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Phase lI Environmental Site Assessment Multi-Modal Stat)on Stockton,San Joaquin County,California Page 5 . bonngs were advanced to evaluate the potential presence of near-surface soil contamination between 0 feet and 15 feet bgs, and were typically advanced on private properties The detection bonngs were installed to investigate the potential for shallow soil contamination between 0 feet and 15 feet bgs, and soil and groundwater contamination between 35 feet and 45 feet bgs The detection borings were advanced on pnvate properties and in public nght-of-ways in the site area The Geoprobe boring procedures consisted of conng through hard surface material such as concrete or asphalt, followed by advancing the bonngs with a hand auger to five feet bgs to check for the presence of buned utilities Once the borings had been advanced to five feet with a hand auger, the direct push sampling equipment was lowered into the holes Continuous soil cores were collected from five feet to 15 feet bgs and retained for soil sample collection The detection boring procedures were identical to the Geoprobe procedures to a depth of 15 feet bgs Between 15 feet and 35 feet bgs, the detection bonngs were advanced with the soil sampler tip closed At 35 feet bgs, the soil sampler tip was opened and continuous soil cores were collected from 35 to 45 feet bgs and retained for soil sample collection and geologic logging After advancement of the detection borings to a depth of 45 feet bgs, a temporary well casing was installed in the open boring to allow groundwater depth measurement and to facilitate groundwater sample collection If field observations indicated that contammation was present, the Geoprobe bonngs were advanced beyond 15 feet bgs and continuous soil cores collected through the apparent extent of impacted soil Continuous cores were also collected between 15 and 35 feet bgs in the detection borings if contamination was noted at 15 feet bgs If contamination was noted in detection bonngs at 45 feet bgs, continuous cores were collected beyond 45 feet bgs through the apparent extent of impacted soil `• A limited number of hydropunch bonngs were advanced to evaluate the potential presence of groundwater contamination at selected locations The hydropunch bonngs were generally coupled with a detection or Geoprobe boring The hydropunch boring procedures consisted of direct push advancement to approximately 40 to 45 feet bgs, unless otherwise noted, and a five to 10-foot retraction of the push rods to allow groundwater influx and sample collection After completion of the Geoprobe, detection and hydropunch boring advancement and associated sampling activities, all borings were backfilled to grade with a neat cement grout Dye was added to the grout as necessary to match the pre-existing surface completion at each bonng location 4 2 4 1 Field Observations The soil cores collected from the direct push borings were logged in general accordance with the Unified. Soil Classification System (USCS) Descriptions of the soil types encountered and other pertinent field observations, including staining, odors, and moisture, were recorded on field geological boring logs Collected soil cores were visually inspected and screened in the field for organic vapor content with a photoionization detector(FID) Groundwater elevation data were collected from the detection bonngs by measuring the depth to groundwater with a battery-operated water level meter Collected groundwater samples were monitored for free-phase petroleum product or sheen and petroleum hydrocarbon odors Pertinent observations were recorded on the corresponding geological boring logs A typical baring log and a few noteworthy boring logs are included in Appendix D 5 3 �C� CONDOR