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.. p !! a <br /> Workplan For Groundter Monitoring Well Installation And ContinW Quarterly Ground-Water Sampling <br /> File 8013-02 <br /> July.12, 1999 <br /> Page z <br /> Oat approximately 20 feet bgs. Ground-water contamination was also detected in this well. No <br /> soil contamination was reportedly detected in well boreholes-MW-1 and MW-3. <br /> In December, 1994, o'verexcavation of .contarhinated soil in the vicinity of the former <br /> underground tank was''conducted. .Approximately 108 cubic.-yards of'contaminated soil was <br /> excavated from the vicinity of the former tank. I <br /> In November 1995 and;January 1996, a total of eleven soil probe holes were.advanced in°the <br /> vicinity of, and hydrologically down-gradient of, the former tank: Soil and grourid=water <br /> samples were'collected to define the lateral extent of soil and groundwater,contamination. The <br /> results were presented, in the February 1996:.report by Wm. J. Hunter & Associates titled <br /> Interim Report Covering Results of Soil& Groundwater Investigation. <br /> In May 1996, a fourth ground-water monitoring well (MW-4).was installed hydrologically down- <br /> gradient of the site (seed Figure 3). This well was installed to a depth of approximately"25 feet <br /> bgs, and screened between the depths of approximately 5 feet and 25ifeet bgs: . Quarterly <br /> ground-water monitoring and ground water sample collection from the four wells has continued, <br /> since then. <br /> In December 1998, JJW Geosciences prepared a workplan for placement and .monitoring of <br /> Oxygen Release Compound (ORCO) in well MW-2. The workplan was' approved`by i San <br /> ;-Joaquin County in December 1998. The field work for the'ORCO placement and monitoring <br /> was conducted by Del-Tech Geotechnical Support Services (Del-Tech). Following collection of <br /> ground-water samples.;, in March 1999, .an Oxygen_ Release- Compound (ORCO) sock <br /> approximately 3% inches in diameter by 10 feet in length was inserted into` monitoring well <br /> MW-2. The. ORCO sock released oxygen into the subsurface as a means of enhancing <br /> biodegradation. Following depletion of the ORCO sock, a determination of:its effectiveness will <br /> be presented. <br /> PROPOSED SCOPE OF WORK <br /> In response to the San' Joaquin County directive, JJW Geosciences proposes :the following <br /> scope of work: <br /> 1.:Upon San Joaquin County approval of this workplan,_we will forward a copy of this <br /> workplan and'fan appropriate permit application and fee to San Joaquin County for <br /> permitting purposes. We will .include copies of the. chosen well driller's license, <br /> OSHA hazardous waste training certificates, and a site-specific" health and safety <br /> plan. <br /> _ 2. Following permit issuance, we will obtain utility clearance through Underground <br /> Service Alert. We will also schedule a grout inspection with San.Joaquin:County at <br /> least 24 hours in advance of the proposed investigative activities. <br /> r 3. We propose to install one ground-water monitoring well at the location presented on <br /> Figure 3. -We will site this-new well approximately 5 feet east of existing monitoring <br /> JJW GEOSCIENCES Inc <br />