Potential effects of anticipated coal mining on salinity of the Price, San Rafael, and Green Rivers, Utah

Abstract

The impact of anticipated coal mining in Utah on the salinity of the Price, San Rafael, and Green Rivers is to be addressed in the repermitting of existing mines and permitting of new mines. To determine the potential impacts, mathematical models were developed for the Price and San Rafael River basins. It was assumed that the maximum quantity of ground water discharged from each mine would occur simultaneously for all mines; thus, a worst-case condition is presented. Little impact on the quantity and quality of streamflow is expected for the Price and San Rafael Rivers. The increase in mean monthly flow of the Price River downstream from Scofield Reservoir is projected as 3.5 cubic feet per second, ranging from 1.7 percent in June to 140 percent in February. The potential increase in dissolved-sol ids concentration downstream from Scofield Reservoir would range from 10.4 percent in June and July (from 202 to 223 milligrams per liter) to 97.0 percent in February (from 202 to 398 milligrams per liter). However, the concentration of the mixture of mine water with the existing flow released from Scofield Reservoir would contain less than 500 milligrams per liter of dissolved solids. At the mouth of the Price River, the potential increase in mean monthly flow is projected as 12.6 cubic feet per second, ranging from 3.7 percent in May to 37.7 percent in January. The potential changes in dissolved-sol ids concentration would range from a 20.7 percent decrease in January (from 3,677 to 2,917 milligrams per liter) to a 1.3 percent increase in June (from 1,911 to 1,935 milligrams per liter). At the mouth of the San Rafael River, the potential increase in mean monthly flow ranges from 2.9 cubic feet per second in February to 6.7 cubic feet per second in May, with the increase ranging from 0.8 percent in June to 12.6 percent in November. The potential changes in dissolved-sol ids concentration would range from a 53 percent decrease in March (from 2,318 to 2,195 milligrams per liter) to a 0.6 percent increase in May (from 1,649 to 1,659 milligrams per liter). The anticipated mining in the Price and San Rafael River basins is not expected to cause a detectable change in the quantity and quality of streamflow in the Green River. Ihe combined average flow of the Price and San Rafael Rivers is about 4 percent of the average flow in the Green River. Ihe projected peak increase in flow resulting from discharge from the mines is less than 0.3 percent of the average flow in the Green River. The combined dissolved-sol ids load from the anticipated mining in the Price and San Rafael River basins represents less than 0.8 percent of the average annual dissolvedsolids load of the Green River. Thus, it would be difficult to detect any change in dissolved-sol ids concentrations of the Green River.