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1 Area A consists of the visual berm which is a 3:1 overall slope but has ' terraces at approximately 15' vertical intervals and is under reclamation. This area also contains a stockpile for limestone chips. Some undisturbed are<< also contributes as part of this subbasin as does the current quarry access road. ' The entire Area A subbasin oP some 6.0 acres will be routed through the sediment basin. ~- ' Area B is a 0.8 acre area that currently contains limestone chip stockpiles The area is in a constant state of change due to dumping; and leveling. Ultimately the area will be reclaimed with a portion draining toward the access road and a portion draining back to the quarry. This area has been ' designated as an "Optional Diversion Area" on Exhibit A. The purpose is to '~ have some flexibility for modifying the contributing basin as it relates to available sediment basin storage volume created by the actual conditions J\ ' encountered during the sediment basin excavation. This variable is further discussed in the "Design Parameters" section that follows. Area C is a 1.5 acre area that currently drains onto an internal a~:cess ' road to the upper portion of the quarry. The road starts just West oP the new Scale Site on a level area. This area has,been designated on Exhibit A as an area to be graded into the quarry so it does not outfall into the sediment ' basin and overload the system. This area will be regraded as an int~arnal operation prior to construction oP the sediment basin in order to creaG~ the appropriate contributing basin area. ' A number of spot elevations were obtained within the quarry operation to demonstrate the current conditions. Spot elevations have been shown Por points indicated A-I with corresponding USGS elevations and descriptions. The ' elevations. at '.'H." and "I" show the floor of the quarry. This elevation. will ultimately be taken down another 80'-100' according to the mining plan. Only minor interior grading will be necessary to divert runoff from the Plant Site ' and subbasin Area C into the quarry area thus eliminating any possibility that sediment laden runoff will leave the site from these parts oP the qus.rry. This onslte grading activity and regrading of the outfall of the drainage ' basins leaving the site will result in a manageable flow entering the sediment basin system below the visual berm in the area of the Old Scale Site. This modified basin is the basis Por the final design oP the sediment basin sy:~tem. ' DESIGN PARAMETERS ' The sediment basin system has been designed in accordance with criteria previously established In the CAP which is consistent with accepted engineering standards and practice for such facillt[es. The system generally ' consists oP two ponds operating in series with 24" CSP outlet pipes and emergency overflow spillways. An access road has Deen designed for maintenance purposes Into each pond and guard rail acts as a safety barrier. 2 1