ARCHIVED REPORTS_QUARTERLY GROUNDWATER MONITORING REPORT 1ST QUARTER 2016

Home Browse Search

QUARTERLY GROUNDWATER MONITORING REPORT— FIRST QUARTER 2016 L&M Operable Unit —West Weber Avenue and North Lincoln Street, Stockton, CA Appendix B Page 9 petroleum hydrocarbons and observed SPH plumes beneath the Waterfront Towers parking facilities; petroleum pipelines potentially associated with historic activities at the L&M OU and the Unocal Operable Unit (UOU) were previously removed from this location. In addition, the report presented a discussion of an aquifer test and system feasibility study conducted at the UOU. The objective of this study was to determine the quantity and quality of groundwater at the UOU, specifically within the previously installed collection trench at the site, to further evaluate the feasibility of remedial technologies currently applied at the L&M OU to groundwater beneath the UOU. Work was performed in accordance with Stantec's Work Plan for Additional Separate Phase Hydrocarbon Assessment, Unocal Groundwater Recovery Well Installation, and Remedial System Feasibility Study dated March 5, 2010 and in response to the California Regional Water Quality Control Board Email Approval dated May 5, 2010. In a meeting on August 8, 2011 , between Stantec and the RWQCB, Stantec requested revisions to the existing MRP (No. R5-2004-0820) which would reduce the monitoring and sampling frequency for several L&M OU groundwater monitoring wells. In a letter dated May 11, 2012, RWQCB concurred with Stantec's requested changes to MRP No. R5-2004-0820; the new MRP was implemented during site investigations beginning third quarter 2012. In April 2012, Stantec submitted a Work Plan for Separate Phase Hydrocarbon Removal at the Waterfront Towers Parking Lot. The system installation began on February 19, 2013 and was started on September 11 , 2013. The Remediation System Installation and Start Up Report was submitted by Stantec to the RWQCB on February 13, 2014. This system remains fully operational. In November 2012, Stantec observed the destruction of groundwater monitoring wells MW-29, MW-30, MW-32, and MW-33 located south and southwest of the Mormon Slough and south of the L&M OU, Delta View Apartments, and West Webber Avenue, Stockton, California. The well destruction was in concurrence with changes in the new MRP No. R5-2004-0820 and emails Stantec received from the RWQCB on October 30, 2012. The Well Destruction Report was submitted on March 8, 2013. On September 24, 2013 Stantec submitted a Request for Onsite Remediation Systems Shutdown and Rebound Test. Based on soil vapor monitoring data below human health screening levels, review of current and historical • groundwater monitoring and sampling data, and review of current system performance data (asymptotic and low removal rates), Stantec recommended (31 Stantec