Engineering Assessment
Introduction
A high level assessment of engineering issues associated with the improvement strategies has been undertaken in relation to the following topics:
- Topography and Land Use
- Geotechnical Considerations
- Water Environment, Hydrology and Drainage
- Alignment and Cross-section
- Pavement
- Structures
- Junctions and Accesses
- Lay-bys and Rest Areas
- Walking, Cycling and Horse Riding (WCH) Provisions
- Roadside Features
- Public Utilities
- Constructability
Topography and Land Use
There are various settlements within and in close proximity to the assessment corridor as shown in Appendix A, Figure A2-1(G). An assessment was undertaken to determine which settlements are within 500m of each of the improvement strategies which are summarised as follows:
- Castle Douglas, Clarebrand, Old Bridge of Urr, Kirkpatrick Durham, Crocketford, Brae and Shawhead are within 500m of Improvement Strategy 1.
- Old Bridge of Urr, Kirkpatrick Durham, Springholm, Crocketford and Brae are within 500m of Improvement Strategy 2.
- Springholm and Crocketford are within 500m of Improvement Strategies 3 and 4.
- Springholm is within 500m of Improvement Strategy 5.
- Castle Douglas, Haugh of Urr, Milton and Lochfoot are within 500m of Improvement Strategy 6.
Geotechnical Considerations
A preliminary assessment has been undertaken to provide a general overview of anticipated ground conditions within the assessment corridor. The superficial deposits and solid geology are as indicated in the Geology section of the Existing Conditions chapter of this report.
The main geotechnical considerations are summarised as follows.
Peat and Compressible Soils:
The presence of soft, compressible soils such as peat and alluvium was mapped across the assessment corridor. These materials are generally expected to be low in strength and highly compressible, posing a risk of settlement, reduced bearing capacity, and possible instability. This may require either ground improvement, avoidance of specific area, or alternative foundation solutions, particularly in areas where peat is extensive and of uncertain thickness. Removal of thick peat layers could also lead to heave or post-construction rebound.
Shallow Bedrock and Excavation Constraints
Bedrock is typically formed of competent greywacke; however, weathering profiles and localised faults may affect excavation and founding conditions. Shallow bedrock is mapped across the south-west and central sections of the route, which may constrain excavation depths and influence construction sequencing. In some areas, transitions from superficial deposits to shallow weathered rock may require localised excavation support or adaptation of foundation design, particularly where ground conditions are variable or differential stiffness is expected. Inferred linear geological features, including possible faulting near Springholm, may further influence ground behaviour and excavation stability.
Chemical Constraints
The presence of organic leachates and naturally occurring sulphates within the superficial deposits may affect the durability and long-term performance of construction materials. These conditions will need to be considered in the specification of concrete mixes and drainage components to ensure chemical resistance and compliance with relevant standards.
Historical Mineral Workings
There is a high density of historical surface mineral workings (BritPits) across the assessment corridor, with numerous ceased quarries, gravel pits, and sandstone extraction sites recorded on or near the assessment corridor. While most are classified as ceased, their presence may indicate areas of variable backfill, localised voids, or ground disturbance that could affect founding conditions and stability. Further investigation may be required to assess the extent and legacy impact of these features on ground behaviour.
Ground Instability Risks
Localised zones of potential ground instability have been identified within the assessment corridor, primarily associated with superficial deposits. While the overall landslide risk is generally low to moderate and confined to isolated areas, further assessment may be required in sloping terrain where till or alluvium are present. Some clay-rich deposits exhibit shrink–swell potential, which may result in surface movement or long-term deformation beneath embankments or along cut slopes. In areas of loose, saturated granular material, there is a potential for running sand conditions, which could affect excavation stability, increase dewatering requirements, and necessitate short-term excavation support. These factors may influence the geometry, construction sequence, and stabilisation requirements of proposed cuttings and embankments.
Unexploded Ordnance (UXO)
The assessment corridor lies within a zone of low to moderate UXO risk, as indicated by Zetica UXO mapping. Historical records show proximity to former strategic targets such as industrial and military facilities around Dalbeattie and Castle Douglas. While there are no known UXO finds within the assessment corridor, the potential presence of buried ordnance cannot be ruled out. A preliminary UXO risk assessment should be undertaken to determine the need for mitigation measures during intrusive ground investigation or construction works, particularly in areas involving deep excavation.
Geotechnical Summary for Improvement Strategy 1
Superficial deposits (excluding peat) intersecting with Improvement Strategy 1 are made up of the following:
- Devensian till (Diamicton)
- Alluvium (silt, sand and gravel)
- Glaciofluvial deposits (gravel, sand and silt)
BGS maps indicate a presence of peat north-east of Crocketford within Improvement Strategy 1.
Bedrock for Improvement Strategy 1 consists of Greywacke (Carghidown, Kirkmaiden and Cairnharrow formations). For linear bedrock features there are two inferred faults, one parallel to the existing A75 (reverse/thrust fault, barbs on hanging wall side, throw in meters) and one perpendicular to the existing A75 north of Springholm Primary School with unknown displacement.
In summary for Improvement Strategy 1 geotechnical considerations are as follows:
- Soft alluvium and peat may result in settlement.
- Aggressive ground conditions for concrete.
- Shallow bedrock may complicate excavation.
- Faulting may cause variable conditions.
Geotechnical Summary for Improvement Strategy 2
Superficial deposits (excluding peat) intersecting with Improvement Strategy 2 are made up of the following:
- Devensian till (Diamicton)
- Alluvium (silt, sand and gravel)
BGS maps indicate a presence of peat north-east of Crocketford and BGS logs indicate peat at the west by Garmatin Burn and east near Route 75 within Improvement Strategy 2.
Bedrock for Improvement Strategy 2 consists of Greywacke (Carghidown and Kirkmaiden formations). For linear bedrock features there are two inferred faults, one parallel to the existing A75 (reverse/thrust fault, barbs on hanging wall side, throw in meters) and one perpendicular to the existing A75 north of Springholm Primary School with unknown displacement.
In summary for Improvement Strategy 2 geotechnical considerations are as follows:
- Soft alluvium and peat may result in settlement.
- Aggressive ground conditions for concrete.
- Shallow bedrock may complicate excavation.
- Faulting may cause variable conditions.
Geotechnical Summary for Improvement Strategy 3
Superficial deposits (excluding peat) intersecting with Improvement Strategy 3 are made up of the following:
- Devensian till (Diamicton)
- Alluvium (silt, sand and gravel)
BGS logs indicate a presence of peat to the south-west of Crocketford.
Bedrock for Improvement Strategy 3 consists of Greywacke (Carghidown and Kirkmaiden formations). For linear bedrock features there is one inferred fault which crosses the A75 perpendicularly north of Springhom Primary School with unknown displacement.
In summary for Improvement Strategy 3, geotechnical considerations are as follows:
- Soft alluvium and peat may result in settlement.
- Aggressive ground conditions for concrete.
- Shallow bedrock may complicate excavation.
- Faulting may cause variable conditions.
Geotechnical Summary for Improvement Strategy 4
Superficial deposits (excluding peat) intersecting with Improvement Strategy 4 are made up of the following:
- Devensian till (Diamicton)
- Alluvium (silt, sand and gravel)
BGS maps and logs indicate a presence of peat to the south-east of Crocketford.
Bedrock for Improvement Strategy 4 consists of Greywacke (Carghidown and Kirkmaiden formations). For linear bedrock features there is one inferred fault which crosses the A75 perpendicularly north of Springhom Primary School with unknown displacement.
In summary for Improvement Strategy 4, geotechnical considerations are as follows:
- Soft alluvium and peat may result in settlement.
- Aggressive ground conditions for concrete.
- Shallow bedrock may complicate excavation.
- Faulting may cause variable conditions.
Geotechnical Summary for Improvement Strategy 5
Superficial deposits (excluding peat) intersecting with Improvement Strategy 5 are made up of the following:
- Devensian till (Diamicton)
- Alluvium (silt, sand and gravel)
- Glaciofluvial deposits (gravel, sand and silt)
BGS maps and logs indicate a presence of peat to the south-east of Crocketford within Improvement Strategy 5.
Bedrock for Improvement Strategy 5 consists of Greywacke (Carghidown and Kirkmaiden formations). For linear bedrock features there is one inferred fault which crosses the A75 perpendicularly north of Springholm Primary School with unknown displacement.
In summary for Improvement Strategy 5, geotechnical considerations are as follows:
- Soft alluvium and peat may result in settlement.
- Aggressive ground conditions for concrete.
- Shallow bedrock may complicate excavation.
- Faulting may cause variable conditions.
Geotechnical Summary for Improvement Strategy 6
Superficial deposits (excluding peat) intersecting with Improvement Strategy 6 are made up of the following:
- Devensian till (Diamicton)
- Alluvium (silt, sand and gravel)
- Glaciofluvial deposits (gravel, sand and silt)
There is no indication of peat presence for Improvement Strategy 6.
Bedrock for Improvement Strategy 6 consists of Greywacke (Carghidown formation). For linear bedrock features there are no inferred faults recorded.
In summary for Improvement Strategy 6, geotechnical considerations are as follows:
- Shallow bedrock may complicate excavation.
Geotechnical Summary
Depending on the depth and extents of the peat this may pose both geotechnical and environmental challenges. These may include low bearing capacity, high compressibility, and potential carbon release upon disturbance.
Inferred bedrock fault structures are mapped near Springholm and may influence local rockhead profiles and excavation stability.
There is limited historic groundwater information available from a review of existing information. However, these are likely to be elevated within peat and alluvial zones, potentially requiring groundwater management during construction. The potential presence of organic leachates and naturally occurring sulphates in these deposits could also impact the specification of concrete and drainage materials.
An assessment of the anticipated ground conditions, geotechnical and land quality constraints will be carried out for each of the improvement strategies and presented in a Preliminary Sources Study Report (PSSR). Existing information from a variety of desktop review sources including but not limited to, historical maps, geological maps, historical exploratory holes and existing reports from the area will be scrutinised. A geotechnical and geo-environmental site visit will be undertaken during the study. This information will be used at DMRB Stage 2 to identify significant geotechnical or land quality constraints, which may influence the preferred route option.
In order to support the geotechnical and environmental input to the DMRB Stage 2 Assessment, a ground investigation is proposed. The investigation will take cognisance of the geotechnical risks identified in the PSSR.
Water Environment, Hydrology, and Drainage
Water Environment and Hydrology
The assessment corridor encompasses numerous watercourses and water bodies. Within 500m of the assessment corridor, there are 19 named watercourses, eight of which are designated Water Framework Directive (WFD) Regulation water bodies. There are also a number of other non-WFD Regulation named watercourses. Table 4‑1 shows a list of these watercourses.
| Watercourse | Watercourse Type | Overall Status | Relevant Improvement Strategy |
|---|---|---|---|
|
Urr Water (d/s Drumhumphrey Burn) |
WFD Regulation water body |
Good |
1, 5, 6 |
|
Spottes Burn |
WFD Regulation water body |
Good |
1, 2, 3, 4, 5 |
|
Cargen Pow/ Bogrie Lane |
WFD Regulation water body |
Moderate |
1, 2, 3, 4, 5 |
|
Lochfoot Burn |
WFD Regulation water body |
Moderate |
1, 6 |
|
Under Brae Lane |
WFD Regulation water body |
Good |
6 |
|
Culloch Burn (u/s Milton Loch) |
WFD Regulation water body |
Good |
5 |
|
Culloch Burn (Milton Loch to Kirkgunzeon Lane) |
WFD Regulation water body |
Good |
6 |
|
Barnshalloch Burn |
Non-WFD Regulation water body |
Not Applicable |
None |
|
Bettyknowes Burn |
Non-WFD Regulation water body |
Not Applicable |
1, 2 |
|
Culmain Burn |
Part of Culloch Burn (Milton Loch to Kirkgunzeon Lane) WFD Regulation water body |
Good |
None |
|
Largela Burn |
Non-WFD Regulation water body |
Not Applicable |
1, 2 |
|
Glenhead Burn |
Non-WFD Regulation water body |
Not Applicable |
1, 2 |
|
Crocketford Burn |
Part of Cargen Pow/ Bogrie Lane WFD Regulation water body |
Moderate |
1, 2, 3 |
|
Cronie Burn |
Non-WFD Regulation water body |
Not Applicable |
1, 2 |
|
Brooklands Burn |
Non-WFD Regulation water body |
Not Applicable |
1, 2 |
|
Minnydow Burn |
Non-WFD Regulation water body |
Not Applicable |
1, 2 |
|
Culshan Burn |
Non-WFD Regulation water body |
Not Applicable |
3 |
|
Barncailzie Lane |
Non-WFD Regulation water body |
Not Applicable |
3 |
|
Garmartin Burn |
Non-WFD Regulation water body |
Not Applicable |
2, 5 |
There are numerous artificial drainage ditches and unnamed ordinary watercourses within 500m of the assessment corridor. All six improvement strategies cross these minor surface water receptors.
There are four named ponds and lochs of varying sizes within 500m of the assessment corridor. These are:
- Milton Loch – WFD Regulations designated with ‘Moderate’ overall status.
- Auchenreoch Loch – non-WFD Regulations water body
- Grange Dam – non-WFD Regulations water body
- Brooklands Pond – non-WFD Regulations water body
There are also numerous unnamed ponds and areas of standing water. Lochrutton Loch, while not within the assessment corridor, is important to consider as it is located within 50m to the south east of the assessment corridor.
In terms of hydromorphology, six watercourses within the assessment corridor show some evidence of morphological features and processes. These watercourses are crossed by the improvement strategies. Structures are observed on numerous watercourses, including minor and major road crossings via bridges and culverts.
Flood Risk
Part of the assessment corridor lies within the Springholm Potentially Vulnerable Area (PVA) which identifies the main risk of flooding as from rivers. A desktop review of SEPA flood mapping has indicated that there are areas of ‘Low’ likelihood flooding (a 0.1% (1 in 1000 year) annual exceedance probability (AEP)) and ‘Medium’ likelihood flooding (a 0.5% (1 in 200 year) AEP) in the study areas. This is associated with the following watercourses:
- Urr Water
- Spottes Burn
- Barnacilzie Lane
- Brooklands Burn
- Minnydow Burn
- Lochfoot Burn
- Culloch Burn
Pluvial flooding is also identified as a potential flood source within the Springholm PVA. Generally, pluvial flooding in the assessment corridor is characterised by ponding of rainfall in surface depressions in the landscape with flooding also associated with small watercourses and drains. Pluvial flooding is likely to affect all six improvement strategies.
Groundwater, reservoir and sewer flooding will be assessed at DMRB Stage 2.
Drainage
Due to the broadly defined nature of the improvement strategies, drainage designs have not been prepared at DMRB Stage 1. Drainage designs will be prepared at DMRB Stage 2 in accordance with the DMRB and will include consideration of Sustainable Drainage Systems (SuDS) to attenuate and treat surface run-off.
Alignment and Cross-section
Due to the broadly defined nature of the improvement strategies, alignment designs have not been prepared at DMRB Stage 1. However, the improvement strategies have been developed with consideration of constraints and DMRB CD 109 – Highway link design . This will allow a range of alignment designs to be developed at DMRB Stage 2.
During the development of the alignment designs, the type of road will be considered with options including single, WS2+1 and dual carriageway. Further consideration of cross-section and design speed will also be undertaken in line with DMRB CD 127 – Cross-sections and Headrooms , hereafter referred to as CD 127.
The types of road and associated design parameters for cross-section and maximum design speed which will be considered at DMRB Stage 2 have been summarised in Table 4‑2.
| Type of Road | DMRB CD 127 Reference | Maximum Design Speed |
|---|---|---|
|
Dual Carriageway |
D2AP |
120kph |
|
Single Carriageway |
S2 |
100kph |
|
WS2+1 Carriageway |
WS2+1 |
100kph |
Pavement
Due to the broadly defined nature of the improvement strategies, pavement designs have not been prepared at DMRB Stage 1. A preliminary pavement design will be developed at DMRB Stage 2 and will include consideration of the existing pavement condition where necessary.
Structures
A high level assessment has been undertaken to determine the indicative maximum number of major structures required for each improvement strategy. The findings of this assessment are summarised in Table 4‑3.
|
Improvement Strategy |
Indicative No. of Major Structures |
Notable Constraints |
|
1 |
4 |
Watercourses – Urr Water, Bettyknowes Burn, Brooklands Burn and side road. Roads - A712 |
|
2 |
2 |
Watercourses - Brooklands Burn and side road. Roads – A712 |
|
3 |
1 |
Watercourses – Spottes Burn. |
|
4 |
2 |
Watercourses – Spottes Burn and lake. |
|
5 |
1 |
Watercourses – Urr Water (Potential to retain Ramhill New Bridge). |
|
6 |
3 |
Watercourses - Urr Water. Roads – Old Military Road (Potential for two crossings). |
Due to the broadly defined nature of the improvement strategies and the negligible influence of minor structures on the structural assessment, the numbers of retaining walls, culverts and minor bridges (expected length of less than 20m) have not been included in Table 4‑3. Minor structures will be assessed at DMRB Stage 2.
Online Existing Structures
There are two existing structures along the existing A75 within the assessment corridor. Ramhill New Bridge, which interacts with Improvement Strategy 5 and Springholm Bridge, which interacts with Improvement Strategy 3. The width of both structures has been considered for compliance with single, WS2+1 and dual carriageway cross-sections, with the minimum compliance listed in Table 4‑4.
| Structure | No. Spans | Span Lengths (m) | Total Span Length (m) | Total Span Width (m) | Form of Construction | Review Summary |
|---|---|---|---|---|---|---|
| A75 410 Ramhill New Bridge | 3 | 13.7, 19.5 and 13.7 | 46.9 | 11.8 | Steel girders composite with a reinforced concrete slab deck. | Cross-section is not compliant with single carriageway standard or wider. |
| A75 400 Springholm Bridge | 1 | 5 | 5 | 10.9 | Steel trough composite with concrete infill deck. | Cross-section is not compliant with single carriageway standard or wider. |
Junctions and Accesses
A high level assessment has been undertaken to determine the potential road interfaces with each improvement strategy.
Improvement Strategy 1 interfaces with the following existing roads:
- A75 at tie-ins to Allanton and Drummore roundabouts
- A712, B795 and B794
- C-Roads and/or unclassified roads
- Residential and/or Commercial private accesses
Improvement Strategy 2 interfaces with the following existing roads:
- A75 and A712 at tie-in points
- C-Roads and/or unclassified roads
- Residential and/or Commercial private accesses
Improvement Strategy 3 and 4 interface with the following existing roads:
- A75 at tie-in points
- C-Roads and/or unclassified roads
- Residential and/or Commercial private accesses
Improvement Strategy 5 interfaces with the following existing roads:
- A75 and B794 at tie-in points
- C-Roads and/or unclassified roads
- Residential and/or Commercial private accesses
Improvement Strategy 6 interfaces with the following existing roads:
- A75 at tie-ins to Allanton and Drummore roundabouts
- B794
- C-Roads and/or unclassified roads
- Residential and/or Commercial private accesses
A junction strategy will be developed at DMRB Stage 2. The junction type will be influenced by the proposed carriageway cross-section. Junctions on dual carriageway options may include roundabouts, grade separated junctions and/or at-grade left-in left-out priority junctions. Junctions on single carriageway and WS2+1 options may include roundabouts and/or at-grade priority junctions.
Lay-bys and Rest Areas
Lay-bys
DMRB design standard CD 169 – The design of lay-bys, maintenance hardstandings, rest areas, service areas and observation platforms recommends spacing of lay-bys for non-emergency stopping provision as follows:
- 2.5km for dual carriageway
- 2km – 5km for single carriageway with AADT greater than 8,000
A lay-by strategy will be developed at DMRB Stage 2 to determine the spacing, type and location of proposed lay-bys.
Rest Areas
A rest area is an off-carriageway (longer duration) stopping provision that includes parking and can include tourist information, toilets, public telephone, picnic area, disabled facilities and/or viewpoints. Provision of potential rest areas will be considered at DMRB Stage 2.
Walking, Cycling and Horse-Riding (WCH) Provisions
A high level assessment to determine the potential interfaces between the improvement strategies and WCH facilities within the assessment corridor has been undertaken. WCH facilities within the assessment corridor are shown in Appendix A, Figure A2-1(A).
Improvement Strategy 1 interfaces with the following WCH facilities:
- A small section of undesignated local path along the A75 which is designated as a shared use route for cyclists and pedestrians east of Barfil and ending east of Glenkiln Farms.
- Core Path IRON/72/1 Bettyknowes to Shawhead at the southern extents.
- Footpaths on the eastbound and westbound sides of the existing A75 linking from bus lay-bys to Drummore Roundabout.
Improvement Strategy 2 interfaces with the following:
- A small section of undesignated local path along the A75 which is designated as a shared use route for cyclists and pedestrians east of Barfil and ending east of Glenkiln Farms.
- Core Path IRON/72/1 Bettyknowes to Shawhead at the southern extents.
Improvement Strategy 3 interfaces with the following:
- Core Path URR/603/1 Springholm to Milton Loch at the western extents.
- Footpaths within Springholm and Crocketford.
Improvement Strategy 4 interfaces with the following:
- Core Path URR/603/1 Springholm to Milton Loch at the western extents.
Improvement Strategy 5 interfaces with the following:
- Core Path URR/603/1 Springholm to Milton Loch at the western extents.
- Core Path IRON/72/1 – Bettyknowes to Shawhead at the southern extents.
- Improvement Strategy 6 interfaces with the following:
- The NCN7 (Old Military Road) at several locations.
- Footpaths on the eastbound and westbound sides of the existing A75 linking from bus lay-bys to Drummore Roundabout.
WCH provisions will be assessed further at DMRB Stage 2.
Roadside Features
Due to the broadly defined nature of the improvement strategies, roadside features have not been assessed at DMRB Stage 1. A number of roadside features will be assessed at DMRB Stage 2, including:
- Road Restraint Systems (RRS)
- Traffic signs
- Traffic signals
- Road markings and studs
- Street furniture (for example bollards and pedestrian guardrails)
- Emergency telephones
- Weather stations
- Safety cameras and CCTV cameras
- Police observation platforms
- Intelligent Transport Systems (ITS)
- Street lighting
Public Utilities
Information on public utilities has been collated in accordance with the C2 Preliminary Inquiries stage of the New Roads and Street Works Act 1991, Measures Necessary where Apparatus is Affected by Major Works (Diversionary Works), A Code of Practice. This is an ongoing exercise with some statutory undertakers still to provide information on their apparatus. The information collated at the time of writing is summarised below.
BT Openreach
BT Openreach currently have existing apparatus in the form of underground and overhead cables, boxes and manhole chambers, running in close proximity to the existing A75 between the Allanton and Drummore roundabouts, with the cables crossing the road in multiple locations, including several through Springholm, Crocketford and Brae. Potential interfaces within each improvement strategy are as follows:
- Improvement Strategy 1 interfaces with BT infrastructure along the A75, A712, B795, B794 and a large number of C-roads/unclassified roads and accesses.
- Improvement Strategy 2 interfaces with BT infrastructure along the A75, A712 and a large number of C-roads/unclassified roads and accesses.
- Improvement Strategy 3 interfaces with BT infrastructure running alongside the existing A75 and a large number of connecting roads including the A712.
- Improvement Strategy 4 interfaces with BT infrastructure running alongside the existing A75 and a large number of C-roads/unclassified roads and accesses.
- Improvement Strategy 5 interfaces with BT infrastructure running alongside the existing A75 and a large number of C-roads/unclassified roads and accesses.
- Improvement Strategy 6 interfaces with BT infrastructure along the existing A75, Old Military Road and a number of C-roads/unclassified roads and accesses.
Gas Networks Ireland (UK) Ltd
Gas Networks Ireland (UK) Ltd currently have existing apparatus in the form of a High Pressure underground gas main which primarily runs through farmland within the assessment corridor. The gas mains cross the existing A75 east of the B794 junction on the westbound lane, east of Brae and west of Drummore Roundabout. Potential interfaces within each improvement strategy are as follows:
- Improvement Strategy 1 interfaces with Gas Networks Ireland pipeline at the north-east of Allanton roundabout, east of Brae and west of Drummore Roundabout.
- Improvement Strategy 2 interfaces with Gas Networks Ireland pipeline where the pipeline crosses the existing A75 east of the B794 junction on the westbound lane and east of Brae.
- Improvement Strategy 3 and 4 do not interface with Gas Network Ireland pipeline.
- Improvement Strategy 5 interfaces with Gas Network Ireland pipeline north-east of the mains crossing on the existing A75 east of the B794 junction on the westbound lane.
- Improvement Strategy 6 interfaces with Gas Network Ireland pipeline west of Drummore roundabout.
Last Mile
Last Mile currently have existing apparatus in the form of Low Voltage Underground Electricity Lines which run within Springholm and Crocketford. Potential interfaces within each improvement strategy are as follows:
- Improvement Strategies 1, 2, 5 and 6 do not interface with Last Mile electricity lines.
- Improvement Strategies 3 and 4 interface with Last Mile electricity lines at Springholm and Crocketford.
SGN
SGN currently have existing apparatus in the form of Medium and Low-Pressure underground gas mains to the south-west of the assessment corridor. The majority of these follow the Old Military Road, School Brae and Cairnduff Place at the south-east extents of the assessment corridor. Potential interfaces with each improvement strategy are as follows:
- Improvement Strategies 1, 2, 3, 4 and 5 do not interface with SGN apparatus.
- Improvement Strategy 6 interfaces with SGN apparatus where the strategy intersects with the Old Military Road.
Scottish Power
Scottish Power currently have existing apparatus in the form of Low Voltage and High Voltage (22kV /11kV) underground and overhead lines. All six improvement strategies interface with Scottish Power apparatus.
Vodafone
Vodafone currently have existing apparatus in the form of underground utility routes and chambers along the A712 heading east into Crocketford. The utilities continue through Crocketford and head east along the existing A75 to the Drummore Roundabout. All six improvement strategies interface with Vodafone apparatus.
Scottish Water
Scottish Water currently have existing apparatus in the form of underground utility routes which cross the existing A75 in multiple locations, including just north of the B795 junction, at Church Road, a number of locations throughout Springholm and Crocketford and approximately 500m north of the Henderland junction. The underground utility routes also run in the verge alongside the existing A75 carriageway between the southern extent of Springholm and the northern extent of Crocketford, as well as between East Brae Cottage and the Drummore Roundabout. All six improvement strategies interface with Scottish Water apparatus.
Constructability
Potential constructability issues have been identified for each improvement strategy. These will be considered further at DMRB Stage 2.
Improvement Strategy 1
- Construction over Urr Water.
- Realignment of the A712.
- Construction on/in proximity to area of peat east of Crocketford.
- Construction on/in proximity to ancient woodland at Blackpark and Brooklands.
Improvement Strategy 2
- Realignment of the A712.
- Construction on/in proximity to areas of peat east of Crocketford, west of Garmartin Burn and east of Brae.
- Construction on/in proximity to ancient woodland at Blackpark and Brooklands.
Improvement Strategy 3
- Construction in proximity of Auchenreoch Loch.
- Construction within Springholm and Crocketford in proximity to a number of residential and commercial properties.
- Traffic Management within Springholm and Crocketford during construction and diversions through surrounding villages.
- Additional safety considerations for online construction adjacent to live traffic.
- Construction on/in proximity to areas of peat south-west of Crocketford.
Improvement Strategy 4
- Construction in proximity of Auchenreoch Loch.
- Construction on/in proximity to areas of peat south and east of Crocketford.
Improvement Strategy 5
- Construction in proximity of Auchenreoch Loch and Milton Loch SSSI.
- Construction on/in proximity to areas of peat south-east of Crocketford.
Improvement Strategy 6
- Construction over Urr Water.
- Realignment of the NCN7.