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A. Legal Nonconforming Uses and Structures May Continue. Overwater uses and structures, and uses and structures 25 feet landward from the OHWM, which were legally created may be maintained, repaired, renovated, remodeled and completely replaced to the extent that nonconformance with the standards and regulations of this chapter is not increased.

B. Expansion of Legal Nonconforming Structures. Expansions of legal nonconforming overwater structures and structures upland 25 feet from the OHWM are permitted; provided, that the expanded portion of the structure is constructed in compliance with this chapter and all other standards and provisions of the Mercer Island development regulations, including this chapter.

C. No Net Loss Standard and Mitigation Sequencing. No development shall be approved unless the applicant demonstrates to the code official’s satisfaction that the shoreline development will not create a net loss of ecological function in the shorelands.

1. Standards Presumed to Meet No Net Loss. When all individual development standards that apply to a development project do not explicitly require a determination of no net loss and the project conforms with all such standards, there is a rebuttable presumption that the project does not create a net loss of ecological function to the shorelands.

2. No Net Loss Plan. Whenever an applicant seeks a variance or conditional use permit or an applicable development standard explicitly requires a determination of no net loss of ecological function, the applicant shall provide the city with a plan that demonstrates the proposed project will not create a net loss in ecological function to the shorelands. The plan shall accomplish no net loss of ecological function by avoiding adverse ecological impacts that are not reasonably necessary to complete the project, minimizing adverse ecological impacts that are reasonably necessary to complete the project, and mitigating or offsetting any adverse impacts to ecological functions or ecosystem-wide processes caused by the project. The code official may require the plan to include reports from qualified professionals with expertise in ecological function. The plan’s compliance with the no net loss requirement may be considered through the SEPA process.

i. Off-Site Mitigation Permitted. While on-site mitigation is preferred, off-site mitigation may be permitted at the discretion of the code official.

ii. Demonstration of No Net Loss Supported by a Qualified Professional. The code official may require any applicant to provide reports by qualified professionals that demonstrate to the code official’s satisfaction that the applicant’s proposed plan avoids a net loss in ecological function.

D. Shoreline Habitat and Natural Enhancements Held Harmless. In those instances where the OHWM moves further landward as a result of any action required by this chapter, or in accordance with permits involving a shoreline habitat and nature systems enhancement approved by the city, or a state or federal agency, the shoreline setback shall be measured from the location of the OHWM that existed immediately prior to the action or enhancement project.

E. The development of two or more dwelling units on a lot abutting the OHWM should provide joint use or community dock facilities, when feasible, rather than allow individual docks for each lot.

F. New development should be located and designed to avoid the need for future shoreline stabilization to the extent feasible. This future shoreline stabilization standard does not apply to stabilization that occurs pursuant to MICC 19.13.050(B)(1). New structural stabilization measures in support of new non-water-dependent development, including single-family residences, shall only be allowed when all of the conditions below apply:

1. The erosion is not being caused by upland conditions, such as the loss of vegetation and drainage.

2. Nonstructural measures, such as placing the development further from the shoreline, planting vegetation, or installing on-site drainage improvements, are not feasible or not sufficient.

3. The need to protect primary structures from damage due to erosion is demonstrated through a geotechnical report, in compliance with subsection MICC 19.13.050(B)(7). The damage must be caused by natural processes, such as currents and waves.

4. The erosion control structure will not result in a net loss of shoreline ecological functions. (Ord. 19C-06 § 1 (Att. A)).