HomeMy WebLinkAboutDrainage Reports - 03/28/2016City of F Collins Approv Plans
Approved by
Date: 3 ze 201(o
FINAL DRAINAGE AND EROSION
CONTROL REPORT
FOR
RAW URTH DESIGNS
(LOT 20, BLOCK 3,
EVERGREEN REPLAT 1)
FINAL DRAINAGE AND EROSION
CONTROL REPORT
RAW URTH DESIGNS
(LOT 20, BLOCK 3,
EVERGREEN REPLAT 1)
Prepared for:
Raw Urth Designs
P.O. Box 369
Bellvue, CO 80537
Prepared by:
North Star Design
700 Automation Drive, Unit I j
Windsor, Colorado 80550
(970)686-6939
February 22, 2016
Job Nwnber 264-10
North Star
Aftw design
700 Automation Drive, Unit I
Windsor, CO 80550
Phone:970-686-6939
Fax:970-686-1188
February 22, 2016
Dan Mogen
City of Fort Collins Stormwater
700 Wood Street
Fort Collins, CO 80522-0580
RE' Final Drainage and Erosion Control Report for Raw Urth.Designs
Dear Dan,
I am pleased to submit for your review and approval, this Final Drainage and Erosion Control
.Report for Raw Urth Designs (Lot 20, Block 3, Evergreen Replat 1). I certify that this report for
the drainage design was prepared in accordance with the criteria in the City of Fort Collins
Storm Drainage Manual.
I appreciate your time and consideration in reviewing this submittal. Please call if you have any
questions.
Sincerely, ... 0,....
:r o?
�a 31306
Patricia Kroetch, P.E.
ii
TABLE OF CONTENTS
TABLE OF CONTENTS .....................................
1. GENERAL LOCATION AND DESCRIPTION
1.1 Location...................................................................................................................1
1.2 Description of Property ............................................................................................I
2. DRAINAGE BASINS AND SUB -BASINS
2.1 Major Basin Description..........................................................................................1
2.2 Sub -Basin Description.............................................................................................I
3. DRAINAGE DESIGN CRITERIA
3.1 Regulations .....
............. :........................................................................................... 2
3.2 Development Criteria Reference and Constraints...................................................2
3.3 Hydrologic Criteria..................................................................................................2
3.4 Hydraulic Criteria................................................................:...................................3
4. DRAINAGE FACILITY DESIGN
4.1 General Concept......................................................................................................3
4.2 Specific Flow Routing.............................................................................................3
4.3 Drainage Summary ..................................................................................................5
5. STORMWATER MANAGEMENT CONTROLS
5.1 Written Analysis.....................................................................................................6
5.2 SWMP Contact Information...................................................................................7
5.3 Identification and location of all potential pollution sources..................................8
5.4 Best Management Practices (BMP's) for Stormwater Pollution Prevention ........... 8
5.5 BMP Implementation.............................................................................................10
6. CONCLUSIONS
6.1 Compliance with Standards..................................................................................13
6.2 Drainage Concept..................................................................................................13
7. REFERENCES..................................................................................................................14
APPENDICES
A Vicinity Map
B Hydrologic Computations
C Detention Pond Sizing Calculations
D BMP Schedule and Cost Estimate
E Figures and Tables
nl
1. GENERAL LOCATION AND DESCRIPTION
1.1 Location
This site is located on the north side of Conifer Street, west of Red Cedar Circle and east
of the existing alley in the Northwest Quarter of Section 1, Township 7 North, Range 69
West of the Sixth Principal Meridian, in the City of Fort Collins, Larimer County,
Colorado. See the Vicinity Map in Appendix A of this report.
This project is bounded on the north by an existing building, on the east by existing Red
Cedar Circle, on the west by a paved alley, and on the south by existing Conifer Street.
1.2 Description of Property
The entire project consists of approximately 0.9 acres. The site is currently undeveloped,
with areas of existing volunteer weeds and grasses. The existing site is flat with existing
slope to the southeast at approximately 0.5% to 1%. The site currently drains into the
adjacent streets and alley.
Proposed development on -site will include one building, a private drive along the north
side of the building, a parking lot and sidewalks. Existing drainage patterns will be
altered to direct flow to a proposed detention pond in the southeast comer of the site
which will release into the existing storm system in this location.
2. DRAINAGE BASINS AND SUB -BASINS
2.1 Major Basin Description
The proposed development lies within the Dry Creek Drainage Basin. Stormwater
detention is required for this basin but water quality extended detention is not required
because it is provided in the North East College Corridor Outfall (NECCO) detention
pond. The City requirement for stormwater detention in the Dry Creek basin is a single -
stage detention with a 100-year release rate of 0.2 cfs per acre.
1
2.2 Sub -basin Description
Runoff from this site currently flows to the existing streets and alley. From there, the
runoff enters an existing inlet near the intersection of Red Cedar and Conifer. With the
proposed drainage concept for this site, the runoff from the site will flow to a proposed
detention pond and be released at the rate of 0.2 cfs per acre into the storm system near
the intersection of Red Cedar and Conifer.
3. DRAINAGE DESIGN CRITERIA
3.1 Regulations
This report was prepared to meet or exceed the "City of Fort Collins Storm Drainage
Design Criteria Manual' specifications except where variances are requested as noted in
Section 4.2 of this report. Where applicable, the criteria established in the "Urban Storm
Drainage Criteria Manual' (UDFCD), 2001, developed by the Denver Regional Council
of Governments, has been used.
3.2 Development Criteria Reference and Constraints
The runoff from this site has been routed to conform to the requirements of the Dry
Creek Drainage Basin and the City of Fort Collins Stormwater Department. Both
stormwater runoff detention and water quality extended detention are required for this
site with on -site detention and offsite water quality. The release rate from the site will be
0.2 cfs per acre.
3.3 Hydrologic Criteria
Runoff computations were prepared for the 10-year minor and 100-year major storm
frequencies utilizing the rational method. All hydrologic calculations associated with the
basins are included in Appendix B of this report. Standard Form 8 (SF-8) provides time
of concentration calculations for all sub -basins.
Detention volume was calculated using the predetermined release rate of 0.2 cfs per acre.
The FAA method for detention pond sizing was utilized to determine the required
volume. Refer to the detention calculations included in Appendix C of this report.,
2
3.4 Hydraulic Criteria
Hydraulic elements have been designed per City of Fort Collins standards to adequately
convey the 100-year storm; runoff from this site to the proposed detention pond. A
proposed 12" storm pipe will convey the detained runoff from the site to the existing
manhole at the southeast comer of the site.
4. DRAINAGE FACILITY DESIGN
4.1 General Concept
The runoff from this site will flow into the drive aisle and parking lot which will be
constructed using conventional materials (asphalt or concrete) and permeable
interlocking pavers. The runoff from the site will either flow on the surface or enter a
storm pipe via the permeable interlocking pavers or inlet. In a situation where the
permeable interlocking pavements are clogged, the runoff will flow on the surface and
enter the detention pond through a metal sidewalk culvert. On -site runoff will also be
conveyed to the detention pond via flows in LID swales along the north property
boundary to an area inlet and storm pipe. The detained runoff will discharge into the
existing storm pipe located at the southeast corner of the site.
4.2 Specific Flow Routing
With this design, the site has been broken into 3 basins which correspond with the LID
feature that the basin flows to. The basin are described in the following paragraphs.
Basin 1 is located in the northmost portion of the site and contains a majority of the
private drive and LID feature #1 which is an LID swale with an underdrain. The runoff
from the paved area will flow to the swale and will be collected in an area inlet. The
storm pipe then conveys the flows to the south into the detention pond.
Basin 2 is located in the eastmost portion of the site and contains a portion of the paved
private drive and the parking lot which is surfaced with porous pavers.. The runoff from
this basin flows to a low point in the private drive then south into the parking lot porous
pavers. The flow, if it exceeds the capacity of the pavers, will flow into the detention
pond via a metal sidewalk culvert.
0
Basin 3 is located in the southwest portion of the site and contains the building and the
detention pond (landscape area). The roof of the storage building is sloped to drain to the
south and the bottom of the detention area is sloped to drain east. This basin accepts
runoff from Basins 1_ and 2. The detained runoff will enter the existing storm system via
a new storm pipe with an orifice to restrict flows to 0.2cfs per acre.
Basin OS is the site area that drains to the street undetained. A majority of the area that
is draining to the street is a narrow landscape strip located between the detention pond
wall and the sidewalk. The impervious area is a portion of the drive entry (approximately
300 square feet) that drains to Red Cedar. The amount of runoff is quantified as 0.0 cfs in
the minor storm and 0.1 cfs in the 100 year storm event.
Drainage design for this site has been designed to convey on -site runoff to the proposed
detention pond and incorporate the required LID enhancement features. On -site runoff
will be conveyed to the detention pond via surface flow in the drive aisles, in the LID
swale and subsurface in the perforated pipes. The detention pond will release the
detained runoff from the site at the rate of 0.2 cfs per acre. The developed 2-year runoff
rate for this site is 1.3 cfs and the developed 100-year runoff rate is 6.2 cfs.
4.3 Drainage Summary
This site has been designed to meet or exceed the "City of Fort Collins Stone Drainage
Design Criteria Manual' specifications. The proposed drainage design for this site has
been designed to convey on -site runoff to the detention pond while minimizing future
maintenance. The site incorporates a LID (Low Impact Development) treatment areas
including an LID swale without underdrain along the north property line, and permeable
interlocking pavers in the parking lot. Refer to the end of Appendix D for a table
indicating the size of the LID treatment area and the area of the site that drains to that
LID treatment area.
All drainage facilities proposed with this project, including the detention pond, LID
features, porous pavers and outlet structure are private and will be owned and maintained
by the property owner.
4
5. STORMWATER MANAGEMENT CONTROLS
5.1 Written Analysis
The soils on this site are classified by the USGS Soil Survey as Nunn Clay Loam and are
classified in the hydrologic group C. The soils are described as having a slow runoff rate
and the hazard of water erosion is moderate and the.hazard of wind erosion is moderate.
The site is surrounded by developed sites including streets and paved areas. The
construction shall utilize silt fence around the perimeter to control sediment transport
from rainfall and from wind. The silt fence that is located in the proposed pavement areas
will be removed prior to placing new pavement. Rock socks will be utilized in the
existing curb and the newly constructed swales to capture sediments that are not fully
contained by the silt fence placement. The locations of the rock socks will be in the areas
of concentrated flow such as in the existing curb, at the new swales and as needed.
The site will also utilize a vehicle tracking control pad to minimize sediment from being
tracked onto adjacent pavements. Sediment that is tracked will be removed and placed
within the site or permanently disposed of offsite. A concrete washout will be used on
site during the concrete placement. All hardened concrete will be disposed of offsite.
These BMP's have not been located on the site map due to the fact that the site is very
small and these BMP's will need to be placed by the contractor in locations that are most
beneficial and will minimize disruption of adjacent traffic.
Permanent erosion control consists of covering the soils with a building, concrete walks,
concrete drives and sod. No soil will be left exposed to erosion after the construction is
complete. Refer to the landscape plan for areas of and instructions for placement of sod
and soil amendments required prior to placement of sod.
5
Refer to Appendix D for the timing of the construction phases and the sequential
installation of all BMP phasing for this site.
Refer to the Appendix D for the Erosion Control Surety calculations.
5.2 SWMP contact information
Permit holder:
Name:
Address:
Phone Number:
Email Address:
Appointed agent:
Name:
Address:
Phone Number:
Email Address:
6
5.3 Identification and location of all notential nolh,tion sn,rrces
Potenha Pollutant Source Activr
fi�[z,
sPotential Pollutant Generated
�v t 5`tr
.B..'ER-
A hcable to,
,�thispib�ect
Disturbed Areas
Sediment
X
Soil stockpiles
Sediment
X
Travel to adjacent public streets
Tracked sediment
X
Contaminated soils
Sediment, chemicals
Loading and unloading chemicals
Chemicals
Unloading of building materials
Trash, debris
X
Outdoor storage of chemicals
Chemicals
On site equipment maintenance
Oil, grease
On site equipment fueling
Diesel, gasoline
X
Dust generating activities
Particulates, sediment
X
Use of fertilizer, pesticides, herbicides
Fertilizer, pesticides
Use of detergents, solvents, oils
Detergents, solvents, oil
X
Waste dumpsters, waste piles
Chemicals, trash, debris
X
Concrete washout
Concrete, sediment, wash water
X
On site equipment washing
Detergents, oil
On site asphalt batch plant
Asphaltic cement, sediment
On site concrete batch plant
Cement, sediment
Portable toilets
Domestic sewage
X
5.4 Best Management Practices (BMP's) for Stormwater Pollution Prevention
Structural Practices for Erosion and Sediment Control
Structural practices for the site will consist mainly of silt fence and rock sock filters and are
described in detail in the following paragraphs. These BMP's are expected to change as the
construction progresses and it is the responsibility of the contractor to ensure appropriate BMP's
are in place and/or removed at the appropriate time in the construction sequence. All temporary
and permanent erosion and sediment control practices must be maintained and repaired as
needed to assure continued performance of their intended function.
Silt fence and rock sock filters shall be in place prior to commencement of construction
activities. During clearing and grubbing necessary for silt fence installation, all cleared material
shall be placed on the uphill side so that if erosion occurs from the cleared material, the sediment
will be trapped and not transported downstream. Rock socks shall be implemented in the existing
curb line as shown on the Drainage & Erosion Control Plan.
7
All BMP's shall be installed per the details shown on the construction plan set.
Temporary & Permanent Structural BMP's:
7 S It
4 Sttvctural BM A w _
"• � � (ay.S � ag.�=��':;�T,,Approximate
fan 1 location • x�
on'
A Itcable to thts'S"
Silt Fence
Site perimeter, refer to site map
X
Straw bale dams
Rock Socks
At sidewalk culverts, in swales, at new inlet,
in existing gutters, refer to site map
X
Earthen diversion dams
Vegetated swales
Sediment trap/pond
Pipe slope drains
Geogrid
Inlet/outlet protection
In the detention Pond
X
Culverts
Riprap
Erosion control mats
Inlet protection
Vehicle Tracking Control Pad
At site entrance, refer to site map
X
Concrete Washout
To be located by Contractor, near site entry
X
Non -Structural Practices for Erosion and Sediment Control:
Soils exposed during the earthwork phase and landscape prep phase shall be kept in a roughened
condition by ripping or disking along land contours until mulch, vegetation, or other permanent
erosion control is installed. No large amount of soils (in excess of 15 yards) will be allowed to be
stock piled on site. Overburden from the utility pipe trenching will be piled adjacent to trenches
upstream of sediment controls and will be replaced in the trenches within 72 hours.
Excess excavated materials from the demolition and grading phases of the project that cannot be
reused on site will be exported as it is excavated. This includes any asphalt pavement from the
existing site that is to be removed.
A vehicle tracking pad will be installed at a location most beneficial to the site construction as
determined by the contractor. Vehicles will not be permitted in the excavated area if soil is
muddy. Gravel sub base will be placed and compacted in the areas indicated for pavement
following excavation. In the current pre construction state the site enables tracking of silt onto
the adjacent streets during wet conditions. During construction activities the street will be
monitored for foreign debris tracked out of the site and mechanical sweeping and clean up will
be performed as needed.
8
No area shall remain exposed by land disturbing activity for more than thirty (30) days before
required temporary or permanent erosion control (e.g. seed/mulch, landscaping, etc.) is installed.
Temporary & Permanent non-structural BMW's:
Structural BMP
.s1 u
Approximate location ''»E
A ltcabl' to`tht$ `.
a PP
1Non ,_ e<
on site _
eci_ e fgp:
Surface roughening
Entire site
X
Soil stockpile height limit (less than
10')
Perimeter vegetative buffer
North boundary of site
X
Minimization of site disturbance
Mulch
Seed & mulch stockpiles after 30 days
Stockpile toe protection (silt fence,
wattles or ditch)
Preservation & protection of existing
vegetation & trees
North boundary of site
X
Good site housekeeping (routine
cleanup of trash & constr debris)
Entire Site
X
Sweeping & scraping of hardscape
areas
On and off site pavements
X
Heavy equip staged on site, properly
maintained & inspected daily (no
Staging area
X
onsite maintenance)
5.5 BMP Implementation
1) Phased BMP Implementation
BMP's are expected to change as the construction progresses and it is the responsibility of
the contractor to ensure appropriate BMP's are in place and/or removed at the appropriate
time in the construction sequence. A construction sequence schedule has been included on
the Drainage & Erosion Control Plan and included in the construction plans for this site.
All BMP's shall be inspected and repaired or replaced as required to satisfy the conditions of
the Stormwater Discharge Permit. All BMP's must be maintained and repaired as needed to
assure continued performance of their intended function. Refer to Appendix D for the BMP
schedule and estimated costs.
9
Niaterrals handlin and S
ill Prevention:
Mafenals Handlmg &Spill
Preventton BMPt*t°� tr#
�� , x„
APProxunate location on situ
A hcable to this
_,*
YYrM rr; < `
�,y
Portable toilets, anchored &
d3}W
located away from drainages
Contractor to determine
x
Fuel storage located in bulk tanks
with secondary containment &
spill kit
Mobile fueling performed at least
200 feet away from drainages &
Contractor to determine
x
fully attended
Fertilizers, form oil, solvents,
cleaners, detergent stored in 55 gal
or smaller containers, kept in
Contractor to determine
x
storage units
Dumpsters containing used
chemicals containers & liquid
Contractor to determine
x
wastes kept covered
Equipment cleaning (on site) uses
no detergents & flows to onsite
retention basin
In case of a release of fuel or other
chemicals, absorbent booms or
earthen berms will be immediately
constructed to contain the spill &
Location of spill
x
prevent runoff to adjacent surface
waters
MSDS sheets for onsite chemicals
will be kept at the construction
trailer to facilitate spill response &
Contractor to determine
x
cleanup
3) Dedicated Asphalt or Concrete Batch Plant:
Not proposed with this development
4) Vehicle Tracking Pad:
Vehicle tracking control pad shall be installed wherever construction vehicle access routes
intersect paved public roads. Vehicle tracking control pads shall be installed to minimize the
transport of sediment (mud) by runoff or vehicles tracking onto the paved surface. Any mud
tracked to public roads shall be removed on a daily basis and after any significant storm that
causes sediment to be transported. It is unlawful to track sediment/mud onto public streets
and may be enforced by the City of Fort Collins, by the State of Colorado or by the EPA.
10
5) Waste Management and Disposal:
Portable toilets will be anchored & periodically maintained by waste management company.
Dumpsters on site will be covered & periodically emptied by waste management company.
Concrete waste will be allowed to harden and then will be removed from site.
No washing activities will occur on site.
Location of the concrete washout is shown on the site map. The washout will be suitably
deep to accommodate all anticipated concrete truck wash water. Waste concrete will be
allowed to harden & be removed from site periodically as the washout reaches 50% of
capacity. Truck wash water will not be allowed to reach the curb & gutter or any other water
course.
6) Groundwater and Stormwater Dewatering:
No groundwater was encountered during soils exploration therefore ground water is not
anticipated to be an issue. If groundwater is encountered a groundwater discharge permit
shall be obtained and a detailed report shall be completed describing the location and the
route of where pumped groundwater will be conveyed and the measures taken to prevent the
transport of any pollutants to downstream waters.
7) Inspection & Maintenance:
_It is required that routine site inspections are performed to effectively address maintenance
and repair of Best Management Practices (BMP's). The site inspections are to be performed
by the contractor or an inspector designated by the administrator at a minimum of once every
fourteen (14) calendar days on active construction sites and after any significant storm event
(an event causing runoff). As part of the site inspections the inspector is required to keep
documentation of all inspections and BMP maintenance, including an updated Site Map
indicating new BMP's or the removal of BMP's since the previous inspection.
Any maintenance, repair, or necessary installation of BMP's that are noted during the
inspection must be completed within seven (7) calendar days from the date of the
inspection
11
6. CONCLUSIONS .
6.1 Compliance with Standards
All computations that have been completed within this report are in compliance with the
"City of Fort Collins Erosion Control Reference Manual for Construction Sites", the
"City of Fort Collins Storm Drainage Design Criteria Manual", and the "Urban Storm
Drainage Criteria Manual".
6.2 Drainage Concept
The proposed drainage concepts presented in this report and on the construction plans
adequately provide for the collection and conveyance of on -site runoff to the detention
area. Conveyance elements exist to adequately convey detained runoff downstream.
If, at the time of construction, groundwater is encountered, a Colorado Department of
Health Construction Dewatering Permit would be required.
12
7. REFERENCES
1. Urban Drainage and Flood Control District, "Urban Storm. Drainage Criteria
Manual", 2001 Edition Volume 1 updated June 2001, January 2004 and April
2008; Volume 2 updated June 2001 and April 2008; and Volume 3 updated
November and December 2010.
2. The Fort Collins Amendments to the Urban Drainage and Flood Control District
Criteria Manual, adopted by the City Council of the City of Fort Collins, as
referenced in Section 26-500 (c) of the Code of the City of Fort Collins.
3. ORDINANCE NO. 152, 2012 of the Council of the City of Fort Collins amending
Chapter 26 of the Code of the City of Fort Collins and the Fort Collins
Stormwater Criterial Manual to incorporate provisions implementing Low Impact
Development (LID) Principles.
13
APPENDIX A
VICINITY MAP
A
PROJECT
LOCATION
VICINITY MAP
-low
ED SWALE
WITHOUT
UNDERDRAJN
LOT 19 PER DETAIL
----------------
-------------------------------- ___
AREA, INLET
FIEFER TO
imw PLAIN
- - -------------
...... . ... ............
---------------
-----------
POROUS
PAVERS I'M
DETUM
,,E, A
A,vN SO
w
w
Lu
Irl
INSTALL
CONCRETE
IMADIVALL. WIN
Nina PLATE
PM DETAIL
- --------------------------------
------------- - --------------
------- ------- --------- ------------------- ----- . . .. .............. -------- ---- -- - - ---- ------ -- ------------- - ----- -------------- - -- -----------------
-12--_���ONIFEIR �STREET� 21l! SPILLWAY
RIEFER M GRADNG
PLAN FOR DETAILS
- - - - - — - - - - - - - - - - - - - - —_
01
20 la 0 20 40
SCALE� 1' 20'
LEGEW
EXISTNG PIPES
- - - - - - 4905 - - - - - - EXISTNG 5' CONTOUR
------------- ___ -------- EXISING V CONTOUR
—.905— PROPOSED 5 CONTOUR
PROPOSED 1' CONTOUR
Ai DESIGN POINT
BASIN CRITERIA
10 " RUNOFF COEFFICIENT
AREA IN ACRES
FLOW aRECTION
"W0.0 0 UNW9.01111 BASIN BOUNDARY
—sF—SF— SILT FEN CE
VEHICLE TRACKING PAD
BECONCRETE WASa,OUT AREA
4-:b ROCX SOCK
�w
16 "5 CS
C� E 0 , (?
0
5 0
U5
a 0 5�
_Zt TO CLILL.
A
z
0
INLET PROTECTION
CA
OL.
Go
IN
it
=RB
IN
RXK SM.
0
it;
c
CONSTRUCTION SEQUENCE
PROJECT: RAW URN DESIGNS DAM: 2/22/16
. . . . . . . . . .
SULT FENCE BARRIERS
CONTOUR FURROWS (RIPPAGAISKING)
METTR
====MMMMM
=1111
MMM=MMMMMM==
MPGRARY SEED PLANTING
MULCHING / SEALANT
PERMANENT SEED PLAN
/.All
31306
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City of Fort Collins, Colorado
ul
UTILITY PLAN APPROVAL
cc
APPROVED:
SHEET
—
City Eng�aer Date
CHECKED BY.—
CALL UnUTY NOTIFICATION
WatW A wasawatw Utility
CHECKED BY:
Date
5
CENTER OF COLORADO
—
st--ter Utility
Date
1-800-922-1987 (811)
CHECKED BY:—
� 2-BUSNESS DAYi IN ADVANCE
Pa.. & R..'eati-
Data
5 OF 8
SEIME YOU DIG. MADE. OR EXCAVAM
FOR THE MARKING OF UNDERCFEENO
CHECKED BY,
'WBER UnUIES, I
Traffic Engineer
Data
No.
177-09
CHECKED BY..
Haii'�
Date
APPENDIX B
HYDROLOGIC COMPUTATIONS
0
tbth Star Design, Inc
700 Auton bon Dme, Unit I
Waksor, 00 80550
LOCATION: Raw Urth Designs
PROJECT NO: 177-06
COMPUTATIONS BY: ppk
DATE: 8/122015
Recommended Runoff Coefficients from Table 3-3 of City of Fort Collins Design Criteria
Recommended % Impervious from Urban Storm Drainage Criteria Manual
% Runoff
Impervious coefficient
C
Streets, parking Ids (asphalt): 100% 0.95
Sidewalks: 96% 0.95
Gravel: 40% 0.50
Roofs: 90 % 0.95
Lawns (Flat <2%, heavy soil): 0 % 0.20
SUBBASIN
DESIGNATION
TOTAL
AREA
ac.)
TOTAL
AREA
sq.ft)
ROOF
AREA
sq,ft
PAVED
AREA
sq.ft
SIDEWALK
AREA
sq,ft
GRAVEL
AREA
(s .ft
LANDS
AREA
s .ft
%
Impervious
RUNOFF
COEFF.
C)
1
2
3
0.19
0.15
0.51
8474
6427
22236
0
0
12415
6368
5,354
0
0
360
004
0
0
0
:506
113
8.917
75Y.
89%
-A%
B76
0.87
0.65
ALL
0.89
38,584
12,415
12,010
1,264
0
12,895
bite
0.70
OS I
0.03
1,178
0 i
300 1
0 1
0 1
878
25X
0.39
Equations
- Calculated C coefficients & % Impervious are area weighted
C=E(Ci Ai)/At
Ci = runoff coefficient for specific area, Ai
Ai = areas of surface with runoff coefficient of Ci
n = number of different surfaces to consider
At = total area over which C is applicable; the sum of all Al's
North Ster Design, hi0
70DN omation Drive, Urm1
wmCeor, rO 80550
LOCATION:
Raw Urth Desiprs
PROJECT NO:
177-06
COMPUTATIONS BY:
ppk
DATE:
9112f'015
2-yr storm
C1= 1.00
STANDARD FORM SF-3
TIME OF CONCENTRATION - 2 YEAR
SUB -BASIN DATA
DESIGN SUBBASIN(s) Area
FAINT (ac)_
(1) (2)
INITIAL (OVERLAND
TIME (a)
C Length Slope 6
(ft) (%) .(min)
(3) (4) (5) IS
TRAVEL TIME I GUTTER OR CHANNEL FLOW
00
Length Slope n Vel. a tc
(ft) (%) Manning (fl/o (min) 6+a
(7) (6) rough. (9) (10) (11)
It: CHE CK
(URBANIZED BASIN)
Total tc�V180)+10
(ft) (min)
(12) (13)
FINAL
tc
(min)
(14)
REMARKS
1
1
1
1
2
3
0.19
0.15
0.51
0.76
0.87
0.65
35
24
67
1.5
1.5
1.0
3.1
1.8
6.5
204
146
283
0.5
0.6
0.6
0.030
0.016
0.030
0.8
1.6
0.8
4.49
1.56
5.68
7.6
3.4
12.3
239
170
350
11.3
00.9
11.9
7.6
5.0
11.9
i
ALL
0.89
0.70
67
1.0
5.9
283
0.6
0.030
0.8
5.f1B
11.6
350
11.9
11.6
1
OS
(53
0.39
13
3.5
3.0
0
0.6
0.030
0.8
0.00
3.0
13
10.1
5.0
tUUAI IUNS:
It: =lf+a
ti=[1.87(1.1-Cq)L05]IS'&
It = L /Vel. Velocity from Manning's Equation with R=0.1 (corresponds to Figure 3-3 of City of Fort Collins Design Manual)
final tc = minimum of ti + It and urbanized basin check .
min. tc = 5 minutes
Nosh sm nedpllrc _
WinAo,. 00 81550 lkd I
WilCsor, CO 96550
LOCATION: Raw Urth Designs
PROJECT Na. 177-06
COMPUI'ATJONS BY: ppk
DATE: 8/12/2015
100-yistorm C/= 1.25
STANOARD FORM Sli
TIME OF CONCENTRATION • 100 YR
SUB -BASIN DATA
DESIGN SUBBASIN(s) Ares
POINT (ac)
(1) (2)
INITIAL /OVERLAND
TIME (D)
C C'Cf Long m Sbpe I
- (0) (%) (min)
(3) (4) (5) (6)
TRAVEL TIME I GUTTER OR CHANNEL FLOW
(It)
Length Slope n Val. It tc=
(n) (%) Mannhg (fUs) (min 0 8+R
(7) (8) naWh. 1 (9) (10) (11)
lc CHECK
(URBANIZED BASIN)
TotalL tt--(U180)t10
(n) (min)
(12) (13)
FINAL
to
(mil)
(14)
REMARKS
1
1
1
1
2
3
0.19
0.15
0.51
O.7fi
0.8]
0.65
0.95
1.00
0.87
35
24
67
1.5
1.5
1.0
1.4
0.8
4.2
204
146
283
0.5
0.6
0.6
0.030
0.016
0.030
0.8
1.6
0.8
4.49
1.56
5.68
5.8
2.3
9.9
239
770
3W
11.3
00.9
11.9
5.8
5.0
9.9
1
ALL
0.89
0.70
0.87
67
1.0
3.3
283
0.6
0.030
0.8
'S.68
9.0
350
11.9
9.0
1
OS
0.03
0.39
0.49
13
3.5
2.6
0
0.6
0.030
0.8
0.00
2.6
13
10.1
5.0
IIVIVJ:
Ic=ti+n
6=(1.87(1.1-CCI)Oil] /S 1n
It = INel. Velocity from Manning's Equation with R=0.1 (corresponds to Figure 3-3 of City of Fort Collin Design Manual)
final tc = minimum of ti + It and urbanized basin check
min. tc = 5 minutes
Wh Star D.*m h
700 Aubmffiion Drive, Unit 1
Winc r, CO 80550
RATIONAL METHOD PEAK RUNOFF'
(2-YEAR)
LOCATION: Raw Urth Designs
PROJECT NO: 177-06
COMPUTATIONS BY: ppk
DATE: 8/12r015
2-r slam, Cf 1.00
DIRECT RUNOFF
CARRY OVER
TOTAL
REMARKS
Design
Point
Tributary
Sub -basin
A
(ac)
CCf
tc
(min)
i
(new)
(iNhr)
Q (2)
(cfs)
from
Design
Point
Q (2)
(cfs)
Q(2pot
(cfs)
1
1
0.19
0.76
7.6
2.45
0.4
0.4
To area inlet
1
2
0.15
0.87
5.0
2.85
0.4
0.4
to sidewalk culvert
1
- 3
0.51
0.65
11.9
2.05
0.7
0.7
To Det Pond
1
ALL
0.89
0.70
11.6
2.08
1.3
1.3
To Det Pond
1
- OS
0.03
0.39
5.0
2.85
0.0
0.0
To Streets
N Star Deaipn, Inc.
700 M mation Dwe, UN I
Windwr, CO e05W RATIONAL METHOD PEAK RUNOFF
(100-YEAR)
LOCATION: Raw Urth Designs
PROJECT NO: 177-06
COMPUTATIONS BY: ppk
DATE: 8111'015
100-yr storm, Cf = 1.25
DIRECT RUNOFF
CARRYOVER
I TOTAL
REMARKS
Des.
Point
Area
Design.
A
(ac)
C'Cf
tc
(min)
i
(new)
(in/hr)
0(100)
WS)
from
Design
Point
O(100)
(cfs)
O(100)lot
(cfs)
1
1
0.19
0.95
5.8
9.41
1.7
1.7
To area inlet
1
2
0.15
1.00
5.0
9.95
1.5
1.5
to sidewalk culvert
1
3
0.51
0.81
9.9
7.74
3.2
3.2
To Det Pond
1
ALL
0.89
0.87
9.0
7.96
6.2
6.2
To Det Pond
1
OS
0.03
0.49
5.0
9.95
1 0.1
1
0.1
To Streets EEI
O=CiA
O = peak discharge (cfs)
C = runoff coefficient
I = rainfall intensity (in/hr) from OF curve
A = drainage area (acres)
FIM.d 0100
AREA INLET IN A TRAPEZOIDAL GRASS -LINED CHANNEL
Inlet 1
TMw, Grass 7 e Llmltirka Mannin 's n'
T A 0.06 - -
_ 0.04
\ d c o.033
fj ,is 'n"" D 0.03
/ E 0.024
1 of Trapezoidal Grass -Lined Channel Using S S M
sgelel Rated. (A, B, C. D. or E)
'a n (Leave cell D16 blank kl manually sow an n value)
unwed Slope
Sandy 6.0 fps 0.50
N�7.O fps 060fps O60
Allowable Top YYmh of Chenal for Mmr a Major Storm
Allowable Water Depth in Chanel for Minor E Major Shorn
eble Channel C=adNBreed On Channel GeomatrvBawtl On Chmnal Gsomatry
R STORM Allowable Capacity Is baud on Top Width Criterion
)R STORM Allowable Capsciry Is based on Top Width Criterion
Pask Flow
Storm max. allowable capacity GOOD - greater than flow given on shael'O-Peak'
storm max. allowable caoaclty GOOD - mortar than Dow given on sheet'O-Peak'
A. B, C, DorE
no
0.000
So =
0.0055
MR
B =
0.00
R
21=
8.00
Pofl
Z2=
400
fvt
Q Sandy
71
® Nan -Sally
Minor Sfarm Major Slum
T.
10.00
10.00
feet
d.e1=
6.00 1
6.00
feet
ro.=I1.00
1 1.00!R
Q..1
cfs
OAO
I 1.70
d-I
o.za 1
0.43
feat
INlet 1.Asm, Area Inlet _ 8l12/2015, 1:17 PM
AREA INLET IN A TRAPEZOIDAL GRASS -LINED CHANNEL
Raw Unh
Inlet 1
Design Information (Noot1
of Imet
Inlet Type =1
User-DeOned
of Inclined Grete(must be <= 30 degrees)
0=
OA0
degrees
of Grate
W =
1.05
feel
not Grate
��„
�f`"-•..._,,,.....1 _
L=
2.00
feel
Area Rate
/
/ • *-••...._.......'
A.T. =
0.42
1 of Inclined Grate
IV I
Jr'
He °
0.00
feet
Ing Factor
._,....,,._ .`..�..
"^.+,.,........._......-,�.
Discharge Coeffion,,,
_....__. _. ,. _.,„
I
Ce=
WA
Aeffic9at
`L.
MINOR
MAJOR
Depth at Inlet (far depressed! inab, l fool is added for depression) d =
Inlet Interception Capacity (assumes clogged condition) Q, _
apaclty IS GOOD for Minor and Major Storms (> 0 PEAK). Bypasead Flow, Q =
Capture Parentage = OJQ = C%
Warning 02: Depth (d) exceeds USDCM Volume 1 recommendation.
028
0.sB
1.18
z01
0.00
0.00
100
IN
INIet 1.Idsm, Area Inlet S/1212015, 1:17 PM
Normal Flow Analysis - Trapezoidal Channel
U Raw' rthc.; `,7
Project:
Channel ID:."-.`7. wit i Sidewalk,Ctjlv'e 11 Basin 2"
A F < -------------T
------------ >
YO
W Z2
ZI < ----- b ------ >
�Channel Invert Slope
so=
Manning's n
n = 0.013
Bottom Width
B = 2.00 ft
Left Side Slope
ZI = 0.00 ft/ft
Right Side Slope
Z2 = 0.00 ft/ft
Height
F = 0.32 fit
,Freeboard
Design Water Depth
Y=
Normal Flow Condtion (Calculated)
Discharge
Q = ,.,,-�'T.52 cis
Froude Number
Fr = 1.91
Flow Velocity
V = -4.,48 fps
Flow Area
A = .0.34 sq ft
Top Width
T = 11 ;.2.00 ft
Wetted Perimeter
P = `-,2.34 ft
Hydraulic Radius
0.15ft
Hydraulic Depth
D =' - 'OA T ft
Specific Energy
Es = 0.48 ft
Centroid of Flow Area
, .",-0.09. fit
Yo = "I"
Specific Force
Fs =:.' i:..!:`'0.021 kip
UD-Channels—v1.04.xis, Basics 12/29/2015, 4:05 PM
LOCATION:
PROJECT NO:
COMPUTATIONS BY:
SUBMITTED BY:
DATE:
Weir Check of Channel Sizing
Raw Urth
177-09
PPk
North Star Design
2/22/2016
Solve for h using Weir Equation
Q = CLH32
where C = weir coefficient
H = overflow height
L = length of the weir
Sidewalk Culvert in Basin 2
Q = 1.50 cfs
C = 2.62
L = 2.00 ft
Solve for H= 0.43 ft
APPENDIX C
DETENTION POND SIZING CALCULATIONS
C
MINIMUM DETENTION VOLUME REQUIRED
FAA METHOD
(100-YEAR)
LOCATION: Raw Urth Designs
PROJECT NO: 177-09
COMPUTATIONS BY: PPK
SUBMITTED BY: North Star Design, Inc.
DATE: 8/12/2015
Equations: A trib. To pond = 0.89 acre
Qo=CiA C100= 0.87
Vi = T*CiA = T*Qu Developed C*A = 0.8 acre
V. =K*QPo*T QPo = 0.18 cfs
S=V1-Va K= 1 (from fig 2.1)
Rainfall intensity from City of Fort Collins IDF Curve
Storm
Duration, T
(min)
Rainfall
Intensity, i
(in/hr)
Qo
(cfs)
Vol. In
V1
(ft3)
Vol. Out
Vo
(ft)
Storage
S
(ft)
Storage
S
(ac-ft)
5
9.95
7.7
2311
55
2256
0.052
10
7.72
6.0
3587
110
3476
0.080
20
5.60
4.3
5203
221
4982
0.114
30
4.52
3.5
6300
331
5969
0.137
40
3.74
2.9
6950
442
6509
0.149
50
3.23
2.5
7503
552
6951
0.160
60
2.86
2.2
7972
662
7310
0.168
70
2.62
2.0
8520
773
7748
0.178
80
2.38
1 1.8
8846
883
7962
0.183
90
2.22
1.7
9282
994
8289
0.190
100
2.05
1.6
9524
1104
8420
0.193
110
1.93
1.5
9863
1214
8649
0.199
120
1.80
1.4
10035
1325
8710
0.200
130
1.60
1.2
9663
1435
8228
0.189
140
1.40
1.1
9106 1
1546
7560 1
0.174
150
1.20
0.9
8362
1656
6706 1
0.154
160
1.15
0.9
8548
1766
6782--1
0.156
170
1.10
0.9
8688
1877
6811 1
0.156
180
1.05
0.8
8781
1987
6793 1
0.156
Required Storage Volume: 8710 It
0.200 acre-ft
STAGE - STORAGE TABLE
LOCATION: Raw Urth Designs
PROJECT NO: 177-09
COMPUTATIONS BY: PPK
SUBMITTED BY: North Star Design, Inc.
DATE: 8/1/2008 .
100 yr WSEL
100 yr Detention Volume Required = 0.200
Water Quality Volume Required = 0.000
Total Volume Required= 0.200
Stage
(ft)
Surface
Area
(f)
Incremental
Storage
(ac-ft)
Total
Storage
(ac-ft)
4768.80
0
4769.0
761
0.001
0.001
4770.0
1,695
0.027
0.029
4771.0
4,321
0.067
0.095
4771.80
7,253
0.104
0.200
4772.0
8,009
0.139
0.235
4 772.3
9337 10.060
0.294
SPILLWAYELEV
Detention Pond Outlet Sizing
--- - - -
LOCATION: Raw Urth Designs
PROJECT NO: 177-09
COMPUTATIONS BY: PPK
SUBMITTED BY: North Star Design, Inc.
DATE: 8/12/2015
Submerged Orifice Outlet:
release rate is described by the orifice equation,
Qo = C,A. sqrt( 2g(h-E,))
where Q. = orifice outflow (cfs)
Ca = orifice discharge coefficient
g = gravitational acceleration = 32.2 ft/s
A. = effective area of the orifice (ft)
E. = greater of geometric center elevation of the orifice or d/s HGL (ft)
h = water surface elevation (ft)
Qo = 0.18 cfs
outlet pipe dia = D = 12.0 in
Invert elev. = 4768.80 ft
Eo = 4768.88 ft
h = 4771.8 ft - 100 yr WSEL
Co = 0.62
solve for effective area of orifice using the orifice equation
Ao = 0.021 ft'
= 3.1 in'
orifice dia. = d = 1.97 in
Check orifice discharge coefficient using Figure 5-21 (Hydraulic Engineering)
d/D= 0.16
kinematic viscosity, u = 1.22E-05 fels
Reynolds no. = Rea = 4Q/(pdu) = 1.14E+05
Co = (K in figure) = 0.62 check
Use d = 1.95 1n
A o = 0.021 ft z. 2.99 in a
Q, = 0.18 cfs
Emergency Overflow Spillway Sizing
LOCATION: Raw Urth Designs
PROJECT NO: 177-09
COMPUTATIONS BY: PPK
SUBMITTED BY: North Star Design, Inc.
DATE: 5/24/2005
Equation for flow over a broad crested weir 7 top of berm
Q = CLH spill elev�4i®n
where C = weir coefficient = 2.8
H = overflow height
L = length of the weir 0 900 n WSEL
The pond has a spill elevation 0 It above the maximum water surface elevation in the pond
Spillways will be designed with 0.25 ft flow depth, thus H = 0.25 ft
Size the spillway assuming that the pond outlet is completely clogged.
Q (100) = 6.2 cfs
Spill elev = 4971.80 ft .100 yr WSEL = 4971.8 ft
Top of berm elev.= 4972.30
Weir length required:
L= 18 ft
Use L = 20 ft
v = 0.89 ft/s
Stormwater Detention and Infiltration Design Data Sheet
Stormwater Facility Name: Raw Urth Designs
Facility Location & Jurisdiction: Raw Urth Designs, Fort Collins, CO
User (Input) Watershed Characteristic
Watershed Slope =
d.008-.='
ft/ft
Watershed Length -to -Width Ratio =
-2.27 =:. -7
L:W
Watershed Area =`-
0.89` -+
acre
Watershed Imperviousness=
- 63.0%:'.
pert
Percentage Hydrologic Soil Group A =
0.0%-'-
pert
Percentage Hydrologic Soil Group B =
--0:0%^°:• -
pert
Percentage Hydrologic Soil Groups C/D =
:: 100.0%,'�.
pert
Location for 1-hr Rainfall Depths (use dropdown):
j Urer Input
zf,
User Input: Detention Basin Characteristics
WQCV Design Drain Time = • ' 40.00 -' hours
After completing and printing this worksheet to a pdf, go to:
https://maperture.digritaidatasemices.com/avh/?viewer--cswdif,
create a new stormwater facility, and
attach the pdf of this worksheet to that record.
Design Storm Return Period ,
One -Hour Rainfall Depth
Calculated Runoff Volume
OPTIONAL Override Runoff Volume
Inflow Hydrograph Volume
Time to Drain 97%of Inflow Volume;
Time to Drain 99%of Inflow Volume:
Maximum Porting Depth
Maximum Ponded Area
Maximum Volume Stored
0n,duA N.,A.,.o.e..6 De J+.
User Defined
Stage [ftl
User Defined
Area [ftA21
-'`0.20
671
.0.70
'.:1,183
1.20
'1,695 ".
1.70 .,
3,008
2.20 :
4,321
3.00
7,253.
)-.3.50:.9,337
User Defined
Sage [ft)
User Defined
Discharge [cfs)
.0.20 -
.0.04-. -
0.70 - ' -
"'^ 0.08
". 1.70
0.13
2.20
- :- 0.15
' 2.70 .
:,' 0.17
. 3.00'.:
_ 0.18
.3.50
'7.20
WQCV
2Year
5Year
10 Year
25 Year
50 Year
100 Year
.�:0.53.
0.98'":
-.- 1.36'1.71
•:-2.31-:
2.91 ."
C'3.67 ,.
0.018
0.044
0.070
0.095
0.140
0.183
0.242
0.017
0.044
0.070
0.095
0.139
0.183
0.241
4
6..9.
11
14
16
19
4
7
9
1 11
14
17
-.:2T,-.,
0.63
1.26
1.68
1.97
2.38
2.69
3.02
0.025
0.043
0.068
0.085
0.114
0.140
0.168
0.010
0.031
0.054
0.076
0.117
0.156
0.207
n
acre-ft
acre-ft
acre-ft
(ours
lours
t
acres
acre-ft
SOI_Drain time check_FC_Rainfall.xlsm, Design Data 2/23/2016, 3:52 PM
r
II' Stormwater Detention and Infiltration Design Data Sheet
SDI —Drain time check_FC_Rainfali.xlsm, Design Data - 2/23/2016, 3:52 PM
APPENDIX D
BMP SCHEDULE & COST ESTIMATE
------------------ ______Raw-Urth -LLD-Table----._----..____
_-----------------_.
New Impervious Area
25689 sq. ft.
Required Minimum Impervious Area to be Treated (50%)
12845 sq. ft.
Impervious Area Treated by LID Treatment Method #1 (LID
swale with underdrain)
6368 sq. ft.
Impervious Area Treated by Porous Pavement
5714 sq. ft.
Total Impervious Area Treated (47`Yo)
12082 sq. ft.
New Pavement Area
12010 sq. ft.
Required Minimum Area of Porous Pavement (25%)
3003 sq. ft.
Area of Paver Section A
3047 sq. ft.
Run-on area for Paver Section A
2667 sq. ft.
Total Porous Pavement Area (25°o)
3047 sq. ft.
CONSTRUCTION SEQUENCE
PROJECT: RAW URTH DESIGNS DATE: 8/10/15
CONSTRUCTION PHASE (MONTH)
1
2
3
4
5
6
7
8
9
10
11
12
GRADING (INCLUDES OVERLOT)
OVERLOT
DETENTION / WQ PONDS
SWALES, DRAINAGEWAYS, STREAMS
PIPELINE INSTALLATION (INCLUDES OFFSITE)
WATER
SAINITARY SEWER
STORM SEWER
CONCRETE INSTALLATION (INCLUDES OFFSITE
SIDEWALK CULVERTS & CHASES
INLETS
POND OUTLET STRUCTURES
CURB AND GUTTER
PAVEMENT INSTALLTATION
FINE GRADING / BASE COURSE INSTALL
PAVEMENT
BEST MANAGEMENT PRACTICES
STRUCTURAL
SILT FENCE BARRIERS
CONTOUR FURROWS (RIPPING/DISKING)
SEDIMENT TRAP / FILTER
VEHICLE TRACKING PADS
FLOW BARRIERS (WATTLES, ETC)
CONCRETE WASHOUT
ROCK SOCKS
BARE SOIL PREPARATION
TERRACING
RIPRAP
VEGETATIVE
TEMPORARY SEED PLANTING
MULCHING / SEALANT
PERMANENT SEED PLANTING
SOD INSTALLATION
NETTING/BLANKETS/MATS
Erosion and Sediment Control Escrow/Security Calculation
for The City of Fort Collins
Project: Raw Urth Designs
Disturbed Acres: 0.90
V w ,
Estimated
Unit
Total
EROSION CONTROL BMPs Units
Quantity
Price
Price
Silt Fence L.F.
730
$3.00
$2,190.00
Rock Sock each
15
$85.00
$1,275.00
Vehicle Tracking Control Pad each
1
$1,500.00
$1,500.00
Concrete Washout each
1
$1,200.00
$1,200.00
(add all other BMPs for the site in this list)
Sub -Total: $6,165.00
1.5 x Sub -Total: $9,247.50
Amount of security: $9,247.50
...�` ,v,.,..}i b,al.a �l^_u i�c.-a,:..,r, +.a:%�:u n.t...v1E.__: ._, .-,go.J., ,.- .. . ., Z �T� u x •a -
Total Acres x Price/acre: $1,080.00
Unit Price of Seeding per acre: $1,200.00 Sub -Total: $1,080.00
1.5 x Sub -Total: $1,620.00
Amount to Re -seed: $1,620.00
_; « m.
r TMr e.
14
Mirnumum Escrow Amount
Minimum escrow amount: $3,000.00
•:' -f Final=Escrdw,Amoi'i'nt -
Erosion Control Escrow: $9,247.50
-The amount of the security must be based on one and one-half times the estimate of the cost to install the approved measures, or one and one-haljtimes
the cost to re -vegetate the disturbed land to dry land grasses based upon unit cost determined by the City's Annual Revegetation and Stabilization Bid,
whichever is greater. In no instance, will the amount of security be less than one thousand five hundred dollars ($1,500) for residential development or three
thousand dollars ($3,000) jar commercial development"
5/12/2015 3:13 PM
N:1MT Raw UMWminagalFsampb Exm
APPENDIX E
FIGURES AND TABLES
E
-(11)-Section 4.O is amended to read as follows:
4.0 Intensity -Duration -Frequency Curves for Rational Method:
The one -hour rainfall Intensity -Duration -Frequency tables for use the Rational Method
of runoff analysis are provided in Table RA-7 and in Table RA-8.
Table RA-7 -- City of Fort Collins
Rainfall Intensity -Duration -Frequency Table
for Use with the Rational Method'
(5 minutes to 30 minutes)
Duration
(min)
5
2-Year
Intensity
(ice)
2.85
10-Year
Intensity
(tom)
4.87
100-Year
Intensity
(in/hr)
9.95
6
2.67
4.56
9.31
7
2.52
4.31
8.8
8
2.4
4.1
8.38
9
2.3
3.93
8.03
10
2.21
3.78
7.72
11
2.13
3.63
7.42
12
2.05
3.5
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
6.3
17
1.75
2.99
6.1
18
1.7
2.9
5.92
19
1.65
2.82
5.75
20
1.61
2.74
5.6
21
1.56
2.67
5.46
22
1.53
2.61
5.32
23
1.49
2.55
5.2
24
1.46
2.49
5.09
25
1.43
2.44
4.98
26
1.4
2.39
4.87
27
1.37
2.34
4.78
28
1.34
2.29
4.69
29
1.32
2.25
4.6
30
1.3
2.21
4.52
33
r "gr
Table RA-8 - City of Fort Collins
Rainfall Intensity -Duration -Frequency Table
for Use with the Rational Method
(31 minutes to 60 minutes)
Duration
(min)
31
2-Year
Intensity
(in/hr)
1.27
10-Year
Intensity
(in/hr) .
2.16
100-Year
Intensity
(in/hr)
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
2.0
4.08
36
1.15
1.96
4.01
37
1.16
1.93
3.93
38
1.11
1.89
3.87
39
1.09
1.86
3.8
40
1.07
1.83
3.74
41
1.05
1.8
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
4.9
0.94
1.6
3.27
50
0.92
1.58
3.23
51
0.91
1.56
3.18
52
0.9
1.54
3.14
53
0.89
1.52
3.1
54
0.88
1.5
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 -
1.4
2.86
34
RAINFALL INTENSITY -DURATION -FREQUENCY CURVE
10.0
9.0(
6.0c
t 7.00
a
m
L
e 6.00
m 5.00
Z
W
F
J
4.00
J
Q
LL
z 3.00
2.00
1.00
0.00
0.00 10.00 20.00 30.00 40.00 50.00 60.00
STORM DURATION (minutes)
2-Year Storm - - - 10-Year Storm -100-Year Stonn
Figure RA-16 City of Fort Collins Rainfall Intensity -Duration -Frequency Curves
(13) Section 5.0 is deleted in its entirety.
(14) Section 6.0 is deleted in its entirety.
(15) Section 70 is deleted in its entirety.
(16) Section 7.1 is deleted in its entirety.
(17) Section 7.2 is deleted in its entirety.
(18) Section 73 is deleted in its entirety.
(19) Section 8.0 is deleted in its entirety.
(20) Table RA-1 is deleted in its entirety.
36
Table RO-10
Rational Method Minor Storm Runoff Coefficients for Zoning Classifications
Description of Area or Zoning
Coefficient
R-F
0.3
U-E
0.3
L-M-In
0.55
R-L, N-C-L
0.6
M-M-N, N-C-M
0.65
N-C-B
0.7
Business:
C-C-N, C-C-R, C-N, N-C, C-S
0.95
R-D-R, C-C, C-L
0.95
D, C
0.95
H-C
0.95
C-S
0.95
Industrial:
E
0.85
1
0.95
Undeveloped:
R-C, T
0.2
P-O-L
0.25
For guidance regarding zoning districts and classifications of such districts please refer to
Article Four of the City Land Use Code, as amended.
40
Table RO-11
Rational Method Runoff Coefficients for Composite Analysis
Character of Surface
Runoff Coefficient
Streets, Parking Lots,
Drives:
Asphalt
0.95
Concrete
0.95
Gravel
0.5
Roofs
0.95
Recycled Asphalt
0.8
Lawns, Sandy Soil:
Flat <2%
0.1
Average 2 to 7%
0.15
Steep >7%
0.2
Lawns, Heavy Soil:
Flat <2%
0.2
Average 2 to 7%
0.25
Steep >7%
0.35
(4) A new Section 2.9 is added, to read as follows:
2.9 Composite Runoff Coefficient
Drainage sub -basins are frequently composed of land that has multiple surfaces 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:
�Ki *A;)
C = '_i A (RO-8)
Where: C = Composite Runoff Coefficient
C; = Runoff Coefficient for. Specific Area (A)
A; = Area of Surface with Runoff Coefficient of C;, acres or feet2
n = Number of different surfaces to be considered
A,= Total Area over which C is applicable, acres or feet2
(5) Anew Section 2.10 is added, to read as follows:
41
2.10 Runoff Coefficient Adjustment for Infrequent Storms
- The runoff coefficients` provided in tables RO-10 and RO-1 fare appropriate for use with
the 2-year storm event. For storms with higher intensities, an adjustment of the runoff
coefficient is required due to the lessening amount of infiltration, depression retention,
evapo-transpiration and other losses that have a proportionally smaller effect on storm
runoff. This adjustment is applied to the composite runoff coefficient.
These frequency adjustment factors are found in Table RO-11
Table RO-12
Rational Method Runoff Coefficients for Composite Analysis
Storm Return Period Frequency Factor
ears Cf
2 to 10 1.00
11 to 25 1.10
26 to 50 1.20
51 to 100 1.25
Note: The product of C times Cfcannot exceed the value of 1, in the cases where it does a value of
1 must be used
(6) Section 3.1 is deleted in its entirety.
(7) Section 3.2 is deleted in its entirety.
(8) Section 3.3 is deleted in its entirety.
(9) A new Section 4.3 is added, to read as follows:
4.3 Computer Modeling Practices
(a) For circumstances requiring computer modeling, the design storm hydrographs must
be determined using the Stormwater Management Model (SWMM). Basin and
conveyance element parameters must be computed based on the physical characteristics
of the site.
(b) Refer to the SWMM Users' Manual for appropriate modeling methodology, practices
and development. The Users' Manual can be found on the Environmental Protection
Agency (EPA) website (htti)://www.epa.gov/ednnrmrl/models/swmm/index.htm).
(c) It is the responsibility of the. design engineer to verify that all of the models used in
the design meet all current City criteria and regulations.
4.3.1 Surface Storage Resistance Factors and Infiltration
Table RO-13 provides values for surface storage for pervious and impervious surfaces
and the infiltration rates to be used with SWMM. Table RO-13 also lists the appropriate
infiltration decay rate, zero detention depth and resistance factors, or Maiming's 'In"
values, for pervious and impervious surfaces to be used for SWMM modeling in the city
of Fort Collins.
42