STORM1_Review CommentsTo:
Date:
Project Name:
STO RM WATE R REVIEW COMMENTS
City of Edmonds
Engineering Division
Applicant
March 5, 2019
Aw Residence
Permit Number: BLD20190116
Address: 9527 190t" PL W
Review Type: Building (SFR)
Submittal Date: 1/30/2019
Reviewer: Zack Richardson, PE
City of Edmonds, Stormwater Engineer
Recommendation: I recommend that BLD20190116 be withheld until the comments
below are adequately addressed.
Review Comments:
1. General: It is not clear that sufficient testing was done to establish a measured
infiltration rate as required by ECDC 18.30 and 2014 SWMMWW; review
Edmonds Addendum Appendix B and revise geotechnical information as needed
to ensure infiltration rate is measured and adjusted consistent with the
requirements.
a. It appears that on -site testing was not performed and grain -size analysis
was not performed and therefore it does not appear that a site -specific
infiltration rate was measured.
b. It is not clear that the stipulated correction factors have been applied to
the measured rate.
c. The report does establish a medium SAND at the infiltration layer (EP2
does note gravel but appears further from the trench than EP1 & EP3
which do not note any gravel) which, per the prescriptive sizing for
downspout full infiltration (Edmonds Checklist #13), would suggest more
like 150' of typical trench is required (75' at the doubled -depth proposed):
4,986 / 1000 X 30 = 150'
2. Report: Update report text to acknowledge the bypass flows from the ROW
portion of driveway and state how they are mitigated (ie. oversized infiltration
trench, etc).
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3. C3.1: Show/list the existing invert elevation at the connection CB in the south-
west corner.
4. C3.1: Label/callout the roof and footing stub connection points (where it joins the
lines surrounding the structure) as "Connect roof drains only" and "Connect
footing drain only" as appropriate.
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