ARCHIVED REPORTS_PRELIMINARY ASSESSMENT_SITE INVESTIGATION REPORT

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Versar, Inc. April 20, 2000 Page 2 DATA ACQUISITION The first task undertaken at the Vehicle Storage Yard area was to establish a survey grid to guide the VMG data acquisition. The grid consisted of north-south lines spaced 5 feet apart. Data measurement points were distributed along each line at 5-foot intervals. Following the grid set- up, we used a proton precession magnetometer to collect VMG data. The data were up-loaded to a field computer and processed to produce a preliminary VMG contour map. We then analyzed this contour map to determine the locations of VMG anomalies that might be caused by buried ferrous objects. Following the VMG survey, we used the MD method to perform site-specific investigations of anomalous areas identified on the VMG contour map. The site-specific MD investigations involved multi-directional traverses overthe VMG anomalies to determine the general extent and orientation of the buried metallic object causing the anomaly. Finally, we obtained two GPR traverses of the areas immediately above the suspected buried objects detected with the MD in • an effort to determine the buried object's approximate size and relative depth. RESULTS The geophysical data and our interpretation of that data is presented on the Geophysical Survey Map shown on Plate 1. This map shows the VMG contour data, the limits of the geophysical survey, the locations of interpreted buried features, above ground cultural features, etc. Our interpretation of the geophysical data delineates three notable suspicious features: a relatively large buried metallic object in the south-central portion of the area and two relatively small metallic objects in the north-central portion of the area. The large metallic object was detected with both VMG and MD methods. This object is depicted on Plate 1 as the shaded blue rectangle. The assemblage of closed contours approximately centered at 90 East/40 North on Plate 1 are attributed to object. The magnitude and areal extent of this VMG anomaly suggest the object(s) responsible is relatively large. Based on the results of the VMG and MD methods it is our opinion that this object is large enough to be one or more large tear gas cannisters (i.e. larger than a 5-gallon can). The GPR results of the data profiles over this body were inconclusive. The suspected metallic objects giving rise to the two smaller VMG anomalies approximately located at 85 East/80 North and 115 East/80 North were not detected using the MD method. This lack of MD instrument response, in addition to the relatively small VMG magnitude and areal extent, suggest the causative objects are likewise relatively small (i.e. smaller than a 5-gallon can). As a result, no GPR profiles of these objects were attempted. It is our opinion these VMG • anomalies are most likely caused by minor amounts of buried metallic debris but they could, in fact, be due to small individual canisters of tear gas.