Description of local environment

Air quality

The scheme is not located within any Air Quality Management Areas (AQMA), and no air quality monitoring stations are located within 300m of the works.

The air quality in the vicinity of the scheme is most likely influenced by the road traffic on the A85.

Cultural heritage

A search of the Historic Environment Scotland (HES) PastMap website indicates that there are two listed buildings within 300m of the proposed scheme:

  • Glen Ogle, Bridge on A85 (ID: LB4137); and
  • Glen Ogle, Bridge on A85 (ID: LB4138).

Glen Ogle, Bridge on A85 (ID: 4137) is a category C listed structure. It is located outwith the site extents, approximately 295m downlink of the replacement culvert 2.

Glen Ogle, Bridge on A85 (ID: 4138) is a category C listed structure. It is located outwith the site extents, approximately 40m uplink of the replacement culvert 1.

There are no World Heritage Sites, Scheduled Monuments, Garden and Designed Landscapes, Conservation Areas or Inventory Battlefields within 300m of the proposed scheme.

The following non-designated cultural heritage assets, which are located outwith the site extents, are recorded by the Historic Environment Record (HER) or the National Record of the Historic Environment (NHRE):

  • HER: Glen Ogle – Ford (ID: 65883);
  • HER: Glen Ogle – Ford (ID: 65884);
  • HER: Glen Ogle – Culvert (ID: 65568);
  • HER: Glen Ogle – Bridge (ID: 65341);
  • HER: Allt An Deabhtaich – Bridge (ID: 65340);
  • NHRE: Glen Ogle, Culvert D – Culvert (ID: ID: 154544);
  • NRHE: Glen Ogle, Bridge – Road Bridge (18th Century) (ID: 24100); and
  • NRHE: Glen Ogle, Allt An Deabhtaich Bridge – Road Bridge (18th Century) (ID: 24099).

Landscape and visual effects

The proposed scheme is located within Loch Lomond and The Trossachs National Park (ID: 8621). There are no National Scenic Areas within 300m of the proposed scheme.

The proposed scheme is located within the ‘Upland Glens – Loch Lomond & the Trossachs’ (LCT) 252, which has the following key characteristics as described on NatureScot’s Scottish Landscape Character Types Map and Descriptions:

  • Often narrow with little flat glen floor, strongly enclosed by steep hill slopes of the adjacent Steep Ridges and Hills and Highland Summits.
  • Steep glen sides often patterned with rocky outcrops, boulders and screes but also extensively forested, particularly on lower slopes.
  • Tributary burns and rivers cut deep gullies into slopes and many feature waterfalls and cascades, pools and rocky outcrops.
  • Walled pastures sometimes occasionally occurring on lower (usually south-facing) slopes. Heather covers better drained areas and bright green flushes appear at spring lines on hill slopes.
  • Some glens covered with extensive coniferous forestry.
  • Notable ancient and semi-ancient woodlands of oak and birch in some glens, Natural regeneration of scrub woodland where grazing has declined as in the Luss Glens.
  • Relict wood pasture and Caledonian pine woodlands evident in some areas,
  • Scattered trees and native woodland trace the edges of burns.
  • Sparsely settled but with some isolated farms in lower reaches of glens, these often south-facing.
  • Significant cultural features in more open glens, including shielings and abandoned field systems.
  • Areas of crofting evident on some lower slopes.
  • Some important historic strategic routes for communications and accommodate key road and rail links today for example.

Classic views channelled up and down the Glens, with steep side slopes framing landscapes that lie beyond them.

Biodiversity

Designated sites

Lochan Lairig Cheile Site of Special Scientific Interest (SSSI) is located approximately 1.56km to the north-west of the proposed scheme.

There are no other ecologically designated sites within 2km of the proposed scheme, including Special Protection Areas, Special Areas of Conservation and Ramsar sites.

Ancient and Native Woodland

There is no ancient woodland recorded on the Ancient Woodand Inventory (AWI) within 300m of the proposed scheme.

There is one area of native woodland recorded on the Native Woodland Survey of Scotland (NWSS) within 300m of the proposed scheme. This area is located approximately 50m south-east of the site extents at its closest point.

Habitats

The land surrounding the proposed scheme is predominantly classified on the Habitat Map of Scotland as ‘woodland fringes and clearings and tall forb stands’ (E5) and ‘dry grasslands’ (E1). There are also patches of ‘broadleaved deciduous woodland’ (G1) and ‘seasonally wet and wet grasslands’ (E3) on the north-bound side of the A85.

Invasive non-native species

The NBN Atlas has one record of invasive and non-native species (INNS) over the past 10 years, under CC-BY and OGL licences within 5km of the proposed scheme:

  • Canada goose (Branta canadensis).

Ecology surveys

Jacobs has undertaken an extensive programme of ecological survey work at A85 Allt an Deabhtaich since 2019. Survey effort has comprised repeated assessments of the retaining wall, protected species surveys, walkovers, and targeted investigations to inform ongoing and proposed works.

Geology and soils

The proposed scheme is not located within an area designated for its geology, nor is it within 300m of a Geological Conservation Review site. Soils within the area are humus-iron podzols with peaty gleyed podzols.

Bedrock geology within the scheme extents is described as Ben Lui Schist Formation - Semipelite, garnet, which is metamorphic bedrock.

Superficial deposits within the proposed scheme area are described as Till and Morainic Deposits - Diamicton, sand and gravel, which is sedimentary superficial deposit.

Material assets and waste

The proposed works at A85 Allt an Deabhtaich include replacement of the existing retaining wall with a new structure, upsizing two culverts, provision of VRS, road drainage works, and minor masonry repairs. Materials to be used to complete the construction works include:

  • Steel threadbars (for the passive anchors)
  • Concrete (for the skin wall)
  • Structural steel mesh (for reinforced concrete skin wall)
  • Square steel plates (for the anchor head plates)
  • Concrete pipe (culvert works)
  • Class 1a backfill (culvert works)
  • Sprayed concrete facing (culvert works)
  • Timber post and four rail fence (culvert works)
  • Stone slabs (culvert works)
  • Concrete aprons (culvert works)
  • Asphalt (road resurfacing)
  • Steel (VRS)
  • Concrete foundations (VRS)
  • Concrete gully (road drainage)
  • Concrete chamber (road drainage)
  • Filter drain materials, including crushed rock and geotextile (road drainage)

Construction works at the site will include the excavation of made ground and natural soils within the site area. It is assumed that soil arisings not re-used from the works will be taken off site and be disposed of in accordance with the Environmental Authorisations (Scotland) Regulations 2018 (EASR). Based on the chemical analysis of ground samples, the excavated material is not assessed to have hazardous properties and, as such, are likely to be classified as either non-hazardous or inert waste depending on compliance with the Waste Acceptance Criteria (WAC).

A Site Waste Management Plan (SWMP) will be prepared for the scheme.

Material re-use and disposal options should be considered during the design and construction stages of the scheme as more information becomes available and construction methods are finalised.

Noise and vibration

The scheme is not located within a Candidate Noise Management Area (CNMA). The scheme is located within a rural area, where the dominant source of noise and vibration is anticipated to be road traffic on the A85.

There are no residential, agricultural and commercial properties located within 300m of the scheme.

The modelled noise level (day-evening-night level (LDEN)) ranges between 65 decibels (dB) and 71dB within the scheme extents (Scotland's Environment Scotland's Noise). 

Population and human health

There are no residential, agricultural and commercial properties located within 300m of the scheme.

National Cycle Network Route 7 is located 360m to the southwest of the proposed scheme; this path is also part of the Rob Roy Way, a popular long-distance walking trail. There are no core paths within proximity of the proposed scheme.

The A85 is a single carriageway within the scheme extents with a 50 miles per hour (mph) speed limit in place. The closest traffic count point (ID: 20774) on the A85 is located at the northern end of Lochan Lairig Cheile, approximately 2.39km northwest of the proposed scheme. An Average Annual Daily Flow (AADF) for this count point was estimated for 4,020 vehicles in 2024.

A search of the LLTNP’s online planning portal was undertaken to identify planning permissions within the study area from the last 2 years. No planning permissions have been granted within 500m of the proposed scheme.

Road drainage and the water environment

There are two existing culverts either side of the retaining wall. These culverts carry two minor watercourses under the A85 into Glen Ogle. These watercourses are not registered with the Scottish Environment Protection Agency (SEPA) and therefore do not have an ID. The existing culverts are in very poor condition with a combination of blockage and structural damage. Flows which exceed the residual culvert capacity overtop the A85 and flow over and along the carriageway posing a hazard to traffic.

The River Ogle (SEPA ID: 6824) is located approximately 150m to the south-west of the A85 and proposed scheme, which was last classified in 2024 as having an overall status of ‘High’. The River Ogle flows into Loch Earn (SEPA ID: 100251), located approximately 3.47km to the south-east, which was last classified in 2024 as having an overall status of ‘Moderate ecological potential’.

The scheme is located within the Killin, Aberfeldy and Angus Glens (SEPA ID: 150699) groundwater body, which SEPA classified as having overall status of ‘Good’ in 2024. 

The proposed scheme is located within an area of high surface water flooding from the Allt an Dèabhtaich, with a 10% chance of flooding each year. There is also high river flooding to the southwest of the proposed scheme, along Glen Ogle. Flooding along the River Ogle would not impact the scheme.

The existing road drainage network consists of a drainage conduit (carrier drain) which commences at an existing gully approximately 12m uplink of Culvert 1. The carrier drain runs downlink beyond Culvert 1, with a second gully located approximately 11m beyond the culvert. The carrier drain eventually discharges upstream of Culvert 2 with a further gully positioned above the culvert which drops directly into the existing pipe.

Climate

The Climate Change (Scotland) Act 2009 (‘The Act’), and its subsequent amendment under the Climate Change (Emissions Reduction Targets) (Scotland) Act 2019, sets the framework for the Scottish Government to address climate change. The Act has an ambitious target to reach Net Zero greenhouse gas emissions by 2045, with any residual emissions balanced by removing carbon dioxide from the atmosphere.

The Act was amended to replace interim targets with carbon budgets. Carbon budgets are legally binding caps on greenhouse gas emissions in Scotland over five-year periods. In line with the Act, the Climate Change Committee (CCC) published advice on the level of Scotland’s four carbon budgets, covering the period 2026 to 2045, recommending what the Scottish Government sets its carbon budgets at for annual average levels of emissions.

Emissions reductions from surface transport are the largest contribution to meeting the first two carbon budgets. The pathway for surface transport emission reduction is primarily driven by the uptake of electric vehicles, in addition to measures to enable a shift from car use to public transport and active travel, which all play a role in reducing emissions from fossil fuel cars. Ensuring efficiency of existing transport infrastructure and improving/providing new active travel facilities is therefore important to support these carbon reduction budgets.

Transport is the largest contributor to harmful climate emissions in Scotland. In response to the climate emergency, Transport Scotland is committed to reducing its emissions by 75% by 2030 and to the above noted legally biding target of net-zero by 2045. Transport Scotland is committed to reducing carbon across Scotland’s transport network and this commitment is being enacted through the Mission Zero for Transport (Mission Zero for Transport – Transport Scotland).