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07 February 1997 <br /> AGE-NC Project No 96-0266 <br /> Page 7 of 8 <br /> the MCL in one sample The MCLs for cadmium,chromium,nickel, lead and zinc are 0 005, <br /> ' 0 005, 0 015, 0 1 and 5 0 ppm, respectively Concentrations of cadmium detected in samples <br /> are 2 4 times the MCL, chromium was detected at 30 times the MCL, nickel was detected <br /> ' at 15 times the MCL, lead was detected at 87 times the MCL, and zinc was detected at 14 <br /> times the MCL <br /> • Site investigations in Central Stockton, within a '/z mile of the site have concluded that <br /> ' shallow ground water in Stockton is of poor quality The Shallow ground water in Central <br /> Stockton contains concentrations of naturally occurring elements and characteristics that <br /> exceed the MCLS for several drinking water standards, and the shallow ground water is not <br /> ' considered potable for human consumption Furthermore, subsurface investigations have <br /> proven that elevated concentrations of the same metals quantified at the site, are commonly <br /> ' found in the shallow ground water and soils throughout Central Stockton Therefore the <br /> ground water at the site likely are "background"concentrations of metals, representing the <br /> naturally occurring concentrations metals in the shallow ground water in Central Stockton <br /> ' area <br /> • However, the CV-RWQCB has established that all ground water in the State of California <br /> should meet the levels of the MCLs for safe drinking water <br /> ' 52 RECOMMENDATIONS <br /> Based on the results of this investigation, AGE recommends the following foi your consideration <br /> • The UST presently located inside Building C should be properly removed or abandoned <br /> ' under permit from the PHS-EHD <br /> • According to Mr Harlin Knoll of the San Joaquin County PHS-EHD, the investigation of <br /> the former UST in San Jose Street will require additional investigation to determine the <br /> ' lateral and vertical extent of gasoline-impacted ground water At a minimum, four ground <br /> water monitoring wells should be installed in this area, including at least one well in the <br /> assumed up-gradient location, near the western property line to confirm the source and <br /> ' migration of the diesel onto the site <br /> • Soil samples collected during additional assessment of the UST area should be analyzed for <br /> ' TPH-d in addition to TPH-g and BTE&X <br /> • In a phone conversation with a representative of the CV-RWQCB, the requirements to <br /> address the ground water and soil associated with the metal plating shop were discussed In <br /> order for the CV-RWQCB to grant certified closure for the suspected release of the metals <br /> on the site, an additional investigation of the plating shop area would be required to evaluate <br /> I ' <br /> 1 <br />