Mining & Exploration

Mining Locations

EP Minerals products are mined at five of U.S. Silica's mining areas with multiple quarries feeding each plant:

• The Celatom^® mining complex is located near Drewsey, Oregon, approximately 90 miles west of Ontario, Oregon.
• The Colado mining complex is located about 20 miles northwest of Lovelock, Nevada.
• The Clark quarries are located anywhere between 5 and 40 miles east of the plant, about 30 miles northeast of Reno, Nevada.
• The Fernley mining complex is located 55 miles northeast of Reno, Nevada.
• The Middleton (montmorillonite clay) mining complex is located near Middleton, Tennessee, with mines in both Tennessee and Mississippi.

Exploration

Diatomaceous earth (DE) and montmorillonite clay are both discovered using a variety of tools including geologic mapping, chip sampling, rotary drilling, and core drilling. Samples are sent to an internal lab where the quality of the ore is determined. Once an orebody of sufficient size and quality is discovered and permits are obtained, large scale testing of the new orebody can begin.

Mining

Once an orebody is ready for mining, the first step is to remove the barren or low grade material overlying the orebody. This material generally consists of volcanic ash, low quality DE, or basalt -- or for clay mines, it may be sand or just top soil. After this overlying material has been removed, mining of the ore commences. Great care is taken to separate the barren seams from the ore to ensure high quality ores are available for the plant consumption. Mining equipment generally consists of excavators, articulated hauling trucks, scrapers, dozers, front end loaders, road graders, and other support equipment.

Ore stockpiling and ore hauling from the mine to the plant

DE ore is loaded into an articulated haul truck, then deposited onto an outdoor stockpile in the desert. It is important to dry the ore as much as possible prior to shipping to the plant so solar and wind drying opportunities are maximized. Once the construction of the stockpile is completed, a front end loader loads the DE into over-the-road trucks for hauling to the plant.

Montmorillonite clay cannot be stored in the open, so mining is carried out on an as-needed basis, storing only a few weeks' supply in a covered barn.

Reclamation

Reclamation is an ongoing activity at all our mining operations. Once mining in an area has been completed, reclamation activity begins. Recontouring and reseeding returns the land to a productive state similar to the surrounding area. Wild animals are often seen in and around our active mining operations.