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Mr. Dave Lewis January 28, 1987 Page 2 Dissolved hydrocarbons have been detected in monitoring well 11 on more than one occasion suggesting that the plume is close to domestic well 9135 . Although sampling of this well through January 19 , 1987 has not detected dissolved hydrocarbon concen- trations above method detection limits, Groundwater Technology recommends that a contingency plan be formulated in the event that the weekly sampling of this domestic well indicates the presence of dissolved hydrocarbons . Should it be warrented, we would recommend the installation of a liquid phase carbon filtration system at the wellhead. If the carbon filtration system needs to be activated the sampling frequency should be increased to (bi-weekly) twice a week, to verify the presence or absence of hydrocarbon constituents within the well and to monitor the effectiveness of the treatment system. The present schedule for sampling includes; weekly sampling of monitoring well 11 and domestic well 9135, bi-monthly sampling of five other domestic wells and monthly sampling of the moni- toring wells at the site. Groundwater Technology recommends that this sampling frequency be continued unless future site condi- tions dictate otherwise. At this time, it is Groundwater Technology' s opinion that excavation of soils beneath the site is not the best approach to addressing the residual soil contamination. The location of existing remedial abatement systems and monitoring points containing free product in the area of highest residual soil contamination would either severely limit the extent of ex- cavation or require the removal and replacement of the remedi- ation systems and monitoring points . As outlined in Groundwater Technology' s correspondance dated October 13, 1986, Soil Contami- nation Abatement Options, Groundwater Technology believes that the best approach for this site is soil venting. Subsequent to the startup and testing of the presently existing initial soil venting system which was installed to prevent vapor impact of the adjacent buildings, Groundwater Technology recommends that the effectiveness of a more comprehensive soil venting system be evaluated for remediation of subsurface soil contamination. Testing of the initial soil venting system is schedule for the week of February 1, 1987.