In addition to the three indicators on water quality in London, we have also looked at other data. This is part of the water quality section of the London State of the Environment Report 2010.
The other data we have analysed is data on:
- the number of water pollution incidents
- sewer misconnections
- bathing waters.
Water pollution incidents in London
Number of serious water pollution incidents
Serious water pollution (category 1 and 2) incidents in London have declined since 2002, and accounted fr only 2% of all water pollution incidents in London in 2009.
The major impact (category 1) incidents have dropped from six in 2005, to two in 2009, although this is an increase from zero in 2008. Significant impact (category 2) incidents have aldo dropped, from 32 in 2005, to 20 in 2009, which is also an increase since 2008 (figure 9).
The main cause of recorded water pollution incodents in London in 2009 was containment and control failure, which includes leaks or spillage of polluting substances. This accounted for 23% of incidents (figure 10). Fire and unauthorised activities were also major causes in 2009.
Cause of pollution incidents
The chart above shows that the main cause of recorded water pollution incidents in London in 2008 was containment and control failure, which includes leaks or spillage of polluting substances. This accounted for 29% of incidents.
Misconnections can occur when a house is extended, when people make other home improvements or when a new house is built. Untreated wastewater from misconnections can flow straight into local river or stream instead of going to the foul sewer and the local wastewater treatment works¹.
The Environment Agency identifies the public surface water outfalls with significant misconnection problems leading to public complaint. Thames Water Utilities carry out surveys of their drainage system to locate misconnections and persuade the owners to get the plumbing connected correctly, if the owner refuses then the local authority have the power to serve Notice under the Building Act to force the owner to carry out the work.
Between 2005 to 2009, action was taken to locate and deal with misconnections in 95 PSWO and address 17 Combined Storm Overflows (CSO). These were predominantly in the sewerage catchments for Beckton, Crossness, Mogden and Riverside sewage treatment works.
It is planed to address 17 CSO sites in the Lower Lee, and investigate 55 PSWOs in the Lower Lee, Brent and Crane, and Roding/Beam/Ingrebourne catchments.
London is a major city with EU-designated bathing waters at Hampstead Heath and the Serpentine within the Greater London area, also outside of London on the tidal Thames at Southend. These provide high quality recreation areas and are also important to tourism.
Compliance with the Bathing Waters Directive
The chart above shows that Hampstead Heath Ponds and the Serpentine have historically complied with the mandatory standards of the Bathing Water Directive, with the exception of 1998 when there was a failure at the Serpentine, and 2006 with a failure at Hampstead Heath Ladies' Pond.
Just outside of the Greater London area, there are eight bathing waters in Southend. These have shown a constant trend of compliance with the Bathing Water Directive, with only three failures recorded in the 1990s. Three of the Bathing Waters in Southend were awarded the Blue Flag, by ENCAMs, in 2009.
The number of sites in London and Southend achieving the more stringent 'guideline' standards is variable over time due to its dependence on the weather. Four sites were compliant with guideline standards in 2009