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Geosyntec '� <br /> consultants Page 11 of 12 <br /> Client: Arcosa LWB Project: Permit Amendment Project No.: DE0374 Task: Exhibit S—Structures Evaluation <br /> Written by: Jonathan Gillen Date: 7/8/2019 Reviewed by: Youngmin Cho Date: 7/9/2019 <br /> Approved by: Poppy Staub Date: 7/15/2019 <br /> of safety for a structure closer to the mine pit slopes is above the minimum target FS,it is assumed <br /> that this stricture is safe from damage due to active mining operations. <br /> Structure #20— Water Main for Hogan Family <br /> This structure is owned, maintained and operated by Arcosa as part of an agreement with the <br /> Hogan Family. The exact location of this structure is currently unknown; however, it generally <br /> runs west from the Arcosa processing facility,then south along the east side of the quarry near the <br /> fence line toward the Hogan Residence. Because the location is unknown, the evaluation of <br /> stability with respect to mining operations cannot be performed, however Arcosa owns and <br /> maintains the line and is responsible for any damages and repairs. <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> Based on the stability model and the evaluation of structures within the permit boundary and within <br /> 200 feet of the permit boundary,the factor of safety for static and seismic slope stability meets the <br /> DRMS requirements for all structures on site and within 200 feet of the permit boundary. <br /> Furthermore, based on the operation information provided by Arcosa regarding the mining <br /> methods used, it is understood that blasting and other machinery that create significant ground <br /> vibrations is not employed. Therefore, the additional potential risk to slope stability and damage <br /> to structures via mining operations is low. <br /> If existing conditions change or are determined to be different than those assumed in this <br /> engineering evaluation, it is recommended that Arcosa revisit the engineering evaluation to re- <br /> assess the stability of the structures, as necessary. <br /> Structures Evaluation <br /> Arcosa LWB Plan—Permit Amendment 2019-07-16 <br />