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Letter to Roger Day 5 June 18, 1999 <br />b) DMG will require AmerAlia to report on the utility of installing dedicated temperature probes at <br />dissolution surface ground water monitoring points. During the multi- agency meeting held on <br />May 26, 1999, it was AmerAlia's position that temperature monitoring would be ineffective in <br />detecting leakage of mining solution into the aquifer at the dissolution surface. This position <br />should be analyzed rigorously before the need for temperature monitoring is eliminated from the <br />plan. Given the large difference in temperature between mining solution and ground water, and <br />the high degree of consistency that can be expected for the temperature of unaffected ground <br />water, temperature monitoring could be a very good indicator of leakage from mining cavities. <br />c) The collection of five calendar quarters of baseline ground water data must be completed prior <br />to initiation of any activities at the site that create the potential for impacts to ground water <br />quality, in particular injection of heated and pressurized mining solutions. <br />d) A sufficient number of ground water monitoring points must be installed to supplement existing <br />ground water data from the immediate area and establish local horizontal gradients in the upper <br />and lower aquifers and the vertical gradient. <br />e) Certain monitoring parameters, for example cadmium and silver, must be analyzed by graphite <br />furnace atomic absorption spectrometry to obtain adequate method detection limits. <br />8. Provide additional detail on the proposed surface and subsurface subsidence monitoring plans. The <br />focus of the plan should be protection of the Mahogany Zone from adverse impacts that may be caused <br />if subsidence were to fracture or otherwise affect the structural integrity of the zone. Structural damage <br />to the Mahogany Zone may impact future minability of oil shale resources and may increase <br />permeability of the Mahogany Zone and allow for increased flow between the upper and lower aquifers <br />and the potential for adverse water quality impacts. The plan provided in the application discusses the <br />use of gamma logs to detect subsurface subsidence but does not specify how often these logs will be <br />run in each well. The application further specifies an annual survey of surface monuments and <br />discusses "a permanent reference monument which will be located each production well" (section U- <br />3.1.2). The reference monument should be located outside the potential zone of subsidence. DMG <br />suggests that a comprehensive subsidence monitoring plan be provided. The plan should illustrate the <br />locations for proposed surface monuments and discuss the duration for monitoring once a cavity has <br />been abandoned. The subsurface subsidence monitoring plan should specify a frequency for <br />conducting gamma logs. AmerAlia should consider using Time Domain Reflectometry (TDR) for <br />monitoring subsurface subsidence in order to provide for a high frequency of subsidence monitoring, <br />e.g. monthly, without the difficulty of running a gamma log. The plan should specify and provide a <br />rationale for actionable levels of subsidence that may be detected and should specify the corrective <br />actions to be employed if unacceptable levels of subsurface subsidence are detected. Surface and <br />subsurface subsidence monitoring information should be included in the annual report for routine data <br />or as soon as possible (within five working days) -if surface subsidence is detected or if subsurface <br />subsidence beyond the actionable criteria is detected. <br />9. Section U -4 to the application discusses using a material balance approach to monitoring the growth <br />a solution mining cavity. It is DMG's position that the material balance may provide a fairly accurate <br />determination of cavity size in the first undercut of the lowest resource interval. However, as the cavity <br />