|
Pacific Gas and
<br /> & Electric Company f
<br /> Technical a4 Ecological 5ewices '3406,Crgw,Canyon Road
<br /> San Rar�dn;CA 94583
<br /> r"' r qua 925.820.2000
<br /> January 11,2000 03
<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: Third Quarter 1999 Groundwater Monitoring Report
<br /> PG&E's McMullin Gas Dehydrator Station,Manteca, CA
<br /> Dear Ms. Serra:
<br /> Enclosed is the Third 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 August 1999:
<br /> • TPH-gas,TPH-diesel, and BTEX were not detected in the samples collected from well MW-1,MW-3,
<br /> MW-4, and MW-8.
<br /> • TPH-gas was detected in the samples collected from wells MW-2,MW-5,MW-6 and MW-7 at
<br /> concentrations of 4,000 micrograms per liter(µg/L)(1,400 gg/L for duplicate),400 gg/L, 2,400 gg/L,
<br /> and 1,600 gg/L,respectively.
<br /> • Hydrocarbons in the diesel range were detected in the samples collected from wells MW-2,MW-5,MW-6
<br /> and MW-7 at concentrations of 3,200 gg/L(1,800 gg/L for duplicate), 1,000 gg/L,4,900 gg/L,and
<br /> 490 µg/L,respectively.
<br /> • Benzene was detected in the samples collected from wells MW-2,MW-5,MW-6,and MW-7 at
<br /> concentrations of 15 gg/L (.13 gg/L for duplicate), 9.4 gg/L, 25 gg/L, and 160 gg/L,respectively.
<br /> • Toluene was detected in the samples collected from well MW-2,MW-6, and MW-7 at concentrations
<br /> of 11 gg/L(4.9 gg/L for duplicate), 14 gg/L, and 7.8 gg/L,respectively. .
<br /> • Ethylbenzene was detected in the samples collected from wells MW-2,MW-5,MW-6,and MW-7 at
<br /> concentrations of 58 gg/L(52 gg/L for duplicate), 1.6 gg/L, 220 gg/L,and 75 gg/L,respectively.
<br /> • Total xylenes were detected in the samples collected from wells MW-2, MW-5,MW-6, and MW-7 at
<br /> concentrations of 140 gg/L(150 gg/L for duplicate), 2.6 gg/L, 170 gg/L, and 57 gg/L,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 shifted west(about 20°)from last quarter's flow direction of south-
<br /> southwest. Historically, groundwater flow has been to the south-southwest.
<br /> 402_331-99_250.doc
<br />
|