The Weber Mine, comprising approximately 80,000 cubic yards of mine waste, is on private patented land holdings surrounded by public lands administered by the USFS. The Conjecture Mine Dam is adjacent to the Weber Mine to the northwest and is comprised of approximately 5,000 cubic yards of mine waste on USFS-administered lands. The CERCLA Removal Action planned for the Conjecture Mine Dam will be funded by an IA with USFS.
Previous investigations conducted by the Idaho Department of Environmental Quality (IDEQ) and the USFS revealed elevated concentrations of heavy metals (especially arsenic and lead) in samples collected from the mining/dump areas. Lead was detected at an average concentration of 1,997 milligrams per kilogram (mg/kg) with a high of 8,440 mg/kg. Arsenic was detected at an average concentration of 1,236 mg/kg with a high of 6,940 mg/kg.
The mine waste area is bisected by the NF 1017 Road, which runs parallel to Gold Creek. Gold Creek flows to the north for approximately 8 miles from its headwaters at the Pend Oreille Divide to its’ mouth at Lake Pend Oreille. Both Gold Creek and Lake Pend Oreille are habitat for the threatened Bull Trout and Lake Pend Oreille is also habitat for threatened Kokanee Salmon as well as the drinking water source for Sand Point, Idaho. The surrounding land is undeveloped public land and used for recreation such as camping, hiking, hunting, fishing and riding recreational vehicles. There is evidence, such as tire tracks and ruts, that the mine waste piles are used by ATV and motorcycle riders. These activities generate clouds of dust from the fines, which can be inhaled by the ATV riders, other drivers on NF 1017 Road, hikers, fishermen, campers or anybody attracted to the mining structures adjacent to the area.
This a collaborative effort between EPA, USFS, and Trout Unlimited.
