DBS are currently working for a private developer on a new residential project in Gateshead, Tyne and Wear. The project gives an example as to the diversity of schemes that DBS are currently working on with regards to size and scale. This project involves the redevelopment of an existing residential garden for a further two residential properties.
Whilst this type of scheme is at the smaller end of the projects that we normally get involved with (in comparison to other sites that we are currently working on that are being redeveloped for hundreds of residential units plus), the actual process of characterising a site for a change of use for planning is the same process, regardless of the size of the site, and obtaining information to support foundation design is generally the same, regardless of the size of the development.
Smaller projects can provide challenging obstacles as much as larger schemes, mainly due to the confined nature of the site and the requirement for any remediation required to mitigate build abnormals to be very cost effective, as the profit from the scheme is proportional to size.
On this project, which appeared very straightforward initially, significant Made Ground was found to be present on site arising form a former mineral railway. Railway lines used to border the site dating from the birth of the Industrial Revolution and the original expansion of the Coal Fields, but were removed decades ago. Any visitor to the site now would not imagine that Made Ground was present, as there is no trace of the former industry.
The Phase 2 intrusive investigation of the site undertaken by DBS identified Made Ground present comprising ash, coal and clinker. This is typical of former mineral railway land. Ash from steam locomotives was often used for track ballast and/or was spread on the surrounding ground. This material is often elevated with heavy metals, and polycyclic aromatic hydrocarbons (PAHs), a product of combustion. The material can also can have combustion potential itself due to the presence of coal fragments.
We are currently awaiting site chemistry data from the testing laboratory in order to undertake the risk assessment for the site, but, based off our initial work it is likely that contamination will be present (as discussed above) and that a cost effective remedial solution will need to be developed for the site. The remedial solution is likely to involve pathway modification comprising property footprints to form a cap to Made Ground, with localised source removal or capping in garden areas. The aim of the scheme will be to leave as much Made Ground on site as possible, whilst mitigating development risks, to ensure that our client does suffer from onerous off site disposal costs.
We will be negotiating with the regulators on our clients behalf to take forward a safe, sensible and sustainable remedial scheme, to enable conditions imposed on the development for contaminated land to be discharged by the LPA and the site to be redeveloped cost effectively.