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West Elk Mine 2.04.6 Geology Description Introduction The following geologic description of the West Elk Mine permit area is based on publications by C.R. Dunrud (1976), W.R. Junge (1978), Ellis, Gaskill, and Dunrud (1987) C. Richard Dunrud (1989), A. Mayo and W. Koontz (2000), and A. Mayo et al (2004); unpublished reports by V. H. Johnson (1948), Geo -Hydro Consulting (1980), Dames & Moore (1983), Intrasearch, Inc. (1993), J. Corbett (1997), Mayo and Assoc (1998, 2000, 2004), and SRK Consulting (1998); considerable subsurface and surface investigations by ARCO (now Arch Coal) and Arch Coal and Ark Land staff geologists, aerial photo and low altitude aerial and field reconnaissance studies by C.R. Dunrud and J.W. Rold (1994 to 2004), and results from more than. 238 drill holes on or near the property. The locations of these drill holes are shown on Map 8. Holes are designated "SOM" for those drilled over Federal coal and "MG" for those drilled over private coal. Four holes were drilled on the lease area by the U.S. Bureau of Mines (USBM) in the 1940's which were given a "G" designation. Twenty-five (25) holes were completed in 1963 by the U.S. Steel Corporation and designated with the "CSM" prefix. Five additional holes were drilled by Grand Mesa Properties in 1981 and designated "MG -***-81." Grand Mesa Properties completed another hole (CP -82-1) in 1982. In 1992 and 1993, MCC completed 13 drill holes through the B - Seam and were given the designation UMB." Three holes were drilled to the southwest of the ranine site in 1994 and were designated "So.W." (These holes should not be confused with the shallow wells completed for the subsidence monitoring program and designated as "SW -1" through "SW_ 6"). Holes drilled from 1993 to 1995, to the cast of the mine site, toward or on Raven Mesa have been designated "RAV". In 1996, 1997, and 2001, 21 holes were drilled and completed through the B -Seam.. They are designated as 96 (or 97 or 01) -*-*. The first entry indicates the year that the hole was drilled. The second entry indicates the section in which the hole was drilled, and the third entry indicates the numbered hole in that section. Subsurface control; coal distribution, coal thickness, and quality; overburden and interburden thickness and chemical characteristics; structural geology and stratigraphy, have been derived using information from all of the drill holes. More than 45 holes have been drilled on or within a quarter mile of the South of Divide permit revision area. The locations of those drill holes are included on Map 8. All holes were drilled with permission of landowners and permits from appropriate state and federal regulators. Monitoring wells shown on Map 34 and other holes shown on Map 8 were completed or abandoned and reclaimed in accordance with all regulations of the CMLRB and the State Engineer's Office (SEO) applicable at the time. Well completion data and test results have been submitted to the CDRMS with MCC's Annual Hydrology Reports. Completion data are also provided in Exhibit 12. Normal practice from 1973 through 1991 entailed rotary drilling to approximately 250 feet above the E -Seam where casing was set and coring continued downward through the B Seam. Since 1992, procedures typically only included spot coring of the E and B Seams and immediately adjacent strata. The typical suite of geophysical logs run on each hole consisted of various combinations of gamma ray, neutron, density, resistivity, self -potential, temperature logs, and caliper. Since 2000, coal quality has . been determined from laboratory analysis conducted by Standard Labs of 2.04-12 Rev, 11/04- PRIG; 07/15- MR413