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DISCO PROPERTY,STOCKTON,CALIFORNIA However,due to the location of the Caltrans' Highway 4"Cross-Town' Freeway,there will be limitations to drilling locations south of the Disco Tanks. Activity II will be conducted according to the same four subtasks described in Activity I: prefield, field activities, laboratory analysis,and reporting. Subtask 1 Prefield Prefield activities for this task are similar to Activity I,requiring: • Updating the well survey in area to identify potential risk receptors, if any. • underground utility clearance, • a drilling permit from PHS,and • an encroachment permit from Caltrans. The encroachment permit is required because the proposed drilling areas(Figure 1) are offsite and are in a Caltrans right-of-way. Caltrans will have to approve a workplan prior to starting work in their right of way. The workplan should include a description of the work, a health and safety plan, a traffic safety plan using Caltrans specifications,and a map showing the locations of the proposed borings. Approval for this work may require up to 6 months.This workplan should also describe a plan to sample any permanent wells installed in the Caltrans right-of-way for the purpose of four quarters of monitoring. Provisions must be made to gain access to any permanent wells in the future. Subtask 2 Field Activities The field activities will start with drilling two borings offsite to determine the lateral extent of downgradient migration of petroleum hydrocarbons.These borings will be drilled and continuously logged to a depth of 10 feet below the top of the current static water elevation. Grab groundwater samples will be collected form both of these borings at the first occurrence of groundwater. Based on the results from these analyses, a possible third boring will be drilled adjacent to one of these shallow borings into a lower portion of the aquifer to determine if impacted groundwater is migrating downward. The following methods and protocol will be employed during this phase of the characterization: • All the borings will be continuously logged. • The soil will be screened in the field with a PID. • A discrete grab groundwater sample will be taken at the top of the uppermost groundwater in each of the shallow boring. • These samples will be submitted to a state certified laboratory for 24-hour analysis of TPH as gasoline,BTEX, and MTBE. • If the grab groundwater results indicate low levels of petroleum hydrocarbons (i.e., benzene less than 100 ug/L), then the boreholes will be considered for conversion to monitoring wells. If the grab groundwater results contain elevated levels of petroleum 5