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• NPDES DISCHARGE SITES <br />Numerous additional NPDES discharge points associated with [he TCC operations are monitored throughout the <br />year with monitoring results submitted to the Division on a periodic basis in accordance with permit requirements. <br />Tables 60 through 65a provide Water Year and period of record data summaries for those NPDES outfall points <br />other than mine de+vatering site 115 which discharged during the year. The reader is referred to the Discharge <br />Monitoring Reports (DMRs) submitted during the year for additional information regarding specific discharge <br />occurrences. Applicable permits include No.'s CO-0027154, CO-0036684, and CO-0042161. Figures 114 <br />through 117 provide graphical representations of Water Yeaz flow rate and field conductivity data for Pond D at <br />the Foidel Creek Mine and for Pond E at the Fish Creek Tipple. Figure 118 depicts period of record total <br />recoverable iron data for Pond E. <br />MINE INFLOW MONITORING <br />The inflow to the Foidel Creek underground mine was monitored in several ways during 1996. The flow rate and <br />water quality of the discharges from the mine (Sites 109 and 1 I S) were monitored before entering Pond D or Fish <br />Creek respectively. In addition, an annual mine inflow study was performed. The 1996 Mine Inflow survey was <br />conducted during December 1996. During the inflow study, flow rates and field parameters are recorded for <br />• measurable inflows into the accessible areas of the mine. Results of the 1996 study are presented as Figure 120. <br />Inflows occurring during the study this year are eenerally noted to be smaller than those recorde~t i~c~gear The <br />[Wining area west of the mains is largely inaccessible at this point in time. Using the water level information at [he <br />Fish Creek Borehole, an estimate of the total available water holding capacity in the strata below the 5960 <br />contour, and an average volume-weighted porosity estimate of 0.24, [he mine inflow rate for the western mine <br />area calculates to approximately 108 gallons per minute for the period behveen July and October, well below <br />predicted intlo+vs for this area of the mine. The porosity value utilized in this calculation is believed [o be <br />conservative and consequently, the calculated inflow rate is conservative as well. TCC will continue to track the <br />inflow rate as derived from the water level readings at the Fish Creek Borehole in this manner. <br />In the 9 and 10 Right ga[eroads, significant inflows were encountered during development mining through the <br />major I'atrlt in this area. The fault was encountered in 10 Right in October 1995 and in 9 Right during August <br />1995. The initial inflows were observed to taper off rather quickly, within approximately one month, and Itad <br />essentially ceased by the time the December 1996 mine inflow survey was conducted. Maximum inflows as <br />measured in 9RT during 1995 immediately after encountering the fault were on the order of 10 gpm and had <br />reduced to 0.5 gpm by December 1995; maximum inflows as measured in TORT during 1995 immediately after <br />encountering the fault were on the order of 25 gpm and had reduced [0 5.5 gpm by December 1995 (see 1995 <br />AHR Figure 93). One inflow point identified in the 9 Right gateroad (Point IS) exhibited persistent inflow during <br />. the year. Witlt the exception of the initial fault inflows, this point represents the most prevalent single source of <br />-14- <br />