Volume-II of IV - GAIL

MECON LIMITED
REGD. OFF : RANCHI (BIHAR)
Document6
PROCESS & PIPING
DESIGN SECTION
NEW DELHI
TITLE MAINLINE CONSTRUCTION
(ONSHORE)
STANDARD SPECIFICATION
SPECIFICATION NO. PAGE 24 OF 53
MEC/S/05/62/01 REVISION A
Where the pipeline crosses areas, whose easements specifically require greater
than normal depths of cover, the trench shall be excavated to extra depth in
accordance with the Right-of-way Agreements or as required.
CONTRACTOR shall excavate all such additional depths as may be necessary
at no extra cost to the COMPANY.
6.7 Grades, Bends and Finish of Trench
6.8 Padding
The trench is to be cut to a grade that will provide a firm, uniform and continuous
support for the pipe. Bends shall be made in the pipe at significant changes in
grade of the trench. COMPANY reserves the right to set the grade of the trench
and locate the bends if so desired, in which case CONTRACTOR shall
excavate, at no extra cost, the trench and bend the pipe to such a grade.
COMPANY desires to reduce to a minimum the required number of cold field
bends to lay the pipe to conform to the general contour of the ground and
maintain a normal cover. This can be accomplished by cutting the trench slightly
deeper at the crest of ridges and by gradually deepening the trench in
aproaches to crossings. Such trenching work shall be done by CONTRACTOR
at no extra cost to the COMPANY.
COMPANY intends that there will be a minmum of hand grading of the trench
bottom. However, to achieve this, CONTRACTOR will have to dig as square a
bottom of the trench as possible with his equipment. This in part can be
obtained by adjusting and adopting the crumbling shoe and digging teeth of the
trenching machines and by use of a drag behind the trenching machines or
manually dressing-up the same. CONTRACTOR shall do such hand work in the
trench as is necessary to free the bottom of the trench from loose rock and hard
clods and to trim protruding roots from the bottom and side walls of the trench.
In all cases where rock or gravel or hard soil is encountered in the bottom of the
trench, COMPANY will decide the exact extent of trench padding, that will be
required. The thickness of the compacted padding shall not be less than
150mm. In those areas that are to be padded, the trench shall be at least
150mm deeper than otherwise required, and evenly and sufficiently padded to
keep the pipe, when in place, at least 150mm above bottom of excavated trench.