UC Berkeley
Researcher Dr. James Hunt
Explores Preventative Solutions for Acid Rock Drainage
Dr. James Hunt
Civil Engineering Professor
University of California, Berkeley
Nestled among the pristine lakes and breath-taking panoramas of the Sierra Mountains, you can find native killers. They don't move on their own, yet they manage to decimate miles of ecosystems, leaving barren scars on the land. If you haven't surmised already, this description references the thousands of abandoned mine sites that plague the state of California. Some of these mines haven't been disturbed in over 100 years, most are abandoned. And they're in some pretty interesting places. In addition to the Sierras, you can find several mine sites around the San Francisco Bay Area - Mt. Diablo, south of San Jose, and in the East Bay hills near Mills College. Waste rock from these mines can have serious toxic effects on the surrounding environment. Regulatory agencies, such as CalEPA and the State Water Control Boards, monitor most of the sites, but have taken little or no action. Why?
UC Berkeley Dr. James Hunt has a few ideas. "Abandoned mines are enormous generators of pollutants. The contaminant levels are very high and the water that runs off from the sites has very low pH is acidic and is called acid rock drainage. The acidity dissolves metals like copper, zinc, and mercury, which are then carried downstream." These metals are commonly present at most of the mine sites in California as sulfide minerals. Once exposed to oxygen and water, the minerals are oxidized, releasing sulfuric acid and the metals, which can prove fatal to ecosystems. "Most of the technology to date has focused on downstream waste treatment facilities," Dr. Hunt explained. "The goal of a downstream facility is to neutralize the water and precipitate the metals, but whenever it rains, the stream volume overloads the facility," says Hunt. "In a very stormy, wet year, like this past one, you couldn't build a facility big enough to handle the runoff." But that isn't the only obstacle. Regulatory agencies have chosen not to engage in remediation of known pollutant sites because of one simple reason: fear of liability.
The Penn Mine cleanup in the foothills of the Central Sierra Nevada set a precedent for the "hands off" policy now taken by the state of California and its agencies. The watershed of the Mokelumne River has been developed to supply water to the San Joaquin Valley and the East Bay Municipal Utility District (EBMUD). The first major dam, Pardee Dam, was constructed by EBMUD in 1929, upstream of the Penn Mine site. The dam captured winter and spring runoff for release later in the year and diminished the volume of water that used to dilute seasonal runoff from the Penn Mine site. In 1963 the Comanche Dam was completed below the Penn Mine site and mine waste started to accumulate in the Comanche reservoir. The effects were evident - it started killing fish in the hatcheries and vegetation was affected. "The East Bay Municipal District and the Central Valley Regional Water Quality Control Board built a treatment facility to help remediate the area, but this facility required a permit," Hunt said, "Even with the facility in place, the discharge was still above the current standards, so now the East Bay Municipal District and the Regional Water Quality Control Board are being sued by several interest groups to do more."
This dilemma intrigued Dr. Hunt, so in 1993, he and several colleagues from UC Berkeley decided to investigate possible technologies that could reduce the production of acid rock drainage. The UC Toxic Substances Research & Teaching Program funded the first year of his proposal, "In-situ Reduction of Acid Rock Drainage" in 1994. This research project focused on development and evaluation of technologies that could replace the expensive and inefficient downstream treatment facilities. Hunt recognized a great need for a technique to locate precisely where acid and metals are being generated. One of two laboratory components they hope to use in future studies would locate sites of acid rock drainage production by non-invasive imaging technology being developed at Lawrence Livermore National Laboratory. By using this technology, locations where contaminants are being generated can potentially be located with minimal disturbance to the ecosystem.
Once such a source is located, a method needs to be applied to seal off the site of acid production. The second component of this research project is evaluating the various laboratory methods to seal off local sites of acid production. "By stopping the flow of oxygen or water over the waste rock from these mines, the oxidation of the pyritic material (iron pyrite) and generation of sulfuric acid will stop," said Dr. Hunt. They are investigating the selective precipitation of inorganic compounds at sites of acid rock generation; another method being tested is "pore plugging" - using fine particles to stop the flow of water and oxygen through the contaminated soils. "We hope the combination of non-invasive imaging with acid production inhibition can be used as a direct means of finding and then stopping acid rock drainage," Hunt stated in the proposal. "What's interesting about mining issues is that the microorganisms are the problem, not the solution. Most of the time when people talk about bioremediation they think - what a good thing it is. For mine waste generation, microbial activity is a major part of the problem."
In addition to the effort in the laboratories, Dr. Hunt has been involved in field research to evaluate mine sites where acid rock drainage is a problem. In partnership with the Lahontan Region Water Quality Control Board, Hunt visited the Leviathan Mine in Alpine County, CA. to observe the extent of damage to that site, where sulfur was once mined. Leviathan Creek flows from the mine site in California into Nevada. Both states are anxious to find a workable solution, since the vegetation and wildlife has suffered tremendously (see picture, inset). The Lahontan Region Water Quality Control Board would like to use this site as a place to demonstrate remediation technologies for acid rock drainage and land surface revegetation.
Dr. Hunt is also serving on the Mt. Diablo Task Force for the Contra Costa County Health Department. Mt Diablo, which is located in the East Bay, has an abandoned mercury mine located on its east side. This committee hopes to identify a workable solution because Marsh Creek, which drains the mine's watershed, has fishing and other restrictions in place due to the high mercury levels in sediments. Dr. Hunt found this site particularly interesting. "There is a stream, separate from the mine site, that has high amounts of nickel similar to those found in mine drainage. It appears that the metal is leaching from a natural deposit that has been exposed to oxidation. So, the question then becomes, do you have to remediate the whole mountain, or just the mine?" Dr. Hunt stated. "With present technology, the cost of such a project would be completely prohibitive, so the field component of this research is essential in developing plans for the eventual expansion from small scale laboratory studies to field testing of the new monitoring and remediation technologies."
This is a new direction for Dr. Hunt. Prior to this work, most of his research has been in assessing groundwater contamination by organic solvents and petroleum hydrocarbons. Now Dr. Hunt is focusing his efforts on inorganic contaminants and in developing reasonable solutions and methods to prevent the production of waste streams. He said, "An important question is if you have a watershed that is degraded because of previous mining activity, how long would you have to wait for these things to return to "normal", and what does this do to the downstream environment?" He hopes to develop processes and technologies that will minimize or eliminate the damage from acid rock drainage and preserve ecosystems that otherwise would be destroyed.
| <-July/Aug. 1995 |