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PRELIMINARY SITE ASSESSMENT REPORT <br /> RMC PACIFIC MATERIALS <br /> KERLINGER AGGREGATE FACILITY <br />' 30350 SOUTH TRACY BLVD. <br /> TRACY, CALIFORNIA <br /> SAN JOAQUIN COUNTY SITE CODE #1737 <br /> IINTRODUCTION <br /> RMC Pacific Materials (RMC)maintains an aggregate mining operation at 30350 South <br /> I Tracy Boulevard in Tracy, California (see Figure 1) The facility has been in operation for over <br /> fifty years in the same location and the site is anticipated to remain an active aggregate quarry <br /> for years to come Between 1996 and 1999 three underground storage tanks (UST's) containing <br /> diesel fuel or diesel based products (State ID# 11073002, 1798001 and 1798005) were removed <br /> from the property under a directive from San Joaquin County (County) and the USEPA Diesel <br /> hydrocarbon product was discovered in the soil beneath each tank during their removals making <br /> it necessary for further work to be carried out <br /> In March 2002, the County directed RMC to develop a workplan to define the vertical <br /> I and horizontal extent of contamination around the location of the former UST's RMC submitted <br /> a plan based on advancing soil borings, dispersed over the subject areas, down to the <br /> groundwater table The plan was accepted by the County and work commenced on August 20, <br /> 2002 The following report describes the location of each of the five soil borings, the lithologies <br /> encountered in each of the borings, the installation details of three groundwater-monitoring wells <br /> and the preliminary laboratory results <br /> I <br /> SOIL BORING AND MONITOR WELL INSTALLATION <br /> As part of a preliminary site assessment five soil borings were drilled down to the <br /> groundwater table (-124 feet bsg) in the areas of the former USTs within the Kerlinger aggregate <br /> facility in Tracy, California(Figure 2) Three of the borings were converted to groundwater <br /> monitoring wells to obtain long-term groundwater data The other two borings were properly <br /> backfilled the full depth up to the surface with a neat grout on the day they were drilled <br /> Drilling commenced on August 20 and was completed by August 28, 2002 All borings <br /> were advanced using a Becker, 9-inch diameter twin-walled percussion, pneumatic drill rig This <br /> type of drill ng was selected because of its superior drilling capability in driving through the <br /> gravel and cobble-rich substrate found in this region of San Joaquin County A copy of the <br /> drilling permit and the driller's log sheets are included in Appendix B The percussion drilling <br /> technique uses very high pneumatic pressure to instantaneously transport all soil cuttings through <br /> the inner drill casing as the boring bit advances The cuttings come up the casing and through the <br /> exhaust manifold at a very rapid rate before they are decelerated in a centrifuge hanging from the <br /> Iside of the drill rig The material then drops down into a large rubber sample-collection tub lying <br />.� beneath the centrifuge's outlet port All soil cuttings were constantly monitored and logged using <br />