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excavated a minimum of 3 feet to expose firm and less permeable <br />bedrock surface. The final depth and configuration of the <br />overexcavation shall be approved by the Engineer. The last 2 feet of <br />excavation shall be conducted with rubber tired equipment. No steel <br />tracked or wheeled equipment shall be allowed within the last 2 feet <br />of excavation. <br />b. Surface preparation in these areas shall be as outlined above with the <br />exceptions or additions presented as follows. The prepared surfaces <br />shall be cleaned in a manner outlined above or as necessary to <br />produce a thoroughly clean surface for fill placement and free of all <br />loose material or other contaminates such as wind blown soils or fall <br />in from adjacent areas. The final surface shall exhibit a geometry, <br />both overall and locally suitable to provide a complete and <br />continuous contact between the fill and the bedrock rock surface. <br />C. Cleaning of all loose material and protection of the underlying <br />material and exposed bedrock surface may require vacuuming with <br />an industrial sized vacuum truck or broomed with a power broom. <br />d. The prepared surface shall be observed by the Engineer and <br />approved prior to fill placement. The approved surface shall be <br />backfilled as soon as possible following approval. The approved <br />surface shall be backfilled or otherwise protected from degradation <br />or contamination within a 6 -hr period following approval unless <br />otherwise approved by the Engineer. <br />e. Surfaces applicable to cleaning and surface preparations under this <br />paragraph shall extend over the foundation or key trench floor and <br />continuous up sidewalls for 18 inches from the floor in areas of <br />earthfill placement. <br />f. Exposed foundation surfaces of the key trench shall be cleaned and <br />approved by the Engineer prior to fill placement. In no case shall the <br />Contractor clean key trench areas for approval that cannot be <br />covered with fill, as applicable, within the same shift. Exposure of <br />the excavated formation surface upon which fill will be placed shall <br />be limited to 6 hours, which time shall commence at the completion <br />of each portion of the excavation, and which will include the time <br />required for final cleanup and surface treatment. <br />13. The Contractor shall mobilize sufficient equipment, materials, and manpower <br />prior to the start of final excavation in order to limit the exposure time so <br />specified. <br />C. PLACING EMBANKMENT MATERIALS <br />The suitability of each part of the foundation for placing embankment <br />materials thereon and of all materials for use in embankment construction <br />will be determined by the Engineer. <br />2. No brush, roots, sod, or other perishable or unsuitable materials shall be <br />placed in the embankment. <br />NCCI Pit #1 Reservoir Liner - Technical Specifications Fill <br />312323 -4 <br />