| Abstract: | The purpose of this EIA report is to fulfil the requirements of the Environment Protection and Preservation Act to undertake an assessment of effects on the natural and human environment of the rehabilitation of the tsunami-damaged harbour of Manadhoo, which is the capital of Noonu Atoll, Maldives. Since EIA was not a requirement at the time Manadhoo harbour was built, there has not been any EIA undertaken for the harbour. Therefore, an EIA has been considered appropriate for the rehabilitation project. This report looks at the proposed project and considers the different impacts and potential mitigation measures. Furthermore, alternatives to proposed design and other alternative considerations have been evaluated. A monitoring programme is also outlined.
The proposed project involves the rehabilitation or reconstruction of the harbour in Manadhoo, which has been damaged by the 2004 tsunami. The rehabilitation works include the construction of a new quaywall at about the same location as the existing quaywall, however, whereby straightening the existing quaywall so that part of the area between the existing and proposed quaywall would be filled by excavated material. The width of the harbour has been increased in order to allow larger vessels to turn inside the harbour as well as to minimize the length of the entrance channel to improve safety during access. These design elements are considered based on public consultation. The existing breakwater made of coral rubble would be reused as core material for the new breakwater, which would be armoured with imported granite stone or rock boulders. The proposed structures would be third generation structures tried and tested in the Maldives, i.e. L-shaped concrete structures for quaywall and armoured rock boulders for breakwaters. Dredging of the harbour basin would be undertaken by using excavator and dredge spoil would be disposed of in the harbour front area that would be filled and also in eroding areas near the harbour. If dredged sand is used for creating beach, the material has been recommended to be sieved and only fine sand placed manually on the forebeach or swash zone behind the high tide line.
Alternatives to the design have also been considered. In fact, sheet pile was initially proposed by the project engineers. However, this option was rejected by the government due to cost. Project engineers also felt that the pre-cast L-shaped concrete quaywalls would be better suited to the environment than sheet pile, especially since the dredge depth would be below 5m. For the breakwater, the option of vegetated breakwater has been considered as a more environment-friendly option. However, this option would require time for vegetation to take effect while the harbour would have to be put to use immediately after construction and even during construction. Maintenance of the vegetation would also be an issue and public participation would have to be guaranteed for that. It is believed that the proposed design is quite suitable for Manadhoo, since the design is long-lasting, requires less maintenance and has improved environmental and aesthetic aspects. The proposed design also meets people’s expectations and the government’s slogan of building better after the tsunami.
Environmental impacts of the project are localised and cumulative including localised, short term dredging impacts such as increased turbidity due to sedimentation. The main impact of the project would be that of sedimentation effects on coral cover in the region. It was observed during the field visit that the recent dredging of the entrance channel have caused high level siltation on the reef flat behind the breakwater as a result of which it was not even possible to undertake any reef transects in that area. It was also found that the live coral cover and fish diversity and abundance in the vicinity of the project site are low with some regeneration observed on the northern lagoon area. Social and economic impacts of the project are mainly positive including improved access with direct and indirect benefits to trade, fisheries, tourism and other economic activities as well as access to social and welfare services on the island provided at atoll level.
Mitigation measures have been proposed mainly for the dredging operation. Since the dredging is confined to existing harbour basin, use of sediment or silt screens may not be necessary. In terms of dredged material disposal, the top layer, which is expected to be contaminated to some degree, would be disposed in the area behind the proposed quaywall. If beaches are created using dredged sand, it has been proposed to use sieved sand for forebeach areas from the high tide line. Other mitigation measures during construction period would be adjustments to working hours such as not working continuously with noisy machinery and not working at night. Also, fuel management and barge and excavator operations shall be supervised. In fact, all aspects of the civil works are required to be appropriately supervised. Work areas shall be clean and free from hazards and all work activities shall minimise risk to workers and public. Mitigation measures have also been proposed for the operational phase, in which solid waste management and harbour operation and maintenance are of specific relevance. Both preventative and corrective maintenance programs along with community education programmes will be required to ensure a clean and safe harbour with maximum serviceability.
Finally, it is recommended that voluntary monitoring by the community and government bodies be undertaken. A monitoring cost has been included in the costing of the project. The purpose of the monitoring programme would be to help take precautionary measures during construction. It would also help to understand the accuracy of the impact assessment and minimize any impact assessment errors in the future and improve environmental aspects of future projects. The monitoring programme would also provoke the benefits of the project to the community and improve the link between the government and the people. The proposed monitoring would involve daily monitoring of turbidity and dissolved oxygen levels in and outside the harbour by the contractor. In addition, three to six-monthly monitoring of coral reef, marine water quality, sedimentation and hydrodynamics would be undertaken by the project environment consultants or by the government. Regular system performance monitoring and monitoring of health and other socio-economic parameters are also recommended. These can be monitored through regular data management by the island office. |
