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Revised Work Plan,Additional Excavation and Confirmation Soil Sampling <br /> Bulk Transportation Facility, Stockton, California <br /> Hygienetics Environmental Services,Inc. <br /> 16 feet below grade. Brown, silty fine-grained sand was observed at the 16-foot depth in the western <br /> portion of the UST excavation. <br /> 1.4.2 Ground Water <br /> No ground water was observed in the UST excavation in October 2002. Depth to first ground <br /> water, therefore, is inferred to be greater than 16 feet below the ground surface. Information from <br /> San Joaquin County Environmental Health Department indicates ground water in the area may be <br /> at a depth of approximately 30 feet below the ground surface. <br /> 2.0 PROPOSED WORK <br /> The results of laboratory analyses of soil samples collected after removal of the UST show <br /> petroleum-hydrocarbons have impacted the shallow soil at two locations along a 20-foot-long <br /> portion of the diesel-fuel pipeline trench. Laboratory analytical results and field observations <br /> made during removal of the UST suggest the area of petroleum-hydrocarbon impact may be <br /> localized around this portion of the pipeline trench. Hygienetics, therefore, proposes <br /> overexcavation and confirmation soil sampling in the pipeline trench area where elevated <br /> concentrations of diesel fuel hydrocarbons were detected during UST removal. The work <br /> elements are described in the following sections. <br /> 2.1 Health and Safety <br /> Work will be performed under the existing Health and Safety Plan prepared by Foss for the initial <br /> UST removal. This plan will be revised to reflect current site conditions before fieldwork begins. <br /> Foss personnel, Hygienetics personnel, and personnel working for subcontractors involved <br /> directly in the excavation and sampling work will be briefed on the contents of the plan and will <br /> be required to follow the provisions of the plan. A copy of the Health and Safety Plan will be <br /> available at the site during fieldwork. <br /> 2.2 Overexcavation <br /> Foss will further excavate in the area of the diesel fuel pipeline and at the junction of the fuel piping <br /> between the two satellite dispensers using a backhoe and/or hand tools, as appropriate. Excavation <br /> will proceed until visual and olfactory evidence indicates soil impacted with petroleum hydrocarbons <br /> has been removed. Hygienetics will also use a photoionization detector to check in-situ soil for <br /> evidence of petroleum vapor. The maximum area of excavation is anticipated to extend the 20-foot <br /> length of the trench, a maximum lateral distance of 2 feet beyond each side of the existing Moot- <br /> wide trench,and to a maximum vertical depth of 15 feet below grade. The maximum volume of soil <br /> that is estimated will be removed is approximately 75 in-place cubic yards (100 uncompacted cubic <br /> yards). The excavated soil will be stockpiled on and covered with plastic at a location that is on the <br /> concrete pad adjacent to the pipeline trench. Plate 3 shows the area of proposed excavation and the <br /> location at which stockpiled soil will be placed. <br /> 2.3 Soil Sampling <br /> When field evidence indicates impacted soil has been removed,Hygienetics will collect soil samples <br /> along the sidewalls and at the base of the excavated area for laboratory analysis. Samples will be <br /> 3 <br />