Drainage Assessment 8.25.16.pdfE
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INSIGHT ENGINEERING CO.
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Applicant:
Echelbarger Investments, LLC
4001 198th St. SW, Suite 2
Lynnwood, WA 98036
(425) 673-1100
Drainage Assessment
For
Paradise Lane SFR
Prepared for
City of Edmonds
121 5th Ave North
Edmonds, WA 98020
425.771.0220
Project Site Location:
523 Paradise Lane
Edmonds, WA 98020
Tax Id: 00646500000300
'IECO Project: 16-0768
Preparation Date:
August 22, 2016
Report created by:
Jacob Mealey
Approximate Construction Date:
October 1, 2016
Contact:
IECO
P.O. Box 1478
Everett, WA 98206
425-303-9363
P.O Box 1478 • Everett, WA 98206 • P: 425.303.9363
F: 425.303.9362 • info@insightengineering.net
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08/23/2016
Project Summary
The proposed project Paradise Lane is located at 523 Paradise Ln, Washington. More
generally, the site is located in Section 25, Township 27 North, and Range 3 East of the
Willamette Meridian in Snohomish County, Washington. The project is considered a Category 1
Small Site Project per handout #E72 B. The project is located within the Willow Creek
watershed basin. The project is exempt from water quality and flow control. A 12 -ft diameter
drywell per handout #E72 B will provide onsite stormwater management for the site. Refer to the
following pages for the minimum requirements summary and the drainage calculations.
Minimum Requirements Summary
MR: Minimum Requirement
SWPPP: Stormwater Pollution Prevention Plan
MR #1 Preparation of a Stormwater Site Plan: The Stormwater Site Plan preparation follows
the City of Edmonds requirements.
MR #2 Erosion and Sediment Control Plan: Refer to the Grading and TESC Plan.
MR #3 Source Control of Pollution: No source control pollutants pertains to the proposed
project, therefore no BMP's are required after construction.
MR #4 Preservation of Natural Drainage Systems and Outfalls: Infiltration is proposed
therefore the project will not negatively affect the downstream path.
MR #5 On-site Stormwater Management/Low Impact Development Techniques: A 12 -ft
diameter drywell per handout #E72 B will provide onsite stormwater management for the site.
BMP T5.13 Post -Construction Soil Quality and Depth is proposed for additional stormwater
management for the site.
MR #6 Runoff Treatment: N/A. Water quality is exempt because the PGIS is 574 SF which is
less than the threshold area of 5,000 SF.
MR #7 Flow Control: N/A. The project results in creating less than 5,000 SF of impervious
surfaces therefore flow control is exempt for the project.
MR #8 Wetlands Protection: N/A. There are no wetlands located on the site.
MR #9 Operations and Maintenance: Refer to the attached pages for the Operations and
Maintenance Manual.
MR #10 Offsite Analysis and Mitigation: All the runoff from the site will be infiltrated onsite
therefore a detailed downstream analysis was not performed.
MR #11 Financial Liability: This will be provided to the city upon approval.
Drywell Sizin
Impervious Areas:
Roof = 2,394 SF (0.06 Acres)
Parkina and Sidewalk = 962 SF (0.02 Acres)
Total Impervious = 3,356 SF (0.08 Acres)
A 12 -ft dia. drywell that is 4 -ft deep is proposed for the site. The drywell was sized using Table
5. of handout #E72 B. With an infiltration rate of 2 iph a sizing factor of 3% was applied:
Drywell Area (square feet) = Impervious Area (square feet) x Sizing Factor (%)/100
Drywell Area (square feet) = 3,356 SF x 0.03 = 100.68 SF
FLAD=
D _ rua�.t,sr _ 11.32'
12 -ft diameter drywell is proposed