2008-03-20_APPLICATION CORRESPONDENCE - C2008086 (2)

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Ms. Catherine Robertson March 20, 2iD08 Page 3 The :narrative on page 3.2-20 needs to be amended to clarify that the proposed coal waste disposal area will be located within the northern section of the project area, not the southern section. In addition, we would recommend that the proposed coal waste disposal location be included on Figure 3-7. The l~oundwater discussion in Section 3.2.5 provides an analysis of bedrock groundwater occurrence and water quality. Based on our review of the well completion information and available water level data there appears to be insufficient information to infer that the estimated bedrock flow direction is to the south. Three wells were constructed and monitored, two wells monitor groundwater within and below the Cameo coal zone (8-2-8 and 8-3-10), one well more than a mile to the northeast monitors groundwater in the overburden (7-34- 7). 'Che overburden well has better water quality and exhibits a substantial head difference. The potentiometric level in the overburden well is significantly above the screen interval whereas water levels in the coal zone wells are at or below the constructed screen interval. There is not sufficient data to determine a hydraulic connection between the water-bearing zone encountered at we117-34-7 and the Cameo coal zone. Rather than assuming that the three wells constructed and monitored are hydraulically connected and represent a water table condition, it is more probable that the water encountered at well 7-34-7 is a perched aquifer or saturated zone. The groundwater flow direction in this perched zone is more likel}~ to be to the northeast following the regional dip of the bedrock. Additional monitoring wells would be required to fully characterize bedrock grou~udwater occurrence and movement in the project study area. The D1ZN[S recommends the following minor modifications to the bedrock groundwater discussion on page 3.2-29. In the third paragraph on page 3.2-29 the following sentence: "The hydraulic connection between the water-bearing zone and the Cameo coal zone that is approximately 570 feet is also unclear."needs to be clarified and the reference to 5'70 feet needs to be explained. We recommend that the last two sentences of the third paragraph on page 3.2-29 be deleted from the text. 4. A couple of typographical errors were noted in Section 3.2.6 and 4.2.6. If appropriate please revise the following pages accordingly. On page 3.2-35, in the first paragraph, third sentence the text should read high-quality water as opposed to "high-quantity water': On pages 4-82 and 4-83 references to well locatiions is given as Figure 3-9, IISGS Stations This is incorrect and the reader should be referred to Figure 3-8 for well locations. 5. Growndwater inflow to the mine is only briefly discussed in Chapter 3, Affected Environment and in Chapter 4, Environmental Consequences and Mitigation. Potential impacts from the inflow are described only with regard to groundwater