Chapter 17.52B


17.52B.010    Purpose and intent of wetland regulations.

17.52B.020    Applicability of wetland provisions.

17.52B.030    Regulated activities.

17.52B.040    Exemptions.

17.52B.070    Wetland inventory maps.

17.52B.080    Wetland permit process and application requirements.

17.52B.090    Wetland rating and classification.

17.52B.100    Buffer areas.

17.52B.110    Density calculations for wetland areas.

17.52B.120    Wetland alteration and mitigation.

17.52B.130    Mitigation standards and criteria.

17.52B.140    Mitigation plan requirements.

17.52B.150    Monitoring program and contingency plan.

17.52B.160    Procedural provisions.

17.52B.010 Purpose and intent of wetland regulations.

A.    The city finds that wetlands perform many important biological and physical functions that benefit the city and its residents, including but not limited to: helping to maintain water quality; storing and conveying stormwater and floodwater; recharging ground water; providing important fish and wildlife habitat; and serving as areas for recreation, education and scientific study and aesthetic appreciation. Protection of wetlands is, therefore, necessary to protect public health, safety, and general welfare.

B.    This chapter contains standards to manage development in association with the city’s wetland resources and enhance and restore wetlands where possible. The intent of these regulations is to avoid and minimize wetland impacts where avoidance and minimization is feasible and reasonable. In appropriate circumstances, impacts to wetlands resulting from regulated activities may be compensated for, consistent with this chapter. The city’s overall goal is to achieve no net loss of wetland function and value, and net acreage may be considered in achieving the overall goal.

C.    It is the intent of this chapter to implement the goals and policies of the city comprehensive plan, including those pertaining to natural features and environmental protection; aesthetics and community character; opportunities for economic development; creating a balanced transportation system; ensuring adequate public facilities; and achieving a mix of land use types and densities consistent with the city’s land use plan.

D.    It is the further intent of this chapter to establish special standards for the protection of wetlands and potential habitat of anadromous fish in compliance with the Washington Growth Management Act of 1990 (Chapter 36.70A RCW and its amendments and WAC 365-195-900 through 365-195-925) and best available science requirements. (Ord. 1112 § 13 (part), 2005)

17.52B.020 Applicability of wetland provisions.

A.    The wetland management provisions of this chapter apply to any regulated activity (Section 17.52B.030) potentially affecting a wetland or its buffer unless otherwise exempt under Section 17.52B.040.

B.    To avoid overlap and duplication, all city permit applications leading to the development or alteration of land, including but not limited to applications for: clearing and grading; subdivision or short subdivision, building permit, planned unit development; shoreline substantial development; variance and conditional use, shall be subject to and coordinated with the wetland requirements of this chapter and the Mukilteo Zoning Code, Chapter 17.13, Project Permit Review Process.

C.    Nonproject actions, including but not limited to rezones, annexations, and adoption of plans and programs, shall be required to comply with the Growth Management Act (GMA), Chapter 36.70A RCW, including submittal of appropriate wetland information as determined by the city according to this chapter.

D.    This chapter shall apply as any other overlay to development or land use regulations established by the city. In the event of a conflict between regulations in this chapter and any other city code, the regulation, which provide greater protection to environmentally sensitive areas shall apply. (Ord. 1112 § 13 (part), 2005)

17.52B.030 Regulated activities.

The following activities associated with any land use development proposal that occurs within a wetland and/or its buffer, or outside a wetland or buffer but potentially affecting the wetland or buffer, shall be regulated pursuant to the standards of this chapter:

A.    Removing, excavating, disturbing or dredging soil, sand, gravel, minerals, organic matter or materials of any kind;

B.    Dumping, discharging or filling any material;

C.    Draining, flooding or disturbing the water level or water table;

D.    Alteration, construction, reconstruction, or demolition of any structure or infrastructure, including driving pilings or placing obstructions;

E.    Destroying or altering wetland vegetation through clearing, harvesting, shading or planting vegetation that would alter the wetland or buffer character; provided, that these activities are not part of a forest practice governed under Chapter 76.09 RCW and its rules;

F.    Activities that result in significant changes in water temperature, physical or chemical characteristics of the wetland or buffer, including water quantity and quality, soil flow, or natural contours;

G.    Any other activity potentially affecting a wetland or wetland buffer not otherwise exempt from this chapter; and

H.    Work to maintain wetlands intentionally created from nonwetland areas as mitigation for wetland impacts. (Ord. 1112 § 13 (part), 2005)

17.52B.040 Exemptions.

A.    The following activities that occur within wetlands and their buffers shall be exempt from this chapter:

1.    Work such as mowing, maintenance, cleaning, excavation, or repair/replacement of flow control structures of artificially created wetlands intentionally created from nonwetland sites, including but not limited to grass-lined swales, irrigation and drainage ditches, detention facilities, and landscaping features. In those cases where stormwater control structures or devices were previously permitted in regulated wetlands, the only exempt activity shall be allowed and it shall be limited to the minimum necessary to maintain the outlet or inlet structure. If the wetland requires additional work to maintain storage capacity as envisioned per the original permit approval, a report shall be prepared by a qualified wetland specialist as defined in Chapter 17.08 that analyzes the extent, type, and function of wetland to determine the extent of the regulated or exempt activity(ies).

2.    Work in those wetlands created after July 1, 1990, that were unintentionally created as a result of road, street, or highway construction.

3.    Maintenance, operation and reconstruction of existing roads, streets, railroad lines, utilities and associated structures undertaken pursuant to best management practices, provided activities shall not increase the impervious area by more than two hundred square feet and disturbed areas are restored to an acceptable usable condition as required by the public works and planning directors.

4.    Normal maintenance, repair and reconstruction of private or publicly-owned structures undertaken pursuant to public works director approved best management practices; provided, that reconstruction of any structures shall not impact any Category I wetland or more than one thousand square feet of Category II wetlands, including their associated buffers, and shall not increase the structural footprint.

5.    Site investigation work and studies necessary to prepare land use applications, including soils tests, water quality studies, wildlife studies and similar tests and investigations; provided, that any disturbance of the wetland shall be the minimum necessary to carry out the work or studies.

6.    Education activities, scientific research, and outdoor recreational activities, including but not limited to, interpretive field trips, bird watching and hiking and associated interpretive signage that will not have a significant effect on the wetland.

7.    Emergency activities that are required due to landslides, floods, earthquakes other acts of nature or emergency utility repairs that are necessary to prevent an immediate threat to public health, safety or property. A mitigation plan prepared in accordance with this chapter shall be submitted to the city within three months of the emergency activity and the approved mitigation shall be implemented within six months of the emergency repair.

8.    Minor activities such as invasive plant management; snagging of dead, dying, or diseased vegetation; and removal of hazardous trees where owners’ property or adjacent properties, or the health and safety of the general public or employees are in danger of damage or where slope stabilization could be negatively affected that are determined by the city to have minimal impacts to wetlands and wetland buffers.

9.    Construction of new utility facilities or improvements to existing utility facilities that take place within existing improved right-of-way or existing impervious surface that does not increase the amount of impervious surface, or the use of trenchless technology that would not disturb the wetland or wetland buffer such as boring, tunneling or jacking under a wetland.

B.    No private or public entity shall undertake exempt activities as listed in this section prior to providing the city written notification of their intent to proceed with an exempt activity. The city shall verbally confirm the activity is exempt and where needed provide written authorization within thirty days of the receipt of the written notice.

C.    In case of any question as to whether a particular activity is exempt from the wetland provisions of this chapter, the city’s determination shall prevail and shall be determinative.

D.    Notwithstanding the exemptions provided by this subsection, any otherwise exempt activity impacting a wetland and buffer should meet the purpose and intent of this chapter and should consider on-site alternatives that avoid or minimize impacts. (Ord. 1112 § 13 (part), 2005)

17.52B.070 Wetland inventory maps.

A.    The city shall maintain wetland maps showing the approximate location and extent of wetlands within city jurisdiction. These maps will only show wetlands identified to date, and shall be used only as a general guide to assist property owners. The location and extent of wetlands are determined on a lot-by-lot, project-by-project basis, and if a wetland is not shown on the inventory map, that does not necessarily mean wetlands do not occur on the lot. The city will update the wetland inventory map as wetlands are mapped in the field and submitted by applicants to the city.

B.    The wetland boundary and type shall be determined by a qualified wetland specialist according to the wetland delineation procedures as defined in the definitions, Chapter 17.08. In the event of any conflict between the wetland location or designation shown on the city’s map and the location or designation as determined in the field by a qualified wetland specialist using the defined wetland delineation procedures, the field determination shall control. (Ord. 1112 § 13 (part), 2005)

17.52B.080 Wetland permit process and application requirements.

A.    Preapplication Conference. All applicants are encouraged to meet with the city prior to submitting an application subject to the wetland provisions of this chapter. The purpose of this meeting shall be to discuss the wetland requirements, process and procedures; to review the critical areas checklist and any conceptual plans prepared by the applicant; to identify potential wetlands impacts and mitigation measures; and to familiarize the applicant with state and federal wetland programs and permitting process. Such conference shall be for the convenience of the applicant and any recommendations shall not be binding on the applicant or the city. Prior to the preapplication meeting, applicants shall identify and rate wetlands on the site, consider design options to avoid and minimize impacts to wetlands or buffers, assess the likely impacts to wetlands and buffers, and consider mitigation options as discussed in the Mukilteo critical areas mitigation program (CAMP).

B.    Wetland Delineation Report. If the city determines that wetland or buffer impacts might occur as a result of the proposal, a wetland delineation report, as defined in Chapter 17.08, must be submitted to the city for review prior to the issuance of a development permit pursuant to Chapter 17.13, project permit review process. The report must be prepared in accordance with city permit application requirements pursuant to Chapter 17.13 and incorporate best available science as defined in Chapter 17.08. The report will analyze the extent, type, and function of wetlands and buffers on any site where regulated or exempt activities are proposed. The report will also be used by the city to determine the appropriate wetland type and buffer requirement for the wetland, and to assist the city in determining appropriate mitigation if required.

C.    Wetland Specialist. A qualified wetland specialist as defined in Chapter 17.08 shall prepare all reports and studies required of the applicant by this chapter. The city may retain a qualified wetland specialist, at the expense of the applicant, to review and confirm the applicant’s reports, studies, and plans.

D.    This section is not intended to create a separate wetland permit process for development proposals. To the extent possible, and pursuant to Chapter 17.13, the city shall consolidate and integrate the review and processing of wetland-related aspects of proposals with other land use and environmental considerations and approvals.

E.    Wetland delineations shall be considered valid for five years following the reviewing agency verification. The buffer required by the critical areas ordinance in effect at the time of complete permit application shall apply. (Ord. 1373 § 1, 2016: Ord. 1309 § 5, 2012; Ord. 1112 § 13 (part), 2005)

17.52B.090 Wetland rating and classification.

A.    Classification. Wetlands shall be classified as Category I, II, III or IV using the 2014 Washington State Department of Ecology’s Wetland Rating System for Western Washington, Publication No. 04-06-025, or as amended hereafter. 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 supplements. All areas within the city meeting the wetland designation criteria in that procedure are hereby designated critical areas and are subject to the provisions of this chapter.

B.    Sources for a preliminary identification of wetlands include, but are not limited to:

1.    United States Department of the Interior, Fish and Wildlife Service, National Wetlands Inventory.

2.    Areas identified as hydric soils, soils with significant soil inclusions and “wet spots” by the United States Department of Agriculture/Natural Resources Conservation Service.

3.    Washington State Department of Natural Resources, Geographic Information System: Hydrography and Soils Survey Layers.

4.    City of Mukilteo critical areas inventory maps. (Ord. 1373 § 2, 2016: Ord. 1309 § 6, 2012: Ord. 1112 § 13 (part), 2005)

17.52B.100 Buffer areas.

A.    The establishment of wetland buffer areas shall be required for all development proposals and activities adjacent to wetlands to protect the functions and integrity of the wetland. Buffers between regulated activities and wetlands help stabilize soil and prevent erosion, filter suspended solids and nutrients and harmful toxic substances, moderate effects of stormwater runoff, support and protect plant and animal species and habitats, enhance plant and wildlife diversity, and discourage adverse human effects in the wetland.

B.    Buffers are not intended to be established or to function independently of the wetland; they are established to protect.

C.    The establishment of a buffer or buffer mitigation shall not prevent a use or activity that would otherwise be permitted in the wetland or buffer as allowed in subsections H and I of this section. Buffer mitigation in the Mukilteo Habitat Reserve (MHR) is an exception to this section, and is managed through the provisions in the Mukilteo CAMP.

D.    Buffer Requirements. The standard buffer widths in Table 1—Wetland Buffer Widths have been established in accordance with the best available science. They are based on the category of wetland and the habitat score as determined by a qualified wetland professional using the Washington State Wetland Rating System for Western Washington.

1.    The use of the buffer widths in Table 1 requires the implementation of the mitigation measures in Table 1A, where applicable, to minimize the impacts of the adjacent land uses.

2.    If an applicant chooses not to apply the mitigation measures in Table 1A, then a thirty-three percent increase in the width of all buffers is required. For example, a seventy-five-foot buffer with the mitigation measures would be a one-hundred-foot buffer without them.

3.    The buffer widths assume that the buffer is vegetated with a native plant community appropriate for the ecoregion. If the existing buffer is unvegetated, sparsely vegetated, or vegetated with invasive species that do not perform needed functions, the buffer should either be planted to create the appropriate plant community or the buffer should be widened to ensure that adequate functions of the buffer are provided.

Table 1—Wetland Buffer Widths

Wetland Category

Buffer width (in feet) based on habitat score






Category I: Based on total score





Category I: Bogs and wetlands of high conservation value



Category I: Coastal lagoons




Category I: Interdunal



Category I: Forested





Category I: Estuarine

150 (buffer width not based on habitat scores)

Category II: Based on score





Category II: Interdunal wetlands




Category II: Estuarine

110 (buffer width not based on habitat scores)

Category III (all)





Category IV (all)


4.    The following list of mitigation measures as referenced in Table 1A—Mitigation Measures shall be used to minimize impacts from proposed development on wetlands:

Table 1A—Mitigation Measures 


Measures to Minimize Impacts


Direct lights away from wetland.


Locate activity that generates noise away from wetland.

If warranted, enhance existing buffer with native vegetation plantings adjacent to noise source.

For activities that generate relatively continuous, potentially disruptive noise, such as certain heavy industry or mining, establish an additional 10-foot heavily vegetated buffer strip immediately adjacent to the outer wetland buffer.

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.

Stormwater Runoff

Retrofit stormwater 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 Puget Sound Water Quality Action Team (PSAT) publication on LID techniques).

Changes in Water Regime

Infiltrate or treat, detain, and disperse into buffer new runoff from impervious surfaces and new lawns.

Pets and Human Disturbance

Use fencing and/or plant dense vegetation to delineate buffer edge and to discourage disturbance using vegetation appropriate for ecoregion; place wetland and its buffer in a separate tract.


Use best management practices to control dust.

Disruption of Corridors or Connections

Maintain connections to off-site areas that are undisturbed.

Restore corridors or connections to off-site habitats by replanting.

*These examples are not necessarily adequate for minimizing toxic runoff if threatened or endangered species are present at the site.

E.    Increased Wetland Buffer Area Width. Buffer widths shall be increased on a case-by-case basis as determined by the planning director when a larger buffer is necessary to protect wetland functions and values. This determination shall be supported by appropriate documentation showing that it is reasonably related to protection of the functions and values of the wetland. The documentation must include but not be limited to the following criteria:

1.    The wetland is used by a plant or animal species listed by the federal government or the state as endangered, threatened, candidate, sensitive, monitored or documented priority species or habitats, or essential or outstanding habitat for those species or has unusual nesting or resting sites such as heron rookeries or raptor nesting trees; or

2.    The adjacent land is susceptible to severe erosion, and erosion-control measures will not effectively prevent adverse wetland impacts; or

3.    The adjacent land has minimal vegetative cover or slopes greater than thirty percent.

F.    Measurement of Wetland. All buffers shall be measured perpendicular from the wetland boundary as surveyed in the field. The buffer for a wetland created, restored, or enhanced as compensation for approved wetland alterations shall be the same as the buffer required for the category of the created, restored, or enhanced wetland. Only fully vegetated buffers will be considered. Lawns, walkways, driveways, and other mowed or paved areas will not be considered buffers or included in buffer area calculations.

G.    Buffer Averaging. The widths of buffers may be averaged if this will improve the protection of wetland functions or if it is the only way to allow for reasonable use of a parcel. There is no scientific information available to determine if averaging the widths of buffers actually protects wetland functions; therefore, averaging shall only be allowed in the below-listed situations. Averaging may be used in conjunction with any of the other provisions for reduction in buffers including off-site buffer mitigation through use of the MHR.

1.    Averaging to improve wetland protection may be permitted when all of the following conditions are met:

a.    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.

b.    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.

c.    The total area of the buffer averaging is equal to the area required without averaging.

d.    The buffer at its narrowest point is never less than fifty percent of the required width.

e.    Mitigation sufficient to compensate for the impacts as determined by a qualified specialist is provided for all buffer averaging proposals.

2.    Averaging to allow reasonable use of a parcel may be permitted when all of the following are met:

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

b.    The averaged buffer will not result in degradation of the wetland’s functions and values as demonstrated by a report from a qualified wetland professional.

c.    The total buffer area after being averaged is equal to the area required without the averaging.

d.    The buffer at its narrowest point is never less than fifty percent of the required buffer width.

e.    Mitigation sufficient to compensate for the impacts as determined by a qualified specialist is provided for all buffer averaging proposals.

H.    The planning director may authorize the following low impact uses and activities within a wetland and wetland buffer upon showing that said uses or activities will be performed in a manner that will not adversely disturb the wetland, significantly increase the impervious surface of the buffer, or decrease the functions of the associated wetland: unpaved pedestrian trails, viewing platforms, interpretative signage, existing utility easements without a maintenance road and little or no vegetation management, and the boring of underground utilities pursuant to best management practices. Uses permitted within the buffer shall be located in the outer portion of the buffer as far as possible from the wetland. Trails should be located in the outer twenty-five percent of the buffer, avoid significant trees and should be no more than five feet wide with a pervious surface.

I.    Except where previously approved stormwater facilities were located in wetlands, all new stormwater management facilities shall be limited to vegetation-lined swales designed for stormwater management and stormwater dispersion outfalls; provided, that they are placed within the outer twenty-five percent of the buffer of a Category III and IV wetland only. Stormwater detention ponds and outlet structures shall not be allowed in wetlands or their buffers. The outer twenty-five percent of the buffer of a Category III and IV wetland can be used for stormwater flow path and dispersion.

J.    Buffers shall be shown on the development site plans or final plat maps along with the notation requirements identified in Section 17.52.035, Native growth protection areas (NGPA) and buffers.

K.    If an existing property has a previously delineated and/or approved wetland and associated buffer approved by the city, the approved wetland buffer will remain in effect. Redevelopment, previously disturbed areas (clearing limits), and/or additions outside of the existing footprint shall be subject to the previously approved buffer, however a buffer enhancement plan may be required in accordance with subsection D of this section if the wetland or buffer has become degraded or is currently not functioning or if the wetland and/or buffer may be negatively affected by proposed new development.

L.    Nonconforming Uses in Buffers. Where a legally established, nonconforming use of the buffer existing (e.g., a road or structure that lies within the width of a wetland buffer), proposed actions in the buffer may be permitted as long as they do not increase the degree of non-conformity. This means no increase in the impacts to the wetland from activities in the buffer. For example, building an urban road is being proposed next to a Category II wetland. A one-hundred-fifty-foot buffer would be needed to protect function. If, however, an existing urban road is already present and only fifty feet from the edge of the Category II wetland, the additional one hundred feet of buffer may not be needed if the road is being widened. A vegetated buffer on the other side of the road would not help buffer the existing impacts to the wetland from the road. If the existing road is resurfaced or widened (e.g., to add a sidewalk) along the upland edge, without any further roadside development that would increase the degree of nonconformity, the additional buffer is not necessary. The associated increase in impervious surface from widening a road, however, may necessitate mitigation for impacts from stormwater. If, however, the proposal is to build a new development (e.g., shopping center or residential development) along the upland side of the road, the impacts to the wetland and its function may increase. This would increase the degree of nonconformity. The project proponent would need to provide the additional one hundred feet of buffer extending beyond the road or apply for buffer averaging.

M.    Minor additions or alterations such as decks and small additions less than one hundred twenty square feet, interior remodels, or tenant improvements which have no impact on the wetland or wetland buffer are exempt from the buffer enhancement requirements. (Ord. 1390 § 9 (Exh. C), 2016; Ord. 1373 § 3, 2016: Ord. 1309 §§ 7—13, 2012; Ord. 1147 § 1, 2005; Ord. 1112 § 13 (part), 2005)

17.52B.110 Density calculations for wetland areas.

A.    An owner of a property containing wetlands may be permitted to transfer the density attributable to the wetland area to another nonwetland, nonsensitive portion of the same site or property, subject to the limitations of this section.

B.    Up to one hundred percent of the density that could be achieved on the wetland and buffer portion of the site can be transferred to the non-wetland portion, subject to:

1.    The density limitations of the underlying zoning classification;

2.    The minimum lot size of the underlying zoning classification may be reduced to three thousand square feet in order to accommodate the transfers in densities;

3.    Applicable setbacks may be reduced to fifteen feet, and the lot coverage standards of underlying zoning regulations may be increased to sixty percent;

4.    The area to which density is transferred shall not be constrained by another environmentally critical area regulation. (Ord. 1112 § 13 (part), 2005)

17.52B.120 Wetland alteration and mitigation.

A.    After careful consideration of the potential impacts and a determination that impacts are unavoidable, unavoidable impacts to wetlands not exempt under Section 17.52B.040 or meeting the criteria for a reasonable use exception in Section 17.52.025 shall be mitigated. Mitigation actions by an applicant shall occur in the following priority sequence:

1.    Avoiding the impact altogether by not taking a certain action or parts of actions;

2.    Minimizing impacts by limiting the degree of magnitude of the action and its implementation (e.g., use of appropriate technology, consideration of alternative site plans and building layouts and/or reductions in the density or scope of the proposal);

3.    Rectifying the impact by repairing, rehabilitating or restoring the affected environment;

4.    Reducing or eliminating the impact or hazard over time by preservation and maintenance operations during the life of the action;

5.    Compensating for the impact by replacing, enhancing or otherwise providing equivalent or greater wetland functions;

6.    Monitoring the impact and taking appropriate corrective measures.

B.    Unless otherwise exempt, or an exception is granted by the city, alteration of wetlands and/or their buffers may be permitted by the city subject to the following criteria:

1.    Category I Wetlands. Alterations of Category I wetlands shall be avoided, subject to the reasonable use provisions in Section 17.52.025.

2.    Category II and III Wetlands. With respect to activities proposed in Category II and III wetlands, the following standards shall apply:

a.    Water-dependent activities may be allowed where there are no practicable alternatives that would have a less adverse impact on the wetland, its buffer, and other critical areas.

b.    Where nonwater-dependent activities are proposed, it shall be presumed that alternative locations are available, and activities and uses shall be prohibited, unless the applicant demonstrates that:

i.    The basic project purpose cannot reasonably be accomplished and successfully avoided, or result in less adverse impact on a wetland on another site or sites in the general region; and

ii.    All alternative designs of the project as proposed, that would avoid or result in less of an adverse impact on a wetland or its buffer, such as a reduction in the size, scope, configuration, or density of the project, are not feasible.

3.    Category IV Wetlands. Activities and uses that result in unavoidable and necessary impacts may be permitted in Category IV wetlands and associated buffers in accordance with an approved critical area report and mitigation plan, and only if the proposed activity is the only reasonable alternative that will accomplish the applicant’s objective. Full mitigation for the acreage and lost functions will be provided under the requirements of this chapter.

C.    Proposals which include less preferred and/or compensatory mitigation shall demonstrate that:

1.    All feasible and reasonable measures will be taken to reduce impacts and losses to the wetlands, or to avoid impacts where avoidance is required by these regulations;

2.    The restored, created, or enhanced wetland will be as available and persistent as the wetland it replaces;

3.    No overall loss will occur in wetland area, function, or values;

4.    The applicant has the financial resources and technical expertise to satisfactorily complete the project;

5.    The applicant can demonstrate the capacity to monitor the site and make corrections during the monitoring period if the project fails to meet projected goals; and

6.    The applicant can protect and manage, or provide for the protection and management of, the compensation area to avoid further development or degradation and to provide long-term persistence of the project area.

D.    Owners of property with Category I through IV wetlands may also provide a comparable alternative mitigation plan which will result in equal or better wetland quality. (Ord. 1112 § 13 (part), 2005)

17.52B.130 Mitigation standards and criteria.

A.    Location and Timing of Mitigation.

1.    Restoration, creation, or enhancement actions should be undertaken on or adjacent to the site where feasible and sustainable, or on sites identified in the CAMP, or on other sites in Mukilteo or its UGA identified through a watershed approach. Replacement in-kind of the impacted wetland is preferred for creation, restoration, or enhancement actions. The city may accept or recommend restoration, creation, or enhancement which is off site and/or out-of-kind if the applicant can demonstrate that on-site or in-kind restoration, creation, or enhancement is infeasible due to constraints such as parcel size or wetland type, or that a wetland of a different type or location is justified based on regional needs or functions.

2.    Whether occurring on site or off site, the mitigation project shall occur near an adequate water supply (river, stream, and ground water) with a source of hydrology to the wetland to ensure a successful development or restoration.

3.    Any agreed upon mitigation plan shall be completed before initiation of other permitted activities, unless a phased or concurrent schedule has been approved by the city.

B.    Wetland Mitigation Ratios.

1.    Where wetland alterations are permitted by the city, the applicant shall restore, create, or enhance equivalent wetland area in order to compensate for wetland losses. Equivalent areas are determined according to wetland category, acreage, function, the length of time it takes for the restored or created wetland to approximate the characteristics of the original wetland, and the probability of success. Where feasible, applicants are encouraged to provide a higher type and quality of wetland than the altered wetland (based on the wetland rating system in Section 17.52B.090 of this chapter).

2.    The following ratios shall be established as a starting point for further discussion with each proponent on a case by case compensatory mitigation analysis and plan. Ratios shall apply to creation or restoration that is in-kind, is on-site, is the same category, is timed prior to or concurrent with alteration, and has a high probability of success. These ratios do not apply to remedial actions resulting from unauthorized alterations; greater ratios shall apply in those cases as required by the permitting agency(ies).

Table 2—Wetland Mitigation Ratios 

Category and Type of Wetland

Reestablishment or Creation


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

Enhancement Only

Category I




1:1 R/C and 10:1 E


Based on Score for Functions



1:1 R/C and 6:1 E



Case by Case

6:1 rehabilitation of an estuarine wetland

Case by Case

Case by Case


Irreplaceable – Avoidance Required

6:1 rehabilitation of a bog

Case by Case

Case by Case

Coastal Lagoon

Irreplaceable – Avoidance Required

6:1 rehabilitation of a coast lagoon

Case by Case

Case by Case

Natural Heritage

Irreplaceable – Avoidance Required

6:1 rehabilitation of a natural heritage site

Case by Case

Case by Case

Category II


Case by Case


Case by Case

Case by Case



Compensation has to be interdunal


Compensation has to be interdunal

1:1 R/C and 2:1 E


All Other



1:1 R/C and 4:1 E


Category III



1:1 R/C and 2:1 E


Category IV



1:1 R/C and 2:1 E


Creation = The manipulation of the physical, chemical, or biological characteristics present to develop a wetland on an upland or deepwater site, where a wetland did not previously exist. Activities typically involve excavation of upland soils to elevation that will produce a wetland hydroperiod, create hydric soils, and support the growth of hydrophytic plant species. Establishment results in a gain in wetland acres.

Reestablishment = The manipulation of the physical, chemical, or biological characteristics of a site with the goal of returning natural or historic functions to a former wetland. Activities could include removing fill material, plugging ditches, or breaking drain tiles. Reestablishment results in a gain in wetland acres.

Rehabilitation = The manipulation of the physical, chemical, or biological characteristics of a site with the goal of repairing natural or historic function of a degraded wetland. Activities could involve breaching a dike or reconnecting wetland to a floodplain or returning tidal influence to a wetland. Rehabilitation results in a gain in wetland function but does not result in a gain in wetland acres.

Enhancement = The manipulation of the physical, chemical, or biological characteristics of a wetland site to heighten, intensify or improve functions or to change the growth stage or composition of the vegetation present. Enhancement is undertaken for specified purposes such as water quality improvement, flood water retention or habitat. Activities typically consist of planting vegetation, controlling nonnative or invasive species, modifying the site elevation or the proportion of open water to influence hydroperiods, or some combination of these. Enhancement results in a change in some wetland functions and can lead to a decline in other wetland function, but does not result in a gain in wetland acres.

Preservation = Preservation of high quality wetland and buffer may be allowed as compensation for wetland impacts on a case-by-case basis. Mitigation ratios for preservation in combination with other forms of mitigation will generally range from 10:1 to 20:1, as determined on a case-by-case basis, depending on the quality of the wetlands being lost or degraded and the quality of the wetlands being preserved. Guidance in the Department of Ecology’s publication “Wetland Mitigation in Washington State, Part 1: Agency Policies and Guidance” will be consulted during consideration of preservation as compensatory mitigation.

C.    Mitigation Banking. The use of a mitigation bank may be approved for use as a compensation for unavoidable impacts to wetland when:

1.    The bank is certified under Chapter 173-700 WAC;

2.    The planning director or his/her designee determines that the wetland mitigation bank provides appropriate mitigation for the authorized impacts;

3.    The proposed use of credits is consistent with the terms and conditions of the bank’s certification;

4.    Replacement ratios for projects using bank credits shall be consistent with replacement ratios specified in the bank’s certification;

5.    Credits from a certified wetland mitigation bank may be used to mitigate for impacts located within the service area specified in the bank’s certification. In some cases, bank service areas may include portions of more than one adjacent drainage basin for specific wetland functions. (Ord. 1309 § 14, 2012; Ord. 1112 § 13 (part), 2005)

17.52B.140 Mitigation plan requirements.

A.    Where it is determined by the city that compensatory wetland mitigation is required or appropriate, a qualified wetland specialist shall prepare a preliminary and final mitigation plan using best available science in accordance with city requirements for city review. The mitigation plan shall include:

1.    Environmental Goals and Objectives. The plan shall include a written report identifying environmental goals and objectives of the compensation proposed and including:

a.    A description of the anticipated impacts to the critical areas and the mitigating actions proposed and the purposes of the compensation measures, including the site selection criteria; identification of compensation goals; identification of resource functions; and dates for beginning and completion of site compensation construction activities. The goals and objectives shall be related to the functions and values of the impacted critical area;

b.    A review of the best available science supporting the proposed mitigation and a description of the report author’s experience to date in restoring or creating the type of critical area proposed; and

c.    An analysis of the likelihood of success of the compensation project.

2.    Performance Standards. The mitigation plan shall include measurable specific criteria for evaluating whether or not the goals and objectives of the mitigation project have been successfully attained and whether or not the requirements of this chapter have been met.

3.    Construction Plans. The mitigation plan shall include written specifications and descriptions of the mitigation proposed and shall include detailed site diagrams, scaled cross-sectional drawings, topographic maps showing slope percentage and final grade elevations, and any other drawings appropriate to show construction techniques. The written plan shall include:

a.    The proposed construction sequencing, timing, and duration;

b.    Grading and excavation details;

c.    Erosion and sediment control features;

d.    A planting plan specifying plant species, quantities, locations, size, spacing, and density; and

e.    Measures to protect and maintain plants until established.

4.    Contingency Plan. The mitigation plan shall include identification of potential courses of action, and any corrective measure to be taken if monitoring or evaluation indicated project performance standards are not being met.

B.    The applicant’s qualified wetland specialist and the city must monitor installation of any construction to ensure mitigation is constructed or otherwise installed according to the approved mitigation plan requirements.

C.    For those projects that are only required to provide buffer enhancement mitigation, an applicant may use the city’s conceptual buffer mitigation plan as a basis to prepare a buffer enhancement plan. The final plan must be approved by the city’s planning director prior to final approval of a proposed project. (Ord. 1112 § 13 (part), 2005)

17.52B.150 Monitoring program and contingency plan.

A.    A monitoring program shall be included as a part of the approved mitigation plan. To insure that the performance standards of the approved mitigation plan have been met, the mitigation and/or buffer enhancement site(s) shall be monitored for a minimum of five years. The monitoring period required by the city may be extended an additional two years if the wetland or buffer is not performing as expected by the mitigation or enhancement plan. The monitoring reports shall be submitted on August 1st of each year during the monitoring period. Monitoring reports shall follow the recommendations contained in the Department of Ecology’s publication “Guidance on Wetland Mitigation in Washington State,” Part Two.

B.    An acceptable surety device is required to ensure the applicant’s compliance with the terms of the mitigation agreement.

1.    Performance Surety. All wetland mitigation and buffer enhancement shall be completed prior to final plat approval and/or building occupancy depending on the type of application. However, when improvements cannot be completed prior to final acceptance due to weather conditions which may negatively affect the success of the project, a performance surety may be used. The surety shall equal one hundred fifty percent of the cost of the mitigation project, and the required improvements shall be installed in a satisfactory manner within six months or less.

2.    Maintenance Surety. A maintenance surety shall be required on all mitigation projects to ensure that the improvement successfully survives the monitoring periods set above.

a.    Wetland Mitigation Projects. The amount of the maintenance surety shall be equal to fifteen percent of the cost of the mitigation project and the term of the surety shall reflect that of the monitoring program.

b.    Buffer Enhancement Projects. The amount of the maintenance surety shall be equal to fifteen percent of the costs of the enhancement project and the term of the surety shall reflect that of the monitoring program.

3.    Monitoring Deposit. A cash deposit shall be submitted with all sureties prior to final acceptance of the project to cover the estimated city’s costs to review the yearly monitoring reports and conduct a site inspection to ensure the performance standards are being met.

C.    Long-Term Maintenance. To ensure the long term success of the wetland, the applicant or their heirs or successors shall be responsible for the long term maintenance of the wetland and its associated buffer. The wetland and buffer shall be kept clear of weeds, invasive plant material, lawn clippings, junk, debris, intrusions or the like. (Ord. 1112 § 13 (part), 2005)

17.52B.160 Procedural provisions.

A.    Interpretation and Conflicts. Any questions regarding interpretation of this Chapter shall be resolved pursuant to the procedures set forth in Section 17.72.020 of this title.

B.    Penalties and Enforcement. Compliance with this chapter and penalties for its violation shall be enforced pursuant to the procedures set forth in Title 18, Land Use Enforcement.

C.    Appeals from Permit Decisions. Appeals from permit decisions shall be governed by the procedures set forth in Section 17.13.090, Appeals. (Ord. 1112 § 13 (part), 2005)