Chapter 16.20
WETLANDS*
Sections:
16.20.010 Designation, rating and mapping wetlands.
16.20.020 Activities allowed in wetlands.
16.20.030 Wetlands report—Additional requirements.
16.20.040 Performance standards—General requirements.
16.20.050 Performance standards—Mitigation requirements.
16.20.060 Performance standards—Wetland categories.
16.20.070 Performance standards—Specific activities and uses.
* Code reviser’s note: Numbered footnotes appear at the end of sections.
16.20.010 Designation, rating and mapping wetlands.
A. Designating Wetlands. Wetlands are those areas, designated in accordance with the “Washington State Wetland Identification and Delineation Manual,” that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation adapted for life in saturated soil conditions. All areas within the city of Prosser meeting the wetland designation criteria in the “Identification and Delineation Manual,” regardless of any formal identification, are hereby designated critical areas and are subject to the provisions of this title.
B. Wetland Ratings. Wetlands shall be rated according to the Department of Ecology wetland rating system found in the Washington State Wetland Rating for Eastern Washington (Ecology Publication No. 14-06-030), or as revised by Ecology. This document contains definitions and methods for determining ratings. (Ord. 2940 § 1, 2015; Ord. 2897 § 3, 2014; Ord. 2417 § 3 (part), 2003).
16.20.020 Activities allowed in wetlands.
The activities listed below are allowed in wetlands in addition to those activities listed in, and consistent with, the provisions established in Section 16.10.110, and do not require submission of a report, except where such activities result in the loss to the functions and values of a wetland or wetland buffer. These activities include:
A. Conservation or preservation of soil, water, vegetation, fish, shellfish, and other wildlife that does not entail changing the structure or functions of the existing wetland.
B. The harvesting of wild crops in a manner that is not injurious to natural reproduction of such crops and provided the harvesting does not require tilling of soil, planting of crops, or alteration of the wetland by changing existing topography, water conditions or water sources.
C. Boat mooring buoys. (Ord. 2417 § 3 (part), 2003).
16.20.030 Wetlands report—Additional requirements.
A. Prepared by a Qualified Professional. A qualified professional shall prepare a report for wetlands. The city shall determine whether a person is a qualified professional based on criteria established in WAC 395-195-905(4).
B. Area Addressed in Report. The following areas shall be addressed in a report for wetlands:
1. The project area of the proposed activity;
2. All wetlands and recommended buffers within two hundred feet of the project area1; and
3. All shoreline areas, water features, floodplains, and other critical areas, and related buffers within two hundred feet of the project area.
C. Wetland Analysis. In addition to the minimum required contents of reports in Sections 16.10.140 and 16.10.150, a report for wetlands shall contain an analysis of the wetlands, including the following site and proposal-related information at a minimum:
1. A written assessment and accompanying maps of the wetlands and buffers within two hundred feet of the project area, including the following information at a minimum:
a. Wetland delineation and required buffers;
b. Existing wetland acreage;
c. Wetland category; vegetative, faunal, and hydrologic characteristics;
d. Soil and substrate conditions.
2. A discussion of measures, including avoidance, minimization and mitigation, proposed to preserve existing wetlands and restore any wetlands that were degraded prior to the current proposed land use activity.
3. Proposed mitigation, if needed, including a written assessment and accompanying maps of the mitigation area, including the following information at a minimum:
a. Existing wetland acreage and proposed impact area;
b. Vegetative, faunal, and hydrologic conditions;
c. Relationship within watershed and to existing waterbodies;
d. Soil and substrate conditions, topographic elevations;
e. Existing and proposed adjacent site conditions;
f. Required wetland buffers; and
g. Property ownership.
4. A discussion of ongoing management practices that will protect wetlands after the project site has been developed, including proposed monitoring and maintenance programs.
D. Additional Information May Be Required. When appropriate, the city may also require the report to include an evaluation by the Department of Ecology or an independent qualified expert regarding the applicant’s analysis and the effectiveness of any proposed mitigating measures or programs, and to include any recommendations as appropriate.
1 Critical area reports should consider wetlands and other critical areas within two hundred feet due to the maximum potential buffer recommended for wetlands.
(Ord. 2417 § 3 (part), 2003).
16.20.040 Performance standards—General requirements.
A. Activities may only be permitted in a wetland or wetland buffer if the applicant can show that the proposed activity will not degrade the functions and values of the wetland and other critical areas.
B. Activities and uses shall be prohibited from wetlands and wetland buffers, except as provided for in this title.
C. Wetland Buffers.
1. Standard Buffer Widths. The standard buffer widths presume the existence of a relatively intact native vegetation community in the buffer zone adequate to protect the wetland functions and values at the time of the proposed activity. If the vegetation is inadequate then the buffer width shall be increased or the buffer should be planted to maintain the standard width. Required standard wetland buffers, based on wetland category and land use intensity, are as follows:
|
WETLAND TYPE |
BUFFER |
|---|---|
|
Category I |
|
|
Category I: 8—9 habitat points |
150 feet |
|
Category I: 6—7 habitat points |
120 feet |
|
Category I: 5 habitat points |
90 feet |
|
Category I: < 3—4 habitat points |
75 feet |
|
Category I: Bogs and wetlands of high conservation value |
190 feet |
|
Category I: Alkali |
150 feet |
|
Category II |
|
|
Category II: 30—36 habitat points |
150 feet |
|
Category II: 26—29 habitat points |
120 feet |
|
Category II: 21—25 habitat points |
90 feet |
|
Category II: < 21 habitat points |
150 feet |
|
Category III |
|
|
Category III: 26—29 habitat points |
200 feet |
|
Category III: 21—25 habitat points |
120 feet |
|
Category III: < 21 habitat points |
90 feet |
|
Category IV (all) |
60 feet |
The following measures shall be incorporated into adjacent development:
|
Type of Potential Disturbance |
Required Measures 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 or mining, establish an additional 10-foot 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. |
|
Storm water runoff |
Retrofit storm water detention and treatment for roads and existing adjacent development. Prevent channelized flow from lawns that directly enters the buffer. Use low intensity development techniques (per Eastern Washington Low Impact Development Guidance Manual, Washington Department of Ecology Publication No. 13-10-036, June 2013 and as may be hereafter amended, supplemented, or replaced). |
|
Change in patterns or water flow |
Infiltrate or treat, detain, and disperse into buffer new runoff from impervious surfaces and new lawns. |
|
Pets and human disturbance |
Use privacy fencing or plant dense vegetation to delineate buffer edge and to discourage disturbance using vegetation appropriate for the ecoregion. Place wetland and its buffer in a separate tract or protect with a conservation easement. |
|
Dust |
Use best management practices to control dust. |
|
Disruption of corridors or connections |
Maintain connections to off-site areas that are undisturbed. Restore corridors or connections to off-site habitats by replanting. |
2. Measurement of Wetland Buffers. All buffers shall be measured from the wetland boundary as surveyed in the field. The width of the wetland buffer shall be determined according to the wetland category and the proposed land use. The buffer for a wetland created, restored, or enhanced as compensation for wetland alterations shall be the same as the buffer required for the category of the created, restored, or enhanced wetland.
3. Increased Wetland Buffer Widths. The city shall require increased buffer widths in accordance with the recommendations of a qualified professional biologist 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. This determination shall be based on one or more of the following criteria:
a. A larger buffer is needed to protect other critical areas;
b. The buffer or adjacent uplands has a slope greater than fifteen percent or is susceptible to erosion and standard erosion-control measures will not prevent adverse impacts to the wetland; or
c. The buffer area has minimal vegetative cover. In lieu of increasing the buffer width where existing buffer vegetation is inadequate to protect the wetland functions and values, implementation of a buffer planting plan may substitute. Where a buffer planting plan is proposed, it shall include provisions for monitoring and maintenance to ensure success.
d. At no time shall wetland buffers be increased to a width two times that of the standard required buffer.
4. Reduction of Wetland Buffer Widths.
a. The city may allow the standard wetland buffer width to be reduced in accordance with the report and the best available science on a case-by-case basis when it is determined that a smaller area is adequate to protect the wetland functions and values based on site-specific characteristics.
b. This determination shall be supported by documentation showing that a reduced buffer is adequate based on all of the following criteria:
i. Requiring the standard buffer poses an extraordinary hardship on the landowner;
ii. The existing buffer area is well vegetated with native species and has less than ten percent slopes; and
iii. No direct or indirect short-term or long-term adverse impacts to wetlands will result from the proposed activity.
c. The city may require long-term monitoring of the buffer and wetland. Subsequent corrective actions may be required if adverse impacts to wetlands are discovered during the monitoring period.
d. In no case shall the standard buffer width be reduced by more than fifty percent, or the buffer width be less than fifty feet, whichever is greater, unless the applicant demonstrates an acceptable reasonable use as described in Section 16.10.120.
e. Isolated Category 3 and 4 wetlands less than one thousand square feet may be exempt from the buffer provisions contained in this chapter and the normal mitigation sequencing process. They may be displaced if impacts are fully mitigated. Such wetlands:
i. Are not associated with riparian areas or buffers.
ii. Are not part of a wetland mosaic.
iii. Do not contain habitat identified as essential for local populations of priority species identified by the Washington Department of Fish and Wildlife.
1 “Wetland Buffers: Use and Effectiveness,” Department of Ecology, 1992, Publication No. 92-10.
(Ord. 2940 § 2, 2015; Ord. 2897 § 4, 2014; Ord. 2417 § 3 (part), 2003).
16.20.050 Performance standards—Mitigation requirements.
A. Mitigation Shall Achieve Equivalent or Greater Biological Functions. Mitigation for alterations to wetlands shall achieve equivalent or greater biologic functions and shall be consistent with the Department of Ecology “Guidelines for Developing Freshwater Wetlands Mitigation Plans and Proposals,” 1994, as revised.
B. Mitigation Shall Result in No Net Loss. Wetland mitigation actions shall not result in a net loss of wetland area except when the following criteria are met:
1. 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 function assessment using Department of Ecology “Methods for Assessing Wetland Functions, Volume 2, Depressional Wetlands in the Columbia Basin of Eastern Washington, Parts 1 and 2,” December 2000; or
2. The lost wetland area provides minimal functions as determined by a site-specific function assessment and other protected or enhanced habitats provide greater benefits to the functioning of the watershed, such as riparian habitat protection and enhancement.
C. Mitigation for Lost Functions and Values. 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:
1. The lost 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 protocol; or
2. Out-of-kind replacement will best meet formally identified regional goals, such as replacement of historically diminished wetland types.
D. Preference of Mitigation Actions. Mitigation actions that require compensation by replacing, enhancing, or substitution shall occur in the following order of preference:
1. Restoring wetlands on upland sites that were formerly wetlands.
2. Creating wetlands on disturbed upland sites such as those with vegetative cover consisting primarily of exotic introduced species.
3. Enhancing significantly degraded wetlands.
4. Preserving high-quality wetlands that are under imminent threat.
E. Type and Location of Mitigation. Mitigation actions shall be conducted within the same subdrainage basin and on the site as the alteration except when the following apply:
1. There are no reasonable on-site opportunities or on-site opportunities do not have a high likelihood of success due to development pressures, adjacent land uses, or on-site buffers or connectivity is inadequate;
2. Off-site mitigation has a greater likelihood of providing equal or improved wetland functions than the impacted wetland; and
3. Off-site locations shall be in the same subdrainage basin and the same water resource inventory area (WRIA) unless:
a. The impact is located near the boundary of a WRIA;
b. Established regional or watershed goals for water quality, flood or conveyance, habitat or other wetland functions have been established and strongly justify location of mitigation at another site; or
c. Credits from a state-certified wetland mitigation bank are used as mitigation and the use of credits is consistent with the terms of the bank’s certification.
F. Mitigation Timing. Where feasible, mitigation projects shall be completed prior to activities that will disturb wetlands. In all other cases, mitigation shall be completed immediately following disturbance and prior to use or occupancy of the activity or development. Construction of mitigation projects shall be timed to reduce impacts to existing wildlife and flora.
The city may authorize a one-time temporary delay, up to one hundred twenty days, in completing minor construction and landscaping when environmental conditions could produce a high probability of failure or significant construction difficulties. The delay shall not create or perpetuate hazardous conditions or environmental damage or degradation, and the delay shall not be injurious to the health, safety and general welfare of the public. The request for the temporary delay must include a written justification that documents the environmental constraints that preclude implementation of the mitigation plan. The justification must be verified and approved by the city, and include a financial guarantee in the form of a cash bond or similar mechanism.
G. Mitigation Ratios.
1. Acreage Replacement Ratios. The following ratios shall apply to creation or restoration that is in-kind, on site, the same category, timed prior to or concurrent with alteration, and has a high probability of success. These ratios do not apply to remedial actions resulting from unauthorized alterations; greater ratios shall apply in those cases. 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 should be consistent with the requirements of the bank’s certification. The first number specifies the acreage of replacement wetlands and the second specifies the acreage of wetlands altered.
|
Category and Type of Wetland |
Creation or Reestablishment |
Rehabilitation |
Enhancement |
|---|---|---|---|
|
Category I: Bog, wetland of high conservation value |
Not considered possible |
Case by case |
Case by case |
|
Category I: Mature 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 |
Note: Impacts to buffers shall be mitigated at a 1:1 ratio. Compensatory buffer mitigation shall replace those buffer functions lost from development.
2. Increased Replacement Ratio. The city may increase the ratios under the following circumstances:
a. Uncertainty exists as to the probable success of the proposed restoration or creation; or
b. A significant period of time will elapse between impact and replication of wetland functions; or
c. Proposed mitigation will result in a lower category wetland or reduced functions relative to the wetland being impacted; or
d. The impact was an unauthorized impact.
3. Decreased Replacement Ratio. The city may decrease these ratios under the following circumstances:
a. Documentation by a qualified wetlands specialist demonstrates that the proposed mitigation actions have a very high likelihood of success;
b. Documentation by a qualified wetlands specialist demonstrates that the proposed mitigation actions will provide functions and values that are significantly greater than the wetland being impacted; or
c. The proposed mitigation actions are conducted in advance of the impact and have been shown to be successful.
4. Minimum Replacement Ratio. In all cases, a minimum acreage replacement ratio of one-to-one shall be required.
H. 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 Chapter 173-700 WAC;
b. The city determines that the wetland mitigation bank provides appropriate compensation for the authorized impacts; and
c. 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 water resource inventory area (WRIA) for specific wetland functions.
I. Wetlands Enhancement as Mitigation.
1. Impacts to wetlands may be mitigated by enhancement of existing significantly degraded wetlands. Applicants proposing to enhance wetlands must produce a report that identifies how enhancement will increase the functions of the degraded wetland and how this increase will adequately mitigate for the loss of wetland area and function at the impact site. An enhancement proposal must also show whether existing wetland functions will be reduced by the enhancement actions.
2. At a minimum, enhancement acreage shall be double the acreage required for creation or restoration under subsection G of this section. The ratios shall be greater than double the required acreage where the enhancement proposal would result in minimal gain in the performance of wetland functions and/or result in the reduction of other wetland functions currently being provided in the wetland.
J. Wetland Preservation as Mitigation. Impacts to wetlands may be mitigated by preservation of wetland areas when used in combination with other forms of mitigation such as creation, restoration, or enhancement at the preservation site or at a separate location. Preservation may also be used by itself, but more restrictions, as outlined below, will apply.
1. Preservation in Combination with Other Forms of Compensation. Preservation as mitigation is acceptable when done in combination with restoration, creation, or enhancement; providing, that a minimum of one-to-one acreage replacement is provided by restoration or creation and the criteria below are met.
a. The impact area is small and/or impacts are to a Category III or IV wetland;
b. Preservation of a high-quality system occurs in the same water resource inventory area (WRIA) or watershed basin as the wetland impact; and
c. Preservation sites include buffer areas adequate to protect the habitat and its functions from encroachment and degradation.
2. Preservation as the Sole Means of Mitigation for Wetland Impacts. Preservation of at-risk, high-quality habitat may be considered as the sole means of mitigation for wetland impacts when all of the following criteria are met:
a. Preservation is used as a form of mitigation only after the standard sequencing of mitigation (avoid, minimize, and then compensate) has been applied;
b. Creation, restoration, and enhancement opportunities have also been considered, and preservation is the best mitigation option;
c. The impact area is small and/or impacts are to a Category III or IV wetland;
d. Preservation of a high-quality system occurs in the same water resource inventory area (WRIA) or a watershed where the wetland impact occurs;
e. Preservation sites include buffer areas adequate to protect the habitat and its functions from encroachment and degradation;
f. The preservation site is determined to be under imminent threat; specifically, sites with the potential to experience a high rate of undesirable ecological change due to on-site or off-site activities (“potential” includes permitted, planned, or perceived actions); and
g. The area proposed for preservation is of high quality and critical for the health of the watershed or basin. Some of the following features may be indicative of high- quality sites:
i. Category I or II wetland rating;
ii. Rare wetland type (for example, bogs, estuaries);
iii. Habitat for threatened or endangered species;
iv. Wetland type that is rare in the area;
v. Provides biological and/or hydrological connectivity;
vi. High regional or watershed importance (for example, listed as priority site in watershed plan); and
vii. Large size with high species diversity (plants and/or animals) and/or high abundance.
3. Mitigation Ratios for Preservation as the Sole Means of Mitigation. Mitigation ratios for preservation as the sole means of mitigation shall range from seven-to-one to twenty-to-one, as determined by the city, depending on the quality of wetlands being mitigated and the quality of the wetlands being preserved.
K. Mitigation Maintenance and Monitoring. Mitigation areas will be maintained and monitored for a minimum of five years after the mitigation has been completed. Annual maintenance and monitoring reports will be submitted to the city and shall include:
1. Descriptive data for vegetation, soils, and hydrology;
2. Itemized list of dead, dying, and replaced vegetation;
3. Quantitative assessment of invasive species;
4. Descriptive photographs;
5. Statement of overall success of mitigation;
6. Schedule of activities for the next year of maintenance and monitoring.
The city may extend maintenance and monitoring for mitigation projects that fail to achieve performance standards outlined in the mitigation plan. An example of a performance failure is less than eighty percent survival of native vegetation or more than ten percent of the mitigation area cover with nonnative invasive species. (Ord. 2940 § 3, 2015: Ord. 2897 § 5, 2014: Ord. 2417 § 3 (part), 2003).
16.20.060 Performance standards—Wetland categories.
A. Category I Wetlands. Activities and uses shall be prohibited from Category I wetlands, except as provided for in the public agency and utility exception, reasonable use exception, and variance sections of this title.
B. Category II and III Wetlands. With respect to activities proposed in Category II and III wetlands, the following standards shall apply:
1. Water-dependent activities may be allowed where there are no practicable alternatives that would not have a less adverse impact on the wetland and other critical areas.
2. Where non-water-dependent activities are proposed, it shall be presumed that alternative locations are available, and activities and uses shall be prohibited, unless the applicant demonstrates that:
a. The basic project purpose cannot reasonably be accomplished and successfully avoid, or result in less adverse impact on, a regulated wetland on another site or sites in the general region; and
b. All alternative designs of the project as proposed, that would avoid, or result in less of an adverse impact on, a regulated wetland or its buffer, such as a reduction in the size, scope, configuration, or density of the project, are not feasible.
C. Category IV Wetlands. Activities and uses that result in unavoidable and necessary impacts may be permitted in Category IV wetlands and associated buffers in accordance with the report and mitigation plan, and only if the proposed activity is the only reasonable alternative that will accomplish the applicant’s objectives. (Ord. 2417 § 3 (part), 2003).
16.20.070 Performance standards—Specific activities and uses.
The following activities may be permitted within a wetland buffer in accordance with the review procedures of this title, provided they are not prohibited by any other applicable law and they are conducted in a manner so as to minimize impacts to the buffer and adjacent wetland:
A. Conservation and Restoration Activities. Conservation or restoration activities aimed at protecting the soil, water, vegetation, or wildlife;
B. Passive Recreation. Passive recreation facilities designed and in accordance with the report, including:
1. Walkways and trails; provided, that those pathways that are generally parallel to the perimeter of the wetland shall be located in the outer twenty-five percent of the buffer area;
2. Wildlife viewing structures; and
3. Fishing access areas.
C. Storm Water Management Facilities. Storm water management facilities are not allowed in buffers of Category I or II wetlands. Storm water management facilities, limited to storm water dispersion outfalls and bioswales, may be allowed within the outer twenty-five percent of the buffer of Category III or IV wetlands only; provided, that:
1. No other location is feasible; and
2. The location of such facilities will not degrade the functions or values of the wetland.
D. Subdivisions. The subdivision and short subdivision of land in wetlands and associated buffers is subject to the following:
1. Land that is located wholly within a wetland or its buffer may not be subdivided;
2. Land that is located partially within a wetland or its buffer may be divided; provided, that an accessible and contiguous portion of each new lot is:
a. Located outside of the wetland and its buffer; and
b. Meets the minimum lot size requirements of the city zoning code (Titles 18 and 19);
3. Access roads and utilities serving the proposed subdivision may be permitted within the wetland and associated buffers only if the city determines that no other feasible alternative exists in and when consistent with this title. (Ord. 2417 § 3 (part), 2003).