The Alder Mill site was an ore concentrating mill for gold and copper. The site is situated on a 75 acre plot located in Okanogan County approximately 0.4 mile from the Town of Twisp, Washington and is in close proximity to the Methow River. The Alder Gold and Copper Company, owned by Mr. Ray Dodge of Portland Oregon, is responsible for the site. The mill was operated from 1949 to 1952. Historically, two unlined and undiked ponds (upper and lower) were used to store wastewater and silt (tailings) from the mill’s operation. The tailings ponds occupy approximately 10 acres of the site. The upper pond is situated in the bed of an unnamed intermittent stream, and is approximately 650 feet long, 150 feet wide, and an average of 12 feet deep. The upper pond is partially vegetated. A perennial standing water pond fed by springs is located at the upstream end of the tailings impoundment. The lower, smaller pond is located approximately 400 feet from an irrigation ditch and is completely unvegetated. Mill tailings were disposed of into the ponds between 1949 and 1952. Runoff events caused by heavy rainfall have sporadically resulted in the release of contaminants of concern off the site. A 1952 failure of the upper pond resulted in the transportation of tailings approximately 2,200 feet downstream to a nearby residence. Contaminated water infiltrated down the sides of the well casing, rendering the water unfit to drink.
