LAHORE - The work on detailed engineering design, preparation of tender documents and Project Cost (PC)-1 of 960-MW Tarbela 4th Extension Hydropower Proje-ct is expected to be completed by September 2011, WAPDA stated on Monday. Afterwards, this mega project will be available for initiating construction work, completion of which has been planned in a short span of four years. According to the WAPDA spokesman, the Tarbela 4th Extension Hydropower Project, on its completion, will provide about 2 billion units low-cost electricity to the National Grid per annum. Most importantly, the project will also provide a cushion to undertake rehabilitation and up-gradation of the existing Tarbela Power House during the lean period. This project, is a part of least-cost energy generation plan, being implemented by WAPDA on priority basis to harness the indigenous hydropower resou-rce of the country with a view to improve the ratio of hydel electricity in the National Grid. The 4th Extension includes installation of two units, 480 MW each, with a total capacity of 960 MW at Tarbela Dam on existing tunnel-4, being used for irrigation releases. Main dam, intake and tunnel already exist. Only construction of powerhouse, penstock, exten-sion of the switchyard and installation of electrical and mechanical equipments are to be materialized for the project to generate the quantum of electricity almost equivalent to the Mangla Power House. The WAPDA has planned to implement the project in two phases. Phase-I relates to the detailed engineering design etc., while Phase-II pertains to construction of the project. At present, a joint venture of two renowned European firms i.e. Mott MacDonald of UK and Coyne ET Billier of France is busy in preparation of detailed engineering design, tender documents and PC-1.It is pertinent to mention that the finances for the Phase-I amounting to $5.5 million have already been arranged under Water Sector Capacity Building and Advisory Services Project (WCAP) of the World Bank. The World Bank has also shown interest to finance the civil works during the construction phase.