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M. Scott Mansholt - 3 - 14 December 2005 Chevron Environmental US Can-Welty Road Soil boring SB-17, was advanced approximately 150 feet east-northeast of the site to evaluate offsite soil and groundwater in that area. However,the boring is closer to the adjacent former Vernalis Pump StationlRoberts OVP site (now referred to as Bellini). Low TPHc concentrations (17 to 60 mg/kg)were reported in shallow soil and 6,700 TPHc and 510 mg/kg TPHg was reported in the 42-foot sample from SB-17. Benzene and MTBE were ND and the PAHs were ND to low concentrations at or above the respective method detection limits (MI)Ls). Groundwater Groundwater samples were obtained from three of the four borings, except SB-15 that was converted to monitoring well MW-5 which was sampled as park of the second (and third)quarterly groundwater monitoring events (discussed in this report). TPHd concentrations of 450, 200, and 150,000 pg/L, were reported in borings SB-13, 14, and 17 groundwater samples, respectively. In addition, TPHg in SB-17 was 480 pg/L and ND in SB-13 and SB-14. BTEX and MTBE results were ND; the PAH compounds were ND and at or slightly above their respective MDLs. Quarterly groundwater monitoring was conducted during July 2005 as part of the third quarter sampling evaluation. Review of the analytical results indicates an increase of TPHd in three of the four on-site monitoring wells previously reporting low concentrations. MW-1 remains unchanged with a sheen; MW-2, located on the northwestern portion of the site, has increased from 2,300 pg/L in 1998 to 150,000 µg/L TPHd and from ND to 310 µg/L TPHg; concentrations of PAH compounds were also detected. Similarly, TPHd in MW-3, located on the east portion of the site,has increased from 300 pg/L in 1998,ND in 2002, 86 in 2003, to 5,700 pg1L during July 2005. TPHg and PAHs were essentially ND in MW-3. Upgradient well MW-4 (SE corner of the site) remains unchanged with TPH compounds ND for the same monitoring period. Based on our review, we have the following comments: • Petroleum-impacted soil appears to occur in close proximity to the OVP at a variety of locations and depths from approximately five to greater than 40-feet,but generally is present at higher concentrations beginning at 10 to 12 feet or deeper. However, according to the findings to date, it appears that there are two separate areas of affected soil (MW-2/GMX-8 and MW-1/MW-3 [next to the waste/bum pit]) that are more heavily impacted as result of leaks from the OVP. However, it appears that impacts contributed from historic site activities have affected conditions in the area of the waste/bum pit. * The report suggests that impacted soil in an area southeast of former boring GMX-11 (east to northeast of MW-3) has yet to be delineated. The vertical extent of impacted soil appears to be defined at approximately 50 feet by on-site borings MW-2 and GMX-1 B and off-site borings GMX-11 and 12. The extent of impacted soil beneath the on-site structures is unknown,but soil boring samples south and upgradient were ND for TPH compounds.