HomeMy WebLinkAboutDrainage Reports - 04/08/1994STEWART&l\SSOCIATES
April 7, 1994
Mr. Glen Schlueter
Storm Water Utility
City of Fort Collins
P. 0. Box 580
Consultin3 En3ineers and Surveyors
Fort Collins, Colorado 80522
Dear Glen:
Re: Construction of an Automobile Garage for
Bohlender Funeral Home at 120 West Magnolia Street
An automobile garage is proposed on the South 80 feet of the East 60 feet
of Lots 15 and 16, in Block 113 of Fort Collins. This site contains 4800 square
feet and is located on the north side of West Magnolia Street between the
telephone company building on the west and the alley on the east. There was
a house on this site which was recently removed. The house was being used
as an office, and there was paved parking along its east side. I discovered,
in our files, a topographic map of the area made in 1975. I have included
a copy of this topographic map on which I have shown in red the proposed
construction.
The construction of the new garage will produce 948 square feet of
additional hardsurface over that which originally existed before the house
was removed. We are considering the historic condition of the site to be when
the house existed. The total volume of runoff which will be generated during
a 3-hour 100-year storm by 948 square feet of hardsurface with a C of 0.95
over that from 948 square feet of lawn with a C of 0.20 is calculated to be
232 cubic feet. This is the required volume of detention. Since the proposed
pond is located south of the new garage, it is much more practical to detain
the runoff from the roof since it can easily be directed into the ponding area.
The total runoff volume from the roof during a 3-hour 100 -year storm is
calculated to be 406 cubic feet. We plan to utilize a retention ponding area
with no outlet, rather than a detention pond with outlet. The roof runoff
will be off the south side of the roof directly into the retention pond, and
the pond we propose has a volume of 692 cubic feet, which is 1.70 times the
total 406 cubic feet of roof runoff. This retention pond will have a flat
bottom which will be seeded and landscaped, probably with some dry land
vegetation.
J ames H . Stewart
a nd Assoc iates, Inc .
103 S. Me ldrum Stree t
P.O . Box 429
Ft. Col lins, CO 80522
303/482-933 1
Fax 303/482-9382
Automobile Garage for B~hlender Funeral Home
at 120 West Magnolia
Page 2
This retention pond method seems to be the most practical method of
handling the increased runoff from the additional hardsurfaced area. The
retention pond will be a shallow landscaped site which will have no adverse
effects on downstream conditions or on adjoining properties.
This site is located in a moderate rainfall and wind erodibility zone.
I have calculated the rainfall performance standard to be 74.6 percent. The
construction of the garage slab and pavement combined with the use of the
retention pond as a sediment trap provides an erosion control effectiveness
of 86.0 percent. Wind erosion will be controlled by the existing structures
and pavement adjacent to the property.,
I am including two plans with this report. One is the previously mentioned
topography plan, and the other is~ site plan of the property showing the
proposed construction and drainage. Please let me know if you need any further
information.
Sincerely,
~)CR~
Phillip I. Robinson, P.E. & L.S.
Vice President
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STEWART&t\SSOCIATES 103 S . MELDRUM, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
Consultin3 En3ineers and Surveyors
By: PIK Date: 3}-z; )"f<[-Client: M;lo 13 07/ender Sheet No. _/_of C T 7
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STEWART&\SSOCIATES
Consultin3 En3ineers and Surveyors
103 S . MELDRUM, FORT COLLINS, CO 80521
PH. 482 -9331 FAX 482-9382
By: P)R Date: 3)z.3')1tJ---Client: IV/1/0 Bo~/e~r°r SheetNo. ~ ot _l r I
Project: N e.\,./ G a ,oje cu v,s i r u c..-) I c"' (f I ·2 O vv' /Vt o Sn c-I 1 ~
Subject: ________________________________ _
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PROJECT:_ J3oh/e nde'I' Gtlr-oJe -. /Z U ~-;rloj'"' fc-. STAIIUARU FORM A
COMPLEJED BY: _____________ DATE: 4-)r)7<!-
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DEVELOPED. ERODIBILITY Asb Lsb • Ssb Lb Sb , PS
SUBBA3IN ZOIIE (ac) (ft) (%) . (feet) (%) (~)
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EFFECTIVENESS CALCULATIONS
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BASIN (%) BASIN (Ac) CALCULATIONS I
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HDI/SF-B:1989
_ CONSTRUCTION SEQUENCE
PROJECT:/3ohle nder' ~n?5e -)20 w'. ;V1~no1 Ci:t
. SEQUE~./CE . FOR 19 ONLY COMPLETED BY: -------
STANDARD FORM C
DATE: 9:j c/ r<J
Indicate by use of a bar line or symbols when erosion control measures will be installed .
Major modifications to an approved schedule may require submitting a new schedule for
approval by t~e City Engineer.
OVERLOT GRADING
YEAR
MONTH
WIND EROSION CONTROL
Soil Roughing
Perimeter Barrier
Additional Barriers
Vegetative Methods
Soil Sealant
Other £x 1sf J;,)~.s 'i r,rv+-
RAINFALL EROSION CONTROL
STRUCTURAL:
Sediment Trap/Basin
Inlet Filters
Straw Barriers
Silt Fence Barriers
Sand Bags
Bare Soil Preparation
Contour Furrows
Terracing
Asphalt/Concrete Paving
Other
VEGETATIVE:
Permanent Seed Planting
Mulching/Sealant
Temporary Seed Planting
Sod Installation
Nettinas/Mats/Blankets ·
Other
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STRUCTURES: INSTALLED BY ---------MAINTAINED BY ________ _
VEGETATION/MULCHING CGNTRACTOR -----------
DATE SUBMITTED ------APPROVED BY CITY OF FORT COLLINS ON -------
HDI/SF-C:1989
JA ~I L\.?:i 1991 8 -2 0 DESIG N C RITE?,!..\
STEWART&\SSOCIATES 103 S . MELDRUM, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
Consultin3 En3ineers and Surveyors
By: P)[(, . Date: ___ _ Client: tlhlo 13ohle'"'d e v-Sheet No . of
Project: Nev,/ G--a.r-0..5< <7-+-1 zo vJ.
subject: E 1 0 S ( Q n L Q r. +r O / · cos+.
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