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5.0 CONCLUSIONS AND RECOMMENDATIONS <br /> The decrease in contaminant levels that occurred during the first quarter of 1999 has not been <br /> sustained, and concentrations have now ieturned to these earlier levels The reason lur this is <br /> somewhat uncertain, but this increase occurred despite a continued rise in the water le%el above <br /> the screened interval in most wells Phis implies that the increase is probably real <br /> Hydrocarbon-degrading bacteria are present in the groundwater in the area of the cootaminant <br /> plume which indicates that there is a potential for natural attenuation of the contamir,ints over <br /> time The rate of decrease is unknown, but could be increased under a program of enhanced <br /> bioremediation involving either an above-ground bioreactor or in-situ stimulation <br /> A work plan to perform a receptor survey, install off-site monitor wells, and wnduLt 'easbility <br /> tests of potential remedial technologies was_submitted to PHS/EHD in early May 19519 and is <br /> currently being reviewed if the plait is approved, Upgradient will submit a cost e'iimate to <br /> perform the investigations so that Valley Motors can request pre-approval of the co°.1 s by the <br /> State UST Cleanup Fund Implementation of the plan is tentatively scheduled to beg n in July <br /> (receptor survey), with drilling planned for late August and the first phase of testing (in-situ <br /> bioremediation) scheduled to occur in September The results of this test will be incluiled in the <br /> Third Quarter Report The second and third phases of testing (pump test and vapor (,,Ktraction <br /> test) gill occur in the fourth quarter, probably in November It should be possible to sL bmit the <br /> Problem Assessment Report by the end of 1999 if no delays are experienced <br /> I <br /> 5 <br />