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'� �, ■ O � :� � 24055. 24055.1 24055.2 ' :;h: special construction methods not shown on the plans, extra compensation shzll be allowed the Contractflr therefor. This section shall govern unless and except where modified by the Special Provisions" or "Specific Requirements". Excavation and Prep�ration of Trench Description: The trench shall be dug to the alignment and depth shown on the plans and only so far in advance of pipe laying as Engineer shall permit. The trench shall be braced (Section 24055.12) and drained that wor�.men may work saf�:ly ther�in and efficiently. It is essential that the discharge puurps be led to natural drainage.,:;` channels, to drains, or to sewers. Width: The trench w� �h may vary with and depend upon the depth of tren+�h and the nature of the excavated material encountered; but in any case shall be of ample width to permit the pipe to be laid and jointed properly and the backfill to be placed and compacted properly. riaximum trench width shall be as stated in the � "Special Provisions" or "Specific Requirements"< The minimum width of unsheeted ';;. trench shall be 18 inches, and for pipe 10 inches or larger, at least one (1`) ;.'t; foot greater than the nominal diameter of the pipe, except by cansent of the Engineer; th� maximum clear width of trench at the top of the pipe shall be not more than 2 feet greater than the pipe diameter� Wherever for any reason the maximum trench width is exceeded, the sewer pipe snall be encased in a concrete cradle six (6") inches in depth and extending two-thirds (2/3) of the diameter up from the bottom. Trench widths shall be measured a� about ;:� the crown of the pipe. Concrete materials shall conform to those specified for manholes and manhole basins. 24055.3 Pipe Foundation in Good Soil: The trench shall have a bottom conforming to the grade to which the pipe is to be laid. The pipe shall be laid upon sound sail cut tiue and even, so that the barrel of the pipe will have a bearing for its full length. Bell holes shall be excavated to insure the pipe resting for its entire `t length upon the bottom of the trench. ; 24055.4 Correcting Faulty Grade: Any part of the trench excavated below grade shall be corrected with approved material, thor.oughly compacted. �4055.5 Pipe Foundation in Poor Soil: When the bottom of the sub-grade is soft and in the opinion of the Engineer, cannot support the pipe, a further depth and/or width shall be e�cavated and refilled to pipe foundation grade as required under Section 24055.4, or other approved means shall be adopted to assure a firm foundation for the pipe with extra compensation allowed therefor as described in the "General Conditio�ns" for unclassified wo.rk and/or as described in the "Special Prcvisions'°. The c].a�s or type of materia�. which is to be used for refilling up to pi�e grade shall be as determin�d by the Engineer unless specifically stated in the "Special Provisions". 24055.6 PipP Clearance in Rock: Ledge rock, boulders, and laroe stones sha�l be removed to provide a clearance of at least six inches below outside barrel of the pipe, valvesy or fittings, and to a clear width of sia inches on each side of all pipe and appurtenances for pipe 15 inches or less in diameter; for pipes larger than 15 inches, a clearance nf 6 inches oalow and a clear width of 9 inches on each side of inside di�meter of pipe shall be provided. Adequate clearance for prop�rly 7ointing pipe laid in rock tr.enches shall be provided at bell holes. 24055.7 Pipe Foundation in Rock: The space between the bottom of the trench and rock and � the bottom of the pipe shall be backfilled �aith suitable material thoroughl_y tamped. Generally spaaki.n� the materi_al fr�m the trench excavation, other than rock er boul- ders, shall be considere.d as suitable material. No additional compensation for plac- L� 24UOU - 5