Early on 12 February, workers at Yorkshire Water's Wheldale sewage works noticed orange coloration in the primary settlement tanks. Domestic effluent from Hickson's site had become contaminated with nitrotoluene, which damaged the works' biological treatment plant.
Nitrotoluene levels in Yorkshire Water's outfall rose to over 100mg/l, and high levels of BOD and suspended solids were also recorded. The Aire is a "poor" Class 3 river at this point, and the NRA says that environmental effects were limited. However, British Coal was forced to cease abstraction from the river at one mine downstream, and the intakes of two power stations were also threatened.
Hickson says that the incident was caused by a leak in an underground pipe which released some 500 gallons of effluent into a nearby domestic sewer before the flow was diverted. The location of the leak was not pinpointed for several days. Ironically, Yorkshire Water recently spent £19 million to separate Hickson's effluent from the domestic sewage flow so that uncontaminated sludge can be sent to land for disposal.
The NRA has served official samples on both Hickson and Yorkshire Water, but has yet to decide whether to prosecute either. Yorkshire Water is also considering legal action against the chemical company - a potential embarrassment for Sir Gordon Jones, who is Chairman of both firms.
Hickson has run into further trouble over its four direct discharges to the Aire. Last April, the firm was fined £4,000 under the Water Resources Act 1991 after a flooded sump led to a direct discharge of trade effluent.
The NRA's consents for the four outfalls, issued in 1991, only permit the discharge of cooling water and uncontaminated surface water. However, the NRA found that effluent from at least four processes was present. A series of tighter limits was due to come into force at the start of 1993, to allow Hickson to separate its waste streams and install new treatment and waste recovery facilities.
Hickson failed to meet the deadline, and last May the NRA announced its intention to prosecute the company for repeated breaches. Routine breaches of both the original and tightened consent conditions continued into 1994, and in early February another spill of nitrotoluene went directly to the Aire through one of the outfalls.
However, all legal proceedings by the NRA are now on hold. Last year, Hickson appealed to the Department of the Environment (DoE) against the terms of its consent. The appeal was rejected, but the company is now seeking a judicial review of the DoE's decision. This is expected to be resolved by June - when the improvements to the site should have been completed.
Existing chemicals processes on the site are now coming under integrated pollution control. The NRA is using its role as a statutory consultee to press for improved separation of effluents and the installation of bunds and other pollution prevention measures. However, in June 1992 Hickson wrote to HM Inspectorate of Pollution to warn that it had "limited resources" and to ask for bunding requirements to be placed within the context of the "overall priorities for the site as a whole". The company says that its programmed environmental expenditure for the last two years was £13 million, although the work has fallen behind schedule. It is not yet clear whether HMIP will choose to force the issue.
There is a further cloud on the horizon for Hickson. In late spring, the Health and Safety Executive (HSE) will publish its report on the cause of the explosion on the site in 1992 which killed five employees. The company was fined £250,000 last August for serious breaches of safety legislation (ENDS Report 223, p 41 ), and the report is expected to be highly critical.