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i' GEOMATRIX <br /> Ms. Mary Meays- <br /> San Joaquin County Public Health Services <br /> 29 September 1993 <br /> Page 3 <br /> SPECIFIC COMMENTS - <br /> Section 1.2, Pages 1-1 and 1-2' <br /> - Alton states that one underground gasoline. storage tank was removed.from the site in <br /> 1988" Based on information you provided in our meeting of 6. August 1993, this does <br /> not accurately reflect the.use of that tank...Also, the report does not mention a tank <br /> that was documented by others-as having been removed from the site in 1986 <br /> (Kaprelian, 1986). <br /> - The report does not describe the,soil contamination documented,at the site during 1986 <br /> tank removal activities and i'soil cleanup activities directed.by your office. , <br /> - The report states that "To the greatest extent possible, hydrocarbon-affected soil was <br /> removed..." This statement is not accurate for two'.reasons. <br /> t First, Alton's December 1990 documentation of the excavation activities, which states <br /> that the excavation extended vertically to a depth of 10 feet, indicates that high <br /> concentrations of diesel and gasoline were generally detected in samples collected from <br /> F 9.5 to 10 feet. There is no"documentation that the contamination stopped abruptly at a <br /> depth of 10 feet, and later;Borings have confirmed that high concentrations are.still <br /> present 10 feet beneath the site. No samples were collected from the bottom of the <br /> excavation to evaluate whether all hydrocarbon-affected soil was removed vertically. <br /> Second,.the excavation boundaries clearly terminate at the property boundaries to the <br /> north, east, and west, even.,-though-very.high. concentrations were detected in pre- <br /> i excavation soil samples collected-near these,property boundaries. Once again, no <br /> samples were taken at the walls-of the excavation to assess whether all hydrocarbon- <br /> affected soil was.removed•laterally: <br /> E Section 1.2.5, Page 1-5 <br />' - Alton does not mention the data collected in 1986. <br /> i <br /> Section 1.2.6.1, Pages 1-6 ands'1-7 <br /> - In describing the soil data'collected when the first four on-site monitoring wells were <br /> installed, Alton states that'no diesel,gasoline or benzene, toluene-, ethyl benzene, or: <br /> r xylenes (BTEX) were detected in soil samples. 'This is;misleading because only <br />