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Site Characterization Work Plan ABF Freight System,Inc. Manteca California Pae 7 • of the other wells will be determined by the information from the first well The collection of samples from this boring will begin at a depth below the eleven-foot depth of the former tank pit excavation Soil samples will be collected using a split spoon sampler at 5 foot intervals and at each change in lithology from each boring Each soil sample will be screened for odors and screened with a photoionization detector (PID) which measures concentrations of volatile organic compounds (VOCs) relative to an isobutylene standard All of the wells will be screened from 5 feet to approximately 25 feet below ground surface Depth to groundwater was observed in the UST excavation at a depth of approximately 11 feet bgs Soil samples from above and below the water table and a grab groundwater sample will be collected from each monitoring well borehole Groundwater samples will also be collected from each monitoring well after well construction and development The monitoring well located in the former UST excavation area will be extended to the depth necessary to determine the vertical extent of the soil contamination Soil samples will be collected using a split spoon sampler every 5 feet beginning 5 feet below ground surface (bgs) The soil will be considered clean when a total of 10 feet of soil with no contaminates found has been detected After soil sample retrieval, Hydropunch H equipment will be used to collect groundwater samples with depth The Hydropunch sampling tip will be driven four feet beyond the existing boring depth into undisturbed aquifer material prior to sampling Once the Hydropunch sampling • tip reaches the desired sampling depth the sampling screen is exposed and groundwater is collected If necessary, the initial boring in the area of the former tank pit will be back grouted to 25 feet bgs for monitoring well installation The soil samples, grab groundwater samples, and groundwater samples collected from the monitoring wells after well development will be analyzed for TPH-D (EPA 8015M), BTEX (EPA 8020), and Oxygenates (EPA 8260) 5.5 Monitoring Well Construction Four monitoring wells will be installed, one at the former UST excavation pit and three perimeter wells The perimeter well locations will be determined from groundwater flow direction information acquired through regulatory file review The monitoring well located in the former UST excavation area will be drilled to the depth necessary to determine the vertical extent of the soil contamination After soil and groundwater sampling is complete the tank pit borehole will be back-grouted to 25 feet, the depth to which the monitoring well will be completed The wells will be constructed oft-mch PVC well casing with 0 010-inch slotted perforations from approximately 5 feet to the total depth of the well (20-40 feet) The annular space of each borehole will be backfilled with #2 sand from 1 foot above the top of the screened interval to total depth The wells will be sealed with a 1 foot thick bentonite chip layer and a Portland cement grout from the ground surface to the top of the bentonite . pellets. All wells will be installed in underground, water-tight vault boxes. N TRO)ECTS0272TIans and Reports\ABF Final Site Charactenzation Work Plan doc 6/13/98