4. STUDY METHODS 4.1. Introduction 4.2. Approach and methods
4. STUDY METHODS
4.1. Introduction
The aims of the environmental impact assessment are:
- to gather information about the environment of the study area and identify environmental constraints and opportunities associated with the area which may influence, or be affected by the proposed scheme;
- to identify and assess predicted environmental impacts; and
- to identify and incorporate into scheme design and operation, features and measures to avoid or mitigate adverse impacts and enhance beneficial impacts.
This chapter discusses the approach and methods used to carry out the assessment and identifies aspects of the proposed development that have been subject to assessment.
4.2. Approach and methods
This EIA has been carried out in accordance with the Design Manual for Roads and Bridges (DMRB), first published in 1993 and subsequently amended and updated by the Highways Agency, The Scottish Executive Development Department, The National Assembly of Wales and The Department of the Environment for Northern Ireland. DMRB is the Government Advice Note that provides guidance on the development of trunk road schemes including motorways and is applicable to this scheme. Within the DMRB Volume 11 specifically provides guidance on the environmental impact assessment of this type of scheme, including the level of assessment required at key stages of development and the requirements for reporting the environmental effects of the scheme.
The DMRB specifies three key levels of assessment to be undertaken, defined as Stage 1, Stage 2 and Stage 3. The objectives of each Stage are identified in Table 4.1.
Table 4.1 Stages of EIA according to DMRB, Volume 11
Stage |
Objectives |
|---|---|
Stage 1 |
Identification of environmental advantages, disadvantages and constraints associated with broadly defined route corridors. |
Stage 2 |
Identification of the factors and effects to be taken into account in the selection of route options and in the identification of the environmental advantages, disadvantages and constraints associated with these routes. |
Stage 3 |
Assessment to be undertaken in accordance with the requirements of Sections 20A and 55A of the Roads (Scotland) Act 1984 and EIA (Scotland) Regulations 1999 (as amended) which implements EC Directive 85/337, with publication of an Environmental Statement or Environmental Assessment Report. |
The assessment of the route options for the Ba Bridge in Glen Coe at Stages 1 and 2 were progressed as part of the studies undertaken in 2002, as referred to in Chapter 2, section 2.2.3.
The assessment covered in this report comprises a Stage 3 assessment, undertaken between December 2005 and July 2008. It comprises a detailed assessment identifying the likely impacts of the proposed scheme and the associated mitigation measures. It builds upon and supplements the work of the previous Stage 1 Scoping Report (Rannoch Moor/Glencoe bridge replacements, 2003).
The assessment for Stage 3 has been carried out as an integral and iterative part of the scheme design and the issues arising from this process have informed decisions in the development and design of the scheme. The process undertaken for the design of the proposed alignment is discussed in more detail in Chapter 2.
Although this Stage 3 assessment has been carried out in accordance with the DMRB, Volume 11, it has been supplemented by further guidance including that detailed in Table 4.2.
Table 4.2 Best practice guidance used for environmental assessment
Environmental assessment area |
Best practice guidance used |
|---|---|
General |
|
Surface Water Quality |
|
Ecology and Nature Conservation |
|
Landscape & Visual Issues |
|
Cultural Heritage |
|
Air Quality |
|
Traffic Noise and Vibration |
|
Policies and Plans |
|
In accordance with DMRB Volume 11, assessment has been undertaken for the following environmental factors:
- Land Use;
- Geology and Soils;
- Road Drainage and the Water Environment;
- Ecology and Nature Conservation;
- Landscape;
- Visual Issues;
- Cultural Heritage;
- Landscape Effects;
- Disruption Due to Construction; and
- Policies and Plans.
Impacts which occur during construction works but are either long term or permanent (and will therefore persist once the scheme is operational) are considered in the Chapters 7 – 11 of this ES, under the relevant headings such as Ecology and Nature Conservation.
Other impacts that are temporary and occur either prior to construction (e.g. assembly of temporary bridge) or during construction of the new bridge are considered separately in Chapter 10 – Disruption Due to Construction. However, there may be some overlap between construction and operational impacts and in these cases the impacts are generally described in the main operational chapter.
The assessment of impacts has followed the overall process outlined below for all subjects. However, individual sections may have used a slightly different layout appropriate to the assessment:
- identification of baseline conditions of the site and its environs;
- consideration of potential causes of impact;
- assessment of the significance of impact, taking into account sensitivity of resources and magnitude of impact;
- identification of mitigation measures; and
- assessment of significance of residual impacts taking account of any mitigation measures.
Further discussion of baseline conditions, predicted impacts, mitigation and the definition of residual impacts is provided below.
The specific assessment for each environmental subject has been undertaken in relation to a ‘baseline’. The ‘baseline’ normally reflects the existing situation and how this would change if the scheme did not go ahead (i.e., the Do Nothing Scenario).
Baseline information has been collected through site visits, and review of maps, data, records, information and reports obtained from statutory and non-statutory organisations and a variety of field surveys. The consultation process with statutory and non-statutory organisations is reported in Chapter 5.
The nature of predicted impacts arising from the scheme has been described and an assessment of the level of significance of the impact (negligible, slight, moderate or major) for each effect determined as far as practical.
There is no universally accepted definition of what constitutes a significant impact. The question of significance varies according to the environmental factor under consideration, the context in which the assessment is made and the background of the assessor. Much depends on the availability of data relating to existing environmental conditions and the value applied to these conditions. However, in general, the level of significance of impact has been defined using a combination of the sensitivity (high, medium and low), of the environmental feature in question, and the magnitude of impact (major, moderate, minor and negligible), each having been assessed independently according to defined criteria. Sensitivity has generally been defined according to the relative importance of the feature, i.e. whether it is of national, regional or local importance or by the characteristics of the receptor. In the definition of magnitude of impact, consideration has been given to any legislative or policy standards or guidelines, and/or the following factors:
- the degree to which the environment is affected, e.g. whether the quality is enhanced or impaired;
- the scale of the development, e.g. the size of land area or number of people affected and degree of change from the existing situation;
- the scale of change resulting from impacts; and
- whether the effect is temporary or permanent.
Impacts may also be wide-ranging in nature, for example, they could result in direct or indirect, secondary, cumulative, short, medium or long-term, permanent or temporary, positive or adverse effects. These factors have also been taken into account.
The approach to mitigation measures adopted for this EIA is consistent with the guidance provided in Planning Advice Note 58 on EIA that considers mitigation as a hierarchy of measures ranging from prevention of environmental effects by avoidance, down to compensatory measures for effects that cannot be remedied. The mitigation hierarchy is summarised in Table 4.3.
Table 4.3 Mitigation hierarchy
Level of Mitigation |
Definition |
|---|---|
Prevent |
To prevent adverse environmental effects at source, for example, through choice of site or specification of construction equipment. |
Reduce |
If adverse effects cannot be prevented, steps taken to reduce them through such methods as minimisation of cause of impact at source, abatement on site and abatement at receptor. |
Remedy/offset |
When effects remain that cannot be prevented or reduced, they are offset by such remedial or compensatory action as provision of environmental improvements, opportunities for access and informal recreation, creation of alternative habitats and prior excavation of archaeological features. |
The approach to the mitigation of adverse environmental impacts has been to avoid them wherever possible. This has been achieved by consideration of ways in which to prevent adverse effects at source, rather than relying on measures to mitigate the effects. For the Ba Bridge, this has been undertaken throughout the design phase
Where avoidance of impacts has not been assessed to be feasible, measures have been proposed to minimise potential impacts through abatement methods at the site (for example, by the use of landscaping and sediment trapping techniques).
4.2.6. The definition of residual effects
Residual effects are those that cannot be mitigated against and last well into the operational phase of the scheme, such as permanent loss of woodland. The assessment of residual effects takes into account mitigation measures to be adopted as specified in this report. Within the assessment of residual effects, the level of significance for each effect is determined as far as practicable as defined above under Predicted Impacts.