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Appendix C Ground Penetrating Radar Investigation Phase II ESA Muiti-Modal Station"Six-Block ProJeCC January 6,2003 Page 3 of 9 . greater than five feet bgs In some cases, boring locations were moved or additional borings advanced after the completion of the GPR investigation These boring locations were not investigated directly by GPR, but were often inferred to be clear for drilling based on GPR data collected nearby In addition to investigating the selected boring locations for possible buried utilities, GPR data were collected on a broader scale for selected properties that were suspected as possible locations of other buried features of environmental concern, such as oil sumps and USTs Properties were selected for more extensive investigation based on observed conditions at the time of the visit, as well as past and current property uses Some selected properties were investigated to the full extent possible based on accessibility, while others were only investigated in areas that were identified as suspicious GPR data lines were generally positioned with the intent to gather as much information regarding the subsurface conditions of the site as possible in a time-effective manner GPR Imes were traversed from west to east or south to north unless otherwise indicated on the included figures Lines were walked at an approximate pace of 1 5 feet per second and data were collected continuously using a Geophysical Survey Systems, Inc (GSSI) SIR-2000 GPR system with a 400 Mega Hertz (MHz) antenna The antenna was either pulled along the lines of interest or was pushed along the lines as part of a cart-mounted operation, depending on property conditions Based on soil type and conditions, a data collection range of 40 0 to 60 0 nanoseconds was selected in order to investigate the subsurface to an estimated depth of six to eight feet bgs The GSSI software package RADAN NT was used to process the raw data collected at the site Processing methods including deconvolution,migration, and spatial filtering were employed to suppress noise,multiple reflections, and antenna ringing 13 GROUND PENETRATING RADAR INVESTIGATION RESULTS A total of 936 GPR data lines were collected from 28 of the private properties within the site For the purposes of this report, only 66 of the 936 collected data lines are discussed A map of the GPR study area and data line locations is provided in Figure 4, Appendix A GPR Imes were traversed from west to east or south to north unless otherwise indicated on the included figures Most of these lines were selected based on the presence of some feature of note in their respective radargrams At least one radargram from each property is included For properties with no notable radargram features, a"representative"radargram for the property is included Radargrams for data lines 1-66, and an index grouping the radargrams by property and block and providing the corresponding data file number for each radargrarn is included at the end of this Appendix Each data file number represents a walked line for a given property 1.3.1 Block 1 722 E Miner Avenue On May 28, 2002, a total of 10 potential boring locations were selected for the eight borings proposed for the property The boring locations were investigated by 60 GPR data lines Two of the potential boring locations were located on a recently poured concrete slab east of the garage and were eliminated at the request of the property owner Radargram 1 shows a typical line of data collected at the property Rebar and a possible buried object are evident in Radargram 2, collected from the concrete slab Radargram. 3 depicts another possible buried object This feature was not evident in adjacent radargrams and the boring location was marked to avoid this possible object The features in Radargrams 2 and 3 appear to be indicative small-scale buried objects and do not suggest the presence of buried pipes or USTs Radargram 4 shows a vertical conduit that had no surface indicators of its presence and was avoided when the location was marked