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 Cottage Grove Reservoir came from natural volcanic rock and minerals and geothermal activity in the upper drainage areas.
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 contaimination in the watershed, including Cottage Grove reservoir, a popular fishing and recreation destination.
Public Health Assessment
EHAP evaluated the public health significance of exposure to mercury and arsenic from the mine's soil and tailings in a Public Health Assessment (pdf) released on April 25, 2012, along with a summary fact sheet (pdf).
The report is open for public comment until July 23, 2012.
To provide public comments:
E-mail the Environmental Health Assessment Program (EHAP) at:ehap.info@state.or.us
Comments can also be submitted in writing to:
The Environmental Health Assessment Program
800 NE Oregon St. Suite 640
Portland, OR 97232
What are the main findings?
- 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.
The fish advisory for the Cottage Grove Reservoir states:
- Women of childbearing age (under 45 years of age), particularly pregnant or breastfeeding women, children under six years of age and people with liver or kidney ailments, should not eat any fish from this reservoir.
- Healthy women beyond childbearing age (over 45 years of age), other healthy adults and healthy children six years of age and older should eat no more than one meal of fish from the reservoir per month. A "meal" is about the size and thickness of the palm of your hand.
- 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 for arsenic, along with nitrates and bacteria, evey year - if you have a well that you use for drinking and cooking. Arsenic is a naturally occurring element in the earth's crust. As water flows through cerain rock formations, it can dissove arsenic and carry it into groundwater that is used for drinking water. There is a list of accredited labs throughout Oregon that provides information and instructions on how to get your well water tested. You can also get information by contacting the Oregon Environmental Laboratory Accreditation Program.
- 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.
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