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Chevron #9-0557 '� 1"`� June 2013 <br /> 139 Center Street South, Stockton <br /> Claim No: 5820 <br /> Most Recent Concentrations of Petroleum Constituents in Groundwater <br /> Sample Sample TPHg Benzene Toluene Ethyl- Xylenes MTBE TBA <br /> Date (Ng/L) (Ng/L) (Ng/L) Benzene (Ng/L) (Ng/L) (Ng/L) <br /> ( /L) <br /> MW-3 08/23/06 <50 <0.5 <0.5 <0.5 <0.5 <0.5 <5 <br /> MW-5 08/01/07 <50 <0.5 <0.5 <0.5 <0.5 <0.5 4 <br /> MW-6 08/23/06 <50 <0.5 <0.5 <0.5 <0.5 0.8 <5 <br /> MW-7 08/10/12 170 <0.5 <0.5 <0.5 <0.5 <0.5 <2 <br /> MW-8 08/10/12 <50 <0.5 <0.5 <0.5 <0.5 <0.5 <2 <br /> MW-13 08/23/06 <50 <0.5 <0.5 <0.5 <0.5 <0.5 <5 <br /> MW-14 08/10/12 <50 <0.5 <0.5 <0.5 <0.5 1 <2 <br /> MW-15 08/10/12 470 <0.5 <0.5 <0.5 <0.5 <0.5 29 <br /> MW-15d 08/10/12 19,000 650 410 960 1,500 <5 <20 <br /> MW-16 08/01/07 <50 <0.5 <0.5 <0.5 <0.5 <0.5 <2 <br /> MW-17 08/10/12 <50 <0.5 <0.5 <0.5 <0.5 <0.5 <2 <br /> MW-18d2 08/10/12 1,200 2 1 0.8 2 <0.5 <2 <br /> WQOS - 5 0.15 42 29 17 5a 1,200 <br /> NA: Not Analyzed, Not Applicable or Data Not Available <br /> pg/L: Micrograms per liter, parts per billion <br /> <: Not detected at or above stated reporting limit <br /> TPHg: Total petroleum hydrocarbons as gasoline <br /> MTBE: Methyl tert-butyl ether <br /> TBA: Tert-butyl alcohol <br /> WQOs: Water Quality Objectives, Regional Water Board Basin Plan <br /> a: Secondary maximum contaminant level (MCL) <br /> b: California Department of Public Health, Response Level <br /> Groundwater Trends <br /> • Since 1991, twenty-one groundwater monitoring wells have been installed and regularly <br /> monitored (nine wells abandoned). Benzene trends are shown below: Source Area <br /> Shallow (MW-15), Source Area Deep (MW-15D), Near Downgradient (MW-7), and Far <br /> Downgradient (MW-8). The concentrations of petroleum hydrocarbon plume is stable, <br /> defined and decreasing. <br /> Source Area Well -shallow Source Area Well -deep <br /> BENZENE Results for MW-15 BENZENE Results for MW-1513 <br /> 3000 15 14001 r 15 <br /> I r <br /> 2500 I t 17 1200�-...-� -._"-___�__ --__.._ ___t• »._ t17 <br /> 19 <br /> 1000 19 <br /> 20001 21 m d I -21 m <br /> j 8001 <br /> z 1So0 23.S23.S <br /> w 600 <br /> 1000' 77/ 25 O tr 400 -! 250 <br /> L 27 ' � r-� -` <br /> 5001 - 'r- w �� � I '� 27 <br /> t29 2004- 1. ___ s,. - <br /> ,y0a X31 0 r31 <br /> s'� 4� a'�p 4� d' s�,a•,� ,`�, r� s'�y � a,p � ,d s�,.n r4,y �, <br /> BENZENE Depth to Water TT.d BENZE <br /> --- NE Depth to Water ---Trend, <br /> Page 9of11 <br />