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Technical Revision 19 <br />Pond 005 As-Built <br />Response to PAR Dated 09/28/92 <br />Response to Comment 1 <br />Please refer to the revised exhibit. <br />Response to Comment 2 <br />Peabody Coal Company will use the reference stake method for <br />sediment determination. If the pond contains water on a permanent <br />basis, sediment levels will be determined by surveying as described <br />in Tab 13. <br />Response to Comment 3 <br />The dewater pipe was installed in the event the pond would have to <br />be dewatered. It is not an integral part of the pond design and <br />therefore should not be viewed in this manner. The elevation of <br />the pipe is 6860.1, the bottom of the pond is 6857. A slotted <br />riser extends one foot above the pipe (6861.1). The intent of <br />setting the pipe at this elevation was to be able to empty the pond <br />with the exception of about three feet (0.58 ac.ft.) of water in <br />the bottom. If the pipe was set at the sediment level elevation, <br />6864.4, and there was no sediment in the pond, 2.5 ac.ft. of water <br />would remain in the pond upon opening the valve. <br />Response to Comment 4 <br />Comparing the proposed pond design with the as-built indicates the <br />angle of the spillway as it intersects the diversion has actually <br />lessened with the construction of the spillway. The velocity of <br />the water as it exits the spillway channel (in the event of a flow <br />through the spillway) will only be approximately 4.5 fps. Also, it <br />can be seen that more riprap was placed on the downstream side of <br />the spillway than originally proposed. Peabody Coal Company will <br />monitor the outflow channel for erosion and place additional <br />armoring if needed. <br />Response to Comment 5 <br />The reference, as quoted from the geotechnical report, was mainly <br />written in regards to road cuts in clay. It was not intended to <br />address the material that the ponding area was constructed in. The <br />fact is that the material in the cut slope in question was <br />described by Ground Engineering as clayey sand (please refer to <br />drill hole L in their report "Geotechnical Investigation Proposed <br />Earthfill Dam for Pond 005") rather than a sandy clay material like <br />many of the road cuts. <br />In a discussion held at Seneca Mine with Susan Morrison on October <br />7, 1992, alternatives were discussed pertaining to the slope in <br />question. It was agreed that a stability analysis of the slope <br />