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Ground tires may help reduce hazards at abandoned mines

In an effort to increase safety at abandoned mines, a New Mexico State University-based consortium is developing a slurry from ground-up old tires and cement to fill dangerous underground passages.

WERC Program Manager Jim Loya is leading an effort to use a mix of tire crumb and cement, shown in samples in front of him, to increase safety at abandoned mines.

WERC: A Consortium for Environmental Education and Technology Development has received two grants from the Bureau of Land Management to research innovative methods using waste materials to reduce hazards at abandoned mine property in the Boston Hill area of Silver City.

The land was purchased by Silver City in 1999 as an open-space preserve to be developed as a hiking and bike trail. Silver and manganese-iron ore were mined in the Boston Hill area beginning in the late 1800s.

Four different parcels of land in Boston Hill remain the property of the BLM. Three have abandoned mine hazards, including various types of underground passages and surface openings.

WERC is researching methods to deal with the safety hazards and identify methods of controlling surface water. The methods must also allow for the protection of the habitats of bat species in the Boston Hill area and preserve mining heritage for educational purposes.

The project began in the summer of 2003 with a physical investigation of the abandoned mines. Research was then conducted to identify current methods and innovative technologies using waste materials as a method to reduce hazards at such sites. As a result of this research, WERC proposes to experiment with the tire-and-cement slurry to fill some of the abandoned mines.

Four interconnected mine passages, totaling 4,000 cubic feet, have been identified to serve as pilot sites to test the effectiveness of the slurry. Biologists have determined that the area is not a bat habitat.

Last spring, WERC Program Manager Jim Loya formed a steering committee composed of representatives of state agencies, the BLM, public interest groups, the town of Silver City and NMSU to develop parameters for laboratory and field testing of new concepts and materials as well as conditions for long-term monitoring of the mine site.

"Initial literature research shows that the material could be used successfully as a fill for abandoned mines," Loya said, "This research also indicates that studies conducted on similar substances did not yield environmental problems, such as leaching from the material."

Laboratory research is needed to find the right combinations of materials and to develop mixing methods. Variables such as strength and shrinkage also will be studied. Once a promising mixture is developed, it will be tested to determine how successfully it can be pumped before it is actually used in the field.

Work is expected to begin this fall at NMSU's civil engineering laboratory and remediation of the site will take place in the spring. Once the formula for the slurry mixture is perfected, it will be made available for use at other BLM sites.

"It's an innovative way to address two environmental problems," Loya said.

The WERC consortium is composed of NMSU, the University of New Mexico, New Mexico Tech, Diné College and Los Alamos and Sandia National Laboratories. WERC's mission is to develop human resources and technologies for addressing environmental issues. For more information about WERC, visit www.werc.net or call (505) 646-2038.