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Furthermore, the stratigraphic location of the elevated nitrate-nitrogen samples are not correlative. Due to the vertical and horizontal distances between locations containing elevated nitrate-nitrogen levels, percolating ground water will not be adversely effected. The dilution al effects of a predicted spoils aquifer should buffer the concentration of nitrate as nitrogen by the time the aquifer discharges to the surface system. Furthermore, the applicant states in the permit application and the Division agrees that the mixing of overburden will mitigate the toxic effects of these materials. D.J. Dollhopf in "Selective Placement of Strip Mine Overburden in Montana" (Chapter 5, Summary Report, 1981) suggests that if the volume of toxic material is less then i5% of the total volume of material to be replaced, dilution of the toxic material can be successful. The applicant states (Volume 2, Tab 6, Pages 6-24 and 6-33) that due to mitigative (avoidance, chemical amendments and dilutional mixing), and topsoiling measures, "...the spoil should be a favorable plant growth medium." The applicant is in compliance with the requirements of this section. V. Ground Water Hydrology -Rules 2.04.5, 2.04.7, 2.05.6(3) and 4.05 Ground water hydrology information can be found in Volumes III and IV, Tab 7, and in Exhibits 7-1 through 7-7. .Appendices 7-1, 7-2, 7-3, and 7-7 also contain ground water information. Ground water studies in conjunction with the Seneca II-W Mine site have been concentrated in the Upper Mesaverde Group and alluvial aquifers. Specifically, aquifer characteristics and/or water quality analyses have been performed in the Wolf Creek coal, Wolf Creek/Wadge Interburden, Wadge coal, Wadge coal overburden, and the Hubberson Gulch alluvium. Quantity and quality data have also been collected from ten springs and seeps in and adjacent to the permit area. The Seneca II-W Mine permit area lies on the western flank of the Sage Creek Anticline, a local structure located within the more regional Sand Wash Basin. The Sage Creek Anticline is thought to control local ground water. flow, as artesian head increases with distance from the anticlinal axis. The Mancos Shale, underlying the Mesaverde Group, is a relatively impermeable unit which essentially separates the Mesaverde from any underlying, regional aquifers. Important water bearing strata identified along the Sage Creek Anticline within the Mesaverde include the Wolf Creek coal, Wadge coal, and the Wadge coal overburden. Recharge to these and other aquifers in the area is a function of infiltration of snow melt and rainfall at outcrops along the anticline. Water table conditions prevail near the aquifer outcrops, while confined conditions exist further downdip. Each of the identified aquifer zones are hydraulically discontinuous with the units above and below. Therefore, each aquifer will be discussed as a separate entity. - 12 -