HomeMy WebLinkAboutSHADELAND TOWNHOMES - PDP - 17-98 - REPORTS - DRAINAGE REPORT5)
VICINITY MAP
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SCALE: 1 "= 1000,
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basin `S" is the rear yards and the rear half of the houses on the South side of the site. Sub -basin
`S" sheet flows onto the site and flows through the detention pond to the Prospect Road storm
drain.
The grading of the site matches the existing grading at the boundary line on the East, West
and South sides of the site. There will not be a need for off -site grading easements.
EROSION CONTROL: The site is in the moderate rainfall and wind zones.
. The foundations for the 5-plex and for the garage will be poured as soon as the excavation is
completed. The existing driveway gravel base will not be disturbed. Gravel base will be placed
between the two foundations as a staging area. A silt fence will be placed along the East property
line and a straw bale filter will be placed at the area inlet.
The effectiveness of the erosion control is 74.2% which is greater than the required 72.3%.
The runoff calculations, the detention pond calculations and the erosion control calculations
are enclosed as a part of this report. The grading and drainage plan is also enclosed.
This drainage report and the design of the drainage system were made in substantial
compliance with the City of Fort Collins Storm Drainage Design Criteria and Construction
Standards.
If you have any questions during your review of this report, please call.
Sincerely,
Caj4.4r. a Richard A. Rutherford, P. . & L. S.
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STEWART&ASSOCIATES
Consulting Engineers and Surveyors
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July 20, 1998
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Mr. Basil Hamdan
Storm Water Utility
City of Fort Collins
P.O. Box 580
Fort Collins, CO 80522
Dear Basil,
The following is the final drainage report for Shadeland Townhomes at 521 East Prospect
Road. The site contains 0.442 acres and is in the Spring Creek Major Drainage Basin. The site is
described as Lot 2, Holsinger First Subdivision.
The site is "T" shaped with the leg being the access from Prospect Road. The site is bounded
by single family detached houses on all sides. The site slopes from Southwest to Northeast at an
approximate slope of 0.4%. The site is zoned L.M.N.
The Fort Collins Housing Authority is proposing to construct five, two-story twnhomes and
a five bay garage on Lot 2.
We have designed an on -site storm water detention pond in the parking area to detain the
difference between the two year historic runoff and the 100 year developed runoff. The required
volume of detention is 3,066 cubic feet.
The two year historic runoff rate is 0.16 c.f. s. and the 100 year developed runoff rate is 2.65
c.f.s. The runoff coefficient increases from a historic "C" of 0.25 to a developed "C" of 0.67.
The detention pond, as designed will have a volume of 3,686 cubic feet. It is proposed to
discharge the storm water from the detention pond in a proposed 12 inch diameter R.C.P. pipe
that will discharge into an existing storm drain in Prospect Road.
The storm water runoff will then flow Easterly in the existing storm drain to Stover Street and
then South to Spring Creek in an existing storm drain. .
The runoff from the South 1/2 of Prospect Road and the North 25 feet of the driveway flows
Easterly in the South gutter of Prospect Road to an existing catch basin at the comer of Prospect
Road and Smith Place. The catch basin discharges into the Prospect Road storm drain.
There are two offsite sub -basins that drain through this site. Off -site basin "A" is the small lot
on the West side of the driveway which will flow through the proposed detention pond. Off -site
James H. Stewart
and Associates, Inc.
103 S. Meldrum Street
P.O. Box 429
Ft. Collins, CO 80522
970/482-9331
Fax 970/482-9382
Table of Contents
1 - 2 Text of Report
3 Vicinity Map
4 - 9 Storm Water Runoff Calculations & Mass Diagram
10 Detention Pond Rating Curve
11 - 12 Restriction Plate Calculation & Area Inlet Capacity
13 - 17 UD Sewer Model & Spillway Design
18 - 21 Erosion Control
22 - 23 Easement Dedication & Plat
24 Freeboard Variance Request
Pocket Grading, Drainage and Erosion Control Plan
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FINAL DRAINAGE RE]
FOR
SHADELAND TOWNHOMES
521 EAST PROSPECT ROAD
SPRING CREEK DRAINAGE BASIN
PREPARED FOR
FORT COLLINS HOUSING AUTHORITY
JULY 2091998
PREPARED BY
STEWART & ASSOCIATES, INC.
103 SOUTH MELDRUM STREET
FORT COLI,INS, COLORADO 80521
970/482-9331