2017-01-30_PERMIT FILE - C1981041 (8)

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FUGRO CONSULTANTS, INC. In the area of the depressions within the trench (where the bulk of the water was poured into) a relatively lower resistivity zone (blue colors in Figure 5 cross-sections SR8 and SR1) is present directly beneath and lateral to the depressions. Higher resistivities occur beneath this zone indicating it does not extend to depth. It is unclear whether this lower resistivity zone is caused by fluid leakage from the depressions or is a naturally occurring formation with a lower bulk resistivity (higher clay content). A linear ERT near surface anomaly (NSA) is identified in Lines SR1 through SR5 (Figures 2 and 5). This anomaly is characterized by low resistivity (< 10 ohm -m). The origin of the anomaly on the west side of the survey area is at the sinkhole within the ditch where a large volume of water was introduced prior to the survey (Position 87 meters, Line SR1). Within the interpreted cross-sections from Lines SR2 and SR3 the top of the anomaly is within 5 to 7 meters of the ground surface at positions 93 meters and 76 meters respectively. In Lines SR4 and SR5 the NSA (Positions 78 meters and 79 meters respectively) joins with an approximately vertical anomaly. The bottom of the NSA at the intersection with the vertical anomaly is approximately 5 meters below the ground surface. These anomalies correlate well with the vertical anomalies identified in Lines L4 and L5 of the April survey. A second approximately linear near surface low resistivity zone is shown approximately 9 to 18 meters north of the anomaly described above. The North NSA extends from Line SR8 through SR7 but does not appear to join with the vertical anomalies in Lines SR4 and SR5. It generally extends from 5 to 8 meters below the ground surface although it is not well resolved since it is located at the edge of the data coverage. As stated in the previous report covering the April survey, low resistivity values are not expected for air-filled or clean water -filled voids. Therefore, it is likely that the horizontal anomaly may be the result of coarser material pathways which may contain a higher distributed clay content that create a horizontal permeability pathway. This zone may have been wetted by the inflow of water introduced into the trench prior to the ERT survey. The increased moisture content in the zone can cause a decrease in the bulk resistivity of the material (especially with high ion exchange capacity clays). The ERT survey cannot determine absolutely the cause of the anomalies identified in the data. The presence of an isolated vertical anomaly in a horizontally layered geologic section is significant especially since the location of the anomaly corresponds to sink hole like surface features and is located in the area of a vertical air shaft. The natural flow of groundwater is expected to be primarily horizontal in the geologic section (interbedded sandstones and shales) which underlies the area. Vertical flow would occur along features that create permeability across the horizontal layering such as fracturing. This fracturing would also tend to decrease the bulk resistivity of the rock units particularly if the fractures are filled or at least wetted with groundwater. The vertical shaft, which is identified to be located in the vertical low resistivity zone (Figure 2), may also act as a vertical pathway for groundwater depending on how it was sealed. The presence of depressions and sinkholes in the area suggest that vertical failure has occurred in the area. The shaft may or may not have contributed to structural weakening of bedrock layers in the area. The size of the vertical anomaly identified in the two ERT Project/Proposal No. 04.79160011 August 23, 2016 Page 6 of 7 TR -69 A14-15-9 09/16