markets; regulators (legislative and environmental); research and monitoring of the seabed and impact on other users;

technology and data management;

materials; resource exploration and development.

The conference also included a site visit to Hanson Aggregates Nederland NV in Amsterdam, Europe's largest marine sand and gravel processing plant outside the UK. The plant produces 1.3 million tonnes per annum, working 24 hours per day, five days a week in three shifts.

Hanson's two largest dredgers supply the wharf, these being Arco Dijk (capacity of 8,300 tonnes) and the Arco Humber (capacity of 8,000 tonnes) with sand and gravel dredged from the English Channel and North Sea. This aggregate is then processed and distributed by barge to customers in and around the Amsterdam area.

Kevin Seaman of the British Marine Aggregates Producers Association (BMAPA) gave a paper that provided a UK perspective on resources and use of marine sand and gravel.

Seaman said the UK marine aggregates industry is second in scale only to Japan, with 22-26 million tones of marine aggregate being dredged annually from more than 70 UK licenses, much of it coming from licenses in the southern North Sea off eastern England. Other important industry centres are the Bristol Channel and Irish Sea, where sand is supplied without the need for onshore processing, noted Seaman.

Seaman said the industry in the UK was continually assessing new dredging areas.

Most importantly, huge deposits have been identified in the eastern English Channel, which, if licensed, can be exploited in place of the diminishing reserves of the southern North Sea, securing supplies for many decades to come.

Ronald de Vree of Certificatieinstelling BMC in the Netherlands gave an overview of European standards for marine sand and gravel extraction. He said CEN TC 154 has been working on the preparation of European Standards and test methods for aggregates, which will be introduced between this summer and can be used alongside national standards until June 2004, when the European standard will replace the existing national standards for aggregates.

David Harrison of the British Geological Survey told the conference that marine sand and gravel make an important contribution to the overall provision of aggregate materials in most countries in north-western Europe. He explained that the aggregates dredging industry has expanded rapidly over the past 40 years and continues to grow, as acceptable land-based sources of sand and gravel are being depleted.

Vera Van Lancker of the University of Ghent gave a paper about the use of sonar techniques for a resource evaluation. She explained that seabed mapping and classification techniques based on sonar technology have been evaluated for their effectiveness in resource prospecting and for their ability in discriminating benthic habitats in soft bottom sedimentary environments.

From this, cost-benefit and time-efficient monitoring tools and strategies were put forward, with applications for seabed mobility studies and benthic habitat mapping. These have had promising results, enhanced through the GIS-integration of very-high-resolution side-scan sonar and multibeam data, and the major environmental parameters, she explained.

Szymon Uscinowicz of the Polish Geological Institute gave a paper about exploration and extraction of sand and gravel resources in the Polish Exclusive Economic Zone (EEZ) in the Baltic, noting that the gravel deposits in the Polish EEZ are a notable resource.

Poul Erick Nielsen of the Danish Forest and Nature Agency took as the subject of his paper marine resources in Danish waters, their exploitation potential and sustainable management.

He explained that, in the last decade, marine resources have become increasing important for the Danish national supply of aggregates for construction, land reclamation and coastal protection.

In the Danish EEZ, marine aggregates are dredged in up to 150 designated dredging areas, located in coastal waters as well as on the continental shelf in the North Sea and Baltic.

Total average yearly extraction is 5-6 million m 3, depending on local and international demands.

Nielsen noted that certain projects have required an increase in sand extraction - including Arhus harbour (which required 12 million m 3of sand fill) and beach nourishment on the west coast of Jylland, which requires 3 million m 3ofsand annually.

Best practice: resource evaluation and dredging management, was the title of a paper by Ian Selby, representing BMAPA and Hanson Marine Ltd. He explained that resource management is a key factor in the operation of a successful marine aggregates business and is integral to the development of sustainability.

Assessing the impact of sand extraction on shore stability: project for a methodological framework, was the title of a paper presented by Florence Cayocca, of Ifremer, the French marine research organisation. Cayocca explained that French regulations require that dredging companies provide an environmental impact assessment (EIA) in order to obtain an authorisation to extract sand, gravel or carbonate sands, but said the content of such EIAs has not been precisely defined.

Cees Laban of the Netherlands Institute of Applied Geoscience TNO gave a paper about monitoring morphological features in relation to sediment transport and ecology and Sian Boyd of CEFAS in the UK gave a review of current state of knowledge of the impact of marine aggregate extraction in the UK.

CEFAS is currently undertaking a range of research programmes on behalf of the UK government to provide the scientific data needed to guide and advise the development of policy in this area and ensure that debate is evidence-based.

She highlighted the fact that aggregates dredging can lead to the creation of 'dredge tracks' or depressions on the seabed, changes in the composition of sediments and effects on benthic fauna. The study has concluded that the effects of extraction are evident up to nine years after the cessation of dredging; that assumptions of recovery rate within two to three years are not always applicable; and there is some evidence that areas of the seabed have changed from a gravelly to sandy substrate as a result of aggregate extraction.

Patrik Schotte of the Fund for Sand Extraction in Belgium focused on Belgian governmental control of the extraction of marine sand and gravel, and noted that, today, every vessel operating in Belgian waters is equipped with a sealed electronic monitoring system, and every aggregate producer wishing to extract sand or gravel in Belgian waters has to obtain a concession from the minister responsible for economic affairs.

Ad Stolk of the Ministry of Transport, Public Works and Water Management, North Sea Directorate, the Netherlands, spoke about legislative and environmental developments in the Netherlands, whilst Brian Marker of the Minerals Planning Division in the Office of the Deputy Prime Minister spoke about policy and consent procedures in the UK.

Timo Nijland of TNO Building and Construction Research in the Netherlands gave details of a phenomenon known as Alkali-Silica Reaction (ASR) in concrete. First mentioned in Dutch literature in 1957, this phenomenon has become much more widespread, affecting bridges and roads built using aggregates. He noted that new guidelines on ASR prevention were published last year.

Jason Golder of the Crown Estate in the UK spoke about using GIS in seabed management, Peter Davis of MARIS BV in the Netherlands gave a paper about EU-SEASED, a European searchable Internet meta-database of seafloor samples, and Chris Vivian of CEFAS gave a paper about the UK approach to environmental assessment of sand and gravel dredging proposals.