The mining company donates the land to Durham Wildlife Trust six years after it closed.
Police say a woman in her 40s was arrested following the collision and taken into custody.
There were objections from those fearing loss of countryside and the impact on local services.
Police say inquiries continue into the fatal crash which involved a silver Audi and a white BMW.
Abbie Devanney died at the scene of the crash near the Jolly Drovers pub in County Durham.
