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HomeMy WebLinkAboutRS_Critical_Areas_Report_and_Mitigation_Plan_250401_v2Boulevard Lane Park Critical Areas Page 1 June 2023 Department of Natural Resources and Parks Parks and Recreation Division King Street Center, KSC-NR-5702 201 South Jackson Street, Suite 5702 Seattle, WA 98104-3855 206-477-4527 TTY Relay: 711 June 30, 2023 TO: City of Renton Permitting Division FM: Lindsey Miller, Wetlands Ecologist, King County Parks and Recreation Division RE: Critical Areas Report and Mitigation Plan: Boulevard Lane Park Play Area Rehabilitation and Restroom Demolition Project Background This project was identified in the 2020-2025 King County Parks Levy as part of the Play Area Rehabilitation Program which aims to routinely replace and upgrade aging playgrounds. The equipment at Boulevard Lane Park is reaching the end of its life and needs to be replaced for safety reasons. This park is located in the City of Renton jurisdiction. In addition, a derelict non-functioning restroom building adjacent to the play area will be demolished. The full project scope includes replacing aging playground equipment and stormwater drainage entirely within the existing playground footprint (2,450 square feet), installing turf safety surfacing, removal of two treated log retaining walls, replacing the existing asphalt playground access pathway for ADA compliance, demolishing an adjacent old non-functioning restroom building, and replanting disturbed area with native species. The existing pathway is not going to be moved or expanded. The playground footprint will not be moved or expanded; however, portions of the concrete border may need to be replaced if it is damaged or broken. Two existing benches also need to be relocated to outside the play area footprint for safety (they are currently located within the footprint). The project will also include removal of two trees of concern and replanting approximately 3,500 square feet of disturbed area and lawn within critical area buffer with native species. Existing Conditions Boulevard Lane Park is located almost entirely in critical area buffers. The developed portion of the park contains a play area, benches, a restroom (currently closed and to be demolished), sports court, asphalt and concreate walkways, landscaping, and maintained lawn area. In 2014, The Watershed Company prepared the Soos Creek Trail Extension Wetland and Stream Delineation Report (Addendum 1) which included the area around Boulevard Lane Park. The information in this report was prepared in 2014; however, King County Parks ecologist performed a field reconnaissance on August 4, 2022 and verified that the existing conditions described in that report are Boulevard Lane Park Critical Areas Page 2 June 2023 still consistent with existing conditions in Boulevard Lane Park. For this reason, the delineations shown and described in that report are adopted for this project and were not redone for this project. The delineations in the Boulevard Lane Park area are shown on Sheet 2 in Appendix A of the Soos Creek Trail Extension Wetland and Stream Delineation Report (Addendum 1). The additional conditions identified and verified during the field reconnaissance are described below. Streams Boulevard Lane Park is located in the Duwamish-Green Water Resource Inventory Area 9 and partially within the buffer for Big Soos Creek. Big Soos Creek flows through a heavily vegetated wetland (referred to as Wetland A) located to the west of the developed park area. The stream is classified as a Type F stream with a 115-foot buffer under Renton Municipal Code (RMC 4-3-050G). Downstream segments of Big Soos Creek are documented to contain coho and Chinook salmon, as well as steelhead trout. It is assumed these species are potentially present in the stream near Boulevard Lane Park as well (The Watershed Company 2014). The ordinary high water mark for Big Soos Creek is poorly defined in the vicinity of Boulevard Lane Park where it disperses within Wetland A, providing the primary source of hydrology (The Watershed Company, 2014); therefore, the ordinary high water mark for Big Soos Creek was not delineated in this area. The approximate centerline of Big Soos Creek is shown on Figure 1. Wetlands Boulevard Lane Park is located within the buffer of the wetland identified as Wetland A in the Soos Creek Trail Stream and Delineation Report (The Watershed Company 2014) (Figure 1) and is identified as Wetland W63K in City of Renton Critical Areas GIS Maps. In 2014, this wetland was rated in that report as Category I under the 2004 Wetland Rating System for Western Washington. During the field reconnaissance on August 4, 2022, Parks ecologist visually confirmed, that the wetland boundary is still in approximately same location and condition as described in the 2014 report. The wetland edge is distinct near the play area due to an abrupt topography change, indicators of hydrology, and presence of hydrophytic vegetation. The project is not located in the wetland itself, only the buffer. For this reason, the wetland was not re- delineated for this project. The wetland also was not re-rated under the 2014 Wetland Rating System for Western Washington because the western edge of the play area is less than 20 feet from the edge of the wetland. The far side of the play area is approximately 90 feet from the edge of the wetland. If rerated under the new rating system, it is likely this wetland would still be classified as a Category I wetland or at a minimum a Category II wetland. Renton Municipal Code 4-3-050G specifies a minimum 100-foot buffer for Category II wetlands and up to a 200-foot buffer for Category I wetlands. Based on these buffers widths, project area is still located in the wetland buffer regardless of whether the wetland is a Category I or Category II. Therefore, King County Parks is assuming that the entire play area and restroom demolition is located within the buffer of Wetland A. Figure 1 shows the buffer if Wetland A is assumed to be a Category I wetland under the 2014 rating system with the maximum buffer width. Floodplain Boulevard Lane Park Critical Areas Page 3 June 2023 A mapped FEMA 100-Year Floodplain (FEMA Zone – AE) extends into the western edge of the park and play area (Figure 1). Project Impacts This project avoids all direct impacts to Big Soos Creek and Wetland A. No work will occur within the wetland or stream. The project in relation to critical areas is shown in Figure 2. The project is located with in the critical area buffer but has been designed to minimize impacts to buffer by keeping the play area rehabilitation entirely within the existing footprint (2,450 square feet). The only adjustment, that is required for safety reasons, is to relocate the two existing benches from inside the play area footprint to outside the play area footprint. The new concrete pads needed to install the benches are approximately 80 square feet and they will be installed immediately adjacent to the playground in an area that is currently maintained lawn. Existing drainage pipes and/or catch basins within the existing play area footprint may be replaced if they are damaged or nonfunctional, but existing drainage patterns will be maintained. Approximately 785 square feet of existing asphalt pathways will be replaced, and root barrier installed, but the pathway will not be relocated or expanded. The restroom demolition will remove a building, two trees, a treated wood retaining wall, and approximately 915 square feet of impervious surface from the critical area buffer. One of the trees to be removed is considered a high-risk tree whose root zone will be impacted by the restroom demolition. The second tree is not high risk but needs to be removed for maintenance purposes, because removal of the aging treated wood timber retaining wall associated regrading would damage its roots. The roots of this tree have also reached inside the play area and will be impacted by the new equipment and safety surfacing installation. Mitigation To mitigate for leaving the existing the play area and pathway footprints in the critical area buffer, approximately 3,500 square feet of disturbed area (previously associated with the restroom footprint) and lawn in the buffer will be restored with native plant species. The planting plan with species and quantities are shown on the design drawings. This results in a net gain of vegetated buffer area providing improved habitat function as part of this project. Table 1 below summarizes the impacts and proposed mitigation for this project. Table 1: Critical Area Buffer Impacts and Mitigation Critical Area Buffer Impact Buffer Mitigation Existing Play Area (to be left in same footprint) 2,450 sf Buffer Restoration removal of restroom removal of treated wood replanting 3,500 sf New Concrete Bench Pads 80 sf Existing Asphalt Pathway Replacement (to be left in same footprint) 785 sf Total Buffer Impact 3,315 sf Total Buffer Mitigation 3,500 sf Tree Removal 2 Trees Plant New Trees 4+ Trees Boulevard Lane Park Critical Areas Page 4 June 2023 Figure 1: Boulevard Lane Park Vicinity Map with Critical Areas Figure 2: Boulevard Lane Park Site Plan with Critical Areas Addendum 1 - Soos Creek Trail Wetland and Stream Delineation Report (2014)