bld20150965 - Greenway SFR-email storm comments.pdf
From:McConnell, Jeanie
To:"ALMARK_CORPORATION@FRONTIER.COM"
Cc:Lambert, Jennifer;Zulauf, JoAnne;Thornquist, Linda
Subject:bld20150965 - Greenway SFR
Date:Monday, September 21, 2015 4:17:00 PM
Good afternoon,
The Engineering Division has not yet been able complete a full review of the permit application
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submitted for the Greenway single family residence at 23917 74 Ave W. However, the City’s
Stormwater Engineer Program Manager, Jerry Shuster, has been able to complete his review. While
these comments are normally sent out in conjunction with the main engineering review, due to our
backlog of project reviews we felt it could be more efficient for you if we provided these comments
to you now. These comments have been provided below and will again be included with the main
engineering review comment letter once that review is complete.
Drainage Report for Almark Corporation, August 2015, LSA Engineering
The project classifies as a Category 1 Small site project. Minimum Requirement #7, Flow
Control, is required per Section 6 5.7 of the Edmonds Stormwater Code Supplement (ESCS).
Flow control must meet the standard of 0.25 cfs/acre impervious; OR 2,833 sf of impervious
area (85% of 3,333 sf of proposed impervious) can be mitigated using on-site techniques
described in Minimum Requirement #5.
1.The report does not discuss meeting MR#7 so it is assumed that it will meet MR#5. The
project proposes a drywell for 455 square feet of driveway and assumes an infiltration
rate of 0.5 inches/hour. Drywells must be designed using site-specific infiltration data
and groundwater level measurements per Section 5.5.2 and Appendix C of the ESCS. A
soil sample at the proposed location of the proposed dry well down to 6 feet and
determination of the groundwater level must be performed and found to be adequate.
2.Dispersion for the room runoff uses a minimum 25 foot flow path. The flow path cannot
be in the wetland. Since the trench is really close to the sanitary sewer easement, move
it to the east slightly so that it is 25 feet away from the west end of the wetland.
3.It is unclear how the sheet flow dispersion will work for the patio. Show a detail with the
2-foot wide transition zone called for in Ecology BMP T5.12. How does the concrete
sidewalk runoff get dispersed?
4.Show the footing drains and their discharge point(s).
Please let me know if you have any questions.
Kind regards,
Jeanie
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jeanie.mcconnell@edmondswa.gov
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