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HomeMy WebLinkAboutYear-1 Monitoring Report February 7, 2020 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-1 Monitoring Report The Watershed Company Reference Number: 160113 Dear Becky: On September 19, 2019, 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-1 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 7, 2020 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 have experienced notable mortality, particularly the buffer enhancement area and the temporary impact area. Mortality appears to be a result of two primary factors: wetter than anticipated conditions and mountain beaver foraging. Buffer Mitigation Year-1 Monitoring Report Becky Hardi, Valley Medical Center February 7, 2020 Page 3 The site has experienced a 77 percent survival rate, applicable to all species as well as tree and shrub species only (per Performance Standard 1). In general, invasive species cover is low, and surviving plants appear healthy. Area A (Buffer Enhancement Area) Area A has experienced approximately 61 percent survival, including 64 percent of trees and shrubs. The most substantial mortality has occurred with Douglas-fir, tall Oregon grape, osoberry, and, to a lesser extent, salmonberry. Sword fern has also experienced substantial mortality, although the species is not held to a survival standard. Note that mountain beavers are eating the sword fern fronds without killing the plant, making an individual count of the species difficult. In general, the wetter than anticipated conditions and mountain beaver foraging appear to be the primary contributors to mortality in this area. Given the predominance of mountain beaver habitat in the surrounding areas, it is not feasible to try and eliminate their presence. Plant replacements should focus on species that are not a preferred food source and can tolerate slightly wetter conditions; salmonberry, sword fern, and Oregon grape are all preferred food for mountain beavers. Invasive species coverage is estimated at less than five percent, with some Canada thistle and Himalayan blackberry present. The blackberry is encroaching from the perimeter and should be cut back from the planting area. Table 1. Area A Plant Quantities Observed Species Plan Quantity Year-1 Quantity Percent Survival Bigleaf maple 18 11 Douglas-fir 10 3 Black cottonwood 10 10 Baldhip rose 18 21 Tall Oregon grape 18 5 Osoberry 18 6 Salmonberry 18 9 Snowberry 18 17 Sword fern 150 87 Total 278 169 61% (64% tree/shrub) Area B (Temporary Impact Area) Area B is experiencing similar issues as Area A, with mountain beaver activity contributing significantly to plant mortality; Area B is not exhibiting wetter than anticipated conditions. Area B has experienced approximately 65 percent survival, including 72 percent of trees and shrubs. Mortality is highest with osoberry, salmonberry, tall Oregon grape, and, to a lesser extent, Douglas-fir. Bigleaf maple Buffer Mitigation Year-1 Monitoring Report Becky Hardi, Valley Medical Center February 7, 2020 Page 4 volunteers are spreading into Area B and should be allowed to establish as long as they do not begin to form a monoculture. A similar approach to Area A is recommended for Area B. Replacement plants should not be a preferred food source for mountain beavers and should not include species that have consistently performed poorly in this location. Invasive species coverage in Area B is approximately five percent and includes mostly Himalayan blackberry and English ivy encroaching from the perimeter. Table 2. Area B Year-1 Plant Quantities Observed Species Plan Quantity Year-1 Quantity Percent Bigleaf maple 24 34 Douglas-fir 13 8 Black cottonwood 13 15 Baldhip rose 26 23 Tall Oregon grape 26 14 Osoberry 26 7 Salmonberry 26 5 Snowberry 26 24 Sword fern 300 184 Total 480 314 65% (72% trees/shrubs) Area C (Buffer Addition Area) Area C is performing very well. This area has experienced very little mortality and, due to overplanting of sword fern and lateral spreading of baldhip rose, is exceeding 100 percent survival. Total survival is approximately 114 percent, with 99 percent survival of trees and shrubs. Plantings generally appear healthy and vigorous. The mountain beaver activity observed in other areas is not as prevalent in Area C. Invasive species cover is less than 10 percent, but Canada thistle, poison hemlock, English ivy, and Himalayan blackberry should be monitored; ivy and blackberry are encroaching from the perimeter. No additional plantings are recommended for this area. Table 3. Area C: Year-1 Plant Quantities Observed Species Plan Quantity Year-1 Quantity Percent Bigleaf maple 15 13 Douglas-fir 9 9 Black cottonwood 9 8 Baldhip rose 18 32 Tall Oregon grape 18 15 Osoberry 18 14 Salmonberry 18 19 Snowberry 18 12 Sword fern 150 189 Buffer Mitigation Year-1 Monitoring Report Becky Hardi, Valley Medical Center February 7, 2020 Page 5 Total 273 311 114% (99% trees/shubs Recommendations • Add replacement plantings in the following quantities: o Area A (Buffer Enhancement Area)  7 Sitka spruce (2 gallon)  7 black cottonwood (2 gallon)  10 Nootka rose (1 gallon)  10 snowberry (1 gallon)  10 black twinberry (1 gallon) o Area B (Temporary Impact Area)  7 Sitka spruce (2 gallon)  15 snowberry (1 gallon)  15 baldhip rose (1 gallon)  13 black twinberry (1 gallon) • 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, English ivy, and poison hemlock. Cut back blackberry canes at least 10 feet from planting areas. • Continue to monitor invasive species presence and treat/remove as necessary. The information contained in this letter or report is based on the application of technical guidelines currently accepted as the best available science and in conjunction with the manuals and criteria outlined in the methods section. All discussions, conclusions and recommendations reflect the best professional judgment of the author(s) and are based upon information available at the time the study was conducted. All work was completed within the constraints of budget, scope, and timing. The findings of this report are subject to verification and agreement by the appropriate local, state and federal regulatory authorities. No other warranty, expressed or implied, is made. Buffer Mitigation Year-1 Monitoring Report Becky Hardi, Valley Medical Center February 7, 2020 Page 6 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, Maintenance Figures 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) TPSBSBSBSBDNUPSTAIR 7403STORAGESTREAM OHWMBUFFER ADDITION THROUGH AVERAGING AND ENHANCEMENT PLANTING AREA (3,422 SF)BUFFER REDUCTION (MITIGATED THROUGH BUFFER AVERAGING) (3,422 SF)BUFFER ENHANCEMENT (3,896 SF)BUFFER REDUCTION (MITIGATED THROUGH BUFFER ENHANCEMENT) (1,948 SF)PROPOSED STREAM BUFFERSTANDARD STREAM BUFFERPROPOSED BSBLTEMPORARY BUFFER IMPACTSPROJECT MANAGER: DESIGNED: DRAFTED: CHECKED:SHEET SIZE:ORIGINAL PLAN IS 22" x 34".SCALE ACCORDINGLY.BY© Copyright- The Watershed CompanyDATE PRINTED BY FILENAME THEWATERSHEDCOMPANYS c i e n c e & D e s i g n750 Sixth Street SouthKirkland WA 98033p 425.822.5242www.watershedco.comJOB NUMBER:SHEET NUMBER:SUBMITTALS & REVISIONS DESCRIPTIONDATENO.RENTON VALLEY MEDICAL CENTER MITIGATION PLAN PREPARED FOR BECKY HARDI FACILITIES PROJECT MANAGER 400 S. 45RD STREET RENTON, WA 98055RKRK/KMBKMBRK160113OF 81 10-10-2016 REVIEW SET KMB 2 10-11-2016 CONSTRUCTION SET KMB 3 11-04-2016 ADDENDUM #2 10/25/2016 KYLE BRAUN 160113_RENTON_VAL_MED_MITIGATION_PLAN.DWGMITIGATION PLANB380'20'10'040'PROPOSED BUFFER ENHANCEMENTBUFFER REDUCTION THROUGH AVERAGINGEXISTING PARKING GARAGEPROPOSED BUFFER ADDITION THROUGHAVERAGING AND ENHANCEMENTLEGENDPROPOSED PARKING GARAGEBUFFER REDUCTION THROUGH ENHANCEMENT