Laserfiche WebLink
45 and all of the aforementioned Shannon and Wilson figures. Please review the plan <br />view for the East Taylor Fill on Map 45, Exhibit 7, Item 20, Figures 1C-4 and 1C-5 and <br />Figure 1 of the Shannon and Wilson report and make the necessary <br />changes/corrections to the temporary overburden stockpile configuration and the <br />toe of the permanent fill. <br />Response: The toe of the East Taylor Fill is correct as shown on Map 45, and represents <br />a point at which the fill meets the existing final pit floor topography, which is a more or less <br />flat surface at approximate El. 7700 and 400 to 500 feet wide. Figure 1 of Shannon and <br />Wilson's original October 21, 2009 report correctly depicted this. Figures 1 C-4 and 1 C-5 of <br />Exhibit 7, Item 20 have been revised to conform to the correct toe geometry. <br />23. The Shannon and Wilson report (21 October 2009 Addendum No. 3 to Geotechnical <br />for Excess Spoil) contains Figure 1 - Temporary Spoil Fill Locations. This is basically the <br />same plan view as shown on Map 45, with the exceptions noted in question 14 above. <br />Please explain why the Shannon and Wilson report does not show the E-E' cross- <br />section that is shown on Map 45 and include if necessary. <br />Response: Because the E-E' cross section was not a critical cross section for slope <br />stability evaluation, Shannon and Wilson did not include it in their Figure 1 referenced <br />above . However, as discussed in response to Comment #4, this cross section has been <br />eliminated. <br />A new cross-section E-E' appears on Map 45 as an east-west section through all three <br />spoil piles, but because its depth is less than the other cross-sections that were analyzed <br />for stability, the new cross-section E-E' is not considered a critical cross section as regards <br />slope stability. As such, it is not included on Shannon and Wilson's Figure 10 in their April <br />15, 2010 Revised Addendum No. 3. <br />24. The original July 2006 Shannon and Wilson Study concluded that no rock toe <br />buttresses or key-way cuts are required for the South Taylor valley fills because the <br />designed slopes were 3.8:1, which are less steep than the 2.8:1 slopes which would have <br />possibly required toe buttresses or key-way cuts, pursuant to Rule 4.09.1(10). In TR-81, <br />the temporary fill outslope is proposed to be 2.5:1. Section 4.09.1(10) requires that, "where <br />the slope in the disposal area is steeper than 2.8h:1v... keyway cuts or rock toe buttresses <br />shall be constructed to stabilize the fill. Where the toe of the spoil rests on a downslope, <br />stability analyses shall be performed in accordance with 2.05.3(6)(b), (c) and (d) to <br />determine the size of the rock toe buttresses and keyway cuts". Paragraph (10) contains <br />no language that would limit these requirements to "final" slopes. Since the temporary fill <br />outslope proposed for the East Taylor valley fill is 2.5h:1v, which is steeper than <br />2.8h:1v, please address the keyway cut/rock toe buttress requirements of Rule <br />4.09.1(10), revising the October 2009 study and permit documents as appropriate. <br />Response: The wording in Rule 4.09.1 (10) requiring rock buttresses or keyways refers to <br />the existing slope in the area before the excess spoil pile is placed and not the external <br />face of the fill itself. This interpretation was confirmed by Marcia Talvitie, P.E. dated April 6, <br />2010, CDRMS. Accordingly, rock toe buttresses or keyways are not included in the design.