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els were determined by the CDOH Hazazdous Waste Division. A plume of free product petroleum hydrocarbons exists north of the permit area and could be drawn down to the permit area during pumping. For this reason, the plan incorporates two trenches dug at least 5' below ground water level located north of the mining area. These trenches will be filled with water and maintained for the life of the mining pits. The water level will initially be kept at 4452' elevation with a tolerance of 1 foot. Since the free product is located at the existing ground water surface of 4448', this should create a positive hydraulic gradient which will counteract the effect of mine pumping in the pits. The water level can be adjusted in the trenches based on the monitoring of contaminant movement in the monitoring wells. More water will likely recirculate from the trenches to the pits, increasing pumping costs, however, it is the consensus of all parties involved that the trenches greatly reduce any chance that the contaminants will migrate towazd the pits or even end up in the trenches them- selves. For this reason, we believe that the plan satisfies the performance standards of Rules 3.1.5(11), 3.1.6 and 3.1.7. The plumes and RCRA metals will not be affected by the mining opera- tion and the water contained in the trenches and mining pits will at all times meet or exceed the NPDES discharge criteria for the site. The CDPHE Hazazdous Waste Division has reviewed the revised plan proposed in this document and has provided comments agreeing with these conclu- sions, which aze included in Appendix D. As discussed earlier, a potential asbestos dump azea shows up on old refinery maps in the location shown on Map C-1. A 200 feet buffer is also shown around this azea that will have no mining or excavation activity. In the event that any type of buried waste material is encountered during the extraction process, solid or liquid, the procedures outlined in the Waste Management Contingency Plan will be in ef- fect. In addition to the notification procedures described in this plan, if any contamination is en- countered in either the pit, trenches, sediment pond or monitoring wells, the CDMG will be notified immediately by telephone describing the details of the occurrence and the plans for mitigation, if any. The Colorado Department of Health has worked for years with the landowner, Fruita Mazket- ing and Management, in analyzing the contamination on the site and developing the plan to allow gravel mining based on the levels of risk found, knowing that the gravel mining will require pump- Gilsonite Pit 9/03 22