BAKER CITY — An official from a Canadian company gave Baker County commissioners an update Wednesday on a proposal to do exploratory mining on a county-owned section of the dredge tailings in Sumpter Valley.
The county owns about 900 acres of tailings left by the dredges that operated from 1915 to 1954. Dredging converted several thousand acres a rich agricultural valley into a gavel-piled wasteland, and converted the former meandering course of the Powder River into a nearly straight channel.
In the new project to re-mine the tailings, Erik Tofsrud of Shukrain Investment Inc. in Vancouver was joined by Mark Ferns, a retired state geologist from Baker City. Both are part of Rainier Skyline Excavators Inc. Special Projects. (Neither Ferns nor Tofsrud could be reached for this article.)
In its proposal Wednesday, Rainier Skyline Excavators wrote that it has researched the dredge’s operation and found that only an estimated 40% of the gold in the gravels that were dredged was recovered. The remainder is still there in the gravels and sediments left behind by the dredge.
The group wants to conduct a “bulk test,” which would involve digging a trench about 900 feet long, 300 feet wide and 80 to 100 feet deep, according to the proposal submitted to the county. Rainier Skyline Excavators would be ready to start the test in March 2020. The process would determine whether it’s financially feasible to do larger-scale gold mining in the tailings. At the recent value of $1,400 per ounce, all the previous mined gold would be worth about $180 million. The value of the remaining gold, if all the dredged area--which is well beyond the County’s 900 acres — were to be extracted, would be around $72 million.
Commissioners will have to put out a request for proposals in case other companies are also interested in doing testing on county property.
“In one year’s time, we can know whether or not we’re going to move forward,” Harvey said. “And then we would need to do public hearings saying we’ve proven that it’s viable and we’re looking at this as a total project and then this will be the end result.”
Because the large gold dredge that devastated Sumpter Valley used a process of amalgamating gold to mercury to remove fine gold from the dredged material, mercury contamination, and remnant mercury in the tailings presented a concern in the 2007 report prepared for DEQ by GeoEngineers of Portland.“Mercury has been detected in tissue from fish caught in Phillips Reservoir (Newell, Drake, and Steifel, 1994) and in the Cracker Creek drainage basin (Hope, 2002). Bioaccumulative metals (arsenic, cadmium, lead, and mercury) have been detected in surface water and sediment at concentrations that appear to exceed basin-wide background concentrations in tributaries to the Powder River (upstream of the site).”
The report concluded that “A number of metals were detected in soil/sediment samples at concentrations that exceed ecological risk screening criteria. Arsenic was present in 28 locations at the site at concentrations exceeding one or more ecological risk screening criteria. Mercury (total and monomethyl mercury) were present in seven locations at concentrations that exceed one or more ecological risk screening criteria.”
Proposals to re-mine the tailings and restore the former river channel and flood-plain began in the mid-1980’s including a proposal by Noranda Corporation, another Canadian gold mining company. Over the past several years county officials have had multiple discussions with miners who expressed an interest in plying the tailings for gold.