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REFUSE PILE EXPANSION placed to a final elevation of 6400 feet above mean sea level (MSL). All sediment control and clear water ditches will be competed. All slopes wil4 be • covered with an average of approximately 18 to 24 inches of topsoil and subsoil and subsequently revegetated. The quantity of cu[, fill and disturbed area for this phase is shown in Table 1.0. 2.2 Storage Capacity Storage capacity for each construction phase is shown in Table 1.0. The expected refuse production for the next ten years is presented in Table 2.0. Based upon these production rates and assuming a wet density of 68 pcf, the life of the pile is predicted in Table 3.0. 2.3 Materials Balance The material balance of the RPE, presented in Table 1.0, is essential to minimize the volume of topsoil and subsoil stockpiled during each phase. The sedimentation pond and initial runoff control berms and ditches was completed prior to beginning Phase ~_ } 1. Construction operations during Phase 1 and 2 consist essentially of: 1) stripping topsoil and subsoil; Z) lining the RPE base with HDPE; 3) continual development of ditches, rock drain, and clear water diversion berms; and 4) initial placement of refuse. Approximately one foot of topsoil and a minimum of one foot of subsoil (to be stripped and stockpiled beginning in Phase 3) will be stripped and stockpiled in areas described in Sections 3.0 and 4.0 of this exhibit. Refuse placed during Phase ] consisted mostly of waste material generated during construction of Shafts 1, 2 and 3. While refuse is placed, concurrent reclamation of completed areas will be performed at applicable times. The maximum amount of topsoil and subsoil needed to be stockpiled at any given time is provided in Table 1.0. Also provided are the areas to be reclaimed at the end of each phase and topsoil and subsoil cover requirements. 2.4 Highway Right-of-Way Mountain Coal Company has received approval from the State of Colorado Department of Highways .:` to locate operations within 100 feet of [he outside right-of--way line of State Highway 133. The letter of request and approval is presented in Appendix C. 3.0 TOPSOIL STORAGE The topsoil stripped from the RPE will be placed on the north side of Highway 133 as shown on Map 53 in the area known as t:te North Soil Storage Area (NSSA). Stormwater runoff from the area is treated by a sediment pond, referred to as the NSSA pond. Clear water diversion berms were placed on the south, east and west sides. The pile is at its maximum storage capacity. Prior to stripping additional topsoil, MCC will designate a new topsoil stockpile. 4.0 SUBSOIL STORAGE Subsoil generated during Phase 3 and 4 of the RPE construction will be stockpiled at a location to be determined prior to beginning Phase 3. 5.0 GEOTECHNICAL STUDIES 5.1 Field Investigations A field investigation was conducted on the proposed RPE site during October, 1995. The field investigation consisted of drilling six soil borings and installing two piezometers in the proposed foundation foot print of the RPE. An additional soil boring was performed in April, 1996. The drilling logs of the seven soil borings are found in Appendix E of this report. The locations of the borings are shown in Figure E-1. The six soil borings were drilled with an Acker MPS drilling rig operated by L.A. Smith Drilling, under the direct supervision of HLA. The soil borings were advanced using an 8-inch hollow stem auger (advancement in soft soils), and a 3-inch hardrock core barrel (advancement in gravel layers or bedrock). Standard Penetration Tests for soft soils were taken at 5-foot boring intervals using the appropriate ASTM procedures. All soil and rock samples retrieved from the drilling were bagged and shipped to a soil testing laboratory. Several Shelby tubes were pushed into [he underlying stratum soils Harding Lawson Associates 3