Halcrow assisted BNFL in several aspects of the development and documentation of the September 2002 LLWR Post-Closure Safety Case (PCSC). This involved preparing two of the PCSC reports that were issued to the Environment Agency in September 2002 and preparation of over 20 supporting documents.

The work included:

	Preparing reviews of international practice in the design of radioactive waste disposal facilities, covering the approaches adopted worldwide for the disposal of intermediate and low-level waste and specifically dealing with international design practice for capping systems, cut-off walls and drainage systems.
	Outline design of several of the proposed barrier and drainage components including the capping system, cut-off walls and leachate drainage. Modifications were also proposed to the design of the vaults and the trench disposal areas to improve the long-term performance of the closure system.
	Design optimisation studies including evaluation of different types of bentonite enhanced soils for use in barrier components, and variants on cap geometry and cap construction. This work covered the very wide range of component performance and climatic conditions that could be anticipated during the life of the capping system (up to 10,000 years).
	Estimation of construction costs for closure system components, including cut-off walls, deep drainage systems, capping systems, slope protection and coastal defences.
	Reporting on the impact on the closure system of a wide range of possible future activities on the site, covering the potential radiological releases from the site resulting from future human actions, and other potentially disruptive events.
	Assisting in developing a detailed FEP (Features, Events and Processes) list identifying the processes that could influence the long-term performance of the closure system. The system will include many components designed to work together to minimise radiological impact. These components are likely to respond differently to changes in the external environment and to the FEPs that will affect the repository over time.