River flood terraces have cleaned up Napa's oily industrial past
Aug 10, 2019 at 11:00am
Napa River flood control terraces where wildlife lives and people stroll along a bike path are officially just short of being squeaky clean from an oily past.
Years of monitoring showed a massive 2004 cleanup effort of an industrial area north of Imola Avenue worked. The San Francisco Bay Regional Water Quality Control Board last month officially rescinded its 2001 cleanup order.
That puts the bureaucratic bow on a cleanup done 15 years ago.
“To take a pretty contaminated industrial area and convert it to a restored wetland, riparian habitat is a good thing for the river, for sure,” said Richard Thomasser of the Napa County Flood Control and Water Conservation District.
Only one monitoring task remains. Thomasser said a small amount of residual contamination is five to six feet below ground along the river near Eighth Street, just below the practical excavation level for the 2004 cleanup.
The flood control district must keep an eye on the site for signs of major river erosion and visually check it after major earthquakes, such as the 2014 South Napa earthquake.
Otherwise, the flood control work has an official clean bill of health.
“We really feel good about what was done out there,” Thomasser said. “We moved all the contaminated materials and then monitored groundwater to show the groundwater conditions were clean.”