Laserfiche WebLink
The seepage velocity could be as high as 0.3 feet per day, depending upon the <br />sandstone permeability. Using a worst case of 0.3 feet /day, this results in a travel <br />of 1000 feet every 10 years. <br />It is strongly believed that spoil water seepage into the lowwall will not have any <br />significant impact on water quality, flow rates, well usage etc. due to four <br />reasons: <br />i) As described in this section, the water quality of the spoil water will be at a <br />maximum 6% to 10% higher in TDS than the existing overburden water <br />quality, which is relatively poor. Therefore, regardless of the seepage rates <br />into the sandstone zones, the water quality will be very similar to what has <br />been consistently tested in the overburden, with a TDS from 2800 to 3500 <br />PPM- <br />ii) Due to the low seepage rates, the movement is very slow (1000 feet every <br />10 years). <br />iii) The sandstones above the Dakota coals have historically been too poor in <br />quality and too low in flow rates to provide useful wells. For this reason, no <br />known wells in the vicinity of the mine area have been completed in the <br />Dakota sandstone. It is very unlikely that any new wells will be completed <br />in the Dakota sandstone in the vicinity since the Burro Canyon Formation <br />provides significantly better water quality and flow and is located only 50 to <br />100 feet deeper than the Dakota sands. <br />iv) The local wells are completed in the Burro Canyon Formation, which is <br />below the Dakota coals. Although this zone has significantly better quality <br />water, these sandstones are separated from the spoil by shale layers with <br />very low permeabilities, therefore these aquifers cannot be affected by the <br />spoil water. <br />4. Impact of spoil water quality on surface water quality. <br />Spoil Water Quality <br />The chemistry of the water interacting with the spoil is described in the previous <br />section. In order to determine the impact of the spoil water quality on the surface <br />water, it is first necessary to predict the expected quality of the spoil leachate for <br />the New Horizon #1 and #2 mines. The principal impact from a quality <br />perspective is that irrigation water will seep rapidly through the spoil, increase in <br />TDS and then discharge through a spoil spring at each mine area. Since the pre - <br />mine site did not have spoil springs, there is a potential impact to the quality of <br />the receiving waters. The spoil spring at the New Horizon 91 Mine enters Tuttle <br />Draw while the predicted spring for the New Horizon #2 Mine will enter a <br />39 <br />