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Ms. Laurie Cotulla October 4, 1991 <br /> Tri Valley Growers, Thornton, CA Page 4 <br /> Response: The WET requires a 10-fold dilution of waste into the extract solution. <br /> The results of the extraction in terms of milligrams of soluble <br /> constituent per liter of extract (mg/1) is, therefore, equal to 1/10 of the <br /> concentration expressed in milligrams of soluble constituent per <br /> kilogram of solid waste. <br /> Clearly then even if all the total lead was in soluble form, the results <br /> of the WET could only be 1/10 of the content in soils in mg/kg. <br /> Therefore, further investigation and analysis of lead is not warranted. <br /> 8. Question: On January 29, 1988, 8 samples of stockpiled soil were field <br /> composited into one sample. This result was used to determine that the <br /> stockpiled soil was no longer contaminated. This method and number <br /> of samples composited is unacceptable. Additional borings will be <br /> necessary to determine that the backfilled soil is uncontaminated. <br /> Response: WaterWork did not perform this work, but we must assume that it was <br /> done with the approval of your office and was acceptable at that time. <br /> In an October 15, 1990 letter from your office, Darlene Ruess had just <br /> finished reviewing the file and had some questions on the analytical <br /> methods used on soil samples from MW1 to MW4, tanks pits and <br /> stockpiled soils. The analyses were correct at the time of collection as <br /> was the method of compositing. If the County had a problem with <br /> method of compositing, it should have been addressed at this time. <br /> Furthermore, at that time and currently in some areas, one composite <br /> sample was/is considered adequately representative for a volume of soil <br /> considerably less than 50 yds . <br /> The soils were backfilled into the former tank pit. The former pit is <br /> surrounded by monitoring wells that would detect any hydrocarbons <br /> leaching into the groundwater. RESNA believes it has adequately <br /> characterized these soils and no further work is warranted. <br /> 9. Question: Please submit a Work Plan for the additional soil investigation within <br /> 60 days from the date of this letter. Please locate the septic system on <br /> the adjacent property, 26500 North Galt Road, as leach lines provide <br /> conduits through which contamination quickly migrates. <br /> TQR1002.WP <br />