HomeMy WebLinkAboutTIMBERLINE - INTERNATIONAL - FDP210020 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT
Prepared for:
Owner/Developer
Mr. Devin Ferrey
FR Holdings, Ltd.
125 S. Howes Street, 2nd Floor
Fort Collins, Colorado 80521
Prepared by:
11582 Colony Row
Broomfield, CO 80021
Phone: (720)259-0965, Fax: (720)259-1519
Project Number: 1805.00-TIM
Drainage Design Considerations
for the
Timberline - International
Final Development Plan (FDP)
Fort Collins, Colorado
August 9, 2021
August 9, 2021
Mr. Matt Simpson
Stormwater Engineering
City of Fort Collins
700 Wood Street
Fort Collins, Colorado 80522
Subject: Drainage Design Considerations for the
Timberline-International Final Development Plan (FDP)
Fort Collins, Colorado
Dear Mr. Simpson:
Wohnrade Civil Engineers, Inc. (WCE) is pleased to resubmit this final hydrologic and
hydraulic report for the subject project for your review. We have addressed staff
comments contained in the document, Timberline-International, PDP200014, Round
Number 3, dated May 21, 2021. This report complies with technical criteria set forth in
the City of Fort Collins, Stormwater Criteria Manual, and Mile High Flood District criteria.
We acknowledge that the City of Fort Collins’s review of this study is only for general
conformance with submittal requirements, current design criteria, and standard
engineering principles and practices.
If you should have any questions or comments as you review this report, please feel free to
contact me at your convenience.
Sincerely,
WOHNRADE CIVIL ENGINEERS, INC.
Jon Rohrer – Staff Civil Designer Mary B. Wohnrade, P.E. - Principal
Professional Engineer - (CO)
Drainage Design Considerations for
Timberline-International FDP
Table of Contents
1. INTRODUCTION ............................................................................................................................. 1
1.1 Objective .......................................................................................................................................... 1
1.2 Project History and Previous Studies ............................................................................................... 1
1.3 Mapping and Surveying ................................................................................................................... 1
2. SITE LOCATION AND DESCRIPTION ....................................................................................... 1
2.1 Site Location ..................................................................................................................................... 1
2.1 Site Description ................................................................................................................................ 2
3. PRE-PROJECT CONDITIONS ....................................................................................................... 2
3.1 Pre-Project Drainage Basins ............................................................................................................. 2
3.2 Pre-Project Drainage Patterns ......................................................................................................... 2
4. POST-PROJECT CONDITIONS .................................................................................................... 3
4.1 Proposed Project Description .......................................................................................................... 3
4.2 Post-Project Drainage Basins ........................................................................................................... 4
4.3 Post-Project Drainage Patterns ........................................................................................................ 4
4.4 Proposed Detention Pond ................................................................................................................ 4
5. DESIGN CRITERIA ......................................................................................................................... 6
5.1 Design References ............................................................................................................................ 6
5.2 Hydrologic Criteria ........................................................................................................................... 6
6. EROSION CONTROL ...................................................................................................................... 7
6.1 Low Impact Design (LID) .................................................................................................................. 7
6.2 Erosion Control Plan ........................................................................................................................ 7
6.3 Site Stabilization ............................................................................................................................... 8
7. CONCLUSIONS ................................................................................................................................ 8
7.1 Compliance with Standards ............................................................................................................. 8
7.2 Variances .......................................................................................................................................... 8
8. REFERENCES ................................................................................................................................... 8
Drainage Design Considerations for
Timberline-International FDP
TABLE OF CONTENTS, cont.
Vicinity Map
APPENDICES
Appendix A: Post-Project Condition Hydrology
Appendix B: Detention Pond Design
Appendix C: LID Design
Appendix D: Future Off-site Storm Sewer Preliminary Design
DRAWINGS
Sheet 1 of 1 Post-Project Drainage Plan
Drainage Design Considerations for
Timberline-International FDP
Fort Collins, Colorado
August 9, 2021
1. INTRODUCTION
1.1 Objective
This study documents the results of a
comprehensive hydrologic and hydraulic
analysis for the proposed
Timberline-International FDP project located in
Fort Collins, Colorado.
The project includes new 2,900 sf and 624 sf
commercial buildings, new water and sewer
services lines, site improvements, and an onsite
stormwater detention pond (Photo 1).
1.2 Project History and Previous Studies
There are no known hydrologic or hydraulic studies for the Timberline-International
property.
1.3 Mapping and Surveying
Intermill Land Surveying, of Loveland, Colorado, provided field survey information and
topographic mapping of the project site, with a contour interval of 1-foot. The survey
was performed in June 2018, and was referenced to NGS Monuments F136 and C402 on
the NAVD88 datum, and the NAD 83, Colorado State Plane (UTM Zone 13) North Zone
survey coordinate system.
2. SITE LOCATION AND DESCRIPTION
2.1 Site Location
The project is located in the Southwest ¼ of Section 8, Township 7 North, and Range 68
West of the 6th Principal Meridian, City of Fort Collins, Larimer County, Colorado.
The site is bounded by N. Timberline Road on the east, International Boulevard on the
south, Lake Canal on the west, and an existing commercial property on the north.
The project is located outside of any FEMA regulated floodplain, as per the FEMA Flood
Insurance Rate Map (FIRM), Community-Panel Number 08069C-0984H, effective on
Photo 1 – Project Site Looking North
Timberline-International FDP
August 9, 2021
Page 2
May 2, 2012 (see Firmette).
The property is also located adjacent to the Lake Canal, which is not a City of Fort
Collins designated floodplain, as per the online mapping application FCMaps.
2.1 Site Description
The project site is roughly 1.39 acres in size, and is located in a commercial area within
Larimer County, Colorado. The property is currently being annexed into the City of
Fort Collins, Colorado.
The site is currently undeveloped and contains an existing ditch access road, a fill pile,
and some existing utilities.
The site is located in the Dry Creek Drainage Basin, as defined by the City of Fort Collins
Master Drainage Plan. A future off-site storm sewer will be located parallel to the east
property line, which begins at East Ridge Second Filing, and ends at the Dry Creek
channel.
No offsite stormwater runoff enters the site from the adjacent property located to the
north. Stormwater runoff from South Timberline Road enters the property along the
east property line.
A geotechnical subsurface exploration report was prepared by CTL Thompson, and is
dated October 1, 2018 (Reference 4). The subsurface materials encountered consist of
2 to 3 feet of sand and clay over sand and gravel. Groundwater was encountered in
three borings at the time of drilling at a depth of roughly 13-feet, and was measured
three days later at depths ranging from 11.5-feet to 12 feet. Bedrock was not
encountered in any of the four borings within the property. The sand and gravel layer
will facilitate a Partial Infiltration Section as it relates to bioretention.
The USGS Web Soil Survey was also used to identify the hydrologic soils group within
the project limits. The site consists entirely of Group B type soils, which exhibits a
moderate infiltration rate.
3. PRE-PROJECT CONDITIONS
3.1 Pre-Project Drainage Basins
The existing project site includes a single onsite drainage basin that includes the entire
property for a total area of 1.39 acres. There is also a single off-site basin of 0.46
acres, which includes the west half of North Timberline Road.
3.2 Pre-Project Drainage Patterns
Stormwater runoff from the entire property drains overland, across gravel and
vegetated surfaces to Lake Canal, which bounds the property on the west and south.
Timberline-International FDP
August 9, 2021
Page 3
Runoff calculations for the pre-project condition have not been performed, since the
maximum allowable developed release rate is a fixed 0.20 cfs/acre, and is independent
of the historic discharges.
4. POST-PROJECT CONDITIONS
4.1 Proposed Project Description
The proposed project includes new 3,364 and 624 sf buildings, new asphalt parking and
drives, new underground utilities, and a new onsite stormwater detention facility.
The widening of N. Timberline Road to the west has also been accounted for in this
drainage analysis. The widening will include a right turn lane for southbound traffic
onto International Boulevard, and a northbound left-turn lane into the site. The street
widening has been designed, and will be constructed as part of this development
proposal. Stormwater runoff from the west half of Timberline Road will be conveyed
along the west flowline of Timberline flowing north to south, and then continue west
along the north flowline of International Boulevard. There are no proposed storm
inlets in the adjacent streets as part of this future improvement.
The preliminary design of a 30-inch diameter off-site storm sewer has also been
included as part of this development proposal (See Appendix D). The off-site sewer
would be located in the center of the existing right-turn lane in N. Timberline Road. A
390-foot long section of this sewer would be constructed as part of this development.
Developed stormwater runoff will be discharged to Lake Canal at a rate not to exceed
0.20 cfs/acre. An agreement has been reached with Lake Canal Company, which
allows for this release. Final engineering plans and the drainage report have been
submitted to Lake Canal Company for review and comment. A written agreement for
this stormwater release has been executed by Lake Canal Company, and is attached to
this report. WCE also provided revised civil construction plans to Lake Canal
Company on April 6, 2021 for their review and comment. The release rate and
discharge location has not changed since the date of the executed agreement.
Standard water quality treatment and Low Impact Development (LID) has also been
incorporated into the stormwater design for this project, as per City of Fort Collins
criteria. The primary LID measure includes a rain garden to treat stormwater runoff
from 100% of the impervious surfaces.
The proposed road improvements to N. Timberline Road and International Boulevard
will necessitate the extension of the existing 6’H x 14’W RCB culvert in Lake Canal.
The existing box culvert will be extended 20-feet to the northwest, and will require a
new concrete headwall, wingwalls, and guardrail. Structural plans for the proposed
extension have been prepared by Weeks & Associates of Fort Collins, Colorado, and will
be submitted to Lake Canal Company for review and approval.
Timberline-International FDP
August 9, 2021
Page 4
4.2 Post-Project Drainage Basins
The proposed project site has been divided into 3 post-project drainage basins for a
total drainage area of 1.28 acres. Offsite Basin O1 (0.46 acres) extends from the
existing centerline in N. Timberline Road, to the proposed back of walk on the west side
of Timberline, and includes the ultimate widening of Timberline.
Post-project drainage basins and patterns will generally mimic pre-project conditions,
with Basin 1 draining in the direction of Lake Canal directly to a detention facility and
Basin 2 draining to a bioretention area that overflows into the detention facility. The
detention facility will release developed runoff to Lake Canal at a rate not to exceed
0.20 cfs/acre, as per the Dry Creek Basin Master Drainage Plan.
4.3 Post-Project Drainage Patterns
Basin 1 (0.28 ac) drains overland across vegetated areas, at slopes ranging from 2.0% to
25%, to the new detention facility, and includes 100% pervious surfaces. The
drainage pattern within this basin will generally mimic pre-project drainage patterns.
The 10 and 100-year peak discharges are estimated to be 0.3 cfs and 0.8 cfs
respectively.
Basin 2 (0.71 ac) drains overland across vegetated areas, and in vertical curb and
gutter, at slopes ranging from 1.67% to 25%, to the new bioretention area. Basin 2
includes 100% of the project impervious surfaces. The drainage pattern within this
basin mimics pre-project drainage patterns. The 10 and 100-year peak discharges are
estimated to be 2.4 cfs and 6.1 cfs respectively.
Basin 3 (0.29 ac) drains overland across the new ditch access road (gravel surface), and
existing vegetated areas at slopes ranging from 1.55% to 4.0%, towards Lake Canal.
The drainage pattern within this basin mimics pre-project drainage patterns. The 10
and 100-year peak discharges are estimated to be 0.5 cfs and 1.2 cfs respectively.
Offsite Basin O1 (0.46 ac) drains overland across the pavement on Timberline Road to
the proposed vertical curb and gutter on the west side of the southbound lane. The 10
and 100-year peak discharges are estimated to be 1.9 cfs and 4.6 cfs respectively.
Calculations made as part of this investigation, along with other supporting material,
are contained in Appendix A.
4.4 Proposed Detention Pond
The proposed detention pond is located in the southeast portion of the property,
adjacent to Lake Canal. The pond will detain stormwater runoff from onsite Basins 1
and 2. Stormwater runoff from Basin 2 will be first be routed through the bioretention
area to meet LID requirements.
Timberline-International FDP
August 9, 2021
Page 5
The pond has been designed to accommodate the 100-yr flood control volume. The
standard City of Fort Collins Water Quality Outlet Structure will be used to control the
100-year stormwater release.
The property lies within the Dry Creek Drainage Basin, which requires runoff from the
100-year developed storm to be released at a maximum rate of 0.20 cfs/ac.
Stormwater runoff from onsite Basins 1 and 2 (0.99 acres) will be released at this rate.
Stormwater runoff from Basin 3 cannot be captured and routed to an onsite facility, and
will therefore drain directly to Lake Canal. The maximum allowable release from the
developed site is 0.20 cfs/ac x 0.99 acres= 0.20 cfs.
As per Colorado Revised Statutes 37-92-602(8), criteria regarding detention drain time
will apply to this project. The spreadsheet (SDI_Design_Data_v1.08.xlsm) developed
by the UDFCD and State of Colorado Division of Water Resources has been used to
verify the 5 and 100-year drain times. The maximum time to drain 97% of all runoff,
from a rainfall event that is less than or equal to a 5-year storm, is within 72 hours after
the end on the event. The estimated drain time for Pond 1 is 4.6 hours, which is much
less than the required maximum. The maximum time to drain 99% of all runoff, for
events greater than the 5-year storm, is within 120 hours after the end of the event.
The estimated drain time for Pond 1 for storms greater than the 5-year event is 12.8
hours, which is much less than the maximum. The completed SDI_Design_Data
spreadsheet has been provided in Appendix B of this report.
The computer program, Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2016
was used to route the 100-year design storm through the detention pond. The Storage
Indication Method was used to route the 100-yr design storm through the proposed
detention pond. An inflow hydrograph was developed to route the 100-year storm
through the detention pond, which includes Basins 1 and 2 (0.99 acres).
Results of the pond routing predict a maximum 100-yr water surface elevation of
4935.91, with an associated storage requirement of 2,682 cu-ft. A 2.25” diameter
orifice will control the release of developed stormwater runoff at a maximum rate of
0.18 cfs. The 100-year storm was routed through the pond, beginning at an elevation
of 4934.00.
An emergency pond overflow weir has also been designed to pass the 100-year peak
inflow (7.1 cfs) to the pond. The notch elevation of the weir will be set at 4937.50, and
the top at an elevation of 4938.00, and will be 10’ in width. The weir will direct
stormwater runoff to the historic discharge location, which is the Lake Canal.
Bioretention has also been incorporated into the Low Impact Development design.
The computer programs UD-BMP (v3.07), developed by the Mile High Flood District
(MHFD), has been used to calculate the required orifice size based on a 12-hour drain
time.
Stormwater runoff from all proposed impervious areas (Basin 2) will be routed through
Timberline-International FDP
August 9, 2021
Page 6
a bioretention area for treatment. Calculations have been determined for this area,
based on fully developed conditions.
Based on the Rain Garden (RG) design procedure in the UD-BMP spreadsheet, the
calculated design volume for the bioretention area is 462 cu-ft, and includes runoff from
onsite Basin 2. The total volume provided in the bioretention area from elevation
4936.5 to 4937.0 is 2,033 cu-ft.
Calculations made as part of this pond analysis, along with other supporting material,
are contained in Appendix C.
5. DESIGN CRITERIA
5.1 Design References
Drainage design criteria outlined in the City of Fort Collins Stormwater Criteria Manual
(Reference 1), and the Urban Storm Drainage Criteria Manual by the Mile High Flood
District (Reference 2), have been referenced in the preparation of this study.
5.2 Hydrologic Criteria
Due to the relatively small basin size, and in keeping with criteria set forth in the City of
Fort Collins, Stormwater Criteria Manual, the Rational Method has been used to
estimate peak stormwater runoff from the project site.
The initial 2 and 10-year, and major 100-year design storms have been used to evaluate
the proposed drainage system. Rainfall intensity data for the Rational Method has
been taken from IDF equations referenced in Table 3.4-1 of the City of Fort Collins
Stormwater Criteria Manual (Reference 1).
Runoff coefficients were derived using the equations described in Chapter 5, Section 3.2
of the Fort Collins Stormwater Criteria Manual. The area of all impervious surfaces
was determined for each drainage basin, including roads, walk, and roofs. It is a much
more laborious effort but provides a more realistic estimate of peak discharge from the
developed site.
Site specific rainfall data from the NOAA Precipitation Server is normally used on all
WCE projects, but will not be used on this project, as requested by the City. We
believe that using the site-specific rainfall data and determining the area of impervious
surfaces for each drainage basin results in the most accurate representation of peak
discharge from both the historic and developed sites. Using the City runoff coefficients
and citywide rainfall data generally results in lower overall peak discharges, and won’t
be as conservative as site specific data.
Timberline-International FDP
August 9, 2021
Page 7
6. EROSION CONTROL
6.1 Low Impact Design (LID)
The proposed project has incorporated the 4-step process developed by the Mile High
Flood District (MHFD), for the protection of receiving waters downstream of the project
site. The BMP Selection Tool within the UD-BMP spreadsheet has been used to select
the appropriate BMPs for Steps 1 and 2 of the 4-step processes. The project
implements volume reduction strategies including grass swales, and BMPs including
Bioretention – Partial Infiltration Basins.
Low Impact Development (LID) is a comprehensive land planning and engineering
design approach to managing stormwater runoff with a goal of replicating the
pre-development hydrologic regime of urban and developing watersheds. Volume 3 of
the UDFCD Drainage Criteria Manual emphasizes LID criteria, including Minimizing
Directly Connected Impervious Areas (MDCIA) as the first step in stormwater quality
planning and has provided guidance on LID techniques such as grass swales, grass
buffers, permeable pavement systems, bioretention, and pollution prevention
(pollutant source controls).
Low Impact Development (LID) design will be required for this project using methods
and techniques described in Volume 3, Chapter 1, Section 4.1, Runoff Reduction
Practices. The opportunity to implementation multiple LID techniques is limited, due
to the size of the site (1.39 acres). Surface runoff from impervious areas drains to the
bioretention area. The length and depth of grass buffers and grass swales is employed
to some extent, but is limited.
The project has also been designed to minimize impacts to the site, and conserve
existing amenities. One example of this would be minimizing the disturbance in
drainage Basin 3 along the east side of Lake Canal, and retaining the existing vegetation.
With the exception of a small portion of the drive entrance, nearly 100% of all newly
added or modified impervious area will be treated by LID techniques, which complies
with criteria set forth in the City of Fort Collins Stormwater Criteria Manual, Chapter 7,
Section 6.0, Low Impact Development. The technique to be employed will include a
bioretention area (rain garden), which will be located adjacent to the stormwater
detention pond. The clayey sand, and sand and gravel layer will facilitate a Partial
Infiltration Section as it relates to bioretention. A perforated underdrain will be
installed beneath the bioretention area in order to hydraulically connect the area to the
detention pond.
Calculations made as part of this LID analysis, along with other supporting material, are
contained in Appendix C.
6.2 Erosion Control Plan
A proposed rainfall erosion control plan during construction will consist of temporary
Timberline-International FDP
August 9, 2021
Page 8
structural erosion control measures. Erosion control measures have been specified on
the Grading and Erosion Control Plan, and on three separate drawings contained in the
written Stormwater Management Plan (SWMP). These drawings include a
Pre-disturbance, Interim, and Final Stabilization Plans.
Wohnrade Civil Engineers, Inc. will prepare a separate report containing the
Stormwater Management Plan (SWMP) for this project. A Colorado Discharge Permit
System (CDPS), Stormwater Discharge Associated with Construction Activities
application will also be submitted to the Colorado Department of Public Health and
Environment.
A City of Fort Collins Erosion and Sediment Control Escrow/Security Calculation has
been prepared for this project, and will be included in the written SWMP report.
6.3 Site Stabilization
All areas disturbed by construction will be landscaped, paved, or re-seeded using the
recommended seed varieties, quantities, and application rates as specified on the
project Landscape Plan.
7. CONCLUSIONS
7.1 Compliance with Standards
The proposed drainage improvements been designed to comply with all applicable
drainage criteria, in accordance with the City of Fort Collins Stormwater Criteria
Manual.
7.2 Variances
There are no variances requested as part of this stormwater drainage design.
8. REFERENCES
1. Stormwater Criteria Manual, City of Fort Collins, adopted December 2011.
2. Urban Storm Drainage Criteria Manual, Mile High Flood District, Denver, Colorado,
Revised April 2008.
3. CDOT Drainage Design Manual, Colorado Department of Transportation.
4. Geotechnical Investigation, Proposed Commercial Development, Lot 1, Industrial
Business Park, CTL Thompson, Inc., October 1, 2018.
Project Location
125
S.
Howes
Street
2nd
Floor
Fort
Collins,
CO
80521
Justin
Green
Lake
Canal
Sent
via
email:
justin@lakecanal.com
RE:
Requested
Storm
Water
Outfall
into
Lake
Canal
Mr.
Green;
FR
Holdings,
Ltd.
is
the
owner
of
Lot
1
in
the
Industrial
Business
Park
PUD
in
Fort
Collins,
a
1.39
acre
parcel
that
borders
Lake
Canal
at
the
north
west
intersection
of
Timberline
Road
and
International
Boulevard.
We
are
pursuing
a
small
mixed-‐use
commercial
development
on
our
property.
In
our
initial
conversations
with
the
City
of
Fort
Collins,
we
were
asked
to
construct
and
pay
for
a
comprehensive
master-‐planned
storm
drainage
system
along
Timberline
Road
which
would
run
not
only
along
our
eastern
frontage,
but
further
south
several
hundred
yards,
well
beyond
our
property
boundary.
This
request
is
obviously
cost
prohibitive.
As
an
alternative,
City
staff
proposed
a
storm
water
outfall
agreement
with
Lake
Canal.
Staff
mentioned
that
other
projects
in
the
area
have
made
similar
arrangements
with
Lake
Canal.
Enclosed
is
a
preliminary
design
for
our
project
including
an
outfall
structure
into
the
canal
as
well
as
a
flow
calculation
from
our
site
based
on
a
100-‐year
event.
We
are
requesting
approval
from
Lake
Canal
for
this
discharge,
and
understand
there
will
be
an
annual
fee
associated
with
the
same.
Please
contact
me
directly
with
any
questions.
Thank
you,
Devin
Ferrey
President,
FR
Holdings,
Ltd.
devin@fr-‐corp.com
970-‐691-‐1234
Appendix A
Timberline-International
Preliminary Development Plan
April 6, 2021
Runoff Coefficient Calculations
Post-Project Condition, Basin 1
NRCS Soil Type B
Surface Type
Asphalt Gravel Concrete Rooftop Lawns,
Clayey
Soil, Avg
Slope
Composite
Runoff
Coefficient
Area (acres)0.000 0.000 0.003 0.000 0.277 0.26
Runoff Coefficients 0.95 0.5 0.95 0.95 0.25
Total Area (acres)0.28
2-Year 5-Year 10-Year 25-Year 50-Year 100-Year
0.26 0.26 0.26 0.28 0.31 0.32
Post-Project Condition, Basin 2 (Rain Garden Inflow)
NRCS Soil Type B
Surface Type
Asphalt Gravel Concrete Rooftop Lawns,
Clayey
Soil, Avg
Slope
Composite
Runoff
Coefficient
Area (acres)0.269 0.000 0.098 0.087 0.256 0.70
Runoff Coefficients 0.95 0.5 0.95 0.95 0.25
Total Area (acres)0.71
2-Year 5-Year 10-Year 25-Year 50-Year 100-Year
0.70 0.70 0.70 0.77 0.84 0.87
Storm Return Period
Runoff coefficient equations taken from Table 3.2-2 of the Fort Collins Stormwater Criteria Manual,
Chapter 5, Section 3.2
Runoff coefficient equations taken from Table 3.2-2 of the Fort Collins Stormwater Criteria Manual,
Chapter 5, Section 3.2
Storm Return Period
Page 1 of 3
Timberline-International
Preliminary Development Plan
April 6, 2021
Runoff Coefficient Calculations
Post-Project Condition, Basin 3
NRCS Soil Type B
Surface Type
Asphalt Gravel Concrete Rooftop Lawns,
Clayey
Soil, Avg
Slope
Composite
Runoff
Coefficient
Area (acres)0.000 0.090 0.000 0.000 0.200 0.33
Runoff Coefficients 0.95 0.5 0.95 0.95 0.25
Total Area (acres)0.29
2-Year 5-Year 10-Year 25-Year 50-Year 100-Year
0.33 0.33 0.33 0.36 0.39 0.41
Post-Project Condition, Basin O1
NRCS Soil Type B
Surface Type
Asphalt Gravel Concrete Rooftop Lawns,
Clayey
Soil, Avg
Slope
Composite
Runoff
Coefficient
Area (acres)0.367 0.000 0.038 0.000 0.055 0.87
Runoff Coefficients 0.95 0.5 0.95 0.95 0.25
Total Area (acres)0.46
2-Year 5-Year 10-Year 25-Year 50-Year 100-Year
0.87 0.87 0.87 0.95 1.00 1.00
Runoff coefficient equations taken from Table 3.2-2 of the Fort Collins Stormwater Criteria Manual,
Chapter 5, Section 3.2
Runoff coefficient equations taken from Table 3.2-2 of the Fort Collins Stormwater Criteria Manual,
Chapter 5, Section 3.2
Storm Return Period
Storm Return Period
Page 2 of 3
Timberline-International
Preliminary Development Plan
April 6, 2021
Runoff Coefficient Calculations
Post-Project Condition, Basins 1 & 2 (Detention Pond Inflow)
NRCS Soil Type B
Surface Type
Asphalt Gravel Concrete Rooftop Lawns,
Clayey
Soil, Avg
Slope
Composite
Runoff
Coefficient
Area (acres)0.269 0.000 0.101 0.087 0.533 0.57
Runoff Coefficients 0.95 0.5 0.95 0.95 0.25
Total Area (acres)0.99
2-Year 5-Year 10-Year 25-Year 50-Year 100-Year
0.57 0.57 0.57 0.63 0.69 0.72
Runoff coefficient equations taken from Table 3.2-2 of the Fort Collins Stormwater Criteria Manual,
Chapter 5, Section 3.2
Storm Return Period
Page 3 of 3
City of Fort Collins, Colorado,
Overland Flow, Time of Concentration:
Ti= 1.87(1.1-CxCf)L1/2 / S1/3
Gutter/Swale Flow, Time of Concentration:
Tt= L / 60V
Tc= Ti + Tt
Intensity, (i) taken from intensity formula for Timberline-International PDP, i =30.04/(Tc+11.30)0.84 Calculations by: M. Wohnrade
Velocity, (V) taken from Figure 3-1 Project: Timberline-International PDP
Rational Equation: Q = ciA Date: April 6, 2021
C5
Length, L
(ft)
Slope, S
(%)
Ti
(min)
Length, L
(ft)
Slope, S
(%)
Velocity, V
(fps)
Tt
(min)
Length, L
(ft)
Slope, S
(%)
Velocity, V
(fps)
Tt
(min)
1 1 0.0 0.28 0.26 0.26 33.8 2.7 6.6 0.0 0.0 0.00 0.0 147.0 4.8 3.53 0.7 7.3 2.55 0.2
2 2 0.0 0.71 0.70 0.70 22.3 2.4 2.6 0.0 0.0 0.00 0.0 186.4 1.9 2.22 1.4 5.0 2.85 1.4
3 3 0.0 0.29 0.33 0.33 25.0 3.2 4.9 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 5.0 2.85 0.3
O1 O1 0.0 0.46 0.87 0.87 52.3 5.0 1.8 233.3 0.4 1.29 3.0 0.0 0.0 0.00 0.0 5.0 2.85 1.1
1 1,2 0.0 0.99 0.57 0.57 33.8 2.7 4.1 0.0 0.0 0.00 0.0 147.0 4.8 3.53 0.7 5.0 2.85 1.6
Post-Project Conditions
2-Yr Runoff Computations
Design
Point Basins
Upstream
Time of
Concentration
Tc
Area, A
(acres)
Runoff
Coefficient
c
Overland Flow Gutter/Pipe Flow Swale Flow
Note:
Tc
(min)
Intensity, i
(in/hr)
Flow, Q
(cfs)
Rainfall intensity values were generated using Table 3.4-1 of the Fort Collins Stormwater Criteria Manual
TIM-DevQ.xlsx Page 1 of 3
City of Fort Collins, Colorado,
Overland Flow, Time of Concentration:
Ti= 1.87(1.1-CxCf)L1/2 / S1/3
Gutter/Swale Flow, Time of Concentration:
Tt= L / 60V
Tc= Ti + Tt
Intensity, (i) taken from intensity formula for Timberline-International PDP, i =46.95/(Tc+10.60)0.83 Calculations by: M. Wohnrade
Velocity, (V) taken from Figure 3-1 Project: Timberline-International PDP
Rational Equation: Q = ciA Date: April 6, 2021
C5
Length, L
(ft)
Slope, S
(%)
Ti
(min)
Length, L
(ft)
Slope, S
(%)
Velocity, V
(fps)
Tt
(min)
Length, L
(ft)
Slope, S
(%)
Velocity, V
(fps)
Tt
(min)
1 1 0.0 0.28 0.26 0.26 33.8 2.7 6.6 0.0 0.0 0.00 0.0 147.0 4.8 3.53 0.7 7.3 4.35 0.3
2 2 0.0 0.71 0.70 0.70 22.3 2.4 2.6 0.0 0.0 0.00 0.0 186.4 1.9 2.22 1.4 5.0 4.87 2.4
3 3 0.0 0.29 0.33 0.33 25.0 3.2 4.9 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 5.0 4.87 0.5
O1 O1 0.0 0.46 0.87 0.87 52.3 5.0 1.8 233.3 0.4 1.29 3.0 0.0 0.0 0.00 0.0 5.0 4.87 1.9
1 1,2 0.0 0.99 0.57 0.57 33.8 2.7 4.1 0.0 0.0 0.00 0.0 147.0 4.8 3.53 0.7 5.0 4.87 2.7
Rainfall intensity values were generated using Table 3.4-1 of the Fort Collins Stormwater Criteria Manual
Note:
Post-Project Conditions
10-Yr Runoff Computations
Design
Point Basins
Upstream
Time of
Concentration
Tc
Area, A
(acres)
Runoff
Coefficient
c
Overland Flow Gutter/Pipe Flow Swale Flow
Tc
(min)
Intensity, i
(in/hr)
Flow, Q
(cfs)
TIM-DevQ.xlsx Page 2 of 3 Wohnrade Civil Engineers, Inc.
City of Fort Collins, Colorado,
Overland Flow, Time of Concentration:
Ti= 1.87(1.1-CxCf)L1/2 / S1/3
Gutter/Swale Flow, Time of Concentration:
Tt= L / 60V
Tc= Ti + Tt
Intensity, (i) taken from intensity formula for Timberline-International PDP, i =98.31/(Tc+10.80)0.83 Calculations by: M. Wohnrade
Velocity, (V) taken from Figure 3-1 Project: Timberline-International PDP
Rational Equation: Q = ciA Date: April 6, 2021
C5
Length, L
(ft)
Slope, S
(%)
Ti
(min)
Length, L
(ft)
Slope, S
(%)
Velocity, V
(fps)
Tt
(min)
Length, L
(ft)
Slope, S
(%)
Velocity, V
(fps)
Tt
(min)
1 1 0.0 0.28 0.32 0.26 33.8 2.7 6.1 0.0 0.0 0.00 0.0 147.0 4.8 3.53 0.7 6.8 9.09 0.8
2 2 0.0 0.71 0.87 0.70 22.3 2.4 1.5 0.0 0.0 0.00 0.0 186.4 1.9 2.22 1.4 5.0 9.94 6.1
3 3 0.0 0.29 0.41 0.33 25.0 3.2 4.4 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 5.0 9.94 1.2
O1 O1 0.0 0.46 1.00 0.87 52.3 5.0 0.8 233.3 0.4 1.29 3.0 0.0 0.0 0.00 0.0 5.0 9.94 4.6
1 1,2 0.0 0.99 0.72 0.57 33.8 2.7 3.0 0.0 0.0 0.00 0.0 147.0 4.8 3.53 0.7 5.0 9.94 7.1
Rainfall intensity values were generated using Table 3.4-1 of the Fort Collins Stormwater Criteria Manual
Note:
Post-Project Conditions
100-Yr Runoff Computations
Design
Point Basins
Upstream
Time of
Concentration
Tc
Area, A
(acres)
Runoff
Coefficient
c
Overland Flow Gutter/Pipe Flow Swale Flow
Tc
(min)
Intensity, i
(in/hr)
Flow, Q
(cfs)
TIM-DevQ.xlsx Page 3 of 3 Wohnrade Civil Engineers, Inc.
WOHNRADE CIVIL ENGINEERS, INC.
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.4 Intensity-Duration-Frequency Curves for Rational Method
Page 8
Table 3.4-1. IDF Table for Rational Method
Duration
(min)
Intensity
2-year
(in/hr)
Intensity
10-year
(in/hr)
Intensity
100-year
(in/hr)
Duration
(min)
Intensity
2-year
(in/hr)
Intensity
10-year
(in/hr)
Intensity
100-year
(in/hr)
5 2.85 4.87 9.95 39 1.09 1.86 3.8
6 2.67 4.56 9.31 40 1.07 1.83 3.74
7 2.52 4.31 8.80 41 1.05 1.80 3.68
8 2.40 4.10 8.38 42 1.04 1.77 3.62
9 2.30 3.93 8.03 43 1.02 1.74 3.56
10 2.21 3.78 7.72 44 1.01 1.72 3.51
11 2.13 3.63 7.42 45 0.99 1.69 3.46
12 2.05 3.50 7.16 46 0.98 1.67 3.41
13 1.98 3.39 6.92 47 0.96 1.64 3.36
14 1.92 3.29 6.71 48 0.95 1.62 3.31
15 1.87 3.19 6.52 49 0.94 1.6 3.27
16 1.81 3.08 6.30 50 0.92 1.58 3.23
17 1.75 2.99 6.10 51 0.91 1.56 3.18
18 1.70 2.90 5.92 52 0.9 1.54 3.14
19 1.65 2.82 5.75 53 0.89 1.52 3.10
20 1.61 2.74 5.60 54 0.88 1.50 3.07
21 1.56 2.67 5.46 55 0.87 1.48 3.03
22 1.53 2.61 5.32 56 0.86 1.47 2.99
23 1.49 2.55 5.20 57 0.85 1.45 2.96
24 1.46 2.49 5.09 58 0.84 1.43 2.92
25 1.43 2.44 4.98 59 0.83 1.42 2.89
26 1.4 2.39 4.87 60 0.82 1.4 2.86
27 1.37 2.34 4.78 65 0.78 1.32 2.71
28 1.34 2.29 4.69 70 0.73 1.25 2.59
29 1.32 2.25 4.60 75 0.70 1.19 2.48
30 1.30 2.21 4.52 80 0.66 1.14 2.38
31 1.27 2.16 4.42 85 0.64 1.09 2.29
32 1.24 2.12 4.33 90 0.61 1.05 2.21
33 1.22 2.08 4.24 95 0.58 1.01 2.13
34 1.19 2.04 4.16 100 0.56 0.97 2.06
35 1.17 2.00 4.08 105 0.54 0.94 2.00
36 1.15 1.96 4.01 110 0.52 0.91 1.94
37 1.16 1.93 3.93 115 0.51 0.88 1.88
38 1.11 1.89 3.87 120 0.49 0.86 1.84
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.2 Runoff Coefficients
Page 5
Table 3.2-2. Surface Type - Runoff Coefficients
Surface Type Runoff Coefficients
Hardscape or Hard Surface
Asphalt, Concrete 0.95
Rooftop 0.95
Recycled Asphalt 0.80
Gravel 0.50
Pavers 0.50
Landscape or Pervious Surface
Lawns, Sandy Soil, Flat Slope < 2% 0.10
Lawns, Sandy Soil, Avg Slope 2-7% 0.15
Lawns, Sandy Soil, Steep Slope >7% 0.20
Lawns, Clayey Soil, Flat Slope < 2% 0.20
Lawns, Clayey Soil, Avg Slope 2-7% 0.25
Lawns, Clayey Soil, Steep Slope >7% 0.35
3.2.1 Composite Runoff Coefficients
Drainage sub-basins are frequently composed of land that has multiple surface types or zoning
classifications. In such cases a composite runoff coefficient must be calculated for any given drainage
sub-basin.
The composite runoff coefficient is obtained using the following formula:
t
n
i
ii
A
xAC
C 1 Equation 5-2
Where: C = Composite Runoff Coefficient
Ci = Runoff Coefficient for Specific Area (Ai), dimensionless
Ai = Area of Surface with Runoff Coefficient of Ci, acres or square feet
n = Number of different surfaces to be considered
At = Total Area over which C is applicable, acres or square feet
3.2.2 Runoff Coefficient Frequency Adjustment Factor
The runoff coefficients provided in Table 3.2-1 and Table 3.2-2 are appropriate for use with the 2-year
storm event. For any analysis of storms with higher intensities, an adjustment of the runoff coefficient is
required due to the lessening amount of infiltration, depression retention, evapotranspiration and other
losses that have a proportionally smaller effect on high-intensity storm runoff. This adjustment is
6-8 Urban Drainage and Flood Control District March 2017
Urban Storm Drainage Criteria Manual Volume 1
Table 6-3. Recommended percentage imperviousness values
Land Use or Percentage Imperviousness
(%)Surface Characteristics
Business:
Downtown Areas 95
Suburban Areas 75
Residential lots (lot area only):
Single-family
2.5 acres or larger 12
0.75 – 2.5 acres 20
0.25 – 0.75 acres 30
0.25 acres or less 45
Apartments 75
Industrial:
Light areas 80
Heavy areas 90
Parks, cemeteries 10
Playgrounds 25
Schools 55
Railroad yard areas 50
Undeveloped Areas:
Historic flow analysis 2
Greenbelts, agricultural 2
Off-site flow analysis (when land use not
defined)45
Streets:
Paved 100
Gravel (packed) 40
Drive and walks 90
Roofs 90
Lawns, sandy soil 2
Lawns, clayey soil 2
Hydraflow Rainfall Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020 Wednesday, 03 / 24 / 2021
Return Intensity-Duration-Frequency Equation Coefficients (FHA)
Period
(Yrs)B D E (N/A)
1 0.0000 0.0000 0.0000 --------
2 30.0397 11.3000 0.8439 --------
3 0.0000 0.0000 0.0000 --------
5 0.0000 0.0000 0.0000 --------
10 46.9523 10.6000 0.8251 --------
25 0.0000 0.0000 0.0000 --------
50 0.0000 0.0000 0.0000 --------
100 98.3129 10.8000 0.8304 --------
File name: TIM.IDF
Intensity = B / (Tc + D)^E
Return Intensity Values (in/hr)
Period
(Yrs) 5 min 10 15 20 25 30 35 40 45 50 55 60
1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
2 2.85 2.27 1.90 1.64 1.45 1.30 1.18 1.08 1.00 0.93 0.87 0.82
3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
10 4.87 3.87 3.23 2.79 2.46 2.21 2.01 1.84 1.70 1.59 1.49 1.40
25 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
50 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
100 9.94 7.91 6.61 5.71 5.04 4.52 4.11 3.77 3.49 3.25 3.04 2.86
Tc = time in minutes. Values may exceed 60.
Rainfall Precipitation Table (in)
Precip. file name: S:\PROJECTS\CR16\DRNG\CR16-Civil 3D Hydroflow Rainfall Data.pcp
Storm
Distribution 1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr
SCS 24-hour 0.00 1.78 0.00 2.28 4.25 5.77 6.80 4.63
SCS 6-Hr 0.00 1.23 0.00 1.61 2.60 0.00 0.00 3.76
Huff-1st 0.00 0.00 0.00 0.00 4.00 5.38 6.50 0.00
Huff-2nd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-3rd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-4th 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-Indy 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Custom 0.00 0.00 0.00 0.00 3.90 5.25 6.00 0.00
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.4 Intensity-Duration-Frequency Curves for Rational Method
Page 9
Figure 3.4-1. Rainfall IDF Curve – Fort Collins
Appendix B
Project:
Basin ID:
Depth Increment = ft
Required Volume Calculation Top of Micropool -- 0.00 -- -- -- 0 0.000
Selected BMP Type =EDB -- 0.50 -- -- -- 484 0.011 116 0.003
Watershed Area = 0.99 acres Note: L / W Ratio < 1 -- 1.00 -- -- -- 1,814 0.042 677 0.016
Watershed Length = 181 ft L / W Ratio = 0.8 -- 1.50 -- -- -- 2,280 0.052 1,696 0.039
Watershed Slope = 0.044 ft/ft -- 2.00 -- -- -- 2,844 0.065 2,972 0.068
Watershed Imperviousness = 57.00% percent -- 2.50 -- -- -- 5,449 0.125 5,073 0.116
Percentage Hydrologic Soil Group A = 0.0% percent -- 3.00 -- -- -- 6,751 0.155 8,123 0.186
Percentage Hydrologic Soil Group B = 100.0% percent -- 3.50 -- -- -- 8,231 0.189 11,869 0.272
Percentage Hydrologic Soil Groups C/D = 0.0% percent -- 4.00 -- -- -- 9,752 0.224 16,364 0.376
Desired WQCV Drain Time = 40.0 hours -- -- -- --
Location for 1-hr Rainfall Depths = Denver - Capitol Building -- -- -- --
Water Quality Capture Volume (WQCV) = 0.019 acre-feet -- -- -- --
Excess Urban Runoff Volume (EURV) = 0.061 acre-feet -- -- -- --
2-yr Runoff Volume (P1 = 0.87 in.) = 0.036 acre-feet 0.87 inches -- -- -- --
5-yr Runoff Volume (P1 = 1.15 in.) = 0.052 acre-feet 1.15 inches -- -- -- --
10-yr Runoff Volume (P1 = 1.45 in.) = 0.073 acre-feet 1.45 inches -- -- -- --
25-yr Runoff Volume (P1 = 1.96 in.) = 0.116 acre-feet 1.96 inches -- -- -- --
50-yr Runoff Volume (P1 = 2.43 in.) = 0.151 acre-feet 2.43 inches -- -- -- --
100-yr Runoff Volume (P1 = 2.97 in.) = 0.198 acre-feet 2.97 inches -- -- -- --
500-yr Runoff Volume (P1 = 4.5 in.) = 0.323 acre-feet 4.50 inches -- -- -- --
Approximate 2-yr Detention Volume = 0.034 acre-feet -- -- -- --
Approximate 5-yr Detention Volume = 0.048 acre-feet -- -- -- --
Approximate 10-yr Detention Volume = 0.068 acre-feet -- -- -- --
Approximate 25-yr Detention Volume = 0.087 acre-feet -- -- -- --
Approximate 50-yr Detention Volume = 0.100 acre-feet -- -- -- --
Approximate 100-yr Detention Volume = 0.120 acre-feet -- -- -- --
-- -- -- --
Stage-Storage Calculation -- -- -- --
Zone 1 Volume (100-year) = 0.120 acre-feet -- -- -- --
Select Zone 2 Storage Volume (Optional) =acre-feet -- -- -- --
Select Zone 3 Storage Volume (Optional) =acre-feet -- -- -- --
Total Detention Basin Volume = 0.120 acre-feet -- -- -- --
Initial Surcharge Volume (ISV) = user ft^3 -- -- -- --
Initial Surcharge Depth (ISD) = user ft -- -- -- --
Total Available Detention Depth (Htotal) =user ft -- -- -- --
Depth of Trickle Channel (HTC) = user ft -- -- -- --
Slope of Trickle Channel (STC) =user ft/ft -- -- -- --
Slopes of Main Basin Sides (Smain) =user H:V -- -- -- --
Basin Length-to-Width Ratio (RL/W) =user -- -- -- --
-- -- -- --
Initial Surcharge Area (AISV) =user ft^2 -- -- -- --
Surcharge Volume Length (LISV) =user ft -- -- -- --
Surcharge Volume Width (WISV) =user ft -- -- -- --
Depth of Basin Floor (HFLOOR) =user ft -- -- -- --
Length of Basin Floor (LFLOOR) =user ft -- -- -- --
Width of Basin Floor (WFLOOR) =user ft -- -- -- --
Area of Basin Floor (AFLOOR) =user ft^2 -- -- -- --
Volume of Basin Floor (VFLOOR) =user ft^3 -- -- -- --
Depth of Main Basin (HMAIN) =user ft -- -- -- --
Length of Main Basin (LMAIN) =user ft -- -- -- --
Width of Main Basin (WMAIN) =user ft -- -- -- --
Area of Main Basin (AMAIN) =user ft^2 -- -- -- --
Volume of Main Basin (VMAIN) =user ft^3 -- -- -- --
Calculated Total Basin Volume (Vtotal) =user acre-feet -- -- -- --
-- -- -- --
-- -- -- --
-- -- -- --
-- -- -- --
-- -- -- --
-- -- -- --
-- -- -- --
-- -- -- --
-- -- -- --
-- -- -- --
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-- -- -- --
DETENTION BASIN STAGE-STORAGE TABLE BUILDER
Optional
Override
Area (ft^2)
Length
(ft)
Optional
Override
Stage (ft)
Stage
(ft)
Stage - Storage
Description
Area
(ft^2)
Width
(ft)
142 Timberline
Detention Pond 1 - Includes Basins 1 and 2
UD-Detention, Version 3.07 (February 2017)
Volume
(ft^3)
Volume
(ac-ft)
Area
(acre)
Optional User Override
1-hr Precipitation
WQCV not provided!
Example Zone Configuration (Retention Pond)
UD-Detention_v3.07.xlsm, Basin 4/21/2021, 1:07 PM
1 User Defined Stage-Area Boolean for Message
1 Equal Stage-Area Inputs 1 Watershed L:W
1 CountA
0 Calc_S_TC
H_FLOOR
L_FLOOR_OTHER
0.00 ISV 0.00 ISV
0.00 Floor 0.00 Floor
2.54 Zone 1 (100-year)2.54 Zone 1 (100-year)
0.00 Zone 2 0.00 Zone 2
0.00 Zone 3 0.00 Zone 3
DETENTION BASIN STAGE-STORAGE TABLE BUILDER
UD-Detention, Version 3.07 (February 2017)
0.000
0.095
0.190
0.285
0.380
0.000
0.060
0.120
0.180
0.240
0.00 1.00 2.00 3.00 4.00 Volume (ac-ft)Area (acres)Stage (ft.)
Area (acres)Volume (ac-ft)
0
100
200
300
400
0
5
10
15
20
0.00 1.00 2.00 3.00 4.00 Area (sq.ft.)Length, Width (ft.)Stage (ft)
Length (ft)Width (ft)Area (sq.ft.)
UD-Detention_v3.07.xlsm, Basin 4/21/2021, 1:07 PM
Project:
Basin ID:
Stage (ft)Zone Volume (ac-ft)Outlet Type
Zone 1 (100-year)2.54 0.120 Circular Orifice
Zone 2
Zone 3
0.120 Total
User Input: Orifice at Underdrain Outlet (typically used to drain WQCV in a Filtration BMP) Calculated Parameters for Underdrain
Underdrain Orifice Invert Depth = N/A ft (distance below the filtration media surface) Underdrain Orifice Area = N/A ft2
Underdrain Orifice Diameter = N/A inches Underdrain Orifice Centroid = N/A feet
User Input: Orifice Plate with one or more orifices or Elliptical Slot Weir (typically used to drain WQCV and/or EURV in a sedimentation BMP) Calculated Parameters for Plate
Invert of Lowest Orifice = N/A ft (relative to basin bottom at Stage = 0 ft) WQ Orifice Area per Row = N/A ft2
Depth at top of Zone using Orifice Plate = N/A ft (relative to basin bottom at Stage = 0 ft) Elliptical Half-Width = N/A feet
Orifice Plate: Orifice Vertical Spacing = N/A inches Elliptical Slot Centroid = N/A feet
Orifice Plate: Orifice Area per Row = N/A inches Elliptical Slot Area = N/A ft2
User Input: Stage and Total Area of Each Orifice Row (numbered from lowest to highest)
Row 1 (optional) Row 2 (optional) Row 3 (optional) Row 4 (optional) Row 5 (optional) Row 6 (optional) Row 7 (optional) Row 8 (optional)
Stage of Orifice Centroid (ft) N/A N/A N/A N/A N/A N/A N/A N/A
Orifice Area (sq. inches) N/A N/A N/A N/A N/A N/A N/A N/A
Row 9 (optional) Row 10 (optional) Row 11 (optional) Row 12 (optional) Row 13 (optional) Row 14 (optional) Row 15 (optional) Row 16 (optional)
Stage of Orifice Centroid (ft) N/A N/A N/A N/A N/A N/A N/A N/A
Orifice Area (sq. inches) N/A N/A N/A N/A N/A N/A N/A N/A
User Input: Vertical Orifice (Circular or Rectangular) Calculated Parameters for Vertical Orifice
Zone 1 Circular Not Selected Zone 1 Circular Not Selected
Invert of Vertical Orifice = 0.00 ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Area =ft2
Depth at top of Zone using Vertical Orifice = 2.54 ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Centroid = feet
Vertical Orifice Diameter = inches
User Input: Overflow Weir (Dropbox) and Grate (Flat or Sloped) Calculated Parameters for Overflow Weir
Not Selected Not Selected Not Selected Not Selected
Overflow Weir Front Edge Height, Ho =ft (relative to basin bottom at Stage = 0 ft)Height of Grate Upper Edge, Ht = feet
Overflow Weir Front Edge Length = feet Over Flow Weir Slope Length = feet
Overflow Weir Slope = H:V (enter zero for flat grate) Grate Open Area / 100-yr Orifice Area =should be > 4
Horiz. Length of Weir Sides = feet Overflow Grate Open Area w/o Debris =ft2
Overflow Grate Open Area % = %, grate open area/total area Overflow Grate Open Area w/ Debris =ft2
Debris Clogging % = %
User Input: Outlet Pipe w/ Flow Restriction Plate (Circular Orifice, Restrictor Plate, or Rectangular Orifice) Calculated Parameters for Outlet Pipe w/ Flow Restriction Plate
Not Selected Not Selected Not Selected Not Selected
Depth to Invert of Outlet Pipe =ft (distance below basin bottom at Stage = 0 ft)Outlet Orifice Area =ft2
Circular Orifice Diameter = inches Outlet Orifice Centroid = feet
Half-Central Angle of Restrictor Plate on Pipe = N/A N/A radians
User Input: Emergency Spillway (Rectangular or Trapezoidal) Calculated Parameters for Spillway
Spillway Invert Stage= 2.60 ft (relative to basin bottom at Stage = 0 ft) Spillway Design Flow Depth= 0.57 feet
Spillway Crest Length = 2.00 feet Stage at Top of Freeboard = 4.17 feet
Spillway End Slopes = 4.00 H:V Basin Area at Top of Freeboard = 0.22 acres
Freeboard above Max Water Surface = 1.00 feet
Routed Hydrograph Results
Design Storm Return Period =WQCV EURV 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year 500 Year
One-Hour Rainfall Depth (in) =0.53 1.07 0.87 1.15 1.45 1.96 2.43 2.97 4.50
Calculated Runoff Volume (acre-ft) =0.019 0.061 0.036 0.052 0.073 0.116 0.151 0.198 0.323
OPTIONAL Override Runoff Volume (acre-ft) =
Inflow Hydrograph Volume (acre-ft) =0.019 0.061 0.035 0.051 0.073 0.116 0.151 0.197 0.323
Predevelopment Unit Peak Flow, q (cfs/acre) =0.00 0.00 0.01 0.02 0.26 0.95 1.45 2.09 3.73
Predevelopment Peak Q (cfs) =0.0 0.0 0.0 0.0 0.3 0.9 1.4 2.1 3.7
Peak Inflow Q (cfs) =0.5 1.6 0.9 1.3 1.9 3.0 3.9 5.0 8.2
Peak Outflow Q (cfs) =0.2 1.0 3.7
Ratio Peak Outflow to Predevelopment Q =0.1 0.5 1.0
Structure Controlling Flow =Spillway Spillway Spillway
Max Velocity through Grate 1 (fps) =N/A N/A N/A
Max Velocity through Grate 2 (fps) =N/A N/A N/A
Time to Drain 97% of Inflow Volume (hours) =>120 >120 >120
Time to Drain 99% of Inflow Volume (hours) =>120 >120 >120
Maximum Ponding Depth (ft) =2.70 2.84 3.09
Area at Maximum Ponding Depth (acres) =0.14 0.15 0.16
Maximum Volume Stored (acre-ft) =0.141 0.162 0.201
Detention Basin Outlet Structure Design
UD-Detention, Version 3.07 (February 2017)
142 Timberline
Detention Pond 1 - Includes Basins 1 and 2
Example Zone Configuration (Retention Pond)
COUNTA for Basin Tab =1 Ao Dia WQ Plate Type Vert Orifice 1 Vert Orifice 2
Count_Underdrain =0 0.11(diameter = 3/8 inch)1 2 1
Count_WQPlate =0 0.14(diameter = 7/16 inch)
Count_VertOrifice1 =0 0.18(diameter = 1/2 inch)Outlet Plate 1 Outlet Plate 2 Drain Time Message Boolean
Count_VertOrifice2 =0 0.24(diameter = 9/16 inch)1 1 5yr, <72hr 0
Count_Weir1 =0 0.29(diameter = 5/8 inch)>5yr, <120hr 0
Count_Weir2 =0 0.36(diameter = 11/16 inch)Max Depth Row
Count_OutletPipe1 =0 0.42(diameter = 3/4 inch)WQCV #VALUE! Watershed Constraint Check
Count_OutletPipe2 =0 0.50(diameter = 13/16 inch)2 Year #VALUE! Slope 0.040
COUNTA_2 (Standard FSD Setup)=0 0.58(diameter = 7/8 inch)EURV #VALUE! Shape 1.00
MaxPondDepth_Error? FALSE 0.67(diameter = 15/16 inch)5 Year #VALUE!
Hidden Parameters & Calculations 0.76 (diameter = 1 inch)10 Year #VALUE! Spillway Depth
0.86(diameter = 1-1/16 inches)25 Year #VALUE! 0.57
WQ Plate Flow at 100yr depth =0.00 0.97(diameter = 1-1/8 inches)50 Year 271
CLOG #1=0%1.08(diameter = 1-3/16 inches)100 Year 285 0 Z1_Boolean
Cdw #1 =1.20(diameter = 1-1/4 inches)500 Year 310 1 Z2_Boolean
Cdo #1 =1.32(diameter = 1-5/16 inches)Zone3_Pulldown Message 1 Z3_Boolean
Overflow Weir #1 Angle =1.45(diameter = 1-3/8 inches)1 Opening Message
CLOG #2=0%1.59(diameter = 1-7/16 inches)Draintime Running
Cdw #2 =1.73(diameter = 1-1/2 inches)Outlet Boolean Outlet Rank Total (1 to 4)
Cdo #2 =1.88(diameter = 1-9/16 inches)Vertical Orifice 1 0 0
0
Overflow Weir #2 Angle =2.03(diameter = 1-5/8 inches)Vertical Orifice 2 0 0 Boolean
Underdrain Q at 100yr depth =0.00 2.20(diameter = 1-11/16 inches)Overflow Weir 1 0 0 0 Max Depth
VertOrifice1 Q at 100yr depth =0.00 2.36(diameter = 1-3/4 inches)Overflow Weir 2 0 0 0 500yr Depth
VertOrifice2 Q at 100yr depth =0.00 2.54(diameter = 1-13/16 inches)Outlet Pipe 1 0 0 1 Freeboard
EURV_draintime_user = 2.72(diameter = 1-7/8 inches)Outlet Pipe 2 0 0 1 Spillway
Count_User_Hydrographs 0 2.90(diameter = 1-15/16 inches)0 Spillway Length
CountA_3 (EURV & 100yr) =0 3.09(diameter = 2 inches)Button Visibility Boolean FALSE Time Interval
CountA_4 (100yr Only) = 0 3.29(use rectangular openings)1 Button_Trigger
0 Underdrain
0 WQCV Plate
0 EURV-WQCV Plate
0 EURV-WQCV VertOrifice
0 Outlet 90% Qpeak
0 Outlet Undetained
S-A-V-D Chart Axis Override X-axis Left Y-Axis Right Y-Axis
minimum bound
maximum bound
UD-Detention, Version 3.07 (February 2017)
Detention Basin Outlet Structure Design
0
1
2
3
4
5
6
7
8
9
0.1 1 10FLOW [cfs]TIME [hr]
500YR IN
500YR OUT
100YR IN
100YR OUT
50YR IN
50YR OUT
25YR IN
25YR OUT
10YR IN
10YR OUT
5YR IN
5YR OUT
2YR IN
2YR OUT
EURV IN
EURV OUT
WQCV IN
WQCV OUT
0
0.5
1
1.5
2
2.5
3
3.5
0.1 1 10 100PONDING DEPTH [ft]DRAIN TIME [hr]
500YR
100YR
50YR
25YR
10YR
5YR
2YR
EURV
WQCV
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
18,000
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 OUTFLOW [cfs]AREA [ft^2], VOLUME [ft^3]PONDING DEPTH [ft]
User Area [ft^2]
Interpolated Area [ft^2]
Summary Area [ft^2]
Volume [ft^3]
Summary Volume [ft^3]
Outflow [cfs]
Summary Outflow [cfs]
Detention Pond 1 Stage-Storage Rating
Project: 142 Timberline
Basin Description: Detention Pond 1
Contour Contour Depth Incremental Cumulative
Elevation Area (ft) Volume Volume
(sq. ft) Conic Conic
(cu. ft.) (cu. ft.)
4,934.00 0.00 N/A N/A 0.00
4,934.50 484.43 0.50 80.74 80.74
4,935.00 1,813.65 0.50 539.24 619.97
4,935.50 2,279.61 0.50 1021.10 1641.07
4,936.00 2,844.42 0.50 1278.41 2919.48
4,936.50 5,448.49 0.50 2038.27 4957.75
4,937.00 6,750.76 0.50 3044.00 8001.76
4,937.50 8,231.33 0.50 3739.41 11741.17
4,938.00 9,751.73 0.50 4490.40 16231.57
100 Year
This is to convert % imp. to a C value
100-year (must insert % imp. and C pervious).
ft3 acre-ft.
'C' value 0.57 (2 yr)7904.8 0.181
'C' * 1.25 0.7125 (100 yr)
Area 0.99 acres Modified Modified
Release Rate 0.2 M. FATER D. JUDISH C. LI
5/95 Nov-97 Nov-98
DETENTION POND SIZING
TIME TIME INTENSITY Q 100 Runoff Release Required Required
cum 100 year Volume Cum total Detention Detention
(mins)(secs)(in/hr)(cfs)(ft^3)(ft^3)(ft^3)(ac-ft)
0 0 0 0.00 0 0.0 0.0 0.0000
5 300 9.950 7.02 2105.544 60.0 2045.5 0.0470
10 600 7.720 5.45 3267.297 120.0 3147.3 0.0723
15 900 6.520 4.60 4139.141 180.0 3959.1 0.0909
20 1200 5.600 3.95 4740.12 240.0 4500.1 0.1033
25 1500 4.980 3.51 5269.151 300.0 4969.2 0.1141
30 1800 4.520 3.19 5738.931 360.0 5378.9 0.1235
35 2100 4.080 2.88 6043.653 420.0 5623.7 0.1291
40 2400 3.740 2.64 6331.446 480.0 5851.4 0.1343
45 2700 3.460 2.44 6589.613 540.0 6049.6 0.1389
50 3000 3.230 2.28 6835.084 600.0 6235.1 0.1431
55 3300 3.030 2.14 7053.045 660.0 6393.0 0.1468
60 3600 2.860 2.02 7262.541 720.0 6542.5 0.1502
65 3900 2.720 1.92 7482.618 780.0 6702.6 0.1539
70 4200 2.590 1.83 7673.069 840.0 6833.1 0.1569
75 4500 2.480 1.75 7871.985 900.0 6972.0 0.1601
80 4800 2.380 1.68 8058.204 960.0 7098.2 0.1630
85 5100 2.290 1.62 8238.075 1020.0 7218.1 0.1657
90 5400 2.210 1.56 8417.945 1080.0 7337.9 0.1685
95 5700 2.130 1.50 8563.958 1140.0 7424.0 0.1704
100 6000 2.060 1.45 8718.435 1200.0 7518.4 0.1726
105 6300 2.000 1.41 8887.725 1260.0 7627.7 0.1751
110 6600 1.940 1.37 9031.622 1320.0 7711.6 0.1770
115 6900 1.890 1.33 9198.795 1380.0 7818.8 0.1795
120 7200 1.840 1.30 9344.808 1440.0 7904.8 0.1815
125 7500 1.790 1.26 9469.659 1500.0 7969.7 0.1830
130 7800 1.750 1.23 9628.369 1560.0 8068.4 0.1852
135 8100 1.710 1.21 9770.149 1620.0 8150.1 0.1871
140 8400 1.670 1.18 9895.001 1680.0 8215.0 0.1886
145 8700 1.630 1.15 10002.92 1740.0 8262.9 0.1897
150 9000 1.600 1.13 10157.4 1800.0 8357.4 0.1919
155 9300 1.570 1.11 10299.18 1860.0 8439.2 0.1937
160 9600 1.540 1.09 10428.26 1920.0 8508.3 0.1953
165 9900 1.510 1.07 10544.65 1980.0 8564.7 0.1966
170 10200 1.480 1.04 10648.34 2040.0 8608.3 0.1976
175 10500 1.450 1.02 10739.33 2100.0 8639.3 0.1983
180 10800 1.420 1.00 10817.63 2160.0 8657.6 0.1988
185 11100 1.400 0.99 10961.53 2220.0 8741.5 0.2007
190 11400 1.380 0.97 11096.96 2280.0 8817.0 0.2024
195 11700 1.360 0.96 11223.93 2340.0 8883.9 0.2039
200 12000 1.340 0.95 11342.43 2400.0 8942.4 0.2053
205 12300 1.320 0.93 11452.47 2460.0 8992.5 0.2064
210 12600 1.300 0.92 11554.04 2520.0 9034.0 0.2074
215 12900 1.280 0.90 11647.15 2580.0 9067.2 0.2082
220 13200 1.260 0.89 11731.8 2640.0 9091.8 0.2087
225 13500 1.240 0.87 11807.98 2700.0 9108.0 0.2091
230 13800 1.220 0.86 11875.69 2760.0 9115.7 0.2093
235 14100 1.210 0.85 12034.4 2820.0 9214.4 0.2115
240 14400 1.200 0.85 12188.88 2880.0 9308.9 0.2137
Required detention
Page 1
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020 Wednesday, 04 / 21 / 2021
Hyd. No. 3
Basins 1-2
Hydrograph type = Combine Peak discharge = 6.714 cfs
Storm frequency = 100 yrs Time to peak = 5 min
Time interval = 1 min Hyd. volume = 2,829 cuft
Inflow hyds. = 1, 2 Contrib. drain. area = 0.990 ac
0 2 4 6 8 10 12 14 16 18
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
5.00 5.00
6.00 6.00
7.00 7.00
Q (cfs)
Time (min)
Basins 1-2
Hyd. No. 3 -- 100 Year
Hyd No. 3 Hyd No. 1 Hyd No. 2
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020 Wednesday, 04 / 21 / 2021
Hyd. No. 4
Pond 1 Routing
Hydrograph type = Reservoir Peak discharge = 0.179 cfs
Storm frequency = 100 yrs Time to peak = 16 min
Time interval = 1 min Hyd. volume = 2,828 cuft
Inflow hyd. No. = 3 - Basins 1-2 Max. Elevation = 4935.91 ft
Reservoir name = Pond 1 Max. Storage = 2,682 cuft
Storage Indication method used.
0 60 120 180 240 300 360 420
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
5.00 5.00
6.00 6.00
7.00 7.00
Q (cfs)
Time (min)
Pond 1 Routing
Hyd. No. 4 -- 100 Year
Hyd No. 4 Hyd No. 3 Total storage used = 2,682 cuft
Pond Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020 Wednesday, 04 / 21 / 2021
Pond No. 1 - Pond 1
Pond Data
Pond storage is based on user-defined values.
Stage / Storage Table
Stage (ft) Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft)
0.00 4934.00 n/a 0 0
0.50 4934.50 n/a 81 81
1.00 4935.00 n/a 539 620
1.50 4935.50 n/a 1,021 1,641
2.00 4936.00 n/a 1,278 2,919
2.50 4936.50 n/a 2,038 4,958
3.00 4937.00 n/a 3,044 8,002
3.50 4937.50 n/a 3,739 11,741
4.00 4938.00 n/a 4,490 16,232
Culvert / Orifice Structures Weir Structures
[A] [B] [C] [PrfRsr] [A] [B] [C] [D]
Rise (in)= 2.25 0.00 0.00 0.00
Span (in)= 2.25 0.00 0.00 0.00
No. Barrels = 1 0 0 0
Invert El. (ft)= 4934.00 0.00 0.00 0.00
Length (ft)= 0.00 0.00 0.00 0.00
Slope (%)= 0.00 0.00 0.00 n/a
N-Value = .013 .013 .013 n/a
Orifice Coeff.= 0.60 0.60 0.60 0.60
Multi-Stage = n/a No No No
Crest Len (ft)= 10.00 0.00 0.00 0.00
Crest El. (ft)= 4937.50 0.00 0.00 0.00
Weir Coeff.= 2.60 3.33 3.33 3.33
Weir Type = Broad --- --- ---
Multi-Stage = No No No No
Exfil.(in/hr)= 0.000 (by Wet area)
TW Elev. (ft)= 0.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
Stage / Storage / Discharge Table
Stage Storage Elevation Clv A Clv B Clv C PrfRsr Wr A Wr B Wr C Wr D Exfil User Total
ft cuft ft cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs
0.00 0 4934.00 0.00 --- --- --- 0.00 --- --- --- --- --- 0.000
0.50 81 4934.50 0.08 ic --- --- --- 0.00 --- --- --- --- --- 0.085
1.00 620 4935.00 0.13 ic --- --- --- 0.00 --- --- --- --- --- 0.127
1.50 1,641 4935.50 0.16 ic --- --- --- 0.00 --- --- --- --- --- 0.158
2.00 2,919 4936.00 0.18 ic --- --- --- 0.00 --- --- --- --- --- 0.184
2.50 4,958 4936.50 0.21 ic --- --- --- 0.00 --- --- --- --- --- 0.206
3.00 8,002 4937.00 0.23 ic --- --- --- 0.00 --- --- --- --- --- 0.227
3.50 11,741 4937.50 0.25 ic --- --- --- 0.00 --- --- --- --- --- 0.245
4.00 16,232 4938.00 0.26 ic --- --- --- 9.19 --- --- --- --- --- 9.455
Weir Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Thursday, Mar 25 2021
Detention Pond 1 - Emergency Overflow Weir - Q100= 6.8 cfs
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) = 7.10
Highlighted
Depth (ft) = 0.35
Q (cfs) = 7.100
Area (sqft) = 3.99
Velocity (ft/s) = 1.78
Top Width (ft) = 12.80
0 2 4 6 8 10 12 14 16 18
Depth (ft) Depth (ft)Detention Pond 1 - Emergency Overflow Weir - Q100= 6.8 cfs
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
Length (ft)Weir W.S.
Stormwater Facility Name:
Facility Location & Jurisdiction:
User Input: Watershed Characteristics User Defined User Defined User Defined User Defined
Watershed Slope =0.044 ft/ft Stage [ft] Area [ft^2] Stage [ft] Discharge [cfs]
Watershed Length =181 ft 0.00 0 0.00 0.00
Watershed Area = 0.99 acres 0.50 484 0.50 0.09
Watershed Imperviousness = 57.0%percent 1.00 1,814 1.00 0.13
Percentage Hydrologic Soil Group A =percent 1.50 2,280 1.50 0.16
Percentage Hydrologic Soil Group B = 100.0%percent 2.00 2,844 2.00 0.18
Percentage Hydrologic Soil Groups C/D =percent 2.50 5,449 2.50 0.21
3.00 6,751 3.00 0.23
User Input 17 3.50 8,231 3.50 0.25
4.00 9,752 4.00 9.46
WQCV Treatment Method =hours
After completing and printing this worksheet to a pdf, go to:
https://maperture.digitaldataservices.com/gvh/?viewer=cswdif
create a new stormwater facility, and
attach the pdf of this worksheet to that record.
Routed Hydrograph Results
Design Storm Return Period =WQCV 2 Year 5 Year 10 Year 50 Year 100 Year
One-Hour Rainfall Depth =0.53 0.85 1.12 1.41 2.34 2.84 in
Calculated Runoff Volume =0.036 0.050 0.071 0.145 0.189 acre-ft
OPTIONAL Override Runoff Volume =acre-ft
Inflow Hydrograph Volume =0.035 0.049 0.071 0.145 0.188 acre-ft
Time to Drain 97% of Inflow Volume =3.7 4.6 6.1 10.1 12.3 hours
Time to Drain 99% of Inflow Volume =3.9 4.9 6.3 10.6 12.8 hours
Maximum Ponding Depth =1.21 1.46 1.81 2.57 2.87 ft
Maximum Ponded Area =0.05 0.05 0.06 0.13 0.15 acres
Maximum Volume Stored = 0.025 0.037 0.057 0.125 0.166 acre-ft
Stormwater Detention and Infiltration Design Data Sheet
Pond 1
N. Timberline Road and International Boulevard, Fort Collins, Colorado
Location for 1-hr Rainfall Depths (use dropdown):
Workbook Protected Worksheet Protected
SDI_Design_Data_v1.08.xlsm, Design Data 4/21/2021, 12:38 PM
WQCV_Trigger = 1
RunOnce= 1
CountA=1
Draintime Coeff= 1.0
0 1 2 3
#N/A
#N/A
0 1 2 3
#N/A
#N/A
Check Data Set 1 Check Data Set 1
Stormwater Detention and Infiltration Design Data Sheet
Area
Discharge
0
1
2
3
4
5
6
0.1 1 10FLOW [cfs]TIME [hr]
100YR IN
100YR OUT
50YR IN
50YR OUT
10YR IN
10YR OUT
5YR IN
5YR OUT
2YR IN
2YR OUT
WQCV IN
WQCV OUT
0
0.5
1
1.5
2
2.5
3
3.5
0.1 1 10 100PONDING DEPTH [ft]DRAIN TIME [hr]
100YR
50YR
10YR
5YR
2YR
WQCV
SDI_Design_Data_v1.08.xlsm, Design Data 4/21/2021, 12:38 PM
Appendix C
Sheet 1 of 1
Designer:
Company:
Date:
Project:
Location:
1. To identify potential BMPs, what best describes
the type of site?
SKIP # 2
2. Does the typical section include a parking lane, shoulder,
median, or otherwise allow for surface BMPs?
3. Is the site comprised of Hydrologic Soil Group A or B soils?
4.Is the tributary impervious area1 greater than 1 acre?
SKIP #6-10
5. Is the depth of bedrock greater than 5 feet?
6.Is the tributary impervious area1 greater than 5 acres?
7. Is a water source available for use?
(baseflow or groundwater)
8.Is the BMP in a developing watershed?
9. Are BMPs allowed in the right-of-way?
10. Does the community have an established Fee in Lieu
Program in place?
11.Step 1 of Four Step Process: Grass Buffer
MDCIA / Volume Reduction (Not WQCV) BMPs Grass Swale
Permeable Pavement- Full Infiltration (5)
Green Roof (3)
12.Step 2 of Four Step Process:Permeable Pavement- Full Infiltration (5)
WQCV BMPs Bioretention- Full Infiltration (5)
Sand Filter Extended Detention Basin- Full Infiltration (5)
Green Roof (3)
Regional Water Quality Treatment (4)
Notes: 1. 'Tributary impervious area' refers to the impervious area draining to the BMP, not the total area of the project site.
2. For a successful wetland channel or basin, a water source (groundwater or baseflow) will be required.
3. In the Front Range of Colorado, irrgation, at least periodically in dry times, will be required to sustain a green roof.
4. If a regional facility will be used to provide the WQCV, some degree of onsite treatment/MDCIA will still likely be required.
5. No Infiltration= underdrain and liner, Partial Infiltration= underdrain and no liner, Full Infiltration= no underdrain and no liner.
6. Consider this BMP for a portion of your site. It's best suited for impervious tributary areas of approximately one acre or less.
Design Procedure Form: BMP Selection Tool
Mary B. Wohnrade, P.E.
Wohnrade Civil Engineers, Inc.
September 10, 2020
Timberline-International
Timberline Road, Fort Collins, CO
UD-BMP (Version 3.07, March 2018)
Choose One
Highly Urbanized Site
Conventional Site
Choose One
YES
NO
Choose One
YES
NO
Choose One
YES
NO
Choose One
YES
NO
Choose One
YES
NO
Choose One
YES
NO
Choose One
YES
NO
Choose One
YES
NO
Linear Construction in Urbanized Area
Choose One
YES
NO
TIM_UD-BMP_v3.07_SELECTION_TOOL.xlsm, BMP Selection Tool 9/10/2020, 6:03 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =70.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.700
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.22 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 30,933 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 =0.35 in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER =462 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 =9 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin =433 sq ft
D) Actual Flat Surface Area AActual =2163 sq ft
E) Area at Design Depth (Top Surface Area)ATop =3188 sq ft
F) Rain Garden Total Volume VT=2,033 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?1
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y =1.5 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =462 cu ft
iii) Orifice Diameter, 3/8" Minimum DO =1/2 in
Design Procedure Form: Rain Garden (RG)
Mary B. Wohnrade, P.E.
Wohnrade Civil Engineers, Inc.
February 15, 2021
Timberline-International - Rain Garden No. 1
Fort Collins, Colorado
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.07-Rain_Garden.xlsm, RG 2/15/2021, 5:16 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
Mary B. Wohnrade, P.E.
Wohnrade Civil Engineers, Inc.
February 15, 2021
Timberline-International - Rain Garden No. 1
Fort Collins, Colorado
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
UD-BMP_v3.07-Rain_Garden.xlsm, RG 2/15/2021, 5:16 PM
Appendix D
Culvert Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Tuesday, Aug 7 2018
Future Storm Sewer Line
Invert Elev Dn (ft) = 4923.48
Pipe Length (ft) = 392.47
Slope (%) = 0.40
Invert Elev Up (ft) = 4925.05
Rise (in) = 30.0
Shape = Circular
Span (in) = 30.0
No. Barrels = 1
n-Value = 0.013
Culvert Type = Circular Concrete
Culvert Entrance = Square edge w/headwall (C)
Coeff. K,M,c,Y,k = 0.0098, 2, 0.0398, 0.67, 0.5
Embankment
Top Elevation (ft) = 4941.89
Top Width (ft) = 24.00
Crest Width (ft) = 100.00
Calculations
Qmin (cfs) = 0.00
Qmax (cfs) = 23.00
Tailwater Elev (ft) = Normal
Highlighted
Qtotal (cfs) = 23.00
Qpipe (cfs) = 23.00
Qovertop (cfs) = 0.00
Veloc Dn (ft/s) = 5.97
Veloc Up (ft/s) = 6.78
HGL Dn (ft) = 4925.31
HGL Up (ft) = 4926.68
Hw Elev (ft) = 4927.61
Hw/D (ft) = 1.02
Flow Regime = Inlet Control
Project:Date:Sheets11582 Colony Row
Broomfield, Colorado 80021
Phone: (720)259-0965
Fax: (720)259-1519
No.Revisions:By:Date:
WOHNRADE CIVIL ENGINEERS, INC.257/22/2021TIM: 1805.00Scale:Designed By:Reviewed By:Sheet16MBWJDM1"=20'CALL UTILITY NOTIFICATION CENTER OFCOLORADOKnow what'sbelow.before you dig.CallR