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Kathy Welt and Christine Johnston March 7, 1997 (DRAFT) Page 15 constituent concentration increases during 1996 were ____ percent for TSS, w percent for TDS, and percent for total iron. These data demonstrate that MCC did not significantly affect water quality in the North Fork during 1996, despite the extraordinary circumstances under which it was operating. In addition to the NPDES exceedances described above, there were exceedances attributable to a rain- on-snow event in February 1996 which was in excess of a I-in-25-yeaz event. Summary of Surface Water Quality PHCs To summarize, there are multiple potential surface water quality implications related to MCC's utilization of the large capacity sealed panel sumps and inflows from the B East Mains fault. From the standpoint of actual chemical or biological impacts to the North Fork, extensive data collected in 1996 indicate that there were no significant impacts. In addition, because streamflow increases were small, there were no adverse physical impacts to the North Fork channel. In 1997 and beyond, water quality impacts are projected to be even smaller than they were in 1996, based on the analysis described herein and the conditions at the mine as ofmid-January 1997. IX. GROUNDWATER QUANTITY PHCs From the perspective of historical groundwater movement, the interception, conveyance and discharge (to the North Fork) or storage of the fault water (in the sumps) seems unlikely to have significant hydrologic consequences, in terms of groundwater quantity, because MCC knows of no claim of reliance on these fault inflows. Isotope ;malyses on samples obtained in November 1996 after a sustained period of constant 85t gpm inflow were conducted for "finger-printing" and age-dating purposes. These analyses indicate this water has been below the ground surface for an extended period of time. Tritium isotope analysis shows there to be no tritium within the samples for all practical purposes. This indicates that the water entered the subsurface prior to the detonation of nuclear explosives in the atmosphere (i.e., before 1943). These analyses were conducted by Dr. Richard Hurst, an isotope geochemist, who observed that, based on his years of experience, waters this depleted in tritium are usually greater than 1,000 years old. Oxygen and hydrogen isotope ratio analyses were also conducted on B East Mains fault inflows from November 1996 samples. The results show a deviation from the ratios expected for meteoric waters in the Rocky Mountain region (i.e., the Meteoric Water Line). This deviation indicates a lack of direct communication or direct recharge from a surface water source. Additional water quality analyses are now being conducted and compared with known water sources in the general vicinity of the mine to assess the potential source of the fault water and the potential impacts to the water resources of the area. Collection of this groundwater within the mine can either increase its downgradient movement time if it is pumped out of the mine and discharged, or it can decrease its downgradient movement time by storage in a sump where the water will eventually migrate down-gradient in or near the B-Seam coal. Using the highest permeability values observed in the coal and overlying strata, the cumulative outflow from these sumps (NW and NE Panel sealed sumps combined) is estimated to be less than