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URS Mr. Robert McClellon Page 2 Supervisor R.E.H.S. August 16, 2004 ■ A minimum of 5 feet of seal at the top of the probes is needed; ■ Pea gravel,rather than sand, should be used in the annulus; and ■ The top of the probes should be completed within a stove pipe/monument (3 feet above the ground surface)rather than within a Christy Box(surface completion). A work plan addendum to address these SJCEHD concerns was transmitted to SJCEHD for approval on December 11, 2003. The work plan and addendum were approved by SJCEH. FIELD ACTIVITIES The following two sections describe the field activities performed to install the monitoring probes and the quarterly monitoring activities. Monitoring Probe Installation The field activities could not be completed following the approval of the work plan due to the wet conditions at the site from the weather until April 2004. On April 7, 2004, URS installed four gas- migration monitoring probes at the World Enterprises site shown on Figure 2. The gas-migration monitoring probes were installed using a truck-mounted drill rig equipped with hollow-stem augers from Gregg Drilling & Testing, Inc., of Martinez, California. Prior to the installation of the probes, URS obtained approval from Mr. Tasiopoulos of SJCEHD of the four probe locations. Mr. Tasiopoulos was present during the mandatory portion of these activities. The borings were installed in the following order: BH-1, BH-2, BH-3, and BH-4. A clean California modified split-spoon sampler fitted with brass liners was used to collect the soil samples. Soil samples were collected on a continuous basis from the first boring (BH-1) and at 5-foot intervals from the remaining three borings (BH-2, BH-3, and BH-4). For each sample interval, the soil from the liners was used to classify the soil and to measure the soil headspace for methane, carbon dioxide, oxygen, and volatile organic compounds (VOCs). The field geologist logged the soil from each boring using the Unified Soil Classification System. The boring logs for each boring are attached. Prior to measuring the soil headspace for methane, carbon dioxide, oxygen, and volatile organic compounds (VOCs), the soil was placed in a resealable plastic bag for a minimum of 10 minutes. A landfill gas monitor, GEM 2000, was used to measure the soil headspace for methane, carbon dioxide, and oxygen. A photoionization meter, MiniRae 2000,was used to measure the soil headspace for VOCs. To measure the soil headspace of the above constituent, the probe of the selected instrument was placed in the plastic bag. These results were logged in the field book. After each boring was advanced to the desired depth, a gas-migration monitoring probe was constructed within the boring. The probes were constructed with 1-inch schedule 40 polyvinyl chloride (PVC) pipe. K:\Wprocess\25532\GMMPIR\081604.doc