1129.05 GENERAL REQUIREMENTS.
   (a)   Minimum Project Area. Minimum area for a PUD District shall be three contiguous acres. When the PUD proposes a mixture of residential uses with commercial or industrial uses, the Planning Commission may limit the development of not more than 12% of the tract to commercial uses and not more than 10% of the tract to industrial uses.
   (b)   Relation to Streets. The PUD District shall be so located with respect to major streets and highways or other transportation facilities as to provide direct access to the districts without creating traffic along minor streets in residential neighborhoods outside the District.
   (c)   Utilities. The PUD District shall be so located in relation to sanitary sewers, water lines, storm and surface drainage systems, and other utilities systems and installations that neither extension nor enlargement of the systems will be required by the City. However, the developer may install utility lines at his expense upon approval of the appropriate agencies.
   (d)   Common Open Space. A minimum of 20% of the land developed in any PUD shall be reserved for common open space and recreational facilities for the residents or users of the area being developed. Every property developed under the PUD should be designed to abut upon common open space or similar areas. A clustering of dwellings is encouraged. In areas where townhouses are used, there shall be no more than eight townhouse units in any contiguous group.
   (e)   Disposition of Open Space. The required amount of common open space land reserved under a PUD shall either be held in corporate ownership by owners of the project area for the use of each owner who buys property within the development or be dedicated to the City and retained a common open space for parks, recreation, and related uses. All land dedicated to the City must meet the Planning Commission's requirements as to size, shape, and location. Public utility and similar easements and rights of way for watercourses and other similar channels are not acceptable for common open space dedication to the City unless the land or right of way is usable as a trail or similar purpose and approved by the Planning Commission. The responsibility for the maintenance of all open spaces shall be specified by the developer before approval of the final development plan.
   (f)   Minimum Lot Sizes.
      (1)   Lot area per dwelling unit may be reduced by not more than 40% of the minimum lot area required in Chapter 1127. A diversification of lot sizes is encouraged.
      (2)   Lot width may be varied to allow for a variety of structural designs. It is also recommended that setbacks be varied.
   (g)   Height Requirements. For each foot of building height over the maximum height regulations specified in Chapter 1127, the distance between these buildings and the side and rear property line of the PUD project area shall be increased by a one-foot addition to the side and rear yard required in the districts.