Clean-up techniques for substrates
Flushing (datasheet)
(sand, stones, rocks, marsh)
Low pressure hoses are used to dislodge residual clusters
of pollutant, to wash and rinse rocks, boulders and stones,
or to move effluents towards a collection point. Other than
underwater agitation, flushing has other uses during final
clean-up, such as removing sand at the foot of rocks, spot
boring to check for buried pollutant etc.
Sediment
removal (datasheet)
(sand, stones, rocks)
As a result of beach growth, oiled rocky areas as well as
patches of pollutant are often buried under a layer of clean
sediment. This cover of clean sediment should therefore
be removed in order to reveal the buried pollution. This
can, according to the case in hand, be done manually, with
pressurised water or mechanically.
Botanical
worksites (datasheet)
(sand, stones, rocks)
Sections of vegetation, in dunes or on rocks, may be polluted
to a varying extent. The decision may be made to intervene
in such areas. If so, these operations should be subject
to a decision and specific recommendations made by expert
botanists. Such worksites, supervised by environmentalists,
were set up after the Erika spill. The term “botanical
worksite” encompasses the sometimes extremely painstaking
and time-consuming operations of scraping, brushing, scything,
manual sand screening, suction and collection. The aim is
to remove the maximum amount of pollutant without damaging
the plant cover or the soil more than it is already damaged.
Effluent
recovery (datasheet)
(datasheet)
(all substrates)
This is an important part of clean-up. Clean-up should not
simply come down to transferring pollution from the shoreline
into the sea; the pollutant which is removed must not return
to oil nearby unpolluted sites or sites that have already
been cleaned. Recovery of effluents from washing or cleaning
operations is a must, no matter what the technique, the
substrate, the pollutant. Recovery is a worksite within
the worksite, which must be set up before clean-up operations
begin.
Effluent containment can be achieved by gravity, drainage
or hosing, with one or two collection points. The systems
used should be suited to the site layout and the nature
of the substrate: natural or dug trenches and basins. It
is useful to take advantage of the relief of the ground,
to identify natural flows and receptacles, to use them but
also to not hesitate to adjust them. The use of a shore-sealing
boom can be considered on certain beaches. Recovery can
be ensured by pumping, mop nets, absorption and/or filtration.
Use
of sorbents (datasheet)
(all substrates)
The use of sorbents in this second phase of clean-up essentially
aims to facilitate recovery of oil removed during washing
operations. Sorbents are used either to line reception trenches
for waste waters, or to stuff booms used on the water. This
process is more selective for small quantities of oil than
pumping.