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Monitoring Frequencies. Water quality monitoring at surface water sites is performed generally <br />during the months of March through October. Heavy snowfall and/or extended winter weather <br />conditions may delay the monthly monitoring and field season sampling start-up until April or May. <br />Continuous flow monitoring at surface water sites is not maintained during the December to March <br />period because surface discharge is very small and weather conditions cause the stilling well float to <br />freeze and thaw. The resolution of actual flow data monitored during the winter is so small, it is <br />masked by the freezing and thawing action recorded by the monitor. Thus, the flow data is suspect <br />and continuous recorders are not maintained during the winter months. However, during the spring <br />snowmelt event from March to May and subsequent precipitation events thereafter through October, <br />continuous flow monitoring at surface water sites is maintained. Monitoring of surface water far flow <br />and chemistry on a tri-annual basis (March-October) provides hydrologic data during seasons of <br />existing and potential surface water usage in the Seneca II-W area. Moreover, the significant <br />hydrologic changes in flow and chemistry that occur in the surface water system (see Tab 7, <br />Hydrologic Description) take place during March through October when continuous flow monitoring, <br />monthly field water chemistry measurements, and triannual water sampling are ongoing. <br />Historic Surface Water Monitoring Program. The Historic Surface Water Monitoring Program is <br />described in Appendix 15-1. Historic surface water monitoring sites are shown in Exhibit 7-1, Tab 7, <br />Hydrologic Description. Table 15-1 contains a summary of historical and descriptive information at <br />Seneca II-W surface water monitoring sites. Surtace water monitoring at Seneca II-W began in 1979 <br />through a cooperative effort between Peabody Coal Company and the U.S. Geological Survey <br />(USGS). Peabody and the USGS established continuous recording stream gaging stations near the <br />mouths of Hubberson and Watering Trough Gulch drainage basins (FG1 and FG2, respectively) in <br />order to collect data that would be useful in the determination of surface water impacts induced by the <br />Seneca II-W operation. Six additional stream monitoring sites were established by Peabody in 1979 <br />at various locations nearby the Seneca II-W Mine: SG1, CG1, SG3, and SG4 in the Sage Creek <br />drainage basin; and SG2 and CG2 in the Watering Trough Gulch drainage basin. Three more sites <br />added in the early 1980's include SG5 in the Dry Creek drainage basin and Sites SG6 and SG7 in the <br />Hubberson Gulch drainage basin. <br />Prior to 1986, water quality monitoring at surface water sites consisted of quarterly long list analyses <br />and monthly short list analyses. After December 1985, water quality monitoring at surface sites <br />consisted of triannual water quality sampling according to the <br />3 Revised 9/98 <br />