Almaden Resident

News

Alien-looking contraption placed at Almaden Lake to control mercury

By Sarah Holcomb

Almaden Lake visitors may notice an alien-looking contraption sharing the water, but the Santa Clara Valley Water District says not to worry; it's just managing the mercury levels.

This is the first time the water district has permanently placed such a device in one location, said spokesman Mike DiMarco.

The solar-powered aerator, called a SolarBee, mixes air into the lake to clean the water and prevent mercury from forming. DiMarco said the district chose to place the SolarBee in Almaden Lake specifically to control the mercury pollution.

"We have used the SolarBee before in our recharge ponds to clean up water quality in them, but this is the first time we've stationed one full-time at one body of water," DiMarco said.

The water district placed the aerator in the lake nearly two weeks ago, away from the swimming area, even though the aerator poses no danger to swimmers. It can be seen floating near the Winfield Drive side of the lake, where people fish and boat.

"What we are concerned about is it's grabbing water from the very bottom, where there is material that has decomposed and can produce a temporary odor," DiMarco said. "I don't think we've noticed one yet."

The mercury initially came from waste that was dumped in the creeks during the quicksilver mining days; today, rainwater carries mercury down the hills from the former New Almaden mines into the creeks, which flow into the lake.

Mercury is absorbed by algae when the oxygen in the lake is used by natural bacteria to decompose dead leaves and other material on the bottom of the lake. When small fish eat the algae, they become contaminated, and the mercury can move up the food chain as larger fish eat the smaller fish.

The water district said the mixing of the air and lakewater is expected to break the menthyl mercury-production cycle.

The SolarBee is part of a larger project to contain the amount of mercury already in the lake and to prevent further contamination.

"We're going to be removing a huge source of mercury from the watershed," DiMarco said. "When the project is finished, we'll neutralize whatever mercury there is now and prevent more mercury menthyl from forming."

The district said it chose the SolarBee because operating costs are minimal and it runs on solar power. The district purchased the device for $45,000 with funds from its Clean, Safe Creeks and Natural Flood Protection program.

DiMarco said the district hasn't received any complaints from the public, and the wildlife at the lake hasn't shown any signs of being disturbed by its new neighbor.