ARCHIVED REPORTS_STOCKTON AVENUE SYSTEM WELL E-2 POST-SHUTDOWN EVALUATION

Home Browse Search

Stockton Avenue System Well E-2 Post-Shutdown Evaluation November 21, 2012 Former Nestle USA, Inc. Facility, Ripon, CA • The concentration of TCE in this well exhibits a decreasing trend since the post- shutdown concentration observed in April 2011. CONCLUSIONS Based on the rebound evaluation, ECM has developed the following conclusions: • Current monitoring well data around extraction well E-2 show that TCE is below 5 µg/L in all wells, with the exception of well M-8B. TCE in well M-8B shows a stable/decreasing trend. TCE and cis-1,2-DCE concentrations in this well have decreased more than 96% since extraction began in well E-2, suggesting significant mass removal in the area, and there is no indication of rebound to pre-remediation conditions. • TCE concentrations in the nearby wells are either decreasing or stable. • Historical data for well M-8B, evaluated in conjunction with post-shutdown stable and decreasing trends in wells M-8B, M-52B, and M-53B, suggest that extraction well E-2, to the extent possible, remediated groundwater that had reportedly been impacted by a sewer line leak near Stockton Avenue and Fourth Street. RECOMMENDATIONS Based on an evaluation of historical data through post-shutdown, ECM recommends the following: • Adoption of the monitoring schedule proposed in the revised Monitoring and Reporting Program (MRP) request sent to RWQCB on November 2, 2012, and • Decommissioning of extraction well E-2. ECM appreciates your review and approval of this post-evaluation report for the Stockton Avenue System. Please do not hesitate to contact me at (661) 255-1693 with any questions or concerns. Best regards, Binayak Acharya Attachments: Figure 1: Stockton Avenue Wells Figure 2: Historical TCE and Cis-1,2-DCE Concentrations in Well M-8B Table 1: Summary of Analytical Results for Rebound Evaluation cc: Marie Joachim Nestle Distribution List Page 3 of 3