses a weighted “C” coefficient, tributary area, and
maximum flow out of the chamber system. Whichever WQCV results in more chambers based on the
received spreadsheet discussed above is the utilized WQCV. The required WQCV for the above ground
on‐Site detention pond was found using the UD‐BMP extended detention basin tab. This tab computes a
WQCV based on a 40‐hour drain time, which is then multiplied by a factor of 1.2 to meet the 120% of
the WQCV requirement from the FCSCM. See Appendix D for the calculation of the WQCV for the above
ground pond, and Appendix F for the calculation of the WQCV and chamber requirements for the
isolator rows.
g. Hydraulic Design Criteria
Detention Pond Infrastructure Sizing ‐ Express Hydraflow will be used to calculate vegetated swale and
emergency overflow spillway capacities for the Site. The FCSCM requires that overflow spillway design
flow depth be no greater than 0.5 feet. UD‐BMP will be used to size trickle channels, forebays, and
forebay notches for the above ground pond. Outlet structures for the Redwood Pond and on‐Site above
ground detention ponds have been preliminarily designed, and only the Redwood Pond will feature a
rating curve in SWMM to act as an outlet. Pond 1 and Pond 3 have been designed in SWMM using
outfall conduits with their maximum flow values set at the 0.2 CFS/acre release rate criteria. This
ensures the facilities will have enough volume without needing to fully design their outlet structure (box
height, restrictor plates, orifice plates). These detention facilities’ outlet structures will be designed fully
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in a future version of this report using stage‐storage‐discharge tables that result in a developed rating
curve. Stage‐area‐release tables for the ponds can be found in Appendix D.
Street Capacity Calculation – Street sections upstream of proposed inlets will be analyzed using the
MHFD spreadsheet “MHFD‐Inlet v5.01” released April 2021. These calculations will be presented in a
later version of this report.
Storm Sewer Sizing – Inlet sizing will be performed using the MHFD‐Inlet spreadsheet. For the
preliminary layout of the storm network inlet sizes were estimated based on contributing area. Inlet
Type 16 curb and valley inlets, Type R curb inlets, and Type C and D areas inlets were utilized for this
Site. Storm pipe sizing and vertical alignment will be analyzed using Bentley StormCAD CONNECT.
StormCAD computes losses and velocities and produces accurate HGLs and EGLs to prove the storm
sewer network works hydraulically. Inlet sizing calculations and StormCAD pipe sizing calculations will be
provided in a later version of this report.
h. Variances
The drainage design for the Site will not require any variance from criteria put forth in the FCSCM,
USDCM, and NECCO Report.
i. Erosion Control
The following drainage design will comply with all erosion control criteria put forth in the USDCM,
FCSCM, and NECCO Report. All erosion control materials will be provided with the final drainage report.
IV. PROPOSED DRAINAGE SYSTEMS
A. General Concept
The Site will include outlet structure design for the Redwood Pond in the northwest of the Site as
detailed in the NECCO report. For the preliminary drainage design of the Site, the outlet structure has
been designed to meet the parameters presented in the NECCO report including pond regrading. The
Site will include development of the NECCO A2 storm lateral, which runs from the new Redwood Pond
outlet structure to an existing stub off of the NECCO main line under E Suniga Rd. There are three
proposed underground chamber facilities and two proposed above ground detention ponds, and the
Redwood Pond, all of which will feature some level of water quality treatment. All of these ponds will
meet the 0.2 CFS/ac release rate criteria, and release to the NECCO A2 storm lateral. For the purpose of
this preliminary drainage design, ponds are shown to be capturing 100% of runoff from the Site in order
to size them conservatively. For the final drainage design of the Site, each of these ponds tributary areas
will be refined and their required volumes will decrease. Site runoff will be conveyed to these ponds via
roof drains, swales, inlets and storm sewer pipes, and landscape drains, all to be designed in a later
version of this report. Runoff from basin 213 consisting of Redwood Meadows will be captured by
proposed on‐Site inlets and routed directly into the NECCO A2 storm lateral. Further breakdown of the
ponds and a summary table can be found below.
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The Site will feature four LID systems all of which being underground infiltration isolator rows. These LID
features are designed to treat at least 75% of the Site’s impervious areas for the WQCV. Unlike the
detention facilities mentioned above, these LID systems are only designed to capture the areas actual
tributary to them and have been sized as such. The systems are conservatively sized by rounding up the
calculated imperviousness of their tributary areas for use in calculations. Runoff will be routed to these
systems via roof drains, swales, inlets and storm sewer pipes, and landscape drains, all to be designed in
a later version of this report. Any on‐Site runoff that is not practicable to route to a stormwater facility
will leave the Site untreated, however more LID facilities may be added in a future revision to the Site’s
drainage design to reduce the amount of area leaving the Site untreated. The above ground detention
pond features water quality detention but does not treat for any areas already accounted for by LID
facilities. Further breakdown of the LID areas and a summary table can be found in Table 3 of Section C.
For the SWMM analysis included in this preliminary drainage design report only seven subcatchments
were used, and the only storm line included was the NECCO A2 storm lateral that receives the outfall
from all five ponds and runoff from basins 213 and 413. This is a high‐level analysis of the Site’s drainage
and the SWMM subcatchments will be further refined for the final drainage report. Below is a
breakdown of the seven subcatchments as well as a table featuring their SWMM input parameters. Also
found below is a table summarizing SWMM model results.
See Appendix C for summary of subcatchments and SWMM input parameters. See Appendix D for
underground detention chamber layouts, stage‐area tables for all ponds, SDI data sheets for all ponds,
and any other pond calculations and information. See Appendix E for SWMM schematic, input report
and output results. See Appendix F for LID calculations, summary table, and exhibit showing areas and
locations of facilities. See Appendix G for drainage map showing pond locations, basins, drainage
patterns, and storm layout.
a. Proposed Basins
Below is Table 1 featuring a summary of all basin input parameters for SWMM and other calculated
parameters.
Table 1:
Pond Subcatchment Summary Table
Basin Area
(ac)
Utilized
Imperviousness
(%)
Width
(ft)
Slope
(%)
2‐Year
Peak
Runoff
(CFS)
100‐
Year
Peak
Runoff
(CFS)
113_1 4.28 55 1863.8 0.75 6.65 32.61
113_2 7.86 50 1342.2 0.50 9.93 45.38
113_3 9.75 65 2831.8 0.80 17.21 77.77
113_4 5.58 68 2432.3 0.60 10.51 47.47
213 7.82 75 1946.5 0.40 14.41 67.65
413 2.19 7 374.3 1.00 0.45 6.62
812 3.75 2 544.5 0.50 0.22 7.21
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Basin 113_1 lies on‐Site and encompasses the southwestern portion of the Site. This basin consists of
multi‐family housing, walks, roadways, alleys, open space, and Isolator Rows IR1 and at grade detention
Pond 1. Runoff from this basin will be conveyed to IR1 in the southern portion of this basin via roof
drains, swales, storm sewer systems, and landscape drains. It is assumed that some potions of this basin
will flow off‐Site undetained and untreated into Redwood St or Lake Canal, but all of this basin is
tributary to Pond 1 for the purpose of this preliminary drainage analysis.
Basin 113_2 lies on‐Site and encompasses the eastern portion and border of the Site. This basin consists
of multi‐family housing, walks, roadways, alleys, open space, portions of Lake Canal irrigation ditch and
underground detention system UD2. Runoff from this basin will be conveyed to UD2 in the
southwestern portion of the basin via roof drains, swales, storm sewer systems, and landscape drains. It
is assumed that some portions of this basin will flow off‐Site undetained and untreated into Lake Canal
or the Northfield development, but all of this basin is tributary to UD2 for the purpose of this
preliminary drainage analysis.
Basin 113_3 lies on‐Site and encompasses the middle portion of the Site spanning from the Redwood
Meadows property boundary to the west to the northeastern corner of the Site. This basin consists of
multi‐family housing, walks, roadways, alleys, open space, isolator rows, and above ground detention
pond Pond 3. A majority of the runoff from this basin will be conveyed to the isolator row system IR 3 in
the middle of the basin via roof drains, swales, storm sewer systems, and landscape drains. All other
runoff from this basin will be conveyed directly into Pond 3 instead of being routed through IR 3. The
area Pond 3 takes up will also be utilized as an open space park. It is assumed that some portions of this
basin will flow undetained and untreated into inlets meant to capture basin 213, but all of this basin is
tributary to Pond 3 for the purpose of this preliminary drainage analysis.
Basin 113_4 lies on‐Site and encompasses the northern portion of the Site. This basin is consisting of
multi‐family housing, walks, roadways, alleys, and open space. Runoff from this basin will be conveyed
to the Redwood Pond in the northwestern portion of the basin via roof drains, swales, storm sewer
systems, and landscape drains. It is assumed some portions of this basin will contribute runoff north off‐
Site undetained and untreated into the Redwood Channel drainage ditch, but all of this basin is tributary
to the Redwood Pond for the purpose of this preliminary drainage analysis.
Basin 213 lies off‐Site to the west of the Site. This basin consists of the Redwood Meadows development
featuring walks, single‐family homes, roadways, and open spaces. Runoff from this basin will not need
detained but will need to be conveyed to the NECCO A2 storm lateral. Two at‐grade inlets are proposed
at the connection of Lupine Dr and the Site to collect runoff from the roadways of this basin. An area
inlet and swale are also proposed sitting just east of the Redwood Meadows development meant to
collect any runoff from this basin that is not collected by the roadways within the basin. This basin
slopes from the south to the northwest generally. This basins imperviousness was assumed to be 75%
for conservative analysis but may decrease to a more exact value for the Final Drainage Report.
Basin 413 lies on‐Site south of E Suniga St. This basin will remain undeveloped and consists entirely of
open space. Runoff from this basin will continue to follow historic patterns and discharge into Lake
Canal. The NECCO report details an additional storm lateral A3 for this basin but will not be constructed
because this lot will remain undeveloped.
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Basin 812 lies off‐Site to the northwest of the Site. This basin consists of the existing Redwood Pond.
Runoff from this basin will be collected by the Redwood Pond.
Preliminary analysis was done to determine the amount of undetained and untreated flow leaving the
Site. Note that for the final drainage design more of these areas may be picked up by on‐Site storm
sewer systems or LID facilities. Approximately 5.58 acres of the Site currently contributes flow off‐Site
untreated and undetained, with 0.21 acres being captured by the NECCO A2 storm lateral, 0.28 acres
discharging into the Northfield development, 0.04 acres discharging into Redwood St, 0.60 acres
discharging into Redwood Channel, and 4.45 acres discharging into Lake Canal. Note that runoff
discharging from the developed Site into Lake Canal and Redwood Channel is mostly coming from open
space. Further analysis of these areas will be conducted with the final drainage design of the Site.
b. Specific Details
The Redwood Pond grading and outlet structure has been preliminarily designed as detailed in the
NECCO report. The NECCO report calls for a pond bottom invert of 4953.10, so the proposed outlet
structure has been set to this elevation and the pond regraded. The pond’s berm and spillway will
remain the same at an elevation of 4962.10, and the existing outlet pipe into Redwood Channel will be
plugged as part of the ultimate condition for this pond. The stage‐storage‐discharge table presented in
Appendix D for this pond was used for information in the SWMM model and begin design of the outlet
structure. The final release rate for this pond will be equal to or less than 15.96 CFS, as presented in the
NECCO report. Basin 113_4 (5.58 ac) is tributary to this system, allowing for an additional release rate of
1.12 CFS for the 100‐year storm event. The system releases directly into the NECCO A2 storm lateral.
The outlet manhole design to be included for final drainage design will feature an orifice plate, weir, and
restrictor plate to hold the release rate to 1.12 CFS. The Redwood Pond overflow spillway will direct
flows north into the Redwood Channel. Please see the table below for SWMM computed results for this
system. The WQCV for this system will be treated by standard
IR 1 is located in the southwestern portion of the Site and features an invert elevation of 4951.40. This
system will be comprised of 20 ADS MC‐4500 Stormtech chambers with 9 inches of stone below the
chambers and 12 inches of stone above the chambers. The total height of the system is 6.75 ft, putting
the top of stone at an elevation of 4958.15. The minimum finished grade above the system is 4960.81
which is more than the 1 ft of required cover above the top of the system. The maximum groundwater
elevation below the system is 4949.40, which is 24 inches below the bottom of the facility, meeting
FCSCM criteria. Flows in excess of the LID event will bypass IR 1 and enter Pond 1. Basin 113_1 (4.28 ac)
is tributary to this system, allowing for a release rate of 0.86 CFS for the 100‐year storm event. The
system releases directly into the NECCO A2 storm lateral. The outlet manhole design to be included for
final drainage design will feature an orifice plate, weir, and restrictor plate to hold the release rate to
0.86 CFS. The Pond3 overflow spillway will direct flows north into Collamer Drive. Please see the table
below for SWMM computed results for this system. The WQCV for this system will be treated entirely by
isolator rows included in the system, see below for more information on these chambers.
Underground detention system UD2 is located in the southwestern portion of the Site and features an
invert elevation of 4950.42. This system will be comprised of ADS MC‐4500 Stormtech chambers with 9
inches of stone below the chambers and 12 inches of stone above the chambers. The total height of the
system is 7.75 ft, putting the top of stone at an elevation of 4957.17. The minimum finished grade above
the system is 4958.26 which is above the 1 ft of required cover above the top of the system. The
maximum groundwater elevation around the system is 4948.42, which is 2.0 ft above the invert of the
Enclave at Redwood
Page 13
December 22, 2021
system. Basin 113_2 (7.86 ac) is tributary to the system, allowing for a release rate of 1.57 CFS for the
100‐year storm event. The system releases directly into the NECCO A2 storm lateral. The outlet manhole
design to be included for final drainage design will feature an orifice plate, weir, and restrictor plate to
hold the release rate to 1.57 CFS. The UD2 overflow spillway will direct flows southwest to East Suniga
Street. Please see the table below for SWMM computed results for this system. The WQCV for this
system will be treated entirely by isolator rows included in the system, see below for more information
on these chambers.
Isolator rows IR3 are located in the middle portion of the Site, just upstream of Pond3. The sizing
process for these chambers is located above in Section III. The result is 42 ADS MC‐3500 Stormtech
chambers. This system has a total height of 5.50 ft, requiring 2 ft below the system clear of
groundwater, and 0.5 ft above the system for cover. The minimum groundwater depth for this system is
approximately 11.50 ft, giving this system more than enough vertical clearance both ways. The 100‐year
runoff entering this system will bypass the system to be detained in Pond 3.
Pond 3 is located in the middle portion of the Site and features a depth of 5.5 ft and a pond bottom
elevation of 4957.50. The spillway has a crest elevation of 4963.00 and a length of 76 ft. The spillway is
situated on the northern edge of the pond and will discharge runoff above the 100‐year event into
public roadway. Basin 113_3 (9.75 ac) is tributary to this pond, allowing for a release rate of 1.95 CFS for
the 100‐year storm event. The runoff from basin 113_3 will be captured and treated for water quality by
the isolator row LID facility named IR 3 directly upstream of the pond. Pond 3 has a WQCV water surface
elevation (WSEL) of 4958.34, modelled as an initial depth of 0.84 ft in the SWMM model. This pond will
feature varying side slopes and aesthetically pleasing design. An outlet box structure has been
preliminarily designed to release 1.95 CFS to the NECCO A2 storm in order to not cause overtopping of
the spillway during the 100‐year storm. The main outlet box will feature orifice holes and a weir grate as
typical to treat the WQCV, and a restrictor plate to be designed during final drainage design that limits
the release rate to 1.95 CFS. The UD2 overflow spillway will direct flows southwest to East Suniga Street.
The minimum groundwater depth below this pond is 6.60 ft, with an elevation of 4950.88. Please see
the table below for SWMM computed results for this pond.
See below for Table 2 showing a summary of pond results from SWMM. The WQCV presented in this
table for the underground detention systems is from the LID isolator rows to be discussed below. The
WQCV for the above ground pond does not include any volume already treated by LID systems. The
WQCV WSELs have been inputted into SWMM and not computed.
Enclave at Redwood
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December 22, 2021
Table 2:
Detention Pond Summary Table
Pond
100‐
Year
Volume
(cu‐ft)
100‐
Year
Volume
(ac‐ft)
100‐Year
WSEL
WQCV
(cu‐ft)
WQCV
WSEL
Max
Release
Rate (CFS)
Total Volume
Required (WQCV
+ Detention) (ac‐
ft)
Total Volume
Provided (WQCV
+ Detention) (ac‐
ft)
Pond1 36,562 0.84 4957.63 0.86
IR 1 3,147 4954.40 0.91 0.91
UD2 66,457 1.53 4951.92 1.57
IR2 5,354 4947.09 1.65 1.65
Pond3 81,471 1.87 4962.52 1.95
IR 3 7,304 4958.34 2.04 2.04
Redwood Pond 226,265 5.19 4958.19 4956.46 15.96
*WQCV in Underground Chamber Systems Explored Further in LID Exhibit and Calculations Found in
Appendix F of Preliminary Drainage Report
**SWMM Model, Inputs, and Outputs Found in Appendix E of Preliminary Drainage Report
Isolator rows IR1, IR2, and IR3 are located within detention systems POND 1, POND 2, and POND 3
respectively. These isolator row chambers will match the inverts and dimensions of the systems they are
within. Table 3 below features a summary of the LID systems for the Site including tributary area,
imperviousness, impervious area, calculated WQCV, and provided WQCV.
Enclave at Redwood
Page 15
December 22, 2021
Table 3:
Table 4 below features a summary of the SWMM results for nodes. Table 5 below features a summary of
the SWMM results for links. See Appendix E for a schematic calling out the nodes summarized below.
Table 4:
SWMM Node Results Summary Table
Node Type Maximum
Depth (ft)
Maximum
HGL (ft)
Maximum Total
Inflow (CFS)
A2_1 JUNCTION 5.15 4951.84 68.25
A2_2 JUNCTION 5.48 4952.48 68.19
A2_3 JUNCTION 6.18 4954.67 69.26
A2_4 JUNCTION 6.00 4955.27 72.02
A2_5 JUNCTION 6.14 4955.71 74.07
A2_6 JUNCTION 6.24 4956.28 71.85
A2_7 JUNCTION 3.83 4955.91 75.65
A2_8 JUNCTION 3.91 4956.45 76.14
A2_9 JUNCTION 3.68 4956.50 13.39
A2_10 JUNCTION 3.90 4957.00 13.39
NECCO_A‐11 JUNCTION 0.69 4956.97 89.97
308‐Redwood STORAGE 5.02 4963.54 73.21
Pond1 STORAGE 6.23 4957.63 32.61
UD2 STORAGE 5.16 4951.92 46.95
Pond3 STORAGE 5.02 4962.52 77.77
Basin Area (sq‐ft) Area (ac)
Calculated
Imperviousness
(%)
*Utilized
Imperviousness
(%)
Impervious
Area (sq‐ft)
120% WQCV
(12‐Hour Drain
Time) (cu‐ft)
FAA
WQCV (cu‐
ft)
LID Treatment
Provided
Volume in
LID (cu‐ft)
IR‐1 143024.90 3.28 65.6 70 93810 3147 1787 Isolator Rows 1 ‐ Pond 1 3252
IR‐2 223433.92 5.13 72.5 75 162057 5354 3855 Isolator Rows 2 ‐ UD2 5366
IR‐3 310215.35 7.12 71.1 74 220625 7304 4429 Isolator Rows 3 ‐ Pond 3 7350
IR‐4 198045.54 4.55 79.3 80 157030 not treated by LID
Total LID
Treated Area 676674.17 15.5 70.4 476492
Total Site Area 1196479.944 27.5 51.9 621093
77%Total LID Treated Impervious Area/Total Site Impervious Area (Must be > 75%)
LOW IMPACT DEVELOPMENT SUMMARY TABLE
**Isolator Rows were sized by comparing 120% of the WQCV based on a 12‐Hour drain time and the City of Fort Collins Modified FAA Method
*In some cases imperviousness was rounded up to be more conservative in sizing LID facilities, exact imperviousness was used to prove 75% of new impervious areas
treated by LID
Enclave at Redwood
Page 16
December 22, 2021
Table 5:
SWMM Link Results Summary Table
Link Type Maximum
Flow (CFS)
Maximum
Velocity
(fps)
Maximum/Full
Flow
Maximum/Full
Depth
A2_1 CONDUIT 66.77 9 0.73 0.6
A2_2 CONDUIT 68.25 5.17 0.63 1.0
A2_3 CONDUIT 67.33 5.14 0.63 1.0
A2_4 CONDUIT 69.26 6.18 0.67 1.0
A2_5 CONDUIT 72.02 5.77 0.67 1.0
A2_6 CONDUIT 72.12 5.41 0.66 1.0
A2_7 CONDUIT 71.85 6.09 0.68 0.9
A2_8 CONDUIT 75.65 6.61 0.71 0.8
A2_9 CONDUIT 13.39 4.4 0.42 1.0
A2_10 CONDUIT 13.39 5.9 1.84 1.0
Redwood_Outlet DUMMY 13.53
POND1_Outlet CONDUIT 0.86 2.22 0.04 1.0
UD2_Outlet CONDUIT 1.57 12.84 0.04 1.0
POND3_Outlet CONDUIT 1.95 4.49 0.13 1.0
V. CONCLUSIONS
A. Compliance with Standards
The drainage design is prepared in compliance with the FCSCM and the USDCM Volumes 1, 2, and 3.
As stated before, the NECCO report details utilizing a release of less than 15.96 CFS for the Redwood
Pond and less than 0.2 CFS/ac for the three on‐Site ponds. This criteria has been met for the proposed
preliminary drainage design.
a. Drainage Concept
The drainage design as described herein; if properly constructed and maintained, will effectively control
stormwater runoff in accordance with the criteria. The proposed development will provide water quality
and detention for the 100‐year event with associated outlets and spillway overflow. This drainage design
for the proposed development does not have any impact on the NECCO report design. The drainage
design for this Site will have no adverse effects to any upstream or downstream adjacent properties.
Enclave at Redwood
Page 17
December 22, 2021
VI. REFERENCES
1. National Flood Hazard Layer FIRMette, City of Fort Collins, Colorado, Map No. 08069C0977G,
Map No. 08069C0981G, June 17, 2008, Federal Emergency Management Agency.
2. Geotechnical Engineering Report for Enclave at Redwood Residential Development, Cole Garner
Geotechnical, August 11, 2021.
3. Fort Collins Stormwater Criteria Manual, City of Fort Collins, revised December 2018.
4. Urban Storm Drainage Criteria Manual Vol. 1, Mile High Flood District, revised August 2018.
5. Urban Storm Drainage Criteria Manual Vol. 2, Mile High Flood District, revised September 2017.
6. Urban Storm Drainage Criteria Manual Vol. 3, Mile High Flood District, revised November 2010
with updates from January 2021.
7. North East College Corridor Outfall (NECCO) Design Report, Ayres Associates, August 2009.
Enclave at Redwood
Page 18
December 22, 2021
VII. APPENDICES
Appendix A Vicinity Map, FIRM, Geotechnical Engineering Report
Appendix B Portions from Relevant Previous Studies
Appendix C Subcatchment Hydrology
Appendix D Detention Storage Sizing
Appendix E SWMM Model and Results
Appendix F Low Impact Development
Appendix G Drainage Map
Enclave at Redwood
Page C
December 22, 2021
Appendix C – Subcatchment Hydrology
Enclave at Redwood
Page D
December 22, 2021
Appendix D – Detention Storage Sizing
Project Name:Enclave at Redwood
Project No:201013
Date:08/16/21
Revised:10/13/21
Design by:MW
Preliminary Design
Stage-Storage-Discharge
Proposed On-Site Pond 1
w.s. elev Total Discharge Q Area Area incremental accumulated Vol.
(cfs) (sf) (acre) volume (ac-ft) (ac-ft)
4951.40 0.86 0 0.00 - -
4952.0 0.86 509 0.01 0.002 0.002
4953.0 0.86 1,606 0.04 0.023 0.025
4954.0 0.86 3,318 0.08 0.055 0.081
4955.0 0.86 9,635 0.22 0.142 0.223
4956.0 0.86 13,052 0.30 0.259 0.483
4957.0 0.86 15,860 0.36 0.331 0.814
Proposed On-Site Pond 3
w.s. elev Total Discharge Q Area Area incremental accumulated Vol.
(cfs) (sf) (acre) volume (ac-ft) (ac-ft)
4957.50 1.65 26 0.00 - -
4958.0 1.65 579 0.01 0.003 0.003
4959.0 1.65 7,116 0.16 0.074 0.077
4960.0 1.65 15,941 0.37 0.258 0.335
4961.0 1.65 27,865 0.64 0.496 0.832
4962.0 1.65 36,158 0.83 0.733 1.564
4963.0 1.65 41,366 0.95 0.889 2.454
Proposed Redwood Pond
w.s. elev Total Discharge Q Area Area incremental accumulated Vol.
(cfs) (sf) (acre) volume (ac-ft) (ac-ft)
4953.10 15.96 0 0.00 - -
4954.0 15.96 26 0.00 0.000 0.000
4955.0 15.96 5,197 0.12 0.043 0.043
4956.0 15.96 24,042 0.55 0.309 0.352
4957.0 15.96 55,735 1.28 0.891 1.243
4958.0 15.96 76,519 1.76 1.512 2.755
4959.0 15.96 124,076 2.85 2.281 5.035
4960.0 15.96 141,572 3.25 3.047 8.082
4961.0 15.96 153,562 3.53 3.387 11.469
4962.0 15.96 163,338 3.75 3.637 15.106
Project:
Chamber Model - MC-4500
Units -Imperial MC-4500
Number of Chambers - 499
Number of End Caps - 18
Voids in the stone (porosity) - 40 %
Base of Stone Elevation - 0.00 ft
Amount of Stone Above Chambers - 12 in
Amount of Stone Below Chambers - 9 in
9
Area of system - 19518 sf Min. Area -
Height of
System
Incremental Single
Chamber
Incremental
Single End Cap
Incremental
Chambers
Incremental
End Cap
Incremental
Stone
Incremental Ch,
EC and Stone
Cumulative
System Elevation
Cumulative
Chamber Elevation Depth Area
(inches) (cubic feet) (cubic feet) (cubic feet) (cubic feet) (cubic feet) (cubic feet)(cubic feet) (feet)(cubic feet) (feet) (feet (feet2)
81 0.00 0.00 0.00 0.00 650.60 650.60 84972.33 6.75 84972.33 6.75 0.00 7807.20
80 0.00 0.00 0.00 0.00 650.60 650.60 84321.73 6.67 84321.73 6.67 0.08 7807.20
79 0.00 0.00 0.00 0.00 650.60 650.60 83671.13 6.58 83671.13 6.58 0.17 7807.20
78 0.00 0.00 0.00 0.00 650.60 650.60 83020.53 6.50 83020.53 6.50 0.25 7807.20
77 0.00 0.00 0.00 0.00 650.60 650.60 82369.93 6.42 82369.93 6.42 0.33 7807.20
76 0.00 0.00 0.00 0.00 650.60 650.60 81719.33 6.33 81719.33 6.33 0.42 7807.20
75 0.00 0.00 0.00 0.00 650.60 650.60 81068.73 6.25 81068.73 6.25 0.50 7807.20
74 0.00 0.00 0.00 0.00 650.60 650.60 80418.13 6.17 80418.13 6.17 0.58 7807.20
73 0.00 0.00 0.00 0.00 650.60 650.60 79767.53 6.08 79767.53 6.08 0.67 7807.20
72 0.00 0.00 0.00 0.00 650.60 650.60 79116.93 6.00 79116.93 6.00 0.75 7807.20
71 0.00 0.00 0.00 0.00 650.60 650.60 78466.33 5.92 78466.33 5.92 0.83 17019.78
70 0.00 0.00 0.00 0.00 650.60 650.60 77815.73 5.83 77815.73 5.83 0.92 16974.85
69 0.04 0.00 20.44 0.00 642.42 662.86 77165.13 5.75 77165.13 5.75 1.00 16944.24
68 0.12 0.01 57.93 0.18 627.35 685.47 76502.27 5.67 76502.27 5.67 1.08 16911.39
67 0.16 0.03 82.20 0.47 617.53 700.21 75816.80 5.58 75816.80 5.58 1.17 16876.28
66 0.21 0.05 104.15 0.86 608.60 713.61 75116.59 5.50 75116.59 5.50 1.25 16839.20
65 0.27 0.07 133.90 1.22 596.55 731.67 74402.99 5.42 74402.99 5.42 1.33 16800.18
64 0.45 0.09 225.94 1.58 559.59 787.11 73671.31 5.33 73671.31 5.33 1.42 16758.78
63 0.67 0.11 331.97 2.03 517.00 851.00 72884.20 5.25 72884.20 5.25 1.50 16715.01
62 0.80 0.14 398.71 2.55 490.10 891.35 72033.20 5.17 72033.20 5.17 1.58 16668.81
61 0.91 0.17 453.15 3.02 468.13 924.30 71141.85 5.08 71141.85 5.08 1.67 16620.19
60 1.00 0.19 500.45 3.45 449.04 952.94 70217.55 5.00 70217.55 5.00 1.75 16569.09
59 1.09 0.22 542.58 3.87 432.02 978.47 69264.61 4.92 69264.61 4.92 1.83 16515.48
58 1.16 0.24 580.58 4.35 416.63 1001.55 68286.14 4.83 68286.14 4.83 1.92 16459.33
57 1.23 0.27 615.77 4.86 402.35 1022.98 67284.58 4.75 67284.58 4.75 2.00 16400.59
56 1.30 0.30 648.54 5.36 389.04 1042.94 66261.60 4.67 66261.60 4.67 2.08 16339.21
55 1.36 0.32 679.15 5.82 376.61 1061.59 65218.66 4.58 65218.66 4.58 2.17 16275.15
54 1.42 0.35 707.94 6.26 364.92 1079.12 64157.08 4.50 64157.08 4.50 2.25 16208.47
53 1.47 0.37 735.19 6.68 353.85 1095.72 63077.96 4.42 63077.96 4.42 2.33 16140.04
52 1.53 0.39 761.05 7.09 343.34 1111.49 61982.24 4.33 61982.24 4.33 2.42 16066.88
51 1.57 0.42 785.67 7.51 333.33 1126.51 60870.75 4.25 60870.75 4.25 2.50 15990.86
50 1.62 0.44 809.07 7.92 323.80 1140.80 59744.24 4.17 59744.24 4.17 2.58 15912.69
49 1.67 0.46 831.45 8.33 314.69 1154.46 58603.44 4.08 58603.44 4.08 2.67 15831.21
48 1.71 0.48 852.85 8.71 305.98 1167.54 57448.98 4.00 57448.98 4.00 2.75 15746.61
47 1.75 0.50 873.29 9.09 297.65 1180.03 56281.44 3.92 56281.44 3.92 2.83 15658.80
46 1.79 0.53 892.86 9.45 289.67 1191.99 55101.41 3.83 55101.41 3.83 2.92 15567.49
45 1.83 0.55 911.77 9.81 281.97 1203.55 53909.43 3.75 53909.43 3.75 3.00 15472.76
44 1.86 0.56 929.86 10.16 274.59 1214.61 52705.88 3.67 52705.88 3.67 3.08 15375.08
43 1.90 0.58 947.26 10.50 267.49 1225.26 51491.27 3.58 51491.27 3.58 3.17 15273.30
42 1.93 0.60 963.99 10.83 260.67 1235.49 50266.01 3.50 50266.01 3.50 3.25 15167.63
41 1.96 0.62 980.08 11.16 254.11 1245.34 49030.52 3.42 49030.52 3.42 3.33 15057.94
40 2.00 0.64 995.56 11.48 247.78 1254.83 47785.18 3.33 47785.18 3.33 3.42 14944.10
39 2.03 0.66 1010.48 11.80 241.69 1263.97 46530.35 3.25 46530.35 3.25 3.50 14825.89
38 2.05 0.67 1024.84 12.12 235.82 1272.77 45266.38 3.17 45266.38 3.17 3.58 14703.09
37 2.08 0.69 1038.67 12.43 230.16 1281.26 43993.60 3.08 43993.60 3.08 3.67 14575.31
36 2.11 0.71 1051.93 12.73 224.74 1289.40 42712.35 3.00 42712.35 3.00 3.75 14442.58
35 2.13 0.72 1064.79 13.03 219.47 1297.29 41422.95 2.92 41422.95 2.92 3.83 14303.85
34 2.16 0.74 1077.18 13.32 214.40 1304.90 40125.66 2.83 40125.66 2.83 3.92 14160.35
33 2.18 0.76 1089.09 13.61 209.52 1312.22 38820.76 2.75 38820.76 2.75 4.00 14010.42
32 2.21 0.77 1100.56 13.89 204.82 1319.27 37508.54 2.67 37508.54 2.67 4.08 13853.57
31 2.23 0.79 1111.60 14.16 200.29 1326.06 36189.28 2.58 36189.28 2.58 4.17 13689.58
30 2.25 0.80 1122.19 14.43 195.95 1332.57 34863.22 2.50 34863.22 2.50 4.25 13518.11
29 2.27 0.82 1132.40 14.77 191.73 1338.91 33530.65 2.42 33530.65 2.42 4.33 13337.85
28 2.29 0.84 1142.20 15.13 187.66 1345.00 32191.74 2.33 32191.74 2.33 4.42 13148.67
27 2.31 0.85 1151.62 15.23 183.86 1350.71 30846.74 2.25 30846.74 2.25 4.50 12949.43
26 2.33 0.86 1160.65 15.46 180.16 1356.26 29496.03 2.17 29496.03 2.17 4.58 12739.03
25 2.34 0.87 1169.30 15.70 176.60 1361.60 28139.77 2.08 28139.77 2.08 4.67 12515.26
24 2.36 0.89 1177.59 15.93 173.19 1366.72 26778.17 2.00 26778.17 2.00 4.75 12275.77
23 2.38 0.90 1185.52 16.16 169.93 1371.61 25411.45 1.92 25411.45 1.92 4.83 12018.64
22 2.39 0.91 1193.10 16.39 166.81 1376.29 24039.84 1.83 24039.84 1.83 4.92 11741.66
21 2.41 0.92 1200.33 16.60 163.83 1380.76 22663.55 1.75 22663.55 1.75 5.00 11435.27
20 2.42 0.93 1207.21 16.82 160.99 1385.02 21282.79 1.67 21282.79 1.67 5.08 11091.62
19 2.43 0.95 1213.76 17.02 158.29 1389.07 19897.78 1.58 19897.78 1.58 5.17 10696.24
18 2.44 0.96 1219.97 17.22 155.72 1392.92 18508.71 1.50 18508.71 1.50 5.25 10211.99
17 2.46 0.97 1225.86 17.41 153.29 1396.57 17115.79 1.42 17115.79 1.42 5.33 9445.36
16 2.47 0.98 1231.42 17.60 150.99 1400.01 15719.23 1.33 15719.23 1.33 5.42 8780.06
15 2.48 0.99 1236.66 17.78 148.82 1403.27 14319.21 1.25 14319.21 1.25 5.50 8563.28
14 2.49 1.00 1241.64 17.96 146.76 1406.36 12915.94 1.17 12915.94 1.17 5.58 8402.47
13 2.50 1.01 1246.35 18.12 144.81 1409.28 11509.59 1.08 11509.59 1.08 5.67 8225.61
12 2.51 1.02 1250.75 18.29 142.99 1412.02 10100.31 1.00 10100.31 1.00 5.75 7954.38
11 2.51 1.02 1254.85 18.44 141.29 1414.57 8688.29 0.92 8688.29 0.92 5.83 7807.20
10 2.53 1.03 1260.94 18.59 138.79 1418.31 7273.71 0.83 7273.71 0.83 5.92 7807.20
9 0.00 0.00 0.00 0.00 650.60 650.60 5855.40 0.75 5855.40 0.75 6.00 7807.20
8 0.00 0.00 0.00 0.00 650.60 650.60 5204.80 0.67 5204.80 0.67 6.08 7807.20
7 0.00 0.00 0.00 0.00 650.60 650.60 4554.20 0.58 4554.20 0.58 6.17 7807.20
6 0.00 0.00 0.00 0.00 650.60 650.60 3903.60 0.50 3903.60 0.50 6.25 7807.20
5 0.00 0.00 0.00 0.00 650.60 650.60 3253.00 0.42 3253.00 0.42 6.33 7807.20
4 0.00 0.00 0.00 0.00 650.60 650.60 2602.40 0.33 2602.40 0.33 6.42 7807.20
3 0.00 0.00 0.00 0.00 650.60 650.60 1951.80 0.25 1951.80 0.25 6.50 7807.20
2 0.00 0.00 0.00 0.00 650.60 650.60 1301.20 0.17 1301.20 0.17 6.58 7807.20
1 0.00 0.00 0.00 0.00 650.60 650.60 650.60 0.08 650.60 0.08 6.67 7807.20
6.75 #VALUE!
StormTech MC-4500 Cumulative Storage Volumes
Enclave at Redwood - UD2
18825 sf min. area
To be copied as stage-area table [copy to new spreadsheet and save as a text (tab delimited
file) or copy and paste directly into software]
Include Perimeter Stone in Calculations
Click Here for Metric
**************** Flow Units ............... CFS Process Models: Rainfall/Runoff ........ YES RDII ................... NO Snowmelt ............... NO Groundwater ............ NO Flow Routing ........... YES Ponding Allowed ........ YES Water Quality .......... NO Infiltration Method ...... HORTON Flow Routing Method ...... DYNWAVE Surcharge Method ......... EXTRAN Starting Date ............ 06/03/2015 00:00:00 Ending Date .............. 06/04/2015 00:00:00 Antecedent Dry Days ...... 0.0 Report Time Step ......... 00:01:00 Wet Time Step ............ 00:05:00 Dry Time Step ............ 01:00:00 Routing Time Step ........ 1.00 sec Variable Time Step ....... YES Maximum Trials ........... 8 Number of Threads ........ 1 Head Tolerance ........... 0.005000 ft ************************** Volume Depth Runoff Quantity Continuity acre‐feet inches ************************** ‐‐‐‐‐‐‐‐‐ ‐‐‐‐‐‐‐ Total Precipitation ...... 1020.521 3.669 Evaporation Loss ......... 0.000 0.000 Infiltration Loss ........ 379.847 1.366 Surface Runoff ........... 635.815 2.286 Final Storage ............ 8.565 0.031 Continuity Error (%) ..... ‐0.363 ************************** Volume Volume Flow Routing Continuity acre‐feet 10^6 gal
Enclave at Redwood
Page F
December 22, 2021
Appendix F – Low Impact Development
DS DSDSDSDS
DSDS
DSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDS
DS DS
DS
DS DS
DS
DS
DS
DSDS
DS
DS
DS DS DS DSDSDSDSDSDSDS
DS
DS DS DSDS
DS
DSDS
DS
DSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDS
DS
DS
DSDSDS DSDS DSDSDS DSDSDSDSDSDS
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7ACBASINAREAIMP%IR-13.2870%ACBASINAREAIMP%IR-25.1375%ACBASINAREAIMP%IR-44.5580%ACBASINAREAIMP%IR-37.1274%ACBASINAREAIMP%IR-37.1274%ACBASINAREAIMP%IR-37.1274%ACBASINAREAIMP%IR-17.1274%ACBASINAREAIMP%IR-25.1375%ACBASINAREAIMP%IR-25.1375%ACBASINAREAIMP%IR-44.5580%SHEET NUMBERISSUE DATE:DATEREVISION COMMENTSDESIGNED BY:CHECKED BY:DRAWN BY:PROJECT #:1120 Lincoln Street, Suite 1000Denver, Colorado 80203P: 303.623.6300 F: 303.623.6311HarrisKocherSmith.comKnow what's below.Call before you dig.®FILEPATH: K:\201013\ENGINEERING\DRAINAGE\FINAL DRAINAGE PLAN.DWG LAYOUT: LID MAP9 XREFs: dhi_logo, e-base, e-legal[U], e-offsite, e-util, fg, p-base, p-legal, p-utilPLOTTED: TUE 12/21/21 3:42:14P BY: MARK WEST
201013ENCLAVE AT REDWOODLOW IMPACT DEVELOPMENT MAP11OF1DHI COMMUNITIES2021-08-18JMRMAWJMR########################################################NO CHANGES ARE TO BE MADE TO THIS DRAWING WITHOUT WRITTEN PERMISSION OF HARRIS KOCHER SMITH.0SCALE: 1" =808016080'BASINDESIGNATIONBASIN SIZEIN ACRESC COEFFICIENTOS 10.671.23ACBASINAREAC100-YR SWMMLOW IMPACT DEVELOPMENT SUMMARY TABLEBasinArea (sq-ft)Area (ac)CalculatedImperviousness(%)*UtilizedImperviousness(%)ImperviousArea (sq-ft)120% WQCV(12-Hour DrainTime) (cu-ft)FAA WQCV(cu-ft)LID TreatmentProvidedVolume in LID(cu-ft)IR-1143024.903.2865.6709381031471787Isolator Rows 1 - Pond 13252IR-2223433.925.1372.57516205753543855Isolator Rows 2 - UD25366IR-3310215.357.1271.17422062573044429Isolator Rows 3 - Pond 37350IR-4198045.544.5579.380157030not treated by LIDTotal LIDTreated Area676674.1715.570.4476492Total Site Area1196479.94427.551.9621093Total LID Treated Impervious Area/Total Site Impervious Area (Must be > 75%)77%*In some cases imperviousness was rounded up to be more conservative in sizing LID facilities, exact imperviousness was used to prove 75% of new impervious areas treated byLID**Isolator Rows were sized by comparing 120% of the WQCV based on a 12-Hour drain time and the City of Fort Collins Modified FAA Method
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =70.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.700
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.22 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 143,025 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =2,622.41 cu ft
Vol = (WQCV / 12) * Area
Design Procedure Form: Rain Garden (RG)
MW
HKS
December 21, 2021
Enclave at Redwood
POND1 - Isolator Rows
UD-BMP (Version 3.07, March 2018)
UD1 MHFD.xlsm, RG 12/21/2021, 9:38 AM
UD1 ISOLATOR ROW VOLUME CALCULATION: MODIFIED FAA METHOD FROM FORT COLLINS IDF
Project #201013
Project Name Enclave at Redwood *Unused
Designer MW
Date 10/12/2021
0.7089
3.2834
0.52
Time (min)WQCV Intensity (1/2 of 2‐Year
Intensity) (in/hr)
Volume In
(cu‐ft)
Out
Factor*
Adjusted
Release (CFS)
Volume Out
(cu‐ft)
Storage
(cu‐ft)
5 1.425 995.050 1.00 0.5200 156.000 839.05
10 1.105 1543.200 1.00 0.5200 312.000 1231.20
15 0.935 1958.677 1.00 0.5200 468.000 1490.68
20 0.805 2248.464 0.95 0.4940 624.000 1624.46
25 0.715 2496.353 0.86 0.4472 780.000 1716.35
30 0.65 2723.295 0.80 0.4160 936.000 1787.29
35 0.585 2859.459 0.76 0.3952 1092.000 1767.46
40 0.535 2988.641 0.73 0.3796 1248.000 1740.64
45 0.495 3110.840 0.70 0.3640 1404.000 1706.84
50 0.46 3212.091 0.68 0.3536 1560.000 1652.09
55 0.435 3341.273 0.66 0.3432 1716.000 1625.27
60 0.41 3435.541 0.65 0.3380 1872.000 1563.54
65 0.39 3540.283 0.64 0.3328 2028.000 1512.28
70 0.365 3568.214 0.63 0.3276 2184.000 1384.21
75 0.35 3665.974 0.62 0.3224 2340.000 1325.97
80 0.33 3686.922 0.61 0.3172 2496.000 1190.92
85 0.32 3798.647 0.61 0.3172 2652.000 1146.65
90 0.305 3833.561 0.60 0.3120 2808.000 1025.56
95 0.29 3847.527 0.59 0.3068 2964.000 883.53
100 0.28 3910.372 0.59 0.3068 3120.000 790.37
105 0.27 3959.251 0.59 0.3068 3276.000 683.25
110 0.26 3994.165 0.58 0.3016 3432.000 562.17
115 0.255 4095.416 0.58 0.3016 3588.000 507.42
120 0.245 4105.890 0.58 0.3016 3744.000 361.89
1787.29
Qout (From ADS maximum chamber flow rate)(CFS)
FAA Method Table
Maximum Storage Represents Required WQCV
C (From Fort Collins Storm Criteria Manual)
Area (ac)
AB C DE F GH IJKLMNVAULT IDTOTAL REQUIRED WQCV(CF)WQ FLOW (CFS) CHAMBER TYPERELEASE RATE/CHAMBER(CFS)CHAMBER VOLUME(CF)CHAMBER VOLUME + AGGREGATE(CF)NUMBER OF CHAMBERSCOMBINED RELEASE RATE WQCV METHOD(CFS)FAA REQUIRED STORAGE VOLUME (CF)NUMBER OF CHAMBERS (FAA)TOTAL VOLUME (CHAMBERS ONLY)(CF)COMBINED RELEASE RATE FAA METHOD (CFS)TOTAL NUMBER OF CHAMBERS REQUIREDTOTAL SYSTEM VOLUME (CF)3146.892 0 MC‐45000.026106.5162.620 0.52 1787.29 17 1811 0.4420 3252CONFIRM CONFIRMA MHFD Rain Garden UD‐BMP WQCV * 120%B 1/2 of the 2‐year developed flow rate for the basin being sizedC Chamber type based on site constraintsD Flwo rate thru the bottom of the isolator row chamber which is equal to the area of the bottom of the chamber multiplied by the flow rate per unit area (see calculations below)E Volume within chamber only, not accounting for void spaces in surrounding aggregate (standard spec)F Volume includes chamber and void space (40%) in surrounding aggregate , per chamber unit. (standard spec)G Number of chambers required to provide full WQCV within total installed system, include aggregate = A / FH Release rate per chamber times number of chambers = D * G I FAA calc based on Flow, WQ and Total Release RateJ Number of chambers required to provide required FAA staorage volume stored within the chamber only (no aggregate stone) = I / EK Volume provided in chambers only (no aggregate storage). This must meet or excheed the required FAA storage volume. Greater of G or J * E L Release rate per chamber times number of chambers = D * J M Total number of chambers (Greater of J or G)N Total system volume. Includes number of chambers plus aggregate. This must meet or exceed required WQCVMC‐4500 MC‐3500 SC‐740 SC‐310 SC‐160LP60.0 45.0 30.0 16.0 12.0100.0 77.0 51.0 34.0 25.048.3 86.0 85.4 85.4 85.433.5 46.0 30.2 20.2 14.8106.5 109.9 85.9 14.7 6.9162.6 175.0 74.9 31.0 15.0CHAMBER FLOW RATE CONVERSION (GPM/SF TO CFS)0.35 GPM/SF1 CF = 7.48052 GAL1 GALLON = 0.133681 CF 1 GPM = 0.002228 CFS*FLOW RATE BASED ON 1/2 OF NOV 07 QMAX IN FIGURE 17 OF UNH TESTING REPORTMC‐4500 MC‐3500 SC‐740 SC‐310 SC‐160LP0.0262 0.036 0.024 0.016 0.012 (COLUMN D)FLOW RATE / CHAMBER (CFS)STORMTECH CHAMBER VOLUME AND RELEASE RATE CALCULATIONSFLOOR AREA (SF)CHAMBER VOLUME (CF)CHAMBER/AGGREGATE VOLUME (CF)STORMTECH CHAMBER DATAFLOW RATE*CHAMBER FLOW RATECHAMBER DIMENSIONSWIDTH (IN)INSTALLED LENGTH (IN)HEIGHT (IN)
Filepath: K:\201013\ENGINEERING\EXHIBIT\UNDERGROUND DETENTION EXHIBIT.DWG Layout: UD27 XREFs: e-base, e-legal, e-offsite, keymap, p-base, p-legal, p-utilPlotted: TUE 12/21/21 12:26:18P By: Mark West NO CHANGES ARE TO BE MADE TO THIS DRAWING WITHOUT WRITTEN PERMISSION OF HARRIS KOCHER SMITH.1120 Lincoln Street, Suite 1000Denver, Colorado 80203P: 303.623.6300 F: 303.623.6311HarrisKocherSmith.com0SCALE: 1" =20204020'UNDERGROUND DETENTION EXHIBIT - UD2KEY MAPSCALE 1" = 500'REDWOOD ST
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T2 OF 3
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =75.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.750
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.24 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area =223433.92 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =4,461.70 cu ft
Vol = (WQCV / 12) * Area
Design Procedure Form: Rain Garden (RG)
JMR
HKS
December 21, 2021
Enclave at Redwood
UD2 - Isolator Rows
UD-BMP (Version 3.07, March 2018)
UD2 MHFD.xlsm, RG 12/21/2021, 10:45 AM
UD2 ISOLATOR ROW VOLUME CALCULATION: MODIFIED FAA METHOD FROM FORT COLLINS IDF
Project #201013
Project Name Enclave at Redwood *Unused
Designer MW
Date 12/21/2021
UD2
0.77
5.13
0.55
Time (min)WQCV Intensity (1/2 of 2‐Year
Intensity) (in/hr)
Volume In
(cu‐ft)
Out
Factor*
Adjusted
Release (CFS)
Volume Out
(cu‐ft)
Storage
(cu‐ft)
5 1.425 1686.255 1.00 0.5500 165.000 1521.26
10 1.105 2615.175 1.00 0.5500 330.000 2285.17
15 0.935 3319.261 1.00 0.5500 495.000 2824.26
20 0.805 3810.345 0.95 0.5225 660.000 3150.35
25 0.715 4230.430 0.86 0.4730 825.000 3405.43
30 0.65 4615.015 0.80 0.4400 990.000 3625.01
35 0.585 4845.765 0.76 0.4180 1155.000 3690.77
40 0.535 5064.683 0.73 0.4015 1320.000 3744.68
45 0.495 5271.767 0.70 0.3850 1485.000 3786.77
50 0.46 5443.351 0.68 0.3740 1650.000 3793.35
55 0.435 5662.268 0.66 0.3630 1815.000 3847.27
60 0.41 5822.019 0.65 0.3575 1980.000 3842.02
65 0.39 5999.519 0.64 0.3520 2145.000 3854.52
70 0.365 6046.853 0.63 0.3465 2310.000 3736.85
75 0.35 6212.520 0.62 0.3410 2475.000 3737.52
80 0.33 6248.020 0.61 0.3355 2640.000 3608.02
85 0.32 6437.354 0.61 0.3355 2805.000 3632.35
90 0.305 6496.521 0.60 0.3300 2970.000 3526.52
95 0.29 6520.187 0.59 0.3245 3135.000 3385.19
100 0.28 6626.688 0.59 0.3245 3300.000 3326.69
105 0.27 6709.521 0.59 0.3245 3465.000 3244.52
110 0.26 6768.688 0.58 0.3190 3630.000 3138.69
115 0.255 6940.272 0.58 0.3190 3795.000 3145.27
120 0.245 6958.022 0.58 0.3190 3960.000 2998.02
3854.52
Qout (From ADS maximum chamber flow rate)(CFS)
FAA Method Table
Maximum Storage Represents Required WQCV
C (From Fort Collins Storm Criteria Manual)
Area (ac)
AB C DE F GH IJKLMNVAULT IDTOTAL REQUIRED WQCV(CF)WQ FLOW (CFS) CHAMBER TYPERELEASE RATE/CHAMBER(CFS)CHAMBER VOLUME(CF)CHAMBER VOLUME + AGGREGATE(CF)NUMBER OF CHAMBERSCOMBINED RELEASE RATE WQCV METHOD(CFS)FAA REQUIRED STORAGE VOLUME (CF)NUMBER OF CHAMBERS (FAA)TOTAL VOLUME (CHAMBERS ONLY)(CF)COMBINED RELEASE RATE FAA METHOD (CFS)TOTAL NUMBER OF CHAMBERS REQUIREDTOTAL SYSTEM VOLUME (CF)5354.0 0 MC‐45000.026106.5162.633 0.86 3854.52 37 3941 0.9733 5365.8CONFIRM CONFIRMA MHFD Rain Garden UD‐BMP WQCV * 120%B 1/2 of the 2‐year developed flow rate for the basin being sizedC Chamber type based on site constraintsD Flwo rate thru the bottom of the isolator row chamber which is equal to the area of the bottom of the chamber multiplied by the flow rate per unit area (see calculations below)E Volume within chamber only, not accounting for void spaces in surrounding aggregate (standard spec)F Volume includes chamber and void space (40%) in surrounding aggregate , per chamber unit. (standard spec)G Number of chambers required to provide full WQCV within total installed system, include aggregate = A / FH Release rate per chamber times number of chambers = D * G I FAA calc based on Flow, WQ and Total Release RateJ Number of chambers required to provide required FAA staorage volume stored within the chamber only (no aggregate stone) = I / EK Volume provided in chambers only (no aggregate storage). This must meet or excheed the required FAA storage volume. Greater of G or J * E L Release rate per chamber times number of chambers = D * J M Total number of chambers (Greater of J or G)N Total system volume. Includes number of chambers plus aggregate. This must meet or exceed required WQCVMC‐4500 MC‐3500 SC‐740 SC‐310 SC‐160LP60.0 45.0 30.0 16.0 12.0100.0 77.0 51.0 34.0 25.048.3 86.0 85.4 85.4 85.433.5 46.0 30.2 20.2 14.8106.5 109.9 85.9 14.7 6.9162.6 175.0 74.9 31.0 15.0CHAMBER FLOW RATE CONVERSION (GPM/SF TO CFS)0.35 GPM/SF1 CF = 7.48052 GAL1 GALLON = 0.133681 CF 1 GPM = 0.002228 CFS*FLOW RATE BASED ON 1/2 OF NOV 07 QMAX IN FIGURE 17 OF UNH TESTING REPORTMC‐4500 MC‐3500 SC‐740 SC‐310 SC‐160LP0.0262 0.036 0.024 0.016 0.012 (COLUMN D)FLOW RATE / CHAMBER (CFS)STORMTECH CHAMBER VOLUME AND RELEASE RATE CALCULATIONSFLOOR AREA (SF)CHAMBER VOLUME (CF)CHAMBER/AGGREGATE VOLUME (CF)STORMTECH CHAMBER DATAFLOW RATE*CHAMBER FLOW RATECHAMBER DIMENSIONSWIDTH (IN)INSTALLED LENGTH (IN)HEIGHT (IN)
X
F
M
RXFMR XFMRFilepath: K:\201013\ENGINEERING\EXHIBIT\UNDERGROUND DETENTION EXHIBIT.DWG Layout: IR37 XREFs: e-base, e-legal, e-offsite, keymap, p-base, p-legal, p-utilPlotted: TUE 12/21/21 12:25:40P By: Mark West NO CHANGES ARE TO BE MADE TO THIS DRAWING WITHOUT WRITTEN PERMISSION OF HARRIS KOCHER SMITH.1120 Lincoln Street, Suite 1000Denver, Colorado 80203P: 303.623.6300 F: 303.623.6311HarrisKocherSmith.com0SCALE: 1" =20204020'UNDERGROUND ISOLATOR ROW EXHIBIT - PARK AREA (IR3)KEY MAPSCALE 1" = 500'REDWOOD ST
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T1 OF 3
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =74.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.740
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.24 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 310,215 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =6,086.63 cu ft
Vol = (WQCV / 12) * Area
Design Procedure Form: Rain Garden (RG)
MW
HKS
December 21, 2021
Enclave at Redwood
IR3 - Isolator Rows
UD-BMP (Version 3.07, March 2018)
IR3 MHFD.xlsm, RG 12/21/2021, 10:08 AM
IR1 ISOLATOR ROW VOLUME CALCULATION: MODIFIED FAA METHOD FROM FORT COLLINS IDF
Project #201013
Project Name Enclave at Redwood *Unused
Designer MW
Date 10/12/2021
0.7549
7.122 310215.35 sq‐ft
1.51
Time (min)WQCV Intensity (1/2 of 2‐Year
Intensity) (in/hr)
Volume In
(cu‐ft)
Out
Factor*
Adjusted
Release (CFS)
Volume Out
(cu‐ft)
Storage
(cu‐ft)
5 1.425 2298.270 1.00 1.5100 453.000 1845.27
10 1.105 3564.334 1.00 1.5100 906.000 2658.33
15 0.935 4523.962 1.00 1.5100 1359.000 3164.96
20 0.805 5193.283 0.95 1.4345 1721.400 3471.88
25 0.715 5765.834 0.86 1.2986 1947.900 3817.93
30 0.65 6290.001 0.80 1.2080 2174.400 4115.60
35 0.585 6604.501 0.76 1.1476 2409.960 4194.54
40 0.535 6902.873 0.73 1.1023 2645.520 4257.35
45 0.495 7185.116 0.70 1.0570 2853.900 4331.22
50 0.46 7418.975 0.68 1.0268 3080.400 4338.58
55 0.435 7717.347 0.66 0.9966 3288.780 4428.57
60 0.41 7935.078 0.65 0.9815 3533.400 4401.68
65 0.39 8177.001 0.64 0.9664 3768.960 4408.04
70 0.365 8241.514 0.63 0.9513 3995.460 4246.05
75 0.35 8467.309 0.62 0.9362 4212.900 4254.41
80 0.33 8515.693 0.61 0.9211 4421.280 4094.41
85 0.32 8773.745 0.61 0.9211 4697.610 4076.13
90 0.305 8854.386 0.60 0.9060 4892.400 3961.99
95 0.29 8886.642 0.59 0.8909 5078.130 3808.51
100 0.28 9031.796 0.59 0.8909 5345.400 3686.40
105 0.27 9144.693 0.59 0.8909 5612.670 3532.02
110 0.26 9225.334 0.58 0.8758 5780.280 3445.05
115 0.255 9459.193 0.58 0.8758 6043.020 3416.17
120 0.245 9483.386 0.58 0.8758 6305.760 3177.63
4428.57
Qout (From ADS maximum chamber flow rate)(CFS)
FAA Method Table
Maximum Storage Represents Required WQCV
C (From Fort Collins Storm Criteria Manual)
Area (ac)
AB C DE F GH IJKLMNVAULT IDTOTAL REQUIRED WQCV(CF)WQ FLOW (CFS) CHAMBER TYPERELEASE RATE/CHAMBER(CFS)CHAMBER VOLUME(CF)CHAMBER VOLUME + AGGREGATE(CF)NUMBER OF CHAMBERSCOMBINED RELEASE RATE WQCV METHOD(CFS)FAA REQUIRED STORAGE VOLUME (CF)NUMBER OF CHAMBERS (FAA)TOTAL VOLUME (CHAMBERS ONLY)(CF)COMBINED RELEASE RATE FAA METHOD (CFS)TOTAL NUMBER OF CHAMBERS REQUIREDTOTAL SYSTEM VOLUME (CF)7303.9 0 MC‐35000.036109.9175.042 1.51 4428.57 41 4506 1.4742 7350CONFIRM CONFIRMA MHFD Rain Garden UD‐BMP WQCV * 120%B 1/2 of the 2‐year developed flow rate for the basin being sizedC Chamber type based on site constraintsD Flwo rate thru the bottom of the isolator row chamber which is equal to the area of the bottom of the chamber multiplied by the flow rate per unit area (see calculations below)E Volume within chamber only, not accounting for void spaces in surrounding aggregate (standard spec)F Volume includes chamber and void space (40%) in surrounding aggregate , per chamber unit. (standard spec)G Number of chambers required to provide full WQCV within total installed system, include aggregate = A / FH Release rate per chamber times number of chambers = D * G I FAA calc based on Flow, WQ and Total Release RateJ Number of chambers required to provide required FAA staorage volume stored within the chamber only (no aggregate stone) = I / EK Volume provided in chambers only (no aggregate storage). This must meet or excheed the required FAA storage volume. Greater of G or J * E L Release rate per chamber times number of chambers = D * J M Total number of chambers (Greater of J or G)N Total system volume. Includes number of chambers plus aggregate. This must meet or exceed required WQCVMC‐4500 MC‐3500 SC‐740 SC‐310 SC‐160LP60.0 45.0 30.0 16.0 12.0100.0 77.0 51.0 34.0 25.048.3 86.0 85.4 85.4 85.433.5 46.0 30.2 20.2 14.8106.5 109.9 85.9 14.7 6.9162.6 175.0 74.9 31.0 15.0CHAMBER FLOW RATE CONVERSION (GPM/SF TO CFS)0.35 GPM/SF1 CF = 7.48052 GAL1 GALLON = 0.133681 CF 1 GPM = 0.002228 CFS*FLOW RATE BASED ON 1/2 OF NOV 07 QMAX IN FIGURE 17 OF UNH TESTING REPORTMC‐4500 MC‐3500 SC‐740 SC‐310 SC‐160LP0.0262 0.036 0.024 0.016 0.012 (COLUMN D)FLOW RATE / CHAMBER (CFS)STORMTECH CHAMBER VOLUME AND RELEASE RATE CALCULATIONSFLOOR AREA (SF)CHAMBER VOLUME (CF)CHAMBER/AGGREGATE VOLUME (CF)STORMTECH CHAMBER DATAFLOW RATE*CHAMBER FLOW RATECHAMBER DIMENSIONSWIDTH (IN)INSTALLED LENGTH (IN)HEIGHT (IN)
DS DSDSDSDS
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7ACBASINAREAC2137.820.889ACBASINAREAC8123.750.516ACBASINAREAC113_14.280.820ACBASINAREAC113_27.860.777ACBASINAREAC113_45.580.868ACBASINAREAC113_39.750.854ACBASINAREAC113_27.860.777ACBASINAREAC113_39.750.854ACBASINAREAC4132.190.585SHEET NUMBERISSUE DATE:DATEREVISION COMMENTSDESIGNED BY:CHECKED BY:DRAWN BY:PROJECT #:1120 Lincoln Street, Suite 1000Denver, Colorado 80203P: 303.623.6300 F: 303.623.6311HarrisKocherSmith.comKnow what's below.Call before you dig.®FILEPATH: K:\201013\ENGINEERING\DRAINAGE\FINAL DRAINAGE PLAN.DWG LAYOUT: FOR UTILITY PLANS9 XREFs: dhi_logo, e-base, e-legal[U], e-offsite, e-util, fg, p-base, p-legal, p-utilPLOTTED: WED 12/22/21 8:28:27A BY: TIM HOFFMAN
201013ENCLAVE AT REDWOODFINAL DRAINAGE PLAN3838OF38DHI COMMUNITIES2021-08-18JMRMAWJMR2021-10-20PER CITY COMMENTS NO CHANGES ARE TO BE MADE TO THIS DRAWING WITHOUT WRITTEN PERMISSION OF HARRIS KOCHER SMITH.0SCALE: 1" =808016080'BASINDESIGNATIONBASIN SIZEIN ACRESC COEFFICIENTOS 10.671.23ACBASINAREAC100-YR SWMMSubcatchment Summary TableBasinOutfall IDArea (ac)CalculatedImperviousness(%)UtilizedImperviousness(%)100-Year TotalRunoff Volume(ac-ft)2-YearPeakRunoff(CFS)100-YearPeakRunoff(CFS)2-Year SWMMCalculatedRunoffCoefficient100-Year SWMMCalculatedRunoffCoefficient113_1Pond14.278752.73550.986.6532.610.5160.753113_2UD27.857541.08501.699.9345.380.4610.703113_3Pond39.751262.05652.3917.2177.770.6030.802113_4Redwood Pond5.580066.84681.4110.5147.470.6320.82213NECCO A2 StormLine7.8200N/A752.1214.4167.650.6890.889413Existing NECCOStub2.1900N/A70.400.456.620.0740.585812Redwood Pond3.7500N/A20.580.227.210.0250.516Detention Pond Summary TablePond100-YearVolume(cu-ft)100-YearVolume(ac-ft)100-YearWSELWQCV(cu-ft)WQCVWSELMax ReleaseRate (CFS)Total VolumeRequired (WQCV +Detention) (ac-ft)Total VolumeProvided (WQCV +Detention) (ac-ft)Pond136,5620.844957.630.86IR 13,1474954.400.910.91UD266,4571.534951.921.57IR25,3544947.091.651.65Pond381,4711.874962.521.95IR 37,3044958.342.042.04Redwood Pond226,2655.194958.194956.4615.96*WQCV in Underground Chamber Systems Explored Further in LID Exhibit and Calculations Found in Appendix Fof Preliminary Drainage Report**SWMM Model, Inputs, and Outputs Found in Appendix E of Preliminary Drainage Report