bld20100395-Whitney_ENG3.pdf
City of Edmonds
TH
121 5 AVENUE NORTH EDMONDS, WA 98020 • (425) 771-0220 FAX(425) 771-0221
Website: www.ci.edmonds.wa.us
DEVELOPMENT SERVICES DEPARTMENT
Planning • Building • Engineering
Engineering Plan Review Comments
Permit Application :Date:
# BLD20100395 7/29/10
Project Name/Address:
Whitney – 20909 Hillcrest PL
Contact Person/Address, Fax or E-mail:
Albert Cohen, alcohendesign@verizon.net
Reviewer: JENNIFER LAMBERT Division:
ENGINEERING
During review of the subject submittal, it was found that the following information, corrections, or
clarifications would need to be addressed. All Handouts referred to in these comments can be accessed at
our website: www.ci.edmonds.wa.us under City Government / Development Services Department /
Engineering Division then scroll down to Handouts:
ST
1 Review 7/6/10
nd
2 Review 7/16/10
rd
3 Review 7/29/10
1)OK
2)OK
3)OK
4)OK
5)OK
6)OK
7)OK
DATE E-MAILED 7/29/2010 PAGE()
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City of Edmonds
TH
121 5 AVENUE NORTH EDMONDS, WA 98020 • (425) 771-0220 FAX(425) 771-0221
Website: www.ci.edmonds.wa.us
DEVELOPMENT SERVICES DEPARTMENT
Planning • Building • Engineering
Engineering Plan Review Comments
We have reviewed the existing storm system along the east side of the lot and have approved the
additional impervious surfaces to go to this system. However, we do need the calculations for the north
infiltration system.
8)OK
9)7/29/10 Comment was partially addressed. We received the report from GeoSource Engineering.
However there are some additional comments from Jerry Shuster, PE; Stormwater Engineer
Program Manager. Please read below.
The report from GeoSource Engineering, Inc. uses a design infiltration rate of 10 in/hr (shows up as 6
min/inch on page 3). This is an infiltration rate for "Clean sandy gravels and gravelly sands " in Table
3.7 in Volume III, Section 3.3.6 of the 2005 Ecology Stormwater Management Manual for Western
Washington. The trench sizing calculations are difficult to follow and do not include the time it takes to
infiltrate the calculated flow.
As a check, I looked at the Manual recommended sizing for infiltration trenches in "Course sands and
cobbles" (Section 3.1.1, p.3-5). The manual recommends 20 lineal feet per 1,000 square feet of
impervious area for a 2 foot wide, 18 inch deep infiltration trench. Using this yardstick, the 1,942 SF of
impervious in this project would require 39 LF of trench with these width and depth dimensions, not the
13 feet calculated in the report.
Please explain the sizing calculation and include the time to infiltrate. Also, reconcile the difference
between the current trench sizing and the sizing in the Manual.
7/16/10 Comment: From response letter to review comments sent 7/6/10 it states that we are to refer to a
report by Gary Lobdell, P.E. of GeoSource Engineering; however, the report does not appear to have
been submitted. Please provide information verifying that the system is either designed to collect the
water runoff from the impervious surfaces it is collecting or show how the system will be rectified to
collect the water runoff.
7/6/10 Comment: Please provide the calculations for the north infiltration trench to verify that the
system is designed properly.
Please resubmit 3 copies of the revised site drawings and associated documents with a written response to
each item to an Engineering Technician. Please contact me at 425-771-0220 ext 1321 or by e-mail at
jennifer.lambert@ci.edmonds.wa.us if you have specific questions regarding these plan corrections.
DATE E-MAILED 7/29/2010 PAGE()
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