APPROVED STM BLD2021-0644+DRAINAGE MEMO 5.25.2021_2.15.13_PM+2216056ROM Fngineering ADDRESS:
B LD2021-0644 1008 WA L N U T
To: City of Edmonds
Engineering Divisio
From: Rob Long, PE
RAM Engineering
COMPLIES WITH APPLICABLE
CITY STORMWATER CODE
Subject: Select Homes Walnut Short Plat- Lot 1
Stormwater Memo
RAM Job No. 19-032
Memorandum
ate: May 25, 2021
RECEIVED
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
This memo provides a summary of the stormwater hard surface allocation for Lot 1 of the Select Homes
Walnut Short Plat (PLN 2020-0033). A site -specific geotechnical evaluation recommends two stormwater
BMPs for the site; Infiltration and BMP T5.13: Post -Construction Soil Quality and Depth. Lot impervious/hard
surface (roof, driveway, walk/patio areas) will be managed by an individual lot infiltration trench system.
The infiltration trench system has been designed as part of the short plat development and includes dedicated
hard surface areas allocated for the individual lot (see Walnut Short Plat Stormwater Site Plan Report). Lot 1
has an allocation of 3,267 sf of impervious/hard surface, which include roof, driveway, patio and walkway
areas.
Below is a stormwater control summary table for Lot 1:
Stormwater Control Summary:
Project Site Category: Category 2 (part of the Walnut Short Plat)
Discharge Location: City's Municipal Separate Storm Sewer System (MS4)
Type of Area
Square Footage
Storm water Facility
Lawn and Landscape
2,943 sf
Soil Amendments (BMP T5.13)
Roofs
2,417 sf
Infiltration Trench
Hard Surfaces
850 sf
Infiltration Trench
25% Retrofit
0 SF
None
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RAM Engineering 1653113`1Ave W,Suite A108 Lynnwood WA 98037 (425)678-6960 RAMengineeringinc.com