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Exhibit Page 15 interior to these basins, which no discharge. Where discharge is necessary, it will be controlled and treated as required by water quality regulationst and permits to ensure that no sediment from the pit is discharged into the Dolores River or Lost Canyon Creek. The Dolores is a Cold- water fishery; but discharge to the river would be through intermittent drainages of '/< mile or longer so discharge temperature regulation is unlikely to be required. As necessary, stockpiles may have perimeter ditches/swales and berms with silt fence, straw bales, or rock check dams, to reduce/prevent sediment in any runoff from the site, but will not have such features for internal drainage. ASSUMPTIONS USED IN MINING PLAN: The mining plan is based on several key assumptions, stated herein for evaluation. These assumptions are not intended to imply or claim that certain actions will be done. 1. Annual demand for sand and gravel from this pit will be approximately 300,000 tons, including approximately 100,000 tons by MCHD ("red" base material) and 200,000 tons by 4SA ("white" materials). Demand, and therefore production, may vary significantly from year to year, and therefore acreages affected during a given year may be either larger or smaller than included in this plan, thus impacting on stockpile size and other matters. 2. Based on this annual tonnage, and assuming an average gravel deposit thickness of 10 feet, the life of this pit is approximately 10 years, with mining of 20-25 acres each year. 3. Activities on the site (stripping, mining, stockpiling, etc.) will be done primarily during the later summer/early fall period, from mid-August to mid-November. 4. The grave! being mined may be covered by up to fifteen to twenty feet of overburden (primarily clay and 3" to 12" of topsoil). For planning and estimating purposes, the upper 6 inches ('h foot) is considered usable topsoil. 5. Generally a layer of unusable material (clay and silt) of 1 to 1-1/2 feet is found between the gravel being mined and the shale bedrock. 6. Overburden ranges from zero to twenty feet in depth and is assumed to average five feet. 7. The water table is not exposed by mining. 8. While all potential areas are shown as being mined, some areas may NOT be mined due to excessive overburden or poor quality of materials. This will be evaluated as mining proceeds. Bypassed areas will be protected from damage by mining, including erosion and sedimentation. ~ This is described in the surface water management plan, which provides detailed information.