Introduction

Background

BEAR Scotland has been commissioned by Transport Scotland to replace the existing A887 road bridge which crosses the watercourse known as Allt Lagain Bhain. The A887 trunk road links the A82 at Invermoriston to the A87 at Bun Loyne. This provides a shorter route from Inverness (and other locations along the A82 north of Invermoriston) to Lochalsh and the Isle of Skye. The site is located 10 km west of Invermoriston, approximately 500 m west of the small settlement of Dundreggan.

The existing structure, shown in Figure 1, consists of a single 5 m span bridge which has been propped up since 2001. The existing road bridge is currently in a very poor condition with the main reinforcement being severely corroded. Maintenance repairs are not feasible due to the extent of the work required and it is considered that the bridge has come to the end of its working life.

Existing road bridge over river
Figure 1 - Allt Lagain Bhain Bridge

Project Location

The Allt Lagain Bhain Bridge is located along the A887 trunk road in Glen Moriston west of the small settlement of Dundreggan as shown in Figure 2. The River Moriston, including the Allt Lagain Bhain watercourse up to the trunk road bridge, is designated as a Special Area of Conservation (SAC).

Map showing location of Allt Lagain Bhain Bridge
Figure 2 - Project Location

The extent of the potential works area is shown in red on Figure 3, and is described more later in this report.

Map showing extent of land take
Figure 3 - Extent of Works

Environmental Impact Assessment

A formal Environmental Impact Assessment has been undertaken for this scheme because of the sensitivity of the site. The Environmental Impact Assessment identifies the existing environmental constraints such as watercourses, wildlife and habitats present, sites of historical interest and the character of the landscape in the area. The process then entails assessing the potential impacts of the scheme during construction and after construction (during operation) on the environmental features. The Environmental Statement reports on the findings of the Environmental Impact Assessment and includes measures to avoid, reduce, remedy or offset predicted adverse impacts.

The Environmental Impact Assessment has assisted the scheme design process through consideration of the environmental constraints and development of measures to reduce or avoid adverse impacts on the environment. 

Approach and Methods

The Environmental Impact Assessment has been carried out in accordance with guidance set out in Volume 11 of the Design Manual for Roads and Bridges.

The focus of an Environmental Impact Assessment is to determine significant impacts and therefore this Environmental Statement specifically focusses on Cultural Heritage; Ecology and Nature Conservation; Landscape Effects; and Road Drainage and the Water Environment as well as an assessment of Cumulative Effects. 

A number of topics have been ‘scoped out’ as they have been considered not likely to cause significant environmental impacts. These include Air Quality; Land Use; Noise and Vibration; Pedestrians, Cyclists and Community Effects; Vehicle Travellers; and Geology and Soils.

Alternatives Considered

Consideration was given to the following options:

  • do nothing;
  • strengthening the existing structure through maintenance repairs; and
  • complete replacement with a new structure.

The ‘Do Nothing’ scenario was not considered viable as this would firstly entail a weight restriction being placed on the bridge, resulting in heavy goods vehicles needing to take a long detour. In addition under this scenario, closure of the trunk road would be the eventual outcome. The second scenario was discounted based on cost benefit analysis, including long-term maintenance considerations. It was determined that the existing bridge had reached the end of its useful life. Therefore the most viable option was to completely replace the old bridge with a new structure and this option is the one taken forward and assessed in the Environmental Statement.