In Commission v UK Case C-301/10, judgment 18 October 2012, the CJEU upheld the Commission’s infringement action against the UK for breach of the Urban Waste Water Treatment Directive 91/271/EEC (UWTD). The action related to discharges from combined sewage overflow (CSO) systems in London and Tyneside. A CSO is a single system for collecting foul drainage and surface water run-off. Rainfall can result in the total flow exceeding the capacity of the wastewater treatment works (WTW). Once storage capacity is exhausted, the CSO discharges its untreated contents into the sea or river. The evidence showed that discharges of untreated sewage were far from rare. They sometimes occurred after moderate rainfall and even in dry weather. At Whitburn on Tyneside, from 2005 and 2008 there were between 27 and 47 incidents a year involving average annual discharges in excess of 500,000m3.

Article 3 of the UWTD requires Member States to provide agglomerations with “collecting systems for urban waste water”. Article 4 provides that water entering those systems must be subject to secondary or equivalent treatment before discharge. By Article 10, WTWs must be designed etc. “to ensure sufficient performance under all normal load conditions”. Annex 1A provides that the “design, construction and maintenance of collecting systems shall be undertaken in accordance with the best technical knowledge not entailing excessive costs” (BTKNEEC). A footnote states that as “it is not possible in practice to construct collecting systems and treatment plants... such that all waste water can be treated during situations such as unusually heavy rainfall, Member States shall decide on measures to limit pollution from storm water overflows [which] could... specify a certain acceptable number of overflows per year.”

The Court affirmed that as a general rule, collecting systems and WTWs had to achieve treatment of the whole of an agglomeration’s waste-water. So “sufficient performance” means that “under usual climatic conditions and account being taken of seasonal variations, all urban waste water must be collected and treated”. The word “unusually”, in the light of the Directive’s general environmental objectives, referred to wholly exceptional circumstances. So the discharges from these CSOs, in “normal and common” climatic conditions, were on the face of it in breach. However, the UK, relying on the BTKNEEC provision, argued that it would be disproportionate to carry out costly works that would only produce a modest improvement in water quality. The Court accepted that BTKNEEC could in principle apply to WTWs as well as collection systems. But that did not assist the UK here. In London, the major Thames Tideway scheme was already underway, undermining any claim that improvements were unnecessary or too costly. And on Tyneside, disagreeing with A-G Menozzi, the Court held that the UK had failed to provide evidence of the actual cost of improvements.

Where does this leave us? First, the CJEU has once again made clear that directives will be interpreted expansively to achieve high standards of environmental protection. Second, the Commission was heavily criticised for failing to issue clear guidance about acceptable “exceptional” discharge volumes or frequencies. The industry might be wary of such guidance, but it may relish even less the alternative of case-bycase judicial elaboration of standards. Finally, the case took 12 years from the original complaint to judgment. So domestic proceedings – despite the cost implications - might in future be the preferred route for those seeking to enforce the UK’s UWTD obligations.