CPSP 143 A303 Stonehenge (Tunnel ERA)

The A303 Stonehenge project has been asked to investigate the impacts of adding emergency refuges or an additional hard shoulder within in the Stonehenge tunnel in order to increase tunnel safety over the 3km bored tunnels. This requires an assessment of the incremental cost and schedule versus the current baseline scheme (D2AP tunnel without refuges or hard shoulder). Two options are to be considered: - The provision of two lay-byes per tunnel, spaced at 1000m centres (four in total), constructed using SCL techniques, to provide an emergency refuge during traffic emergencies / incidents. - Increasing the diameter of the tunnels to incorporate a hard shoulder lane over the entire length of the tunnel

The incremental cost and schedule impacts are to be measured vs the current baseline scheme design. This will require establishing a baseline estimate and schedule with a consistent set of assumptions against which the above options can be compared. The assessment is to include development of design and methodology assumptions in consultation with the A303 Stonehenge project team so that the assessment has a robust design, methodology and schedule basis.

The assessment is to include the following activities - Mobilisation and collection of reference design information for the baseline scheme and definition of the above options - Confirm scope of assessment and output requirements with the A303 Stonehenge project - Establishment of cost and schedule estimate for the baseline scheme - Identification of design and construction methodology for the emergency refuge option - Identification of design and construction methodology for the emergency refuge option

- Production of cost estimates and outline schedule for each option - Comparison with baseline scheme and identification of incremental impacts - Production of report to capture impacts and the design / methodology assumptions. This is to include commentary on risks to delivery of the options. - Presentation of findings

No design cross sections are available for the above options at this time and these are to be developed as part of the assessment. The level of detail within the assessment should be commensurate a concept design / PCF Options Stage 1 level.