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state Rea. <br />in June at SW-S2-2 on 6/12/87 and 6/15/88, respectively, which exoeer3 <br />the predicted June ma~rimm, No July Or August measurements of 'IiJS <br />have been collected at SW-S2-2 since the 1986 water year, so we do <br />not kna.1 if the July or August predicted mwx;mimc have been <br />exceeded. Since water year 1988, PWCC has monitored ZS75 <br />oonoentrations at S~1-S2-2 on1Y diu~ing March, MaY,and September, so we <br />also do not knee if the June (as well as July or August) ZDS max;mmic <br />have been exceeded in recent years. 'Ihe predicted September 'IDS <br />mavimm of 2341 mg/1 has been exceeded every year since 1986 at <br />SW-S2-2, with the highest ~ value (3018 mg/1) ~a~~red on 9/5/90. <br />Since 1986, 'iDS predictions for (Massy Creek were made using data <br />that is not representative of recent conditions at the Seneca II <br />Mine, a re-e~mination of 7AS predictions at SW-S2-2 is appropriate. <br />Using 'IDS data from Spoils Well GW-527, flow aixl 'IUS data from <br />SW-S2-1, and flow data fr®n NPDFS Sites 002 arri 003, ~Y~*~m+ 3D6 <br />values were calculated for June, July, August, attd September in the <br />1986 PHC. Although suitable for the information available in 1986, <br />this approach currently is inappropriate considering the data <br />collected since 1986. `Ihe use of 'IDS data froth Spoils Well GW-527 is <br />not necessary since ZDS levels at GW-827 have stabilized in recent <br />years, and spoils water quality in the Wedge ittq~outxhnent area appears <br />to have an insignificant effect on surface water quality as measured <br />at NPDES 002, where 'IDS concentrations have remained within a <br />~. relatively consistent range since 1980. Under the current Seneca II <br />Mine tmtutoring plan, ZDS data is collected at Sites Sw-S2-2 and <br />SW-S2-1 during the months of March, May, and September, so an <br />estit~te of future ZDS levels in (Massy Creek can only be calculated <br />for September. <br />Flow at Grassy Creek Site SW-S2-2 is potelttially affec.~teci by <br />discharges from Grassy Creels (monitored at SW-S2-1) and NPDES Sites <br />002 and 003. Flow at Site SW-S2-2 is also affec.~ted by gain from, or <br />loss to, the underlying alluvial aquifer, which varies with seasonal <br />• conditions. A review of recent monitoring data (since water year <br />1986) shows that only PfPDF;S Site 003 consistently discharges to <br />7-326 Revised 08/20/93 <br />