ARCHIVED REPORTS_QUARTERLY GROUNDWATER MONITORING REPORT 1ST QUARTER 2016

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Quarterly Groundwater Monitoring Report - First Quarter 2016 L&M Operable Unit-West Weber Avenue and North Lincoln Street, Stockton, CA April 29, 2016 • 3.0 Remedial Systems Status 3.1 DUAL PHASE EXTRACTION SYSTEM The on-site dual phase extraction (DPE) system has been shut down since March 27, 2014. Historical operational data is provided in Appendix D. In a letter dated April 7, 2014 the RWQCB- CVR requested submittal of a proposal to remove the existing DPE remedial equipment while leaving pertinent infrastructure in place to allow for response with a mobile treatment unit if necessary. Stantec submitted a Remediation Equipment Removal Proposal dated May 30, 2014 and additionally proposed to temporarily retain the groundwater extraction and treatment (GWET) portion of the DPE system for processing M&S purge water and any additional groundwater generated by future remedial efforts. Stantec received approval from the RWQCB-CVR in a letter dated November 2, 2014. Stantec removed the remediation system between January 12 and 14, 2015. Details of the removal of the remediation system are discussed below. 3.1.1 DPE System Removal Activities Between January 12, 2015 and January 14, 2015, Stantec oversaw JHA Remediation of Sacramento, CA disassemble and remove the soil vapor extraction (SVE) components of the DPE system from the Site. The GWET components were left in place for use in processing Site monitoring and sampling purge water. 3.1.2 DPE (Groundwater) Operational and Analytical Data - 1Q16 The GWET portion of the DPE system is the only remediation system that remains on-Site. During the 1Q16, the GWET system was used to process purge water generated during Site monitoring and sampling event. On January 14, 2016 approximately 985 gallons of purge water associated with the 1 Q16 M&S event was processed by the GWET system. This resulted in the recovery of 0.003 lbs (0.0004 gallons) of TPHd and 0.001 lbs (0.0002 gallons) of TPHo and 0.0004 lbs. (0.0001 gallons) TPHg. No appreciable amount of MTBE,TBA, or benzene was recovered during 1 Q16. Historic DPE system operating, analytical and mass recovery data can be found in Appendix D. 3.1.3 Historic DPE Mass Removal (Groundwater) Since startup on March 18, 2004 the groundwater portion of the DPE system has treated approximately 7,307,672 gallons of water resulting in the recovery of approximately 153 lbs (25 gallons) of TPHg; 9,572 Ibs (1,333 gallons) of TPHd; 5,154 lbs (676 gallons) of TPHo; 0.08 lbs (0.01 gallons) of benzene; 0.03 lbs (0.005 gallons) of MTBE; and 0.58 lbs (0.09 gallons) of TBA. • ® Stantec 9