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Wetlands User Guide

A. Classification and Rating of Wetlands. To promote consistent application of the standards and requirements of this chapter, wetlands within the City of Redmond shall be classified according to their characteristics, function and value, and/or their sensitivity to disturbance. Wetlands shall be rated and regulated according to the categories defined by the Washington State Department of Ecology Wetland Rating System for Western Washington (Ecology Publication No. 14-06-029) as revised. This document contains the methods for determining the wetland category.

1. Wetland Classification. Wetlands, as defined by this chapter, shall be designated Category I, Category II, Category III, and Category IV.

a. Category I wetlands are those wetlands 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 to replace within a human lifetime, or provide a high level of functions. All wetlands with one or more of the following criteria shall be considered a Category I wetland:

i. Wetlands that are identified by scientists of the Washington Natural Heritage Program/DNE as high-quality, relatively undisturbed wetlands, or wetlands that support state-listed threatened or endangered plants; or

ii. Bogs; or

iii. Mature and old-growth forested wetlands over one acre in size; or

iv. Wetlands that provide a very high level of functions as evidenced by a score of 23 points or more on the Western Washington Rating System form.

b. Category II wetlands are those wetlands that provide high levels of some functions which are difficult to replace. Category II wetlands meet the following criteria:

i. Wetlands scoring between 20 to 22 points on the Western Washington Rating System form; or

ii. Wetlands that do not meet the criteria of Category I.

c. Category III wetlands are those wetlands that provide a moderate level of functions. They are typically more disturbed and have less diversity or are more isolated from other natural resources in the landscape. Category III wetlands meet the following criteria:

i. Wetlands scoring between 16 to 19 points on the Western Washington Rating System form; or

ii. Wetlands that do not meet the criteria of Category I.

d. Category IV wetlands are those wetlands that provide the lowest level of function. These wetlands score less than 16 points on the Western Washington Rating System form.

2. Classification of wetlands shall be determined by the Committee based on consideration of the following factors:

a. Maps adopted pursuant to this chapter, including the wetland map, which identifies the approximate location and extent of wetlands. This map shall be used as a general guide only for the assistance of property owners and other interested parties; boundaries are generalized. The actual type, extent, and boundaries of wetlands shall be determined in the field by a qualified consultant according to the procedures, definition, and criteria established by this chapter. In the event of any conflict between the critical area location and designation shown on the City's map and the criteria or standards of this section, the criteria and standards shall prevail;

b. National Wetlands Inventory Maps prepared by the U.S. Fish and Wildlife Service;

c. Application of the criteria contained in these regulations; and

d. Consideration of the technical reports submitted by qualified consultants in connection with applications subject to these regulations.

3. Identification and Delineation. Identification of wetlands and delineation of their boundaries pursuant to this Chapter shall be done in accordance with the approved federal wetland delineation manual and applicable regional supplement. All areas within the City meeting the wetland designation criteria in that procedure are hereby designated critical areas and are subject to the provisions of this chapter. Wetland delineations are valid for five years; after such date the City shall determine whether a revision or additional assessment is necessary.

B. Wetland Buffers.

1. Required buffer widths shall reflect the sensitivity of the particular wetland or the risks associated with development and, in those circumstances permitted by these regulations, the type and intensity of human activity and site design proposed to be conducted on or near the critical area.

2. Wetland buffers shall be measured perpendicular from the wetland edge as delineated and marked in the field. Wetland buffers shall be established as follows:

Table 21.64.030A.1

Wetland Buffer Requirements

Buffer Width Based on Habitat Score (feet)

Wetland Category

3-5

6-7

8-9

Category 1: Wetlands of High Conservation Value

250

250

300

Category I

100

150

300

Category II

100

150

300

Category III

80

150

300

Category IV

50

50

50

Table 21.64.030A.2

Wetland Buffer Requirements When Table 21.64.030A.3 is Implemented

Buffer Width Based on Habitat Score (feet)

Wetland Category

3-5

6-7

8-9

Category I: Wetlands of High Conservation Value

190

190

225

Category I

75

110

225

Category II

75

110

225

Category III

60

110

225

Category IV

40

40

40

Table 21.64.030A.3

Requirement Measures to Minimize Impacts to Wetlands (All Measures Required)

Disturbance

• Required Measure to Minimize Impacts

Lights

• Direct lights away from wetland

Noise

• Locate activity that generates noise away from wetland

• If warranted, enhance existing buffer with native vegetation plantings adjacent to noise source

• For activities that generate relatively continuous, potentially disruptive noise, such as certain heavy industry, establish an additional 10’ heavily vegetated buffer strip immediately adjacent to the outer wetland buffer

Toxic Runoff

• 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

• Retrofit stormwater detention and treatment for roads and existing adjacent developments

• Prevent channelized flow from lawns that directly enters the buffer

• Use Low Impact Development techniques

Change in Water Regime

• Infiltrate or treat, detain, and disperse into buffer new runoff from impervious surfaces and new lawns

Pets and Human Disturbance

• Use fencing or plant dense vegetation to delineate buffers edge and to discourage disturbance using vegetation appropriate for the ecoregion

• Place wetland and its buffer in a separate tract

Dust

• Use best management practices to control dust 

Elements in Table 21.64.030A.3 shall be fully documented by a qualified wetland professional.

3. The buffer for a wetland created, restored, or enhanced as compensation for approved wetland alterations shall be that required for the category of the wetland.

4. Increased Buffer Widths. The Department may extend the width of the buffer in accordance with the recommendations of a qualified wetland professional and the best available science on a case-by-case basis when a larger buffer is necessary to protect wetland functions and values based on site-specific characteristics.  The determination shall be supported by appropriate documentation showing that it is reasonably related to protection of the functions and values fo the wetland.  The documentation must include the following criteria:

a. The wetland is used by a state or federally listed plant or animal species or has essential or outstanding habitat for those species, or has unusual nesting or resting sites such as heron rookeries or raptor nesting trees; or

b. The adjacent land is susceptible to severe erosion, and erosion-control measure will not effectively prevent adverse wetland impacts; or

c. The adjacent land has minimal vegetation cover or slopes greater than 30 percent.

5. Wetland Buffer Width Averaging. Wetland buffer widths may be modified by averaging buffer widths to improve wetland protection as set forth herein. The Department may allow modification of the standard wetland buffer width in accordance with the best available science on a case-by-case basis by averaging buffer widths. Averaging buffer widths may only be allowed when all of the following conditions are met as demonstrated by a qualified wetland professional:

a. It will not reduce the functions or values;

b. The wetland contains variations in sensitivity due to existing physical characteristics or the character of the buffer varies in slope, soils, or vegetation, and the wetland would benefit from increased buffers adjacent to the higher functioning area of habitat or more sensistive portion of the wetland and would not be adversely impacted by a decreased buffer adjacent to the lower-functioning or less-sensitive portion of the wetland;

c. The total area contained in the buffer area after averaging is equal to the area required in the standard buffer;

d. The buffer width is not reduced more than 25 percent of the width or 75 feet for Category I and II wetlands.  50 feet for Category III wetlands, and 25 feet for Category IV wetlands, whichever is greater and;

e. 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.

6. Stormwater management facilities, such as biofiltration swales and outfalls, may be located within the outer 25 percent of the buffer, provided that no other location is feasible and the location of such facilities will not degrade the functions or values of the wetland. Stormwater ponds must be located outside of the required buffer. Underground vaults are also permitted within the outer 25 percent of the buffer provided that the maintenance access area lies outside of the buffer and the area above the vault is planted with native vegetation.

C. Alteration of Wetlands.

1. Draining or disturbing a wetland is prohibited, except as provided for in this Chapter. Disturbances include changing the physical structure within a wetland, changing the amount and velocity of water, and changing the fluctuation of water levels.

2. Wetland alteration shall result in no net loss of wetland area, except where the following criteria are met:

a. The lost wetland area provides minimal functions and the mitigation action(s) results in a net gain in wetland functions as determined by a site-specific assessment; or

b. The lost wetland area provided minimal functions as determined by a site-specific functional assessment and other replacement habitats provide greater benefits to the functioning of the watershed, such as riparian habitat restoration and enhancement.

3. Category I Wetlands. Alterations of Category I wetlands shall be prohibited subject to the reasonable use provisions of this chapter.

4. Category II, III, and IV Wetlands.

a. Any proposed alteration and mitigation shall comply with the mitigation performance standards and requirements of these regulations; and

b. No net loss of wetland function and value may occur.

c. Where enhancement or replacement is proposed, ratios shall comply with the requirements of subsection C.7 below in this section.

5. Mitigation for alterations to wetlands shall achieve equivalent or greater biological functions. Mitigation plans shall be consistent with the Department of Ecology Guidance on Wetland Mitigation in Washington State, Part 2: Guidelines for Developing Freshwater Wetlands Mitigation Plans and Proposals, April, 2004, as revised.

6. Mitigation actions shall address functions affected by the alteration to achieve functional equivalency or improvement, and shall provide similar wetland functions as those lost except when:

a. The filled/impacted wetland provides minimal functions as determined by a site-specific function assessment; and the proposed mitigation action(s) will provide equal or greater functions, or will provide functions shown to be limiting within a watershed through a formal watershed assessment plan or protocol; or

b. Out-of-kind replacement will best meet formerly identified regional goals, such as replacement of historically diminished wetland types.

7. Mitigation actions that require compensation by replacing, enhancing, or substitution shall occur in the following order of preference:

a. Preserving high-quality wetlands that are under imminent threat.

b. Restoring wetlands on upland sites that were formerly wetlands.

c. Creating wetlands on disturbed upland sites, such as those with vegetative cover consisting primarily of exotic introduced species.

d. Enhancing significantly degraded wetlands.

8. Wetland Replacement Ratios.

a. Where wetland alterations are permitted by the City, the applicant shall restore or create areas of wetlands in order to compensate for wetland losses. Equivalent areas shall be determined according to acreage, function, type, location, timing factors, and projected success of restoration or creation.

b. When creating or enhancing wetlands, the following acreage replacement ratios shall be used:

Table 21.64.030B
Acreage Replacement Ratios

Category and Type of Wetland

Creation or Reestablishment

Rehabilitation (Restoration)

Enhancement Only

Category I Forested

6:1

12:1

24:1

Category I based on functions

4:1

8:1

16:1

Category II

3:1

6:1

12:1

Category III

2:1

4:1

8:1

Category IV

1.5:1

3:1

6:1

c. These ratios do not apply to the use of credits from a state certified wetland mitigation bank.  When credits from a certified bank are used, replacement ratios shall be consistent with the requirements of the mitigation banking instrument.

d. Enhanced and created wetlands shall be appropriately classified and buffered.

D. Wetlands Performance/Design Standards.

1. Use plants indigenous to the Pacific Northwest region (not introduced or foreign species);

2. Use plants adaptable to a broad range of water depths;

3. Plants should be commercially available or available from local sources;

4. Plant species high in food and cover value for fish and wildlife must be used;

5. Avoid committing significant areas of the site to species that have questionable potential for successful establishment;

6. Plant selection must be approved by a qualified wetland specialist;

7. Water depth is not to exceed six and one-half feet (two meters);

8. The grade or slope that water flows through the wetland is not to exceed six percent for wetland creation sites;

9. Slopes within the wetland basin and the buffer zone may not be steeper than 3:1 (horizontal to vertical) for wetland creation sites;

10. Substrate should consist of a minimum of one foot, in depth, of clean (uncontaminated with chemicals or solid/hazardous wastes) inorganic/organic materials for wetland creation sites;

11. Planting densities and placement of plants should be determined by a qualified wetland professional and shown on the design plans;

12. The planting plan must be approved by the Department;

13. Confine stockpiling to upland areas and ensure contract specifications limit stockpiling of earthen materials to durations in accordance with City clearing and grading standards, unless otherwise approved by the Committee;

14. Planting instructions shall be submitted which describe proper placement, diversity, and spacing of seeds, tubers, bulbs, rhizomes, sprigs, plugs, and transplanted stock;

15. Apply controlled-release, non-phosphorus fertilizer at the time of planting and afterward only as plant conditions warrant (determined during the monitoring process);

16. Install an irrigation system, if necessary, for the initial establishment period;

17. Construction specifications and methods must be approved by a qualified consultant and the Department; and

18. Construction management should occur by a qualified consultant and be inspected by the City. (Ord. 2803; Ord. 2968)

Effective on: 10/17/2015