Plans to construct new buildings, construct building expansions or make changes to the exterior of existing structures or other environmental features in the Mixed Use Business District are subject to review by the Planning and Zoning Commission by utilizing the site plan review process set forth in Chapter 1139. This design review shall be conducted as part of the site plan review process and shall be incorporated into the site plan application requirements. The applicant shall submit with the site plan application, drawings, materials, and color samples, and any other aids that would assist the Commission in understanding the proposed project and to determine conformance with the design requirements of this Section.