Introduction

Removing polluted sediment is an important activity in this period of time. It is a pity that so many locations are polluted as well on the land as below waterlevel.

During such projects several questions have to be answered:

Because of the variability of the thickness of the polutted layer it is very expensive to remove all pollution (much clean sediment will also removed), therefore an important question is:
    • Given a certain depth of removing how much pollution will be still in the soil after the project of sanitation?
  • How many samples and drills have to be taken to obtain a sufficient reliable map of the bottom and top of the polluted layer(s)
  • What is the relation between not removed polluted sediment and the volume that have to be removed?
  • How much clean sediment is removed given the fraction of not removed polluted sediment?

The last three questions involve the calculation of an extra dredging depth as a function of the sample density and the estimated spatial variability of the bottom of the polluted layer.

A geostatistical approach is needed to carry out such calculations.

A common problem encountered during the application of geostatistics is how to deal with outliers and to define areas with the same characteristics of spatial variability. It is obvious that a Geographical Information System with the possibility to display maps and the associated information about spatial variablity of the concentrations or the bottom of the polluted layer, is needed.
There are a lot of GIS-programs available on the market. But none of them offer enough functionality to carry out the job.
Therefor a new GIS has been developed (named: ExploStat) that meet the needs to carry out a spatial analysis to answer the questions above.