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14.260.080 Compensatory Mitigation.
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A. Mitigation Sequencing. Before impacting any wetland or its buffer, an applicant shall demonstrate that the following actions have been taken. Actions are listed in the order of preference:

1. Avoid the impact altogether by not taking a certain action or parts of an action.

2. Minimize impacts by limiting the degree or magnitude of the action and its implementation, by using appropriate technology, or by taking affirmative steps to avoid or reduce impacts.

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

4. Reduce or eliminate the impact over time by preservation and maintenance operations.

5. Compensate for the impact by replacing, enhancing, or providing substitute resources or environments.

6. Monitor the required compensation and take remedial or corrective measures when necessary.

B. Requirements for Compensatory Mitigation.

1. Compensatory mitigation for alterations to wetlands shall be used for impacts that cannot be avoided or minimized and shall achieve equivalent or greater biologic functions. Compensatory mitigation plans shall be consistent with Wetland Mitigation in Washington State – Part 2: Developing Mitigation Plans – Version 1 (Ecology Publication No. 06-06-011b), and Selecting Wetland Mitigation Sites Using a Watershed Approach (Western Washington) (Ecology Publication No. 09-06-32, December 2009).

2. Mitigation ratios shall be consistent with subsection H of this section.

C. Compensating for Lost or Affected Functions. Compensatory mitigation shall address the functions affected by the proposed project, with an intention to achieve functional equivalency or improvement of functions. The goal shall be for the compensatory mitigation to provide similar wetland functions as those lost, except when either:

1. The lost wetland provides minimal functions, and the proposed compensatory mitigation action(s) will provide equal or greater functions or will provide functions shown to be limiting within a watershed through a formal Washington State watershed assessment plan or protocol; or

2. Out-of-kind replacement of wetland type or functions will best meet watershed goals if formally identified by the City, such as replacement of historically diminished wetland types.

D. Approaches to Compensatory Mitigation. Mitigation for lost or diminished wetland and buffer functions shall rely on the approaches listed below.

1. Wetland Mitigation Banks. Credits from a certified wetland mitigation bank may be used to compensate for impacts located within the service area specified in the mitigation bank instrument. Use of credits from a wetland mitigation bank certified under Chapter 173-700 WAC is allowed if:

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

b. The impact site is located in the service area of the bank; and

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

d. Replacement ratios for projects using bank credits are consistent with replacement ratios specified in the certified mitigation bank instrument.

2. Permittee-Responsible Mitigation. The permittee performs the mitigation after the permit is issued and is ultimately responsible for implementation and success of the mitigation. Permittee-responsible mitigation may occur at the site of the permitted impacts or at an off-site location within the same watershed. Permittee-responsible mitigation shall be used only if the applicant’s qualified wetland professional demonstrates to the Planning Director’s satisfaction that the proposed approach is consistent with the criteria in this section.

E. Types of Compensatory Mitigation. To offset lost or diminished wetland and buffer functions caused by development, four (4) types of mitigation are acceptable. These acceptable types of mitigation are listed below in preferential order. The mitigation type with the highest preference level shall be required if viable. Mitigation types with lower preference levels shall be allowed only if the applicant’s qualified wetland professional demonstrates to the Planning Director that all mitigation types of a higher preference are not viable.

1. Restoration. Restoration is achieved through the manipulation of the physical, chemical, or biological characteristics of a site with the goal of returning natural or historic functions to a former or degraded wetland or buffer. Restoration actions are either “reestablishment” or “rehabilitation” activities as defined in SMC 14.100.020.

2. Creation. If a site cannot support wetland or buffer restoration to compensate for expected wetland and/or buffer impacts, the Planning Director may authorize creation of a new wetland and buffer upon demonstration by the applicant’s qualified wetland professional that:

a. The hydrology and soil conditions at the proposed mitigation site are conducive for sustaining the proposed wetland and that creation of a wetland at the site will not likely cause hydrologic problems elsewhere; and

b. Adjacent land uses and site conditions do not jeopardize the viability of the proposed wetland and buffer (e.g., due to the presence of invasive plants or noxious weeds, stormwater runoff, noise, light, or other impacts); and

c. The proposed wetland and buffer will eventually be self-sustaining with little or no long-term maintenance.

3. Enhancement. If restoration or creation are not viable options for a site then enhancement shall be undertaken for specified purposes such as water quality improvement, flood water retention, or wildlife habitat improvement. Enhancement may result in a change in some wetland functions and may lead to a decline in other wetland functions, but does not result in a gain in wetland acres. Enhancement activities typically consist of planting vegetation, controlling nonnative or invasive species, modifying site elevations or the proportion of open water to influence hydroperiods, or some combination of these activities. Applicants proposing to enhance wetlands or associated buffers shall demonstrate how the proposed enhancement will increase the wetland’s/buffer’s functions, how this increase in function will adequately compensate for the impacts, and how existing wetland functions at the mitigation site will be protected.

4. Preservation (Permanent Protection/Maintenance). Preservation is achieved by removing a threat to, or preventing the decline of, wetland conditions in or near a Category I or II wetland located within the Snohomish City limits.

a. Preservation shall be used only when none of the other acceptable compensatory mitigation types are viable for an impacted site;

b. Preservation may only be used off site on Category I or II wetlands and their associated buffers that are at risk of degradation;

c. Preservation mechanisms include, but are not limited to, the purchase of land or easements to restrict development potential and repairing water control structures or fences;

d. Preservation does not result in a gain of wetland acres;

e. Preservation can be used only if:

i. The Planning Director determines that the proposed preservation is the best and most viable mitigation type available; and

ii. The proposed preservation site is under threat of undesirable ecological change due to permitted, planned, or likely actions that will not be adequately mitigated under existing regulations; and

iii. The area proposed for preservation is of high quality or critical for the health of the watershed or basin due to its location. Characteristics indicative of high-quality sites include:

ARare or irreplaceable wetland type (for example, bogs, mature forested wetlands);

BAquatic habitat that is rare or a limited resource in the area;

CThe presence of habitat for priority or locally important wildlife species;

DProvides biological and/or hydrological connectivity;

EPriority sites in an adopted watershed plan;

f. Permanent preservation of the wetland and buffer shall be provided through a conservation easement or tract held by an appropriate natural land resource manager, such as a land trust. The Planning Director may approve other legal and administrative mechanisms in lieu of a conservation easement or tract if it is determined they are adequate to protect the site; and

g. Ratios for preservation in combination with other forms of mitigation shall range from ten-to-one (10:1) to twenty-to-one (20:1) (in terms of acres or square feet), as determined on a case-by-case basis by the Planning Director, depending on the quality of the wetlands being impacted and the quality of the wetlands being preserved. Ratios for preservation as the sole means of mitigation shall be at least twenty-to-one (20:1).

F. Location of Compensatory Mitigation. Compensatory mitigation actions shall generally be conducted within the same sub-drainage basin and on the site of the alteration except when the applicant can demonstrate that off-site mitigation is preferable for ecological reasons or because of increased likelihood the mitigation will succeed and eventually be self-sustaining. When considering off-site mitigation, preference should be given to using a mitigation bank.

1. The following criteria shall be used to determine the preferred location of compensatory mitigation:

a. There are no reasonable opportunities on site or within the sub-drainage basin; or opportunities on site or within the sub-drainage basin do not have a high likelihood of success based on a determination of the capacity of the site to compensate for the impacts. Considerations shall include:

i. Anticipated replacement ratios for wetland mitigation;

ii. Buffer conditions and required widths;

iii. Available water to maintain anticipated hydrogeomorphic classes of wetlands when restored;

iv. Proposed flood storage capacity; and

v. Potential to mitigate riparian fish and wildlife impacts (such as connectivity).

b. On-site mitigation would require elimination of high-quality upland habitat.

c. Off-site mitigation has a greater likelihood of providing equal or improved wetland functions than the altered wetland.

2. Off-site locations shall be in the same sub-drainage basin unless:

a. Established watershed goals for water quality, flood storage or conveyance, habitat, or other wetland functions have been established by the City and justify location of mitigation at another site; or

b. Credits from a state-certified wetland mitigation bank are used as compensation, and the use of credits is consistent with the terms of the certified bank instrument.

3. The design for the compensatory mitigation project shall be appropriate for its location (i.e., position in the landscape). Therefore, compensatory mitigation shall not result in the creation, restoration, or enhancement of an atypical wetland.

G. Timing of Compensatory Mitigation. Compensatory mitigation projects shall be completed prior to activities that will impact wetlands.

1. Construction of mitigation projects shall be timed to reduce impacts to existing fisheries, wildlife, and flora.

2. The Planning Director may authorize a one (1) time temporary delay in completing construction or installation of the compensatory mitigation when the applicant provides a written explanation from a qualified wetland professional as to the rationale for the delay. Appropriate rationale would include:

a. An example of appropriate rationale could include the identification of environmental conditions that could produce a high probability of failure or significant construction difficulties (e.g., project delay lapses past a fisheries window, or installing plants should be delayed until the dormant season to ensure greater survival of installed materials).

b. A delay in implementing compensatory mitigation shall only be approved subject to the following criteria and conditions:

i. The delay shall not create or perpetuate hazardous conditions or environmental damage or degradation or be injurious to the health, safety, or general welfare of the public;

ii. Written justification that documents the environmental constraints that preclude implementation of the compensatory mitigation plan shall be provided by the applicant. The justification must be verified and approved by the City;

iii. A performance surety in the amount of one hundred fifty (150) percent of the estimated cost of implementing the compensatory mitigation shall be required whenever compensatory mitigation is delayed.

H. Wetland Mitigation Ratios.

Table 3. 

(Ratios refer to units of area such as acres and square feet)

Category and Type of Wetland

Creation or Reestablishment



Category I:

Bog, natural heritage site

Not considered possible



Category I:

Mature forested




Category I:

Based on functions




Category II




Category III




Category IV




I. Credit/Debit Method. To more fully protect functions and values, and as an alternative to the mitigation ratios found in the joint guidance Wetland Mitigation in Washington State Parts I and II (Ecology Publication No. 06-06-011a-b, March 2006), the Planning Director may allow mitigation based on the “credit/debit” method developed by the Department of Ecology in Calculating Credits and Debits for Compensatory Mitigation in Wetlands of Western Washington: Final Report (Ecology Publication No. 10-06-011, March 2012).

J. Compensatory Mitigation Plan. When a project involves wetland and/or buffer impacts, a compensatory mitigation plan prepared by a qualified wetland professional shall be included as part of the wetland critical area report. The mitigation plan shall include a written report and plan sheets that contain, at a minimum, the following elements. Full guidance can be found in Wetland Mitigation in Washington State – Part 2: Developing Mitigation Plans – Version 1 (Ecology Publication No. 06-06-011b, March 2006).

1. The written report must contain, at a minimum:

a. The name and contact information of the applicant; the name, qualifications, and contact information for the primary author(s) of the compensatory mitigation report; a description of the proposal; a summary of the impacts and proposed compensation concept; identification of all the local, state, and/or federal wetland-related permit(s) required for the project; and a vicinity map for the project.

b. Description of how the project design has been modified to avoid, minimize, or reduce adverse impacts to wetlands.

c. Description of the existing wetland and buffer areas proposed to be altered. Include acreage (or square footage), water regime, vegetation, soils, landscape position, surrounding land uses, and functions and impacts in terms of acreage by Cowardin classification, hydrogeomorphic classification, and wetland rating.

d. Description of the compensatory mitigation site, including location and rationale for selection. Include an assessment of existing conditions:

i. Acreage (or square footage) of wetlands and uplands;

ii. Water regime and sources of water;

iii. Vegetation;

iv. Soils;

v. Landscape position;

vi. Surrounding land uses; and

vii. Functions.

e. Estimate of future conditions in the location if the compensation actions are not undertaken (i.e., how the site would progress through natural succession).

f. Surface and subsurface hydrologic conditions, including an analysis of existing and proposed hydrologic regimes for enhanced, created, or restored compensatory mitigation areas. Include illustrations of how data for existing hydrologic conditions were used to determine the estimates of future hydrologic conditions.

g. A description of the proposed actions for compensation of wetland, buffer, and upland areas affected by the project. Include overall goals of the proposed mitigation, including a description of the targeted functions, hydrogeomorphic classification, and categories of wetlands.

h. A description of the proposed mitigation construction activities and timing of activities.

i. Performance standards (measurable standards for the years post- installation) for buffer areas and wetland communities, a monitoring schedule, and a maintenance schedule and actions proposed by year.

j. A discussion of ongoing management practices that will protect wetlands and buffers after the development project has been implemented, including proposed monitoring and maintenance programs (for remaining wetlands and compensatory mitigation wetlands).

k. A surety estimate for the entire compensatory mitigation project, including cost estimates for the following elements:

i. Site preparation;

ii. Plant materials;

iii. Construction materials;

iv. Installation oversight;

v. Maintenance twice per year;

vi. Monitoring field work and reporting; and

vii. Contingency actions for a maximum of the total required number of years for monitoring.

2. The plan sheets for the mitigation plan must be scaled and contain, at a minimum:

a. Surveyed edges of the existing wetland and buffers, proposed areas of wetland and/or buffer impacts, location of proposed wetland and/or buffer compensation actions with the area of each called out in square feet or acres.

b. Existing topography, ground-proofed, at two (2) foot contour intervals in the zone of the proposed compensation actions if any grading activity is proposed in the compensation area(s). Also include existing cross-sections (estimated one (1) foot intervals) of wetland areas on the development site that are proposed to be altered and for the proposed areas of wetland or buffer compensation.

c. Conditions expected from the proposed actions on site, including future hydrogeomorphic types, vegetation community types by dominant species (wetland and upland), and future water regimes.

d. Required wetland buffers for existing wetlands and proposed compensation areas with any zones where buffers are proposed to be reduced or enlarged outside of the standards identified in this chapter clearly identified.

e. A planting plan for the compensation area, including all species by proposed community type and water regime, size and type of plant material to be installed, spacing of plants, typical clustering patterns, total number of each species by community type, and timing of installation.

3. Performance and maintenance surety devices pursuant to SMC 14.255.080(G)(1) and (G)(2) may be required to ensure compliance with the requirements of the mitigation plan.

a. 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 that may negatively affect the success of the project, a performance surety equal to one hundred fifty (150) percent of the estimated cost of the mitigation project shall be required, and the required improvements shall be installed in a satisfactory manner within six (6) months or less of project completion. After completion of the work the performance surety may be converted into a maintenance surety.

b. A maintenance surety in conformance with the requirements of SMC 14.255.080(G)(2) shall be required on all mitigation projects to ensure that the improvement successfully survives the required monitoring period as required in subsection M of this section.

4. The wetlands and buffers on the project site, including the compensatory mitigation areas, shall be protected by being placed in a separate tract or with a conservation easement to create a native growth protection area.

K. Buffer Mitigation Ratios. Impacts to buffers shall be mitigated at a minimum one-to-one (1:1) ratio. Compensatory buffer mitigation shall replace those buffer functions lost from development.

L. Protection of the Mitigation Site. The mitigation area and any associated buffer shall be located in a critical area tract or a conservation easement consistent with this chapter and designated as a native growth protection area.

M. Monitoring.

1. Mitigation monitoring may be required for up to a ten (10) year period to establish that performance standards have been met. The project mitigation plan shall include monitoring elements that ensure certainty of success for the project’s natural resource values and functions.

2. Monitoring reports prepared by a qualified wetland professional for years one (1), two (2), three (3), five (5), seven (7), and ten (10) of the monitoring period shall be submitted to the City. If the mitigation goals are not obtained within that period, the applicant remains responsible for restoration of the natural resource values and functions until the mitigation goals stipulated in the mitigation plan are achieved. If mitigation goals are obtained and sustained before year ten (10), the monitoring program may be ended based on a recommendation by a qualified wetland professional and as approved by the Planning Director.

N. Advance Mitigation. Mitigation for projects with pre-identified impacts to wetlands may be constructed in advance of the impacts if the mitigation is implemented according to federal rules, state policy on advance mitigation, and state water quality regulations consistent with Interagency Regulatory Guide: Advance Permittee-Responsible Mitigation (Ecology Publication No. 12-06-015, Olympia, WA, December 2012).

O. Alternative Mitigation Plans. The Planning Director may approve alternative wetland mitigation plans that are based on best available science, such as priority restoration plans that achieve restoration goals identified in the City of Snohomish Shoreline Master Program. Alternative mitigation proposals must provide an equivalent or better level of protection of wetland functions and values than would be provided by the strict application of this chapter.

1. The Planning Director may approve alternative mitigation proposals that:

a. Use a watershed approach consistent with Selecting Wetland Mitigation Sites Using a Watershed Approach (Western Washington) (Ecology Publication No. 09-06-32, December 2009).

b. Call for the creation or enhancement of a larger system of natural areas and open space is preferable to the preservation of many individual habitat areas.

c. Are necessary because mitigation pursuant to this section is not feasible due to site constraints such as parcel size, stream type, wetland category, or geologic hazards.

2. All alternative mitigation proposals shall:

a. Have a clear potential for success of the proposed mitigation at the proposed mitigation site.

b. Include clear and measurable standards for achieving compliance with the specific provisions of the plan. A monitoring plan shall, at a minimum, meet the provisions in subsection J of this section.

c. Be reviewed and approved as part of overall approval of the proposed use.

3. Plans may propose a wetland of a different type if justified based on regional needs or functions and values as determined by the Planning Director. However, the replacement ratios may not be reduced or eliminated unless the reduction results in a preferred environmental alternative.

4. Plans shall include mitigation guarantees that meet or exceed the minimum requirements as outlined in subsection J of this section.

5. Plans shall be prepared by a qualified wetland professional. (Ord. 2368, 2019)