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A. Activities that adversely affect wetlands and/or wetland buffers shall include mitigation sufficient to achieve no net loss of wetland function and values in accordance with Section 14.100.070 and this section.

B. Wetland Alterations. Compensatory mitigation shall be provided for all wetland alteration and shall reestablish, create, rehabilitate, enhance and/or preserve equivalent wetland functions and values. Compensation for wetland alterations shall occur in the following order of preference:

1. Reestablishing wetlands on upland sites that were formerly wetlands.

2. Rehabilitating wetlands for the purposes of repairing or restoring natural and/or historic functions.

3. Creating wetlands on disturbed upland sites such as those consisting primarily of nonnative, invasive plant species.

4. Enhancing significantly degraded wetlands.

5. Preserving Category I or II wetlands that are under imminent threat; provided, that preservation shall only be allowed in combination with other forms of mitigation and when the shoreline administrator determines the overall mitigation package fully replaces the functions and values lost due to development.

C. Mitigation Ratios. Compensatory mitigation for wetland alterations shall be based on the wetland category and the type of mitigation activity proposed. The replacement ratio shall be determined according to the ratios provided in Appendix 2: Table A2-4; provided, that replacement ratio for preservation shall be determined by the shoreline administrator on a case-by-case basis. The created, re-established, rehabilitated or enhanced wetland area shall at a minimum provide a level of function equivalent to the wetland being altered and shall be located in an appropriate landscape setting.

Appendix 2: Table A2-4: Mitigation Ratios for Western Washington

Wetland Category

Creation

Rehabilitation Only (1)

Reestablishment or Creation (R/C) and Rehabilitation (RH) (1)

Reestablishment or Creation (R/C) and Enhancement (E) (1)

Enhancement Only (1)

IV

1.5:1

3:1

1:1 R/C and 1:1 RH

1:1 R/C and 2:1 E

6:1

III

2:1

4:1

1:1 R/C and 2:1 RH

1:1 R/C and 4:1 E

8:1

II (Estuarine)

On a case-by-case basis

4:1

Rehabilitation of an estuarine wetland

On a case-by-case basis

On a case-by-case basis

On a case-by-case basis

II

(Interdunal)

2:1

Compensation has to be interdunal wetland

4:1

Compensation has to be interdunal wetland

1:1 R/C and 2:1 RH

Compensation has to be interdunal wetland

Not recommended (2)

Not recommended (2)

II

3:1

6:1

1:1 R/C and 4:1 RH

1:1 R/C and 8:1 E

12:1

I (Forested)

6:1

12:1

1:1 R/C and 10:1 RH

1:1 R/C and 20:1 E

24:1

I (Based on Score for Functions)

4:1

8:1

1:1 R/C and 6:1 RH

1:1 R/C and 12:1 E

16:1

I (Natural Heritage)

Not recommended (3)

6:1

Restoration of a Natural Heritage site

R/C not recommended (3)

R/C not recommended (3)

On a case-by-case basis

I (Coastal Lagoon)

Not recommended (3)

6:1

Rehabilitation of a coastal lagoon

R/C not recommended (3)

R/C not recommended (3)

On a case-by-case basis

I (Bog)

Not recommended (3)

6:1

Rehabilitation of a bog

R/C not recommended (3)

R/C not recommended (3)

On a case-by-case basis

I (Estuarine)

On a case-by-case basis

6:1

Rehabilitation of an estuarine wetland

On a case-by-case basis

On a case-by-case basis

On a case-by-case basis

Notes:

(1)These ratios are based on the assumption that the rehabilitation or enhancement actions implemented represent the average degree of improvement possible for the site. Proposals to implement more effective rehabilitation or enhancement actions may result in a lower ratio, while less effective actions may result in a higher ratio. The distinction between rehabilitation and enhancement is not clear-cut. Instead, rehabilitation and enhancement actions span a continuum. Proposals that fall within the gray area between rehabilitation and enhancement will result in a ratio that lies between the ratios for rehabilitation and enhancement (see Chapter 14.100 Appendix H for further discussion).

(2)Due to the dynamic nature of interdunal systems, enhancement is not considered an ecologically appropriate action.

(3)Natural Heritage sites, coastal lagoons and bogs are considered irreplaceable wetlands because they perform some functions that cannot be replaced through compensatory mitigation. Impacts to such wetlands would therefore result in a net loss of some functions no matter what kind of compensation is proposed.

D. Compensation for wetland buffer impacts shall occur at a minimum 1:1 ratio. Compensatory mitigation for buffer impacts shall include enhancement of degraded buffers by planting native species, removing structures and impervious surfaces within buffers and other measures.

E. Mitigation banks shall not be subject to the replacement ratios outlined in the replacement ratio table above, but shall be determined as part of the mitigation banking agreement and certification process.

F. Buffers. Replacement wetlands established pursuant to these mitigation provisions shall have adequate buffers to ensure their protection and sustainability. The buffer shall be based on the category and land use intensity in Tables 14.100.250.C.1a and 14.100.250.C.1b; provided, that the shoreline administrator shall have the authority to approve a smaller buffer when existing site constraints (such as a road) prohibit attainment of the standard buffer.

G. Adjustment of Ratios. The shoreline administrator shall have the authority to adjust these ratios when a combination of mitigation approaches is proposed. In such cases, the area of altered wetland shall be replaced at a 1:1 ratio through reestablishment or creation and the remainder of the area needed to meet the ratio can be replaced by enhancement at a 2:1 ratio. For example, impacts to one (1) acre of a Category II wetland requiring a 3:1 ratio for creation can be compensated by creating one (1) acre and enhancing four (4) acres (instead of the additional two (2) acres of creation that would otherwise be required).

H. Location. Compensatory mitigation shall be provided on or off site in the location that will provide the greatest ecological benefit and have the greatest likelihood of success; provided, that mitigation occurs as close as possible to the impact area and within the same watershed sub-basin as the permitted alteration. Compensatory mitigation shall use a landscape-based approach sufficient to maintain the functions and values of critical areas. An applicant may be required to provide compensatory mitigation through an aquatic resource restoration, establishment, enhancement and/or preservation activity.

I. Protection. All mitigation areas whether on-site or off-site shall be permanently protected and managed to prevent degradation and ensure protection of critical area functions and values into perpetuity. Permanent protection shall be achieved through deed restriction or other protective covenant in accordance with Sections 14.100.080 and 14.100.081.

J. Timing. Mitigation activities shall be timed to occur in the appropriate season based on weather and moisture conditions and shall occur as soon as possible after the permitted alteration.

(Ord. 6611 § 1, Amended, 08/09/2017)