ENG-COMMENTS-STORM2of EDM caSTO RM WATE R REVIEW COMMENTS
City of Edmonds
Engineering Division
To:
Applicant
Date:
July 9, 2020
Project Name:
Evans SFR
Permit Number:
BLD2020-0250
Address: 20018 83,d Ave W
Review Type: Building (SFR)
Submittal Date: 6/15/2020
Reviewer: Zack Richardson, PE
City of Edmonds, Stormwater Engineer
Recommendation: I recommend that BLD2020-0250 be withheld until the comments below
are adequately addressed.
Review Comments:
1. The project plans show a bypass area which was not reflected in the plat drainage
approval and required further attention. Address as needed, the additional bypass area;
reviewer suggests pursuing one of the following options as feasible:
a. Route the bypass area roof drain line to the detention system as previously
suggested. Things bring the building permit into compliance with the approved
drainage report and makes the drainage memo you provided accurate and true.
b. Revise drainage memo to address bypass area as part of building permit
i. Explain why any other BMP is infeasible (including the using the existing
detention system as suggested above) and why it qualifies for an exemption
from MR #5, AND
ii. Demonstrate that an equal or greater level of mitigation is provided as the
approved plat drainage report (I assume this would need a point of
compliance set up demonstrating that the bypass flows plus discharge from
the over detained site flows would still meet below the design as proposed);
note this is a direct comparison to the approved plat system performance (it's
different than the 0.1/0.15 cfs exemption noted below in option #3)
c. Or update the plat drainage report to address bypass as part of plat
i. Explain why all BMPs are infeasible for this area and why it qualifies for an
exemption from MR #5, AND
ii. Provide continuous model to demonstrate that the project still complies with
drainage code and that flow control is not required (ie. show that a point of
compliance for bypass flows plus detention outflow remains below the
0.1/0.15 cfs increase over existing conditions)
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