Engineered earthworks platform and foundation formation for a nationally significant HVDC converter station.

THE CHALLENGE

Founding nationally significant HVDC converter plant on a former landfill of  heterogeneous, non-engineered made ground carrying a collapse-compression risk. The platform had to achieve a maximum 25mm total settlement without recourse to wholesale piling.

THE SOLUTION

GDL’s in-house geotechnical team statistically quantified the collapse-compression risk, enabling a performance-based excavate, modify and replace design in place of blanket piling. Reusing 100% of site-won soils as engineered structural fill met the 25mm settlement criterion while eliminating imported fill, and was verified through phased settlement release against the geotechnical design model.

DELIVERY OUTCOMES

• Programme – 36 weeks against a 45-week programme: 9 weeks ahead, releasing the platform early to follow-on works.
• Engineering Assurance – Measured settlement verified against the pre-construction model; platform accepted for permanent works.
• Safety – Zero RIDDOR-reportable incidents in 26,000 man-hours; zero community complaints.
• Carbon & circularity – 100% site-won soils reused; no bulk import or off-site disposal; circa 20,000 HGV movements avoided.
• Client value – No wholesale piling and no imported fill, reducing cost and critical-path risk; NEC4 delivered with no disputed CEs.
• Local delivery – Circa 90% Stage V self-delivered plant; 60% local EH-postcode workforce; further works secured at EGL1 Murton.