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- <br /> 7 <br /> n <br /> April 29, 1988 <br /> P81 88-4924.03 Harding Lowman Acsociates <br /> Mr. Hal M=iller <br /> The Southland Corporation <br /> Page 6 <br /> extended to a depth of four feet. Samples will be analyze <br /> r for the following constituents: benzene, toluene e d <br /> erhylbenzene, and TPH. xylenes, <br /> Since a s©il-gas investigation is a reconnaissance <br /> extensions of the original transect or additional transects <br /> may be required to define the distribution of chemicals. <br /> Such a modification can only be made after our field geolo- <br /> gist perforins a preliminary evaluation of initial soil--gas <br /> results. We have assumed that petroleum hydrocarbons have <br /> not migrated far from the site in <br /> ground <br /> of the soil-gas survey indicate a more extensive migrations <br /> then we are assuming, additional soil-gas probes may be <br /> required. <br /> We presently estimate that the 20 to- 25 probes and the field <br /> evaluation can be completed in two days. <br /> I <br /> Task 3 - Field investi ation <br /> Shallow Borin s and Monitorin Wells <br /> 5 <br /> After our evaluation of soil gas-data, we will design an in- <br /> vestigation l plan consisting of a number of borings and shal- <br /> low monitoring wells to obtain confirmatory data from soil t <br /> and water samples. The number of borings and wells we <br /> � install will be a function of the area] extent of Boil-gas <br /> vapors, as determined by the probes, ! <br /> Pate five on-site borings and three toWfive�wellsyortorcoff- <br /> site to evaluate the horizontal extent of petroleum hydro <br /> carbons. The borings and monitoring wells will be located <br /> F either within property boundaries or in the City of Tracy.. <br /> ` right-of-way. If they are within the City's right-of-way, <br /> we will obtain encroachment <br /> permits---from--the SJLHD:. ._ _eva__ .__ o__operats <br /> drill and continuously sampleveachluatborin .e the lathology, we .will <br /> titer continuous hollow-stem augers and ag using 8-inch-diam- <br /> ameter sampler. 2.S-inch-inside-- <br /> trations of volatile lcheinicals witwilh aeGas Tech�afor concen . <br /> I ization detector. The borings will extend into'thepsandion <br /> layer and approximately three feet below the <br /> n ,# <br /> level (a depth of approximately eight feet) , ground-water <br /> The methodology for installing, developing, and samplin <br /> ` wells is described in Appendix B. g the <br /> A <br /> t2 <br />