St. Helena Hybrid RE Structural Peer Review

Project: St. Helena Hybrid RE Project Subject: Structural Design Package for Peer Review and Certification Please find the enclosed structural calculation package for the St. Helena Hybrid RE Project. We are requesting a formal peer review and design check certificate from an ICE-registered Chartered Engineer to satisfy the requirements for this infrastructure project in the British Overseas Territory of St. Helena. The enclosed documentation includes detailed calculations and specifications for the following project components: • 11kV Substation and Transformer Foundations: Includes oil containment (bund) design for 2.42 m3 capacity and switchgear plinths with integrated equipotential grounding. • Solar PV Racking and Foundation Assembly: Utilizes W6x12 steel piles with a 2.0m embedment to ensure lateral stability in volcanic soils. • WTG Foundations and Guy Anchors: Features a central compression pad and four 18.0 m3 concrete gravity anchors for the Vergnet GEV MP C turbine. • Switchgear Control Building: Reinforced masonry structure designed for 35 m/s wind zones with mandatory stainless steel hurricane tie-downs. • Termination H-Pole Structure: Twin steel pole configuration with back-stayed guy wires and concrete collar reinforcements to manage high base-bearing pressures. • Temporary Erection Works: Includes winch anchor "deadman" calculations for turbine tilt-down operations. Standard Compliance Verification: The design has been updated to align with the following Eurocode standards: • BS EN 1990: Basis of structural design (Partial factors: Gamma G = 1.35, Gamma Q = 1.50). • BS EN 1991-1-4: Wind actions based on a 35 m/s fundamental wind velocity. • BS EN 1997: Geotechnical design, specifically addressing the island's volcanic ash and stiff clay soil profiles. Specific Corrective Actions Addressed: We have proactively addressed several critical site-specific issues, including increasing the transformer bund wall to 350mm for environmental compliance , specifying Sulfate Resisting Cement (SRC) for volcanic soil contact , and adding a 0.5m shear key to the guy anchors to resolve sliding factor-of-safety requirements. We look forward to your review.

Project ID: 40189420