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• r ~ \ I ^ ~ AFL ~ I~ _XI rYr_ ~~ ~Q ~~ v(v~rd a'(~Rkyheport Drillhole data from the permit area were combined with outcrop ata to construct structure contour maps of the Ciruela and'Primero co~~ ~. Map 2.04.6-2 is structure isopleth map of the top of the Ciruela seam~Map 2.04.6-3 is structure isopleth ap of the top of the Primero seam. The major geologtF structure in ~area.~s the Raton a m which was undergoing gentle down warping during the.time ot;depositions of a coal. After deposition of the basin sediments, deformation with intense folding and subsequent thrust faulting occurred west of the site. Shears developed in an east-west pattern, and normal tension faults have developed in a complimentary set of fractures trending N10W and N80E. Movement along these faults are expected to be only a few feet at the permit area. Site visits and review of borehole logs and aerial photographs have not revealed surficial evidence of any large scale faulting. The La Veta Syncline bisects the site with the location of the axis located roughly through Lorencito Canyon. Dips on the base of the Ciruela coal seam and the Primero coal seam were determined. Dips on the top of the Ciruela coal seam average~l.5 degrees toward the axis of the syncline. Dips on the top of the Primero coal seam average 1.7 degrees toward the axis of the syncline. Physical/Geochemical Properties of Stratum Surface Mine • Density and the slake durability index (SDI) were identified from 48 samples from BH-1 and 64 samples from BH-2. The average specific gravity from BH-1 was 1.91 and was 2.29 for BH-2/ The slake durability testing yielded a bi-modal population from which it appears that 66 percent of the stratigraphic column near BH-1 have SDIs greater than 65. The comparable value for BH-2 is 48 percent (Tables G-3 and G-4). Cores were obtained from eight boreholes (MWl through MW6 and BH1 and BH2) and examined and submitted for laboratory analyses of salts and toxic elements listed in CDMG's "Guidelines for the Collection of Baseline Water Quality and Overburden Geochemistry Data." The coal to be mined at the surface mine consists potentially of the R, Q, P, O, and O1 seams. Overburden/Interburden r1 LJ All parameters required for analysis were compared with overburden/interburden suitability ratings developed by the Wyoming Department of Environmental Quality and the Montana Department of State Lands to determine potential limitations relative to revegetation and hydrologic consideration. Table G-3 is a statistical summary of the overburden geochemistry. Table G-4 summarizes all overburden/interburden data collected. Some parameters for certain samples were not analyzed due to an insufficient amount of the sample. Parameters above suitability ratings developed by the Wyoming Department of Environmental Quality and/or the Montana Department of State Lands are discussed below: Geology~75/April 23. 1997 10 (revised 4/21/97)