16.55.340 Wetland buffers.
Wetland buffers shall be established to protect the integrity, functions and values of the wetland.
A. Measurement of Wetland Buffers. All buffers shall be measured horizontally from edge of the wetland boundary as surveyed in the field. The width of the wetland buffer shall be determined according to Tables 16.55.340(A), (B) and (C).
B. Buffer Standards. The buffer standards required by this chapter presume the existence of a dense vegetation community in the buffer adequate to protect the wetland functions and values. When a buffer lacks adequate vegetation, the director may increase the standard buffer, require buffer planting or other enhancements, and/or deny a proposal for buffer reduction or buffer averaging. Buffers may not include areas that are functionally and effectively disconnected from the wetland by an existing public or private road as determined by the director. Functionally and effectively disconnected means that the road blocks the protective measures provided by a buffer or it disrupts the life cycle of wildlife documented to be using the area.
The standard buffer shall be based on the wetland category, the adjacent land use, and the functions provided by the wetland. There are three sets of buffer standards, based on these parameters:
1. For wetlands that have a high level of function for wildlife habitat as indicated by a habitat function score of eight or nine points or more on the wetland rating form, the buffers shall be as follows:
|
Buffer Width (feet) |
|||
|---|---|---|---|
|
High Intensity |
Moderate Intensity |
Low Intensity |
|
|
Category I |
200 |
190 |
150 |
|
Category II |
200 |
150 |
100 |
|
Category III |
150 |
110 |
75 |
|
Category IV |
50 |
40 |
25 |
Note: Definitions for high, moderate and low intensity land use are provided in BMC 16.55.510.
2. For wetlands that have a moderate level of function for wildlife habitat as indicated by a habitat function score of five to seven points on the wetland rating form, the buffer shall be as follows:
|
Buffer Width (feet) |
|||
|---|---|---|---|
|
High Intensity |
Moderate Intensity |
Low Intensity |
|
|
Category I |
150 |
110 |
75 |
|
Category II |
150 |
110 |
75 |
|
Category III |
150 |
100 |
60 |
|
Category IV |
50 |
40 |
25 |
Note: Definitions for high, moderate and low intensity land use are provided in BMC 16.55.510.
3. For wetlands that have a low level of function for wildlife habitat as indicated by a habitat function score of less than three to four points on the wetland rating form, the buffers shall be as follows:
|
Buffer Width (feet) |
|||
|---|---|---|---|
|
High Intensity |
Moderate Intensity |
Low Intensity |
|
|
Category I |
100 |
75 |
50 |
|
Category II |
100 |
75 |
50 |
|
Category III |
80 |
60 |
50 |
|
Category IV |
50 |
40 |
25 |
Note: Definitions for high, moderate and low intensity land use are provided in BMC 16.55.510.
C. Modifications to Buffer Widths. Any modifications to the buffer width are to be based on the specific wetland functions, site and/or watershed characteristics, location of the wetland within the watershed or sub-basin, and the proposed land use.
1. Increasing Buffer Widths. The director shall have the authority to increase the standard buffer width on a case-by-case basis when a larger buffer is required by an approved habitat assessment as outlined in BMC 16.55.480(C); or such increase is necessary to:
a. Protect the function and value of that wetland, including but not limited to compensating for a poorly vegetated buffer that has a steep slope (greater than 30 percent); or
b. Prevent wind-throw damage; or
c. Maintain viable populations of species such as herons and other priority wildlife species; or
d. Protect wetlands or other critical areas from landslides, erosion or other hazards.
2. Reducing Wetland Buffer Widths. The director shall have the authority to reduce the standard buffer widths; provided, that all of the following apply:
a. The buffer of a Category I wetland shall not be reduced;
b. The buffer reduction shall not adversely affect the functions and values of the adjacent wetlands;
c. The buffer of a Category II or III wetland shall not be reduced to less than 75 percent of the required buffer or 50 feet, whichever is greater;
d. The buffer of a Category IV wetland shall not be reduced to less than 50 percent of the required buffer, or 25 feet, whichever is greater, provided the buffer reduction does not result in reducing the functions and values of the wetland; and
e. The applicant implements all reasonable measures to reduce the adverse effects of adjacent land uses and ensure no new loss of buffer functions and values. The specific measures that shall be implemented include, but are not limited to, the following:
i. Direct lights away from the wetland and buffer;
ii. Locate facilities that generate substantial noise (such as some manufacturing, industrial and recreational facilities) away from the wetland and buffer;
iii. Implement integrated pest management programs;
iv. Infiltrate or treat, detain and disperse runoff into buffer;
v. Construct a wildlife permeable fence around buffer and post signs at the outer edge of the critical area or buffer to clearly indicate the location of the critical area according to the direction of the city;
vi. Plant buffer with “impenetrable” native vegetation appropriate for the location;
vii. Use low impact development techniques to the greatest extent possible;
viii. Establish and record a permanent conservation easement to protect the wetland and the associated buffer and restrict the use of pesticides and herbicides in the easement.
3. Averaging Buffer Widths. The director has the authority to average wetland buffer widths on a case-by-case basis when all the following criteria are met:
a. The buffer averaging does not reduce the functions or values of the wetland;
b. The total area contained in the buffer area after averaging is no less than that which would be contained within the standard buffer, and all increases in buffer dimension for averaging must be parallel to the wetland boundary;
c. The wetland contains variations in sensitivity due to existing physical characteristics or the character of the buffer varies in slope, soils, or vegetation;
d. The buffer width is not reduced in any location to less than 50 percent of the standard width or 35 feet, whichever is greater, except for buffers for Category IV wetlands, and low intensity land uses in which case the narrowest buffer width can be determined on a case-by-case basis, using the best available science;
e. The buffer has not been reduced in accordance with this section. Buffer averaging is not allowed if the buffer has been reduced; and
f. There were no feasible alternatives to the site design without buffer averaging.
D. Buffer Maintenance. Final buffer conditions shall be maintained and undisturbed from future impacts.
E. Wetland Buffer Impacts. When buffer impacts occur, compensatory mitigation shall be provided at a square footage ratio of 1:1. The mitigation shall occur on the same site when feasible or within the same wetland system preferably. The mitigation shall ensure that the wetland functions and values are not diminished due to the buffer impacts.
F. Buffers on Mitigated Sites. Buffer widths shall be applied to mitigation sites consistent with the wetland ratings and buffer requirements of this chapter for subsequent development proposals and based on expected category of the wetland once the mitigation actions are taken.
G. Building Setbacks from Buffers. Buildings, structures, paving, and other hard surfacing shall be set back a distance of 15 feet from the edge of the wetland buffer, or edge of the wetland if no buffer is required, unless otherwise determined by the director to be a shorter distance. This setback is to avoid conflicts with tree branches and/or critical root zones of trees that are in the buffer or will be planted in the buffer. The following may be allowed in the building setback from the buffer if they do not cause damage to the critical root zone of trees in the buffer:
1. Landscaping;
2. Uncovered decks, roof eaves and overhangs, unroofed stairways and steps;
3. Pervious ground surfaces, such as driveways, patios, and parking may be allowed; provided, that it is engineered as a pervious system as defined in BMC 16.80.050. Such improvements may be subject to the requirements in Chapter 15.42 BMC, Stormwater Management;
4. Above and below ground water conservation cisterns and associated infrastructure, used for residential rainwater catchment but not to exceed 300 square feet total; provided, that if above ground, the necessary foundation is engineered as a pervious system. [Ord. 2016-02-005 § 25; Ord. 2010-08-050; Ord. 2008-04-037; Ord. 2005-11-092].