2018-11-26_GENERAL DOCUMENTS - C1980004

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baseline and "during mining" conditions. The annual report for the previous water year will be submitted no later than March 31 of each year. E. Probable Hydrologic Consequences A determination of the probable hydrologic consequences (PHC) of the mining and reclamation activities at the McClane Canyon Mine site has been made by the applicant and is found in Section 2.4.2.1 and Appendix N of the permit application. Annual PHC updates are included in the annual hydrology report submitted each year by the operator. The Probable Hydrologic Consequences section of this document is divided into two main subsections: Ground Water Effects and Surface Water Effects. Ground Water Effects The occurrence of ground water within and adjacent to the permit area is controlled primarily by the combination of local topography, stratigraphy and geologic structure. Drilling has indicated that the Cameo coal seam becomes increasingly saturated downdip (northeast) from its outcrop along the side slopes of the East Salt Creek Drainage basin. This is depicted on Figure 4.2- 3, of Volume II of the permit application. The saturated zone extends downdip towards the northeast along a northwest -southeast trending line. The outcrop line of the coal, as well as the East Salt Creek drainage, run roughly north -south in the vicinity of the permit area. Recharge to the Cameo coal seam occurs in an area where the coal seam subcrops in the East Salt Creek alluvium approximately two miles north of the McClane Canyon Mine permit area. Very little recharge of the coal seams and sandstones occur along outcrops due to the low precipitation and steep slopes which favor runoff over infiltration. The underground workings extend roughly eastward into the Cameo seam from a point where the coal seam outcrops in McClane Canyon. Drilling in the vicinity of the portals has indicated that saturated sandstone strata are about 210 feet below the Cameo seam, and therefore, beyond any likely impact caused by the mining activities. Associated roof and floor strata are not saturated in the area of the mine. The mined zone is not a recharge area for these strata. The initial mine workings were situated within a geologic structure identified as a graben. This graben is bounded on both sides by faults. Future mining will be primarily to the east of the graben in an area south of the existing mine entries. At the time of the initial permanent regulatory permit approval during the first quarter of 1982, no water was discharged from the mine workings. However, subsequent to the extension of the east mains to the east fault and north mains down dip to the northeast in a parallel line with the east fault, mine inflows increased gradually and required periodic discharge in accordance with an approved CDPS discharge permit (002). Mine inflows peaked at a rate of approximately 5.4 gpm shortly after the mine was idled in 1983, and steadily decreased until operations resumed in 1988. When mining resumed, additional area in the saturated portion of the graben was opened, and inflow increased to approximately 3.9 gpm in 1990. In April, 1990, the mine section from which inflow had originated was sealed, and in July, 1992, all areas to the north of the East Mains were sealed and are now inaccessible. No water has been produced in other areas of the mine since the section which had originally produced water was sealed in 1990. Further dewatering of the mine from areas which previously produced water is not projected to be necessary until water in the originally sealed area backs up to the seals, and is drained to a dewatering sump to be used in the mining process. At the 1990 inflow rate, this would not occur for approximately 60 years.