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Regional Board Staff Recommendations 10 August 1990 <br /> Preliminary Site Investigation <br /> CASE #2 <br /> No Further Action Required <br /> A ground water investigation is not required when all of the <br /> following conditions are met: <br /> A. The total petroleum hydrocarbon and/or total oil and <br /> grease levels are less than 100 ppm in the soil samples <br /> beneath the tank, within the first two feet of native soil . <br /> NOTE AGAIN THAT THE 100 PPM LEVEL IS NOT A CLEAN-UP LEVEL. <br /> THE ORIGIN OF THE 100 PPM LEVEL WAS TO DEVELOP A METHOD TO <br /> PRIORITIZE THE CASE LOAD AND INDICATE WHETHER A SIGNIFICANT <br /> VOLUME OF FUEL HAD BEEN RELEASED OR DISCHARGED. THE LEVEL <br /> OF CLEAN--UP IS TO BE DETERMINED BY ASSESSING THE POTENTIAL <br /> IMPACT OF RESIDUAL SOIL CONTAMINATION ON THE GROUND WATER. <br /> IN MANY INSTANCES IT MAY NOT BE APPROPRIATE TO LEAVE SOIL <br /> IN-PLACE WHICH IS CONTAMINATED WITH TOTAL PETROLEUM <br /> HYDROCARBONS OR OTHER COMPOUNDS AT ANY CONCENTRATION. <br /> B. No detectable residues for petroleum hydrocarbons are <br /> found in the soil at/below the seasonal high ground water <br /> level . <br /> NOTE: At the discretion of the local agency, in addition to <br /> the samples from the base of the excavation, sidewall <br /> samples from the excavation may be taken to verify that no <br /> lateral migration of pollutants has occurred. <br /> C . The soil has low permeability; predominantly silt and <br /> clay with no sand and/or gravel layers . <br /> D. The ground water has not been impacted as evidenced by <br /> non-detectable levels of petroleum hydrocarbons in the water <br /> sample( s ) from the tank excavation. <br /> Regional Board staff concur that if the above conditions are <br /> satisfied the site should not pose a significant water quality <br /> threat. However, conditions may exist, i .e. an extremely <br /> sensitive site, where additional investigation is appropriate . <br /> Site Closure Requirements : All factors in Table 3 must be <br /> considered when evaluating a Case #2 closure. Although all <br /> factors may not be applicable or obtainable, the Local <br /> Implementing Agency and Regional Board expect the Responsible <br /> Party to present as much information as possible; and, where the <br /> information is not applicable or available, explain why it is <br /> not. Submittal of a complete closure request addressing A, B, C, <br /> and D above, and Table 3 will allow the Regulatory Agencies to <br /> evaluate the closure request expeditiously. <br /> 9 <br />