HomeMy WebLinkAboutMULBERRY CONNECTION - FDP200030 - - DRAINAGE REPORT (4)kimley-horn.com 4582 South Ulster Street, Suite 1500, Denver, CO 80237 303 228 2300
DRAINAGE REPORT COVER LETTER
To:
City of Fort Collins
Matt Simpson, P.E., CFM
Development Review Engineer
From:Dan Skeehan, P.E.
Kimley-Horn and Associates, Inc
Date:December 2, 2020
Subject:Mulberry Connection, PDP190015
Drainage Report Cover Letter
Kimley-Horn and Associates, Inc. (Kimley-Horn) is submitting this Drainage Report Cover Letter for the above
referenced project. The purpose of this letter is to serve as an outline for the proposed development and associated
drainage.
PROJECT DESCRIPTION
The proposed Mulberry Connection Project is located within the Northeast Quarter of Section 9, Township 7 North,
Range 68 West of the Sixth Principal Meridian, City of Fort Collins, County of Larimer, Colorado. A vicinity map is
provided below.
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kimley-horn.com 4582 South Ulster Street, Suite 1500, Denver, Colorado, 80237 303 228 2300
The site is approximately 13 acres and is existing farm land. The proposed site includes two industrial buildings
with associated parking and landscape improvements. Drainage improvements include two proposed rain
gardens, proposed underground water quality treatment, and a proposed detention pond. A variance is being
requested to allow for an inflow infiltration basin at the inflow into the detention pond due to existing grades
within the project site and along the adjacent boundaries.
“I hereby attest that this report for the final drainage design for the Mulberry Connection 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.”
SIGNATURE: _________________________________
Dan Skeehan, P.E.
Registered Professional Engineer
State of Colorado No. 46391
ATTACHMENTS
Final Drainage Report
City of Fort Collins
Mulberry Connection
(Redman Drive and I-25 Frontage Road)
Final Drainage Report
DECEMBER 2020 | VERSION 1
Prepared By:
4582 South Ulster Street, Suite 1500
Denver, CO 80237
Dan Skeehan
Registered Professional Engineer
State of Colorado No. 46391
2
INTRODUCTION
The proposed Mulberry Connection Project is located within the Northeast Quarter of Section 9, Township
7 North, Range 68 West of the Sixth Principal Meridian, City of Fort Collins, County of Larimer, Colorado.
The site is bound by:
· North: Existing Farmland
· East: Interstate 25 (“I-25”) Frontage Road
· South: Redman Drive
· West: Existing Farmland
A vicinity map is provided below.
Preliminary Drainage Report
Mulberry Connection – Fort Collins, Colorado
3
PROPOSED DEVELOPMENT
The site is approximately 13.05 acres and is existing farmland. The proposed site includes two industrial
buildings with associated parking and landscape improvements.
EXISTING SITE INFORMATION
The Site is located within the Boxelder Creek and Cooper Slough Basins. The Master Plan for these basins
is currently being updated, according to the City of Fort Collins website. According to the Problem
Identification Map, the Site is not within a high or moderate risk floodplain. The Flooding Solutions Map
indicates that upgrades to pipes and open channels are recommended south of the Site along E. Mulberry
Street. No flooding or water quality improvements are recommended within the vicinity of the Site.
The soil on the site is primarily Nunn loam and Garrett loam, which are classified as Hydrologic Soil Group
C and B, respectively. The soil Classification Map can be found in Appendix A. This Site is a part of the
Boxelder Creek & Cooper Slough Master Drainage Plan, which is currently under revision and has not been
referenced in this design. The existing site is utilized as agricultural land with ground cover primarily made
up of crop.
According to the Geotechnical Evaluation performed by Ninyo & Moore on July 2, 2019, groundwater was
encountered at depths ranging between approximately 8.5 to 12 feet below ground surface.
HISTORIC DRAINAGE
The existing Site is relativity flat with slopes ranging from 0.5% to 3%. There are currently no existing on-
site water quality or detention improvements. The majority of the site currently slopes to the southwest,
conveying water into an existing roadside ditch adjacent to Redman Drive, which discharges into Cooper
Slough approximately 600 feet west of the Site. The property directly north of the Site is collected by an
existing drainage ditch along the northern property line, routing all discharges around the Site. I-25 Frontage
Road is adjacent to the Site to the east. The width of the Frontage Road drains west into an existing
drainage ditch adjacent to the Site in the existing condition.
The site is located within City of Fort Collins Federal Emergency Management Agency (FEMA) Flood
Insurance Rate Map Number 08069C0984H and the property being developed is designated as an area
outside of the 100-year floodplain. The updated FEMA maps is included in Appendix A.
DESIGN CRITERIA
The City of Fort Collins “Stormwater Criteria Manual, December 2018 Edition,” (Criteria Manual) and the
“Urban Drainage and Flood Control District Urban Storm Drainage Criteria Manual” Volumes 1, 2, and 3
(Drainage Manual), with latest revisions, were used to prepare the storm calculations. Weighted impervious
values were calculated and used for the site area in accordance with the Criteria Manual and Drainage
Manual.
This Site is a part of the Boxelder Creek & Cooper Slough Master Drainage Plan, which is currently under
revision. Existing storm sewer infrastructure is not present on the Site. An existing drainage ditch is present
on both sides (north and south) of Redman Drive, in addition to the existing concrete irrigation ditch on the
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adjacent property to the north. An existing drainage ditch adjacent to the Site to the east collects the
Frontage Road runoff.
Hydrologic Criteria
The 2-year and 100-year storm event were evaluated for this Site. Rainfall intensity values provided in the
Criteria Manual were utilized for the analysis. Impervious values for pavement, roof, and landscape area
were taken from the Criteria Manual. Runoff coefficients were calculated per the Criteria Manual. The
Rational Method was utilized to calculate the peak runoff values for the minor and major storm event.
Peak runoff values were calculated for the existing conditions of the Site, which the 2-year existing peak
runoff informed the allowable release from the Site in the proposed conditions in the 100-year storm event.
Topographic survey of the Site was utilized to delineate existing sub-basins for the Site. An Existing
Drainage Map is provided in Appendix B and all hydrologic calculations are provided in Appendix C.
The proposed site layout and grading was utilized to delineate sub-basins for the proposed condition, as
shown in the Proposed Drainage Map included in Appendix B. Peak runoff values for the proposed sub-
basins were calculated using the Rational Method. Hydrologic calculations are provided in Appendix C.
Hydraulic Criteria
Water Quality Capture Volumes for sub-basins A, B, C, and D were calculated per the methods described
in the Criteria Manual. The Modified FAA Method, as described in the Criteria Manual, was utilized to
calculate the required detention volume for the Site in the proposed conditions. Water quality and detention
calculations are provided in Appendix D.
This Final Drainage Report includes the following hydraulic calculations: inlet calculations utilizing Bentley
FlowMaster software; pipe capacity calculations utilizing Bentley StormCAD. Sizing of the overflow
spillways have been done per the methods described in the Criteria Manual. All hydraulic calculations are
included in Appendix D.
DRAINAGE PLAN
GENERAL CONCEPT
The Site in the proposed conditions was divided into four major onsite sub-basins which are described in
greater detail in the following section. BMPs were selected utilizing the four-step process outlined in Volume
3, Chapter 1, Section 4 of the Drainage Manual:
1. Employ runoff reduction practices (Minimize Directly Connected Impervious Area) - The
redevelopment of an urban site provides limited opportunities to employ runoff reduction practices.
The Site has been developed to install landscaping wherever pavement (or building) is not required.
Additionally, impervious areas have been disconnected from storm sewer infrastructure at all
feasible locations, and are routed into the proposed rain gardens within basins A and C.
2. Implement BMPs that provide a water quality capture volume with a slow release – 12.42 acres will
be treated for the water quality capture volume (WQCV). The total on-site proposed impervious
surface area is 8.97 acres (including pavement and roofs), 8.87 acre of which will be treated by
bioretention or underground proprietary system. D sub-basins are directly tributary to the inflow
infiltration basin within the detention pond. WQCV for the D sub-basins will be treated via infiltration.
Drainage basins O1, O2, O3, O4, O5, OS1, and OS2 will not be treated for water quality, a total of
Preliminary Drainage Report
Mulberry Connection – Fort Collins, Colorado
5
0.63 acres on-site and 1.52 acres off-site. A rain garden is proposed to treat the WQCV from sub-
basin C, an underground treatment system is proposed to treat the WQCV from sub-basin B, a rain
garden is proposed to treat the WQCV from sub-basin A, and the WQCV from sub-basin D will be
infiltrated via the inflow infiltration basin in the detention pond, as detailed in Table 1 below.
Table 1. Summary of Impervious Area Treated
On-Site Sub-
Basin
Total
Area
(ac)
Impervious
Area (ac)
Impervious
Area Treated
(ac)
Percent
Impervious
Treated
Water Quality
Feature
A 5.51 3.67 3.67 100%Rain Garden A
B1 2.00 1.70 1.70 100%
Underground
B2 0.91 0.91 0.91 100%
C 3.63 2.54 2.54 100%Rain Garden C
Total to LID 12.05 8.82 8.82 100%--
D1 0.14 0.02 0.02 100%
Inflow Infiltration
Basin within
Detention Pond
D2 0.06 0.00 0.00 100%
D3 0.04 0.00 0.00 100%
D4 0.14 0.02 0.02 100%
Total to
Infiltration
0.38 0.04 0.04 100%--
O1 0.26 0.00 0.00 0%
Flows Off-Site
O2 0.07 0.03 0.00 0%
O3 0.06 0.04 0.00 0%
O4 0.07 0.04 0.00 0%
O5 0.17 0.00 0.00 0%
Total Not
Treated
0.63 0.11 0.00 0%--
Total On-Site 13.05 8.97 8.86 68% (percent impervious treated)
92% (percent total Site to LID)
The three proposed water quality treatment areas are shown on the Proposed Drainage Map in
Appendix B and calculations are provided in Appendix D.
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3. Stabilize streams – Not applicable.
4. Implement site specific and other source control BMPs – During construction, the site will include
silt fence to reduce potential for contamination discharges at the perimeter. Site access will be
provided through an area of vehicle tracking control to reduce tracking of contamination offsite
which will be further controlled with street sweeping and rock socks along Redman Drive. Proposed
storm sewer will have inlet protection. Additionally, diversion ditches routing water to a sediment
basin will be installed at the beginning of construction.
SPECIFIC DETAILS
Runoff generated by three of the on-site basins (sub-basins A B, and C - 12.05 acres of the total 13.05
acres – 92% of the Site) will be routed to LID features and the WQCV treated. Runoff generated by storm
events greater than the WQCV will be routed through the LID features to a proposed detention pond via
proposed storm sewer infrastructure. Runoff generated by one on-site basin (sub-basin D – 0.38 acres of
the total 13.05 acres – 3% of the Site) will be routed to the inflow infiltration basin within the proposed
detention pond. The proposed detention pond will outfall to an existing drainage swale directly upstream of
Cooper Slough and adjacent to the Site. Five on-site basins (0.63 acres – 5% of the Site) will surface flow
off-site and not be treated for water quality or be detained. The 100-year release rate from the proposed
detention pond was calculated to take into account the undetained flows from these basins that are not fully
pervious. Two offsite sub-basins are included in the drainage analysis to properly size all proposed drainage
features. The Proposed Drainage Map included in Appendix B shows the onsite and offsite sub-basins
and each basin is described in further detail below. Table 2 summarizes the tributary areas, impervious
areas, imperviousness, and peak flows from each sub-basin. Full calculations are included in Appendix C.
Sub-basin A
Sub-basin A is 5.51 acres and consists of on-site parking, sidewalk, one of the buildings, and landscape
areas that surface flow to proposed Rain Garden A. Water quality treatment for runoff from this sub-basin
will occur within Rain Garden A. Flows above the WQCV will flow to the detention pond via two overflow
spillways between Rain Garden A and the detention pond.
Sub-basin B1
Sub-basin B1 is 2.00 acres and consists of on-site parking, sidewalk, loading dock, and landscaped areas.
Runoff within this sub-basin surface flows to a proposed double CDOT Type 13 inlet within a proposed
valley gutter.
Sub-basin B2
Sub-basin B1 is 0.91 acres and consists of loading dock. Runoff within this sub-basin surface flows to a
proposed double CDOT Type 13 inlet within a proposed valley gutter.
Both inlets within sub-basin B will connect to the ADS Inflow Manhole. This manhole has been designed
with a low-flow outlet pipe at the bottom of the structure, connected to an underground water quality facility,
which will convey the WQCV. Flows over the WQCV will pond within the manhole structure to the “overflow
outlet pipe”, which will convey flows to the detention pond. The invert of the overflow outlet pipe has been
set at the maximum storage elevation within the underground water quality facility to store the required
WQCV. The stage storage table for the ADS underground system is included in Appendix D.
Preliminary Drainage Report
Mulberry Connection – Fort Collins, Colorado
7
Sub-basin C
Sub-basin C is 3.63 acres and consists of on-site parking, sidewalk, one of the buildings, and landscaped
areas. Runoff within this sub-basin will surface flow east into Rain Garden C, which will provide water quality
treatment. Storm events greater than the WQCV will be routed through Rain Garden C, into the proposed
outlet structure and conveyed via storm pipe to the detention pond.
Sub-basin D1
Sub-basin D1 is 0.14 acres and consists of on-site landscaped area and a portion sidewalk. Runoff within
this sub-basin will surface flow to a proposed CDOT Type D inlet. Flows will be routed to the proposed
inflow infiltration basin within the detention pond via proposed storm sewer.
Sub-basin D2
Sub-basin D2 is 0.06 acres and consists of on-site landscaped area. Runoff within this sub-basin will
surface flow to a proposed CDOT Type D inlet. Flows will be routed to the proposed inflow infiltration basin
within the detention pond via proposed storm sewer.
Sub-basin D3
Sub-basin D3 is 0.04 acres and consists of on-site landscaped area and a portion of sidewalk. Runoff within
this sub-basin will surface flow to a proposed CDOT Type D inlet. Flows will be routed to the proposed
inflow infiltration basin within the detention pond via proposed storm sewer.
Sub-basin D4
Sub-basin D4 is 0.14 acres and consists of on-site landscaped area. Runoff within this sub-basin will
surface flow to a proposed CDOT Type D inlet. Flows will be routed to the proposed inflow infiltration basin
within the detention pond via proposed storm sewer.
Sub-basin O1
Sub-basin O1 is 0.26 acres and consists of on-site landscaped area. Runoff within this sub-basin will
surface flow offsite and water quality treatment nor detention will be provided for this sub-basin.
Sub-basin O2
Sub-basin O2 is 0.07 acres and consists of on-site landscaped area and a portion of the west access drive.
Runoff within this sub-basin will surface flow offsite to Redman Drive. Water quality treatment nor detention
will be provided for this sub-basin.
Sub-basin O3
Sub-basin O3 is 0.06 acres and consists of on-site landscaped area and a portion of the center access
drive. Runoff within this sub-basin will surface flow offsite to Redman Drive. Water quality treatment nor
detention will be provided for this sub-basin.
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Sub-basin O4
Sub-basin O4 is 0.07 acres and consists of on-site landscaped area and a portion of the east access drive.
Runoff within this sub-basin will surface flow offsite to Redman Drive. Water quality treatment nor detention
will be provided for this sub-basin.
Sub-basin O5
Sub-basin O5 is 0.17 acres and consists of on-site landscaped area. Runoff within this sub-basin will
surface flow offsite to the I-25 Frontage Road. Runoff will be collected in the proposed curb and gutter and
will be routed south across Redman Drive via a proposed valley gutter. Runoff will enter an existing drainage
swale south of the intersection via a 2-foot curb cut. Water quality treatment nor detention will be provided
for this sub-basin.
Sub-basin OS1
Sub-basin OS1 is 0.97 acres and consists of off-site landscaped area, sidewalk, and I-25 Frontage Road.
Runoff within this sub-basin will flow to the proposed curb and gutter, following historic drainage patterns.
Flows will be routed across Redman Drive via a proposed valley gutter. Runoff will enter an existing
drainage swale south of the intersection via a 2-foot curb cut. Water quality treatment nor detention will be
provided for this sub-basin on the proposed site. Additionally, this basin is not included as a part of the total
Site improvement area, as proposed off-site improvements will improve existing conditions and maintain
historic drainage patterns.
Sub-basin OS2
Sub-basin OS2 is 0.55 acres and consists of a portion of Redman Drive and offsite landscape area. Runoff
within this sub-basin will surface flow to proposed curb and gutter adjacent to the Site and the existing
drainage ditch on the north side of Redman Drive. Water quality treatment nor detention will be provided
for this sub-basin. Additionally, this basin is not included as a part of the total Site improvement area, as
proposed off-site improvements will improve existing conditions and maintain historic drainage patterns.
Preliminary Drainage Report
Mulberry Connection – Fort Collins, Colorado
9
Table 2. Summary of proposed drainage sub-basins.
Basin ID Total
Tributary
Area (acres)
Impervious
Area (acres)1
Imperviousness 2-Year Peak
Flow (CFS)
100-Year
Peak Flow
(CFS)
A 5.51 3.67 63%8.02 41.40
B1 2.00 1.70 85%4.43 19.90
B2 0.91 0.91 100%3.17 9.96
C 3.63 2.54 66%6.19 32.07
D1 0.14 0.02 18%0.08 0.37
D2 0.06 0.00 2%0.02 0.08
D3 0.04 0.00 2%0.01 0.07
D4 0.14 0.02 19%0.08 0.37
O1 0.26 0.00 2%0.11 0.48
O2 0.07 0.03 41%0.10 0.41
O3 0.06 0.04 58%0.11 0.48
O4 0.07 0.04 60%0.12 0.51
O5 0.17 0.00 2%0.07 0.32
Total On-Site2 13.05 8.97 66%22.51 106.43
Total On-Site
to Detention3
12.42 8.86 69%22.01 104.23
Total On-Site
to Offsite4
0.63 0.11 18%0.50 2.20
OS-1 0.97 0.89 92%2.44 9.65
OS-2 0.55 0.34 62%0.88 4.35
Total Off-Site5 1.52 1.22 81%3.32 14.00
1. Includes pavement and roof areas.
2. Does not include O1 – O5
3. Includes A, B, C, and D
4. Includes O1 – O5
5. Includes OS1 and OS2
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Rain Garden A
Rain Garden A is proposed to treat runoff from, sub-basin A. Runoff will surface flow to a sediment forebay
proposed along the length of the edge of asphalt, along the west side of the parking area. Rain Garden A
is designed with 4:1 side slopes from the sediment forebay to a 12-foot width bottom and 4:1 side slopes
to the berm between the rain garden and detention pond. An underdrain is proposed along the length of
the rain garden. The underdrain will discharge directly into the detention pond, via a manhole with restrictor
plate to ensure the rain garden drains in a minimum of 12 hours. Two spillways will convey flows greater
than the WQCV to the detention pond. Due to the elevations of the crest of each spillway, a small amount
of water will pond within the adjacent parking lot before each spillway is activated. Final design details of
the rain garden are provided in the Construction Documents and are included in Appendix E for reference.
Maintenance: Maintenance access of Rain Garden A is provided via the adjacent parking lot along the east
side of the rain garden. Two cleanouts and two manholes are provided for the underdrain. A drainage
easement has been provided around the Rain Garden.
Overflow: In the case in which the detention pond becomes clogged and ponds to the top of berm height of
4954.50, water will pond within Rain Garden A and the adjacent parking lot. Water will pond to a maximum
elevation of 4954.05 (0.95 feet below FFE) within the parking lot before overtopping the high point within
the access drive and flowing south to Redman Drive.
Underground Facility
An ADS SC-740 underground chamber system is proposed to treat the WQCV from sub-basin B. Runoff
from sub-basin B will be collected by two double CDOT Type 13 inlets. These inlets connect to the ADS
Inflow Manhole. The “low-flow” outlet pipe at the bottom of the manhole will convey the WQCV to the
underground facility. Flows greater than the WQCV will pond within the manhole structure to the maximum
elevation of WQCV storage in the underground facility and then enter the 15” outlet pipe, conveying flows
to the detention pond. The underground facility will be designed per ADS recommendations, including an
underdrain. The underdrain will outfall to the inflow infiltration basin proposed within the detention pond.
The ADS detail sheets and detail of the ADS Inflow Manhole are included in Appendix E for reference.
Maintenance: Maintenance access of the underground facility will be provided by access ports at one end
of each of the chamber rows, per manufacturer recommendations. A drainage easement has been provided
around the underground facility.
Overflow: In the case in which the underground facility becomes plugged, water will pond within the storm
sewer system, surcharging the inlets within the loading court and ponding within this area. Water will pond
to an elevation of 4952.5 (2.5 feet below FFE) within the loading court before overtopping the highpoint in
the access drive and flowing into Redman Drive.
Rain Garden C
Rain Garden C is proposed to treat the WQCV from sub-basin C. Runoff will surface flow to a sediment
forebay proposed along the length of the edge of asphalt, along the east side of the parking area. Rain
Garden C is designed with maximum 4:1 side slopes from the sediment forebay to an approximately 35-
foot width bottom and 4:1 side slopes to the berm between the rain garden and I-25 Frontage Road. An
underdrain is proposed along the length of the rain garden. The underdrain will connect to the overflow inlet
and a restrictor plate is proposed at the inlet connection to ensure the rain garden drains within a minimum
of 12-hours. A proposed CDOT Type D inlet will convey flows greater than the WQCV to the proposed
Preliminary Drainage Report
Mulberry Connection – Fort Collins, Colorado
11
storm system and ultimately the detention pond. Final design details of the rain garden are provided in the
Construction Documents and are included in Appendix E for reference.
Maintenance: Maintenance access of Rain Garden C is provided via the adjacent parking lot along the west
side of the rain garden. Two cleanouts are provided for the underdrain. A drainage easement has been
provided around the Rain Garden.
Overflow: In the case in which the outlet inlet become clogged water will pond within the Rain Garden to an
elevation of 4954 (1 foot below FFE) before spilling over the berm at the southeast corner of the Rain
Garden and flowing south into the I-25 Frontage Road.
Detention Pond
A detention pond is proposed to detain site flows from the 100-year storm event to the 2-year historic
release rate. Due to Site constraints, the inflow pipe to the pond is proposed with an “inflow infiltration
basin”. The bottom elevation of the inflow basin will be approximately 4-feet below the bottom of the pond.
Table 3 summarizes the pond bottom elevation, “inflow infiltration basin” elevation, and groundwater
elevation in the approximate location of the pond (boring B-17) as shown in the Draft Geotechnical
Evaluation prepared by Ninyo & Moore, dated July 2, 2019, included in Appendix E for reference.
Table 3. Comparison of pond elevations and groundwater elevation.
Finished Floor Elevation 4955.00
Pond Crest of Spillway Elevation 4953.50
100-Year Water Surface Elevation 4952.00
Pond Bottom Elevation at Outlet Structure 4949.00
“Inflow Infiltration Basin” Bottom Elevation 4944.50
“Inflow Infiltration Basin” Flat Bottom Area 353 FT2
Depth of Infiltration Rock 1-FT
Percolation Rate of Native Soil 30 min/in (2 in/hr)
“Inflow Infiltration Basin” Spillway Crest Elevation 4948.50
“Inflow Infiltration Basin” Volume 5,082 FT3
Approximate Groundwater Elevation 4942.001
1. Existing ground elevation at approximate location of boring B-17 is 4951.00. Groundwater was encountered
approximately 8-feet below existing ground surface.
The elevation of the bottom of the pond is set to allow positive drainage from the pond outlet to the existing
drainage ditch adjacent to the Site. The inflow infiltration basin is proposed instead of a dry well due to the
proximity of groundwater and installation of a dry well being infeasible. The inflow infiltration basin has a
total volume of 0.12 ac-ft (5,082 cubic feet), as show in Appendix D. The percolation rate, as measured by
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Ninyo & Moore in October 2019, within the detention pond area is 30 mins/inch (2 in/hr). The flat area of
the basin is 353 square feet, therefore, a basin volume of 2,353 cubic feet would be required to drain that
surface area within 40 hours. As designed, the inflow infiltration basin has a total volume of 5,082 cubic
feet, which provides an extra volume of 2,729 cubic feet above the required volume.
Flows greater than the volume of the inflow infiltration basin will overtop the basin at the spillway location
and enter the detention pond, discharging via the outlet structure. The detention pond includes two concrete
forebays at each of the rain garden spillways, a 2-foot wide concrete V trickle channel, and a maintenance
path. A 2-foot wide riprap path is provided from the discharge of each rain garden underdrain to the trickle
channel to prevent low flow erosion in the bottom of the pond.
A modified CDOT Type C inlet is proposed to serve as the outlet structure for the detention pond. The
trickle channel is proposed to flow up to the base of the inlet. A 1.86-inch by 1.86-inch square orifice is
proposed at the trickle channel flowline/bottom of structure on the outside face of the structure. A trash rack
is proposed over the orifice plate. The orifice is sized to release 2.64 CFS, which is less than the required
100-year release rate of 2.67 CFS. The top of the inlet is set at the 100-year water surface elevation of
4952.00, allowing any ponded water above the 100-year water surface elevation to enter the top inlet grate.
A 15-inch RCP storm pipe will convey flows from the outlet structure to the existing roadside swale. The
crest of the emergency overflow spillway is set 1.5 feet above the 100-year water surface elevation and 1-
foot below the top of berm elevation.
Maintenance of the detention pond is provided via a 12-foot gravel maintenance path accessible north of
the pond via mountable curb in the parking lot. A 10-foot grass maintenance path follows the trickle channel
along the bottom of the pond to allow access to the outlet structure. A drainage easement has been provided
around the detention pond. The Construction Document pond details are included in Appendix E for
reference.
Table 3. Detention Pond Summary Table
Approx. Bottom of Pond Elevation 4949.00
100-Year Orifice Open Area 0.31 SF
Top of Outlet Structure 4952.00
100-Year Water Surface Elevation 4952.00
Crest of Spillway Elevation 4953.50
Top of Berm Elevation 4954.50
Storm Sewer Conveyance
Storm sewer pipe is proposed to connect sub-basins A, B, C, and D to the detention pond. The main
stormline (rain garden C to detention pond) has been designed so that the 100-year HGL remains below
the finished grade at each structure. The tailwater condition into the pond was set at an elevation of 4948.50,
which is the maximum ponding elevation with the inflow infiltration basin. Due to the required elevations
within the loading dock area, ponding will occur within this area during the 100-year storm event. In addition
to the HGL surcharging at all these locations, when the detention pond is at the 100-year water surface
elevation (4952.00), the water surface will equalize into this area.
Preliminary Drainage Report
Mulberry Connection – Fort Collins, Colorado
13
Inlet Capacity
The capacity of each proposed inlet was evaluated utilizing Bentley’s FlowMaster software. Inlets B2, D1,
and D4 are located at low points and intended to provide the most volume capture. Inlets B1, D2, and D3
are located to pick up nuisance flows and to provide as junction structures for the pipe system. The results
of the capacity analysis indicate that the CDOT Type D inlets (D1, D2, D3, and D4) have the capacity to
collect contributing runoff with minimal ponding during the 100-year storm event.
In the 100-year event the loading court will have ponding water, therefore, the capacity of inlets B1 and B2
were analyzed for the 2-year storm event. The proposed double CDOT Type 13 inlets have the capacity to
convey the 2-year storm event with minimal ponding.
Street Capacity
Two streets within the project limits were evaluated, private Redman Drive and public I-25 Frontage Road.
Redman Drive is an existing private street with a total width of 40 feet and a crown approximately 20-ft from
the proposed northern curb line. Redman Drive currently has no curb and gutter, with an existing swale
conveying runoff west to Cooper Slough. Curb and gutter and driveway valley gutters are proposed along
the north property frontage. Flows from Redman Drive (sub-basin OS-2) and a small portion of on-site
runoff (sub-basins O2-O5) will be conveyed west via the proposed curb and gutter until the curb is
transitioned back to the existing roadside swale. The total flows to the north curb and gutter along Redman
Drive are 1.3 CFS and 6.1 CFS in the 2-year and 100-year storm events, respectively. These flows are a
sum of calculated flows from sub-basins OS-2, O2, O3, O4, and O5. The street capacity was evaluated
using the MHFD UD-Inlet spreadsheet. The results of the analysis indicate that water will spread 10-feet
into Redman Drive in the 2-year storm event. In the 100-year storm event the north side of the street will
not have capacity to convey the entire 100-year flows, therefore, the runoff will overtop the crown and utilize
both sides of the street.
The I-25 Frontage Road is a public roadway owned and maintained by CDOT. The below typical section
shows the ultimate cross-section of the roadway.
14
As shown in the figure above, the proposed condition will maintain the existing super-elevated condition of
the roadway, with runoff flowing east to west across the roadway. Sub-Basin OS-1 was delineated to
capture the entire portion of the I-25 Frontage Road adjacent to the on-site improvements. Approximately
2.4 CFS and 9.7 CFS of runoff is generated from sub-basin OS-1 in the 2-year and 100-year storm events,
respectively. The UD-Inlet street capacity analysis indicates that in the 2-year storm event flows will spread
8.5 feet from the flowline into the roadway, which will occupy 0.5-feet into the travel lane. In the 100-year
storm event flows will spread 15-feet from the flowline into the roadway, which will occupy 7-feet of the
travel lane.
VARIANCE REQUESTS
A variance is requested to allow the inflow infiltration basin within the detention pond. A separate variance
request will be submitted.
EROSION CONTROL
A separate Erosion Control Report will be provided in addition to this Final Drainage Report.
CONCLUSIONS
COMPLIANCE WITH STANDARDS
The Mulberry Connection project is in compliance with City of Fort Collins criteria for storm drainage design.
The “Fort Collins Stormwater Criteria Manual, December 2018 Edition,” and the Urban Drainage Flood
Control District “Urban Storm Drainage Criteria Manual Volumes 1, 2, and 3 have been utilized for
reference.
SUMMARY OF CONCEPT
The proposed drainage concept is to surface flow runoff from impervious areas to pervious area to the
extent practicable. Two rain gardens and one underground facility are proposed to treat the WQCV from as
much of the Site as possible. A detention pond is proposed to detain the on-site 100-year runoff volume to
the 2-year historic on-site flow. Downstream impacts due to the development of this Site are not anticipated.
REFERENCES
Fort Collins Stormwater Criteria Manual, December 2018 Edition, City of Fort Collins.
Urban Storm Drainage Criteria Manual, Volume 1-3, Urban Drainage and Flood Control District, Denver,
CO; January 2016, with latest revisions.
APPENDICES
A. NRCS Data and FEMA Map
B. Existing and Proposed Drainage Map
C. Hydrologic Calculations
D. Hydraulic Calculations
E. Reference Materials
MULBERRY CONNECTIONCITY OF FORT COLLINSUTILITY PLANS AND CONSTRUCTION DOCUMENTSFOR REVIEW ONLY
NOT FOR
Kimley-Horn and Associates, Inc.
CONSTRUCTION
OF 39
R
Know what's below.
Call before you dig.096501004_DRN_PROP
LEGEND
NORTH
27
NOTES
PROJECT NAME:POUDRE VALLEY DEVELOPMENT DATE:
PROJECT NUMBER:096501004
CALCULATED BY:HMO
CHECKED BY:DLS
REMARKS
DESIGNPOINTDESIGNBASINAREA(AC)RUNOFFCOEFFC100tc(min)C*A(ac)I(in/hr)Q(cfs)tc(max)S(C*A)(ac)I(in/hr)Q(cfs)SLOPE(%)STREETFLOW(cfs)DESIGNFLOW(cfs)SLOPE(%)PIPESIZE(in)LENGTH(ft)VELOCITY(fps)tt(min)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)
EX1 EX1 13.23 0.19 12.78 2.48 6.92 17.17
EX2 EX2 0.55 0.60 10.34 0.33 7.72 2.55
EX3 EX3 0.21 0.23 10.42 0.05 7.72 0.36
A A 5.51 0.85 6.76 4.71 8.80 41.40
B1 B1 2.00 1.00 5.00 2.00 9.95 19.90
B2 B2 0.91 1.00 6.00 0.91 10.95 9.96
C C 3.63 0.89 5.00 3.22 9.95 32.07
D1 D1 0.14 0.35 10.44 0.05 7.72 0.37
D2 D2 0.06 0.19 10.31 0.01 7.72 0.08
D3 D3 0.04 0.19 6.31 0.01 9.31 0.07
D4 D4 0.14 0.37 10.43 0.05 7.42 0.37
O1 O1 0.26 0.19 5.00 0.05 9.95 0.48
O2 O2 0.07 0.59 5.00 0.04 9.95 0.41
O3 O3 0.06 0.76 5.00 0.05 9.95 0.48
O4 O4 0.07 0.78 5.00 0.05 9.95 0.51
O5 O5 0.17 0.19 5.00 0.03 9.95 0.32
OS1 OS1 0.97 1.00 5.00 0.97 9.95 9.65
OS2 OS2 0.55 0.80 5.14 0.44 9.95 4.35
Note: Rainfall intensities are taken from Table 3.4-1 in the FCSCM. Time of concentration values have been rounded to the nearest minute.STORMLINE(1)
EXISTING BASINS
ON-SITE BASINS
OFF-SITE BASINS
STANDARD FORM SF-3
STORM DRAINAGE DESIGN - RATIONAL METHOD 100 YEAR EVENT
11/19/2019
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE TRAVEL TIME
Active Scenario: 100-YR
FlexTable: Conduit Table
Mulberry Connection
Hydraulic
Grade Line
(Out)
(ft)
Hydraulic
Grade
Line (In)
(ft)
Capacity
(Full
Flow)
(cfs)
Flow
(cfs)
Velocity
(ft/s)
Slope
(Calculated)
(ft/ft)
Length
(User
Defined)
(ft)
Invert
(Stop)
(ft)
Stop NodeManning's
n
Invert
(Start)
(ft)
Start NodeMaterialDiameter
(in)
Label
4,948.504,949.4147.1746.286.550.005188.94,944.50POND INFLOW
FES0.0134,945.45MH-1Concrete36.0PIPE -05
4,949.814,950.4547.1646.826.620.005130.24,945.45MH-10.0134,946.10INLET D1Concrete36.0PIPE -17 (1)
4,952.284,952.4647.4125.533.610.005118.74,947.82INLET D30.0134,948.42INLET D4Concrete36.0PIPE -03
4,952.074,952.1947.1525.033.540.00584.04,946.89INLET D20.0134,947.31INLET D3Concrete36.0PIPE -03 (1)
4,950.794,951.5947.1547.136.670.005158.94,946.10INLET D10.0134,946.89INLET D2Concrete36.0PIPE -17
4,952.564,952.9947.0232.944.660.005177.14,948.42INLET D40.0134,949.30
RAIN GARDEN C
OUTLET
STRUCTURE
Concrete36.0PIPE -08
4,952.074,954.2815.9728.409.040.005140.44,946.89INLET D20.0134,947.59ADS INLET MHConcrete24.0PIPE -27
4,949.484,949.794.572.673.870.00556.04,948.82POND
OUTFALL FES0.0134,949.10
DETENTION
POND OUTLET
STUCTURE
Concrete15.0PIPE -04
4,950.694,961.454.5821.6617.650.00595.74,947.75INLET B20.0134,948.23INLET B1Concrete15.0PIPE -31
4,951.264,957.534.5428.4323.170.00532.44,947.59ADS INLET MH0.0134,947.75INLET B2Concrete15.0PIPE -30
Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-
755-1666
11/20/2020
StormCAD
[10.02.03.03]Bentley Systems, Inc. Haestad Methods Solution CenterMulberry.stsw
Active Scenario: 100-YR
FlexTable: Outfall Table
Mulberry Connection
Flow (Total Out)
(cfs)
System
Additional Flow
(cfs)
System Flow
Time
(min)
Boundary Condition TypeHydraulic Grade
(ft)
Elevation
(Invert)
(ft)
Label
2.672.670.241Free Outfall4,949.484,948.82POND OUTFALL
FES
45.530.0012.579User Defined Tailwater4,948.504,944.50POND INFLOW FES
Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-
755-1666
11/20/2020
StormCAD
[10.02.03.03]Bentley Systems, Inc. Haestad Methods Solution CenterMulberry.stsw
Active Scenario: 100-YR
Profile Report
Engineering Profile - Truck court to Mainline (Mulberry.stsw)
Mulberry Connection
4,945.00
4,950.00
4,955.00
4,960.00
4,965.00
4,970.00
-0+50 0+00 0+50 1+00 1+50 2+00 2+50 3+00
Station (ft)Elevation(ft)ADS INLET MH
Rim: 4,951.26 ft
Invert: 4,947.59 ft
HGL: 4,952.28 ft
INLET B1
Rim: 4,951.17 ft
Invert: 4,948.23 ft
HGL: 4,953.59 ft
INLET B2
Rim: 4,950.69 ft
Invert: 4,947.75 ft
HGL: 4,957.36 ft INLET D2
Rim: 4,953.11 ft
Invert: 4,946.89 ft
HGL: 4,952.07 ft
95.7 ft of 15.0in RCP@0.005 ft/ftFlow=21.66 cfsVelocity=17.65 ft/s
140.4 ft of 24.0in RCP@0.005 ft/ftFlow=28.40 cfsVelocity=9.04 ft/s
32.4 ft of 15.0in RCP@0.005 ft/ftFlow=28.43 cfsVelocity=23.17 ft/s
Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-
755-1666
11/20/2020
StormCAD
[10.02.03.03]Bentley Systems, Inc. Haestad Methods Solution CenterMulberry.stsw
4582 S. Ulster Street - Suite 1500
Denver, Colorado 80237
Project:Mulberry Connection Prepared By:HMO
Project Number:096501004 Checked By:DLS
Date:6-Jan-20
Water Quality Capture Volume - Basin B, B1, & OSB
Contributing Basin Characteristics
Site Area =2.91 90%--
Hydrologic Soil Group A =
Hydrologic Soil Group B =
Hydrologic Soil Group C =
Hydrologic Soil Group D =
Water Quality Capture Volume
FCSCM Equation 7-1 WQ Watershed Inches = a*(0.91i3-1.19i2+.078i)
a12 = 0.8 (12-Hr Drain Time)
a40 = 1.0 (40-Hr Drain Time)
FCSCM Equation 7-2 WQCV = (WQCV/12)*(Area)*1.2
WQCV Impervious (Site) =90%
a =0.8
WQ Watershed Inches (Site) =0.321
WQCV Area (Site) =2.91
WQ Capture Volume (Site) =0.093 AC-FT
0.093 AC-FT
4,071 CU-FT
Area
(AC)
Impervious
(%)
Watershed Flow
Length (ft)
Watershed Flow
Slope (ft/ft)
Site WQ Volume
WQCV B (12hr) - 11/22/2020
4582 S. Ulster Street - Suite 1500
Denver, Colorado 80237
Project:Mulberry Connection Prepared By:HMO
Project Number:096501004 Checked By:DLS
Date:24-Feb-20
Water Quality Capture Volume - Basin C & OS1
Contributing Basin Characteristics
Site Area =3.63 66%--
Hydrologic Soil Group A =
Hydrologic Soil Group B =
Hydrologic Soil Group C =
Hydrologic Soil Group D =
Water Quality Capture Volume
FCSCM Equation 7-1 WQ Watershed Inches = a*(0.91i3-1.19i2+.078i)
a12 = 0.8 (12-Hr Drain Time)
a40 = 1.0 (40-Hr Drain Time)
FCSCM Equation 7-2 WQCV = (WQCV/12)*(Area)*1.2
WQCV Impervious (Site) =66%
a =0.8
WQ Watershed Inches (Site) =0.206
WQCV Area (Site) =3.63
WQ Capture Volume (Site) =0.075 AC-FT
0.075 AC-FT
3,264 CU-FT
Area
(AC)
Impervious
(%)
Watershed Flow
Length (ft)
Watershed Flow
Slope (ft/ft)
Site WQ Volume
WQCV C (12hr) - 11/22/2020
PROJECT NAME:
PROJECT NUMBER:096755001
CALCULATED BY:HMO
CHECKED BY:DLS
DATE:11/19/2019
Volume = (D/3)(A + B + (AB)^(1/2))D=depth between two contours, ft
A=area of bottom contour, SF; B=area of top contour, SF
ELEV.AREA VOLUME ACCUM. VOL.ACCUM. VOL.
(FT)(SQ FT.)(CU FT)(CU FT)(AC-FT)
4944.6 381 0 0 0.00
4944.8 443 82 82 0.00
4945 509 95 177 0.00
4945.2 579 109 286 0.01
4945.4 652 123 409 0.01
4945.6 728 138 547 0.01
4945.8 808 154 701 0.02
4946 892 170 871 0.02
4946.2 980 187 1,058 0.02
4946.4 1,075 205 1,263 0.03
4946.6 1,176 225 1,488 0.03
4946.8 1,279 245 1,734 0.04
4947 1,386 266 2,000 0.05
4947.2 1,499 288 2,288 0.05
4947.4 1,618 312 2,600 0.06
4947.6 1,743 336 2,936 0.07
4947.8 1,873 362 3,298 0.08
4948 2,007 388 3,686 0.08
4948.2 2,146 415 4,101 0.09
4948.4 2,290 444 4,544 0.10
4948.6 2,493 478 5,022 0.12
4948.8 3,091 557 5,580 0.13
4949 4,043 711 6,291 0.14
4949.2 5,664 966 7,257 0.17
4949.4 12,603 1,781 9,038 0.21
4949.6 16,460 2,898 11,936 0.27
4949.8 19,347 3,577 15,513 0.36
4950 23,555 4,283 19,796 0.45
4950.2 28,733 5,220 25,016 0.57
4950.4 33,484 6,216 31,232 0.72
4950.6 36,815 7,027 38,259 0.88
4950.8 38,103 7,491 45,751 1.05
4951 39,138 7,724 53,475 1.23
4951.2 40,105 7,924 61,399 1.41
4951.4 41,035 8,114 69,512 1.60
4951.6 41,943 8,298 77,810 1.79
4951.8 42,836 8,478 86,288 1.98
4952 43,720 8,655 94,943 2.18
4952.2 44,602 8,832 103,775 2.38
4952.4 45,490 9,009 112,784 2.59
4952.6 46,387 9,188 121,972 2.80
4952.8 47,290 9,368 131,340 3.02
4953 48,201 9,549 140,888 3.23
4953.2 49,124 9,732 150,621 3.46
4953.4 50,057 9,918 160,539 3.69
4953.6 50,999 10,105 170,644 3.92
4953.8 51,953 10,295 180,939 4.15
4954 52,920 10,487 191,426 4.39
Detention Pond
DETENTION BASIN
STAGE-STORAGE ANALYSIS
PROJECT NAME:Detention Pond
ELEV.AREA VOLUME ACCUM. VOL.ACCUM. VOL.
(FT)(SQ FT.)(CU FT)(CU FT)(AC-FT)
4950.4 111 0 0 0.00
4950.6 1,120 106 106 0.00
4950.8 3,730 460 565 0.01
4951 8,854 1,222 1,787 0.04
4951.2 16,954 2,537 4,325 0.10
4951.4 25,086 4,178 8,502 0.20
4951.6 34,579 5,941 14,443 0.33
4951.8 43,727 7,813 22,256 0.51
4952 50,496 9,414 31,670 0.73
4952.2 56,751 10,719 42,389 0.97
4952.4 62,461 11,917 54,306 1.25
ELEV.AREA VOLUME ACCUM. VOL.ACCUM. VOL.
(FT)(SQ FT.)(CU FT)(CU FT)(AC-FT)
4944.6 381 0 0 0.00
4944.8 443 82 82 0.00
4945 509 95 177 0.00
4945.2 579 109 286 0.01
4945.4 652 123 409 0.01
4945.6 728 138 547 0.01
4945.8 808 154 701 0.02
4946 892 170 871 0.02
4946.2 980 187 1,058 0.02
4946.4 1,075 205 1,263 0.03
4946.6 1,176 225 1,488 0.03
4946.8 1,279 245 1,734 0.04
4947 1,386 266 2,000 0.05
4947.2 1,499 288 2,288 0.05
4947.4 1,618 312 2,600 0.06
4947.6 1,743 336 2,936 0.07
4947.8 1,873 362 3,298 0.08
4948 2,007 388 3,686 0.08
4948.2 2,146 415 4,101 0.09
4948.4 2,290 444 4,544 0.10
4948.6 2,493 478 5,022 0.12
4948.8 3,091 557 5,580 0.13
4949 4,043 711 6,291 0.14
4949.2 5,664 966 7,257 0.17
4949.4 12,603 1,781 9,038 0.21
4949.6 16,460 2,898 11,936 0.27
4949.8 19,347 3,577 15,513 0.36
4950 23,555 4,283 19,796 0.45
4950.2 28,733 5,220 25,016 0.57
4950.4 33,595 6,226 31,243 0.72
4950.6 37,935 7,149 38,391 0.88
4950.8 41,833 7,974 46,365 1.06
4951 47,992 8,976 55,341 1.27
4951.2 57,059 10,492 65,833 1.51
4951.4 66,121 12,307 78,140 1.79
4951.6 76,522 14,252 92,391 2.12
4951.8 86,563 16,298 108,689 2.50
4952 94,216 18,073 126,762 2.91 100-YR (2.84 AC-FT) = 4951.97
4952.2 101,353 19,553 146,314 3.36
4952.4 107,951 20,927 167,241 3.84
4952.6 46,387 15,007 182,248 4.18
4952.8 47,290 9,368 191,616 4.40
4953 48,201 9,549 201,165 4.62
4953.2 49,124 9,732 210,897 4.84
4953.4 50,057 9,918 220,815 5.07
4953.6 50,999 10,105 230,920 5.30
4953.8 51,953 10,295 241,215 5.54
4954 52,920 10,487 251,703 5.78
COMBINED VOLUMES
PARKING LOT PONDING
PROJECT NAME:
PROJECT NUMBER:096755001
CALCULATED BY:HMO
CHECKED BY:DLS
DATE:9/20/2019
Volume = (D/3)(A + B + (AB)^(1/2))D=depth between two contours, ft
A=area of bottom contour, SF; B=area of top contour, SF
ELEV.AREA VOLUME ACCUM. VOL.ACCUM. VOL.
(FT)(SQ FT.) (CU FT)(CU FT)(AC-FT)
4952.5 1,290 0 0 0.00
4952.6 1,378 133 133 0.00
4952.7 1,469 142 276 0.01
4952.8 1,558 151 427 0.01
4952.9 1,642 160 587 0.01
4953 1,728 169 756 0.02
4953.1 1,817 177 933 0.02
4953.2 1,906 186 1,119 0.03
4953.3 1,997 195 1,314 0.03
4953.4 2,090 204 1,518 0.03
4953.5 2,186 214 1,732 0.04
4953.6 2,469 233 1,965 0.05
4953.7 2,623 255 2,219 0.05
4953.8 2,848 274 2,493 0.06
4953.9 3,135 299 2,792 0.06
4954 3,455 329 3,121 0.07
4954.1 3,816 363 3,485 0.08
4954.2 4,227 402 3,887 0.09 CREST OF SPILLWAY
ELEV.AREA VOLUME ACCUM. VOL.ACCUM. VOL.
(FT)(SQ FT.) (CU FT)(CU FT)(AC-FT)
4952.8 2,752 0 0 0.00
4952.9 3,002 288 288 0.01
4953 3,232 312 599 0.01
4953.1 3,462 335 934 0.02
4953.2 3,692 358 1,292 0.03
4953.3 4,109 390 1,681 0.04
4953.4 4,403 426 2,107 0.05
4953.5 4,786 459 2,566 0.06
4953.6 5,247 501 3,068 0.07
4953.7 5,844 554 3,622 0.08
4953.8 6,762 630 4,252 0.10
4953.9 7,859 730 4,982 0.11
4954 9,291 857 5,839 0.13 CREST OF SPILLWAY
RAIN GARDEN A - SOUTH
STAGE-STORAGE ANALYSIS
BASIN A
RAIN GARDEN A - NORTH
PROJECT NAME:BASIN A
ELEV.AREA VOLUME ACCUM. VOL.ACCUM. VOL.
(FT)(SQ FT.) (CU FT)(CU FT)(AC-FT)
4952.5 1,290 0 0 0.00
4952.6 1,378 133 133 0.00
4952.7 1,469 142 276 0.01
4952.8 4,310 277 552 0.01
4952.9 4,644 448 1,000 0.02
4953 4,960 480 1,480 0.03
4953.1 5,279 512 1,992 0.05
4953.2 5,599 544 2,536 0.06
4953.3 6,107 585 3,121 0.07
4953.4 6,494 630 3,751 0.09
4953.5 6,971 673 4,424 0.10 REQUIRED WQCV = 0.093 AC-FT
4953.6 7,715 734 5,158 0.12
4953.7 8,468 809 5,967 0.14
4953.8 9,610 903 6,870 0.16
4953.9 10,995 1,029 7,899 0.18
4954 12,747 1,186 9,085 0.21
RAIN GARDEN A - COMBINED
Stormwater Facility Name:
Facility Location & Jurisdiction:
User Input: Watershed Characteristics User Defined User Defined User Defined User Defined
Watershed Slope =0.010 ft/ft Stage [ft]Area [ft^2]Stage [ft]Discharge [cfs]
Watershed Length =1000 ft 0.00 4,043 0.00 0.00
Watershed Area =12.42 acres 1.00 23,555 1.00 2.67
Watershed Imperviousness =69.0%percent 2.00 39,138 2.00 2.67
Percentage Hydrologic Soil Group A =0.0%percent 3.00 43,720 3.00 2.67
Percentage Hydrologic Soil Group B =100.0%percent 4.00 48,201 4.00 4.57
Percentage Hydrologic Soil Groups C/D =0.0%percent 5.00 52,920 5.00 113.75
User Input 17
WQCV Treatment Method =hours
After completing and printing this worksheet to a pdf, go to:
https://maperture.digitaldataservices.com/gvh/?viewer=cswdif
create a new stormwater facility, and
attach the pdf of this worksheet to that record.
Routed Hydrograph Results
Design Storm Return Period =WQCV 2 Year 5 Year 10 Year 50 Year 100 Year
One-Hour Rainfall Depth =0.53 0.86 1.14 1.44 2.40 2.93 in
Calculated Runoff Volume =0.567 0.791 1.089 2.065 2.647 acre-ft
OPTIONAL Override Runoff Volume =acre-ft
Inflow Hydrograph Volume =0.567 0.791 1.088 2.064 2.647 acre-ft
Time to Drain 97% of Inflow Volume =4.3 5.1 6.2 10.0 12.3 hours
Time to Drain 99% of Inflow Volume =5.0 5.7 6.8 10.9 13.1 hours
Maximum Ponding Depth =1.01 1.31 1.67 2.66 3.21 ft
Maximum Ponded Area =0.54 0.65 0.78 0.97 1.02 acres
Maximum Volume Stored =0.322 0.501 0.757 1.653 2.193 acre-ft
Stormwater Detention and Infiltration Design Data Sheet
Mulberry Connection Detention Pond
Fort Collins, CO
Location for 1-hr Rainfall Depths (use dropdown):
Workbook Protected Worksheet Protected
SDI_Design_Data_v1.08_Detention Pond.xlsm, Design Data 11/24/2020, 8:39 PM
Ninyo & Moore | Proposed Poudre Valley Development, Fort Collins, Colorado | 501710001 R | July 2, 2019
Appendix A
Photographic Documentation
FIGURES
DRAFT
Source: NAVTEQ, 10/14/17.bsm file no: 1710blm0619FIGURE 2
501710001 | 6/19
REDMAN DRIVE AND NORTH WEST FRONTAGE ROAD
FORT COLLINS, COLORADO
POUDRE VALLEY DEVELOPMENT
BORING LOCATIONS
NOTE: DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE.
0 120
FEET
NN
Geotechnical & Environmental Sciences Consultants
B-16
B-9 B-10
B-1
B-2
B-2B-4
B-17
B-14 B-15 B-7 B-8
B-3
B-6
B-13
B-12
B-11
5
REDMAN DRIVE NORTH WEST FRONTAGE ROADU.S. INTERSTATE 25LEGEND
Boring LocationB-17
DRAFT
Ninyo & Moore | Proposed Poudre Valley Development, Fort Collins, Colorado | 501710001 R | July 2, 2019
APPENDIX A
Boring Logs
DRAFT
SOIL CLASSIFICATION CHART PER ASTM D 2488
PRIMARY DIVISIONS SECONDARY DIVISIONS
GROUP SYMBOL GROUP NAME
COARSE-
GRAINED
SOILS
more than
50% retained
on No. 200
sieve
GRAVEL
more than
50% of
coarse
fraction
retained on
No. 4 sieve
CLEAN GRAVEL
less than 5% fines
GW well-graded GRAVEL
GP poorly graded GRAVEL
GRAVEL with
DUAL
CLASSIFICATIONS
5% to 12% fines
GW-GM well-graded GRAVEL with silt
GP-GM poorly graded GRAVEL with silt
GW-GC well-graded GRAVEL with clay
GP-GC poorly graded GRAVEL with clay
GRAVEL with
FINES
more than
12% fines
GM silty GRAVEL
GC clayey GRAVEL
GC-GM silty, clayey GRAVEL
SAND
50% or more
of coarse
fraction
passes
No. 4 sieve
CLEAN SAND
less than 5% fines
SW well-graded SAND
SP poorly graded SAND
SAND with
DUAL
CLASSIFICATIONS
5% to 12% fines
SW-SM well-graded SAND with silt
SP-SM poorly graded SAND with silt
SW-SC well-graded SAND with clay
SP-SC poorly graded SAND with clay
SAND with FINES
more than
12% fines
SM silty SAND
SC clayey SAND
SC-SM silty, clayey SAND
FINE-
GRAINED
SOILS
50% or
more passes
No. 200 sieve
SILT and
CLAY
liquid limit
less than 50%
INORGANIC
CL lean CLAY
ML SILT
CL-ML silty CLAY
ORGANIC
OL (PI > 4)organic CLAY
OL (PI < 4)organic SILT
SILT and
CLAY
liquid limit
50% or more
INORGANIC
CH fat CLAY
MH elastic SILT
ORGANIC
OH (plots on or
above “A”-line)organic CLAY
OH (plots below
“A”-line)organic SILT
Highly Organic Soils PT Peat
USCS METHOD OF SOIL CLASSIFICATION
Explanation of USCS Method of Soil Classification
PROJECT NO.DATE FIGURE
APPARENT DENSITY - COARSE-GRAINED SOIL
APPARENT
DENSITY
SPOOLING CABLE OR CATHEAD AUTOMATIC TRIP HAMMER
SPT
(blows/foot)
MODIFIED SPLIT BARREL
(blows/foot)
SPT
(blows/foot)
MODIFIED SPLIT BARREL
(blows/foot)
Very Loose < 4 < 8 < 3 < 5
Loose 5 - 10 9 - 21 4 - 7 6 - 14
Medium
Dense 11 - 30 22 - 63 8 - 20 15 - 42
Dense 31 - 50 64 - 105 21 - 33 43 - 70
Very Dense > 50 > 105 > 33 > 70
CONSISTENCY - FINE-GRAINED SOIL
CONSIS-TENCY
SPOOLING CABLE OR CATHEAD AUTOMATIC TRIP HAMMER
SPT
(blows/foot)
MODIFIED
SPLIT BARREL
(blows/foot)
SPT
(blows/foot)
MODIFIED
SPLIT BARREL
(blows/foot)
Very Soft < 2 < 3 < 1 < 2
Soft 2 - 4 3 - 5 1 - 3 2 - 3
Firm 5 - 8 6 - 10 4 - 5 4 - 6
Stiff 9 - 15 11 - 20 6 - 10 7 - 13
Very Stiff 16 - 30 21 - 39 11 - 20 14 - 26
Hard > 30 > 39 > 20 > 26
LIQUID LIMIT (LL), %PLASTICITY INDEX (PI), %0 10
107
4
20
30
40
50
60
70
0 20 30 40 50 60 70 80 90 100
MH or OH
ML or OLCL - ML
PLASTICITY CHART
GRAIN SIZE
DESCRIPTION SIEVE
SIZE
GRAIN
SIZE
APPROXIMATE
SIZE
Boulders > 12”> 12”Larger than
basketball-sized
Cobbles 3 - 12”3 - 12”Fist-sized to
basketball-sized
Gravel
Coarse 3/4 - 3”3/4 - 3”Thumb-sized to
fist-sized
Fine #4 - 3/4”0.19 - 0.75”Pea-sized to
thumb-sized
Sand
Coarse #10 - #4 0.079 - 0.19”Rock-salt-sized to
pea-sized
Medium #40 - #10 0.017 - 0.079”Sugar-sized to
rock-salt-sized
Fine #200 - #40 0.0029 -
0.017”
Flour-sized to
sugar-sized
Fines Passing #200 < 0.0029”Flour-sized and
smaller
CH or OH
CL or OL
DRAFT
BORING LOG EXPLANATION SHEET
0
5
XX/XX
10
15
Bulk sample.
Modified split-barrel drive sampler.
2-inch inner diameter split-barrel drive sampler.
No recovery with modified split-barrel drive sampler, or 2-inch inner diameter split-barrel
drive sampler.
Sample retained by others.
Standard Penetration Test (SPT).
No recovery with a SPT.
Shelby tube sample. Distance pushed in inches/length of sample recovered in inches.
No recovery with Shelby tube sampler.
Continuous Push Sample.
Seepage.
Groundwater encountered during drilling.
Groundwater measured after drilling.
SM MAJOR MATERIAL TYPE (SOIL):
Solid line denotes unit change.
CL Dashed line denotes material change.
Attitudes: Strike/Dip
b: Bedding
c: Contact
j: Joint
f: Fracture
F: Fault
cs: Clay Seam
s: Shear
bss: Basal Slide Surface
sf: Shear Fracture
sz: Shear Zone
sbs: Shear Bedding Surface
The total depth line is a solid line that is drawn at the bottom of the boring.
20
BORING LOG
Explanation of Boring Log Symbols
PROJECT NO. DATE FIGUREDEPTH (feet)BLOWS/FOOTMOISTURE (%)DRY DENSITY (PCF)CLASSIFICATION U.S.C.S.6<0%2/%XON'ULYHQ6$03/(6DRAFT
0
10
20
30
40
18
14
29
19
16.7
5.8
8.1
109.9
124.6
132.7
CL
SC
SW
LOAM:Brown with white and red, moist, very stiff, lean CLAY with sand; trace gravel.
ALLUVIUM:Reddish brown to brown, moist, loose, clayey SAND with gravel.
@8': Groundwater encountered during drilling.
Wet; medium dense.
Reddish brown, wet, medium dense, fine to coarse SAND; trace clay and gravel.
Total Depth = 19 feet.
Groundwater was encountered at a depth of approximately 9 feet during drilling.
Backfilled with on-site soils on 06/07/2019.
Notes:
Groundwater may rise to a level higher than that measured in borehole due to seasonal
variations in precipitation and several other factors as discussed in the report.
The ground elevation shown above is an estimation only. It is based on our interpretations
of published maps and other documents reviewed for the purposes of this evaluation. It is
not sufficiently accurate for preparing construction bids and design documents.
FIGURE A- 17
POUDRE VALLEY DEVELOPMENT
FORT COLLINS, COLORADO
501710001 |7/19DEPTH (feet)BulkSAMPLESDrivenBLOWS/FOOTMOISTURE (%)DRY DENSITY (PCF)SYMBOLCLASSIFICATIONU.S.C.S.DESCRIPTION/INTERPRETATION
DATE DRILLED 06/08/2019 BORING NO.B-17
GROUND ELEVATION --SHEET 1 OF
METHOD OF DRILLING CME-45, 4" Solid-Stem Auger (Unlimited Access Drilling)
DRIVE WEIGHT 140 Lbs. (Automatic-Trip Hammer)DROP 30"
SAMPLED BY DLH LOGGED BY DLH REVIEWED BY BFG
1
DRAFT