“The process to remove the York Creek dam started back in the summer of 1992 — 60 or 70 years after the city stopped using it as a primary water source — when a crew was doing some routine maintenance work that led to “an accidental discharge of sediment,” according to an environmental impact report commissioned by the city.
The sediment had been building up behind the dam for decades at the rate of between 1,000 to 5,000 cubic yards per year and when released, it left silt deposits of up to 18 inches deep just below the dam.
By the time those deposits traveled the roughly 3 miles downstream to the confluence of York Creek and the Napa River, they had thinned to a dusting of fine silt, but by that point the damage was done.
It was the fourth such catastrophic discharge from the dam since 1962, and it killed an untold number of fish and other aquatic creatures.
In 1993, after lawyers with the California Department of Fish and Game filed a complaint with the Napa County District Attorney’s Office, a Superior Court judge in Napa ordered the city to remove the dam.
In a settlement agreement, the city also committed to removing the silt and preserving “the stability and natural character of the area,” according to the EIR.
The court order was rescinded in 2001 so the project would be eligible for grant dollars, and momentum really started to build in 2012 when the city was able to acquire grants from the U.S. Environmental Protection Agency and state Proposition 84 for nearly $2 million, said St. Helena’s Public Works Director Erica Ahmann Smithies.”