Eng20160089_Perrinville-Herrara-2.docx
May 11, 2016
City of Edmonds Public Works Department
Engineering Division
121 5th Avenue North
Edmonds, WA 98020
Attn: JoAnne Zulauf
Subject: Stormwater Plan Review of Perrinville Drainage Re-Route (ENG2016-0089)
Dear Ms. Zulauf:
After reviewing the response to comments on the 18502 76th Avenue (Greg Payne Perrinville
Retail Building Upgrade), we have the following comments:
Offsite Drainage Report
8.All of the pipe inverts in the New CB “A” are listed at the same elevation (264.60’) in
the Offsite Drainage Plan and the Offsite Drainage Schematic.
5/11/16 response: Applicant response is that storm drain IE’s are usually the same in a
basin for same sized pipe. This is fine; no design change required.
Sheet 1 of 1 – Offsite Drainage Plan
2.Provide a connection to the existing outfall to prevent over-splash and erosion at the
turn of the ditch.
5/11/16 response: Suggestions for consideration in the existing outfall design include
the following:
Diffuser tee at the bottom of the pipe surrounded by riprap (Figure 4.5.11, Volume
V of the 2014 SWMMWW; Figure 4.11, Volume V of the 2005 SWMMWW)
Gabion baskets filled with quarry spalls (Figure 4.5.10, Volume V of the 2014
SWMMWW; Figure 4.10, Volume V of the 2005 SWMMWW)
Willow stakes to provide protection and screen the gabion basket/diffuser tee
Sincerely,
Rebecca Dugopolski, PE
Senior Engineer
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