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2020-12-28_GENERAL DOCUMENTS - M1977300 (22)
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2020-12-28_GENERAL DOCUMENTS - M1977300 (22)
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Last modified
1/9/2025 6:28:15 AM
Creation date
12/29/2020 5:26:52 PM
Metadata
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Template:
DRMS Permit Index
Permit No
M1977300
IBM Index Class Name
General Documents
Doc Date
12/28/2020
Doc Name Note
Part 1 of 3
Doc Name
North Waste Rock Pile Diversion
From
Colorado Legacy Land
To
DRMS
Email Name
AME
Media Type
D
Archive
No
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_`, Au COLORADO LEGACY LAND <br /> FORMER SCHWARTZWALDER MINE <br /> native hillside in the curved section and along the lower portion of the channel. The alignment was <br /> shifted horizontally where required and vertically up by one foot to better fit the existing ground. <br /> These changes were made using topography data from the surveyors and included in Revision F of the <br /> plan set. When the new alignment was staked for construction,there were still a few deep cuts in the <br /> bottom 400 feet of the alignment.The channel invert was shifted up 0.5 and 1.5 feet to decrease the <br /> amount of excavation required. The resulting new slopes were calculated to fall within the range of <br /> slopes in the design plans. <br /> • Seal Wall:It was imperative for the seal wall to be founded in bedrock. During the design phase of the <br /> project a test pit was dug with an excavator until"bedrock"was hit approximately 3 feet below grade. <br /> During construction it was discovered that the "bedrock" was the top of a large boulder. Once the <br /> boulder was removed,bedrock was found approximately 8 feet below grade. It was decided to pour a <br /> large mass of concrete to fill the unanticipated volume from 3-8 feet below. A rock/boulder wall was <br /> built as the form to the downhill side of the pour while bedrock provided the"forms"for the bottom, <br /> two sides and uphill side. The rebar design was continued per plan all the way down to bedrock and <br /> was embedded and epoxied per plan. The first pour of concrete consisted of 18 cubic yards and filled <br /> the hole up to the elevation"bedrock"was thought to be at in the design plans. A 2x4 was embedded <br /> between the protruding rebar to provide a key for the second pour of concrete to lock into. <br /> Additionally, three strips of SwellStop were placed between the 1st and second pour of concrete to <br /> ensure a water-tight seal. The second pour of concrete matched the design plans <br /> • NWRP Access Road:The access road paralleling the first 400 feet of the channel was designed to be <br /> 10 feet wide. To accommodate haul trucks in the future the road width was increased to 12 feet. <br /> • Geosynthetic Termination:The geosynthetic was mechanically attached to the upstream side of the <br /> seal wall by bolting a Y4"-thick by 3"wide strip of stainless steel to the wall with the geosynthetic in <br /> between(see photo dated 10/9 in Appendix C). <br /> • Riprap Basin:After the channel was completed,the surveyors returned to stake the riprap basin and <br /> roadway crossing. The invert of the channel was one foot higher than expected, so the dissipation <br /> basin,riprap channel,and the road crossing were all raised 1 foot. This correction fit very well with <br /> the existing ground. <br /> • Roadway Crossing: Early in the construction phase of the project the construction subcontractor <br /> noticed that if we built the roadway crossing per plan,heavy construction equipment may potentially <br /> destroy the 4-inch deep concrete-filled Geoweb. The engineer consulted with the producers of the <br /> Geoweb product and they provided a low-flow crossing design adequate for both the future traffic <br /> loading and hydraulic design. The new design replaced the 4-inch Geoweb fill with concrete with 6- <br /> inch Geoweb to be filled with angular gravel. Additionally,a 1-inch thick layer of bedding was placed <br /> on top of the 6-inch Geoweb as a sacrificial wear surface.This design was provided to Ensero by Presto. <br /> All other aspects of the design remained the same. <br /> • NWRP Access Road: The separation geotextile which was to be placed 4 inches below the road grade <br /> was not installed. The original access road did not have a separation fabric and performed great. The <br /> fear was if the fabric was exposed during future construction activities haul truck tires would pull out <br /> the fabric. <br /> • Seed Mix: The approved design sheets specify Jefferson County's native conifer seed mix. However, <br /> the NWRP seed mix identified in Section 2.5 of this report was used. This seed mix was selected <br /> because it is part of the approved MLR Permit for the Site and was previously used on the NWRP and <br /> other upland areas at the Site. <br /> These deviations had a de minimis affect on the overall scope or results of this project. <br /> DECEMBER 2020 6 NWRP CHANNEL RECORD OF CONSTRUCTION <br />
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