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• Mr. Jeff Gregg October 23, 2000 Page 2 C~ Inc •{ -:3°~ . -' S ^ ~ ~v~ S ~- most likely overlying sandstone and claystone bedrock of the Upper Transition Member of the Pierre Shale. Exploratory borings drilled along the south property line of the site (RMC, 1999) encountered approximately five to eight feet of overburden topsoil and clay soils overlying approximately 10.5 to 15 feet of sand and gravel on top of sandstone and claystone bedrock. The bedrock depths ranged from approximately 16.5 to 20 feet below the ground surface. These bedrock depths are consistent with our experience drilling at mines south and west of the site. Based on our experience, the depth to bedrock at the proposed mine should remain fairly consistent in the 15 to 20-foot range, though local deeper areas may be encountered. ~ ~~~ ~~,! ~Q 'v ,~ From a geotechnical standpoint, the sand and gravel will form most of the mine slopes. These soils are generally strong and stable, particularly when dewatered. STRUCTURES WITHIN 200 FEET OF DISTURBED AREAS The mine plan provides a buffer of at least 200 feet between the mined area and most area structures. The outer edge of the "mined disturbed area" allows room for the stockpiling of the site overburden outside of the mine excavation. The actual perimeter of the mine excavation is approximately 50 feet to the interior of the "limit of disturbed area." The mine plan shows setbacks between the mine excavation perimeter and various property lines and above-ground and buried structures near the mine. These setbacks are 143 feet from the west property line, 70 feet from the proposed right-of-way reservation of Highway 392 on the north part of the site, 50 feet from the buried Sinclair gas pipeline passing between the two mine pods, and 55 feet from the east property line. The "limit of disturbed area" on the south part of the site is on the south property line. The property south of the site is the La Poudre gravel mine also owned by Hall-Irwin. All known man-made structures within 200 feet of the "disturbed area" are listed below: State Highway 392 approximately 75 feet to the north of the disturbed area or 125 feet north of the mine excavation; Buried gas, water and phone utilities on the south side of Highway 392 approximately 35 feet to the north of the disturbed area or 85 feet north of the mine excavation; The buried Sinclair gas pipeline between the mine pods 50 feet from the mine excavation; A concrete building located approximately 35 feet north of the disturbed area or 85 feet from the excavation of the west mine pod; Overhead utility lines approximately 80 feet west of the disturbed area or 143 feet west of the excavation of the west mine pod; Overhead utility lines along Highway 392 approximately 40 feet north of the disturbed area or 90 feet north of the excavation;