WORK PLANS_PART 2 FILE 1 - Laserfiche WebLink

Home Browse Search

GEOMATRIX United States and State of California to implement environmental remediation programs related to releases of DBCP, ethylene dibromide(EDB), and sulfolane; these are collectively referred to as Occidental's organic chemicals of concern(CDCs). Ongoing groundwater remediation includes seven groundwater extraction wells, a treatment system for extracted groundwater, and two groundwater injection wells. Occidental has been monitoring groundwater for organic COCs east and west of Howland Road in three groundwater intervals: shallow groundwater (31 to 83 feet below ground surface [bgs]), intermediate groundwater(84 to 150 feet bgs), and deep groundwater(151 to 218 feet bgs). Occidental indicates that these zones overlie the eastern extent of the Corcoran Clay,which is a regional aquitard that confines groundwater below and prevents significant vertical migration of groundwater. Groundwater monitoring results have detected the presence of elevated concentrations of organic CDCs in the shallow, intermediate, and deep groundwater intervals (The Source Group, 2001). Between 1966 and 1975, Occidental operated two groups of surface impoundments located east and west of Howland Road. The eastern impoundments consisted of the current storm water pond and a"pellet plant pond." The pellet plant pond no longer exists and has been replaced by the"west pond." The western impoundments include gypsum settling ponds, "concentrator ponds," and a"southwest wastewater pond." These western impoundments no longer exist. The Lathrop facility currently consists of approximately 341 acres of property on the east and west sides of Howland Road north of Highway 120 and south of Louise Avenue(Figure 1). The area west of Howland Road includes Simplot's fertilizer plant and Occidental's groundwater remediation systems. The area west of Howland Road includes Simplot's wastewater management systems,which currently consists of the storm water pond,three lined wastewater management ponds (west pond,north pond, and south pond as shown on Figure 2), and about 101 acres of agricultural property irrigated with storm water. Simplot's wastewater management systems are currently regulated under WDRs and its associated MRP. 2.2 GROUNDWATER MONITORING Occidental and Simplot have been monitoring shallow groundwater quality(approximately 25 to 50 feet bgs)below the lined wastewater ponds since 1982. Occidental has also been monitoring intermediate and deep groundwater intervals since 1982. Simplot's shallow groundwater monitoring results detected elevated concentrations of dissolved solids in 1982 at the initiation of groundwater monitoring(wells LP-1, LP-2, LP-3, and PW1-48, Table 1 and Figure 1). In 2001, Simplot installed detection monitoring wells to monitor the groundwater table at approximately 10 to 25 feet below the lined ponds(LP-4 1:\6000s\6741.000\Archive\6741-13.doc 2