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<br />• However, coal mining in northwest Colorado and Utah has exposed <br />many significant fossils in the past. If the fossils were <br />destroyed, it would be an adverse. irretrievable and <br />irreversible impact. This impact can be outweighed by the <br />beneficial impact of discovering fossils that would not have <br />been found without mining. <br />A surface paleontological survey will not be required on the two <br />subject parcels due to the limited surface disturbance and the <br />fact that the surface is privately owned. However, the <br />following stipulation would ensure that scientifically <br />significant fossils within the coal beds are available for <br />study. <br />The operator shall immediately cease all operations upon <br />discovery of fossils of scientific value and will immediately <br />notify the authorized officer. The BLM shall evaluate and/or <br />cause to be removed such discoveries within 48 hours. the BLM <br />may negotiate additional time if mutually agreeable to the <br />operator and BLM. <br />The cost of any required paleontologic surveys and recovery of <br />any fossils of scientific value discovered during operations, <br />shall be borne by the operator. <br />. Hydrology <br />Groundwater <br />Typical impacts to water quality include increased levels of TDS <br />and changes to the ion balance and pH as aresult of underground <br />mining because of several factors. <br />-leaching of exposed waste piles of roof and floor rock. <br />-leaching of fill material in final portal closure, <br />-leaching of caved material in the mine, <br />-interconnection of aquifers caused by subsidence. <br />Although subsidence does not generally affect the rocks below <br />the mine, mine floors do tend to heave slightly, and could <br />improve the naturally existing fracture system that currently <br />allows communication between the Trout Creek Sandstone and the <br />Wadge overburden aquifers. Therefore, there may be impacts to <br />the quantity and quality of the water in the Trout Creek <br />Sandstone aquifer locally from communication with the Wadge <br />overburden aquifer. However, increased flows from the Trout <br />Creek Sandstone aquifer to the Wadge overburden aquifer may <br />occur as a result of fracturing and pressure changes from the <br />mining and the higher hydraulic head in the Trout Creek. This <br />would increase water flows into the mine but is not likely to <br />. impair either aquifer. Subsidence would fracture the rocks of <br />the Wadge overburden aquifer, inducing secondary permeability. <br />This would increase the rate at which groundwater flows through <br />the abandoned mine area and increase the amount of rock surface <br />exposed to water, resulting in increased dissolution of salts.