HomeMy WebLinkAboutHORSETOOTH WEST MASTER PLAN - 14-88 - SUBMITTAL DOCUMENTS - ROUND 1 - STORMWATER-RELATED DOCUMENTSMarch 4, 1988
Mr. Ted Shepard
City of Fort Collins
Planning and Development
Box 580
Fort Collins, Colorado 80522
RE: HORSETOOTH WEST MASTER PLAN
PROJECT 87-493
DRAINAGE CONCEPT
FORT COLLINS, COLORADO
Dear Ted:
1
GEFROH HATTMAN INC.
ARCHITECTS/PLANNERS
CONSTRUCTION MANAGEMENT
135 West Swallow Road
Fort Collins, CO 80525
(303) 223-7335
The purpose of this letter is to outline the concept for disposing of storm
water runoff from this 60.45 acre parcel which will be known as the Horse -
tooth West Master Plan. The property is a mixed land use project with such
uses as single-family detached housing, multi -family attached housing, an
elementary school site, a child care center site, a neighborhood center,
and a road side commercial site.
Area -- The site is located at the Northwest intersection of Taft Hill
Road and Horsetooth Road with frontages of approximately 1400 feet and 2000
feet respectfully. The property is developed on three sides with residential
uses of various densities from estate type lots to a mobile home park. The
undeveloped property lies to the West.
Off -Site Contribution -- is considered non-existent when reviewing the
topography. The area crowns approximately in the Southwest corner of the
property. Irrigation canals West of the site will intercept or dam the run-
off from off site. The majority of this adjacent property runoff flows
North and West into Spring Creek.
The subject property is a relatively level property sloping from the South-
west corner to the Northeast corner. Previously used for crop land, there was
no significant topographic changes that occurred on site. The average slope
of the land is between one percent and two percent consistently cross contour.
Historically runoff from the property has flowed to Taft Hill Road then heads
North to Spring Creek.
Criteria -- Due to the size of the study area for purposes of calculations
which will be developed for each individual parcel as it is designed, the
Rational Method as found in the Urban Storm Drainage Manual will be followed.
The Rational Method relates runoff to rainfall intensities:
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If Mr. Ted Shepard
HORSETOOTH WEST MASTER PLAN
DRAINAGE CONCEPT
March 4, 1988
Page 2
Q = CiACf
Q = Maximum Peak Rate - (C.F.S.)
C = Runoff Coefficient - in./hr.
i = Average Rain Intensities - Duration of in./hr.
Cf = Frequency Factor
The runoff coefficiencies will vary from the historic factor due to type of
uses. These factors when used in the calculations will reflect the City of
Fort Collins Storm Drainage criteria. Rain fall intensities will be deter-
mined from City of Fort Collins Storm Drainage Intensity Curves.
Method -- The Master Plan indicates various land uses which will handle storm
drainage in various fashions. The single-family areas are intended to use
a combination of curb inlets and conduits to transport runoff East to the
drainage facility adjacent to Taft Hill. Primary detention for these two
major areas will occur at that facility prior to being released down stream
at historic rates.
The Neighborhood Center and the auto -related commercial area will provide de-
tention on site on hard surfaced parking areas prior to releasing at historic
rates through an inlet and conduit system to the facility at Taft Hill prior
to releasing down stream.
The school site, the child care and the multi -family areas will use combin-
ations of parking lot and landscape area -type detention and release through
swales, concrete channels, curbs and inlet and conduit systems. Runoff will
be transported to the facility at Taft Hill prior to being released down
stream.
Due to the locations of these various parcels from the common detention and
release area flows will be staged to minimize the size of one facility and
providing the majority of the detention being resolved on the individual
parcels will handle nuisance flows and prevent curb topping in storms from
two years through 100-year occurrences.
Sincerely yours,
GEFROH HATTMAN INS.
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