26/04/2005 - Thames Water
was fined £60,000 on 25 April after
a blockage at one of its sewage treatment
works caused raw sewage to pollute an Oxfordshire
brook killing an estimated 12,000 fish.
Oxford Crown Court heard how Thames Water
Utilities Ltd, of Clearwater Court, Vastern
Road, Reading delayed responding to a blockage
at a Sewage Treatment Works despite a series
of alarms notifying their control centre that
there was a problem. The unmanned sewage treatment
works at Cholsey, near Wallingford, Oxfordshire
discharged raw undiluted sewage into the Cholsey
Brook in September 2003.
The case was originally heard before Didcot
Magistrates’ Court on 13 April when Thames
Water pleaded guilty but the case was committed
to the Crown Court for sentencing.
The incident was caused after a blockage
formed at the inlet to the sewage treatment
works, causing the undiluted sewage to divert
into the plant’s storm tanks. These are designed
to operate during wet weather conditions preventing
the sewage system from being overloaded with
excess water, a discharge from them should
only occur during exceptionally wet weather
once the high volume of rainfall dilutes the
sewage. However this incident occurred toward
the end of the long hot summer of 2003 when
the concentration of the sewage was high and
flows in the Cholsey brook were low.
Oxford Crown Court heard how on Sunday 7
September five alarms were activated at the
works during a six-hour period alerting Thames
Water staff that sewer levels were high, storm
tanks were filling and control mechanisms
and pumps were failing. Given the dry weather,
staff should have immediately suspected a
blockage, however each alarm was looked at
individually and the attendance priority was
left to the following day. This allowed the
tanks to fill to capacity and then discharge
their contents untreated into the brook.
The Environment Agency was called to reports
that the Cholsey Brook had turned cloudy and
had a strange smell. Environment officers
arriving at the scene took water quality readings
and met up with Thames Water staff who admitted
there had been a problem at the sewage treatment
works but that it had already been rectified.
The investigating officers walked along a
stretch of the brook downstream of the treatment
works and noted dissolved oxygen levels, necessary
to support aquatic life, were low, and ammonia
levels were higher than normal but not critical.
The officers could only see a handful of dead
fish from the bank.
However, the full extent of the sewage’s
impact only became apparent the next day once
the pollution had cleared. An Environment
Agency fisheries and ecology team was deployed
to establish the full extent of the fish kill
by using a net to scoop the dead fish entangled
in vegetation along the brook’s bed. The study
found that the pollutant had had a significant
impact killing hundreds of fish including
pike, roach, bullheads, and chub as well as
over ten thousand sticklebacks.
Senior Enforcement Officer Rod Gould said:
“This was entirely avoidable, you can have
the most advanced computerised, remote sensing
system in the world – but you still need a
sufficiently trained and capable human to
interpret the readout.
“Thames Water is a multi million pound business
and it has already been criticised for its
priorities. Whilst an individual alarm may
be of a low priority it does not take a genius
to work out that five in quick succession
from the same works indicating a storm event
during one of the driest summers on record
should merit an immediate response.
“Thames Water only antagonised the situation
by being slow to co-operate with our investigation
after the event.”
The case was brought under the Section 58(1)
of the Water Resources Act 1991. Thames Water
was fined £60,000 and was ordered to
pay £4,350 in costs.
Members of the public can report environmental
incidents to the Environment Agency by calling
freephone 0800 80 70 60.
