Wind farm areas may provide an opportunity for the deployment of wave energy converters (WEC) in an environment with reduced risk of collision or accidental disturbance. Complementary use of electric infrastructure (export cable) and maintenance may provide additional economic incentives. In addition, the environmental impact of combined extraction of wind and wave energy may be smaller than the separate alternative. We discuss a number of uncertainties and negative environmental interactions that were identified during the Environmental Impact Assessment (EIA) for the first offshore energy park combining offshore wind and wave energy extraction. Assumptions on possible impacts were inferred from research and monitoring results from both WEC pilot projects and offshore wind farms separately as well as from the Environmental Impact Statement (EIS) submitted by the developer. A number of uncertainties were identified with regards to seabirds, non-indigenous species, marine mammals and maritime safety which will have to be addressed prior to a full scale deployment. As a result, the environmental license that was granted includes a pilot phase during which the above mentioned environmental impacts will be quantified.