PACKAGE : I Bid Document VOLUME : II - Public Health Engineering

5.12 Excavation for appurtenance.
Excavation in trenches for foundation of valve chambers, pedestals etc. shall be as
per the plan or as directed by the Engineer. The dimensions of the excavation shall
be measured as the projection in plan of the outermost edges of the structure.
5.13 Keep excavation clear of water.
Where ground water is encountered or anticipated, the Contractor shall provide
sufficient pumps to handle the ingress of water and must provide and maintain in
working order. Standby pumping units are to be made available and employed in
the event of mechanical failure. The Contractor must also arrange for night and day
operation of the pumps wherever necessary to ensure that the work proceeds at all
times.
5.14 Dewatering in areas of high water table.
The Contractor shall perform dewatering as required so that all works of the
contract are installed on dry areas and excavations, including without limitation the
construction of all structures and underground piping. The Contractor shall ensure
that dewatering is carried out only to a depth sufficient for the required excavation.
The Contractor shall also ensure that, at all times, during construction, no
groundwater shall come into contact with any concrete surface or reinforcement and
that any structure shall be capable of withstanding any hydrostatic pressure to which
it may be subjected during construction and until completed.
The Contractor shall be deemed to have included in the tender price for maintaining
all works in a dry condition during construction. Any water removed from
excavations shall wherever practicable, be pumped directly to the natural drainage
channel or to storm sewers if approved via an efficient system of discharge lines.
No water may be discharged into the sewerage system or onto open spaces.
The Contractor shall include for the diversion of all water courses encountered in
the work until the scheme is completed and put into operation.
Notwithstanding any previous approval, the Contractor shall be fully responsible for
maintaining dry excavations.
GTS : General Technical Specification. Page 37