New treatment plant for mine water discharged at North Star Mine
Newmont Mining Corporation will have to install a temporary water treatment plant for the Drew Tunnel by the end of August, according to a new agreement with the city of Grass Valley. The Drew Tunnel is a component of the North Star Mine site, and currently drains thousands of gallons of mine water into the city’s wastewater treatment plant every day.
That treated water is then discharged into Wolf Creek under the city’s permit — but now Newmont has its own permit (Notice of Applicability, Limited Threat General Waste Discharge Requirements Order RS-2013-0073-01) and it will soon be responsible for treating that mine water itself.
“The agreement requires them to take 99 percent of the flows out of the city system,” said Tim Kiser, Grass Valley director of public works. “So they’re now going to be treating all the Drew Tunnel flows.
“For us it’s a huge volume reduction in our wastewater treatment plant,” Kiser said.
Newmont had already begun the process of getting a temporary water treatment plant into place, which has to happen by Aug. 31. So far, that’s involved a lot of paperwork, but construction will be starting soon, according to Newmont spokesman Omar Jabara.
“We already have the permit and the contractor has been mobilized to the site,” Jabara said. “It should be a pretty fast turnaround here, assuming there’s no challenges.”
What has to happen between now and Aug. 31, Jabara said, is that the hookups to the pipes at Drew Tunnel will need to be plumbed.
Once the temporary treatment plant is in place, a permanent one will have to be constructed by 2018. But from now on, responsibility for treating the Drew Tunnel flows will stay with Newmont, according to Kiser.
The new groundwater treatment facility will use a green sand/multi-media 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 will be tanks filled with sand and anthracite, but in general terms for people to understand, it’s sand,” said Kiser.
“The sand will take those particles out as the water flows through it,” he 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 city will still have to treat that back-flush water in its water treatment plant, Kiser said, but at a maximum rate of 40,000 gallons per day. That will be down from a current range of 300,000 to 1.5 million gallons per day being treated by the city now.
This new groundwater 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, Kiser said.
If Newmont fails to meet its new deadline, Kiser said, that’s where binding arbitration comes into play.
To contact staff writer Dave Brooksher, send emails to firstname.lastname@example.org or call 530-477-4230.
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