Mapping and analyses of the sediments to be dredged
Investigations of dump sites and their suitability
Prediction of spill risks from dredging and after dumping
Suggestions of spill-reducing measures
Monitoring of spill rates during dredging
Monitoring of long-term effects in dredging and dumping areas
Calcareous bedrock makes the spill from this dredger very visual.
State-of-the-Art Tools and Methods
Mapping sediment properties
Combined with a sediment map based on sonographs, an "intelligently" interpolated pollution map can be created, thus eliminating two sources of uncertainty that is inherent in "traditional" sediment pollution studies: Sampling of stratigraphic units with differing history, and interpolating over bottom areas with differing conditions. The result is a state-of-the-art sediment property map.
We have the expertise to measure the geomorphological processes in the sea, as well as the circulation in lakes and reservoirs. The range of techniques, including recording current and wave meters, drifters, and dye dilution methods, guarantees that there is a method for every situation.
Modelling sediment transport and responce
The sediment transport and the geomorphological responce can be modelled using our own MESTSEM software. The results can be confirmed by measuring with the Sedimeter®, which also is useful for detecting unwanted bed erosion or sedimentation in connection to dredging operations.
We have the expertise it takes to measure the sediment concentration in the water using turbidimeters, as well as the density stratification whether caused by temperature, salinity, or turbidity gradients. Regardless of the the size of the water body, we can find a suitable instrument alternative.
We can design a control system for dredging operations using turbidimeters to quantify the spill, either in terms of concentration or in terms of flux, and similarly, we can assist in creating a station network for quantifying sediment transport in rivers and into reservoirs.
Ecological consequence analysis
The effects on the environment of a given spill depends on many factors. We can set up a reference group with experienced scientists from a range of disciplines, that together will be able to prepare a state-of-the-art consequence analysis.
Example: Polluted sediments in Järnsjön
The sediments in this small lake in Småland, Sweden, were leaking PCB to the river Emån that is flowing through it. The pollutant originated from a paper pulp industry upstream, that now has gone over to a more environmental-friendly process. But the legacy of the past was in the sediments, and continued to pollute the river waters downstream.
Hydroconsult contributed with a prediction of the turbidity during the dredgings, which proved accurate. The graph below illustrates how well the permission was met.
Sediment concentrations downstream Järnsjön during the dredgings were consistently below the limit set by the government permission (graph edited from the Järnsjön project page, Hultsfreds kommun).