Inside Seattle's West Point Treatment Plant Disaster

projects.seattletimes.com

18 pointsoptimiz33 comments

A large part of the problem is because of "a combination of raw sewage and stormwater". That is what's called a "combined sewer".[1] It's an insane thing to have in areas like Seattle and Portland where it rains a lot. It means you're periodically dealing with massive amounts of water.

I live in a newer community near Portland and our stormwater drains are independent of our sanitary sewers. Thankfully.

[1] https://en.wikipedia.org/wiki/Combined_sewer

Combined sewers are generally syptom of aged infrastructure. For many years standard practice has been to separate storm and sewer systems -- in part because the cost of treating sewage is roughly proportional to the volume of water passing through the system.

Going further, stormwater systems are also a sign of obsolescent approaches to infrastructure. Contemporary practice and progressive land use regulations require development generated additional runoff to be mitigated on-site to maintain pre-development flow rates at a development site's edges.

Stormwater systems are superior. On-site mitigation supports mosquitoes and lets automotive fluids seep into the soil. On-site is only preferred due to cost, particularly because of who is paying.

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