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X. Cumulative Hydrologic Impact Assessment <br />Currently several existing mining operations are located within the vicinity <br />of the proposed mining area. They include the Raton Creek Mines operated by <br />Energy Fuels Mining Company approximately 1 1/2 miles southwest of the Rimrock <br />permit area and the New Elk and Golden Eagle Mines which are currently being <br />operated by Wyoming Fuel Company along the Purgatoire River about 25 miles <br />west and upstream of the proposed operation. The potential impacts of the <br />Wyoming Fuels Mines coupled with Rimrock Mines and the Raton Creek Mines, have <br />previously been addressed in the Findings Document of the Raton Creek Mines as <br />well as those of the Golden Eagle and New Elk Mines. Due to the separation of <br />Golden Eagle and New Elk Mines from the Raton Creek and proposed Rimrock Strip <br />Mines, no significant cumulative effect is expected on the separate ground <br />water systems that exist in these areas. Since discharges and surface runoff <br />from all of these mines do reach the Purgatoire River, there is some potential <br />for cumulative impacts on the quantity and quality of the water in that <br />river. The Rimrock and Raton Creek Mines do not reduce the volume of surface <br />flow to the Purgatoire River through the tributary drainages that these mines <br />adjoin. Most likely, the discharge from the Raton Creek Mines and <br />Rimrock Mine may increase the volume of flow in Raton Creek. No significant <br />adverse cumulative impact on the quantity of water in the Purgatoire River <br />will then result from Rimrock and Raton Creek Mines. The total dissolved <br />solids (TDS) levels of water in Raton Creek are increased by the mining <br />activity at Raton Creek, but due to the volume of water in the Purgatoire <br />River, any change in TDS values in the river brought about by this increase <br />would not be detectable. The Rimrock Strip Mine is not expected to <br />appreciably raise the TDS level in the surface drainages nearby which are <br />tributaries of the Purgatoire River. This is because of the small size of the <br />operation, 38.7 acres, of which only 19.7 acres will be disturbed. As a <br />result, the impacts of the Raton Creek and Rimrock Mines are cumulatively <br />insignificant with regard to the quality of water in the Purgatoire River. <br />The headwaters of the Purgatoire River system are in excess of 9000 ft. <br />elevation and receive substantial snowfall. The mean annual precipitation at <br />the headwater for the Purgatoire River is 22.55 inches of which 7.48 inches is <br />in the form of snow. Mean annual precipitation at Trinidad where the Rimrock <br />Mine is located is 13.22 inches and only 2.19 inches is in the form of snow. <br />Peak filows in the Purgatoire occur in response to intense precipitation events <br />during the summer. However, the monitoring records demonstrate that the bulk <br />of the flow results from snowmelt during the months of April and May. The <br />average flow during these months is about 100 cfs with the average for the <br />whole year reported to be 38 cfs. During April and May, when peak flows <br />normally occur, the measurements recorded at the Engleville Gulch where the <br />Rimrock Mine is located were all below 1 cfs, Therefore the impact on the <br />Purgatoire is considered to be negligible. <br />- 14 - <br />