Contaminated sites management - step 3: detailed investigation

The objectives and urgency of remediation are established

If the preliminary investigation shows that the polluted site is in need of remediation (= contaminated site), the authorities can demand that the party responsible for remediation performs a so-called detailed investigation. This is basically justified because the results already available have only served to establish the possible need for monitoring or remediation. A detailed investigation discloses exact information about the kind and extent of the pollution as well as its potential impact, thus building on results already obtained. This data is necessary in order for the authorities, together with the party responsible for remediation, to establish the urgency of remediation and the general remediation objectives.

The goal of remediation: Stopping emissions at the source

The primary purpose of remediation is to restrict pollutants from a contaminated site penetrating a protected natural resource to such an extent that over the long-term no need for remediation exists. This means that the levels for water, soil and air that would necessitate remediation as defined by the CSO are not exceeded any more.

Although remediation is aimed at the protected natural resource, this does not mean the goal must be complete removal of the pollutants from the contaminated site. For that reason the remediation objectives as a rule do not prescribe the residual pollutant concentrations that are permitted to remain at a site following its remediation. For, as already noted, it is not the pollution itself, but any possible impact it may have on natural resources that is critical.

Flexibility in setting remediation objectives

It occasionally happens that strict CSO remediation objectives for a contaminated site that endangers ground or surface waters are simply not reasonable or cannot be implemented. Exceptions can be made in such a case under certain circumstances: The CSO allows a certain room to manoeuver in balancing environmental impact (ecobalance of the remediation measures), remediation costs and quality requirements for natural resources. Often a reasonably priced and environmentally sound remediation approach is to be preferred to a radical solution if the former leads to a considerable improvement of the environmental situation even if not quite attaining the remediation objectives. The "reasonableness" of the remediation costs are thus viewed in terms of the costs of possible remediation alternatives and not with regard to the budget of the perpetrater who is obliged to pay.

Remediation urgency

In cases of contamination presenting a great hazard due to environmentally hazardous pollutants, imminent release or the great vulnerability and significance of the protected natural resource being affected, remediation must be commenced as quickly as possible; indeed, immediate measures must be undertaken if necessary. In particular where an existing utilisation (e.g. drinking water supply) has already been impacted or is in immediate danger, remediation cannot suffer any delay. Thus the urgency of remediation is determined by the effective environmental hazard and not by any pending conversion of land use (construction project) or corresponding available funds.

For sites rated as requiring remediation simply for reasons of a substantial danger or concentration levels slightly exceeding threshold levels, the urgency of remediation is determined by estimating if and when an effective, environmentally relevant outcome can take place for a protected natural resource. In particular, urgency is not generally required at a site where the pollutants causing the contamination dissipate over time, whose emissions continue to abate over time and where no vulnerable natural resources are at an immediate risk.

Immediate measures

Immediate measures can be necessary in the wake of extraordinary events such as accidents with liquids presenting a hazard to the water supply or where in the course of a construction project an unexpected, acute, "hidden" hazard comes up during site investigations. Immediate measures are particularly to be taken where high levels of contaminations are found in drinking water supplies.

Immediate measures are intended as the first line of defence in stopping an acute hazard. In an extreme case, this can mean that a site must be evacuated or that the use of the natural resource has to be officially prohibited (e.g., the temporary abandonment of a drinking water supplies). Moreover, immediate measures are intended to prevent (as far as possible) any further penetration of the pollutant into the environment or the protected natural resource. One such measure, for example, is the immediate removal of a pollutant, particularly a "hot spot" (by excavating the polluted material or pumping off the pollutants in an oil spill).

Even though there is generally little time available to plan and implement immediate measures, great care is nevertheless in order: No one wants to endanger later remediation solutions or obstruct options by a rash decision.

Further information


Aids to enforcement



TransSim 2.1 (ZIP, 32 MB, 18.06.2021)Mathematisches Simulationsmodell zur Abschätzung des Schadstofftransportes in der ungesättigten Zone bis zum Eintritt in das Grundwasser. Hilfsmittel für Altlastenfachleute.

PlumBumRisk 1.0 (ZIP, 736 kB, 30.03.2012)Excel-Tool zur Gefährdungsabschätzung bei Schiessanlagen.

Last modification 10.02.2021

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