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Quarterly Groundwater Monitoring Report - First Quarter 2016 <br /> L&M Operable Unit- West Weber Avenue and North Lincoln Street, Stockton, CA <br /> April 29, 2016 <br /> • <br /> 1Q16 MONITORING DATA <br /> Southeast at 0.004 <br /> 2.2.2 Groundwater Sample Analysis <br /> Groundwater samples collected from the groundwater monitoring wells were submitted to Pace <br /> Analytical (Pace), of Davis, California, for analysis of TPHg, benzene, toluene, ethylbenzene,total <br /> xylenes (collectively BTEX), MTBE, and tert-butyl alcohol (TBA) by Environmental Protection <br /> Agency (EPA) Method 8260B. Samples were additionally analyzed for total petroleum <br /> hydrocarbons as diesel (TPHd) and total petroleum hydrocarbons as motor oil (TPHo) by EPA <br /> Method 8015M. All A-zone well samples were also analyzed for dissolved arsenic by EPA method <br /> 60108. <br /> 2.2.3 Groundwater Sampling Results <br /> Frequency of Range of Detected SFRWQCB Tier 1 Frequency of <br /> Constituent Detection Above Concentrations ESLzCB Ti Frequen nces <br /> the LRL /L <br /> TPHg 22 33 55 - 4,400 1004 19 22 <br /> Benzene 9 33 0.60 - 190 1 b 7 9 <br /> . Toluene 5 33 1.1 - 9.9 40a 0 5 <br /> Ethylbenzene 6 33 0.69 5.0 13b 0 6 <br /> Total Xylenes 7 33 1.1 - 22 204 0 7 <br /> MTBE 6 33 0.60 - 14 5a 1 6 <br /> TBA 14 33 5.3 - 83 12b 0 14 <br /> TPHd 33 33 86 - 6,400 NA 32 33 <br /> TPHo 33 33 96 - 4,800 1 1004 31 34 <br /> Notes: <br /> NA=Screening Level Not Available <br /> 1. LRL=laboratory reporting limit. <br /> 2. ESL=CRWQB February 2016 Environmental Screening Level for protection of drinking water(Tier 1-ESL) <br /> a. Based on Nuisance Odor <br /> b. Based on Direct Contact to Groundwater. <br /> 2.2.3.1 Separate Phase Hydrocarbons <br /> A-Zone: <br /> During 1Q16, sheen (SPH thickness of less than 0.1 inch) was observed in A-zone wells 2AMW-13 <br /> and MW-19. <br /> B-Zone: <br /> • During 1Q16, sheen was observed in one B-Zone well, MW-47. Separate phase hydrocarbons <br /> were reported in one B-Zone on-Site well, MW-52, at a measured thickness of 0.04 feet. Off-Site <br /> ® Stantec 6 <br />