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~_ -2- VI. Hvdroloaic Balance -Rules 2.04.5. 2.04.1. 2.05.3(4 A. Ground Water Information 1. The proposed area to be mined in the No. 5 Mine beneath the Utah Tract extension is overlain by two major sandstones, the Middle and Twentymile Sandstones. Thicknesses of these units in the Utah Tract area are shown to be approximately 120 feet each on revised Maps III-4 and III-6, respectively. Head level declines have been recorded in the Middle Sandstone and an estimation of drawdown due to mine dewatering has been made; however, no head declines have been recorded in the Twentymile Sandstone from the one monitor well completed in this unit at which water levels are recorded (Well 259). The applicant has not predicted any impacts to ground water in the Twentymile Sandstone. The Division is concerned that the planned subsidence in the area of proposed longwall panelling could result in ground water depletions in this unit. No Twentymile Sandstone monitor wells are located in th,e area to be undermined by longwall extraction in the No. 5 Mine. Since tYiere is the potential for ground water depletions from this unit due to leakage to the mine workings in this area, the applicant should install and monitor a Twentymile Sandstone monitor well in the vicinity of the proposed longwall extraction area near the Utah Tract extension. This well must: be installed prior to longwall development and should be monitored for water levels and water quality according to the monitoring frequency for the other bedrock wells included in the hydrologic monitoring program. The exact location of this well should be discussed in consultation with the Division. 2. The No. 9 Mine Well is located at the No. 9 Mine portal area and is also completed in the Twentymile Sandstone. This well provides pol;able water supply to the No. 9 Mine. It is stated on page III-47 that tFiis well is not available for water level measurement. The applicant should comment on this. For the reasons stated above, water level measurements should be collected and reported from this well, if possible. With the inclusion of water level monitoring from this well and the additional requested Twentyrnile Sandstone well near the proposed Utah Tract extension (see above), piezometric surface maps for this unit can be constructed. 3. A Middle Sandstone well (Well 83-02) has been installed and is being monitored near the Utah Tract extension; however, this monitor well is not included in the present monitoring program. Monitoring of the Middle Sandstone in this area is an important aspect in the determination of mining impacts upon the hydrologic balance and for verification of drawdown predictions made by the applicant. Therefore, the applicant should include this monitor well in the hydrologic monitoring program for th~=_ No. 5 Mine. Water level information from this site should be used to revise Map III-5a to reflect the piezometric surface of the Middle Sandstone in the vicinity of the proposed Utah tract extension. 4. Monitor Well 259, which is shown on Map IV-13 to be completed in the 7wentymile Sandstone, is located outside of the outcrop area for this unit on Map III-6, Structure & Isopach Map of the Twentymile Sandstone. This discrepency with regard to the completion unit of Well 259 should be resolved.