Coastal Post Online

April 2001

Something's Being Done About Mercury In Tomales Bay

By Karen Nakamura

An investigation into what's being done by officials to solve the mercury poisoning of Tomalas Bay turned up reassuring results, sorta. In December, it was announced that numerous fish in the bay's water are contaminated with methylmercury. The long cherished Marin fishing hole is polluted to a point where fisherman can't eat much of their prized catch.

However, Will Bruhns of the San Francisco Bay Water Quality Control Board wants to assure the public that the Board is on top of the situation. Even though the name infers its jurisdiction is only within the San Francico Bay, it also oversees Tomalas.

The source of the methylmercury that's poisoning Tomalas Bay and Walker Creek, which flows into it, is the Gimbonini mercury mine six miles up the creek. Active from 1968 to 1972, the mine was closed and declared an Environmental Protection Agency Superfund Site. For 30 years, until 1998, mercury flowed into the creek from the mine's tailings.

Mercury is particularly insidious and has been known to be a lethal poison for over 50 years. In its mildest form, it causes disorientation, headaches and nausea. In its worse, it causes cats to commit suicide, symptoms similar to Parkinson's Disease and involuntary spastic reactions, sometimes to total rigidity from brain damage.

In late November, early December of 2000, the SFBWQCB posted signs around Tomalas Bay warning of mercury poisoning in seven species of fish including sharks, which are at the top of the food chain. It also warned fishermen not to eat any quantity of fish for their own safety. Pregnant women were strongly cautioned. As with its monitoring of the San Francisco Bay, only fish that permanently live in the contaminated area were tested. Other fish, such as stripe bass, pass through on their migratory paths and were not tested. These fish are the least likely to be contaminated.

In 1998-99, with the San Francisco Regional Water Quality Control Board acting in an advisory capacity, the EPA spent $2-3 million in Superfund Site moneys to encase the Gimbonini mine in concrete and build back-up holding ponds. It also spent $1 million to clean and restore the 12 acres surrounding it. This left only the mercury already in Walker Creek and the bay to be addressed. There were two choices. Bulldoze the entire creek or let nature take its course by allowing creek water to eventually wash away any residue. It was decided the best avenue was to allow the creek to restore itself while recognizing the process is slow and will take a while.

The delta of sand and rocks, or what some call the Walker Creek mudflats, contain the greatest amount of mercury. The idea is the mercury will settle to the bottom and be covered by sediment. This is currently a popular method of containment. A similar plan was used by the City of San Rafael to deal with the PG&E yards a few years back. The rest will leach into the bay and eventually be swept out to sea by tidal action. According to Dr. Fred Schwartz, Marin County Health Official, the parts per million are extremely low and even the consumption warnings were figured conservatively as an added precaution.

At this point, the San Francisco Bay Water Quality Control Board is monitoring the situation carefully. It was this monitoring, in fact, that uncovered the seven types of fish that are dangerous to eat and which consequently led to the postings. When asked if the mudflats, which contain the most mercury, would be dredged, Will Bruhns said that right now the mudflats are simply being monitored. As Superfund moneys only covered the mine, dredging the mudflats is almost impossible. "Let's put it this way," Bruhns added. "If we notice a surge in mercury levels, we may have to do something."

That also leaves wildlife and landowners along the creek's path in some danger of inadvertent poisoning. However, several ranchers along the creek have been cleaning up their property and local environmental groups, such as the Tomalas Bay Watershed Council, are doing what they can. Tomalas Bay, with its mudflats, is in the greatest danger as the mercury settles on the bottom and is eaten by creatures all the way up the food chain. Like arsenic, mercury is bio-cumlative and builds up in fish, animal and human systems until the possibility of a dangerous dose is reached.


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