In this case, immediately after the cleanup in the mid-90s, the toxic levels did drop in the affected area, but in the past decade those toxic levels are back up at an alarming rate.
Eighteen years after it was first named a Superfund cleanup site, Richmond's Lauritzen Channel is as toxic as ever.
"Within this narrow channel we're now seeing steady increases in fish tissue in the amount of DDT that we find," Environmental Protection Agency regional administrator Jared Blumenfeld said. "And that's a troubling signal."
The EPA's most recent five-year review shows higher levels of the banned pesticide DDT than before the cleanup began in 1994. The waterway was contaminated by a chemical plant in the 1940s. DDT was banned in 1972 after it was found to kills fish and prevent birds from reproducing. It's also harmful to humans.
The higher levels of DDT come despite years of dredging and the replacement of tons of contaminated soil in the 1990s; a $10 million project.
"We thought we dealt with all of it," Blumenfeld said. "Now what we're seeing is from other sources which we haven't yet been able to identify more DDT is creeping back into that channel."
The 2006 EPA review showed level of DDT rising, but the latest study put those levels 30 times greater in Lauritzen Channel anchovies than in 1994.
"The bottom line is that it needs to be taken care of," Richmond City Councilman Tom Butt said. He worries about the larger implications for his community. "There's a significant population of people in Richmond who fish in the bay, and even fish near this area, and this is a big potential health hazard for them."
Lee Chua often casts his line in Richmond Marina Bay, not far from the Lauritzen Channel. He's not planning to eat what he catches.
"I'd love to fish here and actually keep the fish and eat it and not worry about anything," Chua said.
The EPA has received funding from Congress to do further study and figure out where the DDT is coming from and how to clean it up again. In the meantime they are posting no fishing signs inside Lauritzen Channel. As for concerns about the fish in the greater Bay Area, the EPA says so far their studies indicate there are no higher levels of DDT in the fish in that area.
