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V.  WETLANDS
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20.25H.095 Designation of critical area and buffers.
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A. Definition of Wetland. Those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas. Wetlands do not include those artificial wetlands intentionally created from nonwetland sites, including, but not limited to, irrigation and drainage ditches, grass-lined swales, canals, detention facilities, wastewater treatment facilities, farm ponds, and landscape amenities, or those wetlands created after July 1, 1990, that were unintentionally created as a result of the construction of a road, street, or highway. Wetlands may include those artificial wetlands intentionally created from nonwetland areas to mitigate the conversion of wetlands.

B. Delineation of Wetland. Wetland boundaries shall be delineated consistent with the standards and methods described in the U.S. Army Corps of Engineers 1987 Wetlands Delineation Manual, as amended, and the 2010 Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region, as amended.

C. Designation of Critical Area. The following wetlands are hereby designated as critical areas subject to the requirements of this part. Wetlands are classified into category I, category II, category III and category IV wetlands based on the adopted Washington State Wetland Rating System for Western Washington, Washington State Department of Ecology Publication Number 14-06-029, published in October 2014, as amended.

1. Category I Wetlands. Category I wetlands are those that (a) represent a unique or rare wetland type; or (b) are more sensitive to disturbance than most wetlands; or (c) are relatively undisturbed and contain ecological attributes that are impossible to replace within a human lifetime; or (d) provide a high level of functions.

2. Category II Wetlands. Category II wetlands are difficult, though not impossible, to replace, and provide high levels of some functions. These wetlands occur more commonly than category I wetlands, but still need a relatively high level of protection. Category II wetlands in western Washington include: wetlands scoring between 20 and 22 points (out of 27) on the questions related to the functions present. Wetlands scoring 20 to 22 points were judged to perform most functions relatively well, or performed one group of functions very well and the other two moderately well.

3. Category III Wetlands. Category III wetlands are wetlands with a moderate level of functions (score between 16 and 19 points). Wetlands scoring between 16 and 19 points generally have been disturbed in some ways, and are often less diverse or more isolated from other natural resources in the landscape than category II wetlands.

4. Category IV Wetlands Over 2,500 Square Feet. Category IV wetlands have the lowest levels of functions (score less than 16 points) and are often heavily disturbed. These are wetlands that we should be able to replace, and in some cases be able to improve. However, experience has shown that replacement cannot be guaranteed in any specific case. These wetlands may provide some important functions, and also need to be protected.

D. Designation of Wetland Critical Area Buffer. The following critical area buffers are hereby established:

1. Wetland Critical Area Buffer.

a. General.

i. Undeveloped Sites. An undeveloped site is any site where the wetland and wetland buffer have not previously been included within a Native Growth Protection Area (NGPA) or Native Growth Protection Easement (NGPE), regardless of whether the site contains a primary structure. Wetlands on undeveloped sites shall have the following critical area buffers, measured from the wetland boundary:

Category

Wetland Characteristic

Buffer

I

Natural heritage wetlands and bogs – Habitat score 8 – 9

225 feet

Natural heritage wetlands and bogs – All others

190 feet

Forested

Based on score for habitat

Habitat score of 8 – 9

225 feet

Habitat score of 5 – 7

110 feet

Habitat score of 3 – 4

75 feet

II

Habitat score of 8 – 9

225 feet

Habitat score of 5 – 7

110 feet

Habitat score of 3 – 4

75 feet

III

Habitat score of 8 – 9

225 feet

Habitat score of 5 – 7

110 feet

Habitat score of 3 – 4

60 feet

IV over 2,500 square feet

All

40 feet

ii. Developed Site. Wetlands on developed sites shall be governed by the buffer established within the approved and recorded NGPA or NGPE, or approved Critical Areas Land Use Permit. No additional wetland buffer shall apply.

((1)) Previously Approved NGPE/NGPA. A developed site is any site where the wetland and wetland buffer have been included within an NGPE or NGPA approved and recorded prior to August 1, 2006, or any site abutting an NGPA approved and recorded prior to August 1, 2006, containing the wetland and wetland buffer where such site does not also contain a wetland.

((2)) Previously Approved Critical Areas Land Use Permit. A developed site is any site where the wetland and wetland buffer have been identified within a Critical Areas Land Use Permit approved prior to May 21, 2018.

b. Buffer and Setback on Sites with Existing Development. Where a primary structure legally established on a site prior to August 1, 2006, encroaches into the critical area buffer or structure setback established in this section, the critical area buffer and/or structure setback shall be modified to exclude the footprint of the existing primary structure. Expansion of any existing primary structure into the critical area buffer or critical area structure setback shall be allowed only pursuant to the provisions of LUC 20.25H.055 (single-family primary structures) or LUC 20.25H.230 (all other primary structures).

c. Shoreline Lake-Fringe Wetlands. Category III lake-fringe wetlands 2,500 square feet or less with habitat scores of 5 or less that are adjacent to a shoreline are exempt from a wetland buffer. Shoreline vegetation conservation standards per Part 20.25E LUC apply.

2. Buffer Modification. Modifications to the wetland critical area buffer may be approved pursuant to this section. Modifications to the wetland critical area buffer that do not meet the criteria of this subsection may be considered through a critical areas report, LUC 20.25H.230:

a. Buffer Averaging. Buffer averaging may be allowed if all the following criteria are satisfied. Proposals to average the wetland critical area buffer under this subsection shall require a Critical Areas Land Use Permit; provided, that a mitigation or restoration plan is not required for buffer averaging.

i. Buffer averaging may be approved only if the applicant demonstrates that a modification to non-critical area setbacks pursuant to LUC 20.25H.040 would not accommodate the proposed development in a manner consistent with its intended use and function;

ii. Through buffer averaging, the ecological structure and function of the resulting buffer is equivalent to or greater than the structure and function before averaging;

iii. The total buffer area is not reduced;

iv. The buffer area is contiguous;

v. Averaging does not result in any impact to slope stability and does not increase the likelihood of erosion or landslide hazard;

vi. Averaging does not result in a significant adverse impact to habitat associated with species of local importance; and

vii. At no point is the critical area buffer width less than 75 percent of the required buffer dimension.

b. Transportation or Utility Infrastructure. Where a legally established right-of-way, railroad right-of-way or other similar infrastructure of a linear nature crosses a wetland critical area buffer, the edge of the improved right-of-way shall be the extent of the buffer, if the part of the critical area buffer on the other side of the right-of-way provides insignificant biological or hydrological function in relation to the portion of the buffer adjacent to the wetland.

E. Structure Setbacks.

1. General. The requirements of this section apply along with any other dimensional requirements of the Land Use Code (see LUC 20.20.010, 20.20.130, 20.20.190 and Parts 20.25A through 20.25G). The most restrictive dimension controls. Structure setbacks are required in order to:

a. Minimize long-term impacts of development adjacent to critical areas and critical area buffers; and

b. Protect critical areas and critical area buffers from adverse impacts during construction.

2. Minimum Setback of Structures – Undeveloped and Developed Sites. The following structure setbacks apply to both undeveloped and developed sites. Structure setbacks shall be measured from the edge of the critical area buffer on undeveloped sites, or from the edge of the approved and recorded NGPE or NGPA on developed sites:

Category I wetlands

20 feet

Category II wetlands

20 feet

Category III wetlands

15 feet

Category IV wetlands

None required

3. Shoreline Lake-Fringe Wetlands. Category III lake-fringe wetlands 2,500 square feet or less with habitat scores of 5 or less that are adjacent to a shoreline are exempt from a wetland structure setback. Shoreline structure setback standards per Part 20.25E LUC apply.

4. Structure Setback Modification – Undeveloped Sites. The Director may waive or modify the structure setback on an undeveloped site as part of the permit or approval for the underlying proposal if the applicant demonstrates that:

a. Water quality, or slope stability as documented in a geotechnical report, will not be adversely affected;

b. Encroachment into the structure setback will not disturb habitat of a species of local importance within a critical area or critical area buffer;

c. Vegetation in the critical area and critical area buffer will not be disturbed by construction, development, or maintenance activities and will be maintained in a healthy condition for the anticipated life of the development; and

d. Enhancement planting on the boundary between the structure setback and the critical area buffer will reduce impacts of development within the structure setback.

5. Structure Setback Modification – Developed Sites. Structure setbacks on developed sites may be modified only through an approved critical areas report. (Ord. 6417, 5-21-18, § 33; Ord. 5680, 6-26-06, § 3)

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