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1 <br /> 6 REMEDIAL OPTIONS <br /> In light of current conditions, Philip reviewed our February 1, 1995 Final <br /> Remediation Plan, which proposed air spargmg and soil venting as a remedial option <br /> Philip also considered passive monitoring of the natural attenuation at this site <br />' 61 Air Sparging and Soil Venting <br /> Philip's Final Remediation Plan proposed utilizing six sparge wells, which <br /> have already been installed, and four existing monitoring wells (MW-1, <br /> MW-3, MW-4, and MW-7) for soil venting A more minimal approach might <br /> dust utilize two sparge wells (SP-1 and SP-2), which are located within or near <br /> the highest concentrated area of the plume <br /> When originally proposed, the monitoring wells designed for soil venting had <br />' over 20 feet of screen exposed through the vadose zone Under current <br /> groundwater conditions, the length of exposed screen has been reduced to <br /> around 10 feet It is Philip's opinion that at least two new soil venting wells <br /> would have to be installed for proper operation of this remedial method <br /> A sparge and vent operational period of three months was considered at this <br /> site Initial work required to implement this method would be the installation <br /> of equipment, including the construction of two new venting wells, and the <br /> trenching and placement of piping Surface piping would not be acceptable at <br /> this site because of the large volume of traffic Other costs associated with this <br /> method would include compressors and blowers, activated carbon for vapor <br /> treatment, operation and maintenance, laboratory analyses, wastes disposal, <br /> equipment dismantling, and reporting A projected cost for implementing <br /> sparge and vent at this site is estimated to be $60,000 to $70,000 <br /> 6.2 Natural Attenuation <br /> We would propose that groundwater monitoring, on a semi-annual basis, be <br /> performed to assess evolving conditions There has been sufficient historical <br /> data collected where more frequent monitoring would not be cost effective <br /> Groundwater monitoring would be performed on about seven of the site wells <br /> (MW-1, MW-5, MW-7, MW-8, MW-10, MW-12, MW-13) that would <br /> provide the most amount of information The petroleum plume has not 1 <br /> historically impacted site wells not proposed for monitoring, and sampling <br /> from those wells would not be cost effective Groundwater samples would <br /> continue to be analyzed for TPH-G, BTEX, and oxygenate compounds <br /> May 1999 Subsurface Investigation and Groundwater Monitoring Report <br /> The Earlhgrams Company Facility <br /> 2651 South Airport Way <br /> Stockton,CaliforniaPrepared for THE FARTHGRAINS COMPANY Prepared by Philip Services Corp <br /> E 112136211213&2EG1125997W599REP DOC June 22, 1999 <br /> 13 <br />