2009-03-30_PERMIT FILE - C1981019A (3)

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Attn: Mr. Tay Tonozzi November 21, 2008 Page 2 11%fiddle Drain. The current South Taylor (ST) box cut pit shell is shown on Figure 5. The box cut extends further north than the previous planned pit shell. Therefore the south end of the middle drain has been revised to start at the north boundary of the pit shell where excess spoil begins. East Drain. The downstream endpoint of the eastern drain was constructed south of the original plan. The drain terminates past the boundary of mining for the West Pit. Extending the drain further north is technically not required as the drain is no longer below excess spoil. Spoil dumps north of the end point were arranged to produce spoil sorting to create a layer of coarse rock spoil around the end point.. This allows water from the drain increased area to infiltrate the West Pit spoil located below. In our opinion, the drain end-point is satisfactory and stability of the spoil is not reduced; water carried by the drain should seep into the in-pit spoil that fills the mined area below. HIGHWALL MINING Two areas of highwall mining are planned below excess spoil fills at the locations shown on Figure 5. The highwall mining configurations (web widths, barrier pillar criteria, extraction ratios, etc.) were designed by Agapito Associates, Inc. (AAI) in their report "Geotechnical Design and Operational Considerations for Highwall Mining, West Pit South, F 12 and E2 Seams" (November 23, 2005), and Addendum (April 13, 2007). Iii their report, AAI stated on page 10, "Web pillars are designed to remain stable and preclude s~xbsidence." The planned excess spoil fill is generally confined in a valley and the out-slopes at the downstream toes are relatively flat at 3:1 (H:V). In our opinion, the highwall mining will not significantly affect spoil foundation conditions and should not reduce the global stability of the spoil fill. 23-1-01105-200 Exh. 21, Item 1 Revision Date: 11/22/08 Second Intro. Letter - 2 Revision No.: TR-77