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Additional Site Investigation Work Plan Q� UPRR Bunkers—Tracy,CA } October 30, 2023 ~ 3.1 PRELIMINARY ACTIVITIES In preparation for the implementation of the Phase 1 drilling and sampling program,Antea Group will complete the following activities: • Prepare a Health and Safety Plan (HASP)that meets the requirements of Title 8,Section 5192 of the California Code of Regulations.The HASP will include safety protocols applicable to the planned field activities, a list of emergency contacts,and a map to the nearest emergency facility. Field personnel will review the HASP daily and when there are changes in conditions. • Secure soil boring permits from the San Joaquin County Environmental Health Department(SJCEHD) Environmental Health Division.Schedule well/boring seal inspections before backfilling the borings as required in the SJCEHD permit conditions. • Notify the Central Valley RWQCB case manager five(5)working days prior to the implementation of the field activities. • Mark each location in white paint and/or with stakes and open a ticket with Underground Service Alert of Northern California (DigAlert)at least 48 hours prior to ground disturbance. In addition,contact the railroad-specific utility locator services at least 72 hours prior to ground disturbance and arrange track protection if field activities are within 25 feet of the centerline of active tracks. 3.1.1 GEOPHYSICAL INVESTIGATION In preparation for the subsurface investigation,Antea Group will visit the Site with a geophysical subcontractor to confirm and mark the location of the underground structure and utilities.The subcontractor will utilize various technologies including ground-penetrating radar(GPR),electromagnetic induction, and magnetometry and provide a map of the findings. Note that the proposed boring locations may be changed based on the geophysical survey. 3.2 EXPLORATORY BORINGS Antea Group will direct a drilling subcontractor to advance exploratory soil borings around the concrete sump identified at the Site using a hand auger and direct-push technology. If sediment and/or liquid is found inside the structure,additional samples will be collected for laboratory analysis as described in Section 3.4. Prior to drilling,each borehole location will be pre-cleared using a hand auger or air knife and vacuum rig to a depth of at least five(5)feet below ground surface(bgs)and a diameter 120%of the direct-push drill rod diameter.To assess soil beneath the structure,a slant boring will be advanced at each end along the major axis to collect soil from approximately two(2)feet below the bottom of the structure(California State Water Resources Control Board 2015).Within approximately five(5)feet of each side of the structure a vertical boring will be advanced to at least ten (10)feet bgs to assess potential petroleum hydrocarbon impact to soil laterally and vertically relative to the structure(California State Water Resources Control Board 2012). If shallow groundwater is encountered in the borings,a groundwater grab sample will be collected for laboratory analysis from one of the borings upon reaching the proposed depth of ten (10)feet bgs. If shallow groundwater is not present and evidence of petroleum hydrocarbon impact is observed in soil from the bottom of the borings at ten (10)feet bgs,the borings may be advanced deeper until impacts are no longer observed,or until groundwater is encountered.A groundwater grab sample will be collected for laboratory analysis from deeper borings that intersect groundwater. �INOGENIX ALLIANCE uS_atnteagroup.cam 2