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Geological Technics lice. Page 4 <br /> r Groundwater Monitoring Report <br /> I ' Project No. 1030.2 <br /> l May 15,2003 <br /> © MW-2, MW-3, MW-101 and the domestic well were non-detect for all analyzed <br /> constituents. <br /> o MW-2, MW-3 and the domestic well have been non-detect for all analyzed <br /> constituents since January of 1997. <br /> o MW-101 has been non-detect for all analyzed constituents since installation and <br /> [ initial testing in May of 2002. <br /> • TPH-G and BTEX constituents have only been detected in MW-1 and MW-4. Figure 4 <br /> Iis an interpretation of the extent of TPH-G at the site. <br /> Site Characteristics <br /> • The plume is defined vertically by MW-101 and laterally by MW-2 to the southeast and <br /> MW-3 to the southwest. <br /> • MW-4 appears to be located near the leading edge of the plume. <br /> s • The clay layer at 19 feet bgs provides a significant barrier to vertical plume migration. <br /> • Groundwater slope is gradual (<0.005 ft/ft) which impedes the migration of the plume. <br /> • Vertical groundwater gradient is positive (upward) making vertical migration unlikely. <br /> • Measurements of dissolved oxygen in the shallow monitoring wells range between 0.39 <br /> and 1.93 ppm. <br /> ® Background dissolved oxygen measurements of approximately 0.70 ppm, a gradual <br /> I slope and fine grained soils, characterized by silts and clays, may have a positive <br /> contribution to protection of the deeper aquifers and retardation contaminant migration <br /> Iat this site. <br /> 3.0 RECOMMENDATIONS <br /> r • Discontinue testing for fuel oxygenates. <br /> • Prepare a feasibility study and work plan for interim site remediation (in progress). <br /> • Continue quarterly groundwater monitoring. <br /> 4.0 LIMITATIONS <br /> This report was <br /> p prepared in accordance with the generally accepted standard of care and <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 /> 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 /> I <br />