18.08.110 Wetlands – Alteration of buffers

18.08.110 Wetlands – Alteration of buffers.

Alteration of a buffer may occur in two ways: (1) quantitative alteration, in which the boundaries of the designated buffer area are adjusted, so that the actual area within the buffer is altered; and (2) qualitative alteration, in which permitted activities within the buffer area alter its character. In determining appropriate buffer alterations, quantitative and qualitative alterations are generally reviewed concurrently.

A. Wetland Buffer Reductions. Buffer width reductions shall be considered on a case-by-case basis to take varying values of individual portions of a given wetland into consideration. Buffers shall not be reduced where the buffer has been degraded as a result of a documented code violation. Reductions may be allowed where the applicant demonstrates to the department that the wetland contains variations in sensitivity due to existing physical characteristics and that reducing the buffer width would not adversely affect the wetland functions and values.

1. Maximum Buffer Reductions. The buffer widths required for uses of land with “high” impacts to wetlands can be reduced to those required for “moderate” impacts under the conditions below:

a. For wetlands that score moderate or high for habitat (five points or more for the habitat functions), the width of the buffer can be reduced if both of the following conditions are met:

i. A relatively undisturbed, vegetated corridor at least 100 feet wide is protected between the wetland and any other priority habitats as defined by the Washington State Department of Fish and Wildlife. Priority habitats include, but may not be limited to, wetlands, riparian zones, aspen stands, cliffs, prairies, caves, stands of Oregon white oak, old-growth forests, estuaries, marine/estuarine shorelines, eelgrass meadows, talus slopes and urban natural open space. The corridor must be protected for the entire distance between the wetland and the priority habitat via some legal protection such as a conservation easement; and

ii. Measures to minimize the impacts of different land uses on wetlands are applied, as summarized in the following table:

Examples of Disturbance	Activities That Cause Disturbances	Examples of Measures to Minimize Impacts
Lights	Parking lots, warehouses, manufacturing, residential	Direct lights away from wetland.
Noise	Manufacturing, residential	Locate activity that generates noise away from wetland.
Toxic runoff¹	Parking lots, roads, manufacturing, residential areas, application of agricultural pesticides, landscaping	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.
		Apply integrated pest management.
Stormwater runoff	Parking lots, roads, manufacturing, residential areas, commercial, landscaping	Retrofit storm water detention and treatment for roads and existing adjacent development.
Stormwater runoff		Prevent channelized flow from lawns that directly enters the buffer.
Change in water regime	Impermeable surfaces, lawns, tilling	Infiltrate or treat, detain, and disperse into buffer new runoff from impervious surfaces and new lawns.
Pets and human disturbance	Residential areas	Use privacy fencing; 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.
Dust	Tilled fields	Use best management practices to control dust.
This is not a complete list of mitigation measures. Additional mitigation measures that minimize impacts may be proposed.

1These examples are not necessarily adequate for minimizing toxic runoff if threatened or endangered species are present at the site.

b. For wetlands that score less than five points for habitat functions, the width of the buffer can be reduced if measures to minimize the impacts of different uses of land are applied, as summarized in the table in subsection (A)(1)(a) of this section.

2. Decision Criteria. Prior to approval, a buffer reduction proposal shall meet all of the decisional criteria listed below. The buffer modification will be approved in a degraded wetland buffer only if:

a. It will provide an overall improvement in water quality protection for the wetland; and

b. It will not adversely affect fish or wildlife species and will provide an overall enhancement to fish and wildlife habitat; and

c. It will provide a net improvement in drainage and/or storm water detention capabilities; and

d. All exposed areas are stabilized with native vegetation, as appropriate; and

e. It will not lead to unstable earth conditions or create an erosion hazard; and

f. It will not be materially detrimental to any other property or the city as a whole.

3. Buffer Enhancement Plan. As part of the buffer reduction request, the applicant shall submit a buffer enhancement plan prepared by a qualified wetland specialist. The report shall assess the habitat, water quality, storm water detention, ground water recharge, shoreline protection, and erosion protection functions of the buffer; assess the effects of the proposed modification on those functions; and address the six criteria listed in this subsection. The buffer enhancement plan shall also provide the following:

a. A map locating the specific area of enhancement;

b. A planting plan that uses native plant species indigenous to this region including groundcover, shrubs, and trees;

c. Provisions for monitoring and maintenance over the monitoring period.

B. Wetland Buffer Width Averaging. Buffer width averaging shall be considered on a case-by-case basis when the proposed averaging is in accordance with an approved wetland mitigation plan and the best available science. Buffer averaging shall not be used in conjunction with the provisions for buffer reductions in this section. Averaging of buffer widths may only be allowed where a qualified wetland specialist demonstrates that:

1. It will not reduce wetland functions or values;

2. 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 in places and would not be adversely impacted by a narrower buffer in other places;

3. The buffer is increased adjacent to the higher-functioning area of habitat or more sensitive portion of the wetland and decreased adjacent to the lower-functioning or less sensitive portion;

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

5. The buffer width is not reduced, at any single point, to less than 75 percent of the standard buffer width.

C. Wetland Buffer Increases. The department may require increased buffer widths in accordance with the recommendations of a qualified wetland specialist and the best available science on a case-by-case basis when a larger buffer is necessary to protect wetland functions and values based on site-specific characteristics. This determination shall be reasonably related to protection of the functions and values of the regulated wetland. Such determination shall demonstrate that:

1. A larger buffer is necessary to maintain viable populations of existing species; or

2. The wetland is used by species listed by the federal government or the state as endangered, threatened, sensitive or as documented priority species or habitats, or essential or outstanding potential sites such as heron rookeries or raptor nesting areas; or

3. The adjacent land is susceptible to severe erosion and erosion control measures will not effectively prevent adverse wetland impact; or

4. The adjacent land has minimum vegetative cover or slopes greater than 30 percent.

1. Qualitative alteration of buffer for Categories II, III and IV wetlands shall be allowed when it is demonstrated that modification of the existing character of the buffer would not reduce the functions and values of the wetland; and

2. That the alteration does not include structures associated with the development unless identified in GHMC 18.08.120(A)(2) and (3), i.e., wells and associated access; and

3. No net loss of wetland acreage due to the alteration occurs. (Ord. 1322 § 9, 2015; Ord. 1036 § 18, 2006; Ord. 611 § 1, 1991).