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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 meta! 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: 1 V 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 shalt 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 GMP 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 sufficiently 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 />