Environmental impact assessment for the proposed water supply and sewerage system Kolamaafushi Gaafu Alifu, Maldives

Abstract

This report discusses the findings of an environmental impact study under the proposed water supply and sewerage system project at GA. Kolamaafushi. The project is proposed by the Ministry of Environment and Energy. The project entails establishment of a proper island-wide water and sewerage system. The proposed project involves installing a water distribution network to supply desalinated water supplemented with treated rainwater to all households and a comprehensive sewerage system to dispose of domestic sewage and wastewater. At present rainwater tanks of 2500litres connected to household roofs are used for drinking and cooking purposes while groundwater is used for all other purposes. Sewage and wastewater at household level is disposed to the ground via household septic tanks causing aquifer contamination. Groundwater wells are also fixed with electric pumps to draw water which has been the main reason for excessive drawdown and subsequent salinization of the freshwater lens. The small water collection facilities at household level presents water shortage issues during the dry season while contamination of the groundwater lens with wastewater effluent and salinization of the lens has become an increasingly important public health issue. Hence, it is important to provide adequate supply of potable water and provide appropriate wastewater disposal systems to minimize faecal contamination and foul smell in the groundwater. In addition, a number of alternatives to the proposed project components have been identified in this document. Some of these alternatives consider alternative means of wastewater disposal including treatment, alternative means of water supply, alternative outfall locations and alternatives to sustainable groundwater. Treatment is considered as a favourable option while it has been argued that if the effluent can be disposed of at an appropriate location, there would not be a need for treatment since there will be good mixing and flushing in such areas. It has also been recommended to use solar desalination technologies since the initial demand would be low and production capacity minimal. Environmental impacts were assessed for both the construction and operational phase of the project. Most of the environmental impacts identified for the construction phase of the project were minor negative; these include excavation and related difficulties to road uses, sedimentation from installing the outfall and temporary salinization of groundwater from de-watering to lay out the pipe network and pump stations. However, the impacts identified for the operational phase of the project were mostly moderate to major positive; improvement of groundwater quality from stopping the current sewage disposal practise and reduction of related health hazards. Disposal of sewage via a sea outfall is considered as minor negative impact while decommission of existing septic tanks will improve groundwater quality of the island. The provision of safe and adequate supply of potable water enhances living environment and provides economic opportunities such as tourism establishments including guest houses and city hotels. The main mitigation measures for this project during the construction phase are similar to other water and sewerage projects such as dust control plans, working during low- tide as much as possible and rigorous supervision. In case of deterioration of groundwater quality due to potential dewatering during construction of lifting stations in residential area, measures to water plants in the area that may be affected due to dewatering shall be in place. The design shall also ensure that dewatering is minimized. As for the operational phase trained maintenance staff to service the water and sewerage system and regular check-ups has been suggested in addition to monitoring water quality as well as reef health for potential impacts. Increasing awareness on groundwater conservation and promoting sustainable groundwater aquifer management, especially the skimming well technology has been suggested. In conclusion, it appears justified from a technical, administrative, socio-economic, health and an environmental point of view, to carry out the proposed water and sewerage system development project. The alternative of wastewater treatment will involve greater operational costs; therefore, it is recommended to proceed the project as proposed while keeping the option open for future wastewater treatment, as and when required.