The remediation of contaminated sites can have a fundamental impact upon assessments of value. Specifically, the selection of appropriate remediation technologies can be crucial. The value of an interest in property is dependent upon the interaction of four variables: incomes receivable by the investor, costs incurred, the distribution of cash flows over time and the relevant yield or time value of money.

In this context an assessment of value requires forecasts of all the above variables. If the valuation is for market purposes the valuer will try to replicate the expectations of the market. If an assessment of investor worth is required the forecast will be determined by the specific circumstances and expectations of the individual investor. The perceived accuracy or anticipated error of such forecasts is crucial to the usefulness/reception of the valuation.

Where a site is contaminated the cost element, and hence the approach to site remediation, become of particular importance. The remediation of a contaminated site may be achieved through a number of alternative technologies. Broadly these may be classified into civil engineering and process based techniques. Each technology influences the above variables in slightly different ways.

The distribution of costs over time and impacts on the nature and intensity of site uses will potentially affect both appraisal methodologies and results. By categorising technologies on the basis of generic cost characteristics, anticipated life spans and impacts of site use, potential value effects may be more clearly understood.

Additionally, the familiarity of the market and/or individual investor with each technology may alter the degree of confidence with which future cash flows are estimated. One consequence of these perceptions may be the alteration of the relationship between the scientific and economic effectiveness of technologies. In many cases this may mean a developer or investor settling for a familiar 'low tech' solution when, in scientific or indeed economic terms, the optimal procedure would be different.

By combining information on available remediation technologies with property investment appraisal methodologies, uncertainty in the value of a contaminated property investment may be more readily quantified. Additionally, by specifying a solution optimal in both scientific and economic terms investment returns may be enhanced.