HomeMy WebLinkAboutGENERAL CARE HEALTH SERVICES - PDP - 22-00 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT3
Offsite Basin I is that part of the South half of Poudre River Drive that flows to Lemay
Avenue and the East half of Lemay Avenue adjacent to the site. Offsite Basin I does not drain onto
our site.
Offsite Basin 11 is the Northerly half of the Burlington Northern Railroad right-of-way
adjacent to the site. It is fairly flat and does not drain very well. The runoff will run across the
Southeast corner of the lot and also Southeasterly in the railroad Borrow ditch. There is an existing
24 inch culvert that is lower than all the ground in Offsite Basin II.
D.B.-I will have a medical building and a parking lot constructed on it. Due to the limited
capacity in the storm drain system we have designed an onsite storm water detention pond in the
parking lot and a part of the landscaped area. The detention volume provided is 10,169 cubic feet.
The discharge rate is 1.00 c.f.s.. The discharge rate is a small amount larger than the two year
historic rate of 0.41 c.f.s. but is detaining the difference between the 1.00 c.f.s. and the developed
100 year runoff rate of 6.24 c.f.s.. A storm drain will be constructed in the proposed parking lot with
two area inlets to capture the runoff. The storm drain will discharge into the back of the existing inlet
at the Southwest corner of the intersection of Poudre River Drive and Hoffman Mill Road.
EROSION CONTROL: The site is in the moderate rainfall erodibility zone and in the moderate wind
erodibility zone.
A silt fence will be constructed along the North and East property fines. Straw bales will be
placed around the two proposed area inlets when the pipes are laid. After the inlets are constructed,
we will place a rock filter at the two inlets until the pavement is laid.
An extended detention pond will be constructed between the parking area and Poudre River
Drive for water quality requirements.
The stormwater runoff calculations, the erosion control calculations, the water quality
calculations and the grading plan and drainage plan are enclosed as a part of this report.
This drainage report and the design of the drainage system are in compliance with the City
of Fort Collins Storm Drainage Design and Criteria. If you have any questions regarding this report,
please call.
Sincerely,
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Richard A. Rutherford P.E. & .S.
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IJuly 27, 2000
Mr. Basil Harridan
Stormwater Utilities
City of Fort Collins
P.O. Box 580
Fort Collins, CO 80522-0580
Dear Basil,
The following is the final drainage report for Poudre River Business Park, Third Filing situate
in the Northwest 1/4 of Section 18, Township 7 North, Range 68 West of the 6th P.M., Fort Collins,
Colorado.
The site is in the Cache la Poudre River Basin and contains a net area of 1.316 acres and a
gross area of 1.559 acres. The site slopes Southwest to Northeast at an approximate slope of 1.2%.
The site has a good ground cover of grass and weeds. The site is bounded on the North by Poudre
River Drive, on the East by Hoffman Mill Road, on the Southwest by the Burlington Northern
Railroad and on the West by Lemay Avenue.
The site is served by an existing storm drain system. There is an existing curb inlet at the
Southwest corner of the intersection of Poudre River Drive and Hoffman Mill Road. An existing 15"
R.C.P. storm drain flows East in Poudre River Drive to another curb inlet at the Southeast corner of
the intersection. Then an existing 18" R.C.P. storm drain flows North across Poudre River Drive to
another curb inlet. An existing 24" A.D. S. storm drain flows to an existing area inlet in the Internal
Medicine Clinic parking lot and then continues down the bank to the Cache la Poudre River. The
capacity of the 24" A.D.S., N-12 pipe is 23 c.f.s. The 100 year runoff rate for The Poudre River
Business Park, First Filing is 7.98 c.f.s. and for the Second Filing is 5.92 c.f.s., for a total runoff rate
of 13.9 c.f.s.. The 13.9 c.f.s. includes the runoff from the streets that are existing and that drain to
the three curb inlets. The Westerly 150 feet of Poudre River Drive flows West to Lemay Avenue and
North in Lemay Avenue to the Cache la Poudre River. Therefore the unused capacity of the storm
drain system is 9.1 c.f.s..
The site is divided into two historic basins and also two developed basins, which are the same
H.B.-I and D.B.I. are the proposed lot and that part of the right-of-way from the back of the
sidewalks to the right-of-way line. H.B.-1 and D.B.-1 contain 1.316 acres. The two year historic
runoff rate is 0.41 c.f.s. and the 100 year historic runoff rate is 1.84 c.f.s.. The two year developed
runoff rate is 1.34 c.f.s. and the 100 year developed runoff rate is 6.24 c.f.s..
BB -II an D.B.-II are the South half of Poudre River Drive and the West half of Hoffman Mill
Road that are adjacent to this filing and drain to the existing curb inlet at the Southwest corner of the
intersection of Poudre River Drive and Hoffman Mill Road. The area of H.B.-II & D.B.-II is 0.243
acres. The two year historic and developed runoff rate is 0.64 c.f.s. and the 100 year historic and
developed runoff rate is 2.42 c.f.s..
A
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TABLE OF CONTENTS
1 Vicinity Map
2-3 Teat of Report
4-8 Stormwater Runoff Calculations
9-10 Detention Pond Mass Diagram & Pond Volume Table
11 Orifice Sizing
12-15 Erosion Control Calculations
16-18 Extended Detention Calculations
Pocket Grading Plan and Drainage Plan
FINAL DRAINAGE REPORT
FOR
POUDRE RIVER BUSINESS PARK, THIRD FILING
CACHE LA POUDRE BASIN
PREPARED FOR
GENERAL CARE HEALTH SERVICES, INC.
JULY 27, 2000
PREPARED BY
STEWART & ASSOCIATES
103 SOUTH MELDRUM STREET
P.O. BOX 429
FORT COLLINS, CO 80522
TEL. 970-482-9331
FAX. 970-482-9382