Milestone for Murray Combined Sewer Overflow Control Project across from Lowman Beach

| Environment | Utilities | West Seattle news

(The view through the fence from Beach Drive in front of the project site)

Completion is in sight for the project meant to reduce combined-sewer overflows into Puget Sound by Lowman Beach – the Murray Combined Sewer Overflow Control Project. We took the photo after getting this update late today:

King County’s million-gallon underground storage tank is now working after passing all system tests. As early as next week, County operators will work inside the facility to monitor flows at the Murray Pump Station and operate the underground storage tank as needed.

Roadway restoration is complete on Beach Dr. SW. The contractor is now restoring sidewalks near the site. Crews are also working in the access road south of Lowman Beach Park to upgrade a small sewer line. This work is expected to be complete by mid-December.

Schedule update
Landscaping and project art will finish up in early 2017, depending on weather (see schedule in attached update for additional information). A fence will remain around the site until all landscaping is complete. The public staircase on site will not be accessible until all project work is complete. Access to Lowman Beach Park will be maintained as it has been throughout construction.

King County and its contractor appreciate your patience as we work to complete the project as quickly as possible. We will provide another update in December with what to expect during activities that will continue in 2017.

No work at the site during the four-day Thanksgiving weekend.

BACKSTORY: It’s been seven years since first word of a possible storage tank to catch overflows. Six years ago, the storage-tank decision was announced. Major work at the site began in August 2013 with demolition of the residences that used to be on the site. Here’s our pic from two years ago when the tank was halfway done:

When done, the structure will include public-access areas for looking out toward Puget Sound.

Student November 16, 2016 (8:41 pm)

The problem is that the storm drain flows into the sewer so when it rains very hard, this combination of sewage and stormwater overflows. Right?

On its face, the solution is to either not dump stormwater into the sewer or to engineer an overflow for the stormwater *before* it combines with the sewage. Amiright?

Solving the problem by building massive storage tanks seems outlandish. What am I missing?

WSB November 16, 2016 (8:52 pm)

You’re missing the years of discussions that led to this decision (and the dozens of stories we wrote). In short – two areas needed to get stormwater out of the system to avoid overflows. One area lent itself to alternate means – the Barton basin, where raingardens and bioswales were built. The Murray basin, which goes to this pump station, did not lend itself to alternate means, so the storage tank was the solution. – TR
WSPK November 16, 2016 (8:56 pm)

My understanding is that while keeping stormwater and sewage separate would be ideal, but the existing infrastructure puts them into the same system. That’s the “combined” part of the equation. Rebuilding the street drainage system would be a monumental task, a centralized storage tank like this is actually relatively simple.
chemist November 16, 2016 (9:16 pm)

A longer-view of the Seattle sewer system and CSOs is below (the full thing is 26 minutes). Though the city put in a separate stormwater sewer system into many areas starting in the late 1960s, all the homes with waste-sewer connected downspouts weren’t mandated to be disconnected/connected to the stormwater system. I suspect that it might not be as simple as just disconnecting too, because there can be “settled debris-clearing” benefits of sudden inrushes of large volumes of water.

http://www.seattlechannel.org/misc-video?videoid=x25929

An overview of the Seattle Sewer System from 1885 to present, including the program to reduce combined sewer overflows (CSOs) in Seattle between now and 2025.
- dsa November 16, 2016 (9:35 pm)
  
  The city maps show the residential rooftop drain connections to the sanitary sewer system. There must be some legal restriction preventing passing a law forcing a disconnect of those shown.
  - John November 17, 2016 (8:25 am)
    
    dsa,
    
    The only laws restricting it are the laws of physics.
    
    If all rooftop and hard surfaces were disconnected, where would the water go? There is no separate storm drain to connect to and many areas are not feasible for natural drainage.
    
    Homeowners are encouraged by the city to divert roof drains to rain gardens where the ground is permeable.
    
    New homes are required to construct and maintain catchment basins with natural drainage and only overflows are hard lined to the combined sewer.
    
    Older new homes were required to run drains to the street where they flowed to the storm sewers.
    - chemist November 17, 2016 (9:33 am)
      
      Is it no longer permissible to run a stormwater line out curbside to direct into storm sewers, even in a steep slope recognized area ? I figured that would be what was recommended if we ever had to replace the sewer connection on this 1960s-built house with wastewater/combined-connected downspouts.
Sara November 18, 2016 (1:25 pm)

All the the combined sewer overflow infrastructure was built 50+ years ago. Before they understood how bad it was do this to our environment and before even more roadways, buildings and neighborhoods were built, increasing all of the impervious surfaces, which funnel rainwater into our stormwater/waste water systems. They can’t just demolish all of the underground piping networks to un-separate these flows. Therefore they are doing these types of projects to reduce untreated discharges into our waterways.