HomeMy WebLinkAboutTHE LANDING AT LEMAY MULTIFAMILY AND MIXED-USE - PDP230004 - SUBMITTAL DOCUMENTS - ROUND 3 - DRAINAGE REPORT
PRELIMINARY
DRAINAGE REPORT
LANDING AT LEMAY
FORT COLLINS, CO
July 18, 2023
Owner: TJB Partners, Inc.
Planner: Ripley Design, Inc.
970.224.5828
Design Engineer: Avant Civil Group
970.286.7995
AVANTCIVILGROUP.COM
FORT COLLINS, CO 80525
ii
July 18, 2023
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
RE: PRELIMINARY DRAINAGE REPORT FOR THE LANDING AT LEMAY
Dear Staff:
Avant Civil Group is pleased to submit this Preliminary Drainage Report for The Landing at Lemay for your review. This
report accompanies the PDP submittal for the project.
This report has been prepared in accordance with the Fort Collins Stormwater Criteria Manual (FCSCM) and serves to
document the stormwater impacts associated with the proposed Landing at Lemay project. We understand that review
by the City of Fort Collins is to ensure general compliance with FCSCM drainage criteria.
If you should have any questions as you review this report, please feel free to contact us.
Sincerely,
AVANT CIVIL GROUP
Austin Snow, PE
Project Engineer
iii
Engineer Certification:
“I hereby attest that this report for the Preliminary drainage design of The Landing at Lemay was prepared by me, or
under my direct supervision, in accordance with the provisions of the FCSCM. I understand that the City of Fort Collins
does not and shall not assume liability for drainage facilities designed by others.”
Austin Snow, PE
State of Colorado License No. 53340
iv
Table of Contents
General Location and Description .................................................................................................................................................................. 1
Location................................................................................................................................................................................................................ 1
Description of Property .................................................................................................................................................................................. 1
Existing Conditions ...................................................................................................................................................................................... 2
Drainage Basins ..................................................................................................................................................................................................... 2
Major Basin Description ................................................................................................................................................................................. 2
Sub-Basin Description .................................................................................................................................................................................... 2
Drainage Design Criteria .................................................................................................................................................................................... 3
Optional Provisions.......................................................................................................................................................................................... 3
Stormwater Management Strategy ........................................................................................................................................................... 3
Development Criteria Reference and Constraints ............................................................................................................................... 3
Hydrologic Design Criteria ........................................................................................................................................................................... 4
Hydraulic Design Criteria............................................................................................................................................................................... 4
Conformance with Water Quality Treatment Criteria ........................................................................................................................ 4
Conformance with Low Impact Development (LID) Requirements .............................................................................................. 4
Sizing of LID and WQ Facilities ................................................................................................................................................................... 4
Rain Gardens ................................................................................................................................................................................................. 4
Stormtech Chambers .................................................................................................................................................................................. 5
Water Quality ................................................................................................................................................................................................ 5
Drainage Facility Design ................................................................................................................................................................................ 5
General Proposed Concept(s) ................................................................................................................................................................. 5
Sub-Basin Descriptions .............................................................................................................................................................................. 6
Detention Details .............................................................................................................................................................................................. 7
Conclusions ............................................................................................................................................................................................................. 8
v
Compliance With Standards ......................................................................................................................................................................... 8
Drainage Concepts .......................................................................................................................................................................................... 8
References................................................................................................................................................................................................................ 8
APPENDIX A – HYDROLOGIC CALCULATIONS ................................................................................................................................................. A
APPENDIX B – HYDRAULIC CALCULATIONS .................................................................................................................................................... B
APPENDIX C – LID AND WATER QUALITY ...................................................................................................................................................... C
APPENDIX D – USDA SOILS REPORT .............................................................................................................................................................. D
APPENDIX E – FEMA FIRMETTE ........................................................................................................................................................................ E
APPENDIX F – DRAINAGE EXHIBIT .................................................................................................................................................................... F
1
General Location and Description
Location
The Landing at Lemay project site is located in a tract of land located in the Northwest Quarter of Section
7, Township 7 North, Range 68 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer,
State of Colorado.
Figure 1 - Site Location
The project site (see Figure 1) is bordered to the north by open space and E Vine Drive, to the east by
Cordova Road and industrial buildings, to the south by The Cottages of Fort Collins, and to the west by
South Lemay Avenue. There is existing storm drainage infrastructure that was constructed with the Cottage
of Fort Collins.
Description of Property
The Landing at Lemay is comprised of 28.19 acres. The site is currently comprised of undeveloped open
space. The project site resides in the City of Fort Collins Dry Creek Master Drainage Basin. The detention
requirements and release rates of the subject area were considered in the design of the detention ponds for
2
The Landing at Lemay and have been factored into the LID requirements, which are described in further
detail throughout this report.
The proposed development will consist of ten (10) multi-family residential buildings containing 336 units
with on-site and street parking, and a clubhouse. The proposed land use is multi-family, which is a permitted
land use for this area.
ExisƟng CondiƟons
The existing on-site runoff generally drains from the Northwest to the Southeast across flat grades
(e.g., 0.50% - 2.00%) towards the intersection of Duff Drive and Cordova Road. According to the
United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Soil
Survey website: (http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx), the site consists
primarily of Caruso Clay Loam (Hydrologic Soil Group D).
Groundwater was found to be present approximately 7-10 feet below existing ground elevations.
Proposed site development will maintain a minimum of 2 feet between existing groundwater levels
and proposed ground levels. The highest amount of cut on the site occurs where the proposed
detention ponds will be placed.
Table 1 - Groundwater Elevations vs. Proposed Elevations
Pond 1 Pond 2
Existing Ground Elevation 4940.80 4941.15
Groundwater Elevation 4932.80 4932.15
Proposed Elevation 4936.40 4935.00
Floodplain
The entirety of the site is located in a FEMA moderate-risk floodplain zone. There are no
special floodplain considerations required regarding finished floor elevations of building
footprints. A floodplain use permit will be required prior to construction for any work in the
floodplain.
Drainage Basins
Major Basin Description
The project area of The Landing at Lemay is located within the City of Fort Collins Dry Creek Drainage Basin.
Detention requirements for this basin are to detain the difference between the 100-yr developed inflow rate
and the historic 2-year release rate. However, outflow from this property is limited by release rates
determined for the Dry Creek Basin which are 0.2 cfs/acre.
Sub-Basin Description
The outfall for the project site is at the south end of the project site to existing storm infrastructure in Duff
3
Drive. The existing subject site can be defined with 13 distinct drainage basins (see DR1 in the provided map
pocket). The existing site runoff generally drains from Northwest to Southeast towards proposed Cordova
Road. The project area receives offsite runoff from the northeast. This is accounted for in the drainage design
for this project site.
Drainage Design Criteria
Optional Provisions
There are no optional provisions outside of the FCSCM proposed with Landing at Lemay.
Stormwater Management Strategy
The overall stormwater management strategy employed with The Landing at Lemay utilizes the “Four Step
Process” to minimize adverse impacts of urbanization on receiving waters. The following is a description of
how the proposed development has incorporated each step.
Step 1 – Employ Runoff Reduction Practices. The first consideration taken in trying to reduce the stormwater
impacts of this development is the site selection itself. By choosing an already developed site with public
storm sewer currently in place, the burden is significantly less than developing a vacant parcel absent of any
infrastructure.
The Landing at Lemay aims to reduce runoff peaks, volumes and pollutant loads from frequently occurring
storm events (i.e., water quality (i.e., 80th percentile) and 2-year storm events) by implementing Low Impact
Development (LID) strategies. Wherever practical, runoff will be routed across landscaped areas or through
a rain garden or water quality pond. These LID practices reduce the overall amount of impervious area, while
at the same time Minimizing Directly Connected Impervious Areas (MDCIA). The combined LID/MDCIA
techniques will be implemented, where practical, throughout the development, thereby slowing runoff and
increasing opportunities for infiltration.
Step 2 – Implement BMPs that Provide a Water Quality Capture Volume (WQCV) with Slow Release. The
efforts taken in Step 1 will help to minimize excess runoff from frequently occurring storm events; however,
urban development of this intensity will still have stormwater runoff leaving the site. The primary water
quality treatment will occur between several rain gardens between major parking areas of the property and
the existing detention ponds installed for Impala Redevelopment.
Step 3 – Stabilize Drainageways. While not directly applicable to this site, the project will pay one-time
stormwater development fees as well as ongoing monthly stormwater utility fees, both of which help achieve
citywide drainageway stability.
Step 4 – Implement Site Specific and Other Source Control BMPs. This step typically applies to industrial and
commercial developments.
Development Criteria Reference and Constraints
The subject property is not part of an overall development plan. The project area is constrained to the west
4
by N Lemay Avenue, to the north by undeveloped open space, to the east by industrial buildings, and to
south by The Cottages of Fort Collins.
Hydrologic Design Criteria
The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in Figure 3.4-1 of the
FCSCM, serve as the source for all hydrologic computations associated with The Landing at Lemay project.
Tabulated data contained in Table 3.4-1 has been utilized for Rational Method runoff calculations.
The Rational Method has been used to estimate peak developed stormwater runoff from drainage basins
within the developed site for the 2-year, 10-year, and 100-year design storms. Peak runoff discharges
determined using this methodology will be used to check the street capacities, inlets, swales, and storm
drain lines at final design.
Two separate design storms have been utilized to address distinct drainage scenarios. The first event
analyzed is the “Minor,” or “Initial” Storm, which has a 2-year recurrence interval. The second event
considered is the “Major Storm,” which has a 100-year recurrence interval.
Hydraulic Design Criteria
The drainage facilities proposed with The Landing at Lemay project are designed in accordance with criteria
outlined in the FCSCM. As stated above, the subject property is located within a FEMA moderate-risk
floodplain, but is not located within a City regulated floodplain. There are no formal modifications outside
of the FCSCM proposed with Landing at Lemay.
Conformance with Water Quality Treatment Criteria
City Code requires that 100% of runoff from new or modified areas in a project site shall receive some sort
of water quality treatment, of which a majority of the site is receiving. Each proposed drainage basin includes
a rain garden to treat runoff for water quality.
All onsite basins will receive water quality treatment either via a rain garden or detention pond. There are
also two offsite basins that flow directly onsite that will also be treated for water quality. Both proposed
detention ponds will be equipped with outlet structures and appropriately sized water quality structures to
treat runoff from basins that flow directly into the ponds.
Conformance with Low Impact Development (LID) Requirements
The project site will conform with the requirement to treat a minimum of 75% of new or modified impervious
area using a LID technique. The proposed project site will treat approximately 88% of modified area with
LID. 5 rain gardens are responsible for treating a majority of the impervious area on the site.
Sizing of LID and WQ Facilities
Rain Gardens
The rain gardens were sized by first determining the required water quality capture volume (WQCV) for
Sub-Basins A-D and M. Once the WQCV was identified, the rain garden area was sized for its respective
5
WQCV. The rain gardens will be constructed with a biomedia filter and underdrain. An overflow inlet
and spillway will be provided to provide safe conveyance of storms greater than the WQCV.
Stormtech Chambers
Stormtech chambers were used where rain gardens were not feasible due to available space – Sub-Basin
E in this instance. The chambers were sized by first determining the required WQCV for the basin. Once
the WQCV was identified, the chamber area was sized for its respective WQCV. The chambers will be
constructed with stone beds/backfill and underdrain. Overflows will spill directly into the downstream
detention pond.
Table 2 - LID Summary
LID Summary per LID Structure
LID ID Area Weighted %
Impervious
Subbasin
ID
Treatment
Type
Volume
per UD-
BMP (ft3)
Impervious
Area (ft2)
Sq. Ft. Acres
Rain Garden A 98,840 2.27 62% A
Rain
Garden 1,653 61,281
Rain Garden B 66,289 1.52 78% B
Rain
Garden 1,361 51,705
Rain Garden C 160,336 3.68 50% C
Rain
Garden 2,209 80,168
Rain Garden D 68,833 1.58 66% D
Rain
Garden 1,183 45,430
Chambers E 171,002 3.93 61% E Chambers 2,714 104,311
Rain Garden M 119,169 2.74 74% M
Rain
Garden 2,338 88,185
Total 684,469 15.71 431,080
Water Quality
WQCV was calculated for each pond using UDFCD equations. The purpose of these ponds treating for
water quality is to ensure that basins that do not pass through ran gardens, are receiving the proper
water quality treatment to conform to City of Fort Collins water quality criteria.
Drainage Facility Design
General Proposed Concept(s)
The main objective of The Landing at Lemay drainage design is to maintain existing drainage patterns,
while not adversely impacting adjacent properties. All storm drains on the site have been designed to
convey 100-yr flows.
6
Sub-Basin DescripƟons
Drainage for the project site has been analyzed using 16 drainage sub-basins, designated as sub-basins
A-N and OS1. Sub-basins A-N are on-site basins. OS1 is an off-site basins whose flows are collected in
Detention Pond 2.
Sub-Basin A
Sub-Basin A is composed of multi-family residential rooftops, paved roadways, and a clubhouse
and pool. Flows from this basin travel via overland flow and curb and gutter flow to Rain Garden
A where they are treated for water quality.
Sub-Basin B
Sub-Basin B contains multi-family residential rooftops, garages, paved roadways, and a dog park.
These flows travel via overland flow and curb and gutter flow to Rain Garden B where they are
treated for water quality. From here, flows are routed to Detention Pond 1.
Sub-Basin C
Sub-Basin C is composed of multi-family residential rooftops, paved roadways and parking lots,
Rain Garden C and Detention Pond 2. Runoff travels via overland flow and curb and gutter to Rain
Garden C, which treats these flows for water quality. Runoff will then be routed to Detention Pond
2 and then will be released via proposed outlet structure to existing storm drain offsite.
Sub-Basin D
Sub-Basin D consists of multi-family residential rooftops, paved roadways, parking, open space,
and Rain Garden D. Runoff travels via overland flow, curb and gutter, and storm pipe to Rain
Garden D where it is treated for water quality. Rain Garden D then releases to Detention Pond 2.
Sub-Basin E
Sub-Basin E contains multi-family residential rooftops, garages, paved roadways and parking, Rain
Garden E, and Detention Pond 1. Flows from this basin travel via overland flow, curb and gutter
northeast towards a curb cut that conveys flows to Rain Garden E. After being treated for water
quality, these flows continue into Detention Pond 1 which outfalls into Detention Pond 2 (ponds
in series), then to existing storm drain infrastructure offsite.
Sub-Basin F-K
Sub-Basins F-K are composed of a paved roadway on the southeast side of the proposed
multifamily development. Sub-basins F and G are not treated for water quality via a rain garden,
but are directed into Detention Pond 2, where they will be treated for water quality before they
are released offsite. Sub-basins H and I are captured and routed to Rain Garden C for water quality
treatment before continuing to Detention Pond 2. Sub-basins J and K are captured and routed
directly to Detention Pond 1 where they will be treated for water quality before they are routed
offsite.
7
Sub-Basin L
Sub-Basin L contains multi-family residential rooftops and open space. Flows from this basin travel
via overland flow into area inlets, where they are conveyed to Detention Pond 2 via storm drains.
Sub-Basin M
Sub-Basin M contains multi-family residential, garages, paved roadways and parking, and Rain
Garden M. Flows from this basin travel via overland flow and curb and gutter to the center of the
site where a curb cut conveys flows to Rain Garden E. After being treated for water quality, these
flows continue into Detention Pond 2 which outfalls to existing storm drain infrastructure offsite.
Sub-Basin N
Sub-Basin N contains open space and walkways. Flows from this basin travel via overland flow
and a swale/concrete pan south towards an inlet that conveys flows via storm drain to Detention
Pond 2.
Sub-Basin OS1
Sub-Basin OS1 is composed of open space to the northwest of the proposed project site. The
natural landscape of this basin directs flow onto the project site and for this reason, they will be
routed through the site in a proposed swale with concrete pan. These flows are then captured in
a storm pipe and directed to Detention Pond 2.
A full-size copy of the Drainage Exhibit can be found in Appendix F at the end of this report.
Detention Details
There are 2 proposed detention ponds on the project site that will detain up to the 100-year storm event
and release at or below the allowed historic release for the Dry Creek Basin. See Table 2 for detention
summary.
Table 3 - Detention Summary
POND SUMMARY TABLE
Pond ID
Tributary
Area
(Ac)1
Weighted %
Imperviousness
(%)
Extended
Detention
WQCV (Cu. Ft.)2
100-Yr.
Detention
Vol. (Ac-Ft)
100-Yr.
Detention
WSEL(Ft)
Peak
Release
(cfs)3
Pond 1 6.29 67 Provided in Pond
2 1.52 4942.20 1.20
Pond 2 12.91 59 6,231 2.94 4941.60 2.40
Notes:
1. Tributary area shown does not include off-site basin(s)
2. WQCV calculated minus RG/Chamber volume; will be provded in Pond 2
3. Overall site release rate of 3.6 cfs divided between Ponds 1 and 2
8
Detention Ponds 1 and 2 will be constructed in series; Pond 1 will capture flows from sub-basins B, E, J, and
K. Pond 2 will capture flows from sub-basins A, C, D, F, G, H, I, L, M, N, and OS1. The site has a previously-
established allowed release rate of 3.6 cfs; Pond 1 will release at 1.2 cfs, and Pond 2 will release at 2.4 cfs.
All required water quality volume (after accounting for LID) will be provided in Pond 2. The Pond 2 outfall
into existing storm infrastructure will feature a second spill point/inlet set at the Pond 1 100-yr. WSEL, which
is higher than the Pond 2 100-yr WSEL.
LID treatment is being provided within rain gardens and underground chambers. These treat approximately
84% of the modified site impervious runoff, which is more than the required 75% LID treatment. Please see
the LID exhibit and calculations in Appendix C.
The detention allowable release rate is based on the allowed release rate from the Dry Creek Basin, which is
0.2 cfs/acre. Stormwater facility Standard Operations Procedures (SOP) will be provided by the City of Fort
Collins in the Development Agreement.
Final Design details and construction documentation will be provided to the City of Fort Collins for review
prior to Final Development Plan approval.
Conclusions
Compliance With Standards
The drainage design proposed with The Landing at Lemay complies with the City of Fort Collins Master
Drainage Plan for the Canal Importation Basin. The drainage plan and stormwater management measures
proposed with The Landing at Lemay project are compliant with all applicable State and Federal regulations
governing stormwater discharge.
Drainage Concepts
The drainage plan and stormwater management measures proposed with The Landing at Lemay project are
compliant with all applicable regulations governing stormwater discharge. The Landing at Lemay will not
impact the Master Drainage Plan recommendations for the Fort Collins Dry Creek Major Drainage Basin.
References
1. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No.
159, 2018, and referenced in Section 26-500 of the City of Fort Collins Municipal Code.
2. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service,
United States Department of Agriculture.
3. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District,
Wright- McLaughlin Engineers, Denver, Colorado, Revised April 2008.
A
APPENDIX A – HYDROLOGIC CALCULATIONS
B
APPENDIX B – HYDRAULIC CALCULATIONS
*CERTAIN CALCULATIONS, INCLUDING STORM PIPE, INLET, AND STREET CAPACITIES, HAVE BEEN
OMITTED FROM THIS SECTION AND WILL BE APPENDED TO THIS REPORT AT FINAL DESIGN.
C
APPENDIX C – LID AND WATER QUALITY
D
APPENDIX D – USDA SOILS REPORT
E
APPENDIX E – FEMA FIRMETTE
1
General Location and Description
Location
The Landing at Lemay project site is located in a tract of land located in the Northwest Quarter of Section
7, Township 7 North, Range 68 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer,
State of Colorado.
Figure 1 - Site Location
The project site (see Figure 1) is bordered to the north by open space and E Vine Drive, to the east by
Cordova Road and industrial buildings, to the south by The Cottages of Fort Collins, and to the west by
South Lemay Avenue. There is existing storm drainage infrastructure that was constructed with the Cottage
of Fort Collins.
Description of Property
The Landing at Lemay is comprised of 28.19 acres. The site is currently comprised of undeveloped open
space. The project site resides in the City of Fort Collins Dry Creek Master Drainage Basin. The detention
requirements and release rates of the subject area were considered in the design of the detention ponds for
2
The Landing at Lemay and have been factored into the LID requirements, which are described in further
detail throughout this report.
The proposed development will consist of ten (10) multi-family residential buildings containing 336 units
with on-site and street parking, and a clubhouse. The proposed land use is multi-family, which is a permitted
land use for this area.
ExisƟng CondiƟons
The existing on-site runoff generally drains from the Northwest to the Southeast across flat grades
(e.g., 0.50% - 2.00%) towards the intersection of Duff Drive and Cordova Road. According to the
United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Soil
Survey website: (http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx), the site consists
primarily of Caruso Clay Loam (Hydrologic Soil Group D).
Groundwater was found to be present approximately 7-10 feet below existing ground elevations.
Proposed site development will maintain a minimum of 2 feet between existing groundwater levels
and proposed ground levels. The highest amount of cut on the site occurs where the proposed
detention ponds will be placed.
Table 1 - Groundwater Elevations vs. Proposed Elevations
Pond 1 Pond 2
Existing Ground Elevation 4940.80 4941.15
Groundwater Elevation 4932.80 4932.15
Proposed Elevation 4936.40 4935.00
Floodplain
The entirety of the site is located in a FEMA moderate-risk floodplain zone. There are no
special floodplain considerations required regarding finished floor elevations of building
footprints. A floodplain use permit will be required prior to construction for any work in the
floodplain.
Drainage Basins
Major Basin Description
The project area of The Landing at Lemay is located within the City of Fort Collins Dry Creek Drainage Basin.
Detention requirements for this basin are to detain the difference between the 100-yr developed inflow rate
and the historic 2-year release rate. However, outflow from this property is limited by release rates
determined for the Dry Creek Basin which are 0.2 cfs/acre.
Sub-Basin Description
The outfall for the project site is at the south end of the project site to existing storm infrastructure in Duff
3
Drive. The existing subject site can be defined with 13 distinct drainage basins (see DR1 in the provided map
pocket). The existing site runoff generally drains from Northwest to Southeast towards proposed Cordova
Road. The project area receives offsite runoff from the northeast. This is accounted for in the drainage design
for this project site.
Drainage Design Criteria
Optional Provisions
There are no optional provisions outside of the FCSCM proposed with Landing at Lemay.
Stormwater Management Strategy
The overall stormwater management strategy employed with The Landing at Lemay utilizes the “Four Step
Process” to minimize adverse impacts of urbanization on receiving waters. The following is a description of
how the proposed development has incorporated each step.
Step 1 – Employ Runoff Reduction Practices. The first consideration taken in trying to reduce the stormwater
impacts of this development is the site selection itself. By choosing an already developed site with public
storm sewer currently in place, the burden is significantly less than developing a vacant parcel absent of any
infrastructure.
The Landing at Lemay aims to reduce runoff peaks, volumes and pollutant loads from frequently occurring
storm events (i.e., water quality (i.e., 80th percentile) and 2-year storm events) by implementing Low Impact
Development (LID) strategies. Wherever practical, runoff will be routed across landscaped areas or through
a rain garden or water quality pond. These LID practices reduce the overall amount of impervious area, while
at the same time Minimizing Directly Connected Impervious Areas (MDCIA). The combined LID/MDCIA
techniques will be implemented, where practical, throughout the development, thereby slowing runoff and
increasing opportunities for infiltration.
Step 2 – Implement BMPs that Provide a Water Quality Capture Volume (WQCV) with Slow Release. The
efforts taken in Step 1 will help to minimize excess runoff from frequently occurring storm events; however,
urban development of this intensity will still have stormwater runoff leaving the site. The primary water
quality treatment will occur between several rain gardens between major parking areas of the property and
the existing detention ponds installed for Impala Redevelopment.
Step 3 – Stabilize Drainageways. While not directly applicable to this site, the project will pay one-time
stormwater development fees as well as ongoing monthly stormwater utility fees, both of which help achieve
citywide drainageway stability.
Step 4 – Implement Site Specific and Other Source Control BMPs. This step typically applies to industrial and
commercial developments.
Development Criteria Reference and Constraints
The subject property is not part of an overall development plan. The project area is constrained to the west
4
by N Lemay Avenue, to the north by undeveloped open space, to the east by industrial buildings, and to
south by The Cottages of Fort Collins.
Hydrologic Design Criteria
The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in Figure 3.4-1 of the
FCSCM, serve as the source for all hydrologic computations associated with The Landing at Lemay project.
Tabulated data contained in Table 3.4-1 has been utilized for Rational Method runoff calculations.
The Rational Method has been used to estimate peak developed stormwater runoff from drainage basins
within the developed site for the 2-year, 10-year, and 100-year design storms. Peak runoff discharges
determined using this methodology will be used to check the street capacities, inlets, swales, and storm
drain lines at final design.
Two separate design storms have been utilized to address distinct drainage scenarios. The first event
analyzed is the “Minor,” or “Initial” Storm, which has a 2-year recurrence interval. The second event
considered is the “Major Storm,” which has a 100-year recurrence interval.
Hydraulic Design Criteria
The drainage facilities proposed with The Landing at Lemay project are designed in accordance with criteria
outlined in the FCSCM. As stated above, the subject property is located within a FEMA moderate-risk
floodplain, but is not located within a City regulated floodplain. There are no formal modifications outside
of the FCSCM proposed with Landing at Lemay.
Conformance with Water Quality Treatment Criteria
City Code requires that 100% of runoff from new or modified areas in a project site shall receive some sort
of water quality treatment, of which a majority of the site is receiving. Each proposed drainage basin includes
a rain garden to treat runoff for water quality.
All onsite basins will receive water quality treatment either via a rain garden or detention pond. There are
also two offsite basins that flow directly onsite that will also be treated for water quality. Both proposed
detention ponds will be equipped with outlet structures and appropriately sized water quality structures to
treat runoff from basins that flow directly into the ponds.
Conformance with Low Impact Development (LID) Requirements
The project site will conform with the requirement to treat a minimum of 75% of new or modified impervious
area using a LID technique. The proposed project site will treat approximately 88% of modified area with
LID. 5 rain gardens are responsible for treating a majority of the impervious area on the site.
Sizing of LID and WQ Facilities
Rain Gardens
The rain gardens were sized by first determining the required water quality capture volume (WQCV) for
Sub-Basins A-D and M. Once the WQCV was identified, the rain garden area was sized for its respective
5
WQCV. The rain gardens will be constructed with a biomedia filter and underdrain. An overflow inlet
and spillway will be provided to provide safe conveyance of storms greater than the WQCV.
Stormtech Chambers
Stormtech chambers were used where rain gardens were not feasible due to available space – Sub-Basin
E in this instance. The chambers were sized by first determining the required WQCV for the basin. Once
the WQCV was identified, the chamber area was sized for its respective WQCV. The chambers will be
constructed with stone beds/backfill and underdrain. Overflows will spill directly into the downstream
detention pond.
Table 2 - LID Summary
LID Summary per LID Structure
LID ID Area Weighted %
Impervious
Subbasin
ID
Treatment
Type
Volume
per UD-
BMP (ft3)
Impervious
Area (ft2)
Sq. Ft. Acres
Rain Garden A 98,840 2.27 62% A
Rain
Garden 1,653 61,281
Rain Garden B 66,289 1.52 78% B
Rain
Garden 1,361 51,705
Rain Garden C 160,336 3.68 50% C
Rain
Garden 2,209 80,168
Rain Garden D 68,833 1.58 66% D
Rain
Garden 1,183 45,430
Chambers E 171,002 3.93 61% E Chambers 2,714 104,311
Rain Garden M 119,169 2.74 74% M
Rain
Garden 2,338 88,185
Total 684,469 15.71 431,080
Water Quality
WQCV was calculated for each pond using UDFCD equations. The purpose of these ponds treating for
water quality is to ensure that basins that do not pass through ran gardens, are receiving the proper
water quality treatment to conform to City of Fort Collins water quality criteria.
Drainage Facility Design
General Proposed Concept(s)
The main objective of The Landing at Lemay drainage design is to maintain existing drainage patterns,
while not adversely impacting adjacent properties. All storm drains on the site have been designed to
convey 100-yr flows.
6
Sub-Basin DescripƟons
Drainage for the project site has been analyzed using 16 drainage sub-basins, designated as sub-basins
A-N and OS1. Sub-basins A-N are on-site basins. OS1 is an off-site basins whose flows are collected in
Detention Pond 2.
Sub-Basin A
Sub-Basin A is composed of multi-family residential rooftops, paved roadways, and a clubhouse
and pool. Flows from this basin travel via overland flow and curb and gutter flow to Rain Garden
A where they are treated for water quality.
Sub-Basin B
Sub-Basin B contains multi-family residential rooftops, garages, paved roadways, and a dog park.
These flows travel via overland flow and curb and gutter flow to Rain Garden B where they are
treated for water quality. From here, flows are routed to Detention Pond 1.
Sub-Basin C
Sub-Basin C is composed of multi-family residential rooftops, paved roadways and parking lots,
Rain Garden C and Detention Pond 2. Runoff travels via overland flow and curb and gutter to Rain
Garden C, which treats these flows for water quality. Runoff will then be routed to Detention Pond
2 and then will be released via proposed outlet structure to existing storm drain offsite.
Sub-Basin D
Sub-Basin D consists of multi-family residential rooftops, paved roadways, parking, open space,
and Rain Garden D. Runoff travels via overland flow, curb and gutter, and storm pipe to Rain
Garden D where it is treated for water quality. Rain Garden D then releases to Detention Pond 2.
Sub-Basin E
Sub-Basin E contains multi-family residential rooftops, garages, paved roadways and parking, Rain
Garden E, and Detention Pond 1. Flows from this basin travel via overland flow, curb and gutter
northeast towards a curb cut that conveys flows to Rain Garden E. After being treated for water
quality, these flows continue into Detention Pond 1 which outfalls into Detention Pond 2 (ponds
in series), then to existing storm drain infrastructure offsite.
Sub-Basin F-K
Sub-Basins F-K are composed of a paved roadway on the southeast side of the proposed
multifamily development. Sub-basins F and G are not treated for water quality via a rain garden,
but are directed into Detention Pond 2, where they will be treated for water quality before they
are released offsite. Sub-basins H and I are captured and routed to Rain Garden C for water quality
treatment before continuing to Detention Pond 2. Sub-basins J and K are captured and routed
directly to Detention Pond 1 where they will be treated for water quality before they are routed
offsite.
7
Sub-Basin L
Sub-Basin L contains multi-family residential rooftops and open space. Flows from this basin travel
via overland flow into area inlets, where they are conveyed to Detention Pond 2 via storm drains.
Sub-Basin M
Sub-Basin M contains multi-family residential, garages, paved roadways and parking, and Rain
Garden M. Flows from this basin travel via overland flow and curb and gutter to the center of the
site where a curb cut conveys flows to Rain Garden E. After being treated for water quality, these
flows continue into Detention Pond 2 which outfalls to existing storm drain infrastructure offsite.
Sub-Basin N
Sub-Basin N contains open space and walkways. Flows from this basin travel via overland flow
and a swale/concrete pan south towards an inlet that conveys flows via storm drain to Detention
Pond 2.
Sub-Basin OS1
Sub-Basin OS1 is composed of open space to the northwest of the proposed project site. The
natural landscape of this basin directs flow onto the project site and for this reason, they will be
routed through the site in a proposed swale with concrete pan. These flows are then captured in
a storm pipe and directed to Detention Pond 2.
A full-size copy of the Drainage Exhibit can be found in Appendix F at the end of this report.
Detention Details
There are 2 proposed detention ponds on the project site that will detain up to the 100-year storm event
and release at or below the allowed historic release for the Dry Creek Basin. See Table 2 for detention
summary.
Table 3 - Detention Summary
POND SUMMARY TABLE
Pond ID
Tributary
Area
(Ac)1
Weighted %
Imperviousness
(%)
Extended
Detention
WQCV (Cu. Ft.)2
100-Yr.
Detention
Vol. (Ac-Ft)
100-Yr.
Detention
WSEL(Ft)
Peak
Release
(cfs)3
Pond 1 6.29 67 Provided in Pond
2 1.52 4942.20 1.20
Pond 2 12.91 59 6,231 2.94 4941.60 2.40
Notes:
1. Tributary area shown does not include off-site basin(s)
2. WQCV calculated minus RG/Chamber volume; will be provded in Pond 2
3. Overall site release rate of 3.6 cfs divided between Ponds 1 and 2
8
Detention Ponds 1 and 2 will be constructed in series; Pond 1 will capture flows from sub-basins B, E, J, and
K. Pond 2 will capture flows from sub-basins A, C, D, F, G, H, I, L, M, N, and OS1. The site has a previously-
established allowed release rate of 3.6 cfs; Pond 1 will release at 1.2 cfs, and Pond 2 will release at 2.4 cfs.
All required water quality volume (after accounting for LID) will be provided in Pond 2. The Pond 2 outfall
into existing storm infrastructure will feature a second spill point/inlet set at the Pond 1 100-yr. WSEL, which
is higher than the Pond 2 100-yr WSEL.
LID treatment is being provided within rain gardens and underground chambers. These treat approximately
84% of the modified site impervious runoff, which is more than the required 75% LID treatment. Please see
the LID exhibit and calculations in Appendix C.
The detention allowable release rate is based on the allowed release rate from the Dry Creek Basin, which is
0.2 cfs/acre. Stormwater facility Standard Operations Procedures (SOP) will be provided by the City of Fort
Collins in the Development Agreement.
Final Design details and construction documentation will be provided to the City of Fort Collins for review
prior to Final Development Plan approval.
Conclusions
Compliance With Standards
The drainage design proposed with The Landing at Lemay complies with the City of Fort Collins Master
Drainage Plan for the Canal Importation Basin. The drainage plan and stormwater management measures
proposed with The Landing at Lemay project are compliant with all applicable State and Federal regulations
governing stormwater discharge.
Drainage Concepts
The drainage plan and stormwater management measures proposed with The Landing at Lemay project are
compliant with all applicable regulations governing stormwater discharge. The Landing at Lemay will not
impact the Master Drainage Plan recommendations for the Fort Collins Dry Creek Major Drainage Basin.
References
1. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No.
159, 2018, and referenced in Section 26-500 of the City of Fort Collins Municipal Code.
2. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service,
United States Department of Agriculture.
3. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District,
Wright- McLaughlin Engineers, Denver, Colorado, Revised April 2008.
A
APPENDIX A – HYDROLOGIC CALCULATIONS
CHARACTER OF SURFACE1: Percentage
Impervious
2-yr Runoff
Coefficient
100-yr Runoff
Coefficient
Developed
Asphalt .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100% 0.95 1.00
Concrete .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100% 0.95 1.00
Rooftop .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………90% 0.95 1.00
Gravel .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40% 0.50 0.63
Pavers .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40% 0.50 0.63
Landscape or Pervious Surface
Playgrounds .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………25% 0.35 0.44
Lawns Clayey Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2% 0.25 0.31
Lawns Sandy Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.15 0.19
Notes:
Basin ID Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Rooftop
(ac)
Area of
Gravel
(ac)
Area of
Pavers
(ac)
Area of
Playgrounds
(ac)
Area of Lawns
(ac)
Composite
% Imperv.
2-year
Composite Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
A 2.269 0.780 0.181 0.485 0.00 0.00 0.00 0.823 62% 0.70 0.88
B 1.522 0.771 0.09 0.359 0.00 0.00 0.00 0.300 78% 0.81 1.00
C 3.681 0.985 0.21 0.662 0.00 0.00 0.00 1.825 50% 0.60 0.75
D 1.580 0.409 0.17 0.504 0.00 0.00 0.00 0.499 66% 0.73 0.91
E 3.926 1.431 0.34 0.644 0.00 0.00 0.00 1.507 61% 0.68 0.85
F 0.120 0.088 0.00 0.000 0.00 0.00 0.00 0.032 74% 0.76 0.95
G 0.151 0.083 0.02 0.000 0.00 0.00 0.00 0.053 66%0.70 0.88
H 0.314 0.268 0.00 0.000 0.00 0.00 0.00 0.047 85% 0.85 1.00
I 0.449 0.329 0.00 0.000 0.00 0.00 0.00 0.120 74% 0.76 0.95
J 0.349 0.222 0.04 0.000 0.00 0.00 0.00 0.085 76% 0.78 0.98
K 0.494 0.359 0.00 0.000 0.00 0.00 0.00 0.135 73% 0.76 0.95
L 0.637 0.000 0.06 0.332 0.00 0.00 0.00 0.244 57% 0.68 0.85
M 2.736 1.116 0.27 0.682 0.00 0.00 0.00 0.670 74% 0.78 0.98
N 0.967 0.029 0.08 0.000 0.861 13% 0.33 0.41
OS1 0.906 0.000 0.00 0.000 0.00 0.00 0.00 0.906 2% 0.25 0.31
Detention Pond 1 (B, E, J, K)6.291 2.782 0.478 1.003 0.000 0.000 0.000 2.028 67%0.72 0.90
Detention Pond 2 (A, C, D, F, G, H, I, L,
M, N)12.905 4.086 0.980 2.665 0.000 0.000 0.000 5.173 59% 0.67 0.84
DEVELOPED BASIN % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
2) Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Chapter 3. Table 3.2-1 and 3.2-2
1) Percentage impervious taken from the Fort Collins Stormwater Criteria Manual, Chapter 5, Table 4.1-2 and Table 4.1-3
Combined Basins
Overland Flow, Time of Concentration:
Channelized Flow, Time of Concentration:
UPDATE
Total Time of Concentration :
T c is the lesser of the values of Tc calculated using T c = T i + T t
C2
Length,
L
(ft)
Ti2
Length,
L
(ft)
Roughness
Coefficient
Velocity,
V
(ft/s)
Tt
(min)Tc (Eq. 3.3-5) Tc2 = Ti +Tt Tc100 = Ti +Tt Tc2 Tc100
a 0.70 25 2.8 402 0.015 2.53 2.7 12.4 5.4 4.2 5.4 5.0
b 0.81 192 9.2 351 0.015 2.34 2.5 13.0 11.7 5.7 11.7 5.7
c 0.60 26 3.8 286 0.015 1.98 2.4 11.7 6.2 5.1 6.2 5.1
d 0.73 25 2.7 75 0.015 3.46 0.4 10.6 3.1 1.7 5.0 5.0
e 0.68 64 4.3 149 0.015 3.74 0.7 11.2 4.9 3.2 5.0 5.0
f 0.76 25 2.4 107 0.015 1.97 0.9 10.7 3.3 2.0 5.0 5.0
g 0.70 26 2.8 77 0.038 0.72 1.8 10.6 4.6 3.4 5.0 5.0
h 0.85 26 1.9 196 0.015 2.07 1.6 11.2 3.5 2.4 5.0 5.0
i 0.76 26 2.4 203 0.015 1.81 1.9 11.3 4.2 2.9 5.0 5.0
j 0.78 26 2.3 198 0.015 1.87 1.8 11.2 4.0 2.6 5.0 5.0
k 0.76 26 2.4 201 0.015 1.83 1.8 11.3 4.3 2.9 5.0 5.0
l 0.68 26 2.8 0.015 N/A N/A 10.1 2.8 1.7 5.0 5.0
m 0.78 25 2.3 474 0.015 4.88 1.6 12.8 3.9 3.0 5.0 5.0
n 0.33 38 7.1 824 0.015 3.70 3.7 14.8 10.8 10.0 10.8 10.0
DEVELOPED DIRECT TIME OF CONCENTRATION
Channelized Flow
Design
Point
Overland Flow Time of Concentration
Frequency
Adjustment Factor:
(Equation 3.3-2
(Equation 5-5 FCSCM)
(Equation 5-4 FCSCM)
(Equation 3.3-5
Table 3.2-
3 FCSCM Notes:
1) Add 4900 to all elevations.
2) Per Fort Collins Stormwater Manual, minimum Tc = 5 min.
3) Assume a water depth of 6" and a typical curb and gutter per
Larimer County Urban Street Standard Detail 701 for curb and
gutter channelized flow. Assume a water depth of 1', fixed side
slopes, and a triangular swale section for grass channelized flow.
Assume a water depth of 1', 4:1 side slopes, and a 2' wide valley
pan for channelized flow in a valley pan.
Rational Method Equation:
Rainfall Intensity:
a 2.27 5.0 0.88 4.87 4.53 19.75
b 1.52 5.7 1.00 4.72 3.40 14.65
c 3.68 5.1 0.75 4.87 6.29 27.47
d 1.58 5.0 0.91 4.87 3.29 14.35
e 3.93 5.0 0.85 4.87 7.61 33.20
f 0.12 5.0 0.95 4.87 0.26 1.13
g 0.15 5.0 0.88 4.87 0.30 1.32
h 0.31 5.0 1.00 4.87 0.76 3.13
i 0.45 5.0 0.95 4.87 0.97 4.24
j 0.35 5.0 0.98 4.87 0.78 3.39
k 0.49 5.0 0.95 4.87 1.07 4.67
l 0.64 5.0 0.85 4.87 1.24 5.39
m 2.74 5.0 0.98 4.87 6.08 26.54
n 0.97 10.0 0.41 3.78 0.71 3.08
Tc100
(min)
DEVELOPED RUNOFF COMPUTATIONS
Design
Point
Area, A
(acres)
Flow,
Q2
(cfs)
Flow,
Q100
(cfs)
C100
IDF Table for Rational Method - Table 3.4-1 FCSCM
Intensity,
i10
(in/hr)
AiCCQf
Project: 1791-003
By: ARS
Date: 7/18/23
Pond ID
Tributary
Area
(Ac)1
Weighted %
Imperviousness
(%)
Extended
Detention WQCV
(Cu. Ft.)2
100-Yr.
Detention
Vol. (Ac-Ft)
100-Yr.
Detention
WSEL(Ft)
Peak Release
(cfs)3
Pond 1 6.29 67 Provided in Pond 2 1.52 4942.20 1.20
Pond 2 12.91 59 6,231 2.94 4941.60 2.40
Notes:
1. Tributary area shown does not include off-site basin(s)
2. WQCV calculated minus RG/Chamber volume; will be provded in Pond 2
3. Overall site release rate of 3.6 cfs divided between Ponds 1 and 2
POND SUMMARY TABLE
AS
Pond No :Pond 1
1
100-yr
0.90
Area (A)=6.29 acres 66369 ft3
Max Release Rate =1.20 cfs 1.52 ac-ft
Time Time
100-yr
Intensity Q100
Inflow
(Runoff)
Volume
Outflow
(Release)
Volume
Storage
Detention
Volume
(mins) (secs) (in/hr) (cfs)
(ft3) (ft
3) (ft
3)
5 300 9.950 56.34 16901 360.0 16540.8
10 600 7.720 43.71 26226 720.0 25505.9
15 900 6.520 36.92 33224 1080.0 32144.0
20 1200 5.600 31.71 38048 1440.0 36608.0
25 1500 4.980 28.20 42294 1800.0 40494.4
30 1800 4.520 25.59 46065 2160.0 43905.2
35 2100 4.080 23.10 48511 2520.0 45991.2
40 2400 3.740 21.18 50821 2880.0 47941.2
45 2700 3.460 19.59 52893 3240.0 49653.5
50 3000 3.230 18.29 54864 3600.0 51263.8
55 3300 3.030 17.16 56613 3960.0 52653.3
60 3600 2.860 16.19 58295 4320.0 53974.9
65 3900 2.720 15.40 60061 4680.0 55381.4
70 4200 2.590 14.66 61590 5040.0 56550.1
75 4500 2.480 14.04 63187 5400.0 57786.8
80 4800 2.380 13.48 64682 5760.0 58921.5
85 5100 2.290 12.97 66125 6120.0 60005.3
90 5400 2.210 12.51 67569 6480.0 61089.1
95 5700 2.130 12.06 68741 6840.0 61901.1
100 6000 2.060 11.66 69981 7200.0 62781.1
105 6300 2.000 11.32 71340 7560.0 63779.9
110 6600 1.940 10.98 72495 7920.0 64575.0
115 6900 1.890 10.70 73837 8280.0 65556.8
120 7200 1.840 10.42 75009 8640.0 66368.9
DETENTION POND CALCULATION; FAA METHOD
Project Number : 1791-003
Design Point
Design Storm Required Detention Volume
Developed "C" =
Project Location : Fort Collins
Input Variables Results
Calculations By:
Pond: 1
Project: 1791-003
By: ARS
Date: 5/16/23
Stage
(FT)
Contour Area
(SF)
Volume
(CU.FT.)
Volume
(AC-FT)
4,937.00 17.11 0 0.00
4,937.20 373.02 39.01 0.00
4,937.40 893.08 165.62 0.00
4,937.60 1,754.19 430.35 0.01
4,937.80 2,909.10 896.68 0.02
4,938.00 4,833.73 1670.96 0.04
4,938.20 6,967.85 2851.12 0.07
4,938.40 10,376.12 4585.52 0.11
4,938.60 10,983.44 6721.47 0.15
4,938.80 11,595.38 8979.35 0.21
4,939.00 12,211.94 11360.08 0.26
4,939.20 12,833.13 13864.59 0.32
4,939.40 13,464.36 16494.34 0.38
4,939.60 14,102.76 19251.05 0.44
4,939.80 14,749.22 22136.25 0.51
4,940.00 15,402.41 25151.41 0.58
4,940.20 16,062.35 28297.89 0.65
4,940.40 16,729.03 31577.03 0.72
4,940.60 17,398.31 34989.76 0.80
4,940.80 18,053.26 38534.92 0.88
4,941.00 18,693.35 42209.58 0.97
4,941.20 19,320.21 46010.94 1.06
4,941.40 19,947.02 49937.66 1.15
4,941.60 20,565.76 53988.94 1.24
4,941.80 21,152.42 58160.76 1.34
4,942.00 21,743.34 62450.33 1.43
4,942.20 22,338.01 66858.47 1.53 100-YR WSEL
4,942.40 22,936.30 71385.9 1.64
Pond Stage-Storage Curve
ARS
Pond No :Pond 2
2
100-yr
0.84
Area (A)=12.91 acres 126331 ft3
Max Release Rate =2.40 cfs 2.90 ac-ft
Time Time
100-yr
Intensity Q100
Inflow
(Runoff)
Volume
Outflow
(Release)
Volume
Storage
Detention
Volume
(mins) (secs) (in/hr) (cfs)
(ft3) (ft
3) (ft
3)
5 300 9.950 107.86 32358 720.0 31638.0
10 600 7.720 83.69 50212 1440.0 48771.8
15 900 6.520 70.68 63610 2160.0 61450.3
20 1200 5.600 60.71 72846 2880.0 69966.1
25 1500 4.980 53.98 80976 3600.0 77376.3
30 1800 4.520 49.00 88196 4320.0 83875.9
35 2100 4.080 44.23 92879 5040.0 87838.8
40 2400 3.740 40.54 97302 5760.0 91541.6
45 2700 3.460 37.51 101269 6480.0 94789.1
50 3000 3.230 35.01 105042 7200.0 97841.5
55 3300 3.030 32.85 108391 7920.0 100471.2
60 3600 2.860 31.00 111611 8640.0 102970.7
65 3900 2.720 29.49 114993 9360.0 105632.8
70 4200 2.590 28.08 117920 10080.0 107839.7
75 4500 2.480 26.88 120977 10800.0 110176.6
80 4800 2.380 25.80 123838 11520.0 112318.4
85 5100 2.290 24.82 126603 12240.0 114362.7
90 5400 2.210 23.96 129367 12960.0 116406.9
95 5700 2.130 23.09 131611 13680.0 117930.9
100 6000 2.060 22.33 133985 14400.0 119584.9
105 6300 2.000 21.68 136587 15120.0 121466.5
110 6600 1.940 21.03 138798 15840.0 122957.9
115 6900 1.890 20.49 141367 16560.0 124807.0
120 7200 1.840 19.95 143611 17280.0 126331.0
Input Variables Results
Calculations By:
DETENTION POND CALCULATION; FAA METHOD
Project Number : 1791-003
Design Point
Design Storm Required Detention Volume
Developed "C" =
Project Location : Fort Collins
Pond: 2
Project: 1791-001
By: AS
Date: 7/18/23
Stage
(FT)
Contour Area
(SF)
Volume
(CU.FT.)
Volume
(AC-FT)
4,935.00 166.41 0 0.00
4,935.20 1,131.07 129.75 0.00
4,935.40 2,746.87 517.54 0.01
4,935.60 4,868.25 1279.05 0.03
4,935.80 7,520.25 2517.9 0.06
4,936.00 9,803.84 4250.31 0.10
4,936.20 11,735.86 6404.28 0.15
4,936.40 13,453.52 8923.22 0.20
4,936.60 15,018.80 11770.45 0.27
4,936.80 16,448.15 14917.15 0.34
4,937.00 17,525.71 18314.53 0.42 WQ Elevation
4,937.20 18,178.37 21884.94 0.50
4,937.40 18,817.55 25584.53 0.59
4,937.60 19,461.10 29412.4 0.68
4,937.80 20,109.03 33369.41 0.77
4,938.00 20,762.08 37456.52 0.86
4,938.20 21,421.45 41674.88 0.96
4,938.40 22,086.68 46025.69 1.06
4,938.60 22,757.76 50510.13 1.16
4,938.80 23,434.70 55129.38 1.27
4,939.00 24,117.49 59884.6 1.37
4,939.20 24,806.14 64776.96 1.49
4,939.40 25,500.64 69807.64 1.60
4,939.60 26,201.00 74977.8 1.72
4,939.80 26,907.21 80288.62 1.84
4,940.00 27,619.28 85741.27 1.97
4,940.20 28,337.20 91336.92 2.10
4,940.40 29,060.98 97076.73 2.23
4,940.60 29,790.61 102961.89 2.36
4,940.80 30,526.10 108993.56 2.50
4,941.00 31,267.44 115172.92 2.64
4,941.20 32,014.64 121501.12 2.79
4,941.40 35,874.87 128290.08 2.95 100-YR WSEL
4,941.60 36,930.87 135570.65 3.11
4,941.80 38,154.45 143079.18 3.28
4,942.00 39,961.48 150890.77 3.46
4,942.20 42,325.37 159119.46 3.65
4,942.40 44,848.54 167836.85 3.85
4,942.60 47,789.62 177100.67 4.07
4,942.80 52,167.76 187096.41 4.30
Pond Stage-Storage Curve
B
APPENDIX B – HYDRAULIC CALCULATIONS
*CERTAIN CALCULATIONS, INCLUDING STORM PIPE, INLET, AND STREET CAPACITIES, HAVE BEEN
OMITTED FROM THIS SECTION AND WILL BE APPENDED TO THIS REPORT AT FINAL DESIGN.
ORIFICE RATING CURVE
Pond 1
100-yr Orifice
Project: Landing at Lemay
Date: 5/16/2023
By: ARS
100-yr WSEL= 4942
Orifice Plate
Outflow Q 1.2 cfs
Orifice Coefficient Cd 0.65
Gravity Constant g 32.2 ft/s^2
100-year head H 5.00 ft
Orifice Area Ao 0.10 ft^2
Orifice Area Ao 14.82 in^2
Radius r 2.2 in
Diameter d 4.3 in
Orifice Curve
Stage (ft) H (ft) Q (cfs) Stage Note
4937.00 0.00 0.00 0.00 Pond Invert
4937.20 0.20 0.24 0.20
4937.40 0.40 0.34 0.40
4937.60 0.60 0.42 0.60
4937.80 0.80 0.48 0.80
4938.00 1.00 0.54 1.00
4938.20 1.20 0.59 1.20
4938.40 1.40 0.63 1.40
4938.60 1.60 0.68 1.60
4938.80 1.80 0.72 1.80
4939.00 2.00 0.76 2.00
4939.20 2.20 0.80 2.20
4939.40 2.40 0.83 2.40
4939.60 2.60 0.87 2.60
4939.80 2.80 0.90 2.80
4940.00 3.00 0.93 3.00
4940.20 3.20 0.96 3.20
4940.40 3.40 0.99 3.40
4940.60 3.60 1.02 3.60
4940.80 3.80 1.05 3.80
4941.00 4.00 1.07 4.00
4941.20 4.20 1.10 4.20
4941.40 4.40 1.13 4.40
4941.60 4.60 1.15 4.60
4941.80 4.80 1.18 4.80
4942.00 5.00 1.20 5.00
4942.20 5.20 1.22 5.20 100-yr WSEL
4942.40 5.40 1.25 5.40
4942.60 5.60 1.27 5.60
4942.80 5.80 1.29 5.80
ORIFICE RATING CURVE
Pond 2
100-yr Orifice
Project: Landing at Lemay
Date: 7/18/2023
By: ARS
100-yr WSEL= 4941.8
Orifice Plate
Outflow Q 2.4 cfs
Orifice Coefficient Cd 0.65
Gravity Constant g 32.2 ft/s^2
100-year head H 6.40 ft
Orifice Area Ao 0.18 ft^2
Orifice Area Ao 26.19 in^2
Radius r 2.9 in
Diameter d 5.8 in
Orifice Curve
Stage (ft) H (ft) Q (cfs) SWMM Stage Note
4935.00 0.10 0.30 0.00 Pond Invert
4935.20 0.30 0.52 0.20
4935.40 0.50 0.67 0.40
4935.60 0.70 0.79 0.60
4935.80 0.90 0.90 0.80
4936.00 1.10 0.99 1.00
4936.20 1.30 1.08 1.20
4936.40 1.50 1.16 1.40
4936.60 1.70 1.24 1.60
4936.80 1.90 1.31 1.80
4937.00 2.10 1.37 2.00
4937.20 2.30 1.44 2.20
4937.40 2.50 1.50 2.40
4937.60 2.70 1.56 2.60
4937.80 2.90 1.62 2.80
4938.00 3.10 1.67 3.00
4938.20 3.30 1.72 3.20
4938.40 3.50 1.77 3.40
4938.60 3.70 1.82 3.60
4938.80 3.90 1.87 3.80
4939.00 4.10 1.92 4.00
4939.20 4.30 1.97 4.20
4939.40 4.50 2.01 4.40
4939.60 4.70 2.06 4.60
4939.80 4.90 2.10 4.80
4940.00 5.10 2.14 5.00
4940.20 5.30 2.18 5.20
4940.40 5.50 2.22 5.40
4940.60 5.70 2.26 5.60
4940.80 5.90 2.30 5.80
4941.00 6.10 2.34 6.00
4941.20 6.30 2.38 6.20
4941.40 6.50 2.42 6.40 100-yr WSEL
4941.60 6.70 2.46 6.60
4941.80 6.90 2.49 6.80
4942.00 7.10 2.53 7.00
4942.20 7.30 2.56 7.20
4942.40 7.50 2.60 7.40
4942.60 7.70 2.63 7.60
4942.70 7.80 2.65 7.70
C
APPENDIX C – LID AND WATER QUALITY
Project Number:Project:
Project Location:
Calculations By:Date:
Sq. Ft. Acres
A 98,840 2.27 62%Rain Garden A 1,798 2,039 61,281
B 66,289 1.52 78%Rain Garden B 1,361 1,507 51,705
C 160,336 3.68 50%Rain Garden C 2,209 2,295 80,168
D 68,833 1.58 66%Rain Garden D 1,183 1,401 45,430
E 171,002 3.93 61%Chambers E 2,714 2,771 104,311
F 5,206 0.12 74%n/a 0 0 3,852
G 6,594 0.15 66%n/a 0 0 4,352
H 13,692 0.31 85%n/a 0 0 11,638
I 19,551 0.45 74%n/a 0 0 14,468
J 15,206 0.35 76%n/a 0 0 11,557
K 21,523 0.49 73%n/a 0 0 15,712
L 27,767 0.64 57%n/a 0 0 15,827
M 119,169 2.74 74%Rain Garden M 2,338 2,377 88,185
N 42,143 0.97 13%n/a 0 0 5,479
Total 836,151 16.93 12,390 513,965
Sq. Ft.Acres
Rain Garden A 98,840 2.27 62%A Rain Garden 1,798 61,281
Rain Garden B 66,289 1.52 78%B Rain Garden 1,361 51,705
Rain Garden C 160,336 3.68 50%C Rain Garden 2,209 80,168
Rain Garden D 68,833 1.58 66%D Rain Garden 1,183 45,430
Chambers E 171,002 3.93 61%E Chambers 2,714 104,311
Rain Garden M 119,169 2.74 74%M Rain Garden 2,338 88,185
Total 684,469 15.71 431,080
836,151 ft2
513,965 ft2
82,885 ft2
385473.6225 ft3
431,080 ft2
83.9%
LID Summary
AreaBasin ID Percent
Impervious LID ID
Landing at Lemay
5/12/2023
1791-003
Fort Collins, Colorado
ARS
Total Impervious
Area Treated (ft2)
Required
Volume (ft3)
LID Summary per Basin
Provided
Volume (ft3)
Area Weighted
%
Impervious
Impervious Area
(ft2)
LID Summary per LID Structure
LID Site Summary - New Impervious Area
Subbasin ID Treatment TypeLID ID Volume per
UD-BMP (ft3)
Total Treated Area
Percent Impervious Treated by LID
75% Required Minimum Area to be Treated
Total Area of Current Development
Total Impervious Area
Total Impervious Area without LID Treatment:
F, G, H, I, J, K, L, N
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =62.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i =0.620
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.19 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 110,951 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =1,798 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER =cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum)DWQCV =12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin =1376 sq ft
D) Actual Flat Surface Area AActual =1376 sq ft
E) Area at Design Depth (Top Surface Area)ATop =2702 sq ft
F) Rain Garden Total Volume VT=2,039 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?1
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y =50.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =1,798 cu ft
iii) Orifice Diameter, 3/8" Minimum DO =1/2 in
Design Procedure Form: Rain Garden (RG)
AS
Avant Civil Group
July 18, 2023
Landing at Lemay
Rain Garden A
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.07_Rain Garden A, RG 7/18/2023, 2:30 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =60.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i =0.600
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.19 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 86,471 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =1,361 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER =cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum)DWQCV =12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin =1038 sq ft
D) Actual Flat Surface Area AActual =1060 sq ft
E) Area at Design Depth (Top Surface Area)ATop =1954 sq ft
F) Rain Garden Total Volume VT=1,507 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?1
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y =50.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =1,361 cu ft
iii) Orifice Diameter, 3/8" Minimum DO =7/16 in
Design Procedure Form: Rain Garden (RG)
AS
Avant Civil Group
May 16, 2023
Landing at Lemay
Rain Garden B
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.07_Rain Garden B, RG 5/16/2023, 3:13 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
AS
Avant Civil Group
May 16, 2023
Landing at Lemay
Rain Garden B
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
UD-BMP_v3.07_Rain Garden B, RG 5/16/2023, 3:13 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =50.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i =0.500
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.17 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 160,640 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =2,209 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER =cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum)DWQCV =12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin =1606 sq ft
D) Actual Flat Surface Area AActual =1935 sq ft
E) Area at Design Depth (Top Surface Area)ATop =2655 sq ft
F) Rain Garden Total Volume VT=2,295 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?1
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y =50.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =2,209 cu ft
iii) Orifice Diameter, 3/8" Minimum DO =9/16 in
Design Procedure Form: Rain Garden (RG)
AS
Avant Civil Group
May 16, 2023
Landing at Lemay
Rain Garden C
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.07_Rain Garden C, RG 5/16/2023, 3:14 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
AS
Avant Civil Group
May 16, 2023
Landing at Lemay
Rain Garden C
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
UD-BMP_v3.07_Rain Garden C, RG 5/16/2023, 3:14 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =66.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i =0.660
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.21 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 68,789 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =1,183 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER =cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum)DWQCV =12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin =908 sq ft
D) Actual Flat Surface Area AActual =1171 sq ft
E) Area at Design Depth (Top Surface Area)ATop =1725 sq ft
F) Rain Garden Total Volume VT=1,448 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?1
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y =50.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =1,183 cu ft
iii) Orifice Diameter, 3/8" Minimum DO =7/16 in
Design Procedure Form: Rain Garden (RG)
AS
Avant Civil Group
May 16, 2023
Landing at Lemay
Rain Garden D
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.07_Rain Garden D, RG 5/16/2023, 3:14 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
AS
Avant Civil Group
May 16, 2023
Landing at Lemay
Rain Garden D
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
UD-BMP_v3.07_Rain Garden D, RG 5/16/2023, 3:14 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =74.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i =0.740
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.24 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 119,169 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =2,338 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER =cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum)DWQCV =12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 0.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin =1764 sq ft
D) Actual Flat Surface Area AActual =2377 sq ft
E) Area at Design Depth (Top Surface Area)ATop =2377 sq ft
F) Rain Garden Total Volume VT=2,377 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?1
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y =50.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =2,338 cu ft
iii) Orifice Diameter, 3/8" Minimum DO =9/16 in
Design Procedure Form: Rain Garden (RG)
AS
Avant Civil Group
July 18, 2023
Landing at Lemay
Rain Garden M
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.07_Rain Garden M, RG 7/18/2023, 2:34 PM
Vault ID
Total
Required
WQ Volume
(cf)
Flow,
WQ
(cfs)
Chamber
Type
Chamber
Release
Ratea
(cfs)
Chamber
Volumeb
(cf)
Installed
Chamber w/
Aggregatec
(cf)
Mimimum
No. of
Chambersd
Total
Release
Ratee
(cfs)
Required
Storage
Volume by
FAA Method
(cf)
Provided
Number
of
Chambers
Provided
Release
Rate (cfs)
Storage
Provided
within the
Chambersg
(cf)
Total
Installed
System
Volumeh
(cf)
Basin E 2731 1.97 SC-740 0.024 45.90 74.90 37 0.87 3566 37 0.87 1698 2771
a. Release rate per chamber, limited by flow through geotextile with accumulated sediment.
b. Volume within chamber only, not accounting for void spaces in surrounding aggregate.
c. Volume includes chamber and void spaces (40%) in surrounding aggregate, per chamber unit.
d. Number of chambers required to provide full WQCV within total installed system, including aggregate.
e. Release rate per chamber times number of chambers.
f. Number of chambers required to provide required FAA storage volume stored within the chamber only (no aggregate storage).
g. Volume provided in chambers only (no aggregate storage). This number must meet or exceed the required FAA storage volume.
h. System volume includes total number of chambers, plus surrounding aggregate. This number must meet or exceed the required WQCV.
Chamber Configuration Summary
POND 2
Project: The Landing at Lemay
By: AS
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)=19.832 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT =61.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO =0.6100 <-- CALCULATED
Drain Time (hrs)40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) =0.240 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) =0.396 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
WQCV (cu-ft) =17246 <-- CALCULATED
WQCV Provided by LID (cu-ft) =12053 <-- INPUT from UDFCD RG Workbooks
Required WQCV (cu-ft) =6231 <-- CALCULATED, minus Rain Garden, x 120% Per FCSCM
WQ Depth (ft) =1.200 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in2) =0.522 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) =0.82 <-- INPUT from Figure 5
Standard Drill Bit Size =13/16
Drill Bit Area (in2) =0.51849
number of rows =4
t (in) =0.500 <-- INPUT from Figure 5
number of columns =1.000 <-- CALCULATED from WQ Depth and row spacing
WATER QUALITY CONTROL STRUCTURE PLATE
July 18, 2023
D
APPENDIX D – USDA SOILS REPORT
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, ColoradoNatural
Resources
Conservation
Service
January 31, 2023
Preface
Soil surveys contain information that affects land use planning in survey areas.
They highlight soil limitations that affect various land uses and provide information
about the properties of the soils in the survey areas. Soil surveys are designed for
many different users, including farmers, ranchers, foresters, agronomists, urban
planners, community officials, engineers, developers, builders, and home buyers.
Also, conservationists, teachers, students, and specialists in recreation, waste
disposal, and pollution control can use the surveys to help them understand,
protect, or enhance the environment.
Various land use regulations of Federal, State, and local governments may impose
special restrictions on land use or land treatment. Soil surveys identify soil
properties that are used in making various land use or land treatment decisions.
The information is intended to help the land users identify and reduce the effects of
soil limitations on various land uses. The landowner or user is responsible for
identifying and complying with existing laws and regulations.
Although soil survey information can be used for general farm, local, and wider area
planning, onsite investigation is needed to supplement this information in some
cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/
portal/nrcs/main/soils/health/) and certain conservation and engineering
applications. For more detailed information, contact your local USDA Service Center
(https://offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil
Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?
cid=nrcs142p2_053951).
Great differences in soil properties can occur within short distances. Some soils are
seasonally wet or subject to flooding. Some are too unstable to be used as a
foundation for buildings or roads. Clayey or wet soils are poorly suited to use as
septic tank absorption fields. A high water table makes a soil poorly suited to
basements or underground installations.
The National Cooperative Soil Survey is a joint effort of the United States
Department of Agriculture and other Federal agencies, State agencies including the
Agricultural Experiment Stations, and local agencies. The Natural Resources
Conservation Service (NRCS) has leadership for the Federal part of the National
Cooperative Soil Survey.
Information about soils is updated periodically. Updated information is available
through the NRCS Web Soil Survey, the site for official soil survey information.
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its
programs and activities on the basis of race, color, national origin, age, disability,
and where applicable, sex, marital status, familial status, parental status, religion,
sexual orientation, genetic information, political beliefs, reprisal, or because all or a
part of an individual's income is derived from any public assistance program. (Not
all prohibited bases apply to all programs.) Persons with disabilities who require
2
alternative means for communication of program information (Braille, large print,
audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice
and TDD). To file a complaint of discrimination, write to USDA, Director, Office of
Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or
call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity
provider and employer.
3
Contents
Preface....................................................................................................................2
How Soil Surveys Are Made..................................................................................5
Soil Map..................................................................................................................8
Soil Map................................................................................................................9
Legend................................................................................................................10
Map Unit Legend................................................................................................11
Map Unit Descriptions.........................................................................................11
Larimer County Area, Colorado......................................................................13
22—Caruso clay loam, 0 to 1 percent slope...............................................13
35—Fort Collins loam, 0 to 3 percent slopes..............................................14
64—Loveland clay loam, 0 to 1 percent slopes...........................................15
76—Nunn clay loam, wet, 1 to 3 percent slopes.........................................16
105—Table Mountain loam, 0 to 1 percent slopes......................................18
Soil Information for All Uses...............................................................................20
Soil Properties and Qualities..............................................................................20
Soil Erosion Factors........................................................................................20
K Factor, Whole Soil....................................................................................20
References............................................................................................................24
4
How Soil Surveys Are Made
Soil surveys are made to provide information about the soils and miscellaneous
areas in a specific area. They include a description of the soils and miscellaneous
areas and their location on the landscape and tables that show soil properties and
limitations affecting various uses. Soil scientists observed the steepness, length,
and shape of the slopes; the general pattern of drainage; the kinds of crops and
native plants; and the kinds of bedrock. They observed and described many soil
profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The
profile extends from the surface down into the unconsolidated material in which the
soil formed or from the surface down to bedrock. The unconsolidated material is
devoid of roots and other living organisms and has not been changed by other
biological activity.
Currently, soils are mapped according to the boundaries of major land resource
areas (MLRAs). MLRAs are geographically associated land resource units that
share common characteristics related to physiography, geology, climate, water
resources, soils, biological resources, and land uses (USDA, 2006). Soil survey
areas typically consist of parts of one or more MLRA.
The soils and miscellaneous areas in a survey area occur in an orderly pattern that
is related to the geology, landforms, relief, climate, and natural vegetation of the
area. Each kind of soil and miscellaneous area is associated with a particular kind
of landform or with a segment of the landform. By observing the soils and
miscellaneous areas in the survey area and relating their position to specific
segments of the landform, a soil scientist develops a concept, or model, of how they
were formed. Thus, during mapping, this model enables the soil scientist to predict
with a considerable degree of accuracy the kind of soil or miscellaneous area at a
specific location on the landscape.
Commonly, individual soils on the landscape merge into one another as their
characteristics gradually change. To construct an accurate soil map, however, soil
scientists must determine the boundaries between the soils. They can observe only
a limited number of soil profiles. Nevertheless, these observations, supplemented
by an understanding of the soil-vegetation-landscape relationship, are sufficient to
verify predictions of the kinds of soil in an area and to determine the boundaries.
Soil scientists recorded the characteristics of the soil profiles that they studied. They
noted soil color, texture, size and shape of soil aggregates, kind and amount of rock
fragments, distribution of plant roots, reaction, and other features that enable them
to identify soils. After describing the soils in the survey area and determining their
properties, the soil scientists assigned the soils to taxonomic classes (units).
Taxonomic classes are concepts. Each taxonomic class has a set of soil
characteristics with precisely defined limits. The classes are used as a basis for
comparison to classify soils systematically. Soil taxonomy, the system of taxonomic
classification used in the United States, is based mainly on the kind and character
of soil properties and the arrangement of horizons within the profile. After the soil
5
scientists classified and named the soils in the survey area, they compared the
individual soils with similar soils in the same taxonomic class in other areas so that
they could confirm data and assemble additional data based on experience and
research.
The objective of soil mapping is not to delineate pure map unit components; the
objective is to separate the landscape into landforms or landform segments that
have similar use and management requirements. Each map unit is defined by a
unique combination of soil components and/or miscellaneous areas in predictable
proportions. Some components may be highly contrasting to the other components
of the map unit. The presence of minor components in a map unit in no way
diminishes the usefulness or accuracy of the data. The delineation of such
landforms and landform segments on the map provides sufficient information for the
development of resource plans. If intensive use of small areas is planned, onsite
investigation is needed to define and locate the soils and miscellaneous areas.
Soil scientists make many field observations in the process of producing a soil map.
The frequency of observation is dependent upon several factors, including scale of
mapping, intensity of mapping, design of map units, complexity of the landscape,
and experience of the soil scientist. Observations are made to test and refine the
soil-landscape model and predictions and to verify the classification of the soils at
specific locations. Once the soil-landscape model is refined, a significantly smaller
number of measurements of individual soil properties are made and recorded.
These measurements may include field measurements, such as those for color,
depth to bedrock, and texture, and laboratory measurements, such as those for
content of sand, silt, clay, salt, and other components. Properties of each soil
typically vary from one point to another across the landscape.
Observations for map unit components are aggregated to develop ranges of
characteristics for the components. The aggregated values are presented. Direct
measurements do not exist for every property presented for every map unit
component. Values for some properties are estimated from combinations of other
properties.
While a soil survey is in progress, samples of some of the soils in the area generally
are collected for laboratory analyses and for engineering tests. Soil scientists
interpret the data from these analyses and tests as well as the field-observed
characteristics and the soil properties to determine the expected behavior of the
soils under different uses. Interpretations for all of the soils are field tested through
observation of the soils in different uses and under different levels of management.
Some interpretations are modified to fit local conditions, and some new
interpretations are developed to meet local needs. Data are assembled from other
sources, such as research information, production records, and field experience of
specialists. For example, data on crop yields under defined levels of management
are assembled from farm records and from field or plot experiments on the same
kinds of soil.
Predictions about soil behavior are based not only on soil properties but also on
such variables as climate and biological activity. Soil conditions are predictable over
long periods of time, but they are not predictable from year to year. For example,
soil scientists can predict with a fairly high degree of accuracy that a given soil will
have a high water table within certain depths in most years, but they cannot predict
that a high water table will always be at a specific level in the soil on a specific date.
After soil scientists located and identified the significant natural bodies of soil in the
survey area, they drew the boundaries of these bodies on aerial photographs and
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6
identified each as a specific map unit. Aerial photographs show trees, buildings,
fields, roads, and rivers, all of which help in locating boundaries accurately.
Custom Soil Resource Report
7
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
44932004493300449340044935004493600449370044938004493900449400044941004493200449330044934004493500449360044937004493800449390044940004494100495200 495300 495400 495500 495600 495700 495800
495200 495300 495400 495500 495600 495700 495800
40° 35' 52'' N 105° 3' 26'' W40° 35' 52'' N105° 2' 54'' W40° 35' 21'' N
105° 3' 26'' W40° 35' 21'' N
105° 2' 54'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 200 400 800 1200
Feet
0 50 100 200 300
Meters
Map Scale: 1:4,750 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 17, Sep 7, 2022
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jul 2, 2021—Aug 25,
2021
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.
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10
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
22 Caruso clay loam, 0 to 1
percent slope
53.1 52.9%
35 Fort Collins loam, 0 to 3 percent
slopes
14.4 14.4%
64 Loveland clay loam, 0 to 1
percent slopes
10.2 10.2%
76 Nunn clay loam, wet, 1 to 3
percent slopes
18.6 18.5%
105 Table Mountain loam, 0 to 1
percent slopes
4.0 4.0%
Totals for Area of Interest 100.2 100.0%
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.
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11
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
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
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Larimer County Area, Colorado
22—Caruso clay loam, 0 to 1 percent slope
Map Unit Setting
National map unit symbol: jpvt
Elevation: 4,800 to 5,500 feet
Mean annual precipitation: 13 to 15 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 135 to 150 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Caruso and similar soils:85 percent
Minor components:15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Caruso
Setting
Landform:Flood-plain steps, stream terraces
Landform position (three-dimensional):Tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Mixed alluvium
Typical profile
H1 - 0 to 35 inches: clay loam
H2 - 35 to 44 inches: fine sandy loam
H3 - 44 to 60 inches: gravelly sand
Properties and qualities
Slope:0 to 1 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Somewhat poorly drained
Runoff class: 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:About 24 to 48 inches
Frequency of flooding:NoneOccasional
Frequency of ponding:None
Calcium carbonate, maximum content:5 percent
Maximum salinity:Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm)
Available water supply, 0 to 60 inches: Moderate (about 8.4 inches)
Interpretive groups
Land capability classification (irrigated): 3w
Land capability classification (nonirrigated): 5w
Hydrologic Soil Group: D
Ecological site: R067BY036CO - Overflow
Hydric soil rating: No
Minor Components
Loveland
Percent of map unit:9 percent
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Landform:Terraces
Ecological site:R067BY036CO - Overflow
Hydric soil rating: Yes
Fluvaquents
Percent of map unit:6 percent
Landform:Terraces
Hydric soil rating: Yes
35—Fort Collins loam, 0 to 3 percent slopes
Map Unit Setting
National map unit symbol: 2tlnc
Elevation: 4,020 to 6,730 feet
Mean annual precipitation: 14 to 16 inches
Mean annual air temperature: 46 to 48 degrees F
Frost-free period: 135 to 160 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Fort collins and similar soils:85 percent
Minor components:15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Fort Collins
Setting
Landform:Stream terraces, interfluves
Landform position (three-dimensional):Interfluve, tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Pleistocene or older alluvium and/or eolian deposits
Typical profile
Ap - 0 to 4 inches: loam
Bt1 - 4 to 9 inches: clay loam
Bt2 - 9 to 16 inches: clay loam
Bk1 - 16 to 29 inches: loam
Bk2 - 29 to 80 inches: loam
Properties and qualities
Slope:0 to 3 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high
(0.20 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:12 percent
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Maximum salinity:Nonsaline to very slightly saline (0.1 to 2.0 mmhos/cm)
Available water supply, 0 to 60 inches: High (about 9.1 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: C
Ecological site: R067BY002CO - Loamy Plains
Hydric soil rating: No
Minor Components
Nunn
Percent of map unit:10 percent
Landform:Stream terraces
Landform position (three-dimensional):Tread
Down-slope shape:Linear
Across-slope shape:Linear
Ecological site:R067BY002CO - Loamy Plains
Hydric soil rating: No
Vona
Percent of map unit:5 percent
Landform:Interfluves
Landform position (three-dimensional):Interfluve, side slope
Down-slope shape:Linear
Across-slope shape:Linear
Ecological site:R067BY024CO - Sandy Plains
Hydric soil rating: No
64—Loveland clay loam, 0 to 1 percent slopes
Map Unit Setting
National map unit symbol: jpx9
Elevation: 4,800 to 5,500 feet
Mean annual precipitation: 13 to 15 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 135 to 150 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Loveland and similar soils:90 percent
Minor components:10 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Loveland
Setting
Landform:Flood plains, stream terraces
Landform position (three-dimensional):Tread
Down-slope shape:Linear
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Across-slope shape:Linear
Parent material:Alluvium
Typical profile
H1 - 0 to 15 inches: clay loam
H2 - 15 to 32 inches: loam
H3 - 32 to 60 inches: very gravelly sand
Properties and qualities
Slope:0 to 1 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Poorly drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat):Moderately high (0.20
to 0.60 in/hr)
Depth to water table:About 18 to 36 inches
Frequency of flooding:OccasionalNone
Frequency of ponding:None
Calcium carbonate, maximum content:15 percent
Maximum salinity:Very slightly saline to slightly saline (2.0 to 4.0 mmhos/cm)
Available water supply, 0 to 60 inches: Moderate (about 7.5 inches)
Interpretive groups
Land capability classification (irrigated): 3w
Land capability classification (nonirrigated): 3w
Hydrologic Soil Group: C
Ecological site: R067BY036CO - Overflow
Hydric soil rating: No
Minor Components
Aquolls
Percent of map unit:5 percent
Landform:Swales
Hydric soil rating: Yes
Poudre
Percent of map unit:5 percent
Ecological site:R067BY036CO - Overflow
Hydric soil rating: No
76—Nunn clay loam, wet, 1 to 3 percent slopes
Map Unit Setting
National map unit symbol: jpxq
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: Prime farmland if irrigated
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Map Unit Composition
Nunn, wet, and similar soils:90 percent
Minor components:10 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Nunn, Wet
Setting
Landform:Alluvial fans, stream terraces
Landform position (three-dimensional):Base slope, tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Alluvium
Typical profile
H1 - 0 to 10 inches: clay loam
H2 - 10 to 47 inches: clay
H3 - 47 to 60 inches: gravelly loam
Properties and qualities
Slope:1 to 3 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Somewhat poorly drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat):Moderately low to
moderately high (0.06 to 0.60 in/hr)
Depth to water table:About 24 to 36 inches
Frequency of flooding:NoneRare
Frequency of ponding:None
Calcium carbonate, maximum content:10 percent
Maximum salinity:Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm)
Available water supply, 0 to 60 inches: High (about 9.9 inches)
Interpretive groups
Land capability classification (irrigated): 2w
Land capability classification (nonirrigated): 3s
Hydrologic Soil Group: C
Ecological site: R067BY038CO - Wet Meadow
Hydric soil rating: No
Minor Components
Heldt
Percent of map unit:6 percent
Ecological site:R067BY042CO - Clayey Plains
Hydric soil rating: No
Dacono
Percent of map unit:3 percent
Ecological site:R067BY042CO - Clayey Plains
Hydric soil rating: No
Mollic halaquepts
Percent of map unit:1 percent
Landform:Swales
Hydric soil rating: Yes
Custom Soil Resource Report
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105—Table Mountain loam, 0 to 1 percent slopes
Map Unit Setting
National map unit symbol: jpty
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: Prime farmland if irrigated
Map Unit Composition
Table mountain and similar soils:85 percent
Minor components:15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Table Mountain
Setting
Landform:Flood plains, stream terraces
Landform position (three-dimensional):Tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Alluvium
Typical profile
H1 - 0 to 36 inches: loam
H2 - 36 to 60 inches: clay loam
Properties and qualities
Slope:0 to 1 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high
(0.60 to 2.00 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Calcium carbonate, maximum content:15 percent
Maximum salinity:Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm)
Sodium adsorption ratio, maximum:5.0
Available water supply, 0 to 60 inches: High (about 9.8 inches)
Interpretive groups
Land capability classification (irrigated): 1
Land capability classification (nonirrigated): 3c
Hydrologic Soil Group: B
Ecological site: R049XY036CO - Overflow
Hydric soil rating: No
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Minor Components
Caruso
Percent of map unit:7 percent
Hydric soil rating: No
Fluvaquentic haplustolls
Percent of map unit:4 percent
Landform:Terraces
Hydric soil rating: Yes
Paoli
Percent of map unit:4 percent
Hydric soil rating: No
Custom Soil Resource Report
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Soil Information for All Uses
Soil Properties and Qualities
The Soil Properties and Qualities section includes various soil properties and
qualities displayed as thematic maps with a summary table for the soil map units in
the selected area of interest. A single value or rating for each map unit is generated
by aggregating the interpretive ratings of individual map unit components. This
aggregation process is defined for each property or quality.
Soil Erosion Factors
Soil Erosion Factors are soil properties and interpretations used in evaluating the
soil for potential erosion. Example soil erosion factors can include K factor for the
whole soil or on a rock free basis, T factor, wind erodibility group and wind erodibility
index.
K Factor, Whole Soil
Erosion factor K indicates the susceptibility of a soil to sheet and rill erosion by
water. Factor K is one of six factors used in the Universal Soil Loss Equation
(USLE) and the Revised Universal Soil Loss Equation (RUSLE) to predict the
average annual rate of soil loss by sheet and rill erosion in tons per acre per year.
The estimates are based primarily on percentage of silt, sand, and organic matter
and on soil structure and saturated hydraulic conductivity (Ksat). Values of K range
from 0.02 to 0.69. Other factors being equal, the higher the value, the more
susceptible the soil is to sheet and rill erosion by water.
"Erosion factor Kw (whole soil)" indicates the erodibility of the whole soil. The
estimates are modified by the presence of rock fragments.
Factor K does not apply to organic horizons and is not reported for those layers.
20
21
Custom Soil Resource Report
Map—K Factor, Whole Soil
44932004493300449340044935004493600449370044938004493900449400044941004493200449330044934004493500449360044937004493800449390044940004494100495200 495300 495400 495500 495600 495700 495800
495200 495300 495400 495500 495600 495700 495800
40° 35' 52'' N 105° 3' 26'' W40° 35' 52'' N105° 2' 54'' W40° 35' 21'' N
105° 3' 26'' W40° 35' 21'' N
105° 2' 54'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 200 400 800 1200
Feet
0 50 100 200 300
Meters
Map Scale: 1:4,750 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 Rating Polygons
.02
.05
.10
.15
.17
.20
.24
.28
.32
.37
.43
.49
.55
.64
Not rated or not available
Soil Rating Lines
.02
.05
.10
.15
.17
.20
.24
.28
.32
.37
.43
.49
.55
.64
Not rated or not available
Soil Rating Points
.02
.05
.10
.15
.17
.20
.24
.28
.32
.37
.43
.49
.55
.64
Not rated or not available
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 17, Sep 7, 2022
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jul 2, 2021—Aug
25, 2021
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
22
Table—K Factor, Whole Soil
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
22 Caruso clay loam, 0 to 1
percent slope
.32 53.1 52.9%
35 Fort Collins loam, 0 to 3
percent slopes
.43 14.4 14.4%
64 Loveland clay loam, 0 to
1 percent slopes
.20 10.2 10.2%
76 Nunn clay loam, wet, 1 to
3 percent slopes
.24 18.6 18.5%
105 Table Mountain loam, 0
to 1 percent slopes
.37 4.0 4.0%
Totals for Area of Interest 100.2 100.0%
Rating Options—K Factor, Whole Soil
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Layer Options (Horizon Aggregation Method): Surface Layer (Not applicable)
Custom Soil Resource Report
23
References
American Association of State Highway and Transportation Officials (AASHTO).
2004. Standard specifications for transportation materials and methods of sampling
and testing. 24th edition.
American Society for Testing and Materials (ASTM). 2005. Standard classification of
soils for engineering purposes. ASTM Standard D2487-00.
Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of
wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife
Service FWS/OBS-79/31.
Federal Register. July 13, 1994. Changes in hydric soils of the United States.
Federal Register. September 18, 2002. Hydric soils of the United States.
Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric
soils in the United States.
National Research Council. 1995. Wetlands: Characteristics and boundaries.
Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service.
U.S. Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/
nrcs/detail/national/soils/?cid=nrcs142p2_054262
Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for
making and interpreting soil surveys. 2nd edition. Natural Resources Conservation
Service, U.S. Department of Agriculture Handbook 436. http://
www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053577
Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of
Agriculture, Natural Resources Conservation Service. http://
www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580
Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and
Delaware Department of Natural Resources and Environmental Control, Wetlands
Section.
United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of
Engineers wetlands delineation manual. Waterways Experiment Station Technical
Report Y-87-1.
United States Department of Agriculture, Natural Resources Conservation Service.
National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/
home/?cid=nrcs142p2_053374
United States Department of Agriculture, Natural Resources Conservation Service.
National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/
detail/national/landuse/rangepasture/?cid=stelprdb1043084
24
United States Department of Agriculture, Natural Resources Conservation Service.
National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/
nrcs/detail/soils/scientists/?cid=nrcs142p2_054242
United States Department of Agriculture, Natural Resources Conservation Service.
2006. Land resource regions and major land resource areas of the United States,
the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook
296. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?
cid=nrcs142p2_053624
United States Department of Agriculture, Soil Conservation Service. 1961. Land
capability classification. U.S. Department of Agriculture Handbook 210. http://
www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf
Custom Soil Resource Report
25
E
APPENDIX E – FEMA FIRMETTE
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 2/3/2023 at 11:33 AM 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°3'31"W 40°35'47"N
105°2'54"W 40°35'20"N
Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020
F
APPENDIX F – D RAINAGE E XHIBIT
TEST
STA
TEST
STA
V.P.STF.O.XX
XXXXXX
XXXXXFDCFDCFDCUDUDFDC FDCFDCFDCFDC
FDCFDCUDUDUD
UD
UD
UD
NORTH LEMAY AVENUEDUFF DRIVE CORDOVA ROADLINK LANE
A
2.55 ac
B
1.93 ac
D
1.58 ac
C
3.68 ac
E
3.93 ac
F
0.12 ac
G
0.15 ac
H
0.31 ac
I
0.45 ac
J
0.33 ac
K
0.49 ac
OS1
.906 ac
DETENTION
POND 2
RAIN
GARDEN A
RAIN
GARDEN D
RAIN
GARDEN C
DETENTION
POND 1
RAIN
GARDEN B
PROPOSED
STORM DRAIN
PROPOSED
POND OUTFALL
PROPOSED 2'
CONCRETE PAN
PROPOSED
STORM DRAIN
PROPOSED
STORM DRAIN
PROPOSED
STORM DRAIN
PROPOSED 2'
CONCRETE PAN
PROPOSED 2'
CONCRETE PAN
PROPOSED 2'
CONCRETE PAN
PROPOSED
STORM DRAIN
PROPOSED
STORM DRAIN
EXISTING
STORM DRAIN
EXISTING
STORM DRAIN
PROPOSED 2'
CONCRETE PAN
C
D
E
B
A
F G
H I
J
K
OS1
POND OUTLET
STRUCTURE
POND OUTLET
STRUCTURE
M
2.73 ac
L
0.64 ac
N
1.01 ac
DOG PARK
PROPOSED
CULVERT
L
MRAIN
GARDEN M
N
OF
SCALE:
PROJECT NO.PROJECT MANAGER:NO.REVISIONSBY:DATE:SUBMITTAL DATE:SHEET:
HORIZ:
VERT:
CAUTION
The engineer preparing these
plans will not be responsible
for, or liable for, unauthorized
changes to or uses of these
plans. All changes must be
approved by the Professional
Engineer of these plans.07/19/23THE LANDING AT LEMAY25
1791-003 D. Weber1337 RIVERSIDE AVE. #2FORT COLLINS, CO 80524AVANTCIVILGROUP.COM970.286.7995NORTH
( IN FEET )
1 inch = ft.
Feet05050
50
100 150
PROPOSED CONTOUR
PROPOSED STORM SEWER
PROPOSED SWALE
EXISTING CONTOUR
PROPOSED CURB & GUTTER
PROPERTY BOUNDARY
PROPOSED INLET
A
DESIGN POINT
FLOW ARROW
DRAINAGE BASIN LABEL
DRAINAGE BASIN BOUNDARY
PROPOSED SWALE SECTION
11
1.REFER TO THE PRELIMINARY DRAINAGE REPORT, DATED JULY 19, 2023 BY AVANT
CIVIL GROUP FOR ADDITIONAL INFORMATION.
A
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
LEGEND
NOTES
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
before you dig.Call
R DEVELOPED DRAINAGE EXHIBIT22
1" = 50'
N/A