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CIVIL ENGINEERING PROJECT

M5 J4 Lydiate Ash Salt Barn

Collaborative approach delivers cost and carbon savings

Summary

The construction of a new salt barn returned winter service capabilities to a National Highways maintenance depot in time for severe weather during the 2025/2026 winter season. As principal contractor through the scheme delivery framework, we undertook early contractor involvement and managed the construction of an innovative solution, developed by principal designer Amey.

Scheme Development

The original barn was demolished in 2023 but not replaced due to commercial challenges. This had impacted critical winter maintenance resilience on the M5 and surrounding parts of the strategic road network for two years.

National Highways approached Amey to develop a solution which would meet three challenges:

  • A capacity of 800 tonnes of brown salt and 50 tonnes of white salt.
  • Construction costs to be less than 2.7m including all ancillaries.
  • Operational prior to October 2025.


We worked closely with Amey during the detailed design and construction process to fast-track delivery on site to meet client’s demanding delivery and spend profiles.

Carbon Savings

Amey’s approved design also produced a huge reduction in the carbon emissions from the original proposal by cutting the circular salt barn dome into a battered embankment with a significantly reduced retaining structure. The calculated saving was in excess of 550 tonnes CO2e made up from three key element changes:

  • Using gabion baskets instead of a piled concrete retaining wall removing nearly 2,000 tonnes of concrete.
  • The reduction in topsoil removal of nearly 14,000 tonnes and the reduced size of the concrete apron.
  • Modular timber dome structure enabling off-site construction and lifecycle embodied carbon.

The construction phase

To increase confidence in delivery to programme, the Area 9 Maintenance & Response provider Colas, agreed to vacate the depot and allow unhindered access during construction. This included access to office space and welfare which we took full advantage of as our site offices, benefiting from the carbon efficiency of being connected to the grid.

We engaged R&C Williams, a Midlands based small medium enterprise (SME) to deliver the earthworks and concrete slab elements. Specialist salt-barn builder Eurodome undertook the manufacture and installation of the timber building, while we carried out the surface water drainage, installation of an oil interceptor and external lighting. Other SDF providers on the scheme included Toppesfield for surfacing and Jointline for lining and sealing.

Deliverables

Prominent deliverables installed and constructed were:
  • 17.2m diameter salt barn
  • 4m deep oil interceptor
  • 15m3 Salt saturator tank
  • 3,050m3 earthworks
  • 970m2 concrete works (salt barn and yard).
  • 600m surfacing.
  • 184m3 gabion baskets.

We had full time Carnell project management and supervision on site to oversee the works to ensure positive safety, quality and commercial outcomes. We effectively managed our supply chain to provide the engineering solution. This ensured on time completion in July 2025, in time for the first delivery of salt on 1 August, giving time to stock up before the gritting season.

Benefits

Safety
  • The AFR for both National Highways and supply chain staff was 0.0.
  • Zero RIDDOR or Lost Time Incidents.
  • 28 near misses reported, investigated, with risk mitigation adopted as appropriate.
Customer Service
  • As depot operator, Colas were a key stakeholder. Keeping works to programme kept disruption to a minimum.
  • Reopening the salt barn, after two winter seasons without it, improved winter service resilience in the West Midlands.
  • Using the depot facilities rather than a generator powered set-up saved 65t CO2e and reduced noise and air pollution.
Delivery
  • Collaborative working achieved a 15% cost saving (target price compared to final cost) on the project.
  • Agreed design, and to a lesser extent collaboration during ECI, saved c.£3.5m in construction costs compared to previous design.
  • Unrestricted working from not having to work in and around a live depot reduced programme by 5 weeks.
"I would like to share my appreciation for the professional and collaborative approach the Carnell team brought to the project. This was a challenging endeavour at times, but the competence, knowledge and enthusiasm the Carnell project team brought to the table ensured a successful result. The whole project team worked together, raised issues in a timely and proactive manner, and sought solutions as a team. The project was lead professionally and competently."
Jess HayesNational Highways | Programme Delivery Manager
Jess Hayes