2019-09-30_REVISION - M1988108 - Laserfiche WebLink

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ARCOSA Additional tests were conducted on-site to confirm that site specific conditions are the same as in Douglas County. These tests, summarized in Table D-2, show the Pierre Shale Formation at the quarry site to be as impervious as it is in Douglas County. In addition, permeability tests were conducted for compacted shale fines and locally available clay materials to confirm their utility as impervious capping materials. Results of these tests also are presented in Table D-2. Mine Operations Mining occurs within the Quarry Area identified in Exhibit C. Mining progresses incrementally to the south. There are not distinguished phases or sections of mining set. Each southward increment involves stripping overburden to expose additional reserves and placing this overburden on slope and the bottom of the mined-out portion of the quarry. The newly exposed section is mined to the ultimate quarry depth prior to stripping the next increment. The ultimate depth of the quarry floor elevation is 5,860 feet above mean sea level. An existing overburden stock-pile located to the south of the quarry area will be reserved for use in reclaiming the portion of the quarry last mined. Additional reclamation details are discussed in Exhibit E. Shale is mined from the Pierre Shale formation using an excavator to rip the material from the quarry floor and load it directly into off-highway haul trucks of 35- to 50-ton capacity. The trucks haul the shale to a primary crusher (feeder-breaker) located at ground-level above the quarry along a haul road on the western side of State Highway 93 (HWY 93). The rate of excavation is, and will be, approximately 1,200 to 1,400 tons of shale per day. The quarry operates seven days per week, 24 hours per day. The mining and processing schedule may be modified depending on operational demand and the safety of operating conditions; however, no formal stages or phases of mining are planned. Crushing and Conveying The mined shale is crushed by the primary crusher to a nominal minus 5-inch size. The primary crusher mechanically feeds crushed shale to a conveyor that traverses beneath HWY 93 from west to east. Crushed shale is transported by conveyor beneath HWY 93 to the processing plant for further size reduction and storage. Processing Operations Crushed material is fed from the conveyor into a rotary kiln on the east side of HWY 93. The rotary kiln heats the crushed material to 2,000' F to produce lightweight aggregate. The finished product is stored in stockpiles prior to being loaded onto rail cars for shipment. The lightweight aggregate plant will produce at least 200,000 cubic yards of aggregate annually for up to 30 years, depending on market and operational conditions. Products (i.e., primary and secondary commodities) produced at the processing plant include lightweight aggregate. No explosives are used during the mining process.