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California Regional Nater Quality Control Board <br /> Central Valley Region ; <br /> Robert Schneider,Chair <br /> Alan C.Lloyd,Ph.D. Arnold <br /> Secretaryfor Fresno Branch Office Schwarzenegger <br /> Environmental 1585 E Street,Fresno,California 93705 Governor <br /> Protection (559)445-5116•Fax{559}445-5914 <br /> li ttp;lhvww.waterboards.ca.govlcen tralval l ey <br /> 14 December 2005 <br /> M. Scott Mansholt p �n <br /> Chevron Environmental Management Company <br /> 6001 Bollinger Canyon Road, Rm K2066 n nvuanni�'11I'5 <br /> San Ramon, California 94583-2324 <br /> REVIEW-SOIL AND GROUNDWATER INVESTIGATION REPORT, SECOND QUARTERLY <br /> MONITORING REPORT, US CAN— WELTY ROAD, VERNALIS,SAN JOA Q UIN COUNTY <br /> We have reviewed the referenced report, dated 10 October 2005 for the Chevron Old Valley Pipeline <br /> (OVP) project site that was submitted on behalf of Chevron by Science Applications International <br /> Corporation (SAIL). Additionally, we reviewed the Third Quarter 2005 Groundwater Sampling and <br /> Monitoring report dated 25 October 2005. The site is located at the southwest intersection of Welty <br /> Road and Highway 33, south of the unincorporated community of Vernalis, San Joaquin County. <br /> Currently, the site and surrounding area is agricultural,undeveloped land, light commercial properties, <br /> and rural residential. <br /> Background <br /> Previous site investigations completed between 1995 and 2003 indicated the petroleum hydrocarbons in <br /> soil and groundwater was confirmed attributable to historical OVP leaks. Elevated concentrations of <br /> petroleum hydrocarbons were reported at various depths with the vertical depth defined at between 44 <br /> and 50 feet. Review of the historical and current data indicates that elevated total petroleum <br /> hydrocarbon (TPH) concentrations in soil occur primarily at two separate on-site areas: near MW- <br /> 1/MW-3, and at GMX-81MW-2. TPH-impacted soil extends from five feet to approximately 40 feet in <br /> those areas with the highest values generally occurring at greater than ten feet. Bottom hole soil samples <br /> from those areas (approximately 50 feet) were non detect(ND) for TPH compounds. <br /> In addition to evaluating the property along the former OVP alignment, earlier on-site investigations <br /> were conducted near a former wastelburn pit and condensate pipe outlet located at the northeast corner <br /> of the onsite buildings. Concentrations of trichloroethene (TCE), benzene, and elevated levels of TPH <br /> as gasoline (TPHg)were reported in soil samples obtained from borings next to the wastelbum pit. <br /> TPHg and benzene, toluene, ethylbenzene, and xylenes (BTEX) concentrations were also reported in soil <br /> samples collected from the waste/burn pit area; TPHg at 61,000 gglL was detected in the MW-1 (located <br /> next to the former waste/burn pit and condensate discharge pipe) groundwater sample. Apparently, in <br /> 1995 an unspecified amount of material was removed from the waste/bum pit and disposed of at some <br /> unknown location. In a 1998 investigation, several soil samples reported TPH concentrations present <br /> but were ND for MTBE. <br /> California Environmental Protection Agency <br /> C',Recycled Paper <br />