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California Water Service Co any
<br /> Final Closure Report for Underground Storage Tank Removal
<br /> 1602 E. Lafayette St.,Stockton, CA
<br /> A summary of the results from the four confirmation samples collected from the bottom of the
<br /> excavation is provided below:
<br /> • No PCBs were detected above the laboratory reporting limit.
<br /> • The results for VOCs (EPA Method 8260) were all non-detected. The VOCs analyses
<br /> included BTEX, CL HC, Oxygenates (MTBE, TBA, DIPS, ETBE, TAME), 1,2 DCA, and EDB.
<br /> • The cadmium, chromium III, Cr VI, lead, nickel, and zinc results were significantly below the
<br /> Regional Screening Levels (RSL) for industrial sites.
<br /> • The results for TPHg were all non-detect (<1.0 mg/kg).
<br /> • The TPHd results were non-detect (<1.0 mg/kg) in the southeast and southwest corners of
<br /> the excavation (Tank 1 east and west end) and 110 mg/kg and 76 mg/kg, respectively in the
<br /> northeast and northwest (Tank 2 east and west end).
<br /> Likewise the results from the northern trench samples (samples 001, 002, 003) collected on
<br /> December 13, 2011 indicated no detection of PCBs, VOCs, or TPHg above the laboratory reporting
<br /> levels. Cd, Cr III, Cr VI, Pb, Ni, and Zn levels were significantly below RSLs. The TPHd result for the
<br /> easternmost sample (001) was 240 mg/kg and the concentration decreased as the samples moved
<br /> away (west) from the excavation with the middle trench sample (002) at 190 mg/kg, and the
<br /> westernmost trench sample (003) at non-detect (<1.0 mg/kg).
<br /> Similarly, the results of the soil samples collected on December 13, 2011 from the soil stockpiles
<br /> were non-detect for PCBs, VOCs, and TPHg, and were significantly below the RSLs for Cd, Cr III, Cr
<br /> VI, Pb, Ni, and Zn. The TPHd results ranged from 1.9 to 46 mg/kg.
<br /> The results from the southern trench samples collected on December 15, 2011 indicated no
<br /> detection of PCBs, VOCs, or TPHg above the laboratory reporting levels. Cd, Cr III, Cr VI, Pb, Ni, and
<br /> Zn levels were significantly below the RSLs. The TPHd results were 390 mg/kg and 630 mg/kg,
<br /> respectively for the eastern (sample 4E) and western (sample 5W) samples.
<br /> ' Also on December 15, 2011, three confirmation soil samples (samples 6E, 7M, 8W) were collected
<br /> in the northern trench beneath the 4-inch pipeline. The results were non-detect for PCBs, VOCs,
<br /> TPHg and TPHd. The Cd, Cr III, Cr VI, Pb, Ni, and Zn levels were significantly below the RSLs.
<br /> On December 19, 2011, five (5) confirmation soil samples were collected from pot-holes along the
<br /> main pipeline trench including where the pipelines turned 90 degrees south toward the building
<br /> and two samples were collected where the pipelines entered the building, one at 2 feet below the
<br /> pipelines and one at 4 feet below the pipelines. The results were non-detect for PCBs, VOCs, and
<br /> ' TPHg. The Cd, Cr 111, Cr VI, Pb, Ni, and Zn levels were significantly below the RSLs. The TPHd results
<br /> ranged from 19 mg/kg in the easternmost pot-hole to 430 mg/kg in the pot-hole at the building for
<br /> the sample 2 feet below the pipelines. The TPHd result for the sample at 4 feet below the
<br /> ' pipelines at the building was 140 mg/kg.
<br /> CHOW ENGINEERING, INC. 5
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