HomeMy WebLinkAboutPOUDRE R1 JUNIOR HIGH SCIENCE LAB ADDITIONS SITE PLAN ADVISORY REVIEW - 7 93 - DECISION - STORMWATER-RELATED DOCUMENTS1--AKE; 'ETRWJ�-:T
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103S.MELDRUN ORT COLLINS, C080521
PH. 482-9331 FAX 482-9382
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Ms. Kathy Malers
February 19, 1993
Page 2
Due.to the facts that the very small additional runoff generated by the
science room addition will have insignificant downstream impact, and that the
science room runoff peak will be routed through the detention pond before the
larger upstream peak flow reaches the pond, we hereby request a variance from
the onsite detention_ requirement for the additional runoff generated by the
science room addition.
LESHER JUNIOR HIGH SCHOOL
The Lesher Junior High School science room addition will add 3200 square
feet of impervious area: This new hard surface will be constructed over
existing lawn.
The roof drainage from the existing school building drains to an existing
12—inch storm drain in Stover Street. This 12—inch drain line most certainly
is overloaded since it also picks up flow from two (2) inlets. The addition
of the roof runoff from the new science room to this existing 12—inch storm
drain will cause ponding in Stover Street, and probable overflow from Stover
Street onto East Prospect Road.
The building design architects, Robb, Brenner and Brelig, plan to run
this roof drainage into a dry well. This dry well is to be placed on the east
side of the science room addition. The'dry well will be constructed with a
bubbler grate so that the overflow will surface on the athletic field and drain
overland across the grass field to the southeast corner of the school site.
The attached site plan shows the proposed drainage route.
Due to the facts that the additional runoff generated by the science room
addition is relatively small, 573 cubic feet, and that the runoff will be routed
through a dry well and then across the grassed athletic field where the time
of flow will be increased from 4.2 minutes to 9.5 minutes and the infiltration
will be increased, we hereby request a variance from the onsite detention
requirement for the additional runoff generated by the science room addition.
Thank you for your consideration regarding these requests. If you have
any questions regarding these projects, please call.
Sincerely,
Phillip I. Robinson, P.E. & L.S.
Vice President
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Attachments
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cc: Mr. Ron Daggett, Poudre School District R-1 fill
Mr. Bill Brenner, Robb, Brenner and Brelig, Inc.
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Consulting Engineers and Surveyors
February 19, 1993
Ms. Kathy Malers
Stormwater Utility
City of Fort Collins
P.O. Box 580
Fort Collins, Colorado 80522
Dear Kathy:
Mr. William Brenner of Robb, Brenner and Brelig, Inc. is designing science
room additions to Blevins, Boltz, and Lesher Junior High Schools for Poudre
School District R-1. Mr. Brenner and Poudre R-1 have requested that I prepare
an analysis of the additional stormwater generated by these additions and of
its effect on downstream areas.
BLEVINS JUNIOR HIGH SCHOOL
The addition at Blevins Junior High
over an area that is existing pavement;
area will be created, and there will be.
no onsite detention is required.
BOLTZ JUNIOR HIGH SCHOOL
School will be constructed entirely
therefore, no additional impervious
no increase in runoff. Therefore,
The proposed addition will result in an additional 1620 square feet of
impervious area. The new addition is approximately 300 feet upstream from
the Lemay detention pond, and runoff from the addition will drain via gutter
to the pond.
The attached sheets show the calculations which substantiate the following
three statements:
1) The maximum increase in the 100—year peak runoff will be 0.18 c.f.s.
2) The total additional runoff from the increased impervious area will
be 269 cubic feet which, if the detention pond outlets were plugged,
would raise the high water line surface of the pond by 0.00078 feet.
3) The time of concentration from the science room addition to the pond
is approximately five (5) minutes while the time of concentration
from Foothills Fashion Mall, which contributes the largest amount
of runoff to the basin, and which is located at the upper end of
the basin, is 28.6 minutes. This indicates the additional runoff
from the science room addition will be routed through the pond before
the larger runoff from upstream reaches the pond.
James H. Stewart
and Associates, Inc.
103 S. Meldrum Street
P.O. Box 429
Ft. Collins, CO 80522
303/482-9331
Fax 303/482-9382