APPROVED STM RESUB 2-Storm_Drainage_Report+6.21.2022RESUB
Jun 21 2022
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
BLD2021-1418
COMPLIES WITH APPLICABLE
CITY STORMWATER CODE
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FNGINeEP
Drainage Memorandum
To: City of Edmonds
From: Chris Tebaldi, P.E., Tebaldi Engineering, LLC
Date: June 20, 2022
Re: Alexander Single Family Residence Addition
6/20/2022
This project is located in City of Edmonds on tax parcel number 00456000001000. The project proposes to
construct an addition to the existing single-family residence on the subject property. The existing topography
ranges from elevation 358 to elevation 326. The site gently slopes from east to west in the vicinity of the
proposed addition and the slope ranges from 0 to 5 percent. The property is currently an existing single-
family residence with associated driveway, pavement and landscaping. The proposed addition consists of a
re -roof of a portion of the existing roof, additional roof overhang and new deck and stairs.
The proposed project is subject to the City of Edmonds stormwater requirements which follow the 2014
Department of Ecology stormwater requirements. The portion of re -roof would not be considered new or
replaced impervious since there is no demolition down to the foundation of the structure. The new portion
of roof (approx. 568 square feet) is considered new/replaced impervious surface. The proposed deck
(approx. 324 square feet) would not be considered impervious surface. Although, even including the deck,
the project would be less than the thresholds that trigger LID and flow control as the total new/replaced
impervious surface is less than 2,000 square feet. A portion of the roof addition will be directed to the
existing downspout tightline system to the existing drywells. In order to offset an potential capacity issues
with the existing drywells, approximately 620 square feet of new/existing roof area will be tightlined
separately to a downspout splashblock with the required 50 foot flowpath.
www.tebaIdiengineering.com 4625 126t" Ave E, Edgewood, WA 98372 (206) 450-5096