Kendal Bypass Shenstone & Whetstone Culvert Replacement

Design and construction of replacement, larger diameter, culverts at Shenstone and Whetstone to cope with an increase in significant rainfall events
Cumbria County Council
NEC3 Option A


The A591 Kendal By-pass and main route to the south Lake District in recent years has frequently been blocked at Shenstone and Whetstone by flooding. Under Cumbria County Council’s Infrastructure Recovery Programme, Eric Wright Civil Engineering were appointed to design and construct replacement culverts at Shenstone and Whetstone with larger diameter culverts to cope with an increase in significant rainfall events over the past few years.



At Shenstone, we excavated and removed the existing culvert and installed an 1800mm x 650mm pre-cast box culvert section to form a new culvert system along with installation of new upstream and downstream pre-cast head walls, reinstatement of the existing carriageway and ground re-profiling works.

Whilst at Whetstone, we excavated and installed new 750mm diameter concrete pipes to form a new culvert system adjacent to the existing culvert. New RC headwalls upstream and downstream were constructed along with ground re-profiling works.

Key Challenges

  • The A591 is a high speed road making traffic management high importance.
  • No mechanical excavation with 500mm of cable was permitted.
  • Water management.
  • Environmental protection was paramount.
  • Culvert sections were 9.5t resulting in large craning activities.

Both culverts were constructed simultaneously using a contraflow system with traffic directed onto the southbound side of the A591 whilst the drainage works were completed on the northbound side then the contraflow swapped over and the drainage works completed on the southbound side. The traffic management sub-contractor had operatives permanently based 24 hours a day onsite to monitor and review the traffic management as required. They were contactable at all times in case of any issues.

Before any ground breaking works were undertaken, a CAT and Genny survey identified existing services. Vacuum excavation was undertaken to reveal services.

Over pumping of the existing becks and associated land/highway drainage to facilitate construction of the new culverts was undertaken.

During the works, we were up against periods of high rainfall as the works commenced in Autumn and continued well into the depths of Winter. Water management was one of the most challenging aspects of the works due to the volatile nature of the watercourses and its large catchment area resulting in EWCE upgrading over pumping requirements in order not only to keep the works progressing but also to ensure the A591 was not flooded out during the works.

We appointed local company, RG Parkin Consulting Engineers based in Kendal, to provide hydrological and hydraulic calculations and then produce a civil engineering design.

Monitoring water levels and quality was continually undertaken. The watercourses drained into the River Kent, designated as a Special Area of Conservation 400m from the site, so environmental protection was paramount.

Added Value

The project delivery team demonstrated its flexibility and was able to plan, manage and deliver additional works commissioned by the client during the programme of works whilst maintaining the original timescales.

Client Feedback

“The adherence to programme was excellent, workmanship very good and there was good understanding and flexibility to respond to our requirements and needs.”
David Lang
Project Manager, Cumbria County Council

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