SITE INFORMATION AND CORRESPONDENCE 1995-2004

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Mr. Fernando Amador -2- 14 December 1995 3. Page 3-3, Section 3.1.1, Phase I and II Investigations Figure 3-1 shows the locations of soil samples and monitoring wells. Although background soil samples are described in this section, their locations are not shown on any map in the FS. 4. Page 3-6, Section 3.1.3, Supplemental Soil Investigation The summary states that results from the field screening analyses did not correlate well with laboratory analytical results and the soil operable unit feasibility study (OU FS)will use only laboratory data. It is unclear if sufficient soil samples were taken for laboratory testing to characterize the investigated areas. 5. Page 4-1, Section 4, Overview of Site Conditions This section should include a summary of the background soil investigation. The summary should provide the rationale for sample location and number and discuss the results, particularly how background levels were established. 6. Page 4-1, Section 4.1.2, Area H Surface Soils The first paragraph describes polynuclear aromatic hydrocarbon (PNA) concentrations being in the range of background concentrations. This statement is related to Specific Comment No. 5 and should be clarified because the background concentration for chemicals which do not occur naturally should be zero. The subsequent paragraphs describe the presence of arsenic (1.5 to 231 mg/kg), copper (11.3 to 1,480 mg/kg), lead (4.9 to 1,268 mg/kg), and PCBs (<2 to 81 mg/kg) in Area H's surface soils. They also state that arsenic, copper, and lead had maximum background concentrations of 15.2 mg/kg, 76 mg/kg, and 185.6 mg/kg, respectively. Section 4.2.2 states that subsurface soil samples were not collected from Area II because of electrical hazards. Furthermore, based on the absence of facilities which could have been the source for metals or PCBs and relative immobility of the compounds, the FS assumes that the compounds detected in the surface do not extend five feet below ground surface (bgs). PG&E should assess the threat to ground water quality posed by the presence of arsenic, copper, and lead at concentrations which exceed background concentrations. The presence of utility lines should not prevent PG&E from taking additional samples beyond five feet bgs. Sampling techniques, such as using hand auger to clear utility lines and a Geoprobe to take depth samples, have been used successfully at other sites where typical drilling methods are not appropriate. Conclusions should be based on data, which are obtainable, and not on assumptions. 7. Page 4-3, Section 4.1.4, Hazelton Avenue Strip The FS states that PNAs as high as 14,529 mg/kg and lead above background levels were detected along the Hazelton Avenue strip, and an interim measure (concrete cap) approved by DTSC was implemented. The FS should state when the final measure will be proposed. The threat to ground water quality should be assessed at this strip if it has not yet been done.