EHAP has released the final version of the Black Butte Mine Public Health Assessment (PHA). This report evaluated the public health implications of contamination from the mine, to nearby communities and has incorporated public comments received during the report's open comment period. Please find the full report and summary fact sheet.
What were the main findings of the public health assessment?
- Recreational use of Cottage Grove Reservoir: Swimming, boating, playing and wading in & around the water as well as practicing catch and release fishing is not a health concern.
- Mercury contamination in fish at Cottage Grove Reservoir continues to be of concern: In 1979, Cottage Grove Reservoir was the first water body in Oregon to have a fish advisory issued because of mercury contamination found in the fish. The advisory was updated in 2004, and in 2012 OHA issued a "green" fish advisory for the reservoir. The green advisory is for hatchery-raised, stocked rainbow trout in the reservoir, which indicate it is safe for anyone to eat up to 9 meals a month of rainbow trout 12 inches or less in length.
The Cottage Grove Reservoir fish advisory states:
- People of all ages can safely eat nine meals a month of rainbow trout that are 12 inches in length or less.
- Women ages 18-45, children under 6, and people with liver and kidney problems should avoid eating fish from these waters, with the exception of hatchery raised rainbow trout that are 12 inches or less in length.
- Healthy women beyond childbearing age ( over 45 years) and healthy adult males should eat no more than one meal per month, with the exception of hatchery-raised rainbow trout 12" or less in length.
- A "meal" is about the size and thickness of your hand.
- More information on statewide advisories.
- Tailings from the old mine site are considered a health hazard for very small children: Tailings, crushed rocks from the mine, may have been hauled off and used to build roads or for other purposes. It was considered an inexpensive way to reuse the rock, as was the common mining practice for decades. The tailings from Black Butte Mine contain arsenic at levels high enough to be a health concern for very small children, if they were to contact them. Toddlers and children are more susceptible to the effects of arsenic, and their frequent hand to mouth behavior makes it more likely that they might accidentally swallow small amounts.
- Naturally occurring arsenic in local groundwater: While not related to the mine itself, the Oregon Health Authority recommends testing your well water yearly for arsenic, along with nitrates and bacteria. Arsenic is a naturally occurring element in the earth's crust. As water flows through certain rock formations, it can dissolve the arsenic and carry it into groundwater that is used for drinking water. There is a list of accredited labs throughout Oregon that provide information and instructions on how to get your well water tested. You can also get information by contacting the Oregon Environmental Laboratory Accreditation Program.
Black Butte Mine was once the largest and most productive mercury mine in Oregon, operating from the 1890's until the late 1960's. Until 2008, it was thought that the source of mercury in the nearby Cottage Grove Reservoir came from natural volcanic rock and minerals and geothermal activity in the upper drainage areas.
However, we now know that a small creek (Furnace Creek) has been running through one of the mine's abandoned tailings piles for decades, contributing 50% - 75% of the mercury contamination in the watershed, including Cottage Grove reservoir, a popular fishing and recreation destination.
Previous reports and activities:
The final version of the PHA incorporated public comments and was released on March 13, 2013.
On July 11, 2012, several agency representatives participated in an open house sponsored by the Coast Fork Willamette Watershed Council. Agency staff were available to answer questions and provide information about the Black Butte Mine superfund site. Discussion topics included EHAP's Public Health Assessment, mercury contamination in the watershed, consuming fish from Cottage Grove Reservoir, naturally occurring arsenic in local groundwater and the next steps in the Black Butte Mine clean-up effort.
Agencies collaborating on the Black Butte Mine Assessment and Clean-up efforts include:
Oregon Health Authority (EHAP)
United States Environmental Protection Agency (EPA)
Oregon Department of Environmental Quality (DEQ)
Coast Fork Willamette Watershed Council
United States Army Corps of Engineers (USACE)
United States Geological Survey (USGS)