Skip to main content
14.260.060 Wetland Buffers.
This section is included in your selections.

A. Buffer Requirements. The following buffer widths have been established in general 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).

B. Table 1: Wetland Buffer Width Requirements.

Table 1. Wetland Buffer Width Requirements

Standard Buffer Width Based on Habitat Score

Wetland Category

Habitat Score

3 – 5

6 – 7

8 – 9

Buffer Width (in feet)

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

100

225

Category III (all)

60

100

225

Category IV (all)

40

C. Required Measures to Minimize Impacts to Wetlands.

1. For wetlands that score six (6) points or more for habitat function, the following criteria must be met if there is a stream or lake on the site or on a parcel adjacent to the site:

a. If there is an existing vegetated corridor connecting the wetland to the stream/lake it shall be protected in such a manner as to provide a connection for wildlife to use.

b. The corridor shall be protected for the entire distance between the wetland and the stream/lake by some type of legal protection such as a conservation easement and designated as a native growth protection area.

c. Presence or absence of a nearby habitat must be confirmed by a qualified biologist. If no option for providing a corridor is available the Planning Director may determine providing a habitat corridor is not required.

2. All development shall be designed to implement the measures described in Table 2 below in order to ensure the required buffer width will be effective in minimizing the impact of the development on the functionality of the wetland.

Table 2. 

Disturbance

Required Measures to Minimize Impacts

Lights

• Direct lights away from wetland

Noise

• Locate activity that generates noise away from wetland

• 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

Stormwater runoff

• Retrofit to current standards existing stormwater detention and treatment for roads and existing on-site development

• Prevent channelized flow from lawns that directly enters the buffer

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 fencing to delineate buffer edge and to discourage disturbance

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

Dust

• Use best management practices to control dust

D. Increased Wetland Buffer Area Width. Buffer widths may 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 must be supported by documentation showing that it is reasonably related to protection of the functions and values of the wetland. The documentation must demonstrate, at a minimum, the following criteria are met:

1. The wetland is used by a state or federally listed plant or animal species or has 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 (30) percent.

E. Reducing Buffer Width.

1. Buffer widths may be decreased through buffer reduction and/or buffer averaging but shall only be allowed on a case-by-case basis. Buffer reduction and buffer averaging shall be considered as a last resort option available only if decreasing buffer widths below the standard width is unavoidable.

2. Buffer widths may be reduced by up to twenty-five (25) percent through buffer reduction when all of the following conditions are met:

a. There is no practical alternative site design that would completely avoid the need to reduce the buffer.

b. Mitigation sequencing pursuant to SMC 14.260.080(A) demonstrates reducing buffer widths is necessary to allow development of the site.

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

d. Invasive species are removed from the areas where the buffer width is reduced and the areas are replanted to create the appropriate plant community for the ecoregion.

e. A temporary irrigation system is operated in the areas that are replanted and shall be operated for a minimum of the first three (3) summers (June 1st through September 30th) following the planting.

f. The buffer at its narrowest point is never less than either twenty-five (25) percent of the required width pursuant to Table 1 or twenty-five (25) feet for Category IV, whichever is greater.

3. Buffer widths may be reduced by up to fifty (50) percent through buffer averaging when all of the following conditions are met:

a. There is no practical alternative site design that would allow reasonable development of the site that completely avoids the need to reduce the buffer.

b. The areas where the buffer width reduction is more than twenty-five (25) percent are kept to a minimum.

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

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

e. Invasive species are removed from the areas where the buffer width is reduced and the areas are replanted to create the appropriate plant community for the ecoregion.

f. A temporary irrigation system is operated in the areas that are replanted for a minimum of the first three (3) summers (June 1st through September 30th) following the planting.

g. The buffer at its narrowest point is never less than either fifty (50) percent of the required width pursuant to Table 1 or fifty (50) feet for Category I and II wetlands, forty (40) feet for Category III wetlands, and twenty-five (25) feet for Category IV wetlands, whichever is greater.

4. Buffer reduction and buffer averaging may be used in conjunction with each other on the same site; provided, that there is no loss of function and the original buffer width is not reduced by more than fifty (50) percent or to be less than twenty-five (25) feet for a Category IV wetland at any point.

F. Measurement of Wetland Buffers. All buffers shall be measured perpendicular from the wetland boundary as surveyed in the field.

1. When there is an existing developed impervious area within a wetland buffer that is generally parallel to the wetland boundary the wetland buffer measurement stops at the edge of the impervious area.

2. The buffer for a wetland created, restored, or enhanced as compensation for approved wetland alterations shall be the same as the standard buffer width required for the category of the created, restored, or enhanced wetland.

3. With buffer averaging, when buffer width is increased the added areas must be fully vegetated in order to be included in buffer area calculations.

4. With buffer averaging, walkways, driveways, and other paved areas shall not be considered buffers or included in buffer area calculations.

G. Buffers on Wetland Mitigation Sites. All wetland mitigation sites shall have buffers consistent with the buffer requirements of this chapter. Buffers shall be based on the expected or target category of the proposed wetland mitigation site.

H. 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 vegetation is required for the duration of the mitigation surety.

I. Impacts to Buffers. Requirements for the compensation for impacts to buffers are outlined in SMC 14.260.080.

J. Overlapping Critical Area Buffers. If buffers for two (2) contiguous critical areas overlap (such as buffers for a stream and a wetland or between two (2) wetlands with different categories or habitat scores), the wider buffer applies.

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

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

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

a. Walkways and trails; provided, that those pathways are:

i. Limited to crossings that have no adverse impact on water quality;

ii. Generally parallel to the perimeter of the wetland;

iii. Located only in the outer twenty-five (25) percent of the wetland buffer area except the pathway may go outside the outer twenty-five (25) percent if necessary to avoid terrain, vegetation or other natural feature that would otherwise block the pathway;

iv. Located to avoid removal of significant trees;

v. Limited to pervious surfaces no more than five (5) feet in width for pedestrian use only. Raised boardwalks utilizing nontreated pilings may be acceptable but shall be reviewed on a case-by-case basis.

b. Wildlife-viewing structures.

c. Educational and scientific research activities by a reputable organization and as approved by the Planning Director.

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

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

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

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

h. Repair and maintenance of nonconforming uses or structures, where legally established within the buffer, provided they do not increase the degree of nonconformity.

i. Stormwater management facilities including, but not limited to, bioretention ponds, bioswales, low impact development facilities, level spreaders, rain gardens, and treated water outfalls with energy dispersion, but excluding stormwater detention vaults, and detention ponds with a freeboard of greater than two (2) feet, if:

i. Located in the outer fifty (50) percent of the wetland buffer of a Category II to IV wetland; and

ii. There is no significant loss in buffer functionality; and

iii. There is “no net loss” of functions and values of the wetland being protected by the buffer; and

iv. The wetland hydrology is unaltered; and

v. The natural routing of runoff is not significantly altered.

L. Signs and Fencing of Wetlands and Buffers.

1. Temporary Markers. The outer perimeter of the wetland buffer and the clearing limits identified by an approved permit or authorization shall be marked in the field with temporary “clearing limits” fencing in such a way as to ensure that no unauthorized intrusion will occur. The marking is subject to inspection by the Planning Director or designee prior to the commencement of any ground disturbance or other permitted activities. This temporary marking shall be maintained throughout construction and shall not be removed until permanent signs are in place.

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

a. Permanent signs shall be:

i. Made of an enamel-coated metal face and attached to a metal post, a four (4) by four (4) wooden post, or another nontreated material of equal durability;

ii. Posted at an interval of one (1) every fifty (50) feet, or one (1) per lot if the lot is less than fifty (50) feet wide;

iii. Located at least four (4) feet above the ground;

iv. At least eight (8) inches wide and twelve (12) inches tall;

v. Maintained by the property owner in perpetuity; and

vi. Worded as follows or with alternative language allowed if approved by the Planning Director:

Native Growth Protection Area

This upland buffer and critical area is protected to provide wildlife habitat and maintain water quality.

Please do not disturb this valuable resource.

Contact the City of Snohomish Department of Planning & Development Services Regarding Uses, and Restrictions.

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

3. Fencing.

a. A permanent fence shall be installed around or on the outer edge of the buffer to delineate the edge of the protected area. The fence shall be a split rail fence no more than four (4) feet high or similar design as approved by the Planning Director or designee.

b. When the edge of the buffer is adjacent to an area containing a use that necessitates fencing that provides security or safety the Planning Director may approve an alternative to a split rail fence.

c. When domestic grazing animals are present or may be introduced on site, the required permanent fence around the edge of the buffer shall be of construction adequate to prevent the domestic grazing animals from entering the protected area.

d. Fencing installed as required in this subsection shall be designed so as to not interfere with species migration, including fish runs, and shall be constructed in a manner that minimizes impacts to the wetland and associated habitat. (Ord. 2368, 2019)

Loading…