Management of abandoned and contaminated land - Environmental Deterioration and Contamination: Problems and their Management - page 188

Soil remediation intends to eliminate or change the contaminating chemicals in the
soil so that it results in an “acceptable risk'' situation. The remediation technologies
are introduced in depth in Volume 4.
The widespread solution of contaminated soil removal (“changing the soil'' or
“dig and dump'') is in retreat due to its multiple disadvantages: the original soil is lost,
new soil is needed, the contaminant and its risks are transferred to another place, the
removed contaminated soil should be treated or disposed of. Transport is accompanied
with high costs and risks. Nevertheless, in some cases it may be feasible if there are
underground buildings at a contaminated site, or if a soil treatment plant is in the
vicinity, where the soil can be treated and reused efficiently after treatment. “Changing''
the soil of a contaminated site may be acceptable if the risk is extremely high and
clean soil is available on site or close to it. The above conditions are however rarely
encountered.
Urgency of soil remediation may depend on the scale and character of the risk, and
on the socio-economic aspects, specifically the expected and lost benefit from future
land use. Remedial technologies may differ to a large extent in their time requirement.
Ecofriendly, natural and biological technologies generally require more time, but are
soft and gentle to the local ecosystem and the soil's biota, ensuring biological stability
and ecological health of the treated soil over the long term. Rapid physical, chemical
or thermal methods may destroy soil life and their costs inversely relate to the time
requirement. There are good solutions for the enhancement of biological technologies
by soft interventions such as ventilation, heating, controlling of pH, redox potential,
temperature and moisture content, friendly additives, nutrient supply.
In selecting the remedial technology, the contaminant concentration and chem-
ical form in the soil are also determining factors. The target concentration depends
on the land uses and the receptors; the human and ecological targets may be dif-
ferent (see also Volume 2). Remediation technologies have limitations in fulfilling
the target of contaminant concentration; removal or degradation efficiency is never
100%, most of the physical, chemical and mainly biological processes have high time
requirement, and the heterogeneities in the environment also hinder fast and high
performance. The targets for soil and groundwater or water and sediment are not
independent from each other. If the groundwater is used as drinking water, the soil's
target concentration should harmonize with the target concentration of the groundwa-
ter by taking into account the equilibrium partition of the contaminant between solid
and water.
Policy requirements and risk-based targets can be fairly different because the reg-
ulations are not fully risk-based all over Europe. In Hungary, for example, the former
soil screening concentrations in the regulation 10/2000 comprised one multipurpose
(B value) and three intervention values (C1, C2 and C3) related to land sensitivity.
Risk-based target value (D value) was only a voluntary option. The intervention con-
centrations were typically misapplied as target concentrations for different land uses.
Therefore, in 2005, the regulation was modified: the intervention values were elimi-
nated from the regulation and the obligatory application of a risk-based site-specific
target concentration entered into force. It was a fortunate solution because staff at
public authorities and vendors have learned the methodology of risk assessment and
the calculation of the risk-based target concentration.