Beneficial use of contaminated sediments
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Hello,
the following abstract has been submitted for WASCON'97 (Interna-
tional Conference for the Environmental and Technical Implications
of Construction with Alternative Materials; 4 - 6 June 1997, The
Netherlands;for more info about the conference fax: +31.43.6014039).
The abstract describes an alternative way of handling and beneficial
use of contaminated sediments as part of a remediation plan for the
river Maas in The Netherlands.
Perhaps other people are working on a similar subject. An exchange
of experiences could then be well worth-while.
Hoping to hear from you soon,
Kind regards,
Andre Kok and John Heynen (e-mail: J.J.M.Heynen@BWD.RWS.minvenw.nl)
Ministry of transport, public works and water management;
Civil Engineering Division;
P.O. Box 20000;
3501 LA Utrecht;
The Netherlands
fax: +31.30.2857952
Beneficial use of contaminated sediments within the Maas river-
system
A.P. Kok, A.L. Hakstege, H.P. Versteeg, J.J.M. Heynen
Abstract
After two subsequential periods of severe flooding by the river
Maas, the so-called Delta-plan Large rivers has been conceived by
the Dutch government. The project aims at diminishing risks for
future floodings. Also, the river Maas should be adapted to improve
the river for shipping. Both targets are joined in the so-called
"Zandmaas/Maasroute"-project. Several options for improving water
management are available: deepening, broadening, a more gradual
slope of river-banks, construction of parallel conduits, etc. There
are a number of alternatives possible to reach the desired targets.
Each alternative will have a different environmental impact. There
may be about four alternatives to be considered in an environmental
impact assessment.
Sustainable development is one of the key-words in this project:
e.g. river banks will be designed in an ecological friendly way
(gradual slopes, non-erosion protected etc.).
An important issue in the design-process and environmental impact is
the presence of heavy metal contaminated sediments. This
contamination is related to industrial activities upstream and
sedimentation processes in the river-system and is consequently
diffuse. According to present Dutch legislation most of the contami-
nated sediments and soils (ca. 5 million cubic metres) should be
stored in large deposal sites and/or cleaned, mainly because of
exceeding the Dutch intervention level for zinc. However, contami-
nated sediments are still transported by the river: a cleaned up
area would soon be re-contaminated.
Therefore, beneficial use of contaminated sediments, e.g. in nature
development under environmentally sound conditions, is being con-
sidered. An important starting point is the stand-still principle:
re-use of contaminated soils or sediments is acceptable if there is
no local deterioration of environmental quality.
Items to be further defined are: assessment of environmental soil
quality in relation to local back-ground levels and how to
distinguish "Hot-Spots" (which still should be removed).
The following criteria can be used:
- bulk concentration of contaminants: this should be related to
future sediment quality;
- leachability of contaminants: leaching tests on contaminated
sediments (Dutch column test NEN 7343) have shown that leacha-
bility of heavy metals is low and often below detection limits
(despite relatively high bulk concentrations);
- ecotoxicological effects, e.g. by means of bio-assays: an
advantage of this method is an impact assessment of the total
cocktail of contaminants.
When re-use of contaminated sediments within the river-system is
considered, there should be no extra negative environmental effects
on the considered location. The future plan for the considered
location (recreation, industry, nature development etc.) should be
taken into account.
All the above mentioned criteria and assumptions will be used for
judging possibilities of beneficial use of contaminated sediments. A
judgement-system will be developed in the next year and consequently
be validated within the framework of Dutch environmental legisla-
tion.
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