Ports North completed expansion of the Port of Cairns entrance channel in 2019 following a 10 year planning and approvals process. As the port is within the Great Barrier Reef World Heritage Area the planning, compliance, and monitoring requirements were extensive. Two stages of Environmental Impact Statement assessment were required as new legislation banning sea disposal of capital dredged material came into effect part way through, leading the project to be re-scoped to adopt material placement on land. Periodic enhancement of port infrastructure was required to enable regional economic benefits, but this expansion presented significant challenges to attain the balance between growth and protection of the environment. As a protected harbour, Cairns is home to sensitive marine habitats where management of marine water quality was paramount, however the project’s land based activities encountered comparable challenges in regard to vegetation, groundwater, flooding, and acid sulphate soils. Meeting these challenges required the project to adopt innovative partnerships and engagement of leading scientists, to ensure the latest ecological thresholds for water quality could be applied to minimise potential impacts. Establishing an experienced independent oversight committee ensured successful project and environmental management. Good communications between contactors, regulators, and scientific experts was key for rapid and collaborative problem solving. This approach resulted in protection and management of critical marine habitats, while allowing essential development to occur, and provides examples of initiatives to consider for future port development projects.