RWE Npower Plc v Alstom Power Ltd & Ors

Contractual assumptions concerning ground conditions must be interpreted according to the wording incorporated into the contract. An assumption that inflowing groundwater can be controlled by sump pumping does not extend to water which affects excavation stability or cannot be so controlled. The expression “ground water” does not ordinarily include rainwater, seawater or surface water directly entering an excavation, although water from those sources may become groundwater after penetrating the soil. A contractor responsible for temporary works and disposal of water has no contractual right to discharge excavation water through existing outfalls unless the contract expressly provides one. Environmental statements and pollution-control authorisations concerning the completed plant do not create such a construction-phase right.

RWE brought Part 8 proceedings concerning the allocation of contractual responsibility for water entering excavations during the construction of a seawater treatment plant at Aberthaw Power Station. The parties sought declarations on the meaning of an agreed assumption about groundwater, whether excess inflow constituted an error in the presumed physical ground conditions, and whether the contractor was entitled to discharge excavation water through existing outfalls. The court was asked to determine contractual questions without making factual findings about the actual quantities or sources of water.

1. Groundwater assumption. The agreed conclusion incorporated into Schedule 15 was part of the Conditions of Contract. Clause 1.3.7 prevented the Specification from overriding or modifying it. The relevant assumption was that, in open excavations, inflowing groundwater would not affect stability and could be controlled using contractor-provided sump pumping. It did not incorporate the earlier phrase “little more than seepage”.
2. Meaning and application. Water outside those limits could amount to an error in the Presumed Physical Ground Conditions for clause 13.3.4(a)(i), but only if it affected stability or could not be controlled by the sump pumping contemplated by the contract. The precise scope of “sump pumping” required factual and technical evidence and could not be resolved on the Part 8 material. “Ground water” excluded seawater and surface water directly entering the excavation. The court declined to determine when water from another source became groundwater.
3. Discharge rights. The contractor’s extensive obligations included temporary works and proper disposal of water from the Site from whatever source. Nothing in the contract, the Environmental Statement, the Deemed Planning Consent or the Variation Notice gave the contractor an express right to discharge excavation water into the Seal Pit or through Outlets Nos 2 or 3. Those documents principally addressed the completed FGD process and authorised releases from the existing or completed process.
4. Unresolved matters. Because no contractual discharge right existed, questions concerning suspended-solids limits, permits and requests for permits were immaterial or hypothetical. The court declined to decide whether silty water constituted “poisonous noxious or polluting matter”, “solid waste matter” or “trade effluent” under section 85 of the Water Resources Act 1991 without expert evidence.

The court answered Issue 10.1 “No” and gave the corresponding declarations on Issues 10.3 and 10.4.

First-instance Part 8 proceedings. No prior appellate decision is stated in the judgment.