Chapter 16D.07


16D.07.01    Purpose and Intent.

16D.07.02    Designating and Mapping.

16D.07.03    Protection Approach.

16D.07.04    Wetland Functions and Rating.

16D.07.05    Compensatory Mitigation Requirements.

16D.07.06    Wetland Mitigation Banks.

16D.07.01 Purpose and Intent.

The purpose and intent of the provisions protecting wetland critical areas are equivalent to the purpose and intent for Chapter 16D.06.01 (Purpose and Intent).

(Ord. 14-2007 § 1 (Exh. A) (part), 2007).

16D.07.02 Designating and Mapping.

(1)    Wetlands are those areas that meet the definition found in Section 16D.02.425 as provided in RCW 36.70A.030(20). All areas within Yakima County meeting the wetland definition are hereby designated critical areas and are subject to the provisions of this title. The following clarifications guide the application of the wetland definition:

(a)    Due to the inherent design of most irrigation systems, such systems are reasonably and foreseeably expected to result in some leakage or seepage. Such leakage or seepage is a normal result of utilization of irrigation systems and is deemed for the purposes of this title to be a nonregulated, artificial wetland.

(2)    The approximate location and extent of wetlands are shown on maps maintained by Yakima County, which may include information from the National Wetlands Inventory produced by the U.S. Fish and Wildlife Service and soil maps produced by United States Department of Agriculture National Resources Conservation Service that are useful in helping to identify potential wetland areas. These maps are to be used as a guide for Yakima County, project applicants and/or property owners, and may be continuously updated as wetlands are more accurately identified, located and delineated.

(Ord. 14-2007 § 1 (Exh. A) (part), 2007).

16D.07.03 Protection Approach.

(1)    Wetlands will be protected using the protection approach for hydrologically related critical areas found in 16D.06.02 (Protection Approach), which accommodates issues affecting wetlands.

(2)    Wetlands and their functions will be protected using the standards found in the Stream Corridor Chapter (16D.06), which includes provisions to:

(a)    Follow mitigation sequencing as outlined in section 16D.03.10 (Mitigation Requirements);

(b)    Avoid degrading the functions and values of the wetland and other critical areas;

(c)    Provide a zero net loss of wetland functions and values together with, if reasonably possible through voluntary agreements or government incentives, a gain in functions and values through the long term.

(Ord. 14-2007 § 1 (Exh. A) (part), 2007).

16D.07.04 Wetland Functions and Rating.

(1)    Wetlands are unique landscape features that are the interface between the aquatic and terrestrial environments. Wetlands provide the following functions:

(a)    Biogeochemical functions, which are related to trapping and transforming chemicals and include functions that improve water quality in the watershed such as: nutrient retention and transformation, sediment retention, metals and toxics retention, and transformation.

(b)    Hydrologic functions, which are related to maintaining the water regime in a watershed, such as: flood flow attenuation, decreasing erosion, groundwater recharge.

(c)    Food web and habitat functions, which includes habitat for: invertebrates, amphibians, anadromous fish, resident fish, birds, mammals.

(2)    Wetlands shall be rated based on categories that reflect the functions and values of each wetland. Wetland categories shall be based on the criteria provided in the Washington State Wetland Rating System for Eastern Washington, revised August 2004 (Ecology Publication No. 04-06-15, as determined using the appropriate rating forms contained in that publication. These categories are summarized as follows:

(a)    Category I wetlands are those that represent a unique or rare wetland type, are more sensitive to disturbance than most wetlands, are relatively undisturbed and contain ecological attributes that are impossible or too difficult to replace within a human lifetime, and provide a high level of functions. Generally, these wetlands are not common and make up a small percentage of the wetlands within Yakima County. The following types of wetlands are Category I:

(i)    Alkali wetlands;

(ii)    Natural Heritage Wetlands. Wetlands that are identified by scientists of the Washington Department of Natural Resources Natural Heritage Program as high quality, relatively undisturbed wetlands, or wetlands that support state threatened or endangered plant species;

(iii)    Bogs;

(iv)    Mature and old-growth forested wetlands with native slow growing trees, which include Western Red Cedar (Thuja plicata), Alaska Yellow Cedar (Chamaecyparis nootkatensis), pine species (mostly White pine – Pinus monticola), Western Hemlock (Tsuga heterophylla), Oregon White Oak (Quercus garryana) and Englemann Spruce (Picea engelmannii);

(v)    Forested wetlands with stands of aspen;

(vi)    Wetlands scoring 70 points or more (out of 100) in the Eastern Washington Wetland Rating System.

(b)    Category II wetlands are difficult, though not impossible, to replace, and provide high levels of some functions. These wetlands occur more commonly than Category I wetlands, but still need a relatively high level of protection. Category II wetlands include:

(i)    Forested wetlands in the floodplains of rivers;

(ii)    Mature and old-growth forested wetlands with native fast growing trees, which include alders (Red – Alnus rubra, Thin leaf – A. tenuifolia), cottonwoods (Narrow leaf – Populus angustifolia, Black – P. balsamifera), willows (Peach leaf – Salix amygdaloides, Sitka – S. sitchensis, Pacific – S. lasiandra); aspen (Populus tremuloides); or Water Birch (Betula occidentalis);

(iii)    Vernal pools;

(iv)    Wetlands scoring between 51 and 69 points (out of 100) in the Eastern Washington Wetland Rating System.

(c)    Category III wetlands are often smaller, less diverse and/or more isolated from other natural resources in the landscape than Category II wetlands. Category III wetlands include:

(i)    Vernal pools that are isolated; and

(ii)    Wetlands with a moderate level of functions (scoring between 30 and 50 points) in the Eastern Washington Wetland Rating System.

(d)    Category IV wetlands have the lowest levels of functions, scoring less than 30 points in the Eastern Washington Wetland Rating System, and are often heavily disturbed. These are wetlands that should be able to be replaced, and in some cases be improved. These wetlands may provide some important functions, and also need to be protected.

(3)    The wetland rating categories as described in section (2), above, shall be applied to projects which are submitted on or after the date of adoption of these provisions. The wetlands shall be rated as they exist on the day of project application submission, as the wetland naturally changes thereafter, or as the wetland changes in accordance with permitted activities. However, illegal modifications to wetlands which have been made since the amended Critical Areas Ordinance (YCC Title 16A, 1995) shall not be considered when rating the wetland. Information regarding the original condition of illegally modified wetlands that cannot be discerned from aerial photographs or other reliable information sources, which is needed to complete the Eastern Washington Wetland Rating System data sheets, shall use the highest appropriate points value within each missing data field of the rating sheet to complete the rating.

(Ord. 10-2019 (Exh. 1) (part), 2019: Ord. 14-2007 § 1 (Exh. A) (part), 2007).

16D.07.05 Compensatory Mitigation Requirements.

Projects that propose to compensate for wetland acreage and/or functions are subject to state and federal regulations. Compensatory mitigation for alterations to wetlands shall provide no net loss of wetland functions and values, and must be consistent with the mitigation plan requirements in section 16D.03.17(13) (Compensatory Mitigation Plans). The following guidance documents were developed to assist applicants in meeting the regulations and requirements.

(1)    Compensatory mitigation plans must be consistent with Guidance on Wetland Mitigation in Washington State Part 2: Guidelines for Developing Wetland Mitigation Plans and Proposals or as revised (Washington State Department of Ecology, U.S. Army Corps of Engineers Seattle District, and U.S. Environmental Protection Agency Region 10; Ecology publication number 04-06-013B,

(2)    Compensatory mitigation application and ratios for mitigation of wetlands shall be consistent with Wetlands in Washington State – Volume 2: Guidance for Protecting and Managing Wetlands – Appendix 8-D – Section 8-D3 or as revised (Washington State Department of Ecology. Publication number 05-06-008,

(Ord. 14-2007 § 1 (Exh. A) (part), 2007).

16D.07.06 Wetland Mitigation Banks.

(1)    Credits from a wetland mitigation bank may be approved for use as compensation for unavoidable impacts to wetlands when:

(a)    The bank is certified under RCW 90.84 and its administrative rules WAC 173-700;

(i)    The administrative official determines that the wetland mitigation bank provides appropriate compensation for the authorized impacts; and

(ii)    The proposed use of credits is consistent with the terms and conditions of the bank’s certification.

(2)    Replacement ratios for projects using bank credits shall be consistent with replacement ratios specified in the bank’s certification.

(3)    Credits from a certified wetland mitigation bank may be used to compensate for impacts located within the service area specified in the bank’s certification. In some cases, bank service areas may include portions of more than one adjacent drainage basin for specific wetland functions.

(Ord. 14-2007 § 1 (Exh. A) (part), 2007).