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HomeMy WebLinkAboutCritical areas stewardship plan 11241 Willows Road NE, Suite 200 | Redmond, WA 98052 | Phone 425.822.4446 | otak.com Conceptual Critical Areas Stewardship Plan To: John Fleming, Jefferson County From: Jeff Gray, PWS Copies: Nico Vanderhorst, Otak Date: October 20, 2023 Subject: Olympic Discovery Trail - Conceptual CASP and Wetland and Buffer Mitigation Plan USACE Project No. NWS-2023-464 Project No.: Otak Project No. 33425.000 Introduction This Conceptual Critical Areas Stewardship Plan (CASP) has been prepared for the Olympic Discovery Trail project on behalf of Jefferson County Public Works to support permitting with federal, state, and local agencies. This CASP includes the conceptual compensatory wetland and buffer mitigation plan for the project, and has been prepared in accordance with Jefferson County Code (JCC) 18.22.965 (Critical area stewardship plans) as an alternative to the requirements of Article VI (Fish and Wildlife Habitat Conservation Areas) and VII (Wetlands) of JCC Chapter 18.22 (Critical Areas). The goal of this CASP is to maintain existing functions and values of the watershed and subbasin while meeting the development needs of the proposed Olympic Discovery Trail extension project. On-site, permittee-responsible compensatory mitigation is proposed along the southern trail section near Anderson Lake State Park in recently logged forestlands. This conceptual mitigation plan provides a project description, summary of existing site conditions, mitigation sequencing to avoid and minimize project impacts, and characterizes unavoidable impacts. Compensatory wetland and buffer mitigation is proposed in the trail corridor to offset project impacts, including proposed performance standards, monitoring standards, contingency plan to ensure performance standards are met, and long term management and permanent site protection. All feasible and reasonable measures have been taken to avoid and reduce impacts to wetland and stream habitats and associated buffers through the trail design process. Project impacts to regulated wetlands, streams, and associated buffers are shown on the Figure Set 1 in Appendix A, and the proposed mitigation areas are shown on Figure Set 2 in Appendix B. Project Description Jefferson County Public Works is planning to construct a segment of the Olympic Discovery Trail Project approximately three miles in length from the south end of the Larry Scott Trail at Milo Curry Road running east and south to Anderson Lake State Park in Jefferson County. The trail will be part of a coordinated regional system that will eventually connect the Larry Scott Trail to Discovery Bay as part of the Eaglemount segment of the Olympic Discovery Trail. By constructing the trail segment, pedestrians, runners, bicyclists, equestrians, and other trail users with non-motorized equipment will have a safe Page 2 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 alternative to Highway 20 for travel between the existing trail segments. This project will subsequently increase community use of the existing trail systems by increasing the accessibility of the north and south trails and lowering the overall risk to non-motorized traffic along Highway 20. The proposed 10-foot wide paved pedestrian trail includes two-foot wide gravel shoulders to each side, occasionally increasing to four feet wide on one side to accommodate equestrian use. At other locations, the equestrian trail deviates from the paved trail corridor and follows the existing gravel utility access road or soft surface equestrian-only trail. Combined equestrian trail and utility access road segments on grades over 22 percent will be paved to minimize soil erosion over time. Both the pedestrian and equestrian trails are co-located on the existing utility gravel access road at certain locations. The trails separate from the utility access road in other areas to provide a better user experience that also reduces potential conflicts with maintenance work within the utility corridor. Additionally, two berms will be constructed near the southern trail terminus to create visual and physical separation between adjacent residential properties and the pedestrian trail. The paved pedestrian trail has been designed for compliance with the Americans with Disabilities Act (ADA) with no trail section at greater than five percent slope. Stormwater management design includes dispersing sheet flow from the new trail in vegetated areas, collecting runoff in shallow swales and dispersing into natural vegetated areas, and installing bioinfiltration trenches along paved road areas on South Discovery Road and Four Corners Road where vegetated dispersion is not feasible due to lack of space in the road rights of way. Existing Conditions Summary Wetland and stream habitats were delineated by Otak biologists in March 2022 and May 2023 as documented in the Wetland and Stream Delineation Report (Otak 2023) prepared for the project. The extent of the study area includes the right of way and easement boundary along South Discovery Road and Four Corners Road, the entire width of the utility easement south of Four Corners Road, and the 100- foot wide trail easement corridor from the utility easement to Anderson Lake State Park. Areas outside of the right of way and easements were visually assessed to identify wetlands or streams with buffers that could extend back into the study area. Twenty-one wetlands and three watercourses were identified and delineated (Table 1 and 2). Wetland habitats consist of palustrine forested, scrub-shrub, and emergent Cowardin classes, and hydrogeomorphic classes include riverine, depressional, and slope. Wetlands were rated using the Washington State Wetland Rating System for Western Washington – 2014 Update (Hruby 2014) per JCC 18.22.710 (Classification/designation). All wetlands provide a low (Category IV) to moderate (Category III) level of functions due to impacts from periodic clearing within the utility corridor and logging practices on forestlands. Wetland buffer widths range from 40 to 225 feet per JCC 18.22.730 (Standard Wetland Buffer Widths). Page 3 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 Table 1. Summary of Wetlands in Study Area Note: 1. Wetlands shown in Figure Set 7 in Appendix B of the Wetland and Stream Delineation Report (Otak 2023). 2. Cowardin et al. (1979). Class based on vegetation: PFO = Palustrine Forested, PSS = Palustrine Scrub Shrub, PEM = Palustrine Emergent. 3. Wetlands rated according to Hruby 2014 per JCC 18.22.710 (Classification/designation). 4. Wetland sizes are approximate for wetland extending past the easements based on delineated wetland edges, lidar imagery, NWI mapping, and current aerial imagery. 5. Wetland standard buffer width per JCC 18.22.730 is based on a combination of wetland category, habitat function score, and land use intensity. Watercourses within the study area include three non-fish, seasonal streams with 50-foot buffer widths per JCC 18.22.630(1) (Stream buffers) (Table 2). Two streams were delineated within the utility corridor and trail easements (Stream 1 and Stream 2), and one stream (Stream 3) was observed from the ROW. The boundaries of Stream 3 east of the trail easement near Wetland 20 were estimated using LiDAR and aerial ESRI imagery. Wetland1 Wetland Classification Ecology Rating3 Wetland Size4 (Acres) Standard Buffer Width (feet)5 Cowardin2 HGM Category (Habitat Score) 1 PSS, PFO Depressional III (7) 6.72 110 2 PFO Depressional III (7) 2.04 110 3 PSS Depressional IV (6) <0.01 40 4 PEM, PSS, PFO Depressional III (8) 4.09 225 5 PSS Depressional IV (5) 0.04 40 6 PSS Slope IV (5) 0.12 40 7 PFO Riverine III (6) 0.06 110 8 PSS, PFO Riverine III (8) 0.20 225 9-16 PSS Slope IV (6) 0.09 40 17 PSS Slope IV (6) 0.21 40 18 PFO Depressional III (5) 0.02 60 19 PEM, PSS Depressional III (5) 0.12 60 20 PEM, PSS, PFO Depressional III (7) 0.57 110 21 PSS, PFO Slope IV (5) 0.06 40 Page 4 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 Table 2. Summary of Streams in Study Area Stream Name Stream Characteristics Stream Type1 Buffer (ft) Stream 1 Seasonal, nonfish Type Ns 50 Stream 2 Seasonal, nonfish Type Ns 50 Stream 3 Seasonal, nonfish Type Ns 50 1Stream Type determined per JCC 18.22.630 and confirmed with WDFW. Project Mitigation Statement This conceptual wetland and buffer mitigation plan documents mitigation sequencing per JCC 18.22.740(1) to avoid, minimize, restore, and compensate for impacts to critical areas to the greatest extent possible. Restoration opportunities have been maximized on site to increase the ecological functions of the wetlands, streams, and their buffers so that the project will not result in a loss of wetland function, value or area. Project impacts to regulated wetlands, streams, and associated buffers are shown on the Figure Set 1 in Appendix A, and the proposed mitigation areas are shown on Figure Set 2 in Appendix B. Avoidance and Minimization Measures The trail alignment has been designed to avoid direct wetland and buffer impacts to the maximum extent feasible. The project footprint and grading extent for the new trail was carefully designed to avoid 15 of the 21 wetlands within the narrow trail corridor. Direct impacts to wetlands 2, 4, 5, 7, 9, 10, 11, 12, 13, 14, 15, 18, 19, 20, and 21 have been completely avoided. By locating sections of the proposed pedestrian and equestrian trails within the footprint of the existing utility access road, impacts to wetlands and wetland buffer have been avoided and minimized. The project combines the equestrian and pedestrian trails where feasible. The existing gravel access road and the equestrian trail will be paved on slopes greater than 22 percent to minimize potential long term erosion. Where the equestrian trail separates from the pedestrian trail on slopes less than 22 percent, the equestrian trail will be installed at grade and will be either soft surface (e.g., grass) or gravel. Due to design limitations, including a relatively narrow width of the project corridor, steep slopes at Majestic Hill and ravines, and a requirement of less than five percent slope for ADA compliance for trail safety, some impacts to critical areas are unavoidable. These impacts have been considered and minimized to the greatest extent practicable. Locating the trail and grading footprint away from existing critical areas within the ROW/easement boundary reduced vegetation clearing in several wetlands, streams, and their associated buffers. The crossing at Wetland 1 near the southern trail terminus occurs at a narrow constriction in the center of the ROW. The trail was located at this narrow constriction rather than the edge of the ROW because it results in less wetland conversion. During preliminary design review, the Washington Department of Ecology (Ecology) suggested shifting the trail further south to avoid bisecting the wetland. However, this shift resulted in an additional 385 SF of wetland loss. Because Wetland 1 was recently logged, preserving the maximum amount of wetland area for hydrologic and water quality functions was preferred due to the limited habitat value of Wetland 1. A cross drain will be installed at grade to maintain hydrologic connectivity between the wetland areas. Page 5 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 Temporary wetland impacts have been avoided because grading will be limited to the final project footprint. All temporary buffer and riparian vegetation impacts will be restored in-kind with native plants. Temporary buffer impacts outside of the utility corridor will be restored with trees to restore native forest habitat. Long term temporary buffer impacts have largely been avoided because the trail is generally located within the previously cleared utility corridor and the previously logged forestlands at the south end. Long term temporary buffer impacts from tree removal associated with Wetland 6 are discussed below. Unavoidable Impacts The proposed trail system will result in unavoidable permanent and temporary impacts to wetlands, streams, and associated buffers. Permanent wetland and stream impacts include all areas where grading, gravel shoulders and stormwater infiltration trenches, or paved trail surfaces occur within delineated wetland or stream boundaries. Permanent buffer impacts include all areas within existing buffers where vegetation will be permanently removed and replaced with hard surfaces. Temporary buffer impacts include areas where grading will occur and then the native plant community restored following trail construction. Grading is considered a temporary impact within wetland and stream buffers with herbaceous or shrub habitat because the buffer habitat is already in poor condition from the previous clearing and land disturbance within the utility corridor and the forestlands. Direct Permanent Impacts to Wetlands, Streams, and Buffers Permanent impacts to Category III wetlands total 2,536 square feet (SF), and permanent impacts to Category IV wetlands total 2,771 SF (5,307 SF total). Total wetland impacts are summarized in Table 3 and impacts per individual wetlands are listed in Appendix C. Impacts to wetland buffers total 41,313 SF of temporary impacts and 54,677 SF of permanent impacts (Table 4). Table 3. Wetland Area Impact Summary Impacted Wetland Area by Category1 Permanent Impacts (SF) Impact Type Category III [W1 (1,761 SF), W8 (775 SF)] 2,536 Permanent Category IV [W3 (420 SF), W6 (1,618 SF), W16 (376 SF), W17 (357 SF)] 2,771 Permanent Total 5,307 1 W1 = Wetland 1; W8 = Wetland, etc. Table 4. Wetland Buffer Impacts Summary Buffer Impact Type Area (SF) Temporary 41,313 Permanent 54,677 Stream impacts are summarized in Table 5. Approximately 127 linear feet of Stream 1 will be placed in a 30-inch diameter pipe culvert to accommodate fill in a ravine in order to maintain a less than five percent grade on the paved trail at the stream crossing. Stream 2, an approximately 53-foot long groundwater seep that is incised on the hillside and infiltrates lower on the slope, will be incorporated into the grading Page 6 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 and drainage plans. Total stream area impacts are 360 SF [Stream 1 = 254 SF and Stream 2 = 106 SF). Stream buffer impacts include approximately 5,569 SF of temporary impacts associated with Stream 2 and 3,411 SF of permanent impacts. Buffer impacts associated with Stream 1 are included in the Weland 8 buffer impacts because the 225-foot wetland buffer supersedes the 50-foot stream buffer for a Type Ns stream. Wetland 8 is a riverine wetland along the edges of Stream 1. Table 5. Stream Impacts Summary Stream Name Stream Type Permanent Stream Impact Area (SF) Stream Buffer Impacts Area (Square Feet) Linear Feet Permanent (Square Feet) Temporary (Square Feet) Stream 1 Ns 254 127 Included in wetland buffer impacts Included in wetland buffer impacts Stream 2 Ns 106 53 3,411 5,569 Stream 3 Ns 0 0 0 0 Total 360 180 3,411 5,569 Note: Ns = non-fish, seasonal. Stream Type determined per JCC 18.22.630 and confirmed with WDFW. Indirect Impacts to Wetlands Indirect wetland impacts have not been identified for this project due to the existing wetland disturbances from logging and previous construction of the utility corridor, and the expected infrequent use of the trail corridor relative to a vehicular road corridor. Per Wetland Mitigation in Washington State - Part 1: Agency Policies and Guidance (Version 2) (Ecology, et al. 2021), indirect impacts are adverse effects on wetlands that occur outside the footprint of direct impacts and result in a reduction of wetland hydrologic, water quality, or habitat functions. Indirect impacts to Wetland 3 will not occur because the small 420 SF pocket depression will be filled for the trail. Impacts to offsite Wetland 5 and its buffer have been entirely avoided by the project. Buffer impacts to Wetland 7 and Wetlands 9 through 21 will not result in indirect wetland impacts because of the existing gravel access road and utility corridor that is already disturbed and regularly maintained. Impacts to Wetlands 16 and 17 are confined to the existing utility access road, in which gravel will be added to wet areas. Potential indirect wetland impacts were evaluated at the trail crossings at Wetlands 1, 2, 4, 6, and 8. Indirect wetland impacts to Wetlands 1, 2, and 4 are not anticipated because this section of the trail corridor was recently logged. Construction of the trail in the already cleared wetlands and buffers will not impact wildlife functions because the forest habitat has already been cleared. Amphibians who may use these wetlands will not be impacted because the infrequently used trail corridor will not be a barrier to foraging or migration between wetland areas. Indirect hydrologic and water quality functions are also not anticipated because the existing drainage patterns will be maintained through vegetated stormwater dispersion and infiltration. The impervious paved pedestrian trail is also not pollution generating. Potential indirect impacts to Wetlands 6 and 8 are also not anticipated. Wetland 6 is a slope wetland that receives water from groundwater seeps and precipitation, and is impounded by the existing utility road embankment. A drainage pipe will be installed underneath the trail to convey the surface runoff from the east to the remaining Wetland 6 area west of the trail. Groundwater seeps along the side slopes and precipitation will continue to support this wetland. Additionally, the area of Wetland 6 that will not be Page 7 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 impacted is periodically logged PSS habitat within the utility corridor and provides low habitat value. Long term temporary buffer impacts have been identified for Wetland 6 as discussed in the next section. Wetland 8 is a riverine wetland with PSS habitat along a non-fish habitat seasonal stream (Stream 1) within a ravine. Two culverted crossings already exist in the utility corridor for the access roads, and the project will extend the eastern culvert by 127 linear feet further east. The side slopes of the trail embankment will be vegetated. Additional adverse indirect impacts to the forested portion of Wetland 8 that is offsite and outside of the utility corridor are not anticipated because the groundwater seeps and Stream 1 system are upslope of the trail crossing, and water quality and hydrologic functions will not be impacted. Adverse impacts to wildlife functions are also not anticipated because the utility corridor is actively used to service the overhead power lines and by equestrians, and the proposed infrequently used pedestrian trail is not expected to be a constant source of noise that could affect wildlife behavior. Long term temporary buffer impacts associated with Wetland 8, such as from tree removal or habitat conversion that could result in indirect adverse impacts to Wetland 8, have also not been identified due to the existing disturbed condition and use of these areas. Long Term Temporary Impacts to Wetlands and Buffers Long term temporary wetland impacts are not anticipated for this project because temporary wetland impacts have not been identified. Long term temporary wetland buffer impacts have been identified for Wetland 6, in which trees in the buffer will be removed during grading. The 6,112 SF of temporarily impacted buffer areas will be restored with native trees and shrubs following construction, and will require more than a single growing season to restore the existing habitat. Proposed Conceptual Mitigation Plan The proposed CASP and compensatory wetland and buffer mitigation plan proposes a combination of buffer addition (e.g., averaging and preservation), buffer restoration, buffer enhancement, wetland creation, and wetland enhancement. Permanent and temporary wetland and buffer impacts will be fully offset on-site within the project area. Compensatory mitigation options on site are limited to the trail easement areas outside of the utility corridor at the southern end of the project that were previously logged. Alternative compensatory mitigation options that are preferred to permittee-responsible mitigation, such as purchasing mitigation bank credits or payment to an in lieu fee (ILF) program, are not feasible because Interagency Review Team-approved banks and ILF programs do not serve the rural project area. The nearest bank or ILF program is the Hood Canal Coordinating Council’s ILF Program, but its service area does not include the Discovery Bay basin. Due to the existing disturbed condition of the wetlands, streams, and buffers that will be impacted and the overall trail corridor, permittee-responsible mitigation onsite was determined to be the most suitable form of compensatory mitigation to offset project impacts within the watershed. Wetlands Wetland impacts and required mitigation ratios per JCC Table 18.22.740(1) and Wetland Mitigation in Washington State, Part 1: Agency Policies and Guidance (Ecology, et al 2021) are summarized in Table 6. The JCC mitigation requirements are consistent with the 2021 interagency guidance. Page 8 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 Table 6. Wetland Impacts and Mitigation Summary Impacted Wetland Area by Category1 Permanent Impacts Area (SF) Impact Type Required Mitigation Ratio2 (C/R, E) Required Minimum Wetland Creation/Restoration (SF) Required Minimum Wetland Enhancement (SF) Category III (W1, W8) 2,536 Permanent 1:1 C/R plus 4:1 E 2,536 10,144 Category IV (W3, W6) 2,771 Permanent 1:1 C/R plus 2:1 E 2,771 5,542 Total 5,307 5,307 15,686 1 W1 = Wetland 4, W8 = Wetland 10, etc. 2 Mitigation ratios per JCC 18.22.740 (Table 18.22.740(1); C/R = creation/re-establishment; E = enhancement. Total proposed compensatory mitigation is summarized in Table 7 (Wetland Mitigation Summary). Approximately 5,586 SF of wetlands will be created to offset the permanent impacts to 5,307 SF of wetlands by the project. An additional 8,766 SF of wetlands will be enhanced by removing Himalayan blackberry canes and planting native willow species to increase plant species richness and diversity. Proposed wetland mitigation is confined to the southeast section of the trail corridor at the trail terminus where overhead utilities are not present, and the mitigation areas can be placed within a conservation easement for permanent protection. Table 7. Proposed Wetland Mitigation Summary Mitigation Type Minimum Required Mitigation (SF) Proposed Mitigation Area (SF) Credit Balance (SF) Wetland Enhancement 15,686 8,776 -6,910 Wetland Creation 5,307 5,586 +279 Total 14,362 -6,631 The proposed 5,586 SF of wetland creation will occur adjacent to Wetland 4 and east of the southern trail terminus (Appendix B – Figure 4). A raised linear mound, potentially an old logging road, will be excavated approximately three feet to match the adjacent wetland areas (Photos 1 and 2). Wetland 4 will be used as a biological benchmark (e.g., reference) for the wetland creation for the target excavation depths and anticipated hydrological conditions. All tree stumps and root wads from the logging activities will be re-used on site and aligned perpendicular to the flow of water to retain areas of ponded water similar to conditions in Wetland 4 (Photo 3). Low flow channels will be plugged with logs and stumps to disperse water in the wetland creation area and create microhabitats for amphibians. Existing tree saplings will be transplanted in the buffer areas, and the created wetland area will be planted with red- twig dogwood (Cornus sericea), Douglas-spiraea (Spiraea douglasii), and willows (Salix sp.) that are tolerant of a variety of hydroperiods and occasional prolonged inundation. Approximately 500 cubic yards of excavated material would be re-used onsite for the visibility berms to the west. Page 9 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 Photo 1. View looking west of the trail corridor and proposed area for wetland creation. The edge of Wetland 4 is visible on the right side of the photo, and Wetlands 2 and 3 are visible in the background and left side of the photo. Photo 2. View looking east of the proposed wetland creation area south of Wetland 4. The Wetland 4 boundary is delineated by the pink flag in the center of the photo. The uplands to the right of the wetland boundary would be excavated to match the Wetland 4 elevation. The wetland creation area was recently logged. Slash piles and tree stumps would be retained on site for habitat features. Page 10 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 Photo 3. View of aquatic habitat in Wetland 4 dominated by water parsley interspersed with areas of ponding. The proposed wetland mitigation has a credit deficit of -4,258 SF per JCC Table 18.22.740(1) and Wetland Mitigation in Washington State, Part 1: Agency Policies and Guidance (Ecology, et al 2021). The required mitigation ratios incorporate a greater than 1:1 ratio to account for temporal loss of wetland area and functions, and the risk of successfully creating the intended wetland habitats. However, the proposed mitigation is satisfactory to ensure no net loss of wetland values and functions for three reasons: 1) there will be no temporal loss of wetlands (e.g., impacted wetlands have been cleared previously and the mitigation wetlands will be created within the trail corridor during trail construction); 2) the proposed mitigation is low risk (e.g., PSS habitat rather than PFO habitat as the target); and 3) the mitigation wetlands have a high probability of success due to existing wetlands and adjacent source of water in Wetland 4. Additional compensatory wetland mitigation within the existing utility corridor is not feasible because of utility standards which preclude tree growth and require vegetation management to maintain the overhead utilities. Additional potential wetland creation areas in the southeast trail section adjacent to the recently logged forestlands were considered a liability for long term success and protection because they abut the forestlands that will be cleared in the future. There may also be an inadequate source of water since creating wetlands in this area at the top of the gently sloping hillside would rely solely on groundwater without any other source of water other than precipitation. The proposed wetland creation area at the southern trail terminus is buffered by forested state park land to the south, and wetlands to the north and east (Wetland 4). The next trail extension will continue south in Anderson Lake State Park, and will not directly impact the proposed compensatory wetland creation area. Wetland and Stream Buffers All 41,313 SF of temporary wetland buffer impacts and 5,569 SF of temporary stream buffer impacts will be restored on site, in-kind, and within one growing season after project completion. Buffer impacts are Page 11 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 mainly to previously cleared areas that have been maintained as shrub or grass habitat (e.g., the utility corridor) or to early successional scrub habitat (e.g., recently logged forestlands). Of the 41,313 SF of temporary wetland buffer impacts, approximately 6,112 SF will be long term due to tree clearing necessary for grading at Wetland 6. The long term buffer impacts are proposed to be mitigated for at a 2:1 ratio. To offset the 54,677 SF of permanent buffer impacts plus the 6,112 SF of long term temporary buffer impacts (60,789 SF total), proposed buffer mitigation includes 24,584 SF of buffer addition (e.g., averaging) in the southern trail easement and 38,440 SF of buffer enhancement. All buffer averaging and enhancement mitigation areas were last logged in 2016, and will be taken out forest production. Existing conditions in the areas proposed for mitigation are shown in Photo 4. Photo 4. View looking east of typical conditions with invasive plant cover in the recently logged forest lands proposed for buffer mitigation near the southern trail terminus. Invasive plants include Scot’s broom and Himalayan blackberry. Buffer enhancement actions include removing Himalayan blackberry canes and other invasive plants, and re-planting with a variety of native trees and shrubs to restore native buffer habitat. Existing native vegetation would remain. The 24,584 SF of buffer addition (e.g., averaging) will be enhanced with native plants and invasives removal as well. The buffer mitigation areas were re-planted with Douglas-fir (Psuedotsuga menziesii) saplings after the last harvest in July 2016, but Himalayan blackberry and Scot’s broom threatens their survival and species diversity is minimal from the logging activities and replanting over time. Creation of a contiguous wetland buffer throughout the southeast section of the trail corridor will protect mature forested wetland and upland habitat within Anderson Lake State Park to the south from future logging activities. Buffer mitigation actions are summarized in Tabel 8. Page 12 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 Table 8. Buffer Mitigation Summary Impacted Buffer Area (SF) Mitigation Type Proposed Buffer Mitigation (SF) 60,789 (54,677 SF of permanent impacts plus 6,112 SF of long term impacts) Enhancement 38,440 Addition/Averaging 24,584 Total 63,024 Note: Mitigation includes restoration of 41,313 SF of temporary buffer impacts. The proposed 63,024 SF of buffer enhancement and buffer addition/averaging with enhancement exceeds the 60,789 SF of permanent and long term buffer impacts and will not result in a net loss of buffer functions. Implementation Plan and Schedule The proposed project is scheduled for construction in 2024. Implementation of the proposed mitigation actions will occur concurrently with construction. Site preparation will include staking the clearing and grading limits prior to any earthwork to minimize the potential for unauthorized vegetation removal in regulated areas. Following trail construction and grading activities, all exposed soils will be stabilized with a final Best Management Practice (BMP) such as seeding or mulch. The tree and shrub buffer restoration and enhancement areas will then be planted with woody material during the following planting season (estimated to be winter 2024-2025). Prior to planting, all wetland and buffer mitigation areas will be cleared of invasive plants through either manual removal or spraying with an herbicide. Existing early successional native tree sapling and shrubs will be marked for retention prior to removal of the invasive plants. A project biologist or county representative will be on site during installation of the wetland creation and buffer enhancement and restoration areas to ensure the proposed plan is implemented in accordance with the mitigation goals. An As Built Plan will be prepared following construction to document the baseline conditions prior to initiating performance monitoring over the following ten years. Plant species composition in the wetland creation and enhancement areas will include red-twig dogwood, Douglas-spiraea, and willows that are tolerant of a variety of hydroperiods and occasional prolonged inundation. Plants are anticipated to be installed as bare root material or live stakes due to the rural location of the project area and the lack of irrigation to support larger plant stock. Trees will be installed eight feet on-center and shrubs will be installed four feet on-center. Upland buffer areas will be restored or enhanced with native trees and shrubs, such as grand fir (Abies grandis), Western red cedar, Sitka spruce (Picea sitchensis), beaked hazelnut (Corylus cornuta), red flowering currant (Ribes sanguineum), and red-twig dogwood. Mitigation Goals, Objectives, and Performance Standards The primary goal of the proposed mitigation is to replace the functions and values of all temporarily and permanently impacted critical areas in the project area. To accomplish these goals, the proposed mitigation has the following goals, objectives, and performance standards: • Create a minimum of 5,586 SF of PSS wetland habitat. • Enhance 8,776 SF of existing wetland habitat by removing invasive species and supplementing with native plants to increase plant diversity and habitat complexity. Page 13 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 • Enhance 63,024 SF of existing and averaged wetland buffer by removing invasive plants from the formerly logged areas and installing native plants to increase plant diversity and habitat complexity. • Restore a total of 41,313 SF of temporarily impacted wetland buffers. The following performance standards (Table 9) are proposed to ensure success of the mitigation project and enhancement plantings, and ensure that the proposed mitigation goals and objectives are achieved. Performance standards will be amended for the final compensatory wetland mitigation plan and CASP, and will be updated specific to wetland creation and enhancement areas and buffer mitigation areas. The performance standards reflect a 10 year monitoring period for the temporarily impacted Wetland 6 buffer and the wetland and buffer compensatory mitigation areas at the south end of the project. Temporarily impacted herbaceous communities in the utility corridor will be monitored for three years following site stabilization. Table 9. Performance Standards Goal Year Description Plant Survival 1 Survival of planted vegetation in the mitigation area will be 100 percent. The contractor is responsible for ensuring this performance standard is met. Plant Survival 2 Survival of planted vegetation in the mitigation area will be 90 percent. The County is responsible for ensuring this performance standard is met. Plant Survival 3 Survival of planted vegetation in the mitigation area will be 85 percent. The County is responsible for ensuring this performance standard is met. Plant Survival 5 Survival of planted vegetation in the mitigation area will be 80 percent. The County is responsible for ensuring this performance standard is met. Plant Absolute Cover 7 65% absolute cover by installed and volunteer native woody plants. Plant Absolute Cover 10 75% absolute cover by installed and volunteer native woody plants. Plant Diversity All Years A minimum of four native trees or shrubs will have at least five percent cover in wetland and buffer enhancement areas. In intended forest communities, tree species must have a minimum of 30% cover. Invasive Vegetation All Years Non-native, invasive species will not exceed 10 percent aerial cover in restoration areas. Non-native, invasive species with a 10 percent cover threshold may include, but are not limited to: Himalayan blackberry, cutleaf blackberry (Rubus laciniatus), Canada thistle (Cirsium arvense), bull thistle (Citsium vulgare), and reed canarygrass (Phalaris arundinacea). Invasive species with zero cover tolerance include knotweeds (Fallopia sp,), scotch broom (Cytisus scoparius), and English holly (Ilex aquilinum). Page 14 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 The County is responsible for ensuring this performance standard is met. Invasive Vegetation All Years Regulated class A, B, and C noxious weeds as defined by the County Noxious Weed Control Board will be monitored and removed. Wetland Hydrology All Years In years with normal precipitation, within the created wetland area, the area will be inundated or soils will be saturated within twelve inches of the soil surface for at least 30 consecutive days during the growing season. Maintenance and Monitoring Plan The mitigation area will be monitored during and after construction pursuant to JCC 18.22.740 (Mitigation). During construction, the site will be monitored to ensure that Best Management Practices (BMPs) are observed, and the site is constructed as designed. After construction and plant installation, an as-built mitigation report will be prepared as required per JCC 18.22.965(6) to document the Year 0 conditions. The wetland creation areas and buffer enhancement areas will be monitored for ten years following installation. An outline of a site monitoring and maintenance schedule will be provided to track subsequent monitoring to ensure that the goals and objectives of the mitigation plan are being met. Site inspections shall occur semi-annually, and an annual monitoring report will be submitted to the permitting agencies with jurisdiction by the end of each monitoring year in Years 1, 2, 3, 5, 7, and 10. Monitoring will include photopoints to track annual development pursuant to JCC 18.22.965(6) (CASP), census surveys to determine percent survival using line intercept method, and ocular areal estimates of invasive species cover. Maintenance actions will include treating aggressive invasive species through both manual removal methods and herbicide application. Contingency Plan If monitoring indicates a failure to meet performance standards listed above, action will be taken by the applicant. Events outside of the County’s control may occur, including high mortality resulting from improper installation, diseased or infested plants, drought, or extreme weather. If more than 25 percent of new plantings die in a single year, the cause of the high losses will be investigated and corrected before dead plants are replaced. Dead plant material will only be removed after that year’s scheduled monitoring. However, plant mortality can also occur from plant competition with surrounding native plants over time. Contingency measures may include installing additional plants to bring the planting schedule back into original specifications. Correction measures may also include watering by truck, soil amendments, or different plant species selection. Long Term Management Plan and Site Protection Long term management of the compensatory mitigation area at the south end of the project is anticipated to be coordinated by Jefferson County. Removal of trash and invasives plants along the trail corridor may be coordinated with volunteer groups similar to other Olympic Discovery Trail sections. Long term site protection will include placing a restrictive covenant or conservation easement on the mitigation areas to prevent any development or other impacts in the future. Jefferson County owns the proposed mitigation area now, and the restrictive covenant or conservation easement will be filed and recorded at the County to run with the land. Critical areas signs will be posted around the perimeter of the mitigation area, including along the northern property boundaries that face the privately-owned logging lands, to prevent unauthorized logging or other clearing activities in the future. Page 15 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 References [Ecology] Washington State Department of Ecology, U.S. Army Corps of Engineers Seattle District, and U.S. Environmental protection Agency Region 10. 2021. Wetland Mitigation in Washington State – Part 1: Agency Policies and Guidance (Version 2). Washinton State Department of Ecology Publication #21-06-003. Page 16 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 Appendix A – Proposed Critical Area Impacts Figure Set Page 17 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 Appendix B – Proposed Mitigation Areas Figure Set Page 18 of 18 Olympic Discovery Trail – Conceptual CASP October 20, 2023 Appendix C – Individual Wetland Impacts Table 1. Wetlands shown in Figure Set 7 in Appendix B of the Wetland and Stream Delineation Report (Otak 2023). 2. Cowardin et al. (1979). Class based on vegetation: PFO = Palustrine Forested, PSS = Palustrine Scrub Shrub, PEM = Palustrine Emergent. 3. Wetlands rated according to Hruby 2014 per JCC 18.22.710 (Classification/designation). 4. Wetland sizes are approximate for wetland extending past the easements based on delineated wetland edges, lidar imagery, NWI mapping, and current aerial imagery. Wetland1 Wetland Classification Ecology Rating3 Wetland Size4 (Acres) Direct, Permanent Wetland Impacts (SF) Notes Cowardin2 HGM Category (Habitat Score) 1 PSS, PFO Depressional III (7) 6.72 1,761 Logged in July 2016; assumed to be in Anderson Lake sub- basin of Discovery Bay 2 PFO Depressional III (7) 2.04 0 - 3 PSS Depressional IV (6) <0.01 (420 SF) 420 Depression between Wetlands 2 and 4; assumed to be in Anderson Lake sub- basin of Discovery Bay 4 PEM, PSS, PFO Depressional III (8) 4.09 0 - 5 PSS Depressional IV (5) 0.04 0 - 6 PSS Slope IV (5) 0.12 1,618 Depression with no outlet 7 PFO Riverine III (6) 0.06 0 - 8 PSS, PFO Riverine III (8) 0.20 775 Along Stream 1 (UNT to Discovery Bay) 9-15 PSS Slope IV (6) 0.05 0 - 16 PSS Slope IV (6) 0.04 (1,648 SF) 376 17 PSS Slope IV (6) 0.21 357 - 18 PFO Depressional III (5) 0.02 0 - 19 PEM, PSS Depressional III (5) 0.12 0 - 20 PEM, PSS, PFO Depressional III (7) 0.57 0 - 21 PSS, PFO Slope IV (5) 0.06 0 - Total 5,307