Update from King County Wastewater Treatment Division: The wastewater spill in the West Seattle industrial area along the Duwamish River (reported here last night) has been stopped, but they don’t know yet how much spilled, describing it as “large yet currently undetermined.” Read on for the full news-release update:

King County clean-water utility employees reported success around 8 p.m. Monday in stopping a treated wastewater overflow at the intersection of West Marginal Way SW and SW Front Street in West Seattle’s industrial area.

The overflow began before noon on Monday after a contractor removed an access shaft along a section of pressurized line that pushes treated and disinfected wastewater from the South Treatment Plant in Renton to an outfall in Puget Sound off of Duwamish Head. A large yet currently undetermined volume of treated wastewater overflowed into the intersection and a nearby parking lot.

To control the overflow and minimize potential for property damage, operators stored treated wastewater at South Treatment Plant to keep water levels in the line as low as possible. But because tidal conditions in Puget Sound prevented the line from fully draining, the overflow continued throughout the day and made it impossible for workers to safely access the manhole to perform needed repairs.

Skilled divers were eventually able to enter a manhole late Monday evening and replaced and secured the access shaft cover.

With repairs completed, South Plant operators directed treated wastewater to the outfall in Puget Sound and the system is again operating normally.

County staff notified regulatory agencies about the overflow.