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FWM 1997.10-15 1S:48 #S61 P.05/06 October 14, 1997 • Page 2 water case. In a letter dated September 26, 1997, PHS/EHD responded that they could not conclude that the plume was stable and that additional assessment work would be required. A work plan addendum was required to be submitted by Tosco to PHS/EHD by October 14, 1997. A site meeting was held on October 10, 1997 between representatives of PACIFIC, Tosco, and PHS/EHD- Outstanding issues regarding the need for additional site assessment were reiterated by PHS/EHD. RESULTS OF PROJECT REVIEW It is PACIFIC's opinion that ample data exists to establish the size and stability of dissolved hydrocarbon groundwater plume beneath the site. Several years of data exist for wells prior to their destruction or submergence of well screens below the ground- water table. Data clearly shows that the dissolved hydrocarbon plume is small in size and is not migrating. The nearly 3 years of operation of the S VE system has removed a large mass of hydro- carbons(over 11,000 pounds of total petroleum hydrocarbons calculated as gasoline [TPH-g]) from the soil beneath the source area. The most impacted soil was removed to approximately 22 feet during removal of former underground storage tanks. It appears that only low concentrations of hydrocarbons exist in the soil beneath the site. The need for multiple deep borings is unwarranted. PACIFIC concludes that no further action is required based on the State Water Resources Control Board's(SWRCB's) recent rulings on similar sites. The site appears to meet the SWRCB's criteria for low-risk groundwater case closure. • All primary sources of release have been removed. Only double- walled tanks and piping remain at this active station. • The soil has been remediated to the degree practical. • It is unlikely that any hydrocarbon-impacted soil remains beneath the site. • The dissolved hydrocarbon has been defined and is stable. • Separate-phase hydrocarbons have never been detected in any well. • The nearest known municipal water supply is located approximately 1,800 feet crossgradient of the site. • There appears to be no potential for impact of streams or surface water- 3 1 jj657,VkV ater.?1I1657,VkV FTON.DOC