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<br />Mr. Larry E. O'Brian <br />August Id, 1981 <br />Page -2- <br />6) Please explain why such a wide drainage area is being proposed <br />rather than a narrow drainage ditch. In this discussion <br />please include the proposed gradient of the drainage area and <br />the width of the drainage area at its inlet to the settling <br />pond. <br />7) How deep will the settling pond be7 <br />8) What will be the final disposition of the water in the settling <br />pondl <br />9) The comparison of map Exhibits D-1 and F show that the northern <br />portion of Stockpile Area 1 will be mined. Why was this area <br />not contained in stage 0 or 1B7 When will this area be mined? <br />Exhibit E - Reclamation Plan <br />1) Will the backfilled sand material and overburden be compacted to <br />prevent later subsidence? This concern was first raised by the <br />City of Lakewood in their review of the original application. <br />2) Considering the erosive nature of the soils in this area, as <br />evidenced by the need for erosion control dams and erosion <br />ditching, Mark A. Heifner's statement that rill and gully <br />erosion occurs on denuded slopes steeper than 5:1 (see page <br />30, Exhibit I), and ROBCOS~ original reclamation plan which <br />states that no slopes steeper than 3:1 would remain; the <br />staff recommends that no slopes steeper than 4:1 remain as a <br />result of this operation. <br />3) Why will the small drainage located along the eastern portion <br />of stage 11 at approximately 5975 feet not be reestablished <br />after mining is completel The staff is concerned that water <br />will continue to concentrate in this drainage thereby causing <br />slumping and uncontrolled erosion. <br />4) Why are shrubs not included in the revegetation plan? <br />Exhibit I - Soils <br />I) The original application states that the angle of repose for <br />soil is between 1}:I and 2:1. Was this verified by Mark A. <br />Heifner's soil investigation? <br />2) How steep and long are [he slopes covered with salvaged top- <br />soil refered to at the top of page 327 <br />