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December 27, 2023 Page 6-11 <br />Agapito Associates, Inc. <br />6.2 Surface Subsidence Analysis <br />Agapito utilized the numerical modeling software program Surface Deformation Prediction <br />System (SDPS) to assess the likely maximum surface subsidence resulting from the proposed pillar <br />extraction plans. SDPS uses an integrated approach of calculating and predicting ground <br />deformations above undermined areas. Based on empirical or site-specific regional parameters, the <br />model quantifies a variety of ground deformation indices for both longwall and high extraction <br />room-and-pillar mines, including subsidence profile, angle of draw, strain, slope, and curvature. <br />The input parameters used in the model are summarized in Table 6-2. <br />Table 6-2. Input Parameters used in the SDPS Model <br /> <br />The modeling results indicate that a maximum of 3.5 ft of vertical surface subsidence is estimated <br />following the proposed pillar extraction (see Figure 6-8). In terms of the extent of the subsidence <br />trough, the subsidence does not extend beyond the footprint of the pillar extraction area. <br /> <br /> <br />Location Extraction <br />Height (ft) <br />*Total <br />Extraction (%) <br />Percent <br />Hardrock (%) <br />Location of <br />Subsidence <br />Impacts <br />E Seam 10 100 50 Surface <br />Note: *total extrication includes remnant pillars