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The performance standards in this section shall be incorporated into mitigation plans submitted to the city for impacts to critical areas.

A. Wetlands and Streams.

1. Use plants native to the Puget Lowlands or Pacific Northwest ecoregion; non-native, introduced plants or plants listed by the Washington State Department of Agriculture as noxious weeds (Chapter 16-750 WAC) shall not be used;

2. Use plants adapted to and appropriate for the proposed habitats and consider the ecological conditions known or expected to be present on the site. For example, plants assigned a facultative wetland (FACW) wetland indicator status should be used for sites with soils that are inundated or saturated for long periods during the growing season. Use nearby reference wetlands or aerial photos to identify plants suitable to the site conditions and hydrologic regimes planned for the mitigation site. Avoid planting significant areas of the site with species that have questionable potential for successful establishment, such as species with a narrow range of habitat tolerances;

3. Utilize plant species’ heterogeneity and structural diversity that emulates native plant communities described in “Natural Vegetation of Oregon and Washington” (Franklin, J.F. and C.T. Dyrness, 1988) or other regionally recognized publications on native landscapes;

4. Specify plants that are commercially available from native-plant nurseries or available from local sources. If collecting some or all native plants from donor sites, collect in accordance with ecologically accepted methods, such as those described in the “Washington Native Plant Society’s Policy on Collection and Sale of Native Plants,” that do not jeopardize the survival or integrity of donor plant populations;

5. Use perennial plants in preference to annual species; the use of annual species should be limited to a temporary basis in order to provide erosion control, support the establishment of perennial plants, or if mitigation monitoring determines that native plants are not naturally colonizing the site or if species diversity is unacceptably low compared to approved performance standards;

6. Use plant species high in food and cover value for native fish and wildlife species that are known or likely to use the mitigation site (according to reference wetlands, published information, and professional judgment);

7. Install a temporary irrigation system and specify an irrigation schedule and responsible party to maintain unless a sufficient naturally occurring source of water is demonstrated. Temporary irrigation facilities shall be removed after the time specified by the qualified consultant;

8. Identify methods of soil preparation. For stream substrate or wetland soils, at least one foot of clean inorganic and/or organic materials, such as cobble, gravel, sand, silt, clay, muck, soil, or peat, as appropriate, shall be ensured. The stream substrate or wetland soils shall be free from solid, dangerous, or hazardous substance as defined by Chapter 70.105 RCW and implementing rules;

9. Confine temporary stockpiling of soils to upland areas. Identify construction access routes and measures to avoid resultant soil compaction. Unless otherwise approved by the director, comply with all applicable best management practices for clearing, grading, and erosion control to protect any nearby surface waters from sediment and turbidity;

10. Show densities and placement of plants; these should be based on the ecological tolerances of species proposed for planting, as determined by a qualified consultant;

11. Provide sufficient specifications and instructions to ensure proper placement and spacing of seeds, tubers, bulbs, rhizomes, springs, plugs and transplanted stock, and other habitat features, and to provide a high probability of success, and to reduce the likelihood of prolonged losses of wetland functions from proposed development;

12. Do not rely on fertilizers and herbicides to promote establishment of plantings; if fertilizers are used, they must be applied per manufacturer specifications to planting holes in organic or controlled release forms, and never broadcast on the ground surface; if herbicides are used to control invasive species or noxious weeds and to help achieve performance standards, only those approved for use in aquatic ecosystems by the Washington Department of Ecology shall be used; herbicides shall only be used in conformance with all applicable laws and regulations and be applied per manufacturer specifications by an applicator licensed in the state of Washington; and

13. Include the applicant’s mitigation plan consultant in the construction process to ensure the approved mitigation plan is completed as designed. At a minimum, the consultant’s participation will include site visits to inspect completed rough and final grading, installation of in-water or other habitat structures, and to verify the quality and quantity of native plant materials before and after installation;

14. Signs and Fencing of Wetlands and Streams Critical Areas.

a. Temporary Markers. The outer perimeter of the critical area or buffer and the limits of those areas to be disturbed pursuant to an approved permit or authorization shall be marked in the field in such a way as to ensure that no unauthorized intrusion will occur, and verified by the department prior to the commencement of authorized activities. This temporary marking shall be maintained throughout construction, and shall not be removed until permanent signs, if required, are in place.

b. Permanent Signs. As a condition of any permit or authorization issued pursuant to this chapter, the department may require the applicant to install permanent signs along the boundary of a critical area or buffer. Permanent signs shall be made of metal face and attached to a metal post, firmed anchored, or other materials of equal durability approved by the director. Signs must be posted at an interval of one per lot or every 50 feet, whichever is less, and must be maintained by the property owner in perpetuity. The sign shall be worded as follows or with alternative language approved by the director:

Sensitive Area Boundary

“Help protect and care for this area. Trampling or cutting vegetation, placing fill or garbage, and any other activities that may disturb the sensitive area are prohibited, as regulated under Auburn City Code Chapter 16.10.

Please contact city of Auburn at 253-931-3090 with questions or concerns.”

c. Fencing.

i. The director shall condition any permit or authorization issued pursuant to this chapter to require the application to install a permanent fence at the edge of the critical area or buffer, when fencing will prevent future impacts on the critical area.

ii. The applicant shall be required to install a permanent fence around the critical area or buffer when domestic grazing animals are present or may be introduced on site.

iii. Fencing installed as part of a proposed activity or as required in this subsection shall be designed so as to not interfere with species migration, including fish runs, and shall be constructed in a manner that minimizes habitat impacts.

iv. Fencing shall include a permanent natural wood split-rail fence, such as cedar or other non-pressure-treated wood, with fence posts set in concrete footings, or similar, as approved by the director.

B. Wetlands. Do not exceed a maximum water depth of 6.6 feet (two meters) at mean low water unless approved as part of a planned interspersion of wetland vegetation classes and deep-water habitats.

1. Do not exceed a slope of 25 percent (4H:1V) in the wetland unless it can be clearly demonstrated by supporting documentation that wetland hydrology and hydric soils capable of supporting hydrophytic (wetland) vegetation will be created on steeper slopes;

2. Do not exceed a slope of 25 percent (4H:1V) in the wetland buffer; and

3. Limit deep-water habitat (greater than 6.6 feet at mean low water) in compensatory wetland to no more than 60 percent of the total area, and approach this limit only when deep-water habitat is highly interspersed with wetland vegetation classes, including aquatic bed, emergent, scrub-shrub, and forested.

C. Wildlife Habitat Conservation Areas.

1. Incorporate relevant performance standards from subsections A and B of this section, as determined by the director;

2. Include the following additional mitigation measures in mitigation planning:

a. Locate buildings and structures in a manner that minimizes adverse impacts on critical habitats used by threatened or endangered species and identified by the Washington State Department of Fish and Wildlife, NOAA Fisheries, and U.S. Fish and Wildlife Service;

b. Integrate retained habitat into open space and landscaping;

c. Wherever possible, consolidate critical habitats into larger, unfragmented, contiguous blocks;

d. Use native plant species for landscaping of disturbed or undeveloped areas and in any habitat enhancement or restoration activities;

e. Create habitat heterogeneity and structural diversity that emulates native plant communities described in Natural Vegetation of Oregon and Washington (Franklin, J.F. and C.T. Dyrness, 1988) or other regionally recognized publications on native landscapes;

f. Remove and/or control any noxious weeds or exotic animals which are problematic to the critical habitat area as determined by the director or consultant hired by the city to review the mitigation plan; and

g. Preserve significant or existing native trees, preferably in stands or groups, consistent with achieving the goals and standards of this chapter; the plan shall reflect the report prepared pursuant to ACC 16.10.070.

D. Geologically Hazardous Areas.

1. Incorporate relevant performance standards from the preceding subsections, as determined by the director;

2. The following additional performance standards shall be reflected in proposals within geologically hazardous areas:

a. A geotechnical report shall be prepared to identify and evaluate potential hazards and to formulate mitigation measures;

b. Construction methods will not adversely affect geologic hazards or will reduce adverse impacts on geologic hazards;

c. Site planning shall minimize disruption of existing topography and natural vegetation;

d. Impervious surface coverage shall be minimized;

e. Disturbed areas shall be replanted with permanent vegetation as soon as feasible pursuant to a mitigation or landscape plan;

f. Clearing and grading shall be limited to between April 1st and October 31st unless the geotechnical report specifically addresses measures necessary to perform clearing and grading during other portions of the year;

g. The limited use of retaining walls that minimize disturbance or alteration of existing natural slope areas is preferred over graded slopes;

h. Temporary erosion and sedimentation controls, pursuant to an approved plan, shall be implemented during construction;

i. A drainage plan shall be prepared for large projects as required by the city engineer;

j. Development shall not increase instability or create a hazard to the site or adjacent properties, or result in a significant increase in sedimentation or erosion.

E. Aquifer Recharge Areas. Protective measures are required of all development except an individual single-family or two-family (duplex) dwelling unit. Development applications shall include the following minimum measures and incorporate the appropriate responses:

1. Type I Aquifer Recharge Areas.

a. Indicate how hazardous substances shall be stored and used such that any unauthorized release or discharge of the hazardous substances is prevented.

b. Specify that pesticides, herbicides, and fertilizers shall be applied in strict conformance with manufacturer’s instructions and by persons licensed to perform such applications, if applicable.

c. Document hazardous substances management procedures, including, but not limited to, operations plans, drawings and as-built diagrams, emergency response and spill cleanup plans, and employee training documentation. This information can be provided in the form of copies of permits or other documentation required by other authorities.

d. Indicate that any fill material shall be documented to be free of contaminants that exceed Method A and Method B soil cleanup standards specified in Chapter 173-340 WAC prior to placement on the ground, if applicable.

e. Specify that any contaminant release reported to the Washington State Department of Ecology (Ecology) per Chapter 173-340 WAC shall also be reported to the city of Auburn public works department concurrent with notification of Ecology.

f. Include a provision that the implementation of the protective measures will be maintained during the life of the project. Updates shall occur whenever there is a change in use or business occupancy or when there are significant changes in facility operations or hazardous substances management. A copy of the plan is to be available for review by city inspectors at the business or businesses within the development. The plan should cover the facility site in general as well as have a section(s) specific to any tenants within the development.

2. Type II Aquifer Recharge Areas. Property owners shall implement best management practices for water resource protection. (Ord. 6733 § 3 (Exh. B), 2019; Ord. 5894 § 1, 2005.)