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mining. These areas were mitigated by avoidance. Regraded spoil from the Lennox <br />highwall reduction azea was sampled on a 300-foot grid and tested for sodium. <br />Exposed sodic strata was either buried in the final pit or covered with two to three feet <br />of suitable spoil. Several of the poor to unsuitable zones represent less than 15 percent <br />of the overburden volume. These azeas were mitigated by mixing. This includes all <br />unsuitable clay, nickel, zinc, lead, cadmium, pH and acid-base potential zones. <br />Spoil sampling is concentrated in the Wolf Creek reclamation azea. Spoil was sampled <br />on a 300-foot grid prior to soil redistribution and analyzed for pH, EC and acid-base <br />potential. A selectively handled suitable spoil top dressing or lime application was <br />made where acid strata was encountered. Sampling was focused on the high clay areas. <br />The spoil was deeply ripped or chisel plowed where clay strata exist on the spoil <br />surface. <br />Pursuant to 4.05.8(3), temporary storage of acid or toxic forming spoil may exceed 30 <br />days if the operator demonstrates that burial or treatment is not feasible within 30 days <br />due to weather conditions or other specified factors, and will not result in material risk <br />of water pollution or other environmental damage. If deemed necessary by the Division <br />based on the quantity, location, and chemical characteristics ofany temporarily stored <br />acid-forming or toxic-forming spoil, such spoil was placed on impermeable material. <br />E. Surface and Ground Water Monitoring <br />Ground Water <br />Ground water hydrology information can be found in Volumes 4, 5, and 6, Tab 7 ofthe <br />permit application, and in the Annual Hydrology Reports submitted by Seneca Coal <br />Company. <br />An extensive ground water monitoring program which was inexistence prior to 1981, <br />has identified five aquifers at or near the Seneca II Mine site: (1) Trout Creek <br />Sandstone member of the Mesaverde Group, (2) Wolf Creek Coal, (3) Wadge Coal and <br />Overburden, (4) Quaternary alluvium, and (5) replaced spoils. Ground water <br />monitoring well locations aze shown on Exhibit 7-2 in the permit application. <br />With the exception of the Quaternary alluvium and replaced spoils, it is thought that <br />each of the identified aquifers are hydraulically discontinuous with each other. This is <br />because of the relatively impermeable (confining) nature of the intervening strata. For <br />this reason, each aquifer will be discussed as a sepazate entity. <br />Trout Creek Sandstone <br />The Trout Creek Sandstone is stratigraphically 70 feet below the Wolf Creek Coal. <br />This 120 foot thick sandstone body is thought to be a significant source of ground water <br />in this region. <br />17 <br />