Appendix E

Hydrodynamic Analysis Report

DRAFT EVALUATION OF HYDRODYNAMIC AND SEDIMENT TRANSPORT PROCESSES ST. HELENS FIBERBOARD PLANT

Prepared for Armstrong World Industries, Inc. Kaiser Gypsum Company, Inc. Owens Corning Sales LLC

Prepared by Anchor QEA, LLC 305 West Grand Avenue, Suite 300 Montvale, New Jersey 07645

August 2013

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DRAFT

TABLE OF CONTENTS FOREWORD ...... F-1

EXECUTIVE SUMMARY ...... ES-1

1 INTRODUCTION ...... 1 1.1 Study Goals ...... 1 1.2 Overview of Technical Approach ...... 2

2 ANALYSIS OF HISTORICAL AERIAL PHOTOGRAPHS ...... 4 2.1 Description of Historical Aerial Photographs ...... 4 2.2 Morphologic Analysis of Historical Aerial Photographs ...... 6 2.2.1 Extent and Density of Vegetation ...... 6 2.2.2 Stability of McNulty and Milton Creek Channels ...... 7 2.2.3 Evaluation of Small-Scale Morphologic Features ...... 8 2.2.3.1 Mudflats ...... 13 2.2.3.2 McNulty Island ...... 14 2.2.3.3 Southwest Channel ...... 15 2.2.3.4 Highlands ...... 15 2.2.3.5 Bar ...... 16 2.2.3.6 Northeast ...... 16 2.3 Summary ...... 17

3 GEOCHRONOLOGY ANALYSIS OF RADIOISOTOPE CORES ...... 19 3.1 Description of Radioisotope Core Data ...... 19 3.2 Geochronology ...... 19 3.2.1 137Cs Activity Measurements ...... 20 3.2.2 210Pb Activity Measurements ...... 21 3.2.3 Conclusions and Uncertainties of the Radioisotope Analysis ...... 21

4 HYDRODYNAMIC MODEL DEVELOPMENT, CALIBRATION, AND VALIDATION . 23 4.1 Description of Hydrodynamic Model Structure ...... 23 4.2 Far-field Hydrodynamic Model ...... 24 4.2.1 Development of Far-field Model ...... 24 4.2.2 Calibration and Validation Strategy for Far-field Model ...... 25

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DRAFT Table of Contents 4.2.3 Calibration and Validation Results for Far-field Model ...... 27 4.3 Near-field Hydrodynamic Model ...... 29 4.3.1 Development of Near-field Model ...... 29 4.3.2 Calibration and Validation Strategy for Near-field Model ...... 30 4.3.3 Calibration and Validation Results for Near-field Model ...... 31 4.4 Summary ...... 34

5 SEDIMENT STABILITY ANALYSIS ...... 36 5.1 Development of High-flow Event Simulations ...... 36 5.2 Inundation Frequencies Predicted by Hydrodynamic Model ...... 40 5.3 Results of High-flow Event Simulations ...... 41 5.4 Summary ...... 43

6 SUMMARY OF HYDRODYNAMIC CONDITIONS ...... 45

7 REFERENCES ...... 47

List of Tables Table 2-1 Water Surface Elevation and Flow Rate on Day of Aerial Photograph Table 2-2 Construction History of Columbia River Dams Table 2-3 Summary of Historical Discharge Volumes to the Lowland

Table 4-1 Tidal Constituents Evaluated During Tidal Harmonic Analysis Table 4-2 Spatially Variable Effective Bed Roughness for Far-field Model Table 4-3 Root Mean Square Error for Predicted WSE during Far-field Calibration and Validation Periods

Table 5-1 Flow Rates Used in High-flow Event Simulations Table 5-2 Inflow Conditions for High-flow Event Simulations Table 5-3 Comparison of Model Projected and Data Estimated Inundation Frequency

Table A-1 T-distribution values for 95% confidence interval Table A-2 Results of Analysis For Uncertainty in Pb-210 Regression Slope Table A-3 Range of Estimated NSRs Based on Pb-210 Activity Data Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant ii 100703-01 74275387.1 0015549-00007

DRAFT Table of Contents Table A-4 Summary of Columbia River Cs-137 Sediment Data from Priddy et al. (2005) Table A-5 Summary of Cs-137 Activity Data for Study Area Cores Table B-1 Tidal Constituents Evaluated During Tidal Harmonic Analysis Table B-2 Far-field Model Tidal Harmonic Analysis: Amplitude at St. Helens – September 2005 Table B-3 Far-field Model Tidal Harmonic Analysis: Phase at St. Helens – September 2005 Table B-4 Far-field Model Tidal Harmonic Analysis: Amplitude at Vancouver – September 2005 Table B-5 Far-field Model Tidal Harmonic Analysis: Phase at Vancouver – September 2005 Table B-6 Far-field Model Tidal Harmonic Analysis: Amplitude at Columbia Slough – September 2005 Table B-7 Far-field Model Tidal Harmonic Analysis: Phase at Columbia Slough – September 2005 Table B-8 Far-field Model Tidal Harmonic Analysis: Amplitude at Bonneville Dam – September 2005 Table B-9 Far-field Model Tidal Harmonic Analysis: Phase at Bonneville Dam – September 2005 Table B-10 Far-field Model Tidal Harmonic Analysis: Amplitude at Lower Willamette River – September 2005 Table B-11 Far-field Model Tidal Harmonic Analysis: Phase at Lower Willamette River – September 2005 Table B-12 Far-field Model Tidal Harmonic Analysis: Amplitude at St. Helens – May 2006 Table B-13 Far-field Model Tidal Harmonic Analysis: Phase at St. Helens – May 2006 Table B-14 Far-field Model Tidal Harmonic Analysis: Amplitude at Vancouver – May 2006 Table B-15 Far-field Model Tidal Harmonic Analysis: Phase at Vancouver – May 2006 Table B-16 Far-field Model Tidal Harmonic Analysis: Amplitude at Columbia Slough – May 2006 Table B-17 Far-field Model Tidal Harmonic Analysis: Phase at Columbia Slough – May 2006

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DRAFT Table of Contents Table B-18 Far-field Model Tidal Harmonic Analysis: Amplitude at Bonneville Dam – May 2006 Table B-19 Far-field Model Tidal Harmonic Analysis: Phase at Bonneville Dam – May 2006 Table B-20 Far-field Model Tidal Harmonic Analysis: Amplitude at Lower Willamette River – May 2006 Table B-21 Far-field Model Tidal Harmonic Analysis: Phase at Lower Willamette River – May 2006 Table B-22 Skill Assessment Statistics Table B-23 Far-field Model Statistical Analysis during Calibration Period: St. Helens Table B-24 Far-field Model Statistical Analysis during Calibration Period: Vancouver Table B-25 Far-field Model Statistical Analysis during Calibration Period: Columbia Slough Table B-26 Far-field Model Statistical Analysis during Calibration Period: Bonneville Dam Table B-27 Far-field Model Statistical Analysis during Calibration Period: Lower Willamette River Table B-28 Far-field Model Statistical Analysis during Validation Period: St. Helens Table B-29 Far-field Model Statistical Analysis during Validation Period: Vancouver Table B-30 Far-field Model Statistical Analysis during Validation Period: Columbia Slough Table B-31 Far-field Model Statistical Analysis during Validation Period: Bonneville Dam Table B-32 Far-field Model Statistical Analysis during Validation Period: Lower Willamette River Table B-33 Near-field Model Tidal Harmonic Analysis: Amplitude at Old Pier, Scappoose Bay – April to June 2011 Table B-34 Near-field Model Tidal Harmonic Analysis: Phase at Old Pier, Scappoose Bay – April to June 2011 Table B-35 Near-field Model Statistical Analysis: Old Pier, Scappoose Bay – April to June 2011 Table B-36 Near-field Model Statistical Analysis: Old Pier, Scappoose Bay – April to June 2011

Table C-1 Study Area-specific Resuspension Potential Parameters

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DRAFT Table of Contents List of Figures Figure 2-1 Aerial Photograph of Study Area: 1929 Figure 2-2 Aerial Photograph of Study Area: 1948 Figure 2-3 Aerial Photograph of Study Area: 1957 Figure 2-4 Aerial Photograph of Study Area: 1973 Figure 2-5 Aerial Photograph of Study Area: 1983 Figure 2-6 Aerial Photograph of Study Area: 2010 Figure 2-7 Side-by-side Comparison of Extent of Vegetation within Study Area in 1929 and 2010 Figure 2-8 Increase in Vegetation within Study Area in 1929 and 2010 Figure 2-9 Comparison of Channel Location of McNulty and Milton Creeks in 1929 and 1948 Figure 2-10 Comparison of Channel Location of McNulty and Milton Creeks in 1948 and 1957 Figure 2-11 Comparison of Channel Location of McNulty and Milton Creeks in 1957 and 2010 Figure 2-12 Subareas for Aerial Photograph Small Scale Feature Review Figure 2-13 Aerial Photograph for Small-Scale Feature Review: 1948 Figure 2-14 Aerial Photograph for Small-Scale Feature Review: 1953 Figure 2-15 Aerial Photograph for Small-Scale Feature Review: 1966 Figure 2-16 Aerial Photograph for Small-Scale Feature Review: 1970 Figure 2-17 Aerial Photograph for Small-Scale Feature Review: 1975 Figure 2-18 Aerial Photograph for Small-Scale Feature Review: 1980 Figure 2-19 Aerial Photograph for Small-Scale Feature Review: 1988 Figure 2-20 Aerial Photograph for Small-Scale Feature Review: 1992 Figure 2-21 Aerial Photograph for Small-Scale Feature Review: 1996 Figure 2-22 Aerial Photograph for Small-Scale Feature Review: 2000 Figure 2-23 Aerial Photograph for Small-Scale Feature Review: 2005 Figure 2-24 Aerial Photograph for Small-Scale Feature Review: 2010

Figure 3-1 Locations of Radioisotope Cores Collected during June 2011 Figure 3-2 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-01 Figure 3-3 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-02 Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant v 100703-01 74275387.1 0015549-00007

DRAFT Table of Contents Figure 3-4 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-03 Figure 3-5 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-04 Figure 3-6 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-05 Figure 3-7 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-06 Figure 3-8 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-07 Figure 3-9 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-08 Figure 3-10 Vertical Profile of Pb-210 Activity in Ideal Depositional Setting Figure 3-11 Vertical Profiles of Transformed Pb-210 Activity

Figure 4-1 Spatial Extent of Model Domain for Far-field Model Figure 4-2 Portion of Numerical Grid for Far-field Model: Columbia River near St. Helens Figure 4-3 Portion of Numerical Grid for Far-field Model: Lower Willamette River Figure 4-4 Locations of Far-field Model Inputs for WSE at Downstream Boundary and Inflows from Upstream and Tributary Sources Figure 4-5 Daily Average Flow Rate for Columbia River at The Dalles and Lower Willamette River during Far-field Model Calibration Period (July 2005 through September 2006) Figure 4-6 Comparison of Predicted and Measured WSE during September 2005 and May 2006 at St. Helens Figure 4-7 Comparison of Predicted and Measured WSE during September 2005 and May 2006 at Vancouver Figure 4-8 Comparison of Predicted and Measured WSE during September 2005 and May 2006 at Columbia Slough Figure 4-9 Comparison of Predicted and Measured WSE during September 2005 and May 2006 at Bonneville Dam Figure 4-10 Comparison of Predicted and Measured WSE during September 2005 and May 2006 in Lower Willamette River at Portland Figure 4-11 Daily Average Flow Rate for Columbia River at The Dalles and Lower Willamette River during Far-field Model Validation Period (December 2007 through January 2009) Figure 4-12 Comparison of Predicted and Measured WSE during May and September 2008 at St. Helens

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DRAFT Table of Contents Figure 4-13 Comparison of Predicted and Measured WSE during May and September 2008 at Vancouver Figure 4-14 Comparison of Predicted and Measured WSE during May and September 2008 at Columbia Slough Figure 4-15 Comparison of Predicted and Measured WSE during May and September 2008 at Bonneville Dam Figure 4-16 Comparison of Predicted and Measured WSE during May and September 2008 in Lower Willamette River at Portland Figure 4-17 Daily Average Flow Rate for Columbia River at The Dalles and Lower Willamette River during February 1996 Flood Figure 4-18 Comparison of Predicted and Measured WSE during February 1996 Flood at Vancouver Figure 4-19 Comparison of Predicted and Measured WSE during February 1996 Flood at Columbia Slough Figure 4-20 Comparison of Predicted and Measured WSE during February 1996 Flood at Bonneville Dam Figure 4-21 Comparison of Predicted and Measured WSE during February 1996 Flood in Lower Willamette River at Portland Figure 4-22 Near-field Model Domain and Numerical Grid with Bathymetry Figure 4-23 Numerical Grid and Bathymetry for Near-field Model in Vicinity of the Study Area Figure 4-24 Locations of Near-field Model Inputs for WSE at Downstream Boundary and Inflows from Upstream and Tributary Sources Figure 4-25 Locations of Acoustic Doppler Current Profilers (ADCPs) in Scappoose Bay and Multnomah Channel and Tide Gauge at Pier Near Plant Site Figure 4-26 Daily Average Flow Rate for Columbia River at The Dalles, Measured WSE and Current Velocity in Scappoose Bay during Near-field Model Calibration Period: April to June 2011 Figure 4-27 Daily Average Flow Rate for Columbia River at The Dalles and Measured Current Velocity in Multnomah Channel during Near-field Model Validation Period: June 2011

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DRAFT Table of Contents Figure 4-28 Comparison of Predicted and Measured WSE and Current Velocity in Scappoose Bay during Near-field Model Calibration Period: April 5 to May 5, 2011 Figure 4-29 Comparison of Predicted and Measured WSE and Current Velocity in Scappoose Bay during Near-field Model Calibration Period: May 5 to June 4, 2011 Figure 4-30 Comparison of Predicted and Measured WSE and Current Velocity in Multnomah Channel during Near-field Model Validation Period: June 2011 Figure 4-31 Sensitivity Analysis Results for Near-field Model in Scappoose Bay during Calibration Period: April 5 to May 5, 2011 Figure 4-32 Sensitivity Analysis Results for Near-field Model in Scappoose Bay during Calibration Period: May 5 to June 4, 2011 Figure 4-33 Sensitivity Analysis Results for Near-field Model in Multnomah Channel during Validation Period: June 2011

Figure 5-1 Daily Average Flow Rates for Columbia River at The Dalles, Lower Willamette River, and McNulty Creek during October 1994 Flood Figure 5-2 Locations Used for Comparing Inundation Frequencies Predicted by Near-field Hydrodynamic Model and Estimated Using Water Surface Elevation Data Collected at St. Helens Gaging Station Figure 5-3 Spatial Distribution of Inundation Frequency within the Study Area Figure 5-4 Comparison of Inundation Frequencies Predicted by Near-field Hydrodynamic Model and Estimated Using Water Surface Elevation Data Collected at St. Helens Gaging Station Figure 5-5 Spatial Distribution of Predicted Maximum Current Velocity: High-flow Event Simulation 1, 10-year Flood in Columbia River Figure 5-6 Spatial Distribution of Estimated Bed Scour Depth: High-flow Event Simulation 1, 10-year Flood in Columbia River Figure 5-7 Spatial Distribution of Predicted Maximum Current Velocity: High-flow Event Simulation 2, 100-year Flood in Columbia River Figure 5-8 Spatial Distribution of Estimated Bed Scour Depth: High-flow Event Simulation 2, 100-year Flood in Columbia River

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DRAFT Table of Contents Figure 5-9 Spatial Distribution of Predicted Maximum Current Velocity: High-flow Event Simulation 3, 10-year Flood in Lower Willamette River Figure 5-10 Spatial Distribution of Estimated Bed Scour Depth: High-flow Event Simulation 3, 10-year Flood in Lower Willamette River Figure 5-11 Spatial Distribution of Predicted Maximum Current Velocity: High-flow Event Simulation 4, 100-year Flood in Lower Willamette River Figure 5-12 Spatial Distribution of Estimated Bed Scour Depth: High-flow Event Simulation 4, 100-year Flood in Lower Willamette River Figure 5-13 Spatial Distribution of Predicted Maximum Current Velocity: High-flow Event Simulation 5, 10-year Flood in Scappoose Bay Tributaries Figure 5-14 Spatial Distribution of Estimated Bed Scour Depth: High-flow Event Simulation 5, 10-year Flood in Scappoose Bay Tributaries Figure 5-15 Spatial Distribution of Predicted Maximum Current Velocity: High-flow Event Simulation 6, 100-year Flood in Scappoose Bay Tributaries Figure 5-16 Spatial Distribution of Estimated Bed Scour Depth: High-flow Event Simulation 6, 100-year Flood in Scappoose Bay Tributaries Figure 5-17 Spatial Distribution of Predicted Maximum Current Velocity: February 1996 Flood Figure 5-18 Spatial Distribution of Estimated Bed Scour Depth: February 1996 Flood Figure 5-19 Spatial Distribution of Predicted Maximum Current Velocity: October 1994 Flood Figure 5-20 Spatial Distribution of Estimated Bed Scour Depth: October 1994 Flood

Figure A-1 Radioisotope Core Lithology: Cores AQ-01 and AQ-02 Figure A-2 Radioisotope Core Lithology: Cores AQ-03 and AQ-04 Figure A-3 Radioisotope Core Lithology: Cores AQ-05 and AQ-06 Figure A-4 Radioisotope Core Lithology: Cores AQ-07 and AQ-08 Figure A-5 NSR Analysis of Vertical Profile of Pb-210 Activity: Core AQ-01 Figure A-6 NSR Analysis of Vertical Profile of Pb-210 Activity: Core AQ-02 Figure A-7 NSR Analysis of Vertical Profile of Pb-210 Activity: Core AQ-03 Figure A-8 NSR Analysis of Vertical Profile of Pb-210 Activity: Core AQ-04 Figure A-9 NSR Analysis of Vertical Profile of Pb-210 Activity: Core AQ-05

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DRAFT Table of Contents Figure A-10 NSR Analysis of Vertical Profile of Pb-210 Activity: Core AQ-07 Figure A-11 NSR Analysis of Vertical Profile of Pb-210 Activity: Core AQ-08 Figure A-12 Spatial Distribution of Cs-137 Deposition Density Due to All Nevada Test Site Atmospheric Nuclear Weapon Tests

List of Appendices Appendix A Geochronology Analysis Appendix B Results of Harmonic and Statistical Analyses for Near-field and Far-field Hydrodynamic Models Appendix C Approach for Estimating Bed Scour during High-flow Events

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DRAFT

LIST OF ACRONYMS AND ABBREVIATIONS Abbreviation Definition ADCP Acoustic Doppler Current Profiler CF central frequency cfs cubic feet per second cm centimeter cm/s centimeters per second cm/yr centimeters per year CSM Conceptual site model DEA David Evans and Associates EFDC Environmental Fluid Dynamics Code FEMA Federal Emergency Management Agency FIS Flood Insurance Study ft feet ft/s feet per second g/cm3 grams per cubic centimeter hr hour in/yr inches per year m3s-1 cubic meters per second MDNO maximum duration of negative outliers MDPO maximum duration of positive outliers mg/cm2 milligrams per square centimeter mi2 square miles NAVD29 North American Vertical Datum of 1929 NAVD88 North American Vertical Datum of 1988 NDA no data available NGVD29 National Geodetic Vertical Datum of 1929 NOAA National Oceanic and Atmospheric Administration NOF negative outlier frequency NSR net sedimentation rate Pa Pascal pCi/g picoCuries per gram Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant xi 100703-01 74275387.1 0015549-00007

DRAFT List of Acronyms and Abbreviations POF positive outlier frequency QEA Quantitative Environmental Analysis R2 correlation coefficient RI/FS Remedial Investigation/Feasibility Study RMSE root mean square error SCS U.S. Soil Conservation Service SD standard deviation SM series mean (average value) USACE U.S. Army Corps of Engineers USEPA U.S. Environmental Protection Agency USGS U.S. Geological Survey WSE water surface elevation

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DRAFT FOREWORD This report has been revised from the previous November 20, 2012 draft based on comments received from the Oregon Department of Environmental Quality (DEQ) and DEQ’s consultant, Dr. David Jay, during a meeting on March 12, 2013. Many of the comments provided by DEQ and Dr. Jay have been addressed in this report, but some of the comments provided by DEQ during the March, 2013 meeting have not been addressed at this time. For example, and consistent with a May 21, 2013 memorandum to DEQ, the broad-scale hydrodynamic model has not been amended or refined from the one presented in the November 20, 2012 draft report.

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DRAFT EXECUTIVE SUMMARY The primary goal of this study was to support the development of the conceptual site model (CSM) for the remedial investigation and risk assessment, and if necessary, evaluate the efficacy of different remedial alternatives that may warrant consideration at the St. Helens Fiberboard Plant in St. Helens, Oregon. The work was focused toward the Aquatic Lowlands and In-water (including Scappoose Bay) portions of the overall fiberboard plant area (i.e., the “Study Area” for the purposes of this study).

A weight-of-evidence approach was used to develop an understanding of the hydrodynamic conditions in the Study Area. A combination of broad-scale modeling analyses and empirical information (e.g., historical aerial photographs and radioisotope core analyses) provided independent lines-of-evidence toward this objective. The scope of this study was defined by the five study questions listed below.

• What areas are depositional and what areas experience erosion during high-flow events?

• In areas that experience erosion during high-flow events, what is the potential depth of scour?

• What is the potential for re-exposing buried sediments?

• What are the net sedimentation rates in depositional areas?

• Can net sedimentation rates be enhanced by modification of the geometry of the study area?

The first four questions were addressed using a combination of empirical and modeling analyses. The fifth question was not evaluated during this study. Overall, the study considered historical hydrodynamic conditions and processes over the past 80 years, as well as the current hydrodynamic conditions and processes, as a basis to predict potential future hydrodynamic conditions and processes.

In general, the scope of the hydrodynamic analysis consisted of the following:

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DRAFT Executive Summary • Review of approximately 150 aerial photographs, dating from 1929 to 2010, for both broad-scale and small-scale features;

• Collection of eight radioisotope cores from the Study Area and analysis of selected 1- inch sections of the cores for cesium 137 (137Cs) and lead 210 (210Pb) activity;

• Development, calibration, and validation of a broad-scale hydrodynamic model for the Study Area; and

• Assessment of potential sediment stability based on current velocities and associated bed shear stresses predicted from the hydrodynamic model.

The analyses conducted during this study provided insights and understanding of the hydrodynamic conditions within the Study Area, in particular:

• Vegetation has emerged and been established across much of the Study Area between the 1930s and the present. This broad-scale increase in vegetation was primarily caused by the reduction in the magnitude and frequency of flood events as a result of Columbia River dam construction resulting in less frequent inundation and lower current velocities and by reduced disturbance after cessation of process water (i.e., waste water and cooling water) discharges. This emergence of vegetation likely contributed to the historical net sedimentation within the Study Area given the reduced current velocities caused by the vegetation and the accretion of decaying vegetation.

• Review of historical aerial photographs suggests localized erosional events, driven by tidal inundation, have occurred in the lower elevations of the aquatic lowland and these events appear to continue to occur currently, especially in the Mudflat subarea. Localized erosion driven by tidal inundation does not appear to have generally occurred historically (especially since the construction of the Columbia River dams) in the higher elevations of the aquatic lowland; however, erosion associated with the presence and migration of channels transporting process water (i.e., waste water and cooling water) discharges from the plant to the lowland historically caused erosion in higher elevations of the lowland. Any erosion associated with process water flows appears to have ended by the early 1980s, corresponding to cessation of process water discharges from the plant at the end of 1981.

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DRAFT Executive Summary • While geochronology analyses of radioisotope cores indicate the Study Area has, on a broad-scale, historically been net depositional, the estimated magnitude of sedimentation within the Study Area is uncertain due to variability in the radioisotope data and its interpretation and the limited locations of the radioisotope cores. However, the results of the analyses suggest a representative range for historical net sedimentation rate (NSR) at the radioisotope core locations in the aquatic lowland portion of the Study Area is on the order of 0.1 to 0.5 inch/year. These results indicate the historical net sedimentation in areas represented by the radioisotope core locations is on the order of about 1 foot over the past 40 to 100 years. The magnitude of historical net sedimentation at elevations below or above the elevation range represented by the core locations may be substantially different from that estimated from the core analysis.

• The results of the calibration and validation of the broad-scale hydrodynamic model indicate the near-field model can be used to evaluate broad-scale hydrodynamic and sediment transport processes within the Study Area over a wide range of flow and tidal conditions and inform an understanding of the broad-scale hydrodynamic conditions in the Study Area.

• Broad-scale hydrodynamic modeling predicted no broad-scale bed scour in the Study Area for the vast majority of flood event conditions considered, including 100-year floods on the Lower Willamette River and Scappoose Bay tributaries and 10-year flood on the Columbia River. Minimal erosion of the surface-layer of the bed was predicted by the model in small areas in the McNulty Creek channel mudflats during selected extreme events (i.e., episodic, short-term events). Overall, the sediment stability analysis indicates minimal broad-scale scour occurs even under extreme conditions and the sediments at the Study Area are, on a broad-scale, stable. The hydrodynamic model is not sufficiently refined to necessarily describe the localized tidal inundation driven erosional events in the lower elevations of the aquatic lowlands suggested by the historical aerial photographs review.

• Broad-scale hydrodynamic modeling results are consistent with net deposition occurring within the Study Area especially during high-flow events in the Columbia River, which is also consistent with the results of empirical analyses. During floods

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DRAFT Executive Summary on the Columbia and Lower Willamette Rivers, significant increases in water surface elevation (WSE) occur within the Study Area, with subsequent inundation of inter- tidal and lowland areas. Scappoose Bay behaves like a backwater during these floods, with low current velocities and semi-quiescent conditions within inundated floodplain areas. These conditions, which are typically coincident with relatively high suspended sediment concentrations in the water column, are conducive to sediment deposition within the Study Area.

In the absence of major changes to the Columbia River, Lower Willamette River, and Scappoose Bay, current processes are anticipated to continue, including:

• Broad-scale net depositional processes, although the magnitude of those depositional processes may differ from the historical processes due to many factors, including rising bed elevations; and

• Small-scale erosional events in the lower elevations of the aquatic lowland.

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DRAFT

1 INTRODUCTION This hydrodynamic and sediment transport study was performed to support the Remedial Investigation/Feasibility Study (RI/FS) at the St. Helens Fiberboard Plant in St. Helens, Oregon, and was conducted in accordance with the Order on Consent Requiring Remedial Investigation and Feasibility Study (August 23, 2010, LQSR-NWER-10-05) issued by the Oregon Department of Environmental Quality (DEQ) to Armstrong World Industries, Inc. (AWI); Owens Corning Sales, LLC, (Owens); and Kaiser Gypsum Company, Inc., (Kaiser) (collectively referred to as the “Parties”). The St. Helens property encompasses several environments with different hydrologic conditions, including: 1) Uplands, the majority of which are above the maximum flood elevation, where the fiberboard plant is located; 2) Terrestrial Lowlands, consisting of heavily vegetated terrestrial land that is inundated only during very high water conditions; 3) Aquatic Lowlands that consist of vegetated marshes, tidelands, and mudflats; and 4) In-water sediments in Scappoose Bay. Elevated concentrations of chemicals of interest have been detected in upland and lowland soil and in-water sediment within the Study Area. Understanding the hydrodynamic and sediment transport processes in the Aquatic Lowlands and In-water areas of the property (i.e., the “Study Area” for the purposes of this study) is fundamental to the development of the conceptual site model (CSM) for the RI/FS.

1.1 Study Goals The primary goal of this study was to support the development of the CSM for the RI and risk assessment, and if necessary, evaluate the efficacy of different remedial alternatives that may warrant consideration within the Study Area.

A weight-of-evidence approach was used to develop an understanding of the hydrodynamic conditions in the Study Area. A combination of Study Area-wide modeling analyses and empirical information (e.g., historical aerial photographs, current and historical bathymetry and topography data, and radioisotope core analyses) provided independent lines-of- evidence that were used to develop an understanding of the hydrodynamic conditions. The scope of this study was defined by the five study questions presented below.

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DRAFT Introduction • What areas are depositional and what areas experience erosion during high-flow events?

• In areas that experience erosion during high-flow events, what is the potential depth of scour?

• What is the potential for re-exposing buried sediments?

• What are the net sedimentation rates in depositional areas?

• Can net sedimentation rates be enhanced by modification of the geometry of the study area?

The last question was not addressed because it was determined during the course of this study that it would be difficult to provide a reliable evaluation of the effects of modifying geometry within the Study Area on net sedimentation rates based on the results of the analyses discussed in this report.

Finally, given the broad-scale nature of the hydrodynamic modeling, the modeling results may be insufficient to fully evaluate the detailed efficacy of different remedial alternatives that may warrant consideration within the Study Area, if such consideration is found to be necessary.

1.2 Overview of Technical Approach Multiple empirical and modeling analyses were used to develop an understanding of hydrodynamic and sediment transport processes within the Study Area. Three general tasks were performed:

• Historical aerial photographs from the Study Area between 1929 and 2010 were examined to evaluate:

− Large-scale morphological changes; and

− Variations in small-scale localized features (e.g., transitory tidal channels and process water drainage channels).

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DRAFT Introduction • Radioisotope cores were collected from the Study Area and a geochronology analysis was conducted to characterize depositional processes and approximate ranges of rates.

• A Study Area-wide hydrodynamic model was developed, calibrated, and validated. The model was used to evaluate broad-scale sediment stability within the Study Area over a wide range of flow and tidal conditions.

Lines-of-evidence from these tasks were used to address the study questions and develop an understanding of the hydrodynamic conditions in the Study Area.

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DRAFT

2 ANALYSIS OF HISTORICAL AERIAL PHOTOGRAPHS Aerial photographs of the Study Area were taken at various times between 1929 and 2010. The historical aerial photographs provide visual evidence of large-scale morphological changes that occurred within the Study Area during the 81-year period. The photographs also provide visual evidence of localized erosional events within specific areas of the lowland.

2.1 Description of Historical Aerial Photographs Approximately 150 aerial photographs taken between 1929 and 2010 were obtained from the U.S. Army Corps of Engineers (USACE), University of Oregon, and Google Earth. The photographs were geo-referenced to enhance visual comparisons. Table 2-1 notes the specific representative aerial photographs used in the morphologic analysis discussed in Section 2.2. These 16 photographs provide representative visual depictions of changes in the broad-scale physical characteristics of the Study Area (Section 2.2.1 and Section 2.2.2) and changes in smaller-scale features (Section 2.2.3) that occurred during the 81-year period between 1929 and 2010.

Information on flow and water surface elevation (WSE) conditions on the Columbia and Lower Willamette rivers on the days the aerial photographs were taken is provided in Table 2-1. The average flow rates for the Columbia River at Bonneville Dam and Lower Willamette River are 183,000 and 33,000 cubic feet per second (cfs), respectively, for the 40- year period from 1972 through 2011. Thus, a majority of the aerial photographs are believed to represent relatively low-flow conditions in the Columbia River (i.e., flow rate less than average flow rate). Given the uncertainty of the date of the 1929 photograph, estimates of the corresponding water surface elevation and flow rate are not included in Table 2-1. The WSEs in Table 2-1 correspond to values at the National Oceanic and Atmospheric Administration (NOAA) gauging station at St. Helens.

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DRAFT Analysis of Historical Aerial Photographs Table 2-1 Water Surface Elevation and Flow Rate on Day of Aerial Photograph

Daily Average Daily Average Daily Range of Flow Rate: Flow Rate: Morphological Average WSE Columbia River Lower Date of Aerial Analysis WSE (ft, at Bonneville Willamette Year Photograph Performed (ft, NAVD88) NAVD88) Dam (cfs) River (cfs) 1929 NDA Broad-scale NDA NDA NDA NDA Broad-scale 1948 September 5 7.3 5.5 – 9.0 NDA NDA Small-scale 1953 September 9 Small-scale 6.9 5.6 – 8.3 NDA NDA 1957 November 5 Broad-scale 7.6 6.4 – 9.1 NDA NDA 1966 March 22 Small-scale 7.3 6.1 – 8.7 144,000 NDA 1970 May 19 Small-scale 7.2 5.9 – 9.0 321,000 NDA 1973 August 14 Broad-scale 7.7 6.1 – 9.0 108,000 5,300 1975 September 30 Small-scale 6.4 5.1 – 7.6 136,000 14,100 1980 January 30 Small-scale 9.2 7.5 – 10.5 200,000 44,000 1983 September 19 Broad-scale 6.4 5.0 – 7.4 113,000 14,000 1988 September 3 Small-scale 6.2 5.2 – 7.8 111,000 7,900 1992 June 20 Small-scale 7.4 6.0 – 8.8 NDA 8,800 1996 July 6 Small-scale 7.7 6.0 – 9.1 261,000 10,500 2000 July 23 Small-scale 7.4 6.1 – 8.8 148,000 9,900 2005 June 28 Small-scale 9.2 8.0 – 10.2 198,000 13,800 Broad-scale 2010 August 14 8.1 6.4 – 10.0 132,000 9,700 Small-scale

Notes: cfs – cubic feet per second NAVD88 – North American Vertical Datum of 1988

Given the lack of specific water elevations for the 1929 photograph and the uncertainty of whether each photo necessarily represents the “Daily Average WSE” (or is closer to the upper or lower value noted in the range of water surface elevations), the comparison of the historical aerial photographs is primarily focused toward broad trends rather than specific, detailed inferred changes between the individual photographs. Notwithstanding this, the historical photographs were also reviewed to identify clear evidence of changes in small spatial scale features where specific photograph information allowed such evaluation.

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DRAFT Analysis of Historical Aerial Photographs 2.2 Morphologic Analysis of Historical Aerial Photographs 2.2.1 Extent and Density of Vegetation The primary change in the broad-scale geomorphology of the Study Area that occurred during the 81-year period evaluated in the photographic analysis was the significant increase in the extent and density of vegetation in the Study Area, and the expected associated increase in bed elevation (resulting from accumulation of decaying plant material and decreased current velocities). Figures 2-1 through 2-8 show the broad-scale geomorphology in the Study Area

Comparisons of vegetated areas in 1929 and 2010 are provided in Figures 2-7 and 2-8. The vegetated area in the aquatic lowland portion of the Study Area was approximately 6 acres in 1929. Between 1929 and 2010, the vegetated area in this region increased by approximately 300 percent (23 acres total). The total area of the aquatic lowland portion of the Study Area is 62 acres. The increase in vegetation over this 81-year period is believed to be mainly due to changes in the flood characteristics of the Columbia River resulting from dam construction between the 1930s and 1950s. The completion dates of five dams on the Columbia River are presented in Table 2-2.

Table 2-2 Construction History of Columbia River Dams

Columbia River Dam Date of Completion Bonneville 1937 Grand Coulee 1944 McNary 1954 The Dalles 1957 John Day 1971

Several sources have documented changes in Columbia River flooding conditions that resulted from the dam construction. For example, Kukulka and Jay (2003) note:

Flow regulation also now cause spring freshet flows to follow a different time history than they would in the absence of flow regulation (Fig. 2). Reservoir storage

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DRAFT Analysis of Historical Aerial Photographs (amounting to ~60% of mean annual flow volume) has greatly reduced spring freshet amplitude, increased fall and winter flows, and decreased seasonal flow variability [Bottom et al., 1990]. The maximum monthly mean flows during the spring freshets have been reduced by an average of 7,500 m3s-1 and now seldom exceed 15,000 m3s-1 [Bottom et al., 2001].

Another source, Bottom et al. (2005), note the average peak flow rate at Beaver Army Terminal on the Columbia River decreased by 45 percent between the pre-dam construction period (average of 639,000 cfs for the period between 1878 and 1903) and post-dam construction period (average of 353,000 cfs for the period between 1970 and 1999).

Lower peak flow rates and shifts in flow variability during the post-dam construction period have resulted in less frequent inundation at higher elevations, as well as lower current velocities within the Study Area during flood conditions. Less frequent inundation and lower current velocities increase the likelihood of vegetation becoming established and growing in mudflat areas. The conversion of mudflats (i.e., non-vegetated areas) to vegetated areas significantly increased the stability of the sediment bed in the Study Area, primarily because of vegetative rooting structures. Emergent vegetation also tends to decrease flow velocities in the area, which increases depositional processes and accretion of suspended sediments on the sediment bed, which supports further vegetative development.

2.2.2 Stability of McNulty and Milton Creek Channels The lateral migration of McNulty and Milton Creeks in and around the Study Area was evaluated using aerial photographs taken in 1929, 1948, 1957, and 2010. Between 1929 and 1948, the McNulty Creek channel was relatively stable, with the primary change being the occurrence of a cutoff in the meander loop that was located in the upper portion of the creek (Figure 2-9). Larger changes in the channel location of McNulty Creek occurred during the 9-year period between 1948 and 1957 (Figure 2-10). The meander cutoff became the main channel, with the meander loop transitioned to an oxbow, which began to fill in. The channel of the meander cutoff moved laterally by approximately one channel width. An eastward shift of the mid-section of the channel occurred, with a maximum lateral migration of approximately 500 to 600 feet. The locations of the lower portion of the channel and

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DRAFT Analysis of Historical Aerial Photographs creek mouth experienced minimal change during this period. During the 54-year period between 1957 and 2010, the McNulty Creek channel form was generally stable (Figure 2-11). The primary change during this period was the formation of a meander cutoff in the mid- section of the channel.

During the 19-year period between 1929 and 1948, a man-made diversion of Milton Creek occurred, and the mouth of the creek was relocated approximately 2,800 feet from its location in 1929 (Figure 2-9). Another anthropogenic change in the course of Milton Creek occurred between 1948 and 1957 (Figure 2-10). The pre-1948 channel that went through the Study Area was apparently blocked off, and the creek mouth moved to a location that was approximately 800 feet southeast from the 1929 location of the mouth. The removal of this flow has allowed vegetation to become better established in the former channel. Minimal change of the location of Milton Creek occurred between 1957 and 2010 (Figure 2-11).

2.2.3 Evaluation of Small-Scale Morphologic Features The historical aerial photograph analyses discussed above in Section 2.2.2 were focused on morphologic changes over relatively large spatial scales. Additional evaluation of the historical aerial photographs was conducted in order to gain insights related to morphologic features at smaller scales. As noted on Table 2-1, the aerial photographs used in the small- scale analysis were taken during 1948, 1953, 1966, 1970, 1975, 1980, 1988, 1992, 1996, 2000, 2005, and 2010 (Figures 2-13 through 2-24).

The specific photographs for the assessment of small-scale changes in the Study Area were selected to coincide with specific time periods when differing locations and magnitude of discharges were occurring from the upland to the lowland. These discharges are believed to have affected the hydrodynamic conditions in the Study Area, especially in the higher elevations of the aquatic lowland near the historical discharges. Table 2-3 summarizes these times periods and the associated discharge conditions. Figure 2-12 shows the discharge locations noted in Table 2-3 that were included in the small-scale feature review.

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DRAFT Analysis of Historical Aerial Photographs

Table 2-3 Summary of Historical Discharge Volumes to the Lowland

Applicable Time Permits/Discharge Flow Rate Representative Period Conditions Discharge Type Information Aerial Photographs Reference Comments Process 1948 (USACE) Prior to 1967, discharge permits 1930 - Wastewater No Permit Unknown 1953 (U of O) None were not required or available in 1967 and Cooling 1966 (USACE) Oregon Water Followed installation of primary OSSA Waste clarifier in January 1967; Reference Discharge Permit Not Specified None Specified 1968-1-19 1967-11-17 reports "significant #13 - 01/19/68 reduction" in flows compared to earlier years. Does not define outfall(s); flow limit OSSA Waste in permit may not cover cooling Process 0.6 MGD Discharge Permit 1969-7-9 water discharges; followed 1967 - Wastewater (Permit Limit) #464 - 07/09/69 May 1970 (U of O) installation of aeration lagoon and 1975 secondary clarifier. DEQ Waste Discharge Permit Not Specified None Specified 1970-12-15 Does not define outfall(s). #863 - 12/15/70 USACE Application Does not define outfall(s); flow limit for Permit to 0.577 MGD Not Specified 1971-6-28 in permit may not cover cooling Discharge - (Reported Average) water discharges. 06/28/71

Evaluation of Hydrodynamic and Sediment August Transport 2013 Processes St. Helens Fiberboard Plant 9 100703-01 74275387.1 0015549-00007 100703-01 Comments Scappoose Bay. process wastewater. mg/L as of 07/01/77. mg/L as of 07/01/77. relocated to end of dock on relocated to end specifies reduction of arsenic in October 1975 and reduced flow of and reduced flow October 1975 Requires relocation of Outfall 001; 001; Requires relocation of Outfall Letter to DEQ confirms Outfall 001 confirms Outfall 001 to DEQ Letter Wastewater recirculation begins in begins Wastewater recirculation process wastwater effluent to <0.01

Photographs Aerial of Historical Analysis 1975-6-17 1975-6-17 1976-6-14 Reference Smith & Assoc.) Representative Sep 1975 (David (David Sep 1975 Jan 1980 (USACE) Jan 1980 1977-3-8 May 1970 (U of O) (U May 1970 1974-7-5 Aerial Photographs

10 Table 2-3 Limit) Limit) Limit) Limit) 0 MGD(to 0 MGD(to Lowlands) Flow Rate Terrestrial

0.577 MGD 0.577 MGD 0.077 MGD 0.144 MGD Information See comments MGD Permit Limit) Limit) MGD Permit Limit) MGD Permit (Reported Average (Reported Average (Reported Average 0.280 MGD (Permit 0.280 MGD (Permit 0.150 MGD (Permit 0.025 MGD (Permit specified in Permit) in Application; None in Application; 0.080 in Application; 0.150 Summary of Historical Discharge Volumes to the Lowland Summary of Historical Discharge Volumes Process Process Process Wastewater Wastewater Wastewater Wastewater Wastewater (Outfall 002) (Outfall 002) (Outfall 003) (Outfall 002) (Outfall 003) (Outfall 004) Cooling Water Cooling Water Cooling Water Cooling Water Cooling Water

ic and Sediment Transport Processes Processes Transport ic and Sediment 2013 August

06/30/75 07/05/74 01/20/77 Applicable Conditions Discharge Type Discharge Conditions Addendum - Outfall 001 - Relocation of NPDES Permit NPDES Permit - Permits/Discharge

1975 1975 1977 1981 Time 1967 - 1967 - 1975 - 1977 Period

DRAFT of Hydrodynam Evaluation St. HelensPlant Fiberboard 0015549-00007 74275387.1 100703-01

Comments all discharges cease. from 0.094 to 0.500 MGD to relocate Outfall 001 at end of end at 001 to relocate Outfall monthly average flows from 001 monthly average Monitoring Reports from January and daily maximum flows ranging and daily maximum dock in Scappoose Bay. Discharge dock in Scappoose ranging from 0.048 to 0.231 MGD MGD 0.231 to ranging from 0.048 Plant shuts down on 12/13/81 and Plant shuts down on 12/13/81 and Process wastewater discharges are Process wastewater discharges 1979 through December 1981 show December 1981 through 1979

Photographs Aerial of Historical Analysis 1979 1979 1981 through Reference DMRs from 1979-03-28; 1979-03-28; Representative Jan 1980 (USACE) Jan 1980 Aerial Photographs

11 Table 2-3 0 MGD 0 MGD Lowlands) Flow Rate

0.280 MGD 0.280 MGD 0.060 MGD 0.050 MGD Information (Permit Limit) (Permit Limit) (Permit Limit) (Permit Limit) None Specified (0 MGD to Terrestrial MGD to Terrestrial Summary of Historical Discharge Volumes to the Lowland Summary of Historical Discharge Volumes Process Lowlands Terrestrial Wastewater Wastewater (Outfall 002) (Outfall 002) (Outfall 003) (Outfall 004) Cooling Water Cooling Water Cooling Water All discharge to

ic and Sediment Transport Processes Processes Transport ic and Sediment 2013 August

03/28/79 Applicable Conditions Discharge Type Discharge Conditions NPDES Permit - Plant Shutdown Permits/Discharge

1981 1981 Time 1977 - 1977 Period

DRAFT of Hydrodynam Evaluation St. HelensPlant Fiberboard 0015549-00007 74275387.1 100703-01 POTW Comments process; excess wastewater is process; excess wastewater before restarting in 1990. Upon Upon before restarting in 1990. restart, process wastewater and AWI substantially rebuilt the plant AWI substantially rebuilt the discharged to the City of St. Helens discharged to the City of St. and wastewater treatment systems and wastewater treatment systems cooling water are recirculated to the cooling water are recirculated to the

Photographs Aerial of Historical Analysis

Reference Sep 2010 Sep 2010 July 2000 July 2000 June 2005 June 2005 (Google Earth) (Google Earth) (Google Earth) Representative Sep 1988 (U of O) (U of Sep 1988 July 1996 (U of O) (U of July 1996 June 1992 (U of O) (U June 1992 Aerial Photographs

12 Table 2-3 0 MGD 0 MGD Flow Rate

Information

Summary of Historical Discharge Volumes to the Lowland Summary of Historical Discharge Volumes Lowlands. Terrestrial No process wastewater discharges to or cooling water ischarge Elimination System ischarge Elimination System ic and Sediment Transport Processes Processes Transport ic and Sediment 2013 August my Corps my of Engineers

1987. 1987. Applicable Conditions Discharge Type Discharge Conditions Plant Shutdown. not transferred or NPDES permit was purchased plant in Permits/Discharge renewed after AWI

Time 1981 - 1981 Period Present OSSA = Oregon State Sanitary Authority Authority Sanitary State Oregon = OSSA States Ar United = USACE DRAFT Notes: AWI = Armstrong World Industries Quality Environmental of Department Oregon DEQ = day per Millions of gallons MGD = D Pollutant National NPDES = Oregon O = University of U of DEQ to submitted Report Monitoring Discharge = DMR of Hydrodynam Evaluation St. HelensPlant Fiberboard 0015549-00007 74275387.1

DRAFT Because the aquatic lowland is frequently inundated and subjected to varying levels of sedimentation and erosion, this area was further divided into six smaller subareas for the small-scale evaluation. These six zones are (Figure 2-12):

• Mudflats;

• McNulty Island;

• Southwest Channel;

• Highlands;

• Bar; and

• Northeast.

The boundaries dividing the subareas are not considered precise but are meant to conceptualize the varying hydrodynamic conditions in different portions of the aquatic lowland.

2.2.3.1 Mudflats Several transitory tidal channels and other inter-tidal formations were present in the Mudflats during 1948 and 1953 (Figures 2-13 and 2-14). After Milton Creek had been relocated to northeast of the dock between 1948 and 1953 (See Section 2.2.2), channel MF-1 had formed in the vicinity of the old Milton Creek channel by 1953 (Figure 2-14). The primary channel (MF-1) draining the northeast portion of the Mudflats, including apparent process water discharge, was a bifurcated channel with one of the branches being filled in by 1970 (Figure 2-16). Minimal lateral migration of channel MF-1 occurred between 1957 and 1970. By the 1980s, channel MF-1 was a relict channel that was partially infilled (Figure 2-18). The lower portions of channel MF-1 is still apparent in recent photographs in the low elevations of the Mudflats and appears to be continued to be affected by ongoing tidal inundation. However, by the 1990s, there was little expression of the historically longer channel MF-1 that had emanated from the adjacent Northeast subarea in to the Mudflats (Figures 2-20 through 2-24) corresponding to the cessation of upland process water discharges from the Northeast subarea in December 1981.

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DRAFT Analysis of Historical Aerial Photographs One channel (MF-2) in 1953 and 1966 (Figure 2-14 and Figure 2-15) and then a second channel (MF-3) in 1970 (Figure 2-16) are apparent in the Mudflats subarea. Figure 2-13 (1948) and Figure 2-14 (1953) suggest that the upper reaches of Channels MF-2 and MF-3 (i.e., in the Northeast, Southwest Channel, and Highland subareas) may have originated due to discharges from the uplands. These channels appear to extend through portions of the Northeast, Southwest Channel, and Highland subareas and into the Mudflat subarea in the 1948, 1953, and 1966 photographs (Figure 2-13, Figure 2-14, and Figure 2-15). Between 1970 and 1980, the portion of MF-2 and MF-3 in the Mudflats subarea appear to be less influenced by upland discharges (as compared to earlier photographs) and more influenced by tidal processes and were gradually infilled (Figures 2-16, 2-17 and 2-18).

Three channels (i.e., MF-4, MF-5, MF-6) formed, apparently as a result of tidal inundation processes, during the 20-year period between 1980 and 2000 (Figure 2-22). Channels MF-5 and MF-6 were connected via channel MF-1; it does not appear on Figure 2-22 that channel MF-6 had cut through to Scappoose Bay by 2000. Channels MF-1, MF-4, and MF-5 were relatively stable, and experienced minor lateral movement, between 2000 and 2010 (Figures 2-22, 2-23, and 2-24). However, channel MF-6 did cut through to Scappoose Bay by 2005. Shore disturbance appears to have occurred near the mouth of channel MF-6 between 2005 and 2010 (Figure 2-24).

Bed formations are visible in the dynamic inter-tidal portion of the Mudflats near the mouth of McNulty Creek (Figures 2-13 through 2-24). Vegetation in the dynamic inter-tidal area is seasonally and annually variable, with portions of this area alternating between vegetated and bare mudflat over the course of an annual cycle. Small spatial scale bed formations occur within the mudflats and these morphologic features tend to be transitory and dynamic. Several of the larger tidal channels appear to be relatively stable, with minor lateral movement, since about 2000.

2.2.3.2 McNulty Island McNulty Island was created between the 1950s and 1966 due to a channel cutoff (Figures 2-14 and 2-15). Relatively minor changes in the geometry and location of the cutoff channel occurred during the 1970s, 1980s and 1990s (Figures 2-16, 2-18, 2-20 and 21). The

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DRAFT Analysis of Historical Aerial Photographs bifurcated creek channel that flows around McNulty Island was relatively stable, with minimal lateral migration, between 2000 and 2010 (Figures 2-22, 2-23, and 2-24).

2.2.3.3 Southwest Channel Transitory, tidal channels occurred in the western (lower elevation) portion of the Southwest Channel subarea during the 1940s and 1950s (Figures 2-13 and 2-14). The 1948, 1953, and 1966 photographs (Figures 2-13, 2-14, and 2-15, respectively) suggest that during this period the channels in the eastern (higher elevation) portions of the Southwest Channel subarea may have been formed by upland process water discharges from the area west of former outfall 001 (installed in late 1966). By 1970, a channel (SW-1) had formed within the western portion of this subarea (Figure 2-16). Channels in the eastern portion of the Southwest Channel subarea appear to be less influenced by discharges from the uplands by 1970, although some small channels do appear to emanate from the upland and adjacent Northeast subarea into the eastern portion of the Southwest Channel subarea in the 1975 and 1980 photographs (Figures 2-17 and 2-18). By 2000, the small channels in the eastern portion of the Southwest Channel subarea appear to be infilled and vegetated (Figure 2-22). Some lateral migration of channel SW-1 may have occurred between 1970 and 2000 (Figures 2-17, 2-18, and 2-22). Lateral migration of channel SW-1 was relatively minor between 2000 and 2010 (Figures 2-22, 2-23, and 2-24). Overall, channel SW-1 was relatively stable after 2000, with small-scale lateral migration of the channel potentially occurring in a few localized portions of the channel. Similar to the Mudflats, significant variation in the extent and type of vegetation occurs within the Southwest Channel over seasonal and annual time scales.

2.2.3.4 Highlands Between 1948 and 1966, channels and relatively minimal vegetation were evident in the Highlands subarea (Figures 2-13, 2-14, and 2-15). Channel MF-2 extends through the Highlands in the 1953 photograph (Figure 2-14) and appears to originate from upland discharges above the Southwest Channel and Northeast subareas. The 1966 photograph (Figure 2-15) and the 1970 photograph (Figure 2-16) indicate that channels MF-2 and MF-3 in the Highland subarea appear to be less influenced by discharges from the upland. By 1980, the higher elevations of channels MF-2 and MF-3 had generally overgrown with Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant 15 100703-01 74275387.1 0015549-00007

DRAFT Analysis of Historical Aerial Photographs vegetation (Figures 2-17 and 2-18). During the period between the late 1960s (when process water discharge was documented to have started at former outfall OF001) and 2000, the Highlands was relatively stable with most of the area being vegetated and a few small channels continuing to be interspersed within the vegetation near the Highlands boundaries with the Mudflats and Southwest Channel (Figure 2-22). Between 2000 and 2010, the extent and type of vegetation within the Highlands varied over annual time scales (Figures 2- 22, 2-23, and 2-24) and what remnant channels present appeared to be stable.

2.2.3.5 Bar The Bar is a vegetated area that, generally, has experienced relatively minor morphologic changes since 1948. No significant tidal channels were evident within the Bar between 1948 and 2010 (Figures 2-13 through 2-24).

2.2.3.6 Northeast Channels that appear to be associated with discharges from the upland are present in the Northeast subarea between 1948 and 1970 (Figures 2-13 through 2-16). In addition, minimal vegetation was observed within this area during the 1940s, 1950s, and 1960s. By 1970 (Figure 2-16) and continuing through 1980 (Figure 2-18), channel NE-1, emanating from near former outfall 001, had become relatively stable, while a number of the channels observed before 1970 had become vegetated. Channels emanating from the area around former outfall 002 were also present in the 1950s, 1960s, 1970s, and 1980 (Figures 2-14, 2-15, 2-17, and 2-18). Channel NE-1 became vegetated by the late 1980s (Figure 2-19), corresponding to when discharges ceased from former outfall 001 (January 1977) and former outfall 002 (December 1981). Overall, much of the Northeast subarea became vegetated during the 1970s and 1980s. Comparison of Figures 2-20, 2-21, and 2-22 indicates that while a remnant of channel NE-1 remained in the 1990s, as evidenced by the expression of the channel during higher water levels in the 1996 photograph (Figure 2-21), infilling has occurred and vegetation had emerged by that time (Figures 2-20 and 2-22). For at least the last 20 years, the Northeast subarea has been vegetated, with seasonal and annual variations in the extent of vegetation being limited to the lower elevations of this subarea.

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DRAFT Analysis of Historical Aerial Photographs 2.3 Summary The historical aerial photographs provide visual evidence of both broad-scale and small-scale changes in the Study Area morphology that occurred during the 81-year period between 1929 and 2010. The primary morphologic changes evident from the aerial photograph analysis are summarized below.

• On a broad-scale, a significant portion of submerged areas and the previously unvegetated mudflats within the Study Area became vegetated after construction of the Columbia River dams that began in the 1930s. The development of emergent vegetation appears to be primarily attributable to reduction of peak flood flows due to dam construction on the Columbia River and the associated decreased frequency and duration of inundation of relatively higher bed elevations. The emerging vegetation itself caused reduced flow velocities, which in turn resulted in further increased (relative to non-vegetated areas) sediment deposition in these subareas of the Study Area. Finally, accretion of dying plant material is also expected to result in increased bed elevation, which decreased inundation frequency and duration, which, in turn, further enhanced vegetation.

• The channel of McNulty Creek has experienced minimal lateral migration since the 1950s and appears to be generally stable.

• The mouth of Milton Creek was moved (by man) to its current location between 1948 and 1957 and since then appears to be relatively stable.

• Variations in small-scale features (e.g., tidal channels) over time, especially in the lower elevations of the aquatic lowland, suggest localized erosional events have historically occurred in this portion of the Study Area. Channels emanating from former upland process water discharges have generally infilled and become vegetated since the discharges were reduced in the late 1970s and ceased by the early 1980s.

Overall, changes in the broad-scale morphology of the Study Area during the last 81 years, particularly the dramatic emergence of vegetation, indicate the Study Area, in general, is stable with some localized erosional events, driven primarily by tidal inundation, occurring in the lower elevations of the aquatic lowland. Any erosion in higher elevations of the

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DRAFT Analysis of Historical Aerial Photographs aquatic lowland associated with channels created by the discharge of process water from the upland appears to have ended with the cessation of such discharges by December 1981.

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DRAFT

3 GEOCHRONOLOGY ANALYSIS OF RADIOISOTOPE CORES Sediment cores were collected from the Study Area and used to conduct a geochronology analysis. Following recent guidance on sediment stability assessments (EPA 2005, Magar et al. 2009, EPA 2012), the vertical profiles of two radioisotopes (cesium-137 [137Cs] and lead- 210 [210Pb]) within the sediment cores were evaluated and used to provide:

• Order-of-magnitude estimates of historical net deposition; and

• Empirical evidence of sediment stability.

3.1 Description of Radioisotope Core Data Eight radioisotope cores were collected during June 2011 within the Study Area (Figure 3-1). The cores were collected from areas with relatively little emergent vegetation, with the expectation that areas with significant vegetation are presumed to be stable and depositional. Sediment cores were sectioned into 1-inch intervals for analysis of the radioisotopes 137Cs and 210Pb. Cores were sub-sampled in consecutive 1-inch intervals (i.e., 0 to 1 inch, 1 to 2 inches). Sub-samples were submitted for laboratory analysis of 137C and 210Pb activity from every fourth sub-sample interval (i.e., 0 to 1 inch, 4 to 5 inches, 8 to 9 inches), to a depth of 36 inches within the core (i.e., 10 sub-samples per core). In addition, a description of the physical and lithological characteristics of each sample was recorded. The sampling and analysis plan for the radioisotope coring study was provided in Appendix C of Anchor QEA (2011).

3.2 Geochronology The primary purpose of the geochronology analysis was to determine whether net depositional processes have occurred within the Study Area. The occurrence of historical depositional processes, along with the other lines of evidence considered in the overall hydrodynamic analysis (i.e., historical aerial photograph review and hydrodynamic modeling), provide insight into the potential for depositional processes to occur in the future, in general, areas across the Study Area. (EPA 2005, Magar et al. 2009, EPA 2012). The geochronology analysis included the collection of sediment cores and analysis of vertical profiles of 137Cs and 210Pb activity. The results of the radioisotope analysis (i.e., the 137Cs and

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DRAFT Geochronology Analysis of Radioisotope Cores 210Pb activity measurements) provided the primary information for the geochronology analysis. However, the historical aerial photographs and the lithology noted in the sediment cores were also considered in the geochronology analysis. Appendix A presents a geochronology analysis of the sediment cores. Appendix A also presents a discussion of the uncertainties in results of the 137Cs and 210Pb analyses, including the relevance of the lack of 137Cs activity detections in some of the cores and a statistical analysis of the confidence limits around the 210Pb activity results.

Vertical profiles of 137Cs and 210Pb activity for cores AQ-01 through AQ-08 are shown in Figures 3-2 through 3-9. All of the cores were primarily composed of cohesive (muddy) sediment, indicative of a depositional environment with relatively low hydrodynamic energy (i.e., a sandy sediment bed is typically found in areas with relatively high hydrodynamic energy).

3.2.1 137Cs Activity Measurements Peaks of 137Cs activity were observed in three of the eight cores, while the other five cores had 137Cs activities that were below laboratory detection levels. The three cores where 137Cs was detected also corresponded to the three core sampling locations with the highest topographic elevations. Notwithstanding the detection of 137Cs activity in three of the cores (as well as in cores from the Columbia River Slough), relatively low 137Cs activities have been observed in sediment cores collected at other sites in the Pacific Northwest (e.g., Lower Willamette River, Oregon, and Lower Duwamish Waterway, Washington). This regional characteristic may be caused by large-scale global variations in generation, dispersion, and deposition of 137Cs during atmospheric testing of nuclear weapons in the past. Also, the detection limits for the 137Cs analysis for the Study Area were elevated and may have masked the presence of 137Cs in the analysis. Where peaks of 137Cs activity were observed in the cores, the 137Cs measurements suggest 5 to 12 inches of sediment have been deposited since the 1950s/1960s (atmospheric testing of nuclear weapons began in 1954 and peak atmospheric testing occurred during 1963).

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DRAFT Geochronology Analysis of Radioisotope Cores 3.2.2 210Pb Activity Measurements Comparisons of the general characteristics of the 210Pb activity profiles noted in the Study Area cores to an “ideal” 210Pb activity profile (e.g., from a quiescent lake) confirms sediment deposition occurred historically within the Study Area. A sediment core collected from an “ideal” quiescent environment will show 210Pb activity decreasing exponentially with increasing depth in the core (see top panel of Figure 3-10). When the 210Pb activity data for the “ideal” core are transformed to natural log space (see Appendix A.2.2 for further explanation), the transformed data decrease linearly with increasing depth (Figure 3-10, bottom panel). The correlation coefficient (R2) for a perfect linear relationship is 1.0 (i.e., perfect correlation between the independent and dependent variables), which occurs for the “ideal” core. Thus, the correlation coefficient for the linear regression of the transformed 210Pb activity data provides an indication of the extent to which depositional processes are present and the confidence with which the magnitude of sedimentation can be estimated.

Six cores (i.e., cores AQ-01, AQ-02, AQ-03, AQ-04, AQ-05, and AQ-08) located at bed elevations between 7 and 10 feet (North American Vertical Datum of 1988 [NAVD88]) had correlation coefficients ranging between 0.82 and 0.99 (Figure 3-11). All of these R2 values are relatively close to 1, which indicates the 210Pb activity approximately decreases exponentially with increasing depth, as occurs in a quiescent depositional environment.

The lack of high correlation coefficients in cores AQ-06 and AQ-07 (R2 of less than 0.8) suggests these cores are located in areas either not strongly depositional or have experienced past disturbance/mixing. Cores AQ-06 and AQ-07 are located along the main channel of Scappoose Bay where less deposition would be expected relative to the lowland area of the Study Area where the other cores were collected. The main channel area may also have experienced sediment disturbance from vessel traffic, wind, and waves.

3.2.3 Conclusions and Uncertainties of the Radioisotope Analysis Uncertainty exists in the estimated historical magnitudes of net sediment deposition due to variability in 137Cs and 210Pb activity data, and actual net deposition has likely varied across the Study Area and between elevations. However, the results of the analyses discussed in Appendix A suggest that a representative range of historical net sedimentation rates (NSRs)

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DRAFT Geochronology Analysis of Radioisotope Cores within the Study Area is on the order of 0.1 to 0.5 inch/year and on the order of 1 foot of sediment was deposited in portions of the Study Area between elevations 7 to 10 feet (NAVD88) over the past 40 to 100 years.

Notwithstanding the above, the geochronology analysis informs the historical processes at the specific core locations. Processes differing from those suggested by the core analysis (e.g., small-scale, episodic erosional events) may have occurred away from the core locations and such processes would not necessarily be inconsistent with the radioisotope core results.

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DRAFT

4 HYDRODYNAMIC MODEL DEVELOPMENT, CALIBRATION, AND VALIDATION This section presents the development, calibration, and validation of the hydrodynamic model applied to the Study Area. The purpose of the hydrodynamic model was to develop a tool to predict broad-scale temporal and spatial variations in current velocity, water depth, WSE, and bed shear stress over a wide range of flow and tidal conditions and consider those predictions in the overall hydrodynamic conditions.

4.1 Description of Hydrodynamic Model Structure The hydrodynamic model applied in this study is the Environmental Fluid Dynamics Code (EFDC), which was originally developed with support from the U.S. Environmental Protection Agency. The EFDC is a three-dimensional hydrodynamic model capable of simulating time-variable flow in rivers, lakes, reservoirs, estuaries, and coastal areas. The model solves the conservation of mass and momentum equations, which are the fundamental equations governing the movement of water in a tidal river. A critical feature of EFDC applied to the Study Area was the flooding-drying feature, which made it possible to realistically simulate the flooding and drying of intertidal and lowland areas caused by tidal action and periodic, temporal high water conditions. The model has been applied to a wide range of environmental studies in large number of rivers, estuaries, and coastal ocean areas. A complete description of the model is given in Hamrick (1992).

The EFDC hydrodynamic model was used in two-dimensional, vertically averaged mode for this study. Calculation of the vertical variations in current velocity (i.e., three-dimensional mode) was not needed for this study due to the negligible effects of density-driven circulation. This approximation (i.e., calculation of vertically averaged current velocity) is routinely used at other sediment sites in river systems, such as the tidal freshwater portion of the Lower Willamette River.

Accurate and reliable simulations of hydrodynamics within the Study Area were accomplished through use of a nested model structure that consisted of a far-field model, which provided boundary condition information for a near-field model. The far-field model used a coarse-resolution numerical grid that included the Columbia River (from Bonneville

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DRAFT Hydrodynamic Model Development, Calibration, and Validation Dam to Longview), Lower Willamette River, and Multnomah Channel. A fine-resolution numerical grid was used in the near-field model to provide adequate representation of the geometry and bathymetry of the Study Area, Scappoose Bay, and portions of Multnomah Channel and Columbia River.

4.2 Far-field Hydrodynamic Model 4.2.1 Development of Far-field Model The spatial extent of the far-field model domain is shown in Figure 4-1. The upstream and downstream boundaries on the Columbia River are located at Bonneville Dam and Longview, respectively. The upstream boundary on the Lower Willamette River is located approximately 24 miles upstream from the confluence with the Columbia River.

A curvilinear, boundary-fitted numerical grid was used for the far-field model, with a total of 2,040 grid cells. Within the Columbia River, the river channel was delineated using six grid cells in the cross-channel direction (Figure 4-2). Three grid cells were used to delineate the cross-channel bathymetry in the Lower Willamette River (Figure 4-3). Multnomah Channel was treated as a one-dimensional channel. Data used to specify bathymetry inputs for the far-field model were compiled by David Evans and Associates (DEA) from various field surveys and sources for the USACE Portland district. The DEA compilation incorporates Light Detection and Ranging (LiDAR) and bathymetry data collected during single-beam and multi-beam surveys that were conducted between 1990 and 2009, with a majority of the data being collected after 2006.

Locations of boundary condition and tributary inputs for the far-field model are presented in Figure 4-4. WSE at the downstream boundary was specified using 6-minute WSE data collected at the NOAA gauging station at Longview. Flow rate at the upstream boundary on the Columbia River (Bonneville Dam) was specified using daily average flow rate data measured at the U.S. Geological Survey (USGS) gauging station at The Dalles. For the Lower Willamette River, flow rates measured at the USGS gauging station at Portland were used for model input. Inflows from the three primary tributaries (Cowlitz, Lewis, and Sandy Rivers) to the Columbia River were determined using daily average flow rate data collected at USGS gauging stations on those rivers.

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DRAFT Hydrodynamic Model Development, Calibration, and Validation 4.2.2 Calibration and Validation Strategy for Far-field Model The far-field model was calibrated and validated using WSE data collected at five gauging stations (Figure 4-4): 1) St. Helens (NOAA); 2) Vancouver (USGS); 3) Columbia Slough (USGS); 4) Bonneville Dam (USGS); and 5) Lower Willamette River at Portland (USGS). The calibration period corresponded to the 15-month period from July 2005 through September 2006. The peak flow rate in the Columbia River of approximately 400,000 cfs occurred during May 2006, with the peak flow rate in the Lower Willamette River (approximately 200,000 cfs) during January 2006. These floods had return periods between 2 and 5 years.

A 14-month period from December 2007 through January 2009 was used to validate the model. Peak flow rates on the Columbia and Lower Willamette Rivers were 450,000 cfs (5- to 7-year flood) and 150,000 cfs (2-year flood), respectively. Additional validation of the far- field model was accomplished through simulation of the February 1996 flood, where peak flow rates on the Columbia and Lower Willamette rivers were 408,000 and 420,000 cfs, respectively.

Skill assessment for the far-field model consisted of three steps:

• Step 1: graphical comparison of predicted and measured WSE;

• Step 2: tidal harmonic analysis of predicted and measured WSE; and

• Step 3: statistical analysis of differences in predicted and measured values of:

− WSE;

− Amplitude of high water;

− Amplitude of low water;

− Time of high water; and

− Time of low water.

WSE data collected at 6-minute intervals were used in the skill assessment. The tidal harmonic analysis (Step 2) was accomplished using T_TIDE, which is a matrix laboratory (MATLAB) program developed at the University of British Columbia and Woods Hole

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DRAFT Hydrodynamic Model Development, Calibration, and Validation Oceanographic Institution (Pawlowicz et al. 2002). Six primary tidal harmonic constituents were evaluated in this analysis, see Table 4-1.

Table 4-1 Tidal Constituents Evaluated During Tidal Harmonic Analysis

Tidal Harmonic Constituent Description

M2 Principal lunar semi-diurnal

S2 Principal solar semi-diurnal

N2 Larger lunar elliptical semi-diurnal

K1 Luni-solar declinational diurnal

M4 First over-tide of M2

O1 Lunar declinational diurnal

The statistical analysis (Step 3) was conducted using the methodology described in Hess et al. (2003). Differences in the following predicted (upper-case) and measured (lower-case) variables were calculated over the calibration and validation periods:

• WSE: H-h;

• Amplitude of high water: AHW-ahw;

• Amplitude of low water: LHW-lhw;

• Time of high water: THW-thw; and

• Time of low water: TLW-tlw.

Skill assessment statistics were calculated for the five variables listed above as described in Table 3 of Hess et al. (2003) and summarized in Appendix B.

The parameter adjusted during calibration of the far-field model was the effective bed roughness, which affects the bed shear stress (i.e., frictional drag on moving water due to the sediment bed). The optimal agreement between measured and predicted WSE at the five gauging stations was obtained by spatial variation of the effective bed roughness, see Table 4-2. Within the Columbia River, effective bed roughness was higher in the region downstream of Vancouver. Effective bed roughness in the Lower Willamette River was

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DRAFT Hydrodynamic Model Development, Calibration, and Validation higher than in the Columbia River and Multnomah Channel. The range of effective bed roughness values (i.e., 0.1 to 1 centimeters [cm]) was reasonable and consistent with values typically used in similar hydrodynamic models.

Table 4-2 Spatially Variable Effective Bed Roughness for Far-field Model

Effective Bed Roughness Region of Far-field Model (centimeters) Columbia River: downstream of Vancouver 0.3 Columbia River: upstream of Vancouver 0.1 Lower Willamette River 1.0 Multnomah Channel 0.1

4.2.3 Calibration and Validation Results for Far-field Model Temporal variations in daily average flow rates at the upstream boundaries of the far-field model during the 15-month calibration period (July 2005 through September 2006) are shown in Figure 4-5. Two 1-month periods are highlighted in Figure 4-5: 1) September 2005; and 2) May 2006. September 2005 is representative of a low-flow period when flow rates in the Columbia and Lower Willamette Rivers were below long-term average values. The high-flow period (May 2006) corresponds to Columbia River flow rates that were greater than a 2-year flood. Comparisons of predicted and measured WSE during the low- and high- flow periods at the gauging stations located at St. Helens (NOAA), Vancouver (USGS), Columbia Slough (USGS), Bonneville Dam (USGS), and Lower Willamette River at Portland (USGS) are presented in Figures 4-6 through 4-10. Overall, model predictions of WSE are in satisfactory agreement with measured values at all five locations during both low- and high- flow periods, which is consistent with model performance throughout the 15-month calibration period.

The 1-month periods shown in Figures 4-6 through 4-10 (i.e., low- and high-flow periods during September 2005 and May 2006, respectively) were selected for the tidal harmonic analysis. The results of tidal harmonic analyses for WSE at the five locations used for model calibration are presented in Appendix B.1. During September 2005, relative errors for the amplitude of the M2 tidal harmonic constituent ranged from 13% at St. Helens to 38% at Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant 27 100703-01 74275387.1 0015549-00007

DRAFT Hydrodynamic Model Development, Calibration, and Validation

Columbia Slough. During May 2006, relative errors for the amplitude of the M2 tidal harmonic constituent ranged from 32% at St. Helens to 86% at Vancouver. Results of the statistical analysis of predicted WSE during the far-field calibration period (i.e., 15-month period) are summarized in Appendix B.2. The root mean square errors (RMSEs) for predicted WSE at the five gauging during the far-field calibration period are listed in Table 4-3.

Table 4-3 Root Mean Square Error for Predicted WSE during Far-field Calibration and Validation Periods

RMSE: Calibration Period RMSE: Validation Period Gauging Station Location (feet) (feet) St. Helens 0.31 0.27 Vancouver 0.48 0.71 Columbia Slough 0.36 0.38 Bonneville Dam 1.06 1.08 Lower Willamette River 0.30 0.39

Note: RMSE – root mean square error

Daily average flow rates in the Columbia and Lower Willamette rivers during the 14-month validation period (December 2007 through January 2009) are shown in Figure 4-11. September 2008 is representative of a low-flow period when flow rates in the Columbia and Lower Willamette rivers were below long-term average values. May 2008 is a high-flow period in the Columbia River, with peak flow rates corresponding to approximately a 5-year flood. Comparisons of predicted and measured WSE during the low- and high-flow periods at the gauging stations located at St. Helens, Vancouver, Columbia Slough, Bonneville Dam, and Lower Willamette River at Portland are presented in Figures 4-12 through 4-16. Similar to the calibration results, model predictions of WSE are in satisfactory agreement with measured values at all five locations during both low- and high-flow periods. Results of the statistical analysis of predicted WSE throughout the far-field validation period (i.e., 14- month period) are summarized in Appendix B.2. The RMSE for predicted WSE during the far-field validation period are presented in Table 4-3.

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DRAFT Hydrodynamic Model Development, Calibration, and Validation Simulation of the February 1996 flood was used for additional validation of the far-field model. Daily average flow rates in the Columbia and Lower Willamette Rivers during February 1996 are shown in Figure 4-17. Peak flow rate in the Lower Willamette River was over 400,000 cfs, which corresponds to a return period of approximately 100 years. Flow rates in the Columbia River were approximately equal to a 2-year flood when the peak discharge occurred in the Lower Willamette River. WSE data at the NOAA tidal gauging station at Longview were not available during the February 1996 flood. Thus, WSE data collected at the USGS gauging station at Quincy were used to specify model inputs at the downstream boundary during this simulation. The Quincy gauging station is approximately 13 miles downstream of the Longview gauging station. Typically, the tidally averaged WSE at Quincy is lower than at Longview, which introduces uncertainty into the far-field model predictions for this flood.

Comparisons of predicted and measured WSE during February 1996 at the four gauging stations located at Vancouver, Columbia Slough, Bonneville Dam, and Lower Willamette River at Portland are presented in Figures 4-18 through 4-21. Model-data comparisons could not be made for this flood at St. Helens because the NOAA St. Helens gauging station has no data available from the 1996 flood event. Generally, the model consistently under-predicted WSE at all gauging stations during the February 1996 flood by approximately 2 to 3 feet. This offset between measured and predicted WSE is caused by use of data collected at the Quincy gauging station to specify WSE at the downstream boundary of the model. However, the under-prediction of WSE by the far-field model produced conservative results for the bed stability analysis of the February 1996 flood discussed in Section 5.3 (i.e., current velocities and bed scour depths were over-predicted by the near-field model).

4.3 Near-field Hydrodynamic Model 4.3.1 Development of Near-field Model The spatial extent of the numerical grid for the near-field model is shown in Figure 4-22. A rectangular numerical grid was used for the near-field model, with grid cell size within the Study Area being 20 meters (i.e., square grid cells; see Figure 4-23). Larger grid cells were used outside of the Study Area, with the largest grid cells being 50 meters. The total number of grid cells used for the near-field model was approximately 18,400. Simulation time for the

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DRAFT Hydrodynamic Model Development, Calibration, and Validation near-field model was approximately 75 times longer than the far-field model for the same time period (e.g., 1-month simulation). Similar to the far-field model, bathymetry and topography data compiled by DEA were used to specify inputs to the near-field model. These data included: NOAA multi-beam bathymetry surveys, USACE 2009 LiDAR data, and Lower Columbia River Estuary Project 2009 single-beam bathymetry survey.

Temporally variable flow rates predicted by the far-field model in the Columbia River and Multnomah Channel were used to specify inputs at the upstream boundaries of the near-field model (Figure 4-24). Time-varying WSE at the downstream boundary was specified using data collected at the St. Helens gauging station.

4.3.2 Calibration and Validation Strategy for Near-field Model The near-field model was calibrated and validated using WSE and current velocity data collected within Scappoose Bay and Multnomah Channel during April, May, and June of 2011. A tidal gauge was used to measure WSE at the old pier within the Study Area. An Acoustic Doppler Current Profiler (ADCP) was deployed in Scappoose Bay from April 5 through June 4. From June 14 through 27, an ADCP was deployed in Multnomah Channel. The locations of the tidal gauge and ADCP deployments are shown in Figure 4-25. Current velocity data obtained from the ADCPs were processed to provide depth-averaged values for comparison to depth-average velocities predicted by the near-field model.

Temporal variations in Columbia River flow rate, WSE at the old pier, and along-channel current velocity during the 2-month calibration period (i.e., April 5 through June 4, 2011) are shown in Figure 4-26. Examination of these data indicates the following trends and relationships:

• Average WSE increases from 11 to 12 feet NAVD88 for Columbia River flow rates of 250,000 to 300,000 cfs to 18 to 19 feet for flow rates of 450,000 to 500,000 cfs. The tidal range decreases as Columbia River flow rates increases between these two flow regimes;

• When Columbia River flow rates are less than approximately 400,000 to 450,000 cfs, maximum current velocities in Scappoose Bay range between 0.5 and 1.5 feet per

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DRAFT Hydrodynamic Model Development, Calibration, and Validation second (ft/s) during flood tide and approximately 0.25 and 0.75 ft/s during ebb tide; and

• When Columbia River flow rates are greater than approximately 400,000 to 450,000 cfs, maximum current velocities in Scappoose Bay for both flow tide and ebb tide decrease to approximately 0.3 ft/s.

The decrease in current velocities in Scappoose Bay during a period of high flow rate in the Columbia River is caused by the increase in WSE. Generally, Scappoose Bay tends to behave as a backwater area during flood events on the Columbia and Lower Willamette rivers, with tidal effects being minimized.

Current velocity data collected in Multnomah Channel during June 2011 are shown in Figure 4-27. Flow rates in the Columbia River during this 2-week period ranged between approximately 450,000 and 550,000 cfs. Current velocity in Multnomah Channel was uni- directional (i.e., no reverse flow during flood tide), with the magnitude varying between 1.7 and 2.2 ft/s.

The near-field model was calibrated using WSE and current velocity data collected in Scappoose Bay during the 2-month period from April 5 through June 4, 2011. Validation of the near-field model was conducted using data collected during the 2-week period from June 14 through June 27. The effective bed roughness values in channel/inter-tidal areas and vegetated areas of floodplains were adjusted during model calibration. The final calibration values of effective bed roughness were 1 cm in channel/inter-tidal areas and 20 cm in vegetated areas of floodplains. The value of 1 cm for effective bed roughness is within the typical range for channel and inter-tidal areas. The effective bed roughness of 20 cm approximates the complex effects of vegetation on hydrodynamic circulation in floodplain areas. Sensitivity of the hydrodynamic model to this parameter was evaluated, see Section 4.3.3.

4.3.3 Calibration and Validation Results for Near-field Model Similar to the far-field model, WSE data were used to calibrate the near-field model as follows: Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant 31 100703-01 74275387.1 0015549-00007

DRAFT Hydrodynamic Model Development, Calibration, and Validation • Step 1: graphical comparison of predicted and measured WSE;

• Step 2: tidal harmonic analysis of predicted and measured WSE; and

• Step 3: statistical analysis of differences in predicted and measured values of:

− WSE;

− Amplitude of high water;

− Amplitude of low water;

− Time of high water; and

− Time of low water.

The current velocity data were used to evaluate model performance as follows:

• Step 1: graphical comparison of predicted and measured depth-averaged velocities; and

• Step 2: statistical skill assessment of predicted current velocities as described in Section 4.2 of Hess et al. (2003).

The statistical analysis (Step 2) was conducted using the methodology described in Section 4.2 of Hess et al. (2003). Differences in the following predicted (upper-case) and measured (lower-case) variables were calculated over the calibration and validation periods:

• Current speed: U-u;

• Amplitude of maximum flood current: AFC-afc;

• Amplitude of maximum ebb current: AEC-aec;

• Time of maximum flood current: TFC-tfc; and

• Time of maximum ebb current: TEC-tec.

Skill assessment statistics were calculated for the five variables listed above as described in Table 3 of Hess et al. (2003) and summarized in Appendix B.

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DRAFT Hydrodynamic Model Development, Calibration, and Validation Near-field model results during the 2-month calibration period are presented in Figures 4-28 and 4-29. During the first month of the calibration simulation (April 5 to May 5), predicted WSE is in good agreement with measured values at the old pier gauging station (top panel of Figure 4-28). Model predictions of along-channel velocities during ebb and flood tides in Scappoose Bay were in satisfactory agreement with the data between April 5 and May 5. In addition, the model was able to simulate temporal variations in along-channel velocity that occurred over the course of the neap-spring tidal cycle (Figure 4-28, bottom panel).

During the second month (May 5 to June 4), the model simulates the transition in average WSE from approximately 11 to 12 feet before May 13 to approximately 18 to 19 feet after May 18 (Figure 4-29, top panel). As discussed in Section 4.3.2, the observed increase in average WSE was caused by increased flow rate in the Columbia River. However, the model over-predicted WSE by approximately 0.5 to 1 foot after May 18. The model accurately predicted the decrease in along-channel velocity that occurred during the transition from lower WSE before May 13 to higher WSE after May 18 (Figure 4-29, bottom panel).

Model predictions of WSE and along-channel velocity during the 2-week validation period in June 2011 are compared to measured values in Figure 4-30. Similar to model performance during the higher WSE period after May 18, WSE is over-predicted by approximately 0.5 to 1 foot during the validation period (Figure 4-30, top panel). The model predicted the magnitude of along-channel velocity in Multnomah Channel reasonably well (Figure 4-30, bottom panel). The predicted along-channel velocity tends to be out of phase with the tidal oscillations observed in the data. However, the overall performance of the model in Multnomah Channel indicates that the linkage between the near-field and far-field models is functioning satisfactorily.

Summaries of tidal harmonic of WSE, statistical analysis of WSE, and statistical analysis of current velocity for the near-field model calibration are presented in Appendix B.3, B.4, and B.5, respectively. For the 2-month calibration period, relative errors for amplitudes of the six primary tidal harmonic constituent ranged from 11% to 14%. The RMSE for predicted WSE at the old pier during the calibration period was 0.33 feet (10 cm). With respect to predicted

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DRAFT Hydrodynamic Model Development, Calibration, and Validation current velocity in Scappoose Bay during the calibration period, RMSE values for maximum amplitudes during flood and ebb tides were 0.30 and 0.08 ft/s, respectively.

As discussed in Section 4.3.2, the effective bed roughness in vegetated floodplain areas was set at a relatively high value to approximate the effects of vegetation on bed shear stress in the hydrodynamic model. Uncertainty exists in the value assumed within the vegetated floodplain areas (i.e., 20 cm). The sensitivity of the near-field model to the effective bed roughness in vegetated floodplain areas was evaluated to quantify the effects of this uncertainty. The calibration and validation simulations were repeated using lower- and upper-bound values of 10 and 30 cm, respectively, for the effective bed roughness in vegetated floodplain areas. The results of the sensitivity simulations are presented in Figures 4-31, 4-32, and 4-33. Overall, variation in the effective bed roughness in vegetated floodplain areas had minimal effect on predicted WSE and current velocity in Scappoose Bay and Multnomah Channel.

4.4 Summary The calibration and validation results for the far-field model show that WSE is predicted with adequate accuracy in the Columbia and Lower Willamette rivers over a wide range of flow and tidal conditions. At the St. Helens gauging station, relative errors for the amplitude of the M2 tidal harmonic constituent were 13% and 32% during September 2005 (low-flow period) and May 2006 (high-flow period), respectively. During the 15-month calibration period, RMSE for predicted WSE ranged from 0.30 to 0.48 feet (9 to 15 cm) at four gauging stations and it was approximately 1 foot (32 cm) at Bonneville Dam. Successful calibration and validation of the far-field model indicates it can be used to reliably specify boundary condition inputs for the near-field model.

The near-field model is able to adequately predict WSE and current velocity in Scappoose Bay and Multnomah Channel. Model performance during the 2-month calibration period demonstrated the model reproduced key characteristics observed in the Scappoose Bay data: 1) transition in average WSE due to increasing flow rate in the Columbia River; 2) changes in range of along-channel velocity during the neap-spring tidal cycle; 3) magnitude and phase of along-channel velocity during ebb and flood tides; and 4) decrease in along-channel

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DRAFT Hydrodynamic Model Development, Calibration, and Validation velocity during increased flow rates in the Columbia River. The RMSE for predicted WSE at the old pier was 0.33 feet (10 cm). Maximum amplitudes of predicted current velocity in Scappoose Bay during flood and ebb tides had RMSE values of 0.30 and 0.08 ft/s (9 and 2 centimeters per second [cm/s]), respectively. In summary, the near-field model can be used as a management tool to evaluate broad-scale hydrodynamic and sediment transport processes within the Study Area over a wide range of flow and tidal conditions and inform an overall understanding of the hydrodynamic conditions in the Study Area.

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DRAFT

5 SEDIMENT STABILITY ANALYSIS Successful calibration and validation of the near-field and far-field models produced a useful quantitative tool to conduct a broad-scale sediment stability analysis within the Study Area. The models were used as diagnostic and prognostic tools to:

• Develop a general understanding of broad-scale transport processes in the Study Area;

• Predict the broad-scale spatial distribution of current velocity and bed shear stress for a wide range of flow and tidal conditions. These results can be used to develop inferences about broad-scale erosion and deposition processes;

• Predict estimates of maximum scour depths during high-flow events; and

• Predict the extent of floodplain inundation during high-flow events.

Overall, the above understanding and predictions inform the understanding of the hydrodynamic conditions in the Study Area.

5.1 Development of High-flow Event Simulations A flood frequency analysis was conducted using the Log-Pearson Type 3 method (Helsel and Hirsch 2002) to determine inflow conditions during high-flow events in the Columbia and Lower Willamette Rivers. The Log-Pearson Type 3 method is the recommended technique for flood frequency analysis (Interagency Advisory Committee on Water Data 1982). The analysis was conducted following these steps:

• Determine the annual peak discharge for the period of record;

• Calculate the base-10 logarithm of the annual peak discharge for each year;

• Calculate the following statistics for the logarithms of annual peak discharge: mean (M), standard deviation (S), and skewness (g); and

• Calculate the peak discharge (Qp) for a specific annual exceedance probability (AEP) using:

log(Qp) = M + KS (5-1)

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DRAFT Sediment Stability Analysis where:

log(Qp) = base-10 logarithm of the peak discharge with AEP of one in Y years; and

K = the frequency factor for a specific AEP as a function of skewness (g).

Tabulated values of K are presented in Helsel and Hirsch (2002). For example, AEP values of 10% and 1% correspond to high-flow events with return periods of 10 and 100 years, respectively. The flood frequency analysis for the Columbia and Lower Willamette rivers used peak flow rate data for the 37-period from 1972 to 2009. The 10-year and 100-year flood flow rates for the Columbia and Lower Willamette rivers are summarized in Table 5-1.

Minimal flow rate data are available for the four primary tributaries to Scappoose Bay: 1 McNulty Creek (drainage area = 8.3 square miles [mi2]); 2) Milton Creek (drainage area = 32 mi2); 3) Scappoose Creek (drainage area = 60 mi2); and 4) Honeyman Creek (drainage area = 7 mi2). Thus, a flood frequency analysis using Study area-specific data could not be conducted for the Scappoose Bay tributaries.

Flow rates for floods on McNulty, Milton, and Scappoose Creeks with return periods of 10, 50, 100, and 500 years are provided in a Flood Insurance Study (FIS) conducted by the Federal Emergency Management Agency (FEMA) in 1988. The FIS (FEMA 1988) stated that the flood frequency analyses for McNulty and Scappoose Creeks were developed using the USGS regional analysis (USGS 1979). The flood flow rates for these two creeks were checked by using the Myers enveloping curve, which was prepared for the 100-year high-flow event in northwestern Oregon (FEMA 1988). As described in FEMA (1988):

The hydrologic analyses for Milton Creek were performed by the U.S. Soil Conservation Service (SCS). Because there are no stream gauges on Milton Creek, the SCS developed discharge-frequency curves for nine stream gauges in surrounding drainage areas in northwestern Oregon and southwestern Washington using the standard log-Pearson Type III statistical procedure, as described in U.S. Water Resources Council’s Bulletin 17B (Reference 13). Regression equations of peak

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DRAFT Sediment Stability Analysis discharge versus drainage area were developed for several storm frequencies using the discharge-frequency relationship for the nine gauges (Reference 14).

Reference 14 corresponds to U.S. Soil Conservation Service (SCS 1984).

Flow rates for floods on Honeyman Creek were estimated from the runoff rates for McNulty and Scappoose Creeks. Both McNulty and Scappoose Creek have runoff rates of approximately 55 cfs/mi2 for the 10-year flood and 100 cfs/mi2 for the 100-year flood. These runoff rates were multiplied by the Honeyman Creek drainage area (7 mi2) to estimate the flood flow rates. Flow rates for Scappoose Bay tributaries for average, 10-year and 100-year discharge conditions are listed in Table 5-1.

Average flow rates for Scappoose Bay tributaries were estimated using flow rate data collected from a surrogate watershed. East Fork Lewis River was used as the surrogate watershed and it has an average flow rate of approximately 750 cfs and a drainage area of approximately 125 mi2. The East Fork Lewis River flow rate was normalized by the drainage area to compute a runoff rate of 6 cfs/mi2. This runoff rate was used to estimate the average flow rate for the Scappoose Bay tributaries based on the drainage area for each tributary (see Table 5-1).

Table 5-1 Flow Rates Used in High-flow Event Simulations

Average Flow 10-Year Flood 100-Year Flood Inflow Location Rate (cfs) Flow Rate (cfs) Flow Rate (cfs) Columbia River: Bonneville Dam 192,000 501,000 649,000 Lower Willamette River: RM 24 33,000 252,000 360,000 Scappoose Bay Tributary: McNulty Creek 50 440 810 Scappoose Bay Tributary: Milton Creek 190 3,220 4,400 Scappoose Bay Tributary: Scappoose Creek 360 3,470 6,120 Scappoose Bay Tributary: Honeyman Creek 40 390 700

Notes: cfs – cubic feet per second RM – river mile

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DRAFT Sediment Stability Analysis Six simulations were conducted using various combinations of flow conditions in the Columbia River, Lower Willamette River, and Scappoose Bay tributaries (see Table 5-2).

Table 5-2 Inflow Conditions for High-flow Event Simulations

Inflow Condition: Inflow Condition: Lower Inflow Condition: High-flow Event Columbia River at Willamette River at Scappoose Bay Simulation Bonneville Dam RM 24 Tributaries 1 10-year flood Average Average 2 100-year flood Average Average 3 Average 10-year flood Average 4 Average 100-year flood Average 5 Average 10-year flood 10-year flood 6 Average 10-year flood 100-year flood Approximately 7: February 1996 2-year flood Average 100-year flood Approximately 8: October 1994 Below average Approximately average 5- to 10-year flood

The six high-flow events simulated constant inflow rates, but used a time-variable WSE at the downstream far-field boundary condition. The daily average flow rate in the Columbia and Lower Willamette rivers was analyzed for the available WSE record at St. Helens. WSE data collected at the St. Helens gauging were examined to determine time periods during which daily average flow rates on the Columbia and Lower Willamette rivers were approximately equal to 10- and 100-year flood conditions. St. Helens gauging data collected during those time periods were used to specify WSE at the downstream boundary of the near-field model.

The October 1994 (Simulation 7) and February 1996 (Simulation 8) flood events were included in the sediment stability analysis. Section 4.2.3 presents a description of the February 1996 flood simulation. The October 1994 flood was simulated because this flood corresponded to high-flow conditions on Scappoose Bay tributaries during a period when relatively low-flow conditions occurred in the Columbia and Lower Willamette Rivers (Figure 5-1). The Scappoose Bay tributary flow rates during the October 1994 flood were

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DRAFT Sediment Stability Analysis estimated using daily average flow rates measured on the East Fork Lewis River and adjusted based on the drainage area ratios. The peak flow rate in McNulty Creek during October 1994 was estimated to be approximately 300 cfs (Figure 5-1), which corresponds to a return period of less than 10 years.

5.2 Inundation Frequencies Predicted by Hydrodynamic Model The inundation frequency of different bed elevations within the Study Area was estimated using the near-field model described in Section 4. In particular, WSEs predicted by the near- field model during the 2-month calibration period in 2011 (i.e., April 5 to June 4) were used to determine the inundation frequency at ten representative locations within the Study Area (Figure 5-2). The bed elevation, as determined from available LiDAR data, of the ten locations ranged from 10.3 to 16.8 feet NAVD88. Table 5-3 presents the inundation frequencies predicted by the model at the ten locations.

Table 5-3 Comparison of Model Projected and Data Estimated Inundation Frequency

Bed Elevation Inundation Frequency: Inundation Frequency: Estimated Location (feet NAVD88) Predicted by Model (%) Using Tide Gauge Data (%) IF-1 12.8 54 52 IF-2 14.2 39 39 IF-3 11.3 72 71 IF-4 12.7 55 53 IF-5 10.3 92 90 IF-6 10.3 93 90 IF-7 10.4 90 87 IF-8 11.9 65 63 IF-9 16.8 36 26 IF-10 11.6 68 67

The inundation frequency of different bed elevations within the Study Area was previously determined using WSE data collected at the NOAA tidal gauging station located on the Columbia River at St. Helens (Windward 2010). Hourly WSE data collected at the St. Helens gauging station during the 14-year period from April 1996 to April 2010 were used in the

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DRAFT Sediment Stability Analysis analysis, with the data set being comprised of over 120,000 observations. The WSE data were sorted into 1-foot intervals between -2 and 25 feet North American Vertical Datum of 1929 (NAVD29). After the data were sorted, the inundation frequency within each 1-foot interval was calculated; see Table 1 in Windward (2010). Given the relatively short distance between the Study Area and at the St. Helens gauging station (approximately 2.3 miles), WSEs are assumed to be approximately equal. The results of the Windward (2010) analysis were used to estimate the spatial distribution of overall (long-term) inundation frequencies within the Study Area (Figure 5-3).

Comparisons of the results of the empirical and model-projected inundation frequency analyses are presented in Table 5-3 and Figure 5-4. As evidenced by the close agreement between the empirical and modeled inundation frequencies, the Study Area inundation frequencies derived from the tide gauge data are consistent with those predicted by the near- field model.

5.3 Results of High-flow Event Simulations The sediment bed in unvegetated areas at the Study Area is comprised of cohesive (muddy) sediment. A method for calculating bed scour depths in a cohesive sediment bed using an estimation technique is described in Ziegler (2002). That method was used to calculate bed scour depths for the high-flow event simulations. A summary of the estimation technique in Ziegler (2002) is presented in Appendix C.

As discussed in Section 2, significant portions of the sediment bed within the Study Area are vegetated (Figure 2-8 and 2-9). A vegetated sediment bed is highly resistant to erosion due to the presence of roots and other plant matter in the surface layer of the bed. Thus, the predictions of scour depth should be viewed as conservative estimates because the effects of vegetation on bed scour were not incorporated into this analysis.

Spatial distributions of maximum current velocity and estimated bed scour depth for Simulation 1 (i.e., 10-year flood on the Columbia River) are shown in Figures 5-5 and 5-6, respectively. Maximum velocities within the Study Area are less than 0.5 ft/s, and no bed scour is predicted for this flood event at the Study Area or in the adjacent Scappoose Bay.

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DRAFT Sediment Stability Analysis For the 100-year flood on the Columbia River (Simulation 2), maximum current velocity ranges between 1 and 1.5 ft/s in a relatively small region of the Study Area adjacent to the Scappoose Bay channel (Figure 5-7). Bed scour depths of less than 0.1 inch were predicted to occur within that portion of the Study Area with maximum velocity ranging between 1 and 1.5 ft/s (along the eastern edge of the Study Area, adjacent to Scappoose Bay), with no erosion occurring in the rest of the Study Area (Figure 5-8). The extent of floodplain inundation is greater during the 100-year flood than during the 10-year flood due to higher WSE, as would be expected.

Maximum current velocities are predicted to be less than 0.5 ft/s within the Study Area for 10-year (except for along the far eastern edge of the Study Area, along Scappoose Bay) and 100-year floods on the Lower Willamette River (Simulations 3 and 4), see Figures 5-9 and 5- 11. The extent of floodplain inundation during a 100-year flood on the Lower Willamette River is comparable to the extent of floodplain inundation for a 10-year flood on the Columbia River. Due to the low current velocities, no bed scour is predicted to occur within the Study Area or in the adjacent Scappoose Bay during 10-year and 100-year floods on the Lower Willamette River (Figures 5-10 and 5-12).

Spatial distributions of maximum current velocity and bed scour depth during a 10-year flood on Scappoose Bay tributaries (Simulation 5) are presented in Figures 5-13 and 5-14, respectively. Maximum current velocities are predicted to be less than 0.5 ft/s in nearly all locations within the Study Area except at the inflow boundary location of McNulty Creek. Slightly higher velocities are predicted in the adjacent Scappoose Bay. The Study Area is predicted to have no bed scour during a 10-year flood on McNulty Creek (Figure 5-14).

During the 100-year tributary flood, the predicted maximum current velocities and bed scour depths within the Study Area are similar to the 10-year flood. Predicted maximum current velocities in the eastern portion of the Study Area and in McNulty Creek at the western edge of the Study Area are higher during the 100-year tributary flood than during the 10-year flood, with typical maximum values of 0.5 to 1 ft/s (Figure 5-15). The model predicted a maximum velocity of 1 to 1.5 ft/s in one grid cell that was located at the inflow boundary (i.e., western) location of McNulty Creek. No bed scour is predicted within the Study Area

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant 42 100703-01 74275387.1 0015549-00007

DRAFT Sediment Stability Analysis during a 100-year flood on the Scappoose Bay tributaries. Minimal scour (less than 0.1 inch) is predicted in the adjacent Scappoose Bay channel (Figure 5-16).

Maximum current velocities were predicted to range up to 1.5 to 2 ft/s within the Study Area during the February 1996 flood (Figure 5-17). The extent of floodplain inundation during the February 1996 was comparable to the extent of floodplain inundation predicted during the 100-year flood on the Columbia River (Simulation 2). Bed scour depths of less than 0.25 inch were predicted over a small area in the McNulty Creek mudflats during the February 1996 flood (Figure 5-18).

The spatial distribution of maximum current velocity predicted to occur during the October 1994 flood is shown in Figure 5-19. Elevated current velocities were predicted within the channel of McNulty Creek, with the highest values (approximately 2.5 ft/s or greater) at the mouth of the Creek into Scappoose Bay. Bed scour was predicted to occur within the channel of McNulty Creek during this flood event (Figure 5-20). Maximum bed scour depths of approximately 1 to 3 inches were predicted in a few isolated grid cells near the mouth of the creek. No bed scour was predicted to occur in most other portions of the Study Area (i.e., outside of the vicinity of the creek channel).

5.4 Summary The near-field model was used to evaluate broad-scale bed stability within the Study Area for a wide range of flood events on the Columbia River, Lower Willamette River, and Scappoose Bay Tributaries. Results of the bed stability analysis are summarized in the bullets below.

• No broad-scale bed scour was predicted within the Study Area during the following flood events:

− 10-year flood on Columbia River;

− 10-year flood on Lower Willamette River;

− 100-year flood on Lower Willamette River;

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DRAFT Sediment Stability Analysis

− 10-year flood on Scappoose Bay tributaries in conjunction with 10-year flood on Lower Willamette River; and

− 100-year flood on Scappoose Bay tributaries in conjunction with 10-year flood on Lower Willamette River.

• Minimal erosion of the surface-layer of the bed (i.e., less than 0.25 inch) was predicted in some areas of the Study Area during these flood events:

− 100-year flood on Columbia River (along the eastern edge of the Study Area, adjacent to Scappoose Bay);

− February 1996 (in the vicinity of McNulty Creek); and

• During the October 1994 flood, bed scour was predicted in the channel of McNulty Creek (maximum of 1 to 3 inches at isolated locations), with negligible bed scour in portions of the Study Area outside of the creek channel.

Predicted, broad-scale bed scour depths are considered conservative, upper-bound estimates because: 1) the effects of vegetation on bed scour were not incorporated into this analysis; and 2) upper-bound values for the erosion parameters in Equation C-1 (i.e., A and n) were used to calculate bed scour depth.

Overall, the broad-scale sediment stability analysis indicates that minimal scour occurs even under extreme flood conditions and the sediments within the Study Area are generally stable. Based on the near-field hydrodynamic model’s current precision (i.e., grid spacing), the model is not anticipated to capture the small-scale, tidal-inundation-induced, localized movement of sediment suggested by the historical aerial photograph review. Nor was the model intended to capture the presence and possible migration of small-scale channels.

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DRAFT

6 SUMMARY OF HYDRODYNAMIC CONDITIONS The analyses conducted during this study provided insights and understanding of the hydrodynamic conditions within the Study Area, in particular:

• Vegetation has emerged and been established across much of the Study Area between the 1930s and the present. This broad-scale increase in vegetation is assumed to have been primarily caused by the reduction in the magnitude and frequency of flood events as a result of Columbia River dam construction and reduced disturbance after cessation of process water discharge. This emergence of vegetation likely contributed to the historical net sedimentation within the Study Area given the reduced current velocities caused by the vegetation and the accretion of decaying vegetation.

• Review of historical aerial photographs suggests localized tidal inundation-based erosional events have occurred in the lower elevations of the aquatic lowland and these events appear to continue to occur currently, especially in the mud flat area. Any erosion that may have been associated with the channels conveying process water from the uplands to the lowlands has not occurred in the past 30 years in the higher elevation of the lowlands, corresponding to cessation of process water discharges from the upland by the early 1980’s.

• While geochronology analyses of radioisotope cores indicate the Study Area has been, on a broad-scale, historically net depositional, the estimated magnitude of sedimentation within the Study Area is uncertain due to variability in the radioisotope data and its interpretation and the limited locations of the radioisotope cores. However, the results of the analyses suggest a representative range for historical net sedimentation rates at the radioisotope core locations in the aquatic lowland portion of the Study Area is on the order of 0.1 to 0.5 inch/year. This range of net sedimentation rates corresponds to historical net sedimentation, in areas represented by the radioisotope core locations, on the order of about 1 foot over the past 40 to 100 years. The magnitude of historical net sedimentation at elevations below or above the elevation range represented by the core locations may be substantially different from that estimated from the core analysis.

• The results of the calibration and validation of the broad-scale hydrodynamic model indicate the near-field model can be used to evaluate broad-scale hydrodynamic and Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant 45 100703-01 74275387.1 0015549-00007

DRAFT Summary of Hydrodynamic Conditions sediment transport processes within the Study Area over a wide range of flow and tidal conditions and inform an understanding of the broad-scale hydrodynamic conditions in the Study Area.

• Broad-scale hydrodynamic modeling predicted no broad-scale bed scour in the Study Area for the vast majority of flood event conditions considered, including 100-year floods on the Lower Willamette River and Scappoose Bay tributaries and 10-year flood on the Columbia River. Minimal erosion of the surface-layer of the bed was predicted by the model in a limited area of the McNulty Creek mudflats during selected extreme events (i.e., episodic, short-term events). Overall, the sediment stability analysis indicates minimal scour occurs even under extreme flooding conditions and the sediments within the Study Area are, on a broad-scale, stable. The hydrodynamic model is not sufficiently refined to describe the localized erosional events suggested by the historical aerial photographs review.

• Broad-scale hydrodynamic modeling predictions are consistent with a net depositional environment within the Study Area especially during high-flow events in the Columbia River, which is also consistent with the results of empirical analyses. During floods on the Columbia and Lower Willamette Rivers, significant increases in water surface elevation (WSE) occur within the Study Area, with subsequent inundation of inter-tidal and lowland areas. Scappoose Bay behaves like a backwater during these floods, with low current velocities and quiescent conditions within inundated floodplain areas. These conditions, which are typically coincident with relatively high suspended sediment concentrations in the water column, are conducive for sediment deposition within the Study Area.

In the absence of major changes to the Columbia River, Lower Willamette River, and Scappoose Bay, current processes are anticipated to continue including:

• Broad-scale net depositional processes, although the magnitude of those depositional processes may differ from the historical processes due to many factors, including rising bed elevations; and

• Small-scale, tidal inundation driven, erosional events in the lower elevations of the aquatic lowland.

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DRAFT

7 REFERENCES Anchor QEA, 2011. Work Plan. Evaluation of hydrodynamic and sediment transport processes. St. Helens Fiberboard Plant. Prepared for Bridgewater Group, Armstrong World Industries, Kaiser Gypsum and Owens Corning. April 2011.

Anchor QEA, 2012. Chemical Fate and Transport Modeling Study, San Jacinto River Waste Pits Superfund Site. Prepared for USEPA, Region 6, McGinnes Industrial Maintenance Corporation, International Paper Company. October 2012.

Anderson, R.F., S.L. Schiff, and R.H. Hesslein. 1987. Determining sediment accumulation and mixing rates using 210Pb, 137Cs, and other tracers: Problems due to postdepositional mobility or coring artifacts. Can. J. Fish. Aquat. Sci. 44:231-250

Beck, H.L., 1999. External Radiation Exposure to the Population of the Continental U.S. from Nevada Weapons Tests and Estimates of Deposition Density of Radionuclides That Could Contribute to Internal Radiation Exposure Via Ingestion. Report to National Cancer Institute. June 30, 1999.

Bottom, D.L., C.A. Simenstad, J. Burke, A.M. Baptista, D.A. Jay, K.K. Jones, E. Casillas, and M.H. Schiewe, 2005. Salmon at River’s End: The Role of the Estuary in the Decline and Recovery of Columbia River Salmon. NOAA Technical Memorandum NMFS- NWFSC-68. August 2005.

DeMaster, D.J., B.A. McKee, C.A. Nittrouer, D.C. Brewster, and P.E. Biscaye. 1985. Rates of sediment reworking at the Hebble site based on measurements of Th-234, Cs-137 and Pb-210. Mar. Geol. 66:133-148

Federal Emergency Management Agency (FEMA), 1988. Flood Insurance Study. Columbia County, Oregon and Incorporated Areas. August 16, 1988.

Fisher, J.B., W.J. Lick, P.L. McCall, and J.A. Robbins. 1980. Vertical mixing of lake sediments by tubificid Oligochaetes. J. Geophys. Res. 85:3997-4006.

Gailani, J., C.K. Ziegler and W. Lick, 1991. The transport of suspended solids in the Lower Fox River. J. Great Lakes Res. 17(4):479-494.

Graham, D.I., P.W. James, T.E.R. Jones, J.M. Davies and E.A. Delo, 1992. Measurement and prediction of surface stress in annular flume. ASCE J. Hydr. Engr. 118(9):1270-1286.

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DRAFT References Hakanson, L., and A. Kallstrom. 1978. An equation of state for biologically active lake sediments and its implications for interpretations of sediment data. Sedimentology 25:205-226.

Hamrick, J.M., 1992. A Three-Dimensional Environmental Fluid Dynamics Computer Code: Theoretical and Computational Aspects. College of William and Mary, Virginia Institute of Marine Sciences. Special Report 317. 63 pp.

Hawley, N., 1991. Preliminary observations of sediment erosion from a bottom resting flume. J. Great Lakes Res. 17(3):361-367.

Helsel, D.R. and R.M. Hirsch, 2002. Statistical Methods in Water Resources. Chapter A3, Book 4, Hydrologic Analysis and Interpretation, Techniques of Water-Resources Investigations of the United States Geological Survey [Online]. USGS, Washington, DC. Updated 2002.

Hess, K.W., T.F. Gross, R.A. Schmalz, J.G.W. Kelley, F. Aikman, E. Wei and M.S. Vincent, 2003. NOS Standards for Evaluating Operational Nowcast and Forecast Hydrodynamic Model Systems. NOAA Technical Report NOS CS 17. October 2003.

Huntley, S.L., R.J. Wenning, S.H. Su, N.L. Bonnevie and D.J. Paustenbach, 1995. Geochronology and sedimentology of the Lower Passaic River, New Jersey. Estuaries. 18(2):351-361.

Interagency Advisory Committee on Water Data, 1982. Guidelines for Determining Flood Flow Frequency. Bulletin 17B of the Hydrology Subcommittee. USGS. Reston, VA.

Kacieszczenko, J., and Z. Banasik. 1981. An effect of bioturbation on the results of the 137Cs dating technique used for lacustrine sediments. Ekol. Pol. 29:615-623.

Krezoski, J.R., S.C. Mozley, and J.A. Robbins. 1978. Influence of benthic macroinvertebrates on mixing of profundal sediments in southeastern Lake Huron. Limnol. Oceanogr. 23:1011-1016.

Krezoski, J.R., and J.A. Robbins. 1985. Vertical distribution of feeding and particle-selective transport of 137Cs in lake sediments by lumbriculid oligochaetes. J. Geophys. Res. 90:11999-12006.

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DRAFT References Krone, R.B., 1962. Flume studies of the transport of sediment in estuarial processes, final report. Hydraulic Engineering Laboratory and Sanitary Engineering Research Laboratory. Univ. of Calif., Berkeley.

Kukulka, T. and D.A. Jay, 2003. Impacts of Columbia River discharge on salmonid habitat. I. A Non-stationary Fluvial Tide Model. J. Geophys. Res. Oceans 108 (C9): 3293.

Lick, W., Y.J. Xu and J. McNeil, 1995. Resuspension properties of sediments in the Fox, Saginaw and Buffalo Rivers. J. Great Lakes Res. 21(2):257-274.

Magar, V.S., D.B. Chadwick, T.S. Bridges, P.C. Fuchsman, J.M. Conder, T.J. Dekker, J.A. Steevens, K.E. Gustavson, and M.A. Mills, 2009. Monitored Natural Recovery at Contaminated Sediment Sites. Project ER-0622. U.S. Department of Defense Environmental Security Technology Certification Program (ESTCP).

Parchure, T.M. and A.J. Mehta, 1985. Erosion of soft cohesive sediment deposits. ASCE J. Hydr. Engr. 111(10):1308-1326.

Pawlowicz, R., B. Beardsley and S. Lentz, 2002. Classical tidal harmonic analysis including error estimates in MATLAB using T_TIDE. Computers & Geosciences 28:929-937.

Priddy, M., G. Patton, J. Yokel, D. Delistraty and T. Stoops, 2005. Survey of potential Hanford site contaminants in the upper sediment for the reservoirs at McNary, John Day, The Dalles and Bonneville Dams, 2003. Washington State Dept. of Health. February 2005.

Quantitative Environmental Analysis (QEA), 1999. PCBs in the Upper Hudson River, Volume 2, A Model of PCB Fate, Transport and Bioaccumulation. QEA report prepared for General Electric Company, Albany, NY.

Quantitative Environmental Analysis (QEA), 2008. Lower Duwamish Waterway, Sediment Transport Modeling Report, Final. QEA report prepared for USEPA, Region 10, Seattle, WA. October 2008.

Ritchie, J.C. and J. R. McHenry. 1990. Application of radioactive fallout cesium-137 for measuring soil erosion and sediment accumulation rates and patterns: a review. Journal of Environmental Quality 19, 215-233.

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DRAFT References Robbins, J.A. 1986. A model for particle-selective transport of tracers in sediments with conveyor belt deposit feeders. J. Geophys. Res. 91:8542-8558.

Robbins, J. A. and D. N. Eddington. 1975. Determination of recent sedimentation rates in Lake Michigan using 210Pb and 137Cs. Geochimica et Coamochimica Acta 29:285-304.

Robbins, J.A., J.R. Krezoski, and S.C. Mozley. 1977. Radioactivity in sediments of the Great Lakes: Post-depositional redistribution by deposit-feeding organisms. Earth Planet. Sci. Lett. 36:325-333

Robbins, J.A., P.L. McCall, J.B. Fisher, and J.R. Krezoski. 1979. Effect of deposit feeders on migration of 137Cs in lake sediments. Earth Planet. Sci. Lett. 42:277-287.

Sharma, P., L.R. Gardner, W.S. Moore, and M.S. Bollinger. 1987. Sedimentation and bioturbation in a salt marsh as revealed by 210Pb, 137Cs, and 7Be studies. Limnol. Oceanogr. 32:313-326.

Soil Conservation Service (SCS), 1984. Floodplain Management Study, Milton Creek, Columbia County, Oregon. June 1984.

Sokal, R.R. and F.J. Rohlf, 2012. Biometry, The Princples and Practice of Statistics in Biological Research. W.H. Freeman and Company, New York. 937 pages.

Tsai, C.H. and W. Lick, 1987. Resuspension of sediments from Long Island Sound. Water Science Technology 21(6/7):155-184.

U.S. Environmental Protection Agency (USEPA), 2005. Contaminated Sediment Remediation Guidance for Hazardous Waste Sites, OSWER 9355.0-85, EPA-540-R- 05-012.

USEPA, 2012. Performing a Sediment Erosion and Deposition Assessment (SEDA) at Superfund Sites. OSWER Draft Report.

U.S. Geological Survey (USGS), 1979. Magnitude and Frequency of Floods in Western Oregon. Open-file report 79-553.

Windward, 2010. Evaluation of aquatic and terrestrial boundaries of the St. Helens Fiberboard Plant. Memorandum to Debbie Bailey, Oregon Department of Environmental Quality. June 25, 2010.

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DRAFT References Ziegler, C.K. and B. Nisbet, 1994. Fine-Grained Sediment Transport in Pawtuxet River, Rhode Island. ASCE J. Hyd. Engr. 120(5): 561-576.

Ziegler, C.K. and B. Nisbet, 1995. Long-Term Simulation of Fine-Grained Sediment Transport in a Large Reservoir. ASCE J. Hyd. Engr 121(11): 773-781.

Ziegler, C.K., 2002. Evaluating Sediment Stability at Sites with Historic Contamination. Environmental Management 29(3):409-427.

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FIGURES

74275387.1 0015549-00007 U! Radioisotope Core Location Upland-lowland Boundary

AQ-01 AQ-08 U! U!

AQ-05 AQ-03 U! U!AQ-03

AQ-02 AQ-06 U! U!

AQ-04 U!

AQ-07 Locations of radioisotope U! cores collected in 2011 are shown on photograph. M:\Jobs\St_Helens\Report\120406\Decks\StHelens_Aerial_Photos_Fig2-1_to_2-10.mxd vlist 8/20/2012 9:52:16 AM 9:52:16 vlist 8/20/2012 M:\Jobs\St_Helens\Report\120406\Decks\StHelens_Aerial_Photos_Fig2-1_to_2-10.mxd

Figure 2-1 Aerial Photograph of Study Area: 1929 Feet St. Helens Fiberboard Plant [ 0 250 500 U! Radioisotope Core Location Upland-lowland Boundary

AQ-01 AQ-08 U! U!

AQ-05 AQ-03 U! U!AQ-03

AQ-02 AQ-06 U! U!

AQ-04 U!

AQ-07 Locations of radioisotope U! cores collected in 2011 are shown on photograph. \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120904\Decks\StHelens_Aerial_Photos_Fig2-1_to_2-10_120905.mxd vlist 9/5/2012 3:31:42 PM 3:31:42 9/5/2012 vlist \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120904\Decks\StHelens_Aerial_Photos_Fig2-1_to_2-10_120905.mxd

Figure 2-2 Aerial Photograph of Study Area: 1948 Feet St. Helens Fiberboard Plant 0 250 500 Photo taken on September 5, with a daily average water surface elevation of [ 7.3 ft, NAVD88 (ranging from 5.5 to 9.0 ft, NAVD88) at St. Helens gaging station. U! Radioisotope Core Location Upland-lowland Boundary

AQ-01 AQ-08 U! U!

AQ-05 AQ-03 U! U!AQ-03

AQ-02 AQ-06 U! U!

AQ-04 U!

AQ-07 Locations of radioisotope U! cores collected in 2011 are shown on photograph. \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120904\Decks\StHelens_Aerial_Photos_Fig2-1_to_2-10_120905.mxd vlist 9/5/2012 3:31:00 PM 3:31:00 9/5/2012 vlist \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120904\Decks\StHelens_Aerial_Photos_Fig2-1_to_2-10_120905.mxd

Figure 2-3 Aerial Photograph of Study Area: 1957 Feet St. Helens Fiberboard Plant 0 250 500 Photo taken on November 5, with a daily average water surface elevation of [ 7.6 ft, NAVD88 (ranging from 6.4 to 9.1 ft, NAVD88) at St. Helens gaging station. U! Radioisotope Core Location Upland-lowland Boundary

AQ-01 AQ-08 U! U!

AQ-05 AQ-03 U! U!AQ-03

AQ-02 AQ-06 U! U!

AQ-04 U!

AQ-07 Locations of radioisotope U! cores collected in 2011 are shown on photograph. \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120904\Decks\StHelens_Aerial_Photos_Fig2-1_to_2-10_120905.mxd vlist 9/5/2012 3:30:13 PM 3:30:13 9/5/2012 vlist \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120904\Decks\StHelens_Aerial_Photos_Fig2-1_to_2-10_120905.mxd

Figure 2-4 Aerial Photograph of Study Area: 1973 Feet St. Helens Fiberboard Plant 0 250 500 Photo taken on August 14, with a daily average water surface elevation of [ 7.7 ft, NAVD88 (ranging from 6.1 to 9.0 ft, NAVD88) at St. Helens gaging station. U! Radioisotope Core Location Upland-lowland Boundary

AQ-01 AQ-08 U! U!

AQ-05 AQ-03 U! U!AQ-03

AQ-02 AQ-06 U! U!

AQ-04 U!

AQ-07 Locations of radioisotope U! cores collected in 2011 are shown on photograph. \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120904\Decks\StHelens_Aerial_Photos_Fig2-1_to_2-10_120905.mxd vlist 9/5/2012 3:28:52 PM 3:28:52 9/5/2012 vlist \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120904\Decks\StHelens_Aerial_Photos_Fig2-1_to_2-10_120905.mxd

Figure 2-5 Aerial Photograph of Study Area: 1983 Feet St. Helens Fiberboard Plant 0 250 500 Photo taken on September 19, with a daily average water surface elevation of [ 6.4 ft, NAVD88 (ranging from 4.9 to 7.3 ft, NAVD88) at St. Helens gaging station. U! Radioisotope Core Location Upland-lowland Boundary

AQ-01 AQ-08 U! U!

AQ-05 AQ-03 U! U!AQ-03

AQ-02 AQ-06 U! U!

AQ-04 U!

AQ-07 Locations of radioisotope U! cores collected in 2011 are shown on photograph. \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120904\Decks\StHelens_Aerial_Photos_Fig2-1_to_2-10_120905.mxd vlist 9/5/2012 3:29:22 PM 3:29:22 9/5/2012 vlist \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120904\Decks\StHelens_Aerial_Photos_Fig2-1_to_2-10_120905.mxd

Figure 2-6 Aerial Photograph of Study Area: 2010 Feet St. Helens Fiberboard Plant 0 250 500 Photo taken on August 14, with a daily average water surface elevation of [ 8.1 ft, NAVD88 (ranging from 6.3 to 10.1 ft, NAVD88) at St. Helens gaging station. 1929 Vegetation 2010 Vegetation Property Boundary Upland-lowland Boundary Aquatic Lowland Boundary M:\Jobs\St_Helens\Report\120406\Decks\StHelens_Creek_Delineation_Fig2-12.mxd egranger 9/7/2012 12:58:14 PM 12:58:14 egranger 9/7/2012 M:\Jobs\St_Helens\Report\120406\Decks\StHelens_Creek_Delineation_Fig2-12.mxd

Figure 2-7 Side-by-side Comparison of Extent of Vegetation Feet within Study Area in 1929 and 2010 [ 0 500 1,000 St. Helens Fiberboard Plant Vegetation Increase Property Boundary Upland-lowland Boundary Aquatic Lowland Boundary \\montvalebu\jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_Creek_Delineation_Fig2-11.mxd vlist 9/10/2012 11:55:00 AM 11:55:00 vlist 9/10/2012 \\montvalebu\jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_Creek_Delineation_Fig2-11.mxd

Figure 2-8 Increase in Vegetation within Study Area between 1929 and 2010 Feet St. Helens Fiberboard Plant [ 0 500 1,000 1929 1948

Milton Creek

McNulty Creek

Aerial photograph taken on August 14, 2010. M:\Jobs\St_Helens\Report\120406\Decks\StHelens_Creek_Delineation_Fig2-13_to_2-15.mxd vlist 10/23/2012 2:46:49 PM vlist 10/23/2012 M:\Jobs\St_Helens\Report\120406\Decks\StHelens_Creek_Delineation_Fig2-13_to_2-15.mxd

Figure 2-9 Comparison of Channel Location of McNulty Feet and Milton Creeks in 1929 and 1948 [ 0 250 500 St. Helens Fiberboard Plant 1948 1957

Milton Creek

McNulty Creek

Aerial photograph taken on August 14, 2010. M:\Jobs\St_Helens\Report\120406\Decks\StHelens_Creek_Delineation_Fig2-13_to_2-15.mxd vlist 10/23/2012 2:55:00 PM vlist 10/23/2012 M:\Jobs\St_Helens\Report\120406\Decks\StHelens_Creek_Delineation_Fig2-13_to_2-15.mxd

Figure 2-10 Comparison of Channel Location of McNulty Feet and Milton Creeks in 1948 and 1957 [ 0 250 500 St. Helens Fiberboard Plant 1957 2010

Milton Creek

McNulty Creek

Aerial photograph taken on August 14, 2010. M:\Jobs\St_Helens\Report\120406\Decks\StHelens_Creek_Delineation_Fig2-13_to_2-15.mxd vlist 10/23/2012 2:54:41 PM vlist 10/23/2012 M:\Jobs\St_Helens\Report\120406\Decks\StHelens_Creek_Delineation_Fig2-13_to_2-15.mxd

Figure 2-11 Comparison of Channel Location of McNulty Feet and Milton Creeks in 1957 and 2010 [ 0 250 500 St. Helens Fiberboard Plant U! U!

Northeast

AQ-05 AQ-05U! McNulty AQ-03 U! Bar Island Southwest Highlands Channel AQ-02 U!AQ-02 U!AQ-06

AQ-04 U!AQ-04

Mudflats

Upland-lowland Boundary Aquatic Lowland Boundary AQ-07 U! Historical Process Water Discharge U! Radioisotope Core Location \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-12.mxd vlist 8/8/2013 11:05:48 AM 11:05:48 vlist 8/8/2013 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-12.mxd

Figure 2-12 Subareas for Aerial Photograph Small Scale Feature Review Feet St. Helens Fiberboard Plant 0 250 500 [ Photo taken on August 14, 2010 with a daily average water surface elevation of 8.1 ft, NAVD88 (ranging from 6.4 - 10.0 ft, NAVD88) at St. Helens gauging station. U! U!

Apparent Discharge(s) fromfrom UplandUpland

Channels

Channel

AQ-05 AQ-05U! AQ-03U!

AQ-02 U!AQ-02 U!AQ-06 Milton Creek Channels AQ-04 U!AQ-04

Inter-tidal Formations

Upland-lowland Boundary Aquatic Lowland Boundary AQ-07 U! Historical Process Water Discharge U! Radioisotope Core Location \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-13.mxd vlist 8/8/2013 11:07:07 AM 11:07:07 vlist 8/8/2013 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-13.mxd

Figure 2-13 Aerial Photograph for Small Scale Feature Review: 1948 Feet St. Helens Fiberboard Plant 0 250 500 [ Photo taken on September 5, with a daily average water surface elevation of 7.3 ft, NAVD88 (ranging from 5.5 - 9.0 ft, NAVD88) at St. Helens gauging station. U! U!

Apparent Discharge(s) fromfrom UplandUpland

Channels

AQ-05 AQ-05U! AQ-03 U! Channel MF-2

Channel MF-3 AQ-02 U!AQ-02 U!AQ-06

Channel MF-1 AQ-04 U!AQ-04

Inter-tidal Upland-lowland Boundary Formations Aquatic Lowland Boundary AQ-07 U! Historical Process Water Discharge U! Radioisotope Core Location \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-14.mxd vlist 8/8/2013 11:10:58 AM 11:10:58 vlist 8/8/2013 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-14.mxd

Figure 2-14 Aerial Photograph for Small Scale Feature Review: 1953 Feet St. Helens Fiberboard Plant 0 250 500 [ Photo taken on September 9, with a daily average water surface elevation of 6.9 ft, NAVD88 (ranging from 5.6 - 8.3 ft, NAVD88) at St. Helens gauging station. U! U!

Apparent Discharge(s) fromfrom UplandUpland

Channel Cutoff Channels Channels

AQ-05 AQ-05U! AQ-03U!

AQ-02 U! Channel MF-1 AQ-06 Channel MF-2 U!

Channel MF-3

AQ-04 U!AQ-04

Upland-lowland Boundary Aquatic Lowland Boundary AQ-07 U! Historical Process Water Discharge U! Radioisotope Core Location \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-15.mxd vlist 8/8/2013 11:11:35 AM 11:11:35 vlist 8/8/2013 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-15.mxd

Figure 2-15 Aerial Photograph for Small Scale Feature Review: 1966 Feet St. Helens Fiberboard Plant 0 250 500 [ Photo taken on March 22, with a daily average water surface elevation of 7.3 ft, NAVD88 (ranging from 6.1 - 8.7 ft, NAVD88) at St. Helens gauging station. U! U! (Discharge(Discharge ceasedceased December 1981) (Discharge(Discharge ceasedceased December 1981) January 1977) (!OF002 (! OF001 Channel Cutoff Channels Channel NE-1

AQ-05 AQ-05U! AQ-03U! Channel SW-1

AQ-02 U! AQ-06 Channel MF-2 U! Infilled Channel MF-1 Channel MF-3 Bi-furcated Channel AQ-04 U!AQ-04

Inter-tidal Formations Upland-lowland Boundary Aquatic Lowland Boundary AQ-07 U! Historical Process Water Discharge U! Radioisotope Core Location \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-16.mxd vlist 8/6/2013 2:54:11 PM 2:54:11 vlist 8/6/2013 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-16.mxd

Figure 2-16 Aerial Photograph for Small Scale Feature Review: 1970 Feet St. Helens Fiberboard Plant 0 250 500 [ Photo taken on May 19, with a daily average water surface elevation of 7.2 ft, NAVD88 (ranging from 5.9 - 9.0 ft, NAVD88) at St. Helens gauging station. U! U! (Discharge(Discharge ceasedceased December 1981) (Discharge(Discharge ceasedceased December 1981) January 1977) (!OF002 (! OF001

Channels Channel NE-1

AQ-05 AQ-05U! AQ-03U! Channel SW-1

AQ-02 U! AQ-06 Channel MF-2 U! Channel MF-1 Channel MF-3

AQ-04 U!AQ-04

Upland-lowland Boundary Aquatic Lowland Boundary AQ-07 U! Historical Process Water Discharge U! Radioisotope Core Location \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-17.mxd vlist 8/6/2013 2:54:53 PM 2:54:53 vlist 8/6/2013 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-17.mxd

Figure 2-17 Aerial Photograph for Small Scale Feature Review: 1975 Feet St. Helens Fiberboard Plant 0 250 500 [ Photo taken on September 30, with a daily average water surface elevation of 6.4 ft, NAVD88 (ranging from 5.1 - 7.6 ft, NAVD88) at St. Helens gauging station. U! U! (Discharge(Discharge ceasedceased December 1981) (Discharge(Discharge ceasedceased December 1981) January 1977) (!OF002 (! OF001 Channel Channels Cutoff Channel NE-1

AQ-05 AQ-05U! AQ-03U! Channel SW-1

AQ-02 U! AQ-06 Channel MF-2 U! Channel MF-1 Relict Channel AQ-04 with Infilling U!AQ-04

Upland-lowland Boundary Aquatic Lowland Boundary AQ-07 U! Historical Process Water Discharge U! Radioisotope Core Location \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-18.mxd vlist 8/6/2013 2:55:39 PM 2:55:39 vlist 8/6/2013 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-18.mxd

Figure 2-18 Aerial Photograph for Small Scale Feature Review: 1980 Feet St. Helens Fiberboard Plant 0 250 500 [ Photo taken on January 30, with a daily average water surface elevation of 9.2 ft, NAVD88 (ranging from 7.5 - 10.5 ft, NAVD88) at St. Helens gauging station. U! U! (Discharge(Discharge ceasedceased December 1981) (Discharge(Discharge ceasedceased December 1981) January 1977) (!OF002 (! OF001

Channel NE-1 Vegetated

AQ-05 AQ-05U! AQ-03U! Channel SW-1

AQ-02 U!AQ-02 U!AQ-06

Channel MF-1

AQ-04 U!AQ-04

Upland-lowland Boundary Aquatic Lowland Boundary AQ-07 U! Historical Process Water Discharge U! Radioisotope Core Location \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-19.mxd vlist 8/6/2013 2:56:12 PM 2:56:12 vlist 8/6/2013 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-19.mxd

Figure 2-19 Aerial Photograph for Small Scale Feature Review: 1988 Feet St. Helens Fiberboard Plant 0 250 500 [ Photo taken on September 3, with a daily average water surface elevation of 6.2 ft, NAVD88 (ranging from 5.2 - 7.8 ft, NAVD88) at St. Helens gauging station. U! U! (Discharge(Discharge ceasedceased December 1981) (Discharge(Discharge ceasedceased December 1981) January 1977) (!OF002 (! OF001

AQ-05 AQ-05U! AQ-03U! Channel SW-1

AQ-02 U!AQ-02 U!AQ-06 Channel MF-1

AQ-04 U!AQ-04

Upland-lowland Boundary Aquatic Lowland Boundary AQ-07 U! Historical Process Water Discharge U! Radioisotope Core Location \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-20.mxd vlist 8/6/2013 2:56:37 PM 2:56:37 vlist 8/6/2013 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-20.mxd

Figure 2-20 Aerial Photograph for Small Scale Feature Review: 1992 Feet St. Helens Fiberboard Plant 0 250 500 [ Photo taken on June 20, with a daily average water surface elevation of 7.4 ft, NAVD88 (ranging from 6.0 - 8.8 ft, NAVD88) at St. Helens gauging station. U! U! (Discharge(Discharge ceasedceased December 1981) (Discharge(Discharge ceasedceased December 1981) January 1977) (!OF002 (! OF001

AQ-05 AQ-05U! AQ-03U! Channel SW-1

AQ-02 U!AQ-02 U!AQ-06 Channel MF-1

AQ-04 U!AQ-04

Upland-lowland Boundary Aquatic Lowland Boundary AQ-07 U! Historical Process Water Discharge U! Radioisotope Core Location \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-21.mxd vlist 8/6/2013 2:57:23 PM 2:57:23 vlist 8/6/2013 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-21.mxd

Figure 2-21 Aerial Photograph for Small Scale Feature Review: 1996 Feet St. Helens Fiberboard Plant 0 250 500 [ Photo taken on July 6, with a daily average water surface elevation of 7.7 ft, NAVD88 (ranging from 6.0 - 9.1 ft, NAVD88) at St. Helens gauging station. U! U! (Discharge(Discharge ceasedceased December 1981) (Discharge(Discharge ceasedceased December 1981) January 1977) (!OF002 (! OF001

Channel Incision

AQ-05 AQ-05U! AQ-03U! Channel SW-1 Seasonal Vegetation Channel MF-6

AQ-02 U! AQ-06 Channel MF-5 U!

Channel MF-1

AQ-04 U!AQ-04 Channel MF-4

Inter-tidal Formations Upland-lowland Boundary Aquatic Lowland Boundary AQ-07 U! Historical Process Water Discharge U! Radioisotope Core Location \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-22.mxd vlist 8/6/2013 2:58:01 PM 2:58:01 vlist 8/6/2013 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-22.mxd

Figure 2-22 Aerial Photograph for Small Scale Feature Review: 2000 Feet St. Helens Fiberboard Plant 0 250 500 [ Photo taken on July 23, with a daily average water surface elevation of 7.4 ft, NAVD88 (ranging from 6.1 - 8.8 ft, NAVD88) at St. Helens gauging station. U! U! (Discharge(Discharge ceasedceased December 1981) (Discharge(Discharge ceasedceased December 1981) January 1977) (!OF002 (! OF001

AQ-05 AQ-05U! AQ-03U! Channel SW-1 Channel MF-6

AQ-02 U! AQ-06 Channel MF-5 U!

New Channel MF-1 Channel AQ-04 U!AQ-04 Channel MF-4

Seasonal Vegetation

Inter-tidal Upland-lowland Boundary Formations Aquatic Lowland Boundary AQ-07 U! Historical Process Water Discharge U! Radioisotope Core Location \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-23.mxd vlist 8/6/2013 2:58:23 PM 2:58:23 vlist 8/6/2013 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-23.mxd

Figure 2-23 Aerial Photograph for Small Scale Feature Review: 2005 Feet St. Helens Fiberboard Plant 0 250 500 [ Photo taken on June 28, with a daily average water surface elevation of 9.2 ft, NAVD88 (ranging from 8.0 - 10.2 ft, NAVD88) at St. Helens gauging station. U! U! (Discharge(Discharge ceasedceased December 1981) (Discharge(Discharge ceasedceased December 1981) January 1977) (!OF002 (! OF001

AQ-05 AQ-05U! AQ-03U! Channel SW-1 Channel MF-6

AQ-02 U! AQ-06 Channel MF-5 U!

Shore Channel MF-1 Disturbance AQ-04 U!AQ-04 Channel MF-4

Inter-tidal Upland-lowland Boundary Formations Aquatic Lowland Boundary AQ-07 U! Historical Process Water Discharge U! Radioisotope Core Location \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-24.mxd vlist 8/6/2013 2:59:23 PM 2:59:23 vlist 8/6/2013 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\130701\StHelens_Aerial_Fig2-24.mxd

Figure 2-24 Aerial Photograph for Small Scale Feature Review: 2010 Feet St. Helens Fiberboard Plant 0 250 500 [ Photo taken on August 14, with a daily average water surface elevation of 8.1 ft, NAVD88 (ranging from 6.4 - 10.0 ft, NAVD88) at St. Helens gauging station. U! Radioisotope Core Location

AQ-01 AQ-08 U! U!

AQ-05 AQ-03 U! U!

AQ-02 AQ-06 U! U!

AQ-04 U!

AQ-07 U! \\Montvalebu\jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_Radioisotope_Locations_Fig3-1.mxd vlist 9/10/2012 8:47:55 AM 8:47:55 vlist 9/10/2012 \\Montvalebu\jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_Radioisotope_Locations_Fig3-1.mxd

Figure 3-1 Locations of Radioisotope Cores Collected during June 2011 Feet St. Helens Fiberboard Plant [ 0 250 500 Cesium-137 Lead-210 0.0 0.0

Cesium-137 activities 0.5 were below detection 0.5 limits in all samples.

1.0 1.0

1.5 1.5

(ft) Depth

2.0 2.0

2.5 2.5

3.0 3.0

0.00 0.05 0.10 0.15 0.20 0.0 0.2 0.4 0.6 0.8 Activity Activity (pCi/g Dry) (pCi/g Dry)

Figure 3-2 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-01 St. Helens Fiberboard Plant

vkl - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120815.pro Fri Sep 07 13:24:05 2012 Cesium-137 Lead-210 0.0 0.0

0.5 0.5

1.0 1.0

1.5 1.5

(ft) Depth

2.0 2.0

2.5 2.5

3.0 3.0

0.00 0.05 0.10 0.15 0.20 0.25 0.0 0.2 0.4 0.6 0.8 Activity Activity (pCi/g Dry) (pCi/g Dry)

Figure 3-3 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-02 St. Helens Fiberboard Plant Note: Cesium-137 activities below the detection limit were removed.

vkl - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120815.pro Thu Sep 06 08:13:52 2012 Cesium-137 Lead-210 0.0 0.0

Cesium-137 activities 0.5 were below detection 0.5 limits in all samples.

1.0 1.0

1.5 1.5

(ft) Depth

2.0 2.0

2.5 2.5

3.0 3.0

0.00 0.05 0.10 0.15 0.20 0.0 0.2 0.4 0.6 0.8 1.0 Activity Activity (pCi/g Dry) (pCi/g Dry)

Figure 3-4 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-03 St. Helens Fiberboard Plant

vkl - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120815.pro Fri Sep 07 13:24:06 2012 Cesium-137 Lead-210 0.0 0.0

Cesium-137 activities 0.5 were below detection 0.5 limits in all samples.

1.0 1.0

1.5 1.5

(ft) Depth

2.0 2.0

2.5 2.5

3.0 3.0

0.00 0.05 0.10 0.15 0.20 0.0 0.2 0.4 0.6 0.8 Activity Activity (pCi/g Dry) (pCi/g Dry)

Figure 3-5 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-04 St. Helens Fiberboard Plant

vkl - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120815.pro Fri Sep 07 13:24:06 2012 Cesium-137 Lead-210 0.0 0.0

0.5 0.5

1.0 1.0

1.5 1.5

(ft) Depth

2.0 2.0

2.5 2.5

3.0 3.0

0.0 0.1 0.2 0.3 0.4 0.0 0.5 1.0 1.5 2.0 Activity Activity (pCi/g Dry) (pCi/g Dry)

Figure 3-6 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-05 St. Helens Fiberboard Plant Note: Cesium-137 activities below the detection limit were removed.

vkl - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120815.pro Thu Sep 06 08:13:52 2012 Cesium-137 Lead-210 0.0 0.0

Cesium-137 activities 0.5 were below detection 0.5 limits in all samples.

1.0 1.0

1.5 1.5

(ft) Depth

2.0 2.0

2.5 2.5

3.0 3.0

0.00 0.05 0.10 0.15 0.20 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Activity Activity (pCi/g Dry) (pCi/g Dry)

Figure 3-7 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-06 St. Helens Fiberboard Plant

vkl - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120815.pro Fri Sep 07 13:24:06 2012 Cesium-137 Lead-210 0.0 0.0

Cesium-137 activities 0.5 were below detection 0.5 limits in all samples.

1.0 1.0

1.5 1.5

(ft) Depth

2.0 2.0

2.5 2.5

3.0 3.0

0.00 0.05 0.10 0.15 0.20 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Activity Activity (pCi/g Dry) (pCi/g Dry)

Figure 3-8 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-07 St. Helens Fiberboard Plant

vkl - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120815.pro Fri Sep 07 13:24:06 2012 Cesium-137 Lead-210 0.0 0.0

0.5 0.5

1.0 1.0

1.5 1.5

(ft) Depth

2.0 2.0

2.5 2.5

3.0 3.0

0.0 0.2 0.4 0.6 0.8 0.00 0.25 0.50 0.75 1.00 1.25 1.50 Activity Activity (pCi/g Dry) (pCi/g Dry)

Figure 3-9 Vertical Profiles of Cs-137 Activity and Pb-210 Activity: Core AQ-08 St. Helens Fiberboard Plant Note: Cesium-137 activities below the detection limit were removed.

vkl - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120815.pro Thu Sep 06 08:13:53 2012 0

1

2 (ft) Depth

3

4 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Lead-210 Activity (pCi/g Dry)

0 R2 = 1.00

1

2 (ft) Depth

3

Best-fit regression line 4 -7 -6 -5 -4 -3 -2 -1 0 In Unsupported Lead-210

Figure 3-10 Vertical Profile of Pb-210 Activity in Ideal Depositional Setting St. Helens Fiberboard Plant

vkl - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\sthelens_ideal_geochron_120815.pro Wed Sep 05 11:50:49 2012 Core AQ-01 Core AQ-02 Core AQ-03 0 0 0 R2 = 0.99 R2 = 0.82

2 1 1 R = 0.98 1

2 2 2 (ft) (ft) (ft) Depth Depth Depth

3 3 3

4 4 4 -5 -4 -3 -2 -1 -5 -4 -3 -2 -1 0 -5 -4 -3 -2 -1 0 ln Unsupported Lead-210 ln Unsupported Lead-210 ln Unsupported Lead-210

Core AQ-04 Core AQ-05 Core AQ-08 0 0 0 R2 = 0.94 R2 = 0.96 R2 = 0.94

1 1 1

2 2 2 (ft) (ft) (ft) Depth Depth Depth

3 3 3

4 4 4 -5 -4 -3 -2 -1 0 1 -5 -4 -3 -2 -1 0 1 2 -5 -4 -3 -2 -1 0 1 ln Unsupported Lead-210 ln Unsupported Lead-210 ln Unsupported Lead-210

Figure 3-11 Data included in regression analysis Vertical Profiles of Transformed Pb-210 Activity Data excluded from regression analysis St. Helens Fiberboard Plant Best-fit regression line

JF/HS - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120905_summary.pro Wed Sep 05 11:58:04 2012 Station Location NOAA USGS

Longview

St. Helens

Bonneville Multnomah Vancouver Columbia River Dam Channel

Portland

Willamette River

Clackamas River \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_FF_Domain_Fig4-1.mxd lbateman 6/22/2012 10:13:26 AM 10:13:26 lbateman 6/22/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_FF_Domain_Fig4-1.mxd

Figure 4-1 Spatial Extent of Model Domain for Far-field Model Miles St. Helens Fiberboard Plant [ 0 4 8 Station Location NOAA USGS

Flow

St. Helens M:\Jobs\St_Helens\Report\120406\Decks\StHelens_FF_Numerical_Grid_Fig4-2_to_4-3.mxd vlist 8/20/2012 9:46:31 AM 9:46:31 8/20/2012 vlist M:\Jobs\St_Helens\Report\120406\Decks\StHelens_FF_Numerical_Grid_Fig4-2_to_4-3.mxd

Figure 4-2 Portion of Numerical Grid for Far-field Miles Model: Columbia River near St. Helens [ 0 0.5 1 St. Helens Fiberboard Plant Station Location NOAA USGS

Portland

Flow M:\Jobs\St_Helens\Report\120406\Decks\StHelens_FF_Numerical_Grid_Fig4-2_to_4-3.mxd vlist 8/20/2012 9:45:25 AM 9:45:25 8/20/2012 vlist M:\Jobs\St_Helens\Report\120406\Decks\StHelens_FF_Numerical_Grid_Fig4-2_to_4-3.mxd

Figure 4-3 Portion of Numerical Grid for Far-field Miles Model: Lower Willamette River [ 0 0.5 1 St. Helens Fiberboard Plant Station Location NOAA USGS

Cowlitz River

Longview

Lewis River

St. Helens

Bonneville Columbia River Multnomah Vancouver Dam Channel

Portland Willamette River Sandy River

Miles 0 4 8 Clackamas River \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_FF_Numerical_Grid_Fig4-4.mxd lbateman 6/22/2012 10:15:51 AM lbateman 10:15:51 6/22/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_FF_Numerical_Grid_Fig4-4.mxd

Figure 4-4 Locations of Far-field Model Inputs for WSE at Downstream Boundary and Inflows from Upstream and Tributary Sources [ St. Helens Fiberboard Plant Columbia River at The Dalles 800,000 Low-flow High-flow Period Period 100-year Flood 600,000

10-year Flood

400,000

(cfs) 2-year Flood Flow Rate Flow

200,000 Average

0 Jul-01 Aug-01 Sep-01 Oct-01 Nov-01 Dec-01 Jan-01 Feb-01 Mar-01 Apr-01 May-01 Jun-01 Jul-01 Aug-01 Sep-01 Oct-01 2005 2005 2005 2005 2005 2005 2006 2006 2006 2006 2006 2006 2006 2006 2006 2006 Lower Willamette River at Portland 400,000 100-year Flood Low-flow High-flow Period Period 300,000 10-year Flood

200,000 (cfs) 2-year Flood Flow Rate Flow

100,000

Average 0 Jul-01 Aug-01 Sep-01 Oct-01 Nov-01 Dec-01 Jan-01 Feb-01 Mar-01 Apr-01 May-01 Jun-01 Jul-01 Aug-01 Sep-01 Oct-01 2005 2005 2005 2005 2005 2005 2006 2006 2006 2006 2006 2006 2006 2006 2006 2006

Figure 4-5 Daily Average Flow Rate for Columbia River at The Dalles and Lower Willamette River during Far-field Model Calibration Period (July 2005 through September 2006) St. Helens Fiberboard Plant Note: Low-flow and high-flow periods correspond to calibration results shown on Figures 4-6 through 4-10.

BTR - M:\Jobs\St_Helens\Report\120406\Decks\plot_temporal_daily_flow_stage_120408.pro Tue Aug 28 14:40:36 2012 20 Low-flow Period

15

10 (ft, NAVD88) 5 Water Surface Elevation Water Surface

0 Sep-01 Sep-06 Sep-11 Sep-16 Sep-21 Sep-26 Oct-01 2005 2005 2005 2005 2005 2005 2005

20 High-flow Period

15

10 (ft, NAVD88) 5 Water Surface Elevation Water Surface

0 May-01 May-06 May-11 May-16 May-21 May-26 Jun-01 2006 2006 2006 2006 2006 2006 2006

Figure 4-6 Comparison of Predicted and Measured WSE Measured during September 2005 and May 2006 at St. Helens Predicted St. Helens Fiberboard Plant

vkl - \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_comp_stage_model_data_parts_120408.pro Fri Jun 22 10:47:08 2012 25 Low-flow Period

20

15

10 (ft, NAVD88)

5 Water Surface Elevation Water Surface

0 Sep-01 Sep-06 Sep-11 Sep-16 Sep-21 Sep-26 Oct-01 2005 2005 2005 2005 2005 2005 2005

25 High-flow Period 20

15

10 (ft, NAVD88)

5 Water Surface Elevation Water Surface

0 May-01 May-06 May-11 May-16 May-21 May-26 Jun-01 2006 2006 2006 2006 2006 2006 2006

Figure 4-7 Comparison of Predicted and Measured WSE Measured during September 2005 and May 2006 at Vancouver Predicted St. Helens Fiberboard Plant

vkl - \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_comp_stage_model_data_parts_120408.pro Fri Jun 22 10:47:09 2012 20 Low-flow Period

15

10 (ft, NAVD88) 5 Water Surface Elevation Water Surface

0 Sep-01 Sep-06 Sep-11 Sep-16 Sep-21 Sep-26 Oct-01 2005 2005 2005 2005 2005 2005 2005

20 High-flow Period

15

10 (ft, NAVD88) 5 Water Surface Elevation Water Surface

0 May-01 May-06 May-11 May-16 May-21 May-26 Jun-01 2006 2006 2006 2006 2006 2006 2006

Figure 4-8 Comparison of Predicted and Measured WSE Measured during September 2005 and May 2006 at Columbia Slough Predicted St. Helens Fiberboard Plant

vkl - \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_comp_stage_model_data_parts_120408.pro Fri Jun 22 10:47:09 2012 35 Low-flow Period 30

25

20

(ft, NAVD88) 15

Water Surface Elevation Water Surface 10

5 Sep-01 Sep-06 Sep-11 Sep-16 Sep-21 Sep-26 Oct-01 2005 2005 2005 2005 2005 2005 2005

35 High-flow Period 30

25

20

(ft, NAVD88) 15

Water Surface Elevation Water Surface 10

5 May-01 May-06 May-11 May-16 May-21 May-26 Jun-01 2006 2006 2006 2006 2006 2006 2006

Figure 4-9 Comparison of Predicted and Measured WSE Measured during September 2005 and May 2006 at Bonneville Dam Predicted St. Helens Fiberboard Plant

vkl - \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_comp_stage_model_data_parts_120408.pro Fri Jun 22 10:47:09 2012 20 Low-flow Period

15

10 (ft, NAVD88) 5 Water Surface Elevation Water Surface

0 Sep-01 Sep-06 Sep-11 Sep-16 Sep-21 Sep-26 Oct-01 2005 2005 2005 2005 2005 2005 2005

20 High-flow Period

15

10 (ft, NAVD88) 5 Water Surface Elevation Water Surface

0 May-01 May-06 May-11 May-16 May-21 May-26 Jun-01 2006 2006 2006 2006 2006 2006 2006

Figure 4-10 Comparison of Predicted and Measured WSE during September 2005 Measured and May 2006 in Lower Willamette River at Portland Predicted St. Helens Fiberboard Plant

vkl - \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_comp_stage_model_data_parts_120408.pro Fri Jun 22 10:47:09 2012 Columbia River at The Dalles 800,000 High-flow Low-flow Period Period 100-year Flood 600,000

10-year Flood

400,000

(cfs) 2-year Flood Flow Rate Flow

200,000 Average

0 Dec-01 Jan-01 Feb-01 Mar-01 Apr-01 May-01 Jun-01 Jul-01 Aug-01 Sep-01 Oct-01 Nov-01 Dec-01 Jan-01 Feb-01 2007 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2009 2009 Lower Willamette River at Portland 400,000 100-year Flood High-flow Low-flow Period Period 300,000 10-year Flood

200,000 (cfs) 2-year Flood Flow Rate Flow

100,000

Average 0 Dec-01 Jan-01 Feb-01 Mar-01 Apr-01 May-01 Jun-01 Jul-01 Aug-01 Sep-01 Oct-01 Nov-01 Dec-01 Jan-01 Feb-01 2007 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2009 2009

Figure 4-11 Daily Average Flow Rate for Columbia River at The Dalles and Lower Willamette River during Far-field Model Validation Period (December 2007 through January 2009) St. Helens Fiberboard Plant Note: Low-flow and high-flow periods correspond to calibration results shown on Figures 4-12 through 4-16.

BTR - M:\Jobs\St_Helens\Report\120406\Decks\plot_temporal_daily_flow_stage_120408.pro Tue Aug 28 14:26:11 2012 20 High-flow Period

15

10 (ft, NAVD88) 5 Water Surface Elevation Water Surface

0 May-01 May-06 May-11 May-16 May-21 May-26 Jun-01 2008 2008 2008 2008 2008 2008 2008

20 Low-flow Period

15

10 (ft, NAVD88) 5 Water Surface Elevation Water Surface

0 Sep-01 Sep-06 Sep-11 Sep-16 Sep-21 Sep-26 Oct-01 2008 2008 2008 2008 2008 2008 2008

Figure 4-12 Comparison of Predicted and Measured WSE Measured during May and September 2008 at St. Helens Predicted St. Helens Fiberboard Plant

vkl - \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_comp_stage_model_data_parts_120408.pro Fri Jun 22 10:45:08 2012 25 High-flow Period

20

15

10 (ft, NAVD88)

5 Water Surface Elevation Water Surface

0 May-01 May-06 May-11 May-16 May-21 May-26 Jun-01 2008 2008 2008 2008 2008 2008 2008

25 Low-flow Period 20

15

10 (ft, NAVD88)

5 Water Surface Elevation Water Surface

0 Sep-01 Sep-06 Sep-11 Sep-16 Sep-21 Sep-26 Oct-01 2008 2008 2008 2008 2008 2008 2008

Figure 4-13 Comparison of Predicted and Measured WSE Measured during May and September 2008 at Vancouver Predicted St. Helens Fiberboard Plant

vkl - \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_comp_stage_model_data_parts_120408.pro Fri Jun 22 10:45:08 2012 20 High-flow Period

15

10 (ft, NAVD88) 5 Water Surface Elevation Water Surface

0 May-01 May-06 May-11 May-16 May-21 May-26 Jun-01 2008 2008 2008 2008 2008 2008 2008

20 Low-flow Period

15

10 (ft, NAVD88) 5 Water Surface Elevation Water Surface

0 Sep-01 Sep-06 Sep-11 Sep-16 Sep-21 Sep-26 Oct-01 2008 2008 2008 2008 2008 2008 2008

Figure 4-14 Comparison of Predicted and Measured WSE Measured during May and September 2008 at Columbia Slough Predicted St. Helens Fiberboard Plant

vkl - \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_comp_stage_model_data_parts_120408.pro Fri Jun 22 10:45:08 2012 35 High-flow Period 30

25

20

(ft, NAVD88) 15

Water Surface Elevation Water Surface 10

5 May-01 May-06 May-11 May-16 May-21 May-26 Jun-01 2008 2008 2008 2008 2008 2008 2008

35 Low-flow Period 30

25

20

(ft, NAVD88) 15

Water Surface Elevation Water Surface 10

5 Sep-01 Sep-06 Sep-11 Sep-16 Sep-21 Sep-26 Oct-01 2008 2008 2008 2008 2008 2008 2008

Figure 4-15 Comparison of Predicted and Measured WSE Measured during May and September 2008 at Bonneville Dam Predicted St. Helens Fiberboard Plant

vkl - \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_comp_stage_model_data_parts_120408.pro Fri Jun 22 10:45:08 2012 20 High-flow Period

15

10 (ft, NAVD88) 5 Water Surface Elevation Water Surface

0 May-01 May-06 May-11 May-16 May-21 May-26 Jun-01 2008 2008 2008 2008 2008 2008 2008

20 Low-flow Period

15

10 (ft, NAVD88) 5 Water Surface Elevation Water Surface

0 Sep-01 Sep-06 Sep-11 Sep-16 Sep-21 Sep-26 Oct-01 2008 2008 2008 2008 2008 2008 2008

Figure 4-16 Comparison of Predicted and Measured WSE during May and Measured September 2008 in Lower Willamette River at Portland Predicted St. Helens Fiberboard Plant

vkl - \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_comp_stage_model_data_parts_120408.pro Fri Jun 22 10:45:08 2012 Columbia River at The Dalles 800,000

100-year Flood 600,000

10-year Flood

400,000

(cfs) 2-year Flood Flow Rate Flow

200,000 Average

0 Feb-01 Feb-08 Feb-15 Feb-22 Mar-01 1996 1996 1996 1996 1996 Lower Willamette River at Portland 500,000

400,000 100-year Flood

300,000 10-year Flood (cfs) 200,000 Flow Rate Flow 2-year Flood

100,000

Average 0 Feb-01 Feb-08 Feb-15 Feb-22 Mar-01 1996 1996 1996 1996 1996

Figure 4-17 Daily Average Flow Rate for Columbia River at The Dalles and Lower Willamette River during February 1996 Flood St. Helens Fiberboard Plant

vkl - M:\Jobs\St_Helens\Report\120406\Decks\plot_temporal_daily_flow_stage_Feb1996_120408.pro Tue Aug 28 14:26:00 2012 40

35

30

25

(ft, NAVD88) 20 Water Surface Elevation Water Surface

15

10

5 Feb-01 Feb-08 Feb-15 Feb-22 Mar-01 1996 1996 1996 1996 1996

Figure 4-18 Comparison of Predicted and Measured WSE Measured during February 1996 Flood at Vancouver Predicted St. Helens Fiberboard Plant

BTR - \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_comp_stage_model_data_parts_Feb1996_120416.pro Fri Jun 22 10:54:44 2012 40

35

30

25

(ft, NAVD88) 20 Water Surface Elevation Water Surface

15

10

5 Feb-01 Feb-08 Feb-15 Feb-22 Mar-01 1996 1996 1996 1996 1996

Figure 4-19 Comparison of Predicted and Measured WSE Measured during February 1996 Flood at Columbia Slough Predicted St. Helens Fiberboard Plant

BTR - \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_comp_stage_model_data_parts_Feb1996_120416.pro Fri Jun 22 10:54:44 2012 40

35

30

25

(ft, NAVD88) 20 Water Surface Elevation Water Surface

15

10

5 Feb-01 Feb-08 Feb-15 Feb-22 Mar-01 1996 1996 1996 1996 1996

Figure 4-20 Comparison of Predicted and Measured WSE Measured during February 1996 Flood at Bonneville Dam Predicted St. Helens Fiberboard Plant

BTR - \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_comp_stage_model_data_parts_Feb1996_120416.pro Fri Jun 22 10:54:43 2012 40

35

30

25

(ft, NAVD88) 20 Water Surface Elevation Water Surface

15

10

5 Feb-01 Feb-08 Feb-15 Feb-22 Mar-01 1996 1996 1996 1996 1996

Figure 4-21 Comparison of Predicted and Measured WSE during February 1996 Measured Flood in Lower Willamette River at Portland Predicted St. Helens Fiberboard Plant

BTR - \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_comp_stage_model_data_parts_Feb1996_120416.pro Fri Jun 22 10:54:44 2012 Shoreline Elevation (ft, NAVD88) < -40 -40 to -35 -35 to -30 -30 to -25 -25 to -20 -20 to -15 -15 to -10 -10 to -5 -5 to 0 0 to 5 5 to 10 10 to 15 15 to 20 > 20 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Domain_Bathy_Fig4-23_4-24.mxd egranger 6/21/2012 2:29:36 PM egranger 6/21/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Domain_Bathy_Fig4-23_4-24.mxd

Figure 4-22 Near-field Model Domain and

[ Feet Numerical Grid with Bathymetry 0 1,750 3,500 St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Elevation (ft, NAVD88) < -40 -40 to -35 -35 to -30 -30 to -25 -25 to -20 -20 to -15 -15 to -10 -10 to -5 -5 to 0 0 to 5 5 to 10 10 to 15 15 to 20 > 20 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Domain_Bathy_Fig4-23_4-24.mxd egranger 6/21/2012 5:07:42 PM egranger 6/21/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Domain_Bathy_Fig4-23_4-24.mxd

Figure 4-23 Numerical Grid and Bathymetry for Near-field

[ Feet Model in Vicinity of the Study Area 0 400 800 St. Helens Fiberboard Plant Tributary flow rates estimated from Shoreline USGS data at surrogate stations. Elevation (ft, NAVD88) < -40 -40 to -35 -35 to -30 -30 to -25 -25 to -20 -20 to -15 -15 to -10 -10 to -5 -5 to 0 0 to 5 5 to 10 Far-field Grid 10 to 15 15 to 20 > 20

Flow rate predicted by far-field model WSE data from St. Helens gaging station

Flow rate predicted by far-field model

Feet 0 2,300 4,600 M:\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Domain_Bathy_Fig4-25.mxd vlist 8/28/2012 3:41:41 PM 3:41:41 vlist 8/28/2012 M:\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Domain_Bathy_Fig4-25.mxd

Figure 4-24 Locations of Near-field Model Inputs for WSE at Downstream

[ Boundary and Inflows from Upstream and Tributary Sources St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Tidal Gage ADCP Location Elevation (ft, NAVD88) < -40 -40 to -35 -35 to -30 -30 to -25 -25 to -20 -20 to -15 -15 to -10 -10 to -5 -5 to 0 0 to 5 5 to 10 10 to 15 15 to 20 > 20

Feet 0 490 980 M:\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_ADCP_Fig4-26.mxd vlist 8/28/2012 1:36:44 PM 1:36:44 vlist 8/28/2012 M:\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_ADCP_Fig4-26.mxd

Figure 4-25 Locations of Acoustic Doppler Current Profilers (ADCPs) in Scappoose Bay

[ and Multnomah Channel and Tide Gage at Pier near Plant Site St. Helens Fiberboard Plant Columbia River at The Dalles 600,000

500,000

400,000

(cfs) 300,000 Flow Rate Flow 200,000

100,000 Apr-05 Apr-15 Apr-25 May-05 May-15 May-25 Jun-04 2011 2011 2011 2011 2011 2011 2011

Water Surface Elevation at ADCP Location in Scappoose Bay 22 20 18 16 14

(ft, NAVD88) 12 10 Water Surface Elevation Water Surface 8 Apr-05 Apr-15 Apr-25 May-05 May-15 May-25 Jun-04 2011 2011 2011 2011 2011 2011 2011

Along-channel Velocity at ADCP Location in Scappoose Bay 2 Flood Tide

1

0 (ft/s)

-1 Current Velocity Ebb Tide -2 Apr-05 Apr-15 Apr-25 May-05 May-15 May-25 Jun-04 2011 2011 2011 2011 2011 2011 2011

Figure 4-26 Daily Average Flow Rate for Columbia River at The Dalles, Measured WSE and Current Velocity in Scappoose Bay during Near-field Model Calibration Period: April to June 2011 St. Helens Fiberboard Plant

vkl - \\montvalebu\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_plot_adcp_data_3p_ft.pro Fri Oct 19 10:56:59 2012 Columbia River at The Dalles 600,000

500,000

400,000 (cfs) Flow Rate Flow

300,000

200,000 Jun-14 Jun-16 Jun-18 Jun-20 Jun-22 Jun-24 Jun-26 2011 2011 2011 2011 2011 2011 2011 Along-channel Velocity at ADCP Location in Multnomah Channel 3.0

2.5

2.0 (ft/s)

Current Velocity Current 1.5

1.0 Jun-14 Jun-16 Jun-18 Jun-20 Jun-22 Jun-24 Jun-26 2011 2011 2011 2011 2011 2011 2011

Figure 4-27 Daily Average Flow Rate for Columbia River at The Dalles and Measured Current Velocity in Multnomah Channel during Near-field Model Validation Period: June 2011 St. Helens Waterboard Plant

BTR - \\montvalebu\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_plot_adcpc_data_2p_110824.pro Fri Oct 19 10:55:45 2012 Water Surface Elevation at ADCP Location in Scappoose Bay 22 20

18

16

14

(ft, NAVD88) 12

Water Surface Elevation Water Surface 10 8 Apr-05 Apr-10 Apr-15 Apr-20 Apr-25 Apr-30 May-05 2011 2011 2011 2011 2011 2011 2011 Along-channel Velocity at ADCP Location in Scappoose Bay 2 Flood Tide

1

0 (ft/s)

Current Velocity Current -1

Ebb Tide -2 Apr-05 Apr-10 Apr-15 Apr-20 Apr-25 Apr-30 May-05 2011 2011 2011 2011 2011 2011 2011

Figure 4-28 Comparison of Predicted and Measured WSE and Current Velocity in Scappoose Bay Measured during Near-field Model Calibration Period: April 5 to May 5, 2011 Predicted St. Helens Fiberboard Plant

vkl - \\montvalebu\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_plot_adcp_vel_components_nearfield_ft.pro Fri Oct 19 13:20:30 2012 Water Surface Elevation at ADCP Location in Scappoose Bay 22 20

18

16

14

(ft, NAVD88) 12

Water Surface Elevation Water Surface 10 8 May-05 May-10 May-15 May-20 May-25 May-30 Jun-04 2011 2011 2011 2011 2011 2011 2011 Along-channel Velocity at ADCP Location in Scappoose Bay 2 Flood Tide

1

0 (ft/s)

Current Velocity Current -1

Ebb Tide -2 May-05 May-10 May-15 May-20 May-25 May-30 Jun-04 2011 2011 2011 2011 2011 2011 2011

Figure 4-29 Comparison of Predicted and Measured WSE and Current Velocity in Scappoose Bay Measured during Near-field Model Calibration Period: May 5 to June 4, 2011 Predicted St. Helens Fiberboard Plant

vkl - \\montvalebu\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_plot_adcp_vel_components_nearfield_ft.pro Fri Oct 19 13:20:30 2012 Water Surface Elevation at ADCP Location in Multnomah Channel 22 20

18

16

14

(ft, NAVD88) 12

Water Surface Elevation Water Surface 10 8 Jun-14 Jun-16 Jun-18 Jun-20 Jun-22 Jun-24 Jun-26 2011 2011 2011 2011 2011 2011 2011 Along-channel Velocity at ADCP Location in Multnomah Channel 4.0

3.0

2.0 (ft/s)

Current Velocity Current 1.0

0.0 Jun-14 Jun-16 Jun-18 Jun-20 Jun-22 Jun-24 Jun-26 2011 2011 2011 2011 2011 2011 2011

Figure 4-30 Comparison of Predicted and Measured WSE and Current Velocity in Measured Multnomah Channel during Near-field Model Validation Period: June 2011 Predicted St. Helens Fiberboard Plant

vkl - \\montvalebu\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_plot_comp_adcp_vel_nearfield_MC.pro Fri Oct 19 13:21:39 2012 Water Surface Elevation at ADCP Location in Scappoose Bay 22 20

18

16

14

(ft, NAVD88) 12

Water Surface Elevation Water Surface 10 8 Apr-05 Apr-10 Apr-15 Apr-20 Apr-25 Apr-30 May-05 2011 2011 2011 2011 2011 2011 2011 Along-channel Velocity at ADCP Location in Scappoose Bay 2 Flood Tide

1

0 (ft/s)

Current Velocity Current -1

Ebb Tide -2 Apr-05 Apr-10 Apr-15 Apr-20 Apr-25 Apr-30 May-05 2011 2011 2011 2011 2011 2011 2011

Figure 4-31 Sensitivity Analysis Results for Near-field Model in Scappoose Bay 10 cm during Calibration Period: April 5 to May 5, 2011 20 cm St. Helens Fiberboard Plant 30 cm

vkl - \\montvalebu\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_plot_comp_model_vel_components_nearfield_ft.pro Fri Oct 19 13:20:37 2012 Water Surface Elevation at ADCP Location in Scappoose Bay 22 20

18

16

14

(ft, NAVD88) 12

Water Surface Elevation Water Surface 10 8 May-05 May-10 May-15 May-20 May-25 May-30 Jun-04 2011 2011 2011 2011 2011 2011 2011 Along-channel Velocity at ADCP Location in Scappoose Bay 2 Flood Tide

1

0 (ft/s)

Current Velocity Current -1

Ebb Tide -2 May-05 May-10 May-15 May-20 May-25 May-30 Jun-04 2011 2011 2011 2011 2011 2011 2011

Figure 4-32 Sensitivity Analysis Results for Near-field Model in Scappoose Bay 10 cm during Calibration Period: May 5 to June 4, 2011 20 cm St. Helens Fiberboard Plant 30 cm

vkl - \\montvalebu\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_plot_comp_model_vel_components_nearfield_ft.pro Fri Oct 19 13:20:37 2012 Water Surface Elevation at ADCP Location in Multnomah Channel 22 20

18

16

14

(ft, NAVD 88) (ft, NAVD 12

Water Surface Elevation Water Surface 10 8 Jun-14 Jun-16 Jun-18 Jun-20 Jun-22 Jun-24 Jun-26 2011 2011 2011 2011 2011 2011 2011 Along-Channel Velocity at ADCP Location in Multnomah Channel 4.0

3.0

2.0 (ft/s)

Current Velocity Current 1.0

0.0 Jun-14 Jun-16 Jun-18 Jun-20 Jun-22 Jun-24 Jun-26 2011 2011 2011 2011 2011 2011 2011

Figure 4-33 Sensitivity Analysis Results for Near-field Model in Multnomah Channel 10 cm during Validation Period: June 2011 20 cm St. Helens Fiberboard Plant 30 cm

vkl - \\montvalebu\Jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_plot_comp_model_vel_nearfield_MC.pro Fri Oct 19 13:20:58 2012 Lower Willamette River at Portland 400,000 100-year Flood

300,000 10-year Flood

200,000 (cfs) 2-year Flood Flow Rate

100,000

Average 0 Oct-21 Oct-23 Oct-25 Oct-27 Oct-29 Oct-31 Nov-02 Nov-04 Nov-06 Nov-08 Nov-10 1994 1994 1994 1994 1994 1994 1994 1994 1994 1994 1994

Columbia River at The Dalles 800,000

100-year Flood 600,000

10-year Flood

400,000 (cfs) 2-year Flood Flow Rate

200,000 Average

0 Oct-21 Oct-23 Oct-25 Oct-27 Oct-29 Oct-31 Nov-02 Nov-04 Nov-06 Nov-08 Nov-10 1994 1994 1994 1994 1994 1994 1994 1994 1994 1994 1994

McNulty Creek 500

400

300 (cfs)

Flow Rate 200

100

0 Oct-21 Oct-23 Oct-25 Oct-27 Oct-29 Oct-31 Nov-02 Nov-04 Nov-06 Nov-08 Nov-10 1994 1994 1994 1994 1994 1994 1994 1994 1994 1994 1994

Figure 5-1 Daily Average Flow Rates for Columbia River at The Dalles, Lower Willamette River and McNulty Creek during October 1994 Flood St. Helens Fiberboard Plant Note: McNulty Creek flow rates were estimated as discussed in Section 5.1.

LHB - M:\Jobs\St_Helens\Report\120406\Decks\plot_temporal_daily_flow_stage_120410.pro Tue Aug 28 14:49:13 2012 *# Inundation Frequency Analysis Location

*#IF-9 *#IF-8 IF-3 *#IF-6 *# IF-10 IF-5 *# *# IF-2 *#

*#IF-7

*#IF-4

*#IF-1 \\montvalebu\jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_Inundation_Frequency_RTC_FigX-X.mxd vlist 9/10/2012 8:50:34 AM 8:50:34 vlist 9/10/2012 \\montvalebu\jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_Inundation_Frequency_RTC_FigX-X.mxd

Figure 5-2 Locations Used for Comparing Inundation Frequencies Predicted Feet by Near-field Hydrodynamic Model and Estimated Using Water 0 250 500 Surface Elevation Data Collected at St. Helens Gaging Station [ St. Helens Fiberboard Plant Percentage of Time Inundated 100 80 - 99 60 - 80 40 - 60 20 - 40 5 - 20 1 - 5 < 1 \\montvalebu\jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_Inundation_Frequency_Fig3-2.mxd vlist 9/10/2012 8:49:23 AM 8:49:23 vlist 9/10/2012 \\montvalebu\jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_Inundation_Frequency_Fig3-2.mxd

Figure 5-3 Spatial Distribution of Inundation Frequency within the Study Area Feet St. Helens Fiberboard Plant [ 0 250 500 100

80

60 (%)

40 Inundation Frequency Inundation

20

0 IF-1 IF-2 IF-3 IF-4 IF-5 IF-6 IF-7 IF-8 IF-9 IF-10 Location

Figure 5-4 Comparison of Inundation Frequencies Predicted by Near-field Hydrodynamic Model and Estimated Using Water Surface Elevation Data Collected at St. Helens Gaging Station Data-based St. Helens Fiberboard Plant Predicted Note: Inundation frequencies are for 2-month period from April 5 to June 4, 2011.

BTR - \\montvalebu\jobs26a\Jobs\St_Helens\Report\120406\Decks\sthelens_pred_meas_inund_barplot_121019.pro Fri Oct 19 10:52:59 2012 Shoreline Upland-lowland Boundary Maximum Velocity (ft/s) Dry 0 to 0.5 0.5 to 1.0 1.0 to 1.5 1.5 to 2.0 2.0 to 2.5 Greater than 2.5

Feet 0 425 850 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd vlist 6/22/2012 3:16:49 PM 3:16:49 vlist 6/22/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd

Figure 5-5 Spatial Distribution of Predicted Maximum Current Velocity:

[ High-flow Event Simulation 1, 10-year Flood in Columbia River St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Scour Depth (inches) Depositional 0 to 0.1 0.1 to 0.25 0.25 to 0.5 0.5 to 1 1 to 2.5 Greater than 2.5

Feet 0 425 850 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd lbateman 7/30/2012 9:11:56 AM lbateman 9:11:56 7/30/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd

Figure 5-6 Spatial Distribution of Estimated Bed Scour Depth: High-flow

[ Event Simulation 1, 10-year Flood in Columbia River St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Maximum Velocity (ft/s) Dry 0 to 0.5 0.5 to 1.0 1.0 to 1.5 1.5 to 2.0 2.0 to 2.5 Greater than 2.5

Feet 0 425 850 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd vlist 6/22/2012 3:17:42 PM 3:17:42 vlist 6/22/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd

Figure 5-7 Spatial Distribution of Predicted Maximum Current Velocity:

[ High-flow Event Simulation 2, 100-year Flood in Columbia River St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Scour Depth (inches) Depositional 0 to 0.1 0.1 to 0.25 0.25 to 0.5 0.5 to 1 1 to 2.5 Greater than 2.5

Feet 0 425 850 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd lbateman 7/30/2012 9:12:19 AM lbateman 9:12:19 7/30/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd

Figure 5-8 Spatial Distribution of Estimated Bed Scour Depth: High-flow

[ Event Simulation 2, 100-year Flood in Columbia River St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Maximum Velocity (ft/s) Dry 0 to 0.5 0.5 to 1.0 1.0 to 1.5 1.5 to 2.0 2.0 to 2.5 Greater than 2.5

Feet 0 425 850 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd vlist 6/22/2012 3:18:11 PM 3:18:11 vlist 6/22/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd

Figure 5-9 Spatial Distribution of Predicted Maximum Current Velocity: High-flow

[ Event Simulation 3, 10-year Flood in Lower Willamette River St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Scour Depth (inches) Depositional 0 to 0.1 0.1 to 0.25 0.25 to 0.5 0.5 to 1 1 to 2.5 Greater than 2.5

Feet 0 425 850 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd lbateman 7/30/2012 9:12:44 AM lbateman 9:12:44 7/30/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd

Figure 5-10 Spatial Distribution of Estimated Bed Scour Depth: High-flow

[ Event Simulation 3, 10-year Flood in Lower Willamette River St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Maximum Velocity (ft/s) Dry 0 to 0.5 0.5 to 1.0 1.0 to 1.5 1.5 to 2.0 2.0 to 2.5 Greater than 2.5

Feet 0 425 850 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd vlist 6/22/2012 3:18:33 PM 3:18:33 vlist 6/22/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd

Figure 5-11 Spatial Distribution of Predicted Maximum Current Velocity: High-flow

[ Event Simulation 4, 100-year Flood in Lower Willamette River St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Scour Depth (inches) Depositional 0 to 0.1 0.1 to 0.25 0.25 to 0.5 0.5 to 1 1 to 2.5 Greater than 2.5

Feet 0 425 850 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd lbateman 7/30/2012 9:13:05 AM lbateman 9:13:05 7/30/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd

Figure 5-12 Spatial Distribution of Estimated Bed Scour Depth: High-flow

[ Event Simulation 4, 100-year Flood in Lower Willamette River St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Maximum Velocity (ft/s) Dry 0 to 0.5 0.5 to 1.0 1.0 to 1.5 1.5 to 2.0 2.0 to 2.5 Greater than 2.5

Feet 0 425 850 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd vlist 6/22/2012 3:19:49 PM 3:19:49 vlist 6/22/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd

Figure 5-13 Spatial Distribution of Predicted Maximum Current Velocity: High-flow

[ Event Simulation 5, 10-year Flood in Scappoose Bay Tributaries St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Scour Depth (inches) Depositional 0 to 0.1 0.1 to 0.25 0.25 to 0.5 0.5 to 1 1 to 2.5 Greater than 2.5

Feet 0 425 850 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd lbateman 7/30/2012 9:19:29 AM lbateman 9:19:29 7/30/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd

Figure 5-14 Spatial Distribution of Estimated Bed Scour Depth: High-flow

[ Event Simulation 5, 10-year Flood in Scappoose Bay Tributaries St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Maximum Velocity (ft/s) Dry 0 to 0.5 0.5 to 1.0 1.0 to 1.5 1.5 to 2.0 2.0 to 2.5 Greater than 2.5

Feet 0 425 850 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd vlist 6/22/2012 3:20:18 PM 3:20:18 vlist 6/22/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd

Figure 5-15 Spatial Distribution of Predicted Maximum Current Velocity: High-flow

[ Event Simulation 6, 100-year Flood in Scappoose Bay Tributaries St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Scour Depth (inches) Depositional 0 to 0.1 0.1 to 0.25 0.25 to 0.5 0.5 to 1 1 to 2.5 Greater than 2.5

Feet 0 425 850 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd lbateman 7/30/2012 9:13:51 AM lbateman 9:13:51 7/30/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-2_to_5-13.mxd

Figure 5-16 Spatial Distribution of Estimated Bed Scour Depth: High-flow

[ Event Simulation 6, 100-year Flood in Scappoose Bay Tributaries St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Maximum Velocity (ft/s) Dry 0 to 0.5 0.5 to 1.0 1.0 to 1.5 1.5 to 2.0 2.0 to 2.5 Greater than 2.5 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-14_to_5-17.mxd egranger 6/21/2012 5:24:12 PM 5:24:12 6/21/2012 egranger \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-14_to_5-17.mxd

Figure 5-17 Spatial Distribution of Predicted Maximum Feet [ Current Velocity: February 1996 Flood 0 425 850 St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Scour Depth (inches) Depositional 0 to 0.1 0.1 to 0.25 0.25 to 0.5 0.5 to 1 1 to 2.5 Greater than 2.5 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-14_to_5-17.mxd lbateman 7/30/2012 9:11:14 AM lbateman 9:11:14 7/30/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-14_to_5-17.mxd

Figure 5-18 Spatial Distribution of Estimated Bed Feet [ Scour Depth: February 1996 Flood 0 425 850 St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Maximum Velocity (ft/s) Dry 0 to 0.5 0.5 to 1.0 1.0 to 1.5 1.5 to 2.0 2.0 to 2.5 Greater than 2.5 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-14_to_5-17.mxd egranger 6/21/2012 5:25:40 PM 5:25:40 6/21/2012 egranger \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-14_to_5-17.mxd

Figure 5-19 Spatial Distribution of Predicted Maximum Feet [ Current Velocity: October 1994 Flood 0 425 850 St. Helens Fiberboard Plant Shoreline Upland-lowland Boundary Scour Depth (inches) Depositional 0 to 0.1 0.1 to 0.25 0.25 to 0.5 0.5 to 1 1 to 2.5 Greater than 2.5 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-14_to_5-17.mxd lbateman 7/30/2012 9:10:50 AM lbateman 9:10:50 7/30/2012 \\MONTVALEBU\Jobs26a\Jobs\St_Helens\Report\120406\Decks\StHelens_NF_Fig_5-14_to_5-17.mxd

Figure 5-20 Spatial Distribution of Estimated Bed Feet [ Scour Depth: October 1994 Flood 0 425 850 St. Helens Fiberboard Plant

APPENDIX A GEOCHRONOLOGY ANALYSIS

74275387.1 0015549-00007

DRAFT

A.1 GEOCHRONOLOGY ANALYSIS APPROACH The purpose of the geochronology analysis was to assist in assessing whether net depositional processes have occurred within the Study Area and, if so, estimate the order-of-magnitude net sedimentation rates (NSRs) and order-of-magnitude of historical sedimentation over the past century. While the primary line of evidence for the geochronology analysis was the analysis of vertical profiles of 137Cs and 210Pb activity in the cores collected for this study, the lithology observed in the cores and geomorphological changes inferred from the historical aerial photographs were also considered when assessing the historical depositional processes.

Any historical sediment deposition has likely been episodic, with a large portion of the overall deposition occurring during flood conditions on the Columbia and Lower Willamette Rivers. In addition, the annual amount of deposition varies from year to year, depending on flow conditions in the rivers and Scappoose Bay tributaries. Finally, the geochronology analysis informs the historical processes at the specific core locations. Processes differing from those suggested by the core analysis (e.g., small-scale, episodic erosional events) may have occurred away from the core locations and such processes would not necessarily be inconsistent with the radioisotope core results.

The cores reflect the conditions specifically at the core locations. While inferences regarding the areas around the core locations and the overall Study Area can be made from the core analysis, there may be small-scale events and features that are not necessarily reflected in the core analysis if the cores were not specifically located in the precise location of the small- scale event or features.

A.2 CORE LITHOLOGY Core AQ-01 was collected near the channel of McNulty Creek from a non-vegetated area at an elevation of 7.8 feet North American Vertical Datum of 1988 (NAVD88). No vegetation or roots were visible in the core, which consisted of silty sediment in the top 1 foot of the core and sandy silt below the 1-foot depth (Figure A-1, left panel). Core AQ-02 was located near the channel of McNulty Creek at an elevation of 8.5 feet NAVD88. The core was

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant A-1 100703-01 74275387.1 0015549-00007

DRAFT Appendix A comprised of silty sediment, with abundant vegetation or rootlets in the top 1.5 feet of the core (Figure A-1, right panel).

Core AQ-03 was collected from an elevation of 8.2 feet NAVD88. Silt was observed throughout the core, with approximately 20% to 30% of the top 0.4 feet of the core being composed of rootlets and plant matter (Figure A-2, left panel). Core AQ-04 was collected at an elevation of 7.9 feet NAVD88. Silty sediment was observed throughout the core but roughly 70% of the material in the top 1.4 feet of the core was composed of sand-sized wood fibers (Figure A-2, right panel). No wood fibers were found below the 1.4 feet depth.

Core AQ-05 was collected from a location at an elevation of 9.5 feet NAVD88. Plant debris comprised roughly 60% to 70% of the material in the top 0.5 feet of the core and roughly 40% to 50% of the material between 0.5 and 2 feet (Figure A-3, left panel). Silty sediment was found throughout this core. Core AQ-06 was collected from a nearshore area within Scappoose Bay, which had an elevation of 3.5 feet NAVD88. The sediment in this core was described as silt, with 70% to 80% of the material in the top 1 foot being comprised of wood pieces (Figure A-3, right panel).

Similar to core AQ-06, core AQ-07 was located in the nearshore region of Scappoose Bay, with an elevation of 4.7 feet NAVD88. No vegetation was observed in this core, with silty sediment found in the top 1 foot and with a mixture of sand and silt occurring in the core between approximately 1 and 2.7 feet (Figure A-4, left panel). Core AQ-08 was located in the vicinity of the abandoned Milton Creek channel with an elevation of 9.2 feet NAVD88. Abundant rootlets were observed within the top 2 feet of the core, which was comprised of silty sediment (Figure A-4, right panel). Wood pieces and fibers were observed in the core below 2 feet.

A.3 GEOCHRONOLOGY ANALYSIS OF CORES A.3.1 Radioisotope Analysis Methodology The radioisotope analyses of the cores were performed based on two methods:

• Cesium-137 analysis; and

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant A-2 100703-01 74275387.1 0015549-00007

DRAFT Appendix A • Lead-210 analysis.

The following describes how these two analyses were used in the geochronology analysis.

A.3.1.1 Cesium-137 Analysis The first occurrence of detectable 137Cs activity in sediments generally marks the year 1954, while peak activities correspond to 19631. Based on these dates, the best estimate of the long-term average NSR for a particular core is computed by dividing the depth of sediment between the sediment surface and the peak 137Cs activity by the number of years between 1963 and the time of core collection (e.g., 48 years for a core collected in 2011). In addition, the thickness of sediment deposited since the early 1960s can be estimated based on the location of the peak 137Cs activity in the core. It is important to note that this does not inform us as to the temporal nature of the net deposition rate that occurred since the peak 137Cs activity. Deposition likely occurs episodically during large flood events, with the rate of deposition being temporally variable.

For cores with discernible peak values of 137Cs activity, uncertainty exists in the exact location of the peak value in the core due to the sampling method (i.e., every fourth sub- sample interval was submitted for laboratory analysis). The actual location of the peak 137Cs activity value can be located between the samples directly above and below the peak value sample. Thus, the best estimate of historical NSR and sedimentation thickness is determined using the depth of the peak value sample. The uncertainty ranges of NSR and deposition thickness are estimated based on the depths of the samples directly above and below the peak value sample.

A.3.1.2 Lead-210 Analysis Lead-210, which is a decay product of volatilized atmospheric radon-222 (222Rn), is present in sediments primarily as a result of recent atmospheric deposition. Radon-222 is a volatile,

1 1954 and 1963 correspond to the years when atmospheric nuclear weapon testing was first performed and when the peak of such testing occurred, respectively. This atmospheric nuclear weapon testing is the inferred source of 137Cs in the sediment column.

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant A-3 100703-01 74275387.1 0015549-00007

DRAFT Appendix A short-lived, intermediate daughter of uranium-238 (238U), a naturally occurring radioisotope found in the earth’s crust. The 210Pb activity measured in a sediment sample represents the “total” 210Pb activity. Total 210Pb activity consists of two components:

• Unsupported 210Pb, which represents 210Pb that is continuously deposited on the earth’s surface at an approximately constant rate via atmospheric deposition; and

• Supported 210Pb, which is the background 210Pb activity in the sediment.

In aquatic environments, the approximately constant atmospheric flux of 210Pb and its decay half-life of 22.3 years results in relatively homogeneous 210Pb activities within the biologically active surface layer of the sediments. The 210Pb activities decay exponentially below the biologically active surface layer as the deeper layers are not affected by the continuous atmospheric 210Pb deposition occurring on the surface layer. For this reason, 210Pb serves as a useful tracer for assessing depositional processes and mixing depth in aquatic systems.

Estimating NSR using 210Pb activity data requires estimating the unsupported fraction of the

total 210Pb activity, also referred to as excess 210Pb activity. The unsupported fraction (210PbU) is estimated as follows:

210PbU = 210PbT - 210PbS (A-1)

where:

210PbT = total 210Pb activity reported by the laboratory in sediment samples, and;

210PbS = supported 210Pb activity derived from natural decay in sediments.

In particular, supported (210PbS) activity in the sediment bed is estimated based on the measured 210Pb activity in the deepest portions of the sediment cores obtained from the Study Area.

Unsupported 210PbU activities were computed by subtracting the average supported 210PbS activity from the total 210PbT activities throughout the sediment column, as per Equation A-1.

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant A-4 100703-01 74275387.1 0015549-00007

DRAFT Appendix A

The unsupported 210PbU activities were transformed to natural log space (i.e., ln [210PbU]) and

plotted as a function of core depth. A linear regression analysis of ln (210PbU) versus core depth was performed, and the slope of this line was used to estimate an average net sedimentation rate (NSR) (Huntley et al. 1995):

PbNSR = - 0.0311/S (A-2)

where:

S = slope of line determined from linear regression analysis of ln (210PbU) versus core depth.

The PbNSR values calculated using Equation A-2 have units of centimeters per year (cm/yr).

The regression analysis discussed above was conducted using ln (210PbU) as the dependent (i.e., y-axis) variable and core depth as the independent (i.e., x-axis) variable. The figures

discussed below display ln (210PbU) on the x-axis and core depth on the y-axis in order to

clarify presentation of the transformed 210PbU data.

Uncertainty exists in the historical NSR value determined from analyzing the vertical profile of 210Pb activity in a core due to uncertainty in the value of supported 210Pb (210PbS) activity

used in the linear regression of ln (210PbU). Varying the 210PbS activity value affects the NSR

value calculated in the regression analysis. The 210PbS activity, and uncertainty in that value, was estimated by assuming that the two deepest samples in each core (i.e., samples below a

depth of approximately 2.5 feet) are representative of 210PbS activity in the cores. The range of 210Pb activity for the 16 samples below 2.5 feet in the eight cores was 0.20 to 0.48 picoCuries per gram (pCi/g). The 16 210Pb activity values were normally distributed with a median value of 0.35 pCi/g. The average 210Pb activity of these samples was 0.35 pCi/g, with a standard deviation of 0.07 pCi/g. To evaluate the effects of variability in 210PbS activity on estimated NSR values, three values were used in the analysis: 1) average value of 0.35 pCi/g; 2) lower-bound value of 0.28 pCi/g; and 3) upper-bound value of 0.42 pCi/g. The lower- and upper-bound values correspond to + 1 standard deviation from the average value. These

210PbS activity values were used to calculate a range of NSR values for a particular radioisotope core.

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant A-5 100703-01 74275387.1 0015549-00007

DRAFT Appendix A

Using the estimated values for 210PbS, the vertical profiles of measured total 210Pb (210PbT) activities were reviewed for each core sample and order-of-magnitude estimates of historical NSRs were developed using Equations A-1 and A-2 where appropriate. The NSR calculated using the 210Pb activity data represents an average rate over a multi-decade period. The rate of sedimentation was likely highly variable over the period of deposition and assigning specific strata within the sediment column to specific times based solely on the radioisotope data is highly uncertain. In addition, the characterization of the overall magnitude of sedimentation inferred to have occurred at a core location is expressed as the thickness of overall sedimentation inferred to have occurred over a range of decades.

A.4 ANALYSIS OF ESTIMATED HISTORICAL NET SEDIMENTATION The radioisotope data, along with the core lithology and aerial photograph review, were used to estimate the historical net sedimentation at each core location. The results of that analysis are presented below.

A.4.1 Core AQ-01 Location No 137Cs activity peak was evident in this core, with non-detect values existing throughout the core. Thus, it was not possible to estimate a historical NSR or a time frame for deposition of the near surface sediment from the 137Cs activity measurements.

Historical NSRs were estimated based on the vertical profile of 210Pb activity in approximately the top 1 foot of the core (i.e., four data points; see Figure A-5). A historical NSR of 0.2 in/yr was determined using the average supported 210Pb activity, with a correlation coefficient (R2) value of 0.99. The lower-bound supported 210Pb value yielded a historical NSR of 0.5 in/yr, with an R2 value of 0.99. It was not possible to reliably calculate an NSR using the upper-bound supported 210Pb value because only the top two samples in the core could have been used in the linear regression analysis.

The magnitude of historical sedimentation was estimated based on the vertical profile of 210Pb activity in approximately the top 1 foot of the core (i.e., four data points; see Figure A- 5). Based on the 210Pb activity profile, the approximate time frame for deposition of the Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant A-6 100703-01 74275387.1 0015549-00007

DRAFT Appendix A upper 1 foot of sediment ranged from about 30 to 60 years based on the lower-bound and average values of supported 210Pb activity. It was not possible to reliably calculate a time frame for deposition using the upper-bound supported 210Pb activity value because only the top two samples in the core could be used in the linear regression analysis. However, timeframes longer than 60 years are plausible based on the uncertainty in the estimated supported 210Pb activity. High correlation coefficients (R2 of = 0.99) were noted in the 210Pb activity versus depth plots providing a strong indication that deposition has occurred at this location.

The ranges of estimated NSR values and time frames for deposition of the upper approximate 1 foot of sediment at core AQ-01 are consistent with the core lithology and historical aerial photographs. The silt encountered in the upper 1 foot of sediment at core AQ-01 was plausibly deposited within the past 30 to 60 or more years. Historical aerial photographs note a general reduction in the presence of channel meanders in the vicinity of core AQ-01 over the past 80 years, consistent with an increase in bed elevation in this area.

A.4.2 Core AQ-02 Location A peak 137Cs activity of approximately 0.14 pCi/g-dry was observed at a depth of 0.7 feet, see left panel of Figure 3-3. This depth corresponds to a historical NSR of 0.2 in/yr. Uncertainty in the location of the peak 137Cs activity produced an uncertainty range of 0.1 to 0.3 in/yr for the historical NSR. The depth of the peak 137Cs activity, and the depths of the adjacent samples in that core, indicate that the upper 5 to 12 inches of sediment was deposited since the peak of nuclear testing in 1963.

The 137Cs activity of the surface sample is greater than the next sample deeper in the core (i.e., inverse gradient). Similarly, the vertical profile of 210Pb activity at core AQ-02 exhibited increasing values with increasing depth in the core, particularly between the surface sample and sample at 0.7 feet (see right panel of Figure 3-3). These inverse gradients in 137Cs and 210Pb activities may be the result of older sediment being recently deposited at this location.

The five samples collected between depths of 0.7 and 2.1 feet in the core were used in the 210Pb linear regression analysis (Figure A-6). The two near-surface samples were excluded

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DRAFT Appendix A from the linear regression analysis due to the inverse gradient noted above. A historical NSR of 0.3 in/yr was determined using the average supported 210Pb activity, with an R2 value of 0.98. The lower- and upper-bound supported 210Pb values produced historical NSR values of 0.5 (R2 = 0.97) and 0.2 (R2 = 0.96) in/yr, respectively. Based on the 210Pb activity data, the approximate time frame for deposition of the upper 2 feet of sediment ranged from about 50 to 120 years. High R2 values (0.96 to 0.98) were noted in the 210Pb activity versus depth plots providing a strong indication that deposition has occurred at this location.

The ranges of estimated NSR values and time frames for deposition of the upper approximate 1 to 2 feet of sediment at core AQ-02 are consistent with the core lithology and historical aerial photographs. Historical aerial photographs note an emergence of vegetation in the vicinity of core AQ-02 over the past 80 years. The presence of “abundant rootlets and small plant and vegetation pieces” in the core indicates the current presence of vegetation at this location, in contrast to lack of vegetation suggested by the early aerial photographs. The emergence of vegetation is consistent with an increase in bed elevation in this area.

A.4.3 Core AQ-03 Location No 137Cs activity peak was evident in core AQ-03, with non-detect values existing throughout the core. Thus, it was not possible to estimate a historical NSR or a time frame for deposition of the near surface sediment from the 137Cs activity measurements.

The four 210Pb activity samples collected in the top 1 foot of this core were used in the NSR analysis (Figure A-7). A historical NSR of 0.3 in/yr (R2 = 0.82) was calculated for the top 1- foot layer using the average supported 210Pb activity. The lower- and upper-bound supported 210Pb values produced historical NSR values of 0.4 (R2 = 0.84) and 0.1 (R2 = 0.76) in/yr, respectively.

The magnitude of historical sedimentation was estimated based on the vertical profile of 210Pb activity in approximately the top 1 foot of the core. Based on the 210Pb activity data, the estimated approximate time frame for deposition of this upper 1-foot of sediment ranged from about 30 to 120 years. Modest R2 values (0.76 to 0.84) were noted in the 210Pb activity

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DRAFT Appendix A versus depth plots providing a reasonable indication that deposition has occurred at this location.

The ranges of estimated NSRs and time frames for deposition of the upper approximate 1 foot of sediment at core AQ-03 are consistent with the core lithology and historical aerial photographs. Historical aerial photographs indicate an emergence of vegetation in the vicinity of core AQ-03 over the past 80 years. The presence of “rootlets and plant matter” in the core indicates the current presence of vegetation at this location, in contrast to lack of vegetation suggested by the early aerial photographs. The emergence of vegetation is consistent with an increase in bed elevation in this area.

A.4.4 Core AQ-04 Location No 137Cs activity peak was evident in core AQ-04, with non-detect values existing throughout the core. Thus, it was not possible to estimate a historical NSR or a time frame for deposition of the near surface sediment from the 137Cs activity measurements.

The three samples obtained from the top 0.7 feet of the core (the fourth sample in the core was from a depth of about 1.1 feet) were used to estimate the NSR within the upper portions of core AQ-04 (Figure A-8). The average supported 210Pb activity yielded a historical NSR of 0.2 in/yr (R2 = 0.94), with a historical NSR value of 0.3 in/yr (R2 = 0.97) based on the lower- bound supported 210Pb activity. It was not possible to reliably calculate a historical NSR using the upper-bound supported 210Pb value because only the top two samples in the core could have been used in the linear regression analysis.

Based on the 210Pb activity data, the approximate time frame for deposition of the upper approximate 1 foot ranged from about 40 to 60 years. Time frames longer than 60 years are plausible based on the uncertainty in the estimated supported 210Pb activity. High correlation coefficients (R2 of 0.94 to 0.97) were noted in the 210Pb activity versus depth plots, providing a strong indication that deposition has occurred at this location.

The ranges of estimated NSR values and time frames for deposition of the upper approximate 1 foot of sediment at core AQ-04 are consistent with the core lithology and historical aerial

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DRAFT Appendix A photographs. The layer of wood material encountered at a depth of about 1 foot and the general presence of wood material within the silt in the upper 1.5 feet of core AQ-04 were plausibly deposited within the past 60 to 100 years because log rafts were commonly placed in the Study Area from the early 1900s to the 1980s (see historical aerial photographs). Saw mills, pulp and paper mills, and the former Pope & Talbot pole treating facility operating in this time frame may also have contributed to the wood debris noted in AQ-04. Historical aerial photographs note a modest emergence of seasonal vegetation in the vicinity of core AQ-04 over the past 80 years. This emergence of seasonal vegetation is consistent with an increase in bed elevation in this area.

A.4.5 Core AQ-05 Location Similar to core AQ-02, a peak 137Cs activity was observed at a depth of 0.7 feet in core AQ-05 (see Figure 3-6, left panel). This depth corresponds to a historical NSR of 0.2 in/yr. The peak 137Cs activity in core AQ-05 was higher (0.30 pCi/g-dry) than the peak activity in core AQ- 02. Uncertainty in the location of the peak 137Cs activity produced an uncertainty range of 0.1 to 0.3 in/yr in the historical NSR. The depth of peak 137Cs activity, and the depths of the adjacent samples in the core, suggests that the upper 5 to 12 inches of sediment was deposited since the peak of nuclear testing in 1963. The peak 137Cs activity in core AQ-05 was higher (0.30 pCi/g-dry) than the peak activity in core AQ-02.

The three samples obtained from the top 0.8 feet of the core were used to estimate the NSR within the surface layer of core AQ-05 (Figure A-9). The next deepest sample was from a depth of about 1.1 feet. A historical NSR of 0.2 in/yr was estimated using the average supported 210Pb activity. The lower- and upper-bound supported 210Pb values produced historical NSR values of 0.2 and 0.1 in/yr, respectively. The correlation coefficients for the three regression analyses ranged between 0.95 and 0.97. The historical NSR range estimated from the 210Pb activity analysis is consistent with the results of the 137Cs activity analysis.

Based on the 210Pb activity data, the estimated time frame for deposition of the upper approximate 1 foot of sediment ranged from about 60 to 120 years. High R2 values (0.95 to 0.97) were noted in the 210Pb activity versus depth plots providing a strong indication that deposition has occurred at this location.

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DRAFT Appendix A Historical aerial photographs note an emergence of vegetation in the vicinity of core AQ-05 over the past 80 years. The greater relative presence of “plant debris” in the core near the surface is consistent with the gradually emerging vegetation inferred from the historical aerial photographs. The emergence of vegetation is consistent with an increase in bed elevation in this area.

A.4.6 Core AQ-06 Location No 137Cs activity peak was evident in this core, with non-detect values existing throughout the core. Thus, it was not possible to estimate a historical NSR or a time frame for deposition of the near surface sediment from the 137Cs activity measurements. The vertical profile 210Pb activity within core AQ-06 was relatively uniform (Figure 3-7, right panel). Thus, it was not possible to estimate a historical NSR or a time frame for deposition of the near surface sediment from the 210Pb activity measurements. In summary, there are no discernible markers within this core that could be used to provide a reliable estimate of the magnitude of historical sedimentation or to demonstrate that significant sedimentation has occurred in the area around core AQ-06.

The lack of significant sedimentation in the AQ-06 area is consistent with its being located along the Scappoose Bay shoreline. Hydrodynamic modeling indicates greater flow velocities at this location, relative to the locations within the Study Area lowlands, and significant deposition would be less likely to occur in this area. This area has likely been affected by anthropogenic processes (e.g., boats, log rafts) that would have caused disturbances and mixing which would also contribute to the lack of clear indications of depositional processes from the radioisotope core data.

A.4.7 Core AQ-07 Location No 137Cs activity peak was evident in this core, with non-detect values existing throughout the core. Thus, it was not possible to estimate a historical NSR or a time frame for deposition of the near surface sediment from the 137Cs activity measurements.

Based on the 210Pb activity data from the three samples in the upper approximate 1 foot, the average supported 210Pb activity produced a historical NSR of 0.1 in/yr (R2 = 0.57), see Figure

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DRAFT Appendix A A-10. The historical NSR determined using the lower-bound supported 210Pb activity was 0.3 in/yr (R2 = 0.79). An estimate of NSR could not be made using the upper-bound supported 210Pb activity because nearly all of the total 210Pb activities in this core were lower than the upper-bound supported 210Pb activity.

The estimated time frame for deposition of the upper approximate 1 foot of sediment ranged from about 40 to 120 years. An estimate of depositional timeframe could not be made using the upper-bound supported 210Pb activity because nearly all of the total 210Pb activities in this core were lower than the upper-bound supported 210Pb activity. Notwithstanding the estimated time frames, the relatively low R2 values (0.57 to 0.79) noted in the 210Pb activity versus depth plots indicate a relatively low confidence in the estimated time frames for deposition of the upper 1 foot of sediment and the overall nature and extent of depositional processes.

Similar to the core AQ-06 location, the lack of significant sedimentation in the AQ-07 area is consistent with its being located along the Scappoose Bay shoreline. Hydrodynamic modeling indicates greater flow velocities at this location, relative to the locations within the Study Area lowlands, and significant deposition would be less likely to occur in this area. This area has likely been affected by anthropogenic processes (e.g., boats, log rafts) that would have caused disturbances and mixing which would also contribute to the relatively less clear indications of depositional processes from the radioisotope core data.

A.4.8 Core AQ-08 Location A peak 137Cs activity of approximately 0.6 pCi/g-dry occurred at an approximate depth of 2.4 feet (left panel of Figure 3-9). This depth corresponds to a historical NSR of 0.5 in/yr. Uncertainty in the location of the peak 137Cs activity produced an uncertainty range for the historical NSR of 0.4 to 0.6 in/yr. The depth of peak 137Cs activity, and the depth of the adjacent core samples, suggests that the upper 2 to 2.7 feet of sediment was deposited since the peak of nuclear testing in 1963. The peak 137Cs activity in this core was greater than the peak 137Cs activity in the other cores where 137Cs peaks were noted.

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DRAFT Appendix A A consistent, decreasing gradient in 210Pb activity occurred within the top 1 foot of core AQ- 08, with relatively constant 210Pb activities between 1 and 2 feet (Figure 3-9, right panel and Figure A-11). A historical NSR of 0.2 in/yr was estimated for all three values of supported 210Pb activity (Figure A-11). The 210Pb -based NSR (0.2 in/yr) corresponds to the average value for the period during when the top 1 foot of this core was deposited. Based on the observed 210Pb gradient, the estimated approximate time frame for deposition of the upper 1 foot of sediment is about 60 years. High R2 values (0.93 to 0.95) were noted in the 210Pb activity versus depth plots providing a strong indication that deposition has occurred at this location.

Based on current conditions and on historical aerial photographs, core AQ-08 is located in a former channel of Milton Creek. As such, it is anticipated to be representative of the creek channel in this area and not the adjacent lands that lie at an elevation of about 1 to 2 feet higher from the channel. The channel appears to have carried much of the Milton Creek flow from the 1930s through the mid-1950s. Prior to the 1930s, the channel appears to be completely separated from the Milton Creek flow (see 1929 aerial photograph). The pre- 1929 channel may have been dredged to increase the flow from Milton Creek during the 1930s to mid-1950s. The historical aerial photographs from the mid-1950s to the present suggest that, during this period, the channel received little to no flow from Milton Creek and was only submerged during high water conditions in Scappoose Bay.

Given these inferred activities, the radioisotope core data, and the lithology noted in core AQ-08, the upper 1 to 2 feet of core AQ-08 likely represent depositional processes occurring since the 1950s. The core AQ-08 log notes wood material at depths of 2 to 4 feet, which may represent depositional processes that occurred prior to the 1950s, either when the channel was receiving the Milton Creek flow or prior to the 1930s when the channel was only submerged during high-water conditions in Scappoose Bay.

A.5 EVALUATION OF UNCERTAINTY IN GEOCHRONOLOGY ANALYSIS A.5.1 Uncertainty in Lead-210 Data Analysis Uncertainty exists in the NSR estimated using Equation A-2 due to uncertainty in the slope

of line (S) determined from linear regression analysis of ln (210PbU) versus core depth. This Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant A-13 100703-01 74275387.1 0015549-00007

DRAFT Appendix A uncertainty was evaluated and quantified using the following procedure. The log-linear

regression analysis produces this relationship between ln (210PbU) and core depth:

Yp = A + S D (A-3)

where:

Yp = ln (210PbU)

D = depth in sediment core

S = slope of line determined from linear regression analysis of ln (210PbU) versus core depth

A = intercept of line determined from linear regression analysis of ln

(210PbU) versus core depth

The standard error of the slope (SE) is calculated using (Sokal and Rohlf 2012):

SE = [ ∑(Yk – Yp,k)2 / (K -2) ]1/2 / [∑(Dk – Dave) ] ½ (A-4)

where:

Yk = measured value of ln (210PbU) at depth of sample k

Yp,k = predicted value of ln (210PbU) at depth of sample k

Dk = depth of sample k

Dave = average depth of K samples

K = number of samples used in log-linear regression analysis

The summations in Equation A-4 are over the range of k = 1 to K.

The 95% confidence interval for the slope has lower-bound (Slower) and upper-bound (Supper) limits of:

Slower = S - C95 SE (A-5)

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DRAFT Appendix A

Supper = S + C95 SE (A-6)

where:

C95 = t-distribution coefficient for K-2 degrees of freedom

Values of C95 used in this analysis are listed in Table A-1 (Sokal and Rohlf 2012).

Table A-1 T-distribution Values for 95% Confidence Interval

Number of Samples (K) C95 3 12.7 4 4.3 5 3.18

Results of the uncertainty analysis are presented in Table A-2. The upper-bound value of the

95% confidence interval for the slope (Supper) was non-determinant for 13 evaluations (i.e.,

the value of Supper was positive, which results in a negative value for NSR). For those cases when the upper-bound slope was non-determinant, an approximate value of the upper- bound slope was estimated by adjusting the C coefficient in Equation A-6 such that:

Supper = 0.5 S (A-7)

This adjustment roughly corresponds to a confidence level of 50% to 75%.

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DRAFT Appendix A Table A-2 Results of Analysis for Uncertainty in Pb-210 Regression Slope

Supported Number of Best Estimate Lower- Upper- Pb-210 Sample Points Correlation NSR Bound NSR Bound NSR Core Level in Regression Coefficient (in/yr) (in/yr) (in/yr) AQ-01 Lower 4 0.99 0.46 0.37 0.63 AQ-01 Average 4 0.99 0.20 0.16 0.26 AQ-01 Upper NDM AQ-02 Lower 5 0.97 0.53 0.41 0.78 AQ-02 Average 5 0.98 0.35 0.28 0.45 AQ-02 Upper 4 0.96 0.17 0.10 0.51 AQ-03 Lower 4 0.84 0.46 0.20 0.921 AQ-03 Average 4 0.82 0.33 0.14 0.661 AQ-03 Upper 4 0.76 0.17 0.06 0.341 AQ-04 Lower 3 0.97 0.26 0.08 0.521 AQ-04 Average 3 0.94 0.17 0.04 0.341 AQ-04 Upper NDM AQ-05 Lower 3 0.97 0.18 0.06 0.361 AQ-05 Average 3 0.96 0.16 0.05 0.321 AQ-05 Upper 3 0.95 0.14 0.04 0.281 AQ-07 Lower 5 0.79 0.39 0.20 0.781 AQ-07 Average 3 0.57 0.20 0.02 0.401 AQ-07 Upper NDM AQ-08 Lower 3 0.95 0.25 0.06 0.501 AQ-08 Average 3 0.94 0.22 0.05 0.441 AQ-08 Upper 3 0.93 0.18 0.04 0.361

Notes: 1 Approximate upper-bound NSR due to non-determinant NSR for 95% confidence interval NDM = no discernible markers

Results of the analysis of uncertainty in estimated NSR values based on 210Pb activity data are summarized in Table A-3. Two sources of uncertainty were incorporated into this analysis:

1) supported 210Pb activity (210PbS); and 2) slope of line determined from linear regression analysis of ln (210PbU) versus core depth. The results of this analysis indicate that the uncertainty in estimated NSR is approximately a factor of 10 (i.e., order of magnitude).

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DRAFT Appendix A Table A-3 Range of Estimated NSRs Based on Pb-210 Activity Data

Range of Estimated Core NSR (in/yr) AQ-01 0.2 – 0.6 AQ-02 0.1 – 0.8 AQ-03 0.06 – 0.9 AQ-04 0.04 – 0.5 AQ-05 0.04 – 0.3 AQ-06 NDM AQ-07 0.02 – 0.8 AQ-08 0.04 – 0.5

Note: NDM = no discernible markers

A.5.2 Uncertainty in Cesium-137 Data Analysis Cesium-137 activities were below laboratory detection limits in five of the eight cores, see Table A-5. The occurrence of below-detection-limit 137Cs activity introduces uncertainty into the geochronology analysis of those five cores (i.e., AQ-01, AQ-03, AQ-04, AQ-06, AQ- 07). As discussed below, there may be several reasons for the lack of detected 137Cs activity in some of the cores.

A.5.2.1 General Uncertainties from Literature Review Ritchie and McHenry (1990) noted that 137Cs activity data are difficult to use in water bodies with low sediment accumulation rates (i.e., less than 0.4 in/yr) because of sampling issues. Additionally, they noted that if sediment accumulation rate is low, sampling in the detail necessary to determine 137Cs horizons in the profile may be difficult. This issue may be especially applicable to the St. Helens site where only selected 1-inch increments of the core samples were analyzed.

Physical reworking of sediment broadens the 137Cs peaks and makes interpretation more difficult (Ritchie and McHenry 1990). In general, they found the lower the sediment

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DRAFT Appendix A accumulation rate the greater effect reworking of sediments will have on the redistribution of 137Cs in sediment vertical profiles. Ritchie and McHenry (1990) noted that physical reworking of sediments by animals, wave action, or other methods can redistribute 137Cs activity within the vertical profile and spread it over a larger part of the profile and thereby reduce the maximum 137Cs activity. They also cited 12 studies that reported this vertical redistribution of 137Cs in the sediment vertical profile (Robbins and Eddington, 1975; Robbins et al., 1977, 1979; Hakanson and Kallstrom, 1978; Krezoski et al., 1978; Krezoski and Robbins, 1985; Fisher et al., 1980; Kacieszczenko and Banasik, 1981; DeMaster et al., 1985; Robbins, 1986; Anderson et al., 1987; and Sharma et al., 1987). Huntley et al., (1995) found that deposition rate estimates using 137Cs analyses are highly uncertain when mixing processes in sediments (e.g., due to erosion and redeposition, bioturbation by worms and other aquatic organisms) can alter the initially deposited sediment profile.

A.5.2.2 Site-Specific Uncertainty Evaluation Low and Sporadic Sources of 137Cs in the St. Helens Area Atmospheric deposition of 137Cs was spatially variable during the period of atmospheric testing of nuclear weapons during the 1950s and 1960s. The spatial distribution of 137Cs deposition density due to all Nevada Test Site atmospheric nuclear weapon tests is shown on Figure A-12 (Beck 1999). This map shows that significant spatial variability in 137Cs deposition density occurred within the United States, with relatively low atmospheric deposition occurring in the Pacific Northwest. In contrast to 137Cs deposition, the spatial distribution of atmospheric deposition of 210Pb is relatively uniform. Thus, it is reasonable to have measured 210Pb activities indicative of depositional activities while failing to detect 137Cs activity in some of the cores.

During a March 12, 2013 meeting, DEQ and DEQ’s consultant, Dr. David Jay, noted that 137Cs releases from the Hanford site are anticipated to have contributed to 137Cs activity in the Study Area sediment. Cesium-137 releases from the Hanford Site were primarily from surface and sub-surface discharges, with minimal atmospheric releases. The largest releases of radioactivity from the Hanford Site to the Columbia River occurred from 1956 to 1965 (Priddy et al. 2005). It is likely that these releases affected sediments in the Columbia River. Surface sediment samples (top 6 inches) were collected from the reservoirs of McNary, John

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DRAFT Appendix A Day, The Dalles and Bonneville dams during summer 2003 (Priddy et al. 2005). In addition, sediment sample were collected in the Priest Rapids reach of the Columbia River, which is upstream of the Hanford Site. The sediment samples were analyzed for 137Cs activity (detection limit of 0.01 pCi/g). A summary of the 137Cs activity data in Priddy et al. (2005) is shown in Table A-4.

Table A-4 Summary of Columbia River Cs-137 Sediment Data from Priddy et al. (2005)

Number of Sediment Average Cs-137 Activity Range of Cs-137 Activity Dam Samples (pCi/g) (pCi/g) Bonneville 3 0.138 0.094 – 0.173 The Dalles 5 0.140 0.098 – 0.192 John Day 7 0.357 0.220 – 0.627 McNary 10 0.401 0.230 – 0.513 Priest Rapids 2 0.305 0.285 – 0.324

Based on the data shown in Table A-4:

• Potential influence of 137Cs releases from the Hanford Site decreases moving downstream from Hanford.

• Sediment in the Priest Rapids reach, which is upstream of the Hanford Site, has significantly higher 137Cs activity than The Dalles and Bonneville sediment, which demonstrates that relatively large spatial variability in 137Cs deposition density occurred within the Pacific Northwest.

• A primary source of sediment to the Study Area (i.e., upriver Columbia River sediment loads) has relatively low 137Cs activity (i.e., less than 0.15 pCi/g). These values are close to the 137Cs activity detection limits for data collected during this study and the actvity levels would be expected to continue decreasing moving downstream toward the Study Area.

Finally, 137Cs is a radioactive chemical with a half-life of 30 years, which means that it is non- conservative because activity levels decrease with time due to radioactive decay. For

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DRAFT Appendix A example, 137Cs activity of sediment deposited in 1963 will have decreased by about 70% during the 50-year period since deposition and 2013 due to radioactive decay.

Increased Potential for Small-Scale Erosional Events in Lower Elevation Areas Whether or not 137Cs activity was detected in the radioisotope core analysis appears to be correlated with the bed elevation of the core location (Table A-5). In particular, the detection of 137Cs activity was limited to cores at or above bed elevations of 8.5 ft NAVD88, which corresponds to tidal inundation frequencies of about 50% or less. Cores from locations at elevations less than 8.5 ft would be more likely subject to localized, low-energy events or the mechanisms described in Section A.5.2.1 that could have disrupted the 137Cs activity profile.

Table A-5 Summary of Cs-137 Activity Data for Study Area Cores

Inundation Range of Detected Range of Bed Elevation Frequency Cs-137 Activity Cs-137 Detection Core (ft NAVD88) (%) (pCi/g) Limits (pCi/g) AQ-06 3.5 >95 ND 0.038 – 0.131 AQ-07 4.7 >95 ND 0.033 – 0.062 AQ-01 7.8 70 ND 0.034 – 0.057 AQ-04 7.9 70 ND 0.039 – 0.121 AQ-03 8.2 60 ND 0.036 – 0.174 AQ-02 8.5 55 0.034 – 0.062 0.035 – 0.072 AQ-08 9.2 45 0.110 -0.576 0.052 – 0.146 AQ-05 9.5 40 0.162 – 0.297 0.032 – 0.138

Note: ND = non-detected

Elevated Detection Limits The lack of detected 137Cs activity in some of the cores may be due to the relatively elevated detection limit in the core analysis. In particular, the limited sample volume resulted in detection limits greater than often achieved in radioisotope core analysis. The range of laboratory detection limits for 137Cs activity in this study, which had minimum and maximum values of 0.032 and 0.174 pCi/g (Table A-4). A previous geochronology study in

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DRAFT Appendix A the Columbia River had a detection limit of 0.01 pCi/g for 137Cs activity (Priddy et al. 2005). A City of Portland 2012 sediment study in the Columbia Slough noted detection limits generally in the range of 0.01 to 0.03 pCi/g. Thus, the detection limits for 137Cs activity for samples collected from the Study Area were relatively high, which could be one reason that 137Cs activity was not detected in five of the eight cores.

A.5.2.3 Summary of Potential Causes of Lack of Cesium-137 Detections in Cores The observations discussed above indicate that uncertainty in the geochronology analysis due to the occurrence of below-detection-limit 137Cs activity in five of eight sediment cores is likely due to a combination of interrelated physical and chemical processes, including:

• Large spatial variability in 137Cs deposition density, both nationally and regionally, during the 1950s and 1960s when atmospheric testing of nuclear weapons was conducted;

• A primary source of sediment to the Study Area (i.e., Columbia River sediment loads) has relatively low 137Cs activity (i.e., less than 0.15 pCi/g);

• Non-conservative behavior of 137Cs activity due to radioactive decay;

• The increased likelihood for small-scale, localized, periodic erosional events in the lower elevations of the lowland, especially prior to the late 1970s and early 1980s when former process water discharges to the lowland was occurring; and

• Relatively high laboratory detection limits for 137Cs activity.

While the lack of 137Cs activity in five of the eight cores could be the result of erosion during high-flow events (i.e., high-energy hydrodynamic processes over relatively large spatial scales) between the early 1960s and the present, this hypothesis is not consistent with other lines of evidence developed during this study (e.g., historical aerial photograph review, hydrodynamic modeling results, and analysis of 210Pb radioisotope core data).

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant A-21 100703-01 74275387.1 0015549-00007 Core AQ-01 Core AQ-02 0.0 Silt 0.0 Silt dark gray with dark red-brown mottling dark brownish gray stiff wet moist very soft moderate plasticity low plasticity no vegetation abundant rootlets and small plant and no odor vegetation pieces no odor 0.5 0.5

1.0 1.0

Silt with Sand dark gray with trace dark red-brown mottling moist slight plasticity 1.5 fine sand 1.5 no vegetation no odor Silt (ft) (ft) soft dark brownish gray Depth Depth very soft wet low plasticity trace rootlets and vegetation pieces 2.0 2.0 no odor

2.5 2.5 Sandy Silt dark gray wet slight plasticity fine sand no vegetation or debris no odor soft 3.0 3.0

Figure A-1 Radioisotope Core Lithology: Cores AQ-01 and AQ-02 St. Helens Fiberboard Plant

vkl - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120905.pro Wed Sep 05 14:41:08 2012 Core AQ-03 Core AQ-04 0.0 0.0 Silt dark brown wet very soft nonplastic abundant silt to very fine sand-sized wood fibers wood fibers constitute 70 percent of unit 0.9 to 1.1 ft: 100 percent wood fibers 0.5 0.5 turns dark gray when exposed to air 1.1 to 1.2 ft: small fine sand-sized particles of metal

Silt dark grayish brown wet very soft low plasticity no odor 1.0 0.0 to 0.4 ft: 20 to 30 percent of material is 1.0 rootlets and plant matter

Silt 1.5 1.5 dark brownish gray Silt moist dark grayish brown soft wet low plasticity (ft) (ft) soft homogeneous Depth Depth firming with depth no odor high plasticity no plant or organic debris no odor 2.0 2.0

2.5 2.5

3.0 3.0

Figure A-2 Radioisotope Core Lithology: Cores AQ-03 and AQ-04 St. Helens Fiberboard Plant

vkl - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120905.pro Wed Sep 05 14:41:08 2012 Core AQ-05 Core AQ-06 0.0 0.0 Silt dark brown wet nonplastic with wood pieces wood pieces are 70 to 80 percent of unit no odor

0.5 0.5 Silt dark brown wet very soft moderate plasticity trace fine sand trace plant debris no odor Silt firming with depth 1.0 dark reddish brown 1.0 wet soft low plasticity silt with plant matter wood and root debris no odor 0.0 to 0.6 ft: plant debris is 60 to 70 percent of unit 0.6 to 2.0 ft: plant debris is 40 to 50 percent of unit 1.5 1.5 (ft) (ft) Depth Depth

2.0 2.0

2.5 2.5 Silt dark gray soft wet low plasticity trace plant debris (<5 percent) no odor 3.0 2.1 to 2.2 ft: very dark gray band 3.0

Figure A-3 Radioisotope Core Lithology: Cores AQ-05 and AQ-06 St. Helens Fiberboard Plant

vkl - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120905.pro Wed Sep 05 14:41:08 2012 Core AQ-07 Core AQ-08 0.0 Silt 0.0 Silt dark brownish gray dark brown firm wet moist very soft moderate to high plasticity nonplastic trace fine sand (<5 percent) abundant rootlets no plant or organic debris occasional twig or wood piece no odor no odor 0.5 homogeneous 0.5

1.0 1.0

Sandy Silt dark brownish gray soft wet low plasticity fine sand no odor 1.5 no plant or organic debris 1.5 homogeneous (ft) (ft) Depth Depth

2.0 2.0 Silt dark red very soft wet low plasticity abundant very fine grained wood fibers Silty Sand no odor dark brownish gray turns dark brown when exposed to air fine sand wood fibers constitute 70 percent of unit 2.5 wet 2.5 2.7 to 2.8 ft: coarse wood piece layer loose 3.0 to 3.3 ft: unit is entirely wood fibers (100 percent wood fibers)

Silt dark brownish gray soft moist low plasticity 3.0 trace fine sand (<5 percent) 3.0 homogeneous no plant or organic debris no odor

Figure A-4 Radioisotope Core Lithology: Cores AQ-07 and AQ-08 St. Helens Fiberboard Plant

vkl - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120905.pro Wed Sep 05 14:41:08 2012 Lower-bound Supported Pb-210 Average Supported Pb-210 Upper-bound Supported Pb-210 0 0 0

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0 0 0 R2 = 0.99 R2 = 0.99

1 1 1

2 2 2 (ft) (ft) (ft) Depth Depth Depth

3 3 3

4 4 4 -5 -4 -3 -2 -1 -5 -4 -3 -2 -1 -5 -4 -3 -2 -1 ln Unsupported Lead-210 ln Unsupported Lead-210 ln Unsupported Lead-210

Figure A-5 Data included in regression analysis NSR Analysis of Vertical Profile of Pb-210 Activity: Core AQ-01 Data excluded from regression analysis St. Helens Fiberboard Plant Best-fit regression line Supported Pb-210 activity

JF/HS - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120904_noveg.pro Wed Sep 05 12:57:48 2012 Lower-bound Supported Pb-210 Average Supported Pb-210 Upper-bound Supported Pb-210 0 0 0

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0 0 0 R2 = 0.97 R2 = 0.98 R2 = 0.96

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3 3 3

4 4 4 -5 -4 -3 -2 -1 0 -5 -4 -3 -2 -1 0 -5 -4 -3 -2 -1 0 ln Unsupported Lead-210 ln Unsupported Lead-210 ln Unsupported Lead-210

Figure A-6 Data included in regression analysis NSR Analysis of Vertical Profile of Pb-210 Activity: Core AQ-02 Data excluded from regression analysis St. Helens Fiberboard Plant Best-fit regression line Supported Pb-210 activity

JF/HS - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120904_noveg.pro Wed Sep 05 12:57:49 2012 Lower-bound Supported Pb-210 Average Supported Pb-210 Upper-bound Supported Pb-210 0 0 0

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4 4 4 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 Lead-210 Activity Lead-210 Activity Lead-210 Activity (pCi/g Dry) (pCi/g Dry) (pCi/g Dry)

0 0 0 R2 = 0.84 R2 = 0.82 R2 = 0.76

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4 4 4 -5 -4 -3 -2 -1 0 -5 -4 -3 -2 -1 0 -5 -4 -3 -2 -1 0 ln Unsupported Lead-210 ln Unsupported Lead-210 ln Unsupported Lead-210

Figure A-7 Data included in regression analysis NSR Analysis of Vertical Profile of Pb-210 Activity: Core AQ-03 Data excluded from regression analysis St. Helens Fiberboard Plant Best-fit regression line Supported Pb-210 activity

JF/HS - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120904_noveg.pro Wed Sep 05 12:57:49 2012 Lower-bound Supported Pb-210 Average Supported Pb-210 Upper-bound Supported Pb-210 0 0 0

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0 0 0 R2 = 0.97 R2 = 0.94

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4 4 4 -5 -4 -3 -2 -1 0 1 -5 -4 -3 -2 -1 0 1 -5 -4 -3 -2 -1 0 1 ln Unsupported Lead-210 ln Unsupported Lead-210 ln Unsupported Lead-210

Figure A-8 Data included in regression analysis NSR Analysis of Vertical Profile of Pb-210 Activity: Core AQ-04 Data excluded from regression analysis St. Helens Fiberboard Plant Best-fit regression line Supported Pb-210 activity

JF/HS - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120904_noveg.pro Wed Sep 05 12:57:49 2012 Lower-bound Supported Pb-210 Average Supported Pb-210 Upper-bound Supported Pb-210 0 0 0

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0 0 0 R2 = 0.97 R2 = 0.96 R2 = 0.95

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4 4 4 -5 -4 -3 -2 -1 0 1 2 -5 -4 -3 -2 -1 0 1 2 -5 -4 -3 -2 -1 0 1 2 ln Unsupported Lead-210 ln Unsupported Lead-210 ln Unsupported Lead-210

Figure A-9 Data included in regression analysis NSR Analysis of Vertical Profile of Pb-210 Activity: Core AQ-05 Data excluded from regression analysis St. Helens Fiberboard Plant Best-fit regression line Supported Pb-210 activity

JF/HS - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120904_noveg.pro Wed Sep 05 12:57:50 2012 Lower-bound Supported Pb-210 Average Supported Pb-210 Upper-bound Supported Pb-210 0 0 0

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4 4 4 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Lead-210 Activity Lead-210 Activity Lead-210 Activity (pCi/g Dry) (pCi/g Dry) (pCi/g Dry)

0 0 0 R2 = 0.79 R2 = 0.57

1 1 1

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3 3 3

4 4 4 -5 -4 -3 -2 -1 -5 -4 -3 -2 -1 -5 -4 -3 -2 -1 ln Unsupported Lead-210 ln Unsupported Lead-210 ln Unsupported Lead-210

Figure A-10 Data included in regression analysis NSR Analysis of Vertical Profile of Pb-210 Activity: Core AQ-07 Data excluded from regression analysis St. Helens Fiberboard Plant Best-fit regression line Supported Pb-210 activity

JF/HS - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120904_noveg.pro Wed Sep 05 12:57:51 2012 Lower-bound Supported Pb-210 Average Supported Pb-210 Upper-bound Supported Pb-210 0 0 0

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4 4 4 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Lead-210 Activity Lead-210 Activity Lead-210 Activity (pCi/g Dry) (pCi/g Dry) (pCi/g Dry)

0 0 0 R2 = 0.95 R2 = 0.94 R2 = 0.93

1 1 1

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3 3 3

4 4 4 -4 -3 -2 -1 0 1 -4 -3 -2 -1 0 1 -4 -3 -2 -1 0 1 ln Unsupported Lead-210 ln Unsupported Lead-210 ln Unsupported Lead-210

Figure A-11 Data included in regression analysis NSR Analysis of Vertical Profile of Pb-210 Activity: Core AQ-08 Data excluded from regression analysis St. Helens Fiberboard Plant Best-fit regression line Supported Pb-210 activity

JF/HS - \\Montvalebu\Jobs26a\Jobs\St_Helens\Report\120815\Decks\geochron_120904_noveg.pro Wed Sep 05 12:57:51 2012 M:\Jobs\St_Helens\Report\130701\StHelens_AppendixA_12.mxd vlist 7/1/2013 1:26:59 PM AllNevada TestSite Atmospheric NuclearWeapon Tests Spatial Distribution of Cs-137Deposition DensityDue to (Dischargeceased January 1977) (Dischargeceased December1981) St. HelensFiberboard Plant Source: Beck (1999), Figure 1 Figure (1999), Source: Beck Figure A-12

APPENDIX B RESULTS OF HARMONIC AND STATISTICAL ANALYSES FOR NEAR-FIELD AND FAR-FIELD HYDRODYNAMIC MODELS

74275387.1 0015549-00007

DRAFT Appendix B B.1 TIDAL HARMONIC ANALYSIS OF WATER SURFACE ELEVATION: FAR-FIELD MODEL Water surface elevation (WSE) data collected at 6-minute intervals were used in the skill assessment. The tidal harmonic analysis was accomplished using T_TIDE, which is a matrix laboratory (MATLAB) program developed at the University of British Columbia and Woods Hole Oceanographic Institution (Pawlowicz et al. 2002). Six primary tidal harmonic constituents were evaluated in this analysis, see Table B-1.

Table B-1 Tidal Constituents Evaluated During Tidal Harmonic Analysis

Tidal Harmonic Constituent Description

M2 Principal lunar semi-diurnal

S2 Principal solar semi-diurnal

N2 Larger lunar elliptical semi-diurnal

K1 Luni-solar declinational diurnal

M4 First over-tide of M2

O1 Lunar declinational diurnal

Table B-2 Far-field Model Tidal Harmonic Analysis: Amplitude at St. Helens – September 2005

Measured Predicted Tidal Harmonic Amplitude Amplitude Absolute Error Relative Error Constituent (feet) (feet) (feet) (%) M2 3.76 4.26 0.50 13 S2 1.21 1.38 0.17 14 N2 0.71 0.82 0.11 19 K1 1.66 1.66 0.00 -0.3 M4 0.64 0.51 -0.13 -20 O1 0.98 1.15 0.18 18

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant B-1 100703-01 74275387.1 0015549-00007

DRAFT Appendix B Table B-3 Far-field Model Tidal Harmonic Analysis: Phase at St. Helens – September 2005

Tidal Harmonic Measured Phase Predicted Phase Absolute Error Constituent (degrees) (degrees) (degrees) M2 176 180 4 S2 203 209 6 N2 140 147 7 K1 246 244 -2 M4 260 267 7 O1 235 232 -3

Table B-4 Far-field Model Tidal Harmonic Analysis: Amplitude at Vancouver – September 2005

Measured Predicted Tidal Harmonic Amplitude Amplitude Absolute Error Relative Error Constituent (feet) (feet) (feet) (%) M2 3.60 4.66 1.05 29 S2 1.15 1.53 0.38 33 N2 0.65 0.91 0.27 41 K1 1.70 1.68 -0.02 -1 M4 0.72 0.93 0.21 30 O1 0.94 1.21 0.26 28

Table B-5 Far-field Model Tidal Harmonic Analysis: Phase at Vancouver – September 2005

Tidal Harmonic Measured Phase Predicted Phase Absolute Error Constituent (degrees) (degrees) (degrees) M2 215 210 -5 S2 242 239 -3 N2 179 176 -3 K1 265 260 -5 M4 360 353 -7 O1 265 252 -13

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant B-2 100703-01 74275387.1 0015549-00007

DRAFT Appendix B Table B-6 Far-field Model Tidal Harmonic Analysis: Amplitude at Columbia Slough – September 2005

Measured Predicted Tidal Harmonic Amplitude Amplitude Absolute Error Relative Error Constituent (feet) (feet) (feet) (%) M2 3.37 4.64 1.28 38 S2 1.10 1.53 0.43 39 N2 0.61 0.91 0.30 49 K1 1.63 1.68 0.05 3 M4 0.68 0.89 0.21 31 O1 0.92 1.20 0.28 31

Table B-7 Far-field Model Tidal Harmonic Analysis: Phase at Columbia Slough – September 2005

Tidal Harmonic Measured Phase Predicted Phase Absolute Error Constituent (degrees) (degrees) (degrees) M2 215 207 -8 S2 245 237 -8 N2 177 173 -4 K1 270 259 -11 M4 0.3 348 -12 O1 269 250 -19

Table B-8 Far-field Model Tidal Harmonic Analysis: Amplitude at Bonneville Dam – September 2005

Measured Predicted Tidal Harmonic Amplitude Amplitude Absolute Error Relative Error Constituent (feet) (feet) (feet) (%) M2 1.13 0.86 -0.27 -24 S2 0.90 0.34 -0.56 -62 N2 0.47 0.24 -0.23 -49 K1 0.89 0.50 -0.39 -44 M4 0.24 0.18 -0.06 -27 O1 0.94 0.39 -0.55 -59

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant B-3 100703-01 74275387.1 0015549-00007

DRAFT Appendix B Table B-9 Far-field Model Tidal Harmonic Analysis: Phase at Bonneville Dam – September 2005

Tidal Harmonic Measured Phase Predicted Phase Absolute Error Constituent (degrees) (degrees) (degrees) M2 313 304 -9 S2 341 342 1 N2 289 285 -4 K1 190 316 -125 M4 159 154 -5 O1 326 305 -21

Table B-10 Far-field Model Tidal Harmonic Analysis: Amplitude at Lower Willamette River – September 2005

Measured Predicted Tidal Harmonic Amplitude Amplitude Absolute Error Relative Error Constituent (feet) (feet) (feet) (%) M2 3.91 4.95 1.04 27 S2 1.26 1.64 0.37 30 N2 0.70 0.96 0.27 38 K1 1.71 1.71 0.01 0.3 M4 1.03 1.16 0.13 13 O1 0.95 1.22 0.27 28

Table B-11 Far-field Model Tidal Harmonic Analysis: Phase at Lower Willamette River – September 2005

Tidal Harmonic Measured Phase Predicted Phase Absolute Error Constituent (degrees) (degrees) (degrees) M2 211 209 -2 S2 238 238 0 N2 175 175 0 K1 263 260 -3 M4 354 352 -2 O1 262 251 -11

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant B-4 100703-01 74275387.1 0015549-00007

DRAFT Appendix B Table B-12 Far-field Model Tidal Harmonic Analysis: Amplitude at St. Helens – May 2006

Measured Predicted Tidal Harmonic Amplitude Amplitude Absolute Error Relative Error Constituent (feet) (feet) (feet) (%) M2 1.21 1.59 0.39 32 S2 0.33 0.41 0.08 23 N2 0.22 0.27 0.05 22 K1 0.68 0.92 0.24 35 M4 0.19 0.22 0.03 14 O1 0.30 0.37 0.07 25

Table B-13 Far-field Model Tidal Harmonic Analysis: Phase at St. Helens – May 2006

Tidal Harmonic Measured Phase Predicted Phase Absolute Error Constituent (degrees) (degrees) (degrees) M2 191 193 2 S2 199 196 -3 N2 212 198 -14 K1 234 233 -1 M4 300 289 -11 O1 271 268 -3

Table B-14 Far-field Model Tidal Harmonic Analysis: Amplitude at Vancouver – May 2006

Measured Predicted Tidal Harmonic Amplitude Amplitude Absolute Error Relative Error Constituent (feet) (feet) (feet) (%) M2 0.56 1.05 0.49 86 S2 0.20 0.31 0.11 56 N2 0.12 0.19 0.07 50 K1 0.35 0.68 0.33 96 M4 0.10 0.14 0.05 45 O1 0.18 0.31 0.13 72

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant B-5 100703-01 74275387.1 0015549-00007

DRAFT Appendix B Table B-15 Far-field Model Tidal Harmonic Analysis: Phase at Vancouver – May 2006

Tidal Harmonic Measured Phase Predicted Phase Absolute Error Constituent (degrees) (degrees) (degrees) M2 240 240 0 S2 252 242 -10 N2 288 257 -31 K1 270 264 -6 M4 33 23 -10 O1 298 298 0

Table B-16 Far-field Model Tidal Harmonic Analysis: Amplitude at Columbia Slough – May 2006

Measured Predicted Tidal Harmonic Amplitude Amplitude Absolute Error Relative Error Constituent (feet) (feet) (feet) (%) M2 0.44 1.12 0.68 79 S2 0.09 0.32 0.24 94 N2 0.09 0.20 0.11 107 K1 0.47 0.72 0.24 46 M4 0.01 0.15 0.14 264 O1 0.26 0.33 0.07 55

Table B-17 Far-field Model Tidal Harmonic Analysis: Phase at Columbia Slough – May 2006

Tidal Harmonic Measured Phase Predicted Phase Absolute Error Constituent (degrees) (degrees) (degrees) M2 154 234 80 S2 142 236 94 N2 142 248 106 K1 214 260 46 M4 276 12 -264 O1 238 294 56

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant B-6 100703-01 74275387.1 0015549-00007

DRAFT Appendix B Table B-18 Far-field Model Tidal Harmonic Analysis: Amplitude at Bonneville Dam – May 2006

Measured Predicted Tidal Harmonic Amplitude Amplitude Absolute Error Relative Error Constituent (feet) (feet) (feet) (%) M2 0.20 0.12 -0.08 -38 S2 0.32 0.05 -0.27 -85 N2 0.24 0.03 -0.21 -87 K1 0.37 0.16 -0.21 -57 M4 0.03 0.01 -0.02 -63 O1 0.36 0.09 -0.27 -74

Table B-19 Far-field Model Tidal Harmonic Analysis: Phase at Bonneville Dam – May 2006

Tidal Harmonic Measured Phase Predicted Phase Absolute Error Constituent (degrees) (degrees) (degrees) M2 262 339 77 S2 311 318 7 N2 10 346 -24 K1 23 336 -47 M4 248 132 -116 O1 73 351 -84

Table B-20 Far-field Model Tidal Harmonic Analysis: Amplitude at Lower Willamette River – May 2006

Measured Predicted Tidal Harmonic Amplitude Amplitude Absolute Error Relative Error Constituent (feet) (feet) (feet) (%) M2 0.64 1.18 0.54 83 S2 0.23 0.34 0.11 49 N2 0.15 0.21 0.06 38 K1 0.38 0.73 0.34 89 M4 0.14 0.19 0.05 34 O1 0.21 0.33 0.12 60

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant B-7 100703-01 74275387.1 0015549-00007

DRAFT Appendix B Table B-21 Far-field Model Tidal Harmonic Analysis: Phase at Lower Willamette River – May 2006

Tidal Harmonic Measured Phase Predicted Phase Absolute Error Constituent (degrees) (degrees) (degrees) M2 236 235 -1 S2 243 237 -6 N2 279 249 -30 K1 268 260 -8 M4 24 14 -10 O1 296 294 -2

B.2 STATISTICAL ANALYSIS OF WATER SURFACE ELEVATION: FAR-FIELD MODEL The statistical analysis was conducted using the methodology described in Hess et al. (2003). Differences in the following predicted (upper-case) and measured (lower-case) variables were calculated over the calibration and validation periods:

• WSE: H-h;

• Amplitude of high water: AHW-ahw;

• Amplitude of low water: LHW-lhw;

• Time of high water: THW-thw; and

• Time of low water: TLW-tlw.

Skill assessment criteria for WSE were (Hess et al. 2003):

• Central frequency (0.5 feet) greater than or equal to 90%;

• Positive outlier frequency (1 foot) less than or equal to 1%;

• Negative outlier frequency (1 foot) less than or equal to 1%;

• Maximum duration of positive outliers (1 foot) less than 24 hours; and

• Maximum duration of negative outliers (1 foot) less than or equal to 24 hours.

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant B-8 100703-01 74275387.1 0015549-00007

DRAFT Appendix B Skill assessment criteria for amplitudes of high water and low water were (Hess et al. 2003):

• Central frequency (0.5 foot) greater than or equal to 90%;

• Positive outlier frequency (1 foot) less than or equal to 1%;

• Negative outlier frequency (1 foot) less than or equal to 1%;

• Maximum duration of positive outliers (1 foot) less than 24 hours; and

• Maximum duration of negative outliers (1 foot) less than or equal to 24 hours.

Skill assessment criteria for times of high water and low water were (Hess et al. 2003):

• Central frequency (0.5 hour) greater than or equal to 90%;

• Positive outlier frequency (1 hour) less than or equal to 1%;

• Negative outlier frequency (1 hour) less than or equal to 1%;

• Maximum duration of positive outliers (1 hour) less than 24 hours; and

• Maximum duration of negative outliers (1 hour) less than or equal to 24 hours.

Table B-22 Skill Assessment Statistics

Variable Description SM Series mean (average value) RMSE Root mean square error SD Standard deviation CF(X) Central frequency: fraction (percentage) of errors that lie within the limits + X POF(X) Positive outlier frequency: fraction (percentage) of errors that are greater than X NOF(X) Negative outlier frequency: fraction (percentage) of errors that are less than -X Maximum duration of positive outliers: a positive outlier event is two or more MDPO(X) consecutive occurrences of an error greater than X. MDPO is the length of time (based on the number of consecutive occurrences) of the longest event. Maximum duration of negative outliers: a negative outlier event is two or more MDNO(X) consecutive occurrences of an error less than -X. MDNO is the length of time (based on the number of consecutive occurrences) of the longest event.

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant B-9 100703-01 74275387.1 0015549-00007

DRAFT Appendix B Table B-23 Far-field Model Statistical Analysis during Calibration Period: St. Helens

CF POF NOF MDPO MDNO SM RMSE SD (%) (%) (%) (hrs) (hrs) Water Level, H-h 0.22 ft 0.31 ft 0.21 ft 92 0.0 0.0 0.3 0.9 Amplitude of High 0.32 ft 0.38 ft 0.21 ft 82 0.0 0.0 0.0 0.0 Water, AHW-ahw Amplitude of Low 0.11 ft 0.23 ft 0.21 ft 98 0.0 0.0 0.0 0.0 Water, LHW-lhw Time of High Water, 0.2 hr 0.4 hr 0.3 hr 90 1.1 0.1 15 6.0 THW-thw Time of Low Water, 0.0 hr 0.3 hr 0.3 hr 93 0.6 0.3 27 14 TLW-tlw

Note: Bold values indicated skill assessment criteria were achieved.

Table B-24 Far-field Model Statistical Analysis during Calibration Period: Vancouver

CF POF NOF MDPO MDNO SM RMSE SD (%) (%) (%) (hrs) (hrs) Water Level, H-h 0.35 ft 0.48 ft 0.35 ft 65 2.0 0.0 5.8 0.0 Amplitude of High 0.61 ft 0.69 ft 0.31 ft 29 7.9 0.0 39 0.0 Water, AHW-ahw Amplitude of Low 0.13 ft 0.30 ft 0.27 ft 90 0.1 0.0 15 0.0 Water, LHW-lhw Time of High Water, -0.1 hr 0.8 hr 0.8 hr 83 3.9 2.4 51 31 THW-thw Time of Low Water, 0.1 hr 1.0 hr 0.9 hr 88 3.1 1.0 44 15 TLW-tlw

Note: Bold values indicated skill assessment criteria were achieved.

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant B-10 100703-01 74275387.1 0015549-00007

DRAFT Appendix B Table B-25 Far-field Model Statistical Analysis during Calibration Period: Columbia Slough

CF POF NOF MDPO MDNO SM RMSE SD (%) (%) (%) (hrs) (hrs) Water Level, H-h 0.10 ft 0.36 ft 0.35 ft 82 0.3 0.2 2.5 7.0 Amplitude of High 0.36 ft 0.49 ft 0.33 ft 59 0.8 0.0 15 0.0 Water, AHW-ahw Amplitude of Low -0.11 ft 0.31 ft 0.29 ft 88 0.0 0.2 0.0 13 Water, LHW-lhw Time of High Water, -0.2 hr 0.9 hr 0.9 hr 70 4.1 5.8 50 47 THW-thw Time of Low Water, 0.1 hr 1.0 hr 1.0 hr 74 6.8 2.7 42 15 TLW-tlw

Note: Bold values indicated skill assessment criteria were achieved.

Table B-26 Far-field Model Statistical Analysis during Calibration Period: Bonneville Dam

CF POF NOF MDPO MDNO SM RMSE SD (%) (%) (%) (hrs) (hrs) Water Level, H-h -0.44 ft 1.06 ft 0.96 ft 38 5.6 28 15 84 Amplitude of High -0.93 ft 1.34 ft 0.96 ft 30 1.1 47 30 224 Water, AHW-ahw Amplitude of Low -0.02 ft 0.84 ft 0.84 ft 47 11 12 104 76 Water, LHW-lhw Time of High Water, -0.1 hr 3.8 hr 3.8 hr 18 35 37 78 71 THW-thw Time of Low Water, 1.3 hr 4.3 hr 4.1 hr 22 43 23 180 64 TLW-tlw

Note: Bold values indicated skill assessment criteria were achieved.

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant B-11 100703-01 74275387.1 0015549-00007

DRAFT Appendix B Table B-27 Far-field Model Statistical Analysis during Calibration Period: Lower Willamette River

CF POF NOF MDPO MDNO SM RMSE SD (%) (%) (%) (hrs) (hrs) Water Level, H-h 0.20 ft 0.36 ft 0.30 ft 82 0.3 0.0 6.0 1.5 Amplitude of High 0.42 ft 0.49 ft 0.26 ft 63 1.2 0.0 18 0.0 Water, AHW-ahw Amplitude of Low -0.02 ft 0.26 ft 0.25 ft 95 0.0 0.0 0.0 0.0 Water, LHW-lhw Time of High Water, 0.0 hr 0.7 hr 0.7 hr 82 3.6 2.6 54 34 THW-thw Time of Low Water, 0.1 hr 0.8 hr 0.8 hr 84 4.0 1.4 36 14 TLW-tlw

Note: Bold values indicated skill assessment criteria were achieved.

Table B-28 Far-field Model Statistical Analysis during Validation Period: St. Helens

CF POF NOF MDPO MDNO SM RMSE SD (%) (%) (%) (hrs) (hrs) Water Level, H-h 0.18 ft 0.27 ft 0.20 ft 95 0.0 0.0 0.2 0.0 Amplitude of High 0.25 ft 0.32 ft 0.20 ft 89 0.1 0.0 14 0.0 Water, AHW-ahw Amplitude of Low 0.08 ft 0.22 ft 0.20 ft 99 0.0 0.0 0.0 0.0 Water, LHW-lhw Time of High Water, 0.2 hr 0.5 hr 0.5 hr 89 0.4 0.5 11 11 THW-thw Time of Low Water, 0.0 hr 0.5 hr 0.5 hr 85 3.5 1.4 25 4.0 TLW-tlw

Note: Bold values indicated skill assessment criteria were achieved.

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DRAFT Appendix B Table B-29 Far-field Model Statistical Analysis during Validation Period: Vancouver

CF POF NOF MDPO MDNO SM RMSE SD (%) (%) (%) (hrs) (hrs) Water Level, H-h 0.62 ft 0.71 ft 0.34 ft 32 14 0.1 30 3.3 Amplitude of High 0.87 ft 0.91 ft 0.30 ft 8.5 35 0.1 138 26 Water, AHW-ahw Amplitude of Low 0.42 ft 0.53 ft 0.32 ft 58 2.9 0.0 25 0.0 Water, LHW-lhw Time of High -0.1 hr 0.8 hr 0.8 hr 83 3.5 4.2 120 44 Water, THW-thw Time of Low Water, 0.1 hr 1.0 hr 1.0 hr 85 3.5 1.4 58 14 TLW-tlw

Note: Bold values indicated skill assessment criteria were achieved.

Table B-30 Far-field Model Statistical Analysis during Validation Period: Columbia Slough

CF POF NOF MDPO MDNO SM RMSE SD (%) (%) (%) (hrs) (hrs) Water Level, H-h 0.13 ft 0.38 ft 0.35 ft 81 0.4 0.4 3.3 9.5 Amplitude of High 0.36 ft 0.50 ft 0.35 ft 56 0.5 0.3 16 25 Water, AHW-ahw Amplitude of Low -0.07 ft 0.31 ft 0.30 ft 89 0.0 0.7 0.0 45 Water, LHW-lhw Time of High -0.2 hr 0.8 hr 0.8 hr 72 3.4 5.2 47 97 Water, THW-thw Time of Low Water, 0.1 hr 1.1 hr 1.1 hr 73 6.8 2.6 83 14 TLW-tlw

Note: Bold values indicated skill assessment criteria were achieved.

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DRAFT Appendix B Table B-31 Far-field Model Statistical Analysis during Validation Period: Bonneville Dam

CF POF NOF MDPO MDNO SM RMSE SD (%) (%) (%) (hrs) (hrs) Water Level, H-h -0.36 ft 1.08 ft 1.02 ft 40 7.8 25 25 34 Amplitude of High -0.90 ft 1.34 ft 0.99 ft 32 1.7 44 33 179 Water, AHW-ahw Amplitude of Low 0.09 ft 0.87 ft 0.87 ft 45 15 9.4 103 42 Water, LHW-lhw Time of High -0.1 hr 3.8 hr 3.8 hr 21 32 36 66 79 Water, THW-thw Time of Low Water, 1.2 hr 4.1 hr 3.9 hr 23 43 21 142 42 TLW-tlw

Table B-32 Far-field Model Statistical Analysis during Validation Period: Lower Willamette River

CF POF NOF MDPO MDNO SM RMSE SD (%) (%) (%) (hrs) (hrs) Water Level, H-h 0.25 ft 0.39 ft 0.29 ft 79 0.6 0.1 7.0 5.5 Amplitude of High 0.47 ft 0.54 ft 0.28 ft 53 2.2 0.1 25 15 Water, AHW-ahw Amplitude of Low 0.06 ft 0.27 ft 0.26 ft 95 0.1 0.0 13 0.0 Water, LHW-lhw Time of High 0.0 hr 0.7 hr 0.7 hr 83 2.3 3.5 43 35 Water, THW-thw Time of Low Water, 0.1 hr 0.9 hr 0.9 hr 85 3.7 2.0 70 15 TLW-tlw

Note: Bold values indicated skill assessment criteria were achieved.

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DRAFT Appendix B B.3 Tidal Harmonic Analysis of Water Surface Elevation: Near-Field Model

Table B-33 Near-field Model Tidal Harmonic Analysis: Amplitude at Old Pier, Scappoose Bay – April to June 2011

Measured Predicted Tidal Harmonic Amplitude Amplitude Absolute Error Relative Error Constituent (feet) (feet) (feet) (%) M2 0.75 0.85 0.10 14 S2 0.18 0.20 0.02 11 N2 0.21 0.23 0.02 12 K1 0.42 0.05 0.06 14 M4 0.13 0.15 0.02 12 O1 0.18 0.20 0.02 12

Table B-34 Near-field Model Tidal Harmonic Analysis: Phase at Old Pier, Scappoose Bay – April to June 2011

Tidal Harmonic Measured Phase Predicted Phase Absolute Error Constituent (degrees) (degrees) (degrees) M2 197 205 8 S2 202 213 11 N2 177 185 8 K1 240 243 3 M4 310 324 14 O1 288 284 -4

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DRAFT Appendix B B.4 STATISTICAL ANALYSIS OF WATER SURFACE ELEVATION: NEAR-FIELD MODEL

Table B-35 Near-field Model Statistical Analysis: Old Pier, Scappoose Bay – April to June 2011

CF POF NOF MDPO MDNO SM RMSE SD (%) (%) (%) (hrs) (hrs) Water Level, H-h 0.32 ft 0.33 ft 0.10 ft 100 0.0 0.0 0.0 0.0 Amplitude of High 0.34 ft 0.35 ft 0.08 ft 99 0.0 0.0 0.0 0.0 Water, AHW-ahw Amplitude of Low 0.28 ft 0.30 ft 0.12 ft 100 0.0 0.0 0.0 0.0 Water, LHW-lhw Time of High Water, 0.2 hr 0.4 hr 0.4 hr 76 0.6 0.6 12 9.9 THW-thw Time of Low Water, 0.1 hr 0.4 hr 0.4 hr 84 0.0 0.0 0.0 0.0 TLW-tlw

Note: Bold values indicated skill assessment criteria were achieved.

B.5 STATISTICAL ANALYSIS OF CURRENT VELOCITY: NEAR-FIELD MODEL Skill assessment criteria for current speed were (Hess et al. 2003):

• Central frequency (0.85 feet per second [ft/s]) greater than or equal to 90%;

• Positive outlier frequency (1.7 ft/s) less than or equal to 1%;

• Negative outlier frequency (1.7 ft/s) less than or equal to 1%;

• Maximum duration of positive outliers (1.7 ft/s) less than 24 hours;

• Maximum duration of negative outliers (1.7 ft/s) less than or equal to 24 hours; and

• Worst case outlier frequency (1.7 ft/s) less than or equal to 0.5%.

Skill assessment criteria for amplitudes of high water and low water were (Hess et al. 2003):

• Central frequency (0.85 ft/s) greater than or equal to 90%;

• Positive outlier frequency (1.7 ft/s) less than or equal to 1%;

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DRAFT Appendix B • Negative outlier frequency (1.7 ft/s) less than or equal to 1%;

• Maximum duration of positive outliers (1.7 ft/s) less than 24 hours; and

• Maximum duration of negative outliers (1.7 ft/s) less than or equal to 24 hours.

Skill assessment criteria for times of maximum of flood or ebb were (Hess et al. 2003):

• Central frequency (0.5 hour) greater than or equal to 90%;

• Positive outlier frequency (1 hour) less than or equal to 1%;

• Negative outlier frequency (1 hour) less than or equal to 1%;

• Maximum duration of positive outliers (1 hour) less than 24 hours; and

• Maximum duration of negative outliers (1 hour) less than or equal to 24 hours.

Table B-36 Near-field Model Statistical Analysis: Old Pier, Scappoose Bay – April to June 2011

CF POF NOF MDPO MDNO SM RMSE SD (%) (%) (%) (hrs) (hrs) Amplitude of Maximum Flood 0.26 ft/s 0.30 ft/s 0.16 ft/s 100 0.0 0.0 0.0 0.0 Current, AFC-afc Amplitude of Maximum Ebb -0.06 ft/s 0.08 ft/s 0.06 ft/s 100 0.0 0.0 0.0 0.0 Current, AEC-aec Time of Maximum Flood Current, TFC- -0.3 hr 0.5 hr 0.4 hr 66 0.0 3.5 0.0 13 tfc Time of Maximum Ebb Current, TEC- -0.6 hr 1.6 hr 1.5 hr 40 6.1 29 15 49 tec

Note: Bold values indicated skill assessment criteria were achieved.

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APPENDIX C APPROACH FOR ESTIMATING BED SCOUR DURING HIGH-FLOW EVENTS

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DRAFT Appendix C Laboratory and field studies concerning the resuspension of cohesive sediments have been conducted by many researchers during the last 40 years. This research has resulted in formulations to predict cohesive bed erosion rates or scour depths. Bed properties, principally grain-size distribution and inter-particle cohesion, significantly affect resuspension from a cohesive sediment bed. Increased consolidation with depth in the bed, indicated by a decrease in bed porosity with depth, causes surface sediments to be resuspended more easily than sediments buried deeper in the bed. Bed particle size heterogeneity and consolidation effects cause bed armoring, which results in only a finite amount of sediment being resuspended from a cohesive sediment bed at specific bed shear stress. Cohesive bed armoring has been observed and quantified in various laboratory (Parchure and Mehta 1985; Tsai and Lick 1987; Graham et al. 1992) and field studies (Hawley 1991).

Laboratory research on cohesive sediment erosion (Krone 1962; Parchure and Mehta 1985; Tsai and Lick 1987) demonstrated that the amount of sediment resuspended depends on bed shear stress and the state of bed consolidation, which is indicated by bed porosity. Based upon existing laboratory and field data, the following formulation was developed to calculate the mass of sediment resuspended from a cohesive bed (Gailani et al. 1991):

ε = A [(τ – τcr )/ τcr ]n (C-1)

where ε is resuspension potential (i.e., net mass of resuspended sediment per unit surface

area [milligrams per centimeter; mg/cm]), τ is bed shear stress, τcr is critical bed shear stress, and A and n are Study Area-specific parameters. Typically, the critical bed shear stress for cohesive sediment is 0.1 Pascal (Pa). Bed shear stress was calculated using the quadratic stress law:

τsf = ρw Cf U2 (C-2)

where ρw is the density of water, Cf is the bottom friction coefficient, and U is the magnitude of depth-averaged current velocity. A value of 0.004 for the bottom friction coefficient was used in the sediment stability analysis, which is a typical value for a cohesive sediment bed.

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DRAFT Appendix C The density of water was set at 1 gram per cubic centimeter [g/cm3] (i.e., fresh water). Scour depth was calculated using:

Dscour = ε /(1000 ρdry) (C-3)

where Dscour is scour depth (cm) and ρdry is dry density of cohesive sediment (g/cm3). Due to

lack of Study Area-specific data, ρdry was assumed to be 1 g/cm3 (Ziegler 2002).

After calculating bed shear stress at a specific location in the Study Area, the resuspension potential is calculated using Equation C-1. Ideally, a field study is performed to determine the Study Area -specific values of A and n. Site-specific data on the erosion properties of cohesive sediment within the Study Area were not collected. However, resuspension potential data obtained from studies at other contaminated sediment sites were used to make estimates of these parameters. Values of A and n for eight aquatic systems are listed in Table C-1: Upper Hudson River (QEA 1999); Pawtuxet River, Rhode Island (Ziegler and Nisbet 1994); Watts Bar Reservoir, Tennessee (Ziegler and Nisbet 1995); Upper Mississippi River; Green Bay and Fox River, Wisconsin; Saginaw River, Michigan; and Buffalo River, New York (Lick et al. 1995). Based on these data-based parameter values, the average and 95% confidence interval for the parameter A is 0.21 + 0.20 milligram per square centimeter (mg/cm2). Similarly, the average and 95% confidence interval for the exponent n is 2.6 + 0.3. The upper bound values for A and n (0.41 mg/cm2 and 2.9, respectively) were used to estimate bed scour depths during the high-flow event simulations described in Section 5.3. This assumption produced conservative, upper-bound estimates of bed scour depth, which was calculated using Equation C-3.

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DRAFT Appendix C Table C-1 Study Area-specific Resuspension Potential Parameters

Study Area -specific Constant A Study Location (mg/cm2) Study Area -specific Exponent n Upper Hudson River 0.027 3.0 Pawtuxet River 0.24 2.0 Watts Bar Reservoir 0.10 2.7 Upper Mississippi River 0.11 2.6 Green Bay 0.75 2.3 Fox River 0.34 2.5 Saginaw River 0.053 2.7 Buffalo River 0.081 3.1

Note: mg/cm2 – milligram per square centimeter

Evaluation of Hydrodynamic and Sediment Transport Processes August 2013 St. Helens Fiberboard Plant C-3 100703-01 74275387.1 0015549-00007 Appendix F

Data Overview and Quality

Imagine the result

Kaiser Gypsum Company, Inc., Armstrong World Industries, Inc., and Owens Corning Sales LLC

Appendix F: Data Overview and Quality

Lowland/In-water Remedial Investigation St. Helens Fiberboard Plant

July 2013

Appendix F: Data Overview and Quality

Lowland/In-water Remedial Investigation St. Helens Fiberboard Plant

Prepared for: Kaiser Gypsum Company, Inc., Armstrong World Industries, Inc., and Owens Corning Sales LLC

Prepared by: ARCADIS U.S., Inc. 1100 Olive Way Suite 800 Seattle Washington 98101 Tel 206 325 5254 Fax 206 325 8218

Our Ref.: B0039234.0003.00001

Date: July 2013

This document is intended only for the use of the individual or entity for which it was prepared and may contain information that is privileged, confidential and exempt from disclosure under applicable law. Any dissemination, distribution or copying of this document is strictly prohibited.

Table of Contents

Introduction 1

Lowland/In-Water RI Dataset 1

Data Reduction 2

Treatment of Field Replicate Samples 2

Laboratory Replicate Samples 2

Significant Figures and Rounding 3

Non-detect Results 3

EMPC Laboratory Qualifiers 4

Calculating Totals 4

Calculating Whole-body Fish Tissue Concentrations 7

Data Basis 9

Data Verification/Validation 9

References 10

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Introduction

This Appendix presents an overview of data selected for evaluation in the lowland/in- water Remedial Investigation (RI) dataset, the data reduction steps conducted on the lowland/in-water RI dataset, and the suitability of the selected dataset.

Lowland/In-Water RI Dataset

Various site-specific environmental data have been collected from the lowland/in-water portions of the Site over the past several decades. Samples collected from the lowland/in-water areas were analyzed for a broad range of chemical groups, including metals, semi-volatile organic compounds (SVOCs) including polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), polychlorinated biphenyls (PCBs), total petroleum hydrocarbon (TPH), and dioxins/furans. More recent sampling events have focused the list of chemical groups to include those chemicals that are suspected of being site-related; this focused list of chemicals includes metals (primarily arsenic and mercury) and dioxins/furans. Sampling plans and selected analyte lists for all of the site-specific sampling events were submitted to and approved by the Oregon Department of Environmental Quality (DEQ) prior to sample collection and data analysis.

The lowland/in-water RI dataset includes all data collected since 1990 from within the terrestrial lowland, aquatic lowland, and/or in-water areas from the following types of sampling events:

• Soil/sediment and tissue samples collected under DEQ orders;

• Soil/sediment samples collected by other parties as part of investigations conducted by nearby property owners; and

• Soil/sediment samples collected during additional lowland area investigations, excluding data collected as part of the sawdust pile removal action conducted in 2012.

Sediment and aquatic tissue data collected during these types of sampling events also included data from non-Site areas outside of the in-water area. Appendix I presents all Site and non-Site data by individual sample.

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Data Reduction

Data were compiled into a project database by Maul Foster Alongi (MFA) and were reduced for use in the Lowland/In-Water RI Report by Windward Environmental LLC. Data reduction refers to computational methods used to aggregate the data from the project database for use in the Lowland/In-Water RI Report.

Treatment of Field Replicate Samples

Samples were considered to be field replicate samples if they were collected from the same location and on the same day as a parent sample. Soil/sediment field replicate and parent samples were averaged so that a single result was available for a given location at a given sampling time. In cases where an analyte was detected in either the replicate or the parent sample but not in both, the detected value was reported. In cases where an analyte was not detected in either the replicate or the parent sample, the higher detection limit of the two was used to represent the location averaged result. Detection limits may be reported as the method detection limit (MDL), the estimated detection limit (eMDL), or the estimated detection limit (EDL), depending on the laboratory and analytical method.

Tissue field replicate samples were treated as distinct samples and were not averaged because, although tissue replicate samples were collected from the same location as a parent sample, tissue composite replicate samples represent a different set of organisms.

Laboratory Replicate Samples

Chemical concentrations obtained from the analysis of laboratory duplicate or triplicate samples (two or more analyses on the same sample) are averaged for a closer representation of the “true” concentration as compared to the results of a single analysis. Averaging rules are dependent on whether the individual results are detected concentrations or detection limits (MDLs/eMDLs/EDLs) for undetected analytes. If all concentrations are detects for a given parameter, the values are simply averaged arithmetically. If all concentrations are undetected for a given parameter, the maximum MDL/eMDL/EDL is reported. If the concentrations are a mixture of detected concentrations and MDLs/eMDLs/EDLs, any two or more detected concentrations are averaged arithmetically and MDLs/eMDLs/EDLs are ignored. If there is a single detected concentration and one or more MDLs/eMDLs/EDLs, the detected

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Quality Lowland/In-water Remedial Investigation St. Helens Fiberboard Plant concentration is reported. The latter two rules are applied regardless of whether the MDLs/eMDLs/EDLs are higher or lower than the detected concentration.

Significant Figures and Rounding

The laboratories report results with different numbers of significant figures depending on the instrument, parameter, and the concentration relative to the reporting limit (RL). The reported (or assessed) precision of each observation is explicitly stored in the project database as a record of the number of significant figures assigned by the laboratory.

When a calculation involves addition, such as totaling polycyclic aromatic hydrocarbons (PAHs), the calculation can only be as precise as the least precise number that went into the calculation. For example (assuming two significant figures):

210 + 19 = 229, but this would be reported as 230 because the trailing zero in the number 210 is not significant

When a calculation involves multiplication or division, such as when organic carbon normalizing is used, all significant figures are carried through the calculation, and then the total result are rounded at the end of the calculation to reflect the value used in the calculation with the fewest significant figures. For example:

59.9 x 1.2 = 71.88, to be reported as 72 because there are two significant figures in the number 1.2

When rounding, if the number following the last significant figure is less than 5, the digit will be left unchanged. If the number following the last significant figure is equal to or greater than 5, the digit will be increased by 1.

Non-detect Results

The minimum concentration of an analyte that can be detected is reported as the MDL, eMDL, or the EDL, depending on the laboratory and analytical method.

The MDLs, eMDLs, and EDLs that are reported for each sample are adjusted based on the amount of sample extracted, dilution factors, and percent moisture.

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Detected concentrations above the RL are reported without quantification and detected concentrations between the MDL/eMDL/EDL and the RL are reported with a J qualifier, indicating the concentration is an estimated value. Non-detect values are reported at the MDL/eMDL/EDL.

EMPC Laboratory Qualifiers

Chemical concentrations reported by a laboratory with an EMPC qualifier (estimated maximum possible concentration) are interpreted as detected results with a final data qualifier of J (estimated value).

Calculating Totals

Concentrations for chemical sums were calculated for use in the Lowland/In-Water RI Report as follows:

• Dioxin/furan TEQ – The dioxin/furan toxicity equivalent (TEQ) is a sum of the 17 dioxin and furan congeners weighted based on their toxicity relative to 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) (the most toxic of the congeners). Dioxin/furan TEQ were calculated for each sample as the sum of the concentration for each dioxin/furan congener multiplied by the corresponding toxic equivalency factor (TEF) based on the most current World Health Organization (WHO) consensus TEF values for mammals (EPA 2010); these TEFs for each of the 17 congeners are presented below. TEQs based on mammal TEFs are presented in this Lowland/In-Water RI Report. TEQs based on bird and fish TEFs are presented in the lowland/in-water Ecological Risk Assessment (ERA) (Windward 2013).

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Mammal TEF Congener (unitless) Dioxins/Furans 2,3,7,8-TCDD 1 1,2,3,7,8-PeCDD 1 1,2,3,4,7,8-HxCDD 0.1 1,2,3,6,7,8-HxCDD 0.1 1,2,3,7,8,9-HxCDD 0.1 1,2,3,4,6,7,8-HpCDD 0.01 OCDD 0.0003 2,3,7,8-TCDF 0.1 1,2,3,7,8-PeCDF 0.03 2,3,4,7,8-PeCDF 0.3 1,2,3,4,7,8-HxCDF 0.1 1,2,3,6,7,8-HxCDF 0.1 1,2,3,7,8,9-HxCDF 0.1 2,3,4,6,7,8-HxCDF 0.1 1,2,3,4,6,7,8-HpCDF 0.01 1,2,3,4,7,8,9-HpCDF 0.01 OCDF 0.0003 Notes: HpCDD = heptachlorodibenzo-p-dioxin HpCDF = heptachlorodibenzofuran HxCDD = hexachlorodibenzo-p-dioxin HxCDF = hexachlorodibenzofuran OCDD = octachlorodibenzo-p-dioxin OCDF = octachlorodibenzofuran PeCDD = pentachlorodibenzo-p-dioxin PeCDF = pentachlorodibenzofuran TCDD = tetrachlorodibenzo-p-dioxin TCDF = tetrachlorodibenzoruran

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• Polychlorinated biphenyl (PCB) TEQ - The PCB TEQ is a sum of the 12 dioxin- like PCB congeners weighted based on their toxicity relative to 2,3,7,8-TCDD. PCB TEQ were calculated for each sample as the sum of the concentration for each PCB congener multiplied by the corresponding TEF based on the most current WHO consensus TEF values for mammals (EPA 2010); these TEFs for each of the 12 congeners are presented below. TEQs based on mammal TEFs are presented in this Lowland/In-Water RI Report. TEQs based on bird and fish TEFs are presented in the lowland/in-water ERA (Windward 2013).

Mammal TEF PCB Congener (unitless) PCB 077 0.0001 PCB 081 0.0003 PCB 105 0.00003 PCB 114 0.00003 PCB 118 0.00003 PCB 123 0.00003 PCB 126 0.1 PCB 156 0.00003 PCB 157 0.00003 PCB 167 0.00003 PCB 169 0.03

• Total TEQ – Total TEQ was calculated as the sum of the individual TEQs for either dioxin/furan or PCB.

• Total PCBs – Total PCB congeners were calculated as the sum of the 209 PCB congeners and total PCB Aroclors were calculated as the sum of the individual Aroclors.

• Low-molecular-weight PAHs (LPAHs) – LPAHs were calculated as the sum of naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, and anthracene.

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• High-molecular-weight PAHs (HPAHs) - HPAHs were calculated as the sum of concentrations of fluoranthene, pyrene, benzo(a)anthracene, chrysene, total benzofluoranthenes, benzo(a)pyrene, indeno(1,2,3,-c,d)pyrene, dibenzo(a,h)anthracene, and benzo(g,h,i)perylene.

• Total PAHs - Total PAHs were calculated as the sum of LPAHs and HPAHs.

• Carcinogenic PAHs (cPAHs) –The cPAH value is a sum of the seven cPAHs (i.e., benzo(a)pyrene, benzo(b)fluoranthene, benzo(a)anthracene, benzo(k)fluoranthene, indeno(1,2,3-cd)pyrene, dibenzo(a,h)anthracene, and chrysene) weighted based on their toxicity relative to benzo(a)pyrene (the most toxic of the PAHs). For each sample, the cPAH was calculated as the sum of the concentration of each PAH multiplied by the corresponding TEF. TEF values are from DEQ’s 2010 Human Health Risk Assessment Guidance. The TEFs used to calculate cPAHs are presented below:

cPAH TEF (unitless)

Benzo(a)anthracene 0.1 Benzo(a)pyrene 1 Benzo(b)fluoranthene 0.1 Benzo(g,h,i)perylene 0.01 Benzo(k)fluoranthene 0.01 Chrysene 0.001 Dibenzo(a,h)anthracene 1 Indeno(1,2,3-cd)pyrene 0.1

• Total 4,4′-DDx – Total 4,4′-DDx was calculated as the sum of 4,4′ dichlorodiphenyldichloroethane (DDD); 4,4′ dichlorodiphenyldichloroethylene (DDE); and 4,4′-dichlorodiphenyltrichloroethane (DDT).

For all summing calculations, one half the MDL/eMDL/EDL was used for sum components that were not detected.

Calculating Whole-body Fish Tissue Concentrations

Whole-body smallmouth bass and carp tissue concentrations were calculated as reconstituted whole-body fish samples based on the fraction of the whole-body mass

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Quality Lowland/In-water Remedial Investigation St. Helens Fiberboard Plant represented by the two tissue types (i.e., fillet and carcass). Reconstituted whole-body fish tissue concentrations were calculated using the following equation:1

 W   W   fillet   carcass  WB CC fillet   Ccarcass    WWB   WWB 

Where:

CWB = estimated chemical concentration in whole-body tissue (mg/kg wet weight [ww])

Cfillet = chemical concentration in fillet tissue (mg/kg ww)

Wfillet = average fillet weight (of individual fish included in composite sample)

WWB = average whole-body weight (of individual fish included in composite sample)

Ccarcass = chemical concentration in carcass tissue (mg/kg ww)

Wcarcass = average carcass (non-fillet) weight (of individual fish included in composite sample)

When either the fillet or carcass component was not detected, one-half of that MDL/eMDL/EDL was used to calculate the whole-body concentration. When neither the fillet nor the carcass component concentrations were detected, the range of MDL/eMDL/EDL s was used to represent whole-body concentrations. Details on fillet and carcass weights of carp and smallmouth bass are presented in the Armstrong St. Helens Facility: 2010 Aquatic Biota Tissue Data Report (Windward 2011a) and 2011 Smallmouth Bass Tissue Data Report (Windward 2012).

1 The data rules for estimating whole-body tissue concentrations from fillet and carcass data are presented in the DEQ-approved Revised Sample Analysis and Composite Plan for Biota tissue and Co-Located Sediment from the St. Helens Property and Vicinity (Windward 2011b).

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Data Basis

Sediment and soil data are presented on a dry weight basis. Fish, mammal, and invertebrate tissue data are presented on a wet-weight basis.

Data Verification/Validation

All laboratory data used for the lowland/in-water ERA/RI, including data from third parties (i.e., Pope and Talbot and Boise Cascade data) have undergone QA/QC review and are considered acceptable for use as qualified. Laboratory data were reviewed for the following (as applicable): technical holding time compliance, blank sample contamination, laboratory control sample (LCS) recovery, surrogate and internal standard recoveries, and matrix spike/matrix spike duplicate (MS/MSD) recoveries, and precision. Some more recent data (i.e., all mouse and aquatic tissue data, soil/sediment data co-located with the mouse and aquatic tissue data, and all of the aquatic in-water data collected under DEQ orders) underwent third-party summary validation. Summary data validation included a review of all QC summary forms, including initial calibration, continuing calibration verification, internal standard, surrogate, LCS, laboratory control sample duplicate (LCSD), MS/MSD, certified reference material, and interference check sample summary forms. Details and QA/QC reviews of data from each sampling event presented in Table 4-1 and Table 4-2 of the Lowland/In-Water RI Report are available in specific data reports (Bridgewater 2002, 2004, 2005, 2008a, 2008b, 2011; Weston Solutions 2003; Bridgewater and Kennedy/Jenks 2006; Windward 2011a, 2012; MFA 2010).

Percentile Plots

Soil and sediment data were ranked into percentile ranges and cumulative frequency distributions for three depth intervals: shallow (0 to 1 ft), intermediate (1 to 5 ft), and deep (greater than 5 ft). When there are multiple samples in a given depth interval, the data were averaged for the percentile ranges and cumulative frequency distributions. There are ten locations that have multiple results for a given depth interval (Sed15, Sed17, FOF001-05, FOF003-05, SEA-08, OF3-5, OF3-8, OF3-16, OF3-11, and 4-4).

Statistical Data Summary

Statistical summaries of the data, including the number of detections, the range of detected concentrations, and the reporting limit (RL) or range of RLs were prepared.

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Appendix F: Data Overview and

Quality Lowland/In-water Remedial Investigation St. Helens Fiberboard Plant

The statistical data summaries also include the mean concentration of the detected values. Non-detect results were not included in the mean calculation.

References

Bridgewater. 2002. Phase I remedial investigation (RI) work plan for the Armstrong World Industries St. Helens Facility. Prepared for Armstrong World Industries. Bridgewater Group, Inc., Lake Oswego, OR.

Bridgewater. 2004. Phase II remedial investigation, Armstrong World Industries, St. Helens facility. Prepared for Armstrong World Industries and Kaiser Gypsum Co. Bridgewater Group, Inc., Lake Oswego, OR.

Bridgewater. 2005. Phase III remedial investigation, Armstrong World Industries, St. Helens facility. Prepared for Armstrong World Industries and Kaiser Gypsum Co. Bridgewater Group, Inc., Lake Oswego, OR.

Bridgewater. 2008a. In-water investigation sediment data summary report for the St. Helens Fiberboard Plant site. Prepared for Kaiser Gypsum Company, Inc., Armstrong World Industries, and Owens Corning. Bridgewater Group, Inc., Lake Oswego, OR.

Bridgewater. 2008b. Technical memorandum: Armstrong St. Helens, Oregon facility area 4 soil sampling results - revised. Prepared for Armstrong World Industries. Bridgewater Group, Inc., Lake Oswego, OR.

Bridgewater. 2011. Source control evaluation soil sampling data report. Upland phase 2 supplemental remedial investigation/feasibility study, St. Helens Fiberboard Plant, St. Helens, Oregon. Prepared for Kaiser Gypsum Company, Inc., Armstrong World Industries, and Owens Corning. Bridgewater Group, Inc., Lake Oswego, OR.

Bridgewater and Kennedy/Jenks. 2006. Ecological risk assessment summary report, former Pope & Talbot Wood Treating Site, Port of St. Helens, St. Helens, Oregon. Bridgewater Group, Inc., Lake Oswego, OR and Kennedy/Jenks Consultants, Portland, OR.

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Appendix F: Data Overview and

Quality Lowland/In-water Remedial Investigation St. Helens Fiberboard Plant

Maul Foster Alongi (MFA). 2010. Letter report dated June 29, 2010 to S. Rogan: Surface soil investigation, Amstrong World Industries, Inc., St. Helens, Oregon, facility, DEC ECSI no. 91. Maul Foster Alongi, Vancouver, WA.

United States Environmental Protection Agency (EPA). 2010. Recommended toxicity equivalence factors (TEFs) for human health risk assessments of 2,3,7,8- tetrachlorodibenzo-p-dioxin and dioxin-like compounds. EPA/100/R-10/005. Risk Assessment Forum, US Environmental Protection Agency, Washington, DC.

Windward. 2011a. Armstrong St. Helens facility: 2011 aquatic biota tissue data report. Prepared for Kaiser Gypsum Company, Armstrong World Industries, and Owens Corning. Windward Environmental LLC, Seattle, WA.

Windward. 2011b. Revised sample analysis and composite plan for biota tissue and co-located sediment from the St. Helens property and vicinity. Prepared for Kaiser Gypsum Company, Inc, Armstrong World Industries, and Owens Corning. Windward Environmental LLC, Seattle, WA.

Windward. 2012. 2011 Smallmouth bass tissue data report. Windward Environmental LLC, Seattle, WA.

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Analytical Laboratory Reports

(Provided on CD)