--> In Situ Treatability of Mine Spoils Material Used As Road Metal, by M. A. Rogers, G. Barkmann, P. A. Longmire, and D. N. Tafoya; #90986 (1994).
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Abstract: In Situ Treatability of Mine Spoils Material Used As Road Previous HitMetalNext Hit

Margaret Anne Rogers, Gretchen Barkmann, Patrick A. Longmire, Diane N. Tafoya

In 1974, Terrero Mine spoils material was used as road Previous HitmetalNext Hit for upper Pecos campground roads in the Santa Fe National Forest. Studies began in 1990 because of vegetative die-off adjacent to the roads.

The zinc-lead-copper ores at the Terrero Mine are volcanogenic massive suffide deposits. Spoils material would be expected to produce an acidic leachate which would mobilize Previous HitmetalNext Hit ions. Early work showed that higher concentrations of metals were generally associated with lower pH values for samples. With few exceptions, pH values increased with increasing depth of sample at all sample locations. Concentrations of metals decreased with depth. Pb levels proved to be of regulatory concern.

PHREEQE, a geochemical modeling program, determined if the substratum could neutralize road Previous HitmetalNext Hit leachate. Based on titration simulations, approximately 10 volumes of ground water are required to neutralize 1 volume of leachate. Assuming 20 inches of infiltrating precipitation (over a 100 square foot surface area), approximately 125,000 gallons of generated leachate would require approximately 900 pounds of calcite to neutralize each year.

Stabilization/neutralization tests were performed using high calcium hydrated lime and dolomitic hydrated lime. The sub-base samples did not have enough highly active clay for pozzolan development. Maximum removal of Pb and Zn from road Previous HitmetalTop leachate occurred between pH 6.79 and 8.93. Raising the pH to >12 (for pozzolan development) would resolubilize Zn and Pb. If precipitation were free to move through road material alter adding lime, extreme pH conditions should be avoided to prevent leaching of Pb. Remediation is in progress.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994