SITE INFORMATION AND CORRESPONDENCE

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The landfill sites are in the wildlife area, located west of Humphreys Avenue. Prior to 1900, this area was a marshland below mean sea level. Sedimentary deposits resulted from the fluctuation of the groundwater. This resulted in multiple layers of silt, sand, and clay. In the late 1800s, farmers constructed levees to create larger farm areas. A drainage channel was put in to keep the groundwater from flooding the island. The U.S.Naval Supply Annex came on board in 1945;the Naval Communications Station in 1960;-and the Naval Computer and Telecommunications Station in 1998. Three of the ten sites were determined to be geophysical anomalies (Sites 37, 38, and 39). There were no records indicating that these were landfill sites, but geophysical surveys were conducted based on aerial photographs. All of the landfills were closed prior to November 1979, when the Resource Conservation and Recovery Act (RCRA)went into effect. RCRA was the first major regulation that monitored the disposal practices and landfill regulations. The Navy was found to be in compliance with the laws in effect prior to RCRA. According to the NEESA report, the landfills were not defined as hazardous waste landfills, as none contained more than one percent of hazardous waste. The Data Quality Objectives (DQOs)were based on the presumptive remedy that the landfill was to be capped. The investigation was based on the assumption that the top of the landfill cell was clean, as it would be capped with a suitable engineered cap to prevent exposure to its contents. The actual remedy is yet to be determined; options other than the cap are being considered. Public Law 104-160 gives the Navy the option of transferring the installation to the Port of Stockton for use as a port facility. Therefore, the future use of this land will remain industrial, similar to Navy occupancy. There is also an option to do a federal agency-to-agency transfer, as may transpire if the Immigration Naturalization Service (INS) occupies a portion of the island. There were several design aspects that needed to be evaluated, including the size of the caps, whether a gas collection system would be necessary, and the physical properties of existing soil cover. Boundary trenching was conducted from the outside of the geophysical anomalies toward the cell; it defined the actual number, extent, and depth of each cell. The results showed that all of the areas were smaller than expected. For example, Site IAS-03/04 was originally thought to be one cell with an area of 369,000 square feet, and in reality, three cells were identified with a total area of 49,975 square feet. Site 38 did not contain a cell. Samples were collected immediately on the outside of the cells to determine any risks. Assessments for human health risk(HHRA), ecological risk(ERA), and water quality (WQA) were conducted according to guidelines put forth by the Environmental Protection Agency (EPA), RQWCB, and Department of Toxic Substances Control (DTSC). The HHRA was based on a recreational receptor. The ERA utilized the most conservative assumptions published in the EPA document, including the smallest body weight of the receptor, 2