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Powderhorn Coal Company initiated three test plots on the Roadside Refuse Disposal <br />' Area at the Roadside Mine outside Cameo, Colorado in 1983. The purpose of these <br />test plots was to evaluate whether revegetation success could be attained through the <br />use of less than the required four feet of non-toxic, non-combustible material placed <br />' over the conswcted coal refuse disposal area (Colorado Rule 4.10.4(5)). This <br />requirement may be modified based on "physical and chemical analyses which show <br />' that the requirements of 4.15 will be met" (Colorado Rule 4.10.4(5)). The Colorado <br />Division of Minerals and Geology (then Mined Land Reclamation) determined the best <br />way to evaluate revegetation potential at Powderhorn Coal Company was to establish <br />revegetation test plots on the completed Roadside Refuse Disposal Area (RDA). <br />Initial design of the field trials and test plots on the Roadside Refuse Disposal Area was <br />' submitted to the Colorado Division of Minerals and Geology (CDMG) on December <br />30, 1982 in response to Stipulation 11 of Coal Permit C-81-041. The initial submittal <br />was titled Plan for the Field Trials and Tempor~- ry Revegetation of the Roadside Refuse <br />Pile, prepared by Powderhorn Coal staff and Western Resource Development <br />Corporation (PCC, 1982). The Division responded to the proposed plan on January <br />17, 1983 (CMLRD, 1983) with comments and suggestions for modification of the test <br />' plot design. Powderhorn Coal responded to Division comments on August 9, 1983, <br />modifying test plot design and incorporating changes based on Division and <br />' Powderhorn Coal staff discussions. The plan as amended was acceptable to CDMG <br />and was implemented. <br />Powderhorn Coal submitted Technical Revision 15 in March 1993 to the Colorado <br />Division of Minerals and Geology, which contained a plan for the 1993 study and <br />evaluation of the Roadside RDA Vegetation Test Plots. Division staff reviewed the <br />' plan and returned comments to Powderhorn Coal on May 3, 1993. Powderhorn Coal <br />responded to the comments on the 1993 study plan and the Technical Revision <br />(including the 1993 RDA Test Plot study plan) was approved May 20, 1993. <br />The test plots were designed and constructed to approximate the variety of aspects and <br />micro~nvironmental conditions present on the refuse disposal azea and the adjoining <br />Shadscale Shrubland Reference Area (by which Test Plot revegetation success would be <br />judged). Three depths of native soil material (obtained from a nearby borrow area) <br />were selected to test the efficacy of revegetation with less than four feet of material. <br />The depths selected were six inches (6"), twelve inches (12"), twenty four inches <br />(24"), and forty eight inches (48"). Only one Test Plot incorporated the 48" "control" <br />depth. <br />Test plots were drill seeded and covered with straw mulch and an excelsior net in <br />August and September 1983. The seed mix employed contained a mix of perennial <br />grasses, forts, and shrubs (Table 1) judged to be reasonable candidates for successful <br />revegetation in the area. Seeding was done up and down the slope for safety <br />considerations (slopes average >20 degrees). <br />2 <br />