(a) As used in this section, the term "common recreation and open space" means the total amount of improved usable area, including outdoor space, permanently set aside and designated on the site plan as recreational or open space for use by residents of the residential planned unit development.

(b) Twenty-five percent of the gross site acreage shall be delineated as tracts for common recreation and open space.

(c) Common open space shall be integrated throughout the residential planned unit development to provide for a linked recreational and open space system. Such usable space may be in the form of active or passive recreation areas, including but not limited to: playgrounds, golf courses, beach frontage, nature trails and lakes. Common open space shall be improved to the extent necessary to complement the residential uses and may contain compatible and complementary structures for the benefit and enjoyment of the residents of the residential planned unit development. Easements, parking areas, perimeter setback areas, road rights-of-way and minimum yards and minimum spacings between dwelling units may not be included in determining open space. Perimeter setback areas may be included as open space if improvements such as bikeways and pedestrianways are provided. Water bodies may be used to partially fulfill common open space requirements; calculations for such may not exceed 50 percent of the required open space. The exclusion of water bodies which are in whole or part drainage easements may be waived by the city council after adequate measures are provided which guarantee in perpetuity a level of water quality acceptable for recreational purposes. Private navigable canals shall not be utilized in fulfilling the common open space requirement. If golf courses are used to partially fulfill common open space requirements, calculations for such may not exceed 60 percent of the required open space. Where a golf course is utilized to partially fulfill the open space requirement, other facilities to meet the active residential needs of children and adults shall be provided. All water areas included as part of the open space requirement shall be permanent water bodies and shall be improved with 3:1 minimum sloped edge extending at least 20 feet into the water areas and planted with grass and maintained around all sides so as not to harbor mosquitoes, insects and rodents, unless it is determined by an environmental review of the water body that such slope or improvements would be detrimental to the ecology of such water body site.