Northumbrian Water Ltd v Sir Robert McAlpine Ltd

Factual and Procedural Background

The Plaintiff ("Company A") is the statutory sewerage undertaker operating in the North-East of England, appointed under the Water Industry Act 1991. A public sewer operated by Company A passes under Newgate Street in The City. The Defendant ("Company B") is a well-known construction company that was developing a site at Eldon Square Phase 3, The City, adjacent to premises occupied by a third party ("Company C").

In January 2008, Company B's subcontractor carried out piling works, during which concrete was poured for pile 215. Some concrete escaped during the operation. Unknown to both parties, a private drain existed near pile 215, connecting to the public sewer. This drain was discovered only in March 2008 through archival research.

At the end of January 2008, Company C reported sewage backing up into its premises. Company A's investigations revealed concrete had entered the public sewer, necessitating costly removal works completed in May 2009 at a cost of £318,032. Company A seeks to recover this sum from Company B, alleging nuisance and negligence.

Company B denies liability, disputing the connection between the poured concrete and the concrete found in the sewer, denying negligence and nuisance, and asserting that the private drain was undiscoverable by reasonable diligence. Company B also alleged, but later withdrew, claims that Company A was negligent in failing to provide information.

The proceedings were issued in February 2011, transferred to the Technology and Construction Court in January 2012, and experienced multiple delays related to expert reports and trial scheduling. The trial commenced in June 2013 with witnesses called from both parties and a single joint expert.

Legal Issues Presented

1. Whether the concrete found in the public sewer was the same concrete poured by the Defendant's subcontractor.
2. Whether the Defendant was negligent in its piling operations and site investigations.
3. Whether the Defendant is liable in nuisance for the escape of concrete into the sewer.
4. Whether the Plaintiff failed to mitigate its loss.

Arguments of the Parties

Plaintiff's Arguments

• The concrete in the sewer was the same as that poured by the Defendant's subcontractor, supported by circumstantial evidence including location, timing, and absence of other concrete work nearby.
• The Defendant was negligent in failing to discover the private drain and adequately investigate the site.
• The Defendant is liable in nuisance for the escape of concrete causing damage to the sewer.
• The Plaintiff did not fail to mitigate its loss.

Defendant's Arguments

• The concrete found was not the same as that poured by the subcontractor.
• Extensive pre-construction investigations were conducted; the private drain was undiscoverable by reasonable diligence.
• The piling operation was carried out with reasonable care and the amount of concrete lost was not unusual.
• The Plaintiff failed to mitigate its loss by not acting promptly to remove the concrete.
• The damage to the sewer was not reasonably foreseeable.
• The Defendant denies liability in nuisance absent negligence and argues that strict liability under Rylands v Fletcher does not apply.

Table of Precedents Cited

Court's Reasoning and Analysis

The court first addressed whether the concrete found in the sewer was the same as that poured by the Defendant's subcontractor. Expert evidence initially suggested differences in aggregate composition, but after further evidence regarding quarry geology and supply practices, the expert acknowledged it was possible the concrete was the same. Circumstantial evidence—location of pile 215 near the drain, timing of pouring and blockage, loss of concrete during piling, and absence of other concrete pours nearby—supported the Plaintiff's case. The court found on the balance of probabilities that the concrete was indeed the same.

Regarding negligence, the court accepted that the Defendant conducted extensive investigations and took reasonable care. The private drain was not discoverable by reasonable diligence, especially given the site's redevelopment history. No expert evidence criticized the piling operation or investigations. The court found no negligence on the Defendant's part.

On nuisance, the court engaged in detailed legal analysis of the rule in Rylands v Fletcher and its relationship to nuisance. The court noted that Rylands v Fletcher is a sub-species of nuisance imposing strict liability for escape of dangerous things but only if the "mischief or danger" test is met, which is not easily satisfied. Liability requires damage to be reasonably foreseeable. The court found that the damage was not reasonably foreseeable since the existence of the private drain was unknown and undiscoverable. Therefore, the nuisance claim failed.

The court also considered mitigation, finding that the Plaintiff did not fail to mitigate losses. The concrete cured rapidly and could not reasonably have been discovered or removed earlier to reduce costs.

Holding and Implications

The court's final decision was to dismiss the Plaintiff's claims.

Holding: The concrete found in the sewer was the same as that poured by the Defendant's subcontractor, but both negligence and nuisance claims failed as the Defendant took reasonable care and the damage was not reasonably foreseeable. The Plaintiff did not fail to mitigate its loss.

Implications: The decision directly affects the parties by denying the Plaintiff recovery of the costs incurred in removing the concrete. The court reaffirmed the limited scope of strict liability under Rylands v Fletcher and emphasized the importance of reasonable foreseeability in nuisance claims involving isolated escapes. No new legal precedent was established beyond the application of existing principles to the facts.