From Seattle Public Utilities:
Seattle’s Seward Park swimming beach will reopen Saturday, after two consecutive days of testing showed the water safe for recreation. But a four-block stretch of Lake Washington remains closed to contact by humans and pets pending further testing.
The section of Lake Washington shoreline near Wednesday’s sewage spill site — from South Angeline Street north to the 4200 block of Lake Washington Boulevard South (including Lakewood Moorage) — remains closed. Additional testing will be conducted this weekend.
SPU found only "extremely low concentrations of fecal bacteria" after testing eight locations along Lake Washington Boulevard. In the area that will remain closed, they found three times the acceptable level of bacteria.
But what caused the sewage to spill in the lake in the first place? I couldn't make much sense of the press release, so I called up Andy Ryan and Mary Kelley at SPU.
The first thing you need to know is that there's an overflow pipe that directs sewage and stormwater into "local waterways," i.e. the lake. If we didn't have that overflow pipe, sewage and stormwater would rush back up into people's toilets whenever the sewer system overfills.
He said that a repair crew was sent to fix a particular electrical valve within the sewer system. This valve was in a chamber that was overheating. To fix that issue, the crew needed to unplug the valve so that they wouldn't get electrocuted during repairs. The document they consulted showed that unplugging the electrical connection to the valve would leave the valve open.
They really wanted this valve open, because when it's open sewage is not directed into the lake. When it's closed, sewage is redirected through the overflow pipe and winds up in the lake. So they unplugged it, thinking that the valve would remain open. Unfortunately, the document they consulted was outdated, the valve closed, and 12,000 gallons of human waste was diverted into Lake Washington.
