SITE INFORMATION AND CORRESPONDENCE FILE 1

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�i California Tank Lines, Inc. Page 2 1 3105 South El Dorado Street January 12, 2009 I Stockton, California 95206 during quarterly groundwater monitoring events. WRM reported TPHg in MW-4 at 26,300 ltg/L during the second quarter 2008 sampling event in June. Although TPHd has been reported as iron-detect in groundwater samples collected from MW- 1 since December 2007, prior to that, TPHd had been detected in most quarterly sampling events at concentrations greater than 1000 gg/L. WRM presented June 2008 groundwater results for TPHd and TPHmo detected in MW-2 at 10,900 µg/L and 12 ,600 ltg/L, respectively. Included in the SCM was a fate and transport analysis. WRM stated that based on lithological evaluation of CPT borings P1 , P2, P3 , and P4, there appears to be four sand zones located at the following intervals : 25-27, 56-66, 92- 107, and 120425 feet bsg. WRM also stated that depth-to- groundwater at the site is between 25 and 35 feet bsg, and groundwater gradient is toward the south/southeast. Based on results from groundwater samples collected adjacent to the CPT borings, WRM concluded that the TPHd and TPHmo plumes are constrained to an area directly surrounding the former motor oil underground storage tanks (USTs), and noted the residual TPHg portion of the petroleum hydrocarbon plume is constrained "to an area extending down gradient (southeast) of the former motor oil USTs toward MW-4 under South El Dorado Street" with the TPHg plume ranging from approximately 20 to 35 feet bsg. Using Rockworks© software to interpret preferential lithologic pathways for contaminant migration between this site and the adjacent site to the south, WRM determined that a relatively continuous zone of clayey silt with sand interbeds exists at approximately 20 to 35 feet bsg between MW-4 and P-2 at this site, and MW-7, P-7, P-8 , and P-9 at the adjacent site to the south. The sandy zone at first groundwater provided an avenue for lateral migration of TPHg and benzene between the two contaminated sites . WRM also noted that there exists a continuous clay bed from 35 to 40 feet bsg, providing a barrier to vertical migration of contaminants of concern. WRM concluded the following : • Based on lithological data collected from this site and the adjacent site to the south, "a fairly continuous low permeability clay horizon exists at approximately 35 feet bsg that could serve as an aquiclude . " • DIPE, the only contaminant detected below 65 feet bsg, may have been the result of being dragged down by the CPT equipment. • TPHd contamination is localized in the vicinity of MW-2, while TPHg, detected in the vicinity of MW-4 and P2 is the result of either an off-site source or an "overlap from diesel-range constituents . " • WRM presented constituent trend graphs to support the belief that a stable or declining plume of contaminants of concern exists. • WRM stated that "anaerobic natural attenuation processes appear to be operating in the vicinity of P2, based on the parameter trends compared to S-5 . " However, WRM did not explain as to what exactly is implied by groundwater results for dissolved oxygen, ferrous iron, nitrate, and sulfate data reported for P2 at 35 feet bsg, and S-5 reported at 65 feet bsg.