New water treatment plant for Drew Tunnel in Grass Valley |

New water treatment plant for Drew Tunnel in Grass Valley

City officials are holding a press conference Monday morning to celebrate the fact that water flowing downstream from Grass Valley got a little cleaner this year. The Newmont Mining Corporation has installed a water treatment system to remove mining contaminants from Drew Tunnel flows, which discharge to Wolf Creek.

The Drew Tunnel is a component of the North Star Mine site, and it used to drain thousands of gallons of mine water into the city’s wastewater treatment plant on a daily basis. But that all came to an end Sept. 25, when the newly installed water treatment plant went live.

The new groundwater treatment facility uses a green sand/multimedia treatment system with a capacity of 1.73 million gallons of water per day to remove metals from Drew Tunnel flows at a rate of up to 600 gallons per minute.

“These tanks (are) filled with sand and anthracite, but in general terms for people to understand, it’s sand,” said Tim Kiser, director of Grass Valley’s Department of Public Works.

“The sand will take those particles out as the water flows through it,” Kiser said. “Then periodically, they’ve got to do a back-flush, which causes all the impurities to rise up to the top and they can skim them off the surface.”

The equipment was provided on contract with Active Treatment Systems, Inc. in Loomis. According to Newmont, numerous local contractors also contributed to the completion of the project, including Grass Valley Electrical, Hansen Brothers Enterprises, North Star Trucking and several others.

This new treatment plant was supposed to be in place by February 2013, according to the terms of Newmont’s original agreement with Grass Valley. But that agreement had some wiggle room according to Kiser, and that wiggle room became the subject of criticism from the Nevada County Civil Grand Jury.

“To date, the new treatment plant has not been constructed,” the Grand Jury wrote in June. “The Nevada County Grand Jury finds there has been no discernible effort by the City of Grass Valley to seek judicial relief in the enforcement of the civil agreement.”

Three months later, however, the new plant was up and running — just a few weeks after the city officially responded to the grand jury’s report.

To contact Staff Writer Dave Brooksher, email or call 530-477-4230.

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