Environmental Engineering Reference
In-Depth Information
salmon on a daily basis by the owners. However industrial development around
waterside locations usually proceeded without regard to the quality of water.
Not only was the River Irwell utilised as a valuable means of transport but the
factories clustered along its banks also released their waste products into the
river. Water was often seen as a 'convenient dumping ground to carry away
industrial and sewage effluent; out of sight was out of mind' (e.g., Hendry et al.
1993
). The last salmon was caught in the Irwell in 1856 (cited in Boult & Hendry
1995
), and during the 1870s regattas and rowing races were abandoned due
to the condition of the Irwell (Struthers
1993
). Canals, rivers and especially
docks throughout the UK became progressively more polluted and the aquatic
environment was severely degraded (White et al.
1993
).
During the second half of the twentieth century, however, industrial use of
waterways and docks declined. Changes in local manufacturing industries,
shifts in patterns of trade, restrictive trade union practices and increasing
competition on North Atlantic shipping routes all combined to cause a decline
in the market for cargo handling services (Gray
2000
). Ocean-going container
ships and tankers also grew to such a size as could not be accommodated in the
locks of the MSC. By the late 1970s, traffic fell to such an extent that the MSC
Company seriously considered closing the upper reaches altogether (Gray
2000
). Owing to its poor environmental quality, the River Irwell which feeds
the MSC was neglected and allowed to deteriorate further. All that remained
in 1984 following the closure of the docks at Salford was an abandoned 60-ha
site comprising a polluted water course (Radway et al.
1988
). The dramatic
decline in dockland activity that began in the mid 1960s was not confined to
Manchester, and the resulting dereliction was characteristic of many other UK
ports with a previously strong industrial base (Kivell
1993
).
Background to water quality problems
The Mersey Basin drains an area of 4 570 km
2
in the North West of England
and comprises three major waterways: the Rivers Mersey and Irwell and the
MSC (e.g., Hendry et al.
1993
,
Fig. 14.1
). Collectively these are among the most
organically polluted in the UK (Hendry et al.
1993
). Indeed the area of the MSC
examined in this chapter, the Turning Basin located between Trafford Road
Bridge and Mode Wheel Locks (
Fig. 14.2
), was recorded as Grade 4 (grossly
polluted) by the Environment Agency in
1990
(EA
1990
).
Such poor water quality in the upper MSC has been ascribed to discharges
from waste water treatment works (WwTWs), storm sewage overflows, indus-
trial effluent and agricultural activities (Webb
1993
) from the Rivers Irwell,
Medlock and Irk (Hendry et al.
1997
). Mass flux analysis (APEM
1990a
,
b
)
revealed that the River Irwell in particular was a major source of organic
loading into the MSC, with high levels of biological oxygen demand (BOD)
and ammonia combined with low dissolved oxygen (DO). Such a scenario was
