The purpose of this chapter is to provide protection of functions and values of critical areas as classified and designated in the town of Twisp comprehensive plan in a manner that also allows reasonable use of private property as required by RCW 36.70A.060 in the following manner:
(1) 
Implementing the town of Twisp comprehensive plan;
(2) 
Protecting critical areas, in accordance with the Growth Management Act and through the application of best available science, as determined according to WAC 365-195-900 through 365-195-925, as amended, and in consultation with state and federal agencies and other qualified professionals;
(3) 
Protecting the general public, resources and facilities from injury, loss of life, property damage or financial loss due to flooding, erosion, landslides, or steep slopes failure;
(4) 
Protecting unique, fragile and valuable elements of the environment, including ground and surface waters, wetlands, and fish and wildlife and their habitats;
(5) 
Meeting the requirements of the National Flood Insurance Program and maintaining the town as an eligible community for federal flood insurance benefits;
(6) 
Preventing cumulative adverse environmental impacts to water quality and quantity, groundwater, wetlands, and fish and wildlife habitat;
(7) 
Providing appropriate guidance and protection measures for addressing the needs and concerns associated with critical areas that help define the quality of life in the community; and
(8) 
Providing flexibility and attention to site-specific characteristics, so as to ensure reasonable use of property.
(Ord. 610 § 2 (Exh. A § 1), 2009; Ord. 757 § 1, 2020)
The provisions of this chapter shall apply to all development activities in designated critical areas outside of shoreline jurisdiction as regulated under the Twisp shoreline master program within the town's incorporated limits.
(1) 
All land uses and/or development permit applications on all lots or parcels within the town that lie within critical areas as designated in the Twisp comprehensive plan shall comply with the provisions of this chapter. No action shall be taken by any person that results in any alteration of any critical area except as consistent with the purposes, objectives and intent of this chapter.
(2) 
Where two or more types of critical areas overlap, requirements for development shall be consistent with the standards for each critical area.
(3) 
Where it is determined that a designated critical area is located within the shoreline jurisdiction, the provisions of the shoreline master program will be used to provide protection to that particular critical area(s). However, any standards found in this chapter may also be applied to a proposal as optional and/or supplemental items to the provisions of the shoreline master program to ensure adequate protection. For designated critical areas outside of the shoreline jurisdiction the provisions of this chapter shall apply.
(4) 
These critical areas regulations shall apply concurrently with review conducted under the State Environmental Policy Act (SEPA), as locally adopted. Any conditions required pursuant to this chapter shall be included in the SEPA review and threshold determination.
(Ord. 610 § 2 (Exh. A § 1), 2009; Ord. 757 § 2, 2020)
The activities listed below are exempt from the provisions of this chapter. The final determination of whether an activity is exempt is an administrative function of the town. Exempt activities shall be conducted using all reasonable methods to avoid impacts to critical areas. Exemption from the regulations in this chapter shall not be considered permission to degrade a critical area or ignore risks from natural hazards. Incidental damage to, or alteration of, a critical area that is not a necessary outcome of the exempted activity shall be restored and rehabilitated at the responsible party's expense.
(1) 
Emergency construction necessary to protect life or property from immediate damage by the elements. An emergency is an unanticipated event or occurrence which poses an imminent threat to public health, safety, or the environment, and which requires immediate action within a time too short to allow full compliance. Once the threat to the public health, safety, or the environment has dissipated, the construction undertaken as a result of the previous emergency shall then be subject to and brought into full compliance with this title and any subsequent amendments; repairs and restorations resulting from emergency construction must commence no later than three years following the time the threat has dissipated and may be subject to mitigation provisions of this chapter;
(2) 
Normal maintenance or repair of existing legal buildings, structures, roads or development, including damage by accident, fire or natural elements. Normal repair of buildings and structures involves restoring to a state comparable to the original condition, including the replacement of walls, fixtures and plumbing; provided, that the value of work and materials in any 12-month period does not exceed 25 percent of the value of the structure prior to such work as determined by using the fair market value for such structure as established by an appraisal or realtor's market analysis provided by the applicant if requested by the town and the most recent ICBO construction tables, the repair does not expand the number of dwelling units in a residential building, the building or structure is not physically expanded, and, in the case of damaged buildings and structures, a complete application for repair is accepted by the town within six months of the event and repair is completed within the terms of the permit;
(3) 
Existing agricultural activities normal or necessary to general farming conducted according to industry-recognized best management practices including the raising of crops or the grazing of livestock;
(4) 
Site investigative work necessary for land use application submittals such as surveys, soil logs, percolation tests and other related activities. In every case, critical area impacts should be minimized and disturbed areas shall be immediately restored; and
(5) 
Passive recreational activities, including, but not limited to: fishing, bird watching, hiking, hunting, boating, horseback riding, skiing, swimming, canoeing, and bicycling provided the activity does not alter the critical area or its buffer by changing existing topography, water conditions, water sources, or critical wildlife habitat.
(Ord. 610 § 2 (Exh. A § 1), 2009; Ord. 757 § 3, 2020)
(1) 
If application of this title would prohibit a development proposal by a public agency or public utility, the agency or utility may apply for an exception pursuant to this section. To qualify for an exception the agency or utility must demonstrate the following criteria:
(a) 
Criteria for Exception.
(i) 
That there is no other practical alternative to the proposed development which has less impact on critical areas;
(ii) 
That the application of this title would unreasonably restrict the ability to provide necessary utility services to the public;
(iii) 
That the proposed use does not pose a threat to the public health, safety or welfare;
(iv) 
That the proposal protects critical areas functions and values to the extent possible and provides for mitigation in accord with the provisions of this title; and
(v) 
The proposal is consistent with other applicable regulations and standards.
(2) 
A request for exception shall be submitted to the town with the application materials for the particular development proposal. The request shall contain explanation as to how the criteria are satisfied. The administrator may require additional information or studies to supplement the exception request.
(Ord. 610 § 2 (Exh. A § 1), 2009)
(1) 
The town may modify the requirements of this chapter in specific cases when necessary to allow reasonable use of an applicant's property.
(2) 
A request for a reasonable use exception shall be submitted to the town with the application materials for the particular development proposal. The request shall explain how the reasonable use exception criteria are satisfied. The town may require additional information or studies to supplement the reasonable use exception request.
To qualify for an exception the applicant must demonstrate all of the following:
(a) 
That no other reasonable use can be made of the property that will have a lesser adverse impact on the critical area and adjoining and neighboring lands;
(b) 
That the proposed use does not pose a threat to the public health, safety or welfare;
(c) 
Any alteration is the minimum necessary to allow reasonable use of the property; and
(d) 
The inability of the proponent to derive reasonable use of the property is not the result of actions by the applicant after August 11, 2009.
(3) 
A reasonable use exception shall be processed according to the provisions of TMC Title 14, Development Permits, governing a Type II permit process.
(Ord. 610 § 2 (Exh. A § 1), 2009; Ord. 757 § 4, 2020)
The town shall maintain reference maps and materials that provide information on the general locations of critical areas. Since boundaries are generalized, the application of this chapter and the actual type, extent and boundaries of critical areas shall be determined and governed by the classification and designation process established for each critical area in the Twisp comprehensive plan. In the event of any conflict between the critical area location or designation shown on the town's maps and the criteria and standards established in the Twisp comprehensive plan, or the site-specific conditions, the criteria, standards and/or site-specific conditions shall prevail. The administrator of this title shall have the authority to reference new and updated scientific publications and reports as they become available. Reference maps and inventories shall include, but are not limited to, the following:
(1) 
Comprehensive Plan Map CA V – Wetlands Map, based upon U.S. Fish and Wildlife Service National Wetlands Inventory;
(2) 
Comprehensive Plan Map CA IV – Fish and Wildlife Habitat Area Maps, based upon Washington Department of Fish and Wildlife priority habitats and species data;
(3) 
Soils data and maps, based upon Natural Resource Conservation Service Web Soil Survey;
(4) 
Comprehensive Plan Map CA VI – Steep Slopes Map, based on Natural Resource Conservation Service Web Soil Survey;
(5) 
Comprehensive Plan Map CA VIII – Erosion Hazard Areas, based on Natural Resource Conservation Service Web Soil Survey;
(6) 
Comprehensive Plan Map CA VII – Building Limitations Areas, based on Natural Resource Conservation Service Web Soil Survey;
(7) 
Comprehensive Plan Map CA IX – Geologically Hazardous Areas, based on Natural Resource Conservation Service Web Soil Survey;
(8) 
Comprehensive Plan Map CA I – Wellhead Protection Areas, based on town of Twisp comprehensive water system plan;
(9) 
Comprehensive Plan Map CA III – Flood Hazard Map, based on Flood Insurance Rate Map Community Panel No. 530117 0875C, revised December 20, 2000; revised;
(10) 
Comprehensive Plan Map CA IV – Fish and Wildlife Habitat, based on WDFW Priority Habitat and Species data; revised;
(11) 
Town of Twisp comprehensive plan;
(12) 
Town of Twisp shoreline master program and accompanying maps;
(13) 
Washington State Wetlands Identification and Delineation Manual (DOE, March 1997), as revised;
(14) 
Washington State Wetlands Rating System for Eastern Washington (Ecology Publication No. 04-06-015, or as revised and approved by Ecology);
(15) 
Federal Wetlands Delineation Manual (1987);
(16) 
The Flood Insurance Rate Study for the town of Twisp; and
(17) 
Approved special reports previously completed for a subject property.
Each of the above-referenced maps and inventories shall include the reference maps and inventories listed, as well as revised, amended or updated versions.
(Ord. 610 § 2 (Exh. A § 1), 2009; Ord. 757 § 5, 2020)
Development permit applications shall provide appropriate information on forms provided by the town, including without limitation the information described in this section as well as specific requirements of each critical area. Additional reports or information to identify potential impacts and mitigation measures to critical areas may be required if deemed necessary. All land use applications and building permits shall require that applicants disclose activities within 100 feet of a known or suspected critical area. The provisions of this chapter shall be applied to any such proposals.
(1) 
Application and SEPA Checklist. For all proposals occurring within 100 feet of a known or suspected critical area and not exempt under this chapter, the proponent shall submit all relevant land use/development applications, together with a SEPA checklist. The administrator may waive the requirement for a SEPA checklist if the proposal is categorically exempt under SEPA regulations and is unlikely to yield information useful in the review process.
(a) 
Minor Development. Projects processed by the town according to the provisions governing Type I or Type II permits within a designated critical area or its buffer shall disclose, at a minimum, the following information on a site plan drawn to scale:
(i) 
The location and boundaries of the critical areas;
(ii) 
The location and dimensions of all existing and proposed buildings, roads and other improvements, and their physical relationship to the critical area and associated buffers; and
(iii) 
The location and type of any proposed buffers, including the identification of any other protective measures.
(b) 
Major Development. Projects processed by the town according to the provisions governing Type III or Type IV permits within a designated critical area or its buffer shall provide the following information, in addition to the information described in subsection (1)(a) of this section:
(i) 
Critical area boundary survey and ranking evaluation or designation as defined in the Twisp comprehensive plan;
(ii) 
Critical area management and mitigation plan as defined within this chapter;
(iii) 
A drainage and erosion control plan as defined within this chapter; and
(iv) 
A grading and excavation plan as defined within this chapter.
(2) 
The review process shall proceed as follows:
(a) 
Preapplication Meeting/Site Visit. Upon receiving a land use or development proposal, the administrator shall schedule a preapplication meeting and/or site visit with the proponent for purposes of a preliminary determination whether the proposal is likely to result in impacts to the functions and values of critical areas or pose health and safety hazards. At this meeting, the administrator shall discuss the requirements of this chapter and other applicable regulations; provide critical areas maps and other available reference materials; outline the review and permitting processes; and work with the proponent to identify any potential concerns with regards to critical areas.
(b) 
Determination of Need for Critical Areas Report. Based upon the preapplication meeting, application materials, and the SEPA checklist (unless waived), the administrator shall determine if there is cause to require a critical areas report. In addition, the administrator may use critical areas maps and reference materials, information and scientific opinions from appropriate agencies, or any reasonable evidence regarding the existence of critical area(s) on or adjacent to the site of the proposed activity.
(c) 
Documentation and Notification. The administrator shall document the preapplication meeting and/or site visit, application and SEPA threshold determination, and any other steps or findings that inform the determination whether a critical areas report shall be required. The applicant shall receive notice of the determination and any findings which support it.
(Ord. 610 § 2 (Exh. A § 1), 2009; Ord. 757 § 6, 2020)
The following standards shall apply to the activity identified below, in addition to the general standards for each critical area:
(1) 
Boat Launch Facilities. Construction of a boat launch facility may be authorized subject to the following standards:
(a) 
The facility shall be in compliance with the requirements of the Twisp shoreline master program;
(b) 
The facility and landward access shall not significantly alter the existing critical area or buffer vegetation; and
(c) 
For all land divisions, facilities shall be designed, designated and constructed for joint and/or community use.
(2) 
Road Repair and Construction. When no other practical alternative exists, public or private road repair, maintenance, expansion or construction may be authorized within a critical area buffer, subject to the following minimum standards:
(a) 
The road shall serve multiple properties;
(b) 
No unmitigated impacts to the designated critical area or buffer area shall result from the repair, maintenance, expansion or construction of any public or private road;
(c) 
The road shall provide for the location of public utilities, pedestrian or bicycle easements, viewing points, etc.; and
(d) 
Road repair and construction shall be the minimum necessary to provide safe traveling surfaces.
(3) 
Major Developments. All major developments processed by the town according to the provisions governing Type III or Type IV permits authorized within a critical area or critical area buffer shall comply with the following minimum standards:
(a) 
Inundated and/or submerged lands shall not be used in calculating minimum lot area for proposed lots;
(b) 
Only 50 percent of the total wetlands on the property, other than inundated and/or submerged lands, shall be used in calculating minimum lot area for proposed lots. All wetland buffers may be included in the calculation of minimum lot area for proposed lots;
(c) 
All plats shall disclose the presence on each residential lot of one building site, including access, that is suitable for development and which is not within the designated critical area or its associated buffer;
(d) 
All designated critical areas and their proposed buffers shall be clearly identified on all final plats, maps, documents, etc.;
(e) 
Designated critical areas and their associated critical area buffers, when needed for long-term protection, shall be designated and disclosed on the final plats, maps, documents, etc., as open space tracts, nonbuildable lots and buffer areas or common areas, with ownership and control transferred to a homeowner's association. Designated critical areas and associated critical area buffers may alternatively be designated and disclosed on the final plats, maps, documents, etc., as an easement or covenant encumbering the property.
(4) 
Surface Water Management. When no other practical alternative exists, surface water management activities may be authorized within a critical area, subject to the following minimum standards:
(a) 
Critical areas may be used for retention/detention facilities, subject to all of the following criteria:
(i) 
The functions and water quality of the critical area or buffer shall not be adversely impacted;
(ii) 
The rate of flow into or the hydro­period of a wetland shall not increase above natural flow rates; and
(iii) 
All surface water discharged from impervious surfaces shall be treated prior to entering a critical area or buffer.
(b) 
New surface water discharges to critical areas from detention facilities, presettlement ponds, or other surface water management structures may be authorized, subject to all of the following criteria:
(i) 
The discharge does not increase the rate of flow into or the hydroperiod of a wetland above the natural rates;
(ii) 
All surface water discharged from impervious surfaces shall be treated prior to entering a critical area or buffer; and
(iii) 
The water quality of the critical area is not decreased.
(5) 
Stream Crossings. Expansion or construction of stream crossings may be authorized within a designated critical area, subject to the following minimum standards:
(a) 
Bridges are required for streams that support salmonids, unless culvert design and construction ensure proper passage opportunities;
(b) 
All crossings using culverts shall use superspan or oversized culverts;
(c) 
Crossings shall not occur in salmonid spawning areas unless no other feasible crossing site exists;
(d) 
Bridge piers or abutments shall not be placed in either the floodway or between the ordinary high-water marks unless no other feasible alternative placement exists;
(e) 
Crossings shall not diminish flood-carrying capacity; and
(f) 
Crossings shall serve multiple properties whenever possible.
(6) 
Trails and Trail-Related Facilities. Construction of public and private trails and trail-related facilities, such as picnic tables, benches, interpretive centers and signs, viewing platforms and campsites may be authorized within a designated critical area buffer, subject to the following minimum standards:
(a) 
Trail facilities shall, to the extent feasible, be placed on existing road grades, utility corridors, or any other previously disturbed areas;
(b) 
Trail facilities shall minimize the removal of trees, shrubs, snags and important forest and wildlife habitat;
(c) 
Viewing platforms, interpretive centers, campsites, picnic areas, benches and their associated access shall be designed and located to minimize disturbance of wildlife habitat and/or critical characteristics of the designated critical area;
(d) 
Trail facilities shall be located at least a distance equal to the width of the trail corridor away from the wetland edge, as established by the approved critical area boundary survey; and
(e) 
All facilities shall be constructed with materials complementary to the surrounding environment.
(7) 
Utilities. When no other practical alternative exists, construction of utilities within a critical area buffer may be authorized, subject to the following minimum standards:
(a) 
Utility corridors shall be jointly used;
(b) 
Corridor construction and maintenance shall protect the designated critical area buffer, and shall be aligned to avoid cutting trees greater than six inches in diameter at breast height when possible;
(c) 
No pesticides, herbicides or other hazardous or toxic substances shall be used;
(d) 
Utility corridors, including maintenance roads authorized by the town, shall be located at least a distance equal to the width of the utility corridor away from the critical area edge;
(e) 
Corridors shall be revegetated to preconstruction densities with appropriate native vegetation immediately upon completion of construction, or as soon thereafter as possible given seasonal growing constraints. The utility purveyor shall provide an assurance device or surety in accordance with this code that ensures such vegetation survives;
(f) 
Any additional corridor access for maintenance shall be provided as much as possible at specific points rather than by parallel roads. If parallel roads are necessary, they shall be no greater than 15 feet in width, and shall be contiguous to the location of the utility corridor on the side opposite the wetland; and
(g) 
Construction of sewer lines within a designated critical area or critical area buffer which are necessary to meet state and/or local health code requirements shall not adversely impact the function and quality of the designated critical area or buffer.
(Ord. 757 § 7, 2020)
If the administrator determines that the site of a proposed development potentially includes, or is adjacent to, critical area(s), a critical areas report and mitigation plan may be required. The purpose of the critical areas report is to inform the administrator of the degree of impact that can be expected from the development and to establish the need for mitigation. The applicant shall avoid all impacts that degrade the functions and values of critical areas. If alteration is unavoidable, all adverse impacts to critical areas and buffers resulting from the proposal shall be mitigated in accordance with an approved critical areas report and SEPA documents. When mitigation is required, as detailed in TMC § 18.60.090, the applicant shall submit for approval a mitigation plan as part of the critical areas report. The expense of preparing the critical areas and mitigation report shall be borne by the applicant. The content, format and extent of the critical areas report shall be approved by the administrator.
(1) 
The requirement for critical areas reports may be waived by the administrator if there is substantial evidence that:
(a) 
There will be no alteration of the critical area(s) and/or the required buffer(s);
(b) 
The proposal will not impact the critical area(s) in a manner contrary to the purpose, intent and requirements of this chapter and the comprehensive plan; and
(c) 
The minimum standards of this chapter will be met.
(2) 
No critical areas report is required for proposals that are exempt from the provisions of this chapter as set forth in TMC § 18.60.030.
(3) 
Critical areas reports shall be completed by a qualified professional who is knowledgeable about the specific critical area(s) in question, and approved by the administrator.
(4) 
At a minimum, a required critical areas report shall contain the following information:
(a) 
Applicant's name and contact information, permits being sought, and description of the proposal;
(b) 
A copy of the site plan for the development proposal, drawn to scale and showing:
(i) 
Identified critical areas, buffers, and the development proposal with dimensions;
(ii) 
Limits of any areas to be cleared; and
(iii) 
A description of the proposed stormwater management plan for the development and consideration of impacts to drainage alterations;
(c) 
The names and qualifications of the persons preparing the report and documentation of any fieldwork performed on the site;
(d) 
Identification and characterization of all critical areas, wetlands, water bodies, and buffers adjacent to the proposed project area;
(e) 
An assessment of the probable cumulative impacts to critical areas resulting from the proposed development of the site;
(f) 
An analysis of site development alternatives if applicable;
(g) 
A description of reasonable efforts made to apply mitigation sequencing to avoid, minimize, and mitigate impacts to critical areas;
(h) 
A mitigation plan, as needed, in accordance with the mitigation requirements of this chapter, including, but not limited to:
(i) 
The impacts of any proposed development within or adjacent to a critical area or buffer on the critical area; and
(ii) 
The impacts of any proposed alteration of a critical area or buffer on the development proposal, other properties and the environment;
(i) 
A discussion of the performance standards applicable to the critical area and proposed activity;
(j) 
Financial guarantees to ensure compliance; and
(k) 
Any additional information required for specific critical areas as listed in subsequent sections of this chapter.
(5) 
The administrator may request any other information reasonably deemed necessary to understand impacts to critical areas.
(Ord. 610 § 2 (Exh. A § 1), 2009; Ord. 757 § 8, 2020)
Mitigation shall be on site, when possible, and sufficient to maintain the functions and values of the critical area, and to prevent risk from a hazard posed by a critical area.
(1) 
Mitigation Sequencing. Applicants shall demonstrate that all reasonable efforts have been examined with the intent to avoid and minimize impacts to critical areas. When an alteration to a critical area is proposed, such alteration shall be avoided, minimized, or compensated for in the following order of preference:
(a) 
Avoiding the impact altogether by not taking a certain action or parts of an action;
(b) 
Minimizing impacts by limiting the degree or magnitude of the action and its implementation, by using appropriate technology, or by taking affirmative steps, such as project redesign, relocation, or timing, to avoid or reduce impacts;
(c) 
Rectifying the impact to wetlands, critical aquifer recharge areas, frequently flooded areas, and habitat conservation areas by repairing, rehabilitating, or restoring the affected environment to enhance ecological function and conditions impacted or lost to the proposed development;
(d) 
Minimizing or eliminating the hazard by restoring or stabilizing the hazard area through engineered or other methods;
(e) 
Reducing or eliminating the impact or hazard over time by preservation and maintenance operations during the life of the action;
(f) 
Compensating for the impact to wetlands, critical aquifer recharge areas, frequently flooded areas, and habitat conservation areas by replacing, enhancing, or providing substitute resources or environments; and
(g) 
Monitoring the hazard or other required mitigation and taking remedial action when necessary.
(2) 
Mitigation Plan. When alteration of a critical area is unavoidable, mitigation is required. The applicant shall be directed by the administrator to submit for approval a mitigation plan as part of the critical areas report. The mitigation plan shall include:
(a) 
A written report identifying mitigation objectives, including:
(i) 
A description of the anticipated impacts to the critical areas and the mitigating actions proposed and the purposes of the compensation measures, including the site selection criteria; identification of compensation objectives; identification of critical area functions and values; and dates for beginning and completion of site compensation construction activities;
(ii) 
A review of the best available science supporting the proposed mitigation and a description of the report author's experience to date in critical areas mitigation; and
(iii) 
An analysis of the likelihood of success of the compensation project.
(b) 
Measurable criteria for evaluating whether or not the objectives of the mitigation plan have been successfully attained and whether or not the requirements of this chapter have been met.
(c) 
Written specifications and descriptions of the mitigation proposed, including, but not limited to:
(i) 
The proposed construction sequence, timing, and duration;
(ii) 
Grading and excavation details;
(iii) 
Erosion and sediment control features;
(iv) 
A planting plan specifying plant species, quantities, locations, sizes, spacing, and density;
(v) 
Measures to protect and maintain plants until established; and
(vi) 
Hydrologic and ground water reports.
(d) 
A program for monitoring construction of the compensation project, and for assessing the completed project and its effectiveness over time. The program shall include a schedule for site monitoring and methods to be used in evaluating whether performance standards are being met. A monitoring report shall be submitted as needed to document milestones, successes, problems, and contingency actions of the compensation project. The compensation project shall be monitored for a period necessary to establish that performance standards have been met and be reflective of the functions being restored, but not for a period less than five years. For example, 10 years or more may be required to establish adequate reestablishment of forested and scrub-shrub wetlands.
(e) 
Identify potential courses of action, and any corrective measures to be taken if monitoring or evaluation indicates project performance standards are not being met.
(Ord. 610 § 2 (Exh. A § 1), 2009)
(1) 
All drainage and erosion control plans shall be prepared by an engineer licensed in the state of Washington in compliance with the town of Twisp Development Standards Manual (as it exists or is hereinafter amended). Upon the town's review and approval of the drainage and erosion control plans, the identified measures to prevent contaminated stormwater from being discharged off the construction site must be in place prior to any clearing, grading or construction.
(2) 
All drainage and erosion control plans shall address methods to minimize and contain soil within the project boundaries during construction and to provide for stormwater drainage from the site and its surroundings during and after construction. Best management practices (BMPs) must be used to prevent any sediment, oil, gas, pesticide-contaminated soil or other pollutants from entering surface or groundwater.
(3) 
All drainage and erosion control plans shall be prepared using the Type 2 SCS model (see town of Twisp development standards), taking into account a storm event equal to or exceeding two inches of rainfall in 90 minutes.
(Ord. 757 § 9, 2020)
(1) 
All geotechnical reports shall be prepared by a consultant team including a geologist and/or geotechnical engineer; or an engineer or an engineering geologist, who is knowledgeable of regional geologic conditions and who derives his/her livelihood from employment in one of these specialized fields.
(2) 
A geotechnical report shall include a description of the geology of the site, conclusions and recommendations regarding the effect of geologic conditions on the proposed development, and opinions and recommendations on the suitability of the site to be developed. More specifically, the report shall evaluate the actual presence of geologic conditions giving rise to the geologic hazard, including without limitation the following:
(a) 
Documentation of site history, evidence of past geologically hazardous activities in the vicinity, quantitative analysis of slope stability and available geologic information;
(b) 
Surface reconnaissance of the site and adjacent areas;
(c) 
Subsurface exploration of the site to assess potential geologic impacts of the proposal;
(d) 
Hydrologic analysis of slope and/or soil stability;
(e) 
Approximate depth to groundwater;
(f) 
Evaluation of the safety of the proposed project, and identification of construction practices, monitoring programs and other mitigation measures necessary; and
(g) 
Demonstration of the following:
(i) 
There will be no increase in surface water discharge or sedimentation to adjacent properties;
(ii) 
There will be no decrease in slope stability on the site nor on adjacent properties;
(iii) 
There is no hazard as proven by evidence of no past geologically hazardous activity in the vicinity of the proposed development and a quantitative analysis of slope stability indicates no significant risk to the development proposal and adjacent properties; and
(iv) 
The geologically hazardous area can be modified or the development proposal can be designed such that the hazard is eliminated or mitigated, making the site as safe as one without a hazard.
(3) 
The recommendations from a soils engineering report and the engineering geology report shall be incorporated in a geotechnical report and in the grading plan specifications.
(a) 
The soils engineering report, prepared according to Chapter 18 of the International Building Code (IBC), shall include data regarding the nature, distribution and strength of existing soils, conclusions and recommendations for grading procedures and design criteria for corrective measures if necessary.
(b) 
The engineering geology report, prepared according to Chapter 18 of the IBC, shall include an adequate description of the geology of the site, conclusions and recommendations regarding the effect of geologic conditions on the proposed development, and opinion on the adequacy for the intended use of sites to be developed by the proposed grading.
(Ord. 757 § 10, 2020)
All grading and excavation plans shall be prepared by an engineer licensed in the state of Washington, and shall meet the standards and requirements set forth in Chapter 33 of the International Building Code, and shall contain the following information:
(1) 
A cover sheet showing the location of work, the name and address of the owner and the engineer who prepared the plans;
(2) 
General vicinity of the proposed site;
(3) 
Property limits and accurate contours of existing ground and details of terrain and area drainage. Contour intervals for slopes 10 percent or less shall be no more than two feet, and intervals for slopes exceeding 10 percent shall be no more than five feet;
(4) 
Limits of proposed excavation and fill sites, finished contours to be achieved by the grading, and proposed drainage channels to offset stormwater impacts during grading and excavation (and related construction);
(5) 
Detailed plans of all surface and subsurface drainage devices, walls, cribbing, dams and other protective devices to be constructed with, or as part of, the proposed work, together with a map showing the drainage area and the estimated runoff of the area served by any drains;
(6) 
Location of any buildings or structures on the property where the work is to be performed and the location of any buildings or structures on land of adjacent owners which are within 15 feet of the property;
(7) 
Recommendations included in a soils engineering report and the engineering geology report shall be incorporated in the grading plans or specifications. When approved by the building official, specific recommendations contained in the soils engineering report and the engineering geology report, which are applicable to grading, may be included by reference;
(8) 
The dates of the soils engineering and engineering geology reports together with the names, seals, license numbers, addresses and phone numbers of the firms and/or individuals who prepared the reports.
(Ord. 757 § 11, 2020)
In cases where the administrator does not have adequate knowledge or training to determine the sufficiency and accuracy of information contained within a critical areas report or mitigation plan, said reports or plans shall be submitted to the following agencies for review as specified in the Small Communities Critical Areas Ordinance Implementation Guidebook Appendix A: State Agency Contact Information:
(1) 
Department of Community, Trade and Economic Development;
(2) 
Department of Ecology;
(3) 
Department of Fish and Wildlife;
(4) 
Department of Natural Resources.
(Ord. 610 § 2 (Exh. A § 1), 2009)
If a development proposal is subject to mitigation, maintenance or monitoring plans, the town of Twisp may require an assurance device or surety in a form acceptable to the town attorney.
(Ord. 610 § 2 (Exh. A § 1), 2009)
Through the review process, the town of Twisp shall have the authority to attach such conditions to the granting of any approval under this chapter as deemed necessary to alleviate adverse impacts to critical area(s) and to carry out the provisions of this chapter. Such conditions of approval may include, but are not limited to, the following:
(1) 
Specification of allowable lot sizes;
(2) 
Provisions for additional buffers relative to the intensity of a use or activity;
(3) 
Requirements and/or restrictions on the construction, size, location, bulk and/or height, etc., of structure(s);
(4) 
Dedication of necessary easements for utilities, conservation, open space, etc.;
(5) 
Imposition of easement agreements, sureties, deed restrictions, covenants, etc., on the future use and/or division of land;
(6) 
Limitations on the removal of existing vegetation;
(7) 
Additional measures to address issues such as erosion control, storm water management, filling, grading, etc.;
(8) 
Development of a mitigation plan to create, enhance, or restore damaged or degraded critical area(s) on and/or off site; and
(9) 
Any monitoring and/or maintenance plans necessary to implement the provisions of this chapter.
(Ord. 610 § 2 (Exh. A § 1), 2009)
(1) 
Uses and activities allowed within designated aquifer recharge areas are those areas permitted by the zoning district, subject to the provisions of this chapter.
(2) 
Classification. Aquifer recharge areas are classified in accordance with the provisions of the Twisp comprehensive plan and are based on highly permeable soils using data from the most current NRCS Web Soil Survey for Okanogan County. The following classification scheme is used to determine the level of protection necessary for lands that are aquifer recharge areas:
(a) 
Critical Potential. Soils with high permeability ratings according to NRCS Soil Survey.
(3) 
Designation. Critical aquifer recharge areas in Twisp shall be designated based on recharge potential using the classification provisions in the Twisp comprehensive plan. Because the designation focuses on areas where recharge potential exists, protections shall be broad enough to preserve essential aquifer recharge functions and values. Maps CA I and CA II in the Map Appendix to the Twisp comprehensive plan show designated potential aquifer recharge areas.
Additionally, if any of the following areas are established within the town's urban growth area, they shall be included on these maps:
(a) 
Sole source aquifer recharge areas designated pursuant to the Federal Safe Drinking Water Act;
(b) 
Areas established for special protection pursuant to the Washington State groundwater management program;
(c) 
Areas designated for wellhead protection pursuant to the Federal Safe Drinking Water Act; and
(d) 
Aquifer recharge areas mapped and identified by a qualified groundwater scientist.
(4) 
Standards. In addition to the general provisions of this chapter and the requirements of the underlying zone, the following minimum standards shall apply to development activities within and adjacent to aquifer recharge areas:
(a) 
Development activities within an aquifer recharge area shall be designed, developed and operated in a manner that will not potentially degrade groundwater resources nor adversely affect the recharging of the aquifer.
(b) 
A hydrogeologic study and/or ongoing monitoring may be required to assess impacts of development activities on groundwater resources.
(c) 
On-site stormwater facilities shall be designed and installed in all aquifer recharge areas, so as to provide both detention and treatment of all runoff associated with the development. Such stormwater facilities shall comply with all relevant requirements of the Washington Department of Ecology Eastern Washington Stormwater Manual and Twisp Development Standards Manual.
(d) 
All new development occurring within aquifer recharge areas shall be required to connect to town sewer and water where available pursuant to TMC Title 13.
(e) 
Landfills, junkyards/salvage yards, mining, wood treatment facilities, or any other activity which could contaminate ground water in critical potential aquifer recharge areas shall be prohibited. Such activities may be permitted in areas with high or moderate recharge potential in accord with applicable zoning regulations, providing the applicant can satisfactorily demonstrate that potential negative impacts to groundwater can be prevented.
(f) 
All storage tanks, whether above or underground, shall be required to be constructed so as to protect against corrosion for the operational life of the tank, to prevent any release of hazardous substances to the ground, groundwaters, or surface waters, and to utilize appropriate containment methods.
(g) 
Any agricultural activities conducted within aquifer recharge areas shall incorporate best management practices concerning waste disposal, fertilizer/pesticide/herbicide use, and stream corridor management. If necessary, applicants shall seek technical assistance from the Okanogan County Conservation District or the WSU Cooperative Extension Office.
(h) 
Application of pesticides, herbicides and fertilizers within aquifer recharge areas shall comply with timing and rates specified on product packaging.
(i) 
Vehicle repair and servicing activities must be conducted over impermeable pads and within a covered structure capable of withstanding normally expected weather conditions. Chemicals used in the process of vehicle repair and servicing must be stored in a manner that protects them from weather and provides containment should leaks occur.
(j) 
Car washes may be permitted inside critical aquifer recharge areas provided they comply with the Department of Ecology's Best Management Standards for Vehicle and Equipment Washwater Discharges/Best Management Practices Manual (as hereinafter amended).
(Ord. 610 § 2 (Exh. A § 2), 2009; Ord. 757 § 14, 2020)
The flood hazard areas identified by the FEMA maps and study adopted in this chapter are subject to periodic inundation which results in loss of life and property, health, and safety hazards, disruption of commerce and governmental services, extraordinary public expenditures for flood protection and relief, and impairment of the tax base, all of which adversely affect the public health, safety, and general welfare.
These flood losses are caused by the cumulative effect of obstructions in areas of special flood hazards which increase flood heights and velocities, and when inadequately anchored, damage uses in other areas. Uses that are inadequately floodproofed, elevated, or otherwise protected from flood damage also contribute to the flood loss.
(1) 
Classification. The following classification system will be used to determine the level of protection necessary for frequently flooded areas:
(a) 
Class I. The floodway of any river or stream as designated by FEMA; and draws, alluvials and flood channels that are not mapped by FEMA but are areas of local concern that have a historical reoccurrence of flood events characterized by significant damage from flood flows.
(b) 
Class II. All areas mapped by FEMA as the 100-year floodplain; and those areas of local concern that experience recurrences of flooding that are characterized by damage due primarily to inundation.
(2) 
Designation. The town of Twisp designates those areas of special flood hazard indicated in the Flood Hazard Boundary Map/Flood Insurance Rate Map and Flood Boundary/Floodway Map, together with the accompanying Flood Insurance Study for Community No. 5301240001B dated July 18, 1977, or hereafter updated (see Map CA III in the Map Appendix). Since flood hazards are not necessarily constrained to those areas detailed in the flood insurance study and maps, the channel migration zone may provide additional mapping for the areas of local concern.
(3) 
Development Standards. In addition to the general provisions of this chapter and the requirements of the underlying zone, the following minimum standards shall apply to development activities within and adjacent to frequently flooded areas:
(a) 
All development within Class I and Class II frequently flooded areas shall be reviewed under and subject to the requirements of Chapter 16.10 TMC, Flood Damage Prevention.
(b) 
Where frequently flooded areas coincide with other designated critical areas, critical areas reports and mitigation plans shall address any combined functions and values.
(c) 
Structures shall be located outside of frequently flooded areas except where no alternative location exists.
(d) 
Following construction of a structure within the floodplain where base flood elevation is provided, the applicant shall obtain an elevation certificate that records the elevation of the lowest floor. The elevation certificate shall be completed by a surveyor or engineer licensed in the state of Washington and shall be submitted to the town for recording.
(e) 
Fill and grading in the floodplain shall only occur upon a determination by a qualified professional that the fill or grading will not block side channels, inhibit channel migration, increase flood hazards to others, or be placed within a defined channel migration zone, whether or not the town has delineated such zones as of the time of application.
(f) 
Subdivision in frequently flooded areas is subject to the following:
(i) 
All lots created shall have adequate building space outside flood hazard areas, including the floodway, 100-year floodplain, and channel migration zones;
(ii) 
Plat maps shall indicate floodway, 100-year floodplain and channel migration zones;
(iii) 
Subdivisions shall be designed to minimize or eliminate the potential for flood damage;
(iv) 
Subdivisions shall provide for storm water drainage, in accordance with town standards, so as to reduce exposure to flood hazards; and
(v) 
Variances on lot sizes may be granted if it is shown that the floodway, 100-year floodplain, and channel migration zone have been avoided and therefore result in smaller lots than the underlying zone or Twisp shoreline master program requires. Variances may only be granted in accordance with uses described in TMC § 18.60.050, Reasonable use exception.
(Ord. 757 § 15, 2020)
(1) 
Classification. WDFW has identified those fish and wildlife resources that are considered a priority for management and conservation. Priority habitats are those with unique or significant value to many fish or wildlife species. Priority species are those which require special efforts to ensure their perpetuation because of their low numbers, sensitivity to habitat alteration, tendency to form vulnerable aggregations or because they hold commercial, recreational, or tribal importance. Twisp shall use the WDFW priority habitat and species program to classify all fish and wildlife habitat conservation areas within the town and urban growth boundary. The town uses two classifications of habitat conservation areas in accordance with the provisions of the Twisp comprehensive plan as shown on Map CA IV in the Map Appendix to the town of Twisp comprehensive plan.
(2) 
Designation. Fish and wildlife conservation areas are designated in accordance with the provisions of the Twisp comprehensive plan. Map CA IV in the Map Appendix to the Twisp comprehensive plan designates fish and wildlife habitat conservation areas.
(3) 
Development Standards in Habitat Conservation Areas. In addition to the general provisions of this chapter and the requirements of the underlying zone, the following minimum standards shall apply to development activities within and adjacent to fish and wildlife habitat conservation areas:
(a) 
Habitat Assessment. Critical areas reports for fish and wildlife habitat conservation areas shall include a habitat assessment to evaluate the presence or absence of a critical species or habitat.
(b) 
All projects shall comply with the applicable federal, state and local regulations regarding the species and habitats identified upon a site.
(c) 
The Washington State Department of Fish and Wildlife priority habitat and species management recommendations shall be consulted in developing specific measures to protect a specific project site.
(d) 
When needed to protect the functions and values of habitat conservation areas, the administrator shall require the establishment of buffer areas for activities in or adjacent to such areas. Buffers shall consist of an undisturbed area of native vegetation, or areas identified for restoration.
(e) 
Buffer widths shall reflect the classification and sensitivity of the habitat and the intensity of activity proposed, and shall be consistent with the management recommendations issued by the Washington State Department of Fish and Wildlife.
(f) 
Any approved alteration or development shall be required to minimize impacts to native vegetation. Where disturbance is unavoidable, the applicant shall restore the area to the extent possible using native plants appropriate to the site. New plantings shall be monitored and maintained in good growing condition and kept free of invasive weeds until well established upon the site.
(g) 
Within riparian habitat conservation areas, vegetation shall not be removed unless no other alternative exists. In such cases clearing shall be limited to those areas necessary and disturbed areas shall be replanted with site-appropriate native riparian vegetation.
(h) 
Access to habitat conservation areas or buffers may be restricted in accord with the findings of a critical areas report, mitigation report, PHS management recommendations or other best available science. Access restrictions may include fencing and signs as needed to ensure protection of habitat functions and values. Restrictions may be seasonal in nature.
(i) 
Subdivision of lands, including both short and long plats, within habitat conservation areas shall be subject to the following:
(i) 
Uplands.
(A) 
Lot sizes shall conform to the underlying zone. Variances for smaller lots shall not be considered unless a habitat assessment is provided by applicant and a determination that subdivision will not negatively affect habitat quality can be determined.
(B) 
Long plats located in upland habitat areas must reserve ample core habitat and connectivity designated as open space on the plat. Open space must connect adjacent habitat areas outside the project area. Open space must be landscaped and managed in a manner that protects the habitat area for the priority species.
(C) 
Cumulative impacts to habitat fragmentation in uplands from consecutive short plats must be considered prior to approval of the subdivision.
(ii) 
Riparian. Refer to shoreline master program.
(j) 
All activities, uses and alterations proposed to be located in or adjacent to water bodies used by anadromous fish shall give special consideration to the preservation and enhancement of associated habitats.
(Ord. 610 § 2 (Exh. A § 3), 2009; Ord. 757 § 16, 2020)
(1) 
Classification. Wetlands in Twisp shall be classified in accordance with the provisions of the Twisp comprehensive plan using the Washington State Wetlands Rating System for Eastern Washington.
(2) 
Designation. Wetlands in Twisp and its urban growth area are designated using the provisions of the Twisp comprehensive plan. To date, there has been no wetlands mapping done specifically for the Twisp area. To remedy this, the town should pursue an accurate accounting of all wetlands in its planning area based on the Washington State Wetlands Rating System for Eastern Washington.
However, until funding is obtained to conduct a comprehensive inventory of wetlands, the National Wetlands Inventory (NWI) maps are used as a basis for designation. The NWI maps, along with other supportive documentation, shall be used to review development proposals, but because the National Wetlands Inventory was done at such a broad scale, local verification according to the classification criteria shall be part of the standard process for identifying and designating wetlands. Map A9 in the Map Appendix to the Twisp comprehensive plan designates wetlands.
(3) 
Standards. In addition to the general provisions of this chapter and the requirements of the underlying zone, the following minimum standards shall apply to development activities within and adjacent to wetland areas:
(a) 
Activities and uses shall be prohibited from wetlands or wetland buffers unless the applicant can show that the proposed activity will not degrade the functions and values of the wetland or other critical areas, or as otherwise provided in this chapter. The following Table 18.60.160(1) describes the level of impact expected from different land uses:
Table 18.60.160(1)
Types of proposed land use that can result in high, moderate, and low levels of impacts to adjacent wetlands. Level of impact from proposed change in land use
Types of land use based on common zoning designations
High
• Commercial
• Urban
• Industrial
• Institutional
• Retail sales
• Residential (more than 1 du/acre)
• Conversion to high intensity agriculture (dairies, nurseries, greenhouses, growing and harvesting crops requiring annual tillage and raising and maintaining animals)
• High intensity recreation (golf courses, ball fields, etc.)
• Hobby farms
Moderate
• Residential (1 du/acre or less)
• Moderate intensity open space (parks with biking, jogging, etc.)
• Conversion to moderate intensity agriculture (orchards, hayfields, etc.)
• Paved trails
• Building of logging roads
• Utility corridor or right-of-way shared by several utilities and including access/maintenance road
Low
• Forestry (cutting of trees only)
• Low intensity open space (hiking, birdwatching, preservation of natural resources, etc.)
• Unpaved trails
• Utility corridor without a maintenance road and little or no vegetation management
(b) 
Buffer Widths. Buffer widths are to be determined through the combination of the functional score, generated by the wetland classification system described in subsection (2) of this section, and the proposed land use intensity. Buffers shall be vegetated with a native plant community appropriate for the ecoregion or with one that performs similar functions. If the existing buffer is unvegetated, sparsely vegetated, or vegetated with invasive species that do not perform needed functions, the buffer should either be planted to create the appropriate plant community or the buffer should be widened to ensure that adequate functions of the buffer are provided. Generally, improving the vegetation will be more effective than widening the buffer.
Guidelines for establishing high, moderate, and low intensity land uses are provided in Table 18.60.160(1). The use of Table 18.60.160(1) along with the town of Twisp zoning code's development and performance standards set forth in this title shall be used to establish the land use intensity. The following standard buffer widths in Table 18.60.160(2) have been established in accordance with the Department of Ecology's recommendations and are considered best available science to provide predictability in the regulation of wetlands:
Table 18.60.160(2)
Category I (Wetlands Scoring 70 Points or More for All Functions or Having Special Characteristics Identified in the Rating System)
Wetland Characteristic
Buffer Widths by Impact of Use
Other Measures
Wetlands of high conservation value
Low – 125 ft
Moderate – 190 ft
High – 250 ft
• No additional surface discharges to wetland or its tributaries
• No septic systems within 300 ft
• Restore degraded parts of buffer
Bogs
Low – 125 ft
Moderate – 190 ft
High – 250 ft
• No additional surface discharge to wetland or tributaries
• Restore degraded parts of buffer
Forested
Buffer size to be based on score for habitat function or water quality functions
• If forest wetland scores high for habitat, need to maintain connectivity to other natural area
• Restore degraded parts of buffer
Alkali
Low – 100 ft
Moderate – 150 ft
High – 200 ft
• No additional surface discharges to wetland or its tributaries
• Restore degraded parts of buffer
High level of function habitat score (8-9 pts)
Low – 100 ft
Moderate – 150 ft
High – 200 ft
• Maintain connections to other habitat areas
• Restore degraded parts of buffer
Moderate level of function for habitat (score for habitat 6-7 pts)
Low – 75 ft
Moderate – 110 ft
High – 150 ft
• No recommendations at this time
High level of function for water quality improvements (8-9 pts) and low for habitat (< 6 pts)
Low – 50 ft
Moderate – 75 ft
High – 100 ft
• No additional surface discharges of untreated runoff
Not meeting any characteristics
Low – 50 ft
Moderate – 75 ft
High – 100 ft
• No recommendations at this time
Table 18.60.160(3)
Category II (Wetlands Scoring 51 – 69 Points for All Functions or Having Special Characteristics Identified in the Rating System)
Wetland Characteristic
Buffer Widths by Impact of Use
Other Measures
High level of function for habitat (habitat score 8-9 pts)
Low – 100 ft
Moderate – 150 ft
High – 200 ft
• Maintain connections to other habitat areas
Moderate level of functions for habitat (habitat score 6-7 pts)
Low – 75 ft
Moderate – 110 ft
High – 150 ft
• No recommendations (confer with Ecology)
High level of function for water quality improvement (8-9 pts) and low for habitat (< 6 pts)
Low – 50 ft
Moderate – 75 ft
High – 100 ft
• No additional surface discharges of untreated runoff
Vernal pools
Low – 100 ft
Moderate – 150 ft
High – 200 ft
OR
Develop a regional plan to protect the most important vernal pool complexes – buffers of vernal pools outside protection zones can then be reduced to:
Low – 40 ft
Moderate – 60 ft
High – 80 ft
• No intensive grazing or tilling in the wetland
Riparian forest
Buffer widths to be based on habitat and water quality functional scores
• Riparian forest wetlands need to be protected at the watershed or sub-basing scale
• Other protections to be based on habitat and water quality function
Other, not meeting above characteristics
Low – 50 ft
Moderate – 75 ft
High – 100 ft
• No recommendations (confer with Ecology)
Table 18.60.160(4)
Category III (Wetlands Scoring 30 – 50 Points for All Functions or Isolated Vernal Pools)
Wetland Characteristics
Buffer Widths by Impact of Proposed Land Use
Other Measures Recommended for Protection
Moderate level of function for habitat (score for habitat 6-7 pts)
• If wetland scores 8-9 habitat pts, use Category II buffers
Low – 75 ft
Moderate – 110 ft
High – 150 ft
• No recommendations (confer with Ecology)
Score for habitat 3-5 pts
Low – 40 ft
Moderate – 60 ft
High – 80 ft
• No recommendations (confer with Ecology)
Table 18.60.160(5)
Category IV (Wetlands Scoring Less Than 30 Points)
Wetland Characteristics
Buffer Widths by Impact of Proposed Land Use
Other Measures Recommended for Protection
Score for all 3 basic functions < 16 pts
Low – 25 ft
Moderate – 40 ft
High – 50 ft
• No recommendations (confer with Ecology)
The standard buffer widths shall be applied unless the administrator determines through a scientifically supportable method that a greater or lesser buffer width would serve to protect the functions and values of a particular wetland. The buffer widths recommended for proposed land uses with high intensity impacts to wetlands can be reduced to those recommended for moderate intensity impacts under the following conditions:
(i) 
For wetlands that score moderate or high for habitat (six points or more for the habitat functions), the width of the buffer can be reduced if both of the following criteria are met:
(A) 
A relatively undisturbed, vegetated corridor at least 100 feet wide is protected between the wetland and any other priority habitats as defined by the Washington State Department of Fish and Wildlife. (The latest definitions of priority habitats and their locations are available on the WDFW website at: https://wdfw.wa.gov/species-habitats/at-risk/phs/)
The corridor must be protected for the entire distance between the wetland and the priority habitat by some type of legal protection such as a conservation easement.
(B) 
Measures to minimize the impacts of different land uses on wetlands, such as the examples summarized in Table 8D-8, are applied.
(ii) 
For wetlands that score less than six points for habitat, the buffer width can be reduced to that required for moderate land use impacts by applying measures to minimize the impacts of the proposed land uses (see examples in Table 18.60.160(6)).
Greater buffer widths or rehabilitation of an inadequate plant community may be required where necessary to ensure development does not result in adverse impacts to wetlands.
Table 18.60.160(6)
Activities and Uses That Cause Disturbances
Examples of Measures to Minimize Impacts
Lights
• Parking lots
• Warehouses
• Manufacturing
• Residential
• Direct lights away from wetland
Noise
• Manufacturing
• Residential
• Locate activity that generates noise away from wetland
Toxic runoff*
• Parking lots
• Roads
• Manufacturing
• Residential areas
• Application of agricultural pesticides
• Landscaping
• Route all new, untreated runoff away from wetland while ensuring wetland is not dewatered
• Establish covenants limiting use of pesticides within 150 ft of wetland
• Apply integrated pest management
Stormwater runoff
• Parking lots
• Roads
• Manufacturing
• Residential areas
• Commercial
• Landscaping
• Retrofit stormwater detention and treatment for roads and existing adjacent development
• Prevent channelized flow from lawns that directly enters the buffer
Change in water regime
• Impermeable surfaces
• Lawns
• Tilling
• Infiltrate or treat, detain, and disperse into buffer new runoff from impervious surfaces and new lawns
Pets and human disturbance
• Residential areas
• Use privacy fencing; 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
Dust
• Tilled fields
• Use best management practices to control dust
* These examples are not necessarily adequate for minimizing toxic runoff if threatened or endangered species are present at the site.
(c) 
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 same buffer widths and measurement criteria shall apply to any wetland created, restored, or enhanced as compensation for approved wetland alterations. Buffers shall be clearly marked on the ground.
(d) 
Wetland Buffer Width Averaging. The administrator may allow averaging of wetland buffer widths in accordance with an approved critical areas report if it is shown that no alternate configuration for site development exists based on topographical or lot dimensional constraints without averaging, provided the following conditions are met:
(i) 
There will be no reduction in wetland functions and values;
(ii) 
The wetland contains variations in sensitivity due to physical characteristics or the character of the buffer varies in slope, soils, or vegetation such that the wetland would benefit from a wider buffer in some areas and a narrower buffer in other places;
(iii) 
The total area contained in the buffer area is no less than would have otherwise been applied under buffer widths in Tables 18.60.160(2) through (5); and
(iv) 
That the buffer at its narrowest point will never be less than either three-quarters of the required width or 75 feet for Category I and II, 50 feet for Category III and 25 feet for Category IV, whichever is greater.
(e) 
Where other critical areas coincide with wetlands, buffers shall be configured so as to protect aggregate functions and values. Particular consideration shall be given to habitat connectivity.
(f) 
Wetland buffer zones shall be retained in their natural condition. Where buffer disturbances are unavoidable during adjacent construction, revegetation with native plant materials will be required.
(g) 
The following activities shall be allowed within wetland buffers:
(i) 
Conservation or restoration activities aimed at protecting soil, water, vegetation or wildlife;
(ii) 
Pedestrian trails in wetlands or buffers be limited to permeable surfaces no more than five feet in width. Trails should not be permitted in wetlands except for minor crossings that minimize impact. They should be located only in the outer 25 percent of a wetland buffer, and should be designed to avoid removal of significant trees. In most cases, wetland buffer widths should be increased to compensate for the loss due to the width of the trail;
(iii) 
Educational and scientific research activities; and
(iv) 
Normal and routine maintenance and repair of any existing public or private facilities provided appropriate measures are undertaken to minimize impacts to the wetland and its buffer and that disturbed areas are restored to a natural condition.
(v) 
Any permitted activity in a wetland buffer should avoid the removal of vegetation, especially native trees, and keep vegetation removal to an absolute minimum.
(h) 
Category I and II wetlands shall not be used for regional stormwater detention. Category III and IV may be considered for stormwater detention provided pollution measures are approved by the Department of Ecology.
(i) 
The outer 25 percent of buffers, limited to Category II and IV wetlands, may be used for stormwater dispersion outfalls and bioswale facilities provided there is no other feasible location and that the location of such facilities will not adversely impact the functions and values of the wetland or alter the hydroperiod and water quality.
(j) 
Stormwater facilities must conform to standards set forth in the Washington Department of Ecology Stormwater Management Manual for Eastern Washington or any future editions to the manual.
(k) 
As a condition of any permit or authorization pursuant to this title, the administrator may require temporary or permanent signs and/or fencing along the perimeter of a wetland or buffer in order to protect the functions and values of the wetland, or to minimize future impacts or encroachment upon the wetland or buffer.
(l) 
Wetland alteration proposals shall be approved only if no alternative is available. If alteration is unavoidable, all adverse impacts shall be mitigated as set forth in an approved critical areas report and mitigation plan.
(m) 
Mitigation shall achieve equivalent or greater biological functions as existed in the wetland prior to mitigation. When possible, mitigation shall be achieved through a mitigation plan that meets the guidance set forth by the Department of Ecology. Mitigation may occur on site or within the same drainage basin provided and be on site and sufficient to maintain the functions and values of the wetland and buffer areas being mitigated.
(n) 
Mitigation actions that require compensation by replacing, enhancing or substitution shall occur in the following order of preference:
(i) 
Restoring, replacing or enhancing the wetland on the site of the project;
(ii) 
Restoring, replacing or enhancing degraded wetlands in the same subbasin;
(iii) 
Creating wetlands on upland sites that were former wetlands or that are disturbed upland sites;
(iv) 
Preserving high quality wetlands that are under imminent threat.
Mitigation ratios shall be set forth in Table 18.60.160(7) or the administrator shall seek guidance from the Department of Ecology for updated ratio standards. These ratios do not apply to remedial actions resulting from unauthorized alterations.
Table 18.60.160(7)
Category and Type of Wetland
Creation or Reestablishment
Rehabilitation
Enhancement
(A) Category I
6:1
12:1
24:1
(B) Category II
3:1
6:1
12:1
(C) Category III
2:1
4:1
8:1
(D) Category IV
1.5:1
3:1
6:1
(o) 
The mitigation ratio may be increased if the administrator identifies that:
(i) 
Uncertainty exists as to the probable success of the proposed restoration or creation;
(ii) 
A significant time period will elapse between impact and replication of wetland functions;
(iii) 
Proposed mitigation will result in a lower category of wetland or reduced functions relative to the wetland being impacted; or
(iv) 
The impact was due to an unauthorized action.
(p) 
The administrator may decrease the mitigation ratio where:
(i) 
Documentation by a qualified wetlands specialist demonstrates that the proposed mitigation actions have a very high likelihood of success;
(ii) 
Documentation by a qualified wetlands specialist demonstrates that the proposed mitigation actions will provide functions and values greater than the wetland being impacted; or
(iii) 
The proposed mitigation actions are conducted in advance of the impact and have been shown to be successful.
(q) 
The long or short subdivision of lands that include wetlands is subject to the following:
(i) 
Land that is located wholly within a wetland or its buffer may not be subdivided;
(ii) 
Land that is located partially within a wetland or its buffer may be subdivided; provided, that an accessible and contiguous portion of each new lot is located outside of the wetland and its buffer. Lot sizes must conform to the underlying zone unless a density is increased as set forth in subsection (3)(r) of this section;
(iii) 
Access roads and utilities serving a development may be permitted within the wetland and associated buffers only if the town determines that no other feasible alternative exists.
(r) 
The administrator may allow greater density of development (in compliance with the Twisp zoning code) outside of wetland areas and associated buffers through approval of a variance, provided the ability to:
(i) 
Ensure a high level of protection for on-site resources is demonstrated in an approved critical areas report and mitigation plan;
(ii) 
A showing of good and sufficient cause;
(iii) 
A determination that failure to grant the increase in density would result in exceptional hardship to the applicant.
(Ord. 610 § 2 (Exh. A § 4), 2009; Ord. 757 § 17, 2020; Ord. 758 § 1, 2020)
(1) 
Classification. Known geologically hazardous areas within the town of Twisp consist of erosion hazard areas, including steep slopes. As more information is obtained that demonstrates the existence of other types and/or areas of geologically hazardous areas, these types and/or areas shall be classified and protected in accordance with the provisions of this chapter.
(a) 
The following general classification system will be used to determine the level of protection necessary for geologically hazardous areas, based upon the risk to development:
(i) 
Known or suspected risk;
(ii) 
No risk;
(iii) 
Risk unknown.
(b) 
The following criteria shall be used in determining the status of an area as a particular type of geologically hazardous area:
(i) 
Erosion hazard areas are those that contain all three of the following characteristics:
(A) 
A slope of 15 percent or greater;
(B) 
Soils identified by the NRCS as unstable and having a high potential for erosion; and
(C) 
Areas that are exposed to the erosion effects of wind or water.
(ii) 
Landslide hazard areas are those that may contain any of the following circumstances:
(A) 
All areas that have historically been prone to landsliding;
(B) 
All areas containing soil types identified by the NRCS as unstable and prone to landslide hazard;
(C) 
All areas that show evidence of or are at risk from snow avalanches; or
(D) 
All areas that are potentially unstable as a result of rapid stream incision or stream bank erosion.
(2) 
Designations. Each type of geologically hazardous area is designated based on different factors. The designation process for each type follows:
(a) 
Erosion Hazard Areas. NRCS soil erosion hazard ratings are interpretations of the potential for erosion, applied to broadly generalized map units. They do not pinpoint erosion sites, but rather areas that, because of soil properties, availability of water, etc., are more susceptible to severe erosion than others. The NRCS maps will be used to identify areas of erosion potential. The soil information needs to be combined with site-specific information (rills, interrills, and wind erosion) to determine if erosion hazard is present on the site. The soil types that have erosion hazard potential are identified on Map VII.
(b) 
Landslide Hazard Areas. Lands that meet the classification criteria are hereby designated as landslide hazard areas and should be mapped, as resources become available.
(c) 
Mine Hazard Areas. Lands that meet the classification criteria are hereby designated as mine hazard areas and will be mapped, as resources become available.
(d) 
Seismic Hazard Areas. There are no known active faults in Twisp. The majority of the town is located within Seismic Zone D0 in accordance with the International Building Code.
(e) 
Volcanic Hazard Areas. There are no volcanic hazard areas in Twisp. There are, however, several active volcanoes that could have impacts on areas of the town, particularly the fallout of ash. There is no way to prevent the impacts of fallen ash, but there are ways to respond to the ash that could lessen its impacts.
(3) 
Standards. In addition to the general provisions of this chapter and the requirements of the underlying zone, the following minimum standards shall apply to development activities within and adjacent to geologic hazard areas:
(a) 
Critical areas reports for a geologically hazardous area shall include a geotechnical analysis completed by a qualified professional with expertise in the particular hazard(s) present in a given critical area.
(b) 
Alterations of geologically hazardous areas or associated setbacks may only occur for activities that:
(i) 
Will not increase the threat of the geological hazard to adjacent properties beyond predevelopment conditions;
(ii) 
Will not adversely impact other critical areas;
(iii) 
Are designed so that the hazard to the project is eliminated or mitigated to a level equal to or less than predevelopment conditions; and
(iv) 
Are certified as safe as designed and under anticipated conditions by a qualified engineer or geologist, licensed in the state of Washington.
(c) 
Critical areas reports and mitigation plans for geologically hazardous areas shall establish setbacks as needed to eliminate or minimize risks of property damage, death, or injury resulting from development of the hazard area. Where established, setbacks shall be maintained between all permitted uses and activities and the designated geologically hazardous area(s).
(d) 
Unless otherwise provided or as part of an approved alteration, removal of vegetation from an erosion or landslide hazard area or related setback area shall be prohibited.
(e) 
Structures and improvements shall be clustered to avoid geologically hazardous areas and other critical areas in so far as clustering does not alter the underlying zoning densities.
(f) 
Development and activities located within landslide or erosion hazard areas shall provide for long-term slope stability, and design shall incorporate the following standards:
(i) 
Structures and improvements shall minimize alterations to the natural contour of the slope and foundations shall be tiered where possible to conform to existing topography;
(ii) 
Structures and improvements shall be located to preserve the most critical portion of the site and its natural landforms and vegetation;
(iii) 
The proposed development shall not result in greater risk or a need for increased setbacks on neighboring properties;
(iv) 
The use of retaining walls that allow the maintenance of existing natural slope area is preferred over graded artificial slopes; and
(v) 
Development shall be designed to minimize impervious lot coverage.
(g) 
Utility lines and pipes shall be permitted in erosion and landslide hazard areas only when the applicant demonstrates that no other practical alternative is available.
(h) 
Subdivision of lands in erosion, landslide, and mine hazard areas is subject to the following:
(i) 
Land that is located wholly within an erosion, landslide or mine hazard area or associated setback areas may not be subdivided. Land that is located partially within an erosion, landslide, or mine hazard area or associated setback areas may be divided; provided, that each resulting lot has sufficient buildable area outside of, and will not affect, the geologic hazard area.
(ii) 
Access roads and utilities may be permitted within the erosion, landslide or mine hazard area and associated setback areas only if no other feasible alternative exists.
(Ord. 610 § 2 (Exh. A § 6), 2009; Ord. 757 § 19, 2020)
Violation of the provisions of this chapter, or failure to comply with any of its requirements, shall be subject to enforcement actions by the town of Twisp that are authorized in the zoning ordinance, subdivision ordinance, shoreline master program or any other land use regulation of the town of Twisp. The town attorney, when authorized by the mayor and council, shall seek penalties, remedies, injunctions and other legal sanctions necessary for the enforcement of this chapter. In addition to costs allowed by these regulations, the prevailing party in an enforcement action may, at the court's discretion, be allowed interest and reasonable attorney's fees. The town attorney shall seek such costs, interest, and the reasonable attorney's fees on behalf of the town of Twisp when the town is the party.
(Ord. 757 § 13, 2020)