Grayrigg, Slope Stabilisation Works Phases 1 & 2
The project was to protect the A685 west of Grayrigg, with the diversion of the Thurgill Beck into a new channel. The explosive force of the beck was undermining the Kendal to Tebay Road, cutting into a slope on the top of which the road runs.
EWCE were appointed through a two stage design and build competition to design a solution as part of the infrastructure Recovery programme that was in progress since Storm Desmond in 2015 to 2020.
The County Council had intended to introduce a full road closure while these works were carried out. EWCE methodology showed how to avoid the disruption and inconvenience of a full road closure to the local community and travelling public by avoiding a full road closure with resulting very long diversions. EWCE undertook the works under traffic management to ensure the A685 remained open for peak periods of the day.
Phase 2 construction began in spring 2019 with works through the summer period. The Council’s original concept involved a gabion retaining wall. However, EWCE developed a resilient, longer term and environmentally friendly solution that involved diverting the course of the river away from the toe of the slope and re-engineering the slope to provide a long term and sustainable solution.
The proposed solution was cheaper and achieved a net cut/fill balance.
The project included installation of 180m kerb-drains and gullies to capture rainwater on the A685 carriageway above and a new drainage system to protect the slope against surface water flooding from above.
The initial works involved constructing the new, diverted river channel away from the toe of the existing slope together with its diversion in accordance with the environmental permitting that already been approved by the LLFA. This facilitated access to the major slope regrading works.
The works process involved completing sections of slope from the bottom working upwards so as to provide access to the upper sections of the slope some 18m above the river level The new slackened slope was then constructed using a combination of imported and site won material.
- Working on and in the vicinity of unstable slopes
- Working in/around a watercourse
- As part of this project we understood the importance of selecting suitable equipment and plant to complete a slope regrade, including the use of specialist long reach excavators. The methodology for the work was developed considering the particular site conditions and availability of access points. Weather was an important factor to consider as the earthworks had to be effectively suspended during periods of high rainfall as otherwise the formation and new earthworks would be threatened
- Landowner issues and access were also a key aspect of this project and both EWCE and Cumbria County Council played their part in obtaining and negotiating this. This is an important aspect of nearly every project where incursion onto private land is required and that negotiation must begin at a suitably early time
Working on live highway with the installation of Traffic Management
Part of the River Kent SSSI, is an ecological sensitive site with the beck flowing into the River Kent via the River Mint, which are both important salmon rivers and contain native freshwater crayfish. EWCE employed an ecological clerk of works to audit the site regularly.
Pupils from Grayrigg Primary School have been given a first-hand look at engineering works taking place on their doorstep. EWCE staff visited the school to talk about site safety and the potential dangers of plant and machinery operating on site. A group of 24 children from the school, with staff and parent helpers, were then taken along the A685 under a vehicle escort with flashing beacons to visit the works site. Grayrigg Primary School head teacher Kirsty Cooper said: “We’d like to thank EWCE for inviting our children to see the roadworks. It was great for them to see some real engineering in action and the visit has definitely inspired them.”