509_9thAveN_SW_Rev_Comments.pdfRequest for Waiver from onsite detention
The applicant is requesting that the requirement for detention be waived
since he can discharge directly into the - QUQQ fa 4-9.44just west of
his site. This system eventually discharges into Puge oun .
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Waiver Justification: This waiver is justified due to the specific con itio s of P;pe CAV
this site. Since the northwest site area has be de-classffied as a wetla
there is no need to direct some of the site runoff to that area. In addition,
there is a fogional QlatoPUGN faQd4*just downstream of the site which can be
use �--yv-his project. Since this system has direct discharge to the Puget
Sound, there is no need for detention.
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Reviewed and Approved by the City:
Date: By ...............................................
I--- City Engineer
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Section 1: Project Information
Project Name: 98h Avenue N Short Plat
Project Site Address: 503 91h AvenueN.
Edmonds, WA 98020
City File Number: S-05-09
Project Engineer: Lovell-Sauerland &Associates, Inc.
19400 33d Avenue W., Suite 200
Lynnwood, Washington 98036
Phone: (425) 775-1951
Project Applicant: Thuesen Custom Homes
17296 Talbot Road
Edmonds, WA 98026
Phone: (425) 670-2825
Project Total Area: 1. 03 Acres
Number of Lots: 2 - singlefamily
Soils Data: Alderwood 'C' per Sheet #56 of SCS Soil Survey of
Snohomish County
June Revision Executive Summary
This revision incorporates 3rd City review comments as follows:
1. Delete requirement for detention tank.
2. Because Wetland designation has been eliminated, no flows need to
be directed to that area, so drainage can connect to the existing
dof-p-tia , -,--L- to the west of the site.
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3. The sewer extension has been revised to be on the east side of 8th
Avenue N.
Section 2: Existing Site Conditions. r
The site is a rectangular -shape 1.03-acre parcel t at is occupied with one single family house
that is currently under constructio �.pes generally to the northwest at an average
grade of about 30%. Existing vegetation consists of pasture and some trees.
Section 3: Proposed Project:
The applicant proposes to build 2 new single family homes, removing the existing site
improvements. A public alley off of 8 th Avenue N. will serve the west lot. The east lot will be
served by a panhandle driveway in an easement to 9th Avenue N. The onsite water will be
collected in an underground system and the offsite water will be collected in an interceptor
trench. Both will directly discharge to the existing 4e�eft+i-o- at the west of the site.
Section 4: Upstream Analysis
The upstream basin consists of runoff from the natural vegetated portions of the uphill single
family lots to the south of the project. Currently this runoff sheets flows northwesterly across the
site. This offsite flow will be collected in a perimeter rock interceptor ditch with a perforated
pipe and discharged into the onsite stonn system.
Section 5: Downstream Analysis %41P,400 PVTOWts
The project runoff and offsite runoff will discharge directly into the just to the
west of the site. This system eventually discharges to Puget Sound, so the City is not requiring
project detention.
Section 6: Drainage Methodology and Applicable Code
See the discussion in section 5 above.
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Va-ter quality is provided in the detention facility downstream of the project. The onsite ---
,downstream catch basin wd-U_huv4,q4-�m��evarator tee to reduce contaminant discharizeD
Section 8: Temporary Construction Sediment & Erosion Control
During construction standard BMPs will be employed to control potential adverse impacts to
adjacent properties. These methods will include a temporary construction entrance, silt fencing,
existing catch basin protection, dust control, and temporary seeding of disturbed areas as
required. If required, a temporary sediment pond can be constructed to reduce runoff turbidity.
Section 9: Detention Calculations:
None required.
EX. C.S.
iNV.90.18-"N.
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