22.80.090 Wetland development standards.
A. General Standards. Activities and uses shall be prohibited from wetlands and wetland buffers, except as provided by this chapter. The following activities may only be permitted in a wetland or wetland buffer if the applicant can demonstrate that the activity will result in no net loss of the functions and values of the wetland and other critical areas:
1. Category I Wetlands. Activities and uses shall be prohibited from Category I wetlands, except as provided in the public agency and utility exception, reasonable use exception, and variance provisions of this title.
2. Category II and III Wetlands. The following standards shall apply to Category II and III wetlands:
a. Water-dependent activities as provided for under the city’s shoreline master program may be allowed where there are no practicable alternatives that would have a less adverse impact on the wetland and other critical areas.
b. Where non-water-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 accommodated on another site in the general region and successfully avoid, or result in less adverse impacts on, a wetland or its buffer;
ii. There are no feasible 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.
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 areas report and mitigation plan, and only if the proposed activity is the only reasonable alternative that will accomplish the applicant’s objective.
4. Property Access. Any wetland may be altered with the least possible impact and to the minimum extent necessary to gain access to developable property when no other alternative access exists. Alteration proposals shall be subject to city review and shall require compensation pursuant to a mitigation plan (see MMC 22.80.080, Protection and mitigation measures).
5. Storm Water Management. Storm water management facilities are not allowed in wetlands. Storm water management facilities, limited to storm water dispersion outfall and bioswales, may be allowed within the outer twenty-five percent of the buffer of Category III and IV wetlands only; provided, that:
a. No other location is feasible; and
b. The location of such facilities will not degrade the functions and values of the wetland.
6. Trails. Public and private trails may be allowed within all buffers where it can be demonstrated in a critical areas report that the wetland and wetland buffer functions and values will not be degraded by trail construction or use. Trail planning, construction, and maintenance shall adhere to the following criteria:
a. Trail alignment shall follow a path beyond a distance from the wetland edge equal to seventy-five percent of the buffer width except as needed to access viewing platforms. Trails may be placed on existing levees or railroad grades within these limits;
b. Trails shall be constructed of pervious materials. The trail surface shall meet all other requirements, including water quality standards set forth in the storm water manual adopted in MMC 15.01.025;
c. Trail alignment shall avoid trees in excess of six inches in diameter of any tree trunk at a height of four and one-half feet above the ground on the upslope side of the tree. Unavoidable impacts to trees shall be mitigated at a three-to-one replacement ratio;
d. Trail construction and maintenance shall follow the U.S. Forest Service Trails Management Handbook (FSH 2309.18, June 1987) and Standard Specifications for Construction of Trails (EM-7720-102, June 1984 or as revised);
e. Access trails to viewing platforms within the wetland may be provided. Trail access and platforms shall be aligned and constructed to minimize disturbance to valuable functions of the wetland or its buffer and still provide enjoyment of the resource;
f. Buffer widths shall be increased, where possible, equal to the width of the trail corridor, including disturbed areas; and
g. Equestrian trails shall provide measures to assure that runoff from the trail does not directly discharge to the wetland.
7. Utilities. Public and private utility corridors may be allowed within wetland buffers for Category II, III, and IV wetlands when no lesser impacting alternative alignment is feasible, and wetland and wetland buffer functions and values will not be degraded. Utilities, whenever possible, shall be constructed in existing, improved roads, drivable surface or shoulder, subject to compliance with road and maintenance BMPs, or within an existing utility corridor. Otherwise, corridor alignment, construction, restoration and maintenance shall adhere to the following criteria:
a. Corridor alignment shall follow a path beyond a distance from the wetland edge equal to seventy-five percent of the buffer width, except when crossing a Category IV wetland and its buffer;
b. Corridor construction and maintenance shall maintain and protect the hydrologic and hydraulic functions of the wetland and the buffer;
c. Corridors shall be fully revegetated with appropriate native vegetation upon completion of construction; and
d. Utilities requiring maintenance roads shall be prohibited in wetland buffers unless the following criteria are met:
i. There are no lesser impacting alternatives;
ii. Any required maintenance roads shall be no greater than fifteen feet wide. Roads shall closely approximate the location of the utility to minimize disturbances; and
iii. The maintenance road shall be constructed of pervious materials and designed to maintain and protect the hydrologic functions of the wetland and its buffer.
B. Best Available Science. Any approval of alterations of impacts to a wetland or its buffer shall be supported by the best available science.
C. Native Growth Protection Easement/Critical Area Tract. As part of the implementation of approved development applications and alterations, wetlands and their buffers that remain undeveloped pursuant to the critical areas regulations, in accordance with MMC 22.80.080, Protection and mitigation measures, shall be designated as native growth protection easements (NGPE). Any wetland and its associated buffer created as compensation for approved alterations shall also be designated as an NGPE. When the subject development is a formal subdivision or short subdivision, wetlands and their buffers shall be placed in a critical areas tract instead of an NGPE, as described in MMC 22.80.080, Protection and mitigation measures.
D. Buffer Requirements. The following 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: 2014 Update (Ecology Publication No. 14-06-029, or as revised and approved by Ecology). The adjacent land use intensity is assumed to be high.
Wetland buffers shall not include areas that are functionally and effectively disconnected from the wetland by a paved road or other substantially developed surface. This includes parking lots, walkways, and lawns that are of sufficient width and characteristic use such that buffer functions are not provided.
1. For wetlands that score six points or more for habitat function, the buffers in Table 22.80.090(D)(1) can be used if both of the following criteria are met:
a. A relatively undisturbed, vegetated corridor at least one hundred feet wide is protected between the wetland and any other priority habitats as defined by the Washington State Department of Fish and Wildlife. The latest definitions of priority habitats and their locations are available on the WDFW website at:
http://wdfw.wa.gov/hab/phshabs.htm.
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.
Presence or absence of a nearby habitat must be confirmed by a qualified biologist. If no option for providing a corridor is available, Table 22.80.090(D)(1) may be used with the required measures in Table 22.80.090(D)(2) alone.
b. The measures in Table 22.80.090(D)(2) are implemented, where applicable, to minimize the impacts of the adjacent land uses.
2. For wetlands that score three to five habitat points, only the measures in Table 22.80.090(D)(2) are required for the use of Table 22.80.090(D)(1).
3. If an applicant chooses not to apply the mitigation measures in Table 22.80.090(D)(2), or is unable to provide a protected corridor where available, then Table 22.80.090(D)(3) must be used.
4. The buffer widths in Tables 22.80.090(D)(1) and 22.80.090(D)(3) 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.
|
Buffer width (in feet) based on habitat score |
|||
|---|---|---|---|
|
Wetland Category |
3 – 5 |
6 – 7 |
8 – 9 |
|
Category I: Based on total score |
75 |
110 |
225 |
|
Category I: Bogs and wetlands of high conservation value |
190 |
225 |
|
|
Category I: Forested |
75 |
110 |
225 |
|
Category II: Based on score |
75 |
110 |
225 |
|
Category III (all) |
60 |
110 |
225 |
|
Category IV (all) |
40 |
||
|
Disturbance |
Required Measures to Minimize Impacts |
|---|---|
|
Lights |
• Direct lights away from wetland |
|
Noise |
• Locate activity that generates noise away from wetland |
|
• If warranted, enhance existing buffer with native vegetation plantings adjacent to noise source |
|
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• For activities that generate relatively continuous, potentially disruptive noise, such as certain heavy industry or mining, establish an additional 10-ft. 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 ft. of wetland |
|
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• Apply integrated pest management |
|
|
Storm water runoff |
• Retrofit storm water detention and treatment for roads and existing adjacent development |
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• Prevent channelized flow from lawns that directly enters the buffer |
|
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• Use low impact development techniques (for more information refer to Chapter 15.01 MMC) |
|
|
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 |
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• Place wetland and its buffer in a separate tract or protect with a conservation easement |
|
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Dust |
• Use best management practices to control dust |
|
Buffer width (in feet) based on habitat score |
|||
|---|---|---|---|
|
Wetland Category |
3 – 5 |
6 – 7 |
8 – 9 |
|
Category I: Based on total score |
100 |
150 |
300 |
|
Category I: Bogs and wetlands of high conservation value |
250 |
300 |
|
|
Category I: Forested |
100 |
150 |
300 |
|
Category II: Based on score |
100 |
150 |
300 |
|
Category III (all) |
80 |
150 |
300 |
|
Category IV (all) |
50 |
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E. Additional Buffers. The city may require increased buffer sizes as necessary to protect wetlands when either the wetland is particularly sensitive to disturbance or the development poses unusual impacts. Examples of circumstances that may require buffers beyond minimum requirements include, but are not limited to:
1. Unclassified uses;
2. The wetland is in a critical drainage basin;
3. The wetland is a critical fish habitat for spawning or rearing as determined by the Washington Department of Fish and Wildlife;
4. The wetland serves an important groundwater recharge area as determined by a groundwater management plan;
5. The wetland acts as habitat for endangered, threatened, rare, sensitive, or monitor species;
6. The land adjacent to the wetland and its associated buffer and included in the development proposal is classified as an erosion hazard area; or
7. A trail or utility corridor in excess of ten percent of the buffer width is proposed for inclusion in the buffer.
F. Buffer Averaging. The city will consider the allowance of wetland buffer averaging only when the buffer area width after averaging will not adversely impact the critical area and/or buffer functions and values. At a minimum, any proposed buffer averaging must also meet the following criteria:
1. The buffer area after averaging is no less than that which would be contained within the standard buffer; and
2. The buffer width shall not be reduced by more than twenty-five percent at any one point as a result of the buffer averaging.
G. Additional Wetland Mitigation Requirements. No net loss of wetland functions and values shall occur as a result of the overall project. If a wetland alteration is allowed, then the associated impacts will be considered unavoidable and the following mitigation measures to minimize and reduce wetland impacts shall be required, in addition to the requirements in MMC 22.80.080, Protection and mitigation measures.
1. Restoration/rehabilitation is required when a wetland (or stream) or its buffers have been altered on the site in violation of city regulations prior to development approval and as a consequence its functions and values have been degraded. Restoration is also required when the alteration occurs in violation of city regulations during the construction of an approved development proposal. At a minimum, all impacted areas shall be restored to their previous condition pursuant to an approved mitigation plan.
2. Restoration/rehabilitation is required when a wetland (or stream) or its buffers will be temporarily altered during the construction of an approved development proposal. At a minimum, all impacted areas shall be restored to their previous condition pursuant to an approved mitigation plan.
3. Compensation. The overall aim of compensation is no net loss of wetland and/or buffer functions on a development site. Compensation includes replacement or enhancement of wetlands and/or buffer (stream) depending on the scope of the approved alteration and what is needed to maintain or improve wetland and/or buffer functions. Compensation for approved wetland and/or buffer alterations shall meet the following minimum performance standards and shall occur pursuant to an approved mitigation plan.
4. Mitigation shall achieve equivalent or greater biological functions. Mitigation plans shall be consistent with the State Department of Ecology Wetland Mitigation in Washington State, Parts 1 and 2 (Publications No. 06-06-011a and b, 2006), as revised.
a. Preference of Mitigation Actions. Mitigation actions that require compensation shall occur in the following order of preference:
i. Restoring wetlands on upland sites that were formerly wetlands.
ii. Creating wetlands on disturbed upland sites such as those with vegetation cover consisting primarily of exotic introduced species.
iii. Enhancing significantly degraded wetlands only after a minimum one-to-one replacement ratio has been met.
b. On Site and In-Kind. Unless otherwise approved, all wetland impacts shall be compensated for through restoration or creation of replacement wetlands that are in-kind, on site, and of similar or better wetland category. Mitigation shall be timed prior to or concurrent with the approved alteration and shall have a high probability of success. The following ratios shall apply to wetland restoration and creation for mitigation:
|
Category and Type of Wetland |
Creation or Reestablishment |
Rehabilitation |
Enhancement |
|---|---|---|---|
|
I (Bog and wetlands of high conservation value) |
Not considered possible |
Case by case |
Case by case |
|
I (Mature forested) |
6:1 |
12:1 |
24:1 |
|
I (Based on functions) |
4:1 |
8:1 |
16:1 |
|
II |
3:1 |
6:1 |
12:1 |
|
III |
2:1 |
4:1 |
8:1 |
|
IV |
1.5:1 |
3:1 |
6:1 |
c. Off Site and In-Kind. The city may consider and approve off-site compensation where the applicant can demonstrate that equivalent or greater biological and hydrological functions and values will be achieved. The compensation may include restoration, creation, or enhancement of wetland or streams so long as the project is within the same subdrainage basin. The compensation formulas required in subsection (G)(4)(b) of this section shall apply for off-site compensation as well.
d. Increased Replacement Ratios. The zoning administrator may increase the ratios under the following circumstances:
i. Uncertainty exists as to the probable success of the proposed restoration or creation due to an unproven methodology or proponent; or
ii. A significant period will elapse between impact and replication of wetland functions; or
iii. The impact was unauthorized.
5. Decreased Replacement Ratios. The city may decrease the ratios required in subsection (G)(4)(b) of this section when all the following criteria are met:
a. A minimum replacement ratio of one to one will be maintained;
b. Documentation by a qualified wetlands specialist demonstrates that the proposed mitigation actions have a very high rate of success;
c. Documentation by a qualified wetlands specialist demonstrates that the proposed mitigation actions will provide functions and values that are significantly greater than the wetland being impacted; and
d. The proposed mitigation actions are conducted in advance of the impact and have been shown to be successful.
6. 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 Nos. 06-06-011a and b, Olympia, WA, March, 2006), the zoning administrator 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, Olympia, WA, March 2012), or as revised.
7. Wetland Enhancement as Mitigation.
a. Impacts to wetlands may be mitigated by enhancement of existing significantly degraded wetlands only after a one-to-one minimum acreage replacement ratio has been satisfied. Applicants proposing to enhance wetlands must produce a critical areas report that identifies how enhancement will increase the functions and values of the degraded wetland and how this increase will adequately mitigate for the loss of wetland function at the impact site.
b. At a minimum, enhancement acreage shall be four times the acreage required for creation acreage under subsection (G)(4)(b) of this section. The ratios shall be greater than four times the required acreage when the enhancement proposal would result in minimal gain in the performance of wetland functions currently provided in the wetland.
c. Mitigation Plans for Alterations to Wetlands and Wetland Buffers. Mitigation plans shall be consistent with the State Department of Ecology Wetland Mitigation in Washington State, Parts 1 and 2 (Publications Nos. 06-06-011a and b, 2006), or as revised. At a minimum, the following components shall be included in a complete mitigation plan:
i. Baseline Information. Provide existing conditions information for both the impacted critical area and the proposed mitigation site as described in MMC 22.80.070(C), General Critical Area Report Requirements, and (D), Additional Wetland Report Requirements.
ii. Environmental Goals and Objectives. The mitigation plan shall include a written report identifying environmental goals and objectives of the compensation proposed and include:
(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 completing site compensation construction activities. The goals and objectives shall be related to the functions and values of the impacted critical area; and
(B) A review of the best available science supporting the proposed mitigation.
iii. 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. They may include water quality standards, species richness and diversity targets, habitat diversity indices, or other ecological, geological, or hydrological criteria.
iv. Detailed Construction Plan. These are the written specifications and descriptions of mitigation techniques. This plan should include the proposed construction sequencing, grading and excavation details, erosion and sedimentation control features, a native planting plan, and detailed site diagrams and any other drawings appropriate to show construction techniques or anticipated final outcome.
v. Monitoring and/or Evaluation Program. The mitigation plan shall include a program for monitoring construction of the compensation project, and for assessing a completed project. A protocol shall be included outlining the schedule for site monitoring, and how the monitoring data will be evaluated to determine if the performance standards are being met. A monitoring report shall be submitted as needed to document milestones, successes, problems, and contingency actions of the compensation project. The compensation project shall be monitored for a minimum of five years, ten years when establishing woody vegetation, or a period necessary to establish that performance standards have been met.
vi. Contingency Plan. This section identifies potential courses of action, and any corrective measures to be taken when monitoring or evaluation indicates projected performance standards have not been met.
8. Wetland Mitigation Banks. An alternative to on-site permittee-responsible mitigation involves use of wetland mitigation banks.
a. Credits from a wetland mitigation bank may be approved for use as compensation for unavoidable impacts to wetlands when:
i. The bank is certified under state rules (Chapter 173-700 WAC);
ii. The city determines that the wetland mitigation bank provides appropriate compensation for the authorized impacts; and
iii. The proposed use of credits is consistent with the terms and conditions of the certified bank instrument.
b. Replacement ratios for projects using bank credits shall be consistent with replacement ratios specified in the certified bank instrument.
c. Credits from a certified wetland mitigation bank may be used to compensate for impacts located within the service area specified in the certified bank instrument. (Ord. 015/2019 § 3; Ord. 005/2019 § 10 (Exh. B))