bld20080463 Storm Detention Waiver.pdfDecember 2, 2008
Jeanie McConnell
City of Edmonds
121 r0l Avenue XT Ind TA
oor r
Edmonds, WA 98020
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bld2008O463, b1d20080464, bld20080465 Vter,4WLC-
Sunset Condos
121 Sunset Ave
A
Application Number
Project Name:
Project Address:
RE: Detention Waiver
Dear Ms. McConnell,
ViAk)' 0 1 1 s1sWAM5.
Due to the circumstances surrounding the site at 121 Sunset Ave, our firm would
like to submit this request to waive detention requirements for this project.
18.30.065 of the Edmonds Community Development Code lists the requirements
needed to be met in order to waive detention.
o The exemption provides equivalent environmental protection and is the
overriding public interest; and that the objectives q1'safety, fimetion,
environmental protection, acrd Facility maintenance, based on sound
engineering, are fully met.
The impact caused by the site is minimal, with the 100 -year storm in the
developed conditions being on 0.09 cf§ larger than the 100 -year storm in the
existing conditions. In updated editions of the Western Washington DOE
Manual, this allows the development to be exempt from flow control. The
proposed method of conveyance will not cause any environmental, safety, or
functional problems. See Drainage Report for Calculations.
There are special physical circumstances or conditions affecting the
property which the strict application of these provisions would deprive the
applicant of all reasonable use of'the parcel qf'land in question, and every
effort to, creative ways to meet the intent of the minimum standards has
been met.
Groundwater was discovered to feet below the ground surface, as shown in
the geotechnical report. This could vary because of the close vicinity to
Puget Sound or changing seasons. Having a detention pipe Linder the
building structure with this much groundwater would raise concerns, which
are avoided without using detention.
6, Jx z' J"
Detention Waiver December 2, 2008
Application #20080463, -0464, -0465: Sunset Ave Condos Page 2
The granting of'this exemption will not be detrimental to public heath and
welfare, nor injurious to other properties in the vicinity andlor downstream, and
to the quality qfwaters oj*the state.
The quantity of water being added to the existing conveyance system is very
minimal, as stated in (A) above. Pipes downstream appear to be in adequate
condition to convey the water to Puget Sound with little risk of damaging adjacent
properties. Analysis of the off-site: conveyance system including pipe flow
equations is included in the Drainage Report.
• The exception is the least possible exception that could be granted to comply with
the intent qI'the minimum requirements.
This appears to be the most adequate method for successfully conveying
stormwater into Puget Sound. The increased flows are minimal, the site creates
problems with adding a detention system, and the off site conveyance is adequate.
All of these concerns are analyzed in greater detail within the Drainage Report
and the Geotechnical Report.
We look forward to hearing from you.
GregUillen, PE, SE
Principal