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IX. Probable Hydrologic Consequences and Cumulative Impact Assessment - The applicant has provided a statement of probable hydrologic consequences for the operation in Section 2.05.6(3) of the permit application. There are three different ways the operation could affect the hydrologic system: 1) impacts to surface water quality and quantity resulting from surface disturbance and mine water discharge; 2) impacts on groundwater quantity through mine water inflows; and 3) impacts on groundwater quality through infiltration of surface water through exposed unweathered material. In all three cases the Division, after considering the size of the operation, has determined that the probable hydrologic consequences will be minimal. Probable impacts on surface water quality and quantity were previously discussed in Section V of this findings Document. The operation will disturb 19.7 acres of the total permit area of 38.7 acres. The total surface area disturbed by the operation accounts for about 1.4% of the drainage area of Engleville Gulch. A diversion ditch will be placed around the disturbed area to divert undisturbed flow. Total suspended solids concentrations will be controlled through the use of a sedimentation pond within the permit area. The pond will collect runoff and sediment from the disturbed area. This will minimize the impacts of mining on surface water quality, Surface water will also be monitored for changes in water quality and quantity during the operation, The potential for adverse effects on surface water through discharge of impacted water from the Rimrock Mine is therefore negligible. Any potential for adverse effects to ground water resources due to communication of aquifers with the mine workings would also be minimal due to the fact that the water bearing strata (Trinidad Sandstone) is well below the area that will be impacted by the workings. Ground water which could potentially be impacted by the operation will be monitored for changes in water quality and quantity. Phase II mining is expected to impact the quantity of ground water in the Engleville Seam, as the mine water discharge point from the old underground workings will be mined through. This discharge flows 1 to 2 gpn, which is diverted off the permit area into a stock tank. Its water quality is poor, with Total Dissolved Solids concentrations of over 2000 milligrams/liter. No water right has been filed on this water source, and its use is therefore not protected. These old workings are expected to be the principal source of pit inflows, estimated in the permit application to be approximately 1.8 gpm. The water quality of the Engleville mine discharge (underground monitoring well at the Engleville seam) may be representative of the quality of any spoil water sources that will develop. Such sources are predicted to be minor or nonexistent due to the small size of the pit, the low rainfall and high evaporation potential, and the lack of other existing springs and seeps in the pit area. _ 1P _