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Mike Hansen - 2 - 10/8/87 <br /> 4 - We agree that it appears that a minimum of three recovery wells <br /> may be needed to control groundwater movement at the site. We <br /> anticipate that the exact number and placement of recovery wells <br /> will be determined during groundwater flow modeling after <br /> aquifer testing is completed. <br /> 5 - We still believe that well MW-11 was clean when sampled in June. <br /> 1987. The well was sampled after 10 p.m. , and the sample <br /> was examined only under dim artificial light. Also, the water <br /> sample was sandy, and this may have contributed to the <br /> impression of a slight surface film. Also, note that all <br /> surface films are not hydrocarbon-related. <br /> 6 - Du Pont does not have data on the history of operation of the <br /> air stripper. We believe, however, that these data are routinely . <br /> reported by Kayo. "' <br /> 7 - It is possible that: water derive from infiltration through the <br /> bottom base of the onsite pond is percolating down the gravel <br /> pack of well RW-1 . This water m�y prevent the cone of <br /> depression generated by RW-I from reaching far enough east to <br /> recover water from the MW-16 area as fast as it is recovered from <br /> the MW-17 and MW-18 areas. <br /> 8 - MW-16, MW-17, and MW-18 were not found during one sampling visit <br /> because the sampling contractor forgot to bring the required <br /> metal detector. <br /> 9 - The proper data on well RW-1 have been inserted into Table 1 in <br /> the Contamination Assessment Report. <br /> 10 - We will sample and analyze the onsite well at the same frequency <br /> q Y <br /> as monitor wells. <br /> 11 - We have requested assistance from Laurie Cotulla of San Joaquin <br /> Local Health District to obtain access to the offsite wells. We <br /> are happy to sample them when access has been arranged. <br /> 12 - We agree. <br /> 13 - A map of the site distinguishing the different depths of wells <br /> has been prepared and is now included in the Preliminary <br /> Remediation Report. : <br /> 14 - We will assure that' Canonie uses appropriate methods, and state <br />` in their reports the analytical method employed <br /> k <br /> REPLIES TO "IN SITU BIOREMEDIATION" : <br /> 1+2 Air sparging has been considered but its zone of influence is <br /> limited. Hydrogen peroxide has not been shown to be toxic at <br /> the concentration we will use (100-500 ppm generally) . This was <br /> I <br /> 4" <br />