ARCHIVED REPORTS XR0010934 - Laserfiche WebLink

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A 30 X 25 foot area centered on the impacted area at the northern end of the former tanks, as defined by the earlier Site Assessment sampling, was outlined. A large track excavator was used to excavate this area. A six yard dump truck periodically transported contaminated soil to the designated remediation cell at the eastern end of the property. An AGI geologist monitored the progress of the operation by collecting frequent grab samples. The samples were tested for the presence of volatile hydrocarbons using a Flame ionization detector (FID). The samples were placed in a mason jar for approximately 15 minutes at which time the instrument probe was -inserted to obtain a headspace reading. By using the headspace readings, the excavation was controlled and clean soils were segregated from impacted soils. The upper 5 feet of soil excavated consisted of uncontaminated native soil and loose sandy fill material. This material was stockpiled on the southwestern portion of the excavated site and segregated away from the impacted soil. The contaminated soil mass was encountered ata approximately 5 feet. The excavation PP Y was subsequently carried to 35 feet where field measurements indicated all significantly impacted soils were removed. Laterally, contaminated soils were confined to a 35 X 31 foot area. The location of the excavation relative to other site features and the aerial limits of impacted soils is shown on the Exhibit 2. A plot plan and a three dimensional representation of the completed excavation is provided on r Exhibit 3. Volumetric calculations indicated that 840 cubic yards of contaminated soil was excavated. 'In addition to the unimpacted soil stockpiled on-site, supplemental clean fill in the amount of 800 yards was required to backfill the excavation. Once the walls and bottom of the excavation were deemed clean, the walls and base, with the exception of the south wall of the cavity, were sampled in the presence of the ..San Joaquin .Environmental Health inspector, Michael Collins. The south wall was sampled approximately two hours later when access allowed sample collection. The excavation was then backfilled with imported clean fill. During the time when the excavation was left open, the site was secured with temporary fencing. 5.0 CONFIRMATION SAMPLING AND ANALYTICAL RESULTS Confirmation samples were collected, one from each wall of the excavation at varying _ depths.dependent on accessibility by excavator. A bottom sample was also obtained from the center of the pit at a depth of 35 feet. Sample locations are depicted on the Excavation Plot Plan Exhibit 3. Samples were collected in brass sleeves from the excavator bucket, close to the teeth to insure that relatively undisturbed samples were taken. The. samples were immediately sealed with taped teflon-lined caps, labeled and placed in a cooler for later transport to the Smith Emery Company, a State of California certified laboratory under chain of custody control. The samples were analyzed for the aromatic components benzene, toluene, ethylbenzene and xylenes (BTEX) and Total Petroleum Hydrocarbons as diesel (TPHd). Laboratory results are 5of9