Point Reyes Light - September 9, 1999
Gambonini mercury mine nears end of costly clean-up
By Gregory Foley
At long last, the old mercury mine at Marshall's Gambonini Ranch is almost done getting cleaned-up.
Next Wednesday, the San Francisco Bay Regional Quality Control Board will consider a five-year budget of $402,300 to complete the cleanup - which to date has cost the state and federal government more than $3 million.
Staff of Regional Water Quality plan to use the money to finish revegetating the site with some 5,000 native plants that have been nursed from seed collected there.
Over the course of four years, starting in 1994, Regional Water Quality staff documented that mercury-laden sediments were eroding from tons of mining waste at the site.
The EPA then agreed to design a remediation plan and do all the earth-moving.
The majority of the EPA's work was done by November 1998. The work included benching and terracing the mine waste pile, moving approximately 200,000 cubic yards of tailings back into the existing mine pit, diverting stormwater around the waste, and installing a surface and sub-surface drainage system.
Currently, the EPA is pouring concrete ditches and repairing one small slope that continues to erode. It is estimated that the EPA has spent roughly $2.7 million on the Gambonini cleanup.
From 1994 to 1999, Regional Water spent nearly all of $569,000 the state gave it in 1993 for the project.
"EPA was the lead agency, and their work will be done in October," said Whyte. "The Regional Board has been assisting in the short-term, and we will continue to work at the site in the long-term."
By February of this year, state contractors had started the revegetation project by adding compost to the soil, and seeding 16 acres of property.
Texas-based Buttes Gas & Oil leased and operated the mine for six years starting in 1964. Initially, ore was taken from a 50-foot horizontal shaft dug at the site, although later on the ore was mined by bulldozers.
By the time the mine closed in 1970, some 3,541 flasks of quicksilver had been removed from the hill, with each flask cooked down from about 15 tons of ore.
Rancher Alvin Gambonini inherited the ranch in 1981, only to have the storms of 1982 expose the old mine.
Regional Water Quality ultimately sued Buttes Gas & Oil to pay for the cleanup, although the company had since gone bankrupt but agreed to spend $128,000.
In 1998, approximately 180 pounds of heavily diluted mercury flowed from the site during two months of storms.
While mercury can pose a significant health threat, Whyte stressed that tests have confirmed that oysters harvested in Tomales Bay present "no public health threat."
Whyte is scheduled to talk about her work at the Tomales Bay Association's Annual Meeting and Dinner set for 5 p.m. Saturday, Sept. 18 at the Inverness Yacht Club.
Whyte will discuss the Gambonini mine cleanup, and hopes to present results from a recent study of contaminants in fish and shellfish in Tomales Bay.