From the moment John Prescott heralded the start of construction with the ground-breaking ceremony on 15 October 1998, the Channel Tunnel Rail Link (CTRL) project was destined to be a landmark feat of engineering.
The CTRL has been split into two phases of construction. Phase 1, linking the Channel Tunnel to Fawkham Junction near Gravesend in north Kent, is due for completion in 2003. Phase 2, completing the railway to St Pancras, started this year.
After the Channel Tunnel Rail Link Act was passed by parliament in 1996, the government awarded the contract to build and operate the high-speed link to London and Continental Railways (LCR). The company is carrying out the work through subsidiary companies – with Union Railways (South) and Union Railways (North), covering Phase 1 and 2, respectively.
Rail Link Engineering (RLE) is the project management arm of LCR and, through the consortia companies of Bechtel, Ove Arup, Sir William Halcrow and Partners and Systra, is responsible for the project management and most of the design for the scheme. The CTRL management structure is shown in Figure 1.
This paper relates specifically to contract 350/410 of the CTRL and in particular to the North Downs Tunnel.
Contract 350/410
The Eurolink joint venture of Miller Civil Engineering Services (UK), Dumez-GTM (France) and Beton-und-Monierbau (Austria) was awarded the joint 350 and 410 contracts for Phase 1 of the CTRL in October 1998. This included the 3.2km North Downs Tunnel, the 1.3km long Medway crossing, 4km of earthworks between the two structures, three footbridges over the railway, and an extensive series of environmental mitigation schemes and temporary roadworks.
The North Downs Tunnel is the largest and deepest rail tunnel in the UK and will carry twin tracks through the chalk geology of Bluebell Hill between the M2 and M20 motorways. In the first major UK tunnelling contract to use a sprayed concrete lining since the Heathrow Express collapse in 1994, the tender design involved an excavated face area of more than 160m2. With a waterproof membrane and cast in situ secondary lining, the final internal maximum width of the tunnel is 12.8m. Figure 2 shows a typical cross-section through the tunnel.
This paper focuses on the quality system and specifically the self-certification process adopted for the CTRL contracts. The process from training of staff, through primary lining construction and its development for secondary lining installation are discussed and presented in the context of the overall success of the contract.
Standard conditions of contract
It was clear from the outset that the CTRL project needed a contract that was:
– flexible to allow for changes
– clear in its definitions of the parties involved and their responsibilities
– able to offer different basic allocations of risk between the employer and contractor
– simple to follow, using clear English
– adaptable to the project-specific requirements.
The UK’s New Engineering Contract (NEC) was chosen as the form of contract for CTRL. The NEC was renamed the Engineering Construction Contract (ECC) for its second edition in 1995. The form of contract for a project would be the core clauses together with the relevant optional clauses. Of the six main contract options offered by the ECC, the CTRL project has adopted Option C – ‘Target cost with activity schedule’.
Some clauses of the ECC were amended to tailor the contract to suit this project. The CTRL Standard Condition of Contract is priced using an activity schedule, a list of activities that the contractor expects to carry out in providing the works. The contractor prices each activity, or group of activities, in the schedule on a lump sum basis. This is the actual price to be paid by the employer for that activity or group of activities. Under Option C of the ECC, the saving or extra cost is based on the following calculations:
The contractor’s share (as detailed in Clause 53 of the CTRL Standard Conditions of Contract) is
then calculated based on the share range shown in table 1.
The management and supervision of the contract needed to be such that both RLE and Eurolink could make the most of this pain/gain type of contract. Self-certification was specified by the client as the chosen method of supervision on all of the CTRL contracts.
Self-certification
Self-certification is not new to UK tunnelling projects. The Channel Tunnel was the first major civil engineering project in the UK to implement self-certification, and it was also specified for Heathrow Express. However, in the results of the Health and Safety Executive’s investigation into the Heathrow collapse, it is identified that, although in principle the Heathrow Express project was based on contractor self-certification, “to some degree there was a contradiction in the contractual approach. The client chose to let the contract through a traditional competitive tender but had the expectation that self-certification … would provide for quality”.
It was made evident from the outset that contractor self-certification was one of the CTRL conditions of contract. When tendering for the CTRL contracts, bidders were required to demonstrate their knowledge and understanding of the self-certification process and include their proposed system of implementing it.
The process of self-certification is defined in the Contract Works information document as “the contractor’s responsibility for demonstrating that specified requirements have been met”. The client expects not only that its requirements to be met but also that the contractor demonstrates compliance through detailed and documented procedures.
Self-certification requires the contractor to identify its own errors or omissions without being instructed by the client or its representative. The aim is for the end product to be built safely, to be of high quality (ie right first time, every time), to have minimal impact on the environment and to be as financially rewarding as possible to all parties.
ISO 9000 (the Standard relating to quality assurance) requires final inspection and testing work to be carried out by (any) competent personnel. Final inspection has traditionally been a hold point at which the client’s representative must give their approval before work continues. This is no longer the case, as RLE engineers need only witness a percentage of the work completed by Eurolink and document this check as a counter-signature to a Eurolink engineer’s approval. The percentage of work witnessed depends on the criticality or importance of the activity. On the North Downs Tunnel, once an activity was running smoothly, about 10% of work was witnessed by RLE.
Contract documentation
Implementation of self-certification principles requires detailed contract documentation. Eurolink works under a quality plan which ensures that, before any construction activity begins, the programme and work method have been agreed with RLE.
For all construction activities carried out by Eurolink, or one of its subcontractors, an inspection and test plan is produced. This details all approvals, acceptances, consents, inspections and tests required to ensure that the specified requirements have been addressed.
The inspection and test plan identifies the sequence of major operations required in carrying out the activity. Key stages are nominated to be hold points or witness points, for Eurolink and/or RLE. A hold point identifies a stage in the preconstruction or construction activities beyond which work should not progress until the relevant approval, acceptance, inspection, test or other documentation is in place.
All inspection and test plans detail:
– the work activities;
– who is responsible for carrying out the work;
– the instructing document for the work, such as the method statement;
– the client specification that is being addressed;
– inspection criteria, such as hold points;
– frequency of inspection;
– verification documentation.
The inspection and test plan, along with a risk assessment and all self-certification documentation, are collated as part of the Method Statement, which describes exactly how the work is to be carried out. This must be approved by RLE and is distributed to all engineers and discussed with the tunnel gangs before the work begins.
Training
Both Eurolink and RLE engineers were trained in the principle and implementation of the self-certification process. Anyone involved in approving or witnessing any section of work throughout the contract had to be fully trained in the system before they could sign any contract documentation.
Pit bosses and lead miners were also trained in self-certification, ensuring that everyone had an understanding of what was required. This meant that responsibility for supervision, authorisation and the associated completion of the shift documentation did not rest solely with the tunnel engineers. Not only did this free the engineers to look at other aspects of the tunnel advance, such as possible improvements to safety or cycle times, but it allowed everyone involved in the tunnel supervision to take direct responsibility for the quality of the work they were overseeing.
Excavation and installation of the primary lining
Within the context of self-certification, it is worth understanding the tunnel engineers’ duties to ensure specified requirements were met. Figure 4 shows the typical primary lining construction sequence, the associated shift documentation and the relevant contract documents.
As expected with a tunnelling project of this scale, there is a significant set of specifications and method statements. In addition to these, for the excavation and installation of the primary lining, is the required excavation and support sheet (RESS), the equivalent of a one-sheet method statement summarising the construction details which are altered to suit the prevailing ground conditions. A RESS sheet used during crown excavation is shown in Figure 5. Every working day, a formal meeting was held at which the RESS sheet was produced. Without this, tunnelling work would have ceased. The daily RESS meeting was the key control of the tunnelling operation.
The RESS effectively acts as a supplement to the method statements, ensuring that the varying ground conditions and behaviour of the tunnel lining are taken into account while still carrying out work exactly to details in the method statements. Together, these documents show the requirements that must be satisfied for each step of the advance, from excavation and primary lining steel support to application and testing of the sprayed concrete.
The tunnel engineers, in their role of supervising the tunnel advance, used the self-certification process to provide evidence that all these requirements were being met. Initially, there was an extensive amount of shift documentation, as the requirement of a signed document as proof of witness of every stage of the construction cycle, for every advance of the tunnel, was provided. Although this meant that every stage of the tunnel’s construction history was carefully documented and auditable, there was a tendency for the engineer to become too involved in completing mandatory documentation. This inevitably began to seem tiresome and repetitive, producing a significant amount of paperwork that was difficult to refer to and work with when looking for specific information at a later date.
A good quality assurance system must be an easy to use and reliable reference tool. The tunnel section of Eurolink, in conjunction with RLE, made changes to the process of documenting the construction cycle, with all information relating to one tunnel advance presented on a single sheet of paper. While ensuring that every step of the process was still witnessed and approved, the as-built information could now be referred to on a single document for any chainage along the tunnel.
NEXT ISSUE
The second and final part of this paper will appear in the November issue of T&TI, covering self-certification for the North Downs Tunnel secondary lining, handling of defects and remedial works, internal auditing and future development of self-certification.
Related Files
Figure 1: CTRL management structure
Figure 3: Calculations
Figure 2: Typical cross-section
Table 1: Contractor’s share range
Figure 4: Primary lining sequence
