In United Kingdom, Brownfield is defined as "previously developed land" (or PDL) that has the potential to be redeveloped, but need not always refer to land that has been used for industrial and commercial purposes. Though a government survey in UK shows that the 2008 target of constructing 60% of new homes on Brownfields has been achieved, there are still 150,000 sites under the Brownfield sector. In comparison, there are about 80,000 and 100,000 Brownfields in Australia.
The nature of contamination of Brownfields could be real or perceived. When a land is declared a Brownfield, it is possible that the contaminants could include deposits of heavy metals, harmful pesticides and toxic hydrocarbons. This contamination can result from improper environmental management and inefficient waste disposal practices, or unwarranted use of contaminated fill to level the site. It could also result due to unsealed underground storage tanks and random spills in industrial, agricultural or commercial activities. Specific industries and common land activities have been tied to site contamination. The extent of contamination may vary based on the rate and extent of the concerned activities. Brownfield sites pose legal and financial burdens on a community. However, these sites can be redeveloped into powerful engines for economic vitality and community pride.
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Their remediation or redevelopment provides developers and investors desirable sites with existing infrastructure systems for industrial, commercial, residential, agricultural, public and recreational uses. In most cases, connections to water, sewer and energy resources is readily available along with good access to transportation networks. Hence, communities benefit from the remediation of Brownfields by facilitating new businesses, jobs and increased productivity, which otherwise would have been underutilized and unproductive. For example, Commonwealth of Massachusetts in the United States reported that after 20,000 Brownfields sites had been addressed, about 8000 jobs were created thus increasing tax revenues by approximately $1 billion (NALG 2004).
Geotechnics and Environmental Engineering are two branches which assist in developing a deeper understanding of contamination assessment procedures and various remediation solutions of Brownfields. In the consequent sections, we shall discuss these techniques and formulate a unified approach to deal with this issue. We will then critically review this approach with a case study.
Geotechnical Procedures to Assess Properties of the Soil
Geotechnics plays a very important role in Brownfield assessment. Founded in 1985, Geotechnical Engineering involves investigation of existing subsurface conditions and materials in order to determine its physical, mechanical chemical properties for assessing risks posed by site conditions. It also monitors site conditions, earthwork and foundation construction. It is important to establish the sub-soil characteristics of a Brownfield considering its potential to shrink or swell with change in natural water content. Table 1 lists all the geotechnical tests conducted