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NAVCOM 2 30 August 1990 surface water sampling stations were established. This study did not include an assessment of the ten PCB and Pesticide Sites. Table 1-4 of the Kleinfelder study (attached) shows the number of monitoring stations for each study area and the chemical analyses conducted. Kleinfelder concluded that ground water had been contaminated by past waste handling and disposal practices at the Landfill , Fire Fighting, and GSA Damaged Container Storage Areas. The ERM-West 1989 study was directed towards an assessment of contamination (maintenance oil , vehicle fuels, solvents, pesticides, PCBs, and metals) , from the ten PCB and Pesticide Sites. These sites were operational sites and included sumps, an underground tank, wastewater treatment facilities, and storm drains. ERM-West concluded that past waste handling and disposal practices have contaminated soils and ground water at some of these sites as indicated by Table 1-5 (attached) . The MARK Group did a preliminary evaluation of the data collected in the previous investigations, and in concert with information gained from site visits, concluded the following: 1) The islands storm drainage ditches are predominantly unlined and the deeper ditches (10 to 12 feet deep) , in the western portion of the island, show indications of ground water seepage. 2) The hydrogeology of the island is incompletely characterized. A simplified schematic of the hydrostratigraphy, consisting of five hydrostratigraph ic units, was prepared (Figure 1-1, attached) . The water table is shallow with depths from 3 to 5.5 feet BGS across the island. The general flow pattern in the uppermost layer of the upper water-bearing zone (based on piezometer readings) is away from the major channels bordering the island, and towards the island's interior drainage channels. The Duck Pond appears to be a source of recharge. Tidal influences on the water table are ill-defined. Ground water flow within the intermediate water-bearing zone, based upon five wells, is in the southwesterly direction. However, the consultant admits that this needs to be confirmed with additional wells. Upward vertical gradients were measured at four locations, a downward vertical gradient was measured at one location. The degree of interconnection between the two water-bearing zones is unknown, in fact, the formation between these two zones is presumed to be an aquitard. 3) The characterization of soil contamination within the Study Areas is incomplete. Soils were not sampled in Study Areas 1 through 4 and ERM-West sampled, as part of their Site 5 investigation, soils in only a small area of the southwestern portion of the island. According to the MARK Group only three areas show significant soil contamination; subsurface soils at the waste oil tank between Buildings 816B and 816C, surface sediments in the storm drains, and the sludge drying beds (Sites B, I, and F respectively, in the attached Table 1-5) . 4) The primary chemicals of concern within the ground water are volatile organic compounds. VOC contaminated ground water has been detected in Areas 1,3,4,and 5B as illustrated on the next page.