The Seattle Department of  Construction and Inspections has issued a "Determination of non-signficance" regarding the Delridge 99 Gateway project which is a retrofit of the existing sewer system near Delridge Way SW and SW Andover Street.

The project web page states:

What & Why

As part of the Plan to Protect Seattle’s Waterways, Seattle Public Utilities will retrofit the Delridge 99 basin sewer system to reduce combined sewer overflows (CSO) into the Duwamish River. The Delridge 99 Gate Retrofit Project involves replacing the HydroBrake flow restriction device that currently manages basin flows in wet weather with an automated gate that will better use the existing offline storage tank along the north side of Andover Street.

Following this work, SPU will continue to monitor performance and identify if additional action is needed to limit CSOs to less than 1 per year on average.

What’s happening now?

The project is currently in the design phase and scheduled to go into construction in the summer of 2019. Initial community outreach has begun with more planned for later this year.

Project goals and benefits

This project will improve SPU’s ability to monitor and control the Delridge 99 basin flows and will improve water quality by reducing the frequency and volume of CSOs into the Duwamish River.

Description of Proposal

In some areas of the City of Seattle, sewage and stormwater runoff are collected in the same pipes, known as combined sewers.  During storm events, sometimes the flow in these pipes exceeds the combined sewer system capacity.  When this happens, the sewer system overflows at outfall structures designed for this purpose.  These overflows are called combined sewer overflows (CSOs).  

Seattle Public Utilities (SPU) must limit the number of CSOs at each outfall to an average of no more than one per year based on a 20-year moving average.  Combined sewer Basin 99 currently exceeds this performance standard, averaging 2.3 CSOs per year from Outfall 99.  

The proposed project would replace an existing HydroBrake flow regulator with an electric-motor actuated slide gate.  This would allow SPU to make better use of existing sewer system storage and reduce the frequency of CSOs from Outfall 99.  

The gate and its actuator would require installation of a new maintenance hole structure and a new precast concrete vault with a hinged access hatch in the street right-of-way.  The project would also include electrical and instrumentation and control improvements required to operate and monitor the system.  This would include installation of a new roadside electrical cabinet and components, new electrical/communication conduits, wiring, and instrumentation in the SPU sewer system.  Two existing roadside electrical cabinets would be removed. Sewage would be bypassed around the work areas as needed during construction.  All demolished and damaged landscaping and paved surfaces in the right-of-way would be restored as directed by the Seattle Department of Transportation (SDOT).

Proponent

Seattle Public Utilities

Seattle Municipal Tower Suite 4900

P.O. Box 34018

Seattle, WA  98124-4018

Location of Proposal

The project is in street right-of-way for Southwest Andover Street at 26th Avenue Southwest in the City of Seattle’s Delridge neighborhood (zip code 98106).  There is no street address for this project.  The project location is in the southeast quarter of Section 21 and the southeast quarter of Section 13, Township 24N, Range 3E and within the Green-Duwamish Water Resource Inventory Area (WRIA 9).  

Lead Agency

Seattle Public Utilities, the lead agency for this proposal, has determined that it does not have a probable significant adverse impact on the environment.  An environmental impact statement (EIS) is not required under RCW 43.21C.030(2)(c).  This decision was made after review of a completed environmental checklist and other information on file with the lead agency.  This information is available to the public on request.
 

This Determination of Non-Significance (DNS) is issued under WAC 197-11-340(2); the lead agency will not act on this proposal for fourteen (14) days from the issuance date below.  A copy of the environmental checklist is available at:

• Seattle Public Utilities, General Manager/CEO's Office Main Reception Area, Seattle Municipal Tower, Suite 4900, 700 Fifth Avenue, Seattle, Washington

• Seattle Central Library, Public Review Documents, Level 5 Reference

• http://www.seattle.gov/util/EnvironmentConservation/Projects/Delridge99/

   

  Public and Agency Comments

  Comments on this DNS must be submitted by May 3, 2018 and must be sent to:

  Betty Meyer, SEPA Responsible Official

  Seattle Public Utilities

  Seattle Municipal Tower, Suite 4900

  P.O. Box 34018

  Seattle, WA 98124-4018

  betty.meyer@seattle.gov

      

  Issue Date:  April 19, 2018

  Betty Meyer

   

  Appeals

  Appeals of this DNS must be accompanied by an $85.00 filing fee and must be filed by 5:00 p.m. on May 10, 2018.  Delivery of appeals filed by any form of USPS mail service may be delayed by several days.  Allow extra time if mailing an appeal.

• Written appeals must be sent to:  

City of Seattle Hearing Examiner
700 5th Avenue Suite 4000

P.O. Box 94729

Seattle, WA 98124-4729

• Appeals can be filed electronically.  Details on electronic filing procedures are available under “e-File” at the Office of the Hearing Examiner’s web site:  http://www.seattle.gov/examiner/

• Filing fees must be paid by the appeal deadline and can be paid via check (made payable to the City of Seattle) or credit/debit card (Visa and MasterCard only).  Credit/debit card payments can be made in-person or over-the-phone.

• You should be prepared to make specific factual objections.  Please refer to the Hearing Examiner Rules of Practice and Procedure for rules that govern appeals.  These rules are available on the Hearing Examiner’s website at www.seattle.gov/examiner/rules-toc.htm or by calling 206-684-0521.