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Construction on man-made and remediated brownfield sites

ECSMGE Session 3

Audun Hauge graduated with a MSc in geotechnical engineering from the Norwegian Institute of Technology, department of civil engineering, University of Trondheim in 1975.

After working in industry he joined the Norwegian Geotechnical Institute (NGI) in 1985 as senior geotechnical engineer. Since 1988, his main focus has been environmental geotechnology. He has been project manager for major research and development projects and been involved in several projects on biological treatment of hydrocarbonpolluted soil.

Since 1995 contaminated sediments has been a area of focus at NGI and Hauge has been project manager for all work connected to remediation of Oslo Harbour. He has been central in building up of technical knowhow and the group of environmental geotechnology at NGI, and since 1996 he has been heading the environmental engineering division.

Hauge has extensive experience in offshore soil investigations for oil platforms as well as underwater installations and pipelines. Has also been specialist adviser to oil companies on special site investigation techniques.

Co-authors of this article are: AP Oen, E Eek, K Rudolph-Lund and G Breedveld of the Department of Environmental Engineering, Norwegian Geotechnical Institute and L Trauner, Univerza v Maribru, Maribor, Slovenia.

Global urbanisation has caused increased pressure on the environment. This is especially true in Europe, where 70% ofthe population lives in urban areas. The driving forces have been construction and concentration ofindustry, building ofinfrastructure and housing.

The environmental impact created by urbanisation takes place at different scales ranging from local to global. Local impact may concern areas ofhigh economic, recreational and ecological value. Ifthe development for society is 'positive' and the population has the feeling that their standard ofliving is increasing, the awareness ofdamage and negative impact on the environment is low until impact on human health is detected.

Between 1950 and 1970, there was much research and development of new industrial processes. However, this period caused large negative impacts on the environment and human health. Much oftoday's brownfield is abandoned industrial land from that period. And while it is a threat to the environment, these sites also present interesting investment opportunities.

A system to assess the environmental risk and calculate the efficiency of remedial measures is vital for finding the optimal method for remediation ofthese sites.

Industry impact Industry in the last century was often close to city centres and to a river, lake or the coast. The recipients ofemissions or contamination from the industrial processes were staff and, through sewage, surface water and groundwater, plants and animals in the rivers, lakes and sea.

The effects of exposure to highly toxic substances is obvious, causing, among other things, acute damage to human health and killing fish. And while these substances may easily be identified, where they cause damage by accumulating in the food chain they are more difficult to detect. Because ofthis, many brownfeld sites have very complex contamination which requires comprehensive and expensive site remediation.

In most industrialised countries, a very important task has been to establish a tool for evaluating the environmental risks a brownfield site may present. Risk assessment ofcontaminated ground requires fundamental knowledge about human- and eco-toxicology, soil chemistry and hydrogeology. Computer tools are used to perform these analyses and calculate the extent ofadverse effects to the environment.

The risk, in conjunction with soil contamination, is determined by the interaction ofthree elements: the source ofcontamination, how it spreads and its target. Risk assessment should provide enough information to allow the right decisions related to mitigation possible. Over the latest decade many industrialised countries developed their own tools and guidelines for risk assessment.

Organising the specific problems in a systematic manner, as shown in the flowchart, helps locate the main elements of risk to human beings or the environment. It also explains why certain paths represent little risk and consequently can be ignored.

Source Release mechanisms Spreading path Intake Recipient Economic incentives Recently there has been increased focus on risk assessment combined with cost benefit analysis to find optimal alternatives for remediation ofcontaminated sites. The Norwegian Geotechnical Institute has carried out research to develop a system for finding these alternatives.

A classical tool for cost benefit analysis gives figures for the economical benefits from a project to assess if it is commercially viable.

The hazard attached to pollution is assessed through environmental risk assessment and is used to estimate the economic value ofthe pollution in the analysis. A very important and difficult task is to estimate the economic value ofhealth and life quality. To take these questions further, methods for handling of uncertainties are required.

Risk based cost-benefit analysis is based on the calculation and evaluation oftotal costs for alternative remediation measures. Risk in this context is not the same as environmental risk. Total cost (C T) is calculated as all costs for implementing a measure, C is cost for design and construction and R is the risk. R is calculated from the probability of failure (P f) ofthe measure, multiplied by the cost offailure = C f. The formula is as follows (James et al, 1996):

CT= C + (P fx C f)(1) This allows evaluation ofeconomic risk for alternative measures if the environmental objective for the measure is met. For any environmental objective, C fis the cost ofimplementing a more expensive but safer measure, if a cheaper measure does not meet objectives.

Maximum engineering costs and the effect of collecting more data can also be assessed. However, the calculation ofthe probability for failure introduces uncertainties which may have significant influences.

Cost efficiency The effect of a remediation measure may be quantified as the change in one environmental indicator, such as the concentration in soil or groundwater, transport ofcontamination, effect on organisms, or biodiversity in the ecosystem. The costs are defined as direct costs for the measure and not the value ofexternal effects.

Measure efficiency To assess the measure efficiency NGI has developed a method based on quantifying the spreading of environmentally-unfriendly substances as an indicator. Spreading can be monitored before a measure is implemented, and through simple models the effect of different measures on different paths for spreading can be calculated. After implementation, the effect can be controlled by monitoring.

The method accounts for different spreading of substances in three different phases during a remediation project (Figure 1):

lThe situation before start of remediation. Usually unacceptable spreading is one reason for implementing a measure.

lDuring implementation ofa measure. The spreading will in most cases be larger than in the previous phase lAfter implementation - the permanent phase. The spreading has decreased significantly and close to zero. The decrease must be so significant that the increased spreading during implementation is compensated for within a reasonable time period.

Measure efficiency can be described as the reduction in spreading of pollution from a site during an estimated period:

By using this formula the effect of a measure may be calculated with the maximum effect being 1, equal to 100% effect. Different measures can be evaluated by calculating the measure efficiency.

The basis for this method is that spreading of pollution is proportional with the environmental risk (damage to humans, organisms and the ecosystem) and the environmental risk is opposite to the gain of benefit and value. These effects may be difficult to estimate exactly, however there is an obvious qualitative relation between reduced environmental risk and psychological, political and economical values.

References James BR, Huff DD, Trabalka JR, Ketelle RH and Rightmire CT (1996). Allocation ofenvironmental remediation funds using economic risk-cost-benefit analysis: A case study. Fall 1996, Ground Water Monitoring and Remediation, 95105.

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