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 38 OF 53
MEC/S/05/62/01 REVISION A
10.9 When backfilling the trenches in sloping terrains or steep areas, where in the
opinion of the COMPANY, the backfill may be washed out of the trench, sheet
piling or other effective water breakers across the trench shall be provided by
CONTRACTOR. This is to divert the flow of water away from the trench into
normal drainage followed before laying the line. In no case, the water is to be
drained via the trench or via channels other than those followed before the line
was laid.
10.10 CONTRACTOR shall leave the pipe uncovered at certain locations to allow
COMPANY to survey the center line of the pipe and the level of the pipeline in
the backfilled trench. Within 48 hours after backfilling, COMPANY shall have
carried out such survey and informed CONTRACTOR of any realigning, if
required. Thereafter CONTRACTOR shall compact the backfill.
The maximum allowable deviation from the centerline for land sections as
staked out by COMPANY and as referenced by CONTRACTOR after backfilling
is limited to:
Pipeline dia upto and including 24" : 200mm
Pipeline greater than 24" : 300mm
10.11 Before backfilling of the trench, CONTRACTOR shall comply with the
requirements of Clause 6.12 of this specification.
10.12 Stabilization of backfill shall be carried out by the CONTRACTOR in sandy
areas and other such places to obtain consolidated cover as directed by the
COMPANY. CONTRACTOR shall carry out the stabilization over the pipeline at
no extra cost to COMPANY.
The backfill shall be stabilized preferably with 150mm layer of marl, mattresses
of gatch other than straw or other stable materials. The width of stablisation shall
be atleast 5.0 meters on either side of the pipeline, plus one meter for every 10
meters height of dune (where the line passes through the dune areas).
10.13 Temporary workers shall be installed during backfilling and the survey as per
clauses 10.10 to locate the pipeline axis. These markers shall then be replaced
with permanent pipeline markers.