Auldcathie District Park, Winchburgh
Shortlisted for Best Sustainable Brownfield/Urban Regeneration/Infrastructure Scheme
The development at Winchburgh, 12 miles west of Edinburgh, is one of the largest and most exciting placemaking projects currently underway in the UK. When complete, this ambitious development will see the construction of at least 3,800 new homes across the private and social rented sectors, improved transport links, employment opportunities, state-of-the-art schools and new outdoor spaces. A key part of the overall placemaking strategy for Winchburgh has been the creation of a new 36 hectare district park and associated infrastructure in part of the site formerly occupied by the Auldcathie Landfill, as well as a new shared education campus and sports facilities on the eastern periphery of the landfill site.
Auldcathie Landfill received waste over a 16-year period between 1986 and 2002, until the landfill ceased operations as the site operator went into liquidation. A Closure Notice was served by SEPA which required the landfill to close for the acceptance of waste with immediate effect. At the time of closure approximately half of the landfill (19 out of 36 hectares) had waste at or close to the surface. Where a landfill operator has gone into liquidation, responsibility for the management, closure and restoration of a landfill would normally be passed to SEPA, however at Auldcathie, the waste management licence that was associated with the landfill site was effectively terminated by SEPA in 2006 as the operating company had dissolved. The “restoration” of Auldcathie was a key requirement of any development of the Winchburgh Core Development Area allocation, as identified in the 2005 West Lothian Local Plan and taken up by the overall masterplan developer, Winchburgh Developments Ltd. Joint working between Sweco, Winchburgh Developments Ltd and the council’s planning and contaminated land officers at the ground investigation stage allowed for the restoration and remediation of Auldcathie to become a condition of consent in the overall Planning Permission in Principle for the settlement expansion of Winchburgh, granted in 2012.
Figure 1: Auldcathie plan and profile showing site boundary, ground investigations and wastes
Substantial ground investigation of the landfill was carried out on behalf Winchburgh Developments Ltd by Sweco (formerly Grontmij) from 2011 onwards, which included assessment of the type and extent of landfill waste, the status of any existing landfill cap, risk to the water environment, and assessment of human health and ground gas risks. The investigation found a mixture of non-biodegradable waste, biodegradable waste and existing landfill cap material ranging from adequate to absent with exposed waste at the site surface. The perched groundwater beneath the site was found to be impacted by leachate emanating from the degrading waste mass, and biodegradable waste within the site was found to be actively producing landfill gas. The issues identified posed an environmental risk, a risk to existing nearby properties, a constraint to the development of the district park itself, a limitation on residential development potential to the east of the landfill, and an unacceptable risk to the construction and use of a proposed new school campus on the eastern landfill fringes.
The solution to the problems at Auldcathie required a multi-disciplinary consultant (Sweco) providing land quality, civil and environmental engineering expertise for the remediation. This technical team was part of a strong partnership (UN Sustainability Goal 17, Target 17.17 - effective public-private partnership), including the masterplan developer (Winchburgh Developments Ltd), local council (West Lothian Council), masterplanning landscape architects (OP-EN) and the delivery contractor (I & H Brown) to ensure the remediation scheme tied in with the wider aspirations for the district park and adjacent school and delivered the environmental, social and economic benefits envisaged at conception.
Remediation of the Auldcathie site was zoned based on the findings of earlier investigation, waste delineation during remediation and the proposed end use of the area. The core of the
strategy was to provide an engineered landfill cap and gas
Figure 2: Site Overview
collection system across the main biodegradable landfill area, with works comprising waste reprofiling and construction of a composite geosynthetic and geological barrier, and design and construction of a network of gas extraction wells and gas management infrastructure.
Effective drainage of the landfill cap was required in order to control runoff and limit infiltration into the waste mass. Review of the topography and hydrological regime indicated that surface water runoff was best directed as overland flow to drainage channels, followed by infiltration into exposed bedrock rock within a reprofiled gully area. This approach mimicked pre-existing drainage and infiltration whilst mitigating the contamination risk to surface water and ground water. Elsewhere on the site, areas of inert construction and demolition waste were reprofiled to meet the needs of the new district park. Wastes were contained beneath a clean cover system utilising site won rock and soil, and suitable surplus soils from across the wider Winchburgh masterplan development. Soils from within the masterplan planning boundary were used in accordance with SEPA’s guidelines on sustainable reuse of greenfield soils in construction, and on land remediation & waste management to avoid waste disposal and avoid the need to import materials to site. The thickness of the soil cover system was varied as necessary across the site to accommodate specific planting schemes (e.g. woodland, community growing areas and orchard areas required a greater depth of cover than grassland) or infrastructure foundations.
Verification of the remediation commenced ahead of construction with the collection of baseline data on groundwater and surface water quality, construction of a peripheral gas monitoring network and pre-remediation gas monitoring and risk assessment. Verification continued through the construction phase incorporating environmental monitoring and soil testing programmes. Post construction the ground gas, groundwater and surface water testing and assessment continues into the aftercare period with regular annual reviews proposed. Ground gas risk assessment in particular has been instrumental in ensuring that land to the east and south of the landfill is developable, and in allowing the new education campus to be constructed on the eastern fringes of Auldcathie. The landfill site itself is now moving into a carefully managed aftercare phase wherein it will be closely monitored as the remediation solution beds in, gas generation will be reviewed, and control measures adapted, and long term environmental benefits assessed. On and around the site the economic and social benefits continue to be realised.
Figure 3: Typical gas monitoring trace
Sustainability has been at the core of the Auldcathie project since the design stage, and the focus on realising economic, social and environmental benefit has been at the forefront of decision making throughout and has supported to varying degrees a number of the United Nations Sustainable Development Goals. The construction phase of the development has offered tangible and measurable benefits in the form of full employment for approximately 60 staff on site including 2 new graduate positions and a trainee from a local college who’s now in a permanent role (UN Sustainability Goal 8, Target 8.5 - productive employment and decent work), and the re-use of surplus soils resulting in the diversion of almost 400,000 tonnes of waste from landfill (UN Sustainability Goal 12, Target 12.5 – substantially reduce waste generation) to a beneficial end use.
Figure 4: Overall Sustainability Assessment (Sweco Sustainability Sun™)
It is in the long term goals of the project that the most significant benefits will be created. From a human health and environmental protection standpoint the benefits of remediating an abandoned landfill and putting in place a robust control and aftercare scheme are obvious. By capping the former landfill the team have ensured that it no longer vents methane directly to atmosphere, with gas now being collected and managed through a temporary flare while production rates and long term management opportunities are assessed. Gas control means that the risk of landfill gas migrating into existing and new homes, businesses and community facilities is mitigated, and capping of the previously exposed waste mass prevents potential human and animal contact with or dispersal of contaminants, enhancing health and wellbeing in the community (UN Sustainability Goal 3, Target 3.9 – reduce illness and death from hazardous chemicals and pollution). The engineered cap over the landfilled waste and the associated surface water management is intended to help local groundwater quality recover (UN Sustainability Goal 6, Target 6.3 – improve water quality). The capping design for the site also serves to prevent contaminants being transported in run-off towards nearby wet woodland and surface waters, preventing pollution (UN Sustainability Goal 6, Target 6.6 – protect and restore water related ecosystems).
From the early stages of the master planning process, Winchburgh Developments Ltd has sought to build a relationship with the local community to involve them in the important decisions that would shape the future of Winchburgh, such as detailed designs for Auldcathie District Park. This has meant that beyond the environmental benefits of the scheme the project has offered multiple social and economic benefits. De-risking the fringes of the landfill and land to the east of the site has helped enable the development of the new housing masterplan, which when complete will include 840 affordable and social-rented homes (UN Sustainability Goal 11, Target 11.1 – safe and affordable housing). Making this area of Winchburgh developable has also allowed the construction of a new state of the art education facility including a nursery and three schools, opening in 2022 and offering a safe and inclusive learning environment and facilities for over 1,500 pupils (UN Sustainability Goal 4, Target 11.1 – Build new education facilities that are child, disability and gender sensitive). Creation of the district park has provided the growing community in Winchburgh with a new public green space (UN
Sustainability Goal 11, Target 11.7 – access to safe and inclusive green and public spaces) while the new path network being constructed helps link the community to
Figure 5: New Education Campus
the wider rural surroundings and other facilities and helps promote accessible, inclusive and sustainable modes of transport (UN Sustainability Goal 11, Target 11.0 – sustainable cities and communities).
Figure 6: Community Tree Planting
The scheme of landscaping and planting in the new park has been integral to and has influenced the detailed remediation design, meaning that new areas of woodland including approximately 30,000 trees planted, a community orchard and community growing plots for local groups have been safely incorporated into the former landfill area (UN Sustainability Goal 15, Target 15.2 – end deforestation), and have allowed Winchburgh’s residents to become actively involved in the creation of their new environment. Auldcathie’s new public spaces form part of the wider connected network of green space across Winchburgh and out into the rest of West Lothian, supporting the biodiversity aspirations of local government and neighbouring communities (UN Sustainability Goal 15, Target 15.9 – biodiversity in planning).
The remediation of the former Auldcathie landfill provides a clear example of where a multidisciplinary partnership approach can secure the regeneration of a brownfield site to deliver tangible economic, environmental, and social value.