An adopted and implemented basin plan tailored to a specific basin may be used to develop requirements for source control, stormwater treatment, streambank erosion control, wetlands, and water quality sensitive areas. Adopted and implemented watershed-based basin plans may be used to modify any or all of the minimum requirements addressed in the manual; provided, that the level of protection for surface or ground water achieved by the basin plan will equal or exceed that which would otherwise be achieved by implementation of the provisions of this code in the absence of a basin plan. Basin plans shall evaluate and include, as necessary, retrofitting of BMPs for existing development and/or redevelopment in order to achieve watershed-wide pollutant reduction goals. Standards developed from basin plans shall not modify any of the above requirements until the basin plan is formally adopted and fully implemented by the city. (Ord. 1169 § 2, 2009).