Access Engineering completes construction of gated salinity barrier
Monday, 14 October 2013 00:00
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Access Engineering PLC continues their prominent presence in the water sector through the successful completion, commissioning and handing over of the gated salinity barrier across the Walawe River, which is located in close proximity to the Ambalantota Water Treatment Plant.
The National Water Supply and Drainage Board under the Government of Sri Lanka took the initiative to increase the water intake capacity of this water treatment plant in order to meet the increasing demand and long term development plans of the region.
Access Engineering undertook the construction and commissioning of this landmark project, at a cost of Rs. 1.1 billion which was funded by the Asian Development Bank under the Secondary Town Development and Rural Community Water Supply and Sanitary Projects.
“Construction work on this challenging structure commenced in January 2010 and was completed within 3 years. This is yet another project which incorporated numerous value engineering solutions including the use of gabion structures to build cofferdams instead of more expensive and complex installation of sheet piles which was originally proposed,” said Saman Jayasinghe Arachchi, Project Manager of Access Engineering.
Water resources from the Walawe River are used for irrigation, power generation and the supply of drinking water to the community in the Hambantota District. However, during dry seasons, raw water abstraction from the Walawe River intake is highly restricted due to the low flow conditions and the intrusion of the salinity.
Therefore, the gated salinity barrier was designed to prevent salt water intrusion towards the upstream and maintain necessary ponding of water levels above +1.0 m MSL during dry spells of the year. The Project also enhances the raw water extraction intake by 28000 m3/day and this additional amount of raw water would fulfill the high demand for drinking water requirements of the Hambantota District up to 2025.
The salinity barrier structure consists of an 18.7 m wide reinforced concrete base across the river and six RC piers along with two abutment walls. Five vertical wheel gates are installed with hoist mechanisms, one Sluice gate and a Gantry Crane. The scope also covers the installation of the river bed protection system, construction of both upstream and downstream embankment protection walls, landscaping work with necessary supportive structures and fencing to enhance the aesthetic beauty of the surroundings area.
A sophisticated early warning system which consists of two remote level measurement systems, two local level measurement systems and central equipment for overall control is also installed at the main structure location at the Bolana intake and Liyangastota barrage in order to facilitate the smooth and effective function of the salinity barrier.
The system is also equipped with remote level measuring that includes a bubble type level measurement device and radio data transmission equipment for sending station data and receiving control data from centrally located equipment. This system ensures the free flow of the river without any obstructions and eliminates the risk of damages due to potential floods over a distance of 16 km in the catchment.
Construction work was carried out in accordance to an Environmental Impact Assessment Report with the view to mitigate environmental issues that may arise due to construction activities of the structure.
