Dredging
What is dredging?
Dredging is the term given to digging, gathering, or pulling out material to deepen waterways, create harbours, channels, locks, docks and berths, desilt lakes and keep river entrances and approaches to boat ramps clear. The material removed during dredging can vary greatly and can be any combination of rocks, clays, silts or sands.
Why dredge?
Dredging takes place to:
- maintain the depth in existing ports, harbours and channels to provide ready and safe passage for commercial and recreational vessels.
- create new or deeper access or berths for vessels. This may mean the deepening and widening of channels and anchorages as well as the excavation of basins and marinas from areas of previously dry land.
- to provide material for specific purposes, eg. beaches in coastal areas subject to erosion are sometimes ‘renourished’ with sand dredged from other areas.
Impacts of dredging
Dredging activities have the potential to change the environment.
Marine environment/ communities
At the sites of dredging and disposal the seabed and associated communities are disturbed and for some distance, suspended sediment may cause turbidity in water and increased sedimentation on the bottom.
Water quality
Depending upon the nature of the dredged material, its disturbance from the sea bed may lead to changes in the chemical composition of the water. Eg. many toxicants such as heavy metals and organic contaminants tend to stick to particulate matter and sink to the sediment. Some of these contaminants are very persistent in the sediment and some may change their oxidation state during burial, which alters their solubility. If these sediments are disturbed, the contaminants can be released to the water column and affect marine life.
Human health
As well as toxicants, the nutrient elements, particularly nitrogen and phosphorus, which control the rate of marine plant growth can also be released from sediments during dredging, with a risk of triggering algal blooms. Not only nutrients are important here - many of the toxic algal species, which are a health risk for consumers of shellfish, have a resting stage (cyst) which lies in the sediment. If dredging disturbs these cysts when conditions are favourable, a bloom of toxic algae may be caused.
Another biological risk from dredging involves the transport of species in dredgers from one port (or even country) to another. Exotic marine pests are now recognised as a major environmental concern and steps must be taken to minimise their transport to new environments.
The EPA's Best Practice Environmental Management Guidelines for dredging .
The Environment Protection Authority (EPA) has produced Best Practice Environmental Management Guidelines for Dredging, essential reading for any organisation planning to dredge or dispose of spoil in the Victorian marine, estuarine or river environments. The guidelines address the environmental issues and controls involved in dredging. A copy of the Guidelines can be gained from the Environment Protection Authority, www.epa.vic.gov.au/publications
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Gaining approval to dredge - Coastal Management Act 1995
1. Coastal Management Act consent - application.
If you plan to dredge you must gain consent from the Minister or delegate under the Coastal Management Act 1995 to use and develop coastal Crown land.
Coastal Crown land is the sea bed, and banks and any Crown land within 200m of the tidal influence of rivers and streams entering a sea, bay or inlet in Victorian waters.
Applications should be made on a specific application form for dredging. This form can be downloaded below or contained within EPA Best Practice Environmental Guidelines for Dredging. Applications made on this form should meet all requirements of the Guidelines. Applications to dredge should be directed to your local regional DSE Office.
Dredging Application Form (PDF - 29 Kb)
2 Application referred to EPA.
Applications to dredge received by DSE may be referred to EPA for expert advice in relation to compliance with the Best Practice Environmental Management Guidelines for Dredging. This referral is as a request for further information in accordance with section (39) (2) of the Coastal Management Act 1995
3. Decision on an application to dredge.
- Consent to the dredging activity;
- Consent to the dredging activity subject to conditions; or
- refuse to consent to the dredging activity.
The applicant will be informed in writing of any decision made regarding the application.
Taking into account the advice received from the EPA, the Minister or DSE delegate will decide to either:
Other approvals that may be required.
Where new dredging works occur in an area subject to a planning scheme a planning permit is also required.
Proposals likely to involve large environmental, social or economic impacts may also be subject to an EES under the Environmental Effects Act 1978.
On the open coast, the dumping of dredged material, other than beach renourishment and sand by-passing operations, must satisfy the requirements of the Commonwealth Environment Protection (Sea Dumping) Act 1981, administered by the Environment Protection Group of Environment Australia.
In an area of national significance such as a Ramsar listed site, eg. Westernport Bay, the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999 may apply. It is the proponent’s responsibility to determine whether the action/ activity proposed is a ‘controlled action’ under that Act. Contact www.deh.gov.au/assessments for assistance.
Further information on dredging can be sought from your local DSE Regional Coastal Planners.
Contact the DSE Customer Service Centre on 136186 for more details.