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Jared Ebert <br /> July 8,2019 <br /> Page 13 of 18 <br /> 36. On Page 3 of the Tetra Tech report, the Applicant references a report titled "Material Quantities at <br /> Proposed Tucson South Resource dated May 25, 2004 by C. Goss". Please provide a copy of the <br /> report for Division review. <br /> A copy of the requested report is attached with this response. <br /> 37. In Section 4.3 Model Results of the Tetra Tech report, the Applicant indicates the required setback <br /> at 75 feet from Tucson Street. Please clarify is the offset is from the current to future right-of-way <br /> easement. Please label the offset distance on the Exhibit C maps. <br /> Offsets on either side of Tucson Street are a minimum of 35 feet from the future right of way <br /> reservation based on the revised slope stability memorandum. Refer to the response to <br /> comment 33a regarding the depiction of offsets on Exhibit C. <br /> 38. In Section 4.3 Model Results of the Tetra Tech report, the Applicant indicates the required setback <br /> at 110 feet from the water pipeline. The Exhibit C-6 map, Details A and B indicates a 43 feet offset <br /> from the pipeline easement. Please explain this discrepancy and update the Exhibit C-6 map details <br /> accordingly. <br /> Aggregate Industries has an existing agreement with the owner of the pipeline that allows <br /> mining within 20 feet of the pipeline. The slope stability models performed along the <br /> pipeline require an offset of 45-feet(Section L of the revised stability analysis). UDFCD <br /> guidelines for lateral berms recommends a minimum lateral berm width (between two <br /> reservoirs) of 100 feet. It was elected to use an offset of 45 feet from the south edge of the <br /> Todd Creek water easement to satisfy all setback requirements in this section of the mine. <br /> The tables in Exhibit C are updated to clearly show the calculated offsets. <br /> 39. Please update the Exhibit C maps to indicate the required setbacks based on the stability analysis <br /> results as indicated in Section 4.3 Model Results of the Tetra Tech report. <br /> As noted in the response to comment 33a, a table showing the required setback distances <br /> and actual setback distances has been added to Exhibits C-2 and C-3. <br /> 40. Please provide justification for not modeling the mud lens in all of the 2018 cross-section as was <br /> modeled in the 2004 stability analysis for the site. <br /> The statement that mud lens was included in all sections of the 2004 slope stability analysis <br /> is inaccurate. A mud lens was NOT modeled in each section in 2004. In each of the slope <br /> stability analyses (2004, 2018, and 2019), the mud lens is shown in sections where borehole <br /> data indicated the presence of a mud lens. The phreatic surface in sections with a mud lens <br /> where a slurry wall is proposed was modeled as undrained. The offsets are updated per the <br /> results of the slope stability analyses performed in response to these comments. An <br /> updated slope stability memo is included as part of the response to these comments. <br /> Aggregate Industries—WCR,Inc <br /> 1687 Cole Blvd Suite 300 <br /> Golden,CO 80401 <br />