20100129130318319.pdfMessage
From: Lambert, Jennifer
Sent: Friday, January 29, 2010 4V PM
To: 'mem123mb@hotmail.com'
Subject: FW-. Thoughts on English - 8110 206th St SW
Marybeth,
Page I of 2
Please read the storen water comments from Jerry Shuster below, If You have any questions,
please let me know.
Have a wonderfUl weekend!
FeelzTeiciwi
4z'15-�-771-0220 exl 1321
jennifei% I a m be rt avi.edmon ds. w,,mis
-----Original Message -----
From: Shuster, Jerry
Sent: Monday, January 25, 2010 10:10 AM
To: Lambert, Jennifer
Subject: Thoughts on English - 8110 206th St SW
Edmonds Community Development Code Chapter, 18.30.060.,A. 1 requires that projects with
2,000 square feet or more of "new impervious surface" control stormwater discharges to
control stream bank erosion or flooding of the downstream stormwater system by limiting the
peak rate of runoff from the site. "New impervious surfaces" are generally defined as those
created after July 7, 1977, the date oormwater control ordinance. Therefore, the
new impervious for this lot Is 3174 + 48 = 3,222 sf (paving stones proposed to replace part of
the patio do not qualiify as pervious surfaces under our current code),.
1 i ation isr y e r on i esne per V7e—c-urrent colt. e ass,117 IF# soli cf lititions
on the site (Alderwood, gravelly, sandy, loam). The code further says "BMPs [best
management practices] shall be selected, designed, and maintained per the manual." The
11manual" is described in he code in 18.301.020 as the " the latest edon of the Washington
State Department of Ecology Storm Water Technical Manual for Puget Sound (the Technical
Manual)." Since this citation was placed in the code in 1995, this refers to the 1992 version of
this manual. The standard's codified in the ECDC refer to those in the 1992 manual. These
standards are still applicable in the 2001 version of the the manual but the 2005 manual has
1/29/2010
Message
Page 2 of 2
very different methodologies for computing detention volumes for large sites and is not
considered "the latest edition" since it vwouldl conflict with the 1992 standards.
Given all this there appears to be three choices.,
1) Install a detention system per handout #E72 collecting runoi� from the 3,222 sf of
impervious and discharges it to a spreader trench per Edmonds Standard detail 5.1.1 to
disperse the outflow since there is no • • on 1• St. to SW for a connection.
2) Usethe downspout dispersion systems •^ in the 2001 Dept., Ecology
Stormwater manual for Western Washington , Volume 111, Section 3.1.,2 for all the roof
water. The driveway
• •• not need to be included in a system. This is not
available on line but the essence can be found in the 2009 King County Surface Water
Design Man�uial, Appendix C, Section 6.2.4, beginning page C-51
httr /./`yQui-,I<incicouiity.g-Qv/d`or /library s n-
-- rp- - jwgter
rnanual/ap endix-c,pdf
3) Wait until the new code is passed (best guess March - April 2010) and use a
combination of rain gardens and downspout dispersion systems to manage the runoff.,
Due to the amount of impervious and the problems we have had near Goodhope pond, I would
not recommend a exemption from the stormwater control requirement for this site.
1/29/2010