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Looking out on the River Lagan today, it
is hard to believe its waters and riverbanks
were ever smelly, dirty and polluted. The
water quality of the river was poor due
to several factors: There was a large amount
of "domestic" pollution entering the river
system from an outdated sewage system and
poor intermixing of the fresh water from
upstream with the denser seawater from Belfast
Lough and nitrates contained in the fresh
water. The Lagan's water level varied by
three metres between high and low tide so
at low tide unsightly smelly mud flats were
exposed as far up the river as the Ormeau
embankment. The bad smell was due to decomposition
in the mud releasing unpleasant smelling
gases into the air. This increased during
the summer months as the higher temperatures
increased the rate of decomposition.
The odour was particularly noticeable upstream
of the old McConnell Weir, at the outlet
of the Blackstaff River near the Gasworks
site. At this point, because seawater is
denser than fresh water, a pool of stagnant
seawater was trapped under the river water.
This reduced the oxygen levels in the river,
so increasing the rate of decomposition
in the mud. The banks of the river were
overgrown and deserted, wildlife was practically
non-existent and there were few or no fish
to be seen in the murky waters. Something
needed to happen to bring new life to the
river and re-establish the River Lagan as
a focal point for the city of Belfast, re-emerging
from over three decades of the Troubles.
Laganside undertook a successful infrastructure
led approach, which started with the building
of the Lagan Weir. The aim of the weir was
to create an attractive reach of water ensuring
a minimum level, which covers the mud flats
at every stage of the tide. Additional measures
were also taken to improve the water quality,
with a programme of river dredging and the
installation of an aeration system. In the
event of a dangerously high tide, the weir
also acts as a tidal barrage and can be
used to protect the city from flooding.
At a cost of £14 million, which was jointly
funded by Laganside Corporation and the
European Commission, the Lagan Weir was
one of the largest civil engineering projects
ever to be undertaken in Northern Ireland
at the time.
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Lagan
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