Request for SEPA Determination Memo.pdf
MEMORANDUM
Date:
December 19, 2016
To:
Kernan Lein, SeniorPlanner
From:
Ed Sibrel,Capital Projects Manager
Re:Resubmittal:Request for SEPA Determination, Northstream Culvert
Rehabilitaion and Pipe Abandonment Project
The above-noted projectrequiresaas part of documentation an environmental
classification exercise.Below is a brief description of the project, along with
additional facts of note.
1.Overall Scope. The scope of the project is a rehabilitation of the 30”
culvert conveying Northstream Creek under SR 524 approximately 240
feet east of the intersection at Olympic Avenue, together with the
abandonment of approximately 600 feet of 24” and 30” concrete pipe that
formerly conveyed the creek prior to 2006.This pipe is located under
several private propertiesas well as under some housingsouth of SR524
th
and is partially collapsed where is crosses under 12Avenue SW.
2.Culvert Rehabilitation. The culvert is proposed to be religned via a Cured-
In-Place-Pipe (CIPP) process, where a resin-impregnated felt fabric will be
bonded to the inner surface of the culvert, sealing leaks and adding
structural integrity. This will eliminate the need for excavation across a
state road. In order to accomplish this, Northstream Creek will be
temporarily bypassed for the duration of the curing process.
3.Pipe Abandonment. The current pipe is structurally deficient along
approximately its western third, and has failed along its eastern 60 feet.
The balance of the pipe is structurally sound, and is collecting
groundwater along that stretch. It is proposed to plug and fill the upper
stretch with grout, preventing further structural failure, and thread a 4”-6”
HDPE pipe along the downstream western third, and grouting the annular
spaces between the pipes. This abandonment method will address the
structural deficiencies of the pipe, while still allowing a measure of utility
collecting groundwater.
4.Other Items.
City of Edmonds
Public Works Department
Engineering Division
A.Northstream is a perennial creek, and does not support anadromous
fishaccording to Chapter 23.90.010of theEdmonds City Code.
B.Although no evidence of recent earth movement has been seen within
the project area, the area itself is a landslide and erosion hazard area,
according to the City of Edmonds GIS map.
C.A Critical Areas Report and Geologic Hazards Assessment is
appended to the SEPA documentation and made part thereof.
Enclosures: SEPA Checklist
Preliminary Design Drawing
Project Structural Evaluation
Critical Areas Report
Geologic Hazards Assessment