HomeMy WebLinkAbout2106 S. TAFT HILL ROAD (WEST VILLAGE OFF TAFT) - FDP - FDP170015 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFINAL DRAINAGE REPORT
WEST VILLAGE OFF TAFT
Fort Collins, Colorado
May 16, 2017
Prepared for:
Laura Olive
125 S. Howes Street, Suite 120
Fort Collins, CO 80525
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: 1076-001
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.
May 16, 2017
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Final Drainage Report for
West Village Off Taft
Dear Staff:
Northern Engineering is pleased to submit this Final Drainage Report for your review. This report
accompanies the Conceptual Review submittal for the proposed West Village Off Taft.
This report has been prepared in accordance with the City of Fort Collins Stormwater Criteria
Manual (FCSCM) and the Urban Drainage and Flood Control District (UDFCD) Urban Storm
Drainage Criteria Manual and serves to document the stormwater impacts associated with the
proposed West Village Off Taft project. We understand that review by the City of Fort Collins is to
assure general compliance with standardized criteria.
If you should have any questions as you review this report, please feel free to contact us.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
Bud Curtiss Blaine Mathisen, EI
Vice President Project Engineer
West Village Off Taft
Final Drainage Report
TABLE OF CONTENTS
I. General Location and Description ............................................................................... 1
A. Location ............................................................................................................................................. 1
B. Description of Property ..................................................................................................................... 1
C. Floodplain.......................................................................................................................................... 2
II. drainage basins and sub-basins .................................................................................. 3
A. Major Basin Description .................................................................................................................... 3
B. Sub-Basin Description ....................................................................................................................... 3
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 .............................................................................................................................. 5
F. Floodplain Regulations Compliance .................................................................................................. 6
G. Modifications of Criteria ................................................................................................................... 6
IV. drainage FACILITY DESIGN ....................................................................................... 6
A. General Concept ............................................................................................................................... 6
B. Specific Details .................................................................................................................................. 7
V. CONCLUSIONS ........................................................................................................ 9
A. Compliance with Standards .............................................................................................................. 9
B. Drainage Concept .............................................................................................................................. 9
References ....................................................................................................................... 10
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
B.1 – Detention Facilities
APPENDIX C – Water Quality Design Computations
APPENDIX D – Erosion Control Report
APPENDIX E – Soils Resource Report
LIST OF TABLES AND FIGURES:
Figure 1 - Aerial Photograph - Google Earth ............................................................................ 1
Figure 2 - Proposed Site Plan ............................................................................................... 2
Figure 3 - Existing City Floodplain ......................................................................................... 3
Figure 4 - LID Table ............................................................................................................ 4
West Village Off Taft
Final Drainage Report
MAP POCKET:
C7.00 - Drainage Exhibit
C7.01 – Historic Drainage Exhibit
West Village Off Taft
Final Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
Figure 1 - Aerial Photograph - Google Earth
2. West Village Off Taft is in Township 7 North, Range 69 West of the 6th P.M., City of
Fort Collins, County of Larimer, State of Colorado.
3. The project site is located on the east side of S. Taft Hill Rd. near the intersection of
S. Taft Hill Rd. and Sheffield Dr. It is directly across the street from Blevins Middle
School. The project site is surrounded by residential homes to the north, east, and
south.
4. Currently the existing lot remains mostly undeveloped. However, there is currently a
two-story house with an associated detached garage and landscaping. This house has
a historical tag and therefore cannot be demolished but instead must be incorporated
into the over plan for the proposed subdivision. The house sits along the western
property line adjacent to the pedestrian cross walk across S. Taft Hill.
B. Description of Property
1. West Village Off Taft project site is 2.35 net acres. West Village Off Taft is not
proposing any improvements to S. Taft Hill Rd. However, due the lack of storm sewer
infrastructure the proposed project will be discharging east into Dover Dr. through a
sidewalk chase therefore additional offsite improvements will be necessary near the
south-east corner of the project site. Also, West Village Off Taft will leave the historical
house untouched other than two landscaping walls that jutted to far south into the
private drive aisle. Overall, the proposed site will maintain the historic drainage
West Village Off Taft
Final Drainage Report 2
patterns.
2. West Village Off Taft will be maintaining the overall historic drainage characteristics of
this site. There are currently no water quality amenities or any existing storm
infrastructure on site. West Village Off Taft is proposing to install a porous paver
section as well as several retaining walls to help meet required detention and water
quality volumes, this will be discussed in Section IV.B. There is no offsite runoff
entering the site from S. Taft Hill Rd.
3. Per the United States Department of Agriculture (USDA) Natural Resources
Conservation Service (NRCS) Soil Survey, 100 percent of the site consists of Altvan-
Satanta loams, which fall into Hydrologic Soil Groups B.
4. The proposed development will include the clearing of existing vegetation, two (2)
tress, the removal of 180 sf. of sidewalk where the proposed entrance is and the
removal of roughly 135 sf. of concrete walls behind the existing detached garage.
Figure 2 - Proposed Site Plan
5. There are no irrigation facilities, erosion buffer zones, or major drainage ways within
the property limits.
6. The project site is within a Low Density Residential zoning district. Therefore, the
proposed use is permitted within this zone district.
C. Floodplain
1. The subject property does not lie within a FEMA floodplain. The project site falls
within the FIRM Panel 08069C986G for Larimer County, dated May 2nd, 2012.
2. West Village Off Taft does not fall within a city floodplain.
West Village Off Taft
Final Drainage Report 3
Figure 3 - Existing City Floodplain
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. West Village Off Taft is within the Canal Importation drainage basin. This basin,
which suffered significant property damage in the flood of 1997, is almost completely
urbanized with primarily mixed density residential and isolated commercial land uses.
Runoff from the basin empties into the Old Town or Spring creek basins.
2. There are no previous drainage studies for the area associated with this project site.
B. Sub-Basin Description
1. West Village Off Taft historically sheet flows from the northwest towards the southeast
corner of the project site. This historic condition will be maintained to the best of the
engineer’s ability.
Basin H1
Basin H1 is associated with the entire project site and has an overall area of 2.35
acres. Basin H1 has one two story house with a detached garage and an associated
gravel driveway. There is currently no stormwater infrastructure or water quality
amenities. Additionally, there are no offsite flows entering Basin H1. Basin H1 has a
historic 2-year flow of 1.26 cfs.
2. A more detailed description of the projects proposed drainage patterns follows in
Section IV.A.4., below.
West Village Off Taft
Final Drainage Report 4
3. There are no offsite flows associated with West Village Off Taft.
4. 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 West Village Off
Taft project.
B. Four Step Process
The overall stormwater management strategy employed with the West Village Off Taft
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 as much vegetated open areas as possible along the north, east, west and
south 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 either a bio-swale or across concrete
pavers.
Providing on-site detention to increase time of concentration, promote infiltration and
reduce loads on downstream storm infrastructure.
Below is a table that shows the breakdown of the proposed LID amenities compared to the
proposed impervious area.
Figure 4 - LID Table
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 along the northern portion of the
project site will sheet flow north where it will be collected and routed through a grass lined
swale. Runoff generated near the middle of the project site will sheet flow south across the
Design
Point
Basin ID Basin Area Treatment Type
LID
System
Impervious Area
Treated by LID
System
Percent of
Impervious Area
Treated by LID
System
a1 A1 1.168 ac.
Extended
Detention
No 0.227 ac. 0.00%
b1 B1 0.733 ac. Pavers Yes 0.493 ac. 57.59%
b1 B2 0.452 ac.
Extended
Detention
No 0.136 ac. 0.00%
Total 2.353 ac. 0.856 ac. 58%
West Village Off Taft
Final Drainage Report 5
private drive aisle where it will pass over concrete pavers. Eventually all the runoff is
routed to one of the two ponds that border the southern property line. where it will be
released into Dover Drive at the historic 2-year runoff.
Step 3 – Stabilize Drainageways
As stated in Section I.B.5, above, there are no drainageways associated with the project
site.
Step 4 – Implement Site Specific and Other Source Control BMPs.
This step typically applies to industrial and commercial developments and is not
applicable for this project.
C. Development Criteria Reference and Constraints
1. There are no known drainage studies for the existing property.
2. 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 this analysis that will impact the proposed drainage system
including:
Existing elevations along the east, west, north, and south property lines will be
maintained.
During the construction of West Village Off Taft, it is imperative that the house
that currently sites on the project site remains untouched except for the two
concrete walls behind the detached garage that will need to be removed.
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.
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 from the northwest to the
southeast. The entire site drains stormwater via overland flow.
2. All drainage facilities proposed with the West Village Off Taft 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.
West Village Off Taft
Final Drainage Report 6
3. As stated in Section I.C.1, above, the subject property is not located within a City
regulatory floodplain.
4. West Village Off Taft does not propose to modify any natural drainageways.
F. Floodplain Regulations Compliance
1. As previously mentioned, the project site does not fall within a City regulatory
floodplain.
G. Modifications of Criteria
The proposed West Village Off Taft development is requesting that the required
amount of freeboard be reduced from a foot to seven (7) inches. Due to the lack of
space for the detention ponds and to insure the walls along the southern property
edge can tie into existing grade and still be under 30” tall Pond A has a freeboard
height of 7.08”. Pond B has a freeboard height of 8.16”.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of the West Village Off Taft drainage design is to maintain
existing drainage patterns and ensure no adverse impacts to any adjacent properties
or existing infrastructure occurs.
2. As previously mentioned, there are no off-site flows draining onto the project 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. West Village Off Taft has been broken down into three (3) major drainage basins,
designated as Basins A1, B1, and B2.
Basin A1
Basin A1 is located along the northern and eastern edges of the project site. Runoff
from Basin A1 is generated from roofs, back porches, and landscaping. Basin A1
sheet flows south to north where it is collected in grass lined swale. The swale
conveys the collected runoff into Pond A which is situated at the southeast corner of
the project site.
From there the runoff will be released east into a swale and concrete chase into Dover
Drive at the historic 2-year rate.
Basin B1
Basin B1 is in the middle of the project site and drains stormwater via overland flow
from the north to the south. Runoff from Basin B1 is generated from roofs, driveways,
sidewalk, landscaping, and the drive aisle. All the runoff generated in Basin B1 sheet
flows across concrete pavers that are in the middle of the drive aisle. Once, the a
portion runoff has been treated by the concrete pavers an underdrain system will then
convey the runoff south into Pond A. Any surface flow that was not picked up in the
porous pavers will continue to sheet flow south until it enters Pond B via 5’ curb cut.
Pond B releases into Pond A at a reduced release rate. Once the runoff has entered
West Village Off Taft
Final Drainage Report 7
Pond A it will then be released east into a swale and concrete chase into Dover Drive
at the historic 2-year rate.
Basin B2
Basin B2 wraps around the southwest corner of the project site and drains via
overland flow from north to south. Runoff from Basin B2 is generated from the drive
aisle entrance, the roof of the existing house, and landscaping areas. All the runoff
generated in Basin B2 will initially be collected in Pond B1 and just like Basin B1 it
will then be released into Pond A and then conveyed to Dover Drive at the historic 2-
year rate.
B. Specific Details
1. The main drainage problems associated with this project site is the deficiency of
existing stormwater infrastructure present and lack of developable area.
Basins A1, B1, and B2 will all be treated either by an LID amenity or via extended
detention.
A restrictor plate will be placed at the outfall of Pond A to ensure that the site is
not discharging at a rate greater than the 2-year.
Pond B and Pond A were both sized using a reduced historic 2-year release rate.
Ultimately though, Pond A will be releasing the entire site at the historic 2-year
release rate.
2. The release rate for the undeveloped land (pre-development) was established by
calculating the Historic 2-year peak runoff rate for the entire project area (Basin H1)
with no reduction because all the runoff generated on the site is being captured and
treated. The overall historic 2-year peak runoff rate was calculated to be 1.26 cfs.
This release rate was utilized in the FAA procedure detention storage computations
(Refer to Appendix B for these calculations).
3. Detention Pond Calculations
West Village Off Taft has two ponds that are right next to one another and act
hydraulically independent of each other. Pond B is situated directly west of Pond A
and they are separated by a berm and headwall that has a weir and restrictor plate on
it. However, Pond A will have all runoff from the site eventually passing through it
because it is the ultimate discharge location. Pond A will discharge east into a
proposed swale and concrete chase into Dover Drive at the historic 2-year rate (1.26
cfs). Pond B will be releasing into Pond A at 1.00 cfs which will be bypassing Pond A
because Pond A was sized using a release rate of 0.26 cfs.
Pond A
The FAA method was used to size Pond A. The overall historic 2-year release rate is
1.26 cfs and Pond A was sized using a release rate of 0.26 cfs and Pond B was
sized using a release rate of 1.00 cfs. Based on the characteristics of Basins A1 and
an adjusted release rate of 0.26 cfs, formulate a detention volume of 6390 cu. ft.
However, Basin A1 is receiving water quality in the form of extended detention and
following UDFCD standards Basin A1 requires 435 cu. ft. of volume for water quality.
Therefore, the required volume for the 100-yr detention plus the WQCV is 6825 cu
ft. The top of pond for Pond A is at an elevation of 5084.02’ and the top of freeboard
is at 5084.61’ therefore there is slightly more than 7 inches of free board (7.08”).
West Village Off Taft
Final Drainage Report 8
Pond A will be releasing at the full 2-year historic rate (1.26 cfs) and the emergency
flow path for Pond A is at the southeast corner of the site and discharges east into
the swale that will convey the flows into Dover Drive.
Pond B
The FAA method was used to size Pond B as well. As mentioned in the description of
Pond A, Pond B was sized using a release rate of 1.00 cfs. The reason different flow
rates were used in sizing the two ponds was because Pond B is in a spot within the
project site that allows for a larger pond. Based on characteristics from Basins B1
and B2 with an adjusted release rate of 1.00 cfs, formulate a detention volume of
7542 cu. ft. However, Basin B2 will is receiving water quality in the form of
extended detention and following UDFCD standards Basin B2 requires 232 cu. ft. of
volume for water quality. Basin B1 is receiving its water quality through the porous
pavers. Therefore, the required volume for the 100-yr detention plus the WQCV is
7774 cu. ft. The top of Pond B is at an elevation of 5084.97’ and the top of
freeboard is at 5085.65 therefore there is slightly more than 8 inches of free board
(8.16”). Pond B will release at a rate of 1.00 cfs into Pond A through a pipe that
connects the two ponds. Once into Pond A it will release at the historic 2-year rate of
1.26 cfs with Pond A’s runoff. The emergency spillway for Pond B is located at the
headwall that divides Pond A and Pond B. The excess runoff will flow east until it
reaches the swale east of Pond A where it will be conveyed to Dover Drive.
4. Water Quality Results
Basin A1
Water quality for Basin A1 will be provided vai extended detention in Pond A.
Following UDFCD Standards, a required WQCV for Basin A1 is 435.35 cu. ft. This
volume is included within Pond A. Pond A will have an outlet structure located at
design point a1 that detains and attenuates runoff and promotes the settlement of
pollutants.
Basin B1
Basin B1 will have water quality provided via concrete pavers located in the middle
of the private drive aisle. Following UDFCD standards, a required WQCV for Basin B1
is 457 cu. ft. and the volume provided within the permeable pavers is 1464 cu. ft.
Once the runoff has gone through the permeable pavers it will be conveyed to Pond A
via a 6” perforated pipe.
Basin B2
Water quality for Basin B2 will be provided via extended detention in Pond B.
Following UDFCD Standards, a required WQCV for Basin B2 is 231.57 cu. ft. This
volume is included within Pond B. Pond B will have an outlet structure located at
design point b1 that detains and attenuates runoff and promotes the settlement of
pollutants.
5. Pond B’s emergency overflow conveys excess runoff east over the
berm/headwall into Pond A. Pond A’s emergency overflow path is located at
design point a1. From there all excess flow will overtop the pond wall and
flow east via swale into Dover Drive.
West Village Off Taft
Final Drainage Report 9
V. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with the West Village Off Taft project complies with the
City of Fort Collins’ Stormwater Criteria Manual.
2. The drainage design proposed with the West Village Off Taft project complies with the
City of Fort Collins’ Master Drainage Plan.
3. There are no city regulatory floodplains and/or erosion buffer zones associated with
the West Village Off Taft project.
4. The drainage plan and stormwater management measures proposed with the West
Village Off Taft development are compliant with all applicable State and Federal
regulations governing stormwater discharge.
B. Drainage Concept
1. The drainage design proposed with this project will effectively limit potential damage
associated with its stormwater runoff. West Village Off Taft will detain and treat the
entire project site and release at the historic 2-year rate east into Dover Drive during
the developed 100-year storm.
2. West Village Off Taft will provide water quality via an LID feature as well as extended
detention.
West Village Off Taft
Final Drainage Report 10
References
1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities,
November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services.
2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No.
174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code.
3. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and
Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007.
4. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation
Service, United States Department of Agriculture.
5. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control
District, Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008.
APPENDIX A
HYDROLOGIC COMPUTATIONS
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: Taft Hill Village
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 C
f = 1.00 100-year C
f = 1.25
Basin ID
Basin Area
(s.f.)
Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Roofs
(ac)
Area of
Gravel
(ac)
Area of
Pavers
(ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
H1 102457.9 2.352 0.000 0.025 0.043 0.124 0.000 2.16 0.28 0.28 0.35 5%
TOTAL 102458 2.352 0.000 0.025 0.043 0.124 0.000 2.16 0.19 0.19 0.24 5%
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
Overland Flow, Time of Concentration:
Project: Taft Hill Village
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt
= L / 60V
Tc
= Ti
+ 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,
Rational Method Equation: Project: Taft Hill Village
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
h1 H1 2.35 15 15 14 0.28 0.28 0.35 1.90 3.24 6.82 1.26 2.16 5.68
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
DEVELOPED RUNOFF COMPUTATIONS
C100
Design
Point
Flow,
Q100
(cfs)
Flow,
Q2
(cfs)
10-yr
Tc
(min)
2-yr
Tc
(min)
C2
Flow,
Q10
(cfs)
Intensity,
i100
(in/hr)
Basin(s)
B. Mathisen
May 12, 2017
Intensity,
i10
(in/hr)
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
C10
Q = C f ( C )( i )( A )
Page 3 of 23 D:\Projects\1076-001\Drainage\Hydrology\1076-001_Historic Rational-Calcs.xlsx\Direct-Runoff
SUMMARY
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
h1 H1 2.35 0.28 0.35 14.6 13.7 1.26 5.68
Page 7 of 23 Proposed D:\Projects\1076-001\Drainage\Hydrology\1076-001_Historic Rational-Calcs.xlsx\SUMMARY-TABLE
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: West Village Off Taft
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 C
f = 1.00 100-year C
f = 1.25
Basin ID
Basin Area
(s.f.)
Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Roofs
(ac)
Area of
Gravel
(ac)
Area of
Pavers
(ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
A1 50891.7 1.168 0.000 0.014 0.213 0.000 0.000 0.94 0.39 0.39 0.48 17%
B1 31938.0 0.733 0.000 0.251 0.164 0.000 0.079 0.24 0.66 0.66 0.83 53%
B2 19673.7 0.452 0.000 0.128 0.008 0.000 0.000 0.32 0.46 0.46 0.58 27%
TOTAL 102503 2.353 0.000 0.393 0.385 0.000 0.079 1.58 0.43 0.43 0.53 30%
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.
Overland Flow, Time of Concentration:
Project: West Village Off Taft
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt
= L / 60V
Tc
= Ti
+ 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,
Rational Method Equation: Project: West Village Off Taft
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
a1 A1 1.17 16 16 15 0.39 0.39 0.48 1.81 3.08 6.62 0.82 1.39 3.73
b1 B1 0.73 6 6 5 0.66 0.66 0.83 2.67 4.56 9.95 1.30 2.21 6.03
b1 B2 0.45 10 10 9 0.46 0.46 0.58 2.21 3.78 8.21 0.46 0.79 2.14
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
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)
B. Mathisen
May 12, 2017
Q = C f ( C )( i )( A )
Page 3 of 23 Proposed D:\Projects\1076-001\Drainage\Hydrology\1076-001_Rational-Calcs.xlsx\Direct-Runoff
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: West Village Off Taft
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: B. Mathisen
Asphalt ……....……………...……….....…...……………….………………………………….. 0.95 100% Date: May 12, 2017
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.
b B1 and B2 51612 1.18 0.00 0.38 0.17 0.00 0.08 0.56 0.59 0.59 0.73 42%
COMBINED DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
**Soil Classification of site is Sandy 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.
Page 4 of 23 Proposed D:\Projects\1076-001\Drainage\Hydrology\1076-001_Rational-Calcs.xlsx\Comb-C-Values
Overland Flow, Time of Concentration:
Project: West Village Off Taft
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt
= L / 60V
Tc
= Ti
+ 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,
Rational Method Equation: Project: West Village Off Taft
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
b B1 and B2 1.18 9 9 7 0.59 0.59 0.73 2.35 4.02 9.06 1.6 2.8 7.8
Flow,
Q100
(cfs)
C2
C10
C100
Intensity,
i2
(in/hr)
Intensity,
i10
(in/hr)
Intensity,
i100
(in/hr)
COMBINED DEVELOPED RUNOFF COMPUTATIONS
B. Mathisen
May 12, 2017
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)
Q = C f ( C )( i )( A )
Page 6 of 23 Proposed D:\Projects\1076-001\Drainage\Hydrology\1076-001_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)
a1 A1 1.17 0.39 0.48 16.3 14.6 0.82 3.73
b1 B1 0.73 0.66 0.83 6.1 5.0 1.30 6.03
b1 B2 0.45 0.46 0.58 10.0 8.5 0.46 2.14
Page 7 of 23 Proposed D:\Projects\1076-001\Drainage\Hydrology\1076-001_Rational-Calcs.xlsx\SUMMARY-TABLE
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 – Detention Facilities
APPENDIX B.1
DETENTION FACILITIES
Pond No :
a2
100-yr
0.48
13.00 min 6390 ft3
1.17 acres 0.147 ac-ft
Max Release Rate = 0.26 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 1674 1.00 0.26 78 1596
10 7.720 2597 1.00 0.26 156 2441
15 6.520 3290 0.93 0.24 218 3071
20 5.600 3768 0.83 0.21 257 3510
25 4.980 4188 0.76 0.20 296 3892
30 4.520 4561 0.72 0.19 335 4226
35 4.080 4804 0.69 0.18 374 4429
40 3.740 5032 0.66 0.17 413 4619
45 3.460 5237 0.64 0.17 452 4785
50 3.230 5433 0.63 0.16 491 4941
55 3.030 5606 0.62 0.16 530 5075
60 2.860 5772 0.61 0.16 569 5203
65 2.720 5947 0.60 0.16 608 5339
70 2.590 6099 0.59 0.15 647 5451
75 2.480 6257 0.59 0.15 686 5570
80 2.380 6405 0.58 0.15 725 5679
85 2.290 6548 0.58 0.15 764 5783
90 2.210 6691 0.57 0.15 803 5887
95 2.130 6807 0.57 0.15 842 5964
100 2.060 6930 0.57 0.15 881 6048
105 2.000 7064 0.56 0.15 920 6144
110 1.940 7178 0.56 0.15 959 6219
115 1.890 7311 0.56 0.14 998 6313
120 1.840 7427 0.55 0.14 1037 6390
*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
1076-001
West Village Off Taft
Project Number :
Project Name :
Pond A
A =
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Invert Elevation
Water Quality Volume
100-yr Detention Volume
Total Pond Volume
Min Sc
D = Depth between contours (ft.)
A1
= Surface Area lower contour (ft
2
) t
A2
= Surface Area upper contour (ft
2
) Area/Row
No. of Rows
5082.20 170.82 0.14 7.97 7.97 0.0002
5082.40 798.07 0.20 89.21 97.18 0.0022
5082.60 1565.84 0.20 232.12 329.30 0.0076
5082.80 2502.34 0.20 403.18 732.47 0.0168 WQCV
5083.00 3616.63 0.20 608.49 1340.96 0.0308
5083.20 4557.27 0.20 815.58 2156.54 0.0495
5083.40 5166.43 0.20 971.73 3128.27 0.0718
5083.60 5640.89 0.20 1080.38 4208.66 0.0966
5083.80 6251.10 0.20 1188.68 5397.34 0.1239
5084.00 6821.74 0.20 1306.87 6704.20 0.1539 100-yr Vol
5084.20 7394.76 0.20 1421.26 8125.47 0.1865 Total Vol
5084.40 7980.53 0.20 1537.16 9662.63 0.2218
5084.60 8508.61 0.20 1648.63 11311.26 0.2597
5084.80 11116.06 0.20 1956.67 13267.93 0.3046
Elevation Depth Volume
WQCV 5082.65 0.59 0.0100
100-yr Detention 5083.95 1.89 0.1470
Overall Detention 5084.02 1.96 0.1570
Circular Perforation Sizing
Dia (in.)
1
Pond A
0.05
5
0.0100 ac-ft
5082.06 ft
Pond A Volume
Elevation
(ft)
n
1/4
0.027 sq-in
Surface
Area (ft
2
) Total Outlet
Area
0.25 sq. in.
Taft Hill Village 5/15/2017
1076-001 B. Mathisen
0.1570 ac-ft
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Q = 1.26 cfs
C = 0.605
Q = Release Rate (cfs) Eh = 5084.12 ft
C = Discharge Coefficients (unitless) Ei = 5082.06 ft
Aa = Area Allowed of Opening (ft2)
g = Gravity (32.2 ft/s2) 0.180817 ft2
Eh = High Water Surface Elevation (ft) 26.03761 in2
Ei = Elevation of Outlet Invert (ft)
H = Height of Opening (in.)
R = Inner Radius of Outfall Pipe (in.)
Δ = Top of Plate to Center of Pipe (in.)
S = Arc Length of Open Area (in.)
Ac = Area of Opening (in2)
θ = Angle of Plate on Pipe to Center Pipe (radians)
Calculated Area of Opening (Ac)
Design Height of Opening (H)
Proposed Outfall Pipe Diameter
24.74 sq. in.
B. Mathisen
May 15, 2017
Aa =
3-1/4 in
12 in
1076-001
West Village Off Taft
Pond A
[ ( ( ) ) ]
2
2
R
Sin S
R
R S
K
−
=
QCA = 2 g ( E h − E i )
S = R θ
( ) ( R )
Cos
R
Cos → = ∆
= ∆ 2 −1
θ 2 θ
Ac = π R 2 − K
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Monday, May 15 2017
Pond A - Emergency Overflow Weir
Trapezoidal Weir
Crest = Sharp
Bottom Length (ft) = 15.00
Total Depth (ft) = 0.50
Side Slope (z:1) = 4.00
Calculations
Weir Coeff. Cw = 3.10
Compute by: Known Q
Known Q (cfs) = 15.47
Highlighted
Depth (ft) = 0.46
Q (cfs) = 15.47
Area (sqft) = 7.75
Velocity (ft/s) = 2.00
Top Width (ft) = 18.68
0 2 4 6 8 10 12 14 16 18 20 22 24
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
Length (ft)
Weir W.S.
Pond No :
b1
100-yr
0.73
9.00 min 7542 ft3
1.18 acres 0.173 ac-ft
Max Release Rate = 1.00 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 2571 1.00 1.00 300 2271
10 7.720 3990 0.95 0.95 570 3420
15 6.520 5055 0.80 0.80 720 4335
20 5.600 5789 0.73 0.73 870 4919
25 4.980 6435 0.68 0.68 1020 5415
30 4.520 7008 0.65 0.65 1170 5838
35 4.080 7380 0.63 0.63 1320 6060
40 3.740 7732 0.61 0.61 1470 6262
45 3.460 8047 0.60 0.60 1620 6427
50 3.230 8347 0.59 0.59 1770 6577
55 3.030 8613 0.58 0.58 1920 6693
60 2.860 8869 0.58 0.58 2070 6799
65 2.720 9138 0.57 0.57 2220 6918
70 2.590 9370 0.56 0.56 2370 7000
75 2.480 9613 0.56 0.56 2520 7093
80 2.380 9841 0.56 0.56 2670 7171
85 2.290 10060 0.55 0.55 2820 7240
90 2.210 10280 0.55 0.55 2970 7310
95 2.130 10458 0.55 0.55 3120 7338
100 2.060 10647 0.55 0.55 3270 7377
105 2.000 10854 0.54 0.54 3420 7434
110 1.940 11029 0.54 0.54 3570 7459
115 1.890 11234 0.54 0.54 3720 7514
120 1.840 11412 0.54 0.54 3870 7542
*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
1076-001
West Village Off Taft
Project Number :
Project Name :
Pond B
A =
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Invert Elevation
Water Quality Volume
100-yr Detention Volume
Total Pond Volume
Min Sc
D = Depth between contours (ft.)
A1
= Surface Area lower contour (ft
2
) t
A2
= Surface Area upper contour (ft
2
) Area/Row
No. of Rows
5083.20 194.77 0.17 10.91 10.91 0.0003
5083.40 811.59 0.20 93.60 104.50 0.0024
5083.60 1718.55 0.20 247.41 351.91 0.0081 WQCV
5083.80 2931.71 0.20 459.66 811.57 0.0186
5084.00 4439.40 0.20 731.92 1543.49 0.0354
5084.20 5751.29 0.20 1016.24 2559.73 0.0588
5084.40 6558.62 0.20 1230.11 3789.84 0.0870
5084.60 6861.29 0.20 1341.88 5131.71 0.1178
5084.80 7146.38 0.20 1400.67 6532.38 0.1500
5085.00 7465.95 0.20 1461.12 7993.50 0.1835 Total Vol
5085.20 7820.36 0.20 1528.49 9522.00 0.2186
5085.40 8188.25 0.20 1600.72 11122.72 0.2553
5085.60 9272.45 0.20 1744.95 12867.66 0.2954
Elevation Depth Volume
WQCV 5083.50 0.47 0.0053
100-yr Detention 5084.94 1.91 0.1730
Overall Detention 5084.97 1.94 0.1783
Required Area
Per Row
Total Vol.
(ac-ft)
Total Vol.
(ft3)
Incremental
Vol. (ft3)
Incremental
Depth (ft)
Surface
Area (ft2) Total Outlet
Area
0.25 sq. in.
Taft Hill Village 5/15/2017
1076-001 B. Mathisen
0.1783 ac-ft
0.1730 ac-ft
Pond B
0.05
5
0.0053 ac-ft
5083.03 ft
Pond B Volume
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Q = 1.00 cfs
C = 0.605
Q = Release Rate (cfs) Eh = 5084.83 ft
C = Discharge Coefficients (unitless) Ei = 5083.03 ft
Aa = Area Allowed of Opening (ft2)
g = Gravity (32.2 ft/s2) 0.153606 ft2
Eh = High Water Surface Elevation (ft) 22.1192 in2
Ei = Elevation of Outlet Invert (ft)
H = Height of Opening (in.)
R = Inner Radius of Outfall Pipe (in.)
Δ = Top of Plate to Center of Pipe (in.)
S = Arc Length of Open Area (in.)
Ac = Area of Opening (in2)
θ = Angle of Plate on Pipe to Center Pipe (radians)
3 in
12 in
1076-001
West Village Off Taft
Pond B
Calculated Area of Opening (Ac)
Design Height of Opening (H)
Proposed Outfall Pipe Diameter
22.11 sq. in.
B. Mathisen
May 15, 2017
Aa =
[ ( ( ) ) ]
2
2
R
Sin S
R
R S
K
−
=
Q = CA 2 g ( E h − E i )
S = R θ
( ) ( R )
Cos
R
Cos → = ∆
= ∆ 2 −1
θ 2 θ
Ac = π R 2 − K
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Monday, May 15 2017
Pond B - Emergency Overflow Weir
Trapezoidal Weir
Crest = Sharp
Bottom Length (ft) = 10.00
Total Depth (ft) = 0.50
Side Slope (z:1) = 4.00
Calculations
Weir Coeff. Cw = 3.10
Compute by: Known Q
Known Q (cfs) = 10.92
Highlighted
Depth (ft) = 0.46
Q (cfs) = 10.92
Area (sqft) = 5.45
Velocity (ft/s) = 2.00
Top Width (ft) = 13.68
0 2 4 6 8 10 12 14 16 18
Depth (ft) Pond B - Emergency Overflow Weir Depth (ft)
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
Length (ft)
Weir W.S.
APPENDIX C
WATER QUALITY DESIGN COMPUTATIONS
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
1
WQCV = Watershed inches of Runoff (inches) 17.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.103 in
A = 1.17 ac
V = 0.0100 ac-ft 435.35 cu. ft.
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
West Village Off Taft May 15, 2017
1076-001 B. Mathisen
Pond A
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
0.103
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
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
1
WQCV = Watershed inches of Runoff (inches) 27.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.142 in
A = 0.45 ac
V = 0.0053 ac-ft 231.57 cu. ft.
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
West Village Off Taft May 15, 2017
1076-001 B. Mathisen
Pond B
0.142
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
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 Ia = 53.0 %
B) Tributary Area's Imperviousness Ratio (I = Ia / 100) i = 0.530
C) Tributary Watershed Area ATotal = 31,938 sq ft
(including area of permeable pavement system)
D) Area of Permeable Pavement System APPS = 3,445 sq ft
(Minimum recommended permeable pavement area = 6691 sq ft)
E) Impervious Tributary Ratio RT = 4.4 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 = 457 cu ft
(WQCV = (0.8 * (0.91 * i3 - 1.19 * i2 + 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 = 18.0 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 = 1,464 cu ft
Flat or Stepped: V = P * ((Dmin-1)/12) * Area
Sloped: V = P * [(Dmin - (Dmin - 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.)
West Village Off Taft
Basin B1
Design Procedure Form: Permeable Pavement Systems (PPS)
Blaine Mathisen
Northern Engineering
May 15, 2017
Choose One
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
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 = 0.1 ft
(i.e. the bottom of the base course to the center of the orifice)
7. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is there a minimum 30 mil thick impermeable PVC geomembrane
liner on the bottom and sides of the basin, extending up to the top
of the base course?
B) CDOT Class B Separator Fabric
8. Outlet
(Assumes each cell has similar area, subgrade slope, and length
between lateral barriers (unless subgrade is flat). Calculate cells
individually where this varies.)
A) Depth of WQCV in the Reservoir DWQCV = 5.31 inches
(Elevation of the Flood Control Outlet)
B) Diameter of Orifice for 12-hour Drain Time DOrifice = 0.95 inches
(Use a minimum orifice diameter of 3/8-inches)
Notes:
West Village Off Taft
Design Procedure Form: Permeable Pavement Systems (PPS)
Blaine Mathisen
Northern Engineering
May 15, 2017
Basin B1
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
1076-001 Basin B1 PAVER UD-BMP_v3.02.xls, PPS 5/15/2017, 1:31 PM
APPENDIX D
EROSION CONTROL REPORT
South Taft Hill
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 CB2 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
HISTORIC DRAINAGE EXHIBIT
PROPOSED DRAINAGE EXHIBIT
CONTROL
CONTROL IRR
IRR G
CTV
G
G
W
X
X
X
X
X
X
X
X
X
X X
X
X
X
X
X
X X
X
X
X
X X X
X
X
X
X
X
X
LOT 5
OWNER: BLACK J/M/S OWNER: BLACK M/J
LOT 8 LOT 21 LOT 22
LOT 23
VILLAGE WEST NINTH FILING
VILLAGE WEST FOURTH FILING
VILLAGE WEST THIRD FILING
LOT 1 LOT 2 LOT 3 LOT 4
LOT 6
LOT 5 LOT 4
SOUTH TAFT HILL
(ROW VARIES)
B1
A1
a1
B2
UD
UD
UD UD UD UD UD UD
b1
20' EMERGENCY
12' UTILITY ACCESS EASEMENT
EASEMENT
15' DRAINAGE
EASEMENT
6' UTILITY
EASEMENT
CONTROL
CONTROL IRR
IRR G
CTV
CTV
CTV
CTV
CTV CTV
G
G
T
T
T
T
T
W
X
S
S
M
W
X
X
X
X
SS
SS SS SS SS
M
X
X
X
X
X X
X
X
X
X
X
X X
X
X
X
X X X
X
X
X
X
X
X
16" W 16" W 16" W 16" W 16" W 16" W 16" W 16" W
H1
LOT 5
OWNER: BLACK J/M/S OWNER: BLACK M/J
LOT 8 LOT 21 LOT 22
LOT 23
VILLAGE WEST NINTH FILING
VILLAGE WEST FOURTH FILING
VILLAGE WEST THIRD FILING
LOT 1 LOT 2 LOT 3 LOT 4
LOT 6
LOT 5 LOT 4
SOUTH TAFT HILL
(ROW VARIES)
h1
Sheet
of 15
WEST VILLAGE OFF TAFT 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
200 South College Avenue, Suite 010
Fort Collins, Colorado 80524
E NGINEER ING
N O R T H E RN
PHONE: 970.221.4158 FAX: 970.221.4159
www.northernengineering.com
4:1
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
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
Call before you dig.
R
A2
a3
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
1. REFER TO THE "FINAL DRAINAGE REPORT FOR WEST VILLAGE OFF TAFT" BY
NORTHERN ENGINEERING, DATED 05/16/2017 FOR ADDITIONAL INFORMATION.
( IN FEET )
0
1 INCH = 30 FEET
30 30 60 90
LEGEND:
LEGEND:
C7.01
HISTORIC DRAINAGE EXHIBIT
15
SUMMARY TABLE:
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
h1 H1 2.35 0.28 0.35 14.6 13.7 1.26 5.68
LOT 1
LOT 8
LOT 7
LOT 6
LOT 5
LOT 4
LOT 3
LOT 2
TRACT A
WQCV EXTENTS
WQCV EXTENTS
5' CURB
CUT
POND B
STORAGE VOLUME=7993.5 CU. FT.
100-YR ELEV.=5084.94
WQCV ELEV.=5083.50
POND A
STORAGE VOLUME=9662.63 CU. FT.
100-YR ELEV.=5083.95
WQCV ELEV.=5082.65
FES A1
OUTLET
STRUCTURE
EXISTING INLET GRATE
EXISTING DECID. TREE
EXISTING CONIF. TREE
EXISTING LIGHT POLE
EXISTING STUMP
EXISTING CURB/GUTTER FLOWLINE
4950
4:1
BANK SLOPE
PROPOSED OVERLAND FLOW DIRECTION
CONCENTRATED FLOW DIRECTION
PROPOSED CONTOUR
EXISTING CONTOUR
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
Call before you dig.
R
A2
a3
DRAINAGE BASIN AREA
DESIGN POINT
DRAINAGE BASIN ID
DRAINAGE BASIN MINOR/MAJOR COEFF.
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
1. REFER TO THE "FINAL DRAINAGE REPORT FOR WEST VILLAGE OFF TAFT" BY
NORTHERN ENGINEERING, DATED 05/16/2017 FOR ADDITIONAL INFORMATION.
LID TABLE:
Sheet
of 15
WEST VILLAGE OFF TAFT 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
200 South College Avenue, Suite 010
Fort Collins, Colorado 80524
E NGINEER ING
N O R T H E RN
PHONE: 970.221.4158 FAX: 970.221.4159
www.northernengineering.com
C7.00
DRAINAGE EXHIBIT
( IN FEET )
0
1 INCH = 30 FEET
30 30 60 90
14
LEGEND:
LEGEND:
TOP OF POND ELEVATION
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
a1 A1 1.17 0.39 0.48 16.3 14.6 0.82 3.73
b1 B1 0.73 0.66 0.83 6.1 5.0 1.30 6.03
b1 B2 0.45 0.46 0.58 10.0 8.5 0.46 2.14
SUMMARY TABLE:
WQCV ELEVATION
PROPOSED POROUS PAVERS
Design
Point Basin ID Basin Area Treatment Type
LID
System
Impervious Area
Treated by LID
System
Percent of
Impervious Area
Treated by LID
System
a1 A1 1.168 ac. Extended
Detention No 0.227 ac. 0.00%
b1 B1 0.733 ac. Pavers Yes 0.493 ac. 57.59%
b1 B2 0.452 ac. Extended
Detention No 0.136 ac. 0.00%
Total 2.353 ac. 0.856 ac. 58%
PROPOSED 18" VERTICAL CURB AND GUTTER
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
1076-001 Basin B1 PAVER UD-BMP_v3.02.xls, PPS 5/15/2017, 1:31 PM
=
40 hr
=
40 hr
Elevation
(ft)
n
1/4
0.014 sq-in
Circular Perforation Sizing
Dia (in.)
1
Calc.
Depths
( )
3
D * A 1 A 2 A 1 * A 2
V
= + +
Tc =
Project Location :
Design Point
C =
Design Storm
Page 1 of 1
1076-001_DetentionVolume_PondB_FAAModified Method.xls
0.1470 ac-ft
Required Area
Per Row
Total Vol.
(ac-ft)
Total Vol.
(ft
3
)
Incremental
Vol. (ft
3
)
Incremental
Depth (ft)
Calc.
Depths
( )
3
D * A 1 A 2 A 1 * A 2
V
= + +
Tc =
Project Location :
Design Point
C =
Design Storm
Page 1 of 1
1076-001_DetentionVolume_PondA_FAAModified Method.xls
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
b B1 and B2 No 0.59 0.59 0.73 113 3.00% 7.1 7.1 5.1 255 1.60% 2.53 1.7 N/A N/A 9 9 7
COMBINED DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
B. Mathisen
May 12, 2017
Design
Point
Basin IDs
Overland Flow Gutter/Pipe Flow Swale Flow Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
C Cf L
Ti
= −
Page 5 of 23 Proposed D:\Projects\1076-001\Drainage\Hydrology\1076-001_Rational-Calcs.xlsx\Comb-Tc-10-yr_&_100-yr
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
a1 A1 No
0.39 0.39 0.48 95 1.20% 12.2 12.2 10.6 N/A N/A 380 1.10% 1.57 4.0 16 16 15
b1 B1 No
0.66 0.66 0.83 113 2.90% 6.1 6.1 3.8 N/A N/A N/A N/A N/A 6 6 5
b1 B2 No
0.46 0.46 0.58 75 1.90% 8.4 8.4 6.8 255 1.60% 2.53 1.7 N/A N/A N/A 10 10 9
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Gutter/Pipe Flow Swale Flow
Design
Point
Basin
Overland Flow
B. Mathisen
May 12, 2017
Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
C Cf L
Ti
= −
Page 2 of 23 Proposed D:\Projects\1076-001\Drainage\Hydrology\1076-001_Rational-Calcs.xlsx\Tc-10-yr_&_100-yr
10-year Cf
= 1.00
May 12, 2017
**Soil Classification of site is Clay Loam**
Page 1 of 23 Proposed D:\Projects\1076-001\Drainage\Hydrology\1076-001_Rational-Calcs.xlsx\C-Values
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
h1 H1 No
0.28 0.28 0.35 100 3.00% 10.6 10.6 9.7 N/A N/A 380 1.10% 1.57 4.0 15 15 14
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Gutter/Pipe Flow Swale Flow
Design
Point
Basin
Overland Flow
B. Mathisen
May 12, 2017
Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
C Cf L
Ti
= −
Page 2 of 23 D:\Projects\1076-001\Drainage\Hydrology\1076-001_Historic Rational-Calcs.xlsx\Tc-10-yr_&_100-yr
May 12, 2017
**Soil Classification of site is Clay Loam**
Page 1 of 23 D:\Projects\1076-001\Drainage\Hydrology\1076-001_Historic Rational-Calcs.xlsx\C-Values