Minimum open space requirement for the entire tract area: 50%. The stormwater management facilities of the development, including retention basins, detention basins, and infiltration basins, shall be considered structures and shall not be considered as open space for the purpose of meeting the minimum open space requirement. The Planning Board, however, may, in its sole discretion, partially or wholly credit as open space facilities such as bioretention systems, vegetative filters, and other stormwater management features that are designed, landscaped and arranged to visually enhance the open space areas, to provide natural approaches to stormwater management, and to improve the appearance of the development.