HomeMy WebLinkAboutVILLAGE COOPERATIVE FORT COLLINS - FDP - FDP170009 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFINAL DRAINAGE AND
EROSION CONTROL REPORT
February 22, 2017
The Village Cooperative of Fort Collins
Fort Collins, Colorado
Prepared for:
Village Cooperative of Fort Collins
Shane Wright
1400 Corporate Center Circle, Suite 100
Eagan, Minnesota 55121
651-760-8306
Prepared by:
301 N. Howes Street, Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158
www.northernengineering.com
Project Number: 1284-001
This Drainage Report is consciously provided as a PDF.
Please consider the environment before printing this document in its entirety.
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RE: Final Drainage and Erosion Control Report for
The Village Cooperative of Fort Collins
Dear Staff:
Northern Engineering is pleased to submit this Final Drainage and Erosion Control Report for your
review. This report accompanies Final Development Plan submittal for the proposed The Village
Cooperative of Fort Collins development.
This report has been prepared in accordance to Fort Collins Stormwater Criteria Manual (FCSCM),
and serves to document the stormwater impacts associated with the proposed 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.
Stephanie Thomas, PE
Project Engineer
The Village Cooperative of 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 ....................................................................... 4
A. Major Basin Description ............................................................................................................... 4
B. Sub-Basin Description .................................................................................................................. 4
III. DRAINAGE DESIGN CRITERIA ................................................................................... 4
A. Regulations .................................................................................................................................. 4
B. Four Step Process ........................................................................................................................ 4
C. Development Criteria Reference and Constraints ......................................................................... 5
D. Hydrological Criteria .................................................................................................................... 5
E. Hydraulic Criteria ......................................................................................................................... 6
F. Floodplain Regulations Compliance .............................................................................................. 6
G. Modifications of Criteria .............................................................................................................. 6
IV. DRAINAGE FACILITY DESIGN .................................................................................... 6
A. General Concept .......................................................................................................................... 6
B. Water Quality Treatment ........................................................................................................... 10
C. Specific Details ........................................................................................................................... 10
V. CONCLUSIONS ...................................................................................................... 10
A. Compliance with Standards ........................................................................................................ 10
B. Drainage Concept ...................................................................................................................... 11
References ....................................................................................................................... 12
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
B.1 – Detention Ponds and Water Quality
B.2 – Storm Sewers
B.3 – Inlets
APPENDIX C – Erosion Control Report
APPENDIX D – LID Exhibit
APPENDIX E – References
The Village Cooperative of Fort Collins
Final Drainage Report
LIST OF FIGURES:
Figure 1 – Aerial Photograph ................................................................................................ 2
Figure 2– Proposed Site Plan ................................................................................................ 3
Figure 3 – Existing Floodplains ............................................................................................. 3
LIST OF TABLES:
Table 1 - Historic Rational Basin Summary ............................................................................ 7
Table 2 - Proposed Rational Basin Summary .......................................................................... 8
Table 3 - Detention Pond Summary ....................................................................................... 8
Table 4 - Historic Stormwater Release and Allowable Developed Release.................................... 9
Table 5 - Proposed Stormwater Release ................................................................................. 9
MAP POCKET:
HDR1 – Historic Drainage Exhibit
DR1 - Drainage Exhibit
The Village Cooperative of Fort Collins
Final Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. Located in the southwest quarter of Section 25, Township 7 North, Range 69 West of
the 6th Prime Meridian, City of Fort Collins, County of Larimer, State of Colorado. The
site is Lot 1, Bellavista PDP.
3. Bounded to the northeast by the Aspen Leaf Apartments, to the west by Stanford
Road, and to the south by Horsetooth Road.
4. No significant offsite flows are directed into the site. The majority of off-site flows are
are prevented from entering the site by curb and gutter and a small swale on the
northern boundary.
The Village Cooperative of Fort Collins
Final Drainage Report 2
5. The Village Cooperative of Fort Collins property was studied with the previous
Bellavista PDP proposal.
B. Description of Property
1. The site is approximately 2.81 acres of on-site basins. An additional 2.30 acres of
off-site basins were evaluated with this drainage study.
Figure 1 – Aerial Photograph
2. The existing site is comprised of vacant land with natural grasses and vegetation. Off-
site basins include portions of adjacent Horsetooth Road and Stanford Road.
3. The site slopes to the southwest corner. Two existing inlets, located adjacent to the site
at the intersection of Stanford and Horsetooth Road, collect runoff from the subject
property. Existing grades range between 2-20%.
4. A report by Earth Engineering Consultants dated October 21, 2016 lists the soils for the
area as consisting of lean sandy clay and clayey sand, and sandstone/siltstone/claystone
bedrock ranging from 7.5 to 17 feet below the ground surface. These soils are classified
as Hydrologic Soil Group C and have a low infiltration rate.
5. The proposed project site plan is composed of 1 building, sidewalk, asphalt parking lot
and detention ponds. This site will employ water quality features and runoff reduction
facilities including underground detention and water quality chambers, grass swales
with infiltration section and extended detention basins.
The Village Cooperative of Fort Collins
Final Drainage Report 3
Figure 2– Proposed Site Plan
6. No existing irrigation facilities are known at this time.
7. The project site was studied with the previous Bellavista PDP drainage study. The
proposed project is not requesting a change in the land use.
C. Floodplain
1. The subject property is not located in a FEMA or City regulatory floodplain.
Figure 3 – Existing Floodplains
The Village Cooperative of Fort Collins
Final Drainage Report 4
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. The Village Cooperative of Fort Collins project is located within the Foothills Drainage
Basin, which is located between Prospect Road and Larimer #2 Canal from north to
south and approximately between Shields Street and Zeigler Road from west to east.
2. This area generally drains to Warren Reservoir.
B. Sub-Basin Description
1. The site slopes from the northeast to the southwest corner of the site. Adjacent to the
site, at the intersection of Stanford Road and Horsetooth Road, are two inlets. Flows
within the site and the eastern half of Stanford Road and the northern half of
Horsetooth Road are collected in these two inlets. From there, flows are conveyed
and released to Warren Reservoir.
2. The existing inlets are a part of a larger storm network designed and constructed with
the Strachan Third Filing. A large storm sewer junction vault is located at the
southwest corner of the Village Cooperative site. Three parallel 26” x 43” Concrete
Arch pipes enter this structure from the west and exit this structure to the south.
These pipes convey the 100-yr flows from the Strachan Third development to Warren
Reservoir.
3. The proposed plan will generally detain developed flows and release to the existing
storm infrastructure in the southwest corner of the site. This is the historic flow route.
III. DRAINAGE DESIGN CRITERIA
A. Regulations
There are no optional provisions outside of the FCSCM proposed with The Village
Cooperative of Fort Collins project.
B. Four Step Process
The overall stormwater management strategy employed with The Village Cooperative of
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:
Providing vegetated open areas along the west, east and south portions of the site to
reduce the overall impervious area and to minimize directly connected impervious
areas (MDCIA).
Routing flows, to the extent feasible, through StormTech Isolator chambers to remove
sediment migration.
Providing on-site detention to increase time of concentration, promote infiltration and
reduce loads on existing storm infrastructure.
The Village Cooperative of Fort Collins
Final Drainage Report 5
Routing runoff from the proposed impervious areas into StormTech chambers to
promote infiltration, increased contact time, and filtration.
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 majority of stormwater runoff from the site will ultimately be
intercepted and treated in proposed underground Stormtech water quality chambers.
Water quality for areas not routed through the Stormtech chambers will be provided within
the detention pond volume.
Step 3 – Stabilize Drainageways
This property discharges detained stormwater to existing storm infrastructure constructed
with the Strachan Third Filing. The proposed release from this property is expected to be
negligible compared to the total 100-yr design flows in the existing storm infrastructure.
Step 4 – Implement Site Specific and Other Source Control BMPs.
The proposed project will improve upon site specific source controls compared to historic
conditions:
Localized trash enclosures within the development will allow for the disposal of solid
waste.
Underground Water Quality chambers for water treatment prior to flows entering the
extended detention basins.
Water Quality measures to protect and prolong the design life of the BMPs delineated
in Step 1.
C. Development Criteria Reference and Constraints
1. The proposed site is a part of the Foothills Drainage Basin. This basin requires a 2-
year historic stormwater release from the developed property.
2. This site is subject to the LID requirements per the City of Fort Collins. Please see the
LID Exhibit located in the Appendix for calculations concerning LID treatment. The
site must either have the following:
75% of total new impervious areas must be treated through an LID (Low Impact
Development) treatment BMP, or
50% of total new impervious areas must be treated through an LID (Low Impact
Development) treatment BMP and 25% of new pavement shall be pervious.
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 the 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. Modified FAA Method calculations were utilized for detention storage calculations.
4. Three separate design storms have been utilized to address distinct drainage
scenarios. The first event analyzed is the “Minor,” or “Initial” Storm, which has a 2-
The Village Cooperative of Fort Collins
Final Drainage Report 6
year recurrence interval. The second event considered is the “Major Storm,” which
has a 100-year recurrence interval. The third 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 to the southwest. The
stormwater flows are collected in existing inlets at the intersection of Stanford Road
and Horsetooth Road releases to Warren Reservoir.
2. All drainage facilities proposed with The Village Cooperative of 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 previously, the subject property is not located within a FEMA regulatory
floodplain.
4. The Village Cooperative of 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
floodplain, and thus are not subject to any floodplain regulations.
G. Modifications of Criteria
1. The proposed development is not requesting any modifications to criteria at this time.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of The Village Cooperative of Fort Collins drainage design are to
maintain the allowable storm runoffs as outlined within Foothills Drainage Basin.
2. 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.
3. Historic runoff from The Village Cooperative of Fort Collins project site was evaluated.
This evaluation provided the historic 2-yr and 100-yr peak runoff rates for the existing
site.
Basin H1
Basin H1 has an area of 2.04 acres. This basin contains vacant land. The 2-yr and
100-yr peak runoff rates from Basin H1 are 0.84 cfs and 3.83 cfs, respectively.
The Village Cooperative of Fort Collins
Final Drainage Report 7
Basin H2
Basin H2 has an area of 0.44 acres. This basin contains a portion of the existing
Horsetooth Road. The 2-yr and 100-yr peak runoff rates from Basin H2 are 0.75 cfs
and 3.28 cfs, respectively. This basin is planned to be detained and treated with the
Village Cooperative development plan.
Basin H3
Basin H3 has an area of 0.77 acres. This basin contains a portion of the existing site.
The existing basin contains vacant land. The 2-yr and 100-yr peak runoff rates from
Basin H3 are 0.42 cfs and 1.85 cfs, respectively.
Table 1 - Historic Rational Basin Summary
DRAINAGE SUMMARY TABLE
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2
C100
2-yr
Tc
(min)
100-
yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
1 H1 2.04 0.25 0.31 19.3 18.0 0.84 3.83
2 H2 0.44 0.60 0.74 5.0 5.0 0.75 3.28
1 H3 0.77 0.25 0.31 10.9 10.4 0.42 1.85
4. The Village Cooperative of Fort Collins project divided the site into five (5) major
drainage basins, designated as Basins A, OS and UD. The project further subdivided
Basin A in to ten (10) sub-basins and Basin UD into two (2) sub-basins. The
drainage patterns anticipated for each basin and sub-basin are further described
below.
Basin A
Basin A consists of proposed building, parking lot, sidewalk, landscape areas and
Detention Pond A. Runoff from Basins A1-A7 and A9-A10 are collected in proposed
inlets and conveyed by storm sewer to a proposed Stormtech underground water
quality chambers. The underground water quality chambers provide a chance for
water to infiltrate into the ground. Additionally, the underground Stormtech chambers
provide water quality treatment for storm flows prior to being detained in Detention
Pond A. Runoff from Basin A8 overland flows into the Detention Pond A without pre-
treatment.
Basin OS
Basin OS1 consists of the existing Horsetooth Road, adjacent to the proposed Village
Cooperative development. This basin consists of existing asphalt, proposed asphalt,
proposed curb and gutter, proposed sidewalk and proposed landscaping. This area
will be detained within Detention Pond A.Due to grading constraints, no additional
portions of Horsetooth Avenue or Stanford Road are proposed to be detained on-site.
Basin OS2 consists of the existing Horsetooth Road and Stanford Road. This basin
extends north to the highpoint in Stanford Road (adjacent the Aspen Leaf
Apartments). This basin was analyzed in order to size the proposed inlet within the
proposed right turn lane. This basin will not be detained and treated on-site.
The Village Cooperative of Fort Collins
Final Drainage Report 8
Basin UD
Basin UD encompasses all on-site basins that are undetained.
Basin UD1 and UD2 consist of proposed asphalt driveways, curb and gutter, sidewalk
and landscaping. These basins will flow via Horsetooth and Stanford curb and gutter
to the proposed inlet at Horsetooth Road and Stanford Road.
Table 2 - Proposed Rational Basin Summary
DRAINAGE SUMMARY TABLE
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2
C100
2-yr
Tc
(min)
100-
yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
1 A1 0.02 0.95 1.00 5.0 5.0 0.05 0.18
2 A2 0.07 0.25 0.31 5.0 5.0 0.05 0.21
3 A3 0.22 0.72 0.90 5.0 5.0 0.45 1.98
4 A4 0.10 0.76 0.95 5.0 5.0 0.22 0.94
5 A5 0.35 0.95 1.00 5.0 5.0 0.96 3.53
6 A6 0.45 0.74 0.93 5.9 5.0 0.92 4.14
7 A7 0.04 0.41 0.51 5.0 5.0 0.04 0.20
8 A8 0.49 0.27 0.33 7.7 7.1 0.32 1.44
7 A9 0.36 0.95 1.00 5.0 5.0 0.99 3.62
7 A10 0.03 0.60 0.75 5.0 5.0 0.06 0.24
11 UD1 0.03 0.86 1.00 5.0 5.0 0.06 0.26
11 UD2 0.57 0.33 0.41 5.1 5.0 0.54 2.36
10 OS1 0.44 0.68 0.85 5.8 5.0 0.83 3.76
10 OS2 1.86 0.82 1.00 8.8 7.5 3.57 16.33
5. One (1) detention ponds is proposed with The Village Cooperative of Fort Collins
development. Detention Pond A is located within Basin A and detains all of Basin A
and OS1. The detention pond will release via City of Fort Collins approved outlet
structure to a storm sewer that will connect to the existing storm infrastructure in the
southwest corner of the site.
Detention Pond A
Detention Pond A has a total of 0.58 ac-ft storage available. 0.49 ac-ft of storage is
required with this project. Water quality control volume for Basin A8 is included in
the pond volume. Water quality provided within Detention Pond A does not include
the water quality volume provided upstream in the underground water quality
chambers. Emergency Overflow from the pond is directed south over the proposed
earthern weir and sidewalk to the Horsetooth Road. 1.05 ft of freeboard is provided
in Pond A, measured from the proposed building garage elevation.
Table 3 - Detention Pond Summary
Detention Pond Summary | Proposed Condition
Pond
100-yr
The Village Cooperative of Fort Collins
Final Drainage Report 9
Total Stormwater Release from Site
The total allowable 100-yr release from the site is a summation of the historic 2-yr
runoff from Basin H1-H2, plus the historic 100-yr runoff from Basin H3.
Table 4 - Historic Stormwater Release and Allowable Developed Release
Historic Stormwater Release Allowable
Developed
100-yr Release
(cfs)
Pond/ Basin
2-yr Flow
(cfs)
100-yr Flow
(cfs)
H1 0.84 3.83 0.84
H2 0.75 3.28 0.75
H3 0.42 1.85 1.85
TOTAL 2.01 8.96 3.44
Total developed 100-yr release from the site is a combination of the undetained 100-
year flows from Basins UD1-UD2, plus the detained release from Detention Pond A.
Table 5 - Proposed Stormwater Release
Proposed Stormwater
Release
Pond/ Basin
100-yr Flow
(cfs)
Undetained
Basins
(UD1-UD2) 2.63
Pond A
(Basins A1-
A10,OS1) 1.10
TOTAL 3.73
Due to the grading challenges along Horsetooth Road and Stanford Road, the majority
of Basin UD2 was unable to be captured and routed to the proposed detention pond.
Basin UD2 consists mostly of proposed landscaping and sidewalk along Horsetooth
and Stanford. Additionally, due to the increase in slope of this basin, the time of
concentration was decreased. These factors account for more runoff from this basin in
the 100-yr event as compared to the historic condition.
The pond release rate was set based on the capacity of the pond.
The total release from the site during a 100-year event is 0.29 cfs more than the
allowable release rate.
This additional 0.29 cfs is not expected to impact downstream infrastructure. Based
on the utility plans for Strachan Third Filing, the downstream infrastructure was
designed to convey the 100-yr developed flow of approximately 165 cfs. An
additional 0.29 cfs is considered within the range of error for the pipe. Lastly, the total
The Village Cooperative of Fort Collins
Final Drainage Report 10
runoff during a 100-yr event is proposed to be decreased by 5.23 cfs from historic
condition.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
this report.
B. Water Quality Treatment
1. Basins A1-A7 and A9-A10 have water quality provided exclusively via StormTech
chambers. Following UDFCD standards for a 12-hour drain time, a Water Quality
Capture Volume of 1402 cu. ft. is required. Using SC-740 StormTech chambers
designed for water quality, 1423 cu. ft. is provided within the isolator rows. The
initial flush of stormwater will be detained within these isolators and released via
infiltration through the aggregate section to a subdrain. Stormwater volume exceeding
the volume provided in the Stormtech chambers will overflow a weir within the
proposed inlet and be directed into the detention pond.
2. Basins A8 and OS1 will be treated for water quality within the bottom of the
Detention Pond A through an approved outlet structure and extended detention.
C. Specific Details
1. Storm sewers were sized for the 100-yr storm utilizing the program Hydraflow for
AutoCAD Extension.
2. Inlet B2 at Design Point 6 was designed to convey flows to the Storm tech chambers
during a water quality event and divert flows to the Detention Pond A during events
larger than the water quality event. This diversion will be accomplished by a weir
installed in the inlet at an elevation equal to the water quality elevation.
3. An emergency overflow weir for Detention Pond A was provided to convey the 100-yr
storm flowrate from the pond safetly to Horsetooth Road in an emergency event.
Weirs were analyzed by Hydraflow Express.
4. Inlets were sized for the 100-yr event utilizing Urban Drainage spreadsheets and Area
Inlet calculations spreadsheets.
V. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with The Village Cooperative of Fort Collins project
complies with the City of Fort Collins’ Stormwater Criteria Manual with the exception
of an increased release from the site during a 100-year event.
2. The drainage design proposed with The Village Cooperative of Fort Collins project
complies with the City of Fort Collins’ Master Drainage Plan for the Foothills Drainage
Basin.
3. There are no regulatory floodplains associated with the development.
4. The drainage plan and stormwater management measures proposed with the
development are compliant with all applicable State and Federal regulations governing
stormwater discharge.
5. The site achieves the requirements set forth by the City of Fort Collins for Low Impact
Development (LID) by providing 92% total on-site impervious areas as being treated
through an LID treatment. Please see LID Exhibit located in the Appendix.
The Village Cooperative of Fort Collins
Final Drainage Report 11
B. Drainage Concept
1. The drainage design proposed with this project will effectively comply with the Fort
Collins Master Drainage Plan and will limit any potential damage or erosion
associated with its stormwater runoff. All existing downstream drainage facilities are
expected to not be impacted negatively by this development
2. The drainage design is anticipated to be very conservative. We have omitted any
runoff reduction that will manifest due to infiltration from the underground water
quality chambers. This is currently unable to be calculated with available soils data.
The Village Cooperative of Fort Collins
Final Drainage Report 12
References
1. 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.
2. Geotechnical Subsurface Exploration Report Proposed Village Cooperative of Fort Collins
Horsetooth and Stanford Roads Fort Collins, Colorado, October 21, 2016, Earth Engineering
Consultants, Inc.(EEC Project No. 1162088).
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
Village Cooperative
CHARACTER OF SURFACE
1
:
Runoff
Coefficient
Percentage
Impervious Project: Village Cooperative
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: S. Thomas
Asphalt ……....……………...……….....…...……………….………………………………………………………….0.95 . 100% Date: December 6, 2016
Concrete …….......……………….….……….………………..….…………………………………………………….0.95 . 90%
Gravel (packed) ……….…………………….….…………………………..………………………………………….0.50 . 40%
Roofs …….…….………………..……………….……………………………………………………………………… 0.95 90%
Pavers…………………………...………………..……………………………………………………………………… 0.40 22%
Lawns and Landscaping
Sandy Soil
Flat <2% ……………………………………………………………………………………………………………… 0.10 0%
Average 2% to 7% ………………………………………………………………………………………………….0.15 . 0%
Steep >7% …………………………………………………………………………………………………………… 0.20 0%
Clayey Soil
Flat <2% ……………………………………………………………………………………………………………… 0.20 0%
Average 2% to 7% ………………………………………………………………………………………………….0.25 . 0%
Steep >7% …………………………………………………………………………………………………………… 0.35 0% 2-year Cf = 1.00 10-year Cf = 1.00 100-year Cf = 1.25
Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Table RO-11
Sub-Basin ID
Sub-
BasinBasin
Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Pavers
(ac)
Area of
Roofs
(ac)
Soil Type and Average
Slope
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite Runoff
Coefficient
100-year
Composite Runoff
Coefficient
Composite
% Imperv.
H1 2.04 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 2.041 0.25 0.25 0.31 0%
Village Cooperative
Overland Flow, Time of Concentration:
Village Cooperative
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)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
1 H1 No 0.25 0.25 0.31 290 3.66% 17.6 17.6 16.3 267 1.69% 2.60 1.7 19.3 19.3 18.0
2 H2 No 0.60 0.60 0.74 N/A N/A N/A N/A 93 0.57% 1.51 1.0 5.0 5.0 5.0
1 H3 No 0.25 0.25 0.31 79 5.91% 7.8 7.8 7.2 422 1.28% 2.26 3.1 10.9 10.9 10.4
* Time of Concentrations are calculated for the entire basin and used for both the Impervious and Pervious portions of the basins.
EXISTING TIME OF CONCENTRATION COMPUTATIONS
Village Cooperative
Rational Method Equation: Project: Village Cooperative
Calculations By:
Date:
Rainfall Intensity:
1 H1 2.04 19 19 18 0.25 0.25 0.31 1.65 2.82 6.01 0.84 1.44 3.83
2 H2 0.44 5 5 5 0.60 0.60 0.74 2.85 4.87 9.95 0.75 1.28 3.28
1 H3 0.77 11 11 10 0.25 0.25 0.31 2.17 3.71 7.72 0.42 0.71 1.85
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
EXISTING 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)
Sub-Basin(s)
S. Thomas
Rainfall Intensity taken from the Fort Collins Stormwater Criteria Manual (FCSCM), Tables RA-7 and RA-8
December 6, 2016
Intensity,
i10
(in/hr)
C10
Q = C f ( C )( i )( A )
12/6/2016 1:30 PM D:\Projects\1284-001\Drainage\Hydrology\1284-001_Existing_Rational_Calcs.xlsx\Runoff
Village Cooperative of Fort Collins
CHARACTER OF SURFACE1:
Runoff
Coefficient
Percentage
Impervious Project: Village Cooperative
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: S. Thomas
Asphalt ……....……………...……….....…...……………….………………………………………………………….0.95 . 100% Date: February 16, 2017
Concrete …….......……………….….……….………………..….…………………………………………………….0.95 . 90%
Gravel (packed) ……….…………………….….…………………………..………………………………………….0.50 . 40%
Roofs …….…….………………..……………….……………………………………………………………………… 0.95 90%
Pavers…………………………...………………..……………………………………………………………………… 0.40 22%
Lawns and Landscaping
Sandy Soil
Flat <2% ……………………………………………………………………………………………………………… 0.10 0%
Average 2% to 7% ………………………………………………………………………………………………….0.15 . 0%
Steep >7% …………………………………………………………………………………………………………… 0.20 0%
Clayey Soil
Flat <2% ……………………………………………………………………………………………………………… 0.20 0%
Average 2% to 7% ………………………………………………………………………………………………….0.25 . 0%
Steep >7% …………………………………………………………………………………………………………… 0.35 0% 2-year Cf = 1.00 10-year Cf = 1.00 100-year Cf = 1.25
Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Table RO-11
Sub-Basin ID
Sub-
BasinBasin
Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Gravel
(ac)
Area of
Roofs
(ac)
Soil Type and Average
Slope
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite Runoff
Coefficient
100-year
Composite Runoff
Coefficient
Composite
% Imperv.
A1 0.02 0.02 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.000 0.95 0.95 1.00 99%
A2 0.07 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.066 0.25 0.25 0.31 0%
A3 0.22 0.11 0.03 0.00 0.00 Clayey | Average 2% to 7% 0.073 0.72 0.72 0.90 66%
Village Cooperative of Fort Collins
Overland Flow, Time of Concentration:
Village Cooperative
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)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
1 A1 No 0.95 0.95 1.00 57 4.91% 1.2 1.2 0.8 N/A N/A N/A 5.0 5.0 5.0
Village Cooperative of Fort Collins
Rational Method Equation: Project: Village Cooperative
Calculations By:
Date:
Rainfall Intensity:
1 A1 0.02 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.05 0.08 0.18
2 A2 0.07 5 5 5 0.25 0.25 0.31 2.85 4.87 9.95 0.05 0.08 0.21
3 A3 0.22 5 5 5 0.72 0.72 0.90 2.85 4.87 9.95 0.45 0.77 1.98
4 A4 0.10 5 5 5 0.76 0.76 0.95 2.85 4.87 9.95 0.22 0.37 0.94
5 A5 0.35 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.96 1.64 3.53
6 A6 0.45 6 6 5 0.74 0.74 0.93 2.76 4.72 9.95 0.92 1.57 4.14
7 A7 0.04 5 5 5 0.41 0.41 0.51 2.85 4.87 9.95 0.04 0.08 0.20
8 A8 0.49 8 8 7 0.27 0.27 0.33 2.46 4.21 8.80 0.32 0.55 1.44
7 A9 0.36 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.99 1.68 3.62
7 A10 0.03 5 5 5 0.60 0.60 0.75 2.85 4.87 9.95 0.06 0.09 0.24
11 UD1 0.03 5 5 5 0.86 0.86 1.00 2.85 4.87 9.95 0.06 0.11 0.26
11 UD2 0.57 5 5 5 0.33 0.33 0.41 2.85 4.87 9.95 0.54 0.92 2.36
10 OS1 0.44 6 6 5 0.68 0.68 0.85 2.76 4.72 9.95 0.83 1.43 3.76
10 OS2 1.86 9 9 7 0.82 0.82 1.00 2.35 4.02 8.80 3.57 6.10 16.33
10
TOTAL UNDETAINED
BASINS (UD1-UD2)
0.60 5 5 5 0.35 0.35 0.44 2.85 4.87 9.95 0.60 1.03 2.63
8
TOTAL TO POND A
(A1-A10, OS1)
2.57 10 10 8 0.68 0.68 0.85 2.26 3.86 8.59 3.95 6.76 18.82
0
TOTAL TO
STORMTECH (A1-A7,
A9-A10)
1.64 8 8 6 0.80 0.80 1.00 2.40 4.10 9.63 3.16 5.39 15.81
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
PROPOSED RUNOFF COMPUTATIONS
C100
Design
Point
Flow,
Q100
(cfs)
Flow,
Q2
(cfs)
10-yr
Tc
(min)
2-yr
Tc
(min)
C2
Flow,
Q10
(cfs)
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 DETENTION POND SIZING
B.2 STORM SEWER
B.3 INLET
APPENDIX B.1
DETENTION PONDS AND WATER QUALITY
Village Cooperative
1284-001
Fort Collins, Colorado
S. Thomas Date: 2/16/2017
Pond No.: Pond A
8
100-yr
0.86 Approx. WQCV 740 ft3
Area (A)= 2.59 acres Quantity Detention 21589 ft3
Max Release Rate = 1.10 cfs Total Volume 22329 ft3
Total Volume 0.51 ac-ft
Time Time
Ft.Collins
100-yr
Intensity
Q100
Inflow
(Runoff)
Volume
Outflow
(Release) Volume
Storage
Detention
Volume
(mins) (secs) (in/hr) (cfs) (ft3) (ft3) (ft3)
5 300 9.95 22.2 6649 330 6319
10 600 7.72 17.2 10317 660 9657
15 900 6.52 14.5 13070 990 12080
20 1200 5.60 12.5 14968 1320 13648
25 1500 4.98 11.1 16639 1650 14989
30 1800 4.52 10.1 18122 1980 16142
35 2100 4.08 9.1 19084 2310 16774
40 2400 3.74 8.3 19993 2640 17353
45 2700 3.46 7.7 20808 2970 17838
50 3000 3.23 7.2 21584 3300 18284
55 3300 3.03 6.7 22272 3630 18642
60 3600 2.86 6.4 22933 3960 18973
65 3900 2.72 6.1 23628 4290 19338
70 4200 2.59 5.8 24230 4620 19610
75 4500 2.48 5.5 24858 4950 19908
80 4800 2.38 5.3 25446 5280 20166
85 5100 2.29 5.1 26014 5610 20404
90 5400 2.21 4.9 26582 5940 20642
95 5700 2.13 4.7 27043 6270 20773
100 6000 2.06 4.6 27531 6600 20931
105 6300 2.00 4.5 28065 6930 21135
110 6600 1.94 4.3 28520 7260 21260
115 6900 1.89 4.2 29048 7590 21458
120 7200 1.84 4.1 29509 7920 21589
Detention Pond Calculation | FAA Method
Project Number:
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
2/16/2017 2:35 PM D:\Projects\1284-001\Drainage\Detention\1284-001_Detention Pond A.xlsx\FAA_CoFC idf_Pond 1
1284-001
Fort Collins Co
S. Thomas Date: 2/16/2017
Pond No.: Pond A
8
100-yr
0.51 acft 5006.31 ft.
Design Storm WQCV
Required Volume= 740 ft
3 5001.71 ft.
Contour
Elevation (Y-
values)
Contour Area Depth
Column Not
Used
Incremental
Volume
Total Volume Total Volume
ft
3
ft. ft
3
ft
3
ft
3
acre-feet
5,000.80 95 0.00 0 0 0 0
5,001.00 456 0.20 51 51 0.00
5,001.20 796 0.20 124 174 0.00
5,001.40 1071 0.20 186 360 0.01
5,001.60 1339 0.20 240 600 0.01
5,001.80 1603 0.20 293 894 0.02
5,002.00 1862 0.20 346 1239 0.03
5,002.20 2097 0.20 395 1635 0.04
5,002.40 2293 0.20 438 2073 0.05
5,002.60 2496 0.20 478 2552 0.06
5,002.80 2716 0.20 521 3072 0.07
5,003.00 2943 0.20 565 3637 0.08
5,003.20 3179 0.20 611 4249 0.10
5,003.40 3426 0.20 660 4908 0.11
5,003.60 3681 0.20 710 5618 0.13
5,003.80 3948 0.20 762 6380 0.15
5,004.00 4227 0.20 817 7197 0.17
5,004.20 4516 0.20 873 8070 0.19
5,004.40 4818 0.20 932 9002 0.21
5,004.60 5133 0.20 994 9996 0.23
5,004.80 5466 0.20 1059 11055 0.25
5,005.00 5817 0.20 1127 12182 0.28
5,005.20 6186 0.20 1199 13381 0.31
5,005.40 6577 0.20 1275 14656 0.34
5,005.60 7265 0.20 1382 16038 0.37
5,005.80 8314 0.20 1555 17593 0.40
5,006.00 9377 0.20 1766 19359 0.44
5,006.20 9769 0.20 1913 21272 0.49
5,006.40 10192 0.20 1994 23266 0.53
5,006.60 10723 0.20 2089 25355 0.58
Design Point
Design Storm
Village Cooperative of Fort Collins
ORIFICE RATING CURVE
Pond A Outlet
100-yr Orifice
Project: Village Cooperative
Date: 2/16/2017
By: S. Thomas
100-yr WSEL= 5006.31
Orifice Plate
Outflow Q 1.1 cfs
Orifice Coefficient Cd 0.65
Gravity Constant g 32.2 ft/s^2
100-year head H 5.28 ft
Orifice Area Ao 0.09 ft^2
Orifice Area Ao 13.22 in^2
Radius r 2.1 in
Diameter d 4.1 in
Orifice Curve
Stage (ft) H (ft) Q (cfs) SWMM Stage Note
5001.03 0.00 0.00 0.00 Pond Invert
5001.53 0.50 0.34 0.50
5001.37 0.34 0.28 0.34
5001.87 0.84 0.44 0.84
5002.37 1.34 0.55 1.34
5002.87 1.84 0.65 1.84
5003.37 2.34 0.73 2.34
5003.87 2.84 0.81 2.84
5004.37 3.34 0.87 3.34
5004.87 3.84 0.94 3.84
5005.37 4.34 1.00 4.34
5005.87 4.84 1.05 4.84
5006.31 5.28 1.10 5.28 100-yr WSEL
5006.80 5.77 1.15 5.77 Overtopping
2/16/2017 11:07 AM D:\Projects\1284-001\Drainage\Detention\1284-001 Orifice A.xlsx\Orifice Size
POND A
Project: The Village Cooperative of Fort Collins
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 2.570 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 58.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.5800 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.230 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.049 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Stormtech WQCV (ft
3
) = 1402 <-- CALCULATED
Adjusted WQCV (cu-ft) = 740 <-- CALCULATED (minus Stormtech)
WQ Depth (ft) = 1.000 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.074 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 1/3 <-- INPUT from Figure 5
number of rows = 3
t (in) = 0.500 <-- INPUT from Figure 5
number of columns = 1.000 <-- CALCULATED from WQ Depth and row spacing
WATER QUALITY CONTROL STRUCTURE PLATE
February 22, 2017
1008
Project Title Date:
Project Number Calcs By:
Client
Basins
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 = 1.64 ac
V = 0.0322 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
Village Cooperative February 22, 2017
1284-001 S. Thomas
Basin A1-A7, A9-A10
1402 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 :
Basin A
WQ
1.00
5.00 min 1247 ft3
1.64 acres 0.03 ac-ft
Max Release Rate = 0.64 cfs
Time (min) Ft Collins WQ
Intensity (in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 1.425 701 1.00 0.64 192 509
10 1.105 1087 1.00 0.64 384 703
15 0.935 1380 0.67 0.43 384 996
20 0.805 1584 0.63 0.40 480 1104
25 0.715 1759 0.60 0.38 576 1183
30 0.650 1919 0.58 0.37 672 1247
35 0.585 2015 0.57 0.37 768 1247
40 0.535 2106 0.56 0.36 864 1242
45 0.495 2192 0.56 0.36 960 1232
50 0.460 2263 0.55 0.35 1056 1207
55 0.435 2354 0.55 0.35 1152 1202
60 0.410 2421 0.54 0.35 1248 1173
65 0.385 2462 0.54 0.34 1344 1118
70 0.365 2514 0.54 0.34 1440 1074
75 0.345 2546 0.53 0.34 1536 1010
80 0.330 2598 0.53 0.34 1632 966
85 0.315 2635 0.53 0.34 1728 907
90 0.305 2701 0.53 0.34 1824 877
95 0.290 2711 0.53 0.34 1920 791
100 0.280 2755 0.53 0.34 2016 739
105 0.270 2790 0.52 0.34 2112 678
110 0.260 2814 0.52 0.33 2208 606
115 0.255 2886 0.52 0.33 2304 582
120 0.245 2893 0.52 0.33 2400 493
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
STORM TECH CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
1284-001
Village Cooperative
Project Number :
Project Name :
Basin A1-A7, Basin A9-A10
A =
Tc =
Project Location :
Design Point
Vault ID
Total
Required
WQ Volume
(cf)
Flow,
WQ
(cfs)
Chamber
Type
Chamber Release
Ratea
(cfs)
Chamber
Volumeb
(cf)
Installed
Chamber w/
Aggregatec
(cf)
Mimimum
No. of
Chambersd
Total Release
Ratee
(cfs)
Required
Storage
Volume by
FAA Method
(cf)
Mimimum
No. of
Chambersf
Storage
Provided
within the
Chambersg
(cf)
Total
Installed
System
Volumeh
(cf)
Basin A 1402 1.58 SC-740 0.024 45.90 74.90 19 0.45 1247 17 780 1423
SC-740
a. Release rate per chamber, limited by flow through geotextile with accumulated sediment.
b. Volume within chamber only, not accounting for void spaces in surrounding aggregate.
c. Volume includes chamber and void spaces (40%) in surrounding aggregate, per chamber unit.
d. Number of chambers required to provide full WQCV within total installed system, including aggregate.
e. Release rate per chamber times number of chambers.
f. Number of chambers required to provide required FAA storage volume stored within the chamber only (no aggregate storage).
g. Volume provided in chambers only (no aggregate storage). This number must meet or exceed the required FAA storage volume.
h. System volume includes total number of chambers, plus surrounding aggregate. This number must meet or exceed the required WQCV.
Chamber Configuration Summary
D:\Projects\1284-001\Drainage\WatQual\Basin A WQ Chambers.xlsx
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Feb 16 2017
Pond A Emergency Overflow Weir
Trapezoidal Weir
Crest = Sharp
Bottom Length (ft) = 20.00
Total Depth (ft) = 1.00
Side Slope (z:1) = 4.00
Calculations
Weir Coeff. Cw = 3.10
Compute by: Known Q
Known Q (cfs) = 18.82
Highlighted
Depth (ft) = 0.44
Q (cfs) = 18.82
Area (sqft) = 9.57
Velocity (ft/s) = 1.97
Top Width (ft) = 23.52
0 5 10 15 20 25 30 35 40
Depth (ft) Pond A Emergency Overflow Weir Depth (ft)
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
1.50 1.50
2.00 2.00
Length (ft)
Weir W.S.
APPENDIX B.2
STORM SEWERS
APPENDIX B.3
INLETS
Project:
Inlet ID:
Design Information (Input) MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') aLOCAL
= 2.0 2.0 inches
Total Number of Units in the Inlet (Grate or Curb Opening) No = 1 1
Length of a Single Unit Inlet (Grate or Curb Opening) Lo
= 3.00 3.00 ft
Width of a Unit Grate (cannot be greater than W from Q-Allow) Wo
= 2.00 2.00 ft
Clogging Factor for a Single Unit Grate (typical min. value = 0.5) Cf
-G = 0.50 0.50
Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1) Cf
-C = 0.10 0.10
Street Hydraulics: OK - Q < maximum allowable from sheet 'Q-Allow' MINOR MAJOR
Total Inlet Interception Capacity Q = 0.1 0.2 cfs
Total Inlet Carry-Over Flow (flow bypassing inlet) Qb = 0.0 0.0 cfs
Capture Percentage = Qa/Q
o = C% = 100 100 %
INLET ON A CONTINUOUS GRADE
Village Cooperative of Fort Collins
Design Pt 1 - Inlet B8.2
User-Defined Combination
INLET - Design Pt 1.xlsm, Inlet On Grade 2/16/2017, 9:16 AM
Area Inlet Performance Curve:
Design Point 2 - Inlet B8.1
Governing Equations:
At low flow depths, the inlet will act like a weir governed by the following equation:
* where P = 2(L + W)
* where H corresponds to the depth of water above the flowline
At higher flow depths, the inlet will act like an orifice governed by the following equation:
* where A equals the open area of the inlet grate
* where H corresponds to the depth of water above the centroid of the cross-sectional area (A)
The exact depth at which the inlet ceases to act like a weir, and begins to act like an orifice is unknown.
However, what is known, is that the stage-discharge curves of the weir equation and the orifice equation
will cross at a certain flow depth. The two curves can be found below:
If H > 1.792 (A/P), then the grate operates like an orifice; otherwise it operates like a weir.
Input Parameters:
Type of Grate: 12" ADS Drop In Grate 1201DI
Shape Circular
Length of Grate (ft): 1
Width of Grate (ft): 1
Open Area of Grate (ft
2
): 0.28
Flowline Elevation (ft): 5010.690
Allowable Capacity: 50%
Depth vs. Flow:
Depth Above Inlet (ft)
Elevation
(ft)
Shallow
Weir Flow
(cfs)
Orifice
Flow
(cfs)
Actual
Flow
(cfs)
0.00 5010.69 0.00 0.00 0.00
0.08 5010.77 0.11 0.21 0.11
0.16 5010.85 0.30 0.30 0.30 Q100
0.24 5010.93 0.55 0.36 0.36
0.32 5011.01 0.85 0.42 0.42
0.40 5011.090 1.19 0.47 0.47
0.48 5011.17 1.57 0.51 0.51
0.56 5011.25 1.97 0.55 0.55
0.64 5011.33 2.41 0.59 0.59
0.72 5011.41 2.88 0.63 0.63
0.80 5011.490 3.37 0.66 0.66
Inlet at Design Point 2 is designed to intercept the full 100-yr flow of 0.21 cfs at the elevation 5010.81
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80
Discharge (cfs)
Stage (ft)
Stage - Discharge Curves
Project =
Inlet ID =
Design Information (Input) MINOR MAJOR
Type of Inlet Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal
= 2.00 2.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 1 1
Water Depth at Flowline (outside of local depression) Ponding Depth = 6.0 6.0 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo
(G) = 3.00 3.00 feet
Width of a Unit Grate Wo
= 1.73 1.73 feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio
= 0.43 0.43
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf
(G) = 0.50 0.50
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw
(G) = 3.30 3.30
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co
(G) = 0.60 0.60
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo
(C) = 3.00 3.00 feet
Height of Vertical Curb Opening in Inches Hvert
= 6.50 6.50 inches
Height of Curb Orifice Throat in Inches Hthroat
= 5.25 5.25 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 0.00 0.00 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp
= 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf
(C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.6) Cw
(C) = 3.70 3.70
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co
(C) = 0.66 0.66
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa = 3.6 3.6 cfs
Inlet Capacity IS GOOD for Minor and Major Storms (>Q PEAK) Q PEAK REQUIRED
= 0.5 2.0 cfs
INLET IN A SUMP OR SAG LOCATION
Village Cooperative of Fort Collins
Design Pt 3 - Inlet B9
CDOT/Denver 13 Combination
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
Override Depths
INLET - Design Pt 3.xlsm, Inlet In Sump 2/16/2017, 9:18 AM
Area Inlet Performance Curve:
Village Cooperative - Design Point 6 - Inlet B2
Governing Equations:
At low flow depths, the inlet will act like a weir governed by the following equation:
* where P = 2(L + W)
* where H corresponds to the depth of water above the flowline
At higher flow depths, the inlet will act like an orifice governed by the following equation:
* where A equals the open area of the inlet grate
* where H corresponds to the depth of water above the centroid of the cross-sectional area (A)
The exact depth at which the inlet ceases to act like a weir, and begins to act like an orifice is unknown.
However, what is known, is that the stage-discharge curves of the weir equation and the orifice equation
will cross at a certain flow depth. The two curves can be found below:
If H > 1.792 (A/P), then the grate operates like an orifice; otherwise it operates like a weir.
Input Parameters:
Type of Grate: Neenah R-4370-27A
Shape Rectangular
Length of Grate (ft): 3.16
Width of Grate (ft): 3.16
Open Area of Grate (ft
2
): 2.40
Flowline Elevation (ft): 5008.020
Allowable Capacity: 50%
Depth vs. Flow:
Depth Above Inlet (ft)
Elevation
(ft)
Shallow
Weir Flow
(cfs)
Orifice
Flow
(cfs)
Actual
Flow
(cfs)
0.00 5008.02 0.00 0.00 0.00
0.10 5008.12 0.60 2.04 0.60
0.20 5008.22 1.70 2.88 1.70
0.30 5008.32 3.12 3.53 3.12
0.40 5008.42 4.80 4.08 4.08
0.50 5008.520 6.70 4.56 4.56 Q100
0.60 5008.62 8.81 5.00 5.00
0.70 5008.72 11.10 5.40 5.40
0.80 5008.82 13.57 5.77 5.77
0.90 5008.92 16.19 6.12 6.12
1.00 5009.020 18.96 6.45 6.45
Inlet at Design Point 6 is designed to intercept 4.56 cfs of the 100-yr flow of 5.08 cfs at the elevation 5008.52.
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
Discharge (cfs)
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Feb 16 2017
100-yr Overflow Weir in Inlet
Rectangular Weir
Crest = Sharp
Bottom Length (ft) = 3.00
Total Depth (ft) = 2.00
Calculations
Weir Coeff. Cw = 3.33
Compute by: Known Q
Known Q (cfs) = 16.00
Highlighted
Depth (ft) = 1.37
Q (cfs) = 16.00
Area (sqft) = 4.11
Velocity (ft/s) = 3.90
Top Width (ft) = 3.00
0 .5 1 1.5 2 2.5 3 3.5 4
Depth (ft) 100-yr Overflow Weir in Inlet Depth (ft)
-1.00 -1.00
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
Length (ft)
Weir W.S.
Area Inlet Performance Curve:
Village Cooperative - Design Point 7/Inlet C3
Governing Equations:
At low flow depths, the inlet will act like a weir governed by the following equation:
* where P = 2(L + W)
* where H corresponds to the depth of water above the flowline
At higher flow depths, the inlet will act like an orifice governed by the following equation:
* where A equals the open area of the inlet grate
* where H corresponds to the depth of water above the centroid of the cross-sectional area (A)
The exact depth at which the inlet ceases to act like a weir, and begins to act like an orifice is unknown.
However, what is known, is that the stage-discharge curves of the weir equation and the orifice equation
will cross at a certain flow depth. The two curves can be found below:
If H > 1.792 (A/P), then the grate operates like an orifice; otherwise it operates like a weir.
Input Parameters:
Type of Grate: 12" ADS Drop In Grate 1201DI
Shape Circular
Length of Grate (ft): 1
Width of Grate (ft): 1
Open Area of Grate (ft
2
): 0.28
Flowline Elevation (ft): 5005.890
Allowable Capacity: 50%
Depth vs. Flow:
Depth Above Inlet (ft)
Elevation
(ft)
Shallow
Weir Flow
(cfs)
Orifice
Flow
(cfs)
Actual
Flow
(cfs)
0.00 5005.89 0.00 0.00 0.00
0.08 5005.97 0.11 0.21 0.11
0.16 5006.05 0.30 0.30 0.30 Q100
0.24 5006.13 0.55 0.36 0.36
0.32 5006.21 0.85 0.42 0.42
0.40 5006.290 1.19 0.47 0.47
0.48 5006.37 1.57 0.51 0.51
0.56 5006.45 1.97 0.55 0.55
0.64 5006.53 2.41 0.59 0.59
0.72 5006.61 2.88 0.63 0.63
0.80 5006.690 3.37 0.66 0.66
Inlet at Design Point 7 is designed to intercept the full 100-yr flow of 0.20 cfs at the elevation 5006.01
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80
Discharge (cfs)
Stage (ft)
Stage - Discharge Curves
Project:
Inlet ID:
Design Information (Input) MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') aLOCAL
= 3.0 3.0 inches
Total Number of Units in the Inlet (Grate or Curb Opening) No = 2 2
Length of a Single Unit Inlet (Grate or Curb Opening) Lo
= 5.00 5.00 ft
Width of a Unit Grate (cannot be greater than W from Q-Allow) Wo
= N/A N/A ft
Clogging Factor for a Single Unit Grate (typical min. value = 0.5) Cf
-G = N/A N/A
Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1) Cf
-C = 0.10 0.10
Street Hydraulics: OK - Q < maximum allowable from sheet 'Q-Allow' MINOR MAJOR
Total Inlet Interception Capacity Q = 0.8 3.7 cfs
Total Inlet Carry-Over Flow (flow bypassing inlet) Qb = 0.0 0.1 cfs
Capture Percentage = Qa/Q
o = C% = 100 98 %
INLET ON A CONTINUOUS GRADE
Village Cooperative of Fort Collins
Design Pt 9 - Inlet D2
CDOT Type R Curb Opening
INLET - Design Pt 9.xlsm, Inlet On Grade 2/16/2017, 9:19 AM
Project =
Inlet ID =
Design Information (Input) MINOR MAJOR
Type of Inlet Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal
= 3.00 3.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 2 2
Water Depth at Flowline (outside of local depression) Ponding Depth = 6.0 9.0 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo
(G) = N/A N/A feet
Width of a Unit Grate Wo
= N/A N/A feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio
= N/A N/A
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf
(G) = N/A N/A
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw
(G) = N/A N/A
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co
(G) = N/A N/A
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo
(C) = 5.00 5.00 feet
Height of Vertical Curb Opening in Inches Hvert
= 6.00 6.00 inches
Height of Curb Orifice Throat in Inches Hthroat
= 6.00 6.00 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 63.40 63.40 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp
= 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf
(C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.6) Cw
(C) = 3.60 3.60
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co
(C) = 0.67 0.67
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa = 10.5 22.2 cfs
Inlet Capacity IS GOOD for Minor and Major Storms (>Q PEAK) Q PEAK REQUIRED
= 4.5 19.0 cfs
INLET IN A SUMP OR SAG LOCATION
Village Cooperative of Fort Collins
Design Pt 10 - Inlet A4
CDOT Type R Curb Opening
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
Override Depths
INLET - Design Pt 10.xlsm, Inlet In Sump 2/16/2017, 9:19 AM
APPENDIX C
EROSION CONTROL REPORT
The Village Cooperative of Fort Collins
Preliminary 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 existing and 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.
APPENDIX D
LID EXHIBIT
Project: Village Cooperative
Calculations By:
Date:
L1 A1 785 99% 775
A2 2,880 0% 0
A3 9,637 66% 6,315
A4 4,318 73% 3,141
A5 15,440 90% 13,896
A6 19,473 70% 13,549
A7 1,681 20% 341
A9 15,864 90% 14,278
A10 1,423 45% 635
Total L1 71,501 74% 52,928 1,402 1,423
Total Treated 71,501 74% 52,928 1,402 1,423
A8 21,278 4% 832
UD1 1,117 86% 957
UD2 24,944 10% 2,600
Total Proposed
Untreated
47,339 9% 4,389
118,840
N/A
57,317
N/A
42,988
1,402
1,423
52,928
PROPOSED LID COMPUTATIONS
S. Thomas
February 16, 2017
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent
Impervious
Impervious Area,
A
(sf)
Stormtech
WQCV Required
(Cf)
LID TREATMENT SUMMARY
PROPOSED LID UNTREATED AREA
Total Site Area (sf)
PROPOSED LID TREATED AREA
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent
Impervious
Impervious Area,
A
(sf)
Stormtech
WQCV Provided
(cf)
Total Existing Impervious Area (sf)
Total Proposed Impervious Area (sf)
Total Net Proposed Impervious Area (sf)
PARKING
GARAGE
ENTRANCE
UD
TF
TF
X
X
X
X
D CABLE
VAULT
F.O.
D
ST
ST
F.O.
STRACHAN 3RD
OWNER: ARENA I LLC AND ARENA II LLC
HORSETOOTH ROAD
RIGHT OF WAY VARIES
107.5' TO 108.5'
STRACHAN 3RD
OWNER: PETERSON-MOORE LLP
GREENLEE INVESTMENTS LLLP
STRACHAN 1ST
OWNER: ASPEN LEAF SPE LLC
STANFORD ROAD
78' RIGHT OF WAY
PROPOSED
CURB INLET
AND WATER
QUALITY WEIR
PROPOSED STORMTECH
UNDERGROUND DETENTION
AND WATER QUALITY SYSTEM
DETENTION
POND A
LID BASIN L1
TOTAL AREA: 1.64 AC (71,501 SF)
PERCENT IMPERVIOUS: 74%
REQUIRED STORMTECH VOLUME: 1,402 CF
PROVIDED STORMTECH VOLUME: 1,423 CF
A3
A5
A9
A6
A4
A8
A1
A10
A7
A2
UD2
UD1
LID
(LID) EXHIBIT
LOW IMPACT DEVELOPMENT
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
APPENDIX E
REFERENCES
Hydrologic Soil Group—Larimer County Area, Colorado
(Village Cooperative of Fort Collins)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/21/2016
Page 1 of 4
4487450 4487480 4487510 4487540 4487570 4487600 4487630
4487450 4487480 4487510 4487540 4487570 4487600 4487630
494020 494050 494080 494110 494140 494170 494200 494230 494260 494290
494020 494050 494080 494110 494140 494170 494200 494230 494260 494290
40° 32' 22'' N
105° 4' 14'' W
40° 32' 22'' N
105° 4' 1'' W
40° 32' 15'' N
105° 4' 14'' W
40° 32' 15'' N
105° 4' 1'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 50 100 200 300
Feet
0 20 40 80 120
Meters
Map Scale: 1:1,370 if printed on A landscape (11" x 8.5") sheet.
Warning: Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at 1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil line
placement. The maps do not show the small areas of contrasting
soils that could have been shown at a more detailed scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more accurate
calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as of
the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Hydrologic Soil Group
Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644)
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
36 Fort Collins loam, 3 to 5
percent slopes
B 0.9 25.2%
49 Heldt clay loam, 3 to 6
percent slopes
C 0.3 8.1%
73 Nunn clay loam, 0 to 1
percent slopes
C 0.7 18.2%
74 Nunn clay loam, 1 to 3
percent slopes
C 1.8 48.6%
Totals for Area of Interest 3.6 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive precipitation
from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly
wet. These consist mainly of deep, well drained to excessively drained sands or
gravelly sands. These soils have a high rate of water transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well drained
soils that have moderately fine texture to moderately coarse texture. These soils
have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of water
transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay layer
at or near the surface, and soils that are shallow over nearly impervious material.
These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in their
natural condition are in group D are assigned to dual classes.
Hydrologic Soil Group—Larimer County Area, Colorado Village Cooperative of Fort Collins
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/21/2016
Page 3 of 4
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—Larimer County Area, Colorado Village Cooperative of Fort Collins
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/21/2016
Page 4 of 4
MAP POCKET
DR1 – OVERALL DRAINAGE EXHIBIT
X
X
X
X
FO
FO
FO
FO
FO
FO
FO FO FO
FO
FO
FO
FO FO FO FO
FO
FO
FO
G G
G
G
G
G
G
G G
G
G
G
G
G
G
G
G
G
G
SS SS SS SS
SS SS SS
SS SS SS
SS SS SS SS SS SS SS SS SS
SS
SS SS
SS SS
SS
D CABLE
VAULT
ELEC
VAULT
ELEC ELEC
T S
VAULT
F.O.
S S
D
ST
ST
S
W
W
W
W W W
PARKING
GARAGE
ENTRANCE
UD
TF
TF
X
X
X
X
D CABLE
VAULT
F.O.
D
ST
ST
F.O.
1
2
3
4
5
6
7
8
9
10
DETENTION
POND A
STRACHAN 3RD
OWNER: ARENA I LLC AND ARENA II LLC
HORSETOOTH ROAD
RIGHT OF WAY VARIES
107.5' TO 108.5'
STRACHAN 3RD
OWNER: PETERSON-MOORE LLP
GREENLEE INVESTMENTS LLLP
STRACHAN 1ST
OWNER: ASPEN LEAF SPE LLC
STANFORD ROAD
78' RIGHT OF WAY
A3
A5
A9
A6
A4
A8
A1
A10
A7
A2
UD2
UD1
OS1
PROPOSED
CURB INLET
PROPOSED
DRAIN BASIN
PROPOSED
CURB INLET
PROPOSED AREA INLET
BASIN A9 ROOF DRAIN
RELEASE TO INLET
PROPOSED
CURB INLET
EXISTING STORM
JUNCTION STRUCTURE
PROPOSED
CURB INLET
AND WATER
QUALITY WEIR
PROPOSED STORMTECH
UNDERGROUND DETENTION
AND WATER QUALITY SYSTEM
PROPOSED
OUTLET
STRUCTURE
BASIN A5 ROOF
DRAIN RELEASE
TO MANHOLE
OS2
DR1
DRAINAGE PLAN
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
Call before you dig.
R
City Engineer Date
Date
Date
Date
Date
Stormwater Utility
Parks & Recreation
Traffic Engineer
Date
Water & Wastewater Utility
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
Environmental Planner 31
( IN FEET )
0
1 INCH = 40 FEET
40 40 80 120
LEGEND:
5013
PROPOSED CONTOUR 93
EXISTING CONTOUR
PROPERTY BOUNDARY
EXISTING STORM SEWER
1. THE SIZE, TYPE AND LOCATION OF ALL KNOWN UNDERGROUND UTILITIES ARE
APPROXIMATE WHEN SHOWN ON THESE DRAWINGS. IT SHALL BE THE
RESPONSIBILITY OF THE CONTRACTOR TO VERIFY THE EXISTENCE OF ALL
UNDERGROUND UTILITIES IN THE AREA OF THE WORK. BEFORE COMMENCING
NEW CONSTRUCTION, THE CONTRACTOR SHALL BE RESPONSIBLE FOR LOCATING
ALL UNDERGROUND UTILITIES AND SHALL BE RESPONSIBLE FOR FOR ALL
UNKNOWN UNDERGROUND UTILITIES.
2. REFER TO THE "PRELIMINARY DRAINAGE AND EROSION CONTROL REPORT FOR
THE VILLAGE COOPERATIVE OF FORT COLLINS" BY NORTHERN ENGINEERING,
DATED February 22, 2017 FOR ADDITIONAL INFORMATION.
NOTES:
FLOW PATH
DRAINAGE BASIN BUBBLE
A
DESIGN POINT A
BASIN BOUNDARY
PROPOSED STORM SEWER
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
Sheet
Of 32
VILLAGE COOPERATIVE OF 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
301 North Howes Street, Suite 100
Fort Collins, Colorado 80521
E NGINEER ING
N O R T H E RN
PHONE: 970.221.4158
www.northernengineering.com
KEYMAP
DRAINAGE SUMMARY TABLE
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100 2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
1 A1 0.02 0.95 1.00 5.0 5.0 0.05 0.18
2 A2 0.07 0.25 0.31 5.0 5.0 0.05 0.21
3 A3 0.22 0.72 0.90 5.0 5.0 0.45 1.98
4 A4 0.10 0.76 0.95 5.0 5.0 0.22 0.94
5 A5 0.35 0.95 1.00 5.0 5.0 0.96 3.53
6 A6 0.45 0.74 0.93 5.9 5.0 0.92 4.14
7 A7 0.04 0.41 0.51 5.0 5.0 0.04 0.20
8 A8 0.49 0.27 0.33 7.7 7.1 0.32 1.44
7 A9 0.36 0.95 1.00 5.0 5.0 0.99 3.62
7 A10 0.03 0.60 0.75 5.0 5.0 0.06 0.24
11 UD1 0.03 0.86 1.00 5.0 5.0 0.06 0.26
11 UD2 0.57 0.33 0.41 5.1 5.0 0.54 2.36
10 OS1 0.44 0.68 0.85 5.8 5.0 0.83 3.76
10 OS2 1.86 0.88 1.00 8.3 7.5 3.92 16.33
Detention Pond Summary | Proposed Condition
Pond 100-yr Volume
(ac-ft)
100-yr WSEL WQCV
(ft3)
WQCV WSEL Max Release
(cfs)
A 0.51 5006.31 740 5001.71 1.10
W
W W W
W W
W W
W W
W W
W
W
W W W
W W
W
W W W
W
W
W
W
W
W
W
W
W
W
W W W W W W
G
G
G
G
G
G
G
G
FO
FO
FO
FO
FO
FO
FO
FO
W
F
1 .O.
H2
H1
STRACHAN 3RD
OWNER: ARENA I LLC AND ARENA II LLC
HORSETOOTH ROAD
RIGHT OF WAY VARIES
107.5' TO 108.5'
STRACHAN 3RD
OWNER: PETERSON-MOORE LLP
GREENLEE INVESTMENTS LLLP
STRACHAN 1ST
OWNER: ASPEN LEAF SPE LLC
STANFORD ROAD
98' RIGHT OF WAY
2
H3
HDR1
HISTORIC DRAINAGE PLAN
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
Call before you dig.
R
16
( IN FEET )
0
1 INCH = 40 FEET
40 40 80 120
LEGEND:
5013
PROPOSED CONTOUR 93
EXISTING CONTOUR
PROPERTY BOUNDARY
EXISTING STORM SEWER
1. THE SIZE, TYPE AND LOCATION OF ALL KNOWN UNDERGROUND UTILITIES ARE
APPROXIMATE WHEN SHOWN ON THESE DRAWINGS. IT SHALL BE THE
RESPONSIBILITY OF THE CONTRACTOR TO VERIFY THE EXISTENCE OF ALL
UNDERGROUND UTILITIES IN THE AREA OF THE WORK. BEFORE COMMENCING
NEW CONSTRUCTION, THE CONTRACTOR SHALL BE RESPONSIBLE FOR LOCATING
ALL UNDERGROUND UTILITIES AND SHALL BE RESPONSIBLE FOR FOR ALL
UNKNOWN UNDERGROUND UTILITIES.
2. REFER TO THE "PRELIMINARY DRAINAGE AND EROSION CONTROL REPORT FOR
THE VILLAGE COOPERATIVE OF FORT COLLINS BY NORTHERN ENGINEERING,
DATED December 7, 2016 FOR ADDITIONAL INFORMATION.
NOTES:
FLOW PATH
DRAINAGE BASIN BUBBLE
A
DESIGN POINT A
BASIN BOUNDARY
PROPOSED STORM SEWER
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
Sheet
Of 15
VILLAGE COOPERATIVE OF 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
301 North Howes Street, Suite 100
Fort Collins, Colorado 80521
E NGINEER ING
N O R T H E RN
PHONE: 970.221.4158
www.northernengineering.com
DRAINAGE SUMMARY TABLE
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100 2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
1 H1 2.04 0.25 0.31 19.3 18.0 0.84 3.83
2 H2 0.44 0.60 0.74 5.0 5.0 0.75 3.28
1 H3 0.77 0.25 0.31 10.9 10.4 0.42 1.85
Survey Area Data: Version 10, Sep 22, 2015
Soil map units are labeled (as space allows) for map scales 1:50,000
or larger.
Date(s) aerial images were photographed: Apr 22, 2011—Apr 28,
2011
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor shifting
of map unit boundaries may be evident.
Hydrologic Soil Group—Larimer County Area, Colorado
(Village Cooperative of Fort Collins)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/21/2016
Page 2 of 4
Know what'sbelow.
Call before you dig.
R
15
( IN FEET )
0
1 INCH = 40 FEET
40 40 80 120
LEGEND:
5013
PROPOSED CONTOUR 93
EXISTING CONTOUR
PROPERTY BOUNDARY
EXISTING STORM SEWER
FLOW PATH
DRAINAGE BASIN BUBBLE
A
LID BASIN BOUNDARY
PROPOSED STORM SEWER
Sheet
Of 32
VILLAGE COOPERATIVE OF 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
301 North Howes Street, Suite 100
Fort Collins, Colorado 80521
E NGINEER ING
N O R T H E RN
PHONE: 970.221.4158
www.northernengineering.com
KEYMAP
LID TREATMENT
LID TREATMENT SUMMARY
Total Site Area (sf) 118,840
Total Existing Impervious Area (sf) N/A
Total Proposed Impervious Area (sf) 57,317
Total Net Proposed Impervious Area (sf) N/A
75% Required Minimum Area to be Treated
by LID measures (sf)
42,988
Stormtech Treatment
Total Volume Required (cf) 1,402
Total Volume Provided (cf) 1,423
Area treated by Stormtech (sf) 52,928
Total Treated Impervious Area (sf) 52,928
Percent Impervious Treated by LID measures 92%
75% Required Minimum Area to be
Stormtech Treatment
Total Volume Required (cf)
Total Volume Provided (cf)
Area treated by Stormtech (sf)
Weir Flow
Orifice Flow
Q = 3 . 0 P H 1 . 5
Q = 0 . 67 A ( 2 gH ) 0 . 5
Stage (ft)
Stage - Discharge Curves
Weir Flow
Orifice Flow
Q = 3 . 0 P H 1 . 5
Q = 0 . 67 A ( 2 gH ) 0 . 5
Weir Flow
Orifice Flow
Q = 3 . 0 P H 1 . 5
Q = 0 . 67 A ( 2 gH ) 0 . 5
C =
Design Storm
Page 1 of 1
Basin A WQ Chambers.xlsx
ö
ç
è
= æ
12 hr
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
Intensity,
i100
(in/hr)
Sub-Basin(s)
S. Thomas
Rainfall Intensity taken from the Fort Collins Stormwater Criteria Manual (FCSCM), Tables RA-7 and RA-8
February 16, 2017
Intensity,
i10
(in/hr)
C10
Q = C f ( C )( i )( A )
2/16/2017 10:54 AM D:\Projects\1284-001\Drainage\Hydrology\1284-001_Proposed_Rational_Calcs.xlsx\Runoff
2 A2 No 0.25 0.25 0.31 29 17.24% 3.3 3.3 3.0 73 0.50% 1.42 0.9 5.0 5.0 5.0
3 A3 No 0.72 0.72 0.90 98 3.10% 4.8 4.8 2.5 N/A N/A N/A 5.0 5.0 5.0
4 A4 No 0.76 0.76 0.95 67 2.67% 3.7 3.7 1.6 15 0.60% 1.55 0.2 5.0 5.0 5.0
5 A5 No 0.95 0.95 1.00 58 2.00% 1.7 1.7 1.1 N/A N/A N/A 5.0 5.0 5.0
6 A6 No 0.74 0.74 0.93 89 2.73% 4.5 4.5 2.1 251 2.06% 2.87 1.5 5.9 5.9 5.0
7 A7 No 0.41 0.41 0.51 17 16.88% 2.1 2.1 1.8 30 5.67% 4.76 0.1 5.0 5.0 5.0
8 A8 No 0.27 0.27 0.33 120 10.99% 7.7 7.7 7.1 N/A N/A N/A 7.7 7.7 7.1
7 A9 No 0.95 0.95 1.00 58 2.00% 1.7 1.7 1.1 N/A N/A N/A 5.0 5.0 5.0
7 A10 No 0.60 0.60 0.75 32 6.25% 2.9 2.9 2.0 N/A N/A N/A 5.0 5.0 5.0
11 UD1 No 0.86 0.86 1.00 41 6.63% 1.5 1.5 0.6 352 3.38% 3.67 1.6 5.0 5.0 5.0
11 UD2 No 0.33 0.33 0.41 50 17.18% 3.9 3.9 3.5 251 3.14% 3.55 1.2 5.1 5.1 5.0
10 OS1 No 0.68 0.68 0.85 24 4.67% 2.3 2.3 1.4 484 1.34% 2.32 3.5 5.8 5.8 5.0
10 OS2 No 0.82 0.82 1.00 33 3.33% 2.0 2.0 0.7 963 1.41% 2.38 6.8 8.8 8.8 7.5
11
TOTAL
UNDETAINED
BASINS (UD1-
UD2) No
0.35 0.35 0.44 50 17.18% 3.8 3.8 3.4 352 3.38% 3.67 1.6 5.1 5.1 5.0
8
TOTAL TO POND
A (A1-A10, OS1) No
0.68 0.68 0.85 98 3.10% 5.3 5.3 3.2 389 0.54% 1.47 4.4 9.7 9.7 7.6
TOTAL TO
STORMTECH (A1-
A7, A9-A10) No
0.80 0.80 1.00 98 3.10% 3.8 3.8 1.3 389 0.54% 1.47 4.4 8.2 8.2 5.7
PROPOSED TIME OF CONCENTRATION COMPUTATIONS
S. Thomas
February 16, 2017
Design
Point
Sub-Basin
Overland Flow Gutter/Pipe Flow Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
2/16/2017 10:54 AM D:\Projects\1284-001\Drainage\Hydrology\1284-001_Proposed_Rational_Calcs.xlsx\Tc
A4 0.10 0.07 0.01 0.00 0.00 Clayey | Average 2% to 7% 0.027 0.76 0.76 0.95 73%
A5 0.35 0.00 0.00 0.00 0.35 Clayey | Average 2% to 7% 0.000 0.95 0.95 1.00 90%
A6 0.45 0.27 0.05 0.00 0.00 Clayey | Average 2% to 7% 0.131 0.74 0.74 0.93 70%
A7 0.04 0.00 0.01 0.00 0.00 Clayey | Average 2% to 7% 0.030 0.41 0.41 0.51 20%
A8 0.49 0.00 0.00 0.04 0.00 Clayey | Average 2% to 7% 0.446 0.27 0.27 0.33 4%
A9 0.36 0.00 0.00 0.00 0.36 Clayey | Average 2% to 7% 0.000 0.95 0.95 1.00 90%
A10 0.03 0.00 0.02 0.00 0.00 Clayey | Average 2% to 7% 0.016 0.60 0.60 0.75 45%
UD1 0.03 0.02 0.01 0.00 0.00 Clayey | Average 2% to 7% 0.003 0.86 0.86 1.00 86%
UD2 0.57 0.00 0.07 0.00 0.00 Clayey | Average 2% to 7% 0.506 0.33 0.33 0.41 10%
OS1 0.44 0.20 0.07 0.00 0.00 Clayey | Average 2% to 7% 0.169 0.68 0.68 0.85 60%
OS2 1.86 1.31 0.20 0.00 0.00 Clayey | Average 2% to 7% 0.346 0.82 0.82 1.00 80%
TOTAL UNDETAINED BASINS
(UD1-UD2) 0.60 0.02 0.07 0.00 0.00 Clayey | Average 2% to 7% 0.509 0.35 0.35 0.44 14%
TOTAL TO POND A (A1-A10,
OS1) 2.57 0.67 0.19 0.04 0.72 Clayey | Average 2% to 7% 0.958 0.68 0.68 0.85 58%
TOTAL ON-SITE BASINS (A1-
A9,UD1-UD3) 2.73 0.48 0.19 0.04 0.72 Clayey | Average 2% to 7% 1.299 0.61 0.61 0.76 48%
TOTAL TO STORMTECH (A1-A7,
A9-A10) 1.64 0.47 0.11 0.00 0.72 Clayey | Average 2% to 7% 0.327 0.80 0.80 1.00 74%
Composite Runoff Coefficient with Adjustment
PROPOSED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
2/16/2017 10:53 AM D:\Projects\1284-001\Drainage\Hydrology\1284-001_Proposed_Rational_Calcs.xlsx\Composite C
S. Thomas
December 6, 2016
Design
Point
Sub-Basin
Overland Flow Gutter/Pipe Flow Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
12/6/2016 1:29 PM D:\Projects\1284-001\Drainage\Hydrology\1284-001_Existing_Rational_Calcs.xlsx\Tc
H2 0.44 0.20 0.02 0.00 0.00 Clayey | Average 2% to 7% 0.224 0.60 0.60 0.74 49%
H3 0.77 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.767 0.25 0.25 0.31 0%
TOTAL SITE 3.25 0.20 0.02 0.00 0.00 Clayey | Average 2% to 7% 3.032 0.30 0.30 0.37 7%
1. Table RO-11 | Rational Method Runoff Coefficients for Composite Analysis
Composite Runoff Coefficient with Adjustment
EXISTING COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
12/6/2016 1:28 PM D:\Projects\1284-001\Drainage\Hydrology\1284-001_Existing_Rational_Calcs.xlsx\Composite C
Volume
(ac-ft)
100-yr
WSEL
WQCV
(ft3)
WQCV
WSEL
Max
Release
(cfs)
A 0.51 5006.31 740 5001.71 1.10