The WAPP (Western African Power Pool) was established to integrate the operation of national energy networks to a unified regional market for electricity, so that this mechanism, at medium and long term, provide to citizens of ECOWAS Member States, stable and reliable power supply at reasonable costs. This fair situation must facilitate the balanced development of various energy sources in ECOWAS Member States, their collective economic profit, thanks to the long-term cooperation in the energy sector, to free transport of energy and increasing cross-border electricity trade. The CLSG interconnection must enable the interconnection of "Zone A" and "Zone B" of WAPP through Liberia and Sierra Leone, by increasing opportunities for trade and the establishment of a regional market energy. This interconnection should facilitate the implementation of hydropower projects at low cost in Guinea, Sierra Leone and Liberia in particular, in national and regional development goals. This project includes the construction of a 225 kV HV line of about 1350 km, the construction of 10 HV substations, plus the extension of 2 HV substations. The specific objective of the study was to determine the technical feasibility and economic viability of the project in sufficient detail to enable the preparation of tender documents.