Country Estates-CS 930714 NATHAN D. MAIER
CONSULTING ENGINEERS, INC.
Mr. Steve Goram
Director ol Public Works
Oty of Coppen
2,55 Parkway Boulevard
Coppell, Texas 75019
Dear Steve.'
Pl~e accept the attached information as a request for a minor modification to an area storm sewer inlet
on Lot 2, Block B of the Counlry Estates Subdivision. This area inlet was installed to merely accept local
drainage from approximately 9,500 square feet, or less than ewm the minimum lot in this R-12
subdivision.
This area inlet is planned to be raised to accommodate fill in a rather deep area of Lot B-2 and the home
builder is desiring the installation of a "domed-grate" type inlet cover rather than open inlet that is f~lt to
be much less desirable. Und~bly there could be an inlm'est in assuring that area drainage is
accommodated in the unlikely event that a grate inlet becomes dogged. We offer the following multiple
factors to aesure that this will not cause concern.
The size of the drainage area (with a Q of approximately 1.1) is very small. In
fact it is approximately the runoff of 2/3 the size of our smallest Country Estates
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The domed natu~ o~ the specified inlet cover allows for ample drainage even in
the unlikely event that debris was to accumulate around the edges. This cover is
a standard design manufactured by Neenah for this purpose.
Running a worst case scenario, that presumes even 100% closure of this drain,
results in drainage going into a 12' curb inlet in the alley immediately adjoining
this lot. This alley inlet design capad~ e~ceeds 18 e. fs and it cunm~tly accepts
only 11.9 cfs. In other words, this anllre lot could be filled to drain to the alley
and have no problem whatsoever and the alley inlet could still have about 30~
unused capacity. The limited lot fill will be done to make an effort at preserving
as many trees as pmetical on this lot and provide for a gentler swale to the area
The Lot B-2 minimum finished floor elevalion is 505.80. The alley elevation
adjacent to the area inlet is 504.70. a~tr~ given a worst case scenario presuming
100% closure of this area inlet, tl'.e f'mifl~d floor is, at minimum, more than a foot
higher than the ldley with good positive chainage to the 503.5-7 invert of the 12'
Three NorthPark/8800 N. Central Expw¥./Suite 300/Dallas, Texas 75231/(214) 739-4741
Pa~
We therefi~e prolx~e, as per the attached plan, to raise the aree inlet approximately four feet from
current level, lin)vide A)r a two foot diameter inlet, and use a domed standarcl ~rate cover. As you can
NATHAN D. MAma.
A~tunent