habitat parameter identification review

APPENDIX E

Habitat Parameter Identification Review

HABITAT PARAMETER IDENTIFICATION REVIEW Habitat Project Design, Boeing Plant 2

Seattle/Tukwila, Washington

Submitted to: The Boeing Company

Submitted by: AMEC Geomatrix, Inc., Lynnwood, Washington

September 2011

Project 0148440050

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TABLE OF CONTENTS

Page 1.0 INTRODUCTION ............................................................................................................ 1

2.0 LITERATURE REVIEW .................................................................................................. 3 2.1 DUWAMISH WATERWAY/ELLIOTT BAY LITERATURE REVIEW .................................... 3

2.1.1 Marsh Communities on the Duwamish Waterway ................................... 3 2.1.2 Habitat Parameters ................................................................................. 5

2.2 COMMENCEMENT BAY LITERATURE REVIEW ........................................................ 10 2.2.1 Marsh Communities in Commencement Bay ........................................ 10 2.2.2 Habitat Parameters ............................................................................... 10

3.0 RESTORATION SITE INVESTIGATIONS .................................................................... 13 3.1 HERRING’S HOUSE PARK AND INTERTIDAL RESTORATION PROJECT ...................... 14 3.2 SOUTH PARK PUBLIC SHORELINE ........................................................................ 16 3.3 HAMM CREEK HABITAT RESTORATION PROJECT .................................................. 16 3.4 TURNING BASIN #3 ............................................................................................. 18

4.0 RECOMMENDATIONS ................................................................................................. 21 4.1 PLANT SPECIES SELECTION AND PLANTING ......................................................... 21 4.2 HABITAT CHARACTERISTICS ................................................................................ 22

4.2.1 Water and Soil Salinity .......................................................................... 22 4.2.2 Tidal Elevation ....................................................................................... 23 4.2.3 Soil Moisture, TOC, and Grain Size ...................................................... 24 4.2.4 Slope ....................................................................................... 25 4.2.5 Exposure (fetch), Wave, and Other Disturbances ................................. 25 4.2.6 Invasive Species ................................................................................... 26 4.2.7 Herbivore Protection .............................................................................. 26

5.0 REFERENCES ............................................................................................................. 28

TABLES

Table 1 Recommended Plant Species for Intertidal Marsh Establishment Table 2 Recommended Plant Species for Riparian Buffer

FIGURES

Figure 1 Vicinity Map Figure 2a North Site – The Building 2-122 Project Figure 2b South Site – The Building 2-41 and Southwest Bank Project Figure 3 Representative Restoration Sites Visited Figure 4 Representative Restoration Site Cross Sections

APPENDICES

Appendix A Photographs – Duwamish River Restoration Sites Appendix B PSEP Grain-Size Distribution Plot

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HABITAT PARAMETER IDENTIFICATION REVIEW Habitat Project Design, Boeing Plant 2


1.0 INTRODUCTION

In accordance with a Consent Decree between the Natural Resource Trustees (National Oceanic and Atmospheric Administration [NOAA]; U.S. Fish and Wildlife Service [USFWS], Washington State Department of Ecology [Ecology], the Suquamish Tribe, and the Muckleshoot Indian Tribe) and The Boeing Company (Boeing) executed in December 2010, Boeing has agreed to construct two habitat restoration projects at Boeing Plant 2 along the Duwamish Waterway (Figure 1). The two projects will restore and/or create off-channel and riparian habitats in the Lower Duwamish Waterway in an area where they have been largely eliminated due to the channelization and industrialization of the Waterway.

The two projects are:

• North Site – The Building 2-122 Project: the creation of a blind channel at the north end of Plant 2 adjacent to Boeing’s Building 2-122 that will restore shoreline and create off-channel habitat (see Figure 2a), and

• South Site – The Building 2-41 and Southwest Bank Project: the removal of the over-water portion of the Building 2-41 complex at the south end of Plant 2 with subsequent restoration of shoreline along the Southwest Bank and Building 2-41 (see Figure 2b).

A preliminary design of each of the projects has been developed as part of the Consent Decree process. Detailed in the Consent Decree, Boeing and the Trustees will further refine the baseline concepts of the projects within the identified project boundaries to maximize the potential habitat values. The final design of the projects will be influenced by:

• the chemical quality of sediment, soil, and groundwater within and adjacent to the footprint of the habitat projects (Environmental Investigation);

• the stability of the post-construction slopes (Geotechnical Investigation);

• the stability of the post-construction surfaces with respect to prevailing river flows (Geomorphological Investigation); and

• the physical/chemical characteristics of the water that influence plant communities in the Lower Duwamish Waterway (Habitat Parameter Identification).


The influence of each of the above factors is being assessed through a series of reports. This report presents a review of habitat parameters that included two main elements:

• A literature review of habitat projects along the Lower Duwamish Waterway and similar projects in the Tacoma/Commencement Bay area: The literature review was conducted to assist in informing the design of habitat features for the proposed restoration projects. The focus of the review was to determine which plant communities have been successfully restored in these waterways and to identify habitat features and characteristics that may improve the success of the proposed habitat projects.

• Field investigations of habitat restoration sites on the Duwamish Waterway both upstream and downstream of Boeing Plant 2: The field investigations were conducted on August 12, 2010. The fieldwork, conducted in consultation with the Trustees, comprised visits to off-channel and marsh habitat restoration sites that currently exist in the Duwamish Waterway and that are similar to the proposed habitat restoration projects. The existing vegetation within these areas was evaluated, with a particular focus on marsh communities present in the target intertidal zone (+5.5 feet to +12 feet MLLW). This information will be used to develop planting plans for the restoration areas.

This report summarizes the results of the review, in Sections 2.0 and 3.0. The results are then used to provide recommendations for the habitat restoration design, including specific species to be planted, and design parameters for physical habitat.


2.0 LITERATURE REVIEW

AMEC Geomatrix, Inc. (AMEC), conducted a review of available literature on saltmarsh restoration projects in the Lower Duwamish Waterway and similar projects in Commencement Bay to identify general habitat preferences of estuarine marsh plant species, habitat parameters that have the greatest influence on establishment and success of different marsh communities, and candidate plant species for the Boeing Plant 2 restoration sites. Commencement Bay was chosen as a reference location because of its similarities with Elliott Bay and the Duwamish Waterway with respect to geographic position and available information describing similar intertidal marsh habitat restoration projects. AMEC reviewed the following primary literature sources:

• Elliott Bay/Duwamish Restoration Program: Intertidal Habitat Projects Monitoring Report, 2007 Report (USFWS 2008)

• Biological Monitoring at Duwamish River Coastal America Restoration and Reference Sites: A Seven-Year Retrospective (Cordell et al. 2001)

• Tidal Wetland Plants Distribution and Primary Control Factors in Commencement Bay (Thom et al. 2000)

2.1 DUWAMISH WATERWAY/ELLIOTT BAY LITERATURE REVIEW The Elliott Bay/Duwamish Restoration Program (EBDRP) has monitored three intertidal habitat restoration projects (Hamm Creek, Herring’s House, and Cecil B. Moses Park [CBMP]) and their reference sites along the Lower Duwamish since 2001, and an additional intertidal habitat restoration project (Turning Basin #3) since 2007 (USFWS 2008).

The Coastal America program, in partnership with the Port of Seattle and other state and federal agencies, conducted biological monitoring at four wetland restoration sites in the Duwamish estuary from 1993 through 1999: the General Services Administration (GSA) site, Terminal 105 (T-105), and the upper Turning Basin at the head of the Duwamish Waterway, which comprises two restoration areas (Cordell et al. 2001).

2.1.1 Marsh Communities on the Duwamish Waterway Monitoring efforts were targeted on the marsh species Lyngby’s sedge (Carex lyngbyei) and on bulrush (Schoenoplectus sp.) species. The investigators measured areal extent (patch size), species composition, and plant vigor (shoot density and height) at the restoration and reference sites. The monitoring reports suggest that variation in several physical factors along the Duwamish Waterway affects the distribution and site-specific vegetation characteristics of the restored and natural sedge and bulrush sites.


In addition to the target species, numerous non-target species were identified during monitoring. Non-target species identified during the EBDRP monitoring include native, nonnative, and invasive species (USFWS 2008). Reed canarygrass (Phalaris arundinacea) and common reed (Phragmities australis, Synonym [Syn.] P. communis) were invasive species of special concern that were identified during the EBDRP monitoring. Other invasive species noted included yellow flag iris (Iris pseudacorus) and perennial pepperweed (Lepidium latifolium). Narrowleaf cattail (Typha angustifolia), a nonnative species that can grow in brackish waters, and brass buttons (Cotula coronopifolia), a colonizer of mudflats, were also found (USFWS 2008). Native marsh plants, such as seaside arrowgrass (Triglochin maritima), Douglas aster (Symphyotrichum subspicatum, Syn. Aster subspicatus), tufted hairgrass (Deschampsia cespitosa), saltgrass (Distichlis spicata), meadow barley (Hordeum brachyantherum), and Pacific silverweed (Potentilla anserina), were also found (NOAA 2009a).

Monitoring conducted at the Coastal American sites identified 18 species other than Lyngby’s sedge and bulrush species (Cordell et al. 2001). Species diversity at sites dominated by bulrush species was often greater than at sites dominated by Lyngby’s sedge. Bulrush shoots tend to be spaced farther apart than sedge shoots, providing increased free area for colonization by understory plants. The following species were found at both sedge and bulrush sites:

• spear saltbush (Atriplex patula),

• brass buttons,

• grasswort species (Lilaeopsis sp.),

• seaside plantain (Plantago maritima),

• marsh cinquefoil (Comarum palustre, Syn. Potentilla palustris),

• low bulrush (Isolepis cernua, Syn. Scirpus cernuus),

• salt sandspurry (Spergularia salina, Syn. S. marina), and

• seaside arrowgrass.

The following species were seen only at bulrush sites:

• saltgrass,

• Puget Sound gumweed (Grindelia integrifolia),

• pickleweed (Sarcocornia perennis, Syn. Salicornia virginica), and

• creeping buttercup (Ranunculus repens).


The following species were seen only at the sedge sites:

• Douglas aster,

• dwarf spikerush (Eleocharis parvula),

• two-headed water starwort (Callitriche heterophylla),

• swamp smartweed (Persicaria hydropiperoides, Syn. Polygonum hydropiperoides), and

• yellow-green algae (Vaucheria sp.).

The areal extent or percent cover of target species at the restoration sites on the Duwamish Waterway varied from year to year but generally increased or remained stable over the monitoring period. Short-term losses in the extent or density of vegetation were attributed to erosion events, goose herbivory, or other disturbances. Reference areas also showed variation in the areal extent or percent cover, with some showing a steady decline each year. Possible causes of the steady decline at the reference sites included soil erosion, increased density of invasive species, and public use. Some trends in the areal extent or percent cover at individual sites or along transects might also reflect measurement or random errors. In addition, the measurement techniques used are somewhat subjective, and changes in observers over time may account for some of the differences noted.

The number of plant species was generally greater at restoration sites than at reference sites; however, species diversity appeared to decrease over time in dense stands of Lyngby’s sedge at the CBMP site (USFWS 2008). After the period of initial colonization and recruitment, the number of understory species and percent cover of non-target species frequently declines in a healthy marsh due to competition for space between the target and non-target species.

Plant vigor at restoration sites (mean shoot height and shoot density) showed a general increase over time. Shoot height and shoot density appeared to be related in part to grazing pressure by geese. If geese were allowed to graze freely on target species (Lyngby’s sedge and bulrush species), the average shoot height was reduced. One response to continued grazing pressure was increased shoot density. Once plant densities are high enough, the impacts of grazing pressure on the target species are reduced.

2.1.2 Habitat Parameters Information from the Duwamish/Elliott Bay literature review was summarized on the following habitat parameters.


2.1.2.1 Water and Soil Salinity Water and soil salinity data were not collected during the monitoring conducted at EBDRP sites (USFWS 2008) or at the Coastal American sites (Cordell et al. 2001). However, Anchor Environmental, LLC (Anchor), prepared a brackish marsh quality evaluation for Sequalitchew Creek in Dupont, Washington (Anchor 2004). The evaluation consisted of defining the existing salinity regime, sedimentation conditions, and plant communities, and assessing potential impacts from additional freshwater flow into the marsh. This information is useful in interpreting salinity data for marsh communities on the Duwamish.

Anchor (2004) found that water column salinity ranged from 0.1 to approximately 28 parts per thousand (ppt) in plant communities dominated by Lyngby’s sedge and Pacific silverweed. During high tide, most of the monitored stations in the marsh were characterized by water column salinity between 25.5 and 27.6 ppt, which was close to the salinity measured in Puget Sound (27 to 28 ppt). Standing water left in the salt marsh after high tide generally exhibited salinities between 22 and 25 ppt, with salinity at a few locations between 15 and 17 ppt. The soil salinity tolerance of observed plant species were consistent with values referenced by Hutchinson (1989).

2.1.2.2 Soil Moisture, Organic Content, and Grain Size Grain size and total organic carbon was measured at the EBDRP restoration and reference sites in 2001, 2003, and 2005. Sediment samples were collected in vegetated (+10 feet MLLW and above) and unvegetated (+9 feet MLLW and below) areas. Variability of the data and the limited number of samples made it difficult to statistically detect a difference or trend.

“Success” was considered to be an overall decrease in mean grain-size (accumulation of fine-grained sediments) and an increase in total organic carbon (percent TOC). Accumulation of fine-grained sediments and increased organic content are required for a marsh community to support a productive benthic community. It was suggested that extremely hard-packed sediment may not contain sufficient organic matter to hold water and nutrients during low tides at one of the Coastal America sites (Cordell et al. 2001), thereby limiting the potential for marsh development.

2.1.2.3 Slope Cordell et al. (2001) note that relatively steep slopes at the T-105 site limit the width of the intertidal vegetation that can develop on the site. The initial vegetation planted as part of restoration at the site (primarily spear saltbush) did not survive. However, in 1996 patches of spear saltbush, pickleweed, seaside arrowgrass, Lyngby’s sedge, saltgrass, and salt sandspurry began to develop in this narrow band, mostly on the downstream channel margin. In 1997, spear saltbush again dominated the intertidal vegetation. Alkali bulrush


(Bolboschoenus maritimus, Syn. Scirpus maritimus), seaside plantain, saltgrass, salt sandspurry, pickleweed, and common rush (Juncus effusus) were found in a few samples. In 1999, the previously patchy distribution of vegetation at T-105 had become more continuous and more diverse.

At the EBDRP restoration sites the constructed slopes were shallower than at the T-105 site. The North Winds Weir restoration site constructed by the U.S. Army Corps of Engineers had slopes of 6 feet horizontal to 1 foot vertical within the intertidal zone. Similar slopes were constructed at other EBDRP sites.

2.1.2.4 Exposure (fetch), Wave, and Other Disturbances The Hamm Creek restoration site showed signs of erosion in 2005 along both banks and in the creek channel at its mouth, and experienced considerable erosion during winter storm events in 2006/2007. Beaver dams along the creek had caused water to back up and create a new creek channel cutting through the berm that previously separated the freshwater and saltwater marshes (USFWS 2008).

The Hamm Creek site was not constructed with riprap or armoring where the creek flows into the Duwamish Waterway. The confluence of the creek with the Duwamish Waterway is a dynamic area, and the creek’s course continues to meander. King County strategically placed large boulders, cobble, and root wads along the north bank of the creek to protect the eroding peninsula and slow the rate of erosion at the site. In 2005 that erosion appeared to have slowed considerably. However, in 2007 further erosion occurred on the north bank at the mouth of the creek and considerable erosion was caused by the creek cutting a new channel through the freshwater marsh (USFWS 2008).

Herring’s House and the CBMP sites appear to be stable, other than a small “sink hole” in the intertidal area at Herring’s House. Both sites are basins connected to the Duwamish Waterway via riprapped channels. No signs of erosion were seen at the Turning Basin #3 site (USFWS 2008).

The effects of physical and biological stressors, such as wave action and the deposition of large debris, at some of the Coastal America sites apparently resulted in varied length and patchiness of sedge species and bare areas. One of the sites farthest downstream (the GSA site) is frequently disturbed by wave action and boats in the waterway, and large pieces of industrial and woody debris have been observed in the sedge patches. In the past, pioneering species appeared to preferentially colonize this disturbed site rather than other sites with greater sedge cover, but in 1999 the frequency and number of understory species decreased


for unknown reasons. Damage has also been observed to bulrush species at one of the Coastal America sites from wood and other debris tossed by boat wakes (Cordell et al. 2001).

2.1.2.5 Invasive and Nonnative Species Invasive and nonnative species present special challenges to successful establishment of restoration sites. This section summarizes observations related to these species of concern at the restoration sites monitored.

Invasive Species of Concern The EBDRP monitoring plan lists four species as invasive species of special concern for the Duwamish restoration sites: cordgrass (Spartina spp.), purple loosestrife (Lythrum salicaria), reed canarygrass, and common reed (USFWS 2000). None of these four species were found within transect plots at any of the EBDRP restoration sites or the reference site in 2007. However, these and other invasive species were noted outside of the transect plots within the restoration sites and reference site during monitoring events (USFWS 2008). Additional invasive species observed included yellow flag iris and perennial pepperweed (USFWS 2008). Yellow flag iris is listed as a Class C noxious weed and perennial pepperweed is listed as a Class B noxious weed in Washington State (WSNWCB 2010).

Reed canarygrass was found in a transect plot at Hamm Creek in 2005. Reed canarygrass is the only invasive species of special concern found in marsh transects at the restoration and reference sites since 2001. In 2007 several areas of invasive species were noted at the Hamm Creek restoration site growing in areas not sampled, including a clump of common reed and several clumps of reed canarygrass. Some invasive species removal had occurred in May 2007. Narrowleaf cattail was noted, and single occurrences of perennial pepperweed, a state-listed species to be controlled, were found at several of the sites and removed when feasible (USFWS 2008).

While narrowleaf cattail is not a state-listed weed, its prior range was restricted to the Atlantic Coast, west to Colorado, Nebraska, Missouri, and occasionally into Wyoming, Montana, and Eastern Washington. It is currently migrating into the Southwest and along the Pacific Coast (Cooke 1997). Unlike broadleaf cattail (Typha latifolia), narrowleaf cattail grows in brackish waters. Brass buttons, an invasive colonizer of mudflats, also is not a state-listed weed. It occurs in estuarine salt marshes and on tidal mudflats. It is a native of South Africa but is now widespread around the world. In the Pacific Northwest it is found from the coast of British Columbia, south to California (Cooke 1997).


Nonnative Species of Concern The EBDRP monitoring plan identified three nonnative species of special concern in upland and riparian buffers: Himalayan blackberry (Rubus discolor), Scot’s broom (Cytisus scoparius), and Japanese knotweed (Polygonum cuspidatum) (USFWS 2000). Himalayan blackberry and Scot’s broom were encountered at the sites. Percent coverage of these nonnative species of special concern at the monitored sites ranged from 3 to 10 percent in 2007. Percent coverage of these species doubled from 5 percent to 10 percent between 2005 and 2007 at Hamm Creek, increased from 2 percent to 3 percent between 2005 and 2007 at CBMP, and decreased from 8 percent to 5 percent between 2005 and 2007 at Herring’s House (USFWS 2008).

Many other nonnative species were also present. When all nonnative species in the surveys are included, the estimated percent cover of nonnative species at the restoration sites ranges between 6 and 12 percent. This relatively modest percentage of nonnative species is probably due to the work done to remove nonnative and invasive species at the sites. The work to control nonnative species provides evidence that continued maintenance of the sites is important to preserve and provide the best habitat possible. All three restoration sites, excluding Turning Basin #3, meet the site goal of less than 20 percent nonnative species cover by Year 5 and less than 10 percent by Year 3. To date, none of the known knotweed species (Polygonum sp.) has been observed at any of the restoration sites (USFWS 2008).

2.1.2.6 Herbivore Exclusion Patches of Lyngby’s sedge and bulrush increased in size at Herring’s House despite removal of the goose exclusion fence in 2003. Heavy grazing reduces shoot height but may increase the number of shoots present. Despite heavy grazing by geese at the southern end of the reference site, impacts on percent cover and density measurements of target species were not readily apparent, and the species composition and percent cover at the reference site is expected to remain stable over time. It was noted at Turning Basin #3 that goose exclusion fences were not completely successful, as geese were observed swimming over the outer fence at high tide and foraging within the restoration site (USFWS 2008).

The effects of goose grazing pressure at some of the Coastal America sites apparently resulted in varied extent and patchiness of sedge species and bare areas Cordell et al. (2001). One site was in danger of all sedges disappearing due to goose grazing in conjunction with erosion of fine sediments and compaction of remaining sediments. Other Coastal America sites monitored appeared to be stable with relatively stable or high sedge shoot density and height. These sites show little evidence of grazing pressure years after establishment, and are the least disturbed by physical and human disturbances (Cordell et al. 2001).


2.2 COMMENCEMENT BAY LITERATURE REVIEW Numerous marsh restoration projects have been implemented in Commencement Bay. Thom et al. (2000) summarized the factors controlling distribution and success of tidal wetland vegetation.

2.2.1 Marsh Communities in Commencement Bay Thom et al. (2000) identified five plant species that have been the most successful at colonizing, and are most abundant in one natural and four restored Commencement Bay marsh areas: Lyngby’s sedge, tufted hairgrass, pickleweed, saltgrass, and cattail. Pickleweed and Lyngby’s sedge occurred at the most sites, and Lyngby’s sedge occurred at both estuarine and freshwater sites. These five species are identified as likely to be the most successful in new restoration sites planned for Commencement Bay. In general, one or a few species that establish well will enhance the area for colonization of additional species. One restoration site in Commencement Bay that was initially planted with Lyngby’s sedge had more than 57 species of plants in the system after 5 years.

2.2.2 Habitat Parameters Information on the following habitat parameters was summarized from the Commencement Bay literature review (Thom et al. 2000).

2.2.2.1 Water and Soil Salinity Salinity was the primary factor that determined success among species in Commencement Bay. The observed salinity tolerance for wetland plant species agreed well with Hutchinson (1989), and varied with the soil and water column salinity. Pickleweed was the most salt-tolerant plant, followed by saltgrass and tufted hairgrass.

Lyngby’s sedge exhibited the widest range of salinity tolerance in Commencement Bay; however, it cannot tolerate soil salinity above approximately 20 ppt for extended periods. Tufted hairgrass was also generally restricted to areas where salinity did not exceed 20 ppt, but was also found in limited areas where salinity as high as 23 ppt was measured. Saltgrass tolerated higher salinity but generally dominated in areas where salinity ranged from 5 to 20 ppt. Pickleweed is recorded from areas with salinity as high as 45 ppt in the Pacific Northwest and even higher in California. Cattail is the least salt-tolerant marsh dominant in Commencement Bay, rarely occurring in areas with salinity greater than 10 ppt.

Lower soil salinity likely allowed Lyngby’s sedge to reach a high abundance at one of the sites in a zone receiving subsurface freshwater seepage. Pickleweed occurred lowermost in the intertidal zone, and Lyngby’s sedge, saltgrass, and tufted hairgrass dominated the progressively higher elevations.


2.2.2.2 Tidal Elevation Thom et al. (2000) found the five target marsh plant species in Commencement Bay marshes at elevations ranging from about +7 feet MLLW to +14.5 feet MLLW. Elevation range and the elevation of peak cover varied among the five target species. The study identified the following elevation ranges for saltgrass, pickleweed, and Lyngby’s sedge:

• Saltgrass range: +11.5 feet MLLW to +14.5 feet MLLW; peak about +13.2 feet MLLW

• Pickleweed range: +10.2 feet MLLW to +13.2 feet MLLW; peak about +10.5 feet MLLW

• Lyngby’s sedge range: +10.0 feet MLLW to +12.8 feet MLLW; peak at +12.8 feet MLLW

2.2.2.3 Soil Moisture, Organic Content, and Grain Size In Commencement Bay, plant species generally developed best when soil moisture content was greater than 30 percent and soils were sandy. Lush vegetation corresponded with relatively high soil moisture. Greater cover was associated with higher soil nitrogen and phosphate concentrations. Very hard and dry substrata were not conducive to the growth of vegetation.

2.2.2.4 Slope Best marsh development in Commencement Bay occurred in areas where the slope was very gentle (i.e., 50 feet horizontal to 1 foot vertical). Although marshes can develop on steeper slopes, their development depends on retention of water in the soils, as steep slopes tend to result in quicker dewatering of the soils. Slope in areas with highest plant cover ranged from 50 feet horizontal to 1 foot vertical to 20 feet horizontal to 1 foot vertical. Although the latter slope is over twice as steep, the site at which the slope occurred was protected from direct erosion forces by a broad mudflat.

2.2.2.5 Exposure (fetch), Wave, and Other Disturbances In Commencement Bay, erosion affected the development of marshes at some sites. The best plant development occurred at sites that were protected from boat wake and substantial wind-driven wave action by either shoreline structures or broad tidal flats. Development of marsh vegetation was most robust where waves were never likely to exceed 20 centimeters in height. Logs and large floating debris are constant threats to newly developing marshes. Sites where debris accumulated showed long-term damage to the marsh.


2.2.2.6 Invasive Species Invasive species identified at Commencement Bay restoration sites by the City of Tacoma Environmental Stewardship Project include: perennial pepperweed, knotweed, Himalayan blackberry, common reed, birdsfoot trefoil (Lotus corniculatus), St. John’s wort (Hypericum perforatum), purple loosestrife, sweet white clover (Melilotus alba), butterfly bush (Buddleja sp.), pampas grass (Cortaderia araucana), nightshade (Solanum sp.), spotted knapweed (Centaurea stoebe), tansy ragwort (Senecio jacobaea), burdock (Arctium sp.), thistle (Cirsium sp.), Scot’s broom, and morning glory (Ipomoea sp.). These species are actively removed at the restoration sites. Removal actions included injections of herbicide into knotweed (City of Tacoma 2010).

2.2.2.7 Herbivore Exclusion In Commencement Bay, grazing by geese has been a factor in the loss of transplants at restored sites. Goose exclusion efforts consisting of criss-crossed ropes and strings appeared to reduce the rate of grazing. Planting in very large and dense clumps may also be an option to minimize impacts of grazing.


3.0 RESTORATION SITE INVESTIGATIONS

AMEC conducted site investigations on August 12, 2010, at four habitat restoration sites along the Lower Duwamish Waterway to identify physical characteristics of the existing marsh habitats (see Figure 3). At each of the restoration sites, AMEC documented the following marsh characteristics:

• Tidal elevation by plant community and lower limit of emergent marsh plants,

• Plant community dominants,

• Marsh bench slope,

• Exposure (fetch),

• Soil and surface water salinity,

• Grain-size data, and

• Presence/absence and abundance of invasive plants.

Transects were established perpendicular to the water’s edge at three of the restoration sites:

• Hamm Creek,

• Turning Basin #3, and

• South Park Public Shoreline.

Transects were established in areas representative of the restoration site conditions and extended up the elevation gradient to adjacent uplands. Transects were generally established in areas with well-established vegetation and moderate slopes, except at the South Park Public Shoreline (SPPS), which lacked marsh vegetation. A straight-line representative transect could not be established at the Herring’s House restoration site because of the semi-enclosed design of the constructed marsh. Figure 3 identifies the approximate transect locations at the Hamm Creek and Turning Basin #3 locations. Schematic cross sections showing elevation and slope data collected during the site visits are presented on Figure 4 for the Hamm Creek and Turning Basin #3 sites.

Plant communities were generally defined by the one to three most dominant species present within tidal elevation ranges along each transect, and changes in plant communities were defined by a noticeable change in the most dominant plant species. Approximate elevations for the identified vegetation zones were determined using a builder’s level and stadia rod. Elevations were referenced to the water level in the Duwamish and corrected for predicted tidal height from NOAA-published tide tables at the recorded time. Elevation was also measured at evenly spaced intervals along transects to determine the bench slope.


Soil water salinity and in situ water column salinity were measured at each of the visited restoration sites. Water aliquots for soil salinity measurements were extracted from saturated soils by squeezing a soil sample in filter paper. Soil water salinity was measured to parts per thousand (ppt) using a calibrated refractometer. Water column salinity was measured in parts per thousand using a YSI salinity, conductivity, and temperature (SCT) meter. Water column salinity was measured at points in the Waterway immediately adjacent to the four restoration enhancement sites. Water column salinity measurements were taken at the surface (10-centimeter depth) and subsurface (2-meter depth) at most locations; however, a narrow and shallow tidal channel adjacent to the shoreline at the Turning Basin #3 site limited the depth of subsurface measurements to approximately 1 meter. The salinity of standing water in depressions within the vegetation zone at the Herring’s House site was also measured.

Soil samples were collected for grain-size analysis within the vegetated zone. Grain size was analyzed using a Puget Sound Estuary Protocol (PSEP) grain-size method (sieve only analysis). Observations and results of field investigations are described below for each of the four restoration sites visited. Photographs taken during the site visits are presented in Appendix A.

3.1 HERRING’S HOUSE PARK AND INTERTIDAL RESTORATION PROJECT Herring’s House is located at River Mile 2 of the Duwamish Waterway at the site of the former Seaboard Lumber Mill, which operated from around 1929 until the early 1980s. The site is located on the west side of the waterway in the vicinity of Kellogg Island and on the last remaining oxbow of the Duwamish River system (Figure 3). The site contains 5.7 acres of upland and 10 acres of tidelands. Historically, the upland site was occupied by a marsh/ channel of the Duwamish River. Developed as an industrial site, the area was filled with waste-bearing fill material consisting of mixtures of silt, sand, and gravel with broken asphalt, rock, concrete, brick, wood, and metal debris (NOAA 2009b).

Investigations revealed soils with concentrations of contaminants that exceeded Washington State Model Toxics Control Act cleanup criteria. In 1999, a protective outer berm, shoreline armoring, and shoreline modifications were constructed. The armor layer consists of 8- to 9-inch quarry stone with voids filled with fish rock (fine/medium gravel and course sand to 3/8 inch). Parts of the berm serve to completely contain soils containing low levels of industrial contaminants. Project construction was completed in 2000 and consisted of several primary activities (NOAA 2009b):

• Former structures associated with the mill operation were demolished. Demolition work included removal of a 9,200-square-foot shoreline dock structure, 248 creosoted wooden piles supporting the dock, concrete foundations, areas of paving, and partially buried railroad spurs.


• Highly contaminated upland soil was removed and disposed.

• Soil with low levels of contamination was covered with a minimum of 2 feet of clean soil, and erosion control features were constructed to provide containment.

• A 1.8-acre intertidal bay was excavated. The bay was designed with a curvilinear edge to elevations between +6 feet MLLW and +12 feet MLLW, and it is protected by two armored spits forming a mouth opening to the Duwamish Waterway. The shoreline armoring protects the opening to the bay, which is designed to provide a hydraulic connection that balances low flooding and ebbing velocities with the need to allow water recirculation so as to prevent low dissolved oxygen levels and the potential for fish to be stranded within the bay.

• An amended on-site soil mixture of silts and clays with a high organic matter content was distributed to a depth of 18 inches over the basin.

• The site was revegetated with emergent marsh plants at various elevations in the intertidal zone, and transitional scrub-shrub habitat was introduced between the intertidal marsh, upland meadow, and forested habitat.

Herring’s House is relatively well-vegetated and appears to be functioning as a productive saltmarsh habitat (Photos 1 through 3, Appendix A). The riparian zone consists primarily of herbaceous and shrub layers. The total intertidal area (+12 feet MLLW to -2 feet MLLW) covers approximately 2.1 acres, and the tidal regime is linked to the Duwamish Waterway outside of the project area. No obvious areas of slope erosion or slope failures were observed at the site. While ground coverage is good, nonnative invasive species remain a problem at the site. Bird usage and juvenile salmonid usage have been documented for the site (USFWS 2006).

Previous monitoring at the site showed that measured TOC was approximately 6 percent after placement of amended fill, but that the TOC percentage had dropped to approximately 2 percent by 2005, the last year TOC was measured (USFWS 2006).

Sediments within the vegetated zone consisted predominantly of sands with some gravel. The percentage of fines (silt and clay fractions) was less than 10 percent. The percentage of fine-grained sediments measured during the site investigation was less than half the value presented in the 2005 monitoring report (USFWS 2006). A PSEP grain-size distribution plot of the sand gravel fraction is presented in Appendix B.

The salinity of standing water in depressions within the vegetated zone was measured at approximately 17 ppt. Soil salinity in the same area was measured at 22 ppt. Salinity in the Duwamish Waterway was measured at 16.1 ppt at the surface and 19.1 ppt at 2-meter depth.


A typical cross-section profile was not developed for the site. The embayment where the salt marsh was planted does not begin to flood until the tides are above approximately +6 feet MLLW. The lower limit of the pickleweed/brass buttons zone was approximately +7.4 feet MLLW. Softstem bulrush (Schoenoplectus tabernaemontani) appeared at approximately +8.7 feet MLLW, and Lyngby’s sedge and American bulrush (Schoenoplectus americanus) appeared at approximately +9.3 feet MLLW. Dunegrass (Elymus mollis) and upland herbaceous species appeared above +10.5 feet MLLW.

3.2 SOUTH PARK PUBLIC SHORELINE The South Park site is a small public beach located along the Duwamish Waterway in South Seattle at River Mile 3.3, across the waterway from Boeing Plant 2. Improvements at this site were identified in the 1985 Comprehensive Public Access Plan for the Duwamish Waterway. No saltmarsh plants are present at the site, but a narrow fringe of upland dunegrass occurs along vegetated portions of the sandy upper intertidal areas (Photo 4, Appendix A). The site previously consisted of an eroded, rubble-filled bank with little to no shoreline or aquatic habitat value. The existing bank was regraded to create a gradual slope, and the shoreline was stabilized with native plants and large woody debris (Port of Seattle 2006). Steep armored banks covered with riprap are present upstream and downstream of the site. Riprap also protects the entrance to the pocket beach area.

A representative cross-section profile was not developed across the site; however, the overall slope of the sand beach is approximately 10 feet horizontal to 1 foot vertical. Soil salinity in the lower intertidal (approximately +2 feet MLLW) was measured at 28 ppt. Soils from areas higher on the beach with active seeps had soil salinities of approximately 14 ppt. Salinity in the Duwamish Waterway was measured at 5.5 ppt at the surface and 14.4 ppt at 2-meter depth. As previously discussed, no vegetation was present on the intertidal portion of the site.

3.3 HAMM CREEK HABITAT RESTORATION PROJECT Located along the Duwamish Waterway at River Mile 4.3 in unincorporated King County, the Hamm Creek Habitat Restoration project (Hamm Creek) is adjacent to Delta Marine and across the waterway and upstream from Slip 6. The Hamm Creek site is roughly “V-shaped” and occupies approximately 6.2 acres. The site includes a freshwater stream, marsh habitat with associated riparian areas, and approximately 0.7 acre of intertidal habitat between +12 feet MLLW and -2 feet MLLW. It is located within the 21.5-acre Duwamish Substation property owned by Seattle City Light (NOAA 2009c).

Historically, Hamm Creek meandered through an intertidal marsh at the site and flowed into the Duwamish River. From the early 1950s through 1971 the site was used as a dredged material stockpiling area. Consequently, Hamm Creek was “placed” in a ditch and routed into


a culvert with an outfall into the Duwamish Waterway accessible to fish only at higher tides. Together with the Corps of Engineers, King County created 2,300 feet of new productive riparian streambed and channel for Hamm Creek along the northern and western portions of the site. The Elliott Bay/Duwamish Restoration Program has been responsible for the design and monitoring of a 1-acre estuarine marsh with fish-passable connection to the Duwamish Waterway. The enhanced freshwater Hamm Creek channel features meanders, fish pools, and large woody debris. Native trees and shrubs forming a riparian buffer were planted on the upper slopes of the bank. The intertidal habitat was planted with native estuarine marsh vegetation in spring 2000. Construction started in July 1999 and the project was completed in the year 2000 (NOAA 2009c).

The restoration site is well-vegetated and appears to be functioning as a productive saltmarsh habitat. Patches of reed canarygrass and other invasive species were noted during the site visit. The riparian zone consists primarily of herbaceous and shrub layers with some tree species. While ground coverage within the riparian zone is good, nonnative invasive species such as Scot’s broom and Himalayan blackberry remain a problem. Bird usage and juvenile salmonid usage have been documented for the site (USFWS 2006).

No obvious areas of slope erosion or slope failures were observed during the site visit. However, monitoring reports (USFWS 2002, 2004) have documented periodic and extensive erosion events along the freshwater stream channels. Engineering controls appear to have stabilized the intertidal habitats.

Previous monitoring at the site showed that measured TOC was approximately 1 percent after construction (USFWS 2006). The sediments within the vegetated zone consisted predominantly of medium sands. The percentage of fines (silt and clay fractions) was 1 percent.

The sediment within the vegetated upper intertidal zone was well-drained, and therefore soil salinity could not be determined using the available method. Salinity measured in the Duwamish Waterway was 0.7 ppt at the surface and 13.2 ppt at 2-meter depth. Saturated sediments collected just above the incoming tide at approximately +3 feet MLLW showed soil salinities of 4 ppt.

The percentage of fine-grained sediments measured during the site investigation was substantially less than the 35 percent to 45 percent value presented in the 2005 monitoring report (USFWS 2006). The substantially lower percentage of fines represents the grain-size data for a single location within the vegetated zone and may not be representative of the site


as a whole. A PSEP grain-size distribution plot of the sand and gravel fraction is presented in Appendix B.

A typical cross-section profile developed for the site is shown on Figure 4. The approximate location of the profile at Hamm Creek is shown on Figure 3. The lower limit of the pickleweed/brass buttons zone along the profile cross section was approximately +5.0 feet MLLW. An unvegetated zone was observed above the pickleweed/brass buttons zone between +6 feet MLLW and +6.8 feet MLLW. Softstem bulrush appeared at approximately +6.8 feet MLLW and extended up to +12 feet MLLW. Lyngby’s sedge and tufted hairgrass appeared at approximately +9.9 feet MLLW, and these were mixed with bulrush. Patches of the nonnative reed canarygrass were observed between +7.7 feet MLLW and +9.8 feet MLLW mixed with bulrush. Sitka willow (Salix sitchensis) and other upland herbaceous and shrub species appeared above +12 feet MLLW. Slopes along the cross section varied from 16 feet horizontal to 1 foot vertical in the lower intertidal zone below approximately +7 feet MLLW to a steeper 6 feet horizontal to 1 foot vertical in the upper intertidal.

3.4 TURNING BASIN #3 Turning Basin #3 is located at River Mile 4.7 in Tukwila on the former Kenco Marine Services property (Figure 3). The site is located at the western upstream boundary of the maintained navigation channel, where the Duwamish Waterway is formed from the Duwamish River. The upland portion of the site previously consisted of fill material covered with asphalt and concrete pads, in addition to an office/warehouse structure, small storage sheds, and a house. A commercial pier extended 125 feet into the Turning Basin, and barges and other vessels moored in the intertidal and subtidal areas. Portions of the area had already been restored to natural wetlands by federal agencies, including NOAA and USFWS, and the Port of Seattle, under a Coastal America Partnership. Over 1 acre of mudflat was day-lighted by the removal of derelict vessels at the site. The commercial pier and shoreside structures were removed, and the area was recontoured and revegetated to provide an enhanced intertidal wetland area. Project construction began in September 2005 and was completed in April 2006. Additional planting was conducted in 2007 to replace plants that had died. Project implementation included the following (NOAA 2009a):

• Barges and other vessels at the site were removed and moorage was prohibited to allow 18,000 square feet of intertidal and subtidal mudflats to become permanently exposed.

• Former commercial structures, concrete foundations, paved areas, and the dock structure and creosoted wooden supporting piles were demolished and removed.


• The area was recontoured and revegetated to create an enhanced intertidal wetland area consisting of three habitat benches at various elevations:

− A “lower bench” at +2 feet MLLW to +6 feet MLLW of sand over 3/4-inch gravel substrate created 6,500 square feet of intertidal habitat at a slope of 10:1. Bank stabilization was accomplished by using “soft” substrates (wood) in lieu of riprap at the transition to the emergent zone bench.

− An “emergent zone bench” at +9.5 feet MLLW to +11 feet MLLW was created by random rock placement and then planted with native intertidal vegetation to create 6,050 square feet of marsh habitat at a slope of 20:1.

− A “groundcover and shrub zone bench” at elevation +14 feet MLLW to +17 feet MLLW was planted with native riparian vegetation to create 1,850 square feet of riparian habitat at a slope of 3:1.

The restoration site is vegetated and appears to be functioning as a productive saltmarsh habitat (Photos 5 though 7, Appendix A). The adjacent upland riparian zone consists primarily of herbaceous and shrub layers with some tree species. While ground coverage within the riparian zone is satisfactory, nonnative invasive species, such as Scot’s broom and Himalayan blackberry, remain a problem.

No obvious areas of slope erosion or slope failures were observed at the site. The sediments within the vegetated zone were predominantly of medium sand with a trace of gravel. The percentage of fines (silt and clay fractions) was slightly more than 25 percent. A PSEP grain-size distribution plot of the sand and gravel fraction is presented in Appendix B.

The sediment within the vegetated upper intertidal zone was well-drained, and therefore soil salinity could not be determined using the available method. Salinity measured in the Duwamish Waterway was 0.8 ppt at the surface and 3 ppt at 1-meter depth. A narrow tidal channel with a bottom elevation of approximately 0 feet MLLW was present offshore and prevented sampling of water column salinities adjacent to the shoreline. Saturated sediments collected just above the incoming tide at +3.6 feet MLLW showed soil salinities of 13 ppt.

A typical cross-section profile developed for the site is shown on Figure 4. The approximate location of the profile is shown on Figure 3. The lower limit of the pickleweed/ brass buttons zone along the profile cross section was approximately +7 feet MLLW. Softstem bulrush appeared at approximately +8.4 feet MLLW and extended up to +11 feet MLLW. Douglas aster appeared at approximately +9.4 feet MLLW mixed with bulrush. Sitka willow and upland herbaceous and shrub species appeared above +11 feet MLLW.

Slopes along the cross section varied from 5 feet horizontal to 1 foot vertical in the lower to mid-intertidal zone below approximately +7 feet MLLW to a flatter slope of 9 feet horizontal to 1 foot vertical in the upper intertidal zone below +10.4 feet MLLW. The high intertidal zone


above +10.4 feet MLLW and extending into the riparian communities had slopes of 5 feet horizontal to 1 foot vertical.


4.0 RECOMMENDATIONS

This section presents design recommendations for plant species and habitat parameters to be considered for the Boeing Plant 2 restoration sites.

4.1 PLANT SPECIES SELECTION AND PLANTING Based on a review of available literature, the restoration site visits, and anticipated species availability, the following native noninvasive plant species have been identified as candidate species for restoration of intertidal saltmarsh communities at the Boeing Plant 2 Habitat Restoration sites (Table 1).

• Lyngby’s sedge (Carex lyngbyei)

• Bulrush species (Schoenoplectus sp.)

− Softstem bulrush (S. tabernaemontani)

− Hardstem bulrush (S. acutus)

− American bulrush (S. americanus)

• Tufted hairgrass (Deschampsia cespitosa)

• Pacific silverweed (Potentilla anserina)

• Douglas aster (Aster subspicatus)

These species were selected based on their success at colonizing and restoring estuarine marsh sites along Commencement Bay and the Duwamish Waterway, their tolerance to a range of salinity conditions, and their ability to promote natural recruitment and establish diverse communities of native plant species.

Pickleweed and saltgrass are the most salt-tolerant species identified in the literature review, and were two of the most successful and abundant species colonizing the Commencement Bay restoration areas (Thom et al. 2000). Based on their observed abundance and vigor along the Duwamish Waterway, it is anticipated these species will be recruited naturally to the lower portion of the estuarine marsh. These species are not recommended for planting.

The species selected for planting should be installed in distinct bands within discrete elevations based on tidal elevations and the salinity tolerance of individual species to improve chances of successful establishment. It is recommended that the selected species be planted in the following order in the proposed planting zone from lowest to highest elevation: selected bulrush species, Lyngby’s sedge, Pacific silverweed, tufted hairgrass, and Douglas aster. A mix of shrubs and small trees will be planted in the riparian zone above +12 feet MLLW and extending shoreward from the +12 foot MLLW contour a minimum of 25 feet. Open space between plants above +12 feet MLLW should be heavily mulched or seeded with an upland


grass seed mix to control invasive species. Any invasive species present should be removed prior to planting, including root masses. Native noninvasive shrub and tree species that have been identified as candidate species for the riparian zone based on a review of available literature are listed in Table 2.

4.2 HABITAT CHARACTERISTICS The following habitat characteristics will be important for the success of the proposed habitat restoration project at the Boeing Plant 2 site.

4.2.1 Water and Soil Salinity Salinity tolerance was the primary factor that differed among species that were successful in Commencement Bay, and likely the Duwamish Waterway as well. The plant species identified as candidate species for the Boeing Plant 2 restoration sites were chosen based on their ability to not only tolerate, but thrive in saline marsh environments. The salinity measurements collected during the site visits generally fall within the acceptable range for the selected species based on results of the literature review and salinity tolerance reported by Hutchinson (1989).

As expected, water salinity measured in the Duwamish Waterway decreased the farther upstream the measurements were taken, ranging from 0.7 to 19.1 ppt, with the highest salinity at Herring’s House (16.1 ppt at surface, 19.1 ppt at 2 meters), followed by South Park (5.5 ppt at surface, 14.4 ppt at 2 meters), Hamm Creek (0.7 ppt at surface, 13.2 ppt at 2 meters), and Turning Basin #3 (0.8 ppt at surface, 3.0 ppt at 1 meter). As the Boeing Plant 2 site is just upstream of South Park and downstream of Hamm Creek, salinity in the Duwamish Waterway at the project site is expected to generally fall within the range of these sites. AMEC (2009) reported on a salinity profile collected mid-channel, upstream of the South Park Bridge. The sampling location is adjacent to Boeing Plant 2. The profile was collected on July 25, 2008. Salinity values were similar to the values measured in August 2010 (4.8 ppt at surface, 20.5 ppt at 2 meters).

Salinity of standing water left by the tide was 17 ppt in a vegetated backwater area at the Herring’s House site. Anchor (2004) reported the salinity of standing water left in a salt marsh near Sequalitchew Creek after high tide as 25 ppt. This range of salinities is likely for standing water left by the tide in topographically low depressions within the restoration area and is within the salinity range for pickleweed and saltgrass, the two species likely to naturally colonize these areas.

The measured soil salinity also generally decreased the farther upstream the samples were taken, with the exception of South Park. One of the measurements taken at South Park was


28 ppt in the lower intertidal. This measurement was taken just above the incoming tide at approximately +2 feet MLLW. Another soil salinity measurement was taken farther up the slope (higher in the intertidal) and measured at approximately 14 ppt. Hamm Creek and Turning Basin #3 showed soil salinities of 4 and 13 ppt, respectively.

In Commencement Bay, restored plant communities dominated by Lyngby’s sedge and Pacific silverweed experienced water column salinity of 27.6 ppt and 27.2 ppt, respectively, over limited time periods although Lyngby’s sedge cannot tolerate salinity above 20 ppt for extended periods. Pacific silverweed is a common associate of Lyngby’s sedge and tufted hairgrass on substrates with salinities from 0 to 12 ppt, but has also been found growing in areas where salinity approaches 20 ppt (Hutchinson 1989). Tufted hairgrass was generally restricted to areas in Commencement Bay where salinities did not exceed 20 ppt, but was also found in limited areas where salinity was as high as 23 ppt. Douglas aster has the lowest salinity tolerance of the selected species (up to 12 ppt), and therefore will be planted at the highest elevation of the marsh where salinity is expected to be lower.

Of the selected bulrush species, American bulrush has the highest salinity tolerance as it can grow in salinities up to 15 ppt and tolerate short-term exposure to 20 ppt. Softstem bulrush is primarily found at sites where mean salinities during the growing season are less than 5 ppt but can withstand exposure to water salinity of 10 ppt for short periods of time. Hardstem bulrush is generally found in habitats with salinities below 3 ppt and can only withstand salinity of 6 to 7 ppt for short periods of time early in the growing season (Hutchinson 1989). Softstem bulrush was found to be consistently present below the elevation of Lyngby’s sedge, tufted hairgrass, and other bulrush species during the investigation of restoration projects along the Duwamish Waterway. These observations appear to indicate conditions along the Duwamish Waterway are conducive to the establishment of softstem bulrush plantings. As such, it is recommended that the American bulrush and softstem bulrush should be the primary bulrush species in the lower planting zones. Some hardstem bulrush will also be planted at higher elevations due to its low salinity tolerance, primarily to increase species diversity.

4.2.2 Tidal Elevation Tidal fluctuations will be important in development of the estuarine marsh vegetation at the Boeing Plant 2 restoration sites. Tidal exchange between the EBDRP restoration sites and the Duwamish Waterway was unimpeded during the entire monitoring period, indicating that the designs incorporated appropriate grading and slope for selected vegetation based on tidal regimes (USFWS 2004).

David Evans and Associates (DEA 2006) estimated that mean higher high water (MHHW) was approximately +11.4 feet MLLW, with highest tides at +14.5 feet MLLW in the vicinity of the


South Park Bridge. A review of as-built and design drawings for the Turning Basin #3 site, CBMP, and the North Winds Weir restoration sites revealed that comparable values for MHHW and highest tides were used during the design of these projects. The Boeing Plant 2 restoration sites will have a similar tidal regime as these established restoration sites. Given the success and relatively similar design to the Boeing Plant 2 restoration projects, assuming this tidal regime seems appropriate for planning the proposed grading, slopes, and plant species selection.

Thom et al. (2000) found marsh plant species in Commencement Bay marshes at elevations of about +7 feet MLLW to +14.5 feet MLLW. However, pickleweed and brass buttons were found as low as approximately +5 feet MLLW at the Hamm Creek site during the site investigation. Although pickleweed was observed at this relatively low tidal elevation relative to most established vegetation, it should be noted that an unvegetated zone extended above the pickleweed from +6 feet MLLW to +7 feet MLLW. The lowest observed elevation of pickleweed other than at Hamm Creek was +7.4 feet MLLW and +7.0 feet MLLW at Herring’s House and Turning Basin #3, respectively. Based on the restoration site observations and available information, pickleweed can establish at low tidal elevations (+5 feet MLLW) but usually establishes around +7 feet MLLW. The low elevation of pickleweed observed at Hamm Creek may have been due to site-specific conditions that may not be present or achievable at a majority of the Boeing Plant 2 habitat area. Establishment of pickleweed down to +5.5 feet MLLW would likely require favorable conditions with respect to soils, hydrology, salinity, and low levels of disturbance. As previously discussed, it is anticipated that pickleweed and saltgrass will naturally colonize suitable areas in the lower intertidal.

4.2.3 Soil Moisture, TOC, and Grain Size In Commencement Bay, plant species generally developed best when soil moisture was greater than 30 percent and the soils were sandy. Extremely hard-packed sediment may not contain sufficient organic matter to hold water and nutrients during low tides. As lush vegetation corresponds to relatively high soil moisture and soil nitrogen and phosphate concentrations, soils with sufficient organic matter and sandy soils will likely result in better vegetative growth.

TOC at Herring’s House dropped from 6 percent immediately after construction to 2 percent in 2005. TOC content was only 1 percent at Hamm Creek in 2005 (USFWS 2006). Sediments consisted predominantly of sands with some gravel at Herring’s House and medium sands at Hamm Creek (Appendix B). Despite the low organic content in the soil, vegetation at these sites is doing relatively well. One reason may be the fines (silt and clay fractions) that allow the sandy soils to maintain moisture. Based on the literature and site observations and


measurements, it is recommended that soils in the proposed marsh areas consist of sandy soils amended with organic matter to promote vegetation establishment.

4.2.4 Slope Most successful marsh development in Commencement Bay occurred in areas where the slope was very gentle (10 feet horizontal to 1 foot vertical). Vegetation establishment on steeper slopes depends on the retention of water in the soils, which as previously discussed depends largely on organic matter content, as well as fines content. The steepest slope with the highest plant cover found in Commencement Bay was 10 feet horizontal to 1 foot vertical, but the site was also partially protected from direct erosional forces by a broad mudflat. Vegetated slopes at the Duwamish restoration site marshes visited ranged from 16 feet horizontal to 1 foot vertical, to 5 feet horizontal to 1 foot vertical. Cordell et al. (2001), however, showed that diverse native vegetation can become established in narrow bands along relatively steep slopes at the T-105 site.

The 5 feet horizontal to 1 foot vertical slope observed at Turning Basin #3 had an established bulrush and Douglas aster community. The steeper slopes may be stabilized initially with biodegradable jute matting. Coir matting or logs may also be used to control and collect sediment as the plants establish, mimicking the collection and containment of sediment by established vegetation in well-functioning marshes. These approaches may be used to promote soil stability, reduce erosion, and increase vegetative growth, while also protecting the planted vegetation from wave action and other disturbances. Other engineering controls may be employed to stabilize the slopes until vegetation can become established.

4.2.5 Exposure (fetch), Wave, and Other Disturbances Based on a review of available literature, development of estuarine marshes can be affected by the following typical disturbances:

• Erosional forces from wave action (boat wakes, storms, etc.);

• Erosional forces from changes in hydrology (creek rerouting, etc.); and

• Logs and floating debris (garbage).

Marsh development was most successful at sites with the following characteristics:

• Sites protected from boat wake and substantial wind-driven action by either shoreline structures or broad flats;

• Sites located in locations where waves are never likely to exceed 20 centimeters in height;

• Sites where little to no accumulation of debris occurred;


• Sites with little to no erosion due to changes in hydrology; and

• Site where narrow channels leading to the Duwamish Waterway were riprapped to prevent erosion.

To the extent possible the proposed habitat areas and marsh plantings should be temporarily protected from erosion while the marsh is developing.

4.2.6 Invasive Species Success of restoration sites continues to be attributed to, at least in part, the removal of nonnative and invasive species. Significant efforts have been applied to controlling invasive species, planting additional vegetation, replacing dead plants, removing trash and debris, and constructing erosion control measures within restoration sites. Continued site stewardship remains a vital part of maintaining valuable restored habitats. It is critical for the success of restoration sites to control occurrences of nonnative and invasive species while they are relatively small in number and while control methods have a negligible impact on site-restoration efforts (USFWS 2008). Ongoing work to control nonnative and invasive species is evidence that continued maintenance of the sites is important to preserve and provide the best habitat possible.

The EBDRP monitoring plan (USFWS 2000) lists four species as invasive species of special concern for the Duwamish Waterway restoration sites (cordgrass, purple loosestrife, reed canarygrass, and common reed) and three nonnative species of special concern (Himalayan blackberry, Scot’s broom, and Japanese knotweed). In addition, the observed abundance of the nonnative brass buttons within low marshes of the Duwamish during the site investigations indicates this species may also be of concern.

4.2.7 Herbivore Protection Goose (herbivore) exclusion (fencing, overhead grids, etc.) has had mixed results at restoration sites. USFWS (2008) reported that one restoration site (Turning Basin #3) had geese grazing directly beneath the exclusion features during the site monitoring visit. Other sites (including reference sites) without any exclusion features appeared free of impacts from goose grazing. A majority of the information indicates herbivore exclusion features work by reducing the amount of grazing by geese on the newly established emergent vegetation. Well-established marsh vegetation responds to grazing by geese by increasing shoot density. It is recommended that goose or herbivore exclusion devices (fencing and overhead grids of ropes or netting) be installed at the proposed restoration areas, monitored for effectiveness, and routinely maintained as needed. In addition, planting in very large and dense clumps may help to reduce the rate of grazing. The effectiveness of the goose exclusion devices needs to


be monitored and additional methods or techniques applied if the effectiveness diminishes over time.


5.0 REFERENCES

AMEC (AMEC Geomatrix, Inc.). 2009. DSOA Additional Characterization Data Report, Boeing Plant 2 Duwamish Sediment Other Area, Tukwila, Washington. Prepared for The Boeing Company, Seattle, Washington.

Anchor (Anchor Environmental, LLC). 2004. Brackish Marsh Quality Evaluation for Sequalitchew Creek. Prepared for Glacier Northwest. Anchor, Seattle, Washington.

City of Tacoma. 2010. Environmental Stewardship Project, Year 2, Second Quarter Report. Prepared for National Oceanic and Atmospheric Administration. City of Tacoma, Tacoma, Washington.

Cooke, S.S. (editor). 1997. A Field Guide to the Common Wetland Plants of Western Washington and Northwestern Oregon. Seattle Audubon Society, Seattle, Washington.

Cordell, J.R., L.M. Tear, and K. Jensen. 2001. Biological Monitoring at Duwamish River Coastal America Restoration and Reference Sites: A Seven-Year Retrospective. Wetland Ecosystem Team, University of Washington, School of Aquatic and Fishery Sciences, Seattle.

DEA (David Evans and Associates). 2006. South Park Bridge Hydrographic Survey, Seattle, Washington, Summary Report – Contract No. E23011E. Prepared for King County Department of Transportation, Road Services Division.

Ecology (Washington State Department of Ecology). No date. Shoreline Plants. Ecology, Department of Water Quality, http://www.ecy.wa.gov/programs/wq/plants/plantid2/ descriptions/sci.html (accessed October 12, 2010).

eFloras.org. No date. Flora of North America, Carex lyngbyei. Vol. 23, Page 383. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242357310 (accessed October 12, 2010).

Hutchinson, I. 1989. Salinity Tolerance of Plants of Estuarine Wetlands and Associated Uplands. Prepared for Washington State Shorelands and Coastal Zone Management Program: Wetlands Section, Olympia. Report in Fulfillment of Contract No. C0088137.

NOAA (National Oceanic and Atmospheric Administration). 2009a. Northwest Region Damage Assessment, Remediation, & Restoration Program; Restoration Activities; Case: Elliott Bay/Duwamish River, Washington, Turning Basin #3 Restoration Project. NOAA, Seattle, Washington, http:// www.darrp.noaa.gov/northwest/elliott/tb3.html (accessed October 12, 2010). Last updated July 2, 2009.

NOAA. 2009b. Northwest Region Damage Assessment, Remediation, & Restoration Program; Restoration Activities; Case: Elliott Bay/Duwamish River, Washington, Herring’s House Park and Intertidal Habitat Restoration Project. NOAA, Seattle, Washington, http://www.darrp.noaa.gov/ northwest/elliott/seabd.html (accessed October 12, 2010). Last updated May 18, 2009.


NOAA. 2009c. Northwest Region Damage Assessment, Remediation, & Restoration Program; Restoration Activities; Case: Elliott Bay/Duwamish River, Washington, Hamm Creek Habitat Restoration Project. NOAA, Seattle, Washington, http:// www.darrp.noaa.gov/northwest/elliott/scln.html (accessed October 12, 2010). Last updated July 1, 2009.

Port of Seattle. 2006. Final SEPA Decision of Non-Significance (DNS) of Proposed Action, South Park Public Shoreline Access Site Improvements. Port of Seattle, Seattle, Washington, http://www.portseattle.org/downloads/community/environment/ southparkshorelinefinal.pdf (accessed October 12, 2010).

Thom, R.M., A.B. Borde, and D.L. Woodruff. 2000. Tidal Wetland Plants Distribution and Primary Control Factors in Commencement Bay. Battelle Marine Sciences Laboratory, Sequim, Washington.

USDA (United States Department of Agriculture). No date. Plant Fact Sheet: Tufted Hairgrass. Contributed by USDA Natural Resources Conservation Center, Plant Materials Center, Corvallis, Oregon, http://www.plant-materials.nrcs.usda.gov/pubs/ orpmcfs9128.pdf (accessed October 12, 2010).

USFWS (U.S. Fish and Wildlife Service). 2000. Elliott Bay/Duwamish Restoration Program: Intertidal Habitat Projects Monitoring Program. Prepared for the Elliott Bay/Duwamish Restoration Program Panel. USFWS, Western Washington Office, Lacey, Washington.

USFWS. 2002. Elliott Bay/Duwamish Restoration Program: Year 1 Intertidal Habitat Projects Monitoring Report. USFWS, Western Washington Fish and Wildlife Office, Lacey, Washington.

USFWS. 2004. Elliott Bay/Duwamish Restoration Program: Intertidal Habitat Projects Monitoring Report, 2001-2003 Final Report. USFWS, Western Washington Fish and Wildlife Office, Lacey, Washington.

USFWS. 2006. Elliott Bay/Duwamish Restoration Program: Intertidal Habitat Projects Monitoring Report, 2005 Report. USFWS, Western Washington Fish and Wildlife Office, Lacey, Washington.

USFWS. 2008. Elliott Bay/Duwamish Restoration Program: Intertidal Habitat Projects Monitoring Report, 2007 Report. USFWS, Western Washington Fish and Wildlife Office, Lacey, Washington.

UW (University of Washington). 2003. Carex lyngbyei, Lyngby’s sedge. Data compiled by Mike Cooksey. UW, Seattle, http://depts.washington.edu/propplnt/Plants/Clyngby.htm (accessed October 12, 2010).

WSNWCB (Washington State Noxious Weed Control Board). 2010. 2010 Washington State Noxious Weed List. WSNWCB, Olympia.

TABLES

shoreline habitat\habitat parameter id\habitatparameter_tbl-1.docx AMEC Geomatrix, Inc. Page 1 of 2

TABLE 1 RECOMMENDED PLANT SPECIES FOR INTERTIDAL MARSH ESTABLISHMENT

Habitat Project Design, Boeing Plant 2 Seattle/Tukwila, Washington

Plant Species Rationale Characteristics Lyngby’s sedge (Carex lyngbyei)

• “The common sedge in Pacific coastal salt marshes” (eFloras.org, no date). • Pioneer species, one of the first plants to colonize the mud of tidal flats in its range

(UW 2003). • Target species in previous monitoring efforts to determine restoration site health

and success. • Percent cover remained stable or increased at the EBDRP restoration sites during

their entire monitoring period, with substantial increases at North Wind’s Weir and Herring’s House.

• Occupied all observed suitable habitat in intertidal area at North Wind’s Weir, including most of the intertidal area above standing water.

• Increased at Herring’s House even after removal of goose exclusion fence. • Along with bulrush, Lyngby’s sedge patches had 14 other species present at

Coastal America sites on the Duwamish. • Identified as one of the most successful at colonizing and most abundant in one

natural and four restored Commencement Bay marsh areas. • Occurred in more Commencement Bay restoration sites than any other species,

along with pickleweed. • Widest range of salinity tolerance in Commencement Bay (but cannot tolerate

salinity greater than 20 ppt for extended periods). • Occurred at both saltwater and freshwater sites in Commencement Bay. • One restoration site in Commencement Bay was initially planted with Lyngby’s

sedge and after 5 years over 57 species of plants was observed in the system.

• Elevation range found in Commencement Bay (peak cover): +10.0 feet MLLW to +12.8 feet MLLW. • Appeared at +9.3 feet MLLW at Herring’s House, +9.9 feet MLLW at Hamm Creek. • Salinity tolerance: 0 to 20 ppt (Hutchinson 1989). • Forms dense, nearly pure stands (UW 2003). • May be competitively dominant in high marsh (greater biomass makes it superior competitor for light) (UW 2003). • Best when planted in fine-grained sand to silt, but does well on cobble and gravel beaches (UW 2003). • Planting bare rootstock is the best means of propagating these plants as seeds may wash away (UW 2003). • Large plugs may be better able to survive predation from geese than transplanted sprigs (UW 2003).

Bulrush species (Schoenoplectus sp.) Recommended species Softstem bulrush (S. tabernaemontani) Hardstem bulrush (S. acutus) American bulrush (S. americanus)

• Target species in previous monitoring efforts to determine restoration site health and success.

• Percent cover remained stable or increased at the EBDRP restoration sites during their entire monitoring period, with substantial increases at North Wind’s Weir and Herring’s House.

• Increased at Herring’s House even after removal of goose exclusion fence. • Bulrush species height has increased at Hamm Creek since 2001. • Identified as one of the most successful at colonizing and most abundant in one

natural and four restored Commencement Bay marsh areas. • Most species found in bulrush patches at Coastal America sites on the Duwamish. • Along with Lyngby’s sedge, bulrush patches had 14 other species present at

Coastal America sites on the Duwamish.

• Appeared at +8.7 feet MLLW at Herring’s House, +6.8 feet MLLW at Hamm Creek, +8.4 feet MLLW at Turning Basin #3.

• Occurs in marshes and shorelines to 1.5 meters deep (Ecology, no date). • Tolerates alkaline conditions; hardstem bulrush is more tolerant of brackish water (Ecology, no date). • Salinity tolerance 0 to 3 ppt, short-term 6 ppt (S. acutus), 0 to 15 ppt, short-term 20 ppt (S. americanus),

0 to 5 ppt, short-term 10 ppt (S. tabernaemontani) (Hutchinson 1989). • Multiple tall, stout stems arise from horizontal underground rhizomes (Ecology, no date). • Used for bank stabilization and to treat contaminated water (Ecology, no date).

shoreline habitat\habitat parameter id\habitatparameter_tbl-1.docx AMEC Geomatrix, Inc. Page 2 of 2

TABLE 1 RECOMMENDED PLANT SPECIES FOR INTERTIDAL MARSH ESTABLISHMENT


Plant Species Rationale Characteristics Tufted hairgrass (Deschampsia cespitosa)

• Generally found where salinities did not exceed 20 ppt but found in areas with salinity as high as 23 ppt.

• Third most salt-tolerant species in Commencement Bay (after pickleweed and saltgrass).

• Identified as one of the most successful at colonizing and most abundant in one natural and four restored Commencement Bay marsh areas.

• Appeared at +9.9 feet MLLW at Hamm Creek. • Useful for stabilizing disturbed sites, restoring streambanks, shorelines, and upper tidal marshes (USDA, no date). • Salinity tolerance: 0 to 20 ppt (Hutchinson 1989). • Can become a serious competitor with trees (USDA, no date). • Spreads readily into newly disturbed areas (USDA, no date). • Slow to establish the first year, can become large and dominate a site by the end of the second growing

season if sown heavily (USDA, no date). Pacific silverweed (Potentilla anserina)

• Common species associated with Lyngby’s sedge and tufted hairgrass, and therefore will compliment establishment of the native plant community.

• Successfully established in restored and natural salt marshes along the Duwamish Waterway and Commencement Bay.

• Apparent high water column salinity tolerance (evidence of up to 27.2 ppt).

• Common member of high marsh flora of brackish and freshwater marshes in the Pacific Northwest. • Commonly found in association with Lyngby’s sedge and tufted hairgrass. • Salinity tolerance: 0 to 12 ppt (Hutchinson 1989). • Tolerated water column salinity of 0.1 to 27.2 ppt at Sequalitchew Creek site. • Typically occurs at or above mean high water.

Douglas aster (Symphyotrichum subspicatum)

• Common element of the high marsh flora in brackish marshes in the area. • Successfully established in restored and natural salt marshes along the

Duwamish Waterway and Commencement Bay.

• Salinity tolerance: 0 to 12 ppt (Hutchinson 1989). • Established at elevation +9.4 feet MLLW and above at Turning Basin #3, and was mixed with bulrush.

Abbreviation(s)

EBDRP = Elliott Bay/Duwamish Restoration Program Ecology = Washington State Department of Ecology MLLW = mean lower low water ppt = parts per thousand USDA= U.S. Department of Agriculture UW = University of Washington

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TABLE 2 RECOMMENDED PLANT SPECIES FOR RIPARIAN BUFFER


Shrub Plant Species

Common Name Scientific Name ocean spray Holodiscus discolor

Oregon grape Berberis aquifolium, Syn. Mahonia aquifolium

Pacific willow Salix lasiandra

redosier dogwood Cornus sericea, Syn. C. stolonifera

Sitka willow Salix sitchensis

snowberry Symphoricarpos albus

twinberry-black Lonicera involucrata

wild rose Rosa gymnocarpa

Tree Plant Species

Common Name Scientific Name bigleaf maple Acer macrophyllum

bitter cherry Prunus emarginata

black cottonwood Populus trichocarpa

black Douglas hawthorne Crataegus douglasii

Douglas fir Pseudotsuga menziesii

Oregon ash Fraxinus latifolia

red alder Alnus rubra

shore pine Pinus contorta

Sitka spruce Picea sitchensis

western hazelnut Corylus cornuta

FIGURES

By: Project No.

Figure

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VICINITY MAPHabitat Parameter Identification ReviewHabitat Project Design, Boeing Plant 2


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NORTH SITE–THE BUILDING 2-122 PROJECTHabitat Parameter Identification ReviewHabitat Project Design, Boeing Plant 2

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SOUTH SITE–THE BUILDING 2-41 ANDSOUTHWEST BANK PROJECT

Habitat Parameter Identification ReviewHabitat Project Design, Boeing Plant 2

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REPRESENTATIVE RESTORATION SITES VISITEDHabitat Parameter Identification ReviewHabitat Project Design, Boeing Plant 2


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REPRESENTATIVE RESTORATIONSITE CROSS SECTIONS

Habitat Parameter Identification ReviewHabitat Project Design, Boeing Plant 2

Seattle/Tukwia, Washington

Figure 4

7/13/2011

APPENDIX A

Photographs – Duwamish River Restoration Sites

PHOTOGRAPHS – DUWAMISH RIVER RESTORATION SITES Habitat Project Design, Boeing Plant 2


AMEC Geomatrix, Inc. shoreline habitat\habitat parameter id\appendix-a_duwamishrvrphotos.docx 1

Photo 1 View facing southwest of the backwater area at Herring’s House.

Photo 2 View of Herring’s House backwater area shoreline. Species were established in distinct bands along the elevation gradient and included from closest to farthest from the shoreline: pickleweed, brass buttons, saltgrass, softstem bulrush, Lyngby’s sedge, and tufted hairgrass




Photo 3 Another typical view of the Herring’s House backwater area shoreline, showing species growing in distinct bands along the elevation gradient.

Photo 4 View of the South Park shoreline. Vegetation was essentially non-existent within the intertidal area.




Photo 5 View facing southeast along the shoreline at the Turning Basin. Pickleweed, saltgrass, and softstem bulrush dominated the lower portion of the vegetated intertidal area.

Photo 6 View facing northwest along the shoreline at the Turning Basin.




Photo 7 Typical view of the shoreline at the Turning Basin. Softstem bulrush, Pacific silverweed, pickleweed, and Lyngby’s sedge dominated the lower portion of the vegetated intertidal area. Tufted hairgrass dominated the higher elevations of the intertidal area.

APPENDIX B

PSEP Grain-Size Distribution Plot

habitat parameter identification review

Documents