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December 22,1995
<br /> Wright Project No. 4123-S
<br /> ( Site Closure Report
<br /> ✓ 6.6 Summary of Analytical Results
<br /> No detectable TPHG, TPHD, motor oil, or VOC were found in any of the excavation sidewall or
<br /> bottom samples collected during this investigation. No detectable cadmium was found in sample
<br /> EBS-1, and no detectable chromium was found in samples ESW-1, ESW-2, ESW-3, ESW-4, or
<br /> ESW-5. Similarly, no detectable zinc was found in samples ESW-2, ESW-3 or ESW-4. Metals
<br /> (trace elements) were found, however, in the following samples at the following concentrations:
<br /> ESW-1: Cadmium, 2.1 milligrams per kilogram (mg/kg); lead, 5.2 mg/kg; nickel, 23 mg/kg;and
<br /> zinc, 40 mg/kg. ESW-2: Cadmium, 2.5 mglkg; lead, 6.0 mg/kg; and nickel, 19 mg/kg. ESW-3:
<br /> Cadmium, 1.7 mg/kg; lead, 4.8 mglkg; and nickel, 1.2 mg/kg. ESW-4: Cadmium, 1.3 mg/kg;
<br /> lead, 4.2 mg/kg; and nickel, 31 mg/kg. ESW-5: Cadmium, 3.2 mg/kg; lead, 8.2 mg/kg; nickel,
<br /> 22 mg/kg; and zinc, 17.8 mg/kg. EBS-1: Chromium, 3.2 mg/kg; lead, 2.6 mg/kg; nickel, 18
<br /> mg/kg; and zinc,43 mg/kg. In our opinions, these trace element concentrations are typical for the
<br /> geology and soils for the region.
<br /> No detectable TP14G, TPHD, motor oil, BTEX, HVOC, or SVOC were found in Composite
<br /> Sample A. TRPH was found at a concentration of 800 mg/kg in Composite Sample A and
<br /> cadmium was found at a concentration of 3.8 mg/kg in Composite Sample A. In addition,
<br /> chromium was found at a concentration of 20 mg/kg, lead at 10 mg/kg, nickel at 190 mg/kg, and
<br /> zinc at 310 mg/kg in Composite Sample A. No detectable TPHD or motor oil were found in
<br /> Composite Sample B. TRPH was found in Composite Sample B at a concentration of 1,100
<br /> mg/kg.
<br /> 7.4 FIELD ACTIVITIES - GROUNDWATER REMOVAL AND SAMPLING
<br /> 7.1 Groundwater Removal and Sampling
<br /> During the excavation activities, groundwater was encountered at a depth of approximately 13.5
<br /> feet below grade and stabilized at approximately 10 feet below grade. No free product was noticed
<br /> floating on top of the groundwater, however, a slight sheen was observed as a result of the
<br /> affected soils still remaining in the sidewalls of the excavation. Absorbent pads were placed on top
<br /> of the groundwater exposed in the excavation to absorb the sheen. The groundwater was then
<br /> pumped from the excavation into a sanitary sewer in order to over-excavate the remaining affected
<br /> soils. Approval was granted by the City of Tracy to pump the groundwater into the sanitary sewer
<br /> system after the sheen had been removed. On August 23 and 24, 1995, approximately 14,000
<br /> gallons of groundwater were pumped and removed from the excavation to allow for additional soil
<br /> removal. On August 25, 1995, an additional approximately 20,000 gallons of groundwater were
<br /> removed from the excavation to allow for the collection of soil samples above and below the
<br /> groundwater level within the excavation. The groundwater was allowed to recharge prior to its
<br /> confirmatory sampling, which occurred less than three hours following its removal. On August
<br /> 25, 1995, Wright utilized the services of BTSI to collect one groundwater sample from within the
<br /> excavation for laboratory analyses. The groundwater sample was collected using a proprietary
<br /> _ sampling device attached to a long extension pole. The sampler was lowered into the groundwater,
<br /> filled, and closed prior to emerging, then transferred to the appropriate laboratory-supplied bottles.
<br /> BTSI collected the groundwater sample under the direct supervision of Ms. Linda A. Turkatte, of
<br /> the SJCPHS-EHD, and Wright personnel. Each bottle was sealed, clearly labeled, then placed
<br /> inside a ZiplocTM bag, then stored inside a chilled ice cooler for transport to the laboratory. The
<br /> bottles were transported under chain-of-custody documentation.
<br /> Upon completion of the soil and groundwater sampling and following notification of analytical
<br /> data, the excavation was properly backfilled with engineered soil by the general contractor.
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