HomeMy WebLinkAboutTHE STANDARD AT FORT COLLINS - PDP - PDP160035 - REPORTS - DRAINAGE REPORTPRELIMINARY DRAINAGE REPORT
The Standard at Fort Collins
Fort Collins, Colorado
November 29, 2016
Prepared for:
Landmark Properties
4455 Epps Bridge Parkway, Suite 20
Athens, GA 30606
Prepared by:
301 North Howes Street, Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158 Fax: 970.221.4159
www.northernengineering.com
Project Number: 1290-001
P This Drainage Report is consciously provided as a PDF.
Please consider the environment before printing this document in its entirety.
When a hard copy is absolutely necessary, we recommend double-sided printing.
November 29, 2016
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Final Drainage Report for
The Standard @ Fort Collins
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage and Erosion Control Report for
your review. This report accompanies the Preliminary Development Review submittal for the
proposed The Standard @ Fort Collins. Comments from the Preliminary Development Review
Letter dated November 14, 2016 have been addressed. Written responses thereto can be found in
the comprehensive response to comments letter on file with Current Planning.
This report has been prepared in accordance to the Fort Collins Stormwater Criteria Manual
(FCSCM), and serves to document the stormwater impacts associated with the proposed The
Standard @ Fort Collins project. We understand that review by the City is to assure general
compliance with standardized criteria contained in the FCSCM.
If you should have any questions as you review this report, please feel free to contact us.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
Nicholas W. Haws, PE Cody Snowdon
Project Manager Project Engineer
The Standard @ Fort Collins
Final Drainage Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ................................................................... 1
A. Location ....................................................................................................................................... 1
B. Description of Property ................................................................................................................ 2
C. Floodplain .................................................................................................................................... 3
II. DRAINAGE BASINS AND SUB-BASINS ....................................................................... 5
A. Major Basin Description ............................................................................................................... 5
B. Sub-Basin Description .................................................................................................................. 5
III. DRAINAGE DESIGN CRITERIA ................................................................................... 5
A. Regulations .................................................................................................................................. 5
B. Four Step Process ........................................................................................................................ 5
C. Development Criteria Reference and Constraints ......................................................................... 6
D. Hydrological Criteria .................................................................................................................... 7
E. Hydraulic Criteria ......................................................................................................................... 7
F. Floodplain Regulations Compliance .............................................................................................. 7
G. Modifications of Criteria .............................................................................................................. 7
IV. DRAINAGE FACILITY DESIGN .................................................................................... 8
A. General Concept .......................................................................................................................... 8
B. Specific Details ............................................................................................................................. 9
V. CONCLUSIONS ...................................................................................................... 13
A. Compliance with Standards ........................................................................................................ 13
B. Drainage Concept ...................................................................................................................... 13
References ....................................................................................................................... 14
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
B.1 – Storm Sewers (For Future Use)
B.2 – Inlets (For Future Use)
B.3 – Detention Facilities (For Future Use)
APPENDIX C – Water Quality Design Computations
APPENDIX D – Erosion Control Report
The Standard @ Fort Collins
Final Drainage Report
LIST OF TABLES AND FIGURES:
Figure 1 – Aerial Photograph ................................................................................................ 2
Figure 2 – Proposed Site Plan ............................................................................................... 3
Figure 3 – Existing FEMA Floodplains .................................................................................... 4
Figure 4 – Existing City Floodplains ....................................................................................... 4
MAP POCKET:
C8.00 - Drainage Exhibit
C8.01 – Historic Drainage Exhibit
The Standard @ Fort Collins
Final Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. The Standard @ Fort Collins project is located in the southwest quarter of Section 14,
Township 7 North, Range 69 West of the 6th Principal Meridian, City of Fort Collins,
County of Larimer, State of Colorado.
3. The project site is located south of Lake Street and expands all the way to West
Prospect Road. It encompasses Blue Ridge Apartments (775 West Lake Street) and
four single family residences (900, 836 832, and 820 West Prospect Road).
4. Currently the existing lots do not have any stormwater or water quality facilities. The
northern property consists of Blue Ridge Apartments, which includes an existing
building, two parking lots and associated sidewalks. The southern properties consist
of single family residences, which includes, multiple buildings, gravel drives, and
associated sidewalks. The northern project site is composed of 81 percent
imperviousness, while the southern portion of the project is composed of only 20
percent imperviousness, resulting in an overall imperviousness of 49 percent. The
existing site all drains to both West Lake Street and West Prospect Road.
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Final Drainage Report 2
5. The project is currently bordered to the south by West Prospect Road, west by
Plymouth Congregational Church, north by West Lake Street and east by Farmhouse
Fraternity.
B. Description of Property
1. The Standard @ Fort Collins is approximately 4.23 net acres.
Figure 1 – Aerial Photograph
2. The Standard @ Fort Collins consists of five properties with five existing structures
and multiple out buildings. The northern lot consist of Blue Ridge Apartments with
two parking lots and associated sidewalks. The southern lot consists of four single
family residences with associated gravel driveways, multiple accessory buildings and
associated sidewalks. There is no off-site drainage entering the existing properties.
All runoff generated from the project drains either south to West Prospect Road or
north to West Lake Street.
3. According to the United States Department of Agriculture (USDA) Natural Resources
Conservation Service (NRCS) Soil Survey, 100 percent of the site consists of Altvan-
Satanta loam, which falls into Hydrologic Soil Groups B.
4. The proposed development will include the demolition of the existing structures,
parking lots, gravel drives and associated sidewalks. The proposed project will include
two large multi-family buildings, an internal parking structure and a central drive aisle
acting as a pedestrian spine between West Prospect Road and West Lake Street. The
central drive aisle and courtyards are planned to be composed of StormTech
chambers underneath the surface. These areas will act as a portion of the project’s
water quality and detention facility. Internal to Building B, a concrete vault is
proposed to treat stormwater through the use of a sand filter, as well as detaining the
major storm event. The surrounding green space will act as the remaining water
quality.
The Standard @ Fort Collins
Final Drainage Report 3
Figure 2– Proposed Site Plan
5. No irrigation facilities or major drainageways are within the property limits.
6. The project site is within the High Density Mixed-Use Neighborhood District (H-M-N)
Zoning District. The proposed use is permitted within the zone district.
C. Floodplain
1. The subject property is not located in a FEMA or City regulatory floodplain.
2. The FEMA Panel 0801010979H illustrates the proximity of the project site to the
nearest FEMA delineated regulatory floodplain. It is noted that the vertical datum
utilized for site survey work is the City of Fort Collins Benchmark #29-92
Elevation = 5025.67 (NAVD 88)
The Standard @ Fort Collins
Final Drainage Report 4
Figure 3 – Existing FEMA Floodplains
Figure 4 – Existing City Floodplains
The Standard @ Fort Collins
Final Drainage Report 5
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. The Standard @ Fort Collins is located within the Old Town Basin, which is located
primarily in Old Town Fort Collins.
B. Sub-Basin Description
1. The property historically drains from the southeast corner of the southern lots and to
the northeast corner of the northern lot. Stormwater is routed via overland flow across
the existing lots. The project only consists of two basins; Basin HN1 and HS1
representing the historic basin draining to the north and the historic basin draining to
the south, respectively. The stormwater within Historic Basin HN1, historically
discharges directly into West Lake Street at a rate of 4.11 cfs and 20.03 cfs for the
2-year and 100-year storm event, respectively. The stormwater within Historic Basin
HS1, historically discharges directly into West Prospect Road at a rate of 1.36 cfs and
6.21 cfs for the 2-year and 100-year storm event, respectively. See Section IV.A.4.
below, for a more detailed description of the projects proposed drainage patterns.
2. No drainage is routed onto the property from the surrounding properties.
A full-size copy of the Historic and Proposed Drainage Exhibit can be found in the
Map Pocket at the end of this report.
III. DRAINAGE DESIGN CRITERIA
A. Regulations
There are no optional provisions outside of the FCSCM proposed with The Standard @
Fort Collins project.
B. Four Step Process
The overall stormwater management strategy employed with The Standard @ Fort Collins
project 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
Several techniques have been utilized with the proposed development to facilitate the
reduction of runoff peaks, volumes, and pollutant loads as the site is developed from the
current use by implementing multiple Low-Impact Development (LID) strategies including:
Selecting a site that has been previously developed and currently consist of Blue
Ridged Apartments and single family residences, two asphalt parking lots, multiple
gravel access drives and associated sidewalks.
Providing vegetated open areas along the north, south, east and west portion of the
site to reduce the overall impervious area and to minimize directly connected
impervious areas (MDCIA).
Routing flows, to the extent feasible, through drain rock both within the underground
detention section to increase time of concentration, promote infiltration and provide
initial water quality.
The Standard @ Fort Collins
Final Drainage Report 6
Routing runoff through the drain rock within the underground detention area to
increase time of concentration, promote infiltration and provide water quality.
Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with
Slow Release
The efforts taken in Step 1 will facilitate the reduction of runoff; however, this
development will still generate stormwater runoff that will require additional BMPs and
water quality. The stormwater generated from Building B will be routed internally and
discharge into a pond/sand filter located in the garage. The water quality event will be
filtered through the sand layer and discharge into West Lake Street. Stormwater generated
from the northern portion of the central drive will be either treated through the use of
StormTech Chambers or permeable pavers. Stormwater generated from the southern
portion of the central drive will be treated through the use of pavers. Stormwater
generated from Building A will be routed internal and discharge into StormTech Chambers
located around the building where it will be treated through the drain rock section. The
areas running off-site to the west and the east only consist of landscape area and will be
routed across landscape before leaving the site.
Step 3 – Stabilize Drainageways
As stated in Section I.B.5, above, there are no major drainageways in or near the subject
site. While this step may not seem applicable to The Standard @ Fort Collins, the
proposed project indirectly helps achieve stabilized drainageways nonetheless. Once again,
site selection has a positive effect on stream stabilization. By repurposing an already
developed, under-utilized site with existing stormwater infrastructure, combined with LID,
the likelihood of bed and bank erosion is greatly reduced. Furthermore, this 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 and is not
applicable for this project.
C. Development Criteria Reference and Constraints
1. There are no known drainage studies for the existing properties.
2. There are drainage studies for both the Stadium Apartments to the north and The Slab
Project east, but those projects will not have any effect on The Standard @ Fort
Collins project.
3. The subject property is essentially an "in-fill" development project as the property is
surrounded by currently developed properties. As such, several constraints have been
identified during the course of this analysis that will impact the proposed drainage
system including:
Existing elevations along the north property lines adjacent to West Lake Street will
be maintained. Existing elevations along the south property lines adjacent to the
West Prospect Road will be maintained. Existing elevations along the west will
also be maintained. Areas along the southern property line of Building B and east
of the southern half of the alley will be raised through use of a landscape wall.
As previously mentioned, overall drainage patterns within the Master Drainage
Basin will be maintained. To alleviate the current drainage problem within West
Lake Street, the majority of the drainage will be routed to West Prospect Road.
The Standard @ Fort Collins
Final Drainage Report 7
D. Hydrological Criteria
1. The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in
Figure RA-16 of the FCSCM, serve as the source for all hydrologic computations
associated with this development. Tabulated data contained in Table RA-7 has been
utilized for Rational Method runoff calculations.
2. The Rational Method has been employed to compute stormwater runoff utilizing
coefficients contained in Tables RO-11 and RO-12 of the FCSCM.
3. The Rational Formula-based Modified Federal Aviation Administration (FAA)
procedure has been utilized for detention storage calculations.
4. Three separate design storms have been utilized to address distinct drainage
scenarios. A fourth design storm has also been computed for comparison purposes.
The first design storm considered is the 80th percentile rain event, which has been
employed to design the project’s water quality features. The second event analyzed is
the “Minor,” or “Initial” Storm, which has a 2-year recurrence interval. The third
event considered is the “Major Storm,” which has a 100-year recurrence interval.
The fourth storm computed, for comparison purposes only, is the 10-year event.
5. No other assumptions or calculation methods have been used with this development
that are not referenced by current City of Fort Collins criteria.
E. Hydraulic Criteria
1. As previously noted, the subject property historically drains into both West Lake Street
and West Prospect Road. The majority of the site drains stormwater via overland
flow.
2. All drainage facilities proposed with The Standard @ Fort Collins project are designed
in accordance with criteria outlined in the FCSCM and/or the Urban Drainage and
Flood Control District’s (UDFCD) Urban Storm Drainage Criteria Manual.
3. As stated in Section I.C.1, above, the subject property is not located within any
regulatory floodplain.
4. The Standard @ Fort Collins project does not propose to modify any natural
drainageways.
F. Floodplain Regulations Compliance
1. As previously mentioned, all structures are located outside of any FEMA 100-year or
City floodplain, and thus are not subject to any floodplain regulations.
G. Modifications of Criteria
1. The proposed The Standard @ Fort Collins development is not requesting any
modification at this time.
The Standard @ Fort Collins
Final Drainage Report 8
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of The Standard @ Fort Collins drainage design are to maintain
existing drainage patterns, minimize the amount of drainage routed to West Lake
Street and ensure no adverse impacts to any adjacent properties.
2. As previously mentioned, there are no off-site flows draining onto the existing
property.
3. A list of tables and figures used within this report can be found in the Table of
Contents at the front of the document. The tables and figures are located within the
sections to which the content best applies.
4. The Standard @ Fort Collins project is composed of four major drainage basins,
designated as Basins N, S, ON, and OS. The drainage patterns for each major basin
are further described below.
Basin N
Basin N is further subdivided into four (4) sub-basins, designated as Basins N1, N2,
N3 and N4. Sub-basin N1 is composed primarily of the drive located west of Building
B and the fire turnaround located north of Building A. It consists of some landscape
surfacing, but predominantly hardscape. Stormwater generated from this sub-basin is
routed via overland and gutter flow and discharges into underground StormTech
Chambers during the water quality event, while bypassing this system during the
major event and discharging undetained into Sub-basin N2. Sub-basin N2 is
composed primarily of the drive located west of Building B and consists of some
landscape surfacing, but predominantly hardscape. Stormwater generated from this
sub-basin is routed via overland flow and gutter flow and is treated through use of a
paver section. During the major storm event, runoff from both Basin N1 and N2 will
be discharged undetained into West Lake Street. Sub-basin N3 is composed entirely
of Building B. Stormwater generated from this sub-basin is routed internal to the
building and discharges into a detention structure within the parking garage. The
structure has two components incorporated within the design. The lower section of
the structure will include a sand bed and treat the stormwater before releasing the
Water Quality event into West Lake Street. The upper section will be open and used
for detention of storm events larger than the Water Quality event. The stormwater
within this section will be routed to West Prospect Road by use of a siphoned storm
drain. Sub-Basin N4 is composed entirely of the internal courtyards within Building B.
Stormwater generated from this sub-basin is routed internal to the building and
discharges in to Storm Line C. This stormwater is routed through Storm Line C and
discharged undetained into West Lake Street.
Basin S
Basin S is further subdivided into six (6) sub-basins, designated as Basins S1-S6.
Sub-basin S1 is composed of the area to the west and north Building A, as well as a
portion of the roof from Building A. Stormwater generated from this sub-basin will be
routed both internal and external to the building and discharges directly into Detention
Pond S1. Pond S1 was designed with isolator rows to treat the Water Quality Event
and sized to detain the 100-year event. Sub-basin S2 is composed of the western
courtyard, as well as a portion of the roof from Building A. Stormwater generated from
The Standard @ Fort Collins
Final Drainage Report 9
this sub-basin will be routed both internal and external to the building and discharges
directly into Detention Pond S2. Pond S2 was designed with isolator rows to treat the
Water Quality Event and sized to detain the 100-year event. Sub-basin S3 is
composed of the central courtyard, as well as a portion of the roof from Building A.
Stormwater generated from this sub-basin will be routed both internal and external to
the building and discharges directly into Detention Pond S3. Pond S3 was designed
with isolator rows to treat the Water Quality Event and sized to detain the 100-year
event. Sub-basin S4 is composed of the eastern courtyard, as well as a portion of the
roof from Building A. Stormwater generated from this sub-basin will be routed both
internal and external to the building and discharges directly into Detention Pond S4.
Pond S4 was designed with isolator rows to treat the Water Quality Event and sized to
detain the 100-year event. Sub-basin S4 is composed of a portion of the roof from
Building A. Stormwater generated from this sub-basin will be routed internal to the
building and discharges directly into Detention Pond S5. Pond S5 was designed with
isolator rows to treat the Water Quality Event and sized to detain the 100-year event.
Sub-basin S6 is composed primarily of the drive located east of Building A and
consists of some landscape surfacing, but predominantly hardscape. Stormwater
generated from this sub-basin is routed via overland flow and gutter flow and is
treated through use of a paver section. During the major storm event, runoff from
Sub-basin S6 will be discharged undetained into West Prospect Road.
Basin ON
Basin ON is further subdivided into two (2) sub-basins, designated as Basins ON1 and
ON2. Sub-basin ON1 is composed primarily of the area located north of the Building
B, and consists of landscape sand public sidewalk. Stormwater generated from this
sub-basin is routed via overland flow and discharges undetained into West Lake
Street. Sub-basin ON2 is composed of a small area located east and south of Building
B and consists entirely of landscaping. Stormwater generated from this sub-basin is
routed via overland flow and discharges undetained to the east and south.
Basin OS
Basin OS is further subdivided into two (2) sub-basins, designated as Basins OS1 and
OS2. Sub-basin OS1 is composed primarily of the area located south of the Building
A, and consists of landscape sand public sidewalk. Stormwater generated from this
sub-basin is routed via overland flow and discharges undetained into West Prospect
Road. Sub-basin OS2 is composed of a small area located north of Building A and
consists entirely of landscaping. Stormwater generated from this sub-basin is routed
via overland flow and discharges undetained to the north.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
this report.
B. Specific Details
1. The main drainage problem associated with this project site is the deficiency of water
quality present within the existing site. The northern portion of the site (Blue Ridge
Apartments) drains overland and discharges directly into the West Lake Street without
water quality. The southern portion of the site (single family residences) drains
overland flow and discharges directly into the West Prospect Road without water
quality. The proposed site will mitigate this issue by instituting the following water
The Standard @ Fort Collins
Final Drainage Report 10
quality devices:
All of the runoff generated from the proposed roof of Building A (Sub-basin N3)
will be routed through a sand filter before discharging into West Lake Street.
All of the runoff generated from the proposed roof of Building A (Sub-basins S1-
S6) will be routed to StormTech Chambers and filter through the drain rock
surrounding the chambers before discharging in to West Prospect Road.
All of the runoff generated to the west of Building A (Sub-basin S1) will be treated
by a paver section, as well as the StormTech Chambers within the drive aisle.
The runoff generated from the central drive corridor will be treated through a
combination of the paver section and StormTech Chambers.
The landscape areas surrounding the project (Sub-basin ON1, ON2, OS1, and
OS2) will be treated by use of a grass buffer, as the run on area is less that 1:1.
2. The release rate for the undeveloped land (pre-development) was established by
calculating the 2-year peak runoff rate of the existing pervious area and the 100-year
peak runoff rate of the existing impervious area located within the project area,
resulting in an overall release of 23.68 cfs. In excluding all portions of the proposed
project that releases undetained (Sub-basins N1, N2, N4, S6, OS1, OS2, ON1, and
ON2), the overall allowable peak runoff rate for the remaining site was calculated at
14.51 cfs. This remaining release rate was divided among Sub-Basins N2, S1, S2,
S3, S4 and S5. These release rates were utilized in the FAA method for design of
Ponds S1-S5 and N3. (Refer to Appendix B for these calculations).
3. Detention Pond Calculations
Pond N3
Calculations for Pond N3, based on the characteristics of Sub-basin N3 and an
adjusted release rate of 8.61 cfs, indicate a detention volume of 3,764 cu. ft. This
does not included the Water Quality Capture Volume (WQCV) of 1,825 cu. ft.,
resulting in an overall detention volume of 5,589 cu. ft. Water quality will be treated
through the use of a sand filter and discharge into West Lake Street, while overall
quantity detention will be released into West Prospect Road.
Pond S1
Calculations for Pond S1, based on the characteristics of Sub-basin S1 and an
adjusted release rate of 1.96 cfs, indicate a detention volume of 1,013 cu. ft. This
volume includes the 12-hour release WQCV calculated for this basin (345 cu. ft.).
During a Water Quality storm event, the WQCV will be routed directly into an isolator
row. The isolator rows were sized to capture either the 12-hour release WQCV within
the chambers and the surrounding aggregate or the volume required to detain the
Water Quality storm event only within the chambers, whichever is greater.
Pond S2
Calculations for Pond S2, based on the characteristics of Sub-basin S2 and an
adjusted release rate of 1.01 cfs, indicate a detention volume of 1,115 cu. ft. This
volume includes the 12-hour release WQCV calculated for this basin (224 cu. ft.).
During a Water Quality storm event, the WQCV will be routed directly into an isolator
row. The isolator rows were sized to capture either the 12-hour release WQCV within
the chambers and the surrounding aggregate or the volume required to detain the
Water Quality storm event only within the chambers, whichever is greater.
The Standard @ Fort Collins
Final Drainage Report 11
Pond S3
Calculations for Pond S3, based on the characteristics of Sub-basin S3 and an
adjusted release rate of 1.03 cfs, indicate a detention volume of 1,115 cu. ft. This
volume includes the 12-hour release WQCV calculated for this basin (232 cu. ft.).
During a Water Quality storm event, the WQCV will be routed directly into an isolator
row. The isolator rows were sized to capture either the 12-hour release WQCV within
the chambers and the surrounding aggregate or the volume required to detain the
Water Quality storm event only within the chambers, whichever is greater.
Pond S4
Calculations for Pond S4, based on the characteristics of Sub-basin S4 and an
adjusted release rate of 0.88 cfs, indicate a detention volume of 1,107 cu. ft. This
volume includes the 12-hour release WQCV calculated for this basin (215 cu. ft.).
During a Water Quality storm event, the WQCV will be routed directly into an isolator
row. The isolator rows were sized to capture either the 12-hour release WQCV within
the chambers and the surrounding aggregate or the volume required to detain the
Water Quality storm event only within the chambers, whichever is greater.
Pond S5
Calculations for Pond S5, based on the characteristics of Sub-basin S5 and an
adjusted release rate of 1.01 cfs, indicate a detention volume of 635 cu. ft. This
volume includes the 12-hour release WQCV calculated for this basin (236 cu. ft.).
During a Water Quality storm event, the WQCV will be routed directly into an isolator
row. The isolator rows were sized to capture either the 12-hour release WQCV within
the chambers and the surrounding aggregate or the volume required to detain the
Water Quality storm event only within the chambers, whichever is greater.
4. Detention Pond Results
Pond N3
The total storage available within Pond N3 is 5,589 cu. ft at a High Water Surface
Elevation (HWSE) of 5030.4. The top of the structure will provide more than the
required 12-inches of freeboard. The WQCV is achieved at a water surface elevation
of 5028.5 feet, while the 100-year detention volume is achieved at a water surface
elevation of 5028.90 feet. In the case that the outlet structure within Pond N1 were
to clog, stormwater will exit the pond structure through vents within the exterior wall
and discharge into the drainage swale to the east that was designed for The Slab.
Once within this swale, the emergency flow will discharge directly into West Lake
Street.
Pond S1
The storage volume available within StormTech Vault Structure within Pond S1 is
1,230 cu. ft. This includes the volume stored in the aggregate surrounding the
chambers. To achieve water quality, a total of 16 chambers are proposed to be
wrapped and installed as isolator rows. The water quality volume achieved within
isolator rows (aggregate included) is 469 cu. ft., while the volume achieved within
only the chambers of the isolator row is 235 cu. ft. In the case that the area inlet
within Sub-basin S1 should clog or backwatering should occur, stormwater would
overtop the inlet and discharge directly into West Prospect Road.
The Standard @ Fort Collins
Final Drainage Report 12
Pond S2
The storage volume available within StormTech Vault Structure within Pond S2 is
1,124 cu. ft. This includes the volume stored in the aggregate surrounding the
chambers. To achieve water quality, a total of 4 chambers are proposed to be
wrapped and installed as isolator rows. The water quality volume achieved within
isolator rows (aggregate included) is 300 cu. ft., while the volume achieved within
only the chambers of the isolator row is 184 cu. ft. In the case that the outlet
structure within Sub-basin S2 should clog or backwatering should occur, stormwater
will bubble up from the outlet structure and overtop the wall located at the south end
of the courtyard and discharge directly into West Prospect Road.
Pond S3
The storage volume available within StormTech Vault Structure within Pond S3 is
1,124 cu. ft. This includes the volume stored in the aggregate surrounding the
chambers. To achieve water quality, a total of 4 chambers are proposed to be
wrapped and installed as isolator rows. The water quality volume achieved within
isolator rows (aggregate included) is 300 cu. ft., while the volume achieved within
only the chambers of the isolator row is 184 cu. ft. In the case that the outlet
structure within Sub-basin S3 should clog or backwatering should occur, stormwater
will bubble up from the outlet structure and overtop the wall located at the south end
of the courtyard and discharge directly into West Prospect Road.
Pond S4
The storage volume available within StormTech Vault Structure within Pond S4 is
1,124 cu. ft. This includes the volume stored in the aggregate surrounding the
chambers. To achieve water quality, a total of 4 chambers are proposed to be
wrapped and installed as isolator rows. The water quality volume achieved within
isolator rows (aggregate included) is 300 cu. ft., while the volume achieved within
only the chambers of the isolator row is 184 cu. ft. In the case that the outlet
structure within Sub-basin S4 should clog or backwatering should occur, stormwater
will bubble up from the outlet structure and overtop the wall located at the south end
of the courtyard and discharge directly into West Prospect Road.
Pond S5
The storage volume available within StormTech Vault Structure within Pond S5 is
620 cu. ft. This includes the volume stored in the aggregate surrounding the
chambers. To achieve water quality, a total of 4 chambers are proposed to be
wrapped and installed as isolator rows. The water quality volume achieved within
isolator rows (aggregate included) is 117 cu. ft., while the volume achieved within
only the chambers of the isolator row is 59 cu. ft. In the case that the outlet
structure within Sub-basin S2 should clog or backwatering should occur, stormwater
bubble up from the outlet structure and overtop into the central drive aisle, where it
will be routed directly into West Prospect Road.
The Standard @ Fort Collins
Final Drainage Report 13
V. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with The Standard @ Fort Collins project complies with
the City of Fort Collins’ Stormwater Criteria Manual.
2. The drainage design proposed with The Standard @ Fort Collins project complies with
the City of Fort Collins’ Master Drainage Plan for the Old Town Basin.
3. There are no regulatory floodplains associated with The Standard @ Fort Collins
development.
4. The drainage plan and stormwater management measures proposed with The
Standard @ Fort Collins development are compliant with all applicable State and
Federal regulations governing stormwater discharge.
B. Drainage Concept
1. The drainage design proposed with this project will effectively limit potential damage
associated with its stormwater runoff. The Standard @ Fort Collins will detain for the
pervious area converted to impervious areas by releasing at the 2-year existing rate
during the developed100-year storm.
2. The proposed The Standard @ Fort Collins development will not impact the Master
Drainage Plan recommendations for the Old Town major drainage basin.
The Standard @ Fort Collins
Final Drainage Report 14
References
1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities,
November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services.
2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No.
174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code.
3. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and
Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007.
4. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation
Service, United States Department of Agriculture.
5. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control
District, Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008.
APPENDIX A
HYDROLOGIC COMPUTATIONS
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: Standard @ Fort Collins
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: C. Snowdon
Asphalt ……....……………...……….....…...……………….………………………………….. 0.95 100% Date:
Concrete …….......……………….….……….………………..….………………………………… 0.95 90%
Gravel ……….…………………….….…………………………..……………………………….. 0.50 40%
Roofs …….…….………………..……………….…………………………………………….. 0.95 90%
Pavers…………………………...………………..…………………………………………….. 0.40 22%
Lawns and Landscaping
Sandy Soil ……..……………..……………….…………………………………………….. 0.15 0%
Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year Cf
= 1.00 100-year Cf = 1.25
Basin ID
Basin Area
(s.f.)
Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Roofs
(ac)
Area of
Gravel
(ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
HN1 87709 2.01 0.84 0.27 0.61 0.00 0.30 0.83 0.83 1.00 81%
HS1 96447 2.21 0.00 0.14 0.25 0.24 1.58 0.33 0.33 0.41 20%
Total 184156 4.23 0.84 0.41 0.86 0.24 1.88 0.57 0.57 0.71 49%
HN1 (Impervious) 74619 1.71 0.84 0.27 0.61 0.00 0.00 0.95 0.95 1.00 95%
HN1 (Pervious) 13090 0.30 0.00 0.00 0.00 0.00 0.30 0.15 0.15 0.19 0%
HS2 (Impervious) 27620 0.63 0.00 0.14 0.25 0.24 0.00 0.78 0.78 0.97 71%
HS2 (Pervious) 68827 1.58 0.00 0.00 0.00 0.00 1.58 0.15 0.15 0.19 0%
HISTORIC COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
Notes
November 29, 2016
Overland Flow, Time of Concentration:
Project: Standard @ Fort Collins
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V
Tc = Ti + Tt (Equation RO-2)
Velocity (Gutter Flow), V = 20·S½
Velocity (Swale Flow), V = 15·S½
NOTE: C-value for overland flows over grassy surfaces; C = 0.25
Is Length
>500' ?
C*Cf
(2-yr
Cf=1.00)
C*Cf
(10-yr
Cf=1.00)
C*Cf
(100-yr
Cf=1.25)
Length,
L
(ft)
Slope,
S
(%)
Ti
2-yr
(min)
Ti
10-yr
(min)
Ti
100-yr
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
Rational Method Equation: Project: Standard @ Fort Collins
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
hn1 HN1 2.01 8 8 5 0.83 0.83 1.00 2.46 4.21 9.95 4.11 7.03 20.03
hs1 HS1 2.21 15 15 14 0.33 0.33 0.41 1.87 3.19 6.82 1.36 2.33 6.21
N/A HN1 (Impervious) 1.71 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 4.64 7.93 17.04
N/A HN1 (Pervious) 0.30 5 5 5 0.15 0.15 0.19 2.85 4.87 9.95 0.13 0.22 0.56
N/A HS2 (Impervious) 0.63 6 6 5 0.78 0.78 0.97 2.67 4.56 9.95 1.31 2.25 6.12
N/A HS2 (Pervious) 1.58 20 20 19 0.15 0.15 0.19 1.61 2.74 5.75 0.38 0.65 1.70
Total Release = 23.68
HISTORIC RUNOFF COMPUTATIONS
Intensity,
i2
(in/hr)
Intensity,
i10
(in/hr)
Intensity,
i100
(in/hr)
Notes
C. Snowdon
November 29, 2016
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
Design
Point
Basin(s)
Area, A
(acres)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
Flow,
Q2
(cfs)
C2
Total allowable release from Basin Hs1
= 6.51
Total allowable release from Basin HN1
= 17.17
Flow,
Q10
(cfs)
Flow,
Q100
(cfs)
C10 C
100
Q = C f ( C )( i )( A )
Page 3 of 7 \\BRONCOS\Engineers\Projects\1290-001\Drainage\Hydrology\1290-001_Rational-Calcs.xlsx\Hist-Direct-Runoff
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: Standard @ Fort Collins
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By:
Asphalt ……....……………...……….....…...……………….………………………………….0.. 95 100% Date:
Concrete …….......……………….….……….………………..….………………………………… 0.95 90%
Gravel ……….…………………….….…………………………..……………………………….0.. 50 40%
Roofs …….…….………………..……………….…………………………………………….. 0.95 90%
Pavers…………………………...………………..…………………………………………….. 0.40 22%
Lawns and Landscaping
Sandy Soil ……..……………..……………….…………………………………………….. 0.15 0%
Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year Cf
= 1.00 100-year Cf = 1.25
Basin ID
Basin Area
(s.f.)
Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Roofs
(ac)
Area of
Gravel
(ac)
Area of
Pavers
(ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
N1 9833 0.226 0.000 0.152 0.000 0.000 0.020 0.054 0.71 0.71 0.89 61%
N2 6789 0.156 0.000 0.087 0.000 0.000 0.042 0.027 0.66 0.66 0.83 50%
N3 60592 1.391 0.000 0.000 1.391 0.000 0.000 0.000 0.95 0.95 1.00 90%
N4 3856 0.089 0.000 0.000 0.089 0.000 0.000 0.000 0.95 0.95 1.00 90%
S1 16407 0.377 0.000 0.051 0.265 0.000 0.024 0.037 0.84 0.84 1.00 76%
S2 11749 0.270 0.000 0.038 0.179 0.000 0.000 0.053 0.79 0.79 0.99 72%
S3 11749 0.270 0.000 0.043 0.180 0.000 0.000 0.047 0.81 0.81 1.00 74%
Overland Flow, Time of Concentration:
Project: Standard @ Fort Collins
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V
Tc = T
i + Tt
(Equation RO-2)
Velocity (Gutter Flow), V = 20·S
½
Velocity (Swale Flow), V = 15·S
½
NOTE: C-value for overland flows over grassy surfaces; C = 0.25
Is Length
>500' ?
C*Cf
(2-yr
Cf=1.00)
C*Cf
(10-yr
Cf=1.00)
C*Cf
(100-yr
Cf=1.25)
Length,
L
(ft)
Slope,
S
(%)
Ti
2-yr
(min)
Ti
10-yr
(min)
Ti
100-yr
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Rational Method Equation: Project: Standard @ Fort Collins
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
n1 N1 0.23 5 5 5 0.71 0.71 0.89 2.85 4.87 9.95 0.46 0.78 2.00 2.00
n2 N2 0.16 5 5 5 0.66 0.66 0.83 2.85 4.87 9.95 0.29 0.50 1.28 1.28
n3 N3 1.39 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 3.77 6.44 13.84 8.61
n4 N4 0.09 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.24 0.41 0.88 0.88
s1 S1 0.38 5 5 5 0.84 0.84 1.00 2.85 4.87 9.95 0.90 1.54 3.75 1.96
s2 S2 0.27 5 5 5 0.79 0.79 0.99 2.85 4.87 9.95 0.61 1.04 2.66 1.01
s3 S3 0.27 5 5 5 0.81 0.81 1.00 2.85 4.87 9.95 0.62 1.07 2.68 1.03
s4 S4 0.25 5 5 5 0.81 0.81 1.00 2.85 4.87 9.95 0.57 0.98 2.48 0.88
s5 S5 0.21 5 5 5 0.94 0.94 1.00 2.85 4.87 9.95 0.56 0.95 2.06 1.01
s6 S6 0.21 8 8 6 0.60 0.60 0.75 2.46 4.21 9.63 0.32 0.54 1.54 1.54
on1 ON1 0.14 5 5 5 0.43 0.43 0.54 2.85 4.87 9.95 0.17 0.28 0.72 0.72
on2 ON2 0.17 5 5 5 0.15 0.15 0.19 2.85 4.87 9.95 0.07 0.13 0.32 0.32
os1 OS1 0.37 5 5 5 0.49 0.49 0.61 2.85 4.87 9.95 0.51 0.87 2.23 2.23
os2 OS2 0.11 5 5 5 0.15 0.15 0.19 2.85 4.87 9.95 0.05 0.08 0.20 0.20
Total 23.68
November 29, 2016
Intensity,
i10
(in/hr)
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
C10
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
100-year
Release Rate
DEVELOPED RUNOFF COMPUTATIONS
C100
Design
Point
Flow,
Q100
(cfs)
Flow,
Q2
(cfs)
10-yr
Tc
(min)
2-yr
Tc
(min)
C2
Flow,
Q10
(cfs)
Intensity,
i100
(in/hr)
Basin(s)
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
n1 N1 0.226 0.71 0.89 5.0 5.0 0.46 2.00
n2 N2 0.156 0.66 0.83 5.0 5.0 0.29 1.28
n3 N3 1.391 0.95 1.00 5.0 5.0 3.77 13.84
s1 S1 0.377 0.84 1.00 5.0 5.0 0.90 3.75
s2 S2 0.270 0.79 0.99 5.0 5.0 0.61 2.66
s3 S3 0.270 0.81 1.00 5.0 5.0 0.62 2.68
s4 S4 0.249 0.81 1.00 5.0 5.0 0.57 2.48
s5 S5 0.207 0.94 1.00 5.0 5.0 0.56 2.06
s6 S6 0.214 0.60 0.75 8.0 5.9 0.32 1.54
on1 ON1 0.136 0.43 0.54 5.0 5.0 0.17 0.72
on2 ON2 0.173 0.15 0.19 5.0 5.0 0.07 0.32
os1 OS1 0.366 0.49 0.61 5.0 5.0 0.51 2.23
os2 OS2 0.106 0.15 0.19 5.0 5.0 0.05 0.20
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
hn1 HN1 2.014 0.83 1.00 7.7 5.0 4.11 20.03
hs1 HS1 2.214 0.33 0.41 15.1 13.8 1.36 6.21
Page 7 of 7 \\BRONCOS\Engineers\Projects\1290-001\Drainage\Hydrology\1290-001_Rational-Calcs.xlsx\SUMMARY-TABLE
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 – Storm Sewers
B.2 – Inlets
B.3 – Detention Facilities
APPENDIX B.1
STORM SEWERS (FOR FUTURE USE)
APPENDIX B.2
INLETS (FOR FUTURE USE)
APPENDIX B.3
DETENTION FACILITIES
Pond No :
N3
100-yr
1.00
5.00 min 3764 ft3
1.52 acres 0.086 ac-ft
Max Release Rate = 8.61 cfs
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 4540 1.00 8.61 2583 1957
10 7.720 7045 0.75 6.46 3875 3171
15 6.520 8925 0.67 5.74 5166 3759
20 5.600 10221 0.63 5.38 6458 3764
25 4.980 11362 0.60 5.17 7749 3613
30 4.520 12375 0.58 5.02 9041 3334
35 4.080 13032 0.57 4.92 10332 2700
40 3.740 13652 0.56 4.84 11624 2029
45 3.460 14209 0.56 4.78 12915 1294
50 3.230 14738 0.55 4.74 14207 532
55 3.030 15208 0.55 4.70 15498 -290
60 2.860 15660 0.54 4.66 16790 -1129
65 2.720 16135 0.54 4.64 18081 -1946
70 2.590 16545 0.54 4.61 19373 -2827
75 2.480 16974 0.53 4.59 20664 -3690
80 2.380 17376 0.53 4.57 21956 -4580
85 2.290 17764 0.53 4.56 23247 -5483
90 2.210 18152 0.53 4.54 24539 -6387
95 2.130 18466 0.53 4.53 25830 -7364
100 2.060 18800 0.53 4.52 27122 -8322
105 2.000 19165 0.52 4.51 28413 -9248
110 1.940 19475 0.52 4.50 29705 -10230
115 1.890 19835 0.52 4.49 30996 -11161
120 1.840 20150 0.52 4.48 32288 -12137
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
A =
Tc =
Project Location :
Design Point
C =
Design Storm
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
Pond No :
s1
100-yr
0.98
5.00 min 1013 ft3
0.38 acres 0.023 ac-ft
Max Release Rate = 1.96 cfs
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 1103 1.00 1.96 588 515
10 7.720 1711 0.75 1.47 882 829
15 6.520 2168 0.67 1.31 1176 992
20 5.600 2483 0.63 1.23 1470 1013
25 4.980 2760 0.60 1.18 1764 996
30 4.520 3006 0.58 1.14 2058 948
35 4.080 3166 0.57 1.12 2352 814
40 3.740 3316 0.56 1.10 2646 670
45 3.460 3451 0.56 1.09 2940 511
50 3.230 3580 0.55 1.08 3234 346
55 3.030 3694 0.55 1.07 3528 166
60 2.860 3804 0.54 1.06 3822 -18
65 2.720 3919 0.54 1.06 4116 -197
70 2.590 4019 0.54 1.05 4410 -391
75 2.480 4123 0.53 1.05 4704 -581
80 2.380 4221 0.53 1.04 4998 -777
85 2.290 4315 0.53 1.04 5292 -977
90 2.210 4409 0.53 1.03 5586 -1177
95 2.130 4486 0.53 1.03 5880 -1394
100 2.060 4567 0.53 1.03 6174 -1607
105 2.000 4655 0.52 1.03 6468 -1813
110 1.940 4731 0.52 1.02 6762 -2031
115 1.890 4818 0.52 1.02 7056 -2238
120 1.840 4895 0.52 1.02 7350 -2455
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
A =
Tc =
Project Location :
Design Point
C =
Design Storm
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
Pond No :
s2
100-yr
0.99
5.00 min 1115 ft3
0.27 acres 0.026 ac-ft
Max Release Rate = 1.01 cfs
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 798 1.00 1.01 303 495
10 7.720 1238 0.75 0.76 454 784
15 6.520 1569 0.67 0.67 605 963
20 5.600 1796 0.63 0.63 757 1040
25 4.980 1997 0.60 0.61 908 1089
30 4.520 2175 0.58 0.59 1059 1115
35 4.080 2290 0.57 0.58 1211 1079
40 3.740 2399 0.56 0.57 1362 1037
45 3.460 2497 0.56 0.56 1514 984
50 3.230 2590 0.55 0.55 1665 925
55 3.030 2673 0.55 0.55 1816 857
60 2.860 2752 0.54 0.55 1968 785
65 2.720 2836 0.54 0.54 2119 717
70 2.590 2908 0.54 0.54 2270 637
75 2.480 2983 0.53 0.54 2422 561
80 2.380 3054 0.53 0.54 2573 481
85 2.290 3122 0.53 0.53 2724 397
90 2.210 3190 0.53 0.53 2876 314
95 2.130 3245 0.53 0.53 3027 218
100 2.060 3304 0.53 0.53 3178 125
105 2.000 3368 0.52 0.53 3330 38
110 1.940 3423 0.52 0.53 3481 -59
115 1.890 3486 0.52 0.53 3632 -147
120 1.840 3541 0.52 0.53 3784 -243
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
1290-001
The Standard @ Fort Collins
Project Number :
Project Name :
Pond S2
A =
Pond No :
s3
100-yr
1.00
5.00 min 1115 ft3
0.27 acres 0.026 ac-ft
Max Release Rate = 1.03 cfs
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 806 1.00 1.03 309 497
10 7.720 1251 0.75 0.77 464 787
15 6.520 1584 0.67 0.69 618 966
20 5.600 1814 0.63 0.64 773 1042
25 4.980 2017 0.60 0.62 927 1090
30 4.520 2197 0.58 0.60 1082 1115
35 4.080 2313 0.57 0.59 1236 1077
40 3.740 2424 0.56 0.58 1391 1033
45 3.460 2522 0.56 0.57 1545 977
50 3.230 2616 0.55 0.57 1700 917
55 3.030 2700 0.55 0.56 1854 846
60 2.860 2780 0.54 0.56 2009 771
65 2.720 2864 0.54 0.55 2163 701
70 2.590 2937 0.54 0.55 2318 620
75 2.480 3013 0.53 0.55 2472 541
80 2.380 3084 0.53 0.55 2627 458
85 2.290 3153 0.53 0.55 2781 372
90 2.210 3222 0.53 0.54 2936 287
95 2.130 3278 0.53 0.54 3090 188
100 2.060 3337 0.53 0.54 3245 93
105 2.000 3402 0.52 0.54 3399 3
110 1.940 3457 0.52 0.54 3554 -96
115 1.890 3521 0.52 0.54 3708 -187
120 1.840 3577 0.52 0.54 3863 -286
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
1290-001
The Standard @ Fort Collins
Project Number :
Project Name :
Pond S3
A =
Pond No :
s4
100-yr
1.00
5.00 min 1107 ft3
0.25 acres 0.025 ac-ft
Max Release Rate = 0.88 cfs
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 743 1.00 0.88 263 481
10 7.720 1153 0.75 0.66 394 760
15 6.520 1461 0.67 0.58 525 936
20 5.600 1673 0.63 0.55 656 1017
25 4.980 1860 0.60 0.53 788 1073
30 4.520 2026 0.58 0.51 919 1107
35 4.080 2133 0.57 0.50 1050 1083
40 3.740 2235 0.56 0.49 1181 1054
45 3.460 2326 0.56 0.49 1313 1014
50 3.230 2413 0.55 0.48 1444 969
55 3.030 2490 0.55 0.48 1575 915
60 2.860 2564 0.54 0.47 1706 857
65 2.720 2641 0.54 0.47 1838 804
70 2.590 2709 0.54 0.47 1969 740
75 2.480 2779 0.53 0.47 2100 679
80 2.380 2845 0.53 0.46 2231 613
85 2.290 2908 0.53 0.46 2363 546
90 2.210 2972 0.53 0.46 2494 478
95 2.130 3023 0.53 0.46 2625 398
100 2.060 3078 0.53 0.46 2756 321
105 2.000 3137 0.52 0.46 2888 250
110 1.940 3188 0.52 0.46 3019 169
115 1.890 3247 0.52 0.46 3150 97
120 1.840 3299 0.52 0.46 3281 18
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
1290-001
The Standard @ Fort Collins
Project Number :
Project Name :
Pond S4
A =
Pond No :
s5
100-yr
1.00
5.00 min 635 ft3
0.21 acres 0.015 ac-ft
Max Release Rate = 1.01 cfs
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 618 1.00 1.01 304 314
10 7.720 959 0.75 0.76 456 503
15 6.520 1215 0.67 0.68 608 607
20 5.600 1391 0.63 0.63 760 631
25 4.980 1546 0.60 0.61 912 635
30 4.520 1684 0.58 0.59 1064 621
35 4.080 1774 0.57 0.58 1216 558
40 3.740 1858 0.56 0.57 1368 490
45 3.460 1934 0.56 0.56 1520 414
50 3.230 2006 0.55 0.56 1671 334
55 3.030 2070 0.55 0.55 1823 246
60 2.860 2131 0.54 0.55 1975 156
65 2.720 2196 0.54 0.55 2127 69
70 2.590 2252 0.54 0.54 2279 -28
75 2.480 2310 0.53 0.54 2431 -121
80 2.380 2365 0.53 0.54 2583 -218
85 2.290 2418 0.53 0.54 2735 -318
90 2.210 2470 0.53 0.53 2887 -417
95 2.130 2513 0.53 0.53 3039 -526
100 2.060 2559 0.53 0.53 3191 -632
105 2.000 2608 0.52 0.53 3343 -735
110 1.940 2650 0.52 0.53 3495 -844
115 1.890 2699 0.52 0.53 3647 -947
120 1.840 2742 0.52 0.53 3799 -1056
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
A =
Tc =
Project Location :
Design Point
C =
Design Storm
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
APPENDIX C
WATER QUALITY DESIGN COMPUTATIONS
Project Title Date:
Project Number Calcs By:
Client
Basin
0.8
WQCV = Watershed inches of Runoff (inches) 61.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.192 in
A = 0.23 ac
V = 0.0036 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
157 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Standard @ Fort Collins June 22, 2016
1290-001 C. Snowdon
Landmark
N1
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
n1
WQ
0.71
5.00 min 61 ft3
0.23 acres 0.00 ac-ft
Max Release Rate = 0.13 cfs
Time
(min)
Ft Collins
WQ
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustmen
t Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 1.425 69 1.00 0.13 38 31
10 1.105 106 1.00 0.13 75 31
15 0.935 135 0.67 0.08 75 60
20 0.805 155 0.63 0.08 94 61
25 0.715 172 0.60 0.08 113 59
30 0.650 188 0.58 0.07 132 56
35 0.585 197 0.57 0.07 151 46
40 0.535 206 0.56 0.07 170 36
45 0.495 214 0.56 0.07 189 26
50 0.460 221 0.55 0.07 207 14
55 0.435 230 0.55 0.07 226 4
60 0.410 237 0.54 0.07 245 -8
65 0.385 241 0.54 0.07 264 -23
70 0.365 246 0.54 0.07 283 -37
75 0.345 249 0.53 0.07 302 -53
80 0.330 254 0.53 0.07 321 -66
85 0.315 258 0.53 0.07 339 -82
90 0.305 264 0.53 0.07 358 -94
95 0.290 265 0.53 0.07 377 -112
100 0.280 270 0.53 0.07 396 -126
105 0.270 273 0.52 0.07 415 -142
110 0.260 275 0.52 0.07 434 -158
115 0.255 282 0.52 0.07 452 -170
120 0.245 283 0.52 0.07 471 -188
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
C =
Tc =
A =
N1
Input Variables Results
Design Point
Design Storm Required Detention Volume
Client : Landmark
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Type of Permeable Pavement Section
A) What type of section of permeable pavement is used?
(Based on the land use and activities, proximity to adjacent
structures and soil characteristics.)
B) What type of wearing course?
2. Required Storage Volume
A) Effective Imperviousness of Area Tributary to Permeable Pavement, Ia I
a = 50.0 %
B) Tributary Area's Imperviousness Ratio (I = Ia / 100) i = 0.500
C) Tributary Watershed Area ATotal
= 6,789 sq ft
(including area of permeable pavement system)
D) Area of Permeable Pavement System APPS
= 1,843 sq ft
(Minimum recommended permeable pavement area = 1358 sq ft)
E) Impervious Tributary Ratio RT
= 1.3
(Contributing Imperviuos Area / Permeable Pavement Ratio)
F) Water Quality Capture Volume (WQCV) Based on 12-hour Drain Time WQCV = 93 cu ft
(WQCV = (0.8 * (0.91 * i
3
- 1.19 * i
2
+ 0.78 * i) / 12) * Area)
G) Is flood control volume being added?
H) Total Volume Needed VTotal
= cu ft
3. Depth of Reservoir
A) Minimum Depth of Reservoir Dmin
= 16.0 inches
(Minimum recommended depth is 6 inches)
B) Is the slope of the reservoir/subgrade interface equal to 0%?
C) Porosity (Porous Gravel Pavement < 0.3, Others < 0.40) P = 0.30
D) Slope of the Base Course/Subgrade Interface S = ft / ft
E) Length Between Lateral Flow Barriers L = ft
F) Volume Provided Based on Depth of Base Course V = 691 cu ft
Flat or Stepped: V = P * ((Dmin-1)/12) * Area
Sloped: V = P * [(Dmin - (D
min - 6*SL-1)) / 12] * Area
4. Lateral Flow Barriers
A) Type of Lateral Flow Barriers
B) Number of Permeable Pavement Cells Cells =
5. Perimeter Barrier
A) Is a perimeter barrier provided on all sides of the
pavement system?
(Recommeded for PICP, concrete grid pavement, or for any
no-infiltration section.)
The Standard @ Fort Collins - Basin N2
Fort Collins, CO
Design Procedure Form: Permeable Pavement Systems (PPS)
Cody Snowdon
Northern Engineering
November 30, 2016
Choose One
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
6. Filter Material and Underdrain System
A) Is the underdrain placed below a 6-inch thick layer of
CDOT Class C filter material?
B) Diameter of Slotted Pipe (slot dimensions per Table PPs-2)
C) Distance from the Lowest Elevation of the Storage Volume y = 2.0 ft
(i.e. the bottom of the base course to the center of the orifice)
7. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is there a minimum 30 mil thick impermeable PVC geomembrane
liner on the bottom and sides of the basin, extending up to the top
of the base course?
B) CDOT Class B Separator Fabric
8. Outlet
(Assumes each cell has similar area, subgrade slope, and length
between lateral barriers (unless subgrade is flat). Calculate cells
individually where this varies.)
A) Depth of WQCV in the Reservoir DWQCV
= 2.03 inches
(Elevation of the Flood Control Outlet)
B) Diameter of Orifice for 12-hour Drain Time DOrifice
= inches
(Use a minimum orifice diameter of 3/8-inches)
Notes:
The Standard @ Fort Collins - Basin N2
Design Procedure Form: Permeable Pavement Systems (PPS)
Cody Snowdon
Northern Engineering
November 30, 2016
Fort Collins, CO
Choose One
YES
NO
Choose One
4-inch
6-inch
Choose One
Choose One
YES
NO
Placed above the liner
Placed above and below the liner
N/A
WQ - Basin N2 - UD-BMP_v3.03.xlsm, PPS 11/30/2016, 1:06 AM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 90.0 %
(100% if all paved and roofed areas upstream of sand filter)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.900
C) Water Quality Capture Volume (WQCV) Based on 12-hour Drain Time WQCV = 0.36 watershed inches
WQCV= 0.9 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including sand filter area) Area = 60,592 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 1,825 cu ft
VWQCV = WQCV / 12 * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = 0.43 in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = 1,825 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 DWQCV = 0.7 ft
B) Sand Filter Side Slopes (Horizontal distance per unit vertical, Z = 0.00 ft / ft
4:1 or flatter preferred). Use "0" if sand filter has vertical walls.
C) Mimimum Filter Area (Flat Surface Area) AMin = 405 sq ft
D) Actual Filter Area AActual = 2778 sq ft
E) Volume Provided VT = 4167 cu ft
3. Filter Material
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = 0.1 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = 1,825 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 1 - 13 / 16 in
The Standard @ Fort Collins - Basin N3
Fort Collins, CO
Design Procedure Form: Sand Filter (SF)
Cody Snowdon
Northern Engineering
November 30, 2016
Choose One
Choose One
18" CDOT Class C Filter Material
Other (Explain):
YES
NO
WQ - Basin N3 - UD-BMP_v3.03.xlsm, SF 11/30/2016, 1:00 AM
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?
PROVIDE A 30 MIL (MIN) PVC GEOMEMBRANE PER TABLE
SF-4 WITH SEPARATOR FABRIC (PER TABLE SF-3) ABOVE IT.
PROVIDE SEPARATOR FABRIC BELOW THE GEOMEMBRANE
AS WELL IF SUBGRADE IS ANGULAR OR COULD OTHERWISE
PUNCTURE THE GEOMEMBRANE.
6-7. Inlet / Outlet Works
A) Describe the type of energy dissipation at inlet points and means of
conveying flows in excess of the WQCV through the outlet
Notes:
Design Procedure Form: Sand Filter (SF)
Cody Snowdon
Northern Engineering
November 30, 2016
The Standard @ Fort Collins - Basin N3
Fort Collins, CO
Choose One
YES NO
WQ - Basin N3 - UD-BMP_v3.03.xlsm, SF 11/30/2016, 1:00 AM
Project Title Date:
Project Number Calcs By:
Client
Basin
0.8
WQCV = Watershed inches of Runoff (inches) 76.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.244 in
A = 0.38 ac
V = 0.0077 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
The Standard @ Fort Collins June 22, 2016
1290-001 C. Snowdon
Landmark
S1
334 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
s1
WQ
0.84
5.00 min 109 ft3
0.38 acres 0.00 ac-ft
Max Release Rate = 0.26 cfs
Time
(min)
Ft Collins
WQ
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustmen
t Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 1.425 135 1.00 0.26 79 57
10 1.105 210 1.00 0.26 158 52
15 0.935 266 0.67 0.18 158 109
20 0.805 306 0.63 0.16 197 109
25 0.715 340 0.60 0.16 237 103
30 0.650 371 0.58 0.15 276 95
35 0.585 389 0.57 0.15 315 74
40 0.535 407 0.56 0.15 355 52
45 0.495 423 0.56 0.15 394 29
50 0.460 437 0.55 0.14 434 3
55 0.435 455 0.55 0.14 473 -18
60 0.410 467 0.54 0.14 512 -45
65 0.385 475 0.54 0.14 552 -76
70 0.365 485 0.54 0.14 591 -106
75 0.345 492 0.53 0.14 631 -139
80 0.330 502 0.53 0.14 670 -169
85 0.315 509 0.53 0.14 710 -201
90 0.305 522 0.53 0.14 749 -227
95 0.290 523 0.53 0.14 788 -265
100 0.280 532 0.53 0.14 828 -296
105 0.270 539 0.52 0.14 867 -329
110 0.260 543 0.52 0.14 907 -363
115 0.255 557 0.52 0.14 946 -389
120 0.245 559 0.52 0.14 986 -427
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Landmark
The Standard @ Fort Collins
1290-001
Project Name :
Project Number :
S1
Project Title Date:
Project Number Calcs By:
Client
Basin
0.8
WQCV = Watershed inches of Runoff (inches) 72.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.227 in
A = 0.27 ac
V = 0.0051 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Standard @ Fort Collins June 22, 2016
1290-001 C. Snowdon
Landmark
S2
224 cu. ft.
Drain Time
a =
i =
WQCV =
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
s2
WQ
0.79
5.00 min 180 ft3
0.27 acres 0.00 ac-ft
Max Release Rate = 0.07 cfs
Time
(min)
Ft Collins
WQ
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustmen
t Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 1.425 92 1.00 0.07 21 70
10 1.105 142 1.00 0.07 42 99
15 0.935 180 0.67 0.05 42 138
20 0.805 207 0.63 0.04 53 154
25 0.715 230 0.60 0.04 64 166
30 0.650 250 0.58 0.04 74 176
35 0.585 263 0.57 0.04 85 178
40 0.535 275 0.56 0.04 96 179
45 0.495 286 0.56 0.04 106 180
50 0.460 295 0.55 0.04 117 179
55 0.435 307 0.55 0.04 127 180
60 0.410 316 0.54 0.04 138 178
65 0.385 321 0.54 0.04 149 173
70 0.365 328 0.54 0.04 159 169
75 0.345 332 0.53 0.04 170 163
80 0.330 339 0.53 0.04 180 159
85 0.315 344 0.53 0.04 191 153
90 0.305 353 0.53 0.04 202 151
95 0.290 354 0.53 0.04 212 142
100 0.280 360 0.53 0.04 223 137
105 0.270 364 0.52 0.04 233 131
110 0.260 367 0.52 0.04 244 123
115 0.255 377 0.52 0.04 255 122
120 0.245 378 0.52 0.04 265 112
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
Client : Landmark
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Project Name : The Standard @ Fort Collins
Project Number : 1290-001
C =
Tc =
A =
S2
Input Variables Results
Project Title Date:
Project Number Calcs By:
Client
Basin
0.8
WQCV = Watershed inches of Runoff (inches) 74.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.235 in
A = 0.27 ac
V = 0.0053 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Standard @ Fort Collins June 22, 2016
1290-001 C. Snowdon
Landmark
S3
232 cu. ft.
Drain Time
a =
i =
WQCV =
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
s3
WQ
0.81
5.00 min 158 ft3
0.27 acres 0.00 ac-ft
Max Release Rate = 0.09 cfs
Time
(min)
Ft Collins
WQ
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustmen
t Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 1.425 94 1.00 0.09 28 66
10 1.105 146 1.00 0.09 57 89
15 0.935 185 0.67 0.06 57 128
20 0.805 212 0.63 0.06 71 141
25 0.715 235 0.60 0.06 85 151
30 0.650 257 0.58 0.06 99 158
35 0.585 270 0.57 0.05 113 156
40 0.535 282 0.56 0.05 127 154
45 0.495 293 0.56 0.05 142 152
50 0.460 303 0.55 0.05 156 147
55 0.435 315 0.55 0.05 170 145
60 0.410 324 0.54 0.05 184 140
65 0.385 330 0.54 0.05 198 131
70 0.365 337 0.54 0.05 212 124
75 0.345 341 0.53 0.05 226 114
80 0.330 348 0.53 0.05 241 107
85 0.315 353 0.53 0.05 255 98
90 0.305 362 0.53 0.05 269 93
95 0.290 363 0.53 0.05 283 80
100 0.280 369 0.53 0.05 297 72
105 0.270 373 0.52 0.05 311 62
110 0.260 377 0.52 0.05 325 51
115 0.255 386 0.52 0.05 340 47
120 0.245 387 0.52 0.05 354 33
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
Client : Landmark
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Project Name : The Standard @ Fort Collins
Project Number : 1290-001
C =
Tc =
A =
S3
Input Variables Results
Project Title Date:
Project Number Calcs By:
Client
Basin
0.8
WQCV = Watershed inches of Runoff (inches) 74.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.235 in
A = 0.25 ac
V = 0.0049 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Standard @ Fort Collins June 22, 2016
1290-001 C. Snowdon
Landmark
S4
215 cu. ft.
Drain Time
a =
i =
WQCV =
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
s4
WQ
0.81
5.00 min 166 ft3
0.25 acres 0.00 ac-ft
Max Release Rate = 0.07 cfs
Time
(min)
Ft Collins
WQ
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustmen
t Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 1.425 87 1.00 0.07 21 66
10 1.105 135 1.00 0.07 42 92
15 0.935 171 0.67 0.05 42 129
20 0.805 196 0.63 0.04 53 143
25 0.715 218 0.60 0.04 64 154
30 0.650 238 0.58 0.04 74 164
35 0.585 250 0.57 0.04 85 165
40 0.535 261 0.56 0.04 96 166
45 0.495 272 0.56 0.04 106 166
50 0.460 281 0.55 0.04 117 164
55 0.435 292 0.55 0.04 127 164
60 0.410 300 0.54 0.04 138 162
65 0.385 305 0.54 0.04 149 157
70 0.365 312 0.54 0.04 159 152
75 0.345 316 0.53 0.04 170 146
80 0.330 322 0.53 0.04 180 142
85 0.315 327 0.53 0.04 191 136
90 0.305 335 0.53 0.04 202 133
95 0.290 336 0.53 0.04 212 124
100 0.280 342 0.53 0.04 223 119
105 0.270 346 0.52 0.04 233 112
110 0.260 349 0.52 0.04 244 105
115 0.255 358 0.52 0.04 255 103
120 0.245 359 0.52 0.04 265 93
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
Client : Landmark
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Project Name : The Standard @ Fort Collins
Project Number : 1290-001
C =
Tc =
A =
S4
Input Variables Results
Project Title Date:
Project Number Calcs By:
Client
Basin
0.8
WQCV = Watershed inches of Runoff (inches) 89.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.314 in
A = 0.21 ac
V = 0.0054 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Standard @ Fort Collins June 22, 2016
1290-001 C. Snowdon
Landmark
S5
236 cu. ft.
Drain Time
a =
i =
WQCV =
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
s5
WQ
0.94
5.00 min 82 ft3
0.21 acres 0.00 ac-ft
Max Release Rate = 0.14 cfs
Time
(min)
Ft Collins
WQ
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustmen
t Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 1.425 83 1.00 0.14 42 41
10 1.105 129 1.00 0.14 85 44
15 0.935 164 0.67 0.09 85 79
20 0.805 188 0.63 0.09 106 82
25 0.715 209 0.60 0.08 127 81
30 0.650 228 0.58 0.08 149 79
35 0.585 239 0.57 0.08 170 69
40 0.535 250 0.56 0.08 191 59
45 0.495 260 0.56 0.08 212 48
50 0.460 269 0.55 0.08 233 35
55 0.435 279 0.55 0.08 255 25
60 0.410 287 0.54 0.08 276 11
65 0.385 292 0.54 0.08 297 -5
70 0.365 298 0.54 0.08 318 -20
75 0.345 302 0.53 0.08 340 -38
80 0.330 308 0.53 0.08 361 -53
85 0.315 313 0.53 0.07 382 -69
90 0.305 320 0.53 0.07 403 -83
95 0.290 322 0.53 0.07 425 -103
100 0.280 327 0.53 0.07 446 -119
105 0.270 331 0.52 0.07 467 -136
110 0.260 334 0.52 0.07 488 -154
115 0.255 342 0.52 0.07 509 -167
120 0.245 343 0.52 0.07 531 -187
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
Client : Landmark
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Project Name : The Standard @ Fort Collins
Project Number : 1290-001
C =
Tc =
A =
S5
Input Variables Results
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Type of Permeable Pavement Section
A) What type of section of permeable pavement is used?
(Based on the land use and activities, proximity to adjacent
structures and soil characteristics.)
B) What type of wearing course?
2. Required Storage Volume
A) Effective Imperviousness of Area Tributary to Permeable Pavement, Ia I
a = 48.0 %
B) Tributary Area's Imperviousness Ratio (I = Ia / 100) i = 0.480
C) Tributary Watershed Area ATotal
= 9,332 sq ft
(including area of permeable pavement system)
D) Area of Permeable Pavement System APPS
= 982 sq ft
(Minimum recommended permeable pavement area = 1806 sq ft)
E) Impervious Tributary Ratio RT
= 4.1 IMPERVIOUS TRIBUTARY RATIO
(Contributing Imperviuos Area / Permeable Pavement Ratio) EXCEEDS 2.0
F) Water Quality Capture Volume (WQCV) Based on 12-hour Drain Time WQCV = 125 cu ft
(WQCV = (0.8 * (0.91 * i
3
- 1.19 * i
2
+ 0.78 * i) / 12) * Area)
G) Is flood control volume being added?
H) Total Volume Needed VTotal
= cu ft
3. Depth of Reservoir
A) Minimum Depth of Reservoir Dmin
= 16.0 inches
(Minimum recommended depth is 6 inches)
B) Is the slope of the reservoir/subgrade interface equal to 0%?
C) Porosity (Porous Gravel Pavement < 0.3, Others < 0.40) P = 0.30
D) Slope of the Base Course/Subgrade Interface S = ft / ft
E) Length Between Lateral Flow Barriers L = ft
F) Volume Provided Based on Depth of Base Course V = 368 cu ft
Flat or Stepped: V = P * ((Dmin-1)/12) * Area
Sloped: V = P * [(Dmin - (D
min - 6*SL-1)) / 12] * Area
4. Lateral Flow Barriers
A) Type of Lateral Flow Barriers
B) Number of Permeable Pavement Cells Cells =
5. Perimeter Barrier
A) Is a perimeter barrier provided on all sides of the
pavement system?
(Recommeded for PICP, concrete grid pavement, or for any
no-infiltration section.)
The Standard @ Fort Collins - Basin S6
Fort Collins, CO
Design Procedure Form: Permeable Pavement Systems (PPS)
Cody Snowdon
Northern Engineering
November 30, 2016
Choose One
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
6. Filter Material and Underdrain System
A) Is the underdrain placed below a 6-inch thick layer of
CDOT Class C filter material?
B) Diameter of Slotted Pipe (slot dimensions per Table PPs-2)
C) Distance from the Lowest Elevation of the Storage Volume y = 2.0 ft
(i.e. the bottom of the base course to the center of the orifice)
7. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is there a minimum 30 mil thick impermeable PVC geomembrane
liner on the bottom and sides of the basin, extending up to the top
of the base course?
B) CDOT Class B Separator Fabric
8. Outlet
(Assumes each cell has similar area, subgrade slope, and length
between lateral barriers (unless subgrade is flat). Calculate cells
individually where this varies.)
A) Depth of WQCV in the Reservoir DWQCV
= 5.09 inches
(Elevation of the Flood Control Outlet)
B) Diameter of Orifice for 12-hour Drain Time DOrifice
= inches
(Use a minimum orifice diameter of 3/8-inches)
Notes:
Fort Collins, CO
The Standard @ Fort Collins - Basin S6
Design Procedure Form: Permeable Pavement Systems (PPS)
Cody Snowdon
Northern Engineering
November 30, 2016
Choose One
YES
NO
Choose One
4-inch
6-inch
Choose One
Choose One
YES
NO
Placed above the liner
Placed above and below the liner
N/A
WQ - Basin S6 - UD-BMP_v3.03.xlsm, PPS 11/30/2016, 1:08 AM
Vault ID
Total
Required
WQ Volume
(cf)
Flow,
WQ
(cfs)
Chamber
Type
Chamber Release
Ratea
(cfs)
Chamber
Volumeb
(cf)
Installed Camber
w/ Aggregatec
(cf)
Mimimum
No. of
Chambersd
Total Release
Ratee
(cfs)
Required
Storage
Volume by
FAA Method
(cf)
Mimimum
No. of
Chambersf
Storage
Provided
within the
Chambersg
(cf)
Total
Installed
System
Volumeh
(cf)
S1 334 0.46 SC-160 0.011 6.85 15.00 23 0.26 109 16 110 345
S2 224 0.31 SC-740 0.024 45.90 74.90 3 0.07 180 4 184 300
S3 232 0.31 SC-740 0.024 45.90 74.90 4 0.09 158 4 184 300
S4 215 0.29 SC-740 0.024 45.90 74.90 3 0.07 166 4 184 300
S5 236 0.28 SC-310 0.016 14.70 29.30 9 0.14 82 6 88 264
N1 157 0.23 SC-160 0.011 6.85 15.00 11 0.13 61 9 62 165
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.
e. System volume includes total number of chambers, plus surrounding aggregate. This number must meet or exceed the required WQCV.
Chamber Configuration Summary
\\BRONCOS\Engineers\Projects\1290-001\Drainage\WatQual\1290-001 Chamber Summary.xlsx
Chamber Dimensions SC-310 SC-310 SC-740
Width (in) 25.0 34.0 51.0
Length (in) 84.4 85.4 85.4
Height (in) 12.0 16.0 30.0
Floor Area (sf) 14.7 20.2 30.2
Chamber Volume (cf) 6.9 14.7 45.9
Chamber/Aggregate Volume (cf) 15.0 29.3 74.9
Flow Rate* 0.35 gpm/sf
1 cf = 7.48052 gal
1 gallon = 0.133681 cf
1 GPM = 0.002228 cfs
*Flow rate based on 1/2 of Nov 07 QMAX in Figure 17 of UNH Testing Report
SC-160 SC-310 SC-740
Flow Rate/chamber (cfs) 0.011426 0.015724 0.023586
StormTech Chamber Data
Chamber Flow Rate
Chamber Flow Rate Conversion (gpm/sf to cfs)
\\BRONCOS\Engineers\Projects\1290-001\Drainage\WatQual\1290-001 Chamber Summary.xlsx
Design
Point Basin ID Basin Area Treatment Type
LID
System
Area Treated
by LID
System
Percent of Site
Treated by LID
System
Area of
Pavers
Area of
Asphalt
Parking
Percent
Pavers
Run-on Area
for Paver
Section
Run-on Area
Ratio
n1 N1 0.226 ac. StormTech
Chambers Yes 0.226 ac. 5% 0.020 ac. 0.152 ac. 13.16% 0.064 3.2
n2 N2 0.156 ac. Pavers Yes 0.156 ac. 4% 0.042 ac. 0.087 ac. 48.28% 0.087 2.1
n3 N3 1.391 ac. Sand Filter Yes 1.391 ac. 33% 0.000 ac. 0.000 ac. N/A 0 N/A
n4 N4 0.089 ac. No N/A 0% 0.000 ac. 0.000 ac. N/A 0 N/A
s1 S1 0.377 ac. StormTech
Chambers Yes 0.377 ac. 9% 0.024 ac. 0.051 ac. 47.06% 0 N/A
s2 S2 0.270 ac. StormTech
Chambers Yes 0.270 ac. 6% 0.000 ac. 0.038 ac. N/A 0 N/A
s3 S3 0.270 ac. StormTech
Chambers Yes 0.270 ac. 6% 0.000 ac. 0.043 ac. N/A 0 N/A
s4 S4 0.249 ac. StormTech
Chambers Yes 0.249 ac. 6% 0.000 ac. 0.031 ac. N/A 0 N/A
s5 S5 0.207 ac. StormTech
Chambers Yes 0.207 ac. 5% 0.000 ac. 0.000 ac. N/A 0 N/A
s6 S6 0.214 ac. Pavers Yes 0.214 ac. 5% 0.023 ac. 0.113 ac. 20.35% 0.0719 3.1
on1 ON1 0.136 ac. Grass Buffer No N/A 0% 0.000 ac. 0.047 ac. N/A 0 N/A
on2 ON2 0.176 ac. Grass Buffer No N/A 0% 0.000 ac. 0.000 ac. N/A 0 N/A
os1 OS1 0.366 ac. Grass Buffer No N/A 0% 0.000 ac. 0.155 ac. N/A 0 N/A
os2 OS2 0.106 ac. Grass Buffer No N/A 0% 0.000 ac. 0.000 ac. N/A 0 N/A
Total 4.23 ac. 3.360 ac. 79% 0.109 ac. 0.717 ac. 15.20%
APPENDIX D
EROSION CONTROL REPORT
Lake Avenue Apartments
Final Erosion Control Report
A comprehensive Erosion and Sediment Control Plan (along with associated details) will be included
with the final construction drawings. It should be noted, however, that any such Erosion and
Sediment Control Plan serves only as a general guide to the Contractor. Staging and/or phasing of
the BMPs depicted, and additional or different BMPs from those included may be necessary during
construction, or as required by the authorities having jurisdiction.
It shall be the responsibility of the Contractor to ensure erosion control measures are properly
maintained and followed. The Erosion and Sediment Control Plan is intended to be a living
document, constantly adapting to site conditions and needs. The Contractor shall update the
location of BMPs as they are installed, removed or modified in conjunction with construction
activities. It is imperative to appropriately reflect the current site conditions at all times.
The Erosion and Sediment Control Plan shall address both temporary measures to be implemented
during construction, as well as permanent erosion control protection. Best Management Practices
from the Volume 3, Chapter 7 – Construction BMPs will be utilized. Measures may include, but are
not limited to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways
and inlet protection at proposed storm inlets. Vehicle tracking control pads, spill containment and
clean-up procedures, designated concrete washout areas, dumpsters, and job site restrooms shall
also be provided by the Contractor.
Grading and Erosion Control Notes can be found on Sheet CS2 of the Utility Plans. The Utility
Plans at final design will also contain a full-size Erosion Control Plan as well as a separate sheet
dedicated to Erosion Control Details. In addition to this report and the referenced plan sheets, the
Contractor shall be aware of, and adhere to, the applicable requirements outlined in any existing
Development Agreement(s) of record, as well as the Development Agreement, to be recorded prior
to issuance of the Development Construction Permit. Also, the Site Contractor for this project will
be required to secure a Stormwater Construction General Permit from the Colorado Department of
Public Health and Environment (CDPHE), Water Quality Control Division – Stormwater Program,
before commencing any earth disturbing activities. Prior to securing said permit, the Site Contractor
shall develop a comprehensive StormWater Management Plan (SWMP) pursuant to CDPHE
requirements and guidelines. The SWMP will further describe and document the ongoing activities,
inspections, and maintenance of construction BMPs.
MAP POCKET
DR1 – OVERALL DRAINAGE EXHIBIT
UP
D.S. D.S.
R.D.
D.S.
D.S. D.S. D.S.
D.S.
D.S.
R.D. D.S.
D.S.
X X
X
X X
X X
X
X
X X
X X
X
X X
X X
X X
X X
X
X
X
CO
UD UD UD UD UD
UD UD
UD
UD UD UD UD UD
CO
CO
UD UD
UD
MAJOR STORM EVENT
OUTLET FROM INTERNAL
POND STRUCTURE
WATER QUALITY EVENT
OUTLET FROM INTERNAL
POND STRUCTURE
s1
s1
s1
s1
s1
s2 s3 s3 s4
s4
s5
s5
s6
n3
n3
n2
on1
on2
os2
os1
acres
N3
0.95 1.391
1.00
acres
ON1
0.43 0.136
0.54
acres
S1
0.84 0.377
1.00
acres
OS1
0.49 0.366
0.61
acres
S3
0.81 0.270
1.00
acres
S2
0.79 0.270
0.99
acres
S4
0.81 0.249
1.00
acres
OS2
0.15 0.106
0.19
acres
N2
0.66 0.156
0.83
acres
S5
0.94 0.207
1.00
acres
S6
0.60 0.214
0.75
acres
ON2
0.15 0.173
0.19
POND S4
(SC-740 CHAMBERS)
POND S3
(SC-740 CHAMBERS)
POND S2
(SC-740 CHAMBERS)
POND S1
(SC-160 CHAMBERS)
POND S5
(SC-310 CHAMBERS)
POND N2
(WITH SAND FILTER)
PROSPECT ROAD
(60' PUBLIC ROW)
LAKE STREET
(60' PUBLIC ROW)
THE SLAB
STADIUM APARTMENTS
STORM LINE C2
STORM LINE C1
STORM LINE B
STORM LINE A
UNDERDRAIN
PERMEABLE
PAVERS
UNDERDRAIN
PERMEABLE
PAVERS
WATER QUALITY
STRUCTURE
WATER QUALITY
STRUCTURE
WATER QUALITY
STRUCTURE
WATER QUALITY
STRUCTURE
WATER QUALITY
STRUCTURE
POND OUTLET
STRUCTURE
POND OUTLET
STRUCTURE
POND OUTLET
STRUCTURE
POND OUTLET
STRUCTURE
WATER QUALITY
STRUCTURE
ROOF
LEADER
ROOF LEADER ROOF LEADER
ROOF
LEADER
ROOF
LEADER
ROOF
LEADER
ROOF
LEADER
ROOF
LEADER
ROOF
LEADER
ROOF
LEADER
ROOF
LEADER
ROOF
LEADER
AREA INLET
SIDEWALK CHASE
STORM LINE C
OUTFALL
AREA INLET
AREA INLET W/
WATER QUALITY
PLATE
21 SC-160 CHAMBERS
FOR WATER QUALITY
acres
N1
0.71 0.226
0.89
CURB AND GUTTER
n1
SIDEWALK CHASE
(THE SLAB)
STADIUM APARTMENTS
STORM WATER OUTFALL
INLET
BUILDING A
BUILDING B
SIPHONED PIPE
DRY WELL
TRENCH DRAIN
INTERNAL PIPE
OUTFALL FOR
BASIN N4
acres
N4
0.95 0.089
1.00
acres
N4
0.95 0.089
1.00
n3
s2
WATER QUALITY
STRUCTURE POND OUTLET
STRUCTURE
No. Revisions:
By: Date:
REVIEWED BY:
N. HAWS
DESIGNED BY:
DRAWN BY:
SCALE:
DATE:
November 30, 2016
PROJECT:
1290-001
Sheet
of 16
STANDARD AT FORT COLLINS
These drawings are
instruments of service
provided by Northern
Engineering Services, Inc.
and are not to be used for
any type of construction
unless signed and sealed by
a Professional Engineer in
the employ of Northern
Engineering Services, Inc.
NOT FOR CONSTRUCTION
REVIEW SET
11/30/2016
301 North Howes Street, Suite 100
Fort Collins, Colorado 80521
E N G I N E E R I N G
N O R T H E RN
PHONE: 970.221.4158
www.northernengineering.com
C6.00
DRAINAGE EXHIBIT
C. Snowdon
B. Mathisen
1"=30'
GRAPHIC SCALE:
LEGEND:
EXISTING INLET GRATE
EXISTING DECID. TREE
EXISTING CONIF. TREE
EXISTING LIGHT POLE
EXISTING STUMP
ST EXISTING STORM SEWER LINE
EXISTING CURB/GUTTER FLOWLINE
EXISTING EDGE OF ASPHALT
4950
4950
4:1
BANK SLOPE
PROPOSED OVERLAND FLOW DIRECTION
CONCENTRATED FLOW DIRECTION
PROPOSED SWALE FLOWLINE
PROPOSED INFLOW CURB/GUTTER FLOWLINE
PROPOSED STORM DRAIN WITH INLET
PROPOSED CONTOUR
EXISTING CONTOUR
PROPOSED OUTFALL CURB/GUTTER FLOWLINE
City Engineer Date
Date
Date
Date
Date
Stormwater Utility
Parks & Recreation
Traffic Engineer Date
APPROVED:
CHECKED BY:
CHECKED BY:
CHECKED BY:
CHECKED BY:
CHECKED BY:
Water & Wastewater Utility
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
Environmental Planner
NORTH
( IN FEET )
0
1 INCH = 20 FEET
20 20 40 60
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what's below.
Call before you dig.
R
acres
A2
0.25 0.08
0.31
a3
DRAINAGE BASIN AREA
DESIGN POINT
DRAINAGE BASIN ID
DRAINAGE BASIN MINOR/MAJOR COEFF.
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
1.REFER TO THE "PRELIMINARY DRAINAGE REPORT FOR STANDARD AT FORT COLLINS" BY NORTHERN ENGINEERING, DATED 11/30/2016 FOR ADDITIONAL INFORMATION.
NOTES:
16
RUNOFF SUMMARY TABLE:
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
Q2
(cfs)
Q100
(cfs)
N1 0.226 0.71 0.89 0.46 2.00
N2 0.156 0.66 0.83 0.29 1.28
N3 1.391 0.95 1.00 3.77 13.84
N4 0.089 0.95 1.00 0.24 0.88
S1 0.377 0.84 1.00 0.90 3.75
S2 0.270 0.79 0.99 0.61 2.66
S3 0.270 0.81 1.00 0.62 2.68
S4 0.249 0.81 1.00 0.57 2.48
S5 0.207 0.94 1.00 0.56 2.06
S6 0.214 0.60 0.75 0.32 1.54
ON1 0.136 0.43 0.54 0.17 0.72
ON2 0.173 0.15 0.19 0.07 0.32
OS1 0.366 0.49 0.61 0.51 2.23
OS2 0.106 0.15 0.19 0.05 0.20
Design
Point Basin ID Basin Area Treatment Type
LID
System
Area
Treated by
LID System
Percent of Site
Treated by LID
System
Area of
Pavers
Area of
Asphalt
Parking
Percent
Pavers
Run-on Area
for Paver
Section
Run-on Area
Ratio
n1 N1 0.226 ac. StormTech
Chambers Yes 0.226 ac. 5% 0.020 ac. 0.152 ac. 13.16% 0.064 3.2
n2 N2 0.156 ac. Pavers Yes 0.156 ac. 4% 0.042 ac. 0.087 ac. 48.28% 0.087 2.1
n3 N3 1.391 ac. Sand Filter Yes 1.391 ac. 33% 0.000 ac. 0.000 ac. N/A 0 N/A
n4 N4 0.089 ac. No N/A 0% 0.000 ac. 0.000 ac. N/A 0 N/A
s1 S1 0.377 ac. StormTech
Chambers Yes 0.377 ac. 9% 0.024 ac. 0.051 ac. 47.06% 0 N/A
s2 S2 0.270 ac. StormTech
Chambers Yes 0.270 ac. 6% 0.000 ac. 0.038 ac. N/A 0 N/A
s3 S3 0.270 ac. StormTech
Chambers Yes 0.270 ac. 6% 0.000 ac. 0.043 ac. N/A 0 N/A
s4 S4 0.249 ac. StormTech
Chambers Yes 0.249 ac. 6% 0.000 ac. 0.031 ac. N/A 0 N/A
s5 S5 0.207 ac. StormTech
Chambers Yes 0.207 ac. 5% 0.000 ac. 0.000 ac. N/A 0 N/A
s6 S6 0.214 ac. Pavers Yes 0.214 ac. 5% 0.023 ac. 0.113 ac. 20.35% 0.0719 3.1
on1 ON1 0.136 ac. Grass Buffer No N/A 0% 0.000 ac. 0.047 ac. N/A 0 N/A
on2 ON2 0.176 ac. Grass Buffer No N/A 0% 0.000 ac. 0.000 ac. N/A 0 N/A
os1 OS1 0.366 ac. Grass Buffer No N/A 0% 0.000 ac. 0.155 ac. N/A 0 N/A
os2 OS2 0.106 ac. Grass Buffer No N/A 0% 0.000 ac. 0.000 ac. N/A 0 N/A
Total 4.23 ac. 3.360 ac. 79% 0.109 ac. 0.717 ac. 15.20%
LID TABLE:
No Infiltration
Partial Infiltration Section
Full Infiltration Section
Choose One
YES
NO
Choose One
YES- Flat or Stepped Installation
NO- Sloped Installation
Choose One
Concrete Walls
PVC geomembrane installed normal to flow
N/A- Flat installation
Other (Describe):
Choose One
YES
NO
Choose One
PICP
Concrete Grid Pavement
Pervious Concrete
Porous Gravel
WQ - Basin S6 - UD-BMP_v3.03.xlsm, PPS 11/30/2016, 1:08 AM
Design Point
Design Storm Required Detention Volume
Page 10 of 14
1290-001 Chamber Summary.xlsx
ö
ç
è
= æ
12 hr
Design Point
Design Storm Required Detention Volume
Page 8 of 14
1290-001 Chamber Summary.xlsx
ö
ç
è
= æ
12 hr
Design Point
Design Storm Required Detention Volume
Page 6 of 14
1290-001 Chamber Summary.xlsx
ö
ç
è
= æ
12 hr
Design Point
Design Storm Required Detention Volume
Page 4 of 14
1290-001 Chamber Summary.xlsx
ö
ç
è
= æ
12 hr
A =
Tc =
Client :
Design Point
C =
Design Storm
Page 2 of 14
1290-001 Chamber Summary.xlsx
ö
ç
è
= æ
12 hr
No Infiltration
Partial Infiltration Section
Full Infiltration Section
Choose One
YES
NO
Choose One
YES- Flat or Stepped Installation
NO- Sloped Installation
Choose One
Concrete Walls
PVC geomembrane installed normal to flow
N/A- Flat installation
Other (Describe):
Choose One
YES
NO
Choose One
PICP
Concrete Grid Pavement
Pervious Concrete
Porous Gravel
WQ - Basin N2 - UD-BMP_v3.03.xlsm, PPS 11/30/2016, 1:06 AM
Project Name : The Standard @ Fort Collins
Project Number : 1290-001
Page 12 of 14
1290-001 Chamber Summary.xlsx
ö
ç
è
= æ
12 hr
1290-001
The Standard @ Fort Collins
Project Number :
Project Name :
Pond S5
Page 1 of 1
1290-001_Pond S5_DetentionVolume_FAAModified Method.xls
Tc =
Project Location :
Design Point
C =
Design Storm
Page 1 of 1
1290-001_Pond S4_DetentionVolume_FAAModified Method.xls
Tc =
Project Location :
Design Point
C =
Design Storm
Page 1 of 1
1290-001_Pond S3_DetentionVolume_FAAModified Method.xls
Tc =
Project Location :
Design Point
C =
Design Storm
Page 1 of 1
1290-001_Pond S2_DetentionVolume_FAAModified Method.xls
1290-001
The Standard @ Fort Collins
Project Number :
Project Name :
Pond S1
Page 1 of 1
1290-001_Pond S1_DetentionVolume_FAAModified Method.xls
1290-001
The Standard @ Fort Collins
Project Number :
Project Name :
Pond N3
Page 1 of 1
1290-001_Pond N3_DetentionVolume_FAAModified Method.xls
Q = C f ( C )( i )( A ) C. Snowdon
Page 6 of 7 \\BRONCOS\Engineers\Projects\1290-001\Drainage\Hydrology\1290-001_Rational-Calcs.xlsx\Direct-Runoff
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
n1 N1 No 0.71 0.71 0.89 25 9.40% 1.7 1.7 0.9 174 1.01% 2.01 1.4 0.5 N/A N/A 5 5 5
n2 N2 No 0.66 0.66 0.83 27 3.85% 2.7 2.7 1.7 157 1.70% 2.61 1.0 1.5 N/A N/A 5 5 5
n3 N3 No 0.95 0.95 1.00 N/A N/A N/A N/A 345 2.00% 2.83 2.0 1.5 N/A N/A 5 5 5
n4 N4 No 0.95 0.95 1.00 25 2.00% 1.1 1.1 0.7 50 0.50% 1.41 0.6 2.5 N/A N/A 5 5 5
s1 S1 No 0.84 0.84 1.00 N/A N/A N/A N/A 80 2.00% 2.83 0.5 N/A N/A N/A 5 5 5
s2 S2 No 0.79 0.79 0.99 N/A N/A N/A N/A 100 2.00% 2.83 0.6 N/A N/A N/A 5 5 5
s3 S3 No 0.81 0.81 1.00 N/A N/A N/A N/A 100 2.00% 2.83 0.6 N/A N/A N/A 5 5 5
s4 S4 No 0.81 0.81 1.00 N/A N/A N/A N/A 100 2.00% 2.83 0.6 N/A N/A N/A 5 5 5
s5 S5 No 0.94 0.94 1.00 N/A N/A N/A N/A 100 2.00% 2.83 0.6 N/A N/A N/A 5 5 5
s6 S6 No 0.60 0.60 0.75 100 2.47% 6.9 6.9 4.9 120 0.93% 1.93 1.0 N/A N/A N/A 8 8 6
on1 ON1 No 0.43 0.43 0.54 19 5.05% 3.2 3.2 2.7 N/A N/A N/A N/A N/A N/A 5 5 5
on2 ON2 No 0.15 0.15 0.19 12 16.50% 2.4 2.4 2.3 N/A N/A N/A N/A N/A N/A 5 5 5
os1 OS1 No 0.49 0.49 0.61 41 3.56% 4.8 4.8 3.8 N/A N/A N/A N/A N/A N/A 5 5 5
os2 OS2 No 0.15 0.15 0.19 13 18.38% 2.4 2.4 2.3 N/A N/A N/A N/A N/A N/A 5 5 5
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Gutter/Internal Building Flow Swale Flow
Design
Point
Basin
Overland Flow
C. Snowdon
November 29, 2016
Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
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S4 10859 0.249 0.000 0.031 0.174 0.000 0.000 0.044 0.81 0.81 1.00 74%
S5 9015 0.207 0.000 0.000 0.205 0.000 0.000 0.002 0.94 0.94 1.00 89%
S6 9332 0.214 0.000 0.113 0.000 0.000 0.023 0.079 0.60 0.60 0.75 48%
ON1 5913 0.136 0.000 0.047 0.000 0.000 0.000 0.088 0.43 0.43 0.54 31%
ON2 7524 0.173 0.000 0.000 0.000 0.000 0.000 0.173 0.15 0.15 0.19 0%
OS1 15925 0.366 0.000 0.155 0.000 0.000 0.000 0.210 0.49 0.49 0.61 38%
OS2 4609 0.106 0.000 0.000 0.000 0.000 0.000 0.106 0.15 0.15 0.19 0%
TOTAL 184152 4.23 0.000 0.718 2.483 0.000 0.109 1.135 0.77 0.77 0.96 68%
DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I.
10-year Cf = 1.00
November 29, 2016
**Soil Classification of site is Sandy Loam**
C. Snowdon
Page 4 of 7 \\BRONCOS\Engineers\Projects\1290-001\Drainage\Hydrology\1290-001_Rational-Calcs.xlsx\C-Values
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
hn1 HN1 No 0.83 0.83 1.00 77 0.40% 6.0 6.0 2.2 205 1.01% 2.01 1.7 N/A N/A N/A 8 8 5
hs1 HS1 No 0.33 0.33 0.41 118 1.96% 12.5 12.5 11.2 N/A N/A N/A 113 0.23% 0.72 2.6 15 15 14
N/A HN1 (Impervious) No 0.95 0.95 1.00 77 0.40% 3.3 3.3 2.2 205 1.01% 2.01 1.7 N/A N/A N/A 5 5 5
N/A HN1 (Pervious) No 0.15 0.15 0.19 22 4.23% 5.2 5.2 4.9 N/A N/A N/A N/A N/A N/A 5 5 5
N/A HS2 (Impervious) No 0.78 0.78 0.97 84 2.13% 4.3 4.3 1.7 N/A N/A N/A 130 0.50% 1.06 2.0 6 6 5
N/A HS2 (Pervious) No 0.15 0.15 0.19 80 0.50% 20.0 20.0 19.2 N/A N/A N/A N/A N/A N/A 20 20 19
HISTORIC TIME OF CONCENTRATION COMPUTATIONS
C. Snowdon
November 29, 2016
Design
Point
Basin
Overland Flow Gutter Flow Swale Flow Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
Page 2 of 7 \\BRONCOS\Engineers\Projects\1290-001\Drainage\Hydrology\1290-001_Rational-Calcs.xlsx\Hist-Tc-10-yr_&_100-yr
10-year Cf = 1.00
**Soil Classification of site is Sandy Loam**
Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I.
Existing Impervious Area Breakdown
Page 1 of 7 \\BRONCOS\Engineers\Projects\1290-001\Drainage\Hydrology\1290-001_Rational-Calcs.xlsx\Hist-C-Values