Environmental Management Framework (emf) coastal embankment improvement project phase-i project (ceip-i) April 29, 2013 Dhaka Bangladesh Water Development Board Ministry of Water Resources Government of the People’s Republic of Bangladesh
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Chapter 6: Possible Environmental Issues with Mitigation Measures & Benefit of the Project6.1Introduction
6.2Environmental Impacts due to Rehabilitation and Improvement of Polders System
6.2.1Design Issues& Mitigation
Issues: The project will need to acquire land to construct embankments and water control structures. House, shops common properties vegetation will be affected by the project interventions. The significance of this impact is expected to be major. Mitigation- The project will conduct the alternative analysis for the alignment of polder considering environmental, economic and social benefit. The project intervention should consider minimum disturbance of infrastructures, people and vegetation. The resettlement cost estimate should be performed before hand which will include compensation for land acquisition, structures, trees, fish stocks, capacity building training for Environmental Assessment.
Issues- Agricultural land may be permanently lost in case of realignment/retreatment of a certain section of the polder. It has been observed realignment/retreatment of many segments have already done in the field. In terms of loss of agricultural land the loss is irreversible. Mitigation- The technical study should incorporate the necessary information about requirement of retirement/realignment of the polder. Consider realignment option for polders to avoid minimum encroachment of agricultural land. In the long run it is expected the polder will have more cultivable land. If possible, the farmers can be encouraged to cultivate high yield varieties for increasing cropping intensity in the remaining cultivable land during construction.
Issues - Mobilization of construction vehicles for equipment and material transport will deteriorate the noise level at the surrounding sites. The traffic volume will be increased both in the road and river. The polder protected area is populated and number of common infrastructure like schools, madrasa, mosques is inside the polder. The increased traffic volume is anticipated to increase the noise pollution. Mitigation – The contractors need to aware the vehicle drivers not to use hydraulic horns and to avoid unnecessary honking. The contractors should encourage the vehicles to come during day time.
Issues – There will be loss of trees during pre-construction stage due to clearing of land for base widening of polder, realignment of polder in some areas and establishment of construction camps. Mitigation –During impact assessment the information about size, species and number of trees should be recorded. The project has an afforestation component. The component should prepare an afforestation plan based on the local species and number of trees cut. This will reduce the negative impact substantially in the long run. The overall impact is expected to be negative to positive in the long run. However, there will be a transition phase of impact between immature tree at early stage and matured tree at the later stage.
Issues-The construction of embankments and dredging of canals have important consequences on flood plain ecology. The fish spawning will be impacted if canal excavation happens during spawning period. Mitigation- The technical study should incorporate the necessary information about requirement/ repairment of hydraulic structure and the species to be affected by canal excavation. The fish migration route should be determined before commencement of the work. The following actions can be considered to mitigate adverse impact on fisheries:
Issues- During contractor mobilization, equipment, machinery, material, and manpower will be transported to the Polder resulting in additional traffic on roads and in waterways. This traffic may potentially cause traffic congestion particularly at roads and jetties. Mitigation - The following measures will be implemented to address the above concerns:
Issues- Establishing the contractor’s temporary site facilities may involve land clearing, land leveling, excavation, and construction of buildings. These activities may potentially cause air and water contamination, noise generation, safety hazards, hindrance to local communities, and other similar impacts. The locations will be temporarily established. The contractor will propose the possible location of construction yards Mitigation- The following measures will be implemented to address the above concerns:
Issues-Embankments can cause drainage congestion in adjacent areas during period of high rainfall. If the high tide exceeds the height of embankment, due to inadequate water outlet, water logging will occur. This may cause crop damage, and in extreme cases permanent loss of agricultural lands. Mitigation- Excavation/Reexcavation of drainage channels needs to be considered during design phase, if drainage congestion triggers from any activities, reconsider the location of hydraulic structure and alignment of embankment to avoid any drainage congestion.
Issues- Collection of material is a challenge for the project. Earthwork material is expected to be collected locally. The presences of continuous borrow pits on a riverside induces undercutting of the embankment toes and slopes due to complete inundation of the riverbank or seashore during the monsoon. The borrow pits and adjoining low-lands thus inundated induce a parallel water current to flow along very near the embankment toes and thereby eroding the surfaces rapidly. Mitigation- During design the segment wise soil requirement and location of the sources of soil for earthwork for each polder construction/rehabilitation should be identified. The borrow pit chosen for the sources of material should be discontinuous, on the land side and away from the toe line.
Issues- Dredging will be carried out in the silted drainage channels inside the polder. The spoil material obtained from the dredging activity may create hazards on habitat, sediment and water quality. Mitigation- Contractor in consultation with the DoE will submit a spoil plan for approval. The spoil plan should show the location of proposed sites (landfill or borrow pits) to be used and the measures to be taken to rehabilitate these pits upon finalization of the Project. Costs of the spoil disposal will be included into cost break-down provided by contractor within bidding proposal and should be reflected in the contract It is also recommended to utilize any dredged material for the reconstruction/rehabilitation of the polders. However, the soil quality of the dredged material should match the specified requirement of soil quality applicable for reconstruction/rehabilitation of coast polder. Suitable access to the materials will be agreed with the local authorities in consultation with the community. The key information to be collected before commencing dredging is as follows:
Issues- If Tidal River Management (TRM) is followed in some Embankments that may create flooding in the low lying area. Mitigation- If TRM is followed at any embankment; the design consultant should conduct detail study about the regional hydraulic regime specially the flooding pattern, flow of water, ground water table during design. TRM is not encouraged at any site without detail investigation.
Issues- Public cuts and tubes linking a river or seaside with the country side of its embankment are frequently observed. These cuts weaken the embankments, exposing them to slow but continual erosive forces. During flood or cyclonic storm, breaching or major erosion occurs at those points. The people mainly cut the embankments to fulfill their purposes:
Mitigation- Adequate consultation should be carried out segment wise for each polder during design phase to avoid creation of temporary irrigation inlets and penetration of salt water for shrimp cultivation. Responsibility
6.2.2Impacts during Construction & Mitigation
Impact- The Project activities particularly on regulators and sluices and in water channels may block or clog water drainage channels, potentially causing temporary water logging in the surrounding areas and negatively affecting the cultivation and the associated communities. In addition, excavation khals in the Polder is likely to disturb the drainage which takes place through these channels. Mitigation- The following measures will be implemented to address the above concerns:
Impact- Construction machinery and Project vehicles will release exhaust emissions, containing carbon monoxide (CO), sulfur dioxide (SO2), oxides of nitrogen (NOX), and particulate matter (PM). These emissions can deteriorate the ambient air quality in the immediate vicinity of the Project sites (particularly along the embankment, and around the channel excavation sites and borrow areas). Furthermore, construction activities such as excavation, leveling, filling and vehicular movement on unpaved tracks may also cause fugitive dust emissions. These emissions pose health hazards for the nearby communities as well as for the construction workers. In particular, the settlements near the work areas will be exposed to air contamination caused by the Project activities. Mitigation - The following measures will be implemented to address the above concerns:
During construction the handling and transport of construction material, earth movement, raising height of the embankment and excavation may cause dust, noise and air pollution. Mitigation-Impacts during the transportation and storage of construction material will be minimized by covering the material or by keeping the surface wet.
Impact-Establishment of working areas, earthwork and storage of construction materials at the project site may cause damage to soil. The main impacts on the soil during construction are from (i) loss of topsoil from the construction sites; (ii) conversion of the existing land uses such as agriculture and plantations to stockpiles of materials, and damage to the temporarily acquired land; (iii) cut and fill operations, (iv) extraction of fill materials from cut section, and/or borrow pits, (v) soil erosion slope of the embankment, borrow pits and un-compacted embankments and siltation, and (vi) contamination of the land from hazardous and toxic chemicals and construction material spillage. In addition site preparation activities generate spoils consisting of crop residue, grasses, trees and earth (ADB, 2011). Mitigation- Removing the topsoil from the storage sites and storing it in a secure place for later use would mitigate these impacts. After the completion of the construction, the topsoil would be placed to its original place. In areas of no topsoil construction material can be stored directly on top it. However, after the construction, the area would be turfed and trees planted. The storage of topsoil in stockpiles, no more than 2m high with side slopes at a maximum angle of 450, will take into consideration the following:
Impacts- The construction activities particularly demolition of existing structures, excavation, compaction, operation of construction machinery, and vehicular traffic will generate noise and vibration which are likely to affect the nearby communities. In addition, camp sites may also generate noise. Increased noise levels may cause disturbance, nuisance and even health hazards for the nearby communities as well as for the construction workers. In particular, the settlements near the work areas will be exposed to noise and vibration generated by the Project activities; in addition sensitive receptors including nine schools along the embankment are likely to be more severely affected by noise Mitigation-Regular maintenance of construction equipment and vehicles in accordance with manufacturers’ maintenance procedures will greatly reduce the noise levels. Contractors are recommended to monitor the noise levels regularly at the construction sites and take necessary measures to comply with the national standards. High efficiency mufflers are to be fitted to the noise generating equipment. The construction related activities will be restricted between 0600 to 2100 hours.
Impacts - There may be some water pollution from the construction site, labor camps and disposal of dredged material etc. Mitigation - To mitigate this, the following measures will be taken: (i) Provide and maintain appropriate facilities for temporary storage of all wastes before transportation and disposal. (ii) Organize disposal of all wastes generated during construction in an environmentally acceptable manner considering the nature and location of appropriate disposal sites. (iii) During dredging operations, the overflow silt and clay content may increase turbidity of surface water. To overcome this, the site of dredging should be shifted to places where the clay and silt content is low enough to maintain the turbidity within the water quality standards.
Impacts - Construction activities on the sluices can potentially affect aquatic habitat and fish migration in the khals. Though the habitat in these khals is already modified as a result of construction of embankments and sluices in 1960s, some fish migration between outside rivers and internal khals still takes place particularly along those, which do not have any water control structure. During the construction activities, the fish migration between the outside rivers and internal khals is likely to be affected. Similarly, fish migration within the Polder between khals and beels can also be affected by the construction activities particularly the khal excavation. Mitigation -The following measures will be implemented to address the above concerns:
Benthic communities play important role in food chain not only for lentic (standing water) but also for lotic (flowing) water bodies. Construction activities including re-excavation of khals, dredging of rivers and discharge of solid wastes and waste effluents can potentially impact the benthic communities of the water bodies. Most of the construction activities will be implemented during dry season, during which time the benthic fauna would be more vulnerable. Mitigation- The following measures will be implemented to address the above concerns:
Impact-Generally borrow pit sites are the major sources of environmental impact due to dust and noise pollution, loss of biodiversity, and generation of spills. Operation of the quarries above the approved limits may cause change of floodplain hydrology and trigger erosion and landscape degradation. Mitigation- The mitigation plan to be followed by the Contractor at the borrow sites is: (i) only borrow areas approved by the environmental authority will be used for the project; (ii) pits management will be in full compliance with all applicable environmental standards and specifications; (iii) the excavation and restoration of borrow areas and their surroundings, in an environmentally sound manner to the satisfaction of the DoE; (iv) borrow pit areas will be graded to ensure drainage and visual uniformity. Additional borrow pits, if necessary, will not be opened without the restoration of those areas no longer in use, and without the approval of DoE. Topsoil from the opening of borrow pits will be saved and reused to revegetate the pits or turfing the embankment (ADB, 2011).
Impacts - Irrigation is vitally important for the agricultural activities in the Polder. Construction activities particularly on regulators and in water channels can potentially disrupt the crop irrigation thus negatively affecting cultivation. The works on sluices can cut off the incoming water from the river, while the excavation works in water channels can affect water conveyance through them. Mitigation -The following measures will be implemented to address the above concerns:
Impacts - Improving the rural embankments by widening/or increasing height will cause embankment-side agricultural land loss. Agricultural production may be slightly reduced during the implementation of the Project because of construction of labor camps, approach roads, storage sites for construction materials, sites for preparation of concrete blocks, transportation of construction material, etc. Mitigation -It is expected that the contractor will establish camps for laborers and permanent staff supervising, directing, and controlling the works. The owners of the land for these camps will be compensated, and the land restored after demobilization. After construction the agricultural land will be reinstated to its former state, wherever possible. While it is not possible to avoid the agricultural lands, the mitigation measure is to provide steep slopes for the embankment by applying improved soil stabilization means to minimize the land loss. Among others grass turfing or vetiver grass plantation could be effective means in minimizing erosion.
Impacts - The potential implications associated with housing of immigrant workforce include generation of solid waste, adverse water quality impacts arising from discharge of partially treated sewage and refuse, public health impacts through the possible introduction of diseases not prevalent in the surrounding areas, social-cultural conflicts arising from religious, cultural and behavioral discords between immigrants and local residents, and promotion of un-aesthetic practices. Mitigation -It is strongly recommended that the contractor should hire local workers as many as available. The camps should have adequate housing for all workers, safe and reliable water supply, fuel supply, waste disposal facilities, hygienic sanitary facilities and sewerage system, treatment facilities for sewerage of toilet and domestic wastes, storm water drainage facilities, adequate health care facilities, and in-house community/common entertainment facilities. Contractor has to prepare a detailed layout plan of the construction camp and submit with the bidding document. The Contractor shall conduct ongoing training programs to all construction workers on basic sanitation and health care issues and safety matters. The contractor shall restore all the construction camps to original condition after completion of civil works.
Impacts - During the construction phase some tubewells may have to be relocated and some people using the river as their source of drinking water may face inconvenience. This may have a minor local negative impact. Mitigation - To mitigate any such impact the contractor will be required to establish an alternative water supply.
Impacts- The construction activities will involve operation of heavy construction machinery, vehicular traffic, excavation and filling operations. These activities may pose some safety hazards to the local population as well as for the construction workers. The fuel storage at the camp sites may also pose safety hazards for the construction staff as well as for surrounding population. Inappropriate waste disposal at the camps and construction sites, and air quality deterioration caused by the Project’s vehicular traffic and construction activities potentially pose health hazards for the construction staff and nearby population. Unhygienic condition and unavailability of safe drinking water for the construction staff will expose them to health risks. In addition, influx of construction staff can potentially expose the nearby population to communicable diseases. In addition, if proper safety measurement is not taken ion borrow pit or stock piling of materials, dredged material severe accident may happen to the local community. Mitigation-Residents must be able to cross the road safely and particular attention must be given to vulnerable groups such as children, the elderly, and animals. All vehicles should observe speed limits and load restriction. The contractor shall instruct his workers in health and safety matters, and requires the workers to use the provided safety equipment. The scope will need to include transmittable diseases establish all relevant safety measures as required by law and good engineering practices. The contractors will be responsible for the provision of first aid facilities, rapid availability of trained paramedical personnel, and emergency transport to nearest hospital with accident and emergency facilities. The contractor will be responsible for ensuring that all construction vehicles observe speed limits on the construction sites and on public roads. The contractor has to come with a safety plan about the stock piling of earth material and borrow pit area and submit that with the EAP. The construction sites will have protective fencing to avoid any unauthorized entry, where appropriate and possible Responsibility
Impacts- Operation time of Hydraulic Structure can create tension/conflict among the people living in the nearby areas. Agriculture production may be hampered by saline water intrusion where as saline water is the pre-requisite for shrimp farming. Improper operation of hydraulic structure during rainy season or after storm will create water logging. To release the excess water or to let the saline water to enter inside the polder public cut may occur. Mitigation-BWDB should have trained operator on hydraulic structure operation/control mechanism and time. Water Management Organizations (WMOs) should be involved in operating and maintaining the hydraulic structures. The hydraulic structure operation should be based on the need of maintaining minimum water level requirement, agricultural requirement and to remove water logging.
Impacts - Rain cuts and public cuts are the major causes of embankment breaching of the Polder. Lack of regular maintenance has created weak point at the sensitive locations of the embankment. Mal-maintenance and increasing intensity and magnitude of the cyclone and storm surge simultaneously have accelerated the risk of embankment failure. Mitigation - The following measures will be implemented to address the above concerns:
Impacts –Soil Erosion from the polders and lack of sedimentation management will create blockage of streams. Mitigation-BWDB should take quick repairment measure at early stage in case of any erosion of the polders and should take appropriate measure for ensuring proper sedimentation management.
Impacts – Erosion from soil surfaces results from the kinetic energy of raindrops and flowing water. Raindrops dislodge soil particles, and runoff flowing downslope can suspend and transport the loose particles. Livestock and human traffic on polders encourage erosion. Holes created by rodents in the polder also increases possibility of soil erosion. Mitigation-The tops of embankments not routinely used as roads should be covered with grass. Embankment tops subject to regular traffic can be paved or covered with a 2- to 3-inch layer of coarse brick/gravel.
Impacts- Drainage congestion is a key issue in southwest zone of Bangladesh. This problem is localized and reversible by proper re-excavation of khals. It is a recurring problem and silt deposition in the rivers outside and water channels inside the Polder is likely to continue. Particularly, the low lying areas of the Polder and tail ends of khals may face severe drainage congestion in the future. Mitigation- The following measures will be implemented to address the above concerns:
Impacts – Mal-operation and leakage of regulators will result in salinity intrusion during the low flow season, causing severe damage to the soil, water resources, and crops in the Polder. The Proposed project has been designed to address such damages which are currently caused by the salinity intrusion. Mishandling and or poor upkeep and maintenance of these control structures will undermine the very objective of the Project. Mitigation- The following measures will be implemented to address the above concerns:
Impacts - Construction of new water control structures on water channels which are currently directly connected with the outer rivers will potentially result in reduction in fish migration. This can potentially result in decrease of fish population in the Polder thus adversely affecting the fish catch and fishermen. Mitigation- The following measures will be implemented to address the above concerns:
Impacts – The borrow pits often harbor nuisance plants like water hyacinth which invade the croplands during flood and cause considerable crop damage. Mitigation-The nuisance plants should be regularly destructed. The destructed plants can be converted into compost for application as soil conditioner/manure. Community can be involved in this action. Responsibility
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