4 Engineering Assessment 4.1 Engineering Standards 4.2 Climate Differences between the Sub-options 4.3 Geological Difference between the Sub-options 4.4 Public Utilities 4.5 Structures

4 Engineering Assessment

4.1 Engineering Standards

All the route sub-options have been designed in accordance with the DMRB TD9/93 "Highway Link Design", as dual carriageway D2AP standard in accordance with TD27/05 "Cross Sections and Headrooms". Each carriageway is 7.3m wide with 1m hardstrips, 2m verges and a 2.5m minimum central reserve. The new route has a design speed of 120kph.

The grade separated junctions have been designed in accordance with TD22/06 "Layout of Grade Separated Junctions". Merge and diverges tapers have been designed to motorway D2M standard, as advised by Transport Scotland’s standards branch in order to be consistent with the provision on other recent dual carriageway schemes in Scotland.

Previous design work undertaken for the original Stage 2 report was done in accordance with SH2/92 for guidance on cross sections and headrooms, TD 9/93 "Highway Link Design" and TD 40/94 "Layout of Compact Grade Separated Junctions". Since 1995 there have been significant revisions to design standards, such as the bridge clearance requirements for high load routes and to the layouts for grade separated junctions.

A significant consideration in terms of design standards are that routes designated for abnormal high loads now require a bridge clearance of 6.45m. The 1996 scheme previously used a 5.8m clearance. The new Balmedie to Tipperty dual carriageway overbridges will consequentially be designed with 6.45m clearance.

4.1.1 Sub-option 1

Sub-option 1 is 9.05 kilometres long. Alignment details are as follows:

- Minimum Horizontal Radius

1020mR

- Minimum Vertical Crest Curve

Kc = 182

- Minimum Vertical Sag Curve

Ks = 37

- Maximum Gradient

3.2%

- Volume of Suitable Material Generated

580,000m3

- Volume of Unsuitable Material Generated

475,000m3

- Volume of Fill Required

401,800m3


The maximum depth of cutting would be 11.7m and the maximum embankment height of 9.6m. These relatively deep earthworks are not indicative of the overall scheme and would occur only in localised areas.

Even use of excess material for landscaping, visual bunds, acoustic bunds and returning land to agriculture there would still potentially be a need for off-site disposal.

There are nine major structures along the route:

- Balmedie Junction (Grade Separated Junction)

- South Orrock Underpass (Access to South Orrock)

- Boghead Overbridge (Access to Orrock House/Boghead)

- A90 Overbridge (Maintaining existing A90)

- Newburgh Road Junction (Grade Separated Junction)

- Foveran River Bridge (Bridge over Foveran Burn)

- Foveran Overbridge (Access to Foveran School Road)

- Pitmillan Overbridge (Access to Pitmillan Piggery)

- Tipperty Junction (Grade Separated Junction)


The mainline alignment does not contain any departures from standards in accordance with TD9/93 Highway Link Design.

4.1.2 Sub-Option 2

Sub-option 2 is 8.95 kilometres long with the following alignment details:

- Minimum Horizontal Radius

1020mR

- Minimum Vertical Crest Curve

Kc = 182

- Minimum Vertical Sag Curve

Ks = 37

- Maximum Gradient

2.9%

- Volume of Suitable Material Generated

471,500m3

- Volume of Unsuitable Material Generated

576,000m3

- Volume of Fill Required

393,500m3


The maximum depth of cutting would be 16.2m and the maximum embankment height of 9.8m. These deep earthworks are not indicative of the overall scheme and would occur only in localised areas. The large cut area occurs at the hillock at Orrock House. This combined with the location of the existing A90 crossing results in a deep limited area of cutting.

Again even use of excess material for landscaping, visual bunds, acoustic bunds and returning land to agriculture there would still potentially be a need for off-site disposal.

There are nine major structures along the route:

- Balmedie Junction (Grade Separated Junction)

- South Orrock Underpass (Access to South Orrock)

- A90 Overbridge (Maintaining existing A90)

- Menie Overbridge (Access to Menie Estate)

- Newburgh Road Junction (Grade Separated Junction)

- Foveran River Bridge (Bridge over Foveran Burn)

- Foveran Overbridge (Access to Foveran School Road)

- Pitmillan Overbridge (Access to Pitmillan Piggery)

- Tipperty Junction (Grade Separated Junction)


The mainline alignment does not contain any departures from standards in accordance with TD9/93 Highway Link Design.

4.1.3 Sub-Option 3

Sub-option 3 is 8.95 kilometres long with the following alignment details:

- Minimum Horizontal Radius

1020mR

- Minimum Vertical Crest Curve

Kc = 182

- Minimum Vertical Sag Curve

Ks = 37

- Maximum Gradient

3.3%

- Volume of Suitable Material Generated

426,500m3

- Volume of Unsuitable Material Generated

521,500m3

- Volume of Fill Required

250,500m3


The maximum depth of cutting would be 9.4m and the maximum embankment height of 6.0m. Again, these relatively deep earthworks are not indicative of the overall scheme and occur only in localised areas.

Given the earthworks estimates for landscaping, visual bunds, acoustic bunds and returning land to agriculture an excess cut volume is still generated which would potentially need to be disposed of off-site.

There are eight major structures along the route as listed:

- Balmedie Junction (Grade Separated Junction)

- A90 Underpass (Maintaining existing A90)

- Menie Overbridge (Access to Menie Estate)

- Newburgh Road Junction (Grade Separated Junction)

- Foveran River Bridge (Bridge over Foveran Burn)

- Foveran Overbridge (Access to Foveran School Road)

- Pitmillan Overbridge (Access to Pitmillan Piggery)

- Tipperty Junction (Grade Separated Junction)


The mainline alignment contains one departure from standard with respect to TD9/93 Highway Link Design. This departure takes the form of a combination of a two step reduction in horizontal radius (520m) and a one step reduction in vertical crest curvature (Kc = 103).

This is a reduction in horizontal radius to 780m representing a one step relaxation combined with a one step reduction in stopping sight distance. This relaxation is outwith the approach to a junction therefore not classified as a departure.

Both the departure and relaxation occur along the online widening section of the route immediately north of Balmedie.

4.1.4 Sub-Option 5

Sub-option 5 is 8.97 kilometres long with the following alignment details:

- Minimum Horizontal Radius

1020mR

- Minimum Vertical Crest Curve

Kc = 182

- Minimum Vertical Sag Curve

Ks = 37

- Maximum Gradient

4%

- Volume of Suitable Material Generated

429,500m3

- Volume of Unsuitable Material Generated

525,000m3

- Volume of Fill Required

495,500m3


The maximum depth of cutting would be 11.5m and the maximum embankment height of 9.3m. These relatively deep earthworks again would occur only in localised areas of the scheme.

Given earthworks estimates for landscaping, visual bunds, acoustic bunds and returning land to agriculture are taken into account an approximate earthworks balance is achieved.

There are nine major structures along the route:

- Balmedie Junction (Grade Separated Junction)

- South Orrock Underpass (Access to South Orrock)

- Boghead Overbridge (Access to Orrock House/Boghead)

- Dambrae Underpass (Maintaining Access to Side Road Network)

- Newburgh Road Junction (Grade Separated Junction)

- Foveran River Bridge (Bridge over Foveran Burn)

- Foveran Overbridge (Access to Foveran School Road)

- Pitmillan Overbridge (Access to Pitmillan Piggery)

- Tipperty Junction (Grade Separated Junction)


The mainline alignment does not contain any departures from standards in accordance with TD9/93 Highway Link Design.

4.2 Climate Differences between the Sub-options

Climate varies only very slightly between the westerly and easterly options. The main difference between options is in the amounts of snow and fog which are likely to be experienced. The data from the two weather stations at Dyce and Cultery (see Section 2.5) indicate that Sub-option 5 would be more susceptible to snow and sleet and Sub-options 1, 2 and 3 would be likely to be more susceptible to fog.

4.3 Geological Difference between the Sub-options

Sub-Option 1

This option is largely underlain by Glacial Till and some shallow rock would be expected near Fountainbleau. Up to 450m of the route may be underlain by alluvial soils (mainly around Sandend Burn) but other burns may also have associated alluvial deposits. Glacio-Lacustrine deposits would be expected very locally near Delfrigs and Orrock. Made ground is anticipated locally.

Sub-Option 2

This sub-option is mainly underlain by Glacial Till some shallow rock would be expected near Fountainbleau. Up to 450m of the route may be underlain by alluvial soils (mainly around Sandend Burn) but other burns may also have associated alluvial deposits. Glacaio-Lacustrine deposits would be expected very locally near Orrock.

Sub-Option 3

The corridor of Sub-Option 3 is underlain by Glacial Till in most areas with some shallow rock expected near Fountainbleau. Up to 450m of the route may be underlain by alluvial soils (mainly around Sandend Burn) but other burns may also have associated alluvial deposits. Glacio-Lacustrine deposits would be expected very locally near Orrock.

Sub-Option 5

Sub-Option 5 is mainly underlain by Glacial Till with some shallow rock expected near Fountainbleau. Up to 200m of the route may be underlain by alluvial soils associated with burn crossings. Glacio-Lacustrine deposits would be expected very locally near Orrock. Peat is expected locally near the Sandend Burn and some localised area of made ground are anticipated.

4.4 Public Utilities

Sub-Option 1:

The alignment of Sub-option 1 mainline and associated side roads may potentially affect the following services (see Figure 4.1):

  • A total of sixteen BT lines, five of which are overhead lines and eleven of which are underground services;
  • A total of ten Scottish and Southern Energy overhead power lines which are a combination of 11kV and local low voltage spurs;
  • A total of seven Scottish Water mains, six of which are 100mm diameter mains and one 200mm diameter main;
  • A Shell 20" pipeline which bisects the proposed scheme at the north end of the proposed scheme;
  • A BP 36" pipeline which bisects the proposed scheme at the north end of the proposed scheme
  • A total of seven Thus ducts; and
  • A total of nine medium pressure Transco mains and one low pressure Transco main.

Sub-Option 2:

The alignment of Sub-option 2 mainline and associated side roads may potentially affect the following services (see Figure 4.2):

  • A total of nineteen BT lines, six of which are overhead lines and thirteen of which are underground services;
  • A total of seven Scottish and Southern Energy overhead power lines which are a combination of 11kV and local low voltage spurs;
  • A total of six Scottish Water mains, five of which are 100mm dia mains and one 200mm dia main;
  • A Shell 20" pipeline which bisects the proposed scheme at the north end of the proposed scheme;
  • A BP 36" pipeline which bisects the proposed scheme at the north end of the proposed scheme
  • A total of seven Thus ducts; and
  • A total of eleven medium pressure Transco mains and one low pressure Transco main.

Sub-Option 3:

The alignment of Sub-option 3 mainline and associated side roads may potentially affect the following services (see Figure 4.3):

  • A total of eighteen BT lines, six of which are overhead lines and twelve of which are underground services;
  • A total of eight Scottish and Southern Energy overhead power lines which are a combination of 11kV and local low voltage spurs;
  • A total of four Scottish Water mains, three of which are 100mm dia mains and one 200mm dia main;
  • A Shell 20" pipeline which bisects the proposed scheme at the north end of the proposed scheme;
  • A BP 36" pipeline which bisects the proposed scheme at the north end of the proposed scheme
  • A total of five Thus ducts; and
  • A total of eleven medium pressure Transco mains and one low pressure Transco main.

Sub-Option 5:

The alignment of Sub-option 5 mainline and associated side roads may potentially affect the following services (see Figure 4.4):

  • A total of fifteen BT lines, six of which are overhead lines and nine of which are underground services;
  • A total of six Scottish and Southern Energy overhead power lines which are a combination of 11kV and local low voltage spurs;
  • A total of five Scottish Water mains, four of which are 100mm dia mains and one 200mm dia main;
  • A Shell 20" pipeline which bisects the proposed scheme at the north end of the proposed scheme;
  • A BP 36" pipeline which bisects the proposed scheme at the north end of the proposed scheme
  • A total of six Thus ducts; and
  • A total of seven medium pressure Transco mains and one low pressure Transco main.

4.5 Structures

The new dual carriageway would be grade separated from the local road network. A number of bridges would be required to accommodate local traffic movement as described in Table 4.5 below:

Structure

Sub-Option 1

Sub-Option 2

Sub-Option 3

Sub-Option 5

Balmedie Junction

This bridge is required to carry the proposed A90 Northbound and Southbound carriageways together with the slip roads over the proposed link road joining the B977 and Balmedie. An in situ reinforced concrete box or portal structure would be the simplest and potentially the most economical structure at this location. Alternatives such as bankseat foundations on reinforced earth abutments may be prudent given speed of construction. This structure is on line and would require phased traffic management to allow the structure to be constructed.

South Orrock Underpass

This structure is required to maintain east west access below the proposed A90 for local traffic. An in situ reinforced concrete box or portal structure would be an ideal structural form.

N/A

See Sub-Option 1

Orrock Overbridge

This bridge is required to carry the unclassified road over the proposed A90. The bridge would have a skew angle of approximately 15o. Owing to the rural location of the A90 a structure of ‘open’ appearance ia appropriate with an in situ or precast deck consisting of three or four spans to limit structural depth. Abutments are likely to be shallow height bankseats on engineered upfill with spread footings provided at central supports.

N/A

See Sub-Option 1

Existing A90 Crossing

Sub-options 1 and 2 pass under the existing A90 carriageway south of Menie Estate and north of Pettens respectively. Being an overbridge a structure of three or four spans to provide an ‘open’ aspect is proposed. The superstructure would be either a steel composite or precast deck with spread footings as suitable foundations. Owing to the high skew of this overbridge (approximately 60o) an articulated structure to incorporate bearings and inspection galleries at abutments are anticipated which would require long term maintenance.

The structure would be located within close proximity to a number of dwellings and as such substantial diversions and temporary works would be required to maintain local access and operation of the existing A90 during construction.

The existing A90 would traverse Sub-option 3 with a newly constructed section of carriageway east of South Orrock. A single span insitu reinforced concrete box or portal structure would be an ideal structural form. Due to the high skew of this underpass (approximately 60o) the total length of the main structure and wingwalls is likely to be considerable and permanent lighting for safety may be a requirement.

N/A

Dambrae Underpass

N/A

N/A

N/A

This bridge is required to carry the A90 over the existing unclassified road. A similar structure to that proposed for South Orrock Underpass is appropriate.

Menie Overbridge

N/A

This bridge carries the unclassified road over the proposed A90 to re-join the existing A90. Owing to the rural location of the A90 a structure of ‘open’ appearance is appropriate. An in situ or precast deck consisting of three or four spans to limit structural depth. Abutments are likely to be shallow height bankseats on engineered upfill with spread footings provided at central supports.

N/A

Newburgh Road Junction

This overbridge carries the A975 Newburgh Road over the A90 mainline. An open appearance is appropriate with an in-situ or precast deck consisting of 3 or 4 spans to limit structural depth.

A widened structure may need to be provided to accommodate junction visibility from the diverge slip.

This underbridge carries the A90 mainline over the A975 Newburgh Road Junction. An insitu reinforced concrete box or portal would be a suitable structural form.

Foveran Overbridge

Foveran Overbridge carries the unclassified Foveran School Road over the proposed A90 to re-join the existing A90. An open appearance is appropriate with an in-situ or precast deck consisting of 3 or 4 spans to limit structural depth. Piled foundations are anticipated at this location.

Pitmillan Overbridge

This bridge is required to maintain access between Pitmillan Farm and the existing A90. An open appearance is appropriate with an in-situ or precast deck consisting of 3 or 4 spans to limit structural depth. Spread footings would be suitable foundations for this structure.

Tipperty Junction

This structure is required to carry the proposed existing B9000 Road over the proposed A90. An open appearance is appropriate with an in-situ or precast deck consisting of 3 or 4 spans to limit structural depth.

Table 4.5: Proposed Structures

The following major culverts would be required:

  • Tributaries of Blairton Burn;
  • Menie Burn;
  • Sandend Burn; and
  • Foveran Burn and lade.

Additional minor culverts would also be necessary along the route.