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URS Mr. Robert McClellon January 20, 2005 Page 2 "However, one of the changes in the work plan we are requiring is regarding the time that sampling will be performed upon construction of the first two probes. Our understanding is that sampling the probes for gas detection immediately after they are constructed would not suitable/best in obtaining accurate readings. In most cases you will get little or no methane readings on the date of construction.What we need to see from you is an addendum specifying that the sampling will be performed at least one day after the construction,especially since these readings will be used to determine the location for construction of the other two probes." Following receipt of this e-mail message,URS contacted Mr.Tasiopoulos to ascertain additional information regarding the above requirements. Based on our understanding of our discussion with Mr.Tasiopoulos,if the locations of the second set of probes are not determined by the methane measurements from the first two sets of probes,the requirement specified in the SJCEHD e-mail message would not apply. During our conversation with Mr. Tasiopoulos,he was advised of our revised plans to install the second set of probes. Mr.Tasiopoulos thought that the revised plans were acceptable. A work plan addendum to address SJCEHD concerns was transmitted to SJCEHD for approval on October 4, 2004. The work plan and addendum were approved by SJCEHD. FIELD ACTIVITIES The following two sections describe the field activities performed to install the monitoring probes and the quarterly monitoring activities. Monitoring Probe Installation On October 12, 2004, URS installed four dual gas-migration monitoring probes at the World Enterprises site shown on Figure 1. The probes were installed using a truck-mounted drill rig equipped with hollow-stem augers from Gregg Drilling&Testing, Inc.,of Martinez, California. The borings were installed in the following order: VW-5,VW-6,VW-7, and VW-8. A clean California modified split-spoon sampler fitted with brass liners was used to collect the soil samples. Soil samples were collected at 5-foot intervals from each boring(VW-5,VW-6,VW-7,and VW-8). For each sample interval,the soil from the liners was used for soil classification. The field geologist logged the soil from each boring using the Unified Soil Classification System. The boring logs for each boring are attached. After each boring was advanced to the desired depth,dual gas-migration monitoring probes(shallow [S] and deep [D])were constructed within the boring. The probes were constructed with 1-inch schedule 40 polyvinyl chloride(PVC)pipe. Except for within VW-7,the screened interval of the shallow probes was installed at a depth from 6 feet to 11 feet below ground surface(bgs);the screened interval of the shallow probe within VW-7 was installed at a depth from 5 feet to 10 feet bgs. The screened interval of the deep probes(except for VW-7)was installed at a depth from 15 feet to 20 feet bgs. The screened interval of the deep probes within VW-7 was installed at a depth from 14 feet to 19 feet bgs.The annulus between the probe casing and the boring wall for probes VW-5,VW-6, and VW-8 was filled with pea gravel filter pack material from the bottom of the boring(20.5 feet bgs)to 14 feet bgs. The annulus between the probe casing and the boring wall for VW-7 was filled with gravel filter pack material from the bottom of the boring(20.5 feet bgs)to 13 feet bgs. Two-feet of bentonite was placed in the annulus for VW-5,VW-6,VW-7, and VW-8. The annulus between the probe casing and the boring wall for VW-5,VW-6,VW-7, and VW-8 was filled with pea gravel filter pack material. One-