The pollution plume is the largest in the UK and affects a high quality aquifer used for drinking water supply. It stretches more than 20 kilometres east of its source, the former Steetley Chemical works at Sandridge, near St Albans, and consists of bromate, a carcinogen, and bromide.
The site of the former chemical works, which is now a housing estate, was designated under the contaminated land regulations by St Albans council in June 2002 (ENDS Report 329, pp 3-4 ). The Agency issued the remediation notice in November 2005, naming Redland the ‘appropriate person’ for the bromate remediation but making Crest responsible for the bromide as the developer knew the site contained the substance when it bought it.
Each company blames the other for the pollution, which could take many years and millions of pounds to clean up. Their appeals, the first relating to a special site regulated by the Agency, were heard by the planning inspectorate at a public inquiry in May.
Three Valleys Water first noticed the pollution at its Hatfield borehole in 2000 (ENDS Report 313, pp 6-7 ). It was testing for bromate ahead of the introduction of a new 10 microgram-per-litre drinking water standard.
The borehole was closed immediately, resulting in a 9 megalitre -per-day supply shortfall. Bromate concentrations have since risen rapidly at the firm’s more easterly Essendon borehole, from less than 10µg/l in 2000 to 60µg/l.
The water now has to be blended with supplies from another source.
The measures have cost the water company £13 million, but have not fully replaced the lost supply. Three Valleys says it needs a solution by 2008, especially if it is to cope with the changing climate.
Speaking at the inquiry, Three Valleys’ barrister expressed the firm’s frustration that "seven years later… the identity of those with statutory responsibility for remediating the pollution has yet to be confirmed and the two candidate parties have yet to spend a single penny in the cause of undertaking the required remediation, even on a without prejudice basis."
Their only expenditure, he suggested, "has been in the engagement of legal and professional teams to resist the notice".
The pollution has also affected Thames Water’s northern New River wells, which provide up to 121Ml/day of drinking water. The loss of supply was a factor in the company’s application for a drought order last summer (ENDS Report 380, pp 26-29 ).
The firm is installing treatment at its Hornsey waterworks but notes that the contamination can also reach its Coppermills and Chingford South works via the river Lee. These are particularly sensitive because they use ozone disinfection which produces bromate as a by-product from bromide in the raw water.
Steetley Chemical, which used to make bromide and bromate on the site, was eventually taken over by Redland, now owned by Lafarge. Crest Nicholson bought the site in 1983 and built 66 homes before selling it to a property management company in 1987.
The remediation notice required both parties to investigate the pollutant’s entry into the groundwater and assess remediation options.
Shortly before the notice was served, Three Valleys began pumping water from the Hatfield borehole and sending it to two of Thames’ sewage works for decontamination on an experimental basis. The trial proved successful and a long-term programme is now removing 600 kilograms of bromate and 1,400kg of bromide per year. This has halved the pollutant concentration downstream at Essendon and reduced levels at Thames’ wells.
The water companies have called for this ‘scavenge’ pumping to be added to the interim actions listed on the remediation notice. "The virtue of Hatfield is that it is going on, it works and you could start tomorrow," the Three Valleys barrister told the inquiry.
Modifications of a remediation notice on appeal are permitted under the contaminated land regulations, even if the changes are less favourable to the appellants.
The arguments put forward by the water companies during the inquiry appear to have convinced the Agency. Its final submission to the Secretary of State recommended that the company held responsible for the bromate pollution should refund the water companies for the interim pumping. The companies estimate the bill to be about £3 million over ten years.
Redland, however, wants any decision delayed pending a cost-benefit analysis. "Given the measure in question is to be interim, it is necessary only to seek the objective of ensuring that potable water is provided from relevant abstraction points", rather than starting to decontaminate the aquifer, its barrister told the inquiry.
It might be more cost-effective, he argued, to compensate the companies for blending and treating the water and help them look for another source.
Redland also claims pumping at Hatfield could distract attention from long-term remediation - which is likely to involve a pump further upstream and more centrally in the plume - and that water quality targets set by the Agency are unrealistic.
Throughout the hearing, Crest maintained it should not be responsible for the clean-up. It said the site "was developed to the best practicable standards at that time in conjunction, and in agreement with, the then relevant regulatory authorities."
The Agency’s interpretation of the contaminated land regime "would place an impossible burden on developers who would then be expected to anticipate future regulatory changes… [and] undermine the Government’s own stated policy of encouraging urban regeneration and brownfield site redevelopment," it maintained.
The Agency rejected this argument: "Crest cannot simply say [it] did what [it was] required to do at the time and that is the end of it. The test must also be ‘objective’, that is, what would a reasonable person have done…?"
Documents from the time suggest Crest was warned of the risk to the groundwater before it bought the site. It removed some of the contaminated soil before rebuilding but only after the site had been left bare - and open to leaching - for two years. By this stage, bromide had been discovered in the underlying aquifer.
Crest ignored repeated requests from the then Thames Water Authority for more soil to be removed and further groundwater monitoring or the instigation of scavenge pumping, the Agency said. Instead, it did the minimum necessary to obtain planning permission. The local authority was apparently concerned only with protecting the health of those living on the site and the quality of private water supplies.
Crest "knew [the authority] had no direct control over the site" and "consciously ‘sealed’ the remaining contamination into the site," the Agency said.
Redland claimed Crest is also responsible for the bromate pollution because it was told, before the sale, that "bromate/bromide products were produced on site". Redland said soil samples taken at the time also showed the presence of both chemicals - a point contested by Crest.
A final report from the inquiry is expected in September when it will be passed to the Secretary of State for a decision.