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r GRG <br />FUGRO CONSULTANTS, INC. <br />Data Processinq <br />Acquired data were uploaded to AGI Earth Imager© software as an initial QC measure at the end of each field <br />day, to ensure data quality and coverage. Final models for interpretation were generated through RES2DINV <br />ERT processing software from GeoTomo Software. GeoTomo performs electrical resistivity tomography using a <br />least squares approach. Data are viewed and edited for outliers prior to the tomographic inversion to reduce <br />model error and to prevent spurious artifacts. Data positioning (X,Y) were based on handheld WAAS enabled <br />GPR coordinates for the center and both ends of each ERT line. These locations were adjusted based on field <br />notes and photos, to best fit the Google Earth Satellite imagery, then the position of each electrode was <br />interpolated. The elevations for the electrode positions were then extracted from DEMs in ArcGIS and used to <br />establish the ground surface elevations for the 2-D model. <br />Results <br />Figure 5 shows the geo-electric section of each of the ERT lines with the start of each line (south end) shifted <br />relative to an East-West baseline to facilitate correlation between the adjacent lines. All the geo-electric sections <br />use a common color contoured resistivity scale, which is shown at the bottom of the figure. Low resistivity <br />values are shown in cool colors (blues) and high resistivity values are shown in hot colors (reds). In the ERT <br />lines, the south half of each line shows higher resistivity values in the upper approximately 20 meters, while the <br />northern halves show a thin resistive surface layer underlain by a more conductive unit (greens and blues). The <br />thick more resistive unit on the south half of each line likely corresponds to the coarse poorly graded alluvium <br />exposed in the pond excavations. The lower resistivity unit on the north end of each line, suggests the presence <br />of a finer grained materials with greater clay content. <br />ERT anomalies are identified in Lines 4 through 6 (Figure 5). These anomalies are characterized by low <br />resistivity (< 10 ohm -m) and are elongated vertically. These anomalies also correlate well with the suspected <br />location of the vertical mine shaft and align with the surface expressions of the sinkholes. Low resistivity values <br />are not expected for air-filled or clean water -filled voids. Therefore, it is likely that the anomaly may be the result <br />of rubble filled pathways with higher clay content that create a vertical permeability pathway. This zone may <br />have been wetted by the inflow of water introduced into the trench prior to the ERT survey and possibly from <br />lateral infiltration from the pond which intersected the vertical permeability pathway. The increased moisture <br />content of the zone can cause a decrease in the bulk resistivity of the material. <br />The locations of the anomalies beneath the ERT survey lines are: <br />• Line 4 from 153 m to 172 m <br />• Line 5 from 158 m to 177 m <br />• Line 6 from 159 m to 174 m <br />Project/Proposal No. 04.79160011 25 April, 2016 Page 5 of 6 <br />