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'' ate- � ���,• w.,x, ,� � " "�.:"? �'" "� <br /> �'°�x ��� ...�:.a... �e w ,�, .r '�;' •� u'°' :�, mss«--+; � , h %`3�-d.�e::i <br />, <br /> February 8, 1991 <br /> GASCO Gasoline Station �Y <br /> 'r01 j No. 3-3J054-31 Page 2 <br /> ;.� <br /> SCC+E E WGRK <br /> f.x-;wltech proposes to drill f sur exploratory borings at the site and convert them to <br /> ' groundwater coeds, The !Gcsdons of proposed wells are in the approximate <br /> corners of the site as in Figue 2. <br /> Prior to a►;u drilling, Exceltech will contact Underground Service Alert (USA) so that <br /> the underground utilities on adjacent public right-of-ways can be marked by their <br /> respective companies. A site safety plan relating to the investigation is attached in <br /> Appendix A. <br /> Exploratory Drilling <br /> Exceltech will drill the borings using a truck-mounted drill rig and hollow-stem auger. <br /> The auger and other tools used in the hole will be steam cleaned before use. Relatively <br /> undisturbed soil samples will be collected following Exceltech's soil sampling protocol <br /> (Appendix B) at 5-foot depth intervals or at any significant change in lithology. A <br /> - modified California split-spoon sampler with internal brass liners will be used to collect <br /> the samples. The baring will be advanced to the desired sampling depth and the <br /> sampler will be lowered to the bottom of the hole. It will be driven ahead of the auger <br /> with a 140-pound, rig-operated hammer. The sampler will be removed from the hole <br /> and disassembled into its component parts. The lowermost brass liner with sample will <br /> be capped, labeled, logged on a chain-of-custody form, and placed in a chilled ice chest <br /> for transport to a state-certified laboratory for analysis. <br /> An Exceltech geologist will prepare a description of the subsurface colAitions <br /> encountered during drilling. The encountered soils will be classified using the Unified <br /> Soil Classification System. The geologist will also conduct a field test for h,drocarbon <br /> contaminant vapors from selected soil samples using a portable photo ionization <br /> detector. <br /> Drilling cuttings will be placed in Department of Transportation (DOT)-approved 17H <br /> drums. The drums will be left at the site until laboratory analytical results are known, <br /> At that time, the drums will be properly disposed of by Darpetrol. <br /> Groundwater Monitoring Well Construction <br /> Groundwater monitoring wells will be constructed in each of the exploration borings. <br /> All monitoring wells will be built in accordance with permit requirements of San <br /> Joaquin County. The wells will be constructed of 4-inch-inside-diameter flush-threaded <br /> polyvinyl chloride (PWC)casing: no glues or solvents will be used. After drilling the <br /> 4 boring to the desired depth, the PVC casing will be installed in the borehole and a filter <br /> pack of clean sand will be placed in the annular space to approximately 1 to 2 feet above <br />