Open space. No less than 30% of the site shall be provided and maintained in nonvehicular open space. In addition, the developer shall be required where possible to preserve or incorporate natural features, such as woods, streams and open space areas, which add to the overall cohesive development of the high-rise apartment and the overall community development. However, all conditions deemed hazardous by the Planning Commission, including natural feature hazards, are to be eliminated or avoided, or all precautions deemed appropriate by the Planning Commission to reduce the hazard are to be provided by the developer.