1988-04-11_PERMIT FILE - C1981008A (21)

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East mining areas are described in Appendix 15-1 on Pages 15-1-2 through 15-1-4. The current surface water monitoring program at Nucla East mining area is similar to the baseline monitoring program. The major change in the current monitoring program from baseline is that the full suite water quality analysis has been changed from monthly to semiannual (May and September). Monthly field parameters are still collected at each surface water site if water is present at the time of the field inspection. Details of the current monitoring program at Nucla and Nucla East mining areas are outlined in Appendix 15-1. Monitoring site locations are presented on Exhibit 7-1 (Tab 7). As mentioned in the monitoring program, the Stevens digital water level recorders at Sites SW-Nl04 and SW-Nl06, measure water level stage in the west lateral irrigation ditch on 60-minute intervals during the irrigation season (April 15 to October 15). In order to make use of the water level stage information being collected at these sites, stage height versus discharge rating curves are being established. On each monthly inspection and during non-routine site visits, the water level stage heights are noted at each stilling well. The discharge is then determined by taking a current meter measurement. The verticals used at each cross section where velocities are measured are consistent each time a measurement is taken. All techniques and procedures used in measurements of stage and discharge are consistent with those described by Rantz and others (1982). Velocity measurements are collected using a Marsh-McBirney flow meter. Monitor Site SW-Nl07 (see Exhibit 7-1 for location) on Calamity Draw has only a staff gage for instrumentation as described on Table 15-2. Peak discharge at this site is determined by flagging the high water marks and applying the Mannings equation and/or by using an indirect method (slope-area) as described by Lara and Davidian (1978). The above described on-going surface water monitoring program for the entire Nucla operation updates the existing monitoring program as described in the 1987 Annual Hydrology Report. As any changes occur in the monitoring program at Nucla or Nucla East, they will be reflected as minor revisions to the existing permit. NPDES Monitoring. Several minor modifications of monitoring points at NPDES monitoring sites were made during the 1987 water year. As a result of construction activities 15-4 Revised 04/11/88