Water pollution from contaminated sites - an NRA perspective

Compiling a national inventory of contaminated sites has been one of the key steps taken in many countries with progressive land remediation policies.The UK continues to muddle along without one.

In April, however, the National Rivers Authority (NRA) is due to publish a report setting out what it knows about water pollution caused by contaminated land in England and Wales, explaining the legal and practical obstacles which often block its efforts to secure improvements, and making proposals for the way forward.1The report is by no means a comprehensive overview of the problem.Only one of the NRA's regions was able to come up with an estimate of the number of contaminated sites in its area.The others, it says, have so far only identified "a number of sites which were causing water quality problems."

The exception was the Severn Trent region, which has 186 sites known to be, or suspected of, causing pollution of surface or groundwaters.Of these, 45% are landfills.The total is an underestimate because it is based largely on officers' existing knowledge of pollution problems rather than any survey work.

The report does, however, contain more than a dozen case studies illustrating the variety of threats posed to the aquatic environment by contaminated sites.These include:

  • In the NRA's Southern region, leachate from a restored landfill contains high levels of ammonia and chloride, threatening a nearby public supply abstraction borehole as well as an adjacent watercourse.Leachate is now being pumped out of the site as an ameliorative measure.

  • Another landfill, this time in the South West, accepted wastes from the wool scouring industry.Heavily contaminated areas of the site were removed prior to its redevelopment as an industrial estate.Nevertheless, it is now leaking permethrin, dieldrin and lindane insecticides into the river Tone.

  • Trichloroethylene spills at an industrial estate in the Thames region pose a threat to a public supply borehole 1.5 kilometres away.Very high levels of the solvent - about 200mg/l - have been detected in the underlying aquifer.The site owners have agreed to implement a clean-up programme, although this has yet to begin.

  • A former chemical manufacturing site in the Thames region now occupied by a brick factory is contaminated with zinc, ammonia, bromide and bromate.Leachate escaping into a nearby river is causing it to fail its quality objective, and "there is also an impact on a standby water abstraction point".

  • The former British Rail Engineering works at Swindon, complete with its own gas works, has caused unspecified contamination of the underlying aquifer and of water flowing across the site to the river Ray.Because of the size of the site and its piecemeal redevelopment, site investigations "have been sparse".The report notes that "relationships with the developer have improved of late", but pollution risks remain.

  • "One of several sites causing pollution in the Anglian region" is a dry cleaning business.Chlorinated solvents from this source have caused extensive groundwater contamination, reaching concentrations of 40µg/l in the borehole of a nearby brewery and up to 1,500µg/l in others.The most heavily contaminated soil has now been removed.

  • A site where tar-based insecticides were produced has caused severe contamination of Chalk groundwater in the NRA's Southern region.Investigation boreholes have revealed very high levels of phenols (up to 28mg/l) and polycyclic aromatic hydrocarbons (up to 1.7mg/l).The current owner has agreed a clean-up strategy.

  • The site of a former smelter in the South West region which was also used for the disposal of chemical wastes is contaminating local surface and groundwaters.The main contaminants are lead, zinc, cadmium and other metals.No remediation proposals have been forthcoming from the owners.

    Other examples include a landfill in the North West which is leaking PCBs (ENDS Report 191, p 6), a waste dump near a West Midlands copper refinery (ENDS Report 189, pp 7-8), a ship-breaking yard which was the subject of an NRA prosecution that has since contaminated sediments with PCBs (ENDS Report 201, p 37), and a Cornish daffodil farm which polluted local streams with the organochlorine insecticides aldrin and dieldrin (ENDS Report 182, p 7).

    As these older cases have highlighted, the NRA's current powers are of limited utility in securing the clean-up of contaminated sites. The NRA's main powers are in section 161 of the Water

    Resources Act 1991. This enables it to carry out pollution prevention works and recover costs "reasonably incurred in doing so" from the person who "caused or knowingly permitted" the problem. However, the report points out that it is "improbable" that section 161 could easily be used for large-scale clean-up programmes.

    The first obstacle is a lack of cash. Even if just 10% of the known contaminated sites in the Severn Trent region were to be cleaned up, the capital cost would run to £10 million at a modest £0.5 million per site.

    In 1990, the NRA asked the DoE for £34 million over three years to fund investigation and remediation work, but was turned down. The DoE continues to hold the reins, in that it would have to sanction any expenditure by the NRA in this area in excess of £0.5 million.

    The second problem is at the cost recovery stage. The activities which caused the contamination often occurred long ago, the sites may since have changed hands, and the present owners may be unable to pay even if the NRA succeeds in a court action in attributing liability.

    Thirdly, the NRA does not in any event wish to see its role as a regulator compromised by having to retain responsibility for the long-term operation of treatment systems, which would be a necessity at many sites.

    There is a further difficulty. When the DoE rejected the NRA's £34 million bid in 1990, it suggested that other funding sources should first be explored. But its own Derelict Land Grant (DLG) scheme has proved of little value because its main purpose is to bring land into a marketable state as quickly as possible, whereas remediation to deal with groundwater pollution in particular can take up to ten years.

    The report concludes with several suggestions for tackling the problem, broadly within existing legislation:

  • Risks posed to surface waters should be prioritised through the Catchment Management Plans being developed by the NRA in preparation for the introduction of statutory water quality objectives (SWQOs).

    Remedial action should be considered first for sites causing a breach of a specific water quality standard or preventing the achievement of an SWQO; contributing more than 1% of the national load of a pollutant which is subject to a reduction target under the 1990 ministerial agreement on the North Sea; and leaking more than traces of PCBs.

    Identification of risks to groundwater, the report suggests, should be tackled by the Environment Agency, building on the work of the NRA's groundwater centre to compile a national database of priority sites and carry out investigative studies and modelling.

  • Two dormant provisions of section 92 of the 1991 Act should be activated. These are a power enabling the Secretary of State to make regulations laying down construction, design and maintenance standards for chemical stores - which the NRA wants as an extra preventive tool - and enabling it to serve an "improvement notice" requiring site owners to carry out specified remediation works.

  • For cases where the section 92 or 161 powers are of little value because an owner cannot pay, the NRA recommends a change to the DLG rules in the absence of any other source of funding. This would require local authorities to include in their DLG bids sites requiring clean-up in order to meet SWQOs derived from Catchment Management Plans.

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