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.1 ,' company plans to increase the penetration depth up to 200 ft in the near future if tests prove economical. Up to five seams are augured. In some instances, the auger mines two lifts, one over the other, when the seams are thick enough. Augering takes place as soon as possible after surface mining becomes uneconomical and coal removal from the pit has advanced far enough so that one operation will not interfere with the other. GEC has established safety requirements to counter auger mining hazards, including highwall spalling and rnllapse, and hazardous entry into abandoned under- ground workings. Adequate highwall preparation prior to augering reduces spalling. In addition, heary sections of steel with screening material have been added to the auger canopy for operation and equipment protection. With regard to highwall collapse, proper sizing and spacing of auger pillars and adequate monitoring of highwall conditions are critical to the prevention of highwall slide and collapse. The company maintains pillar thickness between auger penetration equivalent to one-sixth or more of the actual seam thickness to elimi- nate highwall collapse. Management also has established a pillar monitoring program to make sure that pillar thickness provides adequate support. Auxiliary supports are used where necessary. Auger machinery hazards and hazards associated with the compactness of the operation have been all but eliminated with the new auger that features automatic controls. It also requires only two operators as opposed to four on older models. Operators must wear protective hearing equipment during regular operating hours. Deci- bel recordings and dust samples are taken periodically by a certified inspector. Backfilling or plugging of auger holes takes place as soon as possible and always within 30 days following In seams thick enough, the twin auger mines two 150-ft-long lifts, over and under, to increase recovery rate. completion of augering. This amount o[ time is often needed to minimize interference with the surface mining operation. Ground water can be a problem i[ it rises above the auger holes. In this case, the holes serve as a conduit for the water that saturates the backfill, resulting in the failure of the backfilled pit surface. If this occurs, the holes are sealed immediately with impermeable overbur- den material (clay) before the pit is backfilled. This material is collected and stored in temporary stockpiles during the routine removal of overburden and it is readily available for sealing the holes. To date, however, no ground water-bearing formations have been encoun- tered. About the Geology Coal seams mined by GEC Minerals are located within the Canon City coalfield of the Upper Cretaceous formation and above the prevalent Trinidad sandstone member. Although up to 17 coal seams are present within the Canon field, only five are minable by surface mining methods within GEC's present operat- ing procedures. The seams, numbered one through five in descending order, vary in thickness from less than 2 ft to as much as 6 ft with an aggregate thickness of 12 ft. The company is capable of mining to a depth of 120 ft. Rocks within the area consist primarily of sand- stone, siltstone, shales, and fire clay. They are inter- bedded and lenticular, varying in thickness and con- tent throughout the mine area. Structurally, the stra- ta dip to the west-southwest from 2 to 5 deg. Mining progresses in asouth-southwest direction. The surface is covered with 12 to 60 ft of colluvium, consisting of large boulders, cobbles and sandy materi- al, which readily absorbs water. This colluvium, washed down from the mountainous terrain from the west, was deposited on an erosional surface over the coal deposits. In many cases, the colluvium eroded the upper one or two seams and actually washed out portions o[ several seams during the formation of ravines. This process formed ridges and valleys that accounts for the contour type of mining practiced by GEC. Within the 7,000 acres owned or leased by GEC, all coal seams have been correlated using data from existing pits and numerous drill holes. Coal analysis on an as received basis reveals a Btu content of 10,600; sulfur, 0.4%; moisture, 11~,; ash, 10%; volatile mat- ter, 34%; and fixed carbon, 45%. r L COAL AGE/MAV, 19a3 /t