The benefits of brownfield

Jeff Wilton discusses why we should embrace brownfield development

In order to stimulate the construction of up to 45,000 new houses, and provide affordable housing for the next generation, the UK government has recently announced the establishment of up to 28 Housing Zones across the country. The development of brownfield sites, defined as ‘previously developed land’ that has the potential for being redeveloped (which is often land that has been used for industrial and commercial purposes and is now derelict and possibly contaminated) will contribute heavily to this plan. At least 30,000 (two thirds) of these homes will be built on such sites – with the dual aim of avoiding green belt construction and maximising currently unused land. To achieve this, some £6.3m has been earmarked as investment to provide developers with the funds to rejuvenate land potentially affected by contamination.

This announcement is a key element of the government’s Housing and Planning Bill, which aims to achieve a target of delivering one million new homes by 2020 and to open the door to aspiring homeowners. The Housing and Planning Bill will place a new legal duty on councils to: guarantee the delivery of ‘starter homes’ on all reasonably sized new development sites; give permission in principle for sites identified in plans and brownfield registers; and introduce planning reforms supporting small builders and local demand for custom build.

The lack of available green spaces for development purposes has meant that brownfield sites have become increasingly popular in recent years, especially in places where demand for residential and commercial property is high. It is estimated that there are over 66,000 hectares of brownfield sites in England, and around a third of these are in the high-growth areas of Greater London and the South East. The government has committed to developing brownfield sites as a priority and has already exceeded its 2008 target of building over 60 per cent of new houses on brownfield sites.

The most common driver behind a contaminated land investigation is the planning conditions imposed on a development by a Local Authority. Such conditions are often associated with a change to a more sensitive end use, from commercial, industrial or agricultural to residential. Alternatively, planning conditions can be stipulated if a Local Authority is aware of a significant source of ground contamination, such as a landfill site or historical pollution incident, in the general vicinity of a study site.

Regardless of the financial incentives and planning reforms, many developers are still wary of the potential pitfalls associated with the development of brownfield sites. Contaminated land investigations can seem overcomplicated and onerous to those unfamiliar with the process, however it is possible to de-risk these projects with targeted and phased investigations to ensure regulatory compliance without significantly impacting either cost or programme. Specialist geotechnical testing partners will assess the risks associated with potentially contaminated land through a phased or tiered approach, referencing current UK policy and technical guidance provided by Contaminated Land Publication CLR11 Model Procedures for the Management of Land Contamination and British Standard BS10175 Investigation of Potentially Contaminated Sites – Code of Practice.

The recognised first phase of any investigation is a desk study, otherwise known as a Phase I Preliminary Risk Assessment (PRA). The PRA uses sitereconnaissance, historical map and environmental database information in order to identifypotential on and off site sources of ground contamination that could pose a risk to human, environmental and built receptors.

To developers, the PRA sometimes feels like an unnecessary expense that hinders progress as it does not involve physically exposing any contamination present beneath the site. However, by carrying out a comprehensive and robust desk based assessment, compliance with current guidance can be ensured as well as providing the developer with advance warning of potentially significant ground risks that could adversely impact their cost and programme.

Upon completion of the Phase I assessment, a site-specific Phase II intrusive investigation must be implemented to address the relationship between conceptual sources, pathways and receptors of contamination established by the PRA. This approach offers benefits to developers as it prevents the undertaking of unnecessary site works and laboratory testing.

Examples of how the findings of the PRA can be used to the benefit of developers are as follows:

• If a point source of contamination such as a fuel tank is identified, intrusive works and sample recovery can be specifically targeted, thus gaining the maximum amount of relevant information during a site visit;
• If the PRA does not identify a potential source of hazardous ground gases, such as landfill site or backfilled pit, it would not be necessary to form boreholes and install and periodically monitor standpipes;
• If the PRA does not establish a sensitive controlled water receptor, such as a potable groundwater abstraction or river/stream, it would not be necessary to recover water samples for chemical testing;
• If the PRA does not identify any current or historical sources of ground contamination either on or in the general vicinity of the study site, it is possible to dismiss the requirement for investigative works entirely.

As the above demonstrates, by adhering to the phased approach stipulated by guidance, CET can ensure regulatory compliance without carrying out superfluous field work at significant cost.

Unfortunately, there are many projects where significant potential ground contamination is identified by the initial phases of risk assessment. This would trigger the requirement for remediation in order to ameliorate the risks posed to identified sensitive receptors. In such instances CET is able to appraise the various available options and formulate an appropriate Remediation Plan. This document would not only detail the nature of the remediation works to be undertake, but would also stipulate the methods of validation that would enable the successful completion of the works to be demonstrated to the regulatory authorities.

In our experience it is vital to liaise with the regulatory authorities during this process so that any comments or concerns they have can be addressed and incorporated into the Remediation Plan. This approach will ensure prompt discharge of the planning condition upon completion and issue of the final verification/ closure report.

Developers should therefore not be fearful of considering residential redevelopment of potentially contaminated sites and although this process may feel complicated, arduous and full of potential pitfalls, support from expert partners such as CET can simplify the procedure and contribute to a successful development.

Jeff Wilton is Managing Director at CET Infrastructure. Trusted by both the insurance and construction sectors, CET supplies a range of specialist outsourced services across the UK. Its services include home emergency response, claims management, subsidence investigations, drainage services, materials testing, environmental consultancy, geotechnical investigations and contaminated land surveys.

For more information, visit www.cet-uk.com