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1 <br /> CTeologzcaf hchtws fac <br /> 1"Quarter 6 <br /> Quarter 2004 Groundwater Monitoring Report <br /> Project No 507 2 <br /> May 19,2004 <br /> 3.0 CONCLUSIONS AND RECOMMENDATIONS <br /> ' Conclusions <br /> 1 Elevated concentrations of BTEX, TPH-G and MTBE are present in a laterally limited <br /> ' groundwater plume that is centered on MW-9 <br /> 2 The MTBE and previously monitored 1,2-DCA plumes are insignificant in comparison <br /> to the BTEX and TPH-G plumes <br /> ' 3 The lateral extent of the contamination plume is defined to the southeast, northeast and <br /> east by wells MW-1, MW-2 and MW-3 respectively <br /> 4 The TPH-G plume is defined to the southwest and northwest by wells MW-7 and MW- <br /> 10 respectively <br /> 5 The BTEX/TPH-G groundwater contamination plume is defined by MW-109 in the <br /> vertical plane, which is screened 40 feet below MW-9 This suggests that the vertical <br /> ' gradient is not moving the contaminants to any degree <br /> 6 The groundwater gradient flows to the northeast or east with relatively flat slopes, which <br /> appears not to significantly influence contaminant migration <br /> ' 7 The site exhibits a predominantly downward component of vertical groundwater flow, <br /> which is approximately the same slope as the horizontal gradient These components of <br /> groundwater flow appear not to cause preferential contaminant migration <br /> 8 The groundwater contaminant concentrations are on the rise, which correlates with a <br /> decrease of groundwater levels The center of the plume has not migrated beyond the <br /> ' source area giving evidence that the plume is not migrating laterally or vertically by <br /> advective flow <br /> 9 The data shows that the plume is stable and is not being degraded by natural <br /> ' biodegradation causes <br /> Recommendations <br /> ' • Maintain the modified quarterly monitoring schedule <br /> S A work plan for "In Situ Remediation Feasibility Study" dated September 20, 2002 and <br /> an addendum to the plan were submitted to San Joaquin County Environmental Health <br />' Department (SJC EHD) SJC EHD approved the study in their March 20, 2003 letter <br /> and requested a detailed work plan for evaluation GTI submitted our June 10, 2003 <br />' "In-Situ Remediation Pilot Test" work plan for an in-situ hydrogen peroxide infection <br /> pilot project and SJC EHD issued approval of the work plan in their September 10, <br /> 2003 letter The installation of three, 314" diameter monitoring wells was completed on <br />' February 5, 2004 and the infections began in mid March 2004 A brief status update is <br /> included in the following section <br />' 4.0 PILOT TEST UPDATE <br /> In accordance with our June 10, 2003 "In-Situ Remediation Pilot Test" work plan GTI <br /> mobilized to the site on March 19, 2004 GTI supervised Applied Process Technologies, <br />