A595 Moresby Hall Embankment

Overview

Join to hear Amey discussing the A595 Moresby Hall Scheme in Cumbria and the many challenges faced delivering the drainage improvement and embankment reconstruction works whilst mitigating road closures, in line with the Sellafield Nuclear Power Station civilian contingency plan.

National Highways commissioned Amey to complete the detailed design for the embankment stabilisation required at Moresby Hall which is located on the A595 between the High Lowca Junction and the Howgate Roundabout in Cumbria, England. The A595 is a primary route between Barrow-in-Furness and Carlisle and is a key transport corridor supporting a mix of uses from local commuting to long distance freight traffic, serving nationally important facilities including Sellafield Nuclear Power Plant.

Inspections of the embankment identified defects comprising creep terracing, local surface slips and associated back scarps. In addition, a stone wall located along the crest of the north-western slope, providing some lateral support to the carriageway, had collapsed in sections and showed vertical distortion.

It is likely that the original slope angle, coupled with surface saturation of the soils over time had led to instability. A significant failure of the embankment could have taken place at any time which would have led to an extended total closure of the A595, having substantial effects on the surrounding National Highways Area 10 road network.

Previous studies on the embankment condition had recommended full removal/reconstruction and even a complete road re-alignment at considerable expense and disruption. However, a more economical ground engineering solution of partial embankment reconstruction, with use of lightweight fill and geosynthetic reinforcement, was taken forward without road closure and incorporating the existing earthworks asset. This option allowed for carriageway widening and steeper slope gradients to be achieved, whilst reducing extensive excavation requirements and stresses on underlying soils.

In conjunction with these works, due to regular flooding of the A595 in the area, Amey designed a proposed drainage system suitable for the scheme extents that improves upon the existing infrastructure which is not fit for purpose. Therefore, the scheme consisted of widening and replacing of the existing embankment, as well as proposed drainage works and resurfacing along the A595 mainline carriageway.