Chapter 17.23 WETLANDS

Chapter 17.23
WETLANDS

Sections:

17.23.010 Designation.

17.23.020 Review and reporting requirements.

17.23.023 Regulated activities.

17.23.030 Buffers.

17.23.040 Provisions for small, isolated wetlands.

17.23.050 Buffer averaging.

17.23.051 Buffer increase.

17.23.052 Allowed activities in wetland buffers.

17.23.053 Compensatory mitigation.

17.23.054 Mitigation plan.

17.23.055 Mitigation monitoring.

17.23.056 Development standards.

17.23.010 Designation.

A. Wetlands are those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Swamps, marshes, bogs, and wet meadows/pastures are examples of wetland. Some riparian areas adjacent to streams are also wetland.

B. Identification of wetlands and delineation of their boundaries pursuant to this chapter shall be done in accordance with the approved federal wetland delineation manual and applicable regional supplement. All areas within the city meeting the wetland definition and designation criteria in that procedure are hereby designated critical areas and are subject to the provisions of this chapter. Wetland delineations are valid for five years; after such date the city shall determine whether a revision or additional assessment is necessary. Wetland delineations will be documented on a ground-verified map using either professional surveying methods or an equivalent professional method using GPS with submeter accuracy.

C. The approximate location and extent of known or suspected wetlands are shown on the city’s critical area maps, which are informed by publicly available datasets such as the National Wetlands Inventory (NWI), Washington State Department of Ecology’s wetland mapping tools, and the Natural Resources Conservation Service (NRCS) Web Soil Survey. Other, unmapped wetlands may exist within the city. These maps are to be used as a guide and do not provide a definitive critical area designation.

D. Wetlands shall be rated based on categories that reflect the functions and values of each wetland. Wetland categories shall be based on the criteria provided in the Washington State Wetland Rating System for Western Washington, Version 2, revised July 2023 (Ecology Publication No. 23-06-009), or as revised.

E. Wetland rating categories shall not change due to illegal modification made to the wetland. [Ord. 1122B § 14, 2025; Ord. 849B § 4, 2009.]

17.23.020 Review and reporting requirements.

A. If the project site is within 300 feet of a National Wetlands Inventory mapped area, the Washington Department of Ecology wetland mapping tools mapped area, or if the site is unmapped but has wetland characteristics, the director shall require a site-specific wetland delineation by a qualified professional at the applicant’s expense to determine whether or not a regulated wetland is present and, if so, its relative location in relation to the proposed project area on site. If the director determines that a wetland or its buffer is more likely than not present, the director shall require a wetlands report. If no regulated wetlands are present, then wetland review will be considered complete.

B. Wetland delineation/characterization shall be performed by a qualified professional and shall be prepared according to Chapter 173-22 WAC.

C. A wetland report describes the characteristics of the subject property and adjacent areas. The wetland report shall be completed pursuant to CMC 17.21.082 and include the following:

1. Existing physical features of the site including buildings, fences, and other structures, roads, parking lots, utilities, water bodies, etc.;

2. Determination of the wetland category and wetland buffers, including a description of methodologies;

3. Field identification and delineation of wetland boundaries. For on-site wetlands, the assessment shall include the dominant and subdominant plant species; soil type, color and texture; sources of hydrology (patterns of surface and subsurface water movement, precipitation, etc.), topography, and other pertinent information;

4. Identification of critical areas and buffers within 300 feet of the site and an estimate of the approximate acreage for each. The assessment of off-site wetlands shall be based on available information and shall not require accessing off-site properties;

5. A detailed description of the effects of the proposed development on wetland and buffer function and value, including the area of direct wetland disturbance; area of buffer reduction or averaging including documentation that functions and values will not be adversely affected by the reduction or averaging; effects of storm water management; proposed hydrologic alteration including changes to natural drainage or infiltration patterns; effects on fish and wildlife species and their habitats; clearing and grading impacts; temporary construction impacts; and effects of increased noise, light or human intrusion;

6. A mitigation plan, if applicable, prepared pursuant to CMC 17.23.054. [Ord. 1122B § 14, 2025; Ord. 849B § 4, 2009.]

17.23.023 Regulated activities.

A. For any proposed regulated activity, a critical area report may be required to support the requested activity.

B. The following activities are regulated if they occur in a wetland or its buffer:

1. The removal, excavation, grading, or dredging of soil, sand, gravel, minerals, organic matter, or material of any kind;

2. The dumping of, discharging of, or filling with any material;

3. The draining, flooding, or disturbing of the water level or water table;

4. Pile driving;

5. The placing of obstructions;

6. The construction, reconstruction, demolition, or expansion of any structure;

7. The destruction or alteration of wetland vegetation through clearing, harvesting, shading, intentional burning, or planting of vegetation that would alter the character of a wetland;

8. Class IV General Forest Practices under the authority of the 1992 Washington State Forest Practices Act rules and regulations, WAC 222-12-030, or as hereafter amended;

9. Activities that result in:

a. A significant change of water temperature;

b. A significant change of physical or chemical characteristics of the sources of water to the wetland;

c. A significant change in the timing, frequency, depth, or duration of water entering or within the wetland;

d. The introduction of pollutants. [Ord. 1122B § 14, 2025.]

17.23.030 Buffers.

A. Wetland buffer zones shall be required for all regulated activities adjacent to regulated wetlands. Any wetland created, restored or enhanced as compensation for approved wetland alterations shall also include the standard buffer required for the category of the created, restored or enhanced wetland. All buffers shall be measured from the wetland boundary as surveyed in the field. The width of the wetland buffer zone shall be determined according to the tables in subsections (C) and (D) of this section. Buffers shall not include areas that are functionally and effectively disconnected from the wetland by a road or other substantially developed surface of sufficient width and with use characteristics such that buffer functions are not provided.

B. The buffer standards required by this chapter presume the existence of a dense vegetation community in the buffer adequate to protect the wetland functions and values. When a buffer lacks adequate vegetation, the director may increase the standard buffer, require buffer planting or enhancement, and/or deny a proposal for buffer reduction or buffer averaging.

C. Buffer Dimensions.

Wetland Category	Wetland Type	Level of Land Use Impact	Buffer Width (In Feet) Based on Habitat Score and/or Land Use Impact
Wetland Category	Wetland Type	Level of Land Use Impact	3-5	6-7	8-9
I	Based on habitat score	Low	N/A	75	150
		Moderate		110	225
		High		150	300
	Based on high level of function for water quality (8-9) and low for habitat (less than 6)	Low	50
		Moderate	75
		High	100
	Wetlands of high conservation value	Low	125
		Moderate	190
		High	250
	Bogs	Low	125
		Moderate	190
		High	250
	Forested	Low	Based on habitat functions or water quality functions
		Moderate
		High
	Not meeting any of the above characteristics	Low	50
		Moderate	75
		High	100
II	Based on habitat score	Low	N/A	75	150
		Moderate		110	225
		High		150	300
	Based on high level of function for water quality (8-9) and low for habitat (less than 6)	Low	50
		Moderate	75
		High	100
	Not meeting above characteristics	Low	50
		Moderate	75
		High	100
III	Based on habitat score	Low	40	75	Use Category II buffer widths
		Moderate	60	110
		High	80	150
IV	All types of wetlands	Low	25
		Moderate	40
		High	50

D. Land Use Impact.

Level of Impact from Proposed Land Use	Types of Land Uses
High	• Commercial
	• Urban
	• Industrial
	• Institutional
	• Retail sales
	• Residential (more than 1 unit/acre)
	• Conversion to high-intensity agriculture (dairies, nurseries, greenhouses, cannabis farms, outdoor cannabis production, growing and harvesting crops requiring annual tilling, and raising and maintaining animals, etc.)
	• High-intensity recreation (golf courses, ball fields, etc.)
	• Hobby farms
Moderate	• Residential (1 unit/acre or less)
	• Moderate-intensity open space (parks with biking, jogging, etc.)
	• Conversion to moderate-intensity agriculture (orchards, hay fields, etc.)
	• Paved trails
	• Building of logging roads
	• Utility corridor or right-of-way shared by several utilities and including access/maintenance road
Low	• Forestry (cutting of trees only)
	• Low-intensity open space (hiking, birdwatching, preservation of natural resources, etc.)
	• Unpaved trails
	• Utility corridor without a maintenance road and little or no vegetation management.

E. Where lands within the wetland buffer have an average continuous slope of 20 percent to 35 percent, and the required buffer width is less than 100 feet, the buffer shall extend to a 30 percent greater dimension. In all cases, where slopes within the buffers exceed 35 percent, the buffer shall extend 25 feet beyond the top of the bank of the sloping area or, if a buffer associated with a geological hazard is present, to whichever extent is greater.

F. Where other critical areas defined in this chapter fall within the wetland buffer, the buffer dimension shall be the most expansive of the buffers applicable to any applicable critical area.

G. The buffer widths for proposed high impact land uses can be reduced to the buffer widths for moderate impact land uses under the following conditions:

1. For wetlands that score six points or more for habitat function, the width of the buffer can be reduced if both of the following criteria are met:

a. A relatively undisturbed, vegetated corridor at least 100 feet wide is protected between the wetland and any other priority habitats as defined by the Washington State Department of Fish and Wildlife, where available. The corridor must be protected for the entire distance between the wetland and the priority habitat by some type of legal protection such as a conservation easement.

b. Measures to minimize the impact of different land uses, such as the examples in the table below, are applied.

2. For wetlands that score three to five habitat points, only application of the measures in the table below are required to reduce the buffer width to those required for moderate-impact land uses.

3. If an applicant chooses not to apply the measures in the table below or is unable to provide a protected corridor where available, then high-impact buffer widths must be applied.

Disturbance	Examples of Measures to Minimize Impacts
Lights	• Direct lights away from wetland
Noise	• Locate activity that generates noise away from wetland
Toxic runoff	• Route all new, untreated runoff away from wetland while ensuring wetland is not dewatered
	• Establish covenants limiting use of pesticides within 150 feet of wetland
	• Apply integrated pest management
Storm water runoff	• Retrofit storm water detention and treatment for roads and existing adjacent development
	• Prevent channelized flow from lawns that directly enters the buffer
	• Use low intensity development techniques (per PSAT publication on LID techniques)
Change in water regime	• Infiltrate or treat, detain, and disperse into buffer new runoff from impervious surfaces and new lawns
Pets and human disturbance	• Use privacy fencing or plant dense vegetation to delineate buffer edge and to discourage disturbance using vegetation appropriate for the ecoregion
Pets and human disturbance	• Place wetland and its buffer in a separate tract or within dedicated open space or easement in a subdivision, or protect with a conservation easement, where available
Dust	• Use best management practices to control dust

H. Measurement of Wetland Buffers. All buffers shall be measured perpendicularly from the wetland boundary as delineated in the field.

I. Functionally Disconnected Buffer Area. Buffers may exclude areas that are functionally and effectively disconnected from the wetland by an existing public or private road or legally established development, as determined by the director. “Functionally and effectively disconnected” means that the road or other significant development blocks the protective measures provided by a buffer.

1. Significant developments shall include built public infrastructure such as roads and railroads, and private developments such as homes or commercial structures. The director shall evaluate whether the interruption will affect the entirety of the buffer. Individual structures may not fully interrupt buffer function. In such cases, the allowable buffer exclusion should be limited in scope to just the portion of the buffer that is affected. Where questions exist regarding whether a development functionally disconnects the buffer, or the extent of that impact, the director may require a critical area report to analyze and document the buffer functionality.

J. Signs and Fencing.

1. Temporary Markers. The outer perimeter of the wetland buffer and the clearing limits identified by an approved permit or authorization shall be marked in the field with temporary high-visibility fencing in such a way as to ensure that no unauthorized intrusion will occur. The marking is subject to inspection by the director prior to the commencement of permitted activities. This temporary marking shall be maintained throughout construction and shall not be removed until permanent signs, if required, are in place.

2. Permanent Signs. As a condition of any permit or authorization issued pursuant to this chapter, the director may require the applicant to install permanent signs along the boundary of a wetland or buffer.

a. Permanent signs shall be made of an enamel-coated metal face attached to a metal post or another nontreated material of equal durability. Signs shall be posted at an interval of one every 50 feet, or one per lot if the lot is less than 50 feet wide, and shall be maintained by the property owner in perpetuity. The signs shall be worded as follows or with alternative language approved by the director:

Protected Wetland Area

Do Not Disturb

Contact City of Chehalis

Regarding Uses, Restrictions,

and Opportunities for Stewardship

b. The provisions of subsection (J)(2)(a) of this section may be modified as necessary to ensure protection of sensitive features or wildlife.

3. Fencing.

a. The applicant shall be required to install a permanent fence along the boundary of the wetland buffer when adjacent activities could degrade the wetland or its buffer. Examples include domestic animal grazing, unauthorized access by humans or pets, etc.

b. Fencing installed as part of a proposed activity or as required in this subsection shall be designed so as to not interfere with species migration, including fish runs, and shall be constructed in a manner that minimizes impacts to the wetland and associated habitat.

K. Allowed Buffer Uses. The following uses may be allowed within a wetland buffer in accordance with the review procedures of this chapter, provided they are not prohibited by any other applicable law, and they are conducted in a manner so as to minimize impacts to the buffer and adjacent wetland:

1. Conservation or restoration activities aimed at protecting the soil, water, vegetation, or wildlife.

2. Passive recreation facilities designed in accordance with an approved critical area report, including:

a. Walkways and trails; provided, that they are limited to minor crossings having no adverse impact on water quality. They should be generally parallel to the perimeter of the wetland, located only in the outer 25 percent of the wetland buffer area, and located to avoid removal of significant (as defined in CMC 17.85.040(A)), old growth, or mature trees. They should be limited to pervious surfaces no more than five feet in width and designed for pedestrian use only. Raised boardwalks utilizing nontreated pilings may be acceptable.

b. Wildlife-viewing structures.

3. Educational and scientific research activities.

4. Normal and routine maintenance and repair of any existing public or private facilities within an existing right-of-way; provided, that the maintenance or repair does not increase the footprint or use of the facility or right-of-way.

5. The harvesting of wild crops in a manner that is not injurious to natural reproduction of such crops and provided the harvesting does not require tilling of soil, planting of crops, chemical applications, or alteration of the wetland by changing existing topography, water conditions, or water sources.

6. Drilling for utilities/utility corridors under a buffer, with entrance/exit portals located completely outside of the wetland buffer boundary; provided, that the drilling does not alter the groundwater connection to the wetland or percolation of surface water down through the soil column. Specific studies by a hydrologist are necessary to determine whether the groundwater connection to the wetland or percolation of surface water down through the soil column would be disturbed.

7. Enhancement of a wetland buffer through the removal of nonnative, invasive plant species. Removal of invasive plant species shall be restricted to hand removal. All removed plant material shall be taken away from the site and appropriately disposed of. Plants that appear on the Washington State Noxious Weed Control Board list of noxious weeds should be handled and disposed of according to a noxious weed control plan appropriate to that species. Revegetation with appropriate native species at natural densities is allowed in conjunction with removal of invasive plant species.

8. Repair and maintenance of legally established nonconforming uses or structures, provided they do not increase the degree of nonconformity. [Ord. 1122B § 14, 2025; Ord. 849B § 4, 2009.]

17.23.040 Provisions for small, isolated wetlands.

A. Wetlands that meet the following criteria are not subject to the avoidance and minimization requirements of the mitigation sequence in accordance with the following provisions, and they may be filled if the impacts are fully mitigated based on rectifying, reducing or eliminating, compensating, or monitoring the impacts. Impacts should be mitigated through the purchase of credits from a mitigation bank or in-lieu fee program, if available, consistent with the terms and conditions of the bank or program. In order to verify whether the following criteria are met, it is essential that a critical area report for wetlands meeting the requirements in CMC 17.23.020 shall be submitted:

1. All Category IV wetlands less than 4,000 square feet that:

a. Are located in the areas covered by the Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region (U.S. Army Corps of Engineers, 2010);

b. Are not associated with riparian areas or their buffers;

c. Are not associated with shorelines of the state or their associated buffers;

d. Are not part of a wetland mosaic;

e. Do not score six or more points for habitat function based on the current wetland rating system; and

f. Do not contain a priority habitat or a priority area for a priority species identified by the Washington Department of Fish and Wildlife and do not contain state or federally listed species or their critical habitat or species of local importance.

2. Wetlands less than 1,000 square feet that meet the above criteria are exempt from the buffer provisions contained in this chapter. [Ord. 1122B § 14, 2025; Ord. 849B § 4, 2009.]

17.23.050 Buffer averaging.

The director may allow wetland buffer averaging on a case-by-case basis when the applicant demonstrates through a critical area study that all the following criteria are met:

A. Averaging to improve wetland protection may be permitted when all of the following conditions are met as demonstrated by a wetland assessment study pursuant to CMC 17.23.020:

1. The wetland has significant differences in characteristics that affect its habitat functions, such as a wetland with a forested component adjacent to a degraded emergent component or a “dual-rated” wetland with a Category I area adjacent to a lower rated area.

2. The buffer is increased adjacent to the higher-functioning area of habitat or more sensitive portion of the wetland and decreased adjacent to the lower-functioning or less sensitive portion.

3. The total area of the buffer after averaging is equal to the area required without averaging and all increases in buffer dimension for averaging are generally parallel to the wetland edge.

4. The buffer at its narrowest point is never less than either 75 percent of the required width or 75 feet for Category I and II wetlands, 50 feet for Category III wetlands, and 25 feet for Category IV wetlands, whichever is greater.

B. Averaging to allow reasonable use of a parcel may be permitted when all of the following are met as demonstrated by a wetland assessment study pursuant to CMC 17.23.020:

1. There are no feasible alternatives to the site design that could be accomplished without buffer averaging;

2. The averaged buffer will not result in degradation of the wetland’s functions and values;

3. The total buffer area after averaging is equal to the area required without averaging and all increases in buffer dimension for averaging are generally parallel to the wetland edge;

4. The buffer at its narrowest point is never less than three-fourths of the required width except where the director finds that there is an existing feature such as a roadway that limits buffer dimension, or an essential element of a proposed development such as access that must be accommodated for reasonable use and requires a smaller buffer.

C. The applicant implements all reasonable measures to reduce the adverse effects of adjacent land uses and ensure no net loss of wetland functions and values in conjunction with a wetland assessment study and mitigation plan. The specific measures that shall be implemented include, but are not limited to, those in CMC 17.23.056. [Ord. 1122B § 14, 2025; Ord. 849B § 4, 2009.]

17.23.051 Buffer increase.

The permit approval authority may increase the width of the standard buffer width on a case-by-case basis, based on a critical area study, when a larger buffer is required to protect critical habitats as outlined in CMC 17.25.010, or such increase is necessary to:

A. Protect the function and value of that wetland from proximity impacts of adjacent land use, including noise, light and other disturbance, not sufficiently limited by buffers provided above;

B. Maintain viable populations of priority species of fish and wildlife; or

C. Protect wetlands or other critical areas from landslides, erosion or other hazards. [Ord. 1122B § 14, 2025; Ord. 849B § 4, 2009.]

17.23.052 Allowed activities in wetland buffers.

A. Activities Allowed in Wetlands. The activities listed below are allowed in wetlands. These activities do not require submission of a critical area report, except where such activities have the potential to result in a loss of the functions, values or area of a wetland or wetland buffer. These activities include:

1. Agricultural activities in and around critical areas that are addressed by the implementation of the VSP work plan, or existing and ongoing agricultural activities, provided they implement applicable best management practices (BMPs) contained in the latest edition of the USDA Natural Resources Conservation Service (NRCS) Field Office Technical Guide (FOTG); or develop a farm conservation plan in coordination with Lewis County Conservation District. BMPs and/or farm plans should address potential impacts to wetlands from livestock, nutrients, chemicals, soil erosion, sediment control, and agricultural drainage infrastructure. BMPs and/or farm plans should ensure that ongoing agricultural activities minimize their effects on wetlands, water quality, riparian ecology, salmonid populations, and wildlife habitat.

2. Those activities and uses conducted pursuant to the Washington State Forest Practices Act and its rules and regulations, WAC 222-12-030, where state law specifically exempts local authority, except those developments requiring local approval for a Class IV general forest practice permit (conversions) as defined in Chapter 76.09 RCW and Chapter 222-12 WAC, provided conditions of that permit are met.

3. Conservation or preservation of soil, water, vegetation, fish, shellfish, and/or other wildlife that does not entail changing the structure or functions of the existing wetland.

4. The harvesting of wild crops in a manner that is not injurious to natural reproduction of such crops and provided the harvesting does not require tilling of soil, planting of crops, chemical applications, or alteration of the wetland by changing existing topography, water conditions, or water sources.

5. Drilling for utilities/utility corridors under a wetland, with entrance/exit portals located completely outside of the wetland buffer; provided, that the drilling does not alter the groundwater connection to the wetland or percolation of surface water down through the soil column. Specific studies by a hydrologist are necessary to determine whether the groundwater connection to the wetland or percolation of surface water down through the soil column will be altered. Trenching is not allowed by this provision.

6. Enhancement of a wetland through the removal of nonnative, invasive plant species. Removal shall be restricted to hand removal unless permits from the appropriate regulatory agencies have been obtained for approved biological or chemical treatments or mechanical methods. All removed plant material shall be taken away from the site and disposed of properly. Plants that are on the Washington State Noxious Weed Control Board list of noxious weeds should be handled and disposed of according to a noxious weed control plan appropriate to that species. Revegetation with appropriate native species to achieve natural densities is allowed and encouraged in conjunction with removal of invasive plants.

7. Educational and scientific research activities that do not result in altering the structure or functions of the wetland.

8. Normal and routine maintenance and repair of any existing, legally established public or private facilities within an existing right-of-way; provided, that the maintenance or repair does not expand the footprint of the facility or right-of-way and has no adverse effect on the wetland or buffer.

9. Storm water management facilities. A wetland or its buffer can be physically or hydrologically altered to meet the requirements of a low impact development (LID) methodology or flow control BMP if all of the following criteria are met:

a. The wetland is classified as a Category IV or a Category III wetland with a habitat score of three to five points;

b. There will be no net loss of functions and values of the wetland;

c. The wetland does not contain a breeding population of any native amphibian species;

d. The hydrologic functions of the wetland can be improved as outlined in questions 3, 4, and 5 of Chart 4 and questions 2, 3, and 4 of Chart 5 in Selecting Mitigation Sites Using a Watershed Approach (Western Washington or Eastern Washington) (Ecology Publication No. 09-06-032 or No. 10-06-007, or as revised); or the wetland is part of a restoration plan intended to achieve restoration goals identified in a shoreline master program or a local or regional watershed plan;

e. The wetland lies in the natural routing of the runoff, and the discharge follows the natural routing;

f. All regulations regarding storm water and wetland management are followed, including but not limited to local and state wetland and storm water codes, manuals, and permits; and

g. Modifications that alter the structure of a wetland or its soils will require permits. Existing functions and values that are lost will need to be compensated.

10. Storm water LID BMPs required as part of new and redevelopment projects may potentially be authorized within wetlands and their buffers. However, these areas may contain features that render LID BMPs infeasible. A site-specific characterization is required to determine whether an LID BMP is feasible at the project site.

B. Public and private roadways and railroad facilities, including bridge construction and culvert installation, if the following criteria are met:

1. There is no reasonable location or route outside the wetland or wetland buffer based on analysis of system needs, available technology and alternative routes. Location within a wetland buffer shall be preferred over a location within a wetland.

2. Facilities parallel to the wetland edge are located as far from the wetland edge as possible and in a manner that minimizes disturbance of soils and vegetation.

3. Clearing, grading, and excavation activities are limited to the minimum necessary, which may include placement on elevated structures as an alternative to fill, where feasible.

4. Impacts on wetland functions are mitigated in accordance with CMC 17.23.053.

C. Access to private development sites may be permitted to cross Category II, III, or IV wetlands or their buffers, pursuant to the criteria in subsection (B) of this section; provided, that alternative access shall be pursued to the maximum extent feasible, including through the provisions of Chapter 8.24 RCW. Exceptions or deviations from technical standards for width or other dimensions, and specific construction standards to minimize impacts may be specified, including placement on elevated structures as an alternative to fill, if feasible.

D. Outdoor recreational or educational activities which do not significantly affect the function of the wetland or regulated buffer or water quality (including wildlife management or viewing structures, outdoor scientific or interpretive facilities, pedestrian trails, hunting blinds, etc.) may be permitted within a Category II, III, or IV wetland or its buffer and within a Category I wetland buffer if the following criteria are met:

1. Trails shall not exceed five feet in width and shall be surfaced with gravel or pervious material or constructed as a boardwalk using nontreated pilings. Trails or facilities shall be placed on an elevated structure as an alternative to fill;

2. The trail or facility is located in the outer 50 percent of the buffer area unless a location closer to the wetland edge or within the wetland is required for interpretive purposes;

3. The trail or facility is constructed and maintained in manner that minimizes disturbance of the wetland or buffer and is located to avoid removal of mature trees;

4. Impacts on wetland functions are mitigated in accordance with CMC 17.23.053. [Ord. 1122B § 14, 2025; Ord. 849B § 4, 2009.]

17.23.053 Compensatory mitigation.

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 the Washington State Department of Ecology Wetland Mitigation in Washington State: Part 2 – Developing Mitigation Plans, March 2006, guidance, as revised, CMC 17.21.087, and this section.

A. 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 purpose 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 director determines that the overall mitigation package fully replaces the functions and values lost due to development.

B. 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 the table below; provided, that replacement ratio for preservation shall be determined by the director on a case-by-case basis. The created, reestablished, 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.

Category of Impacted Wetland (based on score for function)	Reestablishment or Creation	Rehabilitation	Preservation	Enhancement
Category I	4:1	8:1	16:1	16:1
Category II	3:1	6:1	12:1	12:1
Category III	2:1	4:1	8:1	8:1
Category IV	1.5:1	3:1	6:1	6:1

C. 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.

D. Mitigation Approaches.

1. Mitigation Banks. Credits from a wetland mitigation bank certified under Chapter 173-700 WAC may be used to compensate for impacts located within the service area specified in the mitigation bank instrument if all the following are met:

a. The director determines that it would provide appropriate compensation for the proposed impacts; and

b. The proposed use of credits is consistent with the terms and conditions of the mitigation bank instrument.

c. Mitigation ratios are consistent with ratios specified in the mitigation bank instrument.

2. In-Lieu Fee (ILF) Mitigation. Credits from an approved in-lieu fee program may be used when all the following apply:

a. The director determines that it would provide appropriate compensation for the proposed impacts.

b. The proposed use of credits is consistent with the terms and conditions of the approved ILF program instrument.

c. Projects using ILF credits shall have debits associated with the proposed impacts calculated by the applicant’s qualified wetland professional using the credit assessment method specified in the approved instrument for the ILF program.

3. Permittee-Responsible, Advance Mitigation. Advance mitigation is a form of permittee-responsible mitigation implemented before a permitted impact takes place. It is designed to compensate for impacts expected to occur in the future. The applicant proposing the advance mitigation is the only one who can use the credits generated. Credits cannot be sold or transferred to another applicant. Advance mitigation proposals should be developed in accordance with state and federal rules and guidance on advance mitigation (Interagency Regulatory Guide: Advance Permittee-Responsible Mitigation, Ecology Publication No. 12-06-015, and Chapter 4.2 of Wetland Mitigation in Washington State – Part 1: Agency Policies and Guidance, Version 2, Ecology Publication No. 21-06-003, or as revised).

4. Permittee-Responsible, Concurrent Mitigation. Concurrent mitigation is a form of permittee-responsible mitigation implemented at the same time permitted impacts are occurring. The permittee is responsible for implementation and success of the compensation. Concurrent mitigation may occur at the site of the permitted impacts or at an off-site location, usually within the same watershed. Permittee-responsible, concurrent mitigation shall be used only if the applicant’s qualified wetland professional demonstrates to the director’s satisfaction that the proposed approach is ecologically preferable to use of a bank or ILF program, consistent with the criteria in this section.

E. 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 in CMC 17.23.030; provided, that the director shall have the authority to approve a smaller buffer when existing site constraints (such as a road) prohibit attainment of the standard buffer.

F. Adjustment of Ratios. The director shall have the authority to adjust these ratios when a combination of mitigation approaches is proposed. Ratios for rehabilitation, preservation, and enhancement may be reduced when combined with 1:1 replacement through reestablishment or creation. See Table 6B-2 in Wetland Mitigation in Washington State – Part 1: Agency Policies and Guidance, Version 2, or as revised.

G. Location. Compensatory mitigation shall be provided on site or off site in a 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.

H. Protection. All mitigation areas whether on 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 CMC 17.21.085.

I. Timing. It is preferred that compensatory mitigation projects be completed prior to activities that will impact wetlands. At the least, compensatory mitigation shall be completed immediately following wetland impacts and prior to use or occupancy of the action or development. Construction of mitigation projects shall be timed to reduce impacts to existing fisheries, wildlife, and flora.

1. The director may authorize a one-time temporary delay in completing mitigation when the applicant provides a written explanation from a qualified wetland professional as to the rationale for the delay. The delay shall not create or perpetuate hazardous conditions or environmental damage or degradation, and the delay shall not be injurious to the health, safety, or general welfare of the public. The request for the delay shall include a written justification that documents the environmental constraints that preclude timely implementation of the compensatory mitigation plan. [Ord. 1122B § 14, 2025; Ord. 849B § 4, 2009.]

17.23.054 Mitigation plan.

In addition to meeting the requirements of CMC 17.21.087, a compensatory mitigation plan for wetland and wetland buffer impacts shall meet the following requirements:

A. The plan shall be based on the Washington State Department of Ecology interagency guidance documents, Wetland Mitigation in Washington State – Part 2: Developing Mitigation Plans, Version 1, March 2006, Publication No. 6-06-011b, as revised.

B. The plan shall contain sufficient information to demonstrate that the proposed activities are logistically feasible, constructible, ecologically sustainable, and likely to succeed. Specific information to be provided in the plan shall include, but not be limited to:

1. The rationale for site selection;

2. General description and scaled drawings of the activities proposed including, but not limited to, clearing, grading/excavation, drainage alterations, planting, invasive plant management, installation of habitat structures, irrigation, and other site treatments associated with the development activities and proposed mitigation action(s);

3. A description of the ecological functions and values that the proposed alteration will affect and the specific ecological functions and values the proposed mitigation area(s) shall provide, together with a description of required or recommended mitigation ratios and an assessment of factors that may affect the success of the mitigation program;

4. Overall goals of the plan, including wetland function, value, and acreage;

5. Description of baseline (existing) site conditions including topography, vegetation, soils, hydrology, habitat features (i.e., snags), surrounding land use, and other pertinent information;

6. Field data confirming the presence of adequate hydrology (surface and/or groundwater) to support existing and compensatory wetland area(s);

7. Nature of mitigation activities, including area of restored, created, enhanced and preserved wetland, by wetland type;

8. Detailed grading and planting plans showing proposed post-construction topography; general hydrologic patterns; spacing and distribution of plant species; size and type of proposed planting stock; watering or irrigation plans; and other pertinent information;

9. A description of site treatment measures including invasive species removal, use of mulch and fertilizer, placement of erosion and sediment control devices, and best management practices that will be used to protect existing wetlands and desirable vegetation;

10. A demonstration that the site will have adequate buffers sufficient to protect the wetland functions into perpetuity.

C. Specific measurable performance standards that the proposed mitigation action(s) shall achieve together with a description of how the mitigation action(s) will be evaluated and monitored to determine if the performance standards are being met and identification of potential courses of action, and any corrective measures to be taken if monitoring or evaluation indicates that project performance standards are not being met. The performance standards shall be tied to and directly related to the mitigation goals and objectives.

D. Cost estimates for the installation of the mitigation program, monitoring, and potential corrective actions if project performance standards are not being met. [Ord. 1122B § 14, 2025; Ord. 849B § 4, 2009.]

17.23.055 Mitigation monitoring.

A. All compensatory mitigation projects shall be monitored for a period necessary to establish that performance standards have been met, but generally not for a period less than five years. Reports shall be submitted annually for the first three years following construction and at the completion of years five, seven, and 10 if applicable to document milestones, successes, problems, and contingency actions of the compensatory mitigation. The director shall have the authority to modify or extend the monitoring period and require additional monitoring reports for up to 10 years when any of the following conditions apply:

1. The project does not meet the performance standards identified in the mitigation plan.

2. The project does not provide adequate replacement for the functions and values of the impacted critical area.

3. The project involves establishment of forested plant communities, which require longer time for establishment.

B. Mitigation monitoring reports shall include information sufficient to document and assess the degree of mitigation success or failure of mitigation as defined by the performance standards contained in the approved mitigation plan. Information to be provided in annual monitoring reports shall include the following:

1. Number and location of vegetation sample plots used to document compliance with performance standards;

2. Measurements of the percent survival of planted material, plant cover, stem density, presence of invasive species, or other attributes;

3. For sites that involve wetland creation, reestablishment or rehabilitation, hydrologic observations of soil saturation/inundation as needed to demonstrate that a site meets the wetland hydrology criterion;

4. Representative photographs of the site;

5. A written summary of overall site conditions and recommendations for maintenance actions if needed;

6. Other information that the director deems necessary to ensure the success of the site. [Ord. 1122B § 14, 2025; Ord. 849B § 4, 2009.]

17.23.056 Development standards.

A. Development standards for adjacent development shall minimize adverse effects on the wetland, and shall include:

1. Subdivision of land shall ensure that each lot has sufficient and accessible building area outside wetlands and buffers. Lots in subdivisions shall be oriented whenever feasible to provide a rear yard of at least 20 feet between the buffer area and buildings. Wetland and buffer boundaries shall be shown on the plat.

2. Fencing shall be provided at the perimeter of residential development to limit domestic animal entry into wetlands and buffer areas.

3. Activities that generate noise shall be located as far from the wetland and buffer as feasible. Roads, driveways, parking lots and loading areas, mechanical or ventilating equipment shall be located on sides of buildings away from the wetland, or separated by noise-attenuating walls.

4. Light penetration into buffer areas and wetlands shall be limited by locating areas requiring exterior lighting away from the wetland boundary or limiting light mounting heights to a maximum of four feet. Windows that will be lit at night should be minimized on the side of buildings facing wetlands and buffers or screened as provided for in subsection (C) of this section.

B. In order to maintain effective buffer conditions and functions, a vegetation management plan shall be required for all buffer areas within new development, to include:

1. Maintaining adequate cover of native vegetation including trees and understory; if existing tree cover is less than a relative density of 20, planting shall be required consisting of seedlings at a density of 300 stems per acre or the equivalent;

2. Provide a dense screen of native evergreen trees at the perimeter of the buffer if existing vegetation is not sufficient to prevent viewing adjacent development from within the buffer. Planting shall be required equivalent to two rows of three-foot-high stock of native evergreens at a triangular spacing of 15 feet, or three rows of gallon containers at a triangular spacing of eight feet. Fencing may be required if needed to block headlights or other sources of light or to provide an immediate effective visual screen;

3. Provide a plan for control of invasive weeds, and remove existing invasive species;

4. Provide for a monitoring and maintenance plan for a period of at least five years, except this provision may be waived for single-family residential lots.

C. In order to maintain effective buffer conditions and functions, a vegetation management plan shall be required for all buffer areas, to include:

2. Provide a dense screen of native evergreen trees at the perimeter of the buffer. If existing vegetation is not sufficient to prevent viewing adjacent development from within the buffer. Planting shall be required equivalent to two rows of three-foot-high stock of native evergreens at a triangular spacing of 15 feet, or three rows of gallon containers at a triangular spacing of eight feet. Fencing may be required if needed to block headlights or other sources of light or to provide an immediate effective visual screen;

3. Provide a plan for control of invasive weeds, and remove existing invasive species;

4. Provide for a monitoring and maintenance plan for a period of at least five years, except this provision may be waived for single-family residential lots. [Ord. 1122B § 14, 2025; Ord. 849B § 4, 2009.]