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r. f 1.0 INTR OD ACTION This Workplan has been prepared as part of an ongoing research pro- ject. The current research is being performed to evaluate the fate and transport of 1,2-dibromo-3-chl oro propane (DBCP) in subsurface soils in select locations in the San Joaquin Valley. Figure 1 shows the location of the current study areas. 1.1 BACKGROUND DBCP was widely used in California until 1977 as a soil fumigant for nematode control. Subsequently, in 1979, California water pollution control, agricultural, and health authorities discovered that ground- water had been affected by DBCP in areas where DBCP had been applied. The purpose of the previous 1979 study was to determine how DBCP had reached groundwater. The conclusions of the 1979 study indicated that: • DBCP can be found in subsoils between the ground surface and the water table in parts per billion (ppb) of dry soil amounts. • Clays and silts adsorb higher levels of DBCP and may not act as barriers to downward movement of DBCP. • DBCP is persistent in.soil, remaining in the top soil at one site six to seven years after a single application. Considerable time has elapsed since the previous DBCP study and the cessation of DBCP application. This purpose of this study is to replicate the previous 1979 sampling study as closely as possible, to trace DBCP in the subsurface soils where it was previously.identified. 1.2 WORKPLAN CONTENTS This workplan is organized into three sections and: Section 2.0 describes the proposed Sampling Plan for sampling and ana- lyzing soil to replicate the previous DBCP study. Section 3.0 presents the associated Quality Assurance/Quality Control (QA/QC) procedures that will be utilized. ' ri