HomeMy WebLinkAboutHARMONY MARKET PUD, 6TH FILING, RED ROBIN - PRELIMINARY & FINAL - 54-87T - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTa
FINAL DRAINAGE AND EROSION CONTROL REPORT
RED ROBIN RESTAURANT
PART OF LOT 1, HARMONY MARKET P.U.D.
FORT COLLINS, COLORADO
Prepared for:
CS Architects
7555 East Hampden Ave.
Suite 525
Denver, CO 80231
Attn: Craig Cahen
Prepared by:
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Engineering Service Compcn a
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FROM: David R. Addor
March 30, 1994
PROJECT LOCATION
Red Robin Restaurant is located on the southeast corner of Harmony
Road and Boardwalk Drive (Lemay St. extended), in Section 1,
Township 5 North, Range 69 West of the Sixth Principal Meridian,
City of Fort Collins, Larimer County, Colorado. It is part of the
Harmony Market P.U.D, and contains approximately 1.52 acres of
primarily undeveloped land which is to be developed into a
restaurant with. adjacent parking and landscaping.
PROPERTY DESCRIPTION
The site is bounded on the north by landscaping and irrigation
easements with Harmony Road (Colorado Highway 68) beyond, on the
east by vacant land, on the south by an existing access road for
Harmony Market, complete with curb, gutter, and sidewalk, and
commercial development beyond, and on. the west by existing
Boardwalk Drive with agricultural land (the Rule property) beyond.
The ground slopes generally to the southwest at about 2%. The
soils are within the "Moderate Wind Erodibility Zone" as defined
by the Wind Erodibility Map of Fort Collins (City of Fort Collins
Stormwater Utility Storm Drainage Design Criteria and Construction
Standards, May. 1984) ("Ft. Collins Criteria").
The site lies within the drainage area of the McClellands Basin
major drainageway. As part of the McClellands Basin Master Plan
detention for this site will be provided (in an existing detention
pond in the Pace Warehouse/Sam's Club parking area just downstream
to the southeast. Per the "Final Drainage Study for the Harmony
Market P.U.D., RBD, Inc., Engineering Consultants, Fort Collins,
Colorado, April 21, 1989, the detention provided in downstream
ponds in Harmony Market P.U.D. is sufficient to reduce overall site
outflow rates to those required by the City of Fort Collins for
this location (0.2 cfs,/acre). (See Appendix for sketch of drainage
schematic.)
DRAINAGE DESIGN CRITERIA
The Rational Method of storm drainage analysis is used for this
report, with the basic criteria being. taken from the Fort Collins
Criteria. Calculations are included for the 10-year and 100-year
storms, per City requirements. The runoff coefficient. was evaluated
for the actual site layout. The 10-year coefficient was calculated
at 0.82; the 100-year at 0.88.
PROPOSED DRAINAGE
This proposed grading will follow the existing drainage pattern.
The restaurant building pad will be raised to provide visibility,
and the site graded to the southeast to direct runoff via paving
and curb -and -gutter towards the existing detention pond. Offsite
area 0 (0.36 acres of greenbelt along the north and west sides)
will sheet flow onto the site. The onsite area was evaluated as
one basin, Area A. Peak flow rates for Basin a and the offsite
will be 6.6 cfs for the 10-year storm, and 10.0 cfs for the 100-
year storm.
A cobbled swale will be built around the western end of the
building to direct runoff from offsite area 0 and the large
landscaped section of Area A into the parking area.
ER091ON CONTROL
Erosion control during construction will consist of silt fence
along the southern boundary, to prevent soil entering the existing
access road. It is anticipated that because of the small size
of the site, the time during which the ground will be bare, before
installation of permanent paving and other ground cover will be
relatively short (approximately 45-60 days.)
CONCLUSION
This report and the accompanying plan are prepared in accordance
with the Fort Collins Criteria and complies with the McClellands
Basin Master Plan. Drainage will be effectively controlled by
surface treatments and storm sewer. There will be no impact on the
major drainageways caused by this development as it is in
conformance with the planned development for this ground.
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COMPOSITE RUNOFF COEFFICIENT
Onsite area = 1.52 acres: 18% landscaping (slopes 2-7%, heavy
soils), 82-% parking lot and roof
cio = (0.18)(0.25) + (0.82)(.95) = 6.82
cloo (0.18) (0.25) (1.25) + (0.82) (1.00) = 0.88
Offsite = 0.36 acres of landscaping
c io = 0.25
cioo = 0.25 x 1.25 0.31
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VELOCITY IN FEET PER SECOND
FIGURE 3-2. ESTIMATE OF AVERAGE FLOW VELOCITY FOR
USE WITH THE RATIONAL FORMULA.
MOST FREQUENTLY OCCURRING "UNDEVELOPED"
LAND SURFACES IN THE DENVER REGION.
REFERENCE: "Urban Hydrology For Small Watersheds" Technical
Release No. 55. USDA. SCS Jan. 1975.
5-1-84
URBAN DRAINAGE & FLOOD CONTROL DISTRICT
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