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in the pre-existing shall consist of two-inch (2") screened rock, overlain by clean four inch (4") rock. <br /> Durable rock is defined as rock material, which gives off a ringing sound when struck with a <br /> hammer. <br /> Measurement and Payment <br /> Payment for construction of the rolled dips shall be at the unit price bid in Item 2 of the Bid <br /> Schedule per rolled dip constructed. Such payment shall be considered full compensation for all <br /> labor, materials, equipment and all other items necessary and incidental to the construction of the <br /> rolled dips. Payment shall be as this task is completed and approved by the PROJECT <br /> MANAGER. <br /> Task 3 Sediment Pond Dewatering Device Repair <br /> A sediment pond is located at the upper end of the Pit 4 haul road. This pond is known to leak <br /> water from the base of the corrugated metal pipe (CMP) dewatering device. The goal of this Task <br /> is to seal the base of the CMP through excavation and placement of bentonite and concrete. <br /> The pond dewatering device is a forty eight inch (48") CMP riser, which is about ninety two inches <br /> (92") tall, as measured from the base of the CMP at the water line. A horizontal CMP spillway is <br /> connected to the CMP riser on the embankment side of the riser. The integrity of the spillway (i.e.: <br /> its elevation and slope angle, as well as the integrity of the connection to the riser) must be <br /> maintained throughout the duration of the Project. The riser is positioned at the base of the pond <br /> embankment so that the bottom of the riser is located just above the base of the pond. The pond <br /> embankment rises from the base of the pond at an approximately 2H: 1V slope to its crest. The <br /> base of the riser is anchored by a concrete apron of at least ten inches (10") in width. The <br /> thickness of the concrete apron is unknown. Water is observed to pipe around the outside of the <br /> concrete apron. <br /> In order to remediate problems associated with the CMP riser, CONTRACTOR shall accomplish <br /> the following: <br /> The CMP riser shall be cut so that the top surface of the riser is six inches (6") above the <br /> elevation of the embankment immediately adjacent to the riser. Because the embankment <br /> slopes upward to its crest, the CMP cut will parallel the slope angle. CONTRACTOR shall <br /> properly dispose of the remnant CMP material off site. <br /> The embankment shall be excavated a minimum of five feet in all directions (including towards <br /> the pond) from the CMP riser. The depth of the excavation shall be no less than one foot six <br /> inches (1' 6") below the top of the existing concrete apron. CONTRACTOR shall exercise <br /> appropriate care and caution in order to maintain the integrity of the CMP riser and of the <br /> horizontal CMP spillway. <br /> Six inches (6") of hydrated bentonite shall be placed on the base and on the sides of the <br /> excavation. The bentonite shall be sufficientl�r hydrated so that it slumps rapidly when placed <br /> on a board elevated to forty five degrees (45 ). Due to the fluid nature of the bentonite, it will <br /> be necessary to construct and place a form within the excavation prior to placing the bentonite <br /> slurry. <br /> Concrete, having a minimum compressive strength of 3,500 psi at twenty-eight (28) days will <br /> be poured into the excavation after placement of the bentonite. Concrete may be mixed at <br /> the site, or may be delivered as 'ready mix' at CONTRACTOR'S option. If the concrete is <br /> 4 <br />