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Permit C-81-071 1995 Annual Hydrology Report <br />Figures 30 and 31. Plots of the historic flow measurements on Trout Creek are presented on <br />Figures 32 and 33. The flow rate data are summarized on Table 28. <br />The stream flow data shows the typical seasonal variation with a rapid rise and fall of flow rates <br />during Spring runoff. Flows from Stations 16, 69, 1001, 8, and 1002 are not measured during <br />the winter due to the streams being frozen. Station 14 on Foidel Creek often did not record flow <br />in the creek during the fall, winter and late summer because it is located near the top of the <br />drainage. Foidel Creek flows tend to be maintained nearly year-round by discharges from the <br />spoil springs feeding the sediment ponds. 1995 was a near normal rainfall year (see Figure 54) <br />and most gaging stations that are not directly affected by mine related discharges had below <br />normal to normal flows. <br />The data indicates a fairly good correlation between upstream and downstream stations on <br />each stream. As expected the upstream stations generally had a lower flow than the <br />downstream stations on each stream. On Trout Creek the downstream station (69) has a lower <br />flow than the upstream station, probably due to irrigation withdrawals, the effects of which are <br />also reflected in the site 301 data. <br />V1'ater Quality <br />Water quality samples are collected at all the primary sites on a regular basis. The water <br />quality summaries are presented on Tables 29 through 46. Plots of historic water quality data <br />for Foidel Creek are presented on Figures 34 through 37, Figure 50 and Figure 53. A plot of <br />• historic water quality data for Fish Creek is presented on Figure 38. A plot of water quality data <br />for Middle Creek is presented on Figure 39. Plots of historic water quality data for Trout Creek <br />area presented on Figures 40 and 41. <br />The base level of field conductivity measured during spring runoff, was higher in the <br />downstream sites on Foidel Creek. It is approximately 750 umhos/cm in the upstream site (14) <br />and from 1500 to 2000 umhos/cm in the downstream sites (800 and 8). Since 1981 the base <br />level for conductivity at both downstream sites has been increasing although there appears to <br />have been a leveling off since 1989. The upstream site also conductivity also increased in <br />1986, presumably as a result of lower runoff flows since that time. During the second half of <br />the 1995 irrigation season, the field conductivities at Station 14 could not be measured as there <br />was no measurable flow. The field conductivity at Station 8 was approximately 3300 <br />umhos/cm. <br />The difference between the conductivities at the upstream and downstream stations is <br />attributable primarily to spoil spring discharges related to surface mining. These discharges <br />cause increased concentrations of dissolved solids, calcium, magnesium, and sulfate and a <br />reduction in SAR in Foidel Creek. However, the increase in TDS levels during irrigation season <br />is not sufficient to cause material damage. While the spoil springs are adding some <br />manganese to Foidel Creek, the level at Station 8 is still below the total recoverable standard of <br />1000 ug/I for Foidel Creek. Historically, high total recoverable manganese also has been <br />recorded in the upstream station (14), indicating that these values may be attributable to non- <br />mining related causes. <br /> <br />EPSTE%T DOC 07/14/96 Page 5 <br />