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TreadvvelISJU10 <br /> During excavation backfilling, oxygen release compound® (ORCII)was proposed to be placed <br /> into the base of excavation below the groundwater table to stimulate enhanced bioremediation of <br /> groundwater in the vicinity of the excavation Excavation below 23 feet bgs was not proposed <br /> because ORC'�'backfill would address residual groundwater contamination Treadwell &Rollo <br /> estimated that approximately 4,500 pounds of ORC®would be required to address residual <br /> ' contamination in the vicinity of the excavation Treadwell &Rollo based this estimate on <br /> stoichiometric equations and estimated post-remediation contamination concentrations The <br /> SJCEHD did not approve the use of any ORC® as documented in their 16 April 2004 letter but <br /> subsequently requested in their 20 Apnl 2004 letter that up to 500 lbs of ORCO be used <br /> 4.2 Deviations from Workplan <br /> ' The deviations from the approved workplan included <br /> M • fn their lb April 2004 letter, SJCEHD requested the excavation be extended to a depth of <br /> 25 feet Shormg design was modified to accommodate the increased excavation depth <br /> During UST removal activities, fuel pipelines were observed leading to historical pump <br /> islands 20 feet south of the excavation As a result, Treadwell &Rollo characterized and <br /> excavated soil around the former pump islands <br /> i5.0 SOIL AND GROUNDWATER REMEDIATION <br /> ' The soil and groundwater remediation work was conducted and/or observed by Treadwell & <br /> Rollo in June and July 2004 The remedial work included the following <br /> ' • Shoring for the proposed excavation as shown on Figure 2, <br /> ' • Excavating and stockpiling soil for sampling and laboratory analyses, <br /> • Pumping approximately 20,000 gallons of groundwater from the excavation into Baker <br /> ' tanks prior to testing and discharge to the sanitary sewer, <br /> 25971020 DGD 5 23 August 2004 <br />