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Appendix C Ground Penetrating Radar Investigation Phase II ESA Multi-Modal Station `Six-Block Project' January 6,2003 Page 4 of 9 13 2 750 E.Miner Avenue A total of 54 GPR data lines were collected to Investigate nine potential boring locations selected for the five borings proposed for the property Five locations were selected and Investigated on May 23, 2002, and four additional locations were selected and Investigated on May 29, 2002 following review of the May 23 data Access to the property was limited by several parked cars on the southern portion of the property that were not moved Radargram 5 presents a typical line representative of the undisturbed subsurface conditions at the site Radargrams 6 and 7 show a buried pipe that Iikely rums east to west across the property approximately 151 feet south of E Miner Avenue This pipe was avoided during drilling Radargrams 8 and 9 depict buried objects or disturbances at the property Based on its shallow depth, the object in Radargram 9 is likely a pipe However, the hyperbolic reflection signal is wider than a typical pipe reflection, such as those seen in Radargrams 6 and 7, and is similar to a typical reflection signal from a UST 1.33 701 E Channel Street The property was Investigated using 12 GPR data lines to investigate two potential boring locations for the one proposed boring On May 17, 2002, one potential boring location was investigated Radargram 10 depicts possible pipes Identified in the vicinity of this boring location The property was further investigated on May 29, 2002 and a second potential boring location was found to be clear for drilling Radargram 11 shows a representative data line from this location The portion of the property currently occupied by the medical center building was not investigated by GPR • 1.3.4 201 and 213 N. Grant Street One potential boring location and other areas of concern at 201 and 213 N Grant Street were investigated by 28 GPR lines on May 21, 2002 The areas of concern included a concrete slab In the southwestern corner of 213 N Grant Street and an area of old, patched, asphalt with some vegetative cover in the western portion of 201 N Grant Street Radargrams 12 and 13 depict data collected from the concrete slab Evenly spaced rebar is evident in these radargrams A fairly distinct disturbance Is present in Radargram 13, but the diffraction hyperbolas from the near-surface rebar interfere with deeper subsurface features and prevent resolution of this disturbance Radargram 14 depicts a highly disturbed area near the western boundary of 201 N Grant Street Several possible near-surface pipes are evident, along with possible deeper pipes and buried objects The prevalent disturbed character of Radargram 14 is Indicative of miscellaneous buried debris and historical disturbance that may include excavation and backfilling 1.3.5 Block 2 808 E Miner Avenue A gas station was listed in the 1940 Polk City Directory for Stockton at 802 E Miner Avenue (historic address for 808 E Miner Avenue) Based on this listing, a GPR study was conducted at the property on May 28 and 29, 2002 to examine for the possible presence of a UST No further information regarding the gas station or possible UST removal was found Nine potential boring locations and one area of potential concern were investigated on May 28 and 29, 2002 A total of 73 GPR lines were walked at this property Access to portions of the property was limited by parked automobiles on display for sale Radargram 15 depicts an undisturbed portion of the property with a distinct reflection from a buried object A disturbed area is noted in Radargram 16 These radargrams are indicative of the varied subsurface conditions across the property Disturbed areas and buried objects were avoided during the final boring location selections