7 Evaluation of Route Sub-Options 7.1 Introduction 7.2 Engineering Assessment 7.3 Environmental Assessment 7.4 Traffic and Economic Assessment 7.5 Recommendation

7 Evaluation of Route Sub-Options

7.1 Introduction

The sub-options identified at the re-start workshop have been subject to comprehensive appraisals relating to engineering, environmental and traffic/economic factors as reported in Chapters 4, 5 and 6. During the course of these appraisals, and in particular following the public exhibition in June 2006, the sub-options have been refined and re-appraised by the consultant team. In terms of the three main disciplines the findings of the finalised appraisals are summarised below. Section 7.5 draws out those factors that the consultant team have considered to be key in putting forward their recommendation for a preferred route.

7.2 Engineering Assessment

Following the re-start workshop four options were developed in more detail: Sub-option 1, Sub-option 2, Sub-option 3 and Sub-option 5. All the options are predominantly offline with Sub-option 3 being online for approximately two kilometres and the southern end of the scheme. All of the routes proposed construction of a dual carriageway with access only from the designated grade separated junctions.

No departures from standards are envisaged with Sub-option 1, Sub-option 2 and Sub-option 5 mainlines. Departures would be required for Sub-option 3 due to the constraints in the existing corridor.

Geology and hydrogeology are very similar for each route option and have little impact on comparison of the routes. Climate and topography vary slightly between the westerly and easterly options but there is no significant difference to influence the choice of route sub-option. The differences are very subtle in engineering terms with respect to topography.

Construction of Sub-option 3 would cause most disruption due to the on-line nature of the work at the southern end. All the other options would cause slightly less disruption due to this off-line nature.

The cost estimates shown in Table 7.1 indicate that Sub-option 5 to be the least expensive with a total scheme cost of £38.3 million excl VAT. The major cost difference comes from the earthworks discipline with Sub-options 1, 2 and 3 generating excess cut material and Sub-option 5 creating a more of a cut/fill balance.

Sub-option	Total Scheme Cost (Exc VAT)
Sub-option 1	£42.0m
Sub-option 2	£41.8m
Sub-option 3	£42.0m
Sub-option 5	£38.3m

Table 7.1 Scheme Cost Estimates for Sub-options

7.3 Environmental Assessment

A preferred sub-option was identified for each environmental category based on the findings of the appraisal of potential effects from each sub-option. The key findings are shown in Table 7.2 and the preferred sub-option for each topic in Table 7.3.

Environmental Topic	Key Findings
Air Quality	Sub-option 5 has the lowest number of properties within 200m of the road centreline and would give rise to the largest improvement in air quality compared to the existing route
Cultural Heritage	Sub-options 1, 2 and 5 would have limited impact on Orrock House Dovecote (not considered significant). All sub-options would pass close to the Mill of Foveran (B listed building) however there is potential to mitigate with careful planting. Sub-options 2 and 3 have an impact on the setting of both Orrock House and Menie House and subsequently are the sub-options that would have the greatest impact on built heritage. On balance the preferred route would be Sub-option 5 for archaeology because: it impacts on the least number of known sites (actually the same number of sites as Sub-option 1, but the Sidney Cottage sand and gravel workings are considered destroyed in the AC SMR); it has less of an impact on Orrock House (A listed) than the 1996 route and there is potential to mitigate this with planting; it avoids the severance of Menie House from its gatehouse (both B listed); and the other options would have some impact on both Orrock House and Menie House (with 1 and 2 having the greatest impact)
Disruption due to Construction	Differences between all sub-options are small. Sub-option 5 is favoured due to: least disruption due to potential for reduced temporary diversion works; and potential for less traffic movements than other option due to earthworks balance
Ecology and Nature Conservation	No significant difference between sub-options was found in terms of ecology and nature conservation.
Landscape Effects	Critical relationship between the horizontal and vertical alignment and the existing landform. Landscape elements not generally significant. Sub-option 3 has best fit to landscape, Sub-option 5 has most room for mitigation
Visual Impact	Differences between sub-options are small. Sub-option 5 has most room for mitigation
Land Use	On balance Sub-option 3 is the preferred sub-option as it affects: less prime land; a small number of agricultural units; and fewer fields (all in comparison to other sub-options)
Traffic Noise and Vibration	Overall, Sub-option 5 has the lowest number of dwellings within 100m, the lowest number of receptors subject to a noise increase of >1dB and the greatest number of receptors subject to a neutral noise. On this basis, whilst the differences in the sub-options are only subtle. Sub-option 5 is considered to be the preferred sub-option for noise
Pedestrians, Cyclists, Equestrians and Community Effects	All sub-options would benefit pedestrians, equestrians and cyclists as there would be a reduction in traffic on the existing A90. On balance Sub-option 5 is the preferred route as it minimises severance to properties in the vicinity of the scheme
Vehicle Travellers	There are no significant differences between the sub-options for impacts on vehicle travellers
Water Quality and Drainage	There are no significant differences between the sub-options for water quality and drainage impacts
Geology, Soils and Contaminated Land	There are no significant differences between the sub-options for geology, soils and contaminated land
Policies and Plans	Aberdeenshire Council would prefer that Menie House is not severed from its gatehouse. No other known significant planning issues which would differentiate between the sub-options

Table 7.2 Environmental Key Findings

DMRB Topic	Preferred Sub-option
Air Quality	Sub-option 5
Cultural Heritage	Sub-option 5
Disruption due to Construction	Sub-option 5
Ecology and Nature Conservation	Sub-options 1 and 5
Landscape Effects	Sub-options 3 and 5
Visual Impacts	Sub-option 5
Land Use and Agriculture	Sub-option 3
Traffic Noise and Vibration	Sub-option 5
Pedestrians, Cyclists, Equestrians and Community Effects	Sub-option 5
Effects on Vehicle Travellers	No significant difference
Water Quality and Drainage	No significant difference
Geology and Soils and Drainage	No significant difference
Policies and Plans	Sub-options 1 and 5

Table 7.3 Preferred Sub-option - Environmental Topics

Based on the preferred sub-option for each category the overall preferred sub-option is Sub-option 5.

7.4 Traffic and Economic Assessment

Each of the four sub-options performs well in terms of economic factors with benefit cost ratios being between 2.79 and 2.99. In general there are significant travel time and accident saving benefits associated with the route upgrading to dual carriageway. In terms of economics Sub-option 5 is preferred since it provides equivalent level of benefits for a significantly lower cost.

Sub-option	Benefit Cost Ratio (BCR)
Sub-option 1	2.79
Sub-option 2	2.91
Sub-option 3	2.91
Sub-option 5	2.99

Table 7.4 Economic Performance of Sub-Options

7.5 Recommendation

The engineering, environmental and economic appraisals have all concluded that the same sub-option should be taken forward as the preferred route. All of the sub-options performed well in the various appraisals, often with only small differences between them. There were no viability issues that emerged in the work. The further assessments and consultations undertaken after Workshop No 2 (see flowchart in Section 1.8) has however allowed a clear recommendation to emerge.

It is recommended that Sub-option 5 is taken forward for development as the preferred route in the DMRB Stage 3 (see Figure 7.1). This recommendation differs from that in the original Stage 2 Report (1995), which selected the line of Sub-option 1 as the preferred route. The justification for this change in recommendation is summarised by the seven points below:

Sub-option 5 avoids significant intrusion at Delfrigs and adjacent properties. The differences between sub-options for landscape and visual intrusion are generally small but Sub-option 5 provides more room for mitigation earthworks and planting.
Sub-option 5 has fewest properties in close proximity to the new road which would decrease the potential for significant noise and vibration and air quality effects.
Sub-option 5 has potential to affect fewer archaeological sites than other options. Its impact on Orrock House is less than the 1996 route and it would not impact on the Menie Estate.
Sub-option 5 has slightly less potential for community severance effects than other sub-options.
Sub-option 5 has the least challenging construction constraints.
Sub-option 5 is significantly cheaper then the other sub-options mainly due to an earthworks balance between cut and fill material.
Sub-option 5 has the best benefit-cost ratio, however it is very similar to the other sub-options.