The first stage of shoreline clean-up aims to remove the maximum amount
of pollutant from the shoreline to stop it being reclaimed by the sea, via
waves and tides, and contaminating other sites. This first stage of clean-up
requires different techniques depending on the pollutant and whether it
is floating at the water’s edge or has washed up onto the beach.
Skimming, pumping and suction are the most common response options in the event of a major oil spill by a fluid pollutant that has formed large accumulations. These operations can be carried out using agricultural pumps, slurry spreaders and sanitation trucks, as well as pumps and pump-tank units specifically designed for oil. This equipment can be complemented by surface scraping carried out by public works machinery or specially adapted scraper/skimmer mechanisms.
Manual recovery is systematically carried out whatever the pollutant, the site and the extent of the pollution. It is often the main, if not the only, means used in the event of small-scale or scattered pollution. It remains one of the most common options used to respond to a major spill. It is particularly well adapted to scattered
beachings in the form of freshly deposited tar balls or patties, before they are covered over or sink into the sediments. Manual recovery is the method used by default on sites where all other techniques are impossible, either through limited accessibility for equipment or because of the local environment’s high level of sensitivity.
On beaches, mechanical recovery using public works machinery or specially designed equipment (sand screeners, rollers…) is a very productive method. It is however limited by the accessibility of sites to large or heavy machinery.
Public works and agricultural machinery, which is widely available and
can be manoeuvred even on awkward sites, is often used for various tasks
• scraping off thick layers of pollutant
• collecting and transferring offsite large quantities of pollutant and polluted materials
• clearing away clean sediments to uncover buried pollutant.
Selective sand screening equipment, which sieves sand to remove tar balls, has been developed inspired by solid waste screeners. These machines are well adapted to the recovery of tar balls and semi-solid patties on dry sand. The large machines are towed and the small ones self-propelled. Oleophilic rollers are used to remove semi-liquid pollutant deposited on damp sand.
Rock surface washing agents
There are two sorts of products which can be used to wash rocks depending on whether or not the pollutant is to be recovered below the area washed.
• If the pollutant is to be recovered, a non emulsifying washing agent should be used. The pollutant can then be recovered using sorbents or small skimmers.
• If the pollutant is not to be recovered, an emulsifying washing agent should be used. The pollutant should then be dispersed in the seawater. The use of this type of agent is necessarily restricted to small-scale pollution in areas of low ecological sensitivity.
As with all substances designed for use in the natural environment (effluent discharge), these products should undergo tests to check that they are acceptable from an environmental point of view.
Recovery on land
The use of a technique known as flushing, involving washing using low pressure hoses, remobilises fresh clusters of pollutant deposited on the surface or trapped in the crevices of rocks in order to channel them to a collection point.
The technique of flooding, the saturation of a beach with water, involves creating a flow from the upper part of the foreshore to flood the area of sand that needs washing. This can be put in place using a perforated flexible pipe, parallel to the water’s edge, that is supplied with seawater by a high flow pump. The flow sweeps away the freed pollutant with additional aid from hoses. Lighter pollutants float on the water, where they can be contained by a boom and recovered.
Surfwashing involves moving polluted pebbles or sand down to the water’s edge and depositing them in piles at low tide, to expose them to wave action. The waves free the pollutant trapped in the grains of sand or stuck to pebbles, ensuring natural washing by abrasion and collision. The waves disperse the piles and redistribute the sediments over the beach with the following tides. The freed pollutant is deposited on the surface, above the sediments. It can then be recovered by hand or caught using nets.
Initial clean-up worksites