SR 161: Jovita Boulevard to South 360th St. Stage 2 / WSDOT Stream Buffer Mitigation (Agreement Y-9403) 2012 Final Monitoring Report

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1 2012 SR 161: Jovita Boulevard to South 360th St. Stage 2 / WSDOT Stream Buffer Mitigation (Agreement Y-9403) 2012 Final Monitoring Report

2 SR 161: Jovita Boulevard to South 360th St. Stage 2 (MP to MP 34.20) WSDOT Stream Buffer Mitigation Agreement Y Monitoring Report 2012 Final Monitoring Report December 2012 Prepared for Washington State Department of Transportation By Nelson Salisbury EarthCorps 6310 NE 74 th St, Suite 201E Seattle, WA /03/2012 Page 2 EarthCorps, 2012

3 SR 161: Jovita Boulevard to South 360 th St. Stage 2 (MP to MP 34.20) WSDOT Stream Buffer Mitigation Agreement Y-9403 Project Mitigation Location General Site Information Stream Buffer Mitigation West Milton Nature Preserve Monitoring Period (2012) Year of Monitoring 5 of 5 Area of Project Impact 0.28 acre Type of Mitigation Stream Buffer Enhancement Area of Mitigation 0.30 acre 12/03/2012 Page 3 EarthCorps, 2012

4 SR 161: Jovita Boulevard to South 360 th St. Stage 2 WSDOT Stream Buffer Mitigation (Agreement Y-9403) Summary of Monitoring Results (2012) Performance Measures (Year 5) Minimum 50 percent aerial cover by native woody species by year Results 157% Cumulative Cover 95.5% Aerial Cover 17 species observed Maximum 25 percent aerial cover by invasive nonnative species by year 5 11% Report Introduction This report summarizes the results of the year five monitoring activities (and follow-up monitoring completed in year six) at the SR 161: Jovita Boulevard to South 360th Stage 2 WSDOT Stream Buffer Mitigation Site. Included are a project overview, performance measures, description of the monitoring methods, and a summary of monitoring results. The site was monitored in the fall of 2011 and management activities (reed canarygrass control) were performed in summer Final monitoring occurred in October of Project Overview The WSDOT stream buffer mitigation site evaluated in this report is a 0.28 acre stream buffer enhancement project that occurred on both sides of the constructed stream channel along Hylebos Creek within the West Milton Nature Preserve. Below is an excerpt from the Final Conceptual Wetland and Stream Buffer Mitigation Plan - SR 161: Milton Way to South 360 th Stage 2 (MP to MP 34.14) (Northwest Region Environmental Services, September 2005). West Milton Nature Preserve Stream Buffer Enhancement The remaining area of permanent stream buffer impact requiring mitigation for is 0.28 acre from Streams 15, 15A, 06, and 16A. This will be accomplished in a mitigation project planned in conjunction with Friends of the Hylebos Wetlands (FOHW) at the West Milton Nature Preserve (WMNP) (Appendix G). The WMNP is a 3.25-acre open space with floodplain wetlands intersected by Hylebos Creek. The current stream channel and wetlands are degraded with flooding problems, few significant habitat features, minimal spawning habitat, and are dominated by non-native invasive species. The WMNP restoration project will significantly enhance salmon habitat and wetland habitat on the Hylebos Creek. The FOHW project will relocate 900 feet of stream channel from a ditch with minimal habitat into a healthier stream channel with large woody debris and vegetated streamside buffers. Work will also include enhancing the streamside wetland by grading to create favorable topography that will enhance wetland hydrology, controlling invasive weed species, and replanting with native vegetation. The project will provide benefits 12/03/2012 Page 4 EarthCorps, 2012

5 to native salmonid species as well as other native wildlife. The 0.28-acre WSDOT stream buffer mitigation will be incorporated into this larger restoration project, providing greater overall environmental benefits. The mitigation area for the WSDOT stream buffer impacts total 0.30 acre and includes an excess of 0.02 acre. This excess stream buffer mitigation area is provided to compensate for any unforeseen stream buffers impacts that may occur during the roadway project construction. Performance Measures Year five success standards as stated in the Mitigation Plan are: Minimum 50 percent aerial cover by native woody species by year 5. Maximum 25 percent aerial cover by invasive non-native species by year 5. Monitoring Methods These criteria were evaluated using ten 25-m² staking areas as described in the Mitigation Plan. These methods differ from other methods described in the report: Because the WSDOT portion of the WMNP will be monitored and managed by FOHW (Friends of the Hylebos Wetlands) as part of their restoration project, performance measures and success standards are described separately from the wetland and wetland buffer mitigation monitoring, performance measures, and success standards section of this report. In the fall of 2012, ten 25-m² staking areas (plots) were established throughout the mitigation area (six in the eastern area and 4 in the western area). These plots were marked with rebar and GPS locations were collected to allow for re-sampling as needed. Although monitoring was scheduled to occur in years one and three, no data specific to the Stream Buffer Enhancement area could be located. The plan states that: Five years following planting, these study units will be surveyed for aerial coverage of native woody species and invasive non-natives. Cover for individual native woody plant species were ocularly estimated for each plot and totaled to calculate cover for each plot. Additionally, non-native invasive plant species were ocularly estimated by species and totaled to calculate cover for each plot. The Mitigation Plan states (in the wetland and wetland buffer monitoring section) that: Percent aerial cover of each woody plant species will be totaled to calculate the total cover of all woody species per plot. The mean of all plots will determine the woody cover for the site. Percent cover of nonnative plant species will be totaled to determine the total percent cover of non-native species per plot. This approach was used here as no specific methodology is suggested in the stream buffer monitoring section. These methods may result in total covers greater than 100% because of overlap by individual species. Total aerial canopy cover of all combined native woody species was also estimated at each plot as a single value (0-100%) in order 12/03/2012 Page 5 EarthCorps, 2012

6 to determine overall woody cover regardless of strata. Appendix 1 following this report provides the complete text of the monitoring objectives and success standards for the stream buffer mitigation site. Monitoring Results Overall, the site is in very good condition with high percent cover and species richness of native woody plant species, greatly exceeding the year five success standard for woody species cover. Invasive species eradication efforts occurring in the summer of 2012 successfully reduced the cover of non-native invasive species to 11%. This also exceeds the year five performance measure for invasive species. Success Standard: Minimum 50 percent aerial cover by native woody species by year 5. The ten plots were initially surveyed in September of 2011 for cover of native woody species and invasive non-natives. Results of this survey indicate that the site has substantial cover of native woody plant species. Mean total woody cover on site is 157% with a range of % (total combined cover of each woody plant species from each plot averaged across all plots) (Figure 1). Woody shrub species alone average 105%, with a range of %. These data suggest that the site is far exceeding the year five success standard for native woody species. Figure 2 shows the average cover of all woody plant species identified during the September 2011 survey. In addition, overall aerial canopy cover of native woody species (measured as a single value) was estimated to average 95.5% across all plots, ranging from %. These data show that the year five success standard for woody species cover has been exceeded. 12/03/2012 Page 6 EarthCorps, 2012

7 Total Woody Species Cover by Plot Percent Cover Average Plots Figure 1: Combined aerial cover of woody plant species (sum of cover for each individual species) found in ten 25-m² plots surveyed in the West Milton Nature Preserve stream buffer mitigation site on September 02, The last column indicates the average of all ten plots. 60 Average Cover of Native Woody Species (N=10) Average Per cent Cover Indian plum Nootka rose Pacific hawthorn Pacific willow red-osier dogwood salmonberry Scouler's willow Sitka willow thimbleberry twinberry vine maple big-leaf maple black cottonwood Oregon ash red alder western hemlock western red cedar Shrubs Figure 2: Average percent cover of all woody plant species found in ten 25-m² plots surveyed in the West Milton Nature Preserve stream buffer mitigation site on September 02, Bars represent standard error. Trees 12/03/2012 Page 7 EarthCorps, 2012

8 Success Standard: Maximum 25 percent aerial cover by invasive non-native species by year 5. Results from the September 2011 survey show high cover of non-native invasive plant species, most notably reed canarygrass (Phalaris arundinaceae). Average cover of combined non-native invasive species averaged 66% across all plots, with reed canarygrass accounting for 63% of the total and ranging from 40-95%. As a result of the high cover of reed canarygrass, it was determined that management actions would be taken to address this issue. The contingency plan for the stream buffer mitigation site states: Should aerial invasive coverage exceed standards set forth, crews will be hired to weed and mulch the site and additional herbicide application may be considered. Following these guidelines, during the summer of 2012 reed canarygrass and other invasive species were controlled using a combination of mechanical cutting, hand pulling, and herbicide applications. A final round of monitoring was conducted in October, 2012 in order to evaluate the results of these invasive species control efforts. Only non-native invasive plant species were monitored for in Results from this survey show a substantial reduction in the cover of reed canarygrass and other invasive species. Data from the October 2012 survey indicate the average combined cover of non-native invasive species to be 11% across all plots (Figure 3), with reed canarygrass accounting for 9% of that total. Figure 4 shows the average percent cover of all invasive species present during the October 2012 survey. Total Invasive Species Cover by Plot Percent Cover Average Plots Figure 3: Combined aerial cover of non-native invasive plant species (sum of cover for each individual species) found in ten 25-m² plots surveyed in the West Milton Nature Preserve stream buffer mitigation site on September 02, The last column indicates the average of all ten plots. 12/03/2012 Page 8 EarthCorps, 2012

9 18 Average Cover of Invasive Species (N=10) 16 Average Percent Cover hedge false bindweed 0.01 herb Robert reed canarygrass 0.04 creeping buttercup 0.54 Himalayan blackberry Average Invasive Cover Invasive Plant Species Figure 4: Average percent cover of all non-native invasive plant species found in ten 25-m² plots surveyed in the West Milton Nature Preserve stream buffer mitigation site on October 19, Bars represent standard error. It should be noted that invasive species control efforts did not occur in the vicinity of one plot (plot 6) located along the edge of the mitigation area east of the stream. The site boundary is not readily evident due to the overgrown nature of the site and the plot was not determined to be within the mitigation boundary during invasive control efforts. As a result, this plot still has substantial cover of reed canrygrass (65%) and Himalayan blackberry (5%). If this plot is removed from the analysis, the total average invasive cover across the remaining nine plots is 4%, with reed canarygrass accounting for 3% of that total. This plot also contributes to the relatively high error associated with the average cover of reed canarygrass across all plots (the standard error for reed canarygrass drops to below one across the remaining nine plots when the un-treated plot is removed from the analysis). Total Overall, these data suggest that the year five success standard for aerial cover by invasive non-native species has been met. 12/03/2012 Page 9 EarthCorps, 2012

10 Appendix 1: monitoring objectives and success standards The following excerpt is from the Final Conceptual Wetland and Stream Buffer Mitigation Plan - SR 161: Milton Way to South 360 th Stage 2 (MP to MP 34.14) (Northwest Region Environmental Services, September 2005). WEST MILTON NATURE PRESERVE STREAM BUFFER MONITORING Objective 1:. Install and establish a scrub-shrub riparian community dominated by willow and black cottonwood. This will be accomplished by various methods to minimize reed canarygrass and plant willow and cottonwood. Objective 2: Install and establish later seral species in areas that currently have existing shade and minimal coverage by reed canarygrass. Performance Measures Year3 Livestake density of four plants per 100 square feet in the third year after planting. Success Standards Year 1 One hundred percent survival of planted woody species at the end of the first year plant establishment period. If all dead woody species plantings are replaced, the success standard will be met. Year 5 Minimum 50 percent aerial cover by native woody species by year 5. Monitoring Maximum 25 percent aerial cover by invasive non-native species by year 5. An as-planted survey will be conducted and a map of the vegetation units will be drawn. A survival survey will be conducted years one and three after initial planting. The planting areas will be sampled using the following methods: Staked Areas- Friends of the Hylebos Wetlands will monument ten 25-m2 staking areas. A complete stem count and health evaluation will be performed at each area. Five years following planting, these study units will be surveyed for aerial coverage of native woody species and invasive non-natives. 12/03/2012 Page 10 EarthCorps, 2012