18.65.319 Wetlands – Classes and categories.
(1) Different types of wetlands are separated from one another on the basis of wetland class and wetland category. Wetland class is determined by using a scientific system based upon dominant plant communities, substrate conditions, hydrologic regime, and location in the watershed. Wetland category is determined by using a rating system based on specific attributes such as rarity, sensitivity to disturbance, and the functions they provide.
(2) Wetland Class. Two classification systems are commonly used to describe wetlands. The first is a science-based classification system used by the U.S. Fish and Wildlife Service as described in Classification of Wetlands and Deepwater Habitats of the United States, Second Edition (Federal Geographic Data Committee. 2013. FGDC-STD-004-2013).
The second is the hydrogeomorphic method (HGM) classification (Brinson 1993), a system WDOE incorporated for use in the Washington State Wetland Rating System for Western Washington (WDOE Publication No. 14-06-029, or as hereafter amended).
(3) Wetland Category. Wetland category is used to regulate activities in a wetland and in determining the standard width of the required wetland buffer. The wetland category is determined after a wetland has been identified and delineated in accordance with the approved wetland delineation manual.
WDOE Publication No. 14-06-029, or as amended, contains the definitions and scoring methods used for determining wetlands functions and rating. The wetland category of an individual wetland is determined by the total score for the functions which is recorded on the first page of the wetland rating form included in WDOE Publication No. 14-06-029, or as amended. Wetlands are also rated for “special characteristics,” when applicable, the value of which is included in the final category rating.
(a) Category I. Category I wetlands are: (i) wetlands of high conservation value as identified by scientists of the Washington Natural Heritage Program/DNR; (ii) bogs; (iii) mature and old-growth forested wetlands larger than one acre; (iv) wetlands that perform functions at high levels (scoring 23 points or more). These wetlands: (i) represent unique or rare wetland types; (ii) are more sensitive to disturbance than most wetlands; (iii) are relatively undisturbed and contain ecological attributes that are impossible to replace within a human lifetime; or (iv) provide a high level of functions.
(b) Category II. Category II wetlands are wetlands that perform functions well (scoring between 20 and 22 points).
(c) Category III. Category III wetlands are: (i) wetlands with a moderate level of functions (scoring between 16 and 19 points); and (ii) can often be adequately replaced with a well-planned mitigation project. Wetlands scoring between 16 and 19 points generally have been disturbed in some ways and are often less diverse or more isolated from other natural resources in the landscape than Category II wetlands.
(d) Category IV. Category IV wetlands have the lowest levels of functions (scores less than 16 points) and are often heavily disturbed. (Ord. 09-19 § 9 (Exh. D); Ord. 06-17 § 4 (Exh. B))