Full stream ahead at Xayaburi, Lao PDR
Another milestone has been reached at the Xayaburi 1285MW HEP on the Mekong River as water started flowing though the low-level outlet (LLO), part of the Phase I works, earlier this year. The coffer dam is now being constructed for the Phase II works.
KGAL and Whessoe SDN BHD are responsible for the design, manufacture and installation of all the hydraulic steel structures on the project.
Phase I of the project, the construction of the spillway and navigation lock between the right bank and the intermediate island, approximately the mid-point of the completed barrage, is almost complete. Phase II will progress the powerhouse and additional fish pass facility from the intermediate island to the left bank.
The first gates were installed and made ready for the river diversion in January this year. They included four LLO submerged radial gates, 12m span x 16m deep, with a designed head of 37m. Each gate weighs 350 tonnes.
The navigation lock, at 450m in length, 30m deep, and 12m wide, features mitre gates; each pair weighing 320 tonnes. The lock incorporates floating mooring points; hydraulic ship arrestors; a water feed system for raising and lowering the lock level and an independent fish attraction system of culverts and control gates to supplement the extensive fish pass facility.
Construction of the main spillway civil structures is largely complete and the seven spillway radial gates are being installed. These gates, at 19m span and 25m high, are among the largest of their type. Four of these will incorporate a top flap to facilitate trash discharge. Trunnion designs have been standardised to match those of the LLO gates, providing a common arrangement for spares and servicing. Each gate will be operated by two 16m stroke hydraulic cylinders. Each spillway opening will be provided with emergency closure facilities; the main spillway having wheeled stoplog sections and the LLO having wheeled emergency gates, both designed to be deployed under flow conditions should the need arise.