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Chevron 5 - 1 March 2007
<br /> Stone Brothers Management *any
<br /> 5400 and 5606 Pacific Ave, Stockton
<br /> 5- In order to continue to define the existing contaminant plumes, staff will recommend in
<br /> the revised or reissued CAO that all wells should be sampled according to the following
<br /> table for the frequency of sampling.
<br /> Frequency Quarter) Semi-Annually Annuall Discontinue
<br /> Wells MW-1, MW-2, MW-9R, MW-10A, MW-5, MW-7, None
<br /> MW-3, MW-4, MW-12, MW-18D, MW-10, MW-13,
<br /> MW-6, MW-8D, MW-24S, MW-24D MW-14, MW-14A,
<br /> MW-11, MW-16, MW-15R4, MW-17,
<br /> MW-25D, MW-28, MW-18, MW-19D,
<br /> MW-29, MW-30, MW-19S, MW-21D,
<br /> MW-31.. MW-21S, MW-22[),
<br /> MW-22S, MW-23 ,
<br /> AS-26, MW-27
<br /> 1- ENSR will evaluate 1,2-DCA concentrations annually for future recommendations.
<br /> 2- Sample first and third quarters.
<br /> 3- Sample third quarter.
<br /> 4- Sample quarterly for 2 consecutive quarters;then annually if no detections.
<br /> 6- Chevron recently switched laboratories to Lancaster Laboratories in Pennsylvania and
<br /> began analyzing TBA, DIPE, EDBE, and TAME, for compliance with CAO No. 5-00-
<br /> 0707. However, 1,2-DCA was not detected in any well during the Fourth Quarter of
<br /> 2006 for the first time since the First Quarter of 2003. In a phone conversation on
<br /> 22 February 2007, ENSR informed me that 1,2-DCA was detected in samples taken
<br /> during the First Quarter of 2007. Typical Method Detection Limits required in CAOs are
<br /> listed in the table below.
<br /> Constituents EPA Analytical Max. Detection
<br /> Method Limit (jig/1)
<br /> All Volatile Organic
<br /> Compounds (VOCs),
<br /> including Ethylene
<br /> Dibromide (EDB) and
<br /> 1,2-Dichlorethane
<br /> (1.2-DCA) 8260B 0.5
<br /> Total Petroleum
<br /> Hydrocarbons (TPH), as
<br /> Gasoline 8260B or 8015M 50
<br /> Benzene 8260B 0.5
<br /> Toluene 8260B 0.5
<br /> Ethylbenzene 8260B 0.5
<br /> Xylene 82606 0.5
<br /> MTBE 8260B 0.5
<br /> TBA 8260B 5
<br /> TAME 8260B 0.5
<br /> DIPE 8260B 0.5
<br /> ETBE 8260B 0.5
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