By Craig Faull, WSP I Parsons Brinckerhoff Section Executive, Land Restoration & Ground Engineering
The redevelopment of idle, contaminated commercial and industrial properties or ‘brownfields’ sitting in many of our communities presents a prime opportunity to bolster our economy and our communities while improving environmental health. The remediation of urban brownfield sites also offers us a highly sustainable way to manage, at least in part, the need for increased space in our cities.
Brownfields are typically located on industrial or commercial property where chemicals have historically been used. The perceived ‘higher cost’ and longer timeline associated with brownfield redevelopment compared to developing clean ‘greenfields’ has often limited this form of redevelopment with liability concerns also acting as a deterrent.
The benefit of ‘sustainable remediation’ that takes account of end use requirements and looks to deliver outcomes with minimum expenditure, typically will likely far outweigh any perceived or real risks. If remediation evaluation takes account of end use requirements and analyses the cost benefit ratio, brownfield remediation need not be complex, lengthy or overly expensive.
The cost-benefit ratio
Embarking on site remediation can prove daunting for many developers. With significant upfront costs, developers can often discount any kind of land remediation as an option.
However associated cost and timelines fall within a broad spectrum with the degree of remediation work varying considerably from site to site. For example, future residential sites will usually require a higher standard of remediation than a commercial site, such as an office block or car park, and will typically take longer to treat and prove more costly.
Sustainable remediation offers one practical option as it strikes a balance between the cost and benefit of brownfield development both now and into the future.
The sustainable remediation process has been accurately defined by The UK Sustainable Remediation Forum as being ‘the practice of demonstrating, in terms of environmental, economic and social indicators, that the benefit of undertaking remediation is greater than its impact, and that the optimum remediation solution is selected through the use of a balanced decision-making process.’
When considering remediation as an option, it is important to engage with key stakeholders early. By doing this we can build likely constraints into a concept design. Building in this degree of flexibility goes a long way towards ensuring we achieve a balance between development needs and contamination constraints.
If the concept design is tailored to meet contamination constraints, remediation could be as simplistic as creating a barrier to the contamination for instance; by capping open space areas; or by placing a sub slab vapour extraction system underneath a building.
Developing a targeted site environmental management plan will also assist in mitigating future risk. Whatever the chosen remediation method, it is important that the process and the technology used are tailored to achieve the best result while factoring in cost, time and environmental objectives.
Sustainable remediation in action
Every brownfield site differs depending on previous land use and the nature of the contaminants that have been present. A range of different ‘clean-up’ techniques and degrees of remediation can be applied.
It is only through proper analysis of a brownfield site that sustainable management decisions can be made about the extent of proposed remediation, and repurposing of the land. An example of two such projects, one in Queensland and the other in South Australia, perfectly illustrate this point.
The projects centred on the demolition and remediation of two bulk fuel terminals. Each site had very specific and different contamination profiles. This required us to undertake detailed soil classification and a subsequent human health risk assessment to define achievable (and minimum) clean up goals which satisfied the regulatory and contractual obligations that were imposed on the site tenants.
Sustainable remediation objectives were met, as soil treatment requirements (and subsequent costs) were considerably reduced as a consequence.
The sustainable remediation objectives for the project also extended to the demolition phase ensuring that demolition waste was recycled, repurposed or reused wherever possible.
In addition to recycling concrete, hardwood timber and scrap steel from the sites, the recovery extended to the onsite treatment of over 1 million litres of contaminated ballast water to a level that rendered it suitable for reuse. The remainder was disposed to sewer under a Trade Waste Approval – saving a substantial amount of cost in liquid waste disposal.
If brownfield remediation options are assessed and optioneered carefully, developers have a viable and sustainable urban land re-use option at their disposal that is neither too onerous nor too costly to implement.
Brownfield redevelopment projects can also provide an immediate infusion of investment in areas that previously lay vacant as well as contributing to more vibrant and healthy communities.
Another long-term economic benefit of brownfield redevelopment is its impact on public infrastructure costs as the majority of brownfield sites are located in developed areas with redevelopment maximising the use of existing public infrastructure.
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