HomeMy WebLinkAboutTRAILHEAD NEIGHBORHOOD PARK BASIC DEVELOPMENT REVIEW - BDR200002 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTMarch 3, 2020
Wes Lamarque, P.E.
City of Fort Collins Utilities – Stormwater Engineering
700 Wood Street
Fort Collins, CO 80521
RE: Trailhead Park – Final Drainage and Erosion Control Letter
JVA Job No. 3197c
Dear Wes:
This letter has been prepared to summarize the drainage concept, solutions and changes in
impervious area associated with the site improvements for the Trailhead Park redevelopment
project located in the City of Fort Collins.
Existing Drainage Patterns
The existing site, platted as Tract H and Lot 1-Block 9 (same owner: City of Fort Collins) of the
Trail Head Development, is predominantly park turf lawn and vegetation. This site was part of
the master drainage plan for the Trail Head Property. From the existing drainage report, the site
consists of portions of existing sub basins 344.1, 344.2, 345, 352.1 and 352.2. From the existing
drainage report, Lot 1-Block 9 was planned to be a day care building with parking lot
(commercial), while Tract H was planned to be the park. The average proposed imperviousness
for the sub basins was calculated to be 33.2%. The existing ground surface is relatively flat,
generally sloping to the west at grades ranging from 0.1% to 3.0%, with an area of steep slope
down to the group of trees at the southeast of the site. While the site generally conforms to the
existing drainage report, the majority of stormwater runoff is conveyed via surface flow either to
the west into an existing quadruple curb inlet in Wagon Trail Road or to the north into
Greenfields Drive or Yule Trail Drive and conveyed to an existing curb inlet at Yule Trail Drive
and Roaring Creek Drive, with bypass flows continuing down Roaring Creek Drive to the
quadruple curb inlet in Wagon Trail Road. The inlets are conveyed to the public storm drain
system to the west and eventually to the existing Pond A per the existing drainage report. See
Drainage and Erosion Control Report by JR Engineering dated October 13, 2004.
The site is located outside FEMA and City of Fort Collins mapped 100-year and 500-year
floodplains, per FEMA Flood Risk Map Number 08069C0982F, effective date 12/19/2006. The
site is comprised of hydrologic soil group C/D per NRCS soil survey.
Proposed Drainage Patterns
Proposed drainage patterns are to remain generally the same as the current, but will utilize
landscaped areas, inlets, and a grass buffer to capture the majority of runoff before discharging
into the public storm system. The grass buffer will be utilized for water quality and low impact
development treatment. The site will be graded as such to meet the City’s requirements of
treating 75% of the sites modified or added impervious area.
In general, the proposed redevelopment of the site consists of constructing four new structures,
reconfiguring the striping on Roaring Creek Drive to accommodate parallel parking, connecting
proposed pedestrian pathways to existing perimeter pedestrian pathways in multiple locations,
Trailhead Park Final Drainage and Erosion Control Letter
March 3, 2020
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constructing a new basketball court, constructing new playground equipment and garden areas,
and a bioretention/grass buffer. The grass buffer will be located on the west side of the site and
will tie into the existing storm system along Wagon Trail Road.
It follows that the proposed improvements will slightly increase the total impervious area on the
site, from the existing 12.1% to proposed 24.1%. However, the proposed percentage of
imperviousness is less than the 33.2 % that was accounted for in the historical drainage plan.
Detention will not be required as we are meeting the planned design outlined in the previous
master drainage plan, “Drainage and Erosion Control Report – Trail Head Property”, prepared by
JR Engineering dated October 13, 2004.
The proposed grass buffer located on the private storm system will treat storm runoff for a
minimum of 75% of the modified or added impervious area on the site for water quality prior to
discharge into the public storm system, satisfying the City of Fort Collins Low Impact
Development (LID) requirements. These features will facilitate sedimentation and filtration
while limiting erosion, providing both treatment and slowed release of the water quality capture
volume. The proposed redevelopment of this site will serve to limit water quality and quantity
impacts to natural drainageways by decreasing the frequency, rate, duration, and volume of
runoff.
Erosion and Sediment Control
During construction, temporary erosion and sediment control practices will be used to limit soil
erosion and sediment discharge off the site.
Temporary Erosion Control
A temporary erosion control plan is to be implemented for the site during construction.
Temporary erosion control measures include, but are not limited to, slope and swale protection
provided using erosion control wattles/sediment control logs, rock socks, etc. All temporary
erosion control measures are to be removed after they are deemed unnecessary. A general
erosion control plan has been provided in the civil construction documents and attached.
Permanent Erosion Control
Chapter 2 of the Urban Drainage and Flood Control District’s Urban Storm Drainage Criteria
Manual Volume 3 (USDCM) provides guidelines for the selection of appropriate permanent
structural BMPs for a site that is to be developed or redeveloped. The Trail Head Park is best
characterized as a “conventional redevelopment” with under 1 acre of impervious area on the
project site. The BMP decision tree for such sites is provided in Figure 2-2 of the USDCM. As
previously stated, the site and surrounding vicinity is comprised of hydrologic soil group Type
C/D soils, per the NRCS soil survey.
The water quality capture volume (WQCV) for this site is accounted for in the regional detention
pond. No detention is required on the site. Runoff will be collected in the private storm system
before connecting to the public storm system.
Stormwater Management Controls
The Stormwater Management Plan (SWMP) administrator will be determined at the time the
project is bid for construction.
Trailhead Park Final Drainage and Erosion Control Letter
March 3, 2020
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According to the CDPHE Stormwater Fact Sheet – Construction, construction activities produce
many different kinds of pollutants which may cause stormwater contamination problems. The
main pollutant of concern at construction sites is sediment. Grading activities remove grass,
rocks, pavement, and other protective ground covers, resulting in the exposure of underlying soil
to the elements. The soil is then easily picked up by wind and/or washed away by rain or
snowmelt.
In addition, construction activities often require the use of toxic or hazardous materials such as
fuel, fertilizers, pesticides, and herbicides, and building materials such as asphalt, sealants, and
concrete, which may also pollute stormwater. These materials can be harmful to humans, plants,
and aquatic life.
There are no other known potential pollution sources. However, this condition should be
confirmed by the owner/operator or SWMP administrator. Other pollution sources that could be
present include: runoff from vehicle washing, vehicle maintenance and/or fueling, There are no
known existing non-stormwater components of discharge (i.e., springs, landscape irrigation
return flow, and etc.), or any anticipated during construction.
1. All Disturbed and Stored Soil:
The total disturbed area will be approximately 5.05 acres. Soil stockpiles should be
kept below the locally mandated maximum height of 10 feet and surrounded with
sediment control logs. If the storage of these soils occurs over a period greater than 30
days, then consider temporarily seeding the soil to minimize soil loss to wind and
water erosion.
2. Vehicle Tracking of Sediments:
The existing site is developed residential properties with a bisecting gravel/asphalt
alley. A temporary stabilized stone pad and/or Trackout Plate (Vehicle Tracking
Control pad, VTC) will be provided at points of ingress and egress onto the unpaved
area when the parking lot asphalt is removed. The VTC is designed to reduce the
amount of mud transported onto the public roads by construction traffic. If the site is
extraordinarily muddy, then consider designating an area to wash construction
vehicles before they leave the site and enter the public right-of-way. A BMP such as
this is a good way to avoid the costs associated with street cleaning or accidentally
discharging large amounts of sediment into other storm drain systems.
When in doubt, choose methods that prevent pollution rather than ones that force
clean-up at the downstream end just before the stormwater enters the receiving
waters. In other words, the most efficient construction site BMPs are those that
prevent erosion from happening.
3. Inlet Protection (IP): gravel inlet protection will be used on all existing downstream
inlets to prevent sediment and debris from entering the storm drain system.
4. Street sweeping will be conducted as necessary to remove sediment tracked on to
pavement and adjacent streets.
Trailhead Park Final Drainage and Erosion Control Letter
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5. Management of Contaminated Soils:
If contaminated soils are found, the contractor shall report to the SWMP
administrator to be mitigated.
6. Loading and Unloading Operations:
The existing entrance to the site is currently unpaved and loading/unloading activities
will occur within the temporary vehicle access with VTC or a temporary gravel
staging area will be provided.
7. Outdoor Storage Activities:
Materials storage should be designated to a protected area of the site and surrounded
by construction fencing and sediment control logs to reduce the potential for runoff to
occur.
8. Vehicle and Equipment Maintenance and Fueling:
Materials should be stored and handled in covered areas to prevent contact with
stormwater, and chemicals should be stored within berms or secondary containment
devices to prevent leaks and spills from entering stormwater runoff.
Spill Management
In general, spill prevention and response should include the following:
a) Notification procedures to be used in the event of an accident. At the very
least, the SWMP Administrator should be notified. Depending on the nature
of the spill and the material involved, the Colorado Department of Health,
downstream water users, or other agencies may also need to be notified.
b) Instructions for clean-up procedures.
c) Provisions for absorbents are to be made available for use in fuel areas, and
for containers to be available for used absorbents.
d) Procedures for properly washing out concrete trucks and other equipment in a
manner and location so that the materials and wash water cannot discharge
from the site, and never into a storm drain system or stream.
9. Significant Dust or Particulate Generating Processes:
Disturbed areas not yet ready to be seeded, landscaped, paved, or otherwise stabilized
shall be watered, or ripped as necessary to preclude visible dust emissions.
Contractor shall make every effort to minimize particulate emissions from vehicles
performing the work, including but not limited to regular maintenance of construction
equipment. Contractor shall control dust in accordance with the City Fugitive Dust
Control Ordinance.
10. Routine Maintenance Activates Involving Fertilizer, Pesticides, Detergents, Fuels,
Solvents, Oils, Etc:
Materials should be stored and handled in covered areas to prevent contact with
stormwater, and chemicals should be stored within berms or secondary containment
devices to prevent leaks and spills from entering stormwater runoff.
Trailhead Park Final Drainage and Erosion Control Letter
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11. On-site Waste management Practices (Waste Piles, Liquid Wastes, Dumpsters, etc):
Waste management on the site shall be contained in dumpsters that are placed in an
area that can be enclosed with temporary fencing and accessed through a gate with a
lock. Additional measures such as sediment control logs shall be used to protect
potential sediment from migrating our of the waste area.
12. Concrete Truck/Equipment Washing:
A concrete washout facility will be provided onsite. Properly wash out concrete
trucks and other equipment in a manner and location (a minimum of 50 feet away
from any inlet structures) so that the materials and wash water cannot discharge from
the site, and never into a storm drain system or stream.
13. Dedicated Asphalt and Concrete Batch Plants:
There will be no dedicated batch plant on site.
14. Non-Industrial Waste Source Such as Workers Trash And Portable Toilets:
Garbage cans shall be located at break areas and portable toilets shall be provided if
onsite bathroom facilities cannot be used. Locate dumpsters and portable toilets away
from drainage courses (minimum 50 feet from any inlet structures) and stake down
toilets to prevent tipping.
15. Other Areas or Procedures where Potential Spills can Occur:
Records of spills, leaks, or overflows that result in the discharge of pollutants must be
documented and maintained. Record all spills that are responded to, even if they do
not result in a discharge of pollutants. Information that should be recorded for all
occurrences includes the time and date, weather conditions, reasons for the spill, etc.
Some spills may need to be reported to immediately. Specifically, a release of any
chemical, oil, petroleum product, sewage, etc., which may enter waters of the State of
Colorado (which include surface water, ground water and dry gullies or storm sewers
leading to surface water) must be reported. More guidance is available on the web at
www.colorado.gov. The Division’s toll-free 24-hour number for environmental
hazards and chemical spills and releases is 1-877-518-5608.
Sequence of Construction Activities
Construction Start Date (This is the day you expect to begin disturbing soils, including grubbing,
stockpiling, excavating, demolition, and grading activities): May, 2020
Final Stabilization Date (this is when the site is finally stabilized. This means that all disturbed
areas have been either built on, paved, or a uniform vegetative cover reaching over 70% of the
initial vegetative density has been established.) Even if you are doing one part of the project, the
estimated completion date must be for the overall project: August, 2020.
Construction Sequencing: (Detailed construction sequencing to be determined by the contractor)
1. Installation of temporary erosion and sediment control measures.
Trailhead Park Final Drainage and Erosion Control Letter
March 3, 2020
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This includes all sediment control logs, rock socks, erosion control blankets, and silt
fence where all land disturbing activities will occur.
2. Sequence of all land disturbing activity.
Demolition of existing features in preparation of construction of proposed site features.
Installation of grass buffer will occur after demolition.
3. Sod/Seed
Disturbed areas will be sodded and/or seeded upon completing of finish grading. Refer to
the landscape plans for detailed planting and seeding schedule.
4. Mulching.
Spread straw mulch uniformly over seeded areas at a rate of 90 lbs per 1000 square feet
of ground. No more than 25% of the ground should be visible. Crimp or pinch mulch
into soil 2-4 inches by using either a mulch anchoring tool, a farm disk operating on the
contour of the slope, or by cleating with bulldozer tracks operating up and down the
slopes (to prevent tracks from forming gullies).
5. Required maintenance activities (e.g. after-storm checks of all BMPs, etc.).
All temporary sediment control BMPs shall be inspected after each rain event to ensure
proper protection and to determine if cleaning is necessary. Final cleaning of all storm
facilities shall be provided upon final stabilization of site.
Please feel free to contact me to discuss any questions you may have.
Sincerely,
JVA, INCORPORATED
By: ________________________________
Erik Nakos, P.E. .
Project Manager
Enclosures: Figure 1: Drainage Plan Existing, Figure 2: Drainage Plan Proposed, Composite
Runoff Calculations, Grass Buffer BMP Calculation, Drainage and Erosion Control Report for
the Trail Head Property dated October 13, 2004, Sheets from Trail Head Drainage and Erosion
Control Plans
CC: Greg Oakes, City of Fort Collins
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JVA Incorporated Job Name: Trailhead Park I% C2 C5 C10 C100
213 Linden Street, S 200 Job Number: 3197c Streets Paved 100% 0.95 0.00 0.95 1.00
Fort Collins, CO 80524 Date: 3/3/20 Concrete Drives/Walks 90% 0.95 0.00 0.95 1.00
Ph: (970) 225 9099 By: EJK Roof 90% 0.95 0.00 0.95 1.00
Gravel 40% 0.50 0.00 0.50 0.63
Landscaping (B soil) 0% 0.15 0.00 0.15 0.19
Trailhead Park Landscaping (C/D soil) 0% 0.25 0.00 0.25 0.31
Historic Runoff Coefficient & Time of Concentration Calculations Playground 10% 0.11 0.00 0.11 0.14
Location: Fort_Collins Artificial Turf 25% 0.20 0.00 0.20 0.25
Minor Design Storm: 2
Major Design Storm: 100
Soil Type: C/D
Basin Design Data
I (%) = 100% 90% 90% 40% 10% 25% 0% 0% I (%) tc Comp
tc
Final
Basin
Name
Design
Point
Apaved
streets
(sf)
Adrives/co
nc (sf)
Aroof
(sf)
Agravel
(sf)
Aplygnd
(sf)
Aart. turf
(sf)
Alscape (B
soil)
(sf)
Alscape (C/D
soil)
(sf)
ATotal
(sf)
ATotal
(ac)
Imp
(%)
C2 C5 C10 C100
Upper
most
Length
(ft)
Slope
(%)
ti
(min)
Length
(ft)
Slope
(%)
Type of Land Surface K
Velocity
JVA Incorporated Job Name: Trailhead Park I% C2 C5 C10 C100
213 Linden Street, S 200 Job Number: 3197c Streets Paved 100% 0.95 0.00 0.95 1.00
Fort Collins, CO 80524 Date: 3/3/20 Concrete Drives/Walks 90% 0.95 0.00 0.95 1.00
Ph: (970) 225 9099 By: EJK Roof 90% 0.95 0.00 0.95 1.00
Gravel 40% 0.50 0.00 0.50 0.63
Landscaping (B soil) 0% 0.15 0.00 0.15 0.19
Trailhead Park Landscaping (C/D soil) 0% 0.25 0.00 0.25 0.31
Composite Runoff Coefficient Calculations Playground 10% 0.11 0.00 0.11 0.14
Location: Fort_Collins Artificial Turf 25% 0.20 0.00 0.20 0.25
Minor Design Storm: 2
Major Design Storm: 100 CA 100yr = 0.78i + 0.11
Soil Type: C/D CB 100yr = 0.47i + 0.426
CC/D 100yr = 0.41i + 0.484)
Basin Design Data
I (%) = 100% 90% 90% 40% 10% 25% 0% 0% I (%)
Basin Name
Design
Point
Apaved
streets
(sf)
Adrives/c
onc (sf)
Aroof
(sf)
Agravel
(sf)
Aplygnd
(sf)
Aart. turf
(sf)
Alscape (B
soil)
(sf)
Alscape
(C/D soil)
(sf)
ATotal
(sf)
ATotal
(ac)
Imp
(%)
C2 C5 C10 C100
A A 5,700 66,540 72,240 1.66 7.1% 0.31 0.00 0.31 0.37
B B 0 1,170 3,439 18,877 23,486 0.54 10.3% 0.32 0.00 0.32 0.39
C C 2,446 673 6,212 8,479 17,810 0.41 29.7% 0.46 0.00 0.46 0.54
D D 875 588 4,766 6,229 0.14 16.4% 0.37 0.00 0.37 0.44
E E 1,546 13 2,297 15,443 19,299 0.44 12.0% 0.34 0.00 0.34 0.41
F F 1,436 21 867 1,527 6,256 10,107 0.23 17.9% 0.35 0.00 0.35 0.41
G G 857 1,096 3,386 8,267 13,606 0.31 11.4% 0.28 0.00 0.28 0.34
OSA1 OSA1 1,927 11,839 13,766 0.32 12.6% 0.35 0.00 0.35 0.41
OSA2 OSA2 2,631 2,283 4,566 9,480 0.22 27.4% 0.41 0.00 0.41 0.46
OSB1 OSB1 3,056 3,056 0.07 0.0% 0.25 0.00 0.25 0.31
OSC1 OSC1 1,733 1,733 0.04 0.0% 0.25 0.00 0.25 0.31
OSD1 OSD1 757 757 0.02 0.0% 0.25 0.00 0.25 0.31
OSE1 OSE1 7,160 423 1,866 1,404 22,960 33,813 0.78 22.8% 0.41 0.00 0.41 0.48
OS1 OS1 11,810 4,890 4,119 20,819 0.48 77.9% 0.81 0.00 0.81 0.86
OS2 OS2 7,170 4,004 2,189 13,363 0.31 80.6% 0.84 0.00 0.84 0.89
OS3 OS3 2,580 1,659 438 4,677 0.11 87.1% 0.88 0.00 0.88 0.94
JVA Incorporated Job Name: Trailhead Park
213 Linden Street, S 200 Job Number: 3197c
Fort Collins, CO 80524 Date: 3/3/20
Ph: (970) 225 9099 By: EJK
Trailhead Park
Time of Concentration Calculations
Location: Fort_Collins
Minor Design Storm: 2
Major Design Storm: 100
Soil Type: C/D
Sub-Basin Data tc Comp
tc
Final
Basin
Name
Design
Point
ATotal
(ac)
C5
Upper
most
Length
(ft)
Slope
(%)
ti
(min)
Length
(ft)
Slope (%) Type of Land Surface Cv
Velocity
(fps)
tt
(min)
Time of
Conc
ti + tt = tc
Total
Length
(ft)
tc=(L/180)+
10 (min)
Min
tc
A A 1.66 0.00 215 2.0% 23.5 Short Pasture and lawns 7 0.0 0.0 23.5 215 11.2 11.2
B B 1.24 0.00 120 5.0% 12.9 Short Pasture and lawns 7 0.0 0.0 12.9 120 10.7 10.7
C C 0.41 0.00 80 1.5% 15.8 Short Pasture and lawns 7 0.0 0.0 15.8 80 10.4 10.4
D D 0.14 0.00 75 1.5% 15.3 Short Pasture and lawns 7 0.0 0.0 15.3 75 10.4 10.4
E E 0.44 0.00 250 0.8% 34.4 Short Pasture and lawns 7 0.0 0.0 34.4 250 11.4 11.4
F F 0.23 0.00 135 2.0% 18.6 Short Pasture and lawns 7 0.0 0.0 18.6 135 10.8 10.8
G G 0.31 0.00 140 2.0% 18.9 Short Pasture and lawns 7 0.0 0.0 18.9 140 10.8 10.8
OSA1 OSA1 0.32 0.00 40 10.0% 5.9 Short Pasture and lawns 7 0.0 0.0 5.9 40 10.2 5.9
OSA2 OSA2 0.22 0.00 20 5.0% 5.3 Short Pasture and lawns 7 0.0 0.0 5.3 20 10.1 5.3
OSB1 OSB1 0.07 0.00 30 8.0% 5.5 Short Pasture and lawns 7 0.0 0.0 5.5 30 10.2 5.5
OSC1 OSC1 0.04 0.00 30 8.0% 5.5 Short Pasture and lawns 7 0.0 0.0 5.5 30 10.2 5.5
OSD1 OSD1 0.02 0.00 30 8.0% 5.5 Short Pasture and lawns 7 0.0 0.0 5.5 30 10.2 5.5
OSE1 OSE1 0.78 0.00 200 2.0% 22.6 Short Pasture and lawns 7 0.0 0.0 22.6 200 11.1 11.1
OS1 OS1 0.48 0.00 20 4.0% 5.7 500 0.7%
Paved areas & shallow
JVA Incorporated Job Name: Trailhead Park
213 Linden Street, S 200 Job Number: 3197c
Fort Collins, CO 80524 Date: 3/3/20
Ph: (970) 225 9099 By: EJK
Trailhead Park Developed Storm Runoff Calculations
Design Storm : 100 Year Point Hour Rainfall (P
1) : 2.86
Basin Name
Design Point
Area (ac)
Runoff Coeff
tc (min)
C*A (ac)
I (in/hr)
Q (cfs)
Total tc
(min)
ΣC*A (ac)
I (in/hr)
Q (cfs)
Inlet Type
Q
intercepted
Q carryover
Q bypass
Pipe Size
(in) or
equivalent
Pipe Material
Slope (%)
Pipe Flow
(cfs)
Max Pipe
Capacity (cfs)
Length (ft)
Velocity (fps)
tt (min)
Total Time
(min)
Notes
A A 1.66 0.37 11.20 0.61 7.37 4.48 11.20 0.61 7.37 4.48 24" Area Drain 12 in PVC 1.1% 4.5 5.3 370 4.2 1.48 12.68
OSB1 OSB1 0.07 0.31 5.50 0.02 9.63 0.21 5.50 0.02 9.63 0.21
B B 1.24 0.39 10.70 0.49 7.51 3.67 10.70 0.49 7.51 3.67
DS of OSB1 & B 10.70 0.51 7.51 3.83 24" Area Drain 12 in PVC 1.7% 3.8 6.4 130 5.1 0.43 11.13
OSC1 OSC1 0.04 0.31 5.50 0.01 9.63 0.12 5.50 0.01 9.63 0.12
C C 0.03 0.54 10.40 0.02 7.60 0.12 10.40 0.02 7.60 0.12
DS of OSC1 & C 10.40 0.03 7.60 0.22 24" Area Drain
DS of B & C 11.13 0.54 7.39 3.98 12 in PVC 1.4% 4.0 6.0 63 4.7 0.22 11.35
OSD1 OSD1 0.02 0.31 5.50 0.01 9.63 0.05 5.50 0.01 9.63 0.05
D D 0.14 0.44 10.40 0.06 7.60 0.48 10.40 0.06 7.60 0.48
DS of OSD1 & D 10.40 0.07 7.60 0.52 24" Area Drain
DS of C & D 11.35 0.61 7.34 4.46 12 in PVC 1.5% 4.5 6.1 183 4.8 0.63 11.98
OSE1 OSE1 0.78 0.48 11.10 0.37 7.39 2.74 11.10 0.37 7.39 2.74
E E 0.44 0.41 11.40 0.18 7.32 1.31 11.40 0.18 7.32 1.31
DS of OSE1 & E 11.40 0.55 7.32 4.02 24" Area Drain
F F 0.23 0.41 10.80 0.10 7.48 0.72 10.80 0.10 7.48 0.72 24" Area Drain
DS of D,E & F 11.98 1.25 7.19 9.00 12 in PVC 1.5% 9.0 6.1 75 4.8 0.26 12.24
G G 0.31 0.34 10.80 0.11 7.48 0.79 10.80 0.11 7.48 0.79
DS of F & G 11.98 1.36 7.19 9.75 24" Area Drain 12 in PVC 1.9% 9.8 6.9 57 5.4 0.17 12.15
OSA1 OSA1 0.32 0.41 5.90 0.13 9.37 1.21 5.90 0.13 9.37 1.21
JVA Incorporated Job Name: Trailhead Park
213 Linden Street, S 200 Job Number: 3197c
Fort Collins, CO 80524 Date: 3/3/20
Ph: (970) 225 9099 By: EJK
Trailhead Park Developed Storm Runoff Calculations
Design Storm : 2 Year Point Hour Rainfall (P
1) : 0.82
Basin Name
Design Point
Area (ac)
Runoff Coeff
tc (min)
C*A (ac)
I (in/hr)
Q (cfs)
Total tc
(min)
ΣC*A (ac)
I (in/hr)
Q (cfs)
Inlet Type
Q
intercepted
Q carryover
Q bypass
Pipe Size
(in) or
equivalent
Pipe Material
Slope (%)
Pipe Flow
(cfs)
Max Pipe
Capacity (cfs)
Length (ft)
Velocity (fps)
tt (min)
Total Time
(min)
Notes
A A 1.66 0.31 11.20 0.51 2.11 1.07 11.20 0.51 2.11 1.07 24" Area Drain 12 in PVC 1.1% 1.1 5.3 370 4.2 1.48 12.68
OSB1 OSB1 0.07 0.25 5.50 0.02 2.76 0.05 5.50 0.02 2.76 0.05
B B 1.24 0.32 10.70 0.40 2.15 0.86 10.70 0.40 2.15 0.86
DS of OSB1 & B 10.70 0.42 2.15 0.90 24" Area Drain 12 in PVC 1.7% 0.9 6.4 130 5.1 0.43 11.13
OSC1 OSC1 0.04 0.25 5.50 0.01 2.76 0.03 5.50 0.01 2.76 0.03
C C 0.03 0.46 10.40 0.01 2.18 0.03 10.40 0.01 2.18 0.03
DS of OSC1 & C 10.40 0.02 2.18 0.05 24" Area Drain
DS of B & C 11.13 0.44 2.12 0.94 12 in PVC 1.4% 0.9 6.0 63 4.7 0.22 11.35
OSD1 OSD1 0.02 0.25 5.50 0.00 2.76 0.01 5.50 0.00 2.76 0.01
D D 0.14 0.37 10.40 0.05 2.18 0.12 10.40 0.05 2.18 0.12
DS of OSD1 & D 10.40 0.06 2.18 0.13 24" Area Drain
DS of C & D 11.35 0.50 2.11 1.05 12 in PVC 1.5% 1.1 6.1 183 4.8 0.63 11.98
OSE1 OSE1 0.78 0.41 11.10 0.32 2.12 0.68 11.10 0.32 2.12 0.68
E E 0.44 0.34 11.40 0.15 2.10 0.31 11.40 0.15 2.10 0.31
DS of OSE1 & E 11.40 0.47 2.10 0.99 24" Area Drain
F F 0.23 0.35 10.80 0.08 2.15 0.17 10.80 0.08 2.15 0.17 24" Area Drain
DS of D,E & F 11.98 1.05 2.06 2.16 12 in PVC 1.5% 2.2 6.1 75 4.8 0.26 12.24
G G 0.31 0.28 10.80 0.09 2.15 0.19 10.80 0.09 2.15 0.19
DS of F & G 11.98 1.14 2.06 2.34 24" Area Drain 12 in PVC 1.9% 2.3 6.9 57 5.4 0.17 12.15
OSA1 OSA1 0.32 0.35 5.90 0.11 2.69 0.30 5.90 0.11 2.69 0.30
JVA Incorporated Job Name: Trailhead Park
213 Linden Street, S 200 Job Number: 3197c
Fort Collins, CO 80524 Date: 3/3/20
Ph: (970) 225 9099 By: EJK
FRCC Health Care Career Center
LID AREA Calculations per City of Fort Collins
The implementation of LID systems requires one of the following two options:
Acres Notes
Total Site Area = 6.26 Area within the drainage boundary
Total Site Impervious Area = 0.89 Area of impervious surfaces
Added or Modified Impervious Area = 0.11 Area of impervious surfaces - existing impervious surface area
Required Impervious Area to
be treated by LID
= 0.08 75% of added or modified impervious area
Total Site Area to LID = 1.66
Provided Impervious Area to LID = 0.13
3197c-Rational Calculations LID AREA Page 6 of 6
Sheet 1 of 1
Designer:
Company:
Date:
Project:
Location:
1. Design Discharge
A) 2-Year Peak Flow Rate of the Area Draining to the Grass Buffer Q2
= 1.1 cfs
2. Minimum Width of Grass Buffer WG
= 21 ft
3. Length of Grass Buffer (14' or greater recommended) LG
= 250 ft
4. Buffer Slope (in the direction of flow, not to exceed 0.1 ft / ft) SG
= 0.020 ft / ft
5. Flow Characteristics (sheet or concentrated)
A) Does runoff flow into the grass buffer across the
entire width of the buffer?
B) Watershed Flow Length FL
= 50 ft
C) Interface Slope (normal to flow) SI
= 0.020 ft / ft
D) Type of Flow SHEET FLOW
Sheet Flow: FL
* SI
< 1
Concentrated Flow: FL
* SI
> 1
6. Flow Distribution for Concentrated Flows
7 Soil Preparation
(Describe soil amendment)
8 Vegetation (Check the type used or describe "Other")
9. Irrigation
(*Select None if existing buffer area has 80% vegetation
AND will not be disturbed during construction.)
10. Outflow Collection (Check the type used or describe "Other")
Notes:
Drainage Basin A
Till 5 CY of compost per 1000 SF to a depth of 6 inches.
Design Procedure Form: Grass Buffer (GB)
MEC
JVA, Inc.
3197c - Trailhead Park
March 3, 2020
UD-BMP (Version 3.07, March 2018)
Existing Xeric Turf Grass
Irrigated Turf Grass
Other (Explain):
Choose One
Choose One
Grass Swale
Street Gutter
Storm Sewer Inlet
Other (Explain):
None (sheet flow)
Slotted Curbing
Level Spreader
Choose One
Other (Explain):
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Choose One
Yes No
Choose One
Permanent
None*
Temporary
3197c-UD-BMP_v3.07, GB 3/3/2020, 12:56 PM
OSA2 OSA2 0.22 0.41 5.30 0.09 2.80 0.25 5.30 0.09 2.80 0.25
OSE1 OSE1 0.78 0.41 11.10 0.32 2.12 0.68 11.10 0.32 2.12 0.68
OS1 OS1 0.48 0.81 10.70 0.39 2.15 0.84 10.70 0.39 2.15 0.84
OS2 OS2 0.31 0.84 11.10 0.26 2.12 0.54 11.10 0.26 2.12 0.54
OS3 OS3 0.11 0.88 7.50 0.09 2.46 0.23 7.50 0.09 2.46 0.23
OS4 OS4 0.08 0.87 7.10 0.07 2.51 0.18 7.10 0.07 2.51 0.18
OS5 OS5 0.11 0.25 6.30 0.03 2.63 0.07 6.30 0.03 2.63 0.07
Direct Runoff Total Runoff Inlets Pipe Pipe/Swale Travel Time
3197c-Rational Calculations Q Minor Page 5 of 6
OSA2 OSA2 0.22 0.46 5.30 0.10 9.76 0.98 5.30 0.10 9.76 0.98
OSE1 OSE1 0.78 0.48 11.10 0.37 7.39 2.74 11.10 0.37 7.39 2.74
OS1 OS1 0.48 0.86 10.70 0.41 7.51 3.10 10.70 0.41 7.51 3.10
OS2 OS2 0.31 0.89 11.10 0.27 7.39 2.01 11.10 0.27 7.39 2.01
OS3 OS3 0.11 0.94 7.50 0.10 8.59 0.86 7.50 0.10 8.59 0.86
OS4 OS4 0.08 0.93 7.10 0.08 8.76 0.68 7.10 0.08 8.76 0.68
OS5 OS5 0.11 0.31 6.30 0.03 9.16 0.30 6.30 0.03 9.16 0.30
Direct Runoff Total Runoff Inlets Pipe Pipe/Swale Travel Time
3197c-Rational Calculations Q100 Page 4 of 6
paved swales
20 1.7 5.0 10.7 520 12.9 10.7
OS2 OS2 0.31 0.00 20 4.0% 5.7 500 0.6%
Paved areas & shallow
paved swales
20 1.5 5.4 11.1 520 12.9 11.1
OS3 OS3 0.11 0.00 20 3.0% 6.3 160 1.2%
Paved areas & shallow
paved swales
20 2.2 1.2 7.5 180 11.0 7.5
OS4 OS4 0.08 0.00 20 3.5% 5.9 100 0.5%
Paved areas & shallow
paved swales
20 1.4 1.2 7.1 120 10.7 7.1
OS5 OS5 0.11 0.00 20 3.0% 6.3
Paved areas & shallow
paved swales
20 0.0 0.0 6.3 20 10.1 6.3
Initial Overland Time (ti)
Travel Time (tt)
tt=Length/(Velocity x 60)
tc Urbanized Check
ON
3197c-Rational Calculations Developed Tc Page 3 of 6
OS4 OS4 1865 1394 394 3,653 0.08 85.4% 0.87 0.00 0.87 0.93
OS5 OS5 35 4,561 4,596 0.11 0.3% 0.25 0.00 0.25 0.31
TOTAL SITE 23,425 37,695 1,130 16,400 8,600 0 0 185,240 272,490 6.26 24.1% 0.42 0.00 0.42 0.48
Runoff Coeff's
3197c-Rational Calculations Developed C Page 2 of 6
(fps)
tt
(min)
Time of
Conc
ti + tt = tc
Total
Length
(ft)
tc=(L/180)+
10 (min.)
Min
tc
H1 1 7,350 7,350 0.17 0.0% 0.25 0.00 0.25 0.31 40 0.7% 14.4
Short Pasture and
lawns
7 0.0 0.0 14.4 40 10.2 10.2
H2 2 0 65,822 65,822 1.51 0.0% 0.25 0.00 0.25 0.31 250 1.2% 30.0
Short Pasture and
lawns
7 0.0 0.0 30.0 250 11.4 11.4
H3 3 7,580 7,580 0.17 0.0% 0.25 0.00 0.25 0.31 80 1.8% 14.8
Short Pasture and
lawns
7 0.0 0.0 14.8 80 10.4 10.4
D 4 139,077 139,077 3.19 0.0% 0.25 0.00 0.25 0.31 500 0.8% 48.6
Short Pasture and
lawns
7 0.0 0.0 48.6 500 12.8 12.8
OS1 OS1 11,810 4,890 4,119 20,819 0.48 77.9% 0.81 0.00 0.81 0.86 20 4.0% 5.7 500 0.7%
Paved areas & shallow
paved swales
20 1.7 5.0 10.7 520 12.9 10.7
OS2 OS2 7,170 3,505 2,688 13,363 0.31 77.3% 0.81 0.00 0.81 0.86 20 4.0% 5.7 500 0.6%
Paved areas & shallow
paved swales
20 1.5 5.4 11.1 520 12.9 11.1
OS3 OS3 2,580 1,225 872 4,677 0.11 78.7% 0.82 0.00 0.82 0.87 20 3.0% 6.3 160 1.2%
Paved areas & shallow
paved swales
20 2.2 1.2 7.5 180 11.0 7.5
OS4 OS4 1865 1075 713 3,653 0.08 77.5% 0.81 0.00 0.81 0.87 20 3.5% 5.9 100 0.5%
Paved areas & shallow
paved swales
20 1.4 1.2 7.1 120 10.7 7.1
OS5 OS5 10,149 10,149 0.23 0.0% 0.25 0.00 0.25 0.31 30 8.0% 5.5 520 0.8%
Paved areas & shallow
paved swales
20 1.8 4.8 10.4 550 13.1 10.4
TOTAL SITE 23,425 10,695 0 0 0 0 0 238,370 272,490 6.26 12.1% 0.34 0.00 0.34 0.40
Basin
Name
Design
Point
Time of
Conc
(tc)
C2 C5 C10 C100 2 5 10 100 ATotal (sf)
ATotal
(ac)
Q2 Q5 Q10 Q100
H1 1 10.2 0.25 0.00 0.25 0.31 2.19 0.00 3.75 7.66 7,350 0.17 0.09 0.00 0.16 0.40
H2 2 11.4 0.25 0.00 0.25 0.31 2.10 0.00 3.58 7.32 65,822 1.51 0.79 0.00 1.35 3.45
H3 3 10.4 0.25 0.00 0.25 0.31 2.18 0.00 3.72 7.60 7,580 0.17 0.09 0.00 0.16 0.41
D 4 12.8 0.25 0.00 0.25 0.31 1.99 0.00 3.41 6.97 139,077 3.19 1.59 0.00 2.72 6.95
OS5 OS5 10.4 0.25 0.00 0.25 0.31 2.18 0.00 3.72 7.60 10,149 0.23 0.13 0.00 0.22 0.55
TOTAL SITE 272,490 6.26 2.70 0.00 4.61 11.78
Initial Overland Time (ti)
Travel Time (tt) tt=Length/(Velocity x
60)
tc Urbanized Check
ON
Runoff Coeff's Rainfall Intensities (in/hr) Area Flow Rates (cfs)
Runoff Coeff's
3197c-Rational Calculations Historic Page 1 of 6
G
G
G
E
E
E
E
E
E
E
E E
E
E E
E
E
W
W
W
CM
CM
CM
CM
CM
CM
SW SW
SW SW
SW SW
SW SW SW
SW SW
G
CM
CM
CM
CM
CM
CM
CM
CM
CM
DRAINAGE PLAN
PROPOSED
FIGURE 2
PROJ. NO.
DRAWN:
CHECKED:
DATE:
REVISIONS :
SCALE:
SHEET NUMBER
SHEET TITLE:
ISSUED FOR:
APPROVED:
...
DEC 2019
BDR SUBMITTAL
TRAIL HEAD PARK
FOR THE MARKING OF UNDERGROUND
BEFORE YOU DIG, GRADE, OR EXCAVATE
CALL 2 BUSINESS DAYS IN ADVANCE
IN METRO
DENVER
1-800-922-1987
CENTER OF COLORADO
CALL UTILITY NOTIFICATION
MEMBER UTILITIES
OR 534-6700
Park Planning
& Development
City of
215 North Mason Street
Fort Collins, Colorado 80521
tel: 970.221.6360
www.fcgov.com/parkplanning/
Park Planning & Development
CITY OF FORT COLLINS
FORT COLLINS, COLORADO
TRAIL HEAD PARK
BASIC DEVELOPMENT REVIEW SUBMITTAL
EJK
ETN
CRH
G
G
G
G
G
G
G
G
G
G
G
G
G
E
E
E
E
E
E
E
E E
E
E E
E
E
W
W
W
CM
CM
CM
CM
CM
CM
SW SW
SW SW
SW SW
SW SW SW
SW SW
G
CM
CM
CM
CM
CM
CM
CM
CM
CM
DRAINAGE PLAN
EXISTING
FIGURE 1
PROJ. NO.
DRAWN:
CHECKED:
DATE:
REVISIONS :
SCALE:
SHEET NUMBER
SHEET TITLE:
ISSUED FOR:
APPROVED:
...
DEC 2019
BDR SUBMITTAL
TRAIL HEAD PARK
FOR THE MARKING OF UNDERGROUND
BEFORE YOU DIG, GRADE, OR EXCAVATE
CALL 2 BUSINESS DAYS IN ADVANCE
IN METRO
DENVER
1-800-922-1987
CENTER OF COLORADO
CALL UTILITY NOTIFICATION
MEMBER UTILITIES
OR 534-6700
Park Planning
& Development
City of
215 North Mason Street
Fort Collins, Colorado 80521
tel: 970.221.6360
www.fcgov.com/parkplanning/
Park Planning & Development
CITY OF FORT COLLINS
FORT COLLINS, COLORADO
TRAIL HEAD PARK
BASIC DEVELOPMENT REVIEW SUBMITTAL
EJK
ETN
CRH