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RESPONSE TO DIVISION OF MINERALS & GEOLOGY COMMENTS <br />CONCERNING TRAPPER'S GROUNDWATER SAMPLING PROGRAM <br />TECIINICAL REVISION TR-75 <br />Additional information was requested by the Division concerning Trapper's request to modify our Ground Water <br />sampling program. The following responses aze submitted. <br />1. Monitorioe Wells GA-1 and GA-2 <br />In the submittal of Trapper's 1995 Annual Report, the Division was notified of mining activities removing these <br />wells in 1996. TR-75 included this information as part of the program change. Both wells have been sampled since <br />1974 and data reported in required Annual Reports to [he Division. <br />Well GA-1 monitors the QR aquifer in Derringer Pit. Water level elevation for the QR aquifer aze also recorded by <br />wells GD-2, GE-1, GF~i, GP-l, GP-5, GP-6, and bacldtll wells GD-3 and GF-11. Figure 1 illustrates water level <br />elevations recorded at well GA-1 since 1974. As expected, as Derringer Pit advanced from the west, a drawdown <br />effect is observed on well GA-1. Section 2.2 of Trapper's 1995 Annual Report discusses the QR aquifer and effects <br />of mining. Well GA-1 is located between the pairs of bacldill QR aquifer combination of wells (GD-3, GD-2) and <br />(GF-I 1, GF-6). These two combination baclc511 and downgradient QR coal wells show similaz conditions in the <br />bacld-rll and QR aquifer water and, therefore, are adequate to define [his bacldll and downgradien[ aquifer water <br />quality in [his area. <br />Well GA-2 monitors the KLM aquifer in Derringer Pit. Water elevations for this aquifer are also recorded by wells <br />GB-1, GF-3, GP-2, GP-4, and GP-8. Figure 2 illustrates water level elevations recorded a[ well GA-2 since 1974. <br />As expected as Derringer Pit advanced from the west, a drawdown effect was observed on well GA-2. Again, Sec- <br />tion 2.2 of Trapper's 1995 Anneal Report discuss the effects of mining on the KLM aquifer. Figure 2 (attached) <br />shows that the KLM aquifer naturally was dry at times prior to the 1983 high precipitation. Therefore, this shows <br />that the KI.M aquifer at this area is very close to the upper limits of saturation and would be a questionable <br />location for a water supply well in this marginal aquifer. The IU.M aquifer is not as important as the QR and 13) <br />aquifers as faz as a water resource in this area. The monitoring downgradient of GA-2 should be adequate and, <br />therefore, a replacement well for GA-2 is not deemed necessary. <br />Trapper has discussed mining effects on these wells in the annual reports. These shallow aquifers are strongly <br />influenced by precipitation/rechazge activities. The loss of wells GA-1 and GA-2 is insignificant, when considering <br />the number of wells in place monitoring the QR and KLM aquifers. The discussion presented under Section 2.1 of <br />the 1995 Annual Report supports this conclusion. Map M52 shows the location of the referenced wells concerning <br />the QR and KLM aquifers. <br />2. Well GD-1(2) <br />Trapper does not monitor well depths for well GD-1(2). A pump is installed as this well is used to provide water [o <br />Trapper for domestic water use (please refer to Permit page 4-226g). I-listorically, well GF-1 has supplied water <br />level elevation for the twenty mile sandstone. <br />The reason Trapper requested discontinuing sampling of the well was the use of an automatic chlorinator to treat <br />the water prior to incorporation into the mine's domestic water system. We felt chlorination of the well could pos- <br />sibly affect results of some of [he parameter analysis. We are unable to shut off the chlorinator to allow sampling of <br />the well without affecting the domestic water system. I[ is assumed that a minimum of 24 hours would be required <br />to remove the effects of residual chlorine from the well water and pump system. <br />If the Division desires, Trapper will monitor those parameters recommended by the Division that are not affected <br />by the chlorine veatmenls. <br />