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<br /> Pacific Gas and
<br /> r Electric Company
<br /> L.k1 L +Q ' Technical and Ecological Services 9400 Crc v Canon Road
<br /> San Ramon,CA 94593
<br /> 04
<br /> 925.820.2000
<br /> August 18, 1999
<br /> Ms. Mary Serra
<br /> California Regional Water Quality Control Board
<br /> Central Valley Region
<br /> 3443 Routier Road, Suite A
<br /> Sacramento, CA 95827-3003
<br /> RE: Second Quarter 1999 Groundwater Monitoring Report
<br /> PG&E's McMullin Gas Dehydrator Station, Manteca, CA
<br /> Dear Ms. Serra:
<br /> Enclosed is the second quarter 1999 groundwater monitoring report for PG&E's McMullin Gas Dehydrator
<br /> Station. In August 1998, a compound formulated by Regenesis®called Oxygen Releasing Compound (or
<br /> ORC)was injected at this site to enhance biodegradation rates in the subsurface.
<br /> The following is a summary of field and laboratory results performed in May 1999:
<br /> • TPH-gas, and BTEX were not detected in the samples collected from well MW-1, MW-3, MW-4, and
<br /> MW-8.
<br /> • TPH-gas were detected in the samples collected from well MW-2, MW-5,MW-6, and MW-7 at
<br /> concentrations of 3,700 micrograms per liter(gg/L),430 gg/L, 5,100 gg/L, and 3,600 gg/L(3,500
<br /> gg/L for duplicate), respectively.
<br /> • Hydrocarbons in the diesel range were detected in the samples collected from well MW-I to MW-8,
<br /> but they do not match the pattern for diesel standard.
<br /> • Benzene was detected in the samples collected from well MW-2,MW-5, MW-6, and MW-7 at
<br /> concentrations of 78 I.tg/L,20 gg/L, 120 µg/L, and 450 gg/L(420 gg/L for duplicate),respectively.
<br /> • Toluene was detected in the samples collected from well MW-2,MW-5, MW-6, and MW-7 at
<br /> concentrations of 28 gg/L, 1.6 gg/L, 29 gg/L, and 21 gg/L(24 gg/L for duplicate),respectively.
<br /> • Ethylbenzene was detected in the samples collected from well MW-2, MW-5,MW-6,and MW-7 at
<br /> concentrations of 270 gg/L, 6.7 Etg/L, 570 gg/L,and 440 gg/L(420 gg/L for duplicate), respectively.
<br /> • Total xylenes were detected in the samples collected from well MW-2,MW-5, MW-6, and MW-7 at
<br /> concentrations of 490 4g/L, 3.9 gg/L,450 gg/L, and 190 ggIL(170 gg/L for duplicate), respectively.
<br /> • The direction of groundwater flow was to the southwest,with a hydraulic gradient of approximately
<br /> 0.001 foot per foot. The direction has shifted toward west(about 300)from last quarter's south-
<br /> southwest. Historically, groundwater flow has typically been to the south-southwest.
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