ARCHIVED REPORTS XR0009987 - Laserfiche WebLink

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r� Additional facts in further support of the request, • The Client and Wright decided not to use the "in-situ" biologic degradation and enhanced bio-cleanup (Option 3) approach and opted as a next step to reconsider dual phase extraction Wright's preliminary cost estimate of using dual phase (Option 2) evaluated the technology and with an assumed duration of use and therein implied costs of operation for a certain length of time The estimated duration of use and implied cost would rise if the system were used for longer penods of time Upon consultation with EHD and the absence of any compelling history on the effectiveness of Dual Phase in the immediate area of the subject site, Wright and EHD agreed on or about September 25, 2003 that over excavation was the most cost effective and appropriate remedial alternative for the site In its letter (Exhibit 6) dated March 09, 2004, during implementation of the approved work plan, the EHD then documented and reiterated this earlier finding Wright and Claimant assert that prior to the above dated letter that same finding had been agreed to and not committed to written form but was the driving force behind the work plan dated October 10, 2003 (Exhibit-4) ® Dissolved concentrations of TPHG and Benzene were observed at MW-9 and MW-3 Discussions with RWQCB indicated that interim remediation by excavation to remove these high residuals may be performed when collecting soil samples to further define parameters present and evaluate feasibility of the biologic "in-site" approach considering the "Report of Waste Discharge" permit process that would have to be pursued with the RWQCB in order to implement that msitu method In addition, Wright and PHS EHD desired to ascertain whether an additional source was contributing to free phase product in these wells Another source was not apparent and an anomalous small quantity of sheen was occasionally present, this was surmised to be a residual source identified in early site assessment study Moreover, since Wright had initially selected a biologic approach and some additional data was needed to further evaluate that option by developing information to later respond to RWQCB concerns, and further investigate feasibility with Option 1, some excavation was done near these high sources (i a Wells MW-3 and MW-9) Excavations were made to determine precise locations of subsurface constraints, collect samples to evaluate effectiveness of bioremediation, identify indigenous microorganisms and characterize soil for possible landfill disposal under Option 1 i i Page 4 of 7