Environmental impact assessment

Environmental impact assessment is a technique or a process by which information about the environmental effects of a project is collected, both by the developer and from other sources, and taken into account by the relevant decision making body before a decision is given on whether the development should go ahead.

Environmental impacts and sources

Environmental impacts

Potential environmental impacts include:

Water

Surface water hydrology/hydraulics

• Changed surface water run-off
• Changed flow velocities
• Changed magnitude of flooding
• Changed frequency of flooding
• Changed duration of flooding
• Convergence/divergence of flow
• Changed hydraulic roughness
• Regulated flow
• Low flows
• Wave generation
• Reduced tidal flow/flushing/mixing
• Riparian drainage
• Changed flow regime

Groundwater resources and hydraulics

• Changed flow
• Changed infiltration
• Changed direction of flow
• Change in water table (level)
• Barrier to flow
• Change in pressure potential
• Changed storage capacity
• Changed flow capacity

Groundwater quality

• Movement of contaminated water
• Change in quality
• Saline intrusion
• Chemical pollution
• Organic pollution
• Microbial contamination
• Changed dilution capacity
• Change in conductivity/ pH/acidification
• Change in oxygen content
• Change in temperature
• Mobilisation of contaminants

Channel morphology/sediments

• Changed bank/bed stability
• Degradation/erosion of beds or banks
• Deposition/siltation
• Change of bed slope
• Change of platform/pattern
• Disturbance to bed forms (pools, riffles)
• Downstream erosion
• Changed channel size
• Changed suspended sediment load
• Changed bed load
• Contaminated sediment

Surface-water quality

• Altered salinity
• Change in quality
• Chemical pollution
• Eutrophication
• Changed turbidity
• Microbial contamination
• Stratification
• Re-suspension of contaminated sediments
• Changed dilution capacity
• Organic pollution
• Change in residence/flushing time
• Change in oxygen content
• Change in conductivity/ pH/acidification
• Change in temperature

Air and climatic factors

Regional and global climate

• Changes in air moisture
• Reduction in sunlight
• Acid deposition
• Carbon dioxide levels
• Methane levels
• Ozone levels
• Sulphur dioxide levels
• Nitrogen dioxide levels

Local air quality and local climate

• Ponding of cold air
• Alteration to airflow
• Changes in air moisture
• Changes in local air quality parameters (NOx, SOx, O3, etc.)
• Other gaseous pollutants (CO, VOCs,)
• Release of metal pollutants
• Release of chemical pollutants
• Release of toxic organic micro- pollutants (e.g. dioxins, PAHs, PCBs)
• Release of particulates (dust, smoke, PM10)
• Ionising radiation (including naturally occurring radon)

Land

Geology

• Removal of bedrock
• Removal of drift deposits
• Loss of mineral deposits
• Loss of non-renewable resources
• Sterilisation of minerals or resources
• Damage to Regionally Important Geological Sites (RIGS)

Land use and designations

• Change to existing use of site
• Conflict with use of adjacent land
• Changed landscape character including: function as a resource, its scenic quality, degree to which it is unspoilt, sense of place that it engenders, its conservation interests
• Visual intrusion
• Change in amenity value
• Arable intensification
• Change in grade of agricultural land
• Increase in urban land
• Deforestation
• Afforestation
• Change in riparian land
• Development of floodplain
• Development of coastal zone
• Effects on future developments
• Effects on designated sites and other locally important sites

Soils

• Altered soil structure, texture, organic component, mineral component, biotic component, water content of soil
• Changed soil chemistry
• Changed soil fertility
• Changed soil density and compaction tolerances
• Changed soil profile and classification
• Soil erosion (by wind or water)
• Change in ability of soil to support proposed end uses
• Physical damage to soil systems through management practices
• Off-site impacts through deposition of atmospheric pollutants leading to: – Acidification of soils through deposition of SOx, NOx and ammonia – Eutrophication of soils in semi- natural habitats from deposition of NOx and ammonia
• Accumulation of heavy metals and persistent organic pollutants
• Build-up of heavy metals, such as Zn, Cd, Cu, Hg, Ni, and Pb from the application of organic materials on agricultural land
• Accumulation of organic compounds, e.g. PCBs
• PAHs, from the application of contaminated wastes
• Build-up of phosphorus in soils that receive regular applications of sewage sludge and/or livestock manure in addition to phosphorus fertiliser
• Accumulation of pesticides in soils and potential impacts on soil biodiversity

Ecology and biodiversity

Aquatic ecology

• Altered habitat
• Changed fish biomass
• Changed invertebrate biomass
• Changed plant biomass
• Changed species diversity
• Changed fish behaviour
• Change in fish community
• Barrier to fish migration
• Fish kill
• Changes in spawning
• Disturbance of sensitive species
• Loss of rheophilic flora and fauna
• Barrier to mammals
• Loss of sensitive species
• Effects on designated sites and other locally important sites
• Introduction of alien species
• Changes to population dynamics, distribution and abundance of key species, rare species and endemics
• Siltation of gravel spawning areas

Terrestrial and coastal ecology

• Altered habitat quality
• Altered habitat diversity
• Habitat severance
• Habitat fragmentation
• Loss of habitat
• Tree removal
• Wetland changes, including incoming and outgoing water flows
• Changed riparian habitat
• Change in plant biomass
• Change in animal biomass
• Disturbance of sensitive species
• Changed species diversity
• Effects on designated sites and other locally important sites
• Introduction of alien species
• Changes to population dynamics, distribution and abundance of key species, rare species and endemics

Human environment

Socio-economic (inc. planning gain)

• Population movement
• Changes in population size
• Changes in population characteristics (age range, family size, socio- economic groups, etc.)
• Altered settlement patterns
• Altered housing tenure types
• Change in house prices
• Change in demand for public or private housing
• Increase in homelessness
• Change in local economy
• Change in local and non-local employment
• Change in characteristics of employment
• Changed labour supply
• Change in demand for local education, health, social and emergency services
• Community structure and institutional arrangements
• Introduction of divergent views
• Individual and family level impacts
• Altered crime and perceptions of crime rate
• Enhanced opportunities for planning gain
• Need for temporary accommodation during construction

Nuisance

• Odour
• Vibration
• Noise
• Flood discharges, flow of contaminated water
• Soil erosion onto roads, properties, etc
• Light pollution

Architectural and archaeological heritage

• Threat to known sites
• Threat to other sites
• Threat to archaeological sites, monuments and features, above ground
• Threat to archaeological sites and features below ground
• Threat to settings of archaeological sites, monuments and features
• Threat to human artefacts, including historic buildings and sites (e.g. listed buildings), cemeteries and burial grounds, parks, gardens, village greens, bridges and canals and conservation areas
• Threat to designated and locally important sites and features
• Threat to other buildings and features of architectural merit
• Threat to other buildings and features of planning merit
• Threat to other buildings and features of social or economic importance
• Threat to other buildings and features that show technological innovation or virtuosity
• Threat to other buildings and features taken together as having group value

Local transport

• Altered volume of traffic
• Altered traffic profile (vehicle types and weights)
• Changed rates of flow
• Changed times of flow
• Changed waiting times
• Change in traffic speed
• Change in accident rate
• Change in access to parking
• Change in turning movements
• Effects on multi-modal transport profile (cars, buses, trams, trains, walking, cycling)
• Severance
• Effects on ecology
• Effects on pedestrians
• Effects on cyclists
• Effects on car users
• Effects on commercial vehicles
• Effects on frontage land uses

Health and safety

• Changed flood risk
• Loss of property
• Change in air pollution
• Change in water pollution
• Change in land contamination
• Change in noise levels
• Change in vehicles
• Change in equipment
• Change in emergency situations

Amenity, access, leisure and recreation facilities

• Change in access
• Altered facilities
• Altered use
• Effects on users of land-, water- and air-based facilities

Pests/vermin

• Birds
• Invertebrates
• Rodents
• Other mammals
• Micro-organisms

Visual impact

• Altered aesthetic value, including proportion, scale, enclosure, texture, colour, views
• Change in landscape
• Change in townscape
• Visual intrusion

Sources

Potential sources of impact (activities) include:

Preparation and construction phase

• Construction traffic on and offsite
• Erection of screens and fences
• Creation of new or changed landforms
• Trench digging
• Pipeline laying
• Test pits
• Installation of services
• Disposal of building waste
• Preparation of foundations
• Dust creation
• Influx of construction workers
• Provision of lighting
• Clearance or pruning of vegetation
• Storage of chemicals and liquids

Operational phase

• Transport
• Parking
• Buildings and infrastructure
• Use of services (electricity, gas, water, etc.)
• Manufacturing process(es)
• Storage
• Gaseous emissions and odour management
• Stack height
• Liquid discharges
• Waste disposal
• Operational failures
• Site security
• Likely expansion or secondary development

Decommissioning and after-use phase

• Removal of buildings and other structures
• Transportation of material
• Dust creation
• Disposal of inert waste
• Disposal of hazardous and special waste
• Spills or releases during decommissioning

Assessment procedures

John Glasson, Riki Therivel et. al. suggest the following procedures for the environmental impact assessment (EIA) process, which is developed from their earlier book originally published in 1994.

Department of the Environment, Transport and the Regions, a now-dissolved UK governmental agency in charge of environmental affairs, also provides with a checklist of matters that may be considered for inclusion in an EIA. This checklist is often used as a guidance to ensure that all the possible significant effects of the development are considered.

The environmental effects of a development during its construction and commissioning phases should be considered separately from the effects arising while it is operational. Where the operational life of a development is expected to be limited, the effects of decommissioning or reinstating the land should also be considered separately.

Section 1: Information describing the project

1.1 Purpose and physical characteristics of the project, including details of proposed access and transport arrangements, and of numbers to be employed and where they will come from.

1.2 Land-use requirements and other physical features of the project: • during construction; • when operational; • after use has ceased (where appropriate).

1.3 Production processes and operational features of the project:

• type and quantities of raw materials, energy and other resources consumed; • residues and emissions by type, quantity, composition and strength including: discharges to water; emissions to air; noise; vibration; light; heat; radiation; deposits/residues to land and soil; others.

1.4 Main alternative sites and processes considered, where appropriate, and reasons for final choice.

Section 2: Information describing the site and its environment

Physical features

2.1 Population - proximity and numbers.

2.2 Flora and fauna (including both habitats and species) - in particular, protected species and their habitats.

2.3 Soil: agricultural quality, geology and geomorphology.

2.4 Water: aquifers, watercourses, shoreline, including the type, quantity, composition and strength of any existing discharges.

2.5 Air: climatic factors, air quality, etc.

2.6 Architectural and historic heritage, archaeological sites and features, and other material assets.

2.7 Landscape and topography.

2.8 Recreational uses.

2.9 Any other relevant environmental features.

The policy framework

2.10 Where applicable, the information considered under this section should include all relevant statutory designations such as national nature reserves, sites of special scientific interest, national parks, areas of outstanding natural beauty, heritage coasts, regional parks, country parks and designated green belt, local nature reserves, areas affected by tree preservation orders, water protection zones, conservation areas, listed buildings, scheduled ancient monuments and designated areas of archaeological importance. It should also include references to relevant national policies (including Planning Policy Guidance (P P G ) notes) and to regional and local plans and policies (including approved or emerging development plans).

2.11 Reference should also be made to international designations, e.g. those under the EC ‘Wild Birds’ or ‘Habitats' Directives, the Biodiversity Convention and the Ramsar Convention.

Section 3: Assessment of effects

Including direct and indirect, secondary, cumulative, short-, medium- and long-term, permanent and temporary, positive and negative effects of the project.

Effects on human beings, buildings and man-made features

3.1 Change in population arising from the development, and consequential environment effects.

3.2 Visual effects of the development on the surrounding area and landscape.

3.3 Levels and effects of emissions from the development during normal operation.

3.4 Levels and effects of noise from the development.

3.5 Effects of the development on local roads and transport.

3.6 Effects of the development on buildings, the architectural and historic heritage, archaeological features and other human artefacts, e.g. through pollutants, visual intrusion, vibration.

Effects on flora, fauna and geology

3.7 Loss of, and damage to, habitats and plant and animal species.

3.8 Loss of, and damage to, geological, palaeontological and physiographic features.

3.9 Other ecological consequences

Effects on land

3.10 Physical effects of the development, e.g. change in local topography, effect of earth-moving on stability, soil erosion, etc.

3.11 Effects of chemical emissions and deposits on soil of site and surrounding land.

3.12 Land-use/resource effects:

• quality and quantity of agricultural land to be taken; • sterilization of mineral resources; • other alternative uses of the site, including the ‘do nothing1option; • effect on surrounding land uses including agriculture; • waste disposal.

Effects on water

3.13 Effects of development on drainage pattern in the area.

3.14 Changes to other hydrographic characteristics, e.g. groundwater level, watercourses, flow of underground water.

3.15 Effects on coastal or estuarine hydrology.

3.16 Effects of pollutants, waste, etc. on water quality.

Effects on air and climate

3.17 Level and concentration of chemical emissions and their environmental effects.

3.18 Particulate matter.

3.19 Offensive odours.

3.20 Any other climatic effects.

Other indirect and secondary effects associated with the project

3.21 Effects from traffic (road, rail, air, water) related to the development.

3.22 Effects arising from the extraction and consumption of materials, water, energy or other resources bythe development.

3.23 Effects of other development associated with the project, e.g. new roads, sewers, housing, power lines, pipelines, telecommunications, etc.

3.24 Effects of association of the development with other existing or proposed development.

3.25 Secondary effects resulting from the interaction of separate direct effects listed above.

Section 4: Mitigating measures

4.1 Where significant adverse effects are identified, a description of the measures to be taken to avoid, reduce or remedy those effects, e.g.:

(a) site planning;

(b) technical measures, e.g.:

• process selection; • recycling; • pollution control and treatment; • containment (e.g. bunding of storage vessels). (c) aesthetic and ecological measures, e.g.:

• mounding; • design, colour, etc.; • landscaping; • tree plantings; • measures to preserve particular habitats or create alternative habitats; • recording of archaeological sites; • measures to safeguard historic buildings or sites.

4.2 Assessment of the likely effectiveness of mitigating measures.

Section 5: Risk of accidents and hazardous development

5.1 Risk of accidents as such is not covered in the EIA Directive or, consequently, in the implementing Regulations. However, when the proposed development involves materials that could be harmful to the environment (including people) in the event of an accident, the environmental statement should include an indication of the preventive measures that will be adopted so that such an occurrence is not likely to have a significant effect. This could, where appropriate, include reference to compliance with Health and Safety legislation.

5.2 There are separate arrangements in force relating to the keeping or use of hazardous substances and the H S E provides local planning authorities with expert advice about risk assessment on any planning application involving a hazardous installation.

5.3 Nevertheless, it is desirable that, wherever possible, the risk of accidents and the general environmental effects of developments should be considered together, and developers and planning authorities should bear this in mind.

Methods

Checklists

Useful for identifying key impacts and ensuring that they are not overlooked, especially in scoping. Can include information such as data requirements, study options, questions to be answered, and statutory thresholds – but not generally suitable for detailed analysis.

Matrices

Mainly used for impact identification, but provide the facility to show cause–effect links between impact sources (plotted along one axis) and impacts (plotted along the other axis). They can also indicate features of impacts such as their predicted magnitudes and whether they are likely to be localised or extensive, short or long term, etc.

Flowcharts and networks

Can be useful for identifying cause–effect relationships/links/path-ways: between impact sources; between sources and impacts; and between primary and secondary impacts.

Mathematical/statistical models

Based on mathematical or statistical functions which are applied to calculate deterministic or probabilistic quantitative values from numerical input data. They range from simple forms, that can be employed using a calculator or computer spreadsheet, to sophisticated computer models that incorporate many variables.

Maps and GIS

They need adequate/reliable data, can be expensive, may not be suitable for ‘off the peg’ use. The results usually require validation. Maps can indicate feature such as impact areas, and locations and extents of receptor sites. Overlay maps can combine and integrate two or three ‘layers’, e.g. for different impacts and/or environmental components or receptors. GIS can analyse a number of layers, and has facilities for the input and manipulation of quantitative data, including modelling.