Eng20160089_Herrera-8.9.16.docx
August 9, 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
8/9/16 response: The applicant has not shown any details as to how the stormwater
velocity will be dissipated in the channel at the base of the slope prior to entering the
Stilling Basin “D”. Applicant shall show how design meets the requirements of BMP
C209: Outlet Protection of the current SWMMWW.
2200 Sixth Avenue | Suite 1100 | Seattle, Washington | 98121 | p 206 441 9080 | f 206 441 9108
PORTLAND, OR | MISSOULA, MT | OLYMPIA, WA | WINTHROP, WA | BELLINGHAM, WA
Stormwater Plan Review of Perrinville Drainage Re-Route (ENG2016-0089)
August 9, 2016
Page 2
Sincerely,
Colleen Mitchell, PE
Senior Engineer
8.9.16
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eng20160089_herrera
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