Washington ? Washington state environmental regulators say they’ve finally found the source of pollution that has been fouling a creek near Vancouver Lake: the agency’s own sewer pipes.

City workers have discovered that an office building’s sewer line was mistakenly connected to a storm drain, rather than the municipal sewer main.

The 1970s-vintage building houses Washington state Department of Ecology regional offices, as well as those of the Department of Fish and Game and U.S. Army Corps of Engineers.

Sewage from the building has been making its way into Burnt Bridge Creek and eventually into the lake. Jay Manning, the environmental agency’s director, says the discovery was “embarrassing and upsetting.”