Imagine enough battery acid to fill about 625 swimming pools and enough toxic mine waste to fill about 10,000 dump trucks.
Now imagine having to clean that up.
Kit Custis and Steve Reynolds of the California Geological Survey helped do just that at the Spenceville Mine in Nevada County. As a result, DOC was honored with a Governor’s Environmental and Economic Leadership Award at a December 4 ceremony.
Supervising Geologist Trinda Bedrossian made the nomination for the award because, she said, “It was such a great project and it demonstrated how partnerships can work.”
- Kit Custis
The awards recognize individuals, organizations, and businesses that have demonstrated exceptional leadership and made notable contributions in conserving the state’s resources, protecting and enhancing the environment, and building public-private partnerships.
“It was difficult and challenging, but it’s one of the most satisfying projects I’ve ever been involved with,” Reynolds said. “A lot of times it seems as if projects like these are started out with good intentions, but aren’t finished for whatever reason. To follow this through to the end was a great feeling.”
- Steve Reynolds
The Spenceville Copper Mine is located on the western boundary of Nevada County, about 20 miles east/southeast of Marysville as the crow flies.
The mine opened in 1862 and was mined underground for 20 years until the workings collapsed. It was then worked as an open-pit mine until it was abandoned in 1918 – long before advent of the DOC-enforced mining laws that ensure reclamation.
“It wasn’t a major (copper) producer, but it was very profitable because its ore was rich – up to 30 percent copper by weight,” Reynolds said. “It was one of the first mines to have electric lights.”
The San Francisco Paint Company produced “Spenceville Red” from the mine’s tailings. While the color was brilliant, the paint had an unfortunate side effect: Its acidity ate away at the nails holding buildings together.
When the mine shut down, the mess left behind was staggering. The 10-acre site included 60,000 cubic yards of mine waste and a half-acre, water-filled mine pit. The pit contained 7.5 million gallons of pH 2.5 acid mine drainage -- essentially, battery acid -- that was trickling into two creeks. The flooded pit posed a risk not only to wildlife, but also to people recreating in the area.
The acid drainage is caused by the presence of sulfide minerals such as iron pyrite, or “fool’s gold.” The exposed iron sulfide mixes with water to become sulfuric acid. Microbes in the water increase the pH level.
The Department of Fish and Game acquired the site as part of the Spenceville Wildlife Area from the federal government in 1966. DFG started exploring the possibility of cleaning up the site in 1988, bringing CGS aboard in 1993 to provide support in the areas of geotechnics, reclamation and construction oversight. Custis, Jim Pompy of OMR, and Gail Newton, formerly of OMR, produced a reclamation plan in 1995. Karen Wiese of OMR helped determine what it would take to revegetate the site.
“We looked hard at the geochemistry,” said Custis, a senior engineering geologist. “The site still has the potential to generate acid; it puts metals into the streams that kill off fish. What we wanted to do was buffer the acid. Basically, there was no soil left there. What was there looked like the stuff you have in the bottom of your barbecue. We did a number of studies to see what it would take to grow plants.”
Custis and his colleagues came up with a sweet idea for counteracting the acid in the mine waste. They arranged to obtain spent lime – a base – used in the processing of sugar beets to mix with the soil.
“It’s just like putting a Tums in your stomach,” Custis said. “Of course, it’s a larger scale, a lot more acid. It’s a simple technique. It just required a lot of tweaking and controls.”
- Creek bed before restoration
Photos: Steve Reynolds
Not only does lime neutralize the acid, but the organic matter left over from sugar beet processing decays and removes the available oxygen. The lack of oxygen prevents the sulfide minerals from dissolving and generating acid.
However, funding to actually complete the project didn’t become available until 2000. CGS was selected to manage the contract, update the reclamation plan and ensure that the standards of the California Environmental Quality Act were being met. Custis worked on the project up to the point that contracts were awarded, then
transferred to a position in the North Coast Watersheds Assessment Program. Reynolds began riding shotgun on the project.
- Creek bed after restoration.
CGS worked not only with DFG but also with the Regional Water Quality Control Board, UC Davis, and private consultants to address the problem. The pit was drained and the water treated. With copper, zinc, iron, arsenic, aluminum and other dangerous material taken out, the water was used to irrigate wildlife forage in the surrounding area. Treated mine waste was used to backfill the pit. The site was recontoured, covered with topsoil and revegetated.
During the project, exhumed cultural artifacts were surveyed, cataloged
The actual work began in April of 2001 and wrapped up last December. All that remains is monitoring the site and performing routine maintenance until the vegetation is established.
“We put so much effort into developing the plans and went through so many starts and stops, so it’s good to see they
finally got the money to do something, Custis said. “You look at the site, and compared to what it was, it’s pretty amazing.
“If you think about the concept, it’s kind of weird – doing construction to hide something.”
Reynolds’ pet project was the streambed of Little Dry Creek. While the reclamation plan didn’t call for putting the streambed in its rightful place, there were sound reasons for doing so. The addition of that project was made possible by cost savings gained in
other areas of the project.
The Spenceville Mine has become a textbook on reclamation. OMR and CGS use it as a training site for abandoned mines inventories.
“It’s about as close to pristine as it could be,” Reynolds said. “The original civil engineering design wasn’t nearly as pretty. It was more like a landfill. Now, once the final vegetation takes hold and the fences come down, you wouldn’t know there was a mine there.”