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EC ® lR <br /> • 7-Eleven Store#14117 <br /> Work Plan for Interim Remediation <br /> April 19, 2004 <br /> Page 4 <br /> be the most permeable zone underlying the subject site, and should prove to be the most effective <br /> zone for oxygen injection <br /> Downhole drilling equipment will be steam cleaned before drilling each borehole, and sampling <br /> equipment will be cleaned between each sampling interval Each soil sample will be screened for <br /> hydrocarbon vapors using a portable photo-ionization detector (PID) Soils encountered during <br /> drilling will be logged using the Unified Soil Classification System by a SECOR field geologist, <br /> working under the supervision of a California Registered Geologist <br /> All soil samples collected will be sealed with Teflon®sheets and plastic caps then labeled and placed <br /> on ice in an Insulated container for delivery to Kiff Analytical located in Davis, California Sod <br /> samples will be analyzed for BTEX, TPHg, and MtBE using U S Environmental Protection Agency <br /> (EPA) method 8260B <br /> Well Installation <br /> The oxygen injection wells will be completed with 0 75-inch diameter Schedule 80 poly-vinyl chloride <br /> (PVC) casing, and will be screened from approximately 25 to 28 feet bgs with a micro-porous <br /> injection point (Table 4) The injection wells will have a sand filter pack placed within the annulus of <br /> . the well from the bottom of the boring to approximately one foot above the top of the well screen <br /> The annulus of each well will be sealed with two feet of bentonite on top of the sand that will be <br /> capped with a Portland cement/bentonite grout to the surface The wells will be secured at grade <br /> with an 8-inch-diameter traffic-rated street box <br /> Waste Disposal <br /> Soil cuttings and rinsate water generated during drilling operations will be temporarily stored onsite in <br /> properly labeled Department of Transportation (DOT) approved 55-gallon drums pending <br /> characterization and disposal The soil and rinsate water will be removed by SECOR's disposal <br /> contractor to an appropriate disposal facility The drums will be temporarily stored onsite for <br /> approximately 2-3 weeks <br /> OXYGEN INJECTION TEST DETAILS <br /> SECOR personnel will visit the site once or twice a month (depending on effectiveness), to perform <br /> oxygen injection, in conjunction with interim groundwater extraction activities Oxygen injection will <br /> be completed using bottled oxygen transported to the site by SECOR Up to 3 bottles containing 150 <br /> cubic feet (ft ) of oxygen will be used for each event The amount of oxygen injected Into each well <br /> will likely vary between 150 ft3 Into 3 wells (one oxygen bottle each) to 75 ft3 into 3 wells ('/z bottle <br /> each) <br /> Dissolved oxygen measurements will be collected before and after injection, and will be used to <br /> determine the effective ROI The results of the periodic injection will be reported on a quarterly <br /> basis, as part of the normal quarterly groundwater monitoring and sampling reports <br /> Based on SECOR's experience of other, similar sites, reductions in dissolved hydrocarbon <br /> concentrations, due to the increased biodegradation processes (as a result of higher subsurface <br /> • dissolved oxygen concentrations), will not be realized for a period of 6 to 9 months, after oxygen <br /> injection begins <br /> i <br /> 1 17-E=leven%?-11 Stores1141171Workplans114117 WP for Interim Remediation doc SECOR International Incorporated <br />