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nominal pipe diameter plus two feet, unless otherwise shown on the Drawing details or approved by the Engineer. Trench walls shall be vertical from the bottom of the trench to a line measured one foot above the top of the pipe . From one foot above the top of the pipe to the surface, the trench walls shall be as nearly vertical as soil conditions will permit, unless otherwise detailed on the Drawings . Spaces for joints , fittings, manholes and other structures shall be maintained unless otherwise approved by the Engineer, or alternate methods are detailed on the Drawings . Should the specified maximum width of trench be exceeded, the pipe shall be adequately reinforced as directed by the Engineer, at the Contractor' s expense . b . Trench grade for utilities or structures not requiring special bedding material shall be defined as the grade of the bottom surface of the utility or structure to be constructed or placed within the trench. Such shaping of the trench bottom, as may be required to provide suitable bedding, shall be considered to be a part of this work. Trench grade in non-cushioning material shall be defined as 6 inches below the outside of the bottom of the utility, which 6 inches shall be backfilled with suitable bedding material . Unauthorized excavation below trench grade shall be backfilled to trench grade and suitably compacted by the Contractor without additional cost to the Owner. Final trimming and grading of trench bottom shall be done manually . E. Backfill and Bedding Materials 1 ) TYPE l - Type 1 material shall be either well-graded crushed stone or crushed gravel meeting the requirements of ASTM Designation C33 - 71a, Gradation 67 (3 /4 inch to No . 4 Sieve) or air cooled blast furnace slag along or in combination with crushed stone and/or crushed gravel conforming to ASTM Designation C33 -71a requirements . This material shall be used primarily for pipeline and manhole foundations . 2) Type 2 - Type 2 material shall be unclassified material obtained from the Contractor' s excavations and approved by the Engineer. The material shall be substantially free from wood, roots , humus , peat, muck, and other organic materials, and shall not contain clods, stones, masonry rubble, and the like, greater than 6 inches through the largest dimension. In general, the material shall consist of sand, loam, sandy- loam, clayey- sand, gravel, or crushed stone . 3 ) Type 3 - Type 3 material shall be select granular material , free from organic matter, of such size and gradation that the desired compaction can be readily attained and shall meet the requirements for A3 material according to the Revised Bureau of Public Roads Classifications . Material from the Contractor's excavations may be used , if it meets the above requirements . Otherwise it must be imported . C:\Download\techspec-02601 .doc SC601 -5