New problems or old?
Greenfield or brownfield, port construction projects can unearth a range of environmental challenges. Felicity Landon reports
From coral reefs to mangroves, protection of sensitive environmental areas is an accepted priority in port construction projects – but it’s not only greenfield projects that raise environmental issues.
Those embarking on port construction or expansion projects on brownfield or previously industrialised sites can literally find themselves dredging up the sins of our forefathers, as the less than pristine legacy of previous generations come back to haunt us.
“In more industrialised areas, you can have centuries of industrial waste that has been in the river, settled into the bottom and in some cases been stabilised and covered up by later sediment – but when you dredge, you disturb that stable situation,” says Ben Lieberman, senior planner at US-based consultant Louis Berger. “Nineteenth century stuff is OK until you send a grab bucket down there to deepen the channel and disturb it, spreading out potential contaminants.”
Although not strictly a port example, he mentions the former Ithaca Gun Factory site in New York State as an example of the legacy of 19th century manufacturing – heavily polluted with lead, asbestos, arsenic, mercury and uranium, the site has been the subject of a huge demolition and environmental clean-up programme, and concerns have included water run-off from the demolition site.
“Many waterways in Europe and elsewhere have a history of industrial use and use as transportation corridors, and these historic industries are likely to have left environmental impacts,” he says.
Polluted or not, any increase in run-off and silt – anything that might affect water quality – must be considered in any port construction project, he warns.
Environmental issues are different depending on whether it’s a greenfield project in a developing country or developments in more industrialised areas – but in all cases, the issues can be very complex.
“We recently had a port project in Mauritius; right off the coast of the area where they want to do the land reclamation and build another terminal, the charts show extensive coral reefs. But the other legacy there is sugar plantations. To plant all the sugar, many of the trees were cut down, which resulted in quite a bit of soil erosion, and some tricked down to rivers and settled on coral reefs. The coral reefs are not all dead – but certainly they are damaged and not in the condition suggested on the charts.
“We did a masterplan for Santos, Brazil; and there are extensive mangrove swamps, which, a little bit like coral, are an environmental red flag and something you have to pay a lot of attention to.”
People don’t like it, but there is a price to be paid for caring for the environment, says Mr Lieberman. “You need to acknowledge at some point that it is worth spending some money on protecting this. In many cases you have mitigation projects, where you create new wetlands outside of the direct impact area, for example.”
All of this is happening against a very cost-conscious industry, of course; and Mr Lieberman says: “I am not sure that cost-efficient goes hand in hand with green, but if you value the environment, environmental sensitivity is the cost of the development process – to some extent, it can be seen as a minor part of the economic benefit you get from a new port development.”
Singapore-based DHI Water & Environment was heavily involved in the preparation of a technical report on dredging/port construction around coral reefs. Tom Foster, from DHI Singapore, chaired the PIANC working group, and Matthew Jury, head of environmental services at DHI Singapore, was a member of the group. The report was developed in cooperation with the UN Environment Programme (UNEP), and forms the international guideline for implementing best practices of environmental assessment and management of port projects around shallow warm water coral reefs.
DHI has recently been appointed to co-chair a new PIANC working group on dredging and port and waterway construction around coastal plant habitats, to be co-chaired by Tom Foster.
“The working group will collect and analyse available information and ‘good practice’ case studies on dredging and port construction around marine and intertidal plant habitats and their associated communities,” says a spokeswoman for DHI. “These ecosystems such as mangrove, seagrass and salt marshes critically contribute to climate regulation, providing a strong driver for their protection.
“Based on the collected knowledge, the new working group will establish guidelines on how to minimise impacts on the coastal ecosystem services and/or to benefit from these.”
Innovative harbour design can solve a number of problems in one go, as demonstrated by DHI’s project at Hvide Sande, a fishing village on Denmark’s North Sea coast.
Facing problems of limited water depths and heavy sedimentation in the harbour’s access channel, the authorities wanted to increase navigation depth from 4.5 metres to 6 metres, while also reducing sedimentation in the channel.
For five decades, Hvide Sande Harbour has been protected by one breakwater at the northern side of the harbour entrance – but this has blocked the natural drift of sediment along the coast, so that maintenance dredging to remove about 170,000 cu m per year is required to ensure 4.5 metres depth.
Jesper Ulrik Fuchs, DHI head of projects, ports and offshore, says the solution is a combination of streamlined breakwaters and capital dredging. The new set of breakwaters will protect the harbour entrance and also create an increased speed of flow past the harbour mouth, thus reducing sediment deposits in that area. Dredging of the coastline in the updrift area will also help to maintain the water depth.
Construction began in 2011 and is due for completion later this year – after which, maintenance dredging will be unnecessary for keeping 4.5 metres depth, or will be similar to today’s requirements to achieve 6 metres.
DHI’s approach was based on a combination of advanced morphological modelling tools, include analysis of wave conditions, overall sediment and coastal impact. The study also included hourly wave, wind and water level measurements, as well as weekly soundings of the harbour access channel.
Another of DHI’s “clever solutions” is its Decision Support System for Ports, says Mr Fuchs.
The company has set up a system for the Port of Hanstholm on the Danish North Sea coast; by combining DHI’s numerical hydrodynamic and wave models with wind and pressure forecast, the company has created a web-based system giving five-day forecasts of wave and mooring conditions for all the port’s quays, as well as wave energy potential for a local wave energy test site.
This enables the forecasting of conditions that could make some manoeuvres hazardous, such as entering the port with a strong current at the port entrance, or mooring at specific quays – the port master and ship’s captains can plan loading/unloading operations and mooring around the conditions.
“This is an ongoing project at DHI, since we are assisting on a large expansion of this port, doing most of our ‘usual’ stuff like metocean conditions, sediment transport, port layout optimisation, physical model test, etc.,” says the spokeswoman.
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