Final 2011 Year 17 Monitoring Report East Harbor Operable Unit, Wyckoff/Eagle Harbor Superfund Site

Appendix D Sediment Mobility Analysis Report

Operations, Maintenance, and Monitoring Plan Sediment Mobility Analysis

Wyckoff/Eagle Harbor Superfund Site Bainbridge Island, Washington

May 2012

Table of Contents 1 Introduction ...... 3 1.1 Purpose and Scope ...... 3 1.2 Project Site Background ...... 4 2 Data Collection ...... 4 3 Hydrodynamics ...... 5 3.1 Site Conditions ...... 5 3.2 Numerical model application for predicting tidal currents ...... 5 3.3 Numerical model application for predicting wind generated waves ...... 5 3.4 Numerical model application for predicting vessel wake ...... 6 4 Model setup, validation, and results ...... 6 4.1 CMS-FLOW ...... 6 4.2 CMS-WAVE ...... 7 4.3 SWASH-2D ...... 7 5 Sediment Mobility Assessment...... 8 5.1 Tidal Currents ...... 8 5.2 Wave induced currents – wind generated waves ...... 10 5.3 Wave induced currents – vessel wake ...... 10 6 Sediment Transport Potential ...... 10 7 Summary ...... 11 8 References ...... 11 Appendix A. Shear stress calculations at sample locations ...... 33 Appendix B. CMS-FLOW current magnitude and direction ...... 40

1 Introduction A primary objective of the Operations, Maintenance and Monitoring Plan (OMMP) for the Wyckoff/Eagle Harbor Superfund Site is to evaluate the physical stability of the sediment cap in the East Operating Unit. The sediment cap shown in Figure 1 was constructed in multiple phases starting in 1994 and consists of sediment ranging from silt to gravel in depths ranging from subtidal to upper intertidal. Physical cap stability is a function of the sediment composition, or grain size, and the hydrodynamic forces acting on the seabed. In this report field data coupled with numerical modeling tools are utilized to evaluate physical cap stability. A series of 67 sediment grab samples were collected in October 2011 to obtain grain size distributions over the sediment cap. Field instruments collecting current, wave, and suspended sediment data were deployed in September 2010 to validate hydrodynamic models used to simulate wave and tidal induced currents acting on the sediment cap.

1.1 Purpose and Scope The purpose of the study is to identify areas within the East Harbor Operating Unit that may be at risk to erosion and may require more focused monitoring or future remediation. Bed shear stresses from wave and tidal generated currents initiate motion of sediment when they exceed the critical shear stress of the sediment particles on the seabed. A tidal circulation, wind wave generation/transformation, and ship wake numerical model are employed to determine if bed shear stresses exceed the critical shear stress of the sediment cap.

Table 1. Chronology of activities at the Wyckoff Eagle Harbor Project Event/Activity Date The Wyckoff/Eagle Harbor site was added to the National Priority List (NPL) 1987 Completion of the Remedial Investigation (RI) 1989 Completion of the Feasibility Study (FS) for Eagle Harbor 1991 Removal Action (Phase I) -Placement of sand cap over 50 acres of contaminated sediments 1993-1994 Construction monitoring of removal action 1993-1994 Removal of in-water structures (e.g., piers and pilings) 1998-1999 Installation of sheet pile wall around upland site 1999-2001 Intertidal investigation around the Wyckoff facility 1999-2002 Placement of Phase II subtidal cap 2000-2001 Placement of Phase III subtidal nearshore and intertidal cap 2001-2002 Installation of sheet pile wall around upland site 1999-2001 EPA created habitat mitigation beach at West Beach and placed Phase III subtidal nearshore 2001-2002 and intertidal cap. West Beach intertidal sediment investigations 2005-2006 Construction of the West Beach EBS 2008

1.2 Project Site Background Eagle Harbor is a small natural harbor located on the eastern side of Bainbridge Island in Washington State. Over a period of about 80 years, the harbor was severely contaminated by hazardous chemicals released from the Wyckoff Company creosote wood treatment facility and several shipbuilding facilities. The Wyckoff/Eagle Harbor facility was designated a Superfund site in 1987. EPA partnered with the U.S. Army Corps of Engineers (USACE), Washington State Departments of Transportation and Ecology and Association of Bainbridge Communities to clean up the harbor and restore the marine ecosystem. Approximately 28.3 hectares (70 acres) of the contaminated harbor were capped with clean sediments. The sediment caps are monitored to ensure that buried toxins are not re-released into the marine environment. As summarized in Table 1 the Wyckoff/Eagle Harbor project sediment caps were constructed in different phases beginning in 1993 and most recently in 2008 with the construction of the Exposure Barrier System (EBS) on West Beach.

North Shoal

East Beach West Beach

Figure 1. Location of subtidal and intertidal sediment caps in Eagle Harbor

2 Data Collection Two bottom mounted instruments were deployed in Eagle Harbor from 17 September to 20 October 2010 to collect wave, current, water level, temperature, and total suspended solids (TSS) concentration data. The location of each station is shown in Figure 2. Station 1 was located near the harbor entrance at a depth of 12.1 meters mean lower low water (MLLW) immediately east of the 1994 Phase I cap. Station 2 was located immediately offshore of the 2008 Exposure Barrier System shoreline on West Beach at a depth of 4.6 meters MLLW.

Grain size data was collected in October 2011 by SEE, LLC. The 16, 50, and 84 percent coarser grain sizes of the 67 grab samples are plotted in Figures 3-5. These represent the median grain size (d50) and +- one standard deviation from the median grain size, d16 and d86 respectively. These parameters allow for calculation of the sorting parameter of the sediment sample. The sorting is related to the difference of d84 and d16. In general all samples analyzed indicate the sediment is considered poorly sorted, or indicative of a wide range in grain sizes. The skewness parameter indicates whether the distribution is skewed toward coarser or finer sediments. 49 of the 67 samples have a positive skewness which indicates the grain distributions are skewed to smaller grain sizes. Studies have determined positive skewness is generally indicative of depositional or non-erosive environments.

3 Hydrodynamics

3.1 Site Conditions Eagle Harbor has an area of 186.2 hectares (460 acres) at mean higher water (MHW) and measures approximately 2.8 km (1.75 miles) long by 1.2 km (0.75 miles) wide. Water depths range from over 15.2 m (50 feet) near the eastern portion of the harbor to intertidal mud flats at mean lower low water (MLLW) in the western end. Approximately 23 percent of the harbor is tidal flats between MLLW and MHW elevations. The harbor mouth is oriented toward the southeast. An extensive shoal area, about 244 m (800 feet) long with water depths between 0 and 3.3 m (10 feet), extends into the harbor from the point at the site of the former Wyckoff Co. wood treatment facilities and defines the eastern side of the entrance channel. The channel wraps around this shoal to the southwest at a point east of the ferry terminal and follows the general alignment of the Harbor (CH2MHILL 2007). The mean diurnal tidal range is 2.3 m (7.7) feet and is nearly identical to Seattle, Washington. The tidal currents are weak in magnitude, less than 0.5 meters per second (1 knot), and the site is fairly sheltered from wind generated waves due the harbor geometry. The harbor is actively used by recreational vessels and is home to the Washington State Department of Transportation (WSDOT) Bainbridge Island to Seattle vehicle/passenger ferry.

3.2 Numerical model application for predicting tidal currents The Coastal Modeling System (CMS)-FLOW circulation model is used to simulate tidal currents. CMS-FLOW solves the two-dimensional, depth-integrated continuity and momentum equations by applying a finite-volume method. These equations are solved numerically using an implicit finite differencing method (Buttolph et al. 2006). CMS-FLOW version 4 also includes capability of variable grid size for numerical efficiency.

3.3 Numerical model application for predicting wind generated waves The Coastal Modeling System (CMS)-WAVE model is used to simulate wave growth and transformation over spatially varying bathymetry. CMS-WAVE is a two-dimensional spectral wave model formulated from a parabolic approximation equation and includes energy dissipation and terms to represent wave diffraction (Lin et al. 2008).

3.4 Numerical model application for predicting vessel wake SWASH-2D is used to predict waves and currents generated by vessels moving at subcritical, transcritical and supercritical speeds in restricted waterways; it is an extension of BOUSS-2D, a comprehensive numerical model for nearshore wave transformation, based on Boussinesq-type equations for wave propagation in intermediate water depths (Nwogu and Demirbilek, 2001). The model is a phase resolving model, meaning the water surface elevation is computed at discrete time intervals.

4 Model setup, validation, and results

4.1 CMS-FLOW The CMS-FLOW model domain stretches the entire Puget Sound basin as shown in Figure 6. Topographic and bathymetric data are obtained from the University of Washington PSDEM 2005 (Finlayson 2005), the NDGC Coastal Relief Model (Divins and Metzger 2008), NOAA multibeam Survey H12025 (NOAA 2009), and USACE topographic and hydrosurvey from 2010-2011. Two offshore boundaries are used to force the hydrodynamic model. The western offshore boundary is specified in the Strait of Juan de Fuca just east of Neah Bay, WA. The northern offshore boundary is specified at Cherry Point north of Bellingham, WA. A total of 252,435 computation cells are included in the model domain with cell sizes ranging from 50 meters to 800 meters. The regions with the highest grid resolution are located at the various sills (i.e. Deception Pass, Admiralty Inlet, and Tacoma Narrows) in addition to the project area. The grid resolution of Bainbridge Island and Eagle Harbor is shown in Figure 7. A time step of t = 900 sec is specified. Observation cells were specified at all NOAA tide stations and the two oceanographic instruments deployed in Eagle Harbor in September 2010. CMS-FLOW was run for the 31 day period from 18 September to 18 October 2010. Observed water level at the NOS Neah Bay and Cherry Point stations were utilized to force the boundary conditions in the model. Figure 8 compares the measured and modeled water level at the Seattle tide station and Eagle Harbor station S1 near the entrance to the harbor. The model slightly under predicts the highs and lows but in general the results are acceptable. Figure 9 compares the measured and modeled velocities at Stations S1 and S2. Figure 10 plots the principle components of the tidal current ellipse. Both S1 and S2 indicate a weak easterly current direction. Figure 11 displays the maximum computed tidal velocities over the 31 day simulation period. Velocities are strongest near the entrance and over the Phase I cap. Appendix B includes plots of current magnitude and direction at 3 hour intervals over a 24 hour tide cycle. A counter clockwise gyre develops over the Phase I, II, and III sediment caps during slack and peak flood tides. This dissipates during ebb tides where the current directions are oriented primarily east to northeast over the North Shoal. Measured current velocities were consistently higher than the modeled velocities. This is likely a result of residual currents generated from surface winds and ferry wake. The difference is more pronounced at S1 which is in closer proximity to the ferry wake where currents of 0.25 m/s were measured. In contrast the maximum predicted tidal generated currents in CMS-FLOW

were 0.05 m/s. The difference between the measured and modeled currents was less pronounced at S2. Improvements to the model would likely be realized by combining currents created by ferry wake and wind generated wave into the model dynamically within the model simulation. However, investigating hydrodynamic processes individually was determined to provide more value for systematically identifying the processes linked to sediment mobility. In this context the results were deemed acceptable.

4.2 CMS-WAVE The CMS-WAVE model domain stretches across the Whidbey and Central Puget Sound subbasins from Everett, WA to Tacoma, WA. The model domain is shown in Figure 12. The same bathymetric and topographic data are utilized from the CMS-FLOW model for input in CMS-WAVE. However, a uniform grid size of 50 meters by 50 meters is specified. Seven different extreme wind scenarios corresponding to direction of 0, 30, 60, 90, 120, 150 and 180 (ranging from true north to south) were simulated to estimate wave generated velocities on the seabed throughout Eagle Harbor. Return periods for the 100 year (1% annual exceedance) are listed in Table 2. The modeled wave heights in Eagle Harbor for the 100 year return period are shown in Figure 13

Table 2. 100 year return period for 2 minute wind speed at West Point (CMAN ID: WPOW1). Period of Record: 1984-2010 (from Tetra Tech 2012) Wind Direction (degrees, True) Wind Speed (knots) 0 35 30 24 60 16 90 15 120 19 150 33 180 51

4.3 SWASH-2D The SWASH-2D model is employed to simulate a typical WSDOT ferry route through Eagle Harbor. The ferry class along the Seattle-Bainbridge Island route is 140.2 meters long with a beam of 27.4 meters and draft of 5.2 meters. The hull geometry of the Wenatchee ferry was panelized into a mesh to force the initial pressure disturbance generated from the vessels hull. Both inbound and outbound transits were simulated in the model and compared with the observed field data. The model was calibrated with available global positioning system (GPS) data collected on the Wenatchee. Figure 14(a) displays ship speed calculated from GPS tracklines collected on

27 July 2010. These data confirm the approach speed of the Wenatchee slowed to approximately 12 knots is it entered the mouth of Eagle Harbor. Figure 14(b) displays ship speed data collected on 17 June 2011. These data show the ferry accelerates to over 13 knots prior to exiting the harbor. The model was calibrated by varying the ship speed in the model and comparing the bottom pressure time series to the observed data at S1. Turbulent mixing was evident near the propeller of the ferry. Thus in the near field a viscosity coefficient was utilized to represent vertical mixing and wake dissipation processes. Figure 15 and 16 show 30-second time interval snapshots of the modeled water surface elevation for inbound and outbound transits. The associated wake is composed of divergent waves from the sides of the hull and transverse waves in the lee. As shown in Figure 17 an important observation is the large drawdown (min bottom pressure = -0.15 dbar) in water level at S1 during an outbound transit as the vessel accelerates. However the diverging waves do not reach the southern shoreline of the harbor and are directly primarily at North Shoal. In contrast, the inbound transit shows less of an initial drawdown near Station 1 (min pressure = -0.05 dbar) but results in more wave energy directed toward the southern harbor near West Beach. Figure 17 shows the model comparison to the observed data at Station 1. In general the model performs well, but overestimates the initial rise in water level. However the model accurately represents the trend of the wave and the magnitude of drawdown observed and is determined acceptable for estimating bed shear stress.

5 Sediment Mobility Assessment

5.1 Tidal Currents Sediment particle motion is initiated when the critical shear stress on the seabed is exceeded. Critical shear stress (τc) is larger for coarser sediment median grain sizes (d50). Therefore smaller grain sizes such as clay and silts have greater potential for transport under slower velocities. The critical shear stress for incipient motion is expressed as:

(1)

3 3 where ρs is the sediment density (2650 kg/m ), ρw is the water density (1025 kg/m ), g is 2 gravitational acceleration (9.81 m/s ), and θc is the critical Shields parameter, which is a function of the Reynolds number (R). The critical Shields parameter is computed using the explicit formulation from Cao et al. (2006), as:

. 0.1414 , 6.61 . .. , 6.61 282.84 (2) ..

0.045, 282.84 The computed critical shear stress for incipient motion of cap material using sediment properties from the October 2011 grab sample data is listed in Table 3. The 1994 capping material originated from dredge material from the Snohomish River navigation channel and downstream

turning basin. The Phase II and III intertidal caps consisted primarily of sand to gravel and originated from the Glacier Northwest quarry in DuPont, WA. The 2008 Exposure Barrier System (EBS) was constructed as a three layer (sand, cobble, geotextile) composite. The top 0.6 meters habitat fill sand layer of the EBS is exposed to wave action. The shear stress on the seabed is a function of velocity, water depth, and bottom roughness. The relationship of this velocity to the current bed shear stress (τb) retarding fluid motion on the seabed can be expressed by the quadratic friction law:

 f U 2   w c c (3) b 8

Where Uc is the depth averaged current velocity and fc is a current friction factor determined experimentally by Van Rijn (1988) as:

2 12d    fc  0.24log  (4)  ksd 

where d is the still water depth plus tidal amplitude, and ksd = 2.5d50. The mobility index of sediment is represented by the ratio of M = τb/τc where M > 1 represents mobile conditions. Table A.1 lists the grain size, critical shear stress, bed stress, and mobility index for each sediment sample location. No sediment samples were found to encounter the mobility criteria under maximum tidal current velocities computed in CMS-FLOW.

Table 3. Sediment characteristics of 2011 sediment cap grab samples collected in Eagle Harbor Cap Cap Design Cap Material Median grain Material Critical Shear Construction Area, Thickness, Source size (mm) Classification Stress (Pa) (ha) (meters) 1994 (Phase I) 30.1 0.9 Snohomish 0.02 – 0.30 silt to medium 0.1 – 0.4 River sand 2000-2001 4.4 0.3 – 3.0 Glacier NW 0.13 – 2.52 Fine to coarse 0.4 – 2.1 (Phase II) Quarry sand 2001-2002 1.1 0.3 – 3.0 Glacier NW 0.81 – 2.21 coarse sand 0.6 – 1.6 (Phase III) Quarry 2008 (EBS) 2.1 0.6 Glacier NW 0.62 – 1.71 coarse sand 0.4 – 1.6 Quarry

5.2 Wave induced currents – wind generated waves

The wave induced bed shear stress (τb) is related to the near bed orbital velocity amplitude (Uw) under a wave, and is computed as:

(5)

where g is gravitational acceleration, H is wave height, T is wave period, d is water depth. And k is wavenumber (k = 2π/L) where L is the wavelength. The wave induced bed shear stress is then computed as:

(6)

where the wave friction factor is determined experimentally by Nielsen (1992) as:

... (7)

(8)

The maximum bed velocity and bed shear stress calculated for the 100 year return period wind- wave event is listed in Table A.2 for each sample location. Figure 18 shows the maximum bed stress computed within Eagle Harbor for the 100 year return period. The largest bed shear stresses are found close to shore and in shallow regions such as the north shoal and East Beach to the south, and Wing Point to the north. Still, the maximum bed shear stresses generated from wind waves only reach approximately 0.1 Pa within the harbor which does not meet the critical shear stress for any of the sediments comprising the caps in the harbor.

5.3 Wave induced currents – vessel wake Figure 19 and 20 show the predicted maximum bed shear stress for inbound and outbound transits respectively. Maximum bed shear stresses above 1 Pa are shown in color. In general the inbound transits generate the largest potential for sediment mobility on East Beach, while the outbound transits generate the largest potential near the North Shoal. By analyzing the mobility indices computed from SWASH-2D, it is determined the most probable region for sediment mobility is on the east side of the Phase I cap within a 30 meter swath of the ferry route, where predicted bed shear stresses are > 100 Pa and the critical shear stress is 0.1 to 0.4 Pa. Additional areas which indicate mobility are in the intertidal regions of the Phase II and EBS caps where predicted bed stresses exceed 1 Pa during both inbound and outbound ferry transits. The critical shear stress of 0.4 to 2.1 Pa is marginally exceeded, indicating a potential for mobilizing the finer fraction of sediments comprising these caps.

6 Sediment Transport Potential The tidal current ellipses shown in Figure 9 modeled in CMS-FLOW indicate a weak net easterly flow at the harbor mouth and immediately offshore of West Beach. A counter clockwise

gyre is also present during a long portion of the tide cycle immediately offshore of West Beach and is likely indicative a region prone to limited sediment transport outside of this region should sediments be mobilized. In general tidally driven currents are too weak to mobilize sediments from the caps. Longshore sediment transport (within the swash zone) to the west along West Beach has been a concern of the local marina immediately west of the Wyckoff Site. While fetch lengths within Eagle Harbor are fairly short the possibility of a net westerly direction of longshore transport was discussed in prior studies (CH2MHILL 2006; CH2MHILL 2007). Yet, 2005 grain size sampling along eight beach transects at various profile elevations found little evidence of transport of mitigation beach materials toward the marina. The report suggested event based, or episodic wave conditions may control sediment transport versus average wave conditions and thus may occur over longer time intervals than in the years between the installation of the mitigation beach in 2002 and the 2005 sampling. Since these studies the Exposure barrier System was installed. Topographic surveys between 2008 post construction and a 2010 condition survey indicate profile adjustment within the intertidal area of the EBS, with finer materials below mean tide level repositioning to the upper beach profile, see Figure 21. Vessel generated waves were likely a large driver for the profile adjustment occurring in the 2 years following construction. The wave modeling performed in this analysis indicates the bed stresses generated from a 100 year return period waves generates little potential for longshore transport based on the critical stress for incipient motion of sediment particles comprising the Exposure Barrier System. Any longshore transport would likely be confined to the small fraction of fine grained sands positioned in the upper beach profile.

7 Summary The CMS-FLOW, CMS-WAVE, and SWASH-2D numerical models were employed to estimate bed shear stress over the Wyckoff/Eagle Harbor sediment cap from tidal and wave generated currents. Model results coupled with grain size data from recent 2011 sampling were used to determine regions in the existing cap where sediments have potential to be mobilized. In general currents less than 0.1 m/s do not cause mobility of sediments in the cap. CMS-FLOW model results indicate tidal currents do not exceed 0.1 m/s with the exception of the harbor entrance near sample P7. Wind generated storm waves were also analyzed and found to have a relatively low influence on sediment mobility. However, SWASH-2D results indicate ferry wake has a relatively high potential of mobilizing Phase I cap materials due to the combination of fine grained sediments and large bed shear stress generated in the immediate vicinity of the ferry track. Areas with potential for sediment mobility of finer sediment fractions were found in the Phase II and Expose Barrier System. Focused monitoring of the Phase I, Phase II, and the EBS where predicted critical shear stresses in the model are exceeded is recommended for long- term management of the site.

8 References Buttolph, A. M., Reed, C. W., Kraus, N. C., Ono, N., Larson, M., Camenen, B., Hanson, H.,Wamsley, T., and Zundel, A. K. 2006. Two-dimensional depth-averaged circulation model CMS-M2D: Version 3.0, Report 2: Sediment transport and morphology change, Tech.

Rep. ERDC/CHL TR-06-9, U.S. Army Engineer Research and Development Center, Coastal and Hydraulic Engineering, Vicksburg, MS. Cao, Z, Pender, G., Meng, J. 2006. Explicit formulation of the Shields Diagram for incipient motion of sediment. J. Hydraulic. Eng. Technical Note. DOI: 10.1061(ASCE)0733- 9429(2006)132:10(1097) CH2MHILL 2006. West Beach Investigation Data Evaluation Report. Wyckoff/Eagle Harbor Superfund Site. Bainbridge Island , Washington. November 2006. Contract No. 68-S7-04- 01. CH2MHILL 2007. Design Basis for West Beach Cap. Technical Memorandum. Preparation date October 04, 2006. Project Number 316783.DE.05. Divins, D.L. and Metzger, D., 2008. NGDC Coastal Relief Model, http://www.ngdc.noaa.gov/mgg/coastal/coastal.html. Finlayson, D., 2005. Combined bathymetry and topography of the Puget Lowlands, Washington State. School of Oceanography, University of Washington. http://www.ocean.washington.edu/data/pugetsound/. Lin, L.,Demirbilek, Z., Mase, H., Zheng, J. and F. Yamada. 2008. CMS-WAVE: A nearshore spectral wave processes model for coastal inlets and navigation projects. Coastal and Hydraulics Engineering Technical Report ERDC/CHL TR-08-13. Vicksburg, MS NOAA. 2009. Approaches to Elliott Bay Skiff Point to Alki Point. Survey H12025 – April, 2009. NOAA Ship RAINER. Nielsen. P. Coastal Bottom Boundary Layers and Sediment Transport. World Scientific, Singapore, 324pp. Nwogu, O.G., and Demirbilek, Z. 2001. BOUSS-2D: A Boussinesq wave model for coastal regions and harbors. Technical Report ERDC/CHL TR-01-25, U.S. Army Engineer Research and Development Center, Vicksburg, MS. Tetra Tech, Inc. 2012. Coastal Storm Damage Analysis Issue Paper. Elliott Bay Seawall Project. March 2012. Draft.

Figure 2. Oceanographic field data collection station at Eagle Harbor, Washington during Sep 2010 deployment

Figure 3. d16 grain size distribution in October 2011 sampling event

Figure 4. d50 grain size distribution in October 2011 sampling event

Figure 5. d84 grain size distribution in October 2011 sampling event

Figure 6. CMS-FLOW regional model domain

Figure 7. CMS-FLOW grid resolution near Bainbridge Island and Eagle Harbor

Figure 8. Observed and modeled water levels at Seattle NOS tide station 9447130 and Eagle Harbor Station 1 (S1) during 18-Sep to 18 Oct 2010.

Figure 9. Observed and modeled velocities at Eagle Harbor Station 1 (S1) and 2 (S2) during 18-Sep to 18 Oct 2010.

Figure 10. Modeled tidal ellipses for S1 and S2. Note net east direction

Figure 11. Max computed depth averaged current velocities over CMS-FLOW simulation (m/s)

Figure 12. CMS-WAVE model domain

(b)

(c)

Figure 13. (a) CMS-WAVE computed wave height for 100 year return period wind from due east, Dir = 90° at mean tide level (b) Computed wave heights in Eagle Harbor, Dir = 90° (c) Computed wave heights in Eagle Harbor, Dir = 120°

(a)

Figure 14. GPS ship speed time series for (a) inbound and (b) outbound transits; Wenatchee ferry

Figure 15. SWASH-2D Water Surface Elevation prediction for inbound Wenatchee. Model Time (a) 00:03:31 (b) 00:04:00 (c) 00:04:31 (d) 00:05:00 (e) 00:05:31 (f) 00:06:00

Figure 16. SWASH-2D Water Surface Elevation (a) 00:00:30 (b) 00:01:00 (c) 00:01:31 (d) prediction for outbound Wenatchee. Model Time 00:02:00 (e) 00:02:31 (f) 00:03:02

Station 1 ‐ Bottom Pressure (Inbound)

0.04

0.02

0 (dbar) ‐0.02

Observed (Burst 1862; 9/23/10 18:05 UTC) ‐0.04

Pressure Model (Case 3; v = 12 knots) ‐0.06

‐0.08

‐0.1 ‐50 0 50 100 150 200 250 300 Time (seconds)

Station 1 ‐ Bottom Pressure (Outbound) 0.1

0.05

0 (dbar)

‐0.05

Presure Observed (Burst 4715; 10/3/10 15:50 UTC) Model (Case 2; v = 13.6 knots) ‐0.1

‐0.15 ‐50 0 50 100 150 200 Time (seconds)

Figure 17. Model validation to observed bottom pressure time series data. Inbound transit velocity of 12 knots (top graph); Outbound transit velocity of 13.6 knots (bottom graph).

Figure 18. Max Bed stress and direction for 100 year wind return period (maximum bed stress over all directions, at mean tide)

Figure 19. Max bed shear stress during inbound transit, speed 12 knots, where red and dark blue coloration correspond to 100 Pa and 1 Pa, respectively (units: 0.001 kN/m2 = 1 Pa).

Figure 20. Max bed shear stress during outbound transit, speed 13.6 knots, where red and dark blue coloration correspond to 100 Pa and 1 Pa, respectively (units: 0.001 kN/m2 = 1 Pa).

EBS ‐ Beach Profile (West) 16 2008

14 2010

10 MLLW)

8 (feet,

Elevation 6

0 0 20 40 60 80 100 120 140 160 180 Distance Offshore (feet)

Figure 21. Exposure Barrier System profile adjustment from 2008 to 2010.

Appendix A. Shear stress calculations at sample locations

Table A.1. Sediment properties and computed critical and bed stress from tidal currents at discrete grab samples collected in October 2011

Grid depth τb,max Sample Parameters microns (mm) τcr (Pa) R* θcr (m) fc Uc (m/s) (Pa) Mobility coeff C9 d50 24 0.024 0.070 0.331 0.183 14.173 0.031 0.1 0.040 0.567 F7 d50 88 0.088 0.163 2.306 0.117 14.387 0.049 0.1 0.062 0.384 F9 d50 65 0.065 0.134 1.486 0.129 12.771 0.042 0.1 0.053 0.398 F10 d50 971 0.971 0.714 85.177 0.046 11.217 0.146 0.1 0.187 0.262 G9 d50 190 0.190 0.365 7.353 0.121 11.308 0.061 0.1 0.078 0.213 G8 d50 164 0.164 0.245 5.916 0.094 12.405 0.059 0.1 0.076 0.310 H9 d50 909 0.909 0.658 77.212 0.045 12.588 0.151 0.1 0.194 0.294 H10 d50 2261 2.261 1.622 302.845 0.045 10.607 0.272 0.1 0.349 0.215 I10 d50 468 0.468 0.392 28.543 0.053 11.521 0.095 0.1 0.122 0.311 I9 d50 2079 2.079 2.113 266.943 0.064 12.344 0.290 0.1 0.372 0.176 I8 d50 74 0.074 0.146 1.790 0.124 13.777 0.045 0.1 0.058 0.395 J11 d50 2523 2.523 1.810 356.877 0.045 8.656 0.250 0.1 0.320 0.177 B4 d50 152 0.152 0.233 5.258 0.096 7.559 0.047 0.1 0.060 0.258 H4 d50 224 0.224 0.365 9.437 0.102 18.288 0.082 0.1 0.106 0.289 G4 d50 303 0.303 0.367 14.821 0.076 16.855 0.092 0.1 0.118 0.322 L0 d50 157 0.157 0.238 5.518 0.095 16.794 0.067 0.1 0.085 0.358 J9a d50 1684 1.684 1.549 194.700 0.058 4.237 0.112 0.1 0.143 0.092 J9b d50 199 0.199 0.365 7.932 0.115 7.498 0.052 0.1 0.067 0.183 J9c d50 106 0.106 0.184 3.060 0.109 8.687 0.043 0.1 0.055 0.301 J10a d50 664 0.664 0.475 48.158 0.045 9.357 0.103 0.1 0.132 0.278

J10b d50 132 0.132 0.213 4.269 0.101 8.748 0.047 0.1 0.060 0.284 J10c d50 2148 2.148 2.219 280.462 0.065 9.723 0.241 0.1 0.308 0.139 H5 d50 246 0.246 0.365 10.887 0.093 15.728 0.080 0.1 0.103 0.281 I5 d50 258 0.258 0.366 11.665 0.089 13.228 0.075 0.1 0.096 0.264 I4 d50 179 0.179 0.365 6.750 0.128 18.440 0.074 0.1 0.095 0.260 J4 d50 217 0.217 0.365 8.995 0.106 18.136 0.081 0.1 0.103 0.283 I3 d50 234 0.234 0.365 10.065 0.098 16.642 0.080 0.1 0.103 0.282 M3 d50 152 0.152 0.234 5.287 0.096 14.661 0.062 0.1 0.079 0.339 J2 d50 126 0.126 0.206 3.975 0.103 14.265 0.056 0.1 0.072 0.350 H2 d50 201 0.201 0.365 8.037 0.114 11.918 0.064 0.1 0.082 0.224 O13a2 d50 201 0.201 0.365 8.034 0.114 3.536 0.039 0.1 0.051 0.138 N10b4 d50 239 0.239 0.365 10.384 0.096 3.627 0.042 0.1 0.054 0.148 N8 d50 205 0.205 0.365 8.284 0.112 4.115 0.042 0.1 0.054 0.147 K7 d50 437 0.437 0.385 25.695 0.055 8.931 0.080 0.1 0.103 0.268 P7 d50 168 0.168 0.249 6.132 0.093 21.885 0.078 0.1 0.100 0.401 S6 d50 194 0.194 0.365 7.634 0.118 5.121 0.045 0.1 0.057 0.156 P3 d50 293 0.293 0.367 14.139 0.079 3.627 0.046 0.1 0.059 0.160 F12D1 d50 798 0.798 0.566 63.464 0.044 2.000 0.054 0.1 0.069 0.121 G12B2 d50 759 0.759 0.537 58.862 0.044 2.000 0.053 0.1 0.067 0.125 H12A2 d50 467 0.467 0.392 28.393 0.053 2.000 0.044 0.1 0.056 0.142 G11A4 d50 1711 1.711 1.586 199.423 0.058 2.000 0.075 0.1 0.097 0.061 I12C2 d50 620 0.620 0.451 43.506 0.046 2.000 0.048 0.1 0.062 0.138 J11A5 d50 2214 2.214 1.588 293.405 0.045 2.000 0.086 0.1 0.110 0.069

J11D2 d50 809 0.809 0.574 64.797 0.045 2.000 0.054 0.1 0.069 0.120 M9A3 d50 171 0.171 0.252 6.286 0.093 2.000 0.031 0.1 0.040 0.157 L9D4 d50 198 0.198 0.365 7.823 0.116 2.000 0.032 0.1 0.042 0.114 L9B4 d50 122 0.122 0.203 3.817 0.104 2.000 0.028 0.1 0.036 0.177 K9D3 d50 101 0.101 0.179 2.873 0.111 2.000 0.026 0.1 0.034 0.189 N10B4 d50 233 0.233 0.365 10.002 0.098 2.000 0.034 0.1 0.044 0.120 N11A5 d50 239 0.239 0.365 10.440 0.096 2.000 0.034 0.1 0.044 0.121 N11B5 d50 173 0.173 0.254 6.421 0.092 2.000 0.031 0.1 0.040 0.157 N11B4 d50 129 0.129 0.209 4.117 0.102 2.000 0.028 0.1 0.036 0.174 N11B3 d50 108 0.108 0.186 3.153 0.109 2.000 0.027 0.1 0.035 0.185 N11B2 d50 115 0.115 0.194 3.472 0.106 2.000 0.027 0.1 0.035 0.181 N11A2 d50 196 0.196 0.365 7.749 0.117 2.000 0.032 0.1 0.041 0.113 N11A1 d50 119 0.119 0.199 3.668 0.105 2.000 0.028 0.1 0.036 0.178 N10A5 d50 124 0.124 0.205 3.897 0.103 2.000 0.028 0.1 0.036 0.176 N10A4 d50 148 0.148 0.229 5.065 0.097 2.000 0.030 0.1 0.038 0.165 M10E4 d50 186 0.186 0.365 7.174 0.123 2.000 0.032 0.1 0.041 0.112 N11C5 d50 197 0.197 0.365 7.771 0.116 2.000 0.032 0.1 0.041 0.113 N11D5 d50 195 0.195 0.365 7.658 0.118 2.000 0.032 0.1 0.041 0.113 N11C4 d50 182 0.182 0.365 6.917 0.126 2.000 0.032 0.1 0.040 0.111 N11C2 d50 221 0.221 0.365 9.235 0.104 2.000 0.034 0.1 0.043 0.118 N10B5 d50 240 0.240 0.365 10.455 0.096 2.000 0.034 0.1 0.044 0.121

Table A.2. Computed critical and bed stress from wind waves (100 year return period) at discrete grab samples collected in October 2011.

Grid depth τb,max Sample Parameters microns (mm) τcr (Pa) R* θcr (m) fw Uw (m/s) (Pa) Mobility coeff C9 d50 24 0.024 0.070 0.331 0.183 14.173 0.008 0.011 0.000 0.000 F7 d50 88 0.088 0.163 2.306 0.117 14.387 0.011 0.014 0.001 0.006 F9 d50 65 0.065 0.134 1.486 0.129 12.771 0.010 0.012 0.001 0.007 F10 d50 971 0.971 0.714 85.177 0.046 11.217 0.035 0.012 0.003 0.004 G9 d50 190 0.190 0.365 7.353 0.121 11.308 0.018 0.013 0.002 0.005 G8 d50 164 0.164 0.245 5.916 0.094 12.405 0.013 0.013 0.001 0.004 H9 d50 909 0.909 0.658 77.212 0.045 12.588 0.042 0.013 0.003 0.005 H10 d50 2261 2.261 1.622 302.845 0.045 10.607 0.064 0.012 0.005 0.003 I10 d50 468 0.468 0.392 28.543 0.053 11.521 0.033 0.011 0.002 0.005 I9 d50 2079 2.079 2.113 266.943 0.064 12.344 0.042 0.014 0.004 0.002 I8 d50 74 0.074 0.146 1.790 0.124 13.777 0.015 0.015 0.002 0.014 J11 d50 2523 2.523 1.810 356.877 0.045 8.656 0.131 0.006 0.003 0.002 B4 d50 152 0.152 0.233 5.258 0.096 7.559 0.011 0.020 0.002 0.009 H4 d50 224 0.224 0.365 9.437 0.102 18.288 0.016 0.014 0.002 0.005 G4 d50 303 0.303 0.367 14.821 0.076 16.855 0.017 0.014 0.002 0.005 L0 d50 157 0.157 0.238 5.518 0.095 16.794 0.011 0.022 0.003 0.013 J9a d50 1684 1.684 1.549 194.700 0.058 4.237 0.000 0.000 0.000 0.000 J9b d50 199 0.199 0.365 7.932 0.115 7.498 0.013 0.018 0.002 0.005 J9c d50 106 0.106 0.184 3.060 0.109 8.687 0.014 0.016 0.002 0.011

J10a d50 664 0.664 0.475 48.158 0.045 9.357 0.043 0.012 0.003 0.006 J10b d50 132 0.132 0.213 4.269 0.101 8.748 0.017 0.022 0.004 0.019 J10c d50 2148 2.148 2.219 280.462 0.065 9.723 0.043 0.012 0.003 0.001 H5 d50 246 0.246 0.365 10.887 0.093 15.728 0.015 0.015 0.002 0.005 I5 d50 258 0.258 0.366 11.665 0.089 13.228 0.015 0.017 0.002 0.005 I4 d50 179 0.179 0.365 6.750 0.128 18.440 0.014 0.015 0.002 0.005 J4 d50 217 0.217 0.365 8.995 0.106 18.136 0.015 0.015 0.002 0.005 I3 d50 234 0.234 0.365 10.065 0.098 16.642 0.016 0.015 0.002 0.005 M3 d50 152 0.152 0.234 5.287 0.096 14.661 0.010 0.029 0.004 0.017 J2 d50 126 0.126 0.206 3.975 0.103 14.265 0.010 0.021 0.002 0.010 H2 d50 201 0.201 0.365 8.037 0.114 11.918 0.015 0.016 0.002 0.005 O13a2 d50 201 0.201 0.365 8.034 0.114 3.536 0.008 0.068 0.019 0.052 N10b4 d50 239 0.239 0.365 10.384 0.096 3.627 0.007 0.086 0.027 0.074 N8 d50 205 0.205 0.365 8.284 0.112 4.115 0.009 0.062 0.017 0.047 K7 d50 437 0.437 0.385 25.695 0.055 8.931 0.016 0.022 0.004 0.010 P7 d50 168 0.168 0.249 6.132 0.093 21.885 0.009 0.036 0.006 0.024 S6 d50 194 0.194 0.365 7.634 0.118 5.121 0.008 0.086 0.030 0.082 P3 d50 293 0.293 0.367 14.139 0.079 3.627 0.000 0.000 0.000 0.000 F12D1 d50 798 0.798 0.566 63.464 0.044 2.000 0.000 0.000 0.000 0.000 G12B2 d50 759 0.759 0.537 58.862 0.044 2.000 0.028 0.022 0.007 0.013 H12A2 d50 467 0.467 0.392 28.393 0.053 2.000 0.000 0.000 0.000 0.000 G11A4 d50 1711 1.711 1.586 199.423 0.058 2.000 0.000 0.000 0.000 0.000 I12C2 d50 620 0.620 0.451 43.506 0.046 2.000 0.000 0.000 0.000 0.000

J11A5 d50 2214 2.214 1.588 293.405 0.045 2.000 0.060 0.014 0.006 0.004 J11D2 d50 809 0.809 0.574 64.797 0.045 2.000 0.032 0.017 0.005 0.009 M9A3 d50 171 0.171 0.252 6.286 0.093 2.000 0.008 0.060 0.015 0.060 L9D4 d50 198 0.198 0.365 7.823 0.116 2.000 0.009 0.070 0.023 0.063 L9B4 d50 122 0.122 0.203 3.817 0.104 2.000 0.009 0.049 0.011 0.054 K9D3 d50 101 0.101 0.179 2.873 0.111 2.000 0.009 0.037 0.006 0.034 N10B4 d50 233 0.233 0.365 10.002 0.098 2.000 0.007 0.086 0.027 0.074 N11A5 d50 239 0.239 0.365 10.440 0.096 2.000 0.008 0.085 0.031 0.085 N11B5 d50 173 0.173 0.254 6.421 0.092 2.000 0.000 0.000 0.000 0.000 N11B4 d50 129 0.129 0.209 4.117 0.102 2.000 0.008 0.085 0.031 0.148 N11B3 d50 108 0.108 0.186 3.153 0.109 2.000 0.008 0.085 0.031 0.167 N11B2 d50 115 0.115 0.194 3.472 0.106 2.000 0.007 0.076 0.021 0.108 N11A2 d50 196 0.196 0.365 7.749 0.117 2.000 0.007 0.076 0.021 0.058 N11A1 d50 119 0.119 0.199 3.668 0.105 2.000 0.007 0.076 0.021 0.106 N10A5 d50 124 0.124 0.205 3.897 0.103 2.000 0.007 0.076 0.021 0.102 N10A4 d50 148 0.148 0.229 5.065 0.097 2.000 0.007 0.086 0.027 0.118 M10E4 d50 186 0.186 0.365 7.174 0.123 2.000 0.007 0.086 0.027 0.074 N11C5 d50 197 0.197 0.365 7.771 0.116 2.000 0.008 0.061 0.016 0.044 N11D5 d50 195 0.195 0.365 7.658 0.118 2.000 0.008 0.061 0.016 0.044 N11C4 d50 182 0.182 0.365 6.917 0.126 2.000 0.008 0.061 0.016 0.044 N11C2 d50 221 0.221 0.365 9.235 0.104 2.000 0.008 0.065 0.018 0.049 N10B5 d50 240 0.240 0.365 10.455 0.096 2.000 0.007 0.076 0.021 0.058

Appendix B. CMS-FLOW current magnitude and direction

Figure B.1. Peak ebb 1 (4 Oct 2010 02:00)

Figure B.2. slack flood 1 (4 Oct 2010 05:30)

Figure B.3. peak flood 1 (4 Oct 2010 08:00)

Figure B.4. slack ebb 1 (4 Oct 2010 11:00)

Figure B.5. peak ebb 2 (4 Oct 2010 14:00)

Figure B.6. slack flood 2 (4 Oct 2010 17:00)

Figure B.7. peak flood 2 (4 Oct 2010 20:00)

Figure B.8. slack ebb 2 (4 Oct 2010 23:00)