REVIEWED ENG BLD2023-0292+Storm_Drainage_Report+3.7.2023_3.34.15_PM+3407208RAM Engineering RECEIVED
3/13/23
To: City of Edmonds CITY OF EDMONDS
Engineering Division DEVELOPMENT
SERVICES DEPARTMENT
From: Rob Long, PE
RAM Engineering
Subject: Select Homes 8929 220t" St SW Short Plat- Lot 1
Stormwater Memo
RAM Job No. 20-016
APPROVED WITH PLAT
SEE PLN2022-0038
Memorandum
Date: March 6, 2023
BLD2023-0292
This memo provides a summary of the stormwater drainage control system for Lot 1 of the 220th St SW. Short
Plat (PLN 2020-016). A site -specific geotechnical evaluation recommends one stormwater BMP for the site;
BMP T5.13: Post -Construction Soil Quality and Depth 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). The roof top, driveway, walk and patio areas will be managed by a detention pipe designed in
accordance with the Edmonds Stormwater Addendum.
The Lot 1 roof, driveway/apron, walk and patio, as well as half the ROW areas (460 sf) will create 4,932 sf hard
surface and require 40 ft of 36" pipe (4,932 sf x 0.008) for BMP mitigation. The detention pipe will be
constructed (as part of the short plat improvements) along the lower southerly boundary of Lot 1.
Below is a stormwater control summary table for Lot 1:
Stormwater Control Summary:
Project Site Category: Category 2 (part of the 220th 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
5,184 sf
Soil Amendments (BMP T5.13)
Roof
2,575 sf
Detention Pipe (ECDC 18.30.030.D.5.d)
• 40 ft of 36" pipe (4,932 sf x 0.008)
Hard Surfaces
2 357 sf
Detention Pipe (ECDC 18.30.030.D.5.d)
(Driveway/Apron, Walk and Patio)
40 ft of 36" pipe (4,932 sf x 0.008)
25% Retrofit
0 SF
None
RAM Engineering 19109 361h Ave W, Suite 100 Lynnwood WA 98036 (425)678-6960 RAMengineeringinc.com
Select Homes 8929 2001h ST SW Shot Plat- Lot 1
Stormwater Memo
RAM Job No. 20-016
Page 2 of 2
Select Homes 220t" St SW Short Plat Lot 1 Hard Surface Summary:
Roof = 2,575 sf
Driveway = 1,847 sf
Sidewalk/Patio = 50 sf
Half of Row Improvements = 460 sf
Total =
4,yz$L sr
I
SHORT PLAT IMPRO"EN TS
I TO BE CONSTRUCTED AS
-- - - PART OF THE 220TH ST SW
BSBL N8976116'W 88. 59' I SHORT PLAT (PLN2021-0038)
( ) - O D/fY URUDES 4�
RETAINING WALL TO BE o i
CONSTRUCTED AS PART OF - - 1 - - - -
THE 0JRD S 1SWSHORr A_ ' =_==€ II DRIVEWAY = 1,847 SF
PLARoof 2,575 SF 1 " ' CHANNEL DRAIN
- - TOP 435.20
ADS PRO CHANNEL DRAIN
GARAGE OR APPROVED EQUAL
FF 4MM (i (SEE DETAIL ON SHT GN-01)
CO
1O'PRIVATE 0i �> PQPQH r i Ih
SIDE SEVER of
i Iq
EASEMENT PROPOSED HOUSE I INSTALL 1-1/2- P£ (160 PSI)
MAIN FF 435.80 I J6.1 FROM WATER METER TOO HOUSE
S VC EWER 5£RNCE DETAILS (TRACER WRE TO BE
4' P--
2.OX MIN I INSTALLED W/TH WATER LINE)
SSCO
/E 4325E $ WALK= 50 SF
1 I I = 26' DRA/NAGE h JOWT
CPAVEnROED r-19 1 UDUTY EASEMENT(TYP)
CONNECTED TO '
SfMER STUB 'i I 4' PVC STORM
IE 42B2t i ~ PUMP C`; DRAIN O 1.OX MIN
CONNECT >D I 16'PRIVATE ACCESS EASEMENT
4' PVC F0077NO STORM SIUB
DRAIN O 1.OX MIN - 1 - ='.3 /£ 429. 15f 1" WATER SER14CE INSTALLED
j 1 III ' I � PARTO
10' MIN LENGTH F007ING Ns1WATERM
ETER
DRAIN DRYMELL TRENCH�j ,
(PER GEOTFCH
£X F1R£ HYDRANT
RECOMMEND RUNS)
77
............. ...t..... ... _ �.. .. .......-
_ ===o - -. - PRIVATE'
50 /o FRONTAGE - 460 SF DRAINAGE ;8
EASEMENT A
__--G--__G_---G___G----G_—__G;--.--_G_--_G,-._.
_ 220TH ST SW
d
36508
�0 W
WISTEg�t
31612023
RAM Engineering 19109 361h Ave W, Suite 100 Lynnwood WA 98036 (425)678-6960 RAMengineeringinc.com