APPROVED DRAINAGE MEMO 7.09.20Western
Engineers
Inc.
SURVEYORS • PLANNERS • ENGINEERS
9740 Evergreen Way * Everett, Washington 98204
(425) 356-2700
June 11, 2020, Revised July 9, 2020
City of Edmonds Development Services
Attn: Zach Richardson
121— 5th Ave N.
Edmonds, WA 98080
FAX (425) 356-2708
COMPLIES WITH APPLICABLE
C E
Subject: Evans 1" SFR Review Comments, BLD2020-0250 — Drainage Review Memo
As you requested, this letter has been prepared to verify the current building permit design falls within
the design parameters of the previously approved short plat. Approved short plat allotted 3,360 sf. of
hardscape for future house and driveway. Currently as designed, total new roof and driveway area for
the proposed SFR totals 3,349 sf. below the max design amount. Additionally, stormwater BMP's as
previously designed and approved with the short plat appear to be continued through SFR site design.
July 9, 2020 Revision:
Approved short plat civil's noted a potential minor future roof bypass area in the southeasterly area of
the site. As is the case with the building permit civil design, this roof bypass not available to drain to
the installed detention facility has been proposed to be convey to a perforated pipe trench BMP prior to
draining into the city's drainage system along the frontage. Though the site has been deemed an
erosion hazard, erosion hazards are generally established for slopes exceeding 15% slope with soils
containing moderate or high likelihood of erosion. Slopes in the area of the proposed perforated pipe
area appear to be less than 15% in addition to the proposed building area eliminating much of the
erosion hazard concerns. Note that perforated pipe trench stub out BMP's are higher up on the MR#5
feasibility list thus can supersede the need to drain to the recently installed detention facility.
Thanks and let me know if there are any additional questions regarding the proposed project or civil design.
Sincerely,
Jesse Jarrell, P.E.
Project Manager
LAND USE CONSULTANTS * CIVIL ENGINEERS * LAND SURVEYORS * ENGINEERING CORPORATION
RAIDSERVER\2017\ 17-170 1 -A Evans\ENGINEERING\SFR Drainage Memo