6.6.19 Letter from Eng. As-built Storm Drain System.pdfDonna Breske
& Associates
Civil Engineering & Land Use Planning
June 6, 2019
Attn: City of Edmonds
City Hall - second Floor
Edmonds, WA 98020
21 Ave A, Suite 4
Snohomish, WA 98290
Telephone (360) 294-8941
www.donnabreske.com
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Subject: Inspection of As -built Drainage System for 625 Alder St, #BLD20180315
Per the request of the City of Edmonds, a field inspection of the constructed drainage features as part of
the construction for an ADU at 625 Alder St, Edmonds, WA 98020, was conducted by Alex White, EIT
of Donna Breske, & Associates, LLC. The inspection was completed on June 5th, 2019 at approximately
6:3 0 pm.
It appears that the on -site stormwater management elements have been constructed per the civil design
drawings. A transition zone with a vegetated flow path has been placed along the concrete patio, and
several rain barrels have been staged around the ADU downspouts and all appear to have adequate
storage capacity of 50 gallons each.
Additional measures have been provided to ensure that runoff from the neighboring property to the east
does not pond within the property during heavy rainfall events. This included a 24" thick bed of well -
draining course aggregate placed around the ADU foundation, graded and sloped to allow runoff to flow
north, and west along its existing drainage pattern. The aggregate sounding the structure contains
perforated underdrain piping that discharges to a large bed of streambed cobbles located along the south
edge of the gravel driving surface. The underlain system, along with the storage capacity of the
aggregate is anticipated to protect the structure from runoff during heavy storm events. Along the
western edge of the property, a shallow earth berm has been constructed along, with a drainage swale
along its base. The bottom of the swale is lined with aggregate and streambed cobbles, and is anticipated
to prevent erosive or excess flows from entering the neighboring property to the west.
It also appears that BMP T5.13: Post Construction Soil Quality and Depth has been applied to all
pervious surfaces within the project site.
The constructed drainage system is anticipated to meet the intended performance of the approved civil
design, and appears to be in compliance with the approved measures proposed for on -site storinwater
management. Donna Breske, & Associates, LLC approves of the constructed drainage system.
Sincerely,
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Alex White, EIT
COMPLIES WITH APPLICABLE
CITY STPRMW
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Donna Breske
Associates
Civil Engineering & Land Use Planning
Donna L. Breske, P.E.
Phone: 360-294-8941
Mobile: 206-715-9582
21 Ave A, Suite 4
Snohomish, WA 98290
Telephone (360) 294-8941
www.donnabreske.com
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