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• For the shallower alluvial wells, no preliminary work was performed except washing out of the casing prior to abandonment, if necessary. All wells (bedrock & alluvial} were checked for water level and depth prior to any abandonment to ensure the total depth was sealed. ABANDONMENT ACTIVITIES Two methods were developed to abandon the wells depending on their status as a bedrock or alluvial well. For the shallow alluvial wells, the following method of abandonment was followed. The work was accomplished with arubber-fired backhoe. Following the removal of any protective fencing and metal stakes, an attempt to remove the well casing was tried. This usually failed, so the casing was cutoff at ground surface and the casing filled with clean `play' sand to at least three feet below ground surface. The backhoe was then used to dig out the casing to approximately three feet below ground surface. A round concrete tube form (cut to three feet in length) was placed in the small excavation on top of the exposed sand plug. The excavated hole was backfilled. The open tube was then filled with concrete from the bottom of the tube to within six inches of the ground surface. A metal post was then placed in • the concrete. On the post was riveted a metal tag with the well alpha-numeric identification designation (see Well Data Table}. The site was then smoothed with the backhce and the site raked and seeded. Atypical alluvial well abandonment well is shown in figures 3-9. The seed mixture used in this project was similar to that applied on the Kerr Mine. The seed mixture consisted of 5 pounds western wheatgrass, 5 pounds intermediate wheatgrass, and 5 pounds of pubescent wheatgrass. This 15 pound ttuxture is applied at a rate of 15 pounds per acre. The procedure for abandonment of the bedrock wells depended on (1) if the total depth (based on EFC or BLM well data.) had been reached and (2) if the total depth was not reached, whether or not the total depth of the well was below the bottom of the coal (previously recorded or shown on the geophysical log). For the bedrock wells where total depth was reached, the depth and thickness of coal were known and the casing did not have visible slots or there was no data on slots, the well was perforated (as previously discussed). The standazd abandonment procedure for these wells required the drill rig to back over the well and the rig to be set up. Then 1" tremie pipe was lowered into the well to approximately 20 to 40 feet off bottom. Based on the depth of the bedrock well and the diameter of the casing/annulus, a calculated volume to seal the well was then determined. The bedrock wells were plugged with a Portland cement/bentonite plug gel combination. The . water/cement ratio was approximately 16 gallons water to one bag of cement. The plug gel CT&E Geologic Services 2 January 30, 2003 Gillette, Wyoming