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RAM Engineering
To: City of Edmonds
Engineering Division
From: Rob Long, PE
RAM Engineering
RECEIVED
Jan 24 2022
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Subject: Select Homes 811" Ave W Short Plat- Lot 2 8008 203rd St SW
Stormwater Memo
RAM Job No. 20-019
Memorandum
Date: September 29, 2021
COMPLIES WITH APPLICABLE
CITY STORMWATER CODE
04/01 /2022
This memo provides a summary of the stormwater drainage control system for Lot 2 of the 815Y Ave W Short
Plat (PLN 2021-0007). A site -specific geotechnical evaluation recommends two stormwater BMPs for the site;
BMP T5.13: Post -Construction Soil Quality and Depth and BMP T5.10C: Perforated Stub -out Connections based
on the site's soil conditions. In accordance with Edmonds Code, lawn and landscape areas will be managed by
post -construction soil quality and depth (soil amendments); roof tops will be managed by perforated stub -out
connections; and "other hard surfaces" will be managed by detention a pipe designed in accordance with the
Edmonds Stormwater Addendum.
The Lot 2 driveway/apron, walk and patio areas of 1,360 sf hard surface will require 26 ft of 24" pipe (1,360 sf x
0.019) for BMP mitigation. The detention pipe will be constructed along the lower northerly boundary of Lot 2.
A small portion of the Lot 2 driveway apron (525 sf of the 1,260 sf) is located within the right-of-way of 203rd St
SW and cannot be easy collected. The 525 sf is within the 1,000 sf threshold limit allowed by the City of
Edmonds to by-pass the stormwater system of the project.
Below is a stormwater control summary table for Lot 2:
Stormwater Control Summary:
Project Site Category: Category 2 (part of the 203rd St SW 2-Lot Short Plat)
Discharge Location: City's Municipal Separate Storm Sewer System (MS4)
Type of Area
Square Footage
Stormwater Facility
Lawn and Landscape
4,430 sf
Soil Amendments (BMP T5.13)
Roof
2,661 sf
Perforated Stub Outs (BMP T5.10C)
Hard Surfaces
1,360 sf
Detention Pipe (ECDC 18.30.030.D.5.d)
(Driveway/Apron, Walk and Patio)
• 26 ft of 24" pipe (1,360 sf x 0.019)
25% Retrofit
0 SF
None
RAM Engineering 19109 36" Ave W, Suite 100 Lynnwood WA 98036 (425)678-6960 RAMengineeringinc.com
Select Homes 81s' Ave W Short Plot- Lot 2 8008 203id St SW Page 2 of 2
Stormwater Memo
RAM lob No. 20-019
Select Homes 81st Ave W Short Plat Lot 2 Hard Surface Summary:
Roof = 2,661 sf
Driveway = 1,260 sf
Sidewalk/Patio = 100 sf
Total = 4,021 sf
SOLID LOCKING LID
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RAM Engineering 19109 3611 Ave W, Suite 100 Lynnwood WA 98036 (425)678-6960 RAMengineeringinc.com