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wells as opposed to NF-02 which was constructed with a well screen, filter pack, and <br />bentonite seal. If future monitoring wells aze proposed please submit the design plans to <br />the Division for review and approval prior to installation. Guidance for the design and <br />installation of monitoring and observation holes can be found at the Office of the State <br />Engineer (Water Well Construction Rules) 2 CCR 402-2. <br />Northfield Response: Lengthy discussion of previous bedrock well installation. <br />DRMS Response: Response accepted. <br />17. Other than the statement in Exhibit K on page 20 "the impact of the mine on the regional <br />ground water system is expected to be limited to a very short distance from the mine... " <br />there is a general paucity of analysis or scientific evidence to support the contention of <br />minimal or no impact to ground water users in the permit and adjacent area. The report <br />uses generalizations, simplistic mapping, schematic diagrams and a minimum amount of <br />data from the Ocean Wave coal seams to come to relatively broad conclusions regarding <br />ground water impacts. The report offers no substantive information related to the potential <br />for mine related impacts to registered wells. <br />One useful piece of information in the report is the map (Northfield Mine Registered Wells) <br />showing a minimum of SO registered wells within one-half mile of the permit area yet the <br />report completely avoids any meaningful discussion of potential impacts and provides no <br />analysis of drawdown limits and/or estimates, conveys no site-specific hydro-geologic <br />properties, and makes no recommendations regarding monitoring and observation. The <br />report states on page 20 that potential mine inflows have been calculated to range from less <br />than 1 acre-ft per year to 450 acre-ft per year using information and calculations <br />represented in Table 4, one of the few portions of the report that backs up conclusions with <br />supporting information. Assuming those estimates are meaningful, ground water may flow <br />into the mine at the rate of 0-279 gallons per minute. The Division has researched <br />available data for the registered wells, especially in the southeast portion of the permit and <br />adjacent area. Many of the registered welds used for domestic purposes that are in close <br />proximity to the proposed underground workings have yields of 1-3 gallons per minute <br />maximum. Reduction of even a small amount of yield for these wells would be significant to <br />the owners of these wells. <br />Quantification of potential drawdown and impacts to registered wells due to mining <br />impacts is required in order to determine necessary monitoring plans and determine <br />compliance with Rule 2.04.7(3), Alternative Water Supply. <br />Northfield Response: Additional information and analysis included. <br />DRMS response: Exhibit K recommends a "tiered" plan regading monitoring to detect <br />potential mining-related impacts. What is the trigger to move from one recommended <br />monitoring "tier" to the next "tier"? Further details of the plan aze necessary. Please submit <br />this information as additions to the permit text under Exhibit AB, Part VI. Any mitigation <br />measures or monitoring plans must be stated clearly in the permit text and not solely as <br />