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�A • 7-Eleven Store#14117 Work Plan for Interim Remediation April 19, 2004 Page 3 i Groundwater will be extracted at least once per month A SECOR representative will be onsite at all times during pumping, and proper traffic control and safety precautions will be implemented to Insure the safety of all vehicles, workers, and pedestrians Depth to water measurements will be collected before and during the first pumping event (In the pumping well and at least three nearby observation wells) to determine an estimate of the radius of Influence Based on data collected during each extraction event (pumping rates, volumes removed, and analytical data), the Interim extraction program will be modified to optimize extracted volumes and mass removal OXYGEN INJECTION FEASIBILITY STUDY SECOR proposes the Installation of 3 Infection wells (1-1 through 1-3) that will be used to conduct an oxygen Infection feasibility test (Figure 3) Oxygen injection is used to stimulate the biodegradation of gasoline-range petroleum hydrocarbons and oxygenates dissolved in groundwater Past studies on subsurface bacterial colonies (Site Conceptual Model, Shaw Group, June 20, 2002) Indicates that j Indigenous populations of bacteria are present In-situ, and are capable of Intrinsic biodegradation The wells are placed in positions useful for determining radius of Influence (ROI) of oxygen Injection (with observation wells 10, 20, and 35 feet away), and for future use to Intersect the dissolved plume in the down gradient position, as the dissolved gasoline range petroleum hydrocarbon and oxygenates migrate past the line of Injection wells, they will be consumed by aerobic bacteria OXYGEN INJECTION WELL INSTALLATION Site Health and Safety As required by the Occupational Health and Safety Administration (OSHA) Standard "Hazardous Waste Operations and Emergency Response" guidelines (29 CFR 1910120), and by California Occupational Health and Safety Administration (Cal-OSHA) "Hazardous Waste Operations and Emergency Response" guidelines (CCR Title 8, Section 5192), SECOR will prepare a Site-Specific Health and Safety Plan prior to the commencement of field work The Site-Specific Health and Safety Plan will be reviewed by the field staff and contractors before beginning field operations at the site Permitting and Utility Location The permits for the groundwater monitoring well Installations will be obtained from the San Joaquin County Environmental Health Department (SJCEHD) SECOR will contact Underground Service Alert at least 48 hours prior to beginning drilling A private utility locator will also be used to identify the location of undergrounds utilities in the area surrounding the proposed well locations In addition, the boring locations will be hand-cleared to 5 feet bgs prior to beginning drilling activities Soil Borings, Soil Sampling and Analysis SECOR will supervise the drilling and installation of three oxygen injection wells (1-1 through 1-3) at the locations shown on Figure 3 The wells will be drilled to a depth of 30 feet bgs using a truck- mounted drilling rig equipped with 8-inch-diameter hollow-stem augers Soil samples will be collected at 5 foot intervals using a split spoon sampler lined with 2-inch diameter by 6-inch-long brass sample tubes (Table 3) The soil samples will be logged using the Unified Sod Classification System to Insure correct placement of the screened Intervals A consistent sand layer underlies most of the site at depths deeper than about 20 feet bgs (Attachment A) This sand layer appears to I W-Elevenl7-11 Stores1141171Workpians114117 WP for Interim Remediation doc SECOR Intemational Incorporated