1999-12-15_GENERAL DOCUMENTS - M1999051

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Letter to Roger Day 4 June 18, 1999 corrective actions that will be initiated in the allowable leakage rate is exceeded. Find enclosed page no. 59 from a draft DMG guidance document describing methods used to establish allowable leakage rates. 6. Provide a ground water monitoring plan as a technical revision to the application (Rule 1.8). The Monitoring plan should address each item listed in Rule 3.1.7(7) with the exception of item viii. The ambient ground water quality data will be collected through implementation of the plan to be submitted. Please note that for DMOs, five calendar quarters of data are required (Rule 6.4.20(9)) and that DMG requires a minimum of eight data points from each monitoring location to run statistical analyses. It is emphasized that the plan to be submitted is considered by DMG to be an ambient ground and surface water characterization plan and not a final monitoring plan. The information obtained through implementation of the five - quarter characterization plan will be used to formulate the ongoing monitoring plan and to establish numeric protection levels and points of compliance as appropriate. The ongoing monitoring plan will incorporate actionable levels and will specify actions to be taken if those levels are detected by monitoring. The basis for ground and surface water protection under AmerAlia's proposed mine plan is to put in place EPFs (practice -based permit conditions — Rule 3.1.7(2)) that will prevent water quality impacts. Hence, changes in water quality at a monitoring point indicative of an infusion of process solution may be actionable even if ground water quality standards are not exceeded. Likewise, changes in piezometric pressure indicating an excursion of fluid from a mining cavity may be actionable even if there is no corresponding impact on water quality. Schedules and methods of reporting data or excursions wiii also be incorporated into the ongoing plan (Rules 3.1.7(7)(b)(iii) and 3.1.7(9)). 7. As discussed in item 6 above, the items listed in Rule 3.1.7(7) must be addressed in the ground water characterization plan. Item iv. requires applicants to list the parameters to be monitored and to specify the water quality analyses methods to be used for each parameter. For purposes of water quality characterization, DMG requires that the contaminants listed in Tables 1 -4 of the Basic Standards for Ground Water (5 CCR 1002 -41) be analyzed. In terms of the water quality analysis methods to be employed, DMG is primarily interested in the method detection limits. The detection limits should be below the concentration established as the water quality standard for each parameter. Whenever technologically feasible, the detection limit should be no more than one -fifth the water quality standard. Once the ambient ground water quality data is collected and analyzed, DMG may reduce the number of parameters to be analyzed during the life of the project. Some miscellaneous issues relative to the ground water monitoring plan are: a) It is the position of the DMG that baseline characterization of ground water must include monitoring points within the Uinta formation. The Uinta formation contains the ground water resource that is closest to the surface and is generally of the best quality in the Piceance Basin. The proposed mine plan may potentially affect the Uinta formation water through relatively small but steady casing leaks that may not be detectable through systematic pressure monitoring.