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Lean Project Summary

Kier’s A417 team addressed earthworks material imbalance caused by variable ground conditions through a structured Lean problem-solving approach. Using DMAIC, the team reviewed baseline earthworks assumptions, assessed programme and material risks, and analysed delivery constraints. Production control was used to compare planned versus actual earthworks outputs, sequencing and material availability, improving understanding of flow and programme impacts. Collaborative planning sessions brought together construction, design, environmental and planning stakeholders to review evidence, challenge assumptions and assess viable options. This approach led to the adoption of a site-won borrow pit strategy, improving material flow, reducing waste and supporting more reliable programme delivery.

Lean Project Benefits Summary

The Borrow Pit lean improvement project reduced programme risk, delivered the lowest cost solution, and significantly lowered carbon emissions compared with import and stabilisation options. The site‑won material exchange approach enabled the earthworks shortfall to be resolved in around 50 working days, rather than the estimated 416 days required for full import, protecting programme certainty and reducing delivery risk. Carbon emissions were minimised by limiting haulage, with the site‑won solution generating roughly 264 tonnes of CO₂ compared with an estimated 4,565 tonnes for import, avoiding around 4,300 tonnes of CO₂. The approach also avoided the higher carbon impact of lime stabilisation. Overall cost was lowest at approximately £6.6 million, compared with around £8.97 million for import, representing an avoided cost of about £2.3 million, while maintaining full compliance with DCO and Series 600 requirements.

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Lean Construction Development Programme (LCDP) Project

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Problem Solving Strategy (DMAICT)

Define

During earthworks on the A417 Missing Link scheme, volumes of unsuitable Fullers Earth (Class 4) significantly exceeded design expectations. This resulted in a material imbalance and a shortfall of suitable Class 1 material needed to deliver the works in line with Series 600 requirements.
Without intervention, the issue would have led to major programme delays measured in months, multi‑million‑pound cost impacts, increased carbon emissions from importing additional material, and heightened delivery risk. Addressing the challenge required careful consideration of environmental, planning, ecological, and stakeholder constraints arising from the scheme’s location within the Cotswolds AONB and the limitations set by the Development Consent Order (DCO).

Measure

Baseline data was established through ground investigation records, excavation outputs, and material classification results, which confirmed that the quantity of unsuitable Fullers Earth exceeded the allowances made during design. The shortfall in suitable Class 1 material was quantified against the remaining earthworks volumes required for permanent works.
Programme impact, cost implications, haulage requirements, and carbon emissions were assessed for each option using excavation volumes, haulage assumptions, duration estimates, and CO₂ calculations. This provided a measurable comparison of cost, programme, carbon, and risk for each potential solution.

Analyse

The analysis examined the causes of the earthwork's material imbalance and its effect on delivery performance. Excavation outputs, material classifications and programme data were reviewed to understand why design assumptions no longer matched site conditions. Production control principles were applied to assess earthworks flow, planned versus actual outputs, sequencing constraints and material availability, highlighting the impact of unsuitable material on productivity, haulage and programme certainty. Collaborative sessions with construction, design, environmental and planning teams enabled evidence review, challenge of assumptions and identification of constraints. This supported comparison of full import exchange, site‑won exchange and lime stabilisation across cost, programme, carbon, constructability and risk. The assessment confirmed that variable ground conditions were the primary cause and that site‑won exchange offered the most balanced solution

Improve

The project team developed and implemented a site‑won material exchange strategy using a borrow pit located within the DCO boundary. This allowed suitable Class 1 material to be sourced locally and reused across the scheme, replacing unsuitable material without the need for large‑scale importation. The approach reduced programme risk, significantly lowered carbon emissions compared with import and stabilisation options, improved material flow, and delivered the lowest overall cost. Early and continuous engagement with environmental bodies, planners, and stakeholders ensured that appropriate mitigation measures were agreed and that excavation activities could proceed in a controlled and compliant manner.

Control

Controls were established through agreed material management plans, environmental mitigation measures, and continuous monitoring of excavation outputs and material performance. Stakeholder approvals and constraints were embedded into the delivery approach, ensuring compliance with DCO commitments and Series 600 requirements. Progress was reviewed through regular project and stakeholder forums, with clear governance to manage risks associated with ecology, archaeology, and material quality throughout implementation.

Transfer

Lessons learnt from this project demonstrates the value of early option appraisal, whole system thinking, and collaborative stakeholder engagement when addressing earthworks material risk. Future schemes should allow for flexibility in earthworks strategies at design stage, including consideration of borrow pits where appropriate. The approach and decision-making framework used on the A417 Missing Link can be replicated on other major infrastructure projects to reduce waste, carbon, cost, and programme risk when ground conditions differ from initial assumptions.

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Other Project Benefits

Meeting the needs of all users

Meeting the needs of all users - Other

Improving safety, health & wellbeing for all

Improving safety, health & wellbeing for all-Other

Delivering better environmental outcomes

Delivering better environmental outcomes - Other

Sustain a well-maintained and resilient network

Sustain well-maintained & resilient network- Other

Providing fast and reliable journeys

Providing fast and reliable journeys - Other

Achieve efficient delivery

Achieve efficient delivery - Other

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