2018-05-18_PERMIT FILE - C2009087

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in areas farther along the deeper portion of the groundwater flow path and more distant from natural recharge areas. • The recent isotope analysis of samples collected at COV23 show groundwater at this location within the PSCM reserves is greater than 1.15 million years old; indicating groundwater movement at these depths in the formations that comprise the basal Williams Fork acquifer is minimal. Groundwater is likely of similar age or even older in these same units further and deeper to the northwest within the synclinal basin where the monitoring well is proposed to be constructed. The key sandstone beds above the Wadge coal seam below the Lennox Coal have been correlated successfully across the PSCM permit area, and reveal a relatively uniform interburden between the Lennox coal seam and lower Wadge coal seam over an area of about 8 by 8 square miles. PSCM anticipates groundwater information collected at the proposed location will feature similar water level seasonality and water quality as seen at COV23 and CW23, and will provide sufficient baseline groundwater information representative of the bedrock units down-gradient of all possible mining activities at the PSCM. This additional well will provide sufficient water level data to expand the extent of the potentiometric surfaces in both the Wadge Coal and Wadge Overburden through the northwestern portion of the PSCM permit area. Baseline data collection activities proposed at COV 11 include monthly water level measurements, and quarterly sampling collection for the list of analytical parameters shown on Table 2.04.7-10. In addition, PSCM will conduct an aquifer test at COVI I to determine aquifer properties. Upon completion of the baseline monitoring activities, PSCM will submit another minor permit revision to incorporate the new groundwater information in the appropriate text, tables and figures within Section 2.04.7, Hydrologic Description. Surface Water Monitoring A surface water monitoring program will be implemented to allow identification and quantification of the effects the proposed mining activities may have on surface water discharge and water quality. PSCM proposes to maintain the present baseline monitoring regime and add several additional surface water monitoring sites to assess hydrologic impacts from the Seneca II Mine. Table 2.04.7-T11 lists the surface water monitoring points to be included in the monitoring program, and the monitoring frequency. Table 2.04.7-T12 lists the water quality parameters to be measured in the field and those to be measured or analyzed in the laboratory. The outfalls of Ponds 002, 003, and 004 will continue to be NPDES compliance points, and the CDPS Permit Renewal (currently under appeal) has incorporated two spoil springs (SSSPGI and SSSPG2) and a stormwater discharge to Little Grassy Creek as additional NPDES compliance points 006, 005, and 007, respectively. Site YSG5, on Grassy Creek downstream of all potential mine impacts, will be the point of evaluation for surface water impacts under SMCRA. Annual monitoring reports will be provided to CDRMS no later than March 31 st of each year. PSCM Permit App. 2.04-106.1 MT 18-02 04/20/18