Dredging and disposal of sediments in Finland Dr. Jani Salminen

Outline Why are we concerned about dredging and disposal of sediments? How do we manage environmental protection in the context of dredging and disposal of sediments in Finland? Site history and investigations prior to dredging Guidelines instructing the permissions given for dredging and disposal of sediments Choice of disposal site Minimization of environmental impacts at dredging and disposal sites

Why are we concerned about dredging and disposal of sediments? ”Wild” practices resulted in unsuccessful cases No limit values for pollutants in disposed sediments No requirements for disposal sites Case Kuuva, in Turku archipelago

Case Kuuva disposal site = angry citizens, fishermen, summer cottage owners etc. = very bad reputation of dredging & disposal ?

National guidelines for dredging and disposal of sediments First given in 2004, revised in 2015 Not legally binding but in practise quite strictly obeyed Is applied to marine and inland water sediments Only for large projects (>500 m3) that need a permission from the environmental authority Given by the Ministry of Environment Used by water constructors like cities and the Finnish traffic agency, consultants, authorities There are numerous small dredgings by private summer cottage owners (operated by small businesses). They inform the local authority, which decided whether a permission is needed or not        

National guidelines Gives instructions on when and how to investigate the site where dredging will be done Sites are often impacted by polluting activities (harbours, water traffic (anti-fouling agents like tributyltin TBT), industry, shipyards, waste water treatment plants and so on Site history needs to be known It is likely that there are high concentrations of pollutants ( ) in the sediments that will be dredged To avoid pollution of the water environment, these concentrations need to be known Sediments samples have to be taken and analysed to do this For presumably non-contaminated sediments and sandy sediments no sampling and analyses are required Underwater cultural heritage needs to be investigated, evaluated and potentiallyprotected in collaboration with National Board of Antiquities        

Several samples need to be taken Figure: Jyrki Hämäläinen GTK Photo: KVVY Photo: Jyrki Hämäläinen GTK

More samples are required when the site has a high risk for pollution and no earlier data on pollution in the sediments exist Number of individual sampling spots and subsamples in a composite sample at a dredging site with high risks of pollution and no previous data on pollution in the sediments Minimun number of sampling spots Minimun number of subsamples in a composite sample Dredging area (1000 m2) Number of sampling spots and subsamples in a composite sample at a dredging site with low risk of pollution or with good existing datasets on pollution distribution Minimun number of sampling spots Minimun number of subsamples in a composite sample Dredging area (1000 m2)

Several contaminants need to be analyzed Pollutant Cannot be disposed to open water No disposal limitations due to pollution Can potentially be disposed to open water depending on the suitability of the disposal site Oil Organotins

Placement of the sediments Three options: At the see/lake at a disposal site which has a permission by an authority For sediments with relatively low concentrations of pollutants ( ) At the shore behind a semi-(im)permeable barrier Often used for moderately polluted sediments ( ) At land Most expensive, hard to find place for muddy/clayey sediments For polluted sediments ( ) Water quality monitoring Rainfall Water flow through the barrier Water flow through disposed sediment Sea/lake/river Disposed sediment Construted semipermeable barrier

Open-water disposal sites need to meet criteria to get a permission Assessment is based on geological and biological properties Geology, seafloor type, topology, water flow conditions Disposed sediments need to stay where they are placed! Impacted area needs to be estimated Nature conservation areas Fishing areas Fish reproduction areas Recreational areas

Conditions given in permissions for dredging and disposal sites For dreding sites: During the operating and for some time thereafter Time limitations (spring/summer, windy days) Fish populations, physical & chemical parameters (turbidity, nutrients, contaminants) For disposal sites: Long-term monitoring during the operational period (several years… few decades) How much sediments have been disposed How well do the sediments stay where they have been put (soundings, sampling) Water quality in the surrounding areas Limiting the spread-out of the fine particles upon disposal (weather conditions)

Environmental protection measures during dredging SILT CURTAIN Photo: www.canadianpond.ca Photo: Kainuun Sanomat USE OF ENVIRONMENTAL DREDGE HEAD, NAVIGATOR, STOPPING THE WORK WHEN THE CONDITIONS ARE WINDY SILT CURTAIN Photo: Sukellustyö Perlant Photo: National Traffic Agency

Thank you for your attention! jani.salminen@ymparisto.fi