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1)to attempt to collect soil samples at depths below any previously collected at the site, without allowing contaminated groundwater at shallower depths to cross-contamir ate the deeper soil during drilling and/or sample retrieval, 2)to determine the maximum depth of soil contamination in the vicinity of monrtt r well GT-3, where diesel was previously detected at low concentrations between 65 and 85 feet, 3)to obtain data on the lithology and hydraulic conductivity of the Riverbank Forriation below 65 feet PHSIEHD included two other specific objectives inventory potential groundwater receptors and construct a fate-and-transport model These activities were not included in our cost estimate for the investigation. The site receptor survey has been added to this report, without prior cost pre- approval, but the fate-and-transport model has been postponed 2.0 PROCEDURES 2.1 Drilling and Sampling The shallow boring (GT-10) was drilled on March 19, and the deeper boring (GT-11) was drilled on March 22, 1999 V & W Drilling of Rio Vista used 10-meh hollow-stem augers to d3-ill GT-10 . and 8-inch hollow-stem augers to drill GT-I 1 Soil samples were collected from each bo-ing using a 140-pound falling hammer and split-spoon sample barrel loaded with three clean bra3s sample tubes Samples were collected at 5-foot intervals from 40 to 120 feet in GT-11 (this baring was drilled through the former UST excavation, so the backfill material above 40 feet was not sampled) In GT-10, samples were collected where needed to meet the specific objectives listed in section 14, and some intervals were continuously sampled for a few feet One sleeve of each sample was capped, sealed, labeled, and placed in a cooled ice chest for laboratory analysis Another sleeve was extruded into a plastic bag and placed in the suii to allow hydrocarbons to vaporize After several minutes, a Microtip model 2020 photo-ionizatio'i detector (PID) was inserted into the bag to measure the concentration of volatilized organic vapors Vapor readings, grain size, and other observations were noted on the boring logs (Appendix A In some cases,the third sleeve was preserved for hydraulic conductivity or grain size analysis 2.2 Well Construction and Surveying The shallow bonng was completed as monitor well GT-10 using 4-inch PVC casing De-ails of its construction are shown in the boring log The screened interval extends from 60 to 30 feet The elevation of the well casing was surveyed relative to monitor well GT-3 on Marc 1 25 The casing elevation is shown in the Well Monitor Report (Appendix B) As explained in se ction 2 3, all wells were re-surveyed on April 9 . 3