15 Disruption due to Construction 15.1 Scope of the Assessment 15.2 Statutory and Planning Context 15.3 Assessment Methodology 15.4 Baseline Conditions 15.5 Predicted Impacts 15.6 Mitigation 15.7 Residual Effects
15 Disruption due to Construction
15.0.1 This Chapter reports the findings of the assessment undertaken to determine predicted significant impacts that would occur during the construction of the Proposed Scheme.
15.0.2 Whilst it is recognised that such impacts are by definition temporary, they can prove significant over the longer-term (for example, excessive sedimentation of watercourses associated with earthworks could, for instance, result in a significant impact well beyond the construction period).
15.0.3 Many such predicted impacts have been addressed as an integral part of principal environmental topic areas considered in Chapters 6-13. Where this is the case these are briefly referenced in this chapter.
15.1.1 Potential impacts associated with the construction stage of the Proposed Scheme include:
- limited disruption to road users and local travel patterns associated with traffic management to enable construction to proceed;
- disruption to settlements associated with movements of construction plant and delivery vehicles;
- temporary closures or diversions;
- severance of agricultural accesses and disruption to existing services (water, power and drainage)
- dust deposition arising from site works such as earthworks;
- a contaminant/pollutant risk associated with materials handling and storage along with vehicle standing areas;
- visual impacts associated with plant and contractor’s activity on site;
- noise and vibration arising from plant operation, on and offsite vehicle movements (including HGVs); and
- water quality and ground-related impacts associated with excavations, surface water runoff and temporary discharges to watercourses.
15.1.2 The principal interests addressed in this chapter relate to:
- air quality;
- noise and vibration;
- water quality;
- land use;
- pedestrians, equestrians and cyclists;
- ecology and nature conservation;
- visual impact; and
- existing roads.
15.2.1 The legal and regulatory context within which construction related activities, their impacts and mitigation are encompassed and controlled is extensive and covers such aspects as health and safety, the Control of Substances Hazardous to Health (COSHH), traffic management, waste disposal, noise emissions and pollution prevention. A host of best practice guidance documents, codes of practice and British Standards exist regarding construction activities on development sites. They have been identified and referenced where required.
15.2.2 The statutory and planning context outlined in other sections of this ES identifies other applicable construction-related legislation. Where required, cross-references are provided below.
15.3.1 The assessment has been undertaken in accordance with the guidance contained within Volume 11, Section 3, Part 3 of the DMRB along with the mitigation and control measures advocated within various guidance such as those produced by the Construction Industry Research and Information Association (CIRIA) and Building Research Establishment (BRE). Further specific guidance in relation to the assessment of construction-related effects is contained within the various environmental topic Chapters.
15.3.2 The DMRB guidelines acknowledge the relationship between construction-related activities, the receiving environment and overall experience of people/users in the locality of the proposed works. The guidelines also recognise that disruption may be caused beyond the site by other factors such as HGV traffic movements, utility company works and essential offsite works.
15.3.3 The guidance also acknowledges that the distance of sensitive receptors, taken to be residents living in the vicinity of the proposed works, is a good indicator of the potential for the works to result in statutory nuisance. Within the DRMB this distance is set at 100 m from the proposed works; however the guidance further requires that particularly sensitive receptors should be identified beyond this definition.
Stages in the Assessment Process
15.3.4 There have been four key stages in the assessment.
- An estimation of the number of properties within and 100 m beyond the proposed ‘working footprint’; including sensitive receptors within this area and beyond (e.g. schools).
- The identification of the presence of any ecological and culturally sensitive areas and features within 100 m of the route alignment.
- The identification of construction-related activities and machinery that may give rise to temporary detrimental effects on the receiving environment.
- An assessment of the likely impacts in respect of the proposals, taking account of available construction mitigation strategies.
15.3.5 Through applying knowledge and experience of other similar trunk road improvement schemes as adopted into the DMRB guidance documents, the likely range, magnitude and significance of potential effects has been accordingly determined.
15.3.6 The assessment has been undertaken in advance of the identification of a contractor who would be responsible for implementing the works upon approval of the Proposed Scheme by Scottish Ministers. Assumptions relating to the form and extent of the construction activities have accordingly been based on inputs from the planning and design teams responsible for developing the scheme proposals and knowledge.
15.3.7 For the purposes of measurement of the significance of predicted impacts, a three-point scale has been adopted. The scale describes predicted impacts as being Major, Moderate or Minor and Adverse.
- Major Impacts would affect sensitive sites of high conservation interest and/or large areas or numbers of people for the entire period of the contract. The magnitude would be such that there would be noticeable disruption for a substantial part of the construction period.
- Moderate Impacts would affect sites of moderate conservation interest areas and/or notable numbers of people. The magnitude would be such that there would be noticeable disruption for a relatively long, but not substantial, part of the construction period.
- Minor Impacts would be localised, of low magnitude, short duration and would affect few people or other sensitive receptors.
15.4.1 A total of 16 private dwellings (farmsteads and houses), 1 commercial properties and 3 community facility (the village hall, school and post office at Carrutherstown) are located within 100 m of the construction envelope for the Proposed Scheme. These are all regarded as sensitive receptors. There only other sensitive property beyond the 100 m study area is Oakbank located near the current A75/U81a Junction.
15.4.2 A network of local roads and access tracks are contained within the 100 m study area. Some private tracks, which currently serve the farmsteads and residential properties, have direct access onto the existing trunk road; namely Fostermeadow Farm, Whitecroft Gate, Oakbank, Topmuir Farm, Stenries View and Upper Mains and Stenriesgate. The principal roads are the U81a, U82a, and B725.
15.4.3 There are no public rights of way or dedicated cycleways, crossing or following the line of the Proposed Scheme corridor. Despite the presence of the local road network there is no evidence of regular, or significant, NMU use.
15.4.4 There are four watercourses that cross the Proposed Scheme corridor; Pow Water, Stenries Hardgrove Burn and Glen Burn.
15.4.5 As described in Chapter 7, certain sensitive habitats within the considered survey area are assessed as being of value at the local level, i.e. broad-leaved semi-natural woodland; coniferous plantation and mixed plantation. The scheme area is also of value for farmland birds, badger, otter and red squirrel.
15.4.6 Known archaeological and built heritage interests are represented immediately north of the existing trunk road. Those that are considered sensitive in relation to the Proposed Scheme include Braehill Fort and Settlement, Braehill Enclosure, and Whitecroft Gate Piers.
15.5.1 The principal construction activities likely to result in disruption during construction comprise:
- soil stripping and earthworks to establish the proposed horizontal and vertical alignment of the new section of road offline and south of the existing trunk road;
- construction of the underpass to provide grade separation between the new section of trunk road and the U81a;
- construction of new culverts to accommodate watercourses crossing the line of the Proposed Scheme corridor;
- construction of the tie-ins to the existing trunk road at the western and eastern ends of the Proposed Scheme;
- import of essential construction materials, including stone, aggregate, concrete and reinforcement; and
- movement and activity associated with construction plant and delivery vehicles.
15.5.2 Based on the indicative design proposals, it is anticipated there would be a potential excess of cut over fill of some 46,000m3. It is not anticipated there would be a requirement for break out or blasting of rock. This fill would be accommodated within the scheme’s landscape proposals (see Chapter 8).
15.5.3 The anticipated timescale for construction is 52 weeks. Specific short-term operations involving larger plant and delivery of larger loads during this period would involve the use of cranes to move and locate heavy construction components during the construction of the U81a underpass and the culverts. Such operations would last approximately two-to-three days. Of slightly longer duration would be the need for traffic management and temporary disruption to strategic and local traffic flows as the two tie-ins are constructed. It is anticipated there would be short-term disruption in the order of 4-6 weeks as flows are temporarily managed to maintain movement whilst merging the new and existing sections of road. There is also a requirement for more limited traffic management levels at the start of the construction phase to establish site accesses and set out the construction site.
Impacts on Property
15.5.4 The principal impact on property would relate to noise, dust deposition and visual impact as the works proceed.
15.5.5 There would be a significant potential for dust generation and deposition particularly during site stripping and bulk earthworks movements. There would also be potential for dust transport and deposition where there is a requirement for temporary soil stockpiling. Other sources could include deposition where soils and fine materials associated with construction materials are transported to and from site. Such impacts would be primarily related to nuisance associated with deposition on property and loss of amenity where dust impinges on open areas used by members of the community; namely the school playing fields. Potential impacts would vary according to prevailing weather conditions; the impact being potentially greatest during periods of moderate to high winds.
15.5.6 Potential impacts associated with the operation of construction vehicles, site plant and the requirements for traffic management during the construction of the two tie in sections at each end of the Proposed Scheme would involve short-term increases in vehicle emissions; where a proportion of the passing vehicles would be idling as priority is given to passing in each direction of travel. The order of increase would be relatively low and not significant in relation to the volume of traffic currently contributing to local emissions.
Traffic Noise and Vibration
15.5.7 Fifteen of the 16 sensitive receptors identified within the 100 m threshold defined in the DMRB would be located at or close to Carrutherstown, whilst the principal part of the Proposed Scheme where noise generating activity would be of greatest duration (approximately 26 weeks) would be in the vicinity of the existing A75/U81a junction close to the Oakbank property. There are no other receptors closer than 300 m to any of the proposed working areas in this location38.
15.5.8 Much of the construction noise for activities in the vicinity of Carrutherstown would be experienced in the context of existing ambient noise levels dominated by traffic flows on the A75. These have been calculated as being of an order between 60-66 dB(A) 39. Whilst there would undoubtedly be instances when construction activity would involve levels in excess of these, they would be of short duration and for a limited period in the construction programme. Existing levels at Oakbank have been calculated at 66 dB(A). Construction activity would similarly be likely to result in episodes of higher noise levels, which would be of relatively short duration though for a longer overall period in the contract programme; noting that the ambient noise levels associated with the current A75 remain for much of the construction programme until the switch over point to the new alignment. This will only occur approximately 2-3months before the end of the construction phase.
15.5.9 The assessment has concluded that there would be substantial visual impacts for those properties identified within 100 m of the working areas. The impact would therefore be temporary, major and adverse.
15.5.10 There would be the potential for increased sedimentation in watercourses during the construction of the proposed culverts and the undertaking of earthworks close to the watercourses. There would also be the potential for pollution associated with accidental spillage and contamination by construction material such as cement and concrete.
15.5.11 There are 19 listings on the SMR within 1 km of the site, three of which are listed buildings. These include Braehill Fort and Settlement, Braehill Enclosure, and Whitecroft Gate Piers, which are sufficiently close to the scheme to be considered sensitive under the definitions of the DMRB. There would be no direct construction-related impacts on these known features during the construction period.
15.5.12 The potential for impacts on unknown sites and features considered in Chapter 6 would occur during the construction stage of the contract and would be determined during the pre-construction surveys administered by HS. The assessment in Chapter 6 concluded that the likelihood of such impacts would be low.
15.5.13 Should artefacts/remains be encountered during construction, these would be dealt with in accordance with procedures set out in ‘Special Requirements in Relation to Historic Scotland’ (see Appendix D) and agreed with HS, SNH and TS.
Ecology and Nature Conservation
15.5.14 Actual habitat loss and associated impacts on faunal species, which will first occur during the construction period but will be felt throughout the life of the scheme, is covered under the assessment of impacts in Chapter 7.
15.5.15 Given the nature of the Proposed Scheme and is removed location from the nearest statutorily designated and non-statutory sites; no significant impacts on any designated nature conservation sites are anticipated.
15.5.16 The risk of sedimentation and pollution discussed in Paragraph 15.5.10 is assessed in ecological terms as being potentially significant at the local level (unlikely).
15.5.17 Construction activity could potentially encourage the spread of Japanese knotweed, e.g. fragments of stems or rhizomes could be moved during earth movements or become attached to the wheels of construction machinery and thereby spread. The impact associated with the spread of this species could potentially be significant in legal terms although the impact is likely to be not significant in nature conservation terms.
15.5.18 If undertaken during the bird nesting season, construction activity could result in the damage/destruction of birds’ nests, which has associated legal implications.
15.5.19 The potential impact associated with otters becoming trapped in deep excavations during the construction period is assessed as potentially significant in legal terms. Since all construction activity will take place during daylight hours, potential disturbance impacts on otters passing along the watercourses within the construction area are assessed as not significant.
Land Use and Access
15.5.20 The Proposed Scheme sees the retention of the existing trunk road and associated accesses north of the existing road for the substantial part of the anticipated contract period as the new section of road is built offline.
15.5.21 There would be disruption to existing accesses to the retained section of trunk road as the offline section is built for property located south of the new alignment. The principal properties involved would be Upper Mains, Topmuir Farm and Hardgrove Farm. Users of the U81a travelling north to the existing trunk road would also be disrupted as the offline section is built and the proposed grade-separated crossing is constructed and there would be further disruption along the route of the U81a as the new alignment arrangement is developed and the overpass constructed.
15.5.22 It is envisaged that access for Fostermeadow Farm would be transferred to the proposed new link to the B725 at an early stage in the works.
15.5.23 There would be disruption to all properties with existing access from the north and south onto the existing road during the latter part of construction as the merging sections between the existing trunk road either side of the section are tied into the new offline section of road and the new linking sections of road onto the retained section of the existing trunk road are built, which, as discussed, will take in the region of 4-6 weeks.
15.5.24 The disruption in this latter stage of the work would relate to main traffic management period, which might include localised short diversions to maintain movement along the trunk road and access via roads and private access tracks to the north and south of the construction corridor.
15.5.25 The impact on existing access would occur in the context where there are existing difficulties experienced by local-road users and those using private access tracks seeking access onto the existing trunk road
Other Predicted/Potential Impacts
15.5.26 There would be the potential for the spread of Japanese knotweed given that the construction works encroach on areas where the species is established. There are legal obligations relating to the control and eradication of the species.There would be the potential for accidental damage to existing trees within, or close to, the working areas.
15.6.1 The implementation of proposed mitigation measures during construction would be managed and monitored as part of the Construction Environmental Management Plan (cEMP) introduced in Paragraph 4.2.9.
15.6.2 The cEMP provides a framework for:
- the statutory context under which construction related impacts would be controlled;
- the nature of sensitive receptors and environmental assets;
- aspects of the work that would potentially prove detrimental;
- potential risks and impacts related to receptors, assets and aspects of the work;
- procedures for evaluating, avoiding and/or managing potential impacts related to specific construction tasks and site operations;
- method statements for construction tasks; and
- a management and monitoring structure for implementing the plan.
15.6.3 Specific measures, which the contractor would be required to include within the cEMP, are described below.
15.6.4 Mitigation to minimise dust generation and deposition would include:
- the daily use of a road sweeper on paved areas affected and the use of water spraying on unpaved access routes;
- using wheel washers when required for vehicles leaving the site;
- sheeting of all vehicles carrying material prone to wind blow;
- containment of storage areas for materials prone to wind blow;
- enforcement of low speed limits on unmade surfaces;
- temporary seeding of soil stockpiles where storage timescales permit;
- seeding of completed earthworks as soon as is reasonably practicable; and
- cessation of relevant works during periods of high wind.
15.6.5 Dust-monitoring would be undertaken before, and during construction at representative sensitive receptors within 100 m of the working areas to determine the impact and determine the need for additional temporary control measures importantly including the cessation of work.
15.6.6 Whilst the contribution to local emissions associated with the temporary construction phase would be low, limits would set on the permissible idling periods for operational vehicles and plant.
Traffic Noise & Vibration
15.6.7 The contractor would be required to agree a noise management plan with Dumfries and Galloway Council’s Environmental Health Officer. Limits will be agreed relating to timing and levels of specific noise generating operations in proximity to properties and communal facilities; with specific regard to the Oakbank property. The plan would be informed with reference to BS 5228: Part 2: 1997, Construction Noise on Construction Sites. Specific measures would include:
- vehicles and equipment to be fitted with effective exhaust silencers, maintained in good working order and operated to minimise noise emissions in accordance with BS 5228;
- compressors to be fitted with properly lined and sealed acoustic enclosures where environmental noise disturbance may arise and these should be kept closed whenever the machines are in use;
- pneumatic percussive tools to be fitted with mufflers or silencers in accordance with the manufacturer’s recommendations;
- machines in intermittent use to be shut down in the intervening periods between work or throttled down to a minimum (including HGVs waiting to access the site);
- where practicable, all plant to conform with the noise limits presented in the EC Noise Emission in the Environment by Equipment for use Outdoors Directive 2000/14/EC; and
- noise monitoring to be undertaken by the Contractor in proximity to Oakbank and two representative receptors at Carrutherstown to ensure the levels stipulated in the noise management plan are adhered to.
15.6.8 Mitigation would involve adoption of SEPA’s PPGs that include specific recommendations in relation to: working in proximity to watercourses; the management of waste-water associated with construction; and the storage, handling and incorporation of potentially polluting materials. The measures would also allow for ensuring that all site-staff are fully conversant with the guidelines through the use of toolbox talks prior to commencement of any potentially sensitive works. Specific measures would include;
- bunded fuel storage areas;
- specific working distance constraints relating to sensitive locations;
- refuelling guidelines;
- temporary drainage and settlement ponds; and
- vehicle standing areas.
15.6.9 Subject to the findings of the pre-construction surveys proposed in Chapter 6 there may be a requirement to agree and implement stand off areas should currently unknown sites or features be identified in close proximity to the proposed working areas. A suitable allowance within the construction-programme for this eventuality has been made.
Ecology and Nature Conservation
15.6.10 The contractor would be required to prepare a species protection plan based on the framework detailed in 15.6.2 as an integral part of the cEMP.
15.6.11 The cEMP will also cite best practice working procedures, including the need to correctly store hazardous/harmful materials/chemicals, such as the use of double-bunded 110% storage-capacity containers and drip-trays, along with methods to prevent spillages and ensure control of dust emissions in the vicinity of sensitive habitats, e.g. watercourses (see paragraph 15.6.4).
15.6.12 The construction working width will be clearly defined in order to prevent unnecessary encroachment into adjacent areas of woodland.
15.6.13 In order to ensure legal compliance, potential bird nesting habitat, e.g. trees, scrub and buildings, will be undertaken outside the main bird nesting season of March-August if possible (see Section 7.7.5). Where this is not possible, works affecting potential bird nesting habitat will be checked by a suitably experienced ecologist. If bird nests are found, work will be postponed until the young birds have fledged.
15.6.14 As described in the confidential Appendix G3, in order to prevent badgers and otters becoming trapped in deep excavations, wooden boards will be placed in any excavations left overnight in order to allow any trapped animals to climb out. Any pipes and culverts exposed during construction would be capped and checked at the end of each working day to prevent mammal species being trapped.
Land Use and Access
15.6.15 The contractor would be required to retain temporary access for the properties, which currently have direct access onto the existing A75 and for users of the U81a throughout the construction period. This would be implemented and monitored under the cEMP with reference to a contract requirement that the contractor must prepare and agree a traffic and access management plan for all stages of the work with the Regulatory Authority.
Other Proposed Mitigation
15.6.16 A programme of spraying the Japanese knotweed identified within the proposed land-take for the scheme has commenced. Subject to scheme approval and should complete eradication not been achieved by the time of construction, an associated method statement would be prepared, detailing methods to be employed and ensure compliance with legal obligations related to the species.
15.6.17 Where existing trees are to be retained within or near to the working areas, the contractor would be required to evaluate the risk to them in light of the required construction operations and apply the principles of BS 5837: Trees in Relation to Construction.
15.7.1 Taking into account proposed mitigation the assessment has concluded that the effects during construction would be as follows.
The risk of increased sediment/pollution-laden run-off reaching watercourses would be low and consequent impacts would not be significant.
Given the mitigation measures for the eradication of Japanese knotweed, no significant impact associated with the spread of this species is predicted.
The standard approach to mitigation to avoid impacts on birds’ nests whilst in use is considered to result in a potential residual impact that is assessed as not significant in legal terms.
Given the safeguards to prevent animals becoming trapped in exposed excavations and pipes, it is anticipated there would be no significant impact on otters or badgers.
There would be substantial visual impacts for those properties identified within 100 m of the working areas. The impact would be temporary, major and adverse not resulting in an overall long-term residual effect.
Notwithstanding the proposed mitigation of noise impacts during construction there would be occasional episodes of moderate to high noise events. In the context of the contract period and existing background noise levels, these would not be significant.
Despite the general safeguards relating to the control and minimisation of dust there would be an unavoidable level of deposition. This would be further limited by the proposed mitigation and as such would not be significant in the context of the relatively short periods of high risk. The resultant impact therefore is assessed as not being significant.