The Great Stour Project - River Pollution

Light industrial estates

(PHOTO)

A number of light industrial estates exists on the outskirts of Canterbury, including Wincheap, Broad Oak Road, Vauxhall Bridge and Hersden. Chemical or detergent spillage, and the washing and servicing of vehicles seem to be the main risks from such locations. Increased runoff and siltation during the construction phase of these sites can be a problem. Light industrial units may contribute warm water, increasing BOD (cool water holds more oxygen than warmer water); inert suspended solids (such as china clay or coal tip waste) can reduce light levels, smothering established wildlife and plants in the river.

Oil can form a surface film on the river reducing oxygenation from the atmosphere above. Detergents create unsightly frothing, and can dissolve attachment structures in invertebrates and fish; they are a major source of phosphates. Acids, toxins, metals and alkalis can all present added difficulties. Lead and aluminium residues are not significant locally, because of the alkaline nature of the river flow, fed by springs issuing from the Chalk. These contaminants are worse in areas of 'soft' acidic water, such as Dartmoor (granite) or Derbyshire (Millstone Grit), where pH level are lower.

A whole range of vehicle products including engine oil, brake fluid, antifreeze, body fillers, and spray paint can find a route into local watercourses via drains. Cleaning products (bleach, disinfectants, detergents) and decorating materials (paints, stains, varnishes, preservatives, etc.) can all put pressure on the sewerage system, or can be accidentally flushed into nearby streams.

Major incidents involving fuels have fallen in recent years, because of tighter regulations on the handling and storage of oil, for example, bunded storage. There have been two oil pollution incidents from the Broad Oak Road estate over the past five years, but generally industrial effluent has not posed a serious threat to the Great Stour.

See: Landfill (old) and brownfield sites for further details on industrial pollution.

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