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San Joaquin County 0001.5.052.90 Lower Sacramento Road—Harney Curve May 5,2004 WORK PLAN FOR PHASE TWO CONSULTING SERVICES Page 2 WORK PLAN FOR PHASE II OF FORMER GASOLINE STATION We will study the concentration and extents of total petroleum hydrocarbons as gasoline (TPHg) and total petroleum hydrocarbons as waste oil (TPHo), which will assume that the building will be present at the time that soil samples are collected. The samples well be collected using the geoprobe drilling method to collect samples from two borings located within the footprint of the former tank#3 and three borings in the vicinity of the waste oil UST that was closed in place. Data from previous studies indicates that hydrocarbons remaining in site soil are limited to locations that are beneath the southern edge of the former gasoline station building. These data are based on soil samples that were collected from two angle borings that extended beneath the building foundation. We understand soil samples may not be collected from locations within the building because it will be occupied at the time sampling will be conduced. The previously completed angled borings were installed at angles between 10 and 20 degrees from vertical. This resulted in the 25-foot borings extending only slightly beneath the building. We propose to install three borings at an angle approximately 30 degrees from vertical. This angle will allow samples to be collected up to 4.5 feet inside of the building foundation. We have assumed that these borings will require permits issued by San Joaquin County Environmental Health Department. We propose to collect soil samples at five-foot intervals beginning when the drill is extended 5 feet into the ground. We will continue to collect samples every five feet until the drill reach 25 feet into the ground. We propose to submit selected soil samples for analysis of TPHg, total recoverable hydrocarbons as oil and grease (TRHo), benzene, toluene, ethylbenzene, total xylenes (BTEX), and the seven fuel oxygenates (oxygenates). PHASE Il REPORT We will prepare a report describing information from the sample collection and laboratory analyses. Our report will include a sketch map illustrating the sample locations, tables summarizing laboratory results, logs presenting descriptions of soil samples collected, and the laboratory data sheets. REMEDIATION WORK PLAN Assuming that the Phase H study provides sufficient information for developing a remediation plan, we will prepare a work plan for implementing site remediation activities. At this time we anticipate that site remediation will be comprised of activities to remove the waste oil tank that was closed in place beneath the building foundation and excavation of the approximately 65 cubic yards of hydrocarbon impacted soil that was allowed to remain beneath the building foundation at the time that the Regional Board issued its No Further Action determination. Each of the anticipated remediation actions requires that the existing building be demolished to provide access.