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high levels. Well CW2701 displays a sodium bicarbonate type water with <br />relatively high pH values. It is suspected that the high fluoride values <br />are related to this type of water chemistry (Hem, 1989, pg. 121). <br />High manganese values may, in part, be due to recharge from the spoil <br />aquifer, although high values are often common due to naturally <br />occurring geochemical conditions, especially in alluvial material (Hem, <br />1989, pgs. 86-89). Manganese exceedances have occurred at all alluvial <br />wells, including the one Grassy Creek alluvial well upstream of the PSCM <br />(Well 71) and one Wadge coal well located just west of NPDES Pond <br />002(Well 17). This standard is used to protect crops grown in soils with <br />a pH value lower than 6.0. In January 2008, CDPHE revised their ground <br />water agricultural standard to reflect this pH qualifier. In soils with <br />a higher pH (as are found in the PSCM region), a more appropriate <br />standard would be 10 mg/l (EPA, 1976). This year, none of the PSCM <br />alluvial wells displayed a value higher than 0.95 mg/l, and no spoil <br />wells displayed a value higher than 0.99 mg/l. <br />Ground Water Points of Compliance <br />Ground Water Points of Compliance (GWPOC) have been established for the <br />PSCM (PSCM PAP page 2.04-103, Vol.l). Attachment 7-3 of the Seneca II <br />PAP provides the details of how the standards were established. The <br />ground water standards for Grassy Creek Alluvial Well SGAL70 are <br />provided in this AHR on Table 7. No excursions occurred in 2018. <br />However, the standard for cadmium is 5 ug/1 and the May concentration <br />exhibited a <5.0 ug/l value. <br />Ground Water Quality Summary. <br />TDS values at two of the seven wells sampled this year displayed <br />increasing TDS trends. TDS trends at the remaining wells were either <br />stable or decreasing. CDPHE agricultural ground water standards for pH, <br />fluoride and manganese were exceeded at certain monitoring wells. There <br />were no GWPOC exceedances in 2018. In the area surrounding the PSCM, <br />ground water is not being pumped for irrigation or livestock watering <br />purposes, nor has the CDPHE classified any aquifer in this region for <br />any use. The above discussion is provided only to serve as a comparative <br />