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Appendix C Ground Penetrating Radar Investigation Phase 11 ESA Multi-Modal Station"Six-Block Project" January 6,2003 Page 8 of 9 representative line from the property is shown m Radargram 54 By contrast, Radargram 55, from the adjacent property at 147 N Aurora Street, depicts a significant subsurface feature that may be a buried object, a bounded area of fill,or two vertical conduits Radargram 55 was collected from above a concrete pad with no noticeable damage or repair work and the anomaly may be indicative of a possible UST Seven other GPR lines were walked at this property to investigate one proposed boring location The boring was advanced away from,but in the vicinity of, the identified feature 805 E Weber Avenue One potential boring location and an old concrete patch at the property were investigated by seven GPR lines on May 22, 2002 No concerns were identified in the vicinity of the potential boring location Radargram 56 was collected from above the concrete patch and shows a possible void beneath the patch The void anomaly is suggestive of a small vault box rather than a cylindrical UST No other surface features indicative of a void or buried object were noted 815 and 829 E Weber Avenue A total of 60 GPR lines were walked on May 13, 2002 to investigate the property at 815 E Weber Avenue and three potential boring locations Access to portions of the property was limited by automobiles and shop equipment Radargram 57 shows a clear vertical conduit in the vicinity of what appeared to be an oil sump or oil-water separator cover This feature was identified in addition to several pipes, possible small buried objects, and areas of fill in other radargrams Radargram 58, for example, is representative of the subsurface at the property and contains many anomalies Radargram 59 is a similarly representative radargram of the adjacent property, 829 E Weber Avenue, and is also indicative of historical disturbance A total of 28 GPR lines were walked to investigate this adjacent property and three • potential boring locations The bonngs at both properties were advanced to avoid identified subsurface anomalies as much as possible 843 E Weber Avenue Seven potential locations for six borings were selected at the property and investigated by 48 GPR lines An additional 15 lines were walked to investigate other areas of concern All data was collected on May 16, 2002 Like the other Block 5 properties along E Weber Avenue, the characteristic subsurface conditions suggest a history of disturbance and the presence of buried pipes and possible small buried objects, as observed in Radargram 60 Radargram 61 shows another of these subsurface features The anomaly in this radargram is likely a small buried object The borings at this property were advanced to avoid identified subsurface anomalies as much as possible 1.3.9 Block 6 128 N Aurora Street and 915 E Weber Avenue The property at 128 N Aurora Street was investigated as access permitted on May 14, 2002 A total 13 GPR lines were walked at this property to investigate the site for any subsurface features of concern and to select a location for one boring Radargram 62 is characteristic of the subsurface at the property and is indicative of historical disturbance However, there were no large-scale buried objects, pipes, or other features that prevented advancement of one boring at the property One potential boring location in the adjoining shop building at 915 E Weber Avenue was investigated by five GPR lines Radargram 63 shows the rebar of the concrete shop floor as well as a possible buried object or void This potential boring location was not used and no other potential locations were investigated as a result of limited access within the shop •