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HomeMy WebLinkAboutYear-2 Monitoring Report February 2, 2021 Becky Hardi UW Medicine | Valley Medical Center Facilities Project Manager 400 S 43rd Street Renton, WA 98055 Via email: Becky_Hardi@Valleymed.org Re: Valley Medical Center Parking Garage Stream Buffer Mitigation, Year-2 Monitoring Report The Watershed Company Reference Number: 160113 Dear Becky: On October 13, 2020, Senior Ecologist, Ryan Kahlo, visited the Valley Medical Center stream buffer mitigation area to monitor the performance of the areas in accordance with the approved mitigation plan. This report documents the findings of the inspection and provides maintenance recommendations to help the site progress towards future goals and performance standards. Project History The mitigation plan was developed to allow for a parking garage expansion and associated grading activities within a stream buffer. The plan included buffer reductions with enhancement, buffer averaging with enhancement, and restoration of temporary buffer impacts, each of which is a separate, distinct area. The buffer enhancement area (Area A) measures 3,896 square feet; the temporary buffer impact area (Area B) measures 6,271 square feet; and the buffer addition with enhancement area (Area C) measures 1,948 square feet. Area A was installed in the fall-winter of 2017-2018, whereas Areas B and C were installed in late 2018. The as-built condition was documented in the as-built report, Valley Medical Center Parking Garage Stream Buffer Mitigation, As-built Report (The Watershed Company. February 25, 2019). The project is currently in Year-2 of a five-year monitoring program. Project Goals and Performance Standards The following goals and performance standards apply collectively to the planting areas. Buffer Mitigation Year-1 Monitoring Report Becky Hardi, Valley Medical Center February 2, 2021 Page 2 Mitigation Goals and Objectives 1. Within the proposed restoration areas, establish dense native vegetation that is appropriate to the eco-region and site. 2. Where indicated on the plan, areas within the restoration area will remain substantially vegetated with a preponderance of native trees, shrubs, and groundcovers and will contain little invasive or noxious weed cover. Performance Standards 1. Survival: Achieve 100% survival of installed tree and shrub plantings by the end of Year 1. This standard can be met through plant establishment or through replanting as necessary to achieve the required numbers. Individual groundcover plantings cannot be feasibly counted. Therefore, groundcovers shall be monitored for areas of obvious mortality and appropriate replacement quantities recommended by the restoration professional to ensure satisfaction of the native cover standard (below). 2. Native Cover: a. Achieve 50% cover of native trees, shrubs, and groundcovers by Year 3. Native volunteer species (but not grasses) may count towards this cover standard. b. Achieve 80% cover of native trees, shrubs, and groundcovers by Year 5. Native volunteer species (but not grasses) may count towards this cover standard. Trees and shrubs must account for a minimum of 65% cover. c. Species diversity: Establish at least three native tree species, four native shrub species and one native groundcover species by Year 3 and maintain this diversity through Year 5. Native volunteer species (but not naturalized grasses) may count towards this standard. d. Invasive cover: Aerial cover for all non-native, invasive and noxious weeds within the buffer planting areas will not exceed 10% at any year during the monitoring period. Invasive plants are defined as those listed by the Washington State Noxious Weed Control Board as Class A, B, or C. Results The mitigation areas are performing well. Native vegetation is establishing, particularly in the canopy and shrub layers. The planting areas are on-schedule, or even slightly ahead of schedule, as related to native cover. On average, the site has achieved Buffer Mitigation Year-1 Monitoring Report Becky Hardi, Valley Medical Center February 2, 2021 Page 3 approximately 51 percent native woody cover. While there is no native cover standard for year-two, the site has already achieved the year-three standard (50 percent). Invasive species coverage is within the allowable limits of the performance standards. On average, coverage by invasive species is approximately four percent, including Himalayan blackberry and Canada thistle. No areas of substantial mortality or plant stress were noted. See Table 1 for a summary of native and invasive cover data by monitoring transect. Table 1. Monitoring Transect Summary Transect Transect Length Native Cover Invasive Cover T-1 100 feet 49.5% 0.0% T-2 100 feet 64.3% 7.3% T-3 100 feet 32.9% 1.5% T-4 100 feet 54.4% 0.0% T-5 70 feet 34.6% 0.4% T-6 70 feet 38.9% 10.2% Average 50.8% 3.6% *Average is weighted by transect length Area A (Buffer Enhancement Area) Area A currently averages approximately 57 percent native cover. The black cottonwood trees have become well-established and are approaching 20 feet in height. Other prevalent species performing well at this planting area include bigleaf maple, salmonberry, snowberry, Nootka rose, and sword fern. Invasive species coverage measured approximately four percent on average and is composed of Canada thistle and Himalayan blackberry. The blackberry is encroaching from the perimeter and should be cut back from the planting area as part of the routine site maintenance. Mountain beaver browsing observed in previous monitoring inspections continues, although the damage to the installed plantings is less widespread than in previous years. Buffer Mitigation Year-1 Monitoring Report Becky Hardi, Valley Medical Center February 2, 2021 Page 4 Table 2. Area A Cover Measurements Transect Native Species Present Invasive Species Present Percent Cover Native Invasive T-1 Bigleaf maple, black cottonwood, salmonberry, Nootka rose, snowberry, sword fern None 49.5% 0.0% T-2 Bigleaf maple, black cottonwood, salmonberry, Nootka rose, snowberry, osoberry sword fern Canada thistle 64.3% 7.3% Average 56.9% 3.6% Area B (Temporary Impact Area) Area B is performing well, with native cover slightly ahead of where it typically is in the second year post-installation. Native cover averages approximately 44 percent, with bigleaf maple, black cottonwood, twinberry, snowberry, and sword fern being the most prevalent species. Bigleaf maple volunteers are spreading into Area B and should be allowed to establish as long as they do not begin to form a monoculture. Invasive species coverage measured approximately one percent on-average. Himalayan blackberry and trace amounts of Canada thistle were observed in the planting area. The poison hemlock noted in previous monitoring inspections was not present in appreciable quantities, although the species should continue to be monitored for any reintroduction. Table 3. Area B Cover Measurements Transect Native Species Present Invasive Species Present Percent Cover Native Invasive T-3 Bigleaf maple, black cottonwood, beaked hazelnut, Nootka rose, snowberry, osoberry sword fern Himalayan blackberry 32.9% 1.5% T-4 Bigleaf maple, black cottonwood, black twinberry, snowberry, osoberry sword fern None 54.4 0.0% Average 43.7% 0.75% Area C (Buffer Addition Area) Area C is performing well. This area has experienced very little mortality, and the plantings generally appear healthy and vigorous. Native cover is not as high as observed in Areas A and B, but it is still on-track to achieve future cover standards. Currently, native cover is approximately 37 percent. Prevalent native vegetation in Area Buffer Mitigation Year-1 Monitoring Report Becky Hardi, Valley Medical Center February 2, 2021 Page 5 C includes black cottonwood, bigleaf maple, Douglas-fir, tall Oregon grape, sword fern, salmonberry, and snowberry. Invasive species cover approximately five percent of the planting area. Invasive species observed in Area C include Himalayan blackberry, Canada thistle, and English ivy. English ivy is prevalent in the forested areas adjacent Area C and should be cut back from the planting area. Table 4. Area C Cover Measurements Transect Native Species Present Invasive Species Present Percent Cover Native Invasive T-5 Black cottonwood, bigleaf maple, snowberry, Nootka rose, tall Oregon grape, sword fern Himalayan blackberry 34.6% 0.4% T-6 Douglas-fir, Nootka rose, osoberry, snowberry, salmonberry, sword fern Himalayan blackberry, Canada thistle 38.9% 10.2% Average Recommendations • Remove all invasive species by hand from the planting areas, making sure to grub out the roots. Particular attention should be paid to Himalayan blackberry, Canada thistle and English ivy. Cut back blackberry canes and ivy vines back at least 10 feet from planting areas. • Continue to monitor invasive species presence, including poison hemlock, and treat/remove as necessary. Please call if you have any questions or if we can provide you with any additional information. Sincerely, Ryan Kahlo, PWS Senior Ecologist Enclosures: Photopoints Photopoint 1 (Area A) Photopoint 2 (Area B) Photopoint 3 (Area B) Photopoint 4 (Area B) Photopoint 5 (Area C) Photopoint 6 (Area C) Photopoint 7 (Area C)