7 Environmental Considerations 7.1 Overview 7.2 Sustainability Appraisal
7 Environmental Considerations
7.1 Overview
The Managed Crossing Scheme is in effect a shortened version of the Full Corridor Scheme, with the added feature of utilisation of the Forth Road Bridge for public transport.
The Managed Crossing Scheme infrastructure lies within the Full Corridor Scheme corridor but does not extend to its full extent. For this reason it is reasonable to assume that the Managed Crossing Scheme’s environmental impacts would be less than those of the Full Corridor Scheme. The impacts relating to the use of the Forth Road Bridge for public transport were not a feature of the Full Corridor Scheme, but as the number of public transport vehicles on the existing bridge is relatively low, this was not considered a source of significant impacts. A qualitative assessment has been undertaken to provide a commentary on the comparative impacts of the Managed Crossing Scheme and the Full Corridor Scheme.
The key issues identified for the Full Corridor Scheme during the Stage 2 assessment were:
- Ecology: international and national designations in and around the Forth;
- Landscape and visual impacts: various gardens and designed landscapes and other designated areas. Iconic bridges over Forth;
- Cultural Heritage: historic buildings and landscapes in the area. A SAM near Masterton junction potentially directly affected;
- Noise: proximity of communities such as South Queensferry;
- Land use: connecting road footprint;
- Disruption due to construction: length of construction period and proximity of communities; and
- Water environment: new or extended water crossings and road drainage outfalls.
These issues are considered in turn in the following paragraphs.
7.1.1 Ecology
The most sensitive ecological areas are in and around the main crossing, and would be equally affected by the Full Corridor Scheme and the Managed Crossing Scheme. The narrower bridge structure of the Managed Crossing Scheme could result in some reduction in disturbance to species during construction. Elsewhere, the smaller footprint of the Managed Crossing Scheme will lessen habitat loss, habitat fragmentation and disturbance to protected species and other wildlife.
7.1.2 Landscape and Visual Impacts
The reduced footprint and fewer new structures of the Managed Crossing Scheme will tend to reduce impacts on landscape and visual amenity.
7.1.3 Cultural Heritage
There is a high concentration of sites of archaeological interest. Direct impacts on Middlebank Souterrain Scheduled Ancient Monument (SAM) and impacts on the settings of nearby listed buildings may arise from the Full Corridor Scheme proposals at Masterton Junction on the M90. These would be avoided by the Managed Crossing Scheme.
7.1.4 Noise
Both the Full Corridor Scheme and the Managed Crossing Scheme have the potential to create noise impacts on residential properties. It is not envisaged that either scheme would have significantly different noise impacts.
7.1.5 Land Use
Compared to the Full Corridor Scheme, the land use impacts of the Managed Crossing Scheme would be reduced, in terms of both direct loss and severance. The potential impacts of the Full Corridor Scheme for a number of land interests at Masterton and Scotstoun Junctions would be avoided completely by the Managed Crossing Scheme.
7.1.6 Disruption Due to Construction
The smaller scale of the Managed Crossing Scheme means that construction works will be less extensive than for the Full Corridor Scheme. The Managed Crossing Scheme may also allow for a shortening of the construction period or a lessening of the intensity of the works. These could be expected to result in disruption due to construction being less for the Managed Crossing Scheme than for the Full Corridor Scheme.
7.1.7 Water Environment
The Full Corridor Scheme requires a number of new water crossings and lengthening of some existing culverts. Fewer water courses would be affected by the shorter the Managed Crossing Scheme and this would reduce the potential impacts on geomorphology and other water environment characteristics.
In terms of the environmental Scheme Specific Objective, ‘to minimise the impact on people and the natural and cultural heritage of the Forth area’, the Managed Crossing Scheme performs better than the Full Corridor Scheme:
- Impact on People: the Managed Crossing Scheme will use/affect less land and will be less visually intrusive. Construction operations will be less extensive and thus disruption to people will be reduced.
- Impact on Natural Heritage: less habitat loss, fragmentation and disturbance. Fewer water crossings and less impact on the landscape.
- Impact on Cultural Heritage: Fewer known sites affected and less risk of impacts on unknown sites.
7.2 Sustainability Appraisal
A full sustainability appraisal will be undertaken for the preferred scheme. For the purposes of the comparative assessment, sustainability impacts have been considered in relation to embodied carbon.
In terms of resource use, preliminary calculations have been undertaken to provide a high level comparison of the embodied carbon of materials associated with the two scheme alternatives. A summary of the results of the carbon footprinting exercise is provided in Table 7.1. The results show that the Full Corridor Scheme, which would have more roadworks, earthworks and bridge deck compared to the Managed Crossing Scheme would require approximately 102,000 tonnes more embodied carbon than the Managed Crossing Scheme.
Table 7.1: Estimated mass of embodied carbon associated with the construction materials required for the Full Corridor and Managed
Component |
Embodied Carbon (tCO2e) |
|||
|---|---|---|---|---|
Full Corridor Scheme |
Managed Crossing Scheme |
|||
tonnes CO2e |
Proportion of Scheme Carbon Footprint |
tonnes CO2e |
Proportion of Scheme Carbon Footprint |
|
Road Network (main materials i.e. asphalt & aggregate to be used in construction of new pavement and overlay/inlay of existing pavement) |
8,575 |
3% |
5,029 |
3% |
Earthworks associated with Road Network |
62,873 |
25% |
11,750 |
8% |
Main Crossing (Orthotropic Cable Stayed Bridge & Twin Concrete Box Girder Approach Viaducts) |
180,947 |
72% |
130,312 |
87% |
Refurbishment of Forth Road Bridge (main materials i.e. steel concrete & asphalt) to be used in refurbishment |
0 |
0% |
3,028 |
2% |
TOTAL |
252,395 |
150,119 |
||
Crossing Schemes
Carbon emissions associated with earthworks will be refined at the next stage in project development. In order to obtain an initial comparison of the embodied carbon, the carbon conversion factor for soil as an input material, from the Highways Agency (HA) Carbon Accounting Tool for Major Projects has been used, based on the volume of soils requiring import to or export from the site.
The above results are based on estimates of the types and quantities of construction materials to be used in the new road network and main crossing.
These quantities incorporate the majority of carbon emissions associated with construction. It is not possible at this stage of the project to obtain accurate estimates of the likely energy required for other aspects of the construction such as the use of plant and equipment or the removal of waste from site. These aspects are not included in the carbon calculation at this stage. The scope of the carbon footprinting exercise does not currently include the emissions associated with the operation of the Forth Road Crossing i.e. vehicle usage and bridge maintenance.