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I
<br /> ItLrmAn& Henn %Marind-1 ourth Quarrer 19M (,rnundAdtcr Monitoring
<br /> I Lhruarti 7 1999
<br /> I'd 11, K
<br /> 5 SUMMARY/CONCLUSIONS
<br /> On DeLcmbei 30, 1998, C ondor Earth I LLhuolog, , Enc, ((ondor) Conducted quarterly groundwatLr and surtace
<br /> Nvatcr monitoring at Herman & flLlen's Marina IOLdted at VeHILe Island Terry in Stockton California
<br /> Laboratory analyttLal result~ indicated that tliL gasafinL oxygenate MTBE was detected in samples collected
<br />' from monitor wL]ls MW-1 MW-2 MW-3 and MW-1 atLoncentrations of 1 3 ttg/l, 11,000 µg/1, 3 500 jig/] and
<br /> 1 5 µg/1, rLspeLtnVely Icrltan-butanol v<as detected In the groundwater samples collected from monitor wells
<br /> MW-'_ and MW-3 at LonLentrat ions of 150 pg/l and 130 µg/1 respectively I AME was detected In the
<br /> I groundx�ater sainplLs coIILLILd from monitor wells MW-2 and MW-3 at LoncLittrations of 37 µg/l and 8 3 fig/l,
<br /> respLLtiXLlr NonL of the, other oxygenates/addltnLs were de1LLted at or above the laboratory rLported detection
<br /> Inmos In any of thL groundwatLr samples
<br /> I'o[uLnL was dttccted In the, groundkcater Sample. L011CLted from monitor well MW-2 at a concentration of 1 2
<br /> µg/1 13 I FX LoristrtuLIIts were detected in the groundwater sample collected from monitor well MW--f at
<br /> concentrations of 24 tit;/], 0 4 jig/I, 2 3 ttg/l, and 22 pg/I, respects\ely l3TFX constituents were not detected in
<br /> the groundwater samples collected from monttor wells MW-1 and MW-3 rPH-G was detected In the
<br /> groundwater sarnple collected from monitor will MW-4 at a concentration of 0 2 mg/I I PII-G was not detected
<br /> in the groundwater samples collected from monitor wells MW-1, MW-2, or MW-3
<br /> Laboratory analytical results of the groundwater samples collected during the fourth quarter, 1998, monitoring
<br /> event are generally consistent with historical quarterly groundwater analytical data MTBL was detected for the
<br /> first time in the groundwater Sample Lol]cctLd from monitor well MW-1 The M IBE concentration In the
<br /> sample LollectLd from monitor well MW-2 dccrLased significantly with respect to the third quarter, 1998,
<br /> laboratory analytical results Iht. TAME conLcntration In the. sample collected from monitor well MW-2 also
<br /> decreased significantly with respect to the, third quarter, 1998, laboratory analytical rLsufts ILrtiary-butanol was
<br /> detcctcd m the groundwater sample LoIILcted from monitor well MW-3 for the first timL I ertlary-butanol was
<br /> detected (at a similar coiscLntration) in the groundwater sample collected from monitor well MW-2 for the first
<br />' time since the fourth quarter, 1997, sampling CVLnt
<br /> Intrinsic bioremediation parameters were monitored at the site for four quarters beginning with the fourth quarter
<br /> I1997, groundwater monitoring event Intrinsic bioremediation parameters analyzed for by the laboratory
<br /> included nitrate, sulfate, ferrous iron, and total alkalinity Intrinsic bioremediation parameters measured in the
<br /> fiLld include dissolved oxygen, oxidation-reduction potential, pll, electrical conductivity, and temperature
<br /> Intrinsic bioremediation V sting was discontinued at the site following the third quarter, 1998, monitoring event
<br /> because of Inconclusive results and because the purolcum hydrocarbon contamination at thL SOL is probably of
<br /> I secondary concLrn relative to thL presence of gasoline oxygenates `I he intrinsic bioremediation testing results
<br /> for the four quarters beginning with the fourth quarter, 1997, groundwater monitoring event and ending with the
<br /> third quarter, 1998, groundwater monitoring event, indicated that subsurface conditions at the site appeared to be
<br /> conducive to the aerobic and/or anaerobic breakdown of petroleum hydrocarbons however, the results did not
<br /> conclusively indicate that intrinsic bioremediation was occurring at the site No well-defined differences in the
<br /> intrinsic bioremediation parameters wLre established up-gradient (MW-1), in the plume center (MW-4), and
<br /> down-gradient (MW-2 and MW-3) at the site This may be in part related to the relatively Iow concentrations of
<br /> petroleum hydrocarbons present at MW-4 and the very short residence time of groundwater in the soil at the site
<br /> I Groundwater elevation measurements collected at the site on December 30, 1998, indicate that the average depth
<br /> to groundwater was approximately 4 6 feet bgs which is approximately one-half foot higher than the average
<br /> groundwater elevation measured on September 30, 1998 Groundwater elevation contours for December 30,
<br /> 1998, indicate that the groundwater gradient at the site is generally consistent with that measured on Sqgember
<br /> 18, 1997, December 31, 1997, March 27, 1998, June 26, 1998, and September 30, 1998 N&-W
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<br /> It3 CONDOR
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