Buffer widths may be reduced in the following instances without the submittal of a mitigation plan:
(1) Reduction in Buffer Width by Reducing the Intensity of Land Use Impacts. The widths of buffers recommended for proposed land uses with high-intensity impacts can be reduced to the buffers recommended for moderate-intensity impacts under the following conditions:
(a) For wetlands that score moderate or high for habitat (six 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. The latest definitions of priority habitats and their locations are available on the WDFW website at: http://wdfw.wa.gov/hab/phshabs.htm. 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 17.38-4, are applied; provided, that the administrator may approve of alternative impact reduction measures that are demonstrated to have equivalent effectiveness in reducing impacts on wetland functions.
(b) For wetlands that score five or less points for habitat, the buffer width can be reduced to that required for moderate land-use impacts by applying the measures to minimize the impacts of the proposed land uses (see examples in Table 17.38-4).
Table 17.38-4 |
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Impact Type | Activities and Uses that Cause Disturbances | Examples of Measures to Reduce Impacts |
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Stormwater runoff | • Parking lots • Roads • Manufacturing • Residential areas • Commercial • Landscaping | • Provide stormwater detention and treatment meeting the latest adopted Stormwater Management Manual for all impervious surfaces that drain to the wetland • Provide infiltration, except where soil conditions preclude • Prevent flow from lawns that directly enters the buffer through swales or other interception |
Lights | • Residential • Warehouses • Manufacturing • Parking lots | • Direct lights away from wetland |
Noise | • Residential • Commercial • Warehouse • Manufacturing | • Locate activity that generates noise away from wetland • Place loading areas, garbage pickup and other pickup/delivery functions on the building side furthest removed from the wetland |
Toxic runoff | • Parking lots • Roads • Manufacturing • Residential areas • Application of agricultural pesticides • Landscaping • Pesticides • Herbicides • Fertilizer | • 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 • Require development and implementation of integrated pest management plan to reduce chemical use |
Pets and human disturbance | • Residential areas | • Fence buffer area with privacy fencing • Plant dense native vegetation to delineate buffer edge |
Lack of native vegetation in buffer | • Buffer will not provide functions | • Ensure minimum vegetation relative density of 20 or plant to 300 stems per acre |
Change in water regime | • Impermeable surfaces • Lawns • Tilling | • Infiltrate or treat, detain, and disperse into buffer new runoff from impervious surfaces and new lawns |
Dust | • Tilled fields | • Use best management practices to control dust |
(2) Functionally Disconnected Buffer Area Where Existing Roads or Structures Lie Within the Buffer.
(a) The administrator may exclude a buffer area that is functionally disconnected by a legally established substantial improvement such as a road, railroad, or structure that serves to eliminate or greatly reduce the impact of a proposed activity upon a wetland buffer.
(b) Where such a substantial improvement exists, the buffer may be reduced to the critical area edge of the existing substantial improvement.
(c) If a project has the potential to impact the functions of a wetland or its buffer, even though such a substantial improvement exists, the administrator shall require the applicant to submit a wetland assessment report to ensure that no net loss of ecological values and functions occurs. A mitigation plan may be required.
(d) As used within this section only, substantial improvements shall include developed public infrastructure such as roads and railroads, and private improvements such as homes, commercial structures, and paved parking lots. Substantial improvements shall not include paved trails, sidewalks, private driveways, resident parking areas, and accessory buildings that do not require a building permit.
(e) Where questions exist regarding whether a development functionally disconnects the buffer, or the extent of that impact, the administrator may require a critical area report to analyze and document the buffer functionality.
(3) Legally Established Buffers.
(a) Where a buffer has been previously established on a legally created parcel or tract that was legally established according to the regulations in place at the time of establishment and is permanently recorded on title or placed within a separate tract, and the parcels that are included on the plat at the time of recording of the subject parcel or tract, then the buffer shall remain as previously established, provided:
(i) It is equal to or greater than 50 percent of the required standard buffer distance for the applicable wetland category; and
(ii) Impact minimization measures are applied. See Table 17.38-4 for more information.
(Ord. 1284 § 4, 2018; Ord. 1327 § 4, 2021; Ord. 1370 (Exh. B), 2025)