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 Appendix B is Page 6 Additional assessment activities were conducted at the Site in May 2004 to investigate the vertical extent of petroleum hydrocarbons in the vicinity of the Site. SECOR advanced one deep soil boring (SB-7) to a depth of approximately 140 ft bgs in the vicinity of well MW-17, installed shallow off-site well MW-45, and installed deep off-site wells MW-40 through MW-44 and MW-46. Three groundwater samples were collected at 117, 128, and 139 ft bgs using a HydropunchTM sampling device in soil boring SB-7. Results are summarized in SECOR's report entitled Additional Assessment Report and Work Plan for Additional Deep Groundwater Zone Assessment dated July 29, 2004. From March 21 through April 10, 2005, additional assessment activities were conducted at the Site. Seven B-zone groundwater monitoring wells (MW-47 through MW-53), one groundwater monitoring well intended to be a C-zone well (MW-54), and one groundwater monitoring well intended to be a D-zone well (MW-55) were installed, and three Geoprobe soil borings (GP-1 through GP-3) were advanced. Results are summarized in SECOR's report entitled Additional Deep Groundwater Zone Assessment Report, dated May 25, 2005. From July 13 through July 15, 2005, 16 soil vapor points were installed to monitor soil gas concentrations over time and determine radius of influence of the previously installed SVE system. On July 19 and 20, 2005 baseline soil vapor samples were collected from 12 of the 16 vapor points. The SVE system was initiated on August 18, 2005 for select wells. The complete scope of work and results of the soil vapor well installations, SVE start-up, and soil vapor sampling were summarized in SECOR's report entitled Soil Vapor Well Installation and Soil Vapor Extraction Start-Up Report, dated November 30, 2005. From March 21 through March 23, 2006, additional assessment activities were conducted at the Site in accordance with the Work Plan submitted January 4, 2006 entitled Work Plan for Additional DPE Feasibility Testing and Expanded Remedial System Installation. Seven piezometers and one DPE well were advanced for the purpose of conducting radius-of-influence analysis on several existing DPE wells. Pilot testing on DPE wells was conducted between April 4 and April 26, 2006. A temporary above ground extraction line was installed on DPE-13 as part of these • pilot testing activities. Results from the pilot testing were used to design and implement remedial system upgrades to better optimize contaminant mass ® Stantec