DEADWOOD — Following the presentation of 2021 annual reports regarding the Homestake and Richmond Hills mine sites, the Lawrence County Commission July 28 approved conditional use permit for Homestake Mining Company and for LAC Minerals-Richmond Hill Mine.
Mark Tieszen, environmental manager for Homestake/LAC Minerals addressed the commission, beginning with the Homestake report.
“Our 2021 employment contributions, both for Homestake and Richmond Hill combined were 10 FTEs, plus two full-time contract employees and one part-time contract employee,” Tieszen said. “Our contributions for 2021 were $10,760, which includes a $3,000 Homestake scholarship – two $1,500 scholarships that we give out.”
In regard to the Open Cut, Tieszen said reclamation has been completed at the waste rock facilities.
“At the end of 2021, we had 555 acres were released, with approximately 87 remaining affected acres,” Tieszen said. “Reclamation has been completed on all those acres.”
Commissioner Randy Deibert asked if the acres were public or private land.
Tieszen said private land.
“All of the Homestake land is private land,” he added.
No complaints associated with Homestake activities in the Open Cut Mine area were received in 2021 and no technical revisions were submitted or approved in 2021.
“Our 2021 activities included, we entered into an (purchase) option agreement with Dakota Gold Corp. for both the Homestake and Richmond Hill properties. That option can be exercised any time on or before Sept. 2, 2024,” Tieszen said. “We did some improvements at our tailings storage facility pump barge landing. The Grizzly Gulch tailing storage facility barge access road and landing were extended. That allows us to be able to get the barge out into colder, deeper water. That helps with improved access to the pumps. The pumps can be reached with a crane for maintenance.”
In regard to geotechnical monitoring, Homestake employs multiple displacement monitoring techniques, including prisms and survey monuments, piezometers, inclinometers, visual inspections, and InSAR monitoring.
“The Open Cut East Block, that area failed on June 14, 2019. About 3,000 cubic yards failed,” Tieszen said. “It was contained within the pit boundary on Homestake-controlled property. There’s another 3,000 to 5,000 yards there that has the potential for failure, but measurements do not indicate a new area of instability or significant upslope enlargement of existing instability. The remaining crest of the Open Cut looks good. No indications of recent movements that could represent potential for substantial slope failures.”
East Waste Rock Facility data indicates no significant movement from prior monitoring.
“The Bobtail Gulch area of the East Waste Rock Facility from 1994 to 2008 showed shear movement,” Tieszen said. “A buttress was constructed in 2009 and 2010 and since then, movement has slowed and is expected to continue to slow. Movement is primarily settlement and relaxation of the buttress fill.”
In regard to Deadwood Creek Monitoring, Blacktail Water Treatment Plant treats water emanating from the toes of Sawpit and East Waste Rock facilities.
“The water treatment plant removes selenium and total dissolved solids from the water prior to discharging to Deadwood Creek,” Tieszen said. “The Blacktail Water Treatment Plant discharge consistently meets the water quality standards and Deadwood Creek monitoring confirms there are no impacts from the Homestake Mine.”
Homestake projects for 2022 include the continuation of a water treatment agreement with the South Dakota Science and Technology Authority and continued water treatment.
LAC Minerals -Richmond Hill Mine
“We have 266 total released acres, with 76 remaining affected acres, of which 73 are used for water treatment facilities,” Tieszen said. “Reclaimed affected acres of about one-third of an acre and reclamation to be completed in the short-term, which includes our regional sludge basin and discharge pond, 2.66 acres.”
There were no formal complaints received in 2021 at the Richmond Hill Mine and no technical revisions to LAC’s mining permit were submitted or approved in 2021.
“2021 activities included sludge removal from the storage pond. This sludge is being removed in preparation for pond realigning this year,” Tieszen said. “We started that process last year, moved about 300 cubic yards. We had about 5,000 left for this year, probably a little over half-way through that.”
Once it is finished, it will be a double-lined pond.
In regard to water management and treatment, leach pads and ponds, biological water treatment continued.
“We operated the water treatment plant with reverse osmosis, discharging about 14.55 million gallons. The biological water treatment plant was also operated over the winter months, discharging 5.85 million gallons,” Tieszen said. “As of June 1, we had approximately 14.96 million gallons of water in storage. We’re down to about 10.1 million gallons now. We pretty much dried up the storage pond while we were bringing up that sludge.”
Leach pad flows averaged approximately 17.6 gallons per minute in 2021.
“These were lower than the flows during 2020, as we had very low precipitation in 2021,” Tieszen said.
At Spruce Gulch, the reclaimed site of a waste rock disposal facility, water treatment – pH adjustment with sodium hydroxide, or, caustic soda continues as needed and nearby South Gulch water is pumped to Spruce Gulch Treatment Pond for treatment. And that treated water also decreased significantly from last the last couple of years.
In regard to monitoring activities, pit impoundment and leach pad monitoring continue.
“The 2021 pit backfill monitoring/capping system monitoring continues to indicate that the cap is functioning to and better than design expectations,” Tieszen said. “The leach pad capping system continues to perform well limiting infiltration.”
Tieszen said water quality at the site is generally stable or improving.
“Cleopatra Creek water quality monitoring confirms there are no impacts from the Richmond Hill Mine,” Tieszen said. “Monitoring is continuing and site-specific performance criteria were developed in consultation with DENR and approved by the Board of Minerals and Environment to ensure continued protection of the environment in post-closure.”
Plans for 2022 include replacing the storage pond liner, replacing the reverse osmosis unit, continuing with reverse osmosis and biological water treatment, and continuing monitoring activities.
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