ARCHIVED REPORTS XR0001006 - Laserfiche WebLink

Home Browse Search

Geolagual Tec"CS INC Page 6 3"Quai ter 2003 Groundwatei Monitoimg Report Project No 507 2 November 13,2003 ' 3 0 CONCLUSIONS AND RECOMMENDATIONS Conclusions 1 Elevated concentrations of BTEX, TPH-G and MTBE are present in a laterally limited ' groundwater plume that is centered on MW-9 2 The MTBE and previously monitored 1,2-DCA plumes are insignificant in comparison to the BTEX and TPI-I-G plumes ' 3 The lateral extent of the contamination plume is defined to the east, northeast and southeast by wells MW-3, MW-2 and MW-I respectively 4 The TPH-G plume is defined to the northwest and southwest by wells MW-10 and MW- ' 7 respectively 5 The BTEX/TPH-G groundwater contamination plume is defined by MW-109 in the vertical plane, which is seteened 40 feet below MW-9 This suggests that the vertical gradient is not moving the contaminants to any degree 6 The groundwater giadient flows to the northeast or east with relatively flat slopes, which appears not to significantly influence contaminant migration ' 7 The site exhibits a predominantly downward component of vertical groundwater flow, which is approximately the same slope as the horizontal gradient These components of groundwater flow appear not to cause preferential contaminant migration 8 The groundwater contaminant concentrations are on the rise, which correlates with a decrease of groundwatei levels The center of the plume has not migrated beyond the source area giving evidence that the plume is not migrating laterally or vertically by advective flow 9 The data shows that the plume is stable and is not being degraded by natural ' biodegiadation causes Recommendations • Maintain the modified quarterly monitoring schedule • Monitor the site wells ibr indicators of remediation by natural attenuation • A work plan foi "Ira Situ Reniediation Feasibility Study" dated September 20, 2002 and an addendum to the plan were submitted to San Joaquin County Environmental Health Depaitment (SJC EHD) SJC EHD approved the study in their March 20, 2003 letter and requested a detailed work plan for evaluation GTI submitted our June 10, 2003 - - ' "In-Situ Remedtation Pilot Test" work plan for an in-situ remediation pilot project and SJC EHD issued approval of the work plan in their September 10, 2003 letter The ' implementation of the work plan will be scheduled pending cost pre-approval from the USTCFP