Large Chepstow Brownfield Development Site Approved for Housing
The largest brownfield development site in Monmouthshire has been sold to Barratt Homes in a move set to boost Chepstow’s housing stock significantly. Chris Taylor, Commercial Director at Future Climate Info examines the site history, its potential contaminants and remediation approach ahead of construction.
Outline permission for up to 450 new homes has been given and Barrratt is currently proposing to build 345 new properties, offices and a riverside business park on the site. Despite facing multiple objections from local residents about the impact on the local, already strained infrastructure, permission was granted in 2017 to redevelop the site, which has been derelict since 2009.
Known locally as the ‘former Fairfield-Mabey factory’ the 18.2-hectare site is situated between the town centre and the River Wye. It was the Fairfield-Mabey factory from 1965 until 2009, and part of Fairfields Shipbuilding and Engineering Company from 1924 to 1965.
It was also known as National Shipyard No1 in 1918 and was built up to manufacture and launch ships during the First World War and to manufacture landing craft during the Second World War. More recently the site has been used to produce bridge sections that were transported worldwide.
Mabey Group and Barratt’s in-house planning team initially guided a master planning process, culminating in the delivery of an outline planning permission in November 2017. The developer was already fully aware of the “abnormal” construction costs which the Council estimated would be in excess of £13 million.
A Challenging Remediation Strategy
The site presents many challenges, including the removal of industrial buildings and superstructures In addition, site access is only possible via a tunnel below the main railway line, and with over a kilometre of frontage to the River Wye, there are some sensitive ecological issues to address.
There is clear soil and groundwater contamination from 100 years of previous industrial uses. Heavy metals and hydrocarbon contamination has been identified on site, including arsenic, mercury and Benzo[a]pyrene among many others.
The site is also sensitive with respect to controlled water due to the proximity to the River Wye and being located on a Principal aquifer.
The Technical Advice Note (TAN) 15 flood map from Natural Resources Wales shows the site as having little or no risk of fluvial or tidal/coastal flooding. The areas located close to the River Wye are identified as Zone C2, which are on a floodplain not served by significant infrastructure. No major watercourses are located within the site boundary. Flood alleviation measures will require the raising of developed areas of the site to a level of at least 10.60m AOD.
The Environmental Statement recommended a remediation strategy and verification plan to be submitted as part of the planning conditions. Reviewing the strategy, prepared by Quantum Geotechnical building on remediation assessments by Mott MacDonald, the following approach will be undertaken:
- Hotspot areas will be excavated laterally and Made Ground/soft superficial deposits will be treated and replaced by compaction in areas of residential development.
- Where volatile compounds (VOCs) are identified, they will be tested against agreed assessment criteria. If levels exceed this, they shall be excavated and treated to reduce VOC concentrations.
- In areas of residential development, underlying contaminated soils will be capped with layer of 600mm of clean site-won crushed concrete and imported soils.
- Public open space along the River Wye bank will be screened for contaminants at the surface and 300mm of clean soils will be placed where insufficient existing soil is present to maintain the planned landscaping.
- The tidal area will be left untouched to maintain the existing protected environment. Sources of hydrocarbon contamination will be treated to reduce concentrations that may affect controlled waters.
- Contaminated groundwater within the hotspot areas will be pumped and treated prior to disposal to foul sewer under permit. Surface soils within residential development areas will be excavated and re-compacted in layers, reducing permeability.
- A sustainable drainage system (SuDs) will be connected to the River Wye which will reduce infiltration into the underlying ground.
These measures will reduce the potential for residual metals within the site being mobilised and migrating to the River Wye. Additional groundwater monitoring installations have been constructed on site during November 2018.
Whilst the development works are being undertaken, gas monitoring will continue to ensure that site conditions have not changed the findings from the original investigations in respect of both ground gases and groundwater quality. Monitoring of groundwater quality and ground gas will continue on a monthly basis against accepted thresholds for residential developments during the remediation or construction works.
There is a lack of suitable soil on site, so residential garden areas will require 600mm of soil imported to the site. The areas of public open space will have soil provided where necessary to support the planned landscaping to the same standards of testing and acceptance as stated above.
The remediation work will commence in the spring with construction due to begin in the summer.
The development comes at a time when there is a wider debate about the access and infrastructure in Chepstow, bounded by the twisting estuarine River Wye, hills, railways and motorway.
The recent scrapping of the Severn Bridge tolls will make the homes even more attractive, especially to homebuyers from Bristol seeking good access and lower prices.
Clarity on Complex Sites
Future Climate Info’s commercial environmental reports provide a comprehensive, yet concise and clear assessment of site history, potential for contamination and, as a result, follow-on options for more detailed testing or insurance provision.
The Government is seeking imaginative solutions to overcome obstacles in the planning and financing of brownfield projects, such as complex sites like here in Chepstow.
We are all about matching this with easy, intelligent commercial environmental risk solutions that keep the transaction going and provide support to unlock funding and planning consent quicker.
Chris Taylor is one of very few SILCs (Specialist in Land Condition) in the UK. Property professionals including commercial property lawyers and their clients will find direct access to this expertise invaluable in unlocking the true potential of brownfield sites.
For more information on Future Climate Info’s Commercial Environmental Risk Reports, Site Survey and Insurance Solutions, contact us on 01732 755 180 or email us at [email protected]