Environmental impact assessment : for the proposed sewage outfall and minor coastal modifications, Huraa, Kaafu atoll, Maldives

Abstract

This report discusses the findings of an environmental impact study under the proposed sewage outfall of the existing sewerage system and minor coastal modifications at Huraa, Kaafu Atoll. The project is proposed by the Secretariat of K. Huraa Council. The project entails a sea outfall from the collection chamber of the existing sewerage system and minor coastal modifications including the excavation for deepening of the Huraa wetland and installation of concrete piles for a restaurant on the shorezone. The proposed incorporation of sea outfall involves a pumping station and modification or replacement of fiber tanks in the existing sewage treatment plant. The outfall will extend to a depth of at least 7m, as per guidelines. The wetland has been declared by EPA as a Protected area to protect the mangrove forest and the Council feels it important to deepen the water-logged area, especially the inter-tidal opening between the wetland and the lagoon which has been shoaled over the years. The dredge material is to be placed on the eastern side beach area, slightly south of the pumping station location. Environmental impacts were assessed for both the construction and operational phase of the project. Most of the environmental and socio-economic impacts identified for the proposed development were positive to include reduction in smell around the treatment plant, energy consumption for wastewater treatment, minimized groundwater pollution, improved management/ maintenance of the sewerage system and enhanced water circulation in the water-logged areas of the wetland. The negative environmental impacts of the project would include temporary loss of groundwater quality during the construction phase due to dewatering and large siltation in the wetland area and small amount of sedimentation around house-reef induced from installing the outfall. The latter could be regarded as insignificant due to its small magnitude and spatial distribution while the sedimentation or siltation from dredging of the wetland area could be quite significant depending on the method of dredging. Silt and dirt on the dredge material disposal location would also be of concern. Since the project has minor negative impacts, a detailed investigation of alternatives was not considered necessary. Furthermore, there are no feasible alternatives to the outfall or excavation of the water-logged area of the wetland. Therefore, only alternative work methods have been discussed in the report, which include alternative methods of laying the outfall pipeline, alternative methods of excavation, etc. The environmental impact mitigation measures for this project were also of lesser importance due to the scale and low impact. Some of the general construction controls such as working during low- tide as much as possible and rigorous supervision have been discussed. As for the operational phase, implementation of backup systems and trained maintenance staff to service the Sewage Treatment Plant (STP) and regular check-ups were suggested in addition to monitoring seawater quality around the outfall location, wetland water quality and groundwater quality at designated locations around the island. The Proponent is willing to undertake monitoring during and after the construction phase in addition to undertaking the mitigation measures proposed by the consultants. In conclusion, it appears justified from a technical, administrative and environmental point of view, to carry out the proposed project. However, the alternative methods of excavation of the water-logged wetland areas proposed to be excavated may be considered and the works are recommended to be done in the least damaging manner.