RESULTS OF GROUNDWATER MONITORING FOR THE 183-H SOLAR EVAPORATION BASINS AND 300 AREA PROCESS TRENCHES JANUARY-JUNE 2010

This is one of a series of reports on Resource Conservation and Recovery Act of 1976 monitoring at the 183-H Solar Evaporation Basins and the 300 Area Process Trenches. It fulfills the requirement of Washington Administrative Code (WAC) 173-303-645(11) to report twice each year on the effectiveness of the corrective action program. This report covers the period from January through June 2010. The concentrations of 183-H Solar Evaporation Basins contaminants remained below applicable concentration limits during the reporting period. The most recent exceedance of a concentration limit was May 2007. The overall concentration of uranium in 300 Area Process Trenches wells remained above the 20 {micro}g/L concentration limit in the three downgradient wells screened at the water table. Fluctuations of uranium concentration are caused by changes in river stage. The concentration of cis-l ,2-dichloroethene remained above the 70 {micro}g/L concentration limit in one deep well (399-1-16B). Concentrations are relatively steady at this well and are not affected by river stage. Trichloroethene concentrations were below detection limits in all wells during the reporting period.