Laserfiche WebLink
• Section 2 <br />Controlled Placement of Underdrain System <br />The foundation preparation described in Section 1 resulted in a well defined site for <br />controlled placement of the underdrain system. <br />Controlled placement of the underdrain system was accomplished in three phases <br />including 1) construction at the tce area, 2) construction at the head of the underdrain system, <br />and 3) construction at the mid-section of the underdrain. Equipment access necessitated the <br />three phase approach since access road and ramp construction was needed to reach the bottom <br />of the drainage for controlled placement. <br />Prior to construction of the underdrain system, on September 30, Mr. Ed Moyer with <br />Colowyo Coal Company, Mr. Gary Fritz with OSM, and Mr. Larry Routten and Steve Wathen <br />both with Colorado DMG, met to review the change in underdrain location and removal of the <br />colluvial veneer at the toe area. After reviewing the changes on paper in the office, Mr. Moyer <br />took the group to the construction site to inspect and verify the field conditions. All parties were <br />in agreement that the relocation of the underdrain and key cut/removal of colluvial deposits was <br />prudent. <br />During the field inspection Mr. Fritz questioned Mr. Moyer as to the detail of the <br />tmderdrain outlet at the toe of the fill. Specifically, Mr. Fritz questioned as to whether or not <br />the drain would be open or closed. Mr. Moyer informed the group he would prefer an open <br />system, but would discuss the two options with Mr. Robert Trumbly, P.E. <br />On October 1, Mr. Moyer discussed the two alternatives for the outlet of the underdrain <br />with Mr. Trumbly. Mr. Trumbly concurred with Mr. Moyer that the underdrain be left open. <br />The choice to keep the drain open was based on enhancing any drainage from the fill underdrain. <br />By covering the drain at the toe, water migration could be blocked and the result could be <br />potential build up of water that would ultimately seep and/or slump the toe area. By leaving the <br />drain open (similar to the design for the Taylor Creek Fill) water migration will be enhanced <br />out of the underdrain and into the surface drainage system. Across section showing the detail <br />for the outlet of the underdrain at the toe follows. <br /> <br />Section 2 -page 1 <br />