Significant degradation of adiabatic effectiveness can be caused by surface roughness and near-hole obstructions formed from deposition of contaminants. Since obstructions are a randomly occurring event, there are many variables to consider, namely shape, width, length, height, and position in relation to a film cooling hole. In addition to this, the level of overall surface roughness must also be considered. This study investigated these different variables on the suction side of a scaled-up turbine vane using cylindrical holes to determine what is important when considering surface roughness and obstructions. In addition, the use of a transverse trench was tested with a rough wall and near-hole obstructions and was found to be a method to mitigate a large part of the degrading effects caused by a rough surface and near-hole obstructions.