3.2 River Diversion

Phased river diversion is adopted for the project construction, which is divided into three stages.

    In the first stage, the sub-river on the right side of the islet will be enclosed, by taking advantage of the islet to build the earth-and--rock fill cofferdam. In this stage, the open diversion channel will be excavated and the longitudinal RCC cofferdam constructed in the construction pit' Meanwhile, the construction of the temporary shiplock will be finished on the left bank of the river. In this construction period, the river flow and navigation will still go through the main river course.

In the second stage, the construction will be started from bui lding the 2nd stage transverse cofferdams both upstream and downstream, so as to form, together with the completed RCC longitudinal cofferdam, the 2nd stage construction pit, where, the spillway, the intake dam and the power plant on the left bank will be undergoing construction. Simultaneously, the permanent shiplock and the shiplift will be constructed on the left bank. In this stage, the river flow shall be diverted through the open diversion channel, and barge fleets and passenger boats might pass through either the open channel, or the temporary shiplock.

In the third stage, the upstream third stage RCC cofferdam is to be built to cut off the open channel to impound the reservoir to 135 m in elevation. It is at this point that the left bank power station and the permanent shiplock will be put into operation.

In the meantime, the third stage cofferdams together with the longitudinal cofferdam will form the third stage construction pit to build the right bank dam and power plant. In this period, the river flow will be discharged through the permanent bottom outlets and the temporary diversion outlets in the spillway, while the boats will pass through the permanent shiplock.

3.3 Scheduling

The master schedule of TGP is arranged as the following:

--Preparation and 1st stage construction              5 years (1993--1997)

--2nd stage construction                              6 years (1998--2003)

   --3rd stage construction                               6 years (2004--2009)