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NORCAL URS Greiner January 25, 1999 Page 4 ' this map are the locations of detected utility alignments. Since a utility search was not the primary objective of this survey, there may be additional utilities that are not shown. A description of the results for the geophysical surveys in the North and South Areas are presented in the following paragraphs. North Area ' The results of the investigation in the North Area are shown on the Geophysical Survey Anomaly Map, Plate 2. The VMG contours indicate 4 anomalous areas, labeled A through D, that represent effects from buried metal not associated with known above or below ground features. Of these, Anomaly A has closures that are consistent with UST's. This anomaly is characterized as a group of closely spaced high amplitude closures with values ranging from ' 800 to 1,900 nanoTeslas per meter (nT/m). It covers an area of approximately 45 by 100 feet and indicates a large zone of buried metal objects. It has been our experience that VMG anomalies of such magnitudes and areal extent can be due to many different metallic sources. These sources may include small UST's, buried metal debris, and/or portions of reinforced ' concrete slabs associated with former facilities . It should be noted, however, that it is not possible to differentiate, based on the VMG data alone, which anomaly could be related to a UST because of the large number of closures defined in this area. Anomalies B through D are ' characterized as isolated circular closures with low amplitudes ranging from 100 to 200 nT/m. These anomalies probably indicate buried objects that are too small to be UST's. The series of contour closures between anomaly areas A and B are probably caused by an underground t utility line, as shown on Plate 2. Other small, circular closures probably represent scattered debris. The closely spaced contours along the southwest side of the North Area are probably caused by the storm drain shown on Plate 2. The results of the GPR survey in the North Area are shown on the Geophysical Survey Map Plate 2. We obtained GPR data over VMG Anomalies A through D. The GPR data do not indicate hyperbolic signatures within the upper two to four feet that are large enough to represent a UST. However, the GPR data do define reflection patterns typical of small scattered objects, possible utility alignments, and disturbed soils. The reflection patterns ' typical of scattered objects and possible utility alignments generally occur in small isolated areas. Some of these areas correspond with the location of the utilities shown on Plate 2. The reflection patterns indicating disturbed soils occur in three zones. We refer to these zones ' as GPR anomalies on Plate 2. Two zones correspond with portions of VMG anomaly A, and one with Anomaly B. We believe that these areas may represent the location of former excavations. The remainder of the GPR data exhibits continuous reflecting horizons typical ' of undisturbed subsurface strata. Since it is highly unlikely that the small scattered objects and utility lines detected by GPR would create VMG anomalies with the magnitudes exhibited by Anomaly A, we believe that the source of the VMG anomalies is probably buried deeper ' than the detection capabilities of the GPR. 1