Laserfiche WebLink
Sulfolane Remedial ' <br /> Investigation Work Plan <br /> ARCADIS Former Occidental Chemical Corporation <br /> Lathrop, California ' <br /> t <br /> In a letter dated November 19, 2008,the RWQCB requested that soil leaching tests be <br /> conducted to develop a site-specific cleanup criterion for sulfolane in soil that would be I protective of groundwater. Soil samples archived during the PW18 soil investigation <br /> were used for a Waste Extraction Test(WET)and analysis of sulfolane in the leachate. <br /> A site-specific soil cleanup value of 8.6 milligrams per kilogram(mg/kg; 8,600 ' <br /> micrograms per kilogram[•glkg])was recommended using the health-based drinking <br /> water criterion for sulfolane of 0.057 milligrams per liter(mg/L; 57 micrograms per liter <br /> [pg/L](CRA 2009a).The RWQCB approved this soil cleanup criterion and requested ' <br /> that a feasibility study(FS)be conducted to evaluate remedial alternatives for sulfolane <br /> impacted soil in a letter dated March 16, 2009. <br /> A Feasibility Study Work Pian was submitted on May 13, 2009 and approved by the ' <br /> RWQCB on June 3,2009.The FS evaluated four remedial alternatives including <br /> natural attenuation, in-situ soil washing, in-situ chemical oxidation(ISCO),and ' <br /> excavation and offsite disposal of impacted soil. Natural attenuation was proposed as <br /> the remedial alternative to treat the sulfolane affected soil in the vicinity of well PW18 <br /> (CRA 2009b).The RWQCB approved this alternative in November 2009. ' <br /> In March 2010, monitoring well cluster PW26 was installed in the shallow, intermediate, <br /> and deep zones of the unconfined aquifer in the area where the highest sulfolane ' <br /> concentrations were detected during the PW18 soil investigation.The installation of the <br /> well cluster was recommended following the PW 18 soil investigation to monitor the <br /> effectiveness of extraction wells EW-08A and EW-08B(CRA 2010).The location of ' <br /> well cluster PW26 is shown on Figures 3 and 4. <br /> 1.2 Work Plan Objectives ' <br /> ARCADIS has conducted a comprehensive evaluation of the current remedial <br /> approach being implemented at the Site and has developed a strategy to enhance the <br /> remediation and facilitate regulatory closure.Although natural attenuation for residual <br /> impacted soil has been approved by the RWQCB,additional soil and groundwater <br /> investigation activities are now proposed to further delineate the vertical and lateral ' <br /> extent of sulfolane in soil and groundwater..The results of soil sampling activities will be <br /> used to evaluate further soil excavation.The results of groundwater sampling activities <br /> will be used locate additional shallow injection and extraction wells. <br /> Specifically,this Work Plan proposes to: <br /> 2 <br /> Inlnpa d Werk Okn OX21 Ulm <br />