The Historic Design Review Overlay Zone (HDRO) is an overlay district which is intended to be combined with any other district located in an area containing a substantial number of historic buildings where it is determined desirable to protect the overall appearance and integrity of the district by preserving existing structures and regulating the design of new structures and changes in the appearance of existing structures. The purpose of this district is to ensure that proposed buildings, structures, signs, and landscaping and modifications to buildings, structures, signs, and landscaping within these areas are in harmony with the historic nature of the district. The intent of the zone is to promote the overall economic vitality of a district, enhance tourism and to stabilize and increase property values. This district may be applied to areas containing public or private buildings determined to be historically significant.

1. Development standards for the HDRO.
   1. Uses: Permitted, conditional and prohibited uses shall be as set forth in the principal zone.
   2. Minimum parcel or lot size: As established by the principal zone.
   3. Density: As established by the principal zone.
   4. Setbacks, building height, parking requirements and other applicable development standards: As established by the principal zone.
2. Special development standards for the HDRO. Development in the HDRO district shall conform to architectural theme and development guidelines established by the board of supervisors pursuant to subsection 17.67.010(G) of this chapter. In reviewing and approving the application for design review, the planning director shall find that the application complies with the architectural theme and development guidelines established by the board of supervisors. In the instance that a special development standard established by this section conflicts with a development standard of the principal zone, the special development standard established by this section shall apply.
3. HDRO plan review-required. Except as provided in this section, no commercial, industrial or residential use shall be established, no development shall occur, no exterior advertising display shall be installed and no building and grading permit shall be issued for any commercial, industrial or residential development in the HDRO district until an application for design review plan has been submitted to and approved by the planning director in accordance with the procedures established in this section.
4. HDRO plan-application contents. An application for design review shall include the following:
   1. A completed commercial, industrial and multifamily dwelling building permit application form. Complete construction drawings are not necessary for the design review process.
   2. A plot plan drawn to the scale specified by the planning director which contains the information specified in section 17.08.150 of this title.
   3. Elevations of all sides of the proposed building or structure showing:
      1. Dimensions of the buildings or structures.
      2. Proposed architectural treatment, building materials and exterior colors.
      3. Roof design and materials.
      4. Size and spacing of windows, doors, and other openings.
      5. Signs.
      6. Exterior lighting.
      7. Exterior mechanical equipment and above ground utilities. An exemption from the requirement for providing elevations of all sides of the proposed building or structure may be allowed where it can be shown to the satisfaction of the planning director that certain sides of the building/structure are not visible from public property or public rights-of-way. In this instance the elevations of the sides not visible are not required.
   4. Preliminary grading plan indicating grading necessary for the proposed structures, access roads and parking areas. The plan shall indicate the location, height and grade of all cut and fill banks necessary for the proposed project.
   5. Narrative description of the proposed development and how it was designed in accordance with the architectural theme and design guidelines established by the board of supervisors.
5. HDRO plan-application processing procedures. A pre-application meeting with the planning department to discuss a proposed project and the applicable design review standards is strongly encouraged. Upon receipt and acceptance of a design review plan application as complete, the planning department shall, within five (5) days, refer such application to the design review committee appointed by the board of supervisors having jurisdiction over the area in which the development is proposed. The design review committee shall formulate a recommendation to approve, conditionally approve or deny the design review plan within fourteen (14) days of the receipt of a completed application from the planning department. In the instance that no design review committee has been appointed or the appointed design review committee fails to formulate a recommendation by majority vote, the planning director shall consider the design review plan. The planning director shall consider the design review plan application along with the recommendation and act to approve, conditionally approve or deny the application. Action on the design review plan shall occur within five (5) days of receipt of the recommendation from the design review committee. The planning director's action shall be based upon the findings listed in subsection 17.67.010(B) of this section. The planning director shall provide specific findings if the design review plan is denied.
6. HDRO plan application-review exemption. The planning director may approve an exemption from review by the design review committee where it can be determined that the proposed development is a minor alteration or expansion of an existing development that will not affect the achievement of the architectural and design review goals established by the board of supervisors for the affected area. For the purpose of this subsection a minor alteration or expansion is defined as less than ten percent (10%) of the existing building size that will not significantly modify the exterior appearance of the structures and/or site. The applicant shall be required to submit the information required by subsection 17.67.010(D) of this section in order to justify the exemption.
7. Establishment of architectural theme and development guidelines for HDRO districts. The board of supervisors shall establish an architectural theme and development guidelines for each HDRO district established pursuant to this section. The standards may be adopted separately or as part of a Specific Plan for an area and shall be adopted by resolution or ordinance.

1. Demolition permit required. Except as provided in this section no building or structure identified by the county as historically significant as shown in Appendix C of the Mariposa Town Planning Area Specific Plan, or within a designated historic design review overlay zone (HDRO), shall be demolished without first obtaining approval from the planning director.
2. Demolition permit-review findings. No permit shall be issued to demolish or cause to be demolished any building, structure or portion thereof that has been identified by the county as historically significant within any historic design review overlay district unless:
   1. The planning director determines that the building or structure has no historical value or significance and does not contribute to the historical character of the district; or
   2. The planning director determines that the owner would have no economic use of the property unless the structure is removed. It is the applicant's responsibility to submit to the county financial data to substantiate such claim, including the cost, assessed value, taxes, appraisals, listings and income from the property; or
   3. The planning director determines that the structure or building is in such a deteriorated condition that it is determined to be unrepairable and that demolition will not have a significant effect on the achievement of the purpose of this title; or
   4. The planning director determines, upon consultation with the chief building inspector, county engineer, county fire warden or other appropriate individuals that an imminent safety hazard exists, and that demolition is the only feasible means to secure the public safety. The director's determination in this matter shall be guided by the standards and criteria set forth in the current editions of the Uniform Building Code, Uniform Fire Code and State Historic Building Code.
3. Demolition permit-application processing procedures. Consideration of a demolition permit shall follow the procedures outlined in section 17.67.010(E) of this title.
4. Demolition permit-action. After review of all pertinent information the planning director shall exercise one of the options listed below:
   1. Approve the demolition permit if the application conforms with one of the findings listed in subsection 17.67.020(B).
   2. Direct a stay of demolition for a maximum period of four (4) weeks in order to allow time for the applicant and the planning director to seek alternative solutions to demolition. If no alternatives are found, after the period established for the stay of demolition, the director may approve the application.
   3. Deny the application if the findings listed in subsection 17.67.020(B) cannot be made.