2008-12-03_PERMIT FILE - C1992081A (12)

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TAB 7 HYDROLOGICAL DESCRIPTION Regional Hydrogeology and Surface Water Characteristics Hayden Gulch Terminal, Inc.'s (HGTI) Loadout facility is situated principally (coal handling facility area and majority of the railroad spur) in the Dry Creek drainage basin (tributary to the Yampa River). A small portion of the railroad spur exists in the Yampa River drainage basin. A regional hydrological description of this area is presented in detail in Attachment 7-1, Regional Hydrology. Site Specific Ground Water Characteristics The coal handling facility area of the Hayden Gulch Loadout is situated in alluvial and colluvial materials overlying the Lewis shale of upper Cretaceous age. Two alluvial/shallow Lewis shale wells were constructed in the Loadout area prior to 1993 by the pervious operator, H-G Coal Company. One well, identified as HGDALI, is located upgradient of the Loadout area and the second well, identified as HGDAL2, is located downgradient of the Loadout. During October 7Q9"3, a new ~l~,wn3r~~1'.nr~ ~ ^ identified as HGDAL3, was constructed along Dry Creek within the Rail Loop to assure all potential groundwater impacts from the Loadout could be assessed. This downgradient well was installed to alleviate CDMG concerns regarding the possibility that wells HGDALI and HGDAL2 were partially completed in the Lewis shale (a typical completion diagram that is representative of both HGDALI and HGDAL2 is presented in Tab 13 as Figure 13-2). Completion information for monitor well HGDAL3 is presented in Attachment 7-2, Completion and Aquifer Test Data Well HGDAL3. In November 2005, a new upgradient alluvial monitor well, identified as HGDAL4, was constructed along Dry Creek immediately upgradient of the facility area. The well was installed to address CuMG ~~ii~eius LnaL u~~L~ way insufficient background alluvial water quality data against which downgradient alluvial water quality data could be compared. Completion information for monitor well HGDAL4 is presented in Attachment 7-4, Well HGDAL4 We11 Information. The locations of the four alluvial monitor wells are shown on Exhibit 12-2, Surface Water Control Plan, in Tab 12 and Figure 13-1, Monitoring Site Location Map, in Tab 13. As part of the RN-03 adequacy review, CDRMS reviewed the need for establishing groundwater points of compliance for the Hayden Gulch Loadout. In a memorandum dated June 5, 2008, the CDRMS indicated that groundwater points of compliance were unwarranted at the Hayden Gulch Loadout. The basis of the findings were: 1) the alluvial groundwater downgradient of the facilities area can be classified as "Limited Use and Quality" based on natural total dissolved solid's concentrations; and, 2) leachate originating from the facilities area lacks sufficient head to penetrate the underlying bedrock unit, the low-permeability Lewis Shale. The CDRMS' finding is presented in Attachment 7-5, Groundwater Points of Compliance Determination. RN-03 1 Revisea ub/ua