ARCHIVED REPORTS XR0000247 - Laserfiche WebLink

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SECTION 1.0 INTRODUCTION Task 1 —Survey of Public and Private Groundwater Wells At the February 10, 1999 meeting, the CVRWQCB requested a survey of public and private groundwater wells within 500 feet of Stockton Yard In addition, URSGWC proposed to review public well records maintained by the California Department of Water Resources (CDWR) and conduct a survey of well owners within 500 feet of the perimeter of the Stockton Yard site Task 2 —Vertical Delineation of Petroleum Hydrocarbons in Groundwater The CVRWQCB requested that the vertical extent of petroleum hydrocarbons in groundwater be evaluated for the Stockton Yard site To delineate the vertical distribution of petroleum hydrocarbons in groundwater, the KabisTM discrete groundwater sampler was proposed Wells MW-6 (screened from approximately 45 to 75 feet bgs) and VW-2 (screened from approximately 45 to 70 feet bgs) were proposed to be sampled using the KabisTM discrete sampler Both wells are 4-inch diameter PVC wells that are located in areas where petroleum hydrocarbons have been historically detected in groundwater In the scope of work, groundwater samples were proposed to be collected from each of the 4-inch wells at the following locations (1) less than 2 feet from the top of the water table, (2) approximately 10 feet below the top of the water table, and (3) approximately 15 to 20 feet below the top of the water table Groundwater was not to be purged from the wells prior to sample collection Rather, the objective was to collect undisturbed samples (to the extent possible) at up to three sample depths Groundwater sampling procedures are detailed in Appendix A Literature on the KabisTM discrete sampler is provided as Appendix B Groundwater samples were proposed to be analyzed for TPH-gasoline range (TPH-g) and benzene, toluene, ethylbenzene and total xylenes (BTEX) and for methyl tertiary butyl ether (MTBE) in accordance with U S Environmental Protection Agency (EPA) Methods 8015 modified and 8260, respectively In addition, groundwater samples from the selected monitoring wells were proposed to be analyzed for nitrate and sulfate Field measurements were collected for pH, conductivity, temperature, and dissolved oxygen in groundwater Task 3—Estimation of Hydraulic Conductivity To estimate the hydraulic conductivity beneath Stockton Yard, slug tests were proposed in up to three monitoring wells The slug tests entailed measuring the instantaneous response within the respective wells after introducing and removing a mandrel (slug) of specified weight and volume Water elevation data were collected over specified time intervals until static conditions were achieved Standard procedures for slug tests are presented in Appendix C URS Greiner Woodward Clyde S IPRO.A41040100041SYYARDIMAtMARDSADOC 1-3 r