2012-06-20_PERMIT FILE - C2010089A (10)

Home Browse Search

Overburden Zone Ground Water Ouality Water level monitoring and the piezometric maps show the nearly immediate response of most of the nine new monitoring holes to the seasonal surface irrigation, with water levels going up and down corresponding to the periods when water is in the 2 Park Lateral Ditch. The impression is that the Overburden Zone 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 ground water quality data, (see data in 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 Zone, showing the minimum, maximum, and average values of the analyzed parameters. No data for overburden monitoring hole GW -N55 is shown as this hole was nearly dry to the point that there was not enough water to collect water samples. The summary of the analyses for holes GW -N49 and GW -N52 are also compared with the WQCC (Regulation 41, The Basic Standards For Ground Water) drinking water and agricultural quality standards. The results show the overburden water quality to be unsuitable for domestic drinking water primarily for sulfates. With the exception of calcium and bicarbonate, the water quality at GW -N52 is better than that at GW -N49, most probably the result of being located closer to the seasonal more alkaline recharge from the 2 Park Lateral irrigation ditch. The values for pH at GW -N52 are also somewhat higher (more alkaline). Again, suggesting that being closer to the main source of recharge (the ditch) affects the water quality to a greater extent at GW -N52 than at GW -N49. Coal Zone Ground Water Quality Quarterly groundwater quality samples were collected from the three holes (GW -N48, 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, CaCO SO 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 hole 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 -N48 of 1592 mg/1 and an average TDS at GW -N54 of 5058 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 ground water 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 nine of the new monitor holes. The values when compared with the WQCC water quality standards clearly show that water from the Coal Zone is unsuitable for domestic drinking water. Ground water monitoring hole GW -N9 (see Map 2.04.7 -1) was installed by Peabody and quarterly water analyses were conducted on samples from this hole from October 1979 to October 1987. This monitoring hole is located within the NHN permit area and is open to both the Overburden and Coal zones. The quality data for this hole is reported in the New Horizon 1 Mine Area permit, pages 7 -4 -49 to 7 -4 -53. The average TDS for the period was 3785 mg/1 and the average SO4 concentration was 2423 mg/l. The values of these two parameters are significantly higher than the Coal Zone values at GW -N48 and GW -N51. This indicates that water quality in the Coal Zone (and probably the OB Zone as well) is also dependent on depth or isolation beneath the weathered zone as well as distance from the recharge area. Therefore, Section 2.04.7 Page 8 November 2011