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0 0 <br /> James L. Tjosvold, P.E. <br /> August 19, 1996 <br /> Page 10 <br /> Comment: <br /> 7. Page 4-3, Section 4.1.4, Hazelton Avenue Strip <br /> The FS states that PNAs as high as 14,529 mg/kg and lead above background levels were <br /> detected along the Hazelton Avenue strip, and an interim measure (concrete cap) approved <br /> by DTSC was implemented. The FS should state when the final measure will be proposed. <br /> The threat to ground water quality should be assessed at this strip if it has not yet been done. <br /> Response: <br /> 7. The combined FS will evaluate the need further remediation and will indicate <br /> what the final measure will be for the Hazelton Avenue strip. As stated in the draft <br /> Soil OUFS, (pg. 5-4, Section 5.3.1.1) no direct exposure pathway currently exists for <br /> the Hazelton Avenue strip surface soil because this area is paved; however, barrier <br /> controls such as the concrete cap need to be continued and maintained in order for <br /> this exposure pathway to remain incomplete. <br /> Zone A well MW-21 and Zone C wells MW-24 and MW-25 were recently installed <br /> immediately downgradient of the Hazelton Avenue strip. Groundwater samples <br /> from these wells indicate that groundwater has not been impacted by the <br /> concentrations detected in the nearby soil. <br /> Comment: <br /> 8. Page 4-3, Section 4.2.1, Area I Subsurface Soil <br /> The FS states that soil samples were collected at depths of one to 100 feet bgs with most <br /> samples collected within the upper 25 feet bgs. The FS should explain the rationale for the <br /> preponderance of samples at this interval. <br /> Response: <br /> 8. Most of the soil samples collected have been located between 0 and 25 ft below <br /> ground surface (bgs) because MGP residues have been associated primarily with the <br /> occurrence of fill material. Fill material occurs in the upper 5 to 10 feet, and as deep <br /> as 25 feet in places where former MGP structures occurred at these depths. Soil <br /> samples collected from native materials generally underlying the fill have shown <br /> nondetectable or very low concentrations of COPCs. <br /> General response to comments 9 through 13: Comments were raised (in comments <br /> 9 through 13) about inconsistencies in the sampling depths and types of analyses <br /> performed. This site has had several investigations with soil boring and well <br /> installation drilling activities designed for various purposes. The objective and <br /> scope of each phase were approved by DTSC, and since 1993, the RWQCB as well. <br /> As a natural result of this iterative process and the modifications that are made <br />