D Kominkova, Czech Technical University in Prague, Prague, Czech Republic © 2008 Elsevier B.V. All rights reserved.
Structure and Scope of Matters Addressed in an EIS Further Reading EIS Scope for Two Categories of Engineering Projects
Environmental impact assessment (EIA) was developed as a tool to minimize negative impact of human activities on the environment. The purpose of the environmental impact assessment is to
• assess the impact of a proposed activity on the envi ronment before making the decision on whether to carry it out, and
• develop and assess measures to avoid or minimize those impacts if it is decided to carry out the activity.
EIA can be defined as a process of collecting information about environmental impacts of a proposed project and consequent relevant decision making. EIAs also consider aspects such as project alternatives and mitigation meas ures which should be applied if the project is allowed. History of EIA is almost 40 years long. During this time EIA has developed as a complex tool, which helps in decision making in the case of proposed projects and helps to identify variation of the projects which will have a minimal impact on the environment in case of acceptable cost. The process of EIA comprises a number of different stages such as screening, scoping, reviewing, and completion. These stages of EIA may be labeled differently in different parts of the world, but their goals are similar. In the EIA process, a range of organizations may be involved, including government agencies, developers, nongovernmental, and public organizations. The level of involvement may vary significantly depend ing on the type of project that is assessed.
A detailed introduction to EIA is provided in Environmental Impact Assessment and Application - Part 1. Figure 1 shows the general structure of the EIA process, which should be followed while preparing environmental impact statement (EIS) for all types of projects.
The main goal of this article is to provide a broad understanding of the EIA process, for example, of hydro power dam and bridge construction projects. It provides direction on the scope of the EIA, but it is not an EIA by itself. The presentation of a detailed documentation of an EIA is beyond the scope of this book.
The nature and practicality of EIAs will vary. Approaches will vary between countries and between local areas within countries. What may be significant issues in one case may not be considered significant within another jurisdiction. Accordingly, the examples in this article are provided as indicative of approaches to these categories of projects. It is imperative that engineers, planners, and scientists undertaking EIAs con sult their national and/or local EIA legislation and guidelines.
Introduction. Introduction of the project (nature of the project, location, size), details about the activity, project purpose and justification, investor, need for the project, previous study if any, possibility of cumulation with other project, alternatives of the project, time framework.
Approach and methodology. This section describes the process used to identify the potential environmental impact associated with the project.
Project description. This section describes in detail the various components of the project. Information is pro vided on the technical aspects of the project, general activities related to construction, operation, and decommissioning, work force requirement during con struction and operation, waste/emission management, and safety.
Description of existing environment. This is necessary for two reasons:
• to determine which resources may be at risk from the proposed project (inputs and outputs of the project), and
• to provide a baseline for identifying environmental changes in the future.
This section describes the baseline conditions of the bio physical and socioeconomical environment in the area for each environmental component. The description of environmental conditions is based mostly on resources information gathered from the following sources:
• recent direct observations, inventories, consultations, and interviews in the project area;
• secondary sources such as published and unpublished survey reports, project investigating reports and official data reports;
• interviews with environmental resources specialists; and
• interviews with the government representatives.
In some countries, this section is closely related to assess ment of present state of the environment and its capacity to accept more changes.
Valued environmental components. This section describes the process used to identify valued environmental com ponents (VECs) which involves issue scoping and pathway analysis. The VECs are determined on the basis of perceived public concerns related to social, cul tural, economic, or esthetic values. Generally, VECs are defined as those aspects of the ecosystem or associated socioeconomic systems that are important to humans. The components could include the following:
• components which may be important socially,
• components which may be essential to the food web, and/or
• components which may be a reliable indicator of envir onmental changes.
Specifically, VECs are species, habitats, environmental features, and resources that are particularly rare, unique, productive, indicator of environmental change, commer cial, esthetically valuable, or essential to ecosystem function and integrity. They include environmental com ponents, including social and economic components, which are identified as having scientific, social, cultural, economic, or esthetic value.
Environmental impact assessment, mitigation measures, and resi dual effects. This section consists of an assessment of potential impact resulting from the proposed project. The prediction of impact is usually separated into three main categories:
• Impact upon the physical environment;
• Impact upon the biological environment; and
• Impact upon the socioeconomic environment.
Further, these impacts are predicted for the preconstruc tion/construction, operation, and the decommissioning/ abandonment phase of the proposed project. In addition, impact of the environment on the project has to be con sidered as well.
Current standard construction practice generally includes environmental protection measures that will mitigate many potential environmental concerns. Also potential impact associated with accidental events and potential cumulative effects has to be considered.
There are different methods of impact prediction, but they all result in decision making whether or not pre dicted environmental effects are adverse, whether the adverse effects are significant, and whether the significant adverse effects are likely. The potential significance ofthe identified adverse effects is considered for each VEC according to the magnitude or severity of the effects, geographical extent, duration and/or frequency, degree to which adverse effects are reversible, and the environ mental context. The environmental context relates to existing level of disturbance of the VEC and/or the fragility or degree of resilience to imposed stresses. Any activity that is predicted to lead to exceed a regulated or guideline value of a parameter is judged significant.
The likelihood of occurrence includes the probability of occurrence; or where insufficient data are available to permit the estimation of probability, the degree of uncer tainty has to be considered.
It is important that during impact assessment, the 'pre cautionary principle' is applied. The precautionary principle can be defined as follows: ''When an activity raises threats or harm to the environment or human health, precautionary measures should be taken even if certain causes and effect relationships are not established scienti fically.'' This is to be applied to avoid irreversible losses.
In order to be considered a significant environmental impact with respect to the biological environment, a deviation from background must be judged to cause changes in the process or state within the bounded area resulting in a sustained depression of fitness or density below naturally occurring levels. Where such changes are predicted, mitigation has to be recommended, when possible.
Environmental management plan (EMP). The main parts of this section are protection, mitigation, and enhance ment measures which are identified for the areas of environmental concerns of the project. Also the pre scribed monitoring studies are part of the environmental compliance plan (ECP); EMP has to be agreed upon between the proponent and the governmental bodies.
The EMP should ensure, along with ECP, that the environmental commitments and recommendations are implemented in full. This begins by incorporating mitiga tion measures and other environmental considerations into the plans and specifications and then to continue overseeing how they are carried out during construction and operation.
The EMP is usually divided into three different programs:
• The Civil Works Management and Monitoring Program
• The Environmental Components Quality Management and Monitoring Program
• The Socioeconomic Impact Management Program
Comparison of different alternatives of the project as well as taking in account nonaction alternative References Glossary
Appendices. These include the results and reports of all studies, which were concluded as part of the EIA process.
The names of single parts of EIS may vary among countries, but generally the EIS has to contain all the above mentioned information.
EIS Scope for Two Categories of Engineering Projects
The main aim of this part is to provide an outline of the most common impacts resulting from hydropower dam construction and bridge construction. Identification and assessment of environmental impact of projects seems to be the most challenging part of the EIA process for all types of projects. This section is focused primarily on the identification and assessment of environmental impact of the projects. The reader has to keep in mind that the whole EIA contains more activities as is mentioned above and in Environmental Impact Assessment and Application - Part 1.
Construction and Operation of a Hydropower Dam
The goal of this section is to identify the most common impacts resulting from hydropower dam construction and operation.
The construction of hydropower dam belongs to the category of projects, which are universally designed as man datory EIA projects. During the screening stage of the EIA process, it is necessary to identify the proposed project and the investor. The primary information about the proposed project is the type of activity, the capacity, the location, the character of the activity, and possibility of cumulative effects with other types of anthropogenic activities. The identifica tion of necessity of the project for this type of project is usually very similar; the main reason to construct hydro power dam is generation of power to meet growing national demands for electricity and to ensure reliable sources. The secondary reason for building a hydropower dam is flow regulation downstream from the dam contributing to the flood control and irrigation, another reason is a recreational purpose and drinking water supply. Important part of screening stage is the identification of proposed location as well as identification of alternative options is a part of the primary step, together with a short description of technical and operational solutions. Identification of the proposed starting and ending date of the activity is another important information collected during the first step of EIA. This first step is common for all EIAs and there should be little variation in content of this part.
The second stage of EIA process is the scoping stage. This should take into account all key activities which will be connected to the dam construction at different stages. The development would involve the excavation of construction materials, the construction of the dam, the power station, access roads, and power lines. Environmental, economic, and social impacts would occur both during construction and during operation. There are some key operations during preconstruction, construction, and operational periods, which can be used as a guide for assessing impact. The preconstruction program will include
• the construction of new roads to the dam site,
• the improvement of existing roads to facilitate delivery of construction plant and materials,
• the identification of stone quarries and borrow pits,
• the building of housing and other facilities for construc tion workers,
• the building of a site office,
• the identification of villages and hamlets to be relocated and the development of resettlement plans, and
• the harvesting of timber or other type of clearance of the present vegetation, which will otherwise be drowned and may later on cause problems.
All of these activities have the potential to create environmental impacts. Areas of particular concern will relate to the selection of sites for extracting construction materials and the proposals of resettlements.
The construction program will include
• the construction of a coffer dam to regulate flow during building,
• the blasting to obtain rock and prepare the dam site,
• the construction of the dam,
• the construction of power station,
• the construction of replacement villages,
• the erection of pylons and power lines, and
• the construction of replacement access roads to the remaining communities.
The operational phase will include
• the generation of electricity;
• the regulation of river flow in the interest of flood control in the wet season and irrigation in dry season;
• the maintenance of the dam, power station, and power lines;
• transportation on the lake; and
• the possible development of fisheries and recreation.
The above listed activities will follow construction of most hydropower dams; there are some differences which may occur with respect to local conditions.
Even if there is a common consensus on which parameters should be considered while determining envir onmental sustainability of a hydroproject (Table 1), the EIA process should not rely only on these factors, but should look on all possible impacts.
Explanation of factor
Hydro projects sometime necessitate the relocation of people. The less that people are affected,
the better the project.
Biodiversity should not decline as a result of the project and obviously no extinction of species
The issue of fish is related to the loss of protein (how do people depend on fish in their diet for
subsistence?) and loss of revenue from sales (commercial fisheries). (Ecological point of view
is included in the biodiversity factor.)
Generation capabilities of the project must be long term. Reservoir useful life must be long so
that power generation would not be curtailed by sedimentation.
Land requirements are associated with land use in terms of economic activities (agricultural
Project implementation should make sure that acceptable water quality is maintained for
downstream users. All pollutants should be at acceptable level.
Water regulation by hydroprojects should not be detrimental to irrigation or to important
ecosystems (mangrove, wetlands, and floodplains). Benefits such as flood control, urban and
industrial water supply, multiple uses are considered a plus.
Integration of project in the
The project should be well integrated to future activities in the region.
Greenhouse gases emission
Total greenhouse-gas emission should not exceed equivalent emission from gas-fired power
The next part will provide an assessment of the most common potential impacts resulting from construction of a hydropower dam (there can be local and case varia tions). For purpose of this article, the prediction of impacts is separated into three main categories:
• Impact upon the physical environment
• Impact upon the biological environment
• Impact upon the socioeconomic environment
The most common impacts of a hydroproject are listed in Tables 2 and 3 and are separated into impacts originated during the construction phase and during the operation phase, which starts with filling the reservoir with water.
Tables 2 and 3 list the most common effects of hydro power dam construction and operation on physical and biological environment, but it is necessary to take into account local conditions and the size of the dam. In the case of large and deep reservoirs the assessment has to take in account the impact of the large water volume and its weight on induced seismicity and possibility of earthquakes occurrence. The construction of hydropower dam also may have an impact on the socioeconomic environment of local communities. The main impact can be identified as necessity of resettlement, loss of social integrity in resettled commu nities, loss of agricultural land, and impact on or loss of cultural, historical, and archaeological heritage. Conversely new job opportunities are created, usually improvement of transportation occurs, also positive impact on human health and esthetic changes to the landscape are observed. A number of other impacts will be location dependent. The nature and scale of indirect and cumulative impacts as well as impact interactions will also be site specific.
A number of negative impacts may be minimized by proper mitigation measures and best management practices.
The second example is an EIA for the construction and operation of a bridge. Again there are impacts which are similar all around the world while constructing a bridge,
Table 2 Potential impact to the physical and biological environment during construction phase of a hydro project
Water resources and hydrology
Erosion/site runoff Excavation
Alternation/displacements of aquatic and terrestrial habitat Mortality (individuals of different species) Interface with fish passage and animal migration Degradation of aquatic and terrestrial habitat Effects on water quantity
Effects on water quality v n e a c g o o B
Surface water (Hydrology and floodplain) Climate/Air quality
Human health and safety Plant species at risk Animal species at risk Designated areas and other critical habitat features
Benthic invertebrate Fish
Reservoir creation Air emissions
Greenhouse gases emissions Ozone depletion substances Air emissions
Construction activities including clearing, grubbing, blasting, and cut and fill Noise
Accidental release of contaminants Surface runoff grading, and grubbing creating sediment, runoff and erosion River crossing Blasting
Accidental release of contaminants
Effects on surface water quantity Reduction in air quality to unacceptable level
Alternation/displacements of habitat Mortality (individuals of different species) Noise and physical disturbance Alternation/displacements of habitat Mortality (individuals of different species) Degradation of habitat Interference with fish passage
Table 3 Potential impact to the physical and biological environment during operational phase of a hydro project
Erosion/ site runoff Water level fluctuation
Alternation/ displacements of habitat y h P
Water resources and hydrology v n e a c g o o B
Climate and air quality
Hydrology and floodplain
Greenhouse gases emission
Plant species at risk Animal species at risk Designated areas and other critical habitat features Benthic invertebrate Fish
Fish habitats Macrophyta Algae
Erosion/site runoff Thermal stratification Release of contaminants
Increase groundwater elevation
Release of contaminants
Reservoir creation Erosion/ site runoff Reservoir creation Water level fluctuation
Reservoir creation Air emissions
Filling of the reservoir Accidental release of contaminants
Barrier to fish passage Seasonal changes of water quality caused by thermal stratification Disturbance to river continuum
Effects on water quality Effects on water quantity Effects on quality Effects on quantity Effects on surface water quantity Changes of natural flows and their periodicity Local changes in climate Reduction in air quality to unacceptable level
Alternation/ displacement of habitat
Decrease fish production Mortality
Behavior changes while other impacts may vary according to the climate, location, size, or function of the bridge.
As was mentioned above the first steps in EIA process are similar and are not dependent on a project type. The screening stage has to obtain information about proposed project (the project type, the size, the capacity, the loca tion, the character of the activity, and possibility of cumulative effects with other types of anthropogenic activities) and the investor. An important part of the screening stage is an identification of the necessity of the project. In the case of a bridge construction, the most common reasons are to connect two places which are not naturally connected and to improve transportation and decrease time and energy to get from one place to other. The secondary reason for building a bridge can also be protection of natural area with high environmental and ecological value, which would be otherwise exposed to traffic and to all negative consequences connected with it. An important part of the primary step is an identification of the proposed location as well as the identification of alter native options. A description of technical and operational solutions has to be part of the screening stage as well as information about starting and ending date of the activity.
The second stage of EIA process, the scoping stage, takes into account all key activities connected to a bridge construction and operation. The impact can be separated into impact during the preparation, construction, and operational period.
The development would involve the excavation of construction materials, the excavation of abutments, construction of the bridge, access roads, and stabilization of banks. There are some key operations during precon struction, construction, and operational and maintenance periods, which can be used as a guide for assessing impact.
The preconstruction program will include
• the construction of new roads to the bridge if it is necessary,
• the improvement of existing roads to facilitate delivery of construction plant and materials,
• the identification of stone quarries and borrow pits,
• the building of housing and other facilities for construc tion workers,
• the building of a site office,
• the harvesting of timber, or other type of clearance of the present vegetation.
All of these activities have the potential to create environ mental impacts. Areas of particular concern will relate to the selection of sites for extracting construction material. The construction program will include
• temporary diversion of the river course (to allow for construction in riverbed),
• excavation for buried pile cap,
• mobilization of a pile driver to the river bed,
• pile driving for pier support,
• excavation of abutments,
• bending and tying of steel (for the abutments),
• construction of piers and superstructure,
• laying of the asphalt, and
• stabilization of the banks.
The operational and maintenance phase will include
• inspecting the bridge superstructure and piers (for structural integrity and corrosion),
• routine resurfacing of the asphalted concrete surface,
• stripping, priming, and painting ofsteel structural sections,
• removing vegetation from the bridge and its basement, and
• winter maintenance to keep it passable.
During all these three phases of the project, there will be impact on the environment, socioeconomic sphere, cul tural sphere, and the visual/esthetic sphere.
Most of the impacts, which occurred during the pre construction and construction phase of a bridge construction, are similar to those occurring during a hydropower dam construction (see Table 2). In this part more attention is put on each impact on the environment and its short explanation.
Impact on physical environment
Certain project actions will release emissions to the atmos phere. These releases will be primarily due to fuel combustion (construction equipment, power generators, and space heating, and transportation vehicles), explosive detonation and fugitive dusk (excavation, drilling, and quarrying and crushing, wind erosion, and road dust). The key impact results from dust and emissions from heavy equipment during construction period. Following construction, these effects would return to normal (exist ing) level in the region. Dust and emissions from heavy equipment may cause animals and birds to relocate away from areas surrounding the construction site. Over the long time period, the bridge might increase traffic volume on the road, leading to higher emission in the area. However on the other side it will decrease overall fuel consumption by eliminating the necessity to drive the longer original way, and the amount of emissions in the whole region will decrease. In case that the transport over river is managed by ferry, then after bridge construction the fuel consumption to related ferry operation will be elimi nated. Another factor potentially affecting air quality is the release of air contaminants during chemical spill events.
The following potential impacts on soil and terrain are usually identified for activities associated with this type of project (right of way clearing, lay down area cleaning, topsoil salvage and grading):
• permanent loss of soil;
• lowering of soil capability through water/wind erosion, especially on soil with shallow bedrock;
• lowering of soil capability through admixing of topsoil/ subsoil; and
• lowering soil capability through compaction and rutting.
Construction of the bridge and road also can cause slope instability, depending on the slope of terrain, texture and moisture content of the material, and vegetation cover. Alternation of the terrain along the road can be caused by erosion from roadways. Soil erosion can result in alterna tion or loss of soil quality, a process that can subsequently affect vegetation growth. The project causes vegetation removal, thereby exposing the soil and increasing the prob ability for erosion. Soil admixing may result from improper soil handling procedures, and can affect soil fertility and consequently vegetation growth. Soil compaction results in a reduction of porosity and an increase in soil bulk density and also it effects may cause change in vegetation growth. Spills and leaks during all phases of the project may result in the alternation of soil chemistry and physical properties, which in turn can affect vegetation, surface water, and groundwater quality.
Water quality and quantity
The following potential impacts to water quality may be associated with various construction and operational aspects of the project:
• Suspended sediment loading during in stream construction
• Release of sediment from surface runoff
• Water contamination from spill
• Water contamination from fill/construction material
• Sediment or contaminant release during maintenance
• Sediment release from bank erosion or surface runoff
• Water contamination from spills
The main water quality issues related to the bridge pro ject relate to the potential release of sediments or chemicals into the river channel, primarily during con struction. If sediment is released during construction the main impact would occur downstream of the bridge. Sediment loading from bridge construction would be short term. A variety of construction techniques could be used to minimize, or eliminate, the possibility of large and sustained sediment release. Timing of construc tion to avoid critical periods for fish species and life requisite activities (spawning) also may be an effective mitigation tool. Sediment release can also occur during the operation period of the bridge as a result of shoreline erosion, from surface runoff along ditches, and from fine sediments washing off bridge deck into the river (e.g., sand, gravel, and dust from road, maintenance activities, and traffic). Other potential water quality impacts include the release of contaminants into river from fuel or chemical spills. This can occur during construction when heavy equipment is working on near the river as well as during operations from traffic and maintenance activities.
The following potential impacts to water quantity are usually identified for activities associated with a bridge construction (construction of bridge approaches and in stream pier construction/placement):
• Alternation to channel hydraulics preventing fish movement,
• Changes in channel hydraulic form resulting in down stream erosion or deposition,
• Channel blockage (flow restrictions),
• Channel aggradation/degradation over time.
Potential impacts of a bridge include changes to channel hydraulics upstream and downstream of the structure as well as immediately around the bridge piers. Any nar rowing of the channel can restrict flows and increase river velocity at crossing site. This increase of velocity can lead to erosion around the bridge abutments and piers. The channel restriction can also impede the move ment of ice at breakup and lead to ice jams if the bridge is not designed properly. During construction, depending on construction techniques, the river may be constricted to allow construction to occur away from the flow of the river to reduce sediment release. Overall, these types of changes may lead to erosion of the banks or channel bed, increase sedimentation, changes in river velocity in the vicinity of the bridge, deposition of sedi ment in new areas of the channel, and restriction of fish movements.
Increased noise levels in the area are to be expected if the bridge is constructed. Noise due to construction would cause animals and birds to avoid the area around the bridge and their community. Noise is an issue that is present at all phases of the project but is likely to be greatest during construction, which is a relatively short duration activity. Noise during this period would be related to the amount of heavy equipment operating during construction as well as environmental conditions.
Impact on the biological environment
Potential impacts to vegetation could be either direct through clearing or indirect through potential increased dust as a result of traffic, alternation of drainage patterns, and deposition of material. Because vegetation is closely tied to the stage of the environment (terrain, soil, water quality and quantity) most of the impacts are closely related to the changes of environmental parameters.
Primary impacts on wildlife associated with bridge/road construction and operation include reduction/alternation in habitat, effects on wildlife movement, and indirect effect on mortality and interference in nesting, breeding, migrating, and overwintering activities. Potential impacts to wildlife include the following:
Habitat. Reduction in habitat effectiveness along the river due to increased noise from bridge crossing and reduction in wildlife habitat directly through site clearing or indirectly through sensory disturbance and barriers to movement
Movement. Sensory disturbance from road traffic along bridges may obstruct daily or seasonal wildlife movement.
Abundance/biodiversity. Interference in nesting activity, disturbance to wildlife during construction, and increased mortality risks from changes in vehicular access and increased vehicle use.
The following potential impacts to aquatic resources are usually identified in relation to major project activities (i.e., construction of bridge approaches and piers, removal of barge landing area, normal bridge operations):
• Alteration and loss of fish and benthos habitat as a result of the installation of the bridge
• Fish and benthos disturbance caused by the addition of fill, cofferdam construction, and the movement of equipment (sediment impacts to fish health)
• Restriction or blockage of fish passage
• Fish and benthos mortality and disturbance as a result of sediment release or chemical spills
The socioeconomic impact of a bridge construction is mostly positive across a broad range of the society levels. Some of the positive impacts are summarized below.
Local community. The construction and operational phase brings training and employment, opportunities for local business, and opportunities for joint ventures.
Public and consumers. Net saving in consumer goods and services and improved access and reduce isolation.
Truck industry. Reduced travel time and distance, improved scheduling and equipment utilization, and increased volumes.
Business. Lower overall cost for goods, reduced cost for alternative transport, and regional economic stimulus
The negative impact is mostly negative social impact during construction, due to nonresident workforce and increase in community income.
This part gives a brief outline of possible mitigation measures to minimize negative impact of the bridge con struction on environment. The mitigation measures listed here are not a complete list of mitigation measures which can be used in similar cases. To list all possible mitigation measures is not a goal of this 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 dur ing 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 mini mize 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 suc cessful revegetation.
Some ofthe mitigation measures to minimize water quality decrease are as follows:
• Building coffer dams to isolate abutments during construction
• Using industry best management practices for explo sive 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 con struction 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 suc cessful revegetation.
The mitigation measures for reducing/eliminating alter nations 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 if applicable 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 wild life and wildlife habitats are as follows:
• Noise reduction (decrease speed limit, wooded or vege tated buffers) near the bridge would reduce noise levels, which may reduce impacts on wildlife
• Prompt reclamation of habitat where possible; or reve getation 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 fol lowing 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
The environmental impact assessment is in the process of continual dynamic development all around the world. This is in response to new corporate commitments and increases community expectation and concern about the state of the environment.
It is crucial to keep in mind that every EIA is distinct and consideration to local conditions and exact type of project and its implication is essential for successful EIA.
See also: Environmental Impact Assessment and Application - Part 1; Erosion; Impoundments; Invasive Species; Lake Restoration; Landscape Planning.
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