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136. If it is determined that the alluvial groundwater system is an aquifer based on <br />further review and documentation as stated above in Item 13a, then provide a plan <br />to the Division for the design and installation of two additional groundwater <br />monitoring wells in the Chandler Creek alluvium. These should be located near the <br />permit boundary in close proximity to Chandler Creek at an upgradient and <br />downgradient location. Please also add these new wells to the Hydrologic <br />monitoring plan in Exhibit AB. <br />14. Additional discussion and analysis is required regarding the potential for mine-induced <br />dewatering of these private wells. According to Exhibit K, the mine will act as a <br />dewatering well and could potentially impact wells adjacent to areas undermined and <br />subsided. Analysis should include cross sections through registered wells, especially those <br />wells upgradient in Chandler Heights. (Rule 2.04.7(1)(6). <br />Northfield Response: Exhibit K includes additional analysis of well dewatering. <br />DRMS response: Please label the cross-sections on Exhibit K, Appendix 4, Cross <br />Section Location Map and re-submit this map. <br />15. Please submit completion diagrams for the monitoring wells included in the hydrologic <br />monitoring program. The State Engineer also requires that monitoring wells be permitted <br />with the Division of Water Resources. Please submit copies of monitoring well permits for <br />incorporation into the permit application. !t may be convenient to combine the afore- <br />mentioned materials into one new exhibit to the permit. <br />Northfield Response: Exhibit AJ was submitted. <br />DRMS response: Surface elevation of the top of casing should be depicted on the <br />completion diagrams. Please add this important information to the completion <br />diagrams. <br />15a. The construction and integrity of two of the three existing monitoring wells used to <br />monitor the coal seam is a concern. NFOI-A and NF-03A are open-hole construction <br />with no filter pack, well screen, and no bentonite transition seal before placement of <br />the sanitary grout seal. Open hole construction is only advisable in crystalline rock. <br />The water level measurements as shown in Appendix L appear to be inconsistent in <br />these wells as opposed to NF-02 which was constructed with a well screen, filter <br />pack, and bentonite seal. If future monitoring wells are proposed please submit the <br />design plans to the Division for review and approval prior to installation. Guidance <br />for the design and installation of monitoring and observation holes can be found at <br />the Office of the State Engineer (Water Well Construction Rules) 2 CCR 402-2. <br />16. Exhibit K states that "water quality will not be significantly diminished by mining activities <br />and mine openings because ... (2) the low permeability of the Yermejo Formation materials <br />will minimize ground water flows to the mine and effectively protect the ground water <br />