Unocal admits to Gulf discharges of mercury
The Nation
June 18, 1996
By JAMES FAHN

Declaring that contamination of the Gulf of Thailand is an ``issue of
concern', the head of Unocal revealed yesterday that his firm releases
around 90 kilogrammes of mercury into the sea every year.
        Brian Marcotte, president of Unocal Thailand Ltd - which has
been producing natural gas from offshore wells in the gulf since 1981 -
said his firm plans to install pollution control equipment which should
reduce mercury discharge levels dramatically by next year.
        Concern over the issue in Thailand has mounted recently
following reports that the fish around Unocal's platforms are being
contaminated by rising levels of mercury, a dangerous neurotoxin which
builds up in the food chain once it is released into the environment.
        Harmless to fish, mercury can cause birth defects and damage to
the central nervous system in humans if ingested in sufficient
quantities.
        Dr Piamsak Menasvesta, a marine scientist at Chulalongkorn
University who has carried out fish surveys on behalf of Unocal, has
reported that the number of fish around the platforms with mercury
levels over the standard has increased from two per cent in 1992 to
nearly 10 per cent in his most recent survey.
        Piamsak said he has been told by visiting experts that in the
United States, if the number of fish with high mercury levels are found
to exceed 10 per cent, American authorities would close the platform
down.
        However, Marcotte said that the impacts of Unocal's mercury
discharge are ``very localized', affecting the marine environment only
within 500 metres of the company's four production platforms.
        ``It is very unlikely to have had any impact on commercial
fisheries,' claimed the president of the US-based firm. According to
Thai statute, he added, Unocal has a 500-metre exclusive economic zone
in which it can prohibit fishing.
        Mercury is a natural contaminant of the gas produced in the Gulf
of Thailand. While most of the substance is separated and controlled,
Marcotte said, his firm has faced difficulties treating the
mercury-contaminated water - known as
``produced water' or ``toxic brine' - which is pumped up along with the
gas and then discharged into the sea.
        ``We have been pursuing this issue since 1985, and very
aggressively since 1989,' Marcotte told The Nation. ``[But] there's just
no [control] technology found to be acceptable, either here in Southeast
Asia, in the North Sea or in North America.'
        Unocal officials said the average mercury content of the
produced water it discharges is around 200 parts per billion (ppb).
However, the mercury content fluctuates greatly, they said, and at times
can rise to as high as 800 ppb.
        Thailand does not have an offshore standard for mercury
discharges, they added, but in the North Sea the standard is 300 ppb.
        Thailand has set a standard for onshore mercury discharge at
five ppb, but this applies to fresh-water mercury discharges which could
affect drinking water, they said.
        Unocal's latest efforts to treat its produced water include the
use of a purifying device known as a hydrocyclone which can reduce the
mercury content of waste water down to below 30 ppb, according to
Unocal.
        The company plans to install eight of the devices - which cost
Bt14 million each - by next year. Last year, the company announced net
earnings of Bt6.5 billion on sales of Bt211 billion.
        In August of this year, Unocal will test out an alternative
solution of injecting the toxic brine back into disused wells drilled
into seabed of the Gulf of Thailand, Marcotte added.
        The petroleum company already used this method in July of last
year to dispose of 1,459 barrels of mercury-contaminated sludge, he
said. The operation was carried out in conjunction with the DMR and was
carried out successfully, he said.
        However, Prakan Boonchuaydee, director of the Pollution Control
Department's Division of Toxic Substances, said he was not aware this
had been carried out and questioned whether it was an appropriate
solution as it may lead to further long-term damage to the environment.
       According to Piamsak, the natural gas concessionaires in the Gulf
of Thailand were given 60 days to resolve the mercury discharge problem
at a meeting held one month ago by Thailand's National Committee for the
Rehabilitation of the Gulf of Thailand. The Department of Mineral
Resources (DMR) was placed in charge of overseeing the pollution control
activities.
        ``We are committing ourselves to timeframes with the DMR,'
Marcotte said. ``We have every intention of having full retrofit
facilities on our platforms by 1997,' at which time the company hopes to
achieve mercury discharge levels of under 10 ppb.
        According to Marcotte, the toxic sludge and the free mercury
that condenses out of the gas accounts for 65 per cent of the total
mercury produced by Unocal's operations.
        Another 28 per cent is contained in the hydrocarbon condensate
drawn from the wells, most of which is exported to the United States,
while three per cent is contained in the sales gas sent through
pipelines to the Petroleum Authority of Thailand's gas separation plant.
        The produced water contains the remaining four per cent of the
mercury produced by Unocal, which amounts to around 90 kgs of mercury,
or approximately seven litres, per year.