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i <br /> Ge0bgko[Technics Inc. Page 5 <br /> r Groundwater Monitoring Report <br /> Project No.750.2 <br /> July 22,2003 <br /> J <br /> Vertical groundwater gradient was calculated for the event of June 5 2003, and was <br /> i <br /> found to be insignificant. The magnitude of the vertical gradient has been getting <br /> progressively smaller during the last several monitoring events. An upward vertical <br /> gradient has been measured for the last two consecutive events. <br />' • Oxidation-Reduction Potential measurements (Table 4) are positive for all the wells. <br /> This suggests that the volume of contaminants leaching into groundwater has been <br /> stopped and that biodegradation of the contaminants is at a rate sufficient to mitigate the <br /> residual BTEX/TPH-G plume in the area around the source without depleting the <br /> L oxygen. <br /> •'' The dissolved oxygen measured at the site is between 1.7 and 2.9 ppm and is conducive <br />} to natural attenuation of BTEX/TPH-G. <br /> I <br /> Recommendations: <br />{ �, • Continue quarterly groundwater monitoring at the site. <br /> • Restart of the vapor extraction system at the site is in progress. <br /> • Scheduling drilling dates for the site is in progress. <br /> • Test for biodegradation indicators. <br /> 3.0 LIMITATIONS <br /> This report was prepared in accordance with the generally accepted standard of care and <br /> i <br /> practice in effect at the time Services were rendered. It should be recognized that <br /> definition and evaluation of environmental conditions is an inexact science and that the state <br /> or practice of environmental geology/hydrology is changing and evolving and that <br /> standards existing at the present time may change as knowledge increases and the state of <br /> 4 the practice continues to improve. Further, that differing subsurface soil characteristics <br /> can be experienced within a small distance and therefore cannot be known in an absolute <br /> 1 <br /> sense. All conclusions and recommendations are based on the available data and <br /> information. <br /> The tasks proposed and completed during this project were reviewed and approved by the <br /> local regulatory agency for compliance with the law. No warranty, expressed or implied, <br /> is made. <br /> is <br /> i <br /> Lr <br />