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California Re ional Water Quality Control Board <br /> `� <br /> Central Valley Region � �� <br /> Robert Schneider, Chair � <br /> Linda S. Adams Arnold <br /> Secretary for Fresno Branch Office Schwarzenegger <br /> Environmental 1685 E Street, Fresno,California 93706 <br /> 559 445-5116 • Fax 559 445-5910 Governor <br /> Protection � ) � ) <br /> http://www.waterboards.ca.gov/centraIvaIley <br /> 20 November 2006 <br /> M. Scott Mansholt <br /> Chevron Environmental Management Company <br /> 6001 Bollinger Canyon Road <br /> Rm K2066 <br /> San Ramon, CA 94583-2324 <br /> REVIEW OF THIRD QUARTER 2006 GROUNDWATER MONITORING AND SAMPLING <br /> REPORT— VERNALIS PUMP STATION PROPERTY, VERNALIS, SAN JOAQUIN AND <br /> STAN/SLAUS COUNTIES <br /> Regional Water Board staff has reviewed the referenced groundwater sampling report, dated <br /> 25 October 2006 and prepared for Chevron by Science Applications International Corporation <br /> (SAIC). The Vernalis site consists of two properties: Bellini, the northern triangular portion <br /> (formerly Roberts) and the southern Arcos property. The properties were part of the former <br /> Vernalis Pump Station previously owned and operated by predecessors of Chevron as part of <br /> the historical Old Valley Pipeline (OVP) system. <br /> There are two offsite and five onsite monitoring wells (MWs) associated with this site that have <br /> been monitored irregularly since 1998 and on a quarterly basis since early 2005. Monitoring <br /> and sampling were completed 10 August 2006. <br /> Onsite well, MW-1 contains a sheen and is not sampled (a petroleum-absorbing device is <br /> used in this well); one inaccessible well was not sampled. The groundwater elevation has <br /> steadily declined and three onsite wells did not have sufficient water for sampling. The two <br /> offsite wells act as downgradient sentinel wells, this event only the two offsite wells had <br /> sufficient water for purging and sampling. Groundwater flow is easterly at an approximate <br /> gradient of 0.001 ft/ft. Depth to water is between 34 and 38 feet. <br /> Groundwater samples were submitted for analysis of total petroleum hydrocarbons as gasoline <br /> (TPHg), TPH as diesel (TPHd), benzene, toluene, ethylbenzene, and xylenes (BTEX), and <br /> polynuclear aromatic hydrocarbons (PAHs). TPHd was ND and 62 ug/I in MWs-6 and 7, <br /> respectively. TPHg, PAHs, and BTEX were non detect (ND) at their respective method <br /> detection limits. <br /> Historically, TPHg and BTEX compounds have not been detected in groundwater and SAIC <br /> recommends these constituents be eliminated from future sampling events. <br /> California Environmental Protection Agency <br /> ca Recycled Paper <br />