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SECTION 4.0 SITE INVESTIGATION ACTIVITIES feet below the top of the water table Samples were collected using the KabisTM II sampler for 4-inch wells, as described in Appendix B The discrete samples at each depth were collected in three 40-milliliter vials (40 mil VOAs) The 40 nil vials are screwed into the bottom of the ' stainless-steel lid on top of the KabisTM sampler Groundwater fills into each vial via stainless- steel sample ports located on top of the KabIsTM sampler lid As long as the KabisTM sampler remains stationary in the well, groundwater will continue to fill the vials and then cascade from the vials into the KabisTM sampler reservoir The vials and reservoir fill in approximately 10 minutes The discrete groundwater samples were analyzed at the Stockton Yard site using a mobile laboratory operated by Environmental Laboratories (ONSITE) for the following analyses TPH-g in accordance with EPA Method 8015 modified • BTEX and MTBE in accordance with EPA Method 8260B Nitrogen as nitrate and sulfate analyses in accordance with EPA Method 300 0 were conducted by a subcontractor to ONSITE (Curtis and Tompkins) During collection of the discrete samples, URSGWC monitored for the following groundwater quality parameters pH, conductivity, temperature, dissolved oxygen, and turbidity The field monitoring data are recorded on well sampling logs included in Appendix A Quarterly groundwater monitoring at Stockton Yard was conducted during April 1 and 2, 1999 by PSI under contract to Caltrans The routine periodic groundwater monitoring at the site included measunng depth to groundwater in the 12 onsite groundwater monitoring wells and two vapor monitoring wells, purging of each well, and collecting groundwater samples for analytical testing The depth-to-groundwater measurements were used by PSI to evaluate groundwater surface elevations, and horizontal gradients Depth to groundwater measurements and analytical data for the April 1999 monrtonng event are included in Table 3-3 The results for the quarterly monitoring event are discussed along with the discrete vertical sampling in Section 5 0 4.3 SLUG TEST PROCEDURES Single-well hydraulic tests (slug tests) were conducted at three wells at the Stockton Yard site Slug tests consisted of lowenng a mandrel into each of the three wells to cause an instantaneous rise in water level The fall in water level to static water level conditions was measured using a water level meter to the nearest 0 01-foot Once static water level conditions existed, the mandrel was removed from the water column to cause an instantaneous fail to water The subsequent recovery of the water level to static conditions was measured with a water level meter The data were down loaded in the AgtesolvTM groundwater modeling program to the estimate hydraulic conductivity for each slug test The data were analyzed using the Bouer and Rice Method for S 1PROJ141040100044SYYARD4MAINTYAROSIIDOC 4-3 URS Greiner Woodward Clyde