Optimising Site Investigations for Offshore Wind Farm Projects Mark Finch Geotechnical Engineering Manager Hydrosearch A

1. Optimising Site Investigations forOffshore Wind Farm ProjectsMark FinchGeotechnical Engineering ManagerHydrosearch Associates, Aberdeen UK Offshore Wind Conference 26/27 March 2003 London

2. CONTENTS • Introduction • Out with the old, in with the new….. • Challenges of offshore wind farm sites • Integrated site investigations • Seabed risk management • Conclusions

3. OUT WITH THE OLD IN WITH THE NEW…. • Typical North Sea Offshore Oil and Gas Development • “Deep” water (30m +) • Seabed conditions usually well known • Environmental conditions well known • Small development area (1 to 5 km2) • Foundations subject to high axial load+ relatively low overturning moment • Foundations ~ 1% to 2% of total project cost

4. OUT WITH THE OLD IN WITH THE NEW…. • ‘Typical’ Offshore Wind Farm Development • Shallow water (<20m) but increasing • Often placed on sites with little existing knowledge of seabed and environment • Large development areas (10 to 100 km2) • Foundations subject to low axial load + very large overturning moment • Foundations ~ 25%of total project cost After “Dynamics and Design Optimisation of Offshore Wind Energy Conversion Systems”, Kühn, M., 2001

5. ISSUES Close to shore Shallow water Environmentally sensitive areas High wind speeds Limited existing information on seabed conditions CONSEQUENCES Selection of survey equipment Permitting Planning of surveys Consultation Weather downtime (particularly for smaller craft in shallow water) Contracting strategies? Range of survey techniques CHALLENGES OF OFFSHORE WIND FARM SITES

6. DESK STUDY 1) Define Risk FEED Site Survey 2) Reduce Risk Lab Testing RISK ASSESSMENT Parameters 3) Mitigate Risk Engineering Verification 4) Manage Risk Engineering Construction SEABED RISK MANAGEMENT

7. Desk Study FEED z ? ? ? ? ? Geophysical Survey Geotechnical Survey INTEGRATED SITE INVESTIGATION PROCESS

8. METOCEANDATA REGIONAL GEOTECHNICAL & GEOPHYSICAL DATA DESK STUDY NEARBY CONSTRUCTION RECORDS DATA IN PUBLIC DOMAIN INTEGRATED GEOTECHNICAL MODEL A TYPICAL DESK STUDY

9. GEOPHYSICAL SURVEYS

10. GEOTECHNICAL SURVEYS

11. GEOTECHNICAL PARAMETERS

12. SEABED RISK MANAGEMENT

13. SEABED RISK MANAGEMENT A formal seabed risk management framework ensures: • That OPPORTUNITIES are identified • A minimum exposure to seabed risk • Risks are captured and recorded • Risks are effectively communicated • Ownership of risk is defined and accountability promoted • A rational basis for decision making • Costs are controlled • Seabed risk management is inherent in an optimised approach to site investigation

14. PLAN FOR SUCCESS • Desk study & risk assessment • Plan an integrated survey • Make sure that project budgettakes account of significant foundation cost and risk (remember foundation costs can be up to 25% of total project cost) • Plan as far ahead as possible (resources can be scarce) • You get what you pay for

15. CONCLUSIONS • Offshore wind farms present a significant challenge with respect to foundation design and installation and, therefore, site investigations • For a given development geotechnical risks are relatively much higher than for typical offshore oil and gas developments (25% versus 1%) • Significant risks require significant resources • An integrated approach to offshore site investigation is a very powerful tool to quantify and manage seabed risk

16. Thank You