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Ms. Margaret Lagorio, SJCEHD November 30,2007 Work Plan for Additional Assessment Project No.2033-15688-01 15688 Harlan Road,Lathrop,California Page 6 Task 2: Field Activities Task 2A: Soil Boring and Soil Sampling Stratus will oversee the advancement of soil borings MW-1, MW-2, and MW-3 at the approximate locations shown on Figure 3. A C-57 licensed drilling contractor will advance the borings using a truck mounted drill rig equipped with 8-inch diameter hollow stem augers. The initial 5 feet of each boring will be advanced with a hand auger to reduce the possibility of damaging underground utilities. The total depth of borings MW-1, MW-2, and MW-3 is anticipated to be about 15 feet bgs, but will depend upon actual field conditions. Upon completion the soil borings, the resultant boreholes will be converted to permanent monitoring wells (see task 2B below). During advancement, soil will be continuously cored from 5 to 15 feet bgs using either an 18-inch California-type split-spoon sampler lined with three precleaned brass sleeves or a 5-foot core barrel. The ends of one brass sample sleeve from each sample interval will be covered with Teflon TI sheets and tight fitting plastic caps. Each sample will then be labeled, placed in a resealable plastic bag, and stored in an ice-chilled cooler, pending determination of which samples will be submitted for laboratory analyses. Soil samples will remain chilled until relinquished to a state-certified analytical laboratory. Chain-of- custody procedures will be followed from the time the samples are collected until the time the samples are relinquished to the laboratory. Soil will be classified by a Stratus geologist using the Unified Soil Classification System. Soil from each sampled interval will be placed in plastic bags to allow the accumulation of volatile organic compound (VOC) vapors within the airspace in the bags. A portable photo-ionization detector (PID) will be used to measure VOC concentrations from each sample. Stratus will record PID readings, soil types, and other pertinent geologic data on a borehole log. Soil samples collected from borings MW-2 and MW-3 at depths of approximately 5 and 10 feet bgs will be submitted for laboratory analyses; soil samples for chemical analyses will not be collected from well MW-1. Additional samples may be selected for chemical analyses based on soil type and field observations. Details regarding exploratory boring procedures are presented in Attachment I. Task 213: Groundwater Monitoring Well Installation At the termination of soil borings MW-1, MW-2, and MW-3, groundwater monitoring wells will be constructed within the annulus of the augers. Each well will be constructed using 2-inch diameter PVC casing and 10 feet of 0.010-inch machine slotted PVC well casing installed from approximately 5 to 15 feet bgs. A sand filter pack will be placed in the annular space around the well casing from the bottom of the well screen to approximately one foot above the top of the well screen. Following placement of the K:Voe's Truck Plaza\Work Plansuoe's Truck-SOUTH PARCEL-WP for Site Assessment 11-30-07.doc 5TRAT'U5