2018-07-02_PERMIT FILE - C2010089A (19)

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review of additional data and consultation with DRMS, groundwater monitoring wells GW -N56, GW -N57, and GW -N58 have been designated as points of compliance. Overburden Zone Groundwater Quality Water level monitoring and the piezometric maps show the nearly immediate response of most of the monitoring wells to the seasonal surface irrigation with water levels going up and down corresponding to the periods when water is in the 2nd Park Lateral Ditch. The impression is that the overburden is annually being flushed with relatively good quality irrigation water. This further suggests that water quality would improve during periods of irrigation and deteriorate during periods when the ditch is dry. However, comparison of the groundwater quality data (see Appendix 2.04.7-1) with the water level data reveals no such correlation. Table 2.04.7-1 is a summary of the water quality analyses for the overburden, showing the minimum, maximum and average values of the analyzed parameters. No data for overburden monitoring well GW -N55 is shown as this well was nearly dry to the point that there was not enough water to collect water samples. The summary of the analyses for well GW -N52 is also compared with the WQCC (Regulation 41, The Basic Standards for Groundwater) drinking water and agricultural quality standards. The results show the overburden water quality to be unsuitable for domestic drinking water primarily for sulfates. Coal Zone Groundwater Quality Quarterly groundwater quality samples were collected from wells GW -N51 and GW -N54 beginning on October 10, 2008. The groundwater quality data is contained in Appendix 2.04.7-1 along with the water level and graph information. Review of the coal zone quality does not clearly reveal any correlation with the irrigation seasons, although there is a slight increase in Ca, CaCO3, SO4 and total dissolved solids (TDS) during the winter months when the ditch is not running. It may require a few more seasonal irrigation cycles to validate this initial impression. Again, the monitoring well located furthest up -dip and closest to the recharge area (GW -N51) has better water quality. As an example, the average TDS at GW - N51 is 950 mg/1 compared with an average at GW -N54 of 5,058 mg/1 which is located the furthest down -dip and away from the recharge area. Table 2.04.7-2 is a summary of the Coal Zone groundwater quality showing the min/max and average parameter values since monitoring began. Water quality for the Coal Zone at GW -N54 is the poorest of quality of all the monitor wells. The values when compared with the WQCC water quality standards clearly show that water from the Coal Zone is unsuitable for domestic drinking water. Section 2.04.7 Page 9 March 2018 (TR -16)