99-foot bridge for pipeline set in Kirk Gulch
Sanford lab and Homestake Mining Co. Cooperate on water treatment
A crane operator placed a 99-foot concrete bridge across Kirk Gulch on Wednesday morning.
The narrow bridge will support part of a pipeline that will carry water nearly two miles from the Grizzly Gulch tailings reservoir, owned by Homestake Mining Co., to the water treatment plant at the Sanford Underground Laboratory.
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"We love this kind of stuff," said Clair Donovan of Donovan Construction of Spearfish, S.D., one of the four companies building the pipeline.
"We're off to a good start," Sanford Lab Engineering Project Manager Mike Johnson said. Johnson, who designed the line, said it would be ready to use sometime in October.
The pipeline is important to the future of the Sanford Lab, which could become the world's deepest underground laboratory. Before that can happen, the South Dakota Science and Technology Authority must pump water out of Homestake, which was sealed shut for five years. Homestake is 8,000 feet deep. The water level this week is down to 5,130 feet underground -- down 600 feet from the high-water mark reached 2008, when pumping began.
Under a long-term agreement with Homestake Mining Co., the Sanford Lab blends water from underground with water from the Grizzly Gulch reservoir before sending it to the lab's water treatment plant. Grizzly Gulch water cools the Sanford Lab's warm water from underground and also lowers the concentration of suspended solids. The Sanford Lab's treatment plant, in turn, removes ammonia from Grizzly Gulch water and lowers the dissolved solids. "It's a symbiotic relationship," Sanford Lab Environmental Manager John Scheetz says.
The bridge will carry the new double-walled pipeline over Kirk Road and Whitewood Creek. From Kirk Gulch, the pipeline will enter the Oro Hondo tunnel, which intersects Homestake at the 300-foot level. RCS Construction of Rapid City is building the pipeline through the 300 Level to the Ross Shaft. Sanford Lab technicians will install the line up the shaft to another tunnel near the surface. RCS Construction will take over construction from there to Homestake's former Mill Reservoir, a large concrete basin that feeds the water treatment plant.
The treatment plant discharges clean water into Gold Run Creek.
The Sanford Lab had been using existing Homestake pipelines to transport water from Grizzly Gulch, but those lines had to be replaced. The lab will spend $1 million on the part of the pipeline owned by the South Dakota Science and Technology Authority. Homestake Mining Co. is paying for the line across the company's property.