Tuesday Sep 29 2009
Mercury rising: Meadow Vista lake yields toxic traces of Gold Rush
By: Gus Thomson, Journal Staff Writer
Mercury-extraction demonstration on Lake Combie could lead to larger project
MEADOW VISTA – A toxic vestige of the Gold Rush era is getting some special attention at a foothills reservoir near Auburn. Mercury, a byproduct of the gold-extraction process, is sitting in the mud and sand of countless rivers and streams throughout the Gold Country. Eating fish from mercury-laden waters leads to developmental delays in fetuses, infants and children. The Nevada Irrigation District’s Combie Reservoir could soon be in the forefront of efforts to clean up mercury with a dredging effort that could process 200,000 tons of sediment and remove an estimated 100 pounds of mercury. On Tuesday, district officials and the Canadian-based Pegasus Earth Sensing Corp. gave a demonstration of equipment that could separate out mercury without chemicals, also take out gold, and leave much of the cleaned material to be used as aggregate. The environmental study on the project was approved last week by the district board and work could start as early as April, said Assistant General Manager Tim Crough. As a side benefit, the project would help restore water-storage capacity in a lake that has been filling with sand and gravel, he said. While the gravel is expected to be sold to Chevreaux Aggregates, the district was playing host to a representative of U.S. Sen. Dianne Feinstein to win support to tap into federal economic stimulus and grant funding. The initial $100,000 for the environmental study came through the Sierra Fund. Methyl mercury is a neurotoxin absorbed into the food chain, which can have an impact on fish downstream as well as humans. Several foothills water bodies, including Camp Far West Reservoir, have warnings against eating fish caught there. Ted Reimchen, a geologist with Alberta corporation Pegasus, said the equipment can easily be added on by an aggregate operation without impeding its production. Gold is a welcome byproduct, with early tests at the site indicating 2.4 grams to 3 grams per ton. Crough said that the district would retain the gold but, while it could subsidize some of the costs, it would still not pay for the estimated $6 million needed over the life of the project. Carrie Monohan, science director with Nevada City’s Headwater Sciences, said the district found a state-of-the-art silent, electric dredge to answer nearby residents’ concerns about noise from the operation. Placer County and local residents’ group Meadow Vista Protection are locked in a lengthy legal battle over Chevreaux Aggregates building an asphalt plant at the site. Monohan said that a separate traffic study didn’t find the project would have a significant impact on Combie Road and others leading to and from the site. Crough said the project is a “flagship” effort for surrounding water agencies and irrigation districts, that could be replicated in many other reservoirs, including the NID’s own Rollins Lake near Colfax.