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3. Modifications to Approved Plans <br />Mine Sediment Pond <br />A) <br />The mine sediment pond was modified for two reasons: 1) the fence constructed around the water <br />treatment area was extended slightly further north than that shown in the plans, limiting the pond <br />dimensions in this area and 2) a significant amount of large rocks were encountered in the western <br />portion of the pond area which required a re-design of the pond dimensions to obtain the correct <br />volume. Also, the large rock on the west edge would have made it extremely difficult to install the <br />primary spillway pipe to the Lumsden drainage. Blasting would likely have been required. <br />Therefore, the pond was re-designed to allow more volume to the east. The primary spillway pipe <br />was placed <br />in a small low area to the north of the pond. Revised calculations for the pond volume, as well as <br />the elevations of the primary pipe, were made for the pond, which are included in Appendix A. <br />The pond excavation was designed around the constraints of the site until the proper volume was <br />attained. The pond was then constructed to these dimensions. Bruce Norquist, site engineer, <br />surveyed all key locations with precise survey instruments, utilizing the same base points as those <br />in the original survey. <br />The pond utilizes a small fill area of 0.0 to 6.2 feet height for a distance of approximately 213 feet <br />along the north edge of the pond. The majority of this fill is less than 2 feet high but it does reach <br />a height of 6.2 feet near the primary spillway pipe. The total volume of fill used at this location <br />was approximately 190 cubic yards. The top width is no less than 10.0 feet wide and side slopes <br />of the fill are 2.511:1.5V, as opposed to the design cut slopes of 2.OH:1.OV. The installed primary <br />spillway is an 18" diameter CMP, which was also in the original design. The pipe was placed in <br />the compacted fill at the north edge of the pond. Prior to fill construction, we obtained moisture <br />compaction information from a composite sample made form the fill material, which was tested <br />by Koechlein Consulting Engineers of Grand Junction. The material was mostly clay, and was <br />classified as CL material. The optimum moisture from the lab test was 21.4%. <br />As the pond design engineer, I specified that a keyway be placed in the ground along the length of <br />the fill and that 2 seep collar plates be placed over the primary pipe prior to backfilling. These <br />keyway plates are 4 feet x 4 feet in size and were sealed with rubber gaskets to the pipe itself. I <br />also specified that the compaction of the fill be no less than 90% of the maximum dry density, as <br />shown in the Koechlein test data. This maximum dry density is 100.2 ponds per cubic foot, <br />therefore the required density was 90.18 pcf. During the days of filling on site, we specified that a <br />Koechlein qualified person be present to take density samples for quality control. This was done <br />and the results of this testing is included in Appendix B. The results show that all samples met the <br />required density. <br />I personally observed the compaction work that was done in the fill area and around the pipe and <br />it was the best I have ever seen. A water truck was present to supply the necessary water to <br />achieve the correct moisture level and a portable tamper was used to compact areas close to the <br />pipe. I also specified that they use a pole to compact all fill around the seep collars and the bottom <br />of the pipe where the tamper could not reach. This was done manually. The primary spillway <br />pipe, orifice holes, top of pipe, outlet, emergency spillway bottom and top of pond embankment <br />Whirlwind Portal Area As Built Report 2