2020-02-19_PERMIT FILE - C1981008A

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TABLE 2.05.6(3)-4 Flow Rates vs. TDS for Spoil Waters and Receiving Streams The values for the NPDES 001 Discharge and SW -N3 are averaged from measurements made from 1993 to present. Table 2.05.6(3)-3 shows this information for these as well as other sample points. As is seen from the table, the spoil water inflows from both mine areas influence the quality of Tuttle Draw to a minor degree. However, within 4500 feet, this flow enters the San Miguel River where the flow is so much larger than the Tuttle Draw flow that the impact is negligible. During periods of irrigation, Tuttle Draw is flowing at a higher rate while the River is running low, which is the time of maximum impact of the flows. At this time, the increase in TDS of the River is from 620 to 652 ppm, or an increase of 5.1 %. It should be noted that Tuttle Draw flows are always higher in TDS than the River, regardless of the spoil springs, therefore, the impact from the spoil springs may be only 2-3% increase in TDS. During March/April, the River is flowing fast and Tuttle Draw is at low flow, therefore the increase in TDS for the River is only 2 ppm, or an increase of 0.4%. Also, these impacts are for the time when the spoil material is leaching salts at a maximum. As described earlier, the TDS levels will drop as pyrite and salts are leached out of the spoil, lessening the impact to the waters downstream even further. July 2016 (TR -74) 2.05.6(3)-35 Irrigation - Sept/Oct No Irrigation - March/April #1 Mine Spoil Water (NPDES 001 Discharge) TDS 1,967 2,885 #1 Mine Spoil Water (NPDES 001 Discharge) Flow CFS 0.376 0.041 Tuttle Draw #1 Mine Pre -Mix Point (SW -N3) TDS 1,680 2,094 Tuttle Draw #1 Mine Pre -Mix Point (SW -N3) Flow CFS 2.3 0.8 Tuttle Draw #1 Mine Post -Mix Point TDS(calculated) 1,720 2,133 Tuttle Draw #1 Mine Post -Mix Point Flow CFS (calculated) 2.676 0.841 #2 Mine Spoil Water TDS (4% above #1 Mine Levels) 2,045 3,000 #2 Mine Spoil Water Flow CFS (worst case) 1.31 0.113 #2 Mine Spoil Water Flow CFS (realistic case) 0.68 0.113 Tuttle Draw #2 Mine Pre -Mix Point TDS (same as #1 Mine Post -Mix) 1,827 2,235 Tuttle Draw #2 Mine Pre -Mix Point Flow CFS (same as #1 Mine Post -Mix) 3.986 0.954 Tuttle Draw #2 Mine Post -Mix Point TDS (calculated) 1,881 2,316 Tuttle Draw #2 Mine Post -Mix Point Flow CFS (calculated) 5.296 1.067 San Miguel River Pre -Mix Point TDS (Peabody Tab 17) 620 450 San Miguel River Pre -Mix Point Flow CFS (Peabody Tab 17) 141 817 San Miguel River Post -Mix Point TDS (calculated) 666 452 San Miguel River Post -Mix Point Flow CFS (calculated) 146.30 818.07 The values for the NPDES 001 Discharge and SW -N3 are averaged from measurements made from 1993 to present. Table 2.05.6(3)-3 shows this information for these as well as other sample points. As is seen from the table, the spoil water inflows from both mine areas influence the quality of Tuttle Draw to a minor degree. However, within 4500 feet, this flow enters the San Miguel River where the flow is so much larger than the Tuttle Draw flow that the impact is negligible. During periods of irrigation, Tuttle Draw is flowing at a higher rate while the River is running low, which is the time of maximum impact of the flows. At this time, the increase in TDS of the River is from 620 to 652 ppm, or an increase of 5.1 %. It should be noted that Tuttle Draw flows are always higher in TDS than the River, regardless of the spoil springs, therefore, the impact from the spoil springs may be only 2-3% increase in TDS. During March/April, the River is flowing fast and Tuttle Draw is at low flow, therefore the increase in TDS for the River is only 2 ppm, or an increase of 0.4%. Also, these impacts are for the time when the spoil material is leaching salts at a maximum. As described earlier, the TDS levels will drop as pyrite and salts are leached out of the spoil, lessening the impact to the waters downstream even further. July 2016 (TR -74) 2.05.6(3)-35