Dobson & Ors v Thames Water Utilities Ltd (No 2)

Statutory authority to operate sewage-treatment works does not immunise the operator from nuisance where it fails to conduct the works with all reasonable regard and care for neighbouring interests. The assessment takes account of scientific knowledge, practical feasibility and expense. Operational failures, including inadequate maintenance, monitoring, cleaning, chemical dosing and odour-control testing, may be justiciable even where major capital works would fall within the statutory regulatory scheme. A court should not determine priorities for major capital investment entrusted to the industry regulator. Naturally occurring mosquitoes may give rise to a measured duty of care, but liability requires proof of negligence and causation. Human-rights damages are discretionary and are unnecessary where other remedies and an award of nuisance damages provide just satisfaction.

About 1,350 residents near Mogden Sewage Treatment Works claimed damages and an injunction against Thames Water for odour and mosquito nuisance. They also alleged negligence, breaches of the Human Rights Act 1998 and breaches of statutory duties. Thames Water relied on statutory authority, the regulatory scheme under the Water Industry Act 1991, the decision in Marcic v Thames Water Utilities Ltd and limitation.

The court previously determined preliminary issues, including the scope of the Marcic defence. This judgment decided liability and quantum in test cases concerning 30 claimants and 10 lead properties. The central questions were whether Thames Water’s operation and management of Mogden breached the Allen duty, whether the resulting odour was actionable nuisance, whether mosquitoes were attributable to the works, and what remedies followed.

1. Odour liability. Thames Water breached the duty identified in Allen v Gulf Oil Refining Ltd to conduct the works with all reasonable regard and care for the interests of others. Breaches included inadequate control of inlet septicity; poor management of screenings and grit; failure to use chemically assisted settlement in the primary and final settlement tanks; ineffective storm-tank cleaning and hopper emptying; defective settlement-tank scraping and scum removal; inadequate operation, monitoring and maintenance of odour-control units; unsuitable trigger levels; and insufficient olfactometry and dispersion modelling.
2. Justiciability. The court distinguished operational matters and minor capital-maintenance works from major capital projects. Claims concerning major covering schemes, conversion of primary to final settlement tanks, replacement of the PFT process and fixed-roof digesters would conflict with the statutory scheme administered by Ofwat. Claims concerning maintenance, cleaning, monitoring, minor plant replacement, temporary plant and operational control were justiciable. The design of the UWWTD scheme was also justiciable because it had been funded through the regulatory process, but the alleged design negligence was not proved.
3. Funding. No freestanding Allen duty required Thames Water to press Ofwat for capital funding. In any event, Thames Water had acted reasonably in its AMP2 and AMP3 funding submissions, and the alleged chance of obtaining funding for major works was speculative.
4. Mosquitoes. Applying Leakey v National Trust and Goldman v Hargrave, Thames Water owed a measured duty of care concerning naturally occurring mosquitoes. Its surveys, treatments and overwintering works were reasonable. The claimants also failed to establish that bites were caused by mosquitoes originating at Mogden.
5. Remedies. Odour constituted actionable nuisance at the lead properties. Schedule A claimants received general and special damages totalling £20,120. The odour breaches also constituted unlawful interference with Article 8 rights, but no damages under section 8 of the Human Rights Act 1998 were necessary. No injunction was granted because future nuisance was uncertain, the proposed order was imprecise, and it might conflict with the statutory scheme.

• High Court (Technology and Construction Court): preliminary issues were decided in [2007] EWHC 2021 (TCC); the present judgment determined liability and quantum in the test cases.
• Court of Appeal: the appeal from the preliminary judgment was allowed in part in [2009] EWCA Civ 28.