2008-03-03_PERMIT FILE - C2006085 (16)

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Ms. Angela Bellantoni Apri125, 2007 Page 4 seam. We used GIS mapping software to compare the reported bottom of the wells to the • structural top of the Ocean Wave coal seam. This comparison is presented in Appendix 3. The table in Appendix 3 presents the separation between the top of coal and the bottom of wells in the field labeled "coal separation". Many wells are not located over the Ocean Wave Coal seam or structural data were not available for the coal at the location of the wells, and as a result, coal separation data are not presented for many of the wells. As presented in the appendices, only one well (permit number 222887-A) was identified that potentially penetrates the Ocean Wave coal seam, but we believe that that well actually does not penetrate the coal as described below. In addition, we projected the structural contours of the top of the coal elevation to the south to determine whether or not any Chandler Heights wells (other than permit number 222887-A) potentially penetrate the coal. This analysis indicated that none of the Chandler Heights wells located outside of areas covered by Northfield's geologic mapping penetrate the coal. Cross sections A - A' and B - B' (Appendices 1 and 2) illustrate the geologic setting and the well completion interval information discussed above. The cross-section locations are presented in Appendix 4. The cross-sections illustrate the separation between the nearby wells both horizontally and vertically from the mine area and from the Ocean Wave coal seam. The results of this evaluation of potential impact indicate that all the / ~ -7 nearby wells are completed in shallower geologic units not hydraulically connected with v the Ocean Wave coal seam. There appears to be one well potentially penetrating the coal. This well, permit number 222887-A, was constructed in late 2006 to a depth of . approximately 600 feet, and a Northfield representative visited the well site during the construction process. The Northfield representative interviewed the well driller and learned that the well did not penetrate the coal based on the driller's observations and comments. However, we conservatively believe that the well may penetrate close to the coal based on structural mapping of the coal seam and the reported well depth. We note that the original well permit number 222887 was constructed to a depth of 697 feet, and very likely penetrated the Ocean Wave coal seam. However, there was a requirement on the replacement well permit that the old well be plugged and abandoned. Projected Water Level Changes in Nearby Wells We have completed analyses to determine the potential water level changes that may occur in well permit number 222887-A, referenced above, as a result of the mining operations, if the well penetrates the coal. As the coal seam is mined, it will be dewatered, which acts like a pumping well or drain in the coal inducing ground water flow towards the mine. As water flows towards the mine, it will result in water level drawdowns within the coal seam. These water level changes will be greatest close to the mine and will decrease with distance from the mine. Because of the aquitards above and !~-D below the mine, the water level changes will be isolated to the Ocean Wave coal seam. Also, because of the aquitards above and below the Ocean Wave coal seam, the interbedded nature of the Vermejo Formation, the low hydraulic properties of the aquifer and the horizontal distance that separates the mine from the well, we believe that this well represents the worst case scenario for water level impacts to wells, if it penetrates the coal.