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GeologlcalTechnksInc. Page 4 <br /> Groundwater Monitoring Report <br /> Project No.750.2 <br /> LL May 13,2004 <br /> The detection limits for the above analyses are listed in Table 3 of Appendix A and the lab <br /> data are presented in Appendix B. <br /> As required under AB2886, the laboratory data was submitted electronically to GeoTracker <br /> r on April 15, 2004. The confirmation number is 6588197410. <br /> L <br /> 2.0 INTERIM SITE WORK <br /> On March 13, 2004, the well cap on MW-4 was replaced due to corrosion. <br /> L <br /> f 3.0 FINDINGS & RECOMMENDATIONS <br /> L <br /> Findings <br /> The results of the groundwater sample analyses show the following: <br /> • Each of the site's six monitoring wells was non-detect for all analyzed constituents. <br /> • MW-1 was non-detect for the fifth consecutive monitoring event. Chart 1 illustrates the <br /> gradual decrease in groundwater elevation over time and the exponential decrease in <br /> TPH-G concentrations in MW-1. <br /> 0 Vertical groundwater gradient was calculated for the event of March 13, 2004, and was <br /> found to be insignificant. The magnitude of the vertical gradient has been getting <br /> progressively smaller during the last several monitoring events. Eleven of the fourteen <br /> past monitoring events show a downward trend to groundwater flow. <br /> • Oxidation-Reduction Potential measurements (Table 4) are positive for. all the wells. <br /> This shows that the volume of contaminants leaching into groundwater has been stopped <br /> and that biodegradation of the contaminants is at a rate sufficient to mitigate the residual <br /> L BTEX/TPH-G plume in the area around the source without depleting the oxygen. <br /> • The dissolved oxygen measured at the site is between 3.8 and 6.4 ppm and is conducive <br /> to natural attenuation of BTEX/TPH-G. <br /> • It appears that soil contamination has been reduced significantly, ox en has been <br /> Pp oxygen <br /> added to the subsurface and groundwater contamination is absent. <br /> • Excellent progress has been made at this site. Clean-up goals have been met and the <br /> effort has exceeded MCL's for the known constituents at the site. <br /> • Biodegradation indicators suggest that the trace remnants of soil contamination will <br /> degraded by natural attenuation. <br /> 0 Groundwater monitoring data shows that groundwater has returned to background <br /> conditions. <br />