WORK PLANS - Laserfiche WebLink

Home Browse Search

Soil Boring Results and VEG/ISCO Work Plan Field Maintenance Shop #24, Stockton, California October 2016 indicate groundwater typically flows to the north-northeast, exhibiting small, possibly seasonal fluctuations within that range. The groundwater gradient is generally very flat, with an average of approximately 0.0010 feet/foot according to data collected in the second quarter 2016. In April 2013, specific capacity testing data was acquired from two site monitoring wells located inside the source zone area (FMS-MW6 and FMS-MW7) and one site monitoring well outside the source zone area (FMS-MW2). Testing results (OTIE, 2013) showed hydraulic conductivity (Ksat) values are highest in the soils outside the source zone area (between 70.4 and 103 gallons per day per square foot (gpd/ft2) and lowest in the soils inside the source zone area (between 0.4 and 11.16 gpd/ft2). The Ksat value range of the source zone area soils is generally consistent with silty clays (Shevnin V. et al., 2006). 2.0 SOIL CHARACTERIZATION STUDY A Soil Characterization Study was conducted to provide additional data for optimizing remedial actions at the site including VEG for treatment of petroleum compounds in the soil and ISCO for reducing petroleum contaminants in groundwater. The scope of the Soil Characterization Study included performing three (3) soil borings in the source area in the vicinity of FMS-MW6 to a depth of approximately 40 feet and the collection of 15 soil samples for environmental and geotechnical analysis at multiple depths. ECM installed three (3) borings (SB-4, SB-5, and SB-6) on July 20 and 21, 2016 to the west, north and northwest of monitoring well FMS-MW6, respectively (Figure 5). Borings SB-5 and SB-6 were advanced within the footprint of the UST concrete pad. Samples were collected from the borings ranging from 9 to 39 feet bgs at 5 samples per boring. Sample locations were selected based on different lithology, elevated PID readings, and general distribution in the vadose zone. The deepest sample from each boring was collected 1-2 feet below the water table to analyze soil samples to support ISCO injections. Field documentation and boring logs are provided in Appendix A. Soil samples were submitted to BC Laboratories, Inc. (BC Labs) in Bakersfield, California for Environmental and geotechnical analytical laboratory analyses which included the following: Volatile organic compounds (VOCs) by U.S. Environmental Protection Agency (EPA) method 8260B; Total petroleum hydrocarbons as gasoline (TPH-g) by EPA method 8260B Total petroleum hydrocarbons as diesel TPH-d by EPA method 8015B; Soil moisture content by ASTM method D-2216 Soil grain size and distribution by ASTM method D4464(M); and Total organic carbon (TOC) by EPA method 9060A. Investigation derived waste (IDW) including any soil cuttings and equipment decontamination fluids were containerized in DOT-approved, steel, 55-gallon drums. IDW from the soil borings was transported offsite on August 10, 2016. A waste manifest is provided in Appendix B. 2.1. Soil Sample Results A summary of soil sample analytical results is provided in Table 1 and geotechnical data collected from selected samples is provided in Table 2. Laboratory analytical reports are provided in Appendix C. A summary of analytical results is provided below for each soil boring, reporting only the samples within the unsaturated portion of the vadose zone. Page 3 •