The specific purpose of the D Design and Development Control Overlay District is to ensure appropriate review for projects in areas of environmental sensitivity or where urban design and site planning considerations are judged important. Three subdistricts are established to accomplish this objective:

D1 -- Design Control overlay district will require Architectural Review Committee approval of all new construction and exterior alterations and additions. Specific limitations are set on conditions of approval to prohibit the Committee from imposing requirements that are more restrictive than those prescribed by applicable base district regulations of a valid use permit or variance.

D2 -- Development Control overlay district will require Planning Commission and Architectural Review Committee approval of all new construction and exterior alterations and additions. Conditions of approval may impose requirements that are more restrictive than those prescribed by applicable base district regulations if the Planning Commission finds these requirements are necessary to have a harmonious relationship with existing and planned uses in the vicinity and with sensitive environmental resources.

D3 -- Historic Development Control overlay district will require Planning Commission and Architectural Review Committee approval of all new construction, exterior alteration, or addition on a site which could affect a designated historic building or site. Conditions of approval may impose requirements that are more restrictive than those prescribed by applicable base district regulations in the Planning Commission finds these requirements are necessary to preserve the setting or to create a harmonious relationship with adjoining or nearby historic resources.