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- The PROJECT MANAGER may require additional random samples. Testing of any <br /> additional samples will be done at the OWNERS expense. <br /> Safety <br /> It is assumed, but not measured, that the ground surface surrounding the subsidence feature is <br /> potentially unstable. It is also assumed that the base of the subsidence feature, particularly at <br /> the inner hole, is also unstable. Safety of the CONTRACTOR, work crew, PROJECT <br /> MANAGER and others is of paramount importance. Therefore, appropriate safety precautions <br /> must be taken by CONTRACTOR. Any individual working within fifteen feet (15') of the edge of <br /> the subsidence feature must wear a safety harness secured by rope to a secure anchor point. <br /> Hard hats, work gloves, steel toed boots and safety glasses must be worn at all times. Work <br /> conducted within five feet (6) of the western portion of the feature must be preformed from a <br /> safety platform. The safety platform shall be a minimum of five feet wide by ten feet long (5' x <br /> 10') and may be constructed of expanded metal or other sufficiently strong material. Anyone <br /> working from the safety platform will be roped in as described above. No one will be permitted <br /> to work within the subsidence feature. A carbon monoxide monitoring device with an audible <br /> warning system must be used by crew members when working in the vicinity of the subsidence <br /> feature. <br /> Installation Specifications <br /> The estimated volume of fly ash grout (fill) material needed to complete the closure is 205 cubic <br /> yards, with approximately 179 cubic yards dedicated to filling the feature to ground level and 26 <br /> cubic yards needed for the 'cap' material. Note that this volume is an Estimation Only. More or <br /> less materials may be required. Additional slurry above and beyond the total estimated here <br /> (205 cubic yards) will be paid for as per Task 3, Provide and Install Additional Fly Ash Grout <br /> Materials, below. <br /> Structural support needs to be placed over the top of the smaller, inner hole in order to prevent <br /> loss of fill material down this chimney. An acceptable support system would utilize Number 4 <br /> rebar tied at right angles on twelve inch (12") centers. The rebar lattice may be covered by three <br /> quarter inch (3/4') plywood or other suitable material to form a temporary barrier, which may be <br /> lowered onto the crest of the inner hole. Use of native rock materials is another acceptable <br /> support system. If a sufficient quantity of large rock is available, these may be used to bridge <br /> the inner hole in order to prevent the loss of fly ash slurry. <br /> The backfill material will be placed within the feature from the base of the feature to ground <br /> level, and from side to side. The material will be placed in such a manner so that all voids and <br /> irregularities within the feature are filled with the backfill material. Vibration of the backfill is not <br /> required. <br /> A cap, or crown, will be placed over the top of the backfill, using the same material as was <br /> utilized for the fill, so that water cannot accumulate on the fill material. Seethe attached figure. <br /> This cap will be triangular in shape, with the axis of the cap oriented up—and down- hill (parallel <br /> with the fall of the Grand Hogback). The cap will be one foot thick at its center (one foot above <br /> ground level), as measured at the center of the fill, parallel with the fall of the topography, from <br /> the uphill side of the feature to the downhill side of the feature. The fill will extend beyond the <br /> outside margins of the subsidence feature a minimum of eighteen inches (18") on all sides. The <br /> thickness of the fill material at the outside margins will be six inches (6"). <br /> 5 <br />