Laserfiche WebLink
• and Flow that are calculated over time periods (usually greater than 7 years) that vary. The reader is referred to <br />the above document for the exact time periods over which the data for the monitoring stations are averaged. <br />Data for Monitoring Station 29 was taken from the 1993 Annual Hydrology Report for Mitre 3 (C-84-062). <br />Water quality data used to approximate the quality of mine discharge is based on the assumption that water <br />flowing out of the mine will be of similar quality as the water that flows into the mine from tite sutroundins <br />ground water. Ground water inflow to the proposed mine will originate mainly from the Wadge Coal <br />overburden composed of shales, siltstones, and sandstones. Water quality data was taken from hvo wells <br />(93M001 and 93M003) completed in these strata. Analyses for each well, both sampled on 4/21/94 and 5/26/94. <br />were averaged to approximate the quality of inflowing ground water to panels 2 Right - 9 Right. <br />Hydro-Geo recently completed estimates of the rate of ground water inflow into panels 2 Rigltt - 9 Risltt. Tltis <br />analysis is included in sections 2.04 and 2.05 of Twentymile Coal Company's Permit Revision Application <br />Number 3. The data from [Iris inflow analysis was used to estimate the quantity of mine discharge that will be <br />added to Foidel Creek while the 8 panels are being mine. <br />Tltis data is summarized in Table I. <br />Discussion <br />The method for estimating ttte impact of future mine discharge on downstream water quality is to add the <br />quantity and quality of mine water discharge to the quantity and quality of unimpacted water in an adjacent <br />stream. Using the weighted meat[ technique concentrations of water quality parameters are then estimated at the <br />• point of confluence of the two streams. Tire water quality at the first estimated point is then added to another <br />point farther downstream [o estimate [he impact a[ the second point, and so on. <br />With reference [o Tables 2, 3, 4, and 5, this procedure has been implemented where mine discharge (Site 109) <br />[nixes with water in Foidel Creek at Station 8 (Table 2). These estimated concentrations were then added to data <br />for Middle Creek at Station 29 to estimate concentrations at that point (Table 3). Next, the estimated <br />concentrations at Station 29 were added to data for Trout Creek at Station 301 to estimate water quality at the <br />confluence of Middle Creek and Trout Creek (Table 4). Finally, the estimated concentrations at the Middle <br />Creek-Trout Creek confluence were added [op data for Fish Creek at Station 1003 to obtain the estimated <br />concentrations at [he Fish Creek-Trout Creek confluence (Table 5). <br />Table 1 shows that ground water that will flow into the proposed mine is low in Ca and Mg but relatively high itt <br />Na when compared with water in Foidel Creek at Station 8. The high concentration of Na in the expected mine <br />discharge gives a Itiglt SAR (31.08) compared to Station 8 (1.25). TDS concentrations are similar in the two <br />waters, and sulfate is Itiglter in Foidel Creek than in the estimated mine discharge. When these two waters are <br />averaged (Table 2) using the weighted mean method, concentrations of Ca and Mg go down. With respect to <br />Station 8, the Na concentration goes up (97.03 mg/I to 518.55 mg/I), which drives up the SAR to 12.52. The <br />sulfate concentration is reduced from 1,089.55 mg/I at Station at to 794.5 mg/I, while TDS is only slightly <br />increased from 1,822? mg/I to 1,902.9 mg/I. <br />Table 3 combines the estimated water quality from mine discharge water and Foidel Creek waters with water <br />from Middle Creek at Station 29. This estimate shows that Ca and Mg concentrations are now approximately <br />equal to those at Station 29, while Na concentrations remain approximately twice as high (107.08 mg/I versus <br />• 55.92 mg/I) but significantly reduced from the concentration at Station 109 on Foidel Creek near the mine <br />discharge. The SAR is much reduced to 1.87. Sulfate and TDS concentrations are now almost equal (538.89 <br />tng/1 versus 507.1 tng/I sulfate and 1,140.61 mg/I versus 1,045.83 mg/I TDS). <br />PR 93-03 EX. 7h-2 3/12/96 <br />