Abstract

An exploration program to locate high grade limestone was carried out in 1994-95 for the Tri-State Generation & Transmission power plant located at Nucla, Colorado. This plant requires limestone with over 95 percent calcium carbonate to remove sulfur dioxide from flue gas in an advanced application of clean coal technology.

A five phase plan of operation was initiated, consisting of Limestone Evaluation, Preliminary Exploration and Testing, Acquisition, Drilling, Permitting and Plant Construction. Limestone sources were identified in eight different formations from Cretaceous to Devonian Age. Limestone deposits of the Pennsylvanian, Hermosa Formation, found on the flanks of four anticlinal features were determined to be the best prospect.

Following geologic investigation, testing, and economic evaluation, it was concluded that the Lisbon Valley Anticline, south of La Sal, Utah, had the best prospects on the basis of quality, reserves, and cost of mining. Eight lode claims were staked and bids reopened by the power plant for their limestone requirements. Cotter Corporation was low bidder from a property adjacent to the claim block. In the fall of 1994, they began production and are now delivering a high quality product to the Nucla station. A back-up source was also identified and staked in the Little Gypsum Valley Anticline near the Utah-Colorado border.