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Measurement and Payment <br />Payment for construction of the rolled dip shall be at the unit price bid in Item 2 of the Bid Schedule per <br />rolled dip constructed. Such payment shall be considered full compensation for all labor, materials, <br />equipment and all other items necessary and incidental to the construction of the rolled dips. Payment <br />shall be as this task is completed and approved by the PROJECT MANAGER. <br />Task 3 Sediment Pond Dewatering Device Repair <br />A sediment pond is located at the upper end of the Pil 4 haul road. This pond is known tc leak water from the base of <br />the corrugated metal pipe (CMP) dewatering device. The goal of this Task is to seal the base of the CMP through <br />excavaton and placement of benlonile and concrete. <br />The pond dewatering device is a forty eight inch (48') CMP riser, which is about ninety two inches (97) tall, as <br />measured from the base of the CMP at the water line. A horizontal CMP spillway is connected to the CMP riser on the <br />embankment side of the riser. The integrity of the spillway (ie: its elevation and slope angle, as well as the integrity of <br />its connection to the riser) must be maintained throughout the duration of the Project. <br />The riser is positioned al the base of the pond embankment so that the bottom of the riser is located just above the <br />base of the pond. The pond embankment rises from the base of the pond at an approximately 2H: 1 V slope to its <br />crest. The base of the riser is anchored by a concrete apron of approximately ten inches (10') in width. The thickness <br />of the concrete apron is unknown. Water is observed to pipe around the outside of the concrete apron. <br />In order to remediate problems associated with the CMP riser, CONTRACTOR shall accomplish the following: <br />- The CMP riser shall be cut so that the top surface of the riser is six inches (6') above the elevation of the <br />embankment immediately adjacent to the riser. Because the embankment slopes upward to its crest, the CMP cut <br />will parallel the slope angle. CONTRACTOR shall propedy dispose of the remnant CMP material off site. <br />- The embankment shall be excavated a minimum of five feet (5') in all directions (inducting towards the pond) from <br />the CMP riser. The depth of the excavation shall be no less than one foot six inches (1' 6') below the top of the <br />existing concrete apron. CONTRACTOR shall exeroise appropriate care and caution in order to maintain the <br />integrity of the CMP riser and of the horizontal CMP spillway. <br />- Six inches (6') of hydrated benlonile shall be placed on the base and on the sides of the excavation. The <br />benlonile shall be sufficiently hydrated so that it slumps rapidly when placed on a board elevated to forty five <br />degrees (45 c). Due to the fluid nature of the benlonile, it will be necessary to construct and place a form within <br />the excavation prior to placing the benlonile slurry. <br />- Concrete, having a minimum compressive strength of 3,500 psi at twenty eight (28) days will be poured into the <br />excavation after placement of the benlonile. Concrete may be mixed at the site, or may be delivered as'ready <br />mi>t at CONTRACTOR'S option. If the concrete is mixed on-site, equipment and mving procedures shall <br />conform to ACI 301, Chapter 7. If'ready mix' is used, it shall be maed and transported in accordance with ASTM <br />C 94. Concrete shall be thoroughly compacted by means of a suitable mechanical vibrator. <br />- Upon completion of concrete curing, the dirt excavated from the embankment shall be replaced on top of the new <br />concrete. The material shall be replaced in such a manner so that the slope of the embankment is returned to its <br />original condition, and so that the top of the CMP riser is sa inches (6') above the eleval'an of the embankment <br />slopes. The fill shall be mechanically compacted during placement. <br />- A hinged steel grate shall be placed over the top of the CMP riser. The grate shall be constructed using 1-1/4' <br />structural rebar welded on eight inch (8') centers in both directions. Two (2) extra heavy duty hinges, having <br />non-removable pins, shall be welded to the CMP riser and to the steel grate cover on the uphill side of the riser. <br />A hasp, constructed of 3l8' steel, and having a ciroular hole of h' diameter, shall be welded to the CMP riser and <br />the steel grate on the down hill side of the riser. <br />4 <br />