Days Pottle Pond, Exeter

This scheme consisted of the rehabilitation and upsizing of the drainage along a 3.5km stretch of the A30 between the M5 and the A377 junction, to mitigate surface water issues. Works included control and disposal of contaminated material, including asbestos. The works also included construction of a new 4.5m wide, 100m long, maintenance access road, replacement of existing penstock and repairs to the concrete weir, replacement of baffle boards in 2.1m deep water/oil separator (confined space), and installation of by-pass pipework to divert the flows from Berry Brook around the weir to enable construction works to proceed.

We minimised disruption by agreeing a restricted traffic management solution working both during the day and night. We collaborated with the National Highways’ engineer to relocate one of the attenuation tanks to avoid hard ground and to deliver a fully-designed surface water attenuation solution which did not require extensive temporary works.

Optimising the collaborative approach, we obtained Approval in Principle from Devon County Council for temporary sheet piling for the installation of large attenuation tanks adjacent to the live carriageway.

Our change control procedures were set out in our Project Quality Plan and Design Management Plan, with a clear process and technical governance to assess the full implications of any potential change and inform mitigation decisions. We recorded any variances to resources, forecast requirements or outputs in the Change Register, which was created and maintained in CEMAR. The delivery team used Collaborative Planning and Last Planner and worked with all parties to collaboratively plan and build the programme, supporting lean project planning and delivery.

During installation of two 250m³ underground attenuation tanks at the busy A30/A377 roundabout intersection, it became apparent that full consent had not been sought from the local authority to install the new drainage assets. To overcome this challenge, our site team worked with National Highways to identify an alternative location for the tanks within the scheme boundary.

We completed the revised design and construction in just three weeks, minimising impact on the customer.  Our senior site team took the lead in resolving issues and coordinate design acceptability with the local authority on behalf of National Highways, a process that normally takes several months to achieve. Our prompt, agile response prevented delays to this essential highway drainage improvement scheme.

Providing defect-free drainage we delivered more than 2.7km of defect-free drainage at Days Pottle Pond on the A30. We have a proven track record of delivering and handing over highways schemes defect-free. This is evidenced by our most recent KPI scores for the National Highways’ CWF, where we have continuously scored a maximum of 10 points in the 6-month reporting period.

CLIENT: National Highways 
PROJECT VALUE: £2.7m 
START DATE: December 2019
COMPLETION DATE: September 2020
FORM OF CONTRACT: NEX Option C