HomeMy WebLinkAbout800, 808 & 814 W. PROSPECT RD. MIXED-USE (OBSERVATORY PARK) - PDP - 41-02A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTc 3>
detention volume is 2,376 cubic feet for the difference between the two-year historic volume and
the 100-year developed volume.
Developed Basin III contains 0.0760 acres and is the landscape strip along the West
property line and the North property line and the North half of the landscape strip along the East
property line. The runoff coefficient for the developed site is 0.28. The two-year runoff rate is
0.057 C.F.S. and the 100-year rate is 0.248 C.F.S. We are not proposing to detain the runoff
since it is landscaping except for the 1.00 foot wide concrete pan and a 15-foot long sidewalk.
EROSION CONTROL:
The wind erodibility is moderate and the rainfall erodibility is high. A silt fence will be
constructed along the North and East property lines before construction begins. The ponds in the .
Southwest corner of the site and the Southeast corner of the site will be graded and a sediment
trap will be placed at the outlet before the chases are constructed until the Water Quality box is
completed. The contractor will remove any mud off of Prospect Road daily.
The stormwater runoff calculations and the erosion control calculations and the water
quality calculations are enclosed as a part of this drainage report.
This drainage report and the design of the drainage system are in compliance with the
City of Fort Collins Storm Drainage specifications and criteria.
If you have any questions regarding this report, please call.
Sincerely,
G2i'� a.
Richard A. Rutherford, P.E. & L.S.
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STEWART&ASSOCIATES
Consulting Engineers and Surveyors
September 20, 2002
Mr. Basil Hamdan
Stormwater Utility
City of Fort Collins
P.O. Box 580
Fort Collins, CO 80522-0580
Dear Basil,
The following is the Final Drainage Report for 808 West Prospect Frazier PDP which is
situate in the Southeast 1/4 of Section 14, Township 7 North, Range 69 West of the 6th P.M.,
City of Fort Collins, County of Larimer, State of Colorado. The site is part of Lot 20, College
Heights and part metes and bounds which is all being replatted.
The site is in the Spring Creek Basin and contains 0.7605 acres. It is zoned HMN-High
Density Mixed -Use Neighborhood. The proposed uses are 33 apartment units and two offices.
The site is bounded by Prospect Road on the South, a single family residence on the
r West, and apartment building on the North and a single family residence on the East.
The site slopes from West to East at an approximate slope of 1.7%. There are two
existing single family residences on the site and the ground cover is grass, gravel, gardens and
hard surfacing.
The historic site is in one basin. The runoff sheet flows from West to East. The two-year
runoff rate is 0.56 C.F.S. and the 100-year runoff rate is 2.57 C.F.S. There are no storm drains in
the area.
We have three developed basins proposed. Developed Basin I contains 0.3860 acres and
is the West half of the building and the West parking lot. The runoff coefficient for the
developed site is 0.89. The two-year runoff rate is 0.92 C.F.S. and the 100-year runoff rate is
3.84 C.F.S. The runoff will be detained on site in the West parking lot and in the Water Quality
Pond at the Southwest corner of the lot. The required detention volume is 3,067 cubic feet for
the difference between the two-year historic volume and the 100-year developed volume.
Developed Basin II contains 0.2985 acres and is the East half of the building and the
South driveway. The runoff coefficient for the developed site is 0.82. The two-year runoff rate
is 0.59 C.F.S. and the 100-year runoff rate is 2.97 C.F.S. The runoff will be detained on site in
the South driveway and the Water Quality Pond along the South property line. The required
James H. Stewart and Associates, Inc.
8W W Prof fm &ngrpcam 103 S. Meldrum Street • P.O. Box 429 • Ft. Collins, CO 80522
970/482-9331 9 Fax 970/482-9382
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TABLE OF CONTENTS
1
Vicinity Map
2-3
Text of Report
4-9
Stormwater Runoff Calculation
10
Drainage Table
11-12
Detention Mass Diagram
13
Pond Volume Tables
14
Orifice Sizing Calculations
15-18
Erosion Control Calculations
19-21
Extended Detention Calculations
Pocket
Grading, Drainage & Erosion Control Plan
FINAL DRAINAGE REPORT
FOR
808 WEST PROSPECT FRAZIER PDP
SPRING CREEK BASIN
PREPARED FOR
KEVIN FRAZIER
SEPTEMBER 20, 2002
PREPARED BY
STEWART & ASSOCIATES
103 SOUTH MELDRUM STREET
P.O. BOX 429
FORT COLLINS, CO 80522
TEL. 970-482-9331
FAX. 970-482-9382
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