(1) Wetland buffers shall be required for all regulated activities adjacent to regulated wetlands. All buffers shall be measured from the wetland boundary. The width of the wetland buffer zone shall be determined according to the wetland category as follows:
Wetland Rating and Characteristics | Buffer Widths by Impact of Land Use* | Other Measures Recommended for Protection |
|---|
Category IV (score for functions < 30 points) | Low – 25 feet Moderate – 40 feet High – 50 feet | |
Category III – moderate level of function for habitat (score for habitat 20 – 28 points) | Low – 75 feet Moderate – 110 feet High – 150 feet | |
Category III – not meeting above criteria for habitat | Low – 40 feet Moderate – 60 feet High – 80 feet | |
Category II – high level of function for habitat (score for habitat 29 – 36 points) | Low – 150 feet Moderate – 225 feet High – 300 feet | Maintain connectivity to other natural areas. |
Category II – moderate level of function for habitat (score for habitat 20 – 28 points) | Low – 75 feet Moderate – 110 feet High – 150 feet | |
Category II – high level of function for water quality improvement (score for water quality 24 – 32 points) and low level of function for habitat (score for habitat < 20 points) | Low – 50 feet Moderate – 75 feet High – 100 feet | No additional discharges of untreated runoff. |
Category II – not meeting any of above criteria for habitat or water quality | Low – 50 feet Moderate – 75 feet High – 100 feet | |
Category I – Natural Heritage Wetlands | Low – 125 feet Moderate – 190 feet High – 250 feet | No additional discharges of surface water. No septic systems within 300 feet. Restore degraded parts of buffer. |
Category I – Bogs | Low – 125 feet Moderate – 190 feet High – 250 feet | No additional discharges of surface water. Restore degraded parts of buffer. |
Category I – Forested | Buffer size needs to be based on score for habitat functions or water quality functions. | If forested wetland scores high for habitat, need to maintain connectivity to other natural areas. Restore degraded parts of buffer. |
Category I – high level of function for habitat (score for habitat 29 – 36 points) | Low – 150 feet Moderate – 225 feet High – 300 feet | Maintain connectivity to other natural areas. Restore degraded parts of buffer. |
Category I – moderate level of function for habitat (score for habitat 20 – 28 points) | Low – 75 feet Moderate – 110 feet High – 150 feet | |
Category I – high level of function for water quality improvement (score for water quality 24 – 32 points) and low level of function for habitat (score for habitat < 20 points) | Low – 50 feet Moderate – 75 feet High – 100 feet | No additional discharges of untreated runoff. |
Category I – not meeting any of above criteria for habitat or water quality | Low – 50 feet Moderate – 75 feet High – 100 feet | |
* See subsection (2)(c) of this section for definitions of high, moderate, and low impacts. |
(2) Buffer Reduction. The buffer widths recommended for proposed land uses with high-intensity impacts to wetlands can be reduced by the planning director to those recommended for moderate-intensity impacts under the following conditions:
(a) For wetlands that score moderate or high for habitat (20 points or more for the habitat functions), the width of the buffer can be reduced if both of the following criteria 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 (“relatively undisturbed” and “vegetated corridor” are defined in questions H 2.1 and H 2.2.1 of the Washington State Wetland Rating System for Western Washington – Revised, (Hruby 2004b)). Priority habitats in Western Washington include:
Wetlands |
Riparian zones |
Aspen stands |
Cliffs |
Prairies |
Caves |
Stands of Oregon White Oak |
Old-growth forests |
Estuary/estuary-like |
Marine/estuarine shorelines |
Eelgrass meadows |
Talus slopes |
|
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.
(ii) Measures to minimize the impacts of different land uses on wetlands, such as the examples summarized in Table 14.15-1, are applied.
(b) For wetlands that score less than 20 points for habitat, the buffer width can be reduced to that required for moderate land use impacts by applying measures to minimize the impacts of the proposed land uses (see examples in Table 14.15-1).
Table 14.15-1 Examples of Measures to Minimize Impacts to Wetlands from Proposed Change in Land Use That Have High Impacts (this is not a complete list of measures) |
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Examples of Disturbance | Activities and Uses that Cause Disturbances | Examples of Measures to Minimize Impacts |
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Lights | • Parking lots • Warehouses • Manufacturing • Residential areas | • Direct lights away from wetland |
Noise | • Manufacturing • Residential areas | • Locate activity that generates noise away from wetland |
Toxic runoff* | • 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 feet of wetland • Apply integrated pest management |
Stormwater runoff | • Parking lots • Roads • Manufacturing • Residential areas • Commercial • Landscaping | • Retrofit stormwater detention and treatment for roads and existing adjacent development • 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 |
* These examples are not necessarily adequate for minimizing toxic runoff if threatened or endangered species are present at the site. |
(c) Defining of “High, Moderate, and Low Impacts” as Used in Subsection
(1) of This Section. The following table provides examples of the types of land use and their impact upon wetlands:
Level of Impact from Proposed Change in Land Use | Types of Land Use Based upon Zoning Designations |
|---|
High | • High Density Commercial • Forks Industrial Park and Industrial • High and Moderate Density Residential |
Moderate | • Moderate and Low Density Commercial • Low Density Residential • Farming/Agricultural activities conducted pursuant to established plans using best available practices, advice of conservation districts, etc. • Utility corridors with right-of-way shared by utility providers • Paved roads and/or trails |
Low | • Low Density Residential • Forestry activities taken pursuant to appropriate Forest Practice Act permits issued by the Department of Natural Resources |
(3) Buffer Averaging.
(a) The widths of buffers may be averaged if this will improve the protection of wetland functions, or if it is the only way to allow for reasonable use of a parcel. Averaging could be allowed in the following situations:
(i) Averaging to improve wetland protection may be permitted when all of the following conditions are met:
(A) The wetland has significant differences in characteristics that affect its habitat functions, such as a wetland with a forested component adjacent to a degraded emergent component or a “dual-rated” wetland with a Category I area adjacent to a lower-rated area.
(B) 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.
(C) The total area of the buffer after averaging is equal to the area required without averaging.
(D) The buffer at its narrowest point is never less than three-fourths of the required width.
(ii) Averaging to allow reasonable use of a parcel may be permitted when all of the following are met:
(A) There are no feasible alternatives to the site design that could be accomplished without buffer averaging.
(B) The averaged buffer will not result in degradation of the wetland’s functions and values as demonstrated by a report from a qualified wetland professional.
(C) The total buffer area after averaging is equal to the area required without averaging.
(D) The buffer at its narrowest point is never less than three-fourths of the required width.
(b) Averaging may not be used in conjunction with any of the other provisions of this chapter associated with the reduction of a required wetland buffer (listed above).
(4) Measurement of Wetland Buffers. All buffers shall be measured from the wetland boundary as surveyed in the field. The width of the wetland buffer shall be determined according to the wetland category and the proposed land use as identified in this title. 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.
(5) Buffers on Mitigation Sites. All mitigation sites shall have buffers consistent with the buffer requirements of this chapter and based on the expected category of the wetland once the mitigation actions are completed.
(6) 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.
(7) Buffer Uses. The following uses may be permitted within a wetland buffer in accordance with the review procedures of this title, provided they are not prohibited by any other applicable law and they are conducted in a manner so as to minimize 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 area report, including:
(i) 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, located only in the outer 25 percent of the wetland buffer area, and located to avoid removal of significant trees. They should be limited to pervious surfaces no more than five feet in width for pedestrian use only. Raised boardwalks utilizing nontreated pilings may be acceptable; and
(ii) Wildlife viewing structures.
(c) Stormwater Management Facilities. Stormwater management facilities, limited to stormwater dispersion outfalls and bioswales, may be allowed within the outer 25 percent of the buffer of Category III or IV wetlands only; provided, that:
(i) No other location is feasible; and
(ii) The location of such facilities will not degrade the functions or values of the wetland.
(Ord. 341 § 7.1, 1992; Ord. 550 § 9, 2007)