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Introduction This appendix evaluates groundwater chemistry and gradient data for the Dry Creek alluvial system in the vicinity of the Hayden Gulch Loadout (Loadout). The Dry Creek alluvial system was evaluated to address concerns raised by Colorado Division o£ Minerals and Geology (CDMG) staff during the technical adequacy review for Technical Revision TR-06. Specifically, CDMG indicated in their adequacy comments that Hayden Gulch Terminal, Inc.'s (HGTI's) alluvial groundwater monitoring program was inadequate and that a new, upgradient alluvial monitor well was needed to determine potential alluvial groundwater impacts associated with Loadout activities. Tha evaluation presented below demonstrates that CDMG's concerns regarding potential impacts are unfounded, that the upgradient and downgradient alluvial chemistry is similar, and there is no significant impact from the Loadout. Historic Groundwater Chemistry Hia toric groundwater chemistry data at the Loadout was collected during the period 1987 through 1995. H-G Coal Company, the previous operator/permittee, installed both an upgradient, and a downgradient shallow monitor well proximate to the facilities area. The wells, which HGTI identified as HGDALI (upgradient) and HGDAL2 (downgradient) are shown on Figure 1. The wells were installed to assist the operator and CDMG to evaluate potential alluvial water quality impacts. Antidotal information suggests both wells were partially completed in the underlying Lemia shale. To address CDMG concerns that the well data were not representative of the alluvial aquifer chemistry, HGTI installed a monitor well downgradient of facilities area in October 1993. This well, identified as HGDAL3, is also shown on Figure 1. Chemistry data presented in Tab 7, and the Annual Hydrology Reports indicate the alluvial groundwater is unsuitable for agriculture use. Tab 7 summarizes data collected through 1995. The data in Tab 7 shows that alluvial groundwater concentrations of boron and manganese are elevated above agriculture use standards. In addition, the total dissolved solids concen trationa typically exceeded 10,000 mg/1, the threshold Water Quality Control Commission (WQCC) has set for groundwater classified as "limited use and quality." The concentrations in well HGDALI were generally two to three times higher than that seen in wells HGDAL2 and HGDAL3. The high sodium and chloride concentrations strongly suggest that the Dry Creek alluvium is influenced by upgradient agriculture return flow and dryland farming/Lewis shale seepage. Because of the concern regarding Lewis shale influence in TR-06 7-2 .1 Revised OS/06