Impacts on land

The timing of sailing to the dredging area, undertaking extraction and returning to the wharf is strongly influenced by tides, as well as the weather, therefore the timing of unloading a vessel will, inevitably, vary from day to day. Since unloading takes place at wharves in industrial areas of ports this does not cause unusual levels of noise and traffic to nearby residents. Distribution of processed material to the market can be limited to daytime working hours. This causes noise and traffic but since wharves are located in industrial areas of ports they add little to the overall level of disturbance. Overall, impacts of processing and transport are similar to those at on-shore sand and gravel pits but are focussed in industrial, rather than rural, areas. Discharges of water from washing the aggregate can be returned to the sea or estuary and are small enough not to significantly affect the local environment. Solid wastes are managed in a similar way to wastes from other industrial units. Management of wastes and emissions are controlled through permits issued and enforced by the Environment Agency.

Sustainability

Extraction of aggregates from the land, dredging from the sea and use of recycled materials and by-products all have environmental impacts and potential benefits but in varying degrees. Marine extraction has some potential advantages. Extraction from the sea helps to reduce the amount of quarrying from the land. The location of wharves in key coastal market areas helps to reduce the distance travelled by lorries which would be greater if equivalent supplies came from quarries on land. Also some marine processing operations are able to load material on barges to be taken to the place of use (e.g. to the London Olympics site). This helps to reduce carbon emissions compared with supply from quarries. However, it is important to compare the full range of costs and benefits of different sources when developing policies for aggregates supply M0029. ALSF studies have been undertaken to develop approaches to assessing the relative sustainability of supply of sand and gravel from the land compared with that from the sea M0017, M0021. Potential advantages of marine extraction include: The industry has set out a sustainable development strategy and monitors its performance M0046.