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19 June 2000
<br /> AGE-NC Project No 96-0232
<br /> Page 10 of 35
<br /> site are depicted in Figures 25, 26 and 27 The area of the most intense MTBE-impact to
<br /> ground water was encountered in the southwestern dispenser area, extending northward to
<br /> the mini-mart and southwestward to the southwest corner of the subject property
<br /> Ground water monitoring was performed at MW-1, MW-2, MW-4, MW-5, MW-6 and
<br /> MW-7 Ground water depths were recorded at approximately 10 feet bsg(Table 3), general
<br /> ground water flow direction on the site was locally variable between southeast and southwest
<br /> at a general gradient of 0 003 (Figure 28) Laboratory analysis of ground water samples
<br /> coIIected from MW-1, MW-2, MW-4, MW-6A, MW-6B and MW-7 detected MTBE at
<br /> concentrations as high as 3,700 µg/1 (MW-1), TAME, ETBE and TBA were detected in
<br /> samples collected from MW-1 at concentrations of 15 µg/l, 11 jig/]and 54µg/1,respectively
<br /> Methanol was detected in samples collected from MW-5, MW-6A and MW-6B at
<br /> concentrations of 180 µg/l, 120 µg/1 and 97 µg/1, respectively Analytical results of ground
<br /> water samples are summarized in Table 5 Analysis of a grab ground water sample collected
<br /> from RDW-1 detected MTBE at a concentration of 20 µg/I, methanol was detected from the
<br /> CSA-1 and CSA-2 grab water samples at concentrations of 120µg/1 and 73 µg/1,respectively
<br /> (Table 7)
<br /> A report of findings (Quarterly Report-Second Quarter 2000) documenting investigation
<br /> activities performed in April 2000 Is in preparation and will be submitted to the PHS-EHD
<br /> and the RWQCB-CVR upon completion
<br /> May 2000 - Six multi-level ground water monitoring wells (MW-8, MW-9, MW-10,
<br /> MW-11,MW-12 and MW-13)were installed on and off-site to maximum depths of 150 feet
<br /> bsg (Figure 3) As-built well construction diagrams of MW-8, MW-9, MW-10, MW-11,
<br /> MW-12 and MW-13 are depicted in Figures 29, 30, 31, 32, 33 and 34
<br /> Twenty-three initial ground water samples were collected from MW-8, MW-9, MW-10,
<br /> MW-11,MW-12 and MW-13 Laboratory analysis of initial ground water samples detected
<br /> MTBE in seven samples at concentrations as high as 2,500 µg/1 (MW-13A), TPH-g in five
<br /> samples at concentrations as high as 130 µg/l, TPH-d in fourteen samples at concentrations
<br /> as high as 940µg/l, BTEX compounds in two samples at concentrations as high as 33 µg/1,
<br /> TAME in one sample at a concentration of 87 µg/l, ETBE in one sample at a concentration
<br /> of 2 5 µg/1, TBA in four samples at concentrations as high as 24 µg/1 and ethanol in 21
<br /> samples at concentrations as high as 1,200,000 µg/1 Analytical results of ground water
<br /> samples are summanzed In Tables 5
<br /> Due to the high concentrations of ethanol, which were detected only in samples collected
<br /> from the multi-level monitoring wells, samples of the '/4-inch coated bentonite pellets
<br /> (Sinclair Services) were submitted In a VOA container filled with bottled water for
<br /> laboratory analysis for ethanol The laboratory analysis detected dissolved ethanol at a
<br /> RdvancedCeoEn%iron mental,Inc
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