A key element of risk assessment for the geological storage of CO2 offshore is the monitoring of transport of leaks from the subsurface via shallow sediments in the marine environment, including its effect on the ecosystem. In 2012, the NERC-funded QICS project constructed the first marine in situ controlled sub-seabed release facility for CO2 in the world in Ardmucknish Bay, Oban when 4.2 tonnes of CO2 was injected. There is significant international interest in this unique facility and the project provides an opportunity for the UK to consolidate its leadership in environmental monitoring and impact studies for CCS. This scoping project will explore the viability and potential scientific goals for a follow on project, with the capability of delivering useful knowledge at the start of the UK CCS commercialisation program.