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Ponna L. Breske, P.E.
6621 Foster Slough Road, Snohomish, Wa. 98290
Phone: (425) 334-99,80, Fax: (425) 334-7380
March 11, 2008
Mr. Mark Loewen
22029 98"' Place West
Edmonds, Wa 98020
Subject: Proposed Addition to Single Family llouse
17201 72" d Ave. W. Edmonds, WA
Dear Mr. Loewen,
I have review the site drawing dated 2-26-08 and the Geotechnical Engineering
Evaluation dated February 12, 2008 for the above subject project.
The total impervious area for the driveway and garage addition is 1,234 sf. The
existing house was built in 1963. Per city of Edmonds Policy 4E72 only those impervious
areas created after July 1977 are required to have a storm water detention system. Furthermore,
storm water detention is only required for impervious areas greater than 2,000 sf. There is no
detention system proposed for this project.
Dispersion of storm water from the new impervious surfaces is proposed via a
dispersion trench located in the back yard and down hill of the house. The Geotechnical
Evaluation states that no instability of the sloping portion of the site was observed. The
Evaluation goes on to say, "the slope is likely mantled by one foot to two feet of loose to
medium dense, weathered native: till soil that could be susceptible to erosion or shallow
sloughing if surface vegetation is not maintained." Based upon this, it is required that the
contractor take care to maintain existing surface vegetation and replant any areas disturbed
during construction.
The dispersion trench is to be installed at a minimum of 15' from the house. The length
of the trench shall be I 0-fect for each 700 square feet of impervious area.
Sincerely,
Donna L. Breske, P.E.
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