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2. WORKING PLATFORM CONSTRUCTION <br />The construction of the working platform was necessary to produce a stable and flat working area for trench <br />excavation and backfilling. The Contractor cleared the working platform using a PC Komatsu 300 LC trackhoe <br />and a PC Komatsu 400 LC trackhoe. Trees were cut using a chainsaw and hauled off -site by Hall- Irwin. <br />The constructed working platform was approximately 7,015 ft. long and varied in width according to the amount <br />of land available. The working platform consisted of a combination of cuts and fills in order to create a level <br />working platform as specified in the design report. The deepest cut took place on the western portion of the slurry <br />wall to an approximate depth of 5 ft. and the fill height was less than 2ft in various areas. <br />2.1 Slurry Wall Alignment Survey <br />The slurry wall alignment was staked and surveyed by Survey Systems Inc. (SSI) before construction of the <br />working platform and after construction of the slurry wall. Alignment stationing was established by SSI at 100 -ft <br />intervals. The Contractor established construction stationing at 25 ft intervals along the alignment using a tape <br />measure. All stationing referred to in the text and tables of this report correspond to the stationing shown on <br />Sheets 1 through 3. To generate the as -built alignment, Hall -Irwin placed lathe within the centerline of the slurry <br />wall and noted the approximate construction stationing at the location. SSI surveyed the lathe to create the as- <br />built alignment and provide the legal description, sheet 4. <br />2.2 Deviations from the Plans and Specifications <br />The slurry wall alignment was modified from the design alignment during the construction phase and is described <br />below. The alignment changes were discussed by the project team (Weld County, Hall -Irwin and Lyman Henn) <br />prior to the changes being implemented. <br />2.2.1 Constructed Alignment <br />The following alignment changes were made during construction. <br />1. A radius was implemented on the northeastern corner of the project in place of the approximately 90- <br />degree corner that was shown in the original design. The radius eliminated the need for Hall -Irwin to <br />construct a corner at this location. <br />2. The alignment was shortened from approximately 7,200 ft to 7,015 by moving the eastern edge of the <br />alignment to the west approximately 75 ft. <br />2.2.2 Overlap at Corners <br />The overlaps at slurry wall corners were not excavated as shown in the design. Hall-Irwin has extensive <br />experience constructing slurry walls and knowledge of how to excavate a corner without using overlaps. The <br />design showed overlaps at each corner. Lyman Henn and Hall -Irwin discussed the omission of the lead -in <br />trenches prior to construction of the slurry wall. <br />G \PROJECTS \2011 Projects \111025 Gersert Gravel Pa Slurry Wall \O \O1 \Construcuon repon\LH Construcuon Repon -BS doc <br />2 <br />