5.3Alternatives Analysis to Be Assessed During Design and Implementation Phase -
Appropriately conducted alternative analyses are regarded as one of the most important measures to avoid and greatly reduce potentially adverse environmental and social impacts Alternative Analysis should be conducted during the feasibility study for finalization of design, technical options, and construction and operation method which will be reflected during the Initial Environmental Examination and Environmental Impact Assessment. This section outlines the tasks for alternative analysis during environmental assessment.
5.3.1Alignment -
The Environmental Assessment (EIA and IEE ) should address the environmental analysis of the feasibility analysis to choose the alignment. The preferred option should be where possible to avoid impacts on ecosystems, biodiversity, physical cultural resources and communities. The EA should examine in details areas of particular potential environmental sensitivity. The assessment should include the environmental statement of the two sides of the alignment and reflect if major retreat has happened in last few years. For example, as shown in Figure 5.3 the embankment at Khuolia in Polder 35/1 was observed to be badly eroded along its estuarine slope. To counter this BWDB have constructed a new retired embankment 100m landwards. Approximately 15-20 families live in between the retired and new embankment. If the alignment needs to be changed from the retreated one under CEIP the environmental analysis must reflect the environmental change due to the new alignment. If the retreated alignment is kept under CEIP the environmental analysis must reflect the environmental benefit for keeping the existing alignment.
Figure 5 16: Existing Alignment of Polder 35/1 at Khuolia
-
To provide adequate drainage facility the tasks will involve construction of hydraulic structure and excavation/re-excavation of drainage channels. The following are the key factors to upgrade the drainage facility to be considered:
-
The comparative benefit analysis of choosing the new/replacement of hydraulic structure or excavation/re-excavation of drainage channels for facilitating proper drainage will be conducted from environmental perspective.
-
The environmental impact of introducing new/replacement/repairment of new drainage facility will be considered in terms of location, need, number, type and economical benefit.
-
In case of replacement of hydraulic structure, a comparative analysis between the current hydraulic structure and new one will be presented in terms of environmental benefit considering the type of structure, runoff and tidal surge.
5.3.3Construction Method -
Designs should be justified economically, and the optimum choice will vary with regard to choice of construction method.. Construction costs will be related to type of material chosen transportation cost of the material, necessity of constructing/repairmen of hydraulic structure, optimum crest height to withstand possible tidal surge and availability of labor in the local areas.
-
Different types of construction materials such as soil, sand, concretes, wood, bamboo, metals, etc. will be required for implementing the project interventions under CEIP. The types, amount and source of construction materials are not yet determined. Usually construction materials are collected from local markets and suitable places. Especially, soils, required for earth works, would be collected from locally suitable land in the polders and from the excavation/re-excavation of drainage canals considering the required soil quality. The EIA for each polder should reflect the possible sources of material and justified location of the sources of material and analyze the environmental impact for each reconstruction/repairment of embankment in segment.
5.3.5Disposal of Sludge Material -
Within the CEIP polder areas, sedimentation process is accelerated due to controlled water flow in the channels and improper maintenance of the water control structures and channels. In many cases, river bed level outside the polder has become higher than the river beds inside the polder, which resulted in malfunctioning or non operation of regulators/ sluice gates. Consequently, permanent water logging has been created in many polders. The CEIP should take care of these issues while designing and implementing the improvement works in coastal polders. The re-excavation of channels and sludge materials need to be carefully managed.
5.3.6Protective Measures for Reducing Bank/Embankment Erosion -
Afforestation in the foreshore and embankment and concrete block placing are the two options chosen as protection measures for reducing bank/embankment erosion. Technically the choice will be made based on the land availability for afforestation/biological treatment and exposure of the embankment to the loads . The alternative analysis will analyze the environmental benefit from choosing the certain type of protective measure for each polder.
-
Dense vegetative cover of grass turfs on the slope and afforestation of the embankment toes as well as the foreland areas increase the stability of the earthen embankments in coastal areas. The study will contribute in selecting planting material to be raised from seeds originating locally and match well to the local site conditions. The species mixture has to respect the individual growth characteristics and to be geared to generate synergies in the vegetation cover and improvement of soil quality. The study will also reflect polder wise various types of plantation for slope. toe, berm and borrow pit.
5.3.8Location for Labor Camps -
Some labor camps would be established in construction sites during construction period. The EIA should look for alternative analysis for possible locations of labor camps which will have minimum effect on the surrounding environment without hampering the project activities. For example, sometimes labor camps are chosen inside the school compound or in the class rooms due to proximity to the project location and water and sanitation facility availability which has significant negative impact on the education environment.
|
Yüklə 7.67 Mb.