HomeMy WebLinkAboutDrainage Reports - 11/10/1984November 5, 1984
James H. Stewart and Associates, Inc.
214 North Howes Street
Fort Collins, Colorado 80522.
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DRAINAGE.REPORT FOR "SOMERSET"
INTRODUCTION: �.
This final drainage report is submitted in conjunction with the final
site plan and-a�lity plans for Somerset P.U.D. as prepared by Ron Shafer
and James H.-Stewart and Associates, Inc. respectfully.
SITE DESCRIPTION:1 ,
Somerset P.U.D..is a replat of Park Place at the Landings P.U.D. located
in the Southwest-1/4 of Section 36, Township 7 North, Range 69 West of the
6th P.M. .The P.U.D. will contain 220 apartment units in 14 buildings and a
recreation center constructed in one phase. The site contains 10.9 acres
that is presently grassed and slopes from Northwest to Southeast at approxi-
mately 1.00%:;-.-The site is bordered on the East by Landings Park, on the
Northeast by'Boardwalk Drive, on the.North by the Larimer County No. 2 Canal
and on the West and South by vacant agricultural land. Troutman Parkway is
being developed in the North portion of the P.U.D.
HISTORIC DRAINAGE:
Stormwater from the site has historically drained to the southeast to
a major basin thalweg. This thalweg carried stormwater towards the inter-
section of Harmony Road and Lemay Avenue. Due to development in the area,
the site now drains to Harmony Reservoir via an open channel beginning in the
southeast portion of the site, crossing through the city park, then crossing
underneath Boardwalk Drive via two 36 inch RCP culverts. Under City of Fort
Collins Stormwater Criteria and assuming inlet control these culverts have a
combined capacYty of 70 cfs and 110 cfs for the `0-yam a a d 100-year events,
respectively. Historic runoff from the site was calculated as 2.2 cfs and
8.2 cfs for the-2 year and 100 year intensity storms, respectively.
MASTER DRAINAGE:
.The site presently drains to Harmony Reservoir via the open channel
described above as a result of recommendations made in a master storm
drainage report for the Landings P.U.D. by Cornell Consulting Company in
January, 1979. This report concluded that detention on site was unnecessary,
as Harmony Reservoir could safely accomodate all anticipated undetained
tupstream stormwater discharges. However, due. to the fact the owner was
unable a to acquirea drainage easement across_ Landings Park from the City
' `of fort Collins to the existing culverts under Boardwalk Drive, it was
necessary to provide on site detention and release into the channel through
—� Landings;:Park at .the.histori utflow rate.
DRAINAGE, UNDER DEVELOPED CONDITIONS:
Using a mass diagram,.which is att ched, it was determined that to
detain the difference between the t year historic storm and the 100 year .
' developed -storm; 58,320 cubic feet of detention was required. There will.
be five separate p nds'constructedOlin site that have a total volume of
58,410 cubic :feet.- The outflow will be restricted to 2.2 cubic feet per
second out of Pond.Ill into the/Landings Park Channel. The ponds, their
capacities and their outflow/o pes and rates are shown on the site grading
plan which is apart�,o/f the utility plan. Tki,a ak-e no o�fr.10 f/emr e•,+a.,:,9
+611 h'•ope°f7 KS - f "f. Pow.( rResSect 11 �submittedL,��/v,
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JAME)'S H. S,,TEWART AND ASSOCIATES, INC.
Richard A. Rutherford, PPU�.E. & L.S.
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COMPUTATIONS
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James H. Stewart & Assoc. `. -
Fort Collins, Colorado
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COMPUTATIONS
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James H. Stewart &
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Fort Collins, Colorado:
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