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EXIIIBTT D MINING PLAN A. Overview Deposits of sand and gravel, the unconsolidated granulaz materials resulting from the natural disintegration of rock or stone, aze generally found in neaz-surface alluvial deposits in and along drainage ways. Sand and gravel aze products of the weathering of rocks and unconsolidated or poorly consolidated materials. Such deposits are common throughout the western United States. Sand and gravel typically are mined by open pit excavation. Open pit excavation is carried out with power excavators, draglines, front end loaders, and belt conveyors. After mining, the materials are transported to the processing plant by conveyor. Although small amounts of sand and gravel aze used for fill without processing, most domestic sand and gravel are processed prior to use. The processing of sand and gravel for a specific mazket involves the use of different combinations of washers, screens, and classifiers to segregate particle sizes; crushers to reduce oversized material; and storage and loading facilities. A process flow diagram for construction sand and gravel processing is presented on the following page. The following pazagraphs describe the process in more detail. After being transported to the processing plant, the sand and gravel aze stockpiled. Next, the material is transported to fixed or vibrating screens by belt conveyors. The screens separate the oversize material from the smaller, mazketable sizes. The oversize material may be directed to a crusher for size reduction, to produce angular shaped aggregate, or to produce the finer sizes of sands. Crushing generally is carried out in one or two stages, although three-stage crushing may also be performed. Following crushing, the material is retttrned to the screening operation for sizing. The material that passes through the screen is fed into a battery of sizing screens, which generally consist of horizontal or sloped, single or multideck vibrating screens. Screening sepazates the sand and gravel into different size ranges. After screening, the sized gravel is conveyed to stockpiles prior to being transported off-site. The sand is freed from clay and organic impurities by scrubbers. After scrubbing, the sand is sized typically by water classification, although both wet and dry screen- ing are used to size the sand. After classification, the sand is dewatered using repara- tory cones or hydroseparators, followed by fine screening for grading. After process- ing, the sand also is transported to stockpiles by belt conveyors or screw conveyors. Western Mobile Lyons - Rockin' WP D-1