HomeMy WebLinkAboutFORT COLLINS NISSAN-KIA - PDP210017 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTPRELIMINARY DRAINAGE REPORT
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Fossil Creek Subdivision
Fort Collins, CO
Prepared for:
Fort Collins Nissan-Kia
5811 S College Ave
Fort Collins, CO 80526
Date:
January 19, 2022
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January 19, 2022
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Fort Collins Nissan-Kia
Fort Collins, Colorado
Project Number: U21004
Dear Staff:
United Civil Design Group, LLC. is pleased to submit this Preliminary Drainage Report for the Fort Collins Nissan-Kia site in
Fort Collins, Colorado. In general, this report serves to document the stormwater impacts associated with the proposed
improvements related to the existing site.
We understand that review by the City of Fort Collins is to assure general compliance with standardized criteria contained in
the Fort Collins Stormwater Criteria Manual (FCSCM). This report was prepared in compliance with technical criteria set forth
in the Fort Collins Stormwater Criteria Manual.
If you should have any questions or comments as you review this report, please feel free to contact us at your convenience.
Sincerely,
United Civil Design Group
Colton Beck, PE Kevin Brazelton, PE
Project Engineer Principal
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TABLE OF CONTENTS
I. General Location and Description ...................................................................................................................................... 1
A. General Location & Existing Site Information ............................................................................................. 1
B. Description of Property ............................................................................................................................... 2
C. Project Description ..................................................................................................................................... 2
D. Floodplains .................................................................................................................................................. 3
II. Drainage Basins and Sub-Basins ......................................................................................................................................... 3
A. Major Basin Description .............................................................................................................................. 3
B. Sub-Basin Description ................................................................................................................................. 3
III. Drainage Design Criteria ..................................................................................................................................................... 3
A. Regulations ................................................................................................................................................. 3
B. Directly Connected Impervious Area (DCIA) ............................................................................................... 4
C. Hydrological Criteria ................................................................................................................................... 4
D. Hydraulic Criteria ........................................................................................................................................ 4
E. Modifications of Criteria ............................................................................................................................. 5
IV. Drainage Facility Design ..................................................................................................................................................... 5
A. General Concept ......................................................................................................................................... 5
B. Specific Details ............................................................................................................................................ 5
V. Erosion Control ................................................................................................................................................................. 14
VI. Conclusions ...................................................................................................................................................................... 15
A. Compliance with Standards ...................................................................................................................... 15
B. Drainage Concept...................................................................................................................................... 15
C. Stormwater Quality................................................................................................................................... 15
VII. References .................................................................................................................................................................... 16
APPENDICES
APPENDIX A – Hydrology Calculations
APPENDIX B – Hydraulic Calculations
B.1 – Low Impact Development Calculations
B.2 – Water Quality Calculations
B.3 – Detention Pond and Orifice Calculations
B.4 – Channel Capacity Calculations
B.5 – Inlet Sizing Calculations (Reserved for Final Submittal)
B.6 – Storm Pipe Calculations (Reserved for Final Submittal)
B.7 – Curb Channel Calculations (Reserved for Final Submittal)
APPENDIX C – Referenced Materials
APPENDIX D – Drainage Exhibits
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I.GENERAL LOCATION AND DESCRIPTION
A.GENERAL LOCATION &EXISTING SITE INFORMATION
The Fort Collins Nissan-Kia site (referred herein as “the site”) is located within the Fossil Creek Subdivision, situated in the
northeast quarter of Section 11, T6N, R69W of the 6th P.M., City of Fort Collins, Larimer County, Colorado. The property,
consisting of approximately 17.0 acres, is located immediately west of S College Ave. The site is split into two separate areas
divided by Crestridge St. South of Crestridge St. exists a car dealership to be redesigned and redeveloped. This portion of the
property is bounded by Crestridge St to the north, S College Ave to the east, a school facility and residential land to the west,
and a commercial property to the south. On-site stormwater drains off-site undetained to either S College Ave, Crestridge St,
or off-site to the west.
The northern, undeveloped portion of the site is bounded by Crestridge St to the south, S College Ave to the east, and
undeveloped land to the north and west. Stormwater on this portion of the site largely drains the northwest via overland
flow to Fossil Creek. A portion of the site adjacently north of Crestridge St drains to the south via overland flow. All on-site
runoff drains downstream within the City of Fort Collins Fossil Creek master drainage basin.
Storm sewer infrastructure exists on-site south of Crestridge St and drains to the off-site to the east. This storm pipe exists as
an irrigation bypass system. A City of Fort Collins Floodway and an Erosion Buffer are established with Fossil Creek and Lang
Gulch. Also, existing on-site is an underground irrigation pipe owned by North Louden Ditch Company. This irrigation pipe
drains from south to north through the site, ultimately to infrastructure that drains across S College Ave to the east. The on-
site portion of this ditch lateral is planned to be relocated; however, this relocation is unrelated to the drainage design of the
site.
An existing residential subdivision and small commercial property are constructed to drain runoff to Venus Ave, conveyed
through an existing wetland area west of Venus Ave to Lang Gulch and ultimately to Fossil Creek.
FIGURE 1:SITE VICINITY MAP
Smokey St S College AveBueno Dr Venus AveCrestridge St
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B.DESCRIPTION OF PROPERTY
The northern portion of the project site currently exists largely as grass/weed landscape. The southern portion of the site
includes concrete and asphalt pavement, a commercial building, and gravel landscaping. In its historic condition, the site
primarily sheet flows in two general directions: north and south, all conveyed to Fossil Creek.
Below are summaries of key components of the site in its existing conditions.
Land Use - The site’s current land use is commercial.
Ground Cover - The northern portion of the site exists as grass/weed landscape. The weed/grass cover is good (ie.,
heavy or dense cover with nearly all ground surfaces protected by vegetation). The southern portion of the site is
fully developed as consists largely of impervious hardscaping.
Existing Topography – The northern, undeveloped portion of the site is bounded by Crestridge St to the south, S
College Ave to the east, and undeveloped land to the north and west. Stormwater on this portion of the site largely
drains the northwest via overland flow to Fossil Creek. A portion of the site adjacently north of Crestridge St drains
to the south via overland flow. All on-site runoff drains downstream within with the City of Fort Collins Fossil Creek
master drainage basin.
Grades – In general, the northern portion of the site slopes northwesterly at approximately 1.0% to 15.0%; the
southern portion of the site is sloped in several directions at approximately 1.0% to 3.0%
Soil Type – The USDA’s Web Soil Survey shows that the site consists of “Type B”, “Type C”, and “Type D” soils. The
Web Soil Survey indicates the site is comprised of Kim Loam (5.0 to 9.0% slopes), Kim Thedalund Loams (3.0 to 15.0%
slopes), Midway Clay Loam (5.0% to 25.0% slopes) and Thedalund Loam (3.0% to 9.0% slopes). The on-site soils
provide moderate infiltration and are suitable for development.
Utilities – The following utilities exist adjacent to the site in Crestridge St, College Avenue and Venus Drive: potable
water, sanitary sewer, natural gas, electric and telecommunications.
Irrigation Facilities – An existing on-site underground irrigation pipe owned by North Louden Ditch Company. This
irrigation pipe drains from south to north through the site, ultimately to infrastructure that drains across S College
Ave to the east.
Drainage Features and Storm Sewer – Storm sewer infrastructure exists on-site south of Crestridge St. North of the
site exists the Fossil Creek. For development purposes, a City of Fort Collins Floodway and an Erosion Buffer are
established with Fossil Creek. The western side of the site drains via sheet flow to the Lang Gulch. This portion of the
Lang Gulch exists immediately upstream of Fossil Creek and is accounted for within the City of Fort Collins Floodway
boundary.
C.PROJECT DESCRIPTION
The proposed Fort Collins Nissan-Kia site improvements are limited to approximately 19.0 acres of disturbance. South of
Crestridge St, the proposed site improvements consist of the demolition of the existing car dealership building and associated
paving, and ultimately the construction of a new building with associated drive lanes and inventory parking lot. North of
Crestridge St, site improvements include the extension of Venus Ave, and the addition of a car dealership building and
associated drive lanes and inventory parking lot. Designed with the proposed commercial buildings and paving include
underground utilities, underground water quality, and underground detention. On-site stormwater south of Crestridge Dr is
designed to be conveyed via storm sewer to proposed drainage facilities west of Venus Ave.
In addition to an existing school facility adjacent to the site at the intersection of the Venus Ave and Crestridge St, the existing
Skyview Subdivision to the south is associated with the site in regard to stormwater runoff. In its existing state, this
development along with the school facility drains approximately 3.7-acres to an existing on-site wetland area. With a
proposed relocation of the mentioned wetlands, runoff is now designed to be conveyed to a proposed on-site detention
facility.
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D.FLOODPLAINS
The proposed development is not in a FEMA
designated floodplain. According to the FEMA
Flood Insurance Rate Map Panel (08069C1000F),
the site is zoned in an area of minimal flood
hazard. The FEMA FIRM Map is included in the
appendix.
West and Northwest of the site improvements
exists a “High Risk – Floodway” boundary along
Lang Gulch and Fossil Creek, established by the
City of Fort Collins. The Nissan-Kia property
boundaries exist within a City of Fort Collins
Floodway boundary; however, the bounds of
grading construction is to be completed outside
of this boundary. The City of Fort Collins
Floodway boundary is provided on the Drainage
Plan (see Appendix D) and a City of Fort Collins
floodplain map is included in Appendix C.
FIGURE 2:FLOODPLAIN MAP
II.DRAINAGE BASINS AND SUB-BASINS
A.MAJOR BASIN DESCRIPTION
The proposed development is located within the Fossil Creek Basin and will adhere to the Fossil Creek Basin Master Drainage
Plan. In conformance with master plan, the site is designed to release on-site runoff at a rate not to exceed 0.2 cfs/acre.
B.SUB-BASIN DESCRIPTION
Historically the southern portion of the property has been utilized for commercial purposes. The site is designed to operate
in a similar fashion (i.e., commercial), though with significant site improvements. Despite these significant improvements, the
proposed site is largely designed to conform to existing drainage patterns – downstream within the Fossil Creek Basin. In its
existing condition, stormwater on the northern portion of the site is largely conveyed the north to Fossil Creek. The southern
portion of the property drains in a multitude of directions: west to a neighboring property, east to US 287, and north to
Crestridge St. In its improved condition, on-site runoff is intended to drain to multiple downstream underground water quality
and detention facilities by way of sheet flow, swales, pans, inlets, and storm sewer.
III.DRAINAGE DESIGN CRITERIA
A.REGULATIONS
The design criteria for this study are directly from the City of Fort Collins Storm Drainage Design Criteria and Construction
Standards Manual and the Urban Storm Drainage Criteria Manuals Volumes 2, and 3 (referred to herein as USDCM).
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B.DIRECTLY CONNECTED IMPERVIOUS AREA (DCIA)
The City drainage criteria has also adopted the “Four Step Process” that is recommended in Volume 3 of the USDCM in
selecting structural BMPs for the redeveloping urban areas. The following portions of this summary describe each step and
how it has been utilized for this project:
Step 1 – Employ Runoff Reduction Practices
The objective of this step is to reduce runoff peaks and volumes and to employ the technique of “minimizing directly
connected impervious areas” (MDCIA). This project accomplishes this by:
Routing the roof and pavement flows through a bioretention facility, underground water quality treatment/infiltration
facilities and vegetated swales to increase time of concentration, promote infiltration and provide water quality.
Step 2 – Provide Water Quality Capture Volume (WQCV)
The objective of providing WQCV is to reduce the sediment load and other pollutants that exit the site. For this project
WQCV is provided within underground treatment facilities, a bioretention pond and an extended detention pond.
Step 3 – Stabilize Drainageways
The site exists adjacent to lang Gulch. A storm outfall is proposed immediately upstream of the Lang Gulch; stabilization is
planned with this pipe connection. As a result of the pipe connection, additional stabilizing will be provided via the
elimination of existing runoff from traveling down channel banks. This project will pay stormwater development and
stormwater utility fees which the City uses, in part, to maintain the stability of the City drainageway systems.
Step 4 – Consider Need for Site Specific and Source Control BMPs
Site specific and source control BMPs are generally considered for large industrial and commercial sites. The
redevelopment of the existing site will include multiple site specific and source controls, including:
Covered storage areas for vehicles and materials.
Dedicated vehicle maintenance areas within each build with appropriate internal waste collection systems.
Dedicated maintenance personnel providing landscape maintenance and snow and ice management.
Bioretention water quality control ponds.
C.HYDROLOGICAL CRITERIA
City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, provided by Table 3.4-1 of the Fort Collins Stormwater
Criteria Manual, are utilized for all hydrologic computations related to the site in its existing/historic and proposed conditions.
Since this site is relatively small and does not have complex drainage basins, the peak flow rates for design points have been
calculated based on the Rational Method as described in the USDCM and the City of Fort Collins Stormwater Criteria Manual
(FCSCM) with storm duration set equal to the time of concentration for each sub-basin. This method was used to analyze the
developed runoff from the 2-year (minor) and the 100-year (major) storm events. The Rational Method is widely accepted
for drainage design involving small drainage areas (less than 160 acres) and short time of concentrations. Runoff coefficients
are assumed based on impervious area and are given in the Appendices.
D.HYDRAULIC CRITERIA
The developed site will convey runoff to the proposed pond or underground treatment facility via swales, concrete channels,
and pipes. The City of Fort Collins Stormwater Criteria Manual (FCSCM) and USDCM are referenced for all hydraulic
calculations. In addition, the following computer programs are utilized:
Storm Sewer Extension for AutoCAD Civil3D
Hydraflow Express Extension for AutoCAD Civil3D
UD-Inlet by UDFCD
Drainage conveyance facility capacities proposed with the development project, including storm sewer, swales, and inlet
capacities, are designed in accordance with criteria outlined in the FCSCM and/or the Urban Drainage and Flood Control
District’s Urban Storm Drainage Criteria Manual (UDFCD).
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E.MODIFICATIONS OF CRITERIA
The conveyance of a considerable amount of off-site stormwater, in addition to hardships related to on-site detention,
present unique challenges concerning the release of stormwater in the site’s improved condition. To meet The Fossil Creek
Basin release criterion of 0.2 cfs/acre, while decreasing the overall release within the Fossil Creek Basin relative to existing
conditions, the solution presented in this report includes the “swapping” of detention throughout the site. We believe
manipulating the release rate to Lang Gulch and Fossil Creek outside the bounds of 0.2 cfs/acre for specific on-site drainage
basins, while overdetaining off-site stormwater, is beneficial to downstream features. Despite this variance, the overall
release from the site meets the 0.2 cfs/acre criterion, and the overall release from the site is significantly reduced.
IV.DRAINAGE FACILITY DESIGN
A.GENERAL CONCEPT
Developed runoff is designed to be conveyed in a safe and effective manner via swales, concrete channels, and storm sewer
systems/inlets. Stormwater is designed to be released within the Fossil Creek Basin. Runoff that drains off-site to the west
(south of Crestridge St) is heavily reduced with the proposed site. Runoff from the site in its improved condition is primarily
conveyed to underground water quality and detention facilities. Due to grading constraints, not all on-site runoff is fully
detained - these areas are considered in the overall release rate from the site.
B.SPECIFIC DETAILS
Hydrology
As previously stated, hydrology from the developed site is designed to comply with criteria set forth in the City of Fort Collins
Stormwater Criteria Manual. Referenced tables, charts, formulas, etc. are included in the appendices. The area, time of
concentration, and runoff of each proposed sub-basin is summarized in Appendix A. The following information outlines the
basin characteristics and drainage patterns for each basin.
Existing Basins
The following basins provide proposed drainage delineations for the site in its existing condition. Refer to Appendix A for
hydrology computations and Appendix D for visual representation of existing basins.
Basin EX1
Basin EX1 (refer to attached Existing Drainage Map) represents runoff associated with CDOT Right-of-Way in College Ave.
This basin consists of concrete paving, asphalt paving, gravel, and landscaping. Runoff within this basin is conveyed north
along College Ave and ultimately to Fossil Creek.
Basin EX2
Basin EX2 represents on-site runoff that drains to College Ave. This basin consists of concrete paving, asphalt paving, gravel,
and landscaping. Runoff within this basin is conveyed College Ave (i.e., Basin EX1) via sheet flow and concrete curb.
Basin EX3
Basin EX3 represents runoff associated with CDOT Right-of-Way in College Ave. This basin consists of concrete paving, asphalt
paving, gravel, and landscaping. Runoff within this basin is conveyed south along College Ave within the Fossil Creek Basin.
Basin EX4
Basin EX4 represents on-site runoff that drains to College Ave. This basin consists of concrete paving, asphalt paving, gravel,
and landscaping. Runoff within this basin is conveyed to College Ave (i.e., Basin EX3) via sheet flow and concrete curb.
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Basin EX5
Basin EX5 represents on-site runoff that drains to Fossil Creek. This basin is to remain undeveloped, consisting of landscaped
area. Runoff within this basin is conveyed to the northwest, designed to drain to off-site to a culvert system associated with
Fossil Creek.
Basin EX6
Basin EX6 represents on-site runoff that drains to the Lang Gulch, and ultimately Fossil Creek. A portion of this basin is
developed and is designed to drain to existing wetlands located around the southwestern region of the site; other
undeveloped areas drain directly to the Lang Gulch via sheet flow. This basin consists of concrete paving, asphalt paving,
gravel, and landscaping.
Basin OS1
Basin OS1 is a drainage basin associated with and adjacent commercial property and the Skyview Subdivision, located
immediately south of the site. This basin is fully developed and drains on-site via sheet flow along Venus Ave. This basin
accounts for approximately 3.7-acres of off-site drainage.
Basin OS2
Basin OS2 represents off-site runoff that drains to Fossil Creek. This basin is to remain undeveloped, consisting of landscaped
area. Similar to Basin EX5, runoff within this basin is conveyed to the northwest to a culvert system associated with Fossil
Creek.
Proposed Basins
The following basins provide proposed drainage delineations for the site in its improved condition. Refer to Appendix A for
hydrology computations and Appendix B for calculations related to Detention, Water Quality, Low Impact Development, and
other hydraulic features.
Basin A
Sub-basins A1-A16 (see Drainage Plans attached) are generally located around the southern region of the site. These basins
consist of roofs, asphalt and concrete paving, and landscaping. Runoff within these Basins is conveyed to a Bioretention Pond
(Pond A2) via sheet flow, curb, inlets, and storm sewer. Runoff conveyed to the Bioretention Pond is further discharged
southwest to a detention facility (Pond A1). Runoff from Basin A is released to Lang Gulch and ultimately to Fossil Creek.
Basin B
Sub-basins B1-B7 represent on-site drainage basins generally located around the central region of the site. These basins
consist of roofs, asphalt and concrete paving, and landscaping. Runoff within these basins is conveyed to Bioretention Pond
B2 and Detention Pond B1. Runoff from Basin B is released to Lang Gulch via Pond A1 and ultimately to Fossil Creek.
Basin C
Sub-basins C1-C4 represent on-site drainage basins generally located around the northern region of the site. These basins
consist of roofs, asphalt and concrete paving, and landscaping. Runoff within Basins C3 and C4 is conveyed to a proposed
underground water quality and detention pond facility (Pond C) via inlets and storm sewer. Basin C1 and C2 (i.e., Venus Ave)
is conveyed to storm sewer in Venus Ave, treated with Snouts within the inlets and released downstream to Fossil Creek.
Basin D
Basin D1 represents CDOT Right-of-Way in College Ave at the Southeast corner of the site. In accordance with established
drainage patterns, this area of College Ave drains south along College Ave, ultimately to Fossil Creek. The basin consists of
concrete pavement, asphalt pavement, and landscaping.
Basin E
Basin E1, similar to Basins D1, represents CDOT Right-of-Way in College Ave; however, this portion of College Ave drains to
the north. In accordance with established drainage patterns, this area of College Ave drains north along College Ave,
ultimately to Fossil Creek. The basin consists of concrete pavement, asphalt pavement, and landscaping.
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Basin OS1
Basin OS1 is a drainage basin associated with and adjacent commercial property and the Skyview Subdivision, located
immediately south of the site. This basin is fully developed and drains on-site via sheet flow along Venus Ave. This basin
accounts for approximately 3.7-acres of off-site drainage. In its improved condition, Venus Ave is designed to convey Basin
OS1 to a proposed detention facility (i.e., Pond A1) via storm sewer infrastructure.
Basin OS2
Basin OS2 represents off-site runoff that drains to Fossil Creek. This basin is to remain similar to its existing condition; a 12”
culvert system is provided at the downstream Fossil Creek Trail.
Stormwater Quality
I.Bioretention
Bioretention is designed to remove sediment and pollution from stormwater runoff via infiltration through an
engineered sand media. This slows the conveyance rate of storm water runoff, reduces runoff and provides a flow
path across a vegetated surface. Bioretention ponds are proposed with the site improvements and are utilized to
convey and treat stormwater prior to release to downstream proposed detention facilities and ultimately Fossil
Creek.
Bioretention Pond A2 is designed to provide approximately 11,630-sf of bioretention area. Provided 12-inches of
depth, the bioretention pond provides an approximate volume of 7,980-cf – this volume exceeds the required WQCV
for Basin A2 and Basins A4-16 (7,357cf). Ponding above the initial 12-inches of pond depth is intended for head
purposes to discharge the 100-year event through the outlet structure. Runoff is ultimately conveyed to the adjacent
Detention Pond A1. Below is a summary of Bioretention Pond A2:
Pond Bottom of
Pond Elevation
Bioretention
WSEL
Bioretention Volume
Required
(cf)
Bioretention Volume
Provided
(cf)
Pond A2 5009.00 5010.00 7,357 7,980
Bioretention Pond B2 is designed to provide about 3,940-sf of bioretention area. Provided 12-inches of depth, the
bioretention pond provided an approximate volume of 3,385-cf – this volume exceeds the required WQCV for Basins
B1-B7 (2,880-cf). Ponding above the initial 12-inches of pond depth is intended for head purposes to discharge the
100-year event over an overflow weir. Below is a summary of the bioretention pond, recognized as Pond B2:
Pond Bottom of
Pond Elevation
Bioretention
WSEL
Bioretention Volume
Required
(cf)
Bioretention Volume
Provided
(cf)
Pond B2 5006.40 5007.40 2,880 3,385
II.Underground Water Quality
An underground water quality facility is designed to divert storm water runoff during the water quality event and
treat the flows through infiltration prior to being collected within an underdrain system. This provides for the
removal of sediment and other pollutants from the runoff while also promoting infiltration. Underground water
quality chambers are designed to collect and treat storm water runoff from Basins C3-C4 prior to being released to
downstream storm sewer associated with Basin C.
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The underground water quality system, designated as “Pond C1” is designed with a volume of 3,730-cf which exceeds
the minimum design requirements for the area (2,444-cf). Below is a summary table for water quality related to
Basins C3 and C4. Refer to Appendix B for additional information.
Pond
WQCV Required
(cf)
WQCV Provided
(cf)
Pond C1 2,444 3,730
III.Extended Detention - WQCV
The proposed site improvements include water quality for off-site Basin OS1. This 3.70-acre area necessitates a
WQCV approximately 3,582-cf. Pond A1 also considers water quality for Basin A1 (63-cf) and Basin A3 (571-cf). Pond
A1 is sufficiently sized to provide this combined treatment volume of 4216-cf. Below is a summary table for water
quality related to Basins A1, A3 and OS1. Refer to Appendix B for additional information.
Pond
WQCV Necessary
(cf)
WQCV Provided
(cf)
Pond A1 4,216 4,470
IV.Offsite Water Quality
Provided a drainage easement northwest of Venus Ave, multiple solutions for water quality related to Basins C1 and
C2 are provided below
a.Extended Detention – Option 1
A portion of land downstream of the mentioned drainage easement, currently owned by City of Fort Collins
(Natural Areas), is an ideal location for extended detention facility. There is sufficient land to detain the
WQCV required for Basins C1 and C2 (i.e., 1,804-cf). Below is a summary of the water quality treatment for
Basins C1 and C2.
Pond
WQCV Necessary
(cf)
WQCV Provided
(cf)
Pond C2 1,804 2,398
An existing 12” culvert exists under the Fossil Creek Trail – this culvert would continue to be utilized to
release stormwater. In its existing condition, approximately 30.1-cfs is conveyed to the 12” culvert in the
100-year event – this culvert is not designed to convey the 100-year event. Given existing freeboard
constraints above the existing 12” culvert, only 4.5-cfs can be conveyed to Fossil Creek prior to overtopping
the Fossil Creek Trail. In the site’s improved condition, larger storm events would continue to overtop the
Fossil Creek Trail; however, less runoff (i.e., 25.1-cfs) would be conveyed to the 12” culvert. To further
improve the conveyance of stormwater under the Fossil Creek Trail, an additional 12” culvert is proposed
adjacent to the existing 12” culvert.
Constructed upstream of the water quality pond would be a channel (Channel C), sized to convey
stormwater from Underground Pond C1, Basin C1, and Basin C2. Turf reinforcement Matting would be
included with the design of Channel C for channel stabilization purposes. A channel capacity analysis is
included in Appendix B.
Channel C would remain within the drainage easement until the landowner pursues development of the
property. In the case of future development, the landowner would potentially be required to replace the
conveyance feature with an improved feature if removed.
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b. Temporary Plunge Pools – Option 2
In lieu of extended detention, Basin C1 and C2 can be treated for water quality by way of a series of
temporary plunge pools (see Drainage Plans in Appendix D for visual representation). These plunge pools
would be designed in series within the offsite drainage easement only, upstream of the City of Fort Collins
Natural Areas property. The Plunge Pools would be intended to act as hydraulic control features and water
quality features; however, the accumulative WQCV would unlikely meet that of 1,804-cf.
The plunge pools would remain within the drainage easement until the landowner pursues development of
the property. In the case of future development, the landowner would be required to replace the temporary
plunge pools with a permanent water quality feature adequate to treat the WQCV for Basins C1 and C2.
Low Impact Development (LID)
In December of 2015, Fort Collins City Council adopted the revised Low Impact Development (LID) policy and criteria which
requires developments within City limits to meet certain enhanced stormwater treatment requirements in addition to more
standard treatment techniques. The proposed development will be required to meet the newly adopted LID criteria which
requires the following:
-Treat no less than 75% of any newly added impervious area using one or a combination of LID techniques.
-Treat no less than 50% of any newly added impervious area using one or a combination of LID techniques when at
least 25% of any newly added pavement is provided with permeable pavement.
The following measures are implemented with this proposed development:
I.Underground Water Quality
Basins C3-C4, combined for 124,235-sf of proposed impervious area, are designed to be routed through an
underground water quality system located in the northern region of the site. The proposed impervious area treated
through underground water quality includes proposed parking, driveway, and roof areas. The underground water
quality system is designed with an overall capacity of 3,896-cf which exceeds the minimum design requirements for
the area. Refer to Appendix B for additional information.
II.Bioretention
Basins A2-A16, accounting for 210,565-sf of proposed impervious area, are designed to be conveyed to Bioretention
Pond A2. All new or modified impervious area related to Basins A2-A16 is to be treated by Pond A2.
Basins B2-B7, accounting for 85,955-sf of proposed impervious area, are designed to be conveyed to Bioretention
Pond B2. All new or modified impervious area related to Basins B2-B7 is to be treated by Pond B2.
Provided the LID measures noted above, approximately 76% of the site is treated in its improved condition. Refer to Appendix
B for LID calculations and Appendix D for a LID Treatment Map.
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Detention
I.Pond A1
The design of Pond A1 is intended for extended detention purposes for all ‘A” Basins and Basin OS1. This detention
facility is designed to release captured runoff at a rate of 6.00-cfs in the 100-yr event, significantly reducing the
existing undetained release of Basin OS1 to Lang Gulch and ultimately Fossil Creek. For emergency situations, the
pond is designed to spill stormwater through the emergency overflow structure which is located at the western end
of the detention pond. Water discharged from the emergency overflow will be conveyed directly to the Lang Gulch.
Below is a summary of Pond A1 utilizing the FAA method:
Pond Bottom of
Pond
Detention
WSEL
Top of Pond
Elevation
Detention
Volume Required
(ac-ft)
Detention
Volume Provided
(ac-ft)
100-yr
Release Rate
(cfs)
Pond A1 5002.60 5009.50 5010.50 1.73 1.74 *6.00
* Refer to the provided tables in the Drainage Summary section on the following pages for context related to the
100-yr release for Pond A1.
II.Pond B1
The design of Pond B1 is intended for extended detention purposes for all ‘B” Basins. This detention facility is
designed to release captured runoff at a rate of 2.00-cfs in the 100-yr event. For emergency situations, the pond is
designed to spill stormwater through the emergency overflow structure which is located at the southwestern end
of the detention pond. Water discharged from the emergency overflow will be conveyed directly to the Lang Gulch.
Below is a summary of Pond B1 utilizing the FAA method:
Pond Bottom of
Pond
Detention
WSEL
Top of Pond
Elevation
Detention
Volume Required
(ac-ft)
Detention
Volume Provided
(ac-ft)
100-yr
Release Rate
(cfs)
Pond B1 5005.12 5009.50 5010.50 0.46 1.11 *2.00
* Refer to the provided tables in the Drainage Summary section on the following pages for context related to the
100-yr release for Pond B1.
III.Pond C1
Runoff captured within Basins C3-C4 are routed to underground chambers, designed to collect and detain storm
water runoff prior to being released to Fossil Creek. Stormwater events that exceed the water quality event (see
section Stormwater Quality narrative above) are designed to exceed the capacity of the system’s isolator row and
be further conveyed throughout the underground facility to other chambers for detention purposes. The minimum
100-yr release via underground detention is established by a release rate per chamber to an underdrain – this release
rate is limited by flow through geotextile with accumulated sediment.
Below is a summary of Pond C1 utilizing the FAA method:
Pond
Detention Volume
Required
(ac-ft)
Detention Volume
Provided
(ac-ft)
100-yr
Release Rate
(cfs)
Pond C1 0.55 0.56 *2.40
* Refer to the provided tables in the Drainage Summary section on the following pages for context related to the
100-yr release for Pond C1.
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11 U21004_Drainage Report
Drainage Summary
A basin summary table is included below:
Existing/Historic Basins
Basin Area %I C2 C100 Q2 Q100
(acre) (cfs) (cfs)
EX1 2.12 65.0% 0.70 0.87 3.40 14.85
EX2 1.70 60.6% 0.67 0.84 2.63 11.47
EX3 0.41 82.1% 0.82 1.00 0.85 3.65
EX4 0.38 88.9% 0.89 1.00 0.96 3.80
EX5 7.97 2.0% 0.25 0.31 4.08 17.83
EX6 6.44 24.7% 0.41 0.52 5.46 23.85
OS1 3.70 55.6% 0.64 0.80 5.98 26.09
OS2 5.75 2.0% 0.25 0.31 2.95 12.86
Proposed Basins
Basin Area %I C2 C100 Q2 Q100
(acre) (cfs) (cfs)
A1 0.95 2.0% 0.25 0.31 0.51 2.21
A2 0.57 2.0% 0.25 0.31 0.30 1.32
A3 0.49 72.9% 0.76 0.95 1.06 4.64
A4 0.56 63.7% 0.69 0.86 1.03 4.48
A5 0.43 100.0% 0.95 1.00 1.09 3.98
A6 0.20 65.8% 0.71 0.88 0.38 1.66
A7 0.45 72.8% 0.76 0.95 0.96 4.20
A8 0.09 100.0% 0.95 1.00 0.26 0.94
A9 0.12 100.0% 0.95 1.00 0.33 1.22
A10 0.55 77.1% 0.79 0.98 1.24 5.40
A11 0.04 100.0% 0.95 1.00 0.12 0.44
A12 0.98 75.2% 0.77 0.97 2.02 8.81
A13 0.45 90.0% 0.95 1.00 1.15 4.23
A14 0.63 78.9% 0.80 1.00 1.20 5.26
A15 0.73 88.1% 0.86 1.00 1.51 6.08
A16 0.77 90.0% 0.95 1.00 1.95 7.16
B1 0.46 2.0% 0.25 0.31 0.25 1.07
B2 0.48 2.0% 0.25 0.31 0.26 1.12
B3 1.10 70.8% 0.74 0.93 1.80 7.88
B4 0.38 91.8% 0.89 1.00 0.75 2.95
B5 0.54 85.4% 0.85 1.00 1.10 4.53
B6 0.22 61.8% 0.68 0.85 0.40 1.76
B7 0.30 77.2% 0.79 0.98 0.68 2.97
C1 0.61 84.9% 0.84 1.00 1.37 5.68
C2 0.83 58.8% 0.66 0.82 1.46 6.37
C3 2.47 93.6% 0.90 1.00 5.13 19.83
C4 0.50 90.0% 0.95 1.00 1.27 4.66
D1 0.45 73.6% 0.76 0.95 0.97 4.25
E1 2.12 77.4% 0.79 0.99 4.22 18.41
OS1 3.70 55.6% 0.64 0.80 5.98 26.09
OS2 5.84 2.0% 0.25 0.31 2.99 13.07
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100-year Event: Proposed Runoff to College Ave
Basin
Designation
Release Rate
(cfs)
Basin D1 4.25
Basin E1 18.41
Proposed Runoff 22.66
Refer to Appendix D for an Existing Drainage Map that provides a visual representation of Existing Basins EX1-EX6 and OS1-
OS2. In the site’s existing condition, nearly 2.1-acres (i.e., Basin EX2 and EX4) of on-site runoff drains undetained to College
Ave. In addition to on-site basins EX2 and EX4, Basins EX1 and EX2 (i.e., College Ave) also contribute runoff to the west half
of College Ave – the entirety of Basins EX1-EX4 account for approximately 33.77-cfs in the 100-year event. In the site’s
improved condition, this 2.1-acre area is captured and conveyed to on-site detention; runoff related to all “A” basins are
detained. Moreover, the improved site is designed to convey 0.35-acres of College Ave runoff (see Basin A10). Despite the
addition of a drive lane to College Ave (i.e., additional impervious area), there is a significant reduction in runoff conveyed by
College Ave in the 100-year Event. The tables below summarize the impacts of the proposed improvements to College Ave
relative to the site’s existing condition.
100-year Event: Existing Runoff to College Ave
In the site’s its improved condition, the total runoff related to College Ave during the 100-year event is significantly reduced.
In relation to the Fossil Creek, the site is designed to outfall to the west at two locations, including Lang Gulch. Ultimately, all
runoff conveyed to the west (i.e. Lang Gulch and Fossil Creek) has a similar design point in Fossil Creek, northwest of the site.
In relation to the Fossil Creek Basin, the site is limited to a 0.2-cfs/acre release rate in its improved condition – this amounts
to 3.1-cfs over 15.9 acres (i.e., sum of Basins A, B, and C). Provided the 3.7-acre conveyance and detention of off-site runoff
(i.e., Basin OS1), the overall release to Fossil Creek considers the 26.09-cfs that Basin OS1 produces in the 100-year event.
Thus, the total maximum on-site release to Fossil Creek is limited to 29.19-cfs.
The proposed drainage design limits the overall on-site release of Fossil Creek to 22.45-cfs. Per coordination with the City of
Fort Collins Stormwater Engineering Department, swapping of on-site and off-site release flows is permitted given that the
total release to Fossil Creek is less than the required 0.2 cfs/acre plus existing off-site flows. Although Basins C1 and C2 are
released undetained to Fossil Creek beyond the WQCV for Basins C1 and C2, the improved site is designed to overdetain for
Basin OS1 and limit the site’s overall release to Lang Gulch and Fossil Creek. The tables on the following page summarize the
impacts of the proposed improvements to Lang Gulch and Fossil Creek relative to the site’s limiting criteria.
Basin
Designation
Release Rate
(cfs)
Basin EX1 14.85
Basin EX2 11.47
Basin EX3 3.65
Basin EX4 3.80
Existing Runoff 33.77
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100-year Event: Existing Release to Lang Gulch
100-year Event: Existing Release to Fossil Creek
100-year Event: Overall Release to Fossil Creek
(Including upstream Lang Gulch)
Basin
Designation
Release Rate
(cfs)
Basin OS1 26.09
Basin EX6 23.85
Total Release 49.94
Basin
Designation
Release Rate
(cfs)
Basin EX5 17.83
Basin OS2 12.86
Total Release 30.69
Basin
Designation
Release Rate
(cfs)
Basin EX5 17.83
Basin EX6 23.85
Basin OS1 26.09
Basin OS2 12.86
Total Release 80.63
100-yr Event: Proposed Release to Fossil Creek
Basin/Pond
Designation
Release Rate
(cfs)
Pond C1 2.40
Basin C1 5.68
Basin C2 6.37
Basin OS2 13.07
Total Release 27.52
100-yr Event: Proposed On-Site Release to Lang Gulch
Basin/Pond
Designation
Release Rate
(cfs)
Pond A1 6.00
Pond B1 2.00
Total Release 8.00
100-yr Event: Overall Release to Fossil Creek
(Including upstream Lang Gulch)
Basin/Pond
Designation
Release Rate
(cfs)
Pond A1 6.00
Pond B1 2.00
Pond C1 2.40
Basin C1 5.68
Basin C2 6.37
*On-site Release 22.45
Basin OS2 13.07
Total Release 35.52
*The total on-site release of 22.45-cfs is less than the
maximum on-site release of 29.19-cfs.
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Standard Operating Procedures (SOPs)
In order for physical stormwater Best Management Practices (BMPs) to be effective, proper maintenance is essential.
Maintenance includes both routinely scheduled activities, as well as non-routine repairs that may be required after large
storms, or as a result of other unforeseen problems. Standard Operating Procedures should clearly identify BMP maintenance
responsibility. BMP maintenance is typically the responsibility of the entity owning the BMP.
Identifying who is responsible for maintenance of BMPs and ensuring that an adequate budget is allocated for maintenance
is critical to the long-term success of BMPs. Maintenance responsibility may be assigned either publicly or privately. For this
project, the privately owned BMPs including grass swales, underground water quality and detention, and the bioretention
pond, are to be maintained by the property owner.
Storm Sewers
There are multiple storm sewer networks proposed with the site improvements. Several networks including roof drains,
storm drains, and underground water quality and detention features are proposed ultimately with outfalls to Fossil Creek.
Proposed storm sewer systems are both private and public, designed to accommodate the flows from the 100-year storm
event. Hydraulic computations of these systems will be provided with the initial final compliance submittal.
Inlets
There are multiple inlets proposed with the site improvements, including Nyloplast drain basins and Type R inlets. Type R
Inlets are designed throughout the site on-grade and in sump to capture developed runoff for detention. On-site drain basins
are designed in a sump condition and are designed to convey runoff produced within smaller interior basins to on-site
bioretention and detention facilities. All inlets on the site are sized to provide adequate capacity and convey the 100-year
storm event. Hydraulic computations of these systems will be provided with the initial final compliance submittal.
V.EROSION CONTROL
A separate Erosion Control Report / Storm Water Management Plan (SWMP) will be prepared for the site in accordance with
the Stormwater Discharge Permit for Colorado Department of Public Health and Environment as the site will disturb an area
greater than 1-acre. The Erosion Control Report will be completed during the Final Compliance phase of the project and will
include more detailed information on the sediment and erosion control items for this project. It is intended that the proposed
improvements will comply with Erosion Control Criteria per the FCSCM, and all Erosion Control Materials will be provided
with the Final Drainage Report. At a minimum, the following temporary BMP’s will be installed and maintained to control
on-site erosion and prevent sediment from traveling off-site during construction:
Silt Fence – a woven synthetic fabric that filters runoff. The silt fence is a temporary barrier that is placed at the base
of a disturbed area.
Vehicle Tracking Control – a stabilized stone pad located at points of ingress and egress on a construction site. The
stone pad is designed to reduce the amount of mud transported onto public roads by construction traffic.
Riprap – Riprap will be used downstream of all storm sewer outfalls to control erosion of the receiving channels.
Inlet Protection – acts as a sediment filter. It is a temporary BMP and requires proper installation and maintenance
to ensure their performance.
Straw Wattles – wattles act as a sediment filter in swales around inlets. They are a temporary BMP and require
proper installation and maintenance to ensure their performance.
Slope Protection – Slopes should be terraced using a “tracked” vehicle, run perpendicular to slope to inhibit rill/gulley
erosion.
The contractor shall store all construction materials and equipment and shall provide maintenance and fueling of equipment
in confined areas on-site from which runoff will be contained and filtered. Temporary Best Management Practices (BMP’s)
will be inspected by the contractor at a minimum of once every two weeks and after each significant storm event.
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VI.CONCLUSIONS
A.COMPLIANCE WITH STANDARDS
Storm drainage calculations have followed the guidelines provided by the Urban Storm Drainage Criteria Manuals Volumes
1, 2 and 3 and the City of Fort Collins Stormwater Criteria Manual. Moreover, Chapter 10 of the City Code has been adhered
to.
B.DRAINAGE CONCEPT
The drainage system has been designed to convey the runoff to the designated design points and the existing public
infrastructure in an effective, safe manner. No negative impacts are anticipated to the City of Fort Collins Master Drainage
Plan or to downstream properties or infrastructure due to the proposed improvements.
C.STORMWATER QUALITY
Multiple long-term stormwater quality measures have been selected for the site that will provide treatment of stormwater
prior it to being discharged from the site. For this site this includes grass swales, bioretention ponds, and underground water
quality.
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VII.REFERENCES
1.City of Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, November 2017.
2.Urban Storm Drainage Criteria Manual Volume 1 and 2, Urban Drainage and Flood Control District, Denver, Colorado,
June 2001, Revised April 2008.
3.Natural Resources Conservation Service Web Soil Survey at: websoilsurvey.nrcs.usda.gov/app
4.Preliminary Flood Insurance Rate Map, FEMA, Panel 2079E, https://hazards.fema.gov/femaportal/
5.Stormwater Discharges Associated with Construction Activity, Stormwater Management Plan Preparation Guides, State
of Colorado, www.colorado.com
A PPENDIX A
D RAINAGE C ALCULATIONS
RUNOFF COEFFICIENTS AND % IMPERVIOUS
Nissan Dealership, Fort Collins, CO
Basin Design Pt.Composite
Total Total Roof (1)Asphalt Concrete(1)Gravel(1)Lawns(1)Imperviousness C2 C100
acres %I = 90%%I = 100%%I = 100%%I =40%%I=2%(%I)
C=0.95 C=0.95 C=0.95 C=0.50 C=0.25
sf sf sf sf sf sf
EX1 EX1 2.12 92,255 54,030 3,425 4,665 30,135 65.0%0.70 0.87
EX2 EX2 1.70 74,165 4,185 5,225 32,995 6,200 25,560 60.6%0.67 0.84
EX3 EX3 0.41 18,045 10,235 2,435 5,375 -82.1%0.82 1.00
EX4 EX4 0.38 16,625 4,145 10,100 2,380 -88.9%0.89 1.00
EX5 EX5 7.97 347,140 347,140 2.0%0.25 0.31
EX6 EX6 6.44 280,470 7,095 15,390 42,290 2,450 213,245 24.7%0.41 0.52
OS1 OS1 3.70 161,165 18,000 52,870 19,150 71,145 55.6%0.64 0.80
OS2 OS2 5.75 250,410 250,410 2.0%0.25 0.31
Basin Design Pt.Composite
Total Total Roof (1)Asphalt Concrete(1)Pavers(1)Lawns(1)Imperviousness C2 C100
acres sf %I = 90%%I = 100%%I = 100%%I =40%%I=2%(%I)
C=0.95 C=0.95 C=0.95 C=0.50 C=0.25
sf sf sf sf sf
A1 A1 0.95 41,480 41,480 2.0%0.25 0.31
A2 A2 0.57 24,770 24,770 2.0%0.25 0.31
A3 A3 0.49 21,460 11,730 3,805 5,925 72.9%0.76 0.95
A4 A4 0.56 24,280 13,555 1,735 8,990 63.7%0.69 0.86
A5 A5 0.43 18,645 15,850 2,795 -100.0%0.95 1.00
A6 A6 0.20 8,780 5,145 575 3,060 65.8%0.71 0.88
A7 A7 0.45 19,450 13,015 1,045 5,390 72.8%0.76 0.95
A8 A8 0.09 4,110 4,110 -100.0%0.95 1.00
A9 A9 0.12 5,335 5,335 -100.0%0.95 1.00
A10 A10 0.55 24,040 15,255 3,175 5,610 77.1%0.79 0.98
A11 A11 0.04 1,920 1,920 -100.0%0.95 1.00
A12 A12 0.98 42,665 28,705 3,145 10,815 75.2%0.77 0.97
A13 A13 0.45 19,780 19,780 -90.0%0.95 1.00
A14 A14 0.63 27,355 21,460 5,895 78.9%0.80 1.00
A15 A15 0.73 31,595 25,750 2,000 3,845 88.1%0.86 1.00
A16 A16 0.77 33,500 33,500 -90.0%0.95 1.00
B1 B1 0.46 20,160 20,160 2.0%0.25 0.31
B2 B2 0.48 21,090 21,090 2.0%0.25 0.31
B3 B3 1.10 47,980 33,665 14,315 70.8%0.74 0.93
B4 B4 0.38 16,646 15,246 1,400 91.8%0.89 1.00
B5 B5 0.54 23,550 18,230 1,800 3,520 85.4%0.85 1.00
B6 B6 0.22 9,748 4,705 1,240 3,803 61.8%0.68 0.85
B7 B7 0.30 13,195 8,885 1,240 3,070 77.2%0.79 0.98
C1 C1 0.61 26,565 16,845 5,625 4,095 84.9%0.84 1.00
C2 C2 0.83 36,362 15,795 5,275 15,292 58.8%0.66 0.82
C3 C3 2.47 107,575 92,000 8,500 7,075 93.6%0.90 1.00
C4 C4 0.50 21,795 21,795 -90.0%0.95 1.00
D1 D1 0.45 19,550 12,375 1,900 5,275 73.6%0.76 0.95
E1 E1 2.12 92,490 59,100 12,035 21,355 77.4%0.79 0.99
OS1 OS1 3.70 161,165 18,000 52,870 19,150 71,145 55.6%0.64 0.80
OS2 OS2 5.84 254,355 254,355 2.0%0.25 0.31
Notes:
(1) Recommended % Imperviousness Values per Table 4.1-3 Surface Type - Percent Impervious in Fort Collins Stormwater Criteria Manual
(2) Runoff C is based Table 3.2-2. Surface Type - Runoff Coefficients and Table 3.2-3. Frequency Adjustment Factors in Fort Collins Stormwater Manual
Areas Composite Runoff Coefficients (2)
Composite Runoff Coefficients (2)Areas
Existing Basins
Proposed Basins
Date: 1/14/2022 C:\United Civil Dropbox\Projects\U21004 - Nissan Dealership\Reports\Drainage\Calculations\U21004-Drain Calcs-PDP
TIME OF CONCENTRATION (2-YR)
Nissan Dealership, Fort Collins, CO
Basin Design Pt.Area
CXCF(1)Length Slope Ti(2)Slope Length n R Velocity (3)Tt(4)Tc max (5)
acres ft %min %ft fps min min min min
EX1 EX1 2.12 0.70 50 2.2%18.7 2.3%1180 0.016 0.2 4.8 4.1 22.8 16.6 16.6
EX2 EX2 1.70 0.67 160 2.8%33.0 1.0%155 0.016 0.2 3.2 0.8 33.8 10.9 10.9
EX3 EX3 0.41 0.82 40 2.0%12.2 2.5%730 0.016 0.2 5.0 2.4 14.6 14.1 14.1
EX4 EX4 0.38 0.89 45 2.0%9.8 3.5%165 0.016 0.2 6.0 0.5 10.2 10.9 10.2
EX5 EX5 7.97 0.25 500 10.0%76.0 2.0%320 0.25 0.2 0.3 18.5 94.5 11.8 11.8
EX6 EX6 6.44 0.41 200 1.8%68.3 2.6%376 0.016 0.2 5.1 1.2 69.5 12.1 12.1
OS1 OS1 3.70 0.64 65 2.0%25.2 2.0%475 0.016 0.2 4.5 1.8 26.9 12.6 12.6
OS2 OS2 5.75 0.25 380 10.0%66.2 2.0%360 0.25 0.2 0.3 20.8 87.1 12.0 12.0
Basin Design Pt.Area
CXCF(1)Length Slope Ti(2)Slope Length n R Velocity (3)Tt(4)Tc max (5)
acres ft %min %ft fps min min min min
A1 A1 0.95 0.25 120 14.0%33.3 1.0%160 0.016 0.2 3.2 0.8 34.2 10.9 10.9
A2 A2 0.57 0.25 45 12.0%21.5 0.5%170 0.016 0.2 2.3 1.3 22.7 10.9 10.9
A3 A3 0.49 0.76 40 2.0%14.8 1.5%210 0.016 0.2 3.9 0.9 15.7 11.2 11.2
A4 A4 0.56 0.69 70 2.6%21.3 2.8%170 0.016 0.2 5.3 0.5 21.9 10.9 10.9
A5 A5 0.43 0.95 95 3.9%8.0 0.6%100 0.016 0.2 2.5 0.7 8.7 10.6 8.7
A6 A6 0.20 0.71 65 2.2%20.9 2.0%90 0.016 0.2 4.5 0.3 21.3 10.5 10.5
A7 A7 0.45 0.76 45 3.0%13.7 1.0%70 0.016 0.2 3.2 0.4 14.1 10.4 10.4
A8 A8 0.09 0.95 45 2.9%6.1 0.6%50 0.016 0.2 2.5 0.3 6.4 10.3 6.4
A9 A9 0.12 0.95 45 2.2%6.6 0.8%110 0.016 0.2 2.8 0.6 7.3 10.6 7.3
A10 A10 0.55 0.79 20 5.0%7.0 0.8%210 0.016 0.2 2.8 1.2 8.3 11.2 8.3
A11 A11 0.04 0.95 10 2.0%3.2 0.5%50 0.016 0.2 2.3 0.4 3.6 10.3 5.0
A12 A12 0.98 0.77 65 2.3%17.1 1.1%165 0.016 0.2 3.3 0.8 18.0 10.9 10.9
A13 A13 0.45 0.95 70 2.0%8.5 2.0%100 0.016 0.2 4.5 0.4 8.9 10.6 8.9
A14 A14 0.63 0.80 160 3.3%21.9 0.5%40 0.016 0.2 2.3 0.3 22.2 10.2 10.2
A15 A15 0.73 0.86 160 3.3%17.1 0.5%80 0.016 0.2 2.3 0.6 17.7 10.4 10.4
A16 A16 0.77 0.95 75 2.0%8.8 2.0%60 0.016 0.2 4.5 0.2 9.1 10.3 9.1
B1 B1 0.46 0.25 50 25.0%17.8 0.5%110 0.016 0.2 2.3 0.8 18.6 10.6 10.6
B2 B2 0.48 0.25 50 25.0%17.8 1.5%130 0.016 0.2 3.9 0.6 18.3 10.7 10.7
B3 B3 1.10 0.74 200 2.0%34.5 0.8%115 0.016 0.2 2.8 0.7 35.2 10.6 10.6
B4 B4 0.38 0.89 195 1.6%21.3 1.6%15 0.016 0.2 4.0 0.1 21.4 10.1 10.1
B5 B5 0.54 0.85 130 2.7%17.9 0.5%110 0.016 0.2 2.3 0.8 18.7 10.6 10.6
B6 B6 0.22 0.68 95 2.5%26.1 4.0%50 0.016 0.2 6.4 0.1 26.2 10.3 10.3
B7 B7 0.30 0.79 55 3.7%12.9 5.2%40 0.016 0.2 7.3 0.1 13.0 10.2 10.2
0.00
C1 C1 0.61 0.84 55 2.5%12.1 5.0%380 0.016 0.2 7.1 0.9 13.0 12.1 12.1
C2 C2 0.83 0.66 60 2.5%21.7 5.0%300 0.016 0.2 7.1 0.7 22.4 11.7 11.7
C3 C3 2.47 0.90 180 3.5%14.9 2.5%300 0.016 0.2 5.0 1.0 15.9 11.7 11.7
C4 C4 0.50 0.95 65 2.0%8.2 2.0%75 0.016 0.2 4.5 0.3 8.5 10.4 8.5
D1 D1 0.45 0.76 40 2.0%14.6 2.5%210 0.016 0.2 5.0 0.7 15.3 11.2 11.2
E1 E1 2.12 0.79 40 2.0%13.4 2.5%940 0.016 0.2 5.0 3.1 16.5 15.2 15.2
OS1 OS1 3.70 0.64 65 2.0%25.2 2.0%475 0.016 0.2 4.5 1.8 26.9 12.6 12.6
OS2 OS2 5.84 0.25 380 10.0%66.2 2.0%360 0.25 0.2 0.3 20.8 87.1 12.0 12.0
Notes:
(1) C=CX*CF is less than or equal to 1.0 (Cf = 1.0)
(2) ti = [1.87(1.1-CXCF)L1/2]/S1/3, S= slope in %, L=length of overland flow (200' max urban, 500' max rural)
(3) V=(1.49/n)R2/3S1/2, S = slope in ft/ft, FCSCM Equation 5-4
(4) tt=L/(V*60 sec/min)
(5) Maximum tc = total length/180 + 10
(6) Minimum tc = 5 min
Travel/Channelized Time of Flow (Tt)
Existing Basins
Proposed Basins
Overland Flow (Ti)Travel/Channelized Time of Flow (Tt)
Ti+Tt Final Tc
(6)
Ti+Tt Final Tc
(6)
Overland Flow (Ti)
Date: 1/14/2022 C:\United Civil Dropbox\Projects\U21004 - Nissan Dealership\Reports\Drainage\Calculations\U21004-Drain Calcs-PDP
TIME OF CONCENTRATION (100-YR)
Nissan Dealership, Fort Collins, CO
Basin Design Pt.Area
CXCF(1)Length Slope Ti(2)Slope Length n R Velocity (3)Tt(4)Tc max (5)
acres ft %min %ft fps min min min min
EX1 EX1 2.12 1.00 50 2.2%4.7 2.3%1180 0.016 0.2 4.8 4.1 8.8 16.6 8.8
EX2 EX2 1.70 1.00 160 2.8%7.7 1.0%155 0.016 0.2 3.2 0.8 8.5 10.9 8.5
EX3 EX3 0.41 1.00 40 2.0%4.3 2.5%730 0.016 0.2 5.0 2.4 6.7 14.1 6.7
EX4 EX4 0.38 1.00 45 2.0%4.6 3.5%165 0.016 0.2 6.0 0.5 5.0 10.9 5.0
EX5 EX5 7.97 0.39 500 10.0%63.4 2.0%320 0.25 0.2 0.3 18.5 81.9 11.8 11.8
EX6 EX6 6.44 0.65 200 1.8%45.1 2.6%376 0.016 0.2 5.1 1.2 46.4 12.1 12.1
OS1 OS1 3.70 1.00 65 2.0%5.5 2.0%475 0.016 0.2 4.5 1.8 7.2 12.6 7.2
OS2 OS2 5.75 0.39 380 10.0%55.3 2.0%360 0.25 0.2 0.3 20.8 76.1 12.0 12.0
Basin Design Pt.Area
CXCF(1)Length Slope Ti(2)Slope Length n R Velocity (3)Tt(4)Tc max (5)
acres ft %min %ft fps min min min min
A1 A1 0.95 0.39 120 14.0%27.8 1.0%160 0.016 0.2 3.2 0.8 28.6 10.9 10.9
A2 A2 0.57 0.39 45 12.0%17.9 0.5%170 0.016 0.2 2.3 1.3 19.2 10.9 10.9
A3 A3 0.49 1.00 40 2.0%4.3 1.5%210 0.016 0.2 3.9 0.9 5.2 11.2 5.2
A4 A4 0.56 1.00 70 2.6%5.2 2.8%170 0.016 0.2 5.3 0.5 5.7 10.9 5.7
A5 A5 0.43 1.00 95 3.9%5.3 0.6%100 0.016 0.2 2.5 0.7 6.0 10.6 6.0
A6 A6 0.20 1.00 65 2.2%5.3 2.0%90 0.016 0.2 4.5 0.3 5.6 10.5 5.6
A7 A7 0.45 1.00 45 3.0%4.0 1.0%70 0.016 0.2 3.2 0.4 4.4 10.4 5.0
A8 A8 0.09 1.00 45 2.9%4.0 0.6%50 0.016 0.2 2.5 0.3 4.4 10.3 5.0
A9 A9 0.12 1.00 45 2.2%4.4 0.8%110 0.016 0.2 2.8 0.6 5.1 10.6 5.1
A10 A10 0.55 1.00 20 5.0%2.2 0.8%210 0.016 0.2 2.8 1.2 3.5 11.2 5.0
A11 A11 0.04 1.00 10 2.0%2.2 0.5%50 0.016 0.2 2.3 0.4 2.5 10.3 5.0
A12 A12 0.98 1.00 65 2.3%5.2 1.1%165 0.016 0.2 3.3 0.8 6.1 10.9 6.1
A13 A13 0.45 1.00 70 2.0%5.7 2.0%100 0.016 0.2 4.5 0.4 6.1 10.6 6.1
A14 A14 0.63 1.00 160 3.3%7.3 0.5%40 0.016 0.2 2.3 0.3 7.6 10.2 7.6
A15 A15 0.73 1.00 160 3.3%7.3 0.5%80 0.016 0.2 2.3 0.6 7.9 10.4 7.9
A16 A16 0.77 1.00 75 2.0%5.9 2.0%60 0.016 0.2 4.5 0.2 6.1 10.3 6.1
B1 B1 0.46 0.39 50 25.0%14.8 0.5%110 0.016 0.2 2.3 0.8 15.6 10.6 10.6
B2 B2 0.48 0.39 50 25.0%14.8 1.5%130 0.016 0.2 3.9 0.6 15.4 10.7 10.7
B3 B3 1.10 1.00 200 2.0%9.6 0.8%115 0.016 0.2 2.8 0.7 10.3 10.6 10.3
B4 B4 0.38 1.00 195 1.6%10.2 1.6%15 0.016 0.2 4.0 0.1 10.3 10.1 10.1
B5 B5 0.54 1.00 130 2.7%7.0 0.5%110 0.016 0.2 2.3 0.8 7.8 10.6 7.8
B6 B6 0.22 1.00 95 2.5%6.2 4.0%50 0.016 0.2 6.4 0.1 6.3 10.3 6.3
B7 B7 0.30 1.00 55 3.7%4.1 5.2%40 0.016 0.2 7.3 0.1 4.2 10.2 5.0
C1 C1 0.61 1.00 55 2.5%4.7 5.0%380 0.016 0.2 7.1 0.9 5.6 12.1 5.6
C2 C2 0.83 1.00 60 2.5%4.9 5.0%300 0.016 0.2 7.1 0.7 5.6 11.7 5.6
C3 C3 2.47 1.00 180 3.5%7.6 2.5%300 0.016 0.2 5.0 1.0 8.6 11.7 8.6
C4 C4 0.50 1.00 65 2.0%5.5 2.0%75 0.016 0.2 4.5 0.3 5.8 10.4 5.8
D1 D1 0.45 1.00 40 2.0%4.3 2.5%210 0.016 0.2 5.0 0.7 5.0 11.2 5.0
E1 E1 2.12 1.00 40 2.0%4.3 2.5%940 0.016 0.2 5.0 3.1 7.4 15.2 7.4
OS1 OS1 3.70 1.00 65 2.0%5.5 2.0%475 0.016 0.2 4.5 1.8 7.2 12.6 7.2
OS2 OS2 5.84 0.39 380 10.0%55.3 2.0%360 0.25 0.2 0.3 20.8 76.1 12.0 12.0
Notes:
(1) C=CX*CF is less than or equal to 1.0 (Cf = 1.25)
(2) ti = [1.87(1.1-CXCF)L1/2]/S1/3, S= slope in %, L=length of overland flow (200' max urban, 500' max rural)
(3) V=(1.49/n)R2/3S1/2, S = slope in ft/ft, FCSCM Equation 5-4
(4) tt=L/(V*60 sec/min)
(5) Maximum tc = total length/180 + 10
(6) Minimum tc = 5 min
Existing Basins
Overland Flow (Ti)Travel/Channelized Time of Flow (Tt)
Ti+Tt Final Tc
(6)
Proposed Basins
Overland Flow (Ti)Travel/Channelized Time of Flow (Tt)
Ti+Tt Final Tc
(6)
Date: 1/14/2022 C:\United Civil Dropbox\Projects\U21004 - Nissan Dealership\Reports\Drainage\Calculations\U21004-Drain Calcs-PDP
RATIONAL METHOD PEAK RUNOFF
Nissan Dealership, Fort Collins, CO
Basin Design Pt.Area 2-Year 100-Year
acre tc tc C2 C100 I2 I100 Q2 Q100
min min in/hr in/hr cfs cfs
EX1 EX1 2.12 17 9 0.70 0.87 2.30 8.03 3.40 14.85
EX2 EX2 1.70 11 9 0.67 0.84 2.30 8.03 2.63 11.47
EX3 EX3 0.41 14 7 0.82 1.00 2.52 8.80 0.85 3.65
EX4 EX4 0.38 10 5 0.89 1.00 2.85 9.95 0.96 3.80
EX5 EX5 7.97 12 12 0.25 0.31 2.05 7.16 4.08 17.83
EX6 EX6 6.44 12 12 0.41 0.52 2.05 7.16 5.46 23.85
OS1 OS1 3.70 13 7 0.64 0.80 2.52 8.80 5.98 26.09
OS2 OS2 5.75 12 12 0.25 0.31 2.05 7.16 2.95 12.86
Basin Design Pt.Area 2-Year 100-Year
acre tc tc C2 C100 I2 I100 Q2 Q100
min min in/hr in/hr cfs cfs
A1 A1 0.95 11 11 0.25 0.31 2.13 7.42 0.51 2.21
A2 A2 0.57 11 11 0.25 0.31 2.13 7.42 0.30 1.32
A3 A3 0.49 11 5 0.76 0.95 2.85 9.95 1.06 4.64
A4 A4 0.56 11 6 0.69 0.86 2.67 9.31 1.03 4.48
A5 A5 0.43 9 6 0.95 1.00 2.67 9.31 1.09 3.98
A6 A6 0.20 11 6 0.71 0.88 2.67 9.31 0.38 1.66
A7 A7 0.45 10 5 0.76 0.95 2.85 9.95 0.96 4.20
A8 A8 0.09 6 5 0.95 1.00 2.85 9.95 0.26 0.94
A9 A9 0.12 7 5 0.95 1.00 2.85 9.95 0.33 1.22
A10 A10 0.55 8 5 0.79 0.98 2.85 9.95 1.24 5.40
A11 A11 0.04 5 5 0.95 1.00 2.85 9.95 0.12 0.44
A12 A12 0.98 11 6 0.77 0.97 2.67 9.31 2.02 8.81
A13 A13 0.45 9 6 0.95 1.00 2.67 9.31 1.15 4.23
A14 A14 0.63 10 8 0.80 1.00 2.40 8.38 1.20 5.26
A15 A15 0.73 10 8 0.86 1.00 2.40 8.38 1.51 6.08
A16 A16 0.77 9 6 0.95 1.00 2.67 9.31 1.95 7.16
B1 B1 0.46 11 11 0.25 0.31 2.13 7.42 0.25 1.07
B2 B2 0.48 11 11 0.25 0.31 2.13 7.42 0.26 1.12
B3 B3 1.10 11 10 0.74 0.93 2.21 7.72 1.80 7.88
B4 B4 0.38 10 10 0.89 1.00 2.21 7.72 0.75 2.95
B5 B5 0.54 11 8 0.85 1.00 2.40 8.38 1.10 4.53
B6 B6 0.22 10 6 0.68 0.85 2.67 9.31 0.40 1.76
B7 B7 0.30 10 5 0.79 0.98 2.85 9.95 0.68 2.97
C1 C1 0.61 12 6 0.84 1.00 2.67 9.31 1.37 5.68
C2 C2 0.83 12 6 0.66 0.82 2.67 9.31 1.46 6.37
C3 C3 2.47 12 9 0.90 1.00 2.30 8.03 5.13 19.83
C4 C4 0.50 9 6 0.95 1.00 2.67 9.31 1.27 4.66
D1 D1 0.45 11 5 0.76 0.95 2.85 9.95 0.97 4.25
E1 E1 2.12 15 7 0.79 0.99 2.52 8.80 4.22 18.41
OS1 OS1 3.70 13 7 0.64 0.80 2.52 8.80 5.98 26.09
OS2 OS2 5.84 12 12 0.25 0.31 2.05 7.16 2.99 13.07
Existing Basins
Peak Discharge
Proposed Basins
Runoff Coefficients Rainfall Intensity Peak Discharge
Rainfall IntensityRunoff Coefficients
Date: 1/14/2022 C:\United Civil Dropbox\Projects\U21004 - Nissan Dealership\Reports\Drainage\Calculations\U21004-Drain Calcs-PDP
A PPENDIX B
H YDRAULIC C ALCULATIONS
LOW IMPACT DEVELOPMENT SUMMARY
Nissan Dealership, Fort Collins, CO
Basin Proposed
Impervious Area
LID Treatment Area Treated % of Site Treated
(sf)(acres)(sf)(%)
A1 830 None 0 0.0%
A2 495 Bioretention 495 0.1%
A3 15,654 None 0 0.0%
A4 15,470 Bioretention 15,470 2.8%
A5 18,645 Bioretention 18,645 3.4%
A6 5,781 Bioretention 5,781 1.1%
A7 14,168 Bioretention 14,168 2.6%
A8 4,110 Bioretention 4,110 0.8%
A9 5,335 Bioretention 5,335 1.0%
A10 13,154 Bioretention 13,154 2.4%
A11 1,920 Bioretention 2,065 0.4%
A12 32,066 Bioretention 32,066 5.9%
A13 17,802 Bioretention 18,927 3.5%
A14 21,578 Bioretention 21,578 4.0%
A15 27,827 Bioretention 27,827 5.1%
A16 30,150 Bioretention 30,150 5.5%
B1 403 None 0 0.0%
B2 422 Bioretention 422 0.1%
B3 33,951 Bioretention 33,951 6.2%
B4 15,274 Bioretention 15,274 2.8%
B5 20,100 Bioretention 20,100 3.7%
B6 6,021 Bioretention 6,021 1.1%
B7 10,186 Bioretention 10,186 1.9%
C1 22,552 None 0 0.0%
C2 21,376 None 0 0.0%
C3 100,642 Underground Water Quality 100,642 18.4%
C4 19,616 Underground Water Quality 15,039 2.8%
D1 6,866 None 0 0.0%
E1 53,932 None 0 0.0%
OS1 9,795 None 0 0.0%
Total New/Modified Site 546,120 411,407 75.3%
Low Impact Development (LID) Treated Areas
Date: 1/14/2022 C:\United Civil Dropbox\Projects\U21004 - Nissan Dealership\Reports\Drainage\Calculations\U21004-Drain Calcs-PDP
WATER QUALITY
Nissan Dealership, Fort Collins, CO
Required Water Quality Capture Volume
Basin Area Area Imperviousness Watershed WQCV WQ Treatment
(sf)(acres)(%)(inches)(cf)Method
A1 41,480 0.952 2%0.02 63 Extended Detention
A2 24,770 0.569 2%0.01 30 Bioretention
A3(3)21,460 0.493 73%0.29 620 Extended Detention
A4 24,280 0.557 64%0.20 484 Bioretention
A5 18,645 0.428 100%0.40 746 Bioretention
A6 8,780 0.202 66%0.21 181 Bioretention
A7 19,450 0.447 73%0.23 449 Bioretention
A8 4,110 0.094 100%0.40 164 Bioretention
A9 5,335 0.122 100%0.40 213 Bioretention
A10 24,040 0.552 77%0.25 599 Bioretention
A11 1,920 0.044 100%0.40 77 Bioretention
A12 42,665 0.979 75%0.24 1,025 Bioretention
A13 19,780 0.454 90%0.32 635 Bioretention
A14 27,355 0.628 79%0.26 704 Bioretention
A15 31,595 0.725 88%0.31 975 Bioretention
A16 33,500 0.769 90%0.32 1,076 Bioretention
B1 20,160 0.463 2%0.01 24 None
B2 21,090 0.484 2%0.01 26 Bioretention
B3 47,980 1.101 71%0.22 1,069 Bioretention
B4 16,646 0.382 92%0.33 555 Bioretention
B5 23,550 0.541 85%0.29 687 Bioretention
B6 9,748 0.224 62%0.19 189 Bioretention
B7 13,195 0.303 77%0.25 329 Bioretention
---0%
C1 26,565 0.610 85%0.36 960 Extended Detention
C2 36,362 0.835 59%0.23 844 Extended Detention
C3 107,575 2.470 94%0.35 3,729 Underground Water Quality
C4 21,795 0.500 90%0.32 700 Underground Water Quality
D1 19,550 0.449 74%0.29 571 None
E1 92,490 2.123 77%0.31 2,891 None
OS1(3)161,165 3.700 56%0.22 3,582 Extended Detention
(1)Water quality provided by bioretention and based on 12-hour storage
(2)Water quality provided by underground detention and based on 12-hour storage
(3)based on 40 hr storage
(4) Basins D1 & E1 are related to CDOT R.O.W and are not captured with the site improvemens
BMP Facility Summary
Required Proposed
Facility WQCV WQCV
Designation ac-ft ac-ft
Detention Pond A1 0.10 0.14
Bioretention Pond A2 0.17 0.18
Bioretention Pond B2 0.07 0.08
Underground Pond C1 0.05 0.09
WQ Pond C2 0.04 0.06
(2)
(2)
(3)
(3)
(1)
(1)
(1)
Date: 1/19/2022 C:\United Civil Dropbox\Projects\U21004 - Nissan Dealership\Reports\Drainage\Calculations\U21004-Drain Calcs-PDP
UNDERGROUND DETENTION & WATER QUALITY
Nissan Dealership, Fort Collins, CO
Required Underground Detention/WQ Volume
Chamber Total Required Detention/ Chamber Chamber Chamber *Installed Min.End Cap *Installed Min.Min. Req'd Design No. of No. of Provided Provided Total
ID Detention/WQ WQ Type Unit Unit Chamber Unit No. of Unit End Cap WQ Isolator Row Controli Chambers End Caps Release Isolator Installed
Volumea Inflowb Release Volumed Volume inc.Chambersf Volumed Volume inc. Release Volume by Provided Provided Ratej Row System
Ratec Aggregatee Aggregatee Rateg FAA Methodh Volumek Volumel
(cf)(cfs)(cfs)(cf)(cf)(sf)(cf)(cf)(cfs)(cf)(cfs)(cf)(cf)
Pond C1 (LID/WQ)4,429 3.20 MC-4500 0.028 106.50 166.30 26 39.50 118.60 0.73 2,053 WQCV 22 2 0.62 2,343 3,896
Pond C1 (Detention)22,483 24.49 MC-4500 -146.00 284.90 74 39.50 118.60 ---85 12 2.4 N/A 24,217
*Volume assumes minimum aggregate depth below chamber.
a. Total required WQCV calculated per 12-hr drain time.
b. WQ inflow is approximated as one-half the 2-yr peak runoff rate.
c. Release rate per chamber, limited by flow through geotextile with accumulated sediment.
d. Volume within chamber only, not accounting for void spaces in surrounding aggregate. The Isolator Row(s) are sized per this unit volume.
e. Volume includes chamber and void spaces (40%) in surrounding aggregate, per chamber unit. The total system WQCV is sized per this unit volume.
f. Number of chambers required to provide full WQCV within total installed system, including aggregate.
g. Release rate per chamber times number of chambers. This is used at the 'outlet control' for the FAA calculations.
h. Minimum 'chamber-only' volume to ensure dirty water is fully contained within Isolator Row.
i. Determines whether the design is controlled by the Isolator Row volume or WQCV.
j. Release rate per chamber times number of chambers provided.
k. Volume provided in chambers only (no aggregate storage). This number must meet or exceed the required FAA storage volume.
l. System volume includes total number of chambers, plus surrounding aggregate. This number must meet or exceed the required 12-hr WQCV.
Date: 1/14/2022 C:\United Civil Dropbox\Projects\U21004 - Nissan Dealership\Reports\Drainage\Calculations\U21004-Drain Calcs-PDP
DETENTION POND VOLUME (FAA Method)
Nissan Dealership, Fort Collins, CO
POND ID:Pond A1
100 Year Storm Into Detention Facility
Area =468,850 square feet
Area =10.76 acres
C 2 = 0.69
C 100 = 0.83
Release Rate Out of Pond
Q OUT = 6.00 cfs
Notes:
1. Pond area includes all "A" Basins & Basin OS1.
Detention Volume Calculations
Rainfall Rainfall Inflow Rate Inflow Volume Adjustment
Factor
Average Outflow Volume Required
Duration (T)Intensity (I)Qin= ∑C100*Area*I Vi=(Qin*T*60)Factor Outflow Rate Vo=Qav*T *60 Storage Volume
m= 0.5(1 + Tc/T) Qav = m*Qout Vs=Vi-Vo
min in/hr cfs ft 3 cfs ft 3 ft 3
5 9.95 89.0 26,711 1.00 6.00 1,800 24,911
10 7.72 69.1 41,449 1.00 6.00 3,600 37,849
15 6.52 58.3 52,510 1.00 6.00 5,400 47,110
20 5.60 50.1 60,134 1.00 6.00 7,200 52,934
25 4.98 44.6 66,845 1.00 6.00 9,000 57,845
30 4.52 40.4 72,805 1.00 6.00 10,800 62,005
35 4.08 36.5 76,670 1.00 6.00 12,600 64,070
40 3.74 33.5 80,321 1.00 6.00 14,400 65,921
45 3.46 31.0 83,597 1.00 6.00 16,200 67,397
50 3.23 28.9 86,711 1.00 6.00 18,000 68,711
55 3.03 27.1 89,476 1.00 6.00 19,800 69,676
60 2.86 25.6 92,133 1.00 6.00 21,600 70,533
70 2.59 23.2 97,341 1.00 6.00 25,200 72,141
80 2.38 21.3 102,227 1.00 6.00 28,800 73,427
90 2.21 19.8 106,791 1.00 6.00 32,400 74,391
100 2.06 18.4 110,603 1.00 6.00 36,000 74,603
110 1.94 17.4 114,576 1.00 6.00 39,600 74,976
120 1.84 16.5 118,549 1.00 6.00 43,200 75,349
Required Detention Volume
V 100 = 75,349 cubic feet
V 100 = 1.73 acre-ft
Date: 1/19/2022 C:\United Civil Dropbox\Projects\U21004 - Nissan Dealership\Reports\Drainage\Calculations\U21004-Drain Calcs-PDP
DETENTION POND VOLUME (FAA Method)
Nissan Dealership, Fort Collins, CO
POND ID:Pond B1
100 Year Storm Into Detention Facility
Area =152,369 square feet
Area =3.50 acres
C 2 = 0.64
C 100 = 0.74
Release Rate Out of Pond
Q OUT = 2.00 cfs
Notes:
1. Pond area includes all "B" Basins.
Detention Volume Calculations
Rainfall Rainfall Inflow Rate Inflow Volume Adjustment
Factor
Average Outflow Volume Required
Duration (T)Intensity (I)Qin= ∑C100*Area*I Vi=(Qin*T*60)Factor Outflow Rate Vo=Qav*T *60 Storage Volume
m= 0.5(1 + Tc/T) Qav = m*Qout Vs=Vi-Vo
min in/hr cfs ft 3 cfs ft 3 ft 3
5 9.95 25.6 7,687 1.00 2.00 600 7,087
10 7.72 19.9 11,929 1.00 2.00 1,200 10,729
15 6.52 16.8 15,112 1.00 2.00 1,800 13,312
20 5.60 14.4 17,306 1.00 2.00 2,400 14,906
25 4.98 12.8 19,237 1.00 2.00 3,000 16,237
30 4.52 11.6 20,952 1.00 2.00 3,600 17,352
35 4.08 10.5 22,065 1.00 2.00 4,200 17,865
40 3.74 9.6 23,115 1.00 2.00 4,800 18,315
45 3.46 8.9 24,058 1.00 2.00 5,400 18,658
50 3.23 8.3 24,954 1.00 2.00 6,000 18,954
55 3.03 7.8 25,750 1.00 2.00 6,600 19,150
60 2.86 7.4 26,515 1.00 2.00 7,200 19,315
70 2.59 6.7 28,013 1.00 2.00 8,400 19,613
80 2.38 6.1 29,420 1.00 2.00 9,600 19,820
90 2.21 5.7 30,733 1.00 2.00 10,800 19,933
100 2.06 5.3 31,830 1.00 2.00 12,000 19,830
110 1.94 5.0 32,973 1.00 2.00 13,200 19,773
120 1.84 4.7 34,117 1.00 2.00 14,400 19,717
Required Detention Volume
V 100 = 19,933 cubic feet
V 100 = 0.46 acre-ft
Date: 1/19/2022 C:\United Civil Dropbox\Projects\U21004 - Nissan Dealership\Reports\Drainage\Calculations\U21004-Drain Calcs-PDP
DETENTION POND VOLUME (FAA Method)
Nissan Dealership, Fort Collins, CO
POND ID:Pond C1 - Underground Detention
100 Year Storm Into Detention Facility
Area =129,370 square feet
Area =2.97 acres
C 2 = 0.91
C 100 = 1.00
Release Rate Out of Pond
Q OUT = 2.40 cfs
Notes:
1. Pond area includes Basins C3 & C4.
Detention Volume Calculations
Rainfall Rainfall Inflow Rate Inflow Volume Adjustment
Factor
Average Outflow Volume Required
Duration (T)Intensity (I)Qin= ∑C100*Area*I Vi=(Qin*T*60)Factor Outflow Rate Vo=Qav*T *60 Storage Volume
m= 0.5(1 + Tc/T) Qav = m*Qout Vs=Vi-Vo
min in/hr cfs ft 3 cfs ft 3 ft 3
5 9.95 29.6 8,865 1.00 2.40 720 8,145
10 7.72 22.9 13,757 1.00 2.40 1,440 12,317
15 6.52 19.4 17,428 1.00 2.40 2,160 15,268
20 5.60 16.6 19,958 1.00 2.40 2,880 17,078
25 4.98 14.8 22,185 1.00 2.40 3,600 18,585
30 4.52 13.4 24,163 1.00 2.40 4,320 19,843
35 4.08 12.1 25,446 1.00 2.40 5,040 20,406
40 3.74 11.1 26,658 1.00 2.40 5,760 20,898
45 3.46 10.3 27,745 1.00 2.40 6,480 21,265
50 3.23 9.6 28,779 1.00 2.40 7,200 21,579
55 3.03 9.0 29,696 1.00 2.40 7,920 21,776
60 2.86 8.5 30,578 1.00 2.40 8,640 21,938
70 2.59 7.7 32,307 1.00 2.40 10,080 22,227
80 2.38 7.1 33,928 1.00 2.40 11,520 22,408
90 2.21 6.6 35,443 1.00 2.40 12,960 22,483
100 2.06 6.1 36,708 1.00 2.40 14,400 22,308
110 1.94 5.8 38,027 1.00 2.40 15,840 22,187
120 1.84 5.5 39,346 1.00 2.40 17,280 22,066
Required Detention Volume
V 100 = 22,483 cubic feet
V 100 = 0.52 acre-ft
Date: 1/19/2022 C:\United Civil Dropbox\Projects\U21004 - Nissan Dealership\Reports\Drainage\Calculations\U21004-Drain Calcs-PDP
DETENTION POND VOLUME (FAA Method)
Nissan Dealership, Fort Collins, CO
POND ID:Pond C1 (Underground Water Quality)
WQ Basin Characateristics
Area =129,370 square feet
Area =2.97 acres
C 2 = 0.91
C 100 = 1.00
WQ Release Rate Determined from Number of Chambers and Chamber Release Rate
Q OUT = 0.62 cfs
Notes:
1. Release rate out of pond based on number of chambers multiplied by release rate per chamber.
2. Rainfall intensities approximated as one-half the 2-yr peak runoff rate.
3. C2 utilized for water quality event detention calculation.
4. Pond is designed to provide WQ for Basins C3 & C4.
Detention Volume Calculations
Rainfall Rainfall Inflow Rate Inflow Volume Adjustment
Factor
Average Outflow Volume Required
Duration (T)Intensity (I)Qin= ∑C100*Area*I Vi=(Qin*T*60)Factor Outflow Rate Vo=Qav*T *60 Storage Volume
m= 0.5(1 + Tc/T) Qav = m*Qout Vs=Vi-Vo
min in/hr cfs ft 3 cfs ft 3 ft 3
5 1.425 3.9 1,158 1.00 0.62 186 972
10 1.105 3.0 1,795 1.00 0.62 372 1,424
15 0.935 2.5 2,279 1.00 0.62 558 1,721
20 0.805 2.2 2,616 1.00 0.62 743 1,872
25 0.715 1.9 2,904 1.00 0.62 929 1,975
30 0.650 1.8 3,168 1.00 0.62 1,115 2,053
35 0.585 1.6 3,326 1.00 0.62 1,301 2,025
40 0.535 1.4 3,477 1.00 0.62 1,487 1,990
45 0.495 1.3 3,619 1.00 0.62 1,673 1,946
50 0.460 1.2 3,737 1.00 0.62 1,859 1,878
55 0.435 1.2 3,887 1.00 0.62 2,044 1,843
60 0.410 1.1 3,997 1.00 0.62 2,230 1,766
65 0.385 1.0 4,066 1.00 0.62 2,416 1,650
70 0.365 1.0 4,151 1.00 0.62 2,602 1,549
75 0.345 0.9 4,204 1.00 0.62 2,788 1,416
80 0.330 0.9 4,289 1.00 0.62 2,974 1,315
85 0.315 0.9 4,350 1.00 0.62 3,160 1,190
90 0.305 0.8 4,460 1.00 0.62 3,345 1,114
95 0.290 0.8 4,476 1.00 0.62 3,531 945
100 0.280 0.8 4,549 1.00 0.62 3,717 832
105 0.270 0.7 4,606 1.00 0.62 3,903 703
110 0.260 0.7 4,646 1.00 0.62 4,089 558
115 0.255 0.7 4,764 1.00 0.62 4,275 490
120 0.245 0.7 4,776 1.00 0.62 4,460 316
Required Detention Volume
V 100 = 2,053 cubic feet
V 100 = 0.05 acre-ft
Date: 1/19/2022 C:\United Civil Dropbox\Projects\U21004 - Nissan Dealership\Reports\Drainage\Calculations\U21004-Drain Calcs-PDP
DETENTION POND STORAGE AND ORIFICE CALCULATIONS
Nissan Dealership, Fort Collins, CO
POND ID:Detention Pond A1
Stage Storage Calculations
Elevation Area (sf)Depth (ft)
Incremental
Volume (cf)Volume total (cf)
Volume total (ac-
ft)
5,002.60 386.39 0.00 0 0 0.00
5,003.00 2,348.39 0.40 492 492 0.01
5,003.40 5,228.93 0.40 1,478 1,969 0.05
5,003.80 7,339.29 0.40 2,502 4,471 0.10
5,004.20 8,104.02 0.40 3,087 7,558 0.17
5,004.60 8,858.92 0.40 3,391 10,950 0.25
5,005.00 9,622.23 0.40 3,695 14,645 0.34
5,005.40 10,397.70 0.40 4,003 18,648 0.43
5,005.80 11,233.24 0.40 4,325 22,973 0.53
5,006.20 12,212.56 0.40 4,688 27,661 0.64
5,006.60 13,269.49 0.40 5,095 32,756 0.75
5,007.00 14,211.28 0.40 5,495 38,251 0.88
5,007.40 15,230.97 0.40 5,887 44,138 1.01
5,007.80 16,165.72 0.40 6,278 50,417 1.16
5,008.20 17,186.63 0.40 6,669 57,086 1.31
5,008.60 18,311.53 0.40 7,098 64,184 1.47
5,009.00 19,439.12 0.40 7,549 71,733 1.65
5,009.40 20,682.29 0.40 8,023 79,756 1.83
5,009.50 20,710.25 0.10 2,070 81,826 1.88
Detention Pond Storage & Water Quality
Detention Volume Required =75,349 ft3 Water Quality Volume Required =4,265 ft3
1.73 ac-ft 0.10 ac-ft
Elev81 - Elev80 (VolRequired-Vol80)+Elev80 Elev81 - Elev80 (VolRequired-Vol80)+Elev80
Vol81 - Vo80 Vol81 - Vo80
Required W.S. Elevation = 4612.98 ft Required W.S. Elevation = 5003.77 ft
Provided W.S. Elevation = 5009.50 ft Provided W.S. Elevation = 5004.00 ft
Detention Volume Provided =75,811 ft3 Water Quality Volume Provided =6,015 ft3
1.74 ac-ft 0.14 ac-ft
100-year Depth D = 6.90 ft Water Quality Depth D = 1.40 ft
Top-of-Berm = 5010.50 ft 100-year W.S. Elevation = 5009.50 ft
Freeboard = 1.00 ft Freeboard = 5.50 ft
Orifice Opening and Water Quality Plate
Orifice Flow Rate, Q = CoAo(2gHo)0.5 cfs Area Required per WQ Plate Row 0.59 in2
Area of orifice Ao, ft2 = Q diam of WQ Hole = 0.87 in
Co(2gHo)0.5 diam of WQ Hole (fraction) = 7/8 in
C o = 0.65 Space Between Rows 4 in
Q = Q out of pond = 6.00 cfs Number of Columns 1
gravitational acceleration g = 32.2 ft/sec2 Number of Rows 5
diam = 0.757 ft
Effective head on orifice H o = D-1/2diam =6.52 ft
Area of orifice A o = 0.45 ft2
Area of orifice A o = 64.86 in2
100-Year Orifice Diameter = 9.09 9 1/16 inches
100-Year Detention Volume and Elevations Water Quality Volume and Elevations
W.S. Elevation, ft = W.S. Elevation, ft =
100-Year Orifice Calculation Water Quality Plate Calculation
Date: 1/19/2022 C:\United Civil Dropbox\Projects\U21004 - Nissan Dealership\Reports\Drainage\Calculations\U21004-Drain Calcs-PDP
DETENTION POND STORAGE AND ORIFICE CALCULATIONS
Nissan Dealership, Fort Collins, CO
POND ID:Detention Pond B1
Stage Storage Calculations
Elevation Area (sf)Depth (ft)
Incremental
Volume (cf)Volume total (cf)
Volume total (ac-
ft)
5,005.20 101.22 0.00 0 0 0.00
5,005.40 845.29 0.20 83 83 0.00
5,005.60 1,846.91 0.20 263 345 0.01
5,005.80 2,721.64 0.20 454 799 0.02
5,006.00 3,664.58 0.20 636 1,436 0.03
5,006.20 4,762.37 0.20 840 2,276 0.05
5,006.40 6,060.53 0.20 1,080 3,356 0.08
5,006.60 7,766.58 0.20 1,379 4,735 0.11
5,006.80 9,347.25 0.20 1,709 6,444 0.15
5,007.00 10,363.36 0.20 1,970 8,414 0.19
5,007.20 11,322.35 0.20 2,168 10,582 0.24
5,007.40 12,246.48 0.20 2,356 12,938 0.30
5,007.60 13,143.87 0.20 2,539 15,477 0.36
5,007.80 14,022.27 0.20 2,716 18,193 0.42
5,008.00 14,888.24 0.20 2,891 21,083 0.48
5,008.20 15,746.17 0.20 3,063 24,146 0.55
5,008.40 16,600.07 0.20 3,234 27,381 0.63
5,008.60 17,458.93 0.20 3,406 30,786 0.71
5,008.80 18,338.80 0.20 3,579 34,366 0.79
5,009.00 19,235.07 0.20 3,757 38,123 0.88
5,009.20 20,196.20 0.20 3,943 42,065 0.97
5,009.40 21,121.56 0.20 4,131 46,197 1.06
5,009.50 21,670.63 0.10 2,140 48,336 1.11
Detention Pond Storage & Water Quality
Detention Volume Required =19,933 ft3
0.46 ac-ft
Elev81 - Elev80 (VolRequired-Vol80)+Elev80
Vol81 - Vo80
Required W.S. Elevation = 5008.03 ft
Provided W.S. Elevation = 5009.50 ft
Detention Volume Provided =48,336 ft3
1.11 ac-ft
100-year Depth D = 4.30 ft
Top-of-Berm = 5010.50 ft
Freeboard = 1.00 ft
Orifice Opening
Orifice Flow Rate, Q = CoAo(2gHo)0.5 cfs
Area of orifice Ao, ft2 = Q
Co(2gHo)0.5
C o = 0.65
Q = Q out of pond = 2.00 cfs
gravitational acceleration g = 32.2 ft/sec2
diam = 0.492 ft
Effective head on orifice H o = D-1/2diam =4.05 ft
Area of orifice A o = 0.19 ft2
Area of orifice A o = 27.42 in2
100-Year Orifice Diameter = 5.91 5 15/16 inches
100-Year Detention Volume and Elevations
W.S. Elevation, ft =
100-Year Orifice Calculation
Date: 1/19/2022 C:\United Civil Dropbox\Projects\U21004 - Nissan Dealership\Reports\Drainage\Calculations\U21004-Drain Calcs-PDP
DETENTION POND STORAGE AND ORIFICE CALCULATIONS
Nissan Dealership, Fort Collins, CO
POND ID:Offsite Water Quality Pond C2
Stage Storage Calculations
Elevation Area (sf)Depth (ft)
Incremental Volume
(cf)
Volume total
(cf)
Volume total
(ac-ft)
4,964.80 45.30 0.00 0 0 0.00
4,965.00 334.63 0.20 34 34 0.00
4,965.20 922.18 0.20 121 154 0.00
4,965.40 1,809.78 0.20 268 423 0.01
4,965.60 2,909.66 0.20 468 890 0.02
4,965.80 3,875.26 0.20 676 1,566 0.04
4,966.00 4,446.28 0.20 832 2,398 0.06
4,966.20 4,706.65 0.20 915 3,313 0.08
4,966.40 4,971.92 0.20 968 4,281 0.10
4,966.60 5,242.09 0.20 1,021 5,302 0.12
4,966.70 5,311.05 0.10 528 5,830 0.13
Detention Pond Storage & Water Quality
Water Quality Volume Required =1,804 ft3
0.04 ac-ft
Elev81 - Elev80 (VolRequired-Vol80)+Elev80
Vol81 - Vo80
Required W.S. Elevation = 4965.86 ft
Provided W.S. Elevation = 4966.00 ft
Water Quality Volume Provided =2,398 ft3
0.06 ac-ft
Water Quality Depth D = 1.20 ft
100-year W.S. Elevation = 4966.70 ft
Freeboard = 0.70 ft
Water Quality Plate
Area Required per WQ Plate Row 0.30 in2
diam of WQ Hole = 0.62 in
diam of WQ Hole (fraction) = 5/8 in
Space Between Rows 4 in
Number of Columns 1
Number of Rows 4
Water Quality Volume and Elevations
W.S. Elevation, ft =
Water Quality Plate Calculation
Date: 1/19/2022 C:\United Civil Dropbox\Projects\U21004 - Nissan Dealership\Reports\Drainage\Calculations\U21004-Drain Calcs-PDP
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Friday, Jan 14 2022
Channel C: 100-yr Event
User-defined
Invert Elev (ft)= 4971.27
Slope (%)= 4.00
N-Value = 0.033
Calculations
Compute by:Known Q
Known Q (cfs)= 14.45
(Sta, El, n)-(Sta, El, n)...
( 11.16, 4972.46)-(18.77, 4971.27, 0.033)-(23.77, 4971.27, 0.033)-(31.24, 4973.06, 0.033)
Highlighted
Depth (ft)= 0.45
Q (cfs)= 14.45
Area (sqft)= 3.32
Velocity (ft/s)= 4.35
Wetted Perim (ft)= 9.85
Crit Depth, Yc (ft)= 0.53
Top Width (ft)= 9.76
EGL (ft)= 0.74
5 10 15 20 25 30 35 40
Elev (ft)Depth (ft)Section
4970.50 -0.77
4971.00 -0.27
4971.50 0.23
4972.00 0.73
4972.50 1.23
4973.00 1.73
4973.50 2.23
4974.00 2.73
Sta (ft)
Culvert Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Thursday, Jan 13 2022
Existing 12-inch Culvert (Max Capacity)
Invert Elev Dn (ft)= 4963.00
Pipe Length (ft)= 40.00
Slope (%)= 4.25
Invert Elev Up (ft)= 4964.70
Rise (in)= 12.0
Shape = Circular
Span (in)= 12.0
No. Barrels = 1
n-Value = 0.013
Culvert Type = Circular Concrete
Culvert Entrance = Square edge w/headwall (C)
Coeff. K,M,c,Y,k = 0.0098, 2, 0.0398, 0.67, 0.5
Embankment
Top Elevation (ft)= 4966.70
Top Width (ft)= 20.00
Crest Width (ft)= 50.00
Calculations
Qmin (cfs)= 4.55
Qmax (cfs)= 4.55
Tailwater Elev (ft)= Critical
Highlighted
Qtotal (cfs)= 4.55
Qpipe (cfs)= 4.55
Qovertop (cfs)= 0.00
Veloc Dn (ft/s)= 9.41
Veloc Up (ft/s)= 6.17
HGL Dn (ft)= 4963.59
HGL Up (ft)= 4965.59
Hw Elev (ft)= 4966.69
Hw/D (ft)= 1.98
Flow Regime = Inlet Control
A PPENDIX C
R EFERENCED M ATERIALS
4,514
752.3
FCMaps
This map is a user generated static output from the City of Fort Collins FCMaps
Internet mapping site and is for reference only. Data layers that appear on this
map may or may not be accurate, current, or otherwise reliable.
City of Fort Collins - GIS
572.0
1:
WGS_1984_Web_Mercator_Auxiliary_Sphere
Feet572.00286.00
Notes
Legend
3,430
FEMA Floodplain
FEMA High Risk - Floodway
FEMA High Risk - 100 Year
FEMA Moderate Risk - 100 / 500 Year
City Floodplains
City High Risk - Floodway
City High Risk - 100 Year
City Moderate Risk - 100 Year
City Limits
National Flood Hazard Layer FIRMette
0 500 1,000 1,500 2,000250
Feet
Ü
SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT
SPECIAL FLOOD
HAZARD AREAS
Without Base Flood Elevation (BFE)
Zone A, V, A99
With BFE or DepthZone AE, AO, AH, VE, AR
Regulatory Floodway
0.2% Annual Chance Flood Hazard, Areas
of 1% annual chance flood with average
depth less than one foot or with drainage
areas of less than one square mileZone X
Future Conditions 1% Annual
Chance Flood HazardZone X
Area with Reduced Flood Risk due to
Levee. See Notes.Zone X
Area with Flood Risk due to LeveeZone D
NO SCREEN Area of Minimal Flood Hazard Zone X
Area of Undetermined Flood HazardZone D
Channel, Culvert, or Storm Sewer
Levee, Dike, or Floodwall
Cross Sections with 1% Annual Chance
17.5 Water Surface Elevation
Coastal Transect
Coastal Transect Baseline
Profile Baseline
Hydrographic Feature
Base Flood Elevation Line (BFE)
Effective LOMRs
Limit of Study
Jurisdiction Boundary
Digital Data Available
No Digital Data Available
Unmapped
This map complies with FEMA's standards for the use of
digital flood maps if it is not void as described below.
The basemap shown complies with FEMA's basemap
accuracy standards
The flood hazard information is derived directly from the
authoritative NFHL web services provided by FEMA. This map
was exported on 3/4/2021 at 3:31 PM and does not
reflect changes or amendments subsequent to this date and
time. The NFHL and effective information may change or
become superseded by new data over time.
This map image is void if the one or more of the following map
elements do not appear: basemap imagery, flood zone labels,
legend, scale bar, map creation date, community identifiers,
FIRM panel number, and FIRM effective date. Map images for
unmapped and unmodernized areas cannot be used for
regulatory purposes.
Legend
OTHER AREAS OF
FLOOD HAZARD
OTHER AREAS
GENERAL
STRUCTURES
OTHER
FEATURES
MAP PANELS
8
B 20.2
The pin displayed on the map is an approximate
point selected by the user and does not represent
an authoritative property location.
1:6,000
105°5'1"W 40°30'39"N
105°4'24"W 40°30'11"N
Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020
REPORT COVER PAGE
Geotechnical Engineering Report
__________________________________________________________________________
Fort Collins Nissan and Kia Dealerships
Fort Collins, Colorado
April 7, 2021
Terracon Project No. 20215013
Prepared for:
TCC Corporation
Windsor, Colorado
Prepared by:
Terracon Consultants, Inc.
Fort Collins, Colorado
United States
Department of
Agriculture
A product of the National
Cooperative Soil Survey,
a joint effort of the United
States Department of
Agriculture and other
Federal agencies, State
agencies including the
Agricultural Experiment
Stations, and local
participants
Custom Soil Resource
Report for
Larimer County
Area, Colorado
Nissan Dealership
Natural
Resources
Conservation
Service
March 4, 2021
Soil Map
The soil map section includes the soil map for the defined area of interest, a list of
soil map units on the map and extent of each map unit, and cartographic symbols
displayed on the map. Also presented are various metadata about data used to
produce the map, and a description of each soil map unit.
8
9
Custom Soil Resource Report
Soil Map
4483840448390044839604484020448408044841404484200448426044838404483900448396044840204484080448414044842004484260493130 493190 493250 493310 493370 493430 493490
493130 493190 493250 493310 493370 493430 493490
40° 30' 33'' N 105° 4' 52'' W40° 30' 33'' N105° 4' 36'' W40° 30' 17'' N
105° 4' 52'' W40° 30' 17'' N
105° 4' 36'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 100 200 400 600
Feet
0 30 60 120 180
Meters
Map Scale: 1:2,350 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 15, Jun 9, 2020
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Aug 11, 2018—Aug
12, 2018
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Custom Soil Resource Report
10
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
55 Kim loam, 5 to 9 percent slopes 0.3 1.6%
56 Kim-Thedalund loams, 3 to 15
percent slopes
5.8 36.2%
65 Midway clay loam, 5 to 25
percent slopes
2.1 13.0%
108 Thedalund loam, 3 to 9 percent
slopes
7.9 49.2%
Totals for Area of Interest 16.0 100.0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the
soils or miscellaneous areas in the survey area. The map unit descriptions, along
with the maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas. A map unit is identified and named
according to the taxonomic classification of the dominant soils. Within a taxonomic
class there are precisely defined limits for the properties of the soils. On the
landscape, however, the soils are natural phenomena, and they have the
characteristic variability of all natural phenomena. Thus, the range of some
observed properties may extend beyond the limits defined for a taxonomic class.
Areas of soils of a single taxonomic class rarely, if ever, can be mapped without
including areas of other taxonomic classes. Consequently, every map unit is made
up of the soils or miscellaneous areas for which it is named and some minor
components that belong to taxonomic classes other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
noncontrasting, or similar, components. They may or may not be mentioned in a
particular map unit description. Other minor components, however, have properties
and behavioral characteristics divergent enough to affect use or to require different
management. These are called contrasting, or dissimilar, components. They
generally are in small areas and could not be mapped separately because of the
scale used. Some small areas of strongly contrasting soils or miscellaneous areas
are identified by a special symbol on the maps. If included in the database for a
given area, the contrasting minor components are identified in the map unit
descriptions along with some characteristics of each. A few areas of minor
components may not have been observed, and consequently they are not
mentioned in the descriptions, especially where the pattern was so complex that it
was impractical to make enough observations to identify all the soils and
miscellaneous areas on the landscape.
The presence of minor components in a map unit in no way diminishes the
usefulness or accuracy of the data. The objective of mapping is not to delineate
Custom Soil Resource Report
11
pure taxonomic classes but rather to separate the landscape into landforms or
landform segments that have similar use and management requirements. The
delineation of such segments on the map provides sufficient information for the
development of resource plans. If intensive use of small areas is planned, however,
onsite investigation is needed to define and locate the soils and miscellaneous
areas.
An identifying symbol precedes the map unit name in the map unit descriptions.
Each description includes general facts about the unit and gives important soil
properties and qualities.
Soils that have profiles that are almost alike make up a soil series. Except for
differences in texture of the surface layer, all the soils of a series have major
horizons that are similar in composition, thickness, and arrangement.
Soils of one series can differ in texture of the surface layer, slope, stoniness,
salinity, degree of erosion, and other characteristics that affect their use. On the
basis of such differences, a soil series is divided into soil phases. Most of the areas
shown on the detailed soil maps are phases of soil series. The name of a soil phase
commonly indicates a feature that affects use or management. For example, Alpha
silt loam, 0 to 2 percent slopes, is a phase of the Alpha series.
Some map units are made up of two or more major soils or miscellaneous areas.
These map units are complexes, associations, or undifferentiated groups.
A complex consists of two or more soils or miscellaneous areas in such an intricate
pattern or in such small areas that they cannot be shown separately on the maps.
The pattern and proportion of the soils or miscellaneous areas are somewhat similar
in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example.
An association is made up of two or more geographically associated soils or
miscellaneous areas that are shown as one unit on the maps. Because of present
or anticipated uses of the map units in the survey area, it was not considered
practical or necessary to map the soils or miscellaneous areas separately. The
pattern and relative proportion of the soils or miscellaneous areas are somewhat
similar. Alpha-Beta association, 0 to 2 percent slopes, is an example.
An undifferentiated group is made up of two or more soils or miscellaneous areas
that could be mapped individually but are mapped as one unit because similar
interpretations can be made for use and management. The pattern and proportion
of the soils or miscellaneous areas in a mapped area are not uniform. An area can
be made up of only one of the major soils or miscellaneous areas, or it can be made
up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.
Some surveys include miscellaneous areas. Such areas have little or no soil
material and support little or no vegetation. Rock outcrop is an example.
Custom Soil Resource Report
12
Larimer County Area, Colorado
55—Kim loam, 5 to 9 percent slopes
Map Unit Setting
National map unit symbol: jpwz
Elevation: 4,800 to 5,600 feet
Mean annual precipitation: 13 to 15 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 135 to 150 days
Farmland classification: Farmland of local importance
Map Unit Composition
Kim and similar soils:85 percent
Minor components:15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Kim
Setting
Landform:Fans
Landform position (three-dimensional):Base slope, side slope
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Mixed alluvium
Typical profile
H1 - 0 to 7 inches: loam
H2 - 7 to 60 inches: loam, clay loam, sandy clay loam
H2 - 7 to 60 inches:
H2 - 7 to 60 inches:
Properties and qualities
Slope:5 to 9 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high
(0.60 to 2.00 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Calcium carbonate, maximum content:15 percent
Maximum salinity:Nonsaline to slightly saline (0.0 to 4.0 mmhos/cm)
Available water capacity:Very high (about 26.5 inches)
Interpretive groups
Land capability classification (irrigated): 4e
Land capability classification (nonirrigated): 6e
Hydrologic Soil Group: B
Ecological site: R067XY002CO - Loamy Plains
Hydric soil rating: No
Custom Soil Resource Report
13
Minor Components
Thedalund
Percent of map unit:10 percent
Hydric soil rating: No
Stoneham
Percent of map unit:5 percent
Hydric soil rating: No
56—Kim-Thedalund loams, 3 to 15 percent slopes
Map Unit Setting
National map unit symbol: jpx0
Elevation: 4,800 to 5,600 feet
Mean annual precipitation: 13 to 15 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 135 to 150 days
Farmland classification: Not prime farmland
Map Unit Composition
Kim and similar soils:45 percent
Thedalund and similar soils:35 percent
Minor components:20 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Kim
Setting
Landform:Fans, valley sides
Landform position (three-dimensional):Base slope, side slope
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Mixed alluvium
Typical profile
H1 - 0 to 7 inches: loam
H2 - 7 to 60 inches: loam, clay loam, sandy clay loam
H2 - 7 to 60 inches:
H2 - 7 to 60 inches:
Properties and qualities
Slope:3 to 7 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high
(0.60 to 2.00 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Custom Soil Resource Report
14
Frequency of ponding:None
Calcium carbonate, maximum content:15 percent
Maximum salinity:Nonsaline to slightly saline (0.0 to 4.0 mmhos/cm)
Available water capacity:Very high (about 26.5 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirrigated): 4e
Hydrologic Soil Group: B
Ecological site: R067XY002CO - Loamy Plains
Hydric soil rating: No
Description of Thedalund
Setting
Landform position (three-dimensional):Side slope
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Material weathered from sandstone and shale
Typical profile
H1 - 0 to 4 inches: loam
H2 - 4 to 33 inches: clay loam, loam, sandy clay loam
H2 - 4 to 33 inches: weathered bedrock
H2 - 4 to 33 inches:
H3 - 33 to 37 inches:
Properties and qualities
Slope:7 to 15 percent
Depth to restrictive feature:20 to 40 inches to paralithic bedrock
Drainage class:Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat):Moderately low to high
(0.06 to 2.00 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Calcium carbonate, maximum content:15 percent
Maximum salinity:Nonsaline to moderately saline (0.0 to 8.0 mmhos/cm)
Available water capacity:Very high (about 15.5 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 6e
Hydrologic Soil Group: C
Ecological site: R067XY002CO - Loamy Plains
Hydric soil rating: No
Minor Components
Renohill
Percent of map unit:10 percent
Hydric soil rating: No
Midway
Percent of map unit:9 percent
Hydric soil rating: No
Custom Soil Resource Report
15
Aquic haplustolls
Percent of map unit:1 percent
Landform:Swales
Hydric soil rating: Yes
65—Midway clay loam, 5 to 25 percent slopes
Map Unit Setting
National map unit symbol: jpxb
Elevation: 4,800 to 5,800 feet
Mean annual precipitation: 13 to 15 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 135 to 150 days
Farmland classification: Not prime farmland
Map Unit Composition
Midway and similar soils:90 percent
Minor components:10 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Midway
Setting
Landform position (three-dimensional):Side slope
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Material weathered from shale
Typical profile
H1 - 0 to 4 inches: clay loam
H2 - 4 to 19 inches: clay, clay loam, silty clay loam
H2 - 4 to 19 inches: weathered bedrock
H2 - 4 to 19 inches:
H3 - 19 to 23 inches:
Properties and qualities
Slope:5 to 25 percent
Depth to restrictive feature:6 to 20 inches to paralithic bedrock
Drainage class:Well drained
Runoff class: Very high
Capacity of the most limiting layer to transmit water (Ksat):Moderately low to
moderately high (0.06 to 0.20 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Calcium carbonate, maximum content:15 percent
Gypsum, maximum content:15 percent
Maximum salinity:Very slightly saline to moderately saline (2.0 to 8.0 mmhos/cm)
Sodium adsorption ratio, maximum:15.0
Custom Soil Resource Report
16
Available water capacity:Moderate (about 7.9 inches)
Interpretive groups
Land capability classification (irrigated): 6e
Land capability classification (nonirrigated): 6e
Hydrologic Soil Group: D
Ecological site: R067BY045CO - Shaly Plains
Hydric soil rating: No
Minor Components
Renohill
Percent of map unit:10 percent
Hydric soil rating: No
108—Thedalund loam, 3 to 9 percent slopes
Map Unit Setting
National map unit symbol: jpv1
Elevation: 4,800 to 5,600 feet
Mean annual precipitation: 13 to 15 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 135 to 150 days
Farmland classification: Not prime farmland
Map Unit Composition
Thedalund and similar soils:90 percent
Minor components:10 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Thedalund
Setting
Landform position (three-dimensional):Side slope
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Material weathered from sandstone and shale
Typical profile
H1 - 0 to 6 inches: loam
H2 - 6 to 37 inches: clay loam, loam, sandy clay loam
H2 - 6 to 37 inches: weathered bedrock
H2 - 6 to 37 inches:
H3 - 37 to 41 inches:
Properties and qualities
Slope:3 to 9 percent
Depth to restrictive feature:20 to 40 inches to paralithic bedrock
Drainage class:Well drained
Runoff class: Medium
Custom Soil Resource Report
17
Capacity of the most limiting layer to transmit water (Ksat):Moderately low to high
(0.06 to 2.00 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Calcium carbonate, maximum content:15 percent
Maximum salinity:Nonsaline to moderately saline (0.0 to 8.0 mmhos/cm)
Available water capacity:Very high (about 16.8 inches)
Interpretive groups
Land capability classification (irrigated): 4e
Land capability classification (nonirrigated): 6e
Hydrologic Soil Group: C
Ecological site: R067XY002CO - Loamy Plains
Hydric soil rating: No
Minor Components
Kim
Percent of map unit:6 percent
Hydric soil rating: No
Renohill
Percent of map unit:4 percent
Hydric soil rating: No
Custom Soil Resource Report
18
A PPENDIX D
D RAINAGE E XHIBITS
COLLEGE AVE (HWY 287)VENUS AVESKYVIEW SUBDIVISIONZONED RLOS13.70EX12.12EX21.70EX30.41EX40.38EX57.97FOSSIL CREEKS COLLEGE AVER.O.W BOUNDARYEXISTING WETLANDSOS25.75EX66.44EROSION BUFFER LIMITS (TYP)LANG GULCHEXISTING 12" CULVERTPATH:0'150'300'SCALE: 1" = 150'75'C:\UNITED CIVIL DROPBOX\PROJECTS\U21004 - NISSAN DEALERSHIP\CADD\ET\EXISTING DRAINAGE MAP.DWG EXISTING DRAINAGE MAPDRAWING NAME:SHEET SIZE: 11 x 17
FORT COLLINS NISSANEXISTING DRAINAGE MAPDATE:January 14, 2022PREPARED FOR:TCC CORPORATIONJOB NUMBER:U21004NOTE:THIS EXHIBIT WAS PREPARED FOR INFORMATION ONLY AND THE ENGINEER PREPARING THESE PLANS WILL NOT BE RESPONSIBLE FOR UNAUTHORIZED USE OF THEM.SHEETOF11NORTH19 OLD TOWN SQUARE #238 | FORT COLLINS, CO 80524 | (970) 530-4044 | www.unitedcivil.comUNITED CIVILDesign GroupEXISTING MAJOR CONTOUREXISTING MINOR CONTOURXX.XXBASIN DESIGNATIONEXISTING BASINEXISTING BASIN LINELEGENDBASIN AREA (ACRE)
COLLEGE AVE (HWY 287)VENUS AVESKYVIEW SUBDIVISIONZONED RL
FOSSIL CREEKPROPOSEDBUILDINGBIO.POND A2BIO. POND B2UNDERGROUND WATER QUALITY& DETENTION FACILITY C1PROPOSEDBUILDINGBASINSA2, A4-A16BASINSC3-C4BASINSB2-B7LANG GULCHEXISTINGSCHOOL POND A1WATER QUALITY POND C2BASINS C1-C2BASINSA1, OS1POND B1(NO WQ)PATH:0'150'300'SCALE: 1" = 150'75'C:\UNITED CIVIL DROPBOX\PROJECTS\U21004 - NISSAN DEALERSHIP\CADD\ET\LID MAP.DWG LID MAPDRAWING NAME:SHEET SIZE: 11 x 17
FORT COLLINS NISSANLID & BMP TREATMENT MAPDATE:January 17, 2022PREPARED FOR:TCC CORPORATIONJOB NUMBER:U21004NOTE:THIS EXHIBIT WAS PREPARED FOR INFORMATION ONLY AND THE ENGINEER PREPARING THESE PLANS WILL NOT BE RESPONSIBLE FOR UNAUTHORIZED USE OF THEM.SHEETOF11NORTH19 OLD TOWN SQUARE #238 | FORT COLLINS, CO 80524 | (970) 530-4044 | www.unitedcivil.comUNITED CIVILDesign GroupPROPOSED MAJOR CONTOURPROPOSED MINOR CONTOUR BASIN BOUNDARYLEGENDBIORETENTION TREATMENTUNDERGROUND CHAMBERSTREATMENTEXTENDED DETENTIONTREATMENT
SMOKEY DRIVECOLLEGE AVE (HWY 287)
VENUS AVE DETENTION POND A1BIORETENTIONPOND A2NISSAN DEALERSHIP BUILDINGP
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CREEKA8.02B3.50C4.42D0.45FLOODPLAIN CROSS SECTION #31338100-YEAR FLOOD ELEVATION -4952.20 (NGVD 29)4955.41 (NAVD 88)LANG GULCHNATURALHABITATBUFFER ZONE72' ROWPROPOSEDSTORMPOND A1 OUTLET STRUCTUREPROPOSED STORM SEWER (TYP)UNDERGROUNDWQ & DETENTION(POND C1)REROUTED IRRIGATION LINE(LOUDEN DITCH CO.)72' ROWPOND B1 OUTLET STRUCTUREPOND A1 OUTFALLE2.12BUENO DRIVESKYVIEW SUBDIVISIONZONED RLSILVERTHORN LLCZONED MMNRISING SUNMINOR SUBZONED CGSSTM INVESTMENTS LLCZONED CGREDTAIL PONDS NATURAL AREAZONED POLBNSF RAILWAY
KIA DEALERSHIP BUILDINGEXISTINGBUILDINGROCK OUTCROPPING LIMITSOS13.70CITY OF FORT COLLINSFLOODWAY BOUNDARYCITY OF FORT COLLINSFLOODWAY BOUNDARYEROSION BUFFER LIMITSEXISTING WETLANDSEXISTING WETLANDSFLOODPLAIN CROSS SECT
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FLOODPLAIN CROSS SECTION #2000100-YEAR FLOOD ELEVATION -4983.46 (NGVD 29)4986.67 (NAVD 88)LOT 23LOT 24LOT 25LOT 26LOT 27LOT 28LOT 31LOT 29LOT 32LOT 1LOT 2LOT 30MILKY WAY DRIVEMARS DRIVE
MERCURY DRIVE
#5822
#5828
#5834 #200#206#214#218#201#5836
#5835
#5817 EXISTING#224#230#234#5836
LOT 1BLOCK 1LOT 2BLOCK 1LOT 1BLOCK 2TRACT ATRACT BTRACT CTRACT DFLOODPLAIN CROSS SECTION #31971100-YEAR FLOOD ELEVATION -4954.00 (NGVD 29)4957.21 (NAVD 88)OS25.84FOSSIL CREEK TRAIL CULVERTEXISTING Q100 = 30.7 CFSPROPOSED Q100 = 27.5 CFSWETLANDS RESTORATION AREA0.070 ACRES AT BOTTOM OF PONDBIORETENTIONPOND B2EROSION BUFFER LIMITSFLOODPLAIN CROSS SECTION #32338100-YEAR FLOOD ELEVATION -4957.60 (NGVD 29)4960.81 (NAVD 88)FLOODPLAIN CROSS SECTION #32494100-YEAR FLOOD ELEVATION -4958.60 (NGVD 29)4961.81 (NAVD 88)FLOODPLAIN CROSS SECTION #1145100-YEAR FLOOD ELEVATION -4983.42 (NGVD 29)4986.63 (NAVD 88)FLOODPLAIN CROSS SECTION #2304100-YEAR FLOOD ELEVATION -4983.46 (NGVD 29)4986.67 (NAVD 88)WQ POND C2TREATMENT OPTION 1: WQ POND, CHANNEL,AND TURF REINFORCEMENT MATTING(SEE DRAINAGE REPORT)TREATMENT OPTION 2:PLUNGE POOLS(SEE DRAINAGE REPORT)U210041" = 80'1" = N/ANORTH
1/19/2022 12:26:46 AMC:\UNITED CIVIL DROPBOX\PROJECTS\U21004 - NISSAN DEALERSHIP\CADD\CP\C6.00 - OVERALL DRAINAGE PLAN.DWGC6.00 - OVERALL DRAINAGE PLANKRB JRS
OVERALL DRAINAGE PLAN080'160'SCALE: 1" = 80'40'PREPARED FOR:JOB NUMBERSHEET NUMBERSHEETSOFDATE SUBMITTED:VERTICAL:HORIZONTAL:SCALEP
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The engineer preparing these plans will not be responsible for, or liable for, unauthorized
changes to or uses of these plans. All changes to the plans must be in writing and must
be approved by the preparer of these plans.
NO.BY DATE
CAUTIONREVISIONS:CIVIL ENGINEERING & CONSULTINGUNITED CIVILDesign Group19 OLD TOWN SQUARE #238FORT COLLINS, CO 80524(970) 530-4044www.unitedcivil.comTCC CORPORATION
FORT COLLINS NISSAN-KIA
1/19/2022U21004 PROPOSED MAJOR CONTOURPROPOSED MINOR CONTOURLEGENDEXISTING MAJOR CONTOUREXISTING MINOR CONTOUREXISTING PROPERTY BOUNDARYRIGHT OF WAYXX.XXBASIN DESIGNATIONBASIN AREA (ACRE)PROPOSED BASINPROPOSED BASIN LINE1.REFER TO SHEETS C6.01-C6.02 FOR DETAILED DRAINAGE PLANS.NOTES1.THE DEVELOPER SHALL OBTAIN A FLOODPLAIN USE PERMIT FROMTHE CITY OF FORT COLLINS AND PAY ALL APPLICABLEFLOODPLAIN USE PERMIT FEES PRIOR TO COMMENCING ANYCONSTRUCTION ACTIVITY (BUILDING OF STRUCTURES, GRADING,FILL, DETENTION PONDS, BIKE PATHS, PARKING LOTS, UTILITIES,LANDSCAPED AREAS, FLOOD CONTROL CHANNELS, ETC.) WITHINTHE FOSSIL CREEK FLOODPLAIN/FLOODWAY AND EROSIONBUFFER LIMITS. ALL ACTIVITIES WITHIN THE FLOODPLAIN ANDEROSION BUFFER ARE SUBJECT TO THE REQUIREMENTS OFCHAPTER 10 OF THE FORT COLLINS MUNICIPAL CODE.2.CONSTRUCTION OF NEW STRUCTURES, HARD SURFACE PATHS,WALKWAYS, DRIVEWAYS, WALLS, AND PARKING AREAS ISPROHIBITED IN THE FLOODWAY UNLESS NO-RISE CONDITIONS AREMET, PER SECTION 10-45 OF CITY CODE. ANY CONSTRUCTIONACTIVITIES IN THE REGULATORY FLOODWAY MUST ALSO INCLUDEA NO-RISE CERTIFICATION PREPARED BY A PROFESSIONALENGINEER LICENSED IN COLORADO.3.STORAGE OF EQUIPMENT AND MATERIALS (TEMPORARY ORPERMANENT) IS NOT ALLOWED IN THE FLOODWAY.4.ANY ITEMS IN THE FLOODWAY THAT CAN FLOAT SUCH AS BIKERACKS, PICNIC TABLES, ETC. MUST BE ANCHORED.5.A STABILITY STUDY MAY BE REQUIRED FOR WORK WITHIN THEEROSION BUFFER.6.THE NATURAL HABITAT BUFFER ZONE IS INTENDED TO BEMAINTAINED IN A NATIVE LANDSCAPE. PLEASE SEE SECTION 3.4.1OF THE LAND USE CODE FOR ALLOWABLE USES WITHIN THENATURAL HABITAT BUFFER ZONE.FLOODPLAIN NOTESC6.002624
COLLEGE AVE (HWY 287)FOSSIL
CREEK
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CITY OF FORT COLLINSFLOODWAY BOUNDARYEROSION BUFFER LIMITSEXISTING WETLANDSPROPERTY BOUNDARYV
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EA50.430.951.00A130.450.951.00B40.380.891.00B60.220.680.85B70.300.790.98C10.610.841.00C20.830.660.82C32.730.891.00C40.380.951.00E12.120.790.99FLOODPLAIN CROSS SECTION #31338100-YEAR FLOOD ELEVATION -4952.20 (NGVD 29)4955.41 (NAVD 88)FLOODPLAIN CROSS SECTION #31971100-YEAR FLOOD ELEVATION -4954.00 (NGVD 29)4957.21 (NAVD 88)TRACT CTRACT DLOT 1BLOCK 2LOT 1BLOCK 1OS25.840.250.31FOSSIL CREEK TRAIL CULVERTEXISTING Q100 = 30.7 CFSPROPOSED Q100 = 27.5 CFSCCUNDERGROUNDPOND C2WQ POND C2TREATMENT OPTION 1: WQ POND, CHANNEL,AND TURF REINFORCEMENT MATTING(SEE DRAINAGE REPORT)TREATMENT OPTION 2: PLUNGE POOLS(SEE DRAINAGE REPORT)FOSSIL CREEK
1" = 40'1" = N/A1/17/2022 8:31:58 PMC:\UNITED CIVIL DROPBOX\PROJECTS\U21004 - NISSAN DEALERSHIP\CADD\CP\C6.0X - DETAILED DRAINAGE PLANS.DWGC6.0X - DETAILED DRAINAGE PLANS####C6.0126DETAILED DRAINAGE PLAN - NORTH
PREPARED FOR:JOB NUMBERSHEET NUMBERSHEETSOFDATE SUBMITTED:VERTICAL:HORIZONTAL:SCALEPRELIMINARYPLANSNOT FOR CONSTRUCTIONPROJ. MGR:DRAWING NAME:PATH:DESIGNER:DATE:TIME:
The engineer preparing these plans will not be responsible for, or liable for, unauthorized
changes to or uses of these plans. All changes to the plans must be in writing and must
be approved by the preparer of these plans.
NO.BY DATE
CAUTIONREVISIONS:CIVIL ENGINEERING & CONSULTINGUNITED CIVILDesign Group19 OLD TOWN SQUARE #238FORT COLLINS, CO 80524(970) 530-4044www.unitedcivil.comTCC CORPORATION
FORT COLLINS NISSAN-KIA
1/19/2022U2100425X.XXX.XXXX.XXBASIN DESIGNATIONBASIN AREA (ACRE)5 - YR RUNOFF COEFF.100 - YR RUNOFF COEFF.DESIGN POINTFLOW DIRECTIONDPD1LEGENDCOLLEGE AVE (HWY 287)VENUS AVENUEMILKY WAY DRIVENKEYMAP1.REFER TO SHEET C6.00 FOR THE OVERALL DRAINAGE PLAN.NOTES1.THE DEVELOPER SHALL OBTAIN A FLOODPLAIN USE PERMIT FROMTHE CITY OF FORT COLLINS AND PAY ALL APPLICABLEFLOODPLAIN USE PERMIT FEES PRIOR TO COMMENCING ANYCONSTRUCTION ACTIVITY (BUILDING OF STRUCTURES, GRADING,FILL, DETENTION PONDS, BIKE PATHS, PARKING LOTS, UTILITIES,LANDSCAPED AREAS, FLOOD CONTROL CHANNELS, ETC.) WITHINTHE FOSSIL CREEK FLOODPLAIN/FLOODWAY AND EROSIONBUFFER LIMITS. ALL ACTIVITIES WITHIN THE FLOODPLAIN ANDEROSION BUFFER ARE SUBJECT TO THE REQUIREMENTS OFCHAPTER 10 OF THE FORT COLLINS MUNICIPAL CODE.2.CONSTRUCTION OF NEW STRUCTURES, HARD SURFACE PATHS,WALKWAYS, DRIVEWAYS, WALLS, AND PARKING AREAS ISPROHIBITED IN THE FLOODWAY UNLESS NO-RISE CONDITIONS AREMET, PER SECTION 10-45 OF CITY CODE. ANY CONSTRUCTIONACTIVITIES IN THE REGULATORY FLOODWAY MUST ALSO INCLUDEA NO-RISE CERTIFICATION PREPARED BY A PROFESSIONALENGINEER LICENSED IN COLORADO.3.STORAGE OF EQUIPMENT AND MATERIALS (TEMPORARY ORPERMANENT) IS NOT ALLOWED IN THE FLOODWAY.4.ANY ITEMS IN THE FLOODWAY THAT CAN FLOAT SUCH AS BIKERACKS, PICNIC TABLES, ETC. MUST BE ANCHORED.5.A STABILITY STUDY MAY BE REQUIRED FOR WORK WITHIN THEEROSION BUFFER.6.THE NATURAL HABITAT BUFFER ZONE IS INTENDED TO BEMAINTAINED IN A NATIVE LANDSCAPE. PLEASE SEE SECTION 3.4.1OF THE LAND USE CODE FOR ALLOWABLE USES WITHIN THENATURAL HABITAT BUFFER ZONE.FLOODPLAIN NOTES
BIORETENTION POND A2DETENTION POND A1BIORETENTIONVENUS AVENUECOLLEGE AVE (HWY 287)MILKY WAY DRIVEMARS DRIVE
#5822
EXISTING
#5828
EXISTING
#5834
EXISTING #200EXISTING#206EXISTING#214EXISTING#218EXISTING#201EXISTING#5836EXISTING#5835EXISTING
#5817EXISTING#224EXISTING#230EXISTINGLOT 1RISING SONMANORSUBDIVISIONA10.950.250.31A20.570.250.31A30.490.760.95A40.560.690.86A50.430.951.00A60.200.710.88A70.450.760.95A80.090.951.00A90.120.951.00A100.550.790.98A110.040.951.00A120.980.770.97A130.450.951.00A140.630.801.00A150.620.921.00A160.770.951.00B10.460.250.31B31.100.740.93B50.540.851.00B60.220.680.85B70.300.790.98OS13.700.640.80D10.490.720.90POND B2LOT 2BLOCK 1TRACT ATRACT BLOT 1BLOCK 2DETENTIONPOND B1B20.480.250.311" = 40'1" = N/A1/17/2022 8:35:15 PMC:\UNITED CIVIL DROPBOX\PROJECTS\U21004 - NISSAN DEALERSHIP\CADD\CP\C6.0X - DETAILED DRAINAGE PLANS.DWGC6.0X - DETAILED DRAINAGE PLANS####C6.0226DETAILED DRAINAGE PLAN - SOUTH
PREPARED FOR:JOB NUMBERSHEET NUMBERSHEETSOFDATE SUBMITTED:VERTICAL:HORIZONTAL:SCALEP
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The engineer preparing these plans will not be responsible for, or liable for, unauthorized
changes to or uses of these plans. All changes to the plans must be in writing and must
be approved by the preparer of these plans.
NO.BY DATE
CAUTIONREVISIONS:CIVIL ENGINEERING & CONSULTINGUNITED CIVILDesign Group19 OLD TOWN SQUARE #238FORT COLLINS, CO 80524(970) 530-4044www.unitedcivil.comTCC CORPORATION
FORT COLLINS NISSAN-KIA
1/19/2022U2100426X.XXX.XXXX.XXBASIN DESIGNATIONBASIN AREA (ACRE)5 - YR RUNOFF COEFF.100 - YR RUNOFF COEFF.DESIGN POINTFLOW DIRECTIONDPD1LEGENDCOLLEGE AVE (HWY 287)VENUS AVENUEMILKY WAY DRIVENKEYMAP1.REFER TO SHEET C6.00 FOR THE OVERALL DRAINAGE PLAN.NOTES1.THE DEVELOPER SHALL OBTAIN A FLOODPLAIN USE PERMIT FROMTHE CITY OF FORT COLLINS AND PAY ALL APPLICABLEFLOODPLAIN USE PERMIT FEES PRIOR TO COMMENCING ANYCONSTRUCTION ACTIVITY (BUILDING OF STRUCTURES, GRADING,FILL, DETENTION PONDS, BIKE PATHS, PARKING LOTS, UTILITIES,LANDSCAPED AREAS, FLOOD CONTROL CHANNELS, ETC.) WITHINTHE FOSSIL CREEK FLOODPLAIN/FLOODWAY AND EROSIONBUFFER LIMITS. ALL ACTIVITIES WITHIN THE FLOODPLAIN ANDEROSION BUFFER ARE SUBJECT TO THE REQUIREMENTS OFCHAPTER 10 OF THE FORT COLLINS MUNICIPAL CODE.2.CONSTRUCTION OF NEW STRUCTURES, HARD SURFACE PATHS,WALKWAYS, DRIVEWAYS, WALLS, AND PARKING AREAS ISPROHIBITED IN THE FLOODWAY UNLESS NO-RISE CONDITIONS AREMET, PER SECTION 10-45 OF CITY CODE. ANY CONSTRUCTIONACTIVITIES IN THE REGULATORY FLOODWAY MUST ALSO INCLUDEA NO-RISE CERTIFICATION PREPARED BY A PROFESSIONALENGINEER LICENSED IN COLORADO.3.STORAGE OF EQUIPMENT AND MATERIALS (TEMPORARY ORPERMANENT) IS NOT ALLOWED IN THE FLOODWAY.4.ANY ITEMS IN THE FLOODWAY THAT CAN FLOAT SUCH AS BIKERACKS, PICNIC TABLES, ETC. MUST BE ANCHORED.5.A STABILITY STUDY MAY BE REQUIRED FOR WORK WITHIN THEEROSION BUFFER.6.THE NATURAL HABITAT BUFFER ZONE IS INTENDED TO BEMAINTAINED IN A NATIVE LANDSCAPE. PLEASE SEE SECTION 3.4.1OF THE LAND USE CODE FOR ALLOWABLE USES WITHIN THENATURAL HABITAT BUFFER ZONE.FLOODPLAIN NOTES