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Draft Removal Action Completion Report
<br /> Neighborhood C,
<br /> Mountain House,CA
<br /> Page 10
<br /> Samples collected after the first iteration of excavation were labeled with prefix of a single"C" followed
<br /> by the subparcel number followed by a suffix of a single letter designating the quadrant the sample was
<br /> collected from (C5-A), as described in section 3.1 above. Duplicate samples were labeled with a post
<br /> suffix of "D", C18-DD for example. Subsequent samples collected, after additional excavation, were
<br /> labeled with prefix of"CC" or "CCC" or "CCCC" with each iteration of the excavation. Letters were
<br /> transmitted to inform the DTSC of interim progress and requesting concurrence that the cleanup goal had
<br /> been met in specific areas on November 2,November 19, and November 25, 2013. The DTSC concurred
<br /> by e-mail on November 2,November 19, and November 25,2013,respectively(Appendix F).
<br /> 4.2 DISCRETE DEPTH SAMPLING
<br /> On October 23, laboratory analysis of samples collected from the eastern portion of the Site (Area 1)
<br /> indicated that the cleanup goal was not achieved in most subparcels. Analysis of additional samples was
<br /> requested. Discrete depth sampling, outside of the original scope of the RAW, was completed in order to
<br /> determine depth of excavation needed to achieve the cleanup goal. On October 25, preliminary
<br /> confirmation sample results indicated that additional excavation would be required for the Hill Group and
<br /> West Group, Area 2. Additional discrete depth sampling was completed (C2, C7, C 15, C 17, C21, C22,
<br /> C24, C31, C39). On November 5, preliminary confirmation sample results indicated that additional
<br /> excavation would be required for Area 3 in the middle of the dieldrin removal area and some additional
<br /> subparcels. Additional discrete depth sampling was completed(C3, C4,C6,C7,C9, C 10,C 11,C 13,C 16,
<br /> C23 C29). The discrete depth sample analytical results were only used for planning purposes and were
<br /> not used in lieu of confirmation samples after additional excavation was completed.
<br /> Discrete depth sampling was performed using a stainless-steel hand auger to collect samples from discrete
<br /> depths at 3-inch intervals and the sample jar was filled directly from the auger bit. The hand auger was
<br /> thoroughly decontaminated between samples by washing with non-phosphate detergent and double
<br /> rinsing with deionized water. Samples were labeled, placed in chilled coolers, and delivered under chain-
<br /> of-custody procedures to MAI.
<br /> 4.3 SUPPLEMENTAL CONFIRMATION SAMPLING
<br /> Supplemental sampling was required by the DTSC to confirm that dieldrin had not been spread or tracked
<br /> outside of the removal and encapsulation areas onto subparcels that were already confirmed to have met
<br /> the cleanup goal or along equipment routes outside of the dieldrin removal area. The additional sampling
<br /> was required because equipment was operated on haul roads established on sub-parcels that had been
<br /> previously confirmed to have met the cleanup goal. The samples collected to confirm that
<br /> recontamination did not occur were labeled as described above with a suffix of"E" or other notations(C-
<br /> 14E, CCCCI3E, and C17-E for example) (Figure 4,Appendix A). Additional sampling was also required
<br /> along the transit road between the removal area and the location where equipment was parked during
<br /> lunch breaks and overnight. The additional samples were identified as C1-E, DHAUL, LAYDOWN,
<br /> TRANSIT, and C41-DHAUL (Figure 5, Appendix A). All supplemental confirmation samples were
<br /> collected by directly inserting laboratory supplied glass jars into soil. Samples were labeled, placed in
<br /> chilled coolers, and delivered under chain-of-custody procedures to MAI.
<br /> 4.4 WASTE CHARACTERIZATION SAMPLING
<br /> Waste soil characterization sampling was conducted in general accordance with the RAW. During waste
<br /> soil emplacement to the encapsulation area from the excavation, waste characterization samples were
<br /> collected. The encapsulation area was divided into approximately 19 encapsulation zones, each
<br /> approximately 200 feet long, for characterization. Representative waste characterization samples were
<br /> collected from multiple depths within each zone as the trench was filled. The four samples from each
<br /> zone were composited at a 4:1 ratio(northern portion, zones 13 through 1) or 6:1 ratio (southern portion,
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