HomeMy WebLinkAboutNORTH COLLEGE DRIVE THRU - PDP - PDP160014 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTPRELIMINARY DRAINAGE REPORT
NORTH COLLEGE DRIVE-THRU
Fort Collins, Colorado
April 13, 2016
Prepared for:
Chad A. Hirshfield
PO Box 102291
Denver, Colorado 80250
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: 1249-001
3 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.
April 13, 2016
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Final Drainage Report for
North College Drive Thru
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage and Erosion Control Report for
your review. This report accompanies the Conceptual Review submittal for the proposed North
College Drive Thru. Comments from the Preliminary Development Review Letter dated September
14, 2015 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 Fort Collins Stormwater Criteria Manual (FCSCM),
and serves to document the stormwater impacts associated with the proposed Lake Street
Apartments 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 Blaine Mathisen
Project Manager Project Engineer
North College Drive Thru
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 ......................................................................................................................... 6
E. Hydraulic Criteria .............................................................................................................................. 7
F. Floodplain Regulations Compliance .................................................................................................. 7
G. Modifications of Criteria ................................................................................................................... 7
IV. DRAINAGE FACILITY DESIGN ..................................................................................... 7
A. General Concept ............................................................................................................................... 7
B. Specific Details .................................................................................................................................. 8
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 – 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
North College Drive Thru
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
North College Drive Thru
Final Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. North College Drive Thru project is located in the northeast quarter of Section 2,
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 west of North College Avenue between Schroders P.U.D
and North College Mobile Home Park at the address of 1603-1605 N. College Ave.
4. Currently the existing lot does not have any stormwater or water quality facilities. The
existing project site has 1.0% imperviousness, as it has remained undeveloped. The
existing site sheet flows from west to east and north to south towards North College
Avenue.
5. The project is currently bordered to the west and south by single family residences,
north by a car wash, east by North College Avenue.
North College Drive Thru
Final Drainage Report 2
B. Description of Property
1. North College Drive Thru is approximately 0.69 net acres.
Figure 1 – Aerial Photograph
2. North College Drive Thru consists of two separate lots (Lot 1 and Lot 2). There is no
off-site drainage entering the existing property. Runoff generated from the project
drains southeast towards North College Avenue.
3. According to the United States Department of Agriculture (USDA) Natural Resources
Conservation Service (NRCS) Soil Survey, 100 percent of the site consists of Nunn
clay loam, which falls into Hydrologic Soil Groups C. A site specific report prepared
by Earth Engineering Consultants, LLC, dated March 22, 2016 notes that the project
site consists of 2 to 4 feet of apparent fill material which generally consisted of sandy
lean clay to clayey sand with gravel materials. Underlying the apparent surficial fill
materials, was lean clay with varying amount of sand underlain by silty/poorly graded
sand and gravel materials. Groundwater was observed during the time of the borings
to be approximately 5 to 6 feet below existing site grades.
4. The proposed development will include the clearing of existing vegetation and trees.
The proposed project will include one commercial building, exterior parking lots and
associated drive aisle and sidewalks. The exterior parking lot is planned to be
composed of permeable pavers and paving. The section of drive constructed of
permeable pavers will act as a portion of the project’s water quality and detention
facility. Additional water quality will be provided in the form of two rain gardens and
surrounding green space. Underground detention will be provided to meet Fort Collins
stormwater criteria.
North College Drive Thru
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 Service Commercial District (C-S) 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 08069C0977G 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 #1-10
Elevation = 4987.26 (NAVD 88)
North College Drive Thru
Final Drainage Report 4
Figure 3 – Existing FEMA Floodplains
Figure 4 – Existing City Floodplains
North College Drive Thru
Final Drainage Report 5
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. North College Drive Thru is located within the Dry Creek Master Basin, which extends
from near the Wyoming border to the Poudre River near Mulberry and Timberline.
B. Sub-Basin Description
1. The property historically drains east towards North College Avenue. Stormwater is
routed via overland flow across the existing lot.
2. Basin EX1 is historically discharged directly into North College Avenue (0.29 cfs for
the 2-year storm and 1.30 cfs for the 100-year event).
3. A more detailed description of the projects proposed drainage patterns follows in
Section IV.A.4., below.
4. 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 North College
Drive Thru project.
B. Four Step Process
The overall stormwater management strategy employed with the North College Drive Thru
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 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 paver section,
or through bio-media within the rain gardens.
Providing permeable paver areas with underground detention area to increase time of
concentration promote infiltration and provide water quality.
Routing runoff from the proposed roofs into an isolator row to promote infiltration,
biological uptake, and evapotranspiration.
North College Drive Thru
Final Drainage Report 6
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 and provide the necessary
BMPs required for water quality. Stormwater generated from the southern portion of the
project site will be routed through one of the two rain garden. Stormwater generated from
the roof is routed directly into isolator rows located in the underground detention section
surrounding the detention chambers. Stormwater generated from the western portion of
the parking area will be routed via overland flow across permeable pavers and enter the
southern underground detention. Stormwater generated from the northern portion of the
parking area will be routed via overland flow across permeable pavers.
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 North College Drive Thru, the proposed
project indirectly helps achieve stabilized drainageways nonetheless. Once again, site
selection has a positive effect on stream stabilization. By repurposing an undeveloped,
under-utilized site with no 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.
The North College Drive Thru project includes a new building with an associated drive and
parking area, all of which will require the need for site specific source controls including:
A localized trash enclosure at the rear of the building for the disposal of waste.
C. Development Criteria Reference and Constraints
1. There are no known drainage studies for the existing properties.
2. There are no known drainage studies for any adjacent properties that will have any
effect on the North College Drive Thru 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, south, east, and west property lines will be
maintained.
Overall drainage patterns of the existing site will be maintained.
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. Two separate design storms have been utilized to address distinct drainage scenarios.
North College Drive Thru
Final Drainage Report 7
The first event analyzed is the “Minor,” or “Initial” Storm, which has a 2-year
recurrence interval. The second event considered is the “Major Storm,” which has a
100-year recurrence interval.
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 North College Avenue.
The majority of the site drains stormwater via overland flow.
2. All drainage facilities proposed with the North College Drive Thru 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 North College Drive Thru 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 North College Drive Thru development is not requesting any
modification at this time.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of the North College Drive Thru drainage design is to maintain
existing drainage patterns 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 North College Drive Thru project is composed of three major drainage basins,
designated as Basins N, S, and OS. The drainage patterns for each major basin are
further described below.
Basin N
Basin N is further subdivided into two (2) sub-basins. N1 is located north of the
building and consists of permeable pavers, asphalt, and landscape surfacing.
Stormwater generated from this basin is routed via overland and gutter flow and
crosses over permeable pavers to reduce runoff and provide water quality. Runoff from
sub-basin N1 is collected via curb inlet and discharged into Underground Pond N.
North College Drive Thru
Final Drainage Report 8
Sub-basin N2 is composed entirely of the building roof. Stormwater generated from
this sub-basin is routed internal to the building through pipe flow and discharged
directly into an isolator row and then into Underground Pond N.
Basin S
Basin S is further subdivided into three (3) sub-basins. Sub-basin S1 is composed of
the parking area located west of the building and consists of some landscape
surfacing, but predominantly hardscape. Stormwater generated from this basin is
routed via overland and gutter flow across permeable pavers and eventually discharges
through a curb inlet directly into Underground Pond S. Sub-basin S2 is composed of
the area located south of the building and consists of landscape surfacing along with
some hardscape surfaces. Stormwater generated from this basin is routed via
overland and gutter flow and is collected in a rain garden (Rain Garden 1) via curb
cuts. Any flow above the water quality event is routed via pipes to Underground Pond
S. Sub-basin S3 is composed of small area in the southwest corner of the project site
that consists of asphalt and the second rain garden (Rain Garden 2). Flow from this
basin is initially routed to Rain Garden 2 and any flow above the water quality event is
routed via pipes to Underground Pond S.
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 all along the western
and southern property lines and consists of landscape surfacing. Stormwater
generated from this sub-basin is routed via overland flow and discharges undetained
into the adjacent property of North College Mobile Home Park and North College
Avenue. Sub-basin OS2 is composed of a small portion of landscaping and sidewalk
east of the building. Stormwater generated from this sub-basin is routed via overland
flow and discharges undetained into North College Avenue.
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 and lack of stormwater infrastructure within the existing site.
Currently the entire site drains overland and discharges directly into North College
Avenue, adjacent sites, or pools in a central location within the project site. The
proposed site will mitigate these issues by instituting the following water quality
devices:
All of the runoff generated from the proposed building roof (Basin N2) will be
routed into an isolator row within Underground Detention Pond N.
The runoff generated from the majority of the proposed drive aisle and parking
(Basin N1 and S1) will be routed through a permeable paver system.
Basins S2 and S3 will be routed to rain gardens and through bio-media
2. The release rate for the undeveloped land (pre-development) was established by
calculating the 2-year peak runoff rate for the entire project area and excluding all
portions of the proposed project that release undetained (Sub-basins OS1 and OS2)
North College Drive Thru
Final Drainage Report 9
The overall 2-year peak runoff rate was calculated at 0.29 cfs, resulting in a
maximum release rate of 0.25 cfs from Basin N and S. This release rate was utilized
in the FAA procedure detention storage computations (Refer to Appendix B for these
calculations).
3. Detention Pond Calculations
Underground Pond N
The FAA method was used to size the underground ponds for detention. Calculations
for Underground Pond N, based on the characteristics of Basin N and an adjusted
release rate of 0.11 cfs, indicate a detention volume of 2,699 cu. ft. Additional
storage will be provided for 72 cu. ft of water quality capture volume associated with
the runoff generated from the roof that is tying into the underground system. Thus,
the overall required storage volume is 2,771 cf. ft. However, Underground Pond N is
using 174 StormTech SC160 chambers which yields an overall storage volume of
2,779 cu. ft. Water quality will be treated through permeable pavers and
downspouts from the building tying directly into an isolator row and will be released
over 12 hours.
Underground Pond S
Calculations for Pond S, based on the characteristics of Basin S and an adjusted
release rate of 0.14 cfs, indicate a detention volume of 3,577 cu. ft. Underground
Pond S is utilizing 116 StormTech SC-310 chambers which holds an overall storage
volume of 3,596 cu. ft. During the water quality events, the water quality capture
volume will release into and through either the permeable paver section or rain
gardens over 12-hours. There is also additional water quality volume within the
proposed rain gardens.
4. Water Quality Results
Basin N
Basin N has water quality provided via permeable pavers and having the downspouts
from the building drain directly into an isolator row within the underground
chambers. Following UDFCD standards, a required WQCV of 119 cu. ft must be
provided for Basin N1. A 10-inch-deep permeable section with an overall storage
capacity of 637 cu. ft will be constructed which will provide adequate water quality
for Basin N1. Basin N2 requires a WQCV of 72 cu. ft. which will be treated by an
isolator row within Underground Pond N.
Basin S
Basin S has three separate water quality amenities to help provide water quality.
Sub-basin S1 has a required WQCV of 135 cu. ft, dictated by UDFCD, but a
proposed 1,859 sq. ft of permeable pavers with a 10-inch-depth will provide 418 cu.
ft of water quality. Sub-basin S2 has a rain garden (Rain Garden 1) with a required
WQCV of 91.5 cu. ft but it is providing 788 cu. ft of water quality. Sub-basin S3 is
also providing water quality via a rain garden (Rain Garden 2). UDFCD requires sub-
basin S3 to provide 26.8 cu. ft of water quality, however, Rain Garden 2 is providing
127 cu. ft of water quality.
Following Fort Collins LID standards, 25% of new paved areas are pervious and
100% is being treated by LID.
5. To minimize the potential for increased flow to leave the site in the event the
permeable pavers cannot infiltrate fast enough, curb inlets have been provided to
North College Drive Thru
Final Drainage Report 10
capture and direct excess runoff into the underground detention vaults. All inlets will
have a sumped bottom to capture sediment and prevent the vault or surrounding
drainage rock from siltation. Additionally, all runoff generated from the water quality
event will be routed through an isolator row to collect any additional sedimentation.
6. Rain Garden 1 was designed to overtop the pond along its southern edge.
Rain Garden 1 will also have an overflow grate with a rim elevation equal to
the water quality water surface elevation (4981.60) to collect excess runoff
which will be routed via pipes to Underground Pond S. In the case that the
outlet structure should clog, additional storage (696.50 cu. ft) has been
provided within the rain garden. However, if Raingarden 1 was to overtop the
stormwater from Sub-basin S2 would flow into Sub-Basin OS1. Which roughly
half of the additional runoff will route west along the south property line and
the other half will be routed east along the south property line. As the flow is
routed west it will discharge into the adjacent property of North College
Mobile Home Park. As the flow is routed east it will discharge into a
landscape buffer along North College Avenue.
Rain Garden 2 was designed to overtop the pond along its southern edge as
well. Rain Garden 2 will have an overflow grate with a rim elevation equal to
the water quality water surface elevation (4981.60) to collect excess runoff
which will be routed via pipes to Underground Pond S. In the case that the
outlet structure should clog, stormwater would fill the additional storage space
(101 cu. ft) provided but once that was backed up the runoff would overtop
the rain garden and flow from Sub-basin S3 into Sub-basin OS1 where it will
flow southwest until it crosses the property line and enters the adjacent lot of
the North College Mobile Home Park.
In the case that the curb inlet within Sub-basin N1 should clog or
backwatering should occur, stormwater would overtop from Sub-basin N1 into
North College Avenue towards the northeast corner of the project site. In the
case that the curb inlet within Sub-basin S1 should clog or backwatering
should occur, stormwater would overtop from Sub-basin S1 into Sub-basin S3
where additional storage has been provided. However, in the event that the
outlet is clogged and pond is full the runoff would and then enter Sub-basin
OS1. From Sub-Basins OS1 the excess runoff will flow southwest until it
crosses the property line and enters the adjacent lot of the North College
Mobile Home Park.
V. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with the North College Drive Thru project complies with
the City of Fort Collins’ Stormwater Criteria Manual.
2. The drainage design proposed with the North College Drive Thru project complies with
the City of Fort Collins’ Master Drainage Plan for the Dry Creek Basin.
3. There are no regulatory floodplains associated with the Lake Street Apartments
development.
4. The drainage plan and stormwater management measures proposed with the North
College Drive Thru development are compliant with all applicable State and Federal
regulations governing stormwater discharge.
North College Drive Thru
Final Drainage Report 11
B. Drainage Concept
1. The drainage design proposed with this project will effectively limit potential damage
associated with its stormwater runoff. North College Drive Thru will detain for the
pervious area converted to impervious areas by releasing at the 2-year historic rate
during the developed 100-year storm.
2. The proposed North College Drive Thru development will not impact the Master
Drainage Plan recommendations for the Dry Creek major drainage basin.
North College Drive Thru
Final Drainage Report 12
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.
6. Geotechnical Exploration Report Proposed 2500 SF Fast Food Restaurant with Drive-Thru,
March 22, 2016, Earth Engineering Consultants, LLC
North College Drive Thru
Final Drainage Report 13
APPENDIX A
HYDROLOGIC COMPUTATIONS
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: North College Drive-Thru
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: B. Mathisen
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.
EX1 30222 0.69 0.00 0.00 0.00 0.00 0.69 0.25 0.25 0.31 0%
HISTORIC COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
Notes
April 7, 2016
10-year Cf = 1.00
**Soil Classification of site is Clayey 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.
Page 1 of 26 D:\Projects\1249-001\Drainage\Hydrology\1249-001_Rational-Calcs.xlsx\Hist-C-Values
Overland Flow, Time of Concentration:
Project: North College Drive-Thru
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: North College Drive-Thru
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
ex1 EX1 0.69 19 19 18 0.25 0.25 0.31 1.65 2.82 6.01 0.29 0.49 1.30
Flow,
Q10
(cfs)
Flow,
Q100
(cfs)
C2 C
10 C100
HISTORIC RUNOFF COMPUTATIONS
Intensity,
i2
(in/hr)
Intensity,
i10
(in/hr)
Intensity,
i100
(in/hr)
Notes
B. Mathisen
April 7, 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)
Q = C f (C )( i )(A )
Page 3 of 26 D:\Projects\1249-001\Drainage\Hydrology\1249-001_Rational-Calcs.xlsx\Hist-Direct-Runoff
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: North College Drive-Thru
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
(sq ft)
Area of
Asphalt
(ac)
Area of
Concrete
(sq ft)
Area of
Concrete
(ac)
Area of
Roofs
(sq ft)
Area of
Roofs
(ac)
Area of
Gravel
(sq ft)
Area of
Gravel
(ac)
Area of
Pavers
(sq ft)
Area of
Pavers
(ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Overland Flow, Time of Concentration:
Project: North College Drive-Thru
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: North College Drive-Thru
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
NN10.216 6 5 0.62 0.62 0.78 2.76 4.72 9.95 0.36 0.62 1.64
SS10.175 5 5 0.80 0.80 1.00 2.85 4.87 9.95 0.38 0.65 1.65
SS20.155 5 5 0.60 0.60 0.76 2.85 4.87 9.95 0.27 0.46 1.16
NN20.065 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.17 0.28 0.61
SS30.035 5 5 0.73 0.73 0.92 2.85 4.87 9.95 0.07 0.12 0.32
os1 OS1 0.05 8 8 8 0.25 0.25 0.31 2.40 4.10 8.59 0.03 0.05 0.13
os2 OS2 0.02 5 5 5 0.33 0.33 0.41 2.85 4.87 9.95 0.02 0.03 0.07
April 7, 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)
DEVELOPED RUNOFF COMPUTATIONS
C100 Notes
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)
Q = C f (C )( i )(A ) B. Mathisen
Page 6 of 26 D:\Projects\1249-001\Drainage\Hydrology\1249-001_Rational-Calcs.xlsx\Direct-Runoff
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: North College Drive-Thru
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
Design Point Basin IDs
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.
N N1 & N2 11911 0.273 0.056 0.043 0.062 0.000 0.066 0.047 0.70 0.70 0.87 55%
S S1, S2, & S3 15493 0.356 0.161 0.062 0.000 0.000 0.043 0.089 0.71 0.71 0.89 61%
COMBINED DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
April 7, 2016
**Soil Classification of site is Clayey Loam**
10-year Cf = 1.00
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.
Overland Flow, Time of Concentration:
Project: North College Drive-Thru
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: North College Drive-Thru
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
N N1 & N2 0.27 6 6 5 0.70 0.70 0.87 2.76 4.72 9.95 0.5 0.9 2.4
S S1, S2, & S3 0.36 5 5 5 0.71 0.71 0.89 2.85 4.87 9.95 0.7 1.2 3.1
Intensity,
i100
(in/hr)
COMBINED DEVELOPED RUNOFF COMPUTATIONS
B. Mathisen
April 7, 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)
Flow,
Q10
(cfs)
Flow,
Q100
(cfs)
C2 C
10 C100
Intensity,
i2
(in/hr)
Intensity,
i10
(in/hr)
Q = C f (C )( i )(A )
Page 9 of 26 D:\Projects\1249-001\Drainage\Hydrology\1249-001_Rational-Calcs.xlsx\Comb-Direct-Runoff
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
N N1 0.212 0.62 0.78 5.7 5.0 0.36 1.64
S S1 0.166 0.80 1.00 5.0 5.0 0.38 1.65
S S2 0.155 0.60 0.76 5.0 5.0 0.27 1.16
N N2 0.062 0.95 1.00 5.0 5.0 0.17 0.61
S S3 0.035 0.73 0.92 5.0 5.0 0.07 0.32
os1 OS1 0.047 0.25 0.31 8.3 7.7 0.03 0.13
os2 OS2 0.018 0.33 0.41 5.0 5.0 0.02 0.07
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
ex1 EX1 0.694 0.25 0.31 19.4 18.0 0.29 1.30
Page 10 of 26 D:\Projects\1249-001\Drainage\Hydrology\1249-001_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 :
N
100-yr
0.87
5.00 min 2699 ft3
0.27 acres 0.062 ac-ft
Max Release Rate = 0.11 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 9.950 701 1.00 0.11 33 668
10 7.720 1088 0.75 0.08 50 1039
15 6.520 1378 0.67 0.07 66 1312
20 5.600 1579 0.63 0.07 83 1496
25 4.980 1755 0.60 0.07 99 1656
30 4.520 1911 0.58 0.06 116 1796
35 4.080 2013 0.57 0.06 132 1881
40 3.740 2108 0.56 0.06 149 1960
45 3.460 2194 0.56 0.06 165 2029
50 3.230 2276 0.55 0.06 182 2095
55 3.030 2349 0.55 0.06 198 2151
60 2.860 2419 0.54 0.06 215 2204
65 2.720 2492 0.54 0.06 231 2261
70 2.590 2555 0.54 0.06 248 2308
75 2.480 2621 0.53 0.06 264 2357
80 2.380 2683 0.53 0.06 281 2403
85 2.290 2743 0.53 0.06 297 2446
90 2.210 2803 0.53 0.06 314 2490
95 2.130 2852 0.53 0.06 330 2522
100 2.060 2903 0.53 0.06 347 2557
105 2.000 2960 0.52 0.06 363 2597
110 1.940 3008 0.52 0.06 380 2628
115 1.890 3063 0.52 0.06 396 2667
120 1.840 3112 0.52 0.06 413 2699
*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
Project:
Chamber Model - SC-160
Units - Imperial
100
Number of chambers - 170
Voids in the stone (porosity) - 40 %
Base of STONE Elevation - 100.00 ft
Amount of Stone Above Chambers - 6 in
Amount of Stone Below Chambers - 6 in
Height of
System
Incremental Single
Chamber
Incremental
Total Chamber
Incremental
Stone
Incremental Ch
& St
Cumulative
Chamber Elevation
(inches) (cubic feet) (cubic feet) (cubic feet) (cubic feet) (cubic feet) (feet)
24 0.00 0.00 84.02 84.02 2715.46 102.00
23 0.00 0.00 84.02 84.02 2631.44 101.92
22 0.00 0.00 84.02 84.02 2547.42 101.83
21 0.00 0.00 84.02 84.02 2463.41 101.75
20 0.00 0.00 84.02 84.02 2379.39 101.67
19 0.00 0.00 84.02 84.02 2295.37 101.58
18 0.05 8.71 80.53 89.24 2211.36 101.50
17 0.13 22.85 74.88 97.73 2122.12 101.42
16 0.29 49.40 64.26 113.66 2024.39 101.33
15 0.44 75.13 53.97 129.09 1910.73 101.25
14 0.54 91.66 47.35 139.01 1781.64 101.17
13 0.62 104.78 42.11 146.88 1642.63 101.08
12 0.68 115.73 37.73 153.45 1495.75 101.00
11 0.74 125.10 33.98 159.08 1342.30 100.92
10 0.78 133.18 30.74 163.92 1183.22 100.83
9 0.82 140.23 27.92 168.16 1019.30 100.75
8 0.86 146.26 25.51 171.77 851.14 100.67
7 0.89 152.09 23.18 175.27 679.37 100.58
6 0.00 0.00 84.02 84.02 504.10 100.50
5 0.00 0.00 84.02 84.02 420.08 100.42
4 0.00 0.00 84.02 84.02 336.06 100.33
3 0.00 0.00 84.02 84.02 252.05 100.25
2 0.00 0.00 84.02 84.02 168.03 100.17
1 0.00 0.00 84.02 84.02 84.02 100.08
StormTech SC-160 Cumulative Storage Volumes
North College Drive Thru - North Pond
Include Perimeter Stone in Calculations
Click Here for Metric
Pond No :
S
100-yr
0.86
5.00 min 3577 ft3
0.36 acres 0.082 ac-ft
Max Release Rate = 0.14 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 9.950 924 1.00 0.14 42 882
10 7.720 1434 0.75 0.11 63 1371
15 6.520 1817 0.67 0.09 84 1733
20 5.600 2081 0.63 0.09 105 1976
25 4.980 2313 0.60 0.08 126 2187
30 4.520 2519 0.58 0.08 147 2372
35 4.080 2653 0.57 0.08 168 2485
40 3.740 2779 0.56 0.08 189 2590
45 3.460 2892 0.56 0.08 210 2682
50 3.230 3000 0.55 0.08 231 2769
55 3.030 3096 0.55 0.08 252 2844
60 2.860 3188 0.54 0.08 273 2915
65 2.720 3284 0.54 0.08 294 2990
70 2.590 3368 0.54 0.08 315 3053
75 2.480 3455 0.53 0.07 336 3119
80 2.380 3537 0.53 0.07 357 3180
85 2.290 3616 0.53 0.07 378 3238
90 2.210 3695 0.53 0.07 399 3296
95 2.130 3759 0.53 0.07 420 3339
100 2.060 3827 0.53 0.07 441 3386
105 2.000 3901 0.52 0.07 462 3439
110 1.940 3964 0.52 0.07 483 3481
115 1.890 4037 0.52 0.07 504 3533
120 1.840 4102 0.52 0.07 525 3577
*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
1249-001
North College Drive-Thru
Project Number :
Project Name :
Pond S
A =
Project:
Chamber Model - SC-310
Units - Imperial
100
Number of chambers - 116
Voids in the stone (porosity) - 40 %
Base of STONE Elevation - 100.00 ft
Amount of Stone Above Chambers - 6 in
Amount of Stone Below Chambers - 6 in
Height of
System
Incremental Single
Chamber
Incremental
Total Chamber
Incremental
Stone
Incremental Ch
& St
Cumulative
Chamber Elevation
(inches) (cubic feet) (cubic feet) (cubic feet) (cubic feet) (cubic feet) (feet)
28 0.00 0.00 91.73 91.73 3595.63 102.33
27 0.00 0.00 91.73 91.73 3503.90 102.25
26 0.00 0.00 91.73 91.73 3412.18 102.17
25 0.00 0.00 91.73 91.73 3320.45 102.08
24 0.00 0.00 91.73 91.73 3228.73 102.00
23 0.00 0.00 91.73 91.73 3137.00 101.92
22 0.06 6.82 89.00 95.82 3045.27 101.83
21 0.15 17.95 84.55 102.49 2949.46 101.75
20 0.27 30.84 79.39 110.23 2846.96 101.67
19 0.54 63.20 66.45 129.64 2736.73 101.58
18 0.70 81.67 59.06 140.73 2607.09 101.50
17 0.82 95.65 53.47 149.11 2466.36 101.42
16 0.92 107.25 48.83 156.08 2317.25 101.33
15 1.01 117.74 44.63 162.37 2161.17 101.25
14 1.09 126.97 40.94 167.91 1998.80 101.17
13 1.15 133.90 38.17 172.06 1830.90 101.08
12 1.21 140.93 35.35 176.29 1658.83 101.00
11 1.27 147.89 32.57 180.46 1482.55 100.92
10 1.32 153.65 30.27 183.92 1302.09 100.83
9 1.36 158.34 28.39 186.73 1118.17 100.75
8 1.40 162.98 26.53 189.51 931.44 100.67
7 1.43 166.42 25.16 191.58 741.93 100.58
6 0.00 0.00 91.73 91.73 550.36 100.50
5 0.00 0.00 91.73 91.73 458.63 100.42
4 0.00 0.00 91.73 91.73 366.90 100.33
3 0.00 0.00 91.73 91.73 275.18 100.25
2 0.00 0.00 91.73 91.73 183.45 100.17
1 0.00 0.00 91.73 91.73 91.73 100.08
StormTech SC-310 Cumulative Storage Volumes
North College Drive Thru - North Pond
Include Perimeter Stone in Calculations
Click Here for Metric
APPENDIX C
WATER QUALITY DESIGN COMPUTATIONS
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 = 45.0 %
B) Tributary Area's Imperviousness Ratio (I = Ia / 100) i = 0.450
C) Tributary Watershed Area ATotal
= 9,231 sq ft
(including area of permeable pavement system)
D) Area of Permeable Pavement System APPS
= 2,875 sq ft
(Minimum recommended permeable pavement area = 1695 sq ft)
E) Impervious Tributary Ratio RT
= 1.0
(Contributing Imperviuos Area / Permeable Pavement Ratio)
F) Water Quality Capture Volume (WQCV) Based on 12-hour Drain Time WQCV = 119 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
= 10.0 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 = 647 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 = 1
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.)
North College Drive Thru
Basin N1
Design Procedure Form: Permeable Pavement Systems (PPS)
Blaine Mathisen
Northern Engineering
April 11, 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)
Detention Vault no Underdrain
C) Distance from the Lowest Elevation of the Storage Volume y = 0.3 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
= 1.65 inches
(Elevation of the Flood Control Outlet)
B) Diameter of Orifice for 12-hour Drain Time DOrifice
= 0.37 inches MINIMUM ORIFICE SIZE IS 3/8-INCHES
(Use a minimum orifice diameter of 3/8-inches)
Notes:
North College Drive Thru
Design Procedure Form: Permeable Pavement Systems (PPS)
Blaine Mathisen
Northern Engineering
April 11, 2016
Basin N1
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
1249-001 Basin N1 PAVER UD-BMP_v3.02.xls, PPS 4/11/2016, 10:50 AM
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 = 71.0 %
B) Tributary Area's Imperviousness Ratio (I = Ia / 100) i = 0.710
C) Tributary Watershed Area ATotal
= 7,242 sq ft
(including area of permeable pavement system)
D) Area of Permeable Pavement System APPS
= 1,859 sq ft
(Minimum recommended permeable pavement area = 1897 sq ft)
E) Impervious Tributary Ratio RT
= 2.1 IMPERVIOUS TRIBUTARY RATIO EXCEEDS 2.0
(Contributing Imperviuos Area / Permeable Pavement Ratio)
F) Water Quality Capture Volume (WQCV) Based on 12-hour Drain Time WQCV = 135 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
= 10.0 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 = 418 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 = 1
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.)
North College Drive Thru
Basin S1
Design Procedure Form: Permeable Pavement Systems (PPS)
Blaine Mathisen
Northern Engineering
April 11, 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)
Detention Vault no Underdrain
C) Distance from the Lowest Elevation of the Storage Volume y = 0.3 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
= 2.90 inches
(Elevation of the Flood Control Outlet)
B) Diameter of Orifice for 12-hour Drain Time DOrifice
= 0.40 inches
(Use a minimum orifice diameter of 3/8-inches)
Notes:
Basin S1
North College Drive Thru
Design Procedure Form: Permeable Pavement Systems (PPS)
Blaine Mathisen
Northern Engineering
April 11, 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
1249-001 Basin S1 PAVER UD-BMP_v3.02.xls, PPS 4/11/2016, 3:11 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 49.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.490
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.16 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 6,742 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = cu ft
Vol = (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 = 91.5 cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum) DWQCV = 12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 3.00 ft / ft Z < 4:1
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 61 sq ft
D) Actual Flat Surface Area AActual = 512 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 1065 sq ft
F) Rain Garden Total Volume VT= 788 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
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 = 2.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = 91 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 0.22 in MINIMUM DIAMETER = 3/8"
Design Procedure Form: Rain Garden (RG)
Blaine Mathisen
Northern Engineering
April 11, 2016
North College Avenue Drive Thru
Basin S2
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
1249-001 Basin S2 RAIN GARDEN UD-BMP_v3.02.xls, RG 4/11/2016, 10:54 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 LINER WITH CDOT CLASS B
GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW THE
LINER IF THE SUBGRADE IS ANGULAR
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
April 11, 2016
North College Avenue Drive Thru
Basin S2
Design Procedure Form: Rain Garden (RG)
Blaine Mathisen
Northern Engineering
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
1249-001 Basin S2 RAIN GARDEN UD-BMP_v3.02.xls, RG 4/11/2016, 10:54 AM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 68.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.680
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.21 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 1,509 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = cu ft
Vol = (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 = 26.8 cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum) DWQCV = 12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 3.00 ft / ft Z < 4:1
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 18 sq ft
D) Actual Flat Surface Area AActual = 62 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 191 sq ft
F) Rain Garden Total Volume VT= 127 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
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 = 2.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = 27 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 0.12 in MINIMUM DIAMETER = 3/8"
North College Avenue Drive Thru
Basin S3
Design Procedure Form: Rain Garden (RG)
Blaine Mathisen
Northern Engineering
April 11, 2016
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
1249-001 Basin S3 RAIN GARDEN UD-BMP_v3.02.xls, RG 4/11/2016, 10:55 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?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
Blaine Mathisen
Northern Engineering
April 11, 2016
North College Avenue Drive Thru
Basin S3
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
1249-001 Basin S3 RAIN GARDEN UD-BMP_v3.02.xls, RG 4/11/2016, 10:55 AM
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
0.8
WQCV = Watershed inches of Runoff (inches) 90.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.321 in
A =0.06 ac
V = 0.0017 ac‐ft
V = Water Quality Design Volume (ac‐ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
72 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB‐2 ‐ Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
North College Drive‐Thru April 7, 2016
1249‐001 B.Mathisen
Underground Pond N (Basin N2)
0.321
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
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
⎟
⎠
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
D
D
EV
os1
N
S
2' CONCRETE
VALLEY PAN
8' SIDEWALK
NORTH COLLEGE AVE.
SCHRADER P.U.D.
FFE = 84.25
EXISTING
5' CONCRETE
VALLEY PAN
LOT 2
NORTH COLLEGE
MOBILE HOME PARK
NORTH
COLLEGE
MOBILE HOME
PARK
\A1;EXISTING 30" RCP
acres
N1
0.62 0.21
0.78
acres
S1
0.80 0.17
1.00
acres
S2
0.60 0.16
0.76
acres
N2
0.95 0.06
1.00
acres
OS2
0.33 0.02
0.41
acres
OS1
0.25 0.05
0.31
acres
S3
0.73 0.04
0.92
os2
LOT 1
PRIVATE DRIVE
RAIN GARDEN 1
RAIN
GARDEN 2
UNDERGROUND
POND S (SC-310)
UNDERGROUND
D
D
V.P.
C
S
C
S
8' SIDEWALK
NORTH COLLEGE AVE.
SCHRADER P.U.D. EXISTING 6'
CONCRETE CROSS PAN
EXISTING
5' CONCRETE
VALLEY PAN
LOT 2
NORTH COLLEGE
MOBILE HOME PARK
NORTH
COLLEGE
MOBILE HOME
PARK
\A1;EXISTING 30" RCP
acres
EX1
0.25 0.69
0.31
LOT 1
EX1
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU DIG, GRADE, OR EXCAVATE FOR THE MARKING OF UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what's below.
Call before you dig.
R
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
acres
A2
0.25 0.08
0.31
a3
4950
4950
4:1
79.45
SLOPE
PROPOSED OVERLAND FLOW DIRECTION
CONCENTRATED FLOW DIRECTION
PROPOSED SWALE FLOWLINE
PROPOSED INFLOW CURB/GUTTER FLOWLINE
PROPOSED STORM DRAIN WITH INLET
DRAINAGE BASIN
PROPOSED CONTOUR
PROPOSED FLOWLINE ELEVATION
PROPOSED RIPRAP
EXISTING CONTOUR
DRAINAGE BASIN AREA
DESIGN POINT
DRAINAGE BASIN ID
DRAINAGE BASIN MINOR/MAJOR COEFF.
EXISTING OVERLAND FLOW DIRECTION
PROPOSED OUTFALL CURB/GUTTER FLOWLINE
RUNOFF SUMMARY TABLE:
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
1.REFER TO THE "FINAL DRAINAGE & EROSION CONTROL REPORT FOR THE NORTH COLLEGE TACO JOHN'S" BY NORTHERN ENGINEERING, DATED OCTOBER 2010 FOR ADDITIONAL INFORMATION.
NOTES:
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
EX1 0.075 0.25 0.31 7.9 7.4 0.05 0.21
( IN FEET )
10 0 10 20 30
1 INCH = 10 FEET
NORTH
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
No. Revisions:
By: Date:
REVIEWED BY:
N. Haws
DESIGNED BY:
DRAWN BY:
SCALE:
DATE:
04.13.16
PROJECT:
1249-001
Sheet
Of 6 Sheets
NORTH COLLEGE DRIVE THRU
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
04.13.16
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
DR2
HISTORIC DRAINAGE EXHIBIT
C. Snowdon
C. Snowdon
1"=10'
POND S (SC-310)
UNDERGROUND
POND S (SC-310)
UNDERGROUND
POND N (SC-160)
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU DIG, GRADE, OR EXCAVATE FOR THE MARKING OF UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what's below.
Call before you dig.
R
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
acres
A2
0.25 0.08
0.31
a3
4950
4950
4:1
79.45
SLOPE
PROPOSED OVERLAND FLOW DIRECTION
CONCENTRATED FLOW DIRECTION
PROPOSED SWALE FLOWLINE
PROPOSED INFLOW CURB/GUTTER FLOWLINE
PROPOSED STORM DRAIN WITH INLET
DRAINAGE BASIN
PROPOSED CONTOUR
PROPOSED FLOWLINE ELEVATION
PROPOSED RIPRAP
EXISTING CONTOUR
DRAINAGE BASIN AREA
DESIGN POINT
DRAINAGE BASIN ID
DRAINAGE BASIN MINOR/MAJOR COEFF.
EXISTING OVERLAND FLOW DIRECTION
PROPOSED OUTFALL CURB/GUTTER FLOWLINE
RUNOFF SUMMARY TABLE:
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
1.REFER TO THE "FINAL DRAINAGE & EROSION CONTROL REPORT FOR THE NORTH COLLEGE TACO JOHN'S" BY NORTHERN ENGINEERING, DATED OCTOBER 2010 FOR ADDITIONAL INFORMATION.
NOTES:
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
N N1 0.212 0.62 0.78 5.7 5.0 0.36 1.64
S S1 0.166 0.80 1.00 5.0 5.0 0.38 1.65
S S2 0.155 0.60 0.76 5.0 5.0 0.27 1.16
N N2 0.062 0.95 1.00 5.0 5.0 0.17 0.61
S S3 0.035 0.73 0.92 5.0 5.0 0.07 0.32
os1 OS1 0.047 0.25 0.31 8.3 7.7 0.03 0.13
os2 OS2 0.018 0.33 0.41 5.0 5.0 0.02 0.07
( IN FEET )
10 0 10 20 30
1 INCH = 10 FEET
NORTH
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
No. Revisions:
By: Date:
REVIEWED BY:
N. Haws
DESIGNED BY:
DRAWN BY:
SCALE:
DATE:
04.13.16
PROJECT:
1249-001
Sheet
Of 6 Sheets
NORTH COLLEGE DRIVE THRU
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
04.13.16
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
DR1
DRAINAGE EXHIBIT
C. Snowdon
C. Snowdon
1"=10'
⎞
⎜
⎝
= ⎛
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
1249-001 Basin S1 PAVER UD-BMP_v3.02.xls, PPS 4/11/2016, 3:11 PM
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
1249-001 Basin N1 PAVER UD-BMP_v3.02.xls, PPS 4/11/2016, 10:50 AM
Tc =
Project Location :
Design Point
C =
Design Storm
Page 1 of 1
1249-001_Pond S_DetentionVolume_FAAModified Method.xls
1249-001
North College Drive-Thru
Project Number :
Project Name :
Pond N
Page 1 of 1
1249-001_Pond N_DetentionVolume_FAAModified Method.xls
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
N N1 & N2 No 0.62 0.62 0.78 0.02 4.65 4.65 3.13 0.01 1.67 1.02 N/A N/A N/A 665
S S1, S2, & S3 No 0.80 0.80 1.00 0.03 2.74 2.74 0.91 0.01 1.55 1.03 N/A N/A N/A 555
COMBINED DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
B. Mathisen
April 7, 2016
Design
Point
Basin IDs
Overland Flow Pipe Flow Swale Flow Time of Concentration
(Equation RO-4)
()
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
−
=
Page 8 of 26 D:\Projects\1249-001\Drainage\Hydrology\1249-001_Rational-Calcs.xlsx\Comb-Tc-10-yr_&_100-yr
B. Mathisen
Page 7 of 26 D:\Projects\1249-001\Drainage\Hydrology\1249-001_Rational-Calcs.xlsx\Comb-C-Values
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
NN1No0.62 0.62 0.78 46 2.20% 4.6 4.6 3.1 102 0.70% 1.67 1.0 N/A N/A N/A 6 6 5
SS1No0.80 0.80 1.00 45 2.60% 2.7 2.7 0.9 96 0.60% 1.55 1.0 N/A N/A N/A 5 5 5
SS2No0.60 0.60 0.76 12 2.50% 2.3 2.3 1.6 100 1.75% 2.65 0.6 N/A N/A N/A 5 5 5
NN2No0.95 0.95 1.00 16 2.00% 0.9 0.9 0.6 105 1.30% 2.28 0.8 N/A N/A N/A 5 5 5
SS3No0.73 0.73 0.92 25 2.98% 2.4 2.4 1.2 16 1.50% 2.45 0.1 N/A N/A N/A 5 5 5
os1 OS1 No 0.25 0.25 0.31 21 0.67% 8.3 8.3 7.7 N/A N/A N/A N/A N/A N/A 8 8 8
os2 OS2 No 0.33 0.33 0.41 14 1.50% 4.7 4.7 4.2 N/A N/A N/A N/A N/A N/A 5 5 5
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Gutter Flow Swale Flow
Design
Point
Basin
Overland Flow
B. Mathisen
April 7, 2016
Time of Concentration
(Equation RO-4)
()
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
−
=
Page 5 of 26 D:\Projects\1249-001\Drainage\Hydrology\1249-001_Rational-Calcs.xlsx\Tc-10-yr_&_100-yr
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
N1 9231 0.212 2455.620 0.056 1855.330 0.043 0.000 0.000 0.000 0.000 2874.870 0.066 0.047 0.62 0.62 0.78 45%
S1 7242 0.166 3642.000 0.084 1651.320 0.038 0.000 0.000 0.000 0.000 1859.000 0.043 0.002 0.80 0.80 1.00 71%
S2 6742 0.155 2463.019 0.057 950.267 0.022 0.000 0.000 0.000 0.000 0.000 0.000 0.076 0.60 0.60 0.76 49%
N2 2680 0.062 0.000 0.000 0.000 0.000 2679.740 0.062 0.000 0.000 0.000 0.000 0.000 0.95 0.95 1.00 90%
S3 1509 0.035 922.000 0.021 120.315 0.003 0.000 0.000 0.000 0.000 0.000 0.000 0.011 0.73 0.73 0.92 68%
OS1 2038 0.047 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.047 0.25 0.25 0.31 0%
OS2 780 0.018 0.000 0.000 87.705 0.002 0.000 0.000 0.000 0.000 0.000 0.000 0.016 0.33 0.33 0.41 10%
TOTAL 30222 0.69 9482.639 0.218 4664.937 0.107 2679.740 0.062 0.000 0.000 4733.870 0.109 0.199 0.66 0.66 0.83 53%
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
April 7, 2016
**Soil Classification of site is Clayey Loam**
B. Mathisen
Page 4 of 26 D:\Projects\1249-001\Drainage\Hydrology\1249-001_Rational-Calcs.xlsx\C-Values
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
ex1 EX1 No 0.25 0.25 0.31 139 0.90% 19.4 19.4 18.0 N/A N/A N/A N/A N/A N/A 19 19 18
HISTORIC TIME OF CONCENTRATION COMPUTATIONS
B. Mathisen
April 7, 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
−
=
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