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and elevations as may be required to secure a satisfactory footing . Take <br /> care not to disturb the bottom of the excavation . Excavate to final grade for <br /> 1 structures just before concrete reinforcement is placed . For structures , trim <br /> bottom to the required lines and grades to leave a solid base to receive <br /> concrete . All structure excavations shall be trimmed to permit the placing of <br /> full widths and lengths of footings on horizontal beds . Rounded and <br /> undercut edges will not be permitted . <br /> ' C . Excavations shall be extended sufficiently on each side of structures , <br /> footings , etc. , to permit setting of forms , installation of shoring or bracing or <br /> the safe sloping of banks . <br /> D . Subgrades for roadways , structures and trench bottoms shall be firm , <br /> dense , and thoroughly compacted and consolidated ; shall be free from <br /> mud , muck , and other soft or unsuitable materials; and shall remain firm <br /> and intact under all construction operations . Subgrades which are <br /> otherwise solid , but which become soft or mucky on top due to construction <br /> 1 operations , shall be reinforced with crushed stone or gravel . The finished <br /> elevation of stabilized subgrades shall not be above subgrade elevations <br /> shown . <br /> ' E . Pipe Trench Excavation : <br /> 1 . Trench grade for pipe or drainage structures not requiring special <br /> bedding material shall be defined as the grade of the bottom surface of <br /> the utility or structure to be constructed or placed within the trench . <br /> Such shaping of the trench bottom , as may be required to provide <br /> suitable bedding , shall be considered to be a part of this work . Trench <br /> grade in non-cushioning material shall be defined as 6 inches below <br /> the outside of the bottom of the utility, which 6 inches shall be <br /> backfilled with suitable bedding material . Unauthorized excavation <br /> below trench grade shall be backfilled to trench grade and suitably <br /> compacted by the CONTRACTOR without additional cost to the <br /> OWNER . (See also paragraph 3 . 5 , " Unauthorized Excavation . " ) Final <br /> trimming and grading of trench bottom shall be done manually . <br /> 2 . Keep pipe laying operations as close to the excavation operation as <br /> ' possible during the prosecution of the work . No more than 100 feet of <br /> trench may be opened in advance of pipe laying . <br /> 3 . Minimize trench width to the greatest extent practical but conform to <br /> rthe following : <br /> a . Sufficient to provide room for installing , jointing and inspecting <br /> piping , but where possible, no wider at top of pipe than pipe barrel <br /> outside diameter ( OD ) plus 2 feet. If this width is exceeded , <br /> 1 Last revised 9/ 10/02 02220-8 EAST GIFFORD <br /> R\Public Works\KeithM\Stormveter Projects\(afford East\Construction Contract\Technical Specifications\Fnal SpecificationsUvision <br /> 2\02220 - Excavation and Backfll.doc <br />