Cobbles
This type of beach introduced two main problems: oil can penetrate much deeper into the substrate so making it very difficult to clean; and the physical surface makes vehicle mobility more difficult. Oil was usually removed using brushing and scrapping with degreaser. 2 special techniques were used, Pit washing and Surf washing.
Pit Washing
Pit washing was used here for the first time to clean cobbles. Large pits were dug to hold between 50 and 100 t of material and lined with a heavy duty plastic liner, in fact, 2 liners were used with a sand layer between to reduce the risk of puncture. Cobbles were added and washed under high pressure with water and degreaser (De-solvit). Oil was then skimmed off the surface and cleaned cobbles returned to the beach.
In some cases, skips were also buried and used as the pit (e.g. Telpyn, Glen Beach).
Berm Relocation and Surf Washing (AEA Technology)
To be covered by Dr. Tim Lunel.
Shingle
Shingle poses the same problems of oil penetration and vehicle mobility as cobbles. Normally the oil was scooped off mechanically; on beaches with difficult access oil was recovered manually using hand tools, then shovelled into bags.
4 special techniques were used, Surf washing as for cobbles, Stone washing, Tractor harrowing and Bioremediation.
The stone washing technique mimics that used to polish gemstones. On several beaches a washing station was set up in which oily material is added to a lorry-mounted cement mixer together with sea water, and degreaser. The abrasion of the cobbles against each other loosens the oil and the assembly is left to separate. The main advantage of using cement mixers is that the oily run-off water can be contained in watertight skips and the oil recovered from the surface using skimmers. The washing rates are in the region of 6 t per hour.
The Tractor harrowing technique uses agricultural tractors to dig deep into the beach material, thereby releasing oil into the surf zone where it is dispersed naturally. Care had to be taken with this method to avoid releasing too much oil and so causing ecological problems and reoiling. Where used, this technique was carried out after close consultation with the Environment Group.
Bioremediation
To be covered by Dr. Tim Lunel.
Sand
As with cobbles and shingle, soft sandy beaches can bring problems with vehicle mobility and with increased
penetration of oil into the beach. This in turn can lead to larger quantities of beach material being removed to
clear the oil. It was important to monitor how much sand was removed from certain sensitive beaches to
minimise erosion. The mobile oil was scraped off and flushed into trenches.
The oily sand was removed by shovelling and subsequently disposed of. The oil remaining after cleaning dry
sand beaches forms nodules or tar-balls of oils sand up to 50 mm diameter which had to be recovered manually.
Tractor harrowing was also used.
Mud
Many techniques which are effective on other beach surfaces may do more harm environmentally than good if
applied to mudflats. Physical removal of the oil may cause severe damage to the substrate and vegetation and
application of dispersants may cause the oil to penetrate deeper into the substrate and harm animal and plant life.
Where possible, it may be preferable to leave the oil to disperse naturally. There are also problems with this type
of substrate with respect to the load bearing capacity and its ability to support vehicles as the terrain will also
vary considerably with the tide. If cleaning was considered necessary the oil was removed by low pressure
flushing. As this type of shoreline is usually wet on the surface, water flushing floats off the oil into a collection
area. It is important to use only low pressure water to avoid pushing oil into the substrate.
