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Contaminant Testing in Upper Ten Mile Creek Mining Area, Montana

Date Posted: February 5, 2002

Contaminant staff recently assisted the Environmental Protection Agency in conducting tests to see how toxic (poisonous) the water from Ten Mile Creek may be to fish and other aquatic life. Ten Mile Creek is located in the Upper Ten Mile Creek Mining Area and flows through the old mining community of Rimini. This Superfund site, located southwest of Helena, Montana, was heavily mined from 1870 to 1920. Mining activities included extraction of gold, lead, zinc and copper. This site was added to the Superfund National Priorities List in 1999, because of high concentrations of metals detected in surface water and groundwater. The high metals concentrations in surface waters were a special concern as this watershed provides drinking water for the city of Helena. Superfund is the Federal government's program to clean up hazardous waste sites that may endanger public health or the environment.

The toxicity tests were conducted in a mobile toxicity lab using rainbow trout from a Montana Department of Fish, Wildlife and Parks Fish Hatchery, and water from two different reaches of Tenmile Creek. The water collected from the two different locations on Ten Mile Creek had different metals concentrations. Contaminated water from each reach was diluted with stream water from an area not impacted by the mining waste to achieve fourteen different concentrations of mining waste in the water (seven concentrations from each reach). Rainbow trout were placed in each of the 28 tanks (each concentration had a duplicate tank) containing this water for 48 hours to determine what concentrations were lethal to the fish. The toxicity testing was designed to estimate the potential cleanup levels needed for Ten Mile Creek to sustain a trout fishery.

Karen Nelson, 406-449-5225 x210, or Bill Olsen, 406-449-5225 x214.

U.S. Environmental Protection Agency. Upper Ten mile Creek Mining Area

US Fish and Wildlife Service Offices in Montana

Last updated: June 12, 2015