This part gives a brief outline of possible mitigation measures to minimize negative impact of the bridge construction on environment. The mitigation measures listed here are not a complete list ofmitigation measures which can be used in similar cases. To list all possible mitigation measures is not a goal ofthis article; the goal is to give an idea about them.
The overall impact of the project, especially during construction phase, on air quality can be minimized usually by the following mitigation measures:
• Applying water or acceptable chemical suppressants to roadways to reduce dust
• Haulage and grading kept to a minimum
• Installing dust covers, sonic sprays, etc., to suppress dust generation from equipment in the quarrying and crushing facilities
• Servicing all mobile and stationary engines to maintain optimum fuel efficiency
The overall impact of soil erosion on soil capability during the construction phase may be minimized by the following mitigation measures:
• Working surface and slopes will be graded to minimize runoff erosion.
• Progressive reclamation during operations will minimize slope erosion.
• The road right-of-way will be seeded with and erosion controlling plant cover as soon as practical following access road construction.
• Where required, diversion berms can be placed and designed to minimize erosion and sedimentation.
• Topsoil stripping will be discontinued during periods of high winds.
Possible mitigation measures to avoid soil erosion and degradation are mitigation measures which can be adopted during the vegetation clearance process as
• minimizing right-of-way width and the extent of new clearing where possible, and
• salving and replacing the surface soil to support successful revegetation.
Some of the mitigation measures to minimize water-quality decrease are as follows:
• Building coffer dams to isolate abutments during construction
• Using industry best management practices for explosive use, to reduce potential effects of nitrogen residues on quarried rock
• Ensure appropriate spill response equipment is on site during all projects, provide adequate spill response training, and ensure that immediate spill response takes place if an incident occurs
• In case of rivers which froze: complete construction of abutments during winter conditions, maximizing construction during frozen river conditions
• Minimizing right-of-way width and the extent of new clearing where possible
• Salving and replacing the surface soil to support successful revegetation.
The mitigation measures for reducing/eliminating alternations to the river channel form and scour/erosion include the following:
• Narrowing of channel during construction is minimized
• Bridge alignment is compatible with river morphology
• Deck height planned to account for 100-year flood levels (it may vary according to local regulation) and to allow navigation and minimize the potential for complete channel blockage by ice jams under severe flood conditions if applicable
• Bridge abutments, approaches, and piers have to be constructed to prevent erosion and ifapplicable also ice scour.
Some of the mitigation measures to minimize effect on aquatic resources and habitat are as follows:
• Design piers and abutments to provide new, higher-quality habitat to compensate for any losses
• Design the bridge work to prevent channel and bank erosion, and subsequently sediment input
• Follow best management practice during construction and maintenance to prevent sediment release and spills
• Timing major in-stream construction to avoid critical spawning, egg incubation, and early-rearing periods
• Implementation of a water-quality monitoring program during major in-stream construction periods
• Application of appropriate controls to prevent surface runoff and, where required the installation of sediment control devices
• Recountouring and revegetation of banks with native species
Some of mitigation measures to minimize impact on wildlife and wildlife habitats are as follows:
• Noise reduction (decrease speed limit, wooded or vegetated buffers) near the bridge would reduce noise levels, which may reduce impacts on wildlife
• Prompt reclamation of habitat where possible; or revegetation with nonpalatable species, using native seed mix
• Markers, such as aviation spheres, can be used to mark suspension lines, guy wires, and appropriate infrastructure
• Open span bridge to allow for wildlife movement underneath
• Maintain maximum line of sight along road to reduce collisions
• Low-impact construction techniques
• Ensure bridge visual inspections are as unobtrusive as possible, particularly during the breeding season
• During years of intensive bridge maintenance, prevent nesting of species, if required through strategies such as visual deterrents or surface gels
The overall impact of the project, especially during the construction phase, noise, can be minimized by the following mitigation measures:
• Limiting activities to nonsensitive time periods (i.e., during peak waterfowl migration times)
• Limiting extent of heavy equipment
• Ensuring all equipments are installed with appropriate noise reduction devices
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