Laserfiche WebLink
2012 Annual Groundwater Monitoring and Evaluation Report <br /> Full-Scale In Situ Hexavalent Chromium Reduction Treatment Implementation <br /> Former Marley Cooling Tower Site, Stockton,California February 2013 <br /> quarter results were the lowest since January 2011. MW-8 is located in the shallow zone adjacent <br /> to MW-4 at the western edge of the North Yard. <br /> MW-102: Concentrations of Cr and Cr6+decreased slightly during the reporting period. It can be <br /> seen in Graph 9 that concentrations at this well have a slightly decreasing trend since fourth <br /> quarter 2010. MW-102 is located in the shallow zone west of the Former Retort Pit area. <br /> MW-106: Concentrations of Cr and Cr 6+ remained relatively stable during the reporting period. <br /> It can be seen in Graph 12 that concentrations at this well have been relatively stable since third <br /> quarter 2010. MW-106 is located southeast of the Former Retort Pit area. <br /> MW-213: Monitoring well MW-213 is located in the intermediate zone in the southwest <br /> quadrant of the North Yard area. Since 2008, when concentrations of Cr and Cr+6 initially <br /> decreased as a result of nearby supplemental injection, concentrations have fluctuated over a <br /> wide range. Cr and Cr 6+were not detected in the first quarter 2012 sample but increased to 5,410 <br /> and 5,120 µg/L, respectively, in second quarter 2012 (Graph 23). Concentrations decreased in <br /> third quarter 2012 to 670 and 561 gg/L, respectively, but increased in fourth quarter to 2,880 and <br /> 2,710 µg/L, respectively. <br /> MW-321: Concentrations of Cr and Cr+6 had decreased below the WQO for the first time in <br /> second quarter 2012. However, in third quarter 2012 concentrations of Cr and Cr+6 increased to <br /> 150 and 149 gg/L, respectively. In fourth quarter 2012, concentrations decreased to 57 and <br /> 49.5 µg/L, respectively. MW-321 is located in the intermediate zone in the southern South Yard <br /> Area. <br /> MW-447S: Concentrations of Cr and Cr+6decreased from 2,060 and 1,950 gg/L, respectively, in <br /> third quarter 2012 to 716 and 700 gg/L, respectively, in fourth quarter 2012. First quarter 2013 <br /> sampling results indicate that Cr and Cr+6 concentrations decreased to 590 and 590 gg/L, <br /> respectively. <br /> MW-447D: Concentrations of Cr and Cr+6 remained static during the reporting period, at or near <br /> 2,350 and 2,250 gg/L, respectively. However, first quarter 2013 sampling results indicate that <br /> Cr and Cr+6 concentrations decreased to 1,630 and 1,620 gg/L, respectively. <br /> (a AAWH <br /> 4-4 <br />