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Water quality impacts to the stream/alluvial aquifer system of Fish Creek could result from two additional processes: mine water discharge through [he Fish Creek borehole,~shaft durine mining and contamination of tributary ground water through seepage from the underground workings after mining has ceased and [he workings have flooded. Impacts from mine water discharge during operation will be discussed first. Originally, mine water discharge was projected to have an electrical conductivity of Immhos/cm at a projected discharge rate of 0.41 cfs. Actual data from numerous years of operation reveals mine water discharge values of approximately 0.20 cfs but an electrical conductivity of nearly 3 mmhos/cm. Discharge and conductivity in this range would cause a measurable increase in salinity downstream on Fish Creek. Stream flow modeling conducted during the CHIA produced EC values in the area of .750 mmhos/cm, given a conservative TDS/EC ratio of .8, for areas downstream of the Fish Creek dewatering borehole. Electrical conductivity values at this level would not materially damage crop production from either flood irrigation or sub-irrigation. In 1998, degradation of water beyond the original predictions occurred, primarily in the sump area of the mined-out WMD. Due to operational considerations, this water must be pumped out of the mine at the Fish Creek Borehole Treatment Facility to achieve a relatively static elevation of this sump in the mined-out area. TDS values of this water have exceeded 6500 mg/I on a regular basis since pumping from the Fish Creek Borehole was resumed in 1998. Technical Revision No.32 (TR-32) re-evaluated the discharge of this water to Fish Creek, Foidel Creek, Middle Creek, and ultimately Trout Creek downstream of the mine. The applicant has committed to a plan to discharge water at a rate (dependent on quality) that will ensure that downstream waters do not exceed the Division's material damage standard for the upper Trout Creek basin of 1500 umhos/cm.(see Probable Hydrologic Consequences section of this document) As was the case on Trout Creek, the majority of the plant species identified in surveys conducted by the applicant and summarized in the supplemental package of September 22, 1986 are rated moderately tolerant to salinity. Only 3.7% of the relative vegetative cover on Fish Creek was made up of moderately sensitive species. No production sampling was conducted on Fish Creek, and so a ratio of 4.5 obtained from sampled fields at the Foidel Creek/Middle Creek confluence was used to convert relative cover of 3.7% to assumed relative production of 16.6% for moderately sensitive species. Cover and productivity data were collected in 1997 in and adjacent to the Fish Creek AVF. AVF species are dominated by Smooth bromegrass, Kentucky bluegrass, Common yarrow, sage, Arremesia cans, and Timothy. Projected Fish Creek water quality for flood irrigation is conservatively estimated at 0.9 mmhos/cm electrical conductivity. Projected root zone soil salinity would be less than l.5 mmhos/cm and therefore no decrease in crop production would occur. Moderately sensitive species would be expected to exhibit some decline in productivity if irrigation water conductivity were to exceed I.0 mmhos/cm. Due to the relatively small component of moderately sensitive species, material damage would not occur unless flood irrigation water conductivity were to exceed 2.0 mmhos/cm (which is assumed to correspond to a root zone conductivity of 3.0 mmhos/cm). A 1.5:1 relationship between soil salinity and irrigation water salinity is considered to be a conservative assumption (the actual relationship may be less than I.5:1). Data collected by the Division on August I5, 1986, showed root zone soil conductivity to be slightly lower than Fish Creek surface water conductivity. C: U H B\C82056\R N03\R N03 F I N D. doc 31