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~' Z-~ Sy the southeast. This slope averages l.Ole, dropping only 1 foot in about I00 feet horizontally. Runoff is so slow it essentially does not occur as the rate of percolation into the soil greatly exceeds the runoff flow rate. This is both good and bad. It is good in that sediment control is very easy to accomplish because, in essence, no sediment leaves the site. It is also good in that the percolation allows for accelerated illuviation and • therefore more rapid soil development in a replaced topsoil material. The bad aspect is that standing water and its resulting mud can cause operational problems where the ground material contains soil and is not of a more porous gravel that allows for rapid drying. Also, the percolation through the soil can eventually create hard pans, caliche layers, and other soil features that are not especially desirable. Water cannot flow out of the pits but collects in the bottom of the pits. Because the pit floor is generally level and composed of sand and gravel several feet above the water table drying usually o-curs rather rapidly. Therefore, no diversion or impoundment of water is needed to handle the water. Also, no • discharges occur. LAND STRUCTURE: As indicated in the soild exhibit, the gravel is overlain by a soil and overburden layer that averages about 5 feet deep and varies from 3 to 8 feet. Under the soil is a layer of sand and gravel that varies from very coarse to fine depending on depth and location. Apparently, the gravels were deposited in many different erosion episodes that varied in intensity from gentle to intense. The gravels were deposited on top of a eroded shale layer. She contact between gravel and shale is variable in depth and reflects the original surface. During mining, excavations are kept about 6 feet above the gravel/shale contact thereby avoiding the problems of exposing heavy, clayey materials as well as the water table that generally lies along this contact zone. Because the shale layer tends to vary somewhat the excavation by necessity can, on occassion, contact the shale. It has been found that staying an average of • six feet above the shale allows for nearly all variations in the configuration of the shale and any shale exposures are small and easily managed. TIMETABLE: At a mining rate of four acres per year in each pit (a total of eight acres per year), it will take approximately 95 years to mine the rest of the area. This is based on a total of 280 acres left to be mined. This rate is based upon past experience which has proven to be reasonably accurate. Demand may well increase in the future in which case more acreage could be mined per year. If that were to occur, then a technical revision to the permit would be requested to appropriately adjust the timetable. DISTURBANCE AREAS: Because a floating bond is requested, a delineation of • the major, moderate, and minor disturbance areas is necessary. The following acreages apply to both pits, that is, it describes the total acreage in each category allowed under the permit and bond. These acreages are distributed between both pits. A precise breakdown related to costs is presented in Exhibit L. -2- ~[ 4 ~