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depth aoound the staging azea which will drain towazd the pit excavation and 3) a sediment pond of <br />approximately 1.0 acres in size immediately east of Phase 1 to temporazily detain the water from pit <br />pumping prior to discharge. <br />Since the surrounding azea is so flat and there is no chance that runoff from the site could cause any <br />damage to the surrounding industrial azeas, the only sediment control measure to be employed is a <br />1' deep trench around the staging azea which will grade to the trench excavation. Sideslopes of this <br />ditch will be 2.OH:1.OV. Gravel extraction will begin in the winter of 2003. FMM has the combined <br />process water/storm water dischazge permit for this operation and they aze responsible for compli- <br />ance under the permit. This permit is included in Appendix D. <br />The site will contain the dischazge fora 100 yeaz event in the permit area so long as pumping from <br />the sediment pond does not occur. The site is located entirely outside the 100 yeaz floodplain of the <br />Colorado River, as shown on Map C-1, except for the western 6.2 acres of the permit that will not <br />be disturbed. All active azeas cannot be inundated for the 100 yeaz event. If water inundates part of <br />the pit for a lazger storm, all mobile equipment will be moved to higher ground and the pit will be <br />allowed to fill. In this case, the pit will serve to lower peak flows downstream and possibly lessen <br />damage by storing some water in the excavated azea. It is not likely that the pit lake will be cap- <br />tured by the river since it is over 600 feet away and the river does not have a main channel outside <br />bend neaz the permit azea. Also, the floodplain at this area is very wide and shallow and does not <br />contain highly erosive velocities. <br />8. CONTAMINATION ISSUES WITH THE GILSONITE REFINERY LANDS <br />From considerable testing performed by the landowner and the Colorado Department of Health, <br />Hazardous Waste Division, a number of contaminants aze present on the FMM property. Soil tests <br />have shown that petroleum hydrocarbons, BTEX, benzene, and arsenic aze present in the soil above <br />desirable levels in a few instances within the gravel permit azea. Other metals and petroleum com- <br />pounds aze present but aze not above levels of SRO (Soil Remediation Objectives). These SRO lev- <br />Gilsonite Pit 9/03 21 <br />