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Mr. Martin W. Inderbitzen <br /> May 27, 1986 <br /> Page 6 T <br /> <br /> length of flexible 1/4-inch diameter tubing to the probe of the meter.' <br />and inserting the tubing into the monitoring probe. Using this <br />method, measurements were obtained at S-foot intervals. <br /> <br /> Site Geology <br /> <br />The Ralph Martin property is directly underlain by 2 to 3 feet of <br />clayey top soil. Beneath the soil the materials generally consist of <br />stiff silt and clay mixtures with interbedded sand lenses. <br /> <br />When Borehole B4 was drilled during the previous investigation, three <br />distinct sand or sand and gravel layers were identified. When <br />Borehole B4R was drilled during this investigation, samples indicated <br />that there is only one sand layer present. The newer B4R log is more <br />tel iable because it is based on examination of undisturbed soil <br />samples. <br /> <br />The sand lenses identified are not continuous beneath the entire <br />property, but may be interconnected. The thickest occurrence of sand <br />occurs to the west and southwest in the direction of Boreholes M4 and <br />MS, where the highest concentrations of methane have been <br />identified. A thick sand layer was also identified in Borehole MS. <br /> <br />Any of the sand layers identified beneath the hill portion of the <br />Martin Property are probably not continuous with the sand layers that <br />occur in the majority of the low lying area to the east. The ground <br />surface elevation of much of the low lying area is less than the <br />elevation of the bottom of the landfill. <br /> <br />Conclusions and Recommendations <br /> <br />Based on the field test results, we conclude that.- <br /> <br /> 1. Combustible gas exists on the Martin Property in <br /> concentrations that exceed the legal regulatory limits for <br /> LFG. <br /> <br /> 2. Lithologic logs and the location and trend of concentrations <br /> of combustible gas indicate that the gas is LFG from the <br /> closed landfill. <br /> <br /> 3. The LFG migration boundary is roughly defined by Boreholes <br /> M6, M2, AND M9. <br /> <br /> 4. AlthOugh the soil samples do not indicate continuous sand <br /> lenses, gas has moved between lenses. <br /> <br />BROWN AND CALDWELL <br />PO BOX 8045 WALNUT CREEK. CA 94596-1220 · (415) 937-9010 TELEX 33-6490 · OFFICE AT 3480 BUSKIRK AVENUE PLEASANT HILL 94523 <br /> <br /> <br />