Laserfiche WebLink
shale seepage. Because of the concern regarding Lewis shale influence in <br />wells HGDALI and HGDAL2, and the similarity of chemistry in wells HGDAL2 and <br />HGDAL3, HGTI stopped monitoring wells HGDALI and HGDAL2 in 1995. Since 1996, <br />groundwater monitoring has only occurred at well HGDAL3. Data collected <br />since 1996, which is presented in the Annual Hydrology Reports, indicate <br />similar constituent concentrations as observed between 1993 and 1995, and <br />that there are no long-term trends evident for any chemical constituent <br />monitored in HGDAL3. <br />TR-06 Groundwater Evaluation <br />In the adequacy comment letter, dated January 18, 2005, CDMG staff indicated <br />HGTI's opinion that the alluvial aquifer has been, and continues to be <br />unsuitable for irrigation and stock water use, had not been validated. <br />Furthermore, CDMG recommended that one additional upgradient monitor well be <br />installed to quantify background alluvial chemistry upgradient of the <br />Loadout, and to assist in determining potential impacts to groundwater from <br />the Loadout. During a site visit on February 1, 2005, representatives of <br />HGTI and CDMG discussed the appropriate course o£ action in response to Item <br />• 16 0£ the TR-06 adequacy review letter. The representatives agreed on a two <br />step approach: 1) review existing off-site Dry Creek alluvial groundwater <br />monitor well data and provide a demonstration that validates HGTI's opinion <br />that the Dry Creek alluvial groundwater, both upgradient and downgradient of <br />the Loadout, is unsuitable for agriculture use; and, 2) if the existing data <br />can not be utilized for background chemistry, then install a new upgradient <br />monitor well at an agreeable location and implement monitoring. <br />Peabody Holding Company, Inc. (PHCI), HGTI's parent company, conducted <br />exploratory drilling south and west of the Loadout during early spring 1998. <br />As part of the drilling program, PHCI installed several alluvial groundwater <br />monitor wells in the vicinity of the Loadout. Locations o£ the Dry Creek <br />alluvial wells installed by PHCI are shown on Figure 1. Appendix 7-2A <br />presents the PHCI boring logs and well completion information; completion <br />information for well HGDAL3 is presented in Attachment 7-2 0£ the existing <br />permit package. The boring logs indicate that monitor wells DCAL-3A, DCAL- <br />3B, and DCAL-5 were completed just into the Lewis shale. Wells SGAL-3 and <br />DCAL-6 were completed at the alluvium/shale interface. The logs show that <br />wells HGDAL-3 and DCAL-4A/4H were completed above the Lewis shale. Table 1 <br />summarizes well completion information for the PHCI alluvial wells and <br />HGDAL3. <br />TR-06 7-2.2 Revised 06/05 <br />