HomeMy WebLinkAbout625 S. PETERSON MULTI-FAMILY - PDP - PDP160005 - REPORTS - DRAINAGE REPORTProject Development Plan (PDP)
Preliminary Drainage Report
for
625 Peterson Street Redevelopment
submitted to:
City of Fort Collins,
Colorado
May 25, 2016
760 Whalers Way
Bldg C, Suite 200
Fort Collins, CO 80525
970.226.0557 main
303.595.9103 metro
970.226.0204 fax
ideas@tstinc.com
www.tstinc.com
May 25, 2016
Mr. Mark Taylor, P.E., CFM
City of Fort Collins Utilities
700 Wood Street
Fort Collins, CO 80521
Re: 625 Peterson Street Redevelopment
Project No. 0663.0012.00
Dear Mr. Taylor:
We are pleased to submit this Preliminary Drainage Report for the 625 Peterson
Street Redevelopment. This report analyzes the developed stormwater runoff from
the project and provides stormwater infrastructure and water quality management
for runoff. The 625 Peterson Street Redevelopment is located in the City of Fort
Collins Old Town Moderate Risk Floodplain. It is understood that there are no
floodplain elevation standards for this development, but we have taken the
elevation recommendations into account when designing this site.
This report has been prepared based on the City of Fort Collins Stormwater Criteria
Manual and complies with the PDP submittal requirements for a final drainage
report.
Respectfully,
TST, INC. CONSULTING ENGINEERS
Jon Sweet, P.E. Eric M. Fuhrman, P.E.
JFS/EMF/jrm
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
TABLE OF CONTENTS
Page
1.0 Introduction
1.1 Scope and Purpose ..................................................................................................... 1
1.2 Project Location and Description ................................................................................. 1
2.0 Existing Conditions .......................................................................................................... 3
3.0 Developed Conditions Plan
3.1 Design Criteria for Hydrologic Analysis ....................................................................... 3
3.2 Drainage Plan Development ....................................................................................... 4
3.2.1 Channel Design .................................................................................................. 4
3.2.2 Detention Requirements and Water Quality Capture Volume Design ................ 5
3.3 Low Impact Development ............................................................................................ 5
3.4 Old Town Moderate Risk Floodplain Management ..................................................... 7
4.0 Conclusion ......................................................................................................................... 7
5.0 References ......................................................................................................................... 8
Figures
Figure 1. Vicinity Map ................................................................................................................... 2
Figure 2. Four-Step Process for Stormwater Quality Management .............................................. 6
Tables
Table 1. Existing VS. Proposed Impervious Area ......................................................................... 5
Appendices
Appendix A: Rational Method Hydrologic Analysis
Appendix B: Channel Design
Appendix C: Water Quality Capture Volume
Appendix D: Low Impact Development
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Page 1
1.0 Introduction
1.1 Scope and Purpose
This report has been developed in accordance with the City of Fort Collins Stormwater Criteria
Manual requirements and complies with Project Development Plan (PDP) submittal
requirements which present the results of a preliminary drainage analysis for the 625 Peterson
Street Redevelopment.
1.2 Project Location and Description
The 625 Peterson Street Redevelopment is a 12,000 s.f. existing single family lot located in the
northwest quarter of Section 13, Township 7 North, Range 69 West. The site is located on the
west side of Peterson Street approximately halfway between East Laurel Street and East Myrtle
Street. Please refer to Figure 1 on the next page for a Vicinity Map.
This development is located within the City of Fort Collins Old Town Moderate Risk Floodplain.
The Base Flood Elevation (BFE) at the rear of the property is approximately 4989.9 and the
front is at roughly 4988.9 (NAVD88). This floodplain has no elevation standards for
development, but it is recommended that the lowest finished floor and all duct work, heating,
ventilation and air conditioning, hot water heaters, electric, etc. be elevated a minimum of 24”
above the BFE.
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Page 2
Figure 1.
2.0 Existing Conditions
The existing site contains a single family residence, shed/garage type structures and
interconnecting paver/concrete pathways and patios. The site generally drains to the east, or
toward the front of the lot, at roughly 0.8%. There is an existing concrete alley in the back of the
lot that flows north at approximately 0.3% and is captured by area inlets in the alley roughly 185’
to the north. The front of the lot has a vertical curb and gutter. This gutter flows south at roughly
0.3% to the intersection of Peterson Street and East Laurel Street where runoff is picked up by
a curb inlet.
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Page 3
3.0 Developed Conditions Plan
3.1 Design Criteria for Hydrologic Analysis
The drainage plan presented in this report has been developed in accordance with the City of
Fort Collins Stormwater Criteria Manual and the City of Fort Collins submittal requirements for a
Project Development Plan (PDP).
The drainage basin presented in this report is less than 90 acres, therefore, the method used to
analyze drainage for this project will be the Rational Method. Runoff calculations for both the 2-year
and 100-year storms will be presented here.
The Rational Method is given by:
Q = C(Cf)IA where
Q is the maximum rate of runoff in cfs
C is the runoff coefficient
Cf is the runoff coefficient frequency factor adjustment
I is the rainfall intensity in inches per hour for a storm duration equal to the time of
concentration
A is the total area of the basin in acres
The runoff coefficient C has different values depending on the design storm recurrence interval.
The runoff coefficient is also dependent on land use or surface characteristics/imperviousness.
Runoff coefficients were assigned using Table RO-11 from the Fort Collins Stormwater Criteria
Manual. The frequency factor adjustment, Cf, varies depending on the storm frequency and can be
found in Table RO-12 of the Fort Collins Stormwater Criteria Manual.
The rainfall intensity is selected from Rainfall Intensity Duration Frequency Curves for the City of
Fort Collins (Tables RA-7 through RA-9 of the Fort Collins Stormwater Criteria Manual).
In order to utilize the Rainfall Intensity Duration Curves, the time of concentration is required. The
following equation is used to determine the time of concentration
tc = ti + tt where
tc is the time of concentration in minutes
ti is the initial or overland flow time in minutes
tt is the conveyance travel time in minutes
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Page 4
The initial or overland flow time is calculated with the UDFCD equation:
0.33
f
i S
1.87 1.1 * C D
t
C
3.2 Drainage Plan Development
The 625 Peterson Street project is proposed to remodel the existing single family home and
expand the footprint on the west side to accommodate 3 new rental units. A new parking area
will be required off the rear alley.
The existing property to the north has a shallow swale along it’s south property line that
captures flow from this property and routes it to Peterson Street. The property to the south has
roof drains directed onto their driveway, which directs runoff east, to Peterson Street. Therefore
offsite flows onto the property are assumed to be zero for this analysis.
Basin A, as shown on the Drainage Plan, is located in the rear of the property along the existing
concrete alley. This basin consists of the parking area and trash enclosure. The parking will
sheet flow in a southeast direction at a 1.65% slope toward the curb-cut and 2’ gutter.
Basin B is located along the south property line and extends from the front to the back of the lot.
This basin is a mixture of grass, landscaping, concrete walkways and half of the existing and
proposed roof area. These areas will generally sheet flow at 1% - 2% toward the southeast
where runoff will be captured in a 2’ wide gutter, located on the south property line, and directed
toward Peterson Street.
Basin C encompasses the northern portion of the property and consisted of grass, landscaping,
concrete walkways, a new concrete driveway and half of the proposed and existing roof area.
This basin will drain toward the northeast and will be directed toward Peterson Street in a 2’
wide concrete.
Basin runoff results are provided in Appendix A.
3.2.1 Channel Design
Proposed channels and swales at this project site have been analyzed using Bentley
Flowmaster V8i, Select Series 1 software. These swales have been designed to include 133%
of design flow. The standard 1’ of freeboard above the normal water depth is not possible due
to existing conditions and the flat nature of the site.
Swale A-A, B-B, and C-C are 2’ concrete gutters located on the south property line and sloped
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Page 5
at a minimum of 0.5%, and maximum of 0.93%, to the east. This swale will convey runoff from
Basin A and B. Swale D-D is a 2’ concrete gutter located on the north property line and will
convey Basin C at a 0.8% slope toward Peterson Street.
The results of the channel design are provided in Appendix B.
3.2.2 Detention Requirements and Water Quality Capture Volume Design
As per the City standard, developments with less than 5,000 sf of new impervious area are not
required to provide detention. This site has a new impervious area total less than 5,000 sf and
therefore this project will not provide detention. Please see Table 1 below for existing versus
proposed impervious area information.
Hardscape/Pavement* 3960
Roof 3058
Hardscape/Pavement 940
Roof 2378
New Impervious Area 3700
*Hardscape/Pavement area excludes proposed pervious paver area.
EX SITE 3318
PROPOSED SITE 7018
Table 1
Existing VS. Proposed Impervious Area
Basin/ Sub-Basin Attribute Attribute Area (sf) Total Impervious Area (sf)
The Water Quality Capture Volume (WQCV) has been calculated using Equation 3-3 and Figure
3-2 from the Urban Storm Drainage Criteria Manual Volume 3. The WQCV for this site is
0.0039 ac-ft, or 170 cu-ft. Permeable pavement areas proposed for this project site are capable
of storing approximately 0.007 ac-ft, or 293 cu-ft of WQCV within the sub-structure of these
paved areas. However, this water quality will be implemented within Basin A only. Due to
significant site constraints, including a small site, and the inability to daylight an underdrain,
Basins B and C will not have a water quality component. A variance to cover this non-standard
approach is included with this report.
WQCV calculations are presented in Appendix C, and the permeable pavements storage
calculations are shown in Appendix D.
3.3 Low Impact Development
With the building coverage and parking areas on this small lot, the amount of imperviousness
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Page 6
on this site will be fairly high. However, the grading design aims to minimize the “directly
connected impervious area” (DCIA) as much as possible. Strategies to minimize directly
connected impervious areas follow the Four-Step Process for Stormwater Quality Management,
as outlined in Volume 3 of the Urban Storm Drainage Criteria Manual. The four-step process is
shown below.
Figure 2. Four-Step Process for Stormwater Quality Management
Step 1: Runoff Reduction Practices for this project site are planned to include porous pavers in
the parking area and maintaining grassed/landscaped areas where possible. The porous
pavers will aid in the stormwater filtration for runoff generated by the parking area. The
grassed/landscaped areas will help to minimize the directly connected impervious roof and
hardscape areas. This will also provide the opportunity for runoff infiltration and increase the
time of concentration.
Step 2: BMP’s to Provide WQCV with Slow Release for this project site will employ LID
techniques such as a permeable pavement system and grassed/landscaped areas within the
project site.
The City of Fort Collins criteria for low impact development, as outlined in the Stormwater
Criteria Manual in Volume 3, Chapter 3, are as follows:
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Page 7
No less than 50% of any newly added impervious area must be treated using one or a
combination of LID techniques, and
No less than 25% of any newly added pavement areas must be treated using a
permeable pavement technology that is considered a LID technique
Step 3: Stabilized Drainageways will come in the form of reseeding and/or sodding the open
areas between downspout locations and the swales on the north and south property lines.
Step 4: Site Specific Source Control BMP’s may include things like proper maintenance of the
permeable pavers.
LID calculations are included in Appendix D.
3.4 Old Town Moderate Risk Floodplain Management
This development is located within the City of Fort Collins Old Town Moderate Risk Floodplain.
The Base Flood Elevations (BFE’s) have been provided by the City Stormwater Department and
are approximately 4989.9 at the rear of the property and 4988.9 (NAVD88) at the front. This
floodplain has no elevation standards for development, but it is recommended that the lowest
finished floor and all duct work, heating, ventilation and air conditioning, hot water heaters,
electric, etc. be elevated a minimum of 24” above the BFE. The new units are to be located in
the center of the site, so we have assumed a BFE of 4989.5 at this location. Due to site
constraints the finished floor (and duct work, HVAC, etc.) will be set 18”, rather than 24”, above
this BFE at 4991.00. The finished floor elevation of the existing home is 4988.21 and will need
to stay at this elevation.
4.0 Conclusion
The City of Fort Collins Stormwater Criteria Manual has been used to establish the criteria for a
developed condition runoff plan within the 625 Peterson Street Redeveloped area. This PDP
drainage design report has highlighted the following items:
Project site development is within the confines of the City regulatory Old Town Moderate
Risk Floodplain.
Stormwater detention will not be required due to the fact that this project will add less than
5,000 s.f. of new impervious area.
Water quality has been provided through the use of permeable pavers. Areas that we have
been unable to provide water quality for are covered under the attached variance.
LID techniques are planned to be implemented within the site design that include the use of
minimizing directly connected impervious areas. These are through the use of permeable
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Page 8
pavement.
5.0 References
1. City of Fort Collins Stormwater Criteria Manual, Amendments to the Urban Drainage
and Flood Control District Criteria Manual, Adopted December 2011, Last Revision
April 2012.
2. Urban Drainage and Flood Control District Criteria Manual, Volume 3, August 2011
3. Natural Resources Conservation Services, 2013, Web Soil Survey: Soil Survey Area
Larimer County Area, Version 8, Dec 23, 2013
4. Chapter 10 of the Fort Collins Municipal Code, http://colocode.com/fcmunihtml.html
APPENDIX A
Rational Method Hydrologic Analysis
+\GURORJLF6RLO*URXS²/DULPHU&RXQW\$UHD&RORUDGR
3HWHUVRQ6WUHHW
1DWXUDO5HVRXUFHV
&RQVHUYDWLRQ6HUYLFH
:HE6RLO6XUYH\
1DWLRQDO&RRSHUDWLYH6RLO6XUYH\
3DJHRI
1
:
1
:
1
:
1
:
1
0DSSURMHFWLRQ :HE0HUFDWRU&RUQHUFRRUGLQDWHV :*6(GJHWLFV 870=RQH1:*6
)HHW
0HWHUV
0DS6FDOH LISULQWHGRQ$ODQGVFDSH [
0$3/(*(1' 0$3,1)250$7,21
$UHDRI,QWHUHVW $2,
$UHDRI,QWHUHVW $2,
6RLOV
6RLO5DWLQJ3RO\JRQV
$
$'
%
%'
&
&'
'
1RWUDWHGRUQRWDYDLODEOH
6RLO5DWLQJ/LQHV
$
$'
%
%'
&
&'
'
1RWUDWHGRUQRWDYDLODEOH
6RLO5DWLQJ3RLQWV
$
$'
%
%'
&
&'
'
1RWUDWHGRUQRWDYDLODEOH
:DWHU)HDWXUHV
6WUHDPVDQG&DQDOV
7UDQVSRUWDWLRQ
5DLOV
,QWHUVWDWH+LJKZD\V
865RXWHV
0DMRU5RDGV
/RFDO5RDGV
%DFNJURXQG
$HULDO3KRWRJUDSK\
7KHVRLOVXUYH\VWKDWFRPSULVH\RXU$2,ZHUHPDSSHGDW
:DUQLQJ 6RLO0DSPD\QRWEHYDOLGDWWKLVVFDOH
(QODUJHPHQWRIPDSVEH\RQGWKHVFDOHRIPDSSLQJFDQFDXVH
PLVXQGHUVWDQGLQJRIWKHGHWDLORIPDSSLQJDQGDFFXUDF\RIVRLOOLQH
SODFHPHQW7KHPDSVGRQRWVKRZWKHVPDOODUHDVRIFRQWUDVWLQJ
VRLOVWKDWFRXOGKDYHEHHQVKRZQDWDPRUHGHWDLOHGVFDOH
3OHDVHUHO\RQWKHEDUVFDOHRQHDFKPDSVKHHWIRUPDS
PHDVXUHPHQWV
6RXUFHRI0DS 1DWXUDO5HVRXUFHV&RQVHUYDWLRQ6HUYLFH
:HE6RLO6XUYH\85/ KWWS ZHEVRLOVXUYH\QUFVXVGDJRY
&RRUGLQDWH6\VWHP :HE0HUFDWRU (36*
0DSVIURPWKH:HE6RLO6XUYH\DUHEDVHGRQWKH:HE0HUFDWRU
SURMHFWLRQZKLFKSUHVHUYHVGLUHFWLRQDQGVKDSHEXWGLVWRUWV
GLVWDQFHDQGDUHD$SURMHFWLRQWKDWSUHVHUYHVDUHDVXFKDVWKH
$OEHUVHTXDODUHDFRQLFSURMHFWLRQVKRXOGEHXVHGLIPRUHDFFXUDWH
FDOFXODWLRQVRIGLVWDQFHRUDUHDDUHUHTXLUHG
7KLVSURGXFWLVJHQHUDWHGIURPWKH86'$15&6FHUWLILHGGDWDDVRI
WKHYHUVLRQGDWH V
+\GURORJLF6RLO*URXS
+\GURORJLF6RLO*URXS²6XPPDU\E\0DS8QLW²/DULPHU&RXQW\$UHD&RORUDGR &2
0DSXQLWV\PERO 0DSXQLWQDPH 5DWLQJ $FUHVLQ$2, 3HUFHQWRI$2,
)RUW&ROOLQVORDPWR
SHUFHQWVORSHV
&
7RWDOVIRU$UHDRI,QWHUHVW
'HVFULSWLRQ
+\GURORJLFVRLOJURXSVDUHEDVHGRQHVWLPDWHVRIUXQRIISRWHQWLDO6RLOVDUH
DVVLJQHGWRRQHRIIRXUJURXSVDFFRUGLQJWRWKHUDWHRIZDWHULQILOWUDWLRQZKHQWKH
VRLOVDUHQRWSURWHFWHGE\YHJHWDWLRQDUHWKRURXJKO\ZHWDQGUHFHLYHSUHFLSLWDWLRQ
IURPORQJGXUDWLRQVWRUPV
7KHVRLOVLQWKH8QLWHG6WDWHVDUHDVVLJQHGWRIRXUJURXSV $%&DQG'
7LHEUHDN5XOH +LJKHU
+\GURORJLF6RLO*URXS²/DULPHU&RXQW\$UHD&RORUDGR 3HWHUVRQ6WUHHW
1DWXUDO5HVRXUFHV
&RQVHUYDWLRQ6HUYLFH
:HE6RLO6XUYH\
1DWLRQDO&RRSHUDWLYH6RLO6XUYH\
3DJHRI
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Appendix A
Developed Runoff
Developed condition runoff was evaluated in accordance with the criteria established by the City
of Fort Collins Stormwater Criteria Manual dated February 26, 2013. Design guidelines and
information were also obtained from the Urban Storm Drainage Criteria Manual (USDCM) where
applicable. A full description of this method is available through those manuals. The Rational
Method computes only the peak flow at a design point and does not provide hydrograph
information.
Rational Method
City of Fort Collins
The Rational Method calculates peak runoff using the equation:
Q = CCfIA
Where: Q = The maximum rate of runoff (cfs)
C = Rational Method Runoff Coefficient for the design storm frequency. City of Fort
Collins runoff coefficients are found in Table 3-3 of the SDDC manual.
Cf = Storm Frequency Coefficient found in Table 3-4 of the SDDC manual.
I = Average intensity of rainfall in inches per hour for a duration equal to the time of
concentration, Tc. City of Fort Collins rainfall intensity data are shown in this
Appendix.
A = Basin Area (acres)
Rational Method Runoff Coefficients, C, are a function of the basin land use and the design
storm frequency. They are listed in Table 3-3 of the Storm Drainage Design Criteria manual. For
basins containing more than one land use, a weighted average runoff coefficient has been
computed.
Time of Concentration, Tc, is the sum of the overland travel time, to, and the channel or conduit
flow time, tt. Time of concentration is used to select the correct rainfall intensity for the rational
method equation.
T c t i t t
where: Tc = Time of Concentration (min),
to = Overland Travel Time (min),
tt = Channel or Conduit flow time (min).
Overland Travel Time, to, is computed using the frequency adjusted runoff coefficient and is
applicable to all design storm intervals.
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Appendix A
( ) 3
1
1 . 8 ( 1 . 1 ) 0 . 5
S
t CC f L
o
Where:
to = Overland Travel Time (min)
C5 = The Rational Method runoff coefficient for the 5 – year storm
L = Length of overland flow (ft), Maximum = 400 feet.
S = Average basin slope (%)
Channel or Conduit Travel Time, tt, is determined from the velocity of flow computed for the
hydraulic properties of the channel, ditch, gutter, pipe or sewer. For the purposes of this report,
the following equation was used:
V
tt 60 L *
Where:
tt = Channel or Conduit Travel Time (min)
L = Length of channel or conduit flow (ft)
V = Velocity of flow (fps), determined from Figure 3-2
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Appendix A
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
City of Fort Collins
IDF Curves
Duration 2-yr 10-yr 100-yr
5 2.85 4.87 9.95
6 2.67 4.56 9.31
7 2.52 4.31 8.80
8 2.40 4.10 8.38
9 2.30 3.93 8.03
10 2.21 3.78 7.72
11 2.13 3.63 7.42
12 2.05 3.50 7.16
13 1.98 3.39 6.92
14 1.92 3.29 6.71
15 1.87 3.19 6.52
16 1.81 3.08 6.30
17 1.75 2.99 6.10
18 1.70 2.90 5.92
19 1.65 2.82 5.75
20 1.61 2.74 5.60
21 1.56 2.67 5.46
22 1.53 2.61 5.32
23 1.49 2.55 5.20
24 1.46 2.49 5.09
25 1.43 2.44 4.98
26 1.40 2.39 4.87
27 1.37 2.34 4.78
28 1.34 2.29 4.69
29 1.32 2.25 4.60
30 1.30 2.21 4.52
31 1.27 2.16 4.42
32 1.24 2.12 4.33
33 1.22 2.08 4.24
34 1.19 2.04 4.16
35 1.17 2.00 4.08
36 1.15 1.96 4.01
37 1.13 1.93 3.93
38 1.11 1.89 3.87
39 1.09 1.86 3.80
40 1.07 1.83 3.74
41 1.05 1.80 3.68
42 1.04 1.77 3.62
43 1.02 1.74 3.56
44 1.01 1.72 3.51
45 0.99 1.69 3.46
46 0.98 1.67 3.41
47 0.96 1.64 3.36
48 0.95 1.62 3.31
49 0.94 1.60 3.27
50 0.92 1.58 3.23
51 0.91 1.56 3.18
52 0.90 1.54 3.14
53 0.89 1.52 3.10
54 0.88 1.50 3.07
55 0.87 1.48 3.03
56 0.86 1.47 2.99
57 0.85 1.45 2.96
58 0.84 1.43 2.92
59 0.83 1.42 2.89
60 0.82 1.40 2.86
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
From the Town of Timnath Design Criteria Manual and Construction Specifications
y = 2.5665e-0.021x
R² = 0.9633
y = 26.332x-0.53
R² = 0.9879
0.00
2.00
4.00
6.00
8.00
10.00
12.00
010203040506070
Rainfall Intensity (in/hr)
Storm Duration (min)
City of Fort Collins IDF Curves
2-yr
10-yr
100-yr
Expon. (2-yr)
Power (100-yr)
Appendix A
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
City of Fort Collins
Rational Method Runoff Coefficients
Lawn, Heavy, <2% Slope 0.20
Lawn, Heavy, >7% Slope 0.35
Lawn, Heavy, 2-7% Slope 0.25
Lawn, Sandy, <2% Slope 0.10
Lawn, Sandy, >7% Slope 0.20
Lawn, Sandy, 2-7% Slope 0.15
Roofs 0.95
Streets: Permeable Pavers 0.30
Streets: Gravel 0.50
Streets: Paved 0.95
From Table 3-3 of the City of Fort Collins, Stormwater Criteria
Runoff
Coefficient
Appendix A
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
C2 C10 C100
Streets: Paved 0.057 0.95
Streets: Permeable Pavers 0.022 0.30
Lawn, Heavy, <2% Slope 0.000 0.20
Roofs 0.000 0.95
Streets: Paved 0.023 0.95
Streets: Permeable Pavers 0.000 0.30
Lawn, Heavy, <2% Slope 0.040 0.20
Roofs 0.033 0.95
Streets: Paved 0.016 0.95
Lawn, Heavy, <2% Slope 0.048 0.20
Roofs 0.036 0.95
Total 0.28 Total % Imp. 59.7%
Streets: Paved 0.024 0.95
Lawn, Heavy, <2% Slope 0.197 0.20
Roofs 0.055 0.95
Rational Method Frequency Adjustment Factors
Min year Max year Frequency Factor, Cf
210 1
11 25 1.1
26 50 1.2
51 100 1.25
From Table 3-4 in the City of Fort Collins, SDDCCS
Frequency Adjusted Runoff Coefficients (C*Cf)
0.59
Basin Composite Runoff Coefficients
Basin/ Sub-
Basin Area (ac) Attribute
Attribute
Area (ac)
Runoff
Coefficient, C
Percent
Impervious Composite C
0.41
Table A-1
0.79
A 0.08 0.96
0.52
C 0.10 51.6%
0.77
0.64
0.59 0.59 0.73
EX 0.28 28.5% 0.41 0.41
B 0.10 58.1% 0.64 0.64
72.1% 0.77 0.77
Appendix A
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Overland Flow Average Channelized Channel Channel Channelized
Length, D Overland Slope Tov Tov Tov Flow Length Slope Velocity Time (Tt)
(ft) (%) 2-year 10-year 100-year (ft) (%) (ft/s) (min) 2-year 10-year 100-year
A 0.77 0.77 0.96 45 1 4 4 2 48 0.5 1.4 0.6 5 5 5
B 0.64 0.64 0.79 35 1 5 5 3 115 0.5 1.4 1.4 6 6 5
C 0.59 0.59 0.73 25 1 5 5 3 130 0.8 1.7 1.3 6 6 5
Basin
Table A-2
Basin Time of Concentration
Frequency Adj. Runoff Coefficients (C*Cf)
C2 C
10 C100
Overland Travel Time Time of Concentration
Tc = Tov + Tt (min)
Appendix A
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
2 - year 10 - year 100 - year 2 - year 10 - year 100 - year 2 - Year 10 - Year 100 - Year 2 - Year 10 - Year 100 - Year
A 0.08 0.77 0.77 0.96 5 5 5 2.85 4.87 9.95 0.2 0.3 0.8
B 0.10 0.64 0.64 0.79 6 6 5 2.67 4.56 9.95 0.2 0.3 0.8
C 0.10 0.59 0.59 0.73 6 6 5 2.67 4.56 9.95 0.2 0.3 0.7
Total 0.5 0.8 2.2
Time of Concentration, Tc (min)
Table A-3
Basin Peak Discharge
Basin Rainfall Intensity (in/hr) Peak Discharge (cfs)
Basin Area
(ac)
Frequency Adj. Runoff Coefficients
Appendix A
APPENDIX B
Channel Design
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Channel ID 100-yr Design
Flow (cfs) Slope (%)
Bottom Width
(ft)
Side Slope
(H:V)
Flow Depth
(ft)
Max Velocity
(fps)
Protection
Required?
A-A* 0.80 0.50% 0 6.7 0.30 2.71 no
B-B* 1.60 0.93% 0 6.7 0.34 4.07 no
C-C* 1.60 0.50% 0 6.7 0.39 3.23 no
D-D** 0.70 0.80% 0 3 0.29 2.74 no
SOUTH SIDEWALK CHASE 1.60 4.00% 2 vertical 0.14 5.67 no
NORTH SIDEWALK CHASE 0.70 5.00% 2 vertical 0.08 4.47 no
**Swale D is a 2 foot trickle pan.
Table B-1
Channel Summary
*Swale A, B and C are 2 foot gutter sections.
Appendix D
Project Description
Solve For Spread
Input Data
Channel Slope 0.00500 ft/ft
Discharge 0.80 ft³/s
Gutter Width 2.00 ft
Gutter Cross Slope 0.15 ft/ft
Road Cross Slope 0.15 ft/ft
Roughness Coefficient 0.013
Results
Spread 1.98 ft
Flow Area 0.29 ft²
Depth 0.30 ft
Gutter Depression 0.00 ft
Velocity 2.71 ft/s
Worksheet for Peterson Gutter Flow A-A
12/16/2015 8:48:29 AM
Bentley Systems, Inc. Haestad Methods Solution Bentley Center FlowMaster V8i (SELECTseries 1) [08.11.01.03]
27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 1 of 1
Project Description
Solve For Spread
Input Data
Channel Slope 0.00930 ft/ft
Discharge 1.60 ft³/s
Gutter Width 2.00 ft
Gutter Cross Slope 0.15 ft/ft
Road Cross Slope 0.15 ft/ft
Roughness Coefficient 0.013
Results
Spread 2.29 ft
Flow Area 0.39 ft²
Depth 0.34 ft
Gutter Depression 0.00 ft
Velocity 4.07 ft/s
Worksheet for Peterson Gutter Flow B-B
12/16/2015 8:47:58 AM
Bentley Systems, Inc. Haestad Methods Solution Bentley Center FlowMaster V8i (SELECTseries 1) [08.11.01.03]
27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 1 of 1
Project Description
Solve For Spread
Input Data
Channel Slope 0.00500 ft/ft
Discharge 1.60 ft³/s
Gutter Width 2.00 ft
Gutter Cross Slope 0.15 ft/ft
Road Cross Slope 0.15 ft/ft
Roughness Coefficient 0.013
Results
Spread 2.57 ft
Flow Area 0.50 ft²
Depth 0.39 ft
Gutter Depression 0.00 ft
Velocity 3.23 ft/s
Worksheet for Peterson Gutter Flow C-C
12/16/2015 8:47:38 AM
Bentley Systems, Inc. Haestad Methods Solution Bentley Center FlowMaster V8i (SELECTseries 1) [08.11.01.03]
27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 1 of 1
Project Description
Friction Method Manning Formula
Solve For Normal Depth
Input Data
Roughness Coefficient 0.013
Channel Slope 0.00800 ft/ft
Left Side Slope 3.00 ft/ft (H:V)
Right Side Slope 3.00 ft/ft (H:V)
Discharge 0.70 ft³/s
Results
Normal Depth 0.29 ft
Flow Area 0.26 ft²
Wetted Perimeter 1.85 ft
Hydraulic Radius 0.14 ft
Top Width 1.75 ft
Critical Depth 0.32 ft
Critical Slope 0.00486 ft/ft
Velocity 2.74 ft/s
Velocity Head 0.12 ft
Specific Energy 0.41 ft
Froude Number 1.26
Flow Type Supercritical
GVF Input Data
Downstream Depth 0.00 ft
Length 0.00 ft
Number Of Steps 0
GVF Output Data
Upstream Depth 0.00 ft
Profile Description
Profile Headloss 0.00 ft
Downstream Velocity Infinity ft/s
Upstream Velocity Infinity ft/s
Normal Depth 0.29 ft
Critical Depth 0.32 ft
Channel Slope 0.00800 ft/ft
Critical Slope 0.00486 ft/ft
Worksheet for Peterson Concrete Swale D-D
5/18/2016 3:01:13 PM
Bentley Systems, Inc. Haestad Methods Solution Bentley Center FlowMaster V8i (SELECTseries 1) [08.11.01.03]
27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 1 of 1
Project Description
Friction Method Manning Formula
Solve For Normal Depth
Input Data
Roughness Coefficient 0.013
Channel Slope 0.04000 ft/ft
Bottom Width 2.00 ft
Discharge 1.60 ft³/s
Results
Normal Depth 0.14 ft
Flow Area 0.28 ft²
Wetted Perimeter 2.28 ft
Hydraulic Radius 0.12 ft
Top Width 2.00 ft
Critical Depth 0.27 ft
Critical Slope 0.00524 ft/ft
Velocity 5.67 ft/s
Velocity Head 0.50 ft
Specific Energy 0.64 ft
Froude Number 2.66
Flow Type Supercritical
GVF Input Data
Downstream Depth 0.00 ft
Length 0.00 ft
Number Of Steps 0
GVF Output Data
Upstream Depth 0.00 ft
Profile Description
Profile Headloss 0.00 ft
Downstream Velocity Infinity ft/s
Upstream Velocity Infinity ft/s
Normal Depth 0.14 ft
Critical Depth 0.27 ft
Channel Slope 0.04000 ft/ft
Critical Slope 0.00524 ft/ft
Worksheet for Peterson South Sidewalk Chase
5/18/2016 2:55:15 PM
Bentley Systems, Inc. Haestad Methods Solution Bentley Center FlowMaster V8i (SELECTseries 1) [08.11.01.03]
27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 1 of 1
Project Description
Friction Method Manning Formula
Solve For Normal Depth
Input Data
Roughness Coefficient 0.013
Channel Slope 0.05000 ft/ft
Bottom Width 2.00 ft
Discharge 0.70 ft³/s
Results
Normal Depth 0.08 ft
Flow Area 0.16 ft²
Wetted Perimeter 2.16 ft
Hydraulic Radius 0.07 ft
Top Width 2.00 ft
Critical Depth 0.16 ft
Critical Slope 0.00555 ft/ft
Velocity 4.47 ft/s
Velocity Head 0.31 ft
Specific Energy 0.39 ft
Froude Number 2.81
Flow Type Supercritical
GVF Input Data
Downstream Depth 0.00 ft
Length 0.00 ft
Number Of Steps 0
GVF Output Data
Upstream Depth 0.00 ft
Profile Description
Profile Headloss 0.00 ft
Downstream Velocity Infinity ft/s
Upstream Velocity Infinity ft/s
Normal Depth 0.08 ft
Critical Depth 0.16 ft
Channel Slope 0.05000 ft/ft
Critical Slope 0.00555 ft/ft
Worksheet for Peterson Nouth Sidewalk Chase
5/18/2016 3:00:15 PM
Bentley Systems, Inc. Haestad Methods Solution Bentley Center FlowMaster V8i (SELECTseries 1) [08.11.01.03]
27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 1 of 1
APPENDIX C
Water Quality Capture Volume
Calculating the WQCV and Volume Reduction Chapter 3
3-6 Urban Drainage and Flood Control District August 2011
Urban Storm Drainage Criteria Manual Volume 3
Once the WQCV in watershed inches is found from Figure 3-2 or using Equation 3-1 and/or 3-2, the
required BMP storage volume in acre-feet can be calculated as follows:
𝑉 = �
WQCV
12
� 𝐴 Equation 3-3
Where:
V = required storage volume (acre-ft)
A = tributary catchment area upstream (acres)
WQCV = Water Quality Capture Volume (watershed inches)
Figure 3-2. Water Quality Capture Volume (WQCV) Based on BMP Drain Time
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
% Imperviousness 59.74%
WQCV (inches)* 0.17 inches
Volume = (WQCV/12)xA 0.0039 ac-ft
*WQCV in 12-hr drain time
from Figure 3-2. Water Quality Capture Volume (WQCV) Based on BMP Drain Time
UDFCD Storm Drainage Criteria Manual Volume 3
Table C-1
Water Quality Capture Volume (WQCV)
Appendix C
APPENDIX D
Low Impact Development
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Low Impact Development (LID)
Table D-1
Volume 3, Chapter 3, Section 3.1 Low Impact Development Criteria
Basin Proposed Impervious
Area (acres) Overall Area (acres)
Impervious Area
routed to LID (acres) LID Technique to be Applied
A 0.057 0.079 0.079 Permeable Pavers
B 0.040 0.096 0.000 None
C 0.037 0.100 0.000 None
Total 0.134 0.275 0.079 59.05%
No less than 50% of any newly added impervious area must be treated using one or a combination of LID techniques
Appendix D
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Table D-2
Volume 3, Chapter 3, Section 3.1 Low Impact Development Criteria
Basin Newly Added
Pavement Area (acres)
Permeable Pavement
Area (acres)
% of Permeable
Pavement
A 0.079 0.022 27.85%
B 0.000 0.000 0.00%
C 0.000 0.000 0.00%
Total 0.079 0.022 27.85%
No less than 25% of any newly added pavement areas must be treated using a permeable pavement
technology that is considered an LID technique
Appendix D
625 Peterson Street Redevelopment PDP Preliminary Drainage Report
Table D-3
Permeable Pavement Reservoirs
Sloped Installations
V = P[(D-6sL-1)/12]A
Basin Slope of Permeable
Pavement (ft/ft)
Length Between
Lateral Flow Barriers
(ft)
Permeable Pavement
Area (ft2)
Volume Available in Reservoir
(ft3)
Length Between
Lateral Flow
Barriers (ft)
A 0.0165 18.5 960 293 18.5
Total (ft
3
) 293
Total (acre-ft) 0.007
where
P (porosity) ~ 0.4
D (depth in inches) = 12
s (slope in ft/ft) varies, see table
L (Length between flow
barriers) varies, see table
A (Area in ft
2
) varies, see table
UDFCD Design Procedure Form for Permeable
Pavement Systems (PPS)
Appendix D
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Type of Permeable Pavement Section
A) What type of section of permeable pavement is used?
(Based on the land use and activities, proximity to adjacent
structures and soil characteristics.)
B) What type of wearing course?
2. Required Storage Volume
A) Effective Imperviousness of Area Tributary to Permeable Pavement, Ia I
a = 72.1 %
B) Tributary Area's Imperviousness Ratio (I = Ia / 100) i = 0.721
C) Tributary Watershed Area ATotal
= 3,445 sq ft
(including area of permeable pavement system)
D) Area of Permeable Pavement System APPS
= 960 sq ft
(Minimum recommended permeable pavement area = 913 sq ft)
E) Impervious Tributary Ratio RT
= 1.9
(Contributing Imperviuos Area / Permeable Pavement Ratio)
F) Water Quality Capture Volume (WQCV) Based on 12-hour Drain Time WQCV = 65 cu ft
(WQCV = (0.8 * (0.91 * i
3
- 1.19 * i
2
+ 0.78 * i) / 12) * Area)
G) Is flood control volume being added?
H) Total Volume Needed VTotal
= cu ft
3. Depth of Reservoir
A) Minimum Depth of Reservoir Dmin
= 12.0 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 = 0.40
D) Slope of the Base Course/Subgrade Interface S = 0.017 ft / ft
E) Length Between Lateral Flow Barriers (max = 20.65 ft.) L = 18.5 ft
F) Volume Provided Based on Depth of Base Course V = 293 cu ft
Flat or Stepped: V = P * ((Dmin-1)/12) * Area
Sloped: V = P * [(Dmin - (D
min - 6*SL-1)) / 12] * Area Volume assumes uniform slope & lateral flow barrier spacing.
Calculate the volume of each cell individually when this varies.
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.)
625 Peterson Redevelopment
Basin A
Design Procedure Form: Permeable Pavement Systems (PPS)
Jon Sweet
TST, Inc. Consulting Engineers
December 16, 2015
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
6. Filter Material and Underdrain System
A) Is the underdrain placed below a 6-inch thick layer of
CDOT Class C filter material?
B) Diameter of Slotted Pipe (slot dimensions per Table PPs-2)
C) Distance from the Lowest Elevation of the Storage Volume y = 0.2 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
= 3.88 inches
(Elevation of the Flood Control Outlet)
B) Diameter of Orifice for 12-hour Drain Time DOrifice
= 0.30 inches
(Use a minimum orifice diameter of 3/8-inches)
Notes:
625 Peterson Redevelopment
Design Procedure Form: Permeable Pavement Systems (PPS)
Jon Sweet
TST, Inc. Consulting Engineers
December 16, 2015
Basin A
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
LID BASIN A.xlsm, PPS 12/16/2015, 9:22 AM
760 Whalers Way Bldg C, Suite 200 Fort Collins, CO 80525 ideas@tstinc.com
970.226.0557 main 303.595.9103 metro 970.226.0204 fax www.tstinc.com
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
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
LID BASIN A.xlsm, PPS 12/16/2015, 9:22 AM
From the City of Fort Collins Storm Drainage Design Criteria and Construction Standards
Appendix A
DQG
WKUHHGXDOFODVVHV $'%'DQG&'
7KHJURXSVDUHGHILQHGDVIROORZV
*URXS$6RLOVKDYLQJDKLJKLQILOWUDWLRQUDWH ORZUXQRIISRWHQWLDO
ZKHQWKRURXJKO\
ZHW7KHVHFRQVLVWPDLQO\RIGHHSZHOOGUDLQHGWRH[FHVVLYHO\GUDLQHGVDQGVRU
JUDYHOO\VDQGV7KHVHVRLOVKDYHDKLJKUDWHRIZDWHUWUDQVPLVVLRQ
*URXS%6RLOVKDYLQJDPRGHUDWHLQILOWUDWLRQUDWHZKHQWKRURXJKO\ZHW7KHVH
FRQVLVWFKLHIO\RIPRGHUDWHO\GHHSRUGHHSPRGHUDWHO\ZHOOGUDLQHGRUZHOOGUDLQHG
VRLOVWKDWKDYHPRGHUDWHO\ILQHWH[WXUHWRPRGHUDWHO\FRDUVHWH[WXUH7KHVHVRLOV
KDYHDPRGHUDWHUDWHRIZDWHUWUDQVPLVVLRQ
*URXS&6RLOVKDYLQJDVORZLQILOWUDWLRQUDWHZKHQWKRURXJKO\ZHW7KHVHFRQVLVW
FKLHIO\RIVRLOVKDYLQJDOD\HUWKDWLPSHGHVWKHGRZQZDUGPRYHPHQWRIZDWHURU
VRLOVRIPRGHUDWHO\ILQHWH[WXUHRUILQHWH[WXUH7KHVHVRLOVKDYHDVORZUDWHRIZDWHU
WUDQVPLVVLRQ
*URXS'6RLOVKDYLQJDYHU\VORZLQILOWUDWLRQUDWH KLJKUXQRIISRWHQWLDO
ZKHQ
WKRURXJKO\ZHW7KHVHFRQVLVWFKLHIO\RIFOD\VWKDWKDYHDKLJKVKULQNVZHOO
SRWHQWLDOVRLOVWKDWKDYHDKLJKZDWHUWDEOHVRLOVWKDWKDYHDFOD\SDQRUFOD\OD\HU
DWRUQHDUWKHVXUIDFHDQGVRLOVWKDWDUHVKDOORZRYHUQHDUO\LPSHUYLRXVPDWHULDO
7KHVHVRLOVKDYHDYHU\VORZUDWHRIZDWHUWUDQVPLVVLRQ
,IDVRLOLVDVVLJQHGWRDGXDOK\GURORJLFJURXS $'%'RU&'
WKHILUVWOHWWHULV
IRUGUDLQHGDUHDVDQGWKHVHFRQGLVIRUXQGUDLQHGDUHDV2QO\WKHVRLOVWKDWLQWKHLU
QDWXUDOFRQGLWLRQDUHLQJURXS'DUHDVVLJQHGWRGXDOFODVVHV
5DWLQJ2SWLRQV
$JJUHJDWLRQ0HWKRG 'RPLQDQW&RQGLWLRQ
&RPSRQHQW3HUFHQW&XWRII 1RQH6SHFLILHG
+\GURORJLF6RLO*URXS²/DULPHU&RXQW\$UHD&RORUDGR 3HWHUVRQ6WUHHW
1DWXUDO5HVRXUFHV
&RQVHUYDWLRQ6HUYLFH
:HE6RLO6XUYH\
1DWLRQDO&RRSHUDWLYH6RLO6XUYH\
3DJHRI
OLVWHGEHORZ
6RLO6XUYH\$UHD /DULPHU&RXQW\$UHD&RORUDGR
6XUYH\$UHD'DWD 9HUVLRQ6HS
6RLOPDSXQLWVDUHODEHOHG DVVSDFHDOORZV
IRUPDSVFDOHV
RUODUJHU
'DWH V
DHULDOLPDJHVZHUHSKRWRJUDSKHG $SU²$SU
7KHRUWKRSKRWRRURWKHUEDVHPDSRQZKLFKWKHVRLOOLQHVZHUH
FRPSLOHGDQGGLJLWL]HGSUREDEO\GLIIHUVIURPWKHEDFNJURXQG
LPDJHU\GLVSOD\HGRQWKHVHPDSV$VDUHVXOWVRPHPLQRUVKLIWLQJ
RIPDSXQLWERXQGDULHVPD\EHHYLGHQW
+\GURORJLF6RLO*URXS²/DULPHU&RXQW\$UHD&RORUDGR
3HWHUVRQ6WUHHW
1DWXUDO5HVRXUFHV
&RQVHUYDWLRQ6HUYLFH
:HE6RLO6XUYH\
1DWLRQDO&RRSHUDWLYH6RLO6XUYH\
3DJHRI
VKHHW