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Performance Standards
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A. Activities may only be permitted in a wetland or wetland buffer without mitigation if the applicant can show that the proposed activity will not degrade the functions and functional performance of the wetland and other critical areas. Mitigation shall be performed in accordance with the preferred sequencing shown in BMC 14.04.540(B).

B. Activities and uses shall be prohibited in wetlands and wetland buffers, except as provided for in this chapter.

C. Category I Wetlands. Activities and uses shall be prohibited from Category I wetlands, except for low-impact public access and recreation facilities, such as raised boardwalks or platforms for hiking or bird/wildlife watching, that provide opportunities for the public to enjoy the natural environment. Such facilities shall be designed to avoid or minimize native vegetation removal. Projects shall be designed to result in no net loss of ecological functions, and all adverse impacts shall be mitigated. Other activities and uses may only be allowed as provided for in the public agency and utility exception, reasonable use exception, and variance sections of this chapter.

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

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

2. Low-impact public access and recreation facilities, such as raised boardwalks, may be allowed if they provide opportunities for the public to enjoy the natural environment. Such facilities shall be designed to avoid or minimize native vegetation removal. Projects shall be designed to result in no net loss of ecological functions, and all adverse impacts shall be mitigated. Public access and recreational facilities shall incorporate interpretive signs or other mechanism to educate the public about wetland functions.

3. Where activities are proposed that are neither water-dependent nor related to public access and recreation, it shall be presumed that alternative locations are available, and activities and uses shall be prohibited, unless the applicant demonstrates that:

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

b. 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.

E. Category IV Wetlands. Activities and uses that result in unavoidable and necessary adverse 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 objectives. Full compensation for the acreage and loss functions will be provided under the terms established under BMC 14.04.510(B) or 14.04.540.

F. Wetland Buffers.

1. Vegetative Condition. The buffer widths presume the existence of a relatively intact native vegetation community in the buffer zone adequate to protect the existing wetland functions and values at the time of the proposed activity. If the existing buffer is unvegetated, sparsely vegetated, or vegetated with invasive species that do not perform needed functions, then the buffer shall either be planted to maintain the required width or the buffer shall be widened to ensure that adequate functions of the buffer are provided.

2. Buffer Widths.

a. The wetland buffers in Table 14.04.530-1, based on wetland category and habitat score, apply if the following criteria are met:

(1) The minimization measures of Table 14.04.530-2 are implemented.

(2) For wetlands that score six points or more for habitat function, a relatively undisturbed, vegetated corridor at least 100 feet wide shall be protected when feasible between the wetland and any other priority habitats as defined by the Washington State Department of Fish and Wildlife. Presence or absence of a nearby priority habitat must be confirmed by a qualified professional and documented in a critical areas report. 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 or critical area tract.

Table 14.04.530-1. Wetland Buffer Widths If Table 14.04.530-2 Is Implemented and Corridor Provided

Buffer width (in feet) based on habitat score1

Wetland Category

3 – 5 points

6 – 7 points

8 – 9 points

I

75

110

225

II

75

110

225

III

60

110

225

IV

40

1For detailed description see the Washington State Wetland Rating System for Western Washington (revised), Department of Ecology Publication No. 14-06-029.

Table 14.04.530-2. Required Measures to Minimize Impacts to Wetlands (if applicable to a specific proposal)

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

• 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

Storm water runoff

• Retrofit storm water detention and treatment for roads and existing adjacent development

• Prevent channelized flow from lawns that directly enters the buffer

• Use low intensity development techniques (for more information refer to the drainage ordinance and manual)

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

• Place wetland and its buffer in a separate tract or protect with a conservation easement

Dust

• Use best management practices to control dust

b. The wetland buffers in Table 14.04.530-3, based on wetland category and habitat score, apply if the proposal does not meet the criteria listed within subsection (F)(2)(a) of this section.

Table 14.04.530-3. Wetland Buffer Widths If Table 14.04.530-2 Is Not Implemented or Corridor Not Provided

Buffer width (in feet) based on habitat score1

Wetland Category

3 – 5 points

6 – 7 points

8 – 9 points

I

100

150

300

II

100

150

300

III

80

150

300

IV

50

1For detailed description see the Washington State Wetland Rating System for Western Washington (revised), Department of Ecology Publication No. 14-06-029.

3. Modified Buffer Widths. The city may approve a modification of the required buffer width where the proposed development or use is isolated from the critical area and its contiguous buffer by an existing legally established nonconforming roadway; building; detached garage; accessory dwelling unit; commercial or multifamily residential parking area, including drive aisles and fire lanes; or retaining walls over six feet in height. The modified buffer width would extend to the edge of the legally established nonconforming improvement nearest the wetland. The modification may not be requested for such minor nonconforming improvements as fences, sheds, patios, decks, residential driveways, or other similar structures and impervious surfaces. For the buffer modification to be approved, the applicant must demonstrate conclusively in a critical area report that all the following criteria are met:

a. The existing legal nonconforming improvement between the proposed development or use and the wetland creates a substantial barrier to buffer function;

b. The buffer area modified by an existing legal nonconforming improvement or the section of buffer isolated from the wetland by a legal improvement does not provide additional protection of the critical area from the proposed development; and

c. The buffer area modified by an existing legal nonconforming improvement or the section of buffer isolated from the wetland by a legal improvement does not provide significant hydrological, water quality, and wildlife buffer functions relating to the portion of the buffer adjacent to the critical area.

4. Increased Wetland Buffer Widths. The director shall require increased buffer widths, up to 25 feet, in accordance with the recommendations of a qualified professional and the best available science on a case-by-case basis when a larger buffer is necessary to protect existing wetland functions and values based on site-specific characteristics. This determination shall be based on one or more of the following criteria:

a. A larger buffer is needed to protect other critical areas.

b. Wetlands within 25 feet of the toe of slopes equal to or greater than 15 percent shall have the following buffers:

(1) Where the horizontal length of the slope including small benches and terraces is within the buffer for that wetland category, the buffer width shall be the greater of:

(A) The required buffer for that wetland category; or

(B) Twenty-five feet beyond the toe of the slope.

(2) Where the horizontal length of the slope extends beyond the required buffer for that wetland category, the buffer shall extend to a point 25 feet beyond the required buffer for that wetland category.

c. The buffer area has minimal vegetative cover. In lieu of increasing the buffer width where existing buffer vegetation is inadequate to protect the existing wetland functions and values, implementation of a buffer planting plan developed by a qualified wetland scientist in accordance with an approved critical areas report may substitute. Existing buffer vegetation is considered “inadequate” and will need to be enhanced through additional native plantings and (if appropriate) removal of nonnative plants when: (1) nonnative or invasive plant species provide the dominant cover, (2) vegetation is lacking due to disturbance and wetland resources could be adversely affected, or (3) enhancement plantings in the buffer could significantly improve buffer functions.

d. Buffer widths may vary for any one wetland based on its existing characteristics. It is understood that gradual transition zones will be employed between one buffer width and another. The required buffer width may be increased if any of the following circumstances exist:

(1) Species listed by the federal government or the state of Washington as endangered, threatened, sensitive or priority, or essential or outstanding actual habitat for those species, or plant associations of infrequent occurrence are present;

(2) Unusual nesting or resting sites such as heron rookeries or raptor nesting or lookout trees are present;

(3) The wetland has been identified as providing a particularly important water quality maintenance or flood control function, or is particularly sensitive to erosion and/or sedimentation.

5. Wetland Buffer Width Averaging. The director may allow modification of the wetland buffer width in accordance with an approved critical areas report and the best available science on a case-by-case basis by averaging buffer widths. Averaging of buffer widths may only be allowed where a qualified professional demonstrates that:

a. It will not reduce wetland functions or functional performance;

b. The wetland contains variations in sensitivity due to existing physical characteristics or the character of the buffer varies in slope, soils, or vegetation, and the wetland would benefit from a wider buffer adjacent to the higher-functioning area of habitat or more sensitive portion of the wetland and would not be adversely impacted by a narrower buffer adjacent to the lower-functioning or less sensitive portions of the wetland;

c. The total area contained in the buffer area after averaging is no less than that which would be contained within the buffer; and

d. The buffer width is not reduced to less than the greater of 75 percent of the buffer width or 75 feet for Category I and II, 50 feet for Category III, and 30 feet for Category IV wetlands.

6. Measurement of Wetland Buffers.

a. All buffers shall be measured from the wetland boundary as surveyed in the field.

b. 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.

7. Buffer Consistency. All mitigation sites shall have buffers consistent with the buffer requirements of this chapter.

8. Buffer Maintenance. Except as otherwise specified or allowed in accordance with this chapter, wetland buffers shall be retained in an undisturbed or enhanced condition. In the case of compensatory mitigation sites, removal of invasive nonnative weeds is required for the duration of the mitigation bond.

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

a. Conservation and Restoration Activities. Conservation or restoration activities aimed at protecting the soil, water, vegetation, or wildlife.

b. Passive Recreation. Passive recreation facilities designed and in accordance with an approved critical areas report, including:

(1) Walkways and trails; provided, that those pathways are limited to minor crossings having no adverse impact on water quality. They should be generally parallel to the perimeter of the wetland, where practicable, in the outer 25 percent of the buffer area, and located to avoid removal of significant trees. Surface permeability of walkways and trails shall be considered where applicable. Raised boardwalks utilizing nontreated pilings may be acceptable. Buffer widths shall be increased, where practicable, equal to the width of the trail corridor;

(2) Wildlife viewing structures; and

(3) Fishing access areas down to the water’s edge that shall be no larger than six feet wide.

c. Storm Water Management Facilities. Storm water management facilities, except conveyance facilities and dispersion outfalls for which no alternative location is feasible, are prohibited within Category I and II wetland buffers. Storm water management facilities may be located within the outer 25 percent of the buffer of Category III or IV wetlands; provided, that:

(1) No other location is feasible; and

(2) The location of such facilities will not degrade the functions or values of the wetland.

G. Signs and Fencing of Wetlands.

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

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

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

Protected Wetland Area

Do Not Disturb

Contact the City of Bothell

Regarding Uses and Restriction

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

3. Fencing.

a. The director shall determine if fencing is necessary to protect the functions and values of the critical area. If found to be necessary, the director shall condition any permit or authorization issued pursuant to this chapter to require the applicant to install a permanent fence at the edge of the wetland buffer, when fencing will prevent future adverse impacts to the wetland.

b. The applicant shall be required to install a permanent fence around the wetland or buffer when domestic grazing animals are present or may be introduced on site.

c. Fencing installed as part of a proposed activity or as required in this subsection shall be designed so as to not interfere with species migration, including fish runs, and shall be constructed in a manner that minimizes adverse impacts to the wetland and associated habitat. (Ord. 2349 §§ 1, 2, 2021; Ord. 2010 § 1 (Exh. B), 2009; Ord. 1946 § 3, 2005).