Memorandum submitted by CCNG Inc.
INTRODUCTION AND
SUMMARY
CCNG Incorporated is a US company based in Houston,
Texas. Its business consists of a diversified energy based portfolio
providing energy services and fuel management services. CCNG is
also active in natural gas exploration and supply, and is a leading
brine supplier to the energy industry in its region. Based on
its experience in the US, CCNG wishes to submit evidence to the
Committee to illustrate the benefits of brine cavity disposal
as an innovative waste management option in the UK.
The controlled use of brine cavities for the
deposition of solid wastes in a saturated brine carrier represents
a long term, safe and highly reliable method of waste deposition
which has been used since the 1950s. It has now been accepted
by Senior Officials at DEFRA and the Environment Agency as a sustainable
waste management option. Future regulations in the UK should acknowledge
the benefits of this activity.
USE OF
BRINE CAVITIES
In the UK some wastes are currently disposed
of to "brine cavities" full of saturated brine created
by the solution extraction of salt from deep underground salt
strata. Solid wastes from brine purification or soda ash production
are pumped into the cavities by pipeline, using saturated brine
as a carrier.
In the UK brine cavities are generated during
the extraction of saturated sodium chloride brine by a process
of solution extraction. After drilling of the initial shaft (450mm
diameter) which is lined to avoid any contact with surface and
sub-surface geology water is pumped to the target area to start
the cavity formation. The cavity is usually developed over a period
of five to 10 years to its full working capacity. The overall
life depends upon rates of extraction of the saturated brine but
when fully worked the cavity is a pear shaped void of approximately
one to two million cubic metres filled with saturated brine. During
the life of the cavity, while salt extraction is being carried
out, it is regularly monitored for shape and size both of which
can be controlled by specially developed sonar techniques. The
salt deposits are typically 200m thick overlain by 200m of boulder
clay. Each cavity is a mechanically stable structure, and represents
an independent cell and is not in any way connected to any of
the adjacent cells.
When a brine cavity is fully worked out it is
potentially available for the deposition of certain wastes. In
particular, they are currently used for the deposition of residues
derived from the purification of raw brine and the production
of soda ash using the Solvay ammonia soda process.
Disposal in a brine cavity brings benefits as
the salt is impermeable and "creeps" such that it is
self-healing. The stresses within the salt beds as a result of
solution extraction are well within the elastic limits of the
salt, and plastic deformation or other modes of failure will not
occur due to the inherent qualities of the rock salt strata. Dissolution
of the salt affecting the stability of the cavity does not occur
as the cavities are created in rock strata unaffected by water.
It is widely known that salt cavities are used
throughout the world including Europe for the strategic storage
of a range of materials such as methane/natural gas, ethylene,
propane, petrol, aviation fuel, crude oil and other hydrocarbon
storage. Whilst some of these materials are stored as normal operational
reserves of raw materials, other national strategic stocks may
be held for many years. Each is subject to an appropriate risk
assessment and licensing regime but the method used is widely
accepted as good practice due to the long term geological and
structural stability of underground brine cavities. The use of
similar geological cavities for waste storage throughout Europe
and the US is quite extensive.
Although the Landfill Directive prohibits the
deposit of liquid waste into surface or underground landfill,
it must permit the use of liquid, such as brine, as a carrier
to facilitate emplacement of solids, into a brine cavity.
CONCLUSIONS
DEFRA and the Environment Agency recognize that
brine cavity disposal is a safe and sustainable waste management
option. Wastes for disposal in underground brine cavity disposal
can therefore be inert waste or non-hazardous non-biodegradable
waste disposed of, with the use of brine as a carrier. Except
in the case of inert waste this would normally be subject to a
specific risk assessment to determine whether there might be any
unacceptable level of risk of environmental pollution.
It is important that the Government accepts
that the established waste hierarchy is not, and should not by
regarded as, a fixed and rigid system, but must allow for exceptional
cases.
For the reasons given above and, in view of
its long term environmental benefits the use of brine cavities
for waste disposal should, despite being classed as landfill,
in appropriate circumstances be seen as a desirable form of waste
management and should be regarded as an exception to the waste
hierarchy. Brine cavity disposal is operated under techniques
that have been developed for almost 50 years but should now be
considered as an environmentally beneficial and innovative waste
management solution for the present and future.
CCNG Inc.
24 December 2002
| 
