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During the life of the mine, groundwater is not expected to be exposed and the applicant plans <br />on leaving at least 10 feet of overburden above the water table undisturbed. This coupled with the <br />operations use of only mechanical means of separating the materials, i.e. no chemicals, there is very <br />little chance of groundwater quality being affected by the mining process itself. A question concerning <br />the possible release of naturally occurring chemicals being released during mining was been brought <br />forward in scoping. This concern is minor in this case because the material being mined is not hard <br />rock, or first ever exposed crystalline rock, but rather alluvium. Alluvium has been exposed and <br />weathered over many years as the sediments get deposited by flowing rivers. Acidic mine waste <br />concerns, or other substantial potential changes to naturally occurring compounds within the rock <br />chemistry signature from exposure due to mining operations is likely not measurable. Water soaking <br />into the pit and emerging in a spring or well elsewhere will not be substantially altered chemically to <br />any measurable degree. Sub - surface geo- chemistry interaction upon storm- waters entering the ground <br />water should be similar to that soaking in on native surface soils. The single largest threat to <br />groundwater quality from the proposal is the potential of spills resulting from the everyday use of <br />petroleum products in site operations. The project operations plan and associated permits contain spill <br />containment requirements and mitigation that should protect groundwater from potential releases. <br />Overall, the Proposed Action would have very little measurable impact to either surface or <br />groundwater if permit stipulations are enforced. <br />Cumulative Impacts: The Middle Fork of the South Platte watershed above Highway 285 is <br />moderately developed with two towns, several rural subdivisions and a major highway. There are <br />many factors effecting water quality in the watershed starting with historic mining and highway gravel <br />in the headwaters to subdivisions in the lower elevations; however due to its high flow volumes in a <br />headwaters area, water quality is good. The addition of the Proposed Action to these other factors <br />would have an immeasurable effect on the watershed in the future. <br />Mitigation/Residual Effects: Topsoil (A horizon) and the B soil horizon, or 18 inches depth, <br />whichever is greater, needs to be kept separate from lower soil layers so that there are separate <br />stockpiles of each. Upon reclamation, these layers would then be placed on top so that the soil layers <br />remain in order. The State Division of Reclamation, Mining, and Safety 110(2) permit would further <br />outline reclamation and the BLM should be included in the development of that plan. Residual effects <br />to water quality from the Proposed Action after reclamation completion would be immeasurable from <br />the current conditions as vegetation returns to the site. <br />No Action Alternative <br />Direct and Indirect Impacts: If no action is taken, the proposal would not be discretionary <br />under the 1872 mining law. The applicant would still be able to proceed with mining on the parcel; <br />however the sale of sand and gravel would not be permitted. Overall, this would have the same effects <br />on water quality as the Proposed Action, but there would probably be a hill left after reclamation rather <br />than a pit. <br />Cumulative Impacts: Cumulative impacts under the No Action Alternative would be similar to <br />the Proposed Action. <br />Mitigation/Residual Effects: Mitigation and Residual Effects would be similar to the Proposed <br />Action. <br />Alternative 1 <br />26 <br />