A684 Birklands Culvert
Overview
Following the extraordinary damage caused by Storm Desmond and its impact on the Birklands Culverts on the A684, EWCE was commissioned under the Cumbria Infrastructure Recovery Programme by the County Council to design and construct a solution to provide resilience for future flooding events and continued connectivity for this important section of the South Lakeland highway. Two parallel culverts crossed beneath the A684 at Birklands, and were susceptible to surcharge during heavy rainfall events and commonly flooded the public highway.
Flooding of the highway occurred on six occasions during 2016 and was becoming an increasing problem. A single flood event could cause the closure of the A684 for several days with associated issues lasting for several weeks after the rainfall. This is one of two routes into Kendal from the M6 and flooding caused long diversions.
Key Challenges
- Buried Services
- Environmental protection
- Water Management
Before any ground breaking works were undertaken, a CAT and Genny survey identified existing services. Vacuum excavation was undertaken to reveal services. An 11kv electrical cable was in the vicinity of the works. The cable was trial holed and clearly marked out before works commenced. No mechanical excavation within 500mm of cables was permitted. Similarly an 11kv cable crossed the line of the excavation for the new culvert. The electrical cable was exposed during vac ex and then split ducted and protected whilst works were undertaken around it. Similarly Vodaphone, BT Virgin Media ducts, and water main were identified and protected.
The channel bed immediately upstream of the inlet headwall was protected by filled mattresses, with banks protected by biodegradable mats and new unreinforced slopes created. A stilling basin was installed at the culvert outfall to dissipate energy and reduce the potential for scouring of the outfall headwall and channel downstream.
The watercourses drained into the River Kent, designated as a Special Area of Conservation, 400m from the sites, so environmental protection was paramount. Temporary works included the construction of cofferdams. A Groundforce Shorco trench support system was used to facilitate concrete culvert box section and pipe installation. Over pumping of the existing becks/drains to facilitate construction of the new culverts was undertaken. Monitoring water levels was continually undertaken.
The works required the installation and maintenance of a full road closure for 7 weeks with 4 weeks 2-way lights.
Client Feedback
Very good aesthetically to design and the land owners satisfaction”