Chapter 17.23
WETLANDS
Sections:
17.23.020 Review and reporting requirements.
17.23.040 Provisions for small isolated wetlands.
17.23.052 Allowed activities in wetlands and buffers.
17.23.055 Mitigation monitoring.
17.23.056 Development standards.
17.23.010 Designation.
A. Wetlands are those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support a prevalence of vegetation typically adapted for life in saturated soil conditions. Swamps, marshes, bogs, and wet meadows/pastures are examples of wetland. Some riparian areas adjacent to streams are also wetland.
B. Wetlands shall be identified in accordance with the requirements of RCW 36.70A.175 and 90.58.380. Unless otherwise provided for in this chapter, all areas within the city meeting the criteria in the Washington State Wetland Identification and Delineation Manual (Ecology Publication 96-94), regardless of any formal identification, are hereby designated critical areas and are subject to the provisions of this chapter.
C. The approximate location and extent of known or suspected wetlands are shown on the city’s critical area maps. Other, unmapped wetlands may exist within the city. These maps are to be used as a guide and do not provide a definitive critical area designation.
D. 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 Western Washington, revised August 2004 (Ecology Publication No. 04-06-025). These categories are generally defined as follows:
1. Category I Wetlands. Category I wetlands are those wetlands of exceptional value in terms of protecting water quality, storing flood and storm water, and/or providing habitat for wildlife as indicated by a rating system score of 70 points or more. These are wetland communities of infrequent occurrence that often provide documented habitat for critical, threatened or endangered species, and/or have other attributes that are very difficult or impossible to replace if altered.
2. Category II Wetlands. Category II wetlands have significant value based on their function as indicated by a rating system score of between 51 and 69 points. They do not meet the criteria for Category I rating but occur infrequently and have qualities that are difficult to replace if altered.
3. Category III Wetlands. Category III wetlands have important resource value as indicated by a rating system score of between 30 and 50 points.
4. Category IV Wetlands. Category IV wetlands are wetlands of limited resource value as indicated by a rating system score of less than 30 points. They typically have vegetation of similar age and class, lack special habitat features, and/or are isolated or disconnected from other aquatic systems or high quality upland habitats. [Ord. 849B § 4, 2009.]
17.23.020 Review and reporting requirements.
A. If the project site is within 300 feet of a National Wetland Index mapped area, the director shall require a site evaluation (field investigation) by a qualified professional to determine whether or not a regulated wetland is present and if so, its relative location in relation to the proposed project area on site. If the director determines that a wetland is more likely than not present, the director shall require a critical area study. If no regulated wetlands are present, then wetland review will be considered complete.
B. A critical area study (wetland assessment study) describes the characteristics of the subject property and adjacent areas. The assessment shall be completed pursuant to CMC 17.21.082 and include the following:
1. Existing physical features of the site including buildings, fences, and other structures, roads, parking lots, utilities, water bodies, etc.;
2. Determination of the wetland category and wetland buffers;
3. Field identification and delineation of wetland boundaries. For on-site wetlands, the assessment shall include the dominant and subdominant plant species; soil type, color and texture; sources of hydrology (patterns of surface and subsurface water movement, precipitation, etc.), topography, and other pertinent information;
4. Identification of critical areas and buffers within 300 feet of the site and an estimate of the approximate acreage for each. The assessment of off-site wetlands shall be based on available information and shall not require accessing off-site properties;
5. A detailed description of the effects of the proposed development on wetland and buffer function and value, including the area of direct wetland disturbance; area of buffer reduction or averaging including documentation that functions and values will not be adversely affected by the reduction or averaging; effects of storm water management; proposed hydrologic alteration including changes to natural drainage or infiltration patterns; effects on fish and wildlife species and their habitats; clearing and grading impacts; temporary construction impacts; and effects of increased noise, light or human intrusion;
6. A mitigation plan, if applicable. [Ord. 849B § 4, 2009.]
17.23.030 Buffers.
A. Wetland buffer zones shall be required for all regulated activities adjacent to regulated wetlands. Any wetland created, restored or enhanced as compensation for approved wetland alterations shall also include the standard buffer required for the category of the created, restored or enhanced wetland. All buffers shall be measured from the wetland boundary as surveyed in the field. The width of the wetland buffer zone shall be determined according to wetland category. Buffers shall not include areas that are functionally and effectively disconnected from the wetland by a road or other substantially developed surface of sufficient width and with use characteristics such that buffer functions are not provided.
B. The buffer standards required by this chapter presume the existence of a dense vegetation community in the buffer adequate to protect the wetland functions and values. When a buffer lacks adequate vegetation, the director may increase the standard buffer, require buffer planting or enhancement, and/or deny a proposal for buffer reduction or buffer averaging.
C. Buffer Dimensions.
|
|
Low Wildlife Function (less than 20 points) |
Moderate Wildlife Function (20 – 26 points) |
High Wildlife Function (27 or more points) |
|
Wetland Category |
Buffer Width (feet) |
||
|
Category IV |
50 |
50 |
501 |
|
Category III |
80 |
100 |
1501 |
|
Category II |
100 |
150 |
See table in subsection (D) of this section |
|
Category I |
100 |
150 |
See table in subsection (D) of this section |
1. Habitat scores over 26 points would be very rare for Category III wetlands and almost impossible for Category IV wetlands that have a total rating of 30 or less.
D. Buffers for Wetlands with High Wildlife Function (27 Points or More).
|
Wetland Category |
Points for Habitat from Wetland Rating Form |
|||||||||
|
27 |
28 |
29 |
30 |
31 |
32 |
33 |
34 |
35 |
36 |
|
|
Category I and II |
165 |
180 |
195 |
215 |
225 |
225 |
225 |
225 |
225 |
225 |
E. Where lands within the wetland buffer have an average continuous slope of 20 percent to 35 percent, and the required buffer width is less than 100 feet, the buffer shall extend to a 30 percent greater dimension. In all cases, where slopes within the buffers exceed 35 percent, the buffer shall extend 25 feet beyond the top of the bank of the sloping area or, if a buffer associated with a geological hazard is present, to whichever extent is greater.
F. Where other critical areas defined in this chapter fall within the wetland buffer, the buffer dimension shall be the most expansive of the buffers applicable to any applicable critical area. [Ord. 849B § 4, 2009.]
17.23.040 Provisions for small isolated wetlands.
A. All wetlands shall be regulated regardless of size; provided, that the director shall assure that preservation of isolated wetlands and associated buffers of less than 10,000 square feet of combined wetland and buffer shall maintain effective wetland functions, or be mitigated as provided below.
B. Wetlands and associated buffers of less than 1,000 square feet may be displaced when the wetland meets all of the following criteria, as documented in a wetland critical area study:
1. The wetland is not associated with a riparian corridor;
2. The wetland is not part of a wetland mosaic;
3. The wetland does not contain habitat identified as essential for local populations of priority species identified by Washington Department of Fish and Wildlife; and
4. Impacts of displaced wetlands are mitigated pursuant to CMC 17.21.087.
C. Category III and IV wetlands between 1,000 and 4,000 square feet may be displaced without meeting the provisions of CMC 17.21.087 regarding avoidance, minimization, rectification, and reducing and eliminating the impact over time; provided, that the criteria in subsection (B) of this section are met and the wetland does not score 20 points or greater for habitat in the 2004 Western Washington Rating System.
D. Preservation of isolated wetlands with a total area of the combined wetland and buffer of 10,000 square feet or less shall meet the following provisions, or if the said provisions cannot be demonstrated, as specified by the director, they may be displaced and shall be mitigated as specified in CMC 17.23.053:
1. Depressional wetlands recharged only by precipitation, interflow or groundwater shall be assured a source of recharge to maintain its hydrologic character through storm water infiltration, or other means.
2. Wetlands that have a potential to reduce flooding or erosion or has the potential and opportunity to maintain or improve water quality as evidenced by a score of at least 10 points on the applicable criteria of the wetland rating form for Western Washington shall maintain a hydraulic connection to surface water that maintains effective wetland function for flood or erosion reduction or water quality and does not substantially alter the existing hydroperiod of the wetland.
3. Wetlands that achieve a score of at least 20 points on the habitat functions criteria of the wetland rating form for Western Washington shall maintain a connection to a linear corridor maintained as a stream buffer, a buffer associated with a geological hazard or other designated open space buffer sufficient to allow movement of terrestrial wildlife to and from the wetland and buffer complex without interruption by roads, paved areas or buildings within 50 feet. [Ord. 849B § 4, 2009.]
17.23.050 Buffer averaging.
The permit approval authority may average wetland buffer widths on a case-by-case basis when the applicant demonstrates through a critical area study to the satisfaction of the director that all the following criteria are met:
A. Averaging to improve wetland protection may be permitted when all of the following conditions are met as demonstrated by a wetland assessment study pursuant to CMC 17.23.020:
1. 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 or a “dual-rated” wetland with a Category I area adjacent to a lower rated area.
2. The buffer is increased adjacent to the higher-functioning area of habitat or more sensitive portion of the wetland and decreased adjacent to the lower-functioning or less sensitive portion.
3. The total area of the buffer after averaging is equal to the area required without averaging and all increases in buffer dimension for averaging are generally parallel to the wetland edge.
4. The buffer at its narrowest point is never less than three-fourths of the required width.
B. Averaging to allow reasonable use of a parcel may be permitted when all of the following are met as demonstrated by a wetland assessment study pursuant to CMC 17.23.020:
1. There are no feasible alternatives to the site design that could be accomplished without buffer averaging;
2. The averaged buffer will not result in degradation of the wetland’s functions and values;
3. The total buffer area after averaging is equal to the area required without averaging and all increases in buffer dimension for averaging are generally parallel to the wetland edge;
4. The buffer at its narrowest point is never less than three-fourths of the required width except where the director finds that there is an existing feature such as a roadway that limits buffer dimension, or an essential element of a proposed development such as access that must be accommodated for reasonable use and requires a smaller buffer.
C. The applicant implements all reasonable measures to reduce the adverse effects of adjacent land uses and ensure no net loss of wetland functions and values in conjunction with a wetland assessment study and mitigation plan. The specific measures that shall be implemented include, but are not limited to, those in CMC 17.23.056. [Ord. 849B § 4, 2009.]
17.23.051 Buffer increase.
The permit approval authority may increase the width of the standard buffer width on a case-by-case basis, based on a critical area study, when a larger buffer is required to protect critical habitats as outlined in CMC 17.25.010, or such increase is necessary to:
A. Protect the function and value of that wetland from proximity impacts of adjacent land use, including noise, light and other disturbance, not sufficiently limited by buffers provided above;
B. To maintain viable populations of priority species of fish and wildlife; or
C. Protect wetlands or other critical areas from landslides, erosion or other hazards. [Ord. 849B § 4, 2009.]
17.23.052 Allowed activities in wetlands and buffers.
The following uses and activities may be allowed in wetlands or buffer areas subject to the priorities, protection, and mitigation requirements of this section:
A. Utility lines and facilities providing local delivery service, not including facilities such as electrical substations, water and sewage pumping stations, water storage tanks, petroleum products pipelines and not including transformers or other facilities containing hazardous substances, may be located in Category II, III, and IV wetlands and their buffers and/or Category I wetland buffers if the following criteria are met:
1. There is no reasonable location or route outside the wetland or wetland buffer based on analysis of system needs, available technology and alternative routes. Location within a wetland buffer shall be preferred over a location within a wetlands.
2. The utility line is located as far from the wetland edge as possible and in a manner that minimizes disturbance of soils and vegetation.
3. Clearing, grading, and excavation activities are limited to the minimum necessary to install the utility line, which may include boring, and the area is restored following utility installation.
4. Buried utility lines shall be constructed in a manner that prevents adverse impacts to subsurface drainage. This may include the use of trench plugs or other devices as needed to maintain hydrology.
5. Impacts on wetland functions are mitigated in accordance with CMC 17.23.053.
B. Public and private roadways and railroad facilities, including bridge construction and culvert installation, if the following criteria are met:
1. There is no reasonable location or route outside the wetland or wetland buffer based on analysis of system needs, available technology and alternative routes. Location within a wetland buffer shall be preferred over a location within a wetland.
2. Facilities parallel to the wetland edge are located as far from the wetland edge as possible and in a manner that minimizes disturbance of soils and vegetation.
3. Clearing, grading, and excavation activities are limited to the minimum necessary, which may include placement on elevated structures as an alternative to fill, where feasible.
4. Impacts on wetland functions are mitigated in accordance with CMC 17.23.053.
C. Access to private development sites may be permitted to cross Category II, III, or IV wetlands or their buffers, pursuant to the criteria in subsection (B) of this section; provided, that alternative access shall be pursued to the maximum extent feasible, including through the provisions of Chapter 8.24 RCW. Exceptions or deviations from technical standards for width or other dimensions, and specific construction standards to minimize impacts may be specified, including placement on elevated structures as an alternative to fill, if feasible.
D. Maintenance, repair, or operation of existing structures, facilities, or improved areas, including minor modification of existing serviceable structures within a buffer zone where modification does not adversely impact wetland functions, and subject to the provisions for nonconforming use and facilities.
E. Storm water conveyance or discharge facilities such as dispersion trenches, level spreaders, and outfalls may be permitted within a Category II, III, or IV wetland buffer on a case-by-case basis if the following are met:
1. Due to topographic or other physical constraints, there are no feasible locations for these facilities to discharge to surface water through existing systems or outside the buffer. Locations and designs that infiltrate water shall be preferred over a design that crosses the buffer.
2. The discharge is located as far from the wetland edge as possible and in a manner that minimizes disturbance of soils and vegetation and avoids long-term rill or channel erosion.
F. On-site sewage disposal system conventional drainfields may be permitted in the outer 25 percent of a Category II, III and IV wetland buffer when accessory to an approved residential structure, if the following conditions are met:
1. It is not feasible to connect to a public sanitary sewer system;
2. There is no reasonable location outside the wetland buffer based on analysis of conditions within the contiguous property owned by the applicant;
3. The facility is located as far from the wetland edge as possible and is designed and constructed in a manner that minimizes disturbance of soils and vegetation, and no trees in excess of four inches in diameter are removed or disturbed;
4. Clearing, grading, and excavation activities are limited to the minimum necessary and the area is restored following installation.
G. Outdoor recreational or educational activities which do not significantly affect the function of the wetland or regulated buffer (including wildlife management or viewing structures, outdoor scientific or interpretive facilities, trails, hunting blinds, etc.) may be permitted within a Category II, III, or IV wetlands or their buffers and within a Category I wetland buffer if the following criteria are met:
1. Trails shall not exceed four feet in width and shall be surfaced with gravel or pervious material, including boardwalks;
2. The trail or facility is located in the outer 50 percent of the buffer area unless a location closer to the wetland edge or within the wetland is required for interpretive purposes;
3. The trail or facility is constructed and maintained in manner that minimizes disturbance of the wetland or buffer. Trails or facilities within wetlands shall be placed on an elevated structure as an alternative to fill;
4. Wetland mitigation in accordance with CMC 17.23.053. [Ord. 849B § 4, 2009.]
17.23.053 Mitigation.
Activities that adversely affect wetlands and/or wetland buffers shall include mitigation sufficient to achieve no net loss of wetland function and values in accordance with CMC 17.21.087 and this section.
A. Wetland Alterations. Compensatory mitigation shall be provided for all wetland alternation and shall reestablish, create, rehabilitate, enhance, and/or preserve equivalent wetland functions and values. Compensation for wetland alterations shall occur in the following order of preference:
1. Reestablishing wetlands on upland sites that were formerly wetlands.
2. Rehabilitating wetlands for the purposes of repairing or restoring natural and/or historic functions.
3. Creating wetlands on disturbed upland sites such as those consisting primarily of nonnative, invasive plant species.
4. Enhancing significantly degraded wetlands.
5. Preserving Category I or II wetlands that are under imminent threat; provided, that preservation shall only be allowed in combination with other forms of mitigation and when the director determines that the overall mitigation package fully replaces the functions and values lost due to development.
B. Mitigation Ratios. Compensatory mitigation for wetland alterations shall be based on the wetland category and the type of mitigation activity proposed. The replacement ratio shall be determined according to the ratios provided in the table below; provided, that replacement ratio for preservation shall be determined by the director on a case-by-case basis. The created, reestablished, rehabilitated, or enhanced wetland area shall at a minimum provide a level of function equivalent to the wetland being altered and shall be located in an appropriate landscape setting.
|
Wetland Mitigation Type and Replacement Ratio* |
||||
|
Wetland Category |
Creation |
Reestablishment |
Rehabilitation |
Enhancement Only |
|
Category IV |
1.5:1 |
1.5:1 |
2:1 |
3:1 |
|
Category III |
2:1 |
2:1 |
3:1 |
4:1 |
|
Category II |
3:1 |
3:1 |
4:1 |
6:1 |
|
Category I |
6:1 |
6:1 |
8:1 |
Not allowed |
* Ratio is the replacement area:impact area.
C. Compensation for wetland buffer impacts shall occur at a minimum 1:1 ratio. Compensatory mitigation for buffer impacts shall include enhancement of degraded buffers by planting native species, removing structures and impervious surfaces within buffers, and other measures.
D. Mitigation banks shall not be subject to the replacement ratios outlined in the replacement ratio table in subsection (B) of this section, but shall be determined as part of the mitigation banking agreement and certification process.
E. Buffers. Replacement wetlands established pursuant to these mitigation provisions shall have adequate buffers to ensure their protection and sustainability. The buffer shall be based on the category in CMC 17.23.030; provided, that the director shall have the authority to approve a smaller buffer when existing site constraints (such as a road) prohibit attainment of the standard buffer.
F. Adjustment of Ratios. The director shall have the authority to adjust these ratios when a combination of mitigation approaches is proposed. In such cases, the area of altered wetland shall be replaced at a 1:1 ratio through reestablishment or creation, and the remainder of the area needed to meet the ratio can be replaced by enhancement at a 2:1 ratio. For example, impacts to one acre of a Category II wetland requiring a 3:1 ratio for creation can be compensated by creating one acre and enhancing four acres (instead of the additional two acres of creation that would otherwise be required).
G. Location. Compensatory mitigation shall be provided on site or off site in the location that will provide the greatest ecological benefit and have the greatest likelihood of success; provided, that mitigation occurs as close as possible to the impact area and within the same watershed sub-basin as the permitted alteration.
H. Protection. All mitigation areas whether on or off site shall be permanently protected and managed to prevent degradation and ensure protection of critical area functions and values into perpetuity. Permanent protection shall be achieved through deed restriction or other protective covenant in accordance with CMC 17.21.085.
I. Timing. Mitigation activities shall be timed to occur in the appropriate season based on weather and moisture conditions and shall occur as soon as possible after the permitted alteration. [Ord. 849B § 4, 2009.]
17.23.054 Mitigation plan.
In addition to meeting the requirements of CMC 17.21.087, a compensatory mitigation plan for wetland and wetland buffer impacts shall meet the following requirements:
A. The plan shall be based on applicable portions of the Washington State Department of Ecology’s Guidelines for Developing Freshwater Wetland Mitigation Plans and Proposals, 2004, or other appropriate guidance document that is consistent with best available science.
B. The plan shall contain sufficient information to demonstrate that the proposed activities are logistically feasible, constructible, ecologically sustainable, and likely to succeed. Specific information to be provided in the plan shall include:
1. The rationale for site selection;
2. General description and scaled drawings of the activities proposed including, but not limited to, clearing, grading/excavation, drainage alterations, planting, invasive plant management, installation of habitat structures, irrigation, and other site treatments associated with the development activities and proposed mitigation action(s);
3. A description of the ecological functions and values that the proposed alteration will affect and the specific ecological functions and values the proposed mitigation area(s) shall provide, together with a description of required or recommended mitigation ratios and an assessment of factors that may affect the success of the mitigation program;
4. Overall goals of the plan, including wetland function, value, and acreage;
5. Description of baseline (existing) site conditions including topography, vegetation, soils, hydrology, habitat features (i.e., snags), surrounding land use, and other pertinent information;
6. Field data confirming the presence of adequate hydrology (surface and/or groundwater) to support existing and compensatory wetland area(s);
7. Nature of mitigation activities, including area of restored, created, enhanced and preserved wetland, by wetland type;
8. Detailed grading and planting plans showing proposed post-construction topography; general hydrologic patterns; spacing and distribution of plant species, size and type of proposed planting stock, watering or irrigation plans, and other pertinent information;
9. A description of site treatment measures including invasive species removal, use of mulch and fertilizer, placement of erosion and sediment control devices, and best management practices that will be used to protect existing wetlands and desirable vegetation;
10. A demonstration that the site will have adequate buffers sufficient to protect the wetland functions into perpetuity.
C. Specific measurable performance standards that the proposed mitigation action(s) shall achieve together with a description of how the mitigation action(s) will be evaluated and monitored to determine if the performance standards are being met and identification of potential courses of action, and any corrective measures to be taken if monitoring or evaluation indicates that project performance standards are not being met. The performance standards shall be tied to and directly related to the mitigation goals and objectives.
D. Cost estimates for the installation of the mitigation program, monitoring, and potential corrective actions if project performance standards are not being met. [Ord. 849B § 4, 2009.]
17.23.055 Mitigation monitoring.
A. All compensatory mitigation projects shall be monitored for a period necessary to establish that performance standards have been met, but generally not for a period less than five years. Reports shall be submitted annually for the first three years following construction and at the completion of years five, seven, and 10 if applicable to document milestones, successes, problems, and contingency actions of the compensatory mitigation. The director shall have the authority to modify or extend the monitoring period and require additional monitoring reports for up to 10 years when any of the following conditions apply:
1. The project does not meet the performance standards identified in the mitigation plan.
2. The project does not provide adequate replacement for the functions and values of the impacted critical area.
3. The project involves establishment of forested plant communities, which require longer time for establishment.
B. Mitigation monitoring reports shall include information sufficient to document and assess the degree of mitigation success or failure as defined by the performance standards contained in the approved mitigation plan. Information to be provided in annual monitoring reports shall include the following:
1. Number and location of vegetation sample plots used to document compliance with performance standards;
2. Measurements of the percent survival of planted material, plant cover, stem density, presence of invasive species, or other attributes;
3. For sites that involve wetland creation, re-establishment or rehabilitation, hydrologic observations of soil saturation/inundation as needed to demonstrate that a site meets the wetland hydrology criterion;
4. Representative photographs of the site;
5. A written summary of overall site conditions and recommendations for maintenance actions if needed;
6. Other information that the director deems necessary to ensure the success of the site. [Ord. 849B § 4, 2009.]
17.23.056 Development standards.
A. Development standards for adjacent development shall minimize adverse effects on the wetland, and shall include:
1. Subdivision of land shall assure that each lot has sufficient building area outside wetlands and buffers. Lots in subdivisions shall be oriented whenever feasible to provide a rear yard of at least 20 feet between the buffer area and buildings.
2. Fencing shall be provided at the perimeter of residential development to limit domestic animal entry into wetlands and buffer areas.
3. Activities that generate noise shall be located as far from the wetland and buffer as feasible. Roads, driveways, parking lots and loading areas, mechanical or ventilating equipment shall be located on sides of buildings away from the wetland, or separated by noise attenuating walls.
4. Light penetration into buffer areas and wetlands shall be limited by locating areas requiring exterior lighting away from the wetland boundary, or limiting light mounting heights to a maximum of four feet. Windows that will be lit at night should be minimized on the side of buildings facing wetlands and buffers, or screened as provided for in subsection (C) of this section.
B. Management of surface runoff from adjacent land shall minimize adverse effects on wetland ecological functions and shall include:
1. Control of surface water peak flow and duration of flow should be maintained at rates typical of native forest cover.
2. Runoff should be routed to infiltration systems, to the maximum extent feasible, to provide groundwater interflow recharge to wetlands and/or water bodies and to limit overland flow and erosion.
3. Surface or piped storm water should be routed to existing conveyances or to other areas, wherever hydraulic gradients allow. Where storm water is routed to wetlands, system design shall assure that erosion and sedimentation will be avoided to the maximum extent feasible.
4. To prevent channelized flow from lawns and other landscaped areas from entering the buffer, and to prevent washing of fertilizers, herbicides and pesticides into the buffer, if slopes adjacent to the buffer exceed 15 percent, a 10-foot-wide swale to intercept runoff or other effective interception facility approved by the director shall be provided at the edge of the buffer.
5. Adopt and implement an integrated pest management system including limiting use of fertilizers, herbicides and pesticides within 25 feet of the buffer.
C. In order to maintain effective buffer conditions and functions, a vegetation management plan shall be required for all buffer areas, to include:
1. Maintaining adequate cover of native vegetation including trees and understory; if existing tree cover is less than a relative density of 20, planting shall be required consisting of seedlings at a density of 300 stems per acre or the equivalent;
2. Provide a dense screen of native evergreen trees at the perimeter of the buffer. If existing vegetation is not sufficient to prevent viewing adjacent development from within the buffer. Planting shall be required equivalent to two rows of three-foot-high stock of native evergreens at a triangular spacing of 15 feet, or three rows of gallon containers at a triangular spacing of eight feet. Fencing may be required if needed to block headlights or other sources of light or to provide an immediate effective visual screen;
3. Provide a plan for control of invasive weeds, and remove existing invasive species;
4. Provide for a monitoring and maintenance plan for a period of at least five years, except this provision may be waived for single-family residential lots. [Ord. 849B § 4, 2009.]