HomeMy WebLinkAboutDrainage Reports - 01/17/1989STORM DRAINAGE REPORT
REPLAT OF LOT 1
SOUTHMOOR VILLAGE EAST SECOND FILING
Lot 1 of Southmoor Village East Second Filing presently has one residence,
a pool, two out —buildings, a barn, and a paved driveway and parking area.
The entire area drains to the southwest corner of the property, from
which a drain swale runs south to the Shepardson channel.
There is very little to no offsite drainage onto this site. Drainage
from the west is intercepted by Lemay Avenue, the lots to the south drain
southerly, the lots to the east drain to the east, and the lots to the
north drain north to Springwood Drive except for a part of the rear yards
of lots 7 and 8 of the Southmoor Village East Third Filing. This off —
site drainage drains toward the existing drain swale along the west
property line.
The existing impervious area of the site is 21,440 square feet, which
calculates a run—off coefficient of 0.338. The proposed developed site
will have an impervious area of 25,280 square feet, due to the additional
driveway required for fire access. The calculated run—off coefficient
will be 0.363, which is below the 0.5 coefficient normally used for
residential areas and which is below the coefficient of 0.4 which was
originally used for the Southmoor Village East development.
The existing regional detention pond located along the east boundary
of the Southmoor Village East subdivisions was sized to detain run—off
from the entire Southmoor Village East development, as well as the run—
off from Bartran's property to the south. Therefore, the run—off from
the proposed replat of Lot 1 was to be detained in the regional pond.
The existing and developed storm run—off quantities for a 2, 10 and 100
year storm are calculated on the attached sheet. There is a very small
increase in the run—off for the developed condition.
We request that additional detention not be required for this replat
because the regional pond is supposed to detain for this site, and also
because the very small increase in run—off should not cause any problems
to the Shepardson channel, which drains into the regional pond.
Sheet 2 of this report shows calculations, and sheet 3 is a map of the
area showing existing and proposed conditions.
Phillip I. Robinson, P.E. & L.S.
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James H. Stewart & Associates, Inc. 214 N. Howes St. Ft. Collins, CO 80521 (303) 482-9331
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