MONITORED NATURAL ATTENUATION DEMONSTRATION

transcript

FINAL REPORT: MONITORED NATURAL ATTENUATION DEMONSTRATION Former Koppers Facility

Wauna, Oregon Prepared for:

Beazer East, Inc. Pittsburgh, Pennsylvania

Georgia-Pacific Consumer Products Atlanta, Georgia

Prepared by:

Amec Foster Wheeler Environment & Infrastructure, Inc. 600 University Street, Suite 600 Seattle, Washington 98101 (206) 342-1760

March 2016

Project No. 0091510120

Amec Foster Wheeler

Project No. 0091510120.MNA i K:\13000\13200\13236\SEA MNA Report\2016 MNA Report.docx

Final Report Monitored Natural Attenuation Demonstration

Former Koppers Facility Wauna, Oregon

Date: March 31, 2016 Project No: 0091510120 This Final Report: Monitored Natural Attenuation Demonstration was prepared by the staff of Amec Foster Wheeler Environment & Infrastructure, Inc., under the supervision of the State of Oregon Registered Geologist whose seal and signature appear hereon. The findings, recommendations, specifications, or professional opinions are presented within the limits described by the client, in accordance with generally accepted professional geology practice. No warranty is expressed or implied. J Stephen Barnett, RG Senior Associate Amec Foster Wheeler Environment & Infrastructure, Inc.

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TABLE OF CONTENTS

1.0 INTRODUCTION ..................................................................................................................... 1 1.1 BACKGROUND ............................................................................................................... 2

2.0 MONITORED NATURAL ATTENUATION MONITORING RESULTS ...................................... 4 2.1 MNA PARAMETER MONITORING RESULTS ....................................................................... 5 2.2 MONITORING RESULTS FOR SITE COCS ......................................................................... 5

3.0 GROUNDWATER MODELING ................................................................................................ 7 3.1 TRANSPORT MODEL METHODOLOGY .............................................................................. 7

3.1.1 Modified Groundwater Flow Model ................................................................... 8 3.1.2 Transport Model Overview ............................................................................... 9

3.2 TRANSPORT MODEL CALIBRATION ................................................................................ 10 3.2.1 Historical Soil Data and the Model Source Term ............................................ 11 3.2.2 Historical Groundwater Data .......................................................................... 12 3.2.3 Groundwater Model Calibration Results ......................................................... 12

3.3 TRANSPORT MODEL PREDICTIONS ................................................................................ 15 3.3.1 Naphthalene Attenuation Predictions.............................................................. 15 3.3.2 Other Site COCs ............................................................................................ 16

4.0 CONCLUSIONS .................................................................................................................... 19

5.0 PROPOSED MNA IMPLEMENTATION ................................................................................. 20 5.1 GROUNDWATER MONITORING AND REPORTING ............................................................. 20 5.2 CONTINGENCY PLAN .................................................................................................... 21

5.2.1 Groundwater Quality Evaluation ..................................................................... 21 5.2.2 Contingent Remedy ........................................................................................ 22 5.2.3 Long-Term Aeration Trench Maintenance ...................................................... 22

6.0 REFERENCES ...................................................................................................................... 23

TABLE OF CONTENTS (Continued)

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TABLES

Table 1 Literature-Reported Attenuation Parameters Table 2 2003 Remedial Investigation Soil Boring Data Table 3 Maximum and Average Constituent of Concern Concentrations Table 4 MT3D Model Inputs for Other Site Constituents of Concern

FIGURES

Figure 1 Site Location Figure 2 Final Remedy Layout Figure 3 Groundwater Flow Model Comparison Figure 4 Approximate Extent of Naphthalene Soil Source Area Figure 5 Naphthalene Source Area Groundwater Concentrations Figure 6 1954 – 2002 Naphthalene Transport Model Calibration Figure 7 ATT-02 Naphthalene Trend Plot Figure 8 Simulated vs. Observed Naphthalene Concentrations 2002 Figure 9 Simulated 2015 Naphthalene Distribution Figure 10 Simulated vs. Observed Naphthalene Concentrations 2005 – 2015 Figure 11 Groundwater Naphthalene Calibration Summary, ATT-05 & ATT-06 Figure 12 Groundwater Naphthalene Calibration Summary, ATT-02, ATT-03, & ATT-04 Figure 13 Historical Naphthalene Flow Path Model Simulation Figure 14 Naphthalene Flow Path Predictions Figure 15 Point of Compliance Predictions – Naphthalene Figure 16 Ethylbenzene and Dibenzofuran Concentration Upgradient of Aeration Trench Figure 17 Fluorene and Phenanthrene Concentration Upgradient of Aeration Trench Figure 18 Residual COC Point Source Areas Figure 19 Ethylbenzene Flow Path Predictions Figure 20 Dibenzofuran Flow Path Predictions Figure 21 Fluorene Flow Path Predictions Figure 22 Phenanthrene Flow Path Predictions

APPENDICES

Appendix A Western Discharge Area Trend Plots Appendix B Supplemental RI Soil Boring Data

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FINAL REPORT: MONITORED NATURAL ATTENUATION DEMONSTRATION

Former Koppers Facility Wauna, Oregon

1.0 INTRODUCTION

On behalf of Beazer East, Inc. and Georgia-Pacific Consumer Products, Amec Foster Wheeler Environment & Infrastructure, Inc. (Amec Foster Wheeler) has prepared this report to present the demonstration of monitored natural attenuation (MNA) at the former Koppers wood treating facility in Wauna, Oregon (the site). The site location map and the site layout are shown in Figures 1 and 2, respectively. Groundwater monitoring and MNA data have been collected since field evaluation of MNA was initiated in February 2011, following Oregon Department of Environmental Quality (DEQ) approval of the MNA Demonstration Work Plan (AMEC Geomatrix, 2010). The objective of the MNA demonstration is to assess the effectiveness of MNA in achieving the groundwater cleanup objective, which is to reduce concentrations of constituents of concern (COCs) at the defined points of compliance (POCs) to below the Oregon Level II Ecological Screening Level Values (SLVs). Two POCs have been defined for the site; one is located east of the contained area and the other west of the aeration trench (Figure 2). MNA has achieved the cleanup objective for the eastern point of compliance since installation of the barrier wall was constructed in 2004/2005.

The final site remedy was implemented in accordance with DEQ Record of Decision ECSI #649. The remedy includes a subsurface barrier wall and aeration trench constructed in 2004/2005 as part of an interim remedial measure, to address contamination within a shallow, perched groundwater unit. The barrier wall redirects groundwater flow from site source areas, primarily to the Western Discharge Area (the area where groundwater flows to the western POC), and a small portion of groundwater flowing to the east through the southeast corner of the contained area (Figure 2). An aeration trench approximately 400 feet in length was constructed at the western end of the contained area; the aeration trench has been actively aerated to support biodegradation of site COCs flowing through the trench to the Western Discharge Area. Site contaminants present in groundwater flowing to the Eastern Discharge Area are remediated by natural attenuation processes. Groundwater monitoring data for the two POCs indicate full compliance with the SLVs since implementation of the interim measure in early 2005.

In order to reduce energy consumption, improve long-term sustainability of the site remedy, and reduce remediation costs, a several-year study was initiated in 2011 to assess the effectiveness of

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MNA for the Western Discharge Area. The MNA Demonstration Work Plan (AMEC Geomatrix, 2010) proposed to study the effectiveness of MNA in the Western Discharge Area by shutting down the southern half of the aeration trench and collecting biological and chemical data to assess natural attenuation of site COCs downgradient of the aeration trench, as well as geochemical parameters throughout the site. The southern half of the aeration trench was shut down in February 2011, following DEQ approval of the MNA Demonstration Work Plan, and has remained shut down ever since. An MNA interim evaluation report, documenting initial results from the MNA demonstration and proposing an extended evaluation period, was submitted to DEQ in December 2012 (AMEC, 2012). Key results from the interim MNA report are summarized in Section 2. MNA data collected during the extended evaluation period are presented and evaluated in this report.

The findings of the five-year evaluation program indicate that MNA would be a viable and effective approach to achieve groundwater remediation objectives for the Western Discharge Area. Recommendations and plans for implementing MNA as the long-term, sustainable remedy for this site are presented in this report.

1.1 BACKGROUND

The site was used by Koppers for preservative treatment of wood, primarily with creosote, from 1936 to 1966. Releases within the former process area contributed to soil and groundwater contamination by creosote. The site COCs are organic compounds that have been grouped into polycyclic aromatic hydrocarbons (PAHs), monoaromatic hydrocarbons, and furans, as follows:

PAHs Monoaromatic Hydrocarbons Furans

Fluoranthene 2-Methylphenol (o-Cresol) Dibenzofuran

Fluorene Pentachlorophenol

Naphthalene bis (2-ethylhexyl) Phthalate (DEHP) Phenanthrene Benzoic acid Ethylbenzene

An interim measure, including a subsurface barrier wall and aeration trench, was implemented in 2005 to redirect groundwater flow from the source areas primarily beneath the pavement cap area (see Figure 2). The barrier wall modified the historical groundwater flow path to the Columbia River, forcing most of the flow to go toward the west around the barrier wall, through the aeration trench. The most recent documentation of groundwater flow patterns for the site will be included in the 2015 Annual

Operations, Maintenance, and Monitoring Report (2015 Annual Report) (Amec Foster Wheeler, 2016). As shown in the 2015 Annual Report, a small portion of groundwater flows from the contained area to the east, ultimately discharging to the Columbia River. Most of the groundwater flows from the contained area to the west, through the aeration trench, then north to the Columbia River, as shown with conservative, non-reactive particle tracking from ATT-05 and ATT-06 (Figure 2). The groundwater discharge area located near the western end of the contained area is designated the Western Discharge Area in this report. Generally, the Western Discharge Area includes the area from the vicinity of wells ATT-05, -06, and -10 to the western POC (Figure 2). The interim measure, which requires routine operation and maintenance (O&M) of the aeration compressor and sparge lines, was incorporated into the final site remedy.

The MNA demonstration was conducted in accordance with the MNA Demonstration Work Plan (AMEC Geomatrix, 2010) and the recommendations presented in the MNA Interim Evaluation (AMEC, 2012). MNA demonstration data collection continued through the end of 2015 (Amec Foster Wheeler, 2016). The laboratory and field MNA data, as presented in the MNA Interim Evaluation and the 2014 Annual Report (Amec Foster Wheeler, 2015), demonstrate that groundwater at the site is generally anaerobic, mildly reducing, and is predominantly under iron-reducing condition; these conditions are fairly uniform over the entire site. Figure 2 shows the final remedy layout, including the aeration trench, the subsurface barrier wall, monitoring wells, and the two POCs. Figure 2 also shows a groundwater flow path between the southern portion of the aeration trench and the Columbia River, and approximate groundwater travel times from well ATT-05, as was included in the MNA Interim Evaluation (AMEC, 2012).

The scope of the MNA demonstration included characterizing the subsurface chemistry, in situ testing to assess biodegradation processes, monitoring site COCs, and long-term evaluation of MNA in the Western Discharge Area with the southern portion of the aeration trench shut down. Characterization of the subsurface geochemistry involved measuring the MNA parameters identified in the work plan within site monitoring wells. In situ biodegradation testing included installing Bio-Trap® samplers (Microbial Insights, Inc., Rockford, Tennessee) in two site wells and subsequently removing them at appropriate intervals for microbiological and chemical analyses. Long-term MNA monitoring included evaluating groundwater quality and COC concentration data along a flow path downgradient of the inactive portion of the aeration trench and upgradient of the Columbia River from April 2011 to October 2015.

This evaluation has determined that MNA will be effective for attaining cleanup levels within the Western Discharge Area at the site. Monitoring data for the southern half of the aeration trench collected over five years have demonstrated that MNA has been effective at reducing COC

concentrations to levels below the SLVs. The site-specific biodegradation rate estimated for naphthalene, coupled with conservative fate and transport modeling for the Western Discharge Area, predicts that naphthalene, the COC that has consistently defined the extent of the groundwater plume at the site, would not exceed the Level II Ecological Screening Levels at the western POC in the absence of the aeration trench. Extrapolation of the site-specific naphthalene data to other site COCs indicates that MNA also would achieve compliance with all site cleanup levels at the western POC without operation of the existing aeration trench. The evaluation supporting these results is presented below.

2.0 MONITORED NATURAL ATTENUATION MONITORING RESULTS

The MNA demonstration has been conducted in accordance with the MNA Demonstration Work Plan and recommendations presented in the MNA Interim Evaluation. This work commenced in October 2010 with collection of baseline data for MNA parameters. In February 2011, the southern portion of the aeration trench was shut down to assess MNA in the southern portion of the Western Discharge Area. The demonstration has included collection of groundwater quality data and COC concentration data within the Western Discharge Area. In addition, Bio-Trap® samplers were placed in monitoring wells in 2011 that used radiocarbon-labeled naphthalene to verify that naphthalene was being mineralized through biodegradation pathways.

The activities completed for the MNA demonstration are listed below in chronological order:

• October 2010 – Baseline MNA parameter sampling and groundwater quality sampling were performed.

• January 23, 2011 – The MNA parameter sampling results were reported to DEQ in a technical memorandum.

• February 3, 2011 – The MNA demonstration was initiated by shutting off the air flow to the southern half of the aeration trench (sparge zones 7–11). The northern half of the aeration trench continued normal operation.

• April 2011 through April 2016 – MNA parameter sampling and groundwater COC sampling were performed each April.

• June 23, 2011 – Bio-Trap® samplers baited with radiocarbon-labeled naphthalene were deployed in wells ATT-05 and ATT-06. Three Bio-Trap® samplers were stacked vertically in the water column in each of these two wells.

• July 2011 – MNA parameter sampling was performed on July 18, 2011. One Bio-Trap® sampler was removed from each well on July 20, 2011 (after 27 days in the wells) and sent to the laboratory for analysis.

• September 27, 2011 – A second Bio-Trap® sampler was removed from each well (after 96 days in the wells) and sent to the laboratory for analysis.

• October 2011 through October 2014 – MNA parameter sampling and groundwater COC sampling were performed each October.

• December 13, 2011 – The last Bio-Trap® sampler was removed from each well (after 173 days in the wells) and sent to the laboratory for analysis.

• January 26, 2012 – MNA parameter sampling was performed.

2.1 MNA PARAMETER MONITORING RESULTS

The results from monitoring MNA parameters and site COCs are presented in the 2015 Annual Report (Amec Foster Wheeler, 2016). Monitoring data collected prior to 2015 are included in Appendices E and F of the 2015 Annual Report. The results for MNA monitoring show that geochemical conditions are uniform across the site and are conducive to in situ biodegradation of the following site COCs, which are present in the Western Discharge Area:

• Dissolved oxygen (DO) and oxidation/reduction potential (ORP) data suggest that site groundwater is generally anaerobic and mildly reducing, except in areas affected by aeration within the aeration trench.

• Anion and cation concentrations suggest that site groundwater is predominantly iron-reducing.

• Groundwater temperature and pH are within ranges appropriate for favorable microbial activity.

• The stoichiometric ratio of nutrients (nitrogen and phosphorus) to carbon in groundwater indicate that site groundwater is not nutrient limited and will support microbial activity.

2.2 MONITORING RESULTS FOR SITE COCS

An evaluation of groundwater monitoring results for site COCs over the past 11 years is presented in the 2015 Annual Report, including long-term trend charts for several COCs. These data show that groundwater at the two site POCs has been in full compliance with the Level II SLVs since construction of the interim measure was completed in 2005. Site monitoring wells are currently sampled semiannually and analyzed for site COCs; monitoring has been performed regularly since 2005. A discussion of monitoring results and trends is included in the 2015 Annual Report.

Groundwater quality immediately upgradient of the aeration trench is reflected by the monitoring data for wells ATT-05, -06, and -10 (see Figure 2 for well locations). The area immediately downgradient of the aeration trench is reflected by data from wells ATT-01, -02, -03, and -04; the northern portion of

the Western Discharge Area, where aeration in the trench has been maintained, is monitored by wells ATT-03 and -04, while the southern portion, where aeration has been shut down since February 2011, is monitored by wells ATT-01 and -02. Thus, monitoring data from wells ATT-01 and -02 reflects passive conditions and the effects of natural attenuation. The portions of the Western Discharge Area that are further downgradient, including the western POC, are monitored by wells ATT-11, ATT-12, and PMW-7R (replacement well for PMW-7). As noted in the 2014 Annual Report (Amec Foster Wheeler, 2015), monitoring data for naphthalene show substantial attenuation along the flow path passing near wells ATT-05, -02, -11, and -12.

Trend plots for selected COCs in the Western Discharge Area from the 2015 Annual Report are included as Appendix A to this report. Figures A1–A3 present trend charts for naphthalene in wells located upgradient of the aeration trench (Figure A1) and in the area downgradient of the aeration trench (Figures A2 and A3). Data for wells ATT-01 and -02, which are located in the southern portion of the Western Discharge Area, are plotted separately from the other downgradient wells due to the higher naphthalene concentrations in the southern area wells (Figure A2). Trend charts for the other COCs frequently detected above reporting limits in Western Discharge Area wells are presented in Figures A4–A7.

Figures A1, A4, A5, and A6 show trends for site COCs in the wells located just upgradient of the aeration trench. These wells monitor groundwater quality that flows from the contained area to the Western Discharge Area. Naphthalene concentrations in well ATT-05 are substantially higher than for wells ATT-06 and -10 (Figure A1). Similar results are generally seen for the other COCs plotted in Figures A4, A5, and A6. These results demonstrate that the flow path along wells ATT-05, -02, -11, and -12 provide a good basis for assessment of MNA for the Western Discharge Area. The data plotted in Figures A2 and A3 show that naphthalene began migrating into the Western Discharge Area after shutdown of the aeration trench, and that naphthalene attenuated as groundwater flowed toward the river. The naphthalene data plotted for ATT-06 and ATT-10 in Figure A1 show a generally decreasing trend. Monitoring results for ATT-06, located upgradient of the northern, aerated portion of the trench, has been well below the Level II SLV of 620 micrograms per liter (µg/L) since April 2011 and has only exceeded the SLV once since April 2008. The Figure A5 data show that other COCs detected in ATT-06 are either decreasing or remaining fairly constant. The data included in the 2015 Annual Report show that the only COC regularly detected in well ATT-06 at concentrations above the Level II SLVs is fluorene; however, fluorene concentrations are gradually decreasing in this well, with concentrations approximately twice the Level II SLV of 3.9 µg/L during the past two years (Figure A5). These data show that site COCs upgradient of the northern portion of the aeration trench require only moderate attenuation to achieve the Level II SLVs.

The data plotted in Figure A1 show that in late 2015 naphthalene increased substantially in well ATT-05, which is located upgradient of the southern portion of the aeration trench. Similar results were seen for the other site COCs in ATT-05 (Figure A4). The reason for these increases is not known, as no unusual activities have been conducted at the site. However, they may be related to the extended period of below-average rainfall measured in Clatskanie from November 2014 through October 2015 (http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?or1643). Due to the increase in COC concentrations upgradient of the Western Discharge Area, these concentrations were considered in the fate and transport modeling discussed in Section 3.0.

3.0 GROUNDWATER MODELING

To support the evaluation of natural attenuation for the site, chemical fate and transport modeling (henceforth referred to as the transport model) was used to analyze the extent of natural attenuation that is occurring within the Western Discharge Area downgradient of the southern portion of the aeration trench. The transport model was also used to assess the future effectiveness of MNA, assuming shutdown of aeration throughout the aeration trench beginning in early 2016. The transport model was developed using historical contaminant data presented in the Supplemental Remedial Investigation (RI) Report (CH2MHILL, 2003) and semi-annual monitoring results presented in the 2015 Annual Report (Amec Foster Wheeler, 2016). The transport model was an MT3D model coupled with a modified version of the MODFLOW groundwater flow model that was used in the 2009 Feasibility Study (FS) (Bridgewater, 2009).

Historical and recent groundwater monitoring data were used to assess the natural attenuation in the model. Soil and groundwater data collected prior to the installation of the barrier wall were used to establish initial conditions for the transport model. Data collected after the barrier wall and aeration trench were installed and placed in full operation, as well as monitoring data collected following shutdown of the southern half of the aeration trench, were used for transport model calibration. As part of transport model calibration, site-specific first order biodegradation rates and site-specific retardation coefficient rates for the appropriate site COCs were estimated. The calibrated transport model was then used to predict future COC concentrations in the Western Discharge Area, assuming permanent shutdown of aeration in the aeration trench. A conservative approach was followed in estimating biodegradation and retarding parameters for the calibrated transport model, and the results were used to make a recommendation based on the modeled effectiveness of MNA for the site.

3.1 TRANSPORT MODEL METHODOLOGY

Model calibration and predictions were performed in several steps to ensure that the transport model could adequately predict the fate and transport of site COCs. Naphthalene was selected as the COC

for transport model calibration, based on its history of higher mobility relative to other site COCs, and its use to assess biodegradation as part of the MNA evaluation. Additionally, naphthalene is generally present at higher concentrations in groundwater relative to the other site COCs, and has historically defined the areal extent of site groundwater contamination. Development of the transport model consisted of the following steps:

1. The existing, calibrated MODFLOW groundwater flow model for the 2009 FS (Bridgewater Group, 2009) was used as the starting point for the transport model.

2. The chemical fate and transport model MT3D was used in conjunction with the 2009 MODFLOW model to simulate COC transport and to estimate site-specific biological degradation rates and retardation coefficients for naphthalene.

3. The conceptual site model and remedial investigation data, as presented in the Supplemental RI (CH2MHILL, 2003) were used for model calibration.

4. Modelling was performed assuming the initial release event occurred around 1954 (the year when Koppers Company, Inc. began leasing the property and began using the property for wood treating operations).

5. The transport model was calibrated with a defined source area and period of releases that match RI data, which was collected primarily at the end of 2001.

6. Groundwater quality data from the period following barrier wall construction, as well as after the period of natural attenuation following shutdown of the southern half of the aeration trench (Amec Foster Wheeler, 2016), was used to calibrate the transport model.

7. The calibrated transport model was used to predict future concentrations in the Western Discharge Area following complete aeration shutdown in the aeration trench. Predicted COCs in the Western Discharge Area include naphthalene and several other COCs that have been detected at concentrations exceeding their respective SLVs in the area immediately upgradient of the aeration trench (i.e., in wells ATT-05 and ATT-06) during the past four years.

3.1.1 Modified Groundwater Flow Model As part of the 2009 FS (Bridgewater, 2009), a steady-state MODFLOW groundwater flow model that included a surface drain feature was developed and used for the site. The MODFLOW groundwater model that was used in the FS and as a starting place for the transport model uses long term average rainfall in simulating groundwater flow. While using the surface drain feature is an acceptable practice for groundwater flow modeling, it may create issues related to removal of COC mass when conducting contaminant transport modeling. The groundwater flow model from the FS was modified for the purposes of the contaminant fate and transport modeling by removing the site-wide drain used in the 2009 FS modeling; surface water interactions in the modified flow model were limited to discharge to the slough in the southwestern portion of the site, where water is channelized and drained to the river. The modified MODFLOW groundwater flow model was recalibrated to the observed pre-trench (2004)

groundwater elevations by modifying the areal recharge rate and hydraulic conductivity distribution in the subsurface, using the MODFLOW toolkit Modular Groundwater Optimizer. The hydraulic conductivity and effective porosity used in the calibrated transport model was the same as was used in the 2009 groundwater flow model. The hydraulic conductivity was 55 feet/day and the effective porosity was 0.25, as described in the 2009 FS.

The 2009 model was originally calibrated using groundwater elevation data collected in 2004, prior to construction of the barrier wall and aeration trench. The modified/re-calibrated model was also calibrated using the 2004 groundwater elevation measurements. The 2009 model was previously run to predict groundwater elevations with the barrier wall and aeration trench in place. The two model outputs were compared after adding the barrier wall and aeration trench to the modified/recalibrated model. The 2009 model output and the modified/recalibrated model output are presented in Figure 3, along with groundwater contours prepared from the outputs from the two models. The predicted groundwater contour outputs from the two models compare favorably within the contained area and the Western Discharge Area. Minor differences are noted in the area west of the Western Discharge Area. The particle tracks from the two models using the same particle starting locations are also compared in Figure 3; the particle tracks show very similar results. In general, the modified/recalibrated model shows a slightly steeper gradient in the immediate vicinity of the riverbank. Based on this comparison, the modified/recalibrated groundwater model was considered acceptable for use in contaminant transport modeling.

3.1.2 Transport Model Overview The transport model used the contaminant fate and transport MT3D model in conjunction with the modified/recalibrated MODFLOW groundwater flow model described in Section 3.1.1. The MT3D model uses the MODFLOW groundwater flow model that assumes a single layer, variable thickness flow unit based on site surface topography and a constant flat bottom, which acts as a no-flow boundary, consistent with the groundwater flow model discussed in the 2009 FS. The transport model was calibrated using data for naphthalene. The calibrated transport model was then used to predict fate and transport for other site COCs with recent detections (i.e., within the past four years) at or above the Level II SLVs in the area immediately upgradient of the aeration trench.

MT3D allows for complexity to be incorporated into the transport model. This capability was necessary due to the effects of the barrier wall and aeration trench on groundwater flow, the variable effects of aerobic biodegradation in the aeration trench, and intrinsic biodegradation in the Western Discharge Area. The transport model was calibrated as described in Section 3.2 to duplicate observed naphthalene concentrations measured during the RI, prior to construction of the barrier wall and aeration trench, which were completed in 2005. Both these features induced significant changes to

groundwater flow (direction and velocity) and the aeration trench induced increased biodegradation rates of site COCs due to creating an aerobic treatment zone in the vicinity of the aeration trench. The transport model, calibrated to initial conditions (i.e., pre-barrier wall and aeration trench), was then run to reproduce naphthalene concentrations following startup of the aeration trench and shutdown of the southern portion of the trench in 2011. Results and methodology are discussed below. The naphthalene concentrations in the Western Discharge Area following shutdown of the southern portion of the aeration trench were used to estimate the site-specific degradation rate and retardation factor by adjusting these parameters to measured concentrations in the Western Discharge Area.

For modeling fate and transport of the other COCs, it was assumed that the site-specific retardation parameters and degradation rate constants would compare to literature data similar to the way naphthalene parameters compared to literature data (i.e., the ratio of the site-specific parameters for naphthalene to literature data would be the same for other site COCs). Based on the estimated site-specific retardation parameters and degradation rate constant for naphthalene, site-specific parameters were estimated for other site COCs as follows:

• The site-specific retardation fraction was calculated by dividing the site-specific value of the organic carbon partitioning coefficient (Koc) for naphthalene by the literature Koc value for naphthalene presented in Table 1.

• The site-specific value of Koc for other COCs were calculated by multiplying the literature value for each constituent presented in Table 1 by the site-specific retardation fraction calculated for naphthalene.

• The site-specific degradation fraction was calculated by dividing the site-specific degradation rate estimated by modeling naphthalene by the average naphthalene first order degradation rate constant presented in Table 1.

• The site-specific degradation rate constants for other COCs were calculated by multiplying the average degradation rate constants in Table 1 by the site-specific degradation fraction.

The results of the transport model calibration and parameter estimation are described below.

3.2 TRANSPORT MODEL CALIBRATION

The transport model was calibrated using naphthalene groundwater monitoring data. As described in Section 3.1, the calibrated transport model was used to estimate the site-specific retardation factor and site-specific degradation rate for naphthalene, which were then used to proportion the Koc partitioning coefficients and degradation rates for other site COCs to be representative of site specific conditions. Model calibration using naphthalene was performed by comparing model-predicted

groundwater concentrations from several groundwater monitoring locations to data presented in the 2003 Supplemental RI and 2005–2015 groundwater data presented in the 2015 Annual Report.

3.2.1 Historical Soil Data and the Model Source Term The areal extent of the source area used in the transport model was based on soil boring data presented in the 2003 Supplemental RI. The boring locations generally had multiple soil samples collected across a 2.5–12.5 foot depth. The soil boring data for the area beneath and adjacent to the pavement cap area shown on Figure 2 is provided in Appendix B. For those soil boring locations with multiple soil sample results, the results were averaged (Table 2). In general, boring locations with average soil sample results greater than 10 milligrams per kilogram (mg/kg) were used to delineate the areal extent of the soil source area for the transport model. Figure 4 shows the approximate areal extent of the naphthalene soil source area used in the model. The naphthalene soil source area is primarily contained within the pavement cap area and is located in the vicinity of PMW-05.

For modeling purposes, the transport model defined the source area (i.e., the area delineated in Figure 4) as a groundwater source with the groundwater concentration defined based on historical groundwater data in the vicinity of the source area and assuming a maximum groundwater concentration equal to the water solubility for naphthalene presented in Table 1 (i.e., assuming groundwater in the source area was saturated). The source area groundwater concentration was developed by evaluating historical site operations and data from the source area well PMW-05 and groundwater samples collected adjacent to PMW-05, as presented in the 2003 Supplemental RI (CH2MHILL, 2003).

The source term as used in the model is a groundwater concentration that is a function of time and chemical properties of naphthalene. For transport modeling purposes, it was conservatively assumed that releases began shortly after wood treating operations commenced and that groundwater within the source area became saturated with naphthalene. The maximum solubility of naphthalene is reported as 31 milligrams per liter (mg/L) (Table 1). The assumed groundwater source area concentrations are shown as a function of time on Figure 5, and consist of the following segments:

• The period from 1954 to 1958 was an assumed release period in which groundwater became saturated with naphthalene due to releases from wood treating operations that began in 1954. The concentration ramp-up was assumed to be linear and increases to the maximum solubility of naphthalene (31 mg/L).

• The period from 1958 to 1975 was assumed to be a period of constant naphthalene concentration in groundwater at the solubility limit (31 mg/L). Extrapolating the linear trend developed from groundwater source area data from 1998 and 2001 that were presented in

the 2003 Supplemental RI showed that 1975 was the year concentrations began to decline.

• The period from 1975 to 2004 shows source area groundwater concentrations declining to match sampling data presented in the 2003 Supplemental RI report for well PMW-05 and groundwater collected from soil boring locations B-1, B-2, and B-3 (Figure 4) in 1998. It is assumed that the decay rate of the groundwater source term was linear.

• The rapid increase in naphthalene concentrations in PMW-5 after barrier wall installation (assumed to be one year, from January 2004 to January 2005) shows the change in source area concentrations observed after the barrier wall significantly altered groundwater flow in the vicinity of PMW-5.

• A linear source area decay period from 2005 to 2015 was based on PMW-05 groundwater data collected after the barrier wall was installed. The use of a linear decay function during this period provides a slightly more conservative estimate of source area groundwater concentrations than an exponential fit would provide.

• The groundwater source term decay after 2015 was estimated as an exponential decay with a half-life of approximately 6.3 years, based on an exponential curve fit to the PMW-05 groundwater data collected between 2005 and 2010. The exponential function was used after 2015 to provide a more conservative estimate of the groundwater source area concentrations.

The source area groundwater concentrations shown in Figure 5 were used to calibrate the transport model.

3.2.2 Historical Groundwater Data Naphthalene concentrations from groundwater collected from the PMW monitoring wells, as presented in the 2003 Supplemental RI (generally from May 2001 through January 2002), were used to calibrate the transport model for pre-barrier wall conditions. Figure 6 shows a naphthalene plume map from the 2003 Supplemental RI compared to transport model calibration results. (See Section 3.2.3 for further discussion.)

Groundwater data were collected after barrier wall and aeration trench construction - from June 2005 up through October 2015, the most recent monitoring event at the time the model was calibrated. Results for groundwater monitoring data are included in the 2015 Annual Report. These results were also used to assess transport model calibration, as discussed in Section 3.2.3.

3.2.3 Groundwater Model Calibration Results The groundwater model for naphthalene used a longitudinal dispersivity of 50 feet, based on the observed plume length from PMW-05 to the Columbia River to the north. A bulk density of 115 pounds/cubic foot was used for the poorly graded sand. In order to estimate a site-specific Koc for

naphthalene using the transport model, the retardation factor was estimated using data from ATT-02, given the proximity of this monitoring well to the upgradient aeration trench. ATT-02 was used to assess the approximate time it took for the first groundwater concentration spike for naphthalene to travel from the aeration trench to ATT-02 after the southern half of the aeration trench was shut down.

Based on groundwater flow modeling results presented in the 2009 FS, groundwater would take approximately one year to travel from ATT-05 to a location slightly south of ATT-02 (Figure 2). During active operation of the southern portion of the trench, naphthalene was detected only at very low levels in ATT-02. According to Figure 7, a trend plot for ATT-02 monitoring results reproduced from data presented in the 2015 Annual Report, it appears that it took approximately 268 days for the first spike in naphthalene concentration, which occurred during the October 2011 monitoring event (10/27/2011), to be observed in groundwater from ATT-02. . The model predicts that it would take a conservative tracer approximately 75 days to travel the same distance, which implies that the retardation factor (R) for naphthalene is approximately 3.5 (i.e., the ratio of the time it took for naphthalene to travel from the aeration trench to ATT-02 and the time it would take a conservative tracer to travel from the aeration trench to ATT-02). Based on these observations, this retardation factor was used in the model for naphthalene. The value of Koc associated with this value of R is significantly lower than literature values, indicating that the site COCs appear to be highly mobile. The use of a lower Koc value in the transport model is conservative, as it results in a larger contaminant travel velocity compared to the literature value in Table 1. The increase in contaminant velocity results in less time for groundwater naphthalene attenuation in the model.

Groundwater calibration results are separated into two individual periods. The first period is the historical time period between the initial assumed contaminant releases between 1954 and 1958 (CH2MHILL, 2003) the period where the RI groundwater data were collected, around the end of 2001. The transport model results for January 2002 were compared to the data presented in the 2003 Supplemental RI for naphthalene to determine if the model was properly calibrated. The model results were deemed acceptable if the scaled root mean square (RMS) error between the groundwater observations and the transport model predictions was less than 10 percent. This was achieved using a naphthalene retardation factor of 3.5 and a half-life of 1,600 days (corresponding to a degradation rate of approximately 0.16 year-1). The transport model results using a retardation factor of 3.5 and a half-life of 1,600 days match the RI groundwater observations with reasonable accuracy. A good linear fit of the simulated naphthalene concentrations versus the observed groundwater naphthalene concentrations was based on 12 data points, as shown in Figure 8. Figure 6 compares the groundwater plume distribution map presented in the 2003 Supplemental RI for naphthalene to the transport model simulations; the predicted naphthalene distribution compares favorably to the observed distribution.

Given that the model was able to simulate groundwater naphthalene concentrations from 2002 with reasonable accuracy, the model was run through 2015 to evaluate the model’s ability to simulate naphthalene concentrations from groundwater monitoring results during the period after barrier wall construction and operation of the aeration trench (between 2005 and 2015). In order to address changes in the groundwater flow conditions, the model was run without the barrier wall until the end of 2004 and the predicted distribution of naphthalene groundwater concentrations for the end of 2004 were used as initial conditions for modeling with the barrier wall installed and the entire aeration trench in operation at the beginning of 2005. Naphthalene within the aeration trench was assigned a half-life of 0.1 day with a 10-foot thickness and a hydraulic conductivity of 55 feet per day (corresponding to a gravel unit). The small half-life was used to support rapid biodegradation within the aeration trench. The model was then run from 2005 until 2011 with the entire aeration trench active. In 2011 the southern portion of the aeration trench was shut off in the model and the model was run from 2011 up through the end of 2015. A 2015 groundwater naphthalene plume distribution map from the transport model output is shown in Figure 9 and a summary of the simulated naphthalene concentrations versus the observed groundwater naphthalene concentrations is shown in Figure 10. The model simulation results matched observed naphthalene concentrations, as indicated by the linear correlation coefficient (more than 90 percent) and the RMS error (less than 10 percent) shown on Figure 10.

Groundwater monitoring data trend plots for ATT-05 and ATT-06 are compared to model simulation results on Figure 11. As shown in Figure 11, the model simulation provided a good match to mean naphthalene concentrations in the two wells immediately upgradient of the aeration trench. The model tended to under-predict peak concentrations for well ATT-05 and conservatively over-predicted peak concentrations for well ATT-06, which is located closer to the river. Figure 12 shows groundwater monitoring trend plots for the monitoring wells immediately downgradient of the aeration trench (ATT-02, ATT-03, and ATT-04) and compares the trend plots to transport model simulation results. Figure 12 shows that the model did well simulating concentrations in these three wells. The model under-predicted peak concentrations in ATT-02 (furthest from the river) and conservatively over-predicted naphthalene concentrations in ATT-03 and ATT-04, with the exception of the October 2015 groundwater monitoring result for ATT-04. ATT-03 and ATT-04 are closer to the river then ATT-02.

As noted previously and shown on Figure 2, groundwater in the southern portion of the aeration trench generally flows from ATT-05 to ATT-07 to ATT-02 to ATT-11, and finally to ATT-12 prior to discharge to the Columbia River. Groundwater in the northern portion of the aeration trench flows generally from ATT-06 to ATT-08 to ATT-03 to PMW-07/07R prior to discharge to the Columbia River. The model simulations for naphthalene in wells along both of these flow paths from 2004 through January 2016 are shown on Figure 13. Comparison of the plots shown on Figure 13 and Figures A1

to A3 in Appendix A show that the calibrated model tends to under-predict concentrations in the southern flow path and to over-predict concentrations in the northern flow path. Since the calibrated model predicted conservative results in the area closest to the river, the calibration was accepted for use in simulating natural attenuation in the absence of aeration in the trench.

3.3 TRANSPORT MODEL PREDICTIONS

The calibrated transport model results indicate that the transport model simulations for naphthalene groundwater concentrations throughout the area upgradient of the aeration trench are good. As discussed in Section 3.2, the calibrated transport model was, in general, predicting conservatively for groundwater in the Western Discharge Area. Using the calibrated transport model, simulations were performed to evaluate naphthalene attenuation in the Western Discharge Area without the active aeration in the trench. In addition, model results for naphthalene were used to extrapolate naphthalene attenuation to other site COCs, as discussed in Section 3.1.2. Model predictions for naphthalene are presented in Section 3.3.1 and the results from extrapolation to other COCs are presented in Section 3.3.2.

3.3.1 Naphthalene Attenuation Predictions The transport model was used to simulate natural attenuation of naphthalene concentrations in the Western Discharge Area in the absence of active aeration in the trench. This was performed by changing the degradation rate in the aeration trench to be consistent with the plume-wide degradation rate (a half-life of 1,600 days). As discussed in Section 3.2.1, the groundwater concentration in the source area was given a decay half-life of 6.3 years to provide a conservative estimate of the groundwater concentrations in the source area. The modeled source area groundwater concentrations from 2016 through the end of the prediction period (2046) are shown on Figure 5 and were discussed in Section 3.2.1.

As noted in the trend plot presented in Figures A1–A3 in Appendix A and Figure 11, ATT-05 had a substantial increase in naphthalene concentration in October 2015, increasing from a non-detection result in April 2015 up to 2,000 μg/L in October 2015. As noted above, the calibrated model tended to under-predict naphthalene concentrations in the southern portion of the Western Discharge Area. As discussed in the 2015 Annual Report, this increase was attributed to lower than average rainfall in the months preceding the October 2015 sample collection event. To conservatively evaluate attenuation in the southern portion of the Western Discharge Area, the maximum groundwater concentration that has been observed in ATT-05 over the past four years was simulated as a point source located at ATT-05 in the beginning of 2016. The point source was given an area of approximately 60 feet by 60 feet around ATT-05 and a concentration of 2,000 μg/L. The simulation was then run with the

calibrated transport model, including a source decay for naphthalene adjacent to PMW-05 based on a half-life of 1,600 days, consistent with the site-wide half-life for naphthalene.

Figure 14a shows the model prediction results for natural attenuation of naphthalene in the Western Discharge Area from 2016 through 2044 for the groundwater monitoring wells along the southern flow path (ATT-05, ATT-07, ATT-02, ATT-11, and ATT-12). The simulated results are compared to the Level II SLV for naphthalene (620 μg/L). As shown on Figure 14a, based on an initial concentration of 2,000 µg/L for ATT-05, the naphthalene concentration is predicted to attenuate to well below the Level II SLV prior to reaching the POC. This prediction is consistent with observations of naphthalene collected in the Western Discharge Area after shutting down the southern portion of the aeration trench in early 2011.

Figure 14b shows the model simulation results for naphthalene from 2016 through 2044 for the groundwater monitoring wells along the northern flow path (ATT-06, ATT-08, ATT-03, ATT-04, and PMW-07). The simulated results are also compared to the SLV for naphthalene (620 μg/L). As noted above, the calibrated model predicted conservatively high concentrations in the northern portion of the Western Discharge Area. The model predictions on Figure 14b show effective attenuation of naphthalene in the northern portion of the Western Discharge Area. The model simulation predicts that the highest observed groundwater concentrations for the wells immediately downgradient of the inactive aeration trench are 14.8 μg/L for ATT-03 in mid-2018 and 0.3 μg/L for ATT-04 in the end of 2017.

Figure 15 shows the groundwater monitoring wells along the POC for the Western Discharge Area. Following complete shutdown of aeration in the trench, the model predicts that the highest concentration that would be observed along the POC would be at the location for former well PMW-07, and that all POC wells would be well below the Level II SLV for naphthalene. The concentrations for naphthalene in the Western Discharge Area POC are predicted to comply with the cleanup goals under natural attenuation conditions. The model predicts that the maximum concentration in PMW-07 would be 40.3 μg/L in the end of 2018, less than 7 percent of the SLV for naphthalene.

3.3.2 Other Site COCs The transport model was also used to predict Western Discharge Area concentrations for other site COCs under natural attenuation conditions. Table 3 summarizes the maximum and average concentrations for site COCs in the groundwater monitoring wells immediately upgradient of the aeration trench (i.e., ATT-05, ATT-06, and ATT-10). The data presented in Table 3 are based on groundwater monitoring results from April 2011 through October 2015. Based on these data, only ethylbenzene, naphthalene, dibenzofuran, fluorene, and phenanthrene have been detected above

their respective SLVs since 2011. Since the other COCs were in compliance with the Level II SLVs upgradient of the aeration trench, only ethylbenzene, naphthalene, dibenzofuran, fluorene, and phenanthrene were evaluated for natural attenuation in the Western Discharge Area using the transport model.

Figure 16 shows trend plots for groundwater monitoring results for ethylbenzene (Figure 16a) and dibenzofuran (Figure 16b) from April 2011 through October 2015, compared to their respective Level II SLVs. Figure 17 shows similar trend plots for fluorene (Figure 17a) and phenanthrene (Figure 17b) compared to their respective SLVs. Figures 16 and 17 show that all COCs appear to be generally exhibiting a constant or declining trend in the area upgradient of the trench. The most recent data for ATT-05 (October 2015) appears anomalously high and may indicate a change in the historical trend; however, it is likely that the unusually high result may be related to an extended period of lower-than-average rainfall and related lower groundwater flows. These figures show that COC concentrations in ATT-05 are generally higher than in the other two wells, and that fluorene concentrations (Figure 17a) are uniformly above its Level II SLV upgradient of the aeration trench.

To conservatively assess natural attenuation of these COCs and to account for potential spikes in groundwater concentrations upgradient of the trench, the maximum concentration listed in Table 3 for each COC in ATT-05 and ATT-06 were established as a point source in the transport model. A 60-foot by 60-foot source area was assigned around these two wells for the transport model, as shown on Figure 18.

To evaluate natural attenuation of these COCs, the site-specific Koc and the site-specific degradation rate constants were estimated as discussed in Section 3.1.2 and as shown on Table 4. The retardation rate for naphthalene was determined to be 3.5, as discussed in Section 3.2.3. Based on a soil bulk density and an effective porosity of 1.85 kilograms per liter (kg/L) and 0.25 kg/L, respectively, and a fraction of organic carbon of 0.003 kilograms per kilogram (provided in the 2009 FS), the Koc was calculated to be 113 liters per kilogram (L/kg) or 12.6 percent of the reported Koc value from Table 1 (891 L/kg). The reported Koc value for each COC presented on Table 1 was than proportioned by 12.6 percent, and the resulting retardation factor was calculated (Table 4). The same methodology was used for the site-specific degradation rate. A half-life of 1,600 days corresponds to a site-specific degradation rate of 4.3x10-4 day-1, or approximately 0.1 percent of the average value reported in Table 1. The percentage was then used to proportion the average degradation rates reported in Table 1 for the other COCs in order to determine a conservative site-specific degradation rate for each of the other COCs. The model input parameters for the retardation factor calculation and the site-specific degradation rates/half-lives are presented in the footnotes to Table 4. Table 4 also shows the point source concentrations placed by ATT-05 and ATT-06 for each COC. The point source concentrations

were taken to be the maximum groundwater concentration for each COC observed at AT-05 and ATT-06 (Table 3).

Figure 19 shows the model predictions for ethylbenzene along the southern groundwater flow path (from ATT-05 to ATT-12) and the northern groundwater flow path (from ATT-06 to PMW-07). As expected, the model predicts that ethylbenzene migrates fairly quickly, as shown by the minimal lag between predicted groundwater concentration spikes in downgradient wells, but ethylbenzene also attenuates rapidly, as indicated by the reduction in predicted peak concentrations in downgradient wells. The transport model prediction indicates that the maximum concentration at ATT-11 would be approximately 1.3 μg/L, or about 18 percent of the SLV of 7.3 μg/L for ethylbenzene. The model prediction indicates that the maximum concentration for ATT-03 would be approximately 1.5 μg/L, or about 20 percent of the SLV for ethylbenzene. The predicted concentrations at the POC wells (i.e., ATT-12, PMW-07, and ATT-04) are all well below the SLV for ethylbenzene under natural attenuation conditions.

Figure 20 shows the model predicted concentrations for dibenzofuran in the Western Discharge Area along the southern groundwater flow path (from ATT-05 to ATT-12) and the northern groundwater flow path (from ATT-06 to PMW-07). These results predict that dibenzofuran migrates much slower, as indicated by the longer lag between predicted maximum concentration spikes in downgradient wells and the extended tailing of the concentration decline. The transport model predicts that none of the wells within the Western Discharge Area on both flow paths will exceed the SLV for dibenzofuran of 3.7 μg/L under natural attenuation conditions.

Figure 21 shows the predicted concentrations for fluorene along the southern groundwater flow path (from ATT-05 to ATT-12) and the northern groundwater flow path (rom ATT-06 to PMW-07). These plots show that fluorene is predicted to migrate through the system fairly slowly, as observed by the three-year lag between the maximum concentrations in ATT-05 and in downgradient well ATT-07. Similar behavior is observed for the northern flow path. The model predictions for fluorene indicate that all Western Discharge Area wells downgradient of the trench will remain below the SLV under natural attenuation conditions.

Figure 22 shows the predicted concentrations for phenanthrene along the southern groundwater flow path (from ATT-05 to ATT-12) and the northern groundwater flow path (from ATT-06 to PMW-07). As noted for fluorene and dibenzofuran, the model predicts that phenanthrene would migrate relatively slowly compared to naphthalene and ethylbenzene. This is a result of its higher retardation factor (Table 4). Figure 22 indicates shows that the model predicts that phenanthrene concentrations would remain below its SLV downgradient of the trench.

4.0 CONCLUSIONS

The transport model, an MT3D model coupled with a modified version of the MODFLOW groundwater flow model from the 2009 FS (Bridgewater, 2009), was developed and calibrated to conservatively evaluate natural attenuation of site COCs in the Western Discharge Area. Based on the results presented in this report, the calibrated transport model was in agreement with measured groundwater concentrations for naphthalene for the site. The calibrated transport model was used to conservatively assess the effectiveness of natural attenuation in achieving cleanup objectives in the Western Discharge Area without active aeration of the trench.

Based on the results presented in this report, the following conclusions are made:

• The calibrated transport model was able to simulate the observed naphthalene groundwater concentrations presented in the 2003 Supplemental RI with good agreement, achieving a correlation coefficient over 97 percent and a RMS error of 6.3 percent.

• The calibrated transport model was able to simulate observed naphthalene groundwater concentrations presented in the 2015 Annual Report well, with a correlation coefficient of 98 percent and a RMS error of 3.6 percent for 212 observations collected over time across the site area, including the area inside the barrier wall and within the Western Discharge Area.

• The calibrated model used a conservative estimate for the naphthalene retardation factor (i.e., a Koc that was 12.6 percent of the reported Koc value in Table 1), indicating that naphthalene is fairly mobile at the site.

• The calibrated model used a conservative estimate for the site-specific degradation rate constant, using a degradation rate constant that is 0.11 percent of the reported average value from Table 1. This indicates that naphthalene degrades slowly at the site.

• The low values used for retardation (due to the site specific Koc) and site-specific degradation rates for the other COCs provided for a conservative evaluation of predicted natural attenuation within the Western Discharge Area.

• The calibrated transport model predicts that with complete shutdown of active aeration in the trench, naphthalene will still attenuate to well below the SLV of 620 μg/L prior to reaching the western POC.

• The transport model, using conservatively high COC concentrations immediately upgradient of the aeration trench and conservatively low factors for retardation and site-specific degradation rates, also predicts that ethylbenzene, dibenzofuran, fluorene, and phenanthrene will all attenuate to well below their respective SLVs prior to reaching the western POC without active aeration in the trench.

• The MNA demonstration, which has been conducted since early 2011, indicates that natural attenuation would achieve cleanup objectives for the entire site under existing conditions.

5.0 PROPOSED MNA IMPLEMENTATION

Based on the five-year evaluation of natural attenuation for the site, we recommend that the aeration trench be completely shut down and natural attenuation be incorporated into the final remedy. The MNA demonstration that was initiated in February 2011 and conducted in accordance with the MNA Demonstration Work Plan (AMEC Geomatrix, 2010), is expected to reliably achieve cleanup objectives at the POCs that have been defined for the site. Implementing MNA will improve overall reliability and sustainability of the site remedy. Existing facilities will provide a contingent remedy that can be implemented if MNA is found to be unsuccessful in achieving cleanup objectives. The proposed modifications for implementing MNA as a key component of the long-term site remedy are:

• Revised groundwater monitoring and reporting.

• Contingency plan implementation if monitoring indicates MNA may not achieve cleanup criteria.

These proposed modifications to the existing program are described below.

5.1 GROUNDWATER MONITORING AND REPORTING

Groundwater monitoring has been performed regularly since early 2005. Quarterly monitoring was conducted initially, after completing implementation of the interim measure (barrier wall and aeration trench). Monitoring frequency decreased to semiannual monitoring after quarterly monitoring demonstrated the effectiveness of the interim measure.

It is proposed that semiannual monitoring continue in the wells that are currently being monitored for the site. This monitoring frequency has been found to be adequate, based on historical results. The predictions using the transport model indicate that semiannual monitoring will continue to be appropriate for the future. The sampling and analysis protocols for the existing list of COCs will continue to be monitored.

Reporting for the site currently consists of quarterly and annual reporting. The quarterly reports document operations and maintenance of the aeration trench, describe inspections, and provide an overall update regarding compliance with the Order, the O&M Plan, and any work conducted within the soil and groundwater management area that is subject to institutional controls. Analytical data are

attached to the quarterly reports in which the results are received from the laboratory. Quarterly reports are currently due to DEQ by the tenth day of the month following each calendar quarter. Annual reports are prepared to review overall performance of the site remedy and to discuss trends in groundwater monitoring results.

It is proposed that reporting be modified in conjunction with implementation of MNA at the site to prepare one semiannual report and one annual report. It is proposed that a semiannual report be prepared after June of each year. The semiannual report would include the information currently covered in the quarterly reports, but would cover the first six months of the year. It would include the first semiannual monitoring data and site inspections, and would be submitted to DEQ by the end of July each year. The annual report would be similar to the existing annual reports, but would include information normally included in the quarterly reports for the last half of each year. It is proposed that the annual reports be submitted to DEQ by the end of February each year.

5.2 CONTINGENCY PLAN

If the data collected during semiannual monitoring events indicate that natural attenuation is not likely to achieve cleanup criteria at the western POC, as determined following the protocol outlined below, the following contingency plan will be implemented. This approach will ensure that the final remedy is fully protective of human health and the environment.

5.2.1 Groundwater Quality Evaluation The groundwater quality at monitoring wells ATT-03, ATT-04, and ATT-11 will be evaluated after each monitoring event to assess the effectiveness of natural attenuation and the need to implement the contingent remedy. The contingent remedy would be triggered by either of the following two events:

1. The detected concentration(s) of one or more COCs at western POC wells ATT-12 or PMW-7R exceeds one-half of the respective Level II SLV(s) for two consecutive semiannual monitoring events.

2. The detected concentration(s) of one or more COCs at Western Discharge Area wells ATT-11, ATT-04, or ATT-03 (located upgradient of the POC) exceeds the respective Level II SLV(s) for two consecutive semiannual monitoring events.

If either of the above events occurs, DEQ will be notified via email within one week after receiving final analytical results from the analytical laboratory. The contingent remedy described in Section 5.2.2 will be implemented following DEQ notification.

5.2.2 Contingent Remedy The contingency action will consist of restarting aeration in the portion of the aeration trench that is upgradient of the wells initiating the contingent action. Restarting aeration would be done by reopening the aeration valves, starting the compressor, and balancing airflow in accordance with the O&M Plan. Airflow to the aeration trench would also be evaluated to assess fouling of the aeration zones; fouling treatment would be implemented as appropriate to provide adequate airflow to the aeration trench. Biweekly inspections of the aeration trench would resume if the contingent remedy is implemented; the reporting schedule would remain as proposed above, with semiannual reporting. The procedures in the O&M Plan would be followed for operation, maintenance, and inspection of the aeration trench. Groundwater monitoring would continue as described above. Monitoring results will be evaluated semiannually. Shutdown of the aeration trench may be proposed to DEQ if determined to be appropriate, based on site groundwater monitoring data.

5.2.3 Long-Term Aeration Trench Maintenance The contingent remedy requires that the existing aeration trench equipment be operable. Following shutdown of aeration and implementation of MNA, it is proposed that the aeration trench be inspected annually to confirm operability of the compressor. The annual inspection would be performed during one of the semiannual groundwater monitoring events, and results would be documented in the reports submitted to DEQ. After DEQ approves implementation of MNA for the site, the O&M Manual will be revised to incorporate details regarding inspection procedures. The revised O&M Plan will be submitted to DEQ for review.

6.0 REFERENCES

Amec Foster Wheeler Environment & Infrastructure, Inc. (Amec Foster Wheeler), 2016, 2015 Annual Operations, Maintenance, and Monitoring Report, Final Site Remedy, Former Koppers Wood Treating Facility, Wauna, Oregon, March.

Amec Foster Wheeler, 2015, 2014 Annual Operations, Maintenance, and Monitoring Report, Final Site Remedy, Former Koppers Wood Treating Facility, Wauna, Oregon, March.

AMEC Environment & Infrastructure, Inc. (AMEC), 2012, Monitored Natural Attenuation Interim Evaluation, Former Koppers Facility, Wauna, Oregon: Prepared for Beazer East, Inc., Pittsburg, Pennsylvania, December.

AMEC Geomatrix, Inc. (AMEC Geomatrix), 2010, Monitored Natural Attenuation Demonstration Work Plan, Former Koppers Wood Treating Facility, Wauna, Oregon: Submitted to Beazer East, Inc. and Georgia-Pacific Consumer Products LP, Former Koppers Facility, Wauna Oregon, January.

Bridgewater Group, Inc. (Bridgewater), 2009, Feasibility Study, Former Koppers Wood-Treating Site, Wauna, Oregon, February.

CH2MHILL, 2003, Supplemental Remedial Investigation Report, Former Koppers Wood-Treating Site, Wauna, Oregon, October.

TABLES

TABLE 1

LITERATURE-REPORTED ATTENUATION PARAMETERS

Former Koppers Facility

Wauna, Oregon

Constituent

Range, First Order

Rate Constant1

(day-1

Average First Order

Rate Constant1

(day-1

Organic Carbon

Partitioning

Coefficient2

(Koc) (L/Kg)

Water Solubility2

(mg/L)

Oregon Level II SLV

for Surface Water

(mg/L)

Ethylbenzene 0.11 0.113 209 161 0.0073

Acenaphthene 0.012 0.012 2,978 3.74 0.52

Anthracene 0.014 0.014 17,420 0.643 0.013

Benzo(a)anthracene 0.001 - 0.052 0.010 789,500 0.00940 2.70E-05

Benzo(a)pyrene 0.0034 - 0.057 0.015 3,677,080 0.00162 1.40E-05

Benzoic Acid 0.19 - 3.47 1.400 182 2,700 0.042

Dibenzofuran 0.099 0.099 8,128 3.10 0.0037

2,4-Dimethylphenol 0.17 0.173 18 7,870 0.042

Fluoranthene 0.0031 - 0.045 0.012 41,550 0 0.0062

Fluorene 0.003 - 0.33 0.070 5,585 2 0.0039

2-Methylphenol 0.069 - 0.88 0.346 103 25,950 0.013

Naphthalene 0.007 - 1.85 0.386 891 31 0.62

Phenanthrene 0.043 0.043 8,721 1 0.0063

Phenol 0.021 0.210 16 82,800 0.11

Pentachlorophenol 0.03 0.030 11,688 1,950 0.015

bis(2-ethylhexyl)Phthalate 0.0205 0.021 87,420 0.380 0.003

TPH-Diesel 0.48 - .61 0.545 NA NA NA

TPH-Gasoline 0.14 - 0.55 0.335 NA NA NA

Arsenic NA NA NA NA 0.15

Chromium, Hexavalent NA NA NA NA 0.011

Copper NA NA NA NA 0.009

Notes:

1. First order biodegradation rate constants taken from "Aerobic Biodegradatoin of Organic Chemicals in Environmental Media: A Summary of Field

Agency and Laboratory Studies," prepared for the U.S. Environmental Protection by the Environmental Science Center (January 27, 1999), from

Handbook of Environmental Degradation Rates by Philip H. Howard, Robert S. Boethling, William F. Jarvis, William M. Meylan, and Edward M.

Michalenko (1991), Handbook of Fate and Exposure Data for Organic Chemicals by Philip H. Howard (1989), and

P.H. Howard, 1989, and Intrinsic Bioremediation by Robert E. Hinchee, John T. Wilson, and Douglas C. Downey (1995).

2. Solubility and Koc data taken from the U.S. Environmental Protection Agency 1994 RREL Treatability Database.

Abbreviations:

Koc = organic carbon partitioning coefficient

mg/L = milligrams per liter

NA = not applicable

SLV = screening level value

TPH = total petroleum hydrocarbons

Former Koppers Facility | Wauna, Oregon

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Table 1, Page 1 of 1

TABLE 2

2003 REMEDIAL INVESTIGATION SOIL BORING DATA1, 2, 3

Wauna, Oregon

Naphthalene

(mg/kg)

SB-05 13,000

B-1 235

B-21 219

B-10 187

B-22 145

B-4 138

B-2 130

B-3 113

B-12 74

B-11 62

B-8 18

B-5 15

B-23 8.5

B-9 6.2

B-7 1.1

B-20 0.38

B-17 0.10

B-16 0.10

B-14 0.10

B-13 0.10

B-6 0.10

B-15 NA

Notes:

1. Soil boring data represents average soil concentrations

across 10-foot depth intervals, generally within the

Pavement Cap Area presented in the Supplemental

Remedial Investigation report (CH2MHILL, 2003).

2. Soil data was collected from August 1998–November 2001.

3. The modeled source area generally included soil

boring areas with average soil detections above 10 mg/kg.

Abbreviations:

mg/kg = milligrams per kilogram

NA = not analyzed

Soil Boring

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March 2016

TABLE 3

AVERAGE AND MAXIMUM CONSTITUENT OF CONCERN CONCENTRATIONS1, 2, 3

Wauna, Oregon

Avg Max Avg Max Avg Max

Ethylbenzene 7.3 18 53 5.8 23 0.64 2.6

2-Methylphenol 13 0.16 0.55 0.15 0.55 0.16 0.55

Benzoic acid 42 1.8 5.5 2.0 5.5 1.6 5.5

Naphthalene 620 533 2,000 136 670 55 240

Dibenzofuran 3.7 8.0 17 1.4 4.9 1.3 2.4

Fluorene 3.9 11.2 28 10 19 6.8 10

Pentachlorophenol 15 0.51 1.7 0.48 1.7 0.49 1.7

Phenanthrene 6.3 2.8 6.3 4.7 10 0.82 1.6

Fluoranthene 6.2 0.04 0.1 0.05 0.12 0.03 0.10

bis(2-ethylhexyl)

Phthalate3 0.29 0.65 0.21 0.65 0.24 0.65

Notes:

Abbreviations:

Avg = average

Max = maximum

3. All concentrations are in micrograms per liter.

2. Bold values exceed SLV.

1. Data from April 2011 to October 2015.

ATT-05 ATT-06 ATT-10

Constituent of

Concern

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March 2016

TABLE 4

MT3D MODEL INPUTS FOR OTHER SITE COONSTITUENTS OF CONCERN

Wauna, Oregon

Parameter Units Naphthalene Phenanthrene Fluorene Dibenzofuran Ethylbenzene

Retardation Parameters

Retardation Factor1 (MT3D Input) -- 3.5 25.5 16.7 23.8 1.6

Site-specific Koc2

L/kg 113 1,102 706 1,027 26

Koc from Table 1 L/kg 891 8,721 5,585 8,128 209

Site-specific λ3

day-1 4.33E-04 4.83E-05 7.86E-05 1.11E-04 1.27E-04

Half Life (MT3D Input)4

days 1,600 14,363 8,823 6,238 5,465

Average λ, from Table 1 day-1 0.386 0.043 0.07 0.099 0.113

ATT-05 Concentration µg/L 2,000 6.3 28 17 53

ATT-06 Concentration µg/L -- 10 19 4.9 23

Notes:

Soil Bulk Density (rho) = 1.85 kg/L

Soil Organic Carbon (foc) = 0.25 kg/kg

Soil Porosity (n) = 0.25

2. Site-specific Koc for COCs other than naphthalene calculated from tabulated literature value multiplied by Fr

Retardation Fraction (Fr) = [Site-Specific Koc for Naphthalene] / [Literature Koc for Naphthalene] = 113/891 = 0.126

3. Site-specific λ for COCs other than naphthalene calculated from tabulated literature value mulitpied by Fd.

Degradation Fraction (Fd) = [Site-Specific λ for Naphthalene] / [Literature Average λ for Naphthalene] = 4.3e-04/0.386 = 0.00112

4. The half-life and site-specific degradation rates are related by the following expression: Half-Life = LN (0.5)/(-λ)

Abbreviations:

λ = degradation rate kg/L = kilograms per liter

µg/L = micrograms per liter kg/kg = kilogram per kilogram

COCs = constituents of concern Koc = organic carbon partitioning coefficient

Fd = degradation fraction L/kg = liters per kilogram

Fr = retardation fraction R = retardation factor

1. Retardation Calcs, R = 1+(rho/n)*Koc*foc. R is calculated for model input.

Degradation Rate Calculations

Modeled COC Concentration Point Sources

K:\13000\13200\13236\SEA MNA Report\Table 4 MT3D Model Inputs-CD

March 2016

FIGURES

Project No.Date:By: APS 03/07/16 09151

Figure 1

SITE LOCATION MAPFormer Koppers Facility

Wauna, Oregon

OREGON

TRUENORTH

PLANTNORTH

Amec Foster WheelerEnvironment & Infrastructure, Inc.

Notes:

2. Red lines/arrows represent particle flow paths.3. Blue shaded areas represent surface water ponding areas.

1. Yellow highlighted areas represent areas with surface drainage (model removes surface water from model domain).

Figure 3b: 2015 model with surface drains limited to slough.

Figure 3a: 2008 calibrated flow model with surface drains across domain.

GROUNDWATER FLOW MODEL COMPARISON

Former Koppers FacilityWauna, Oregon

Figure 3By: CDHProject No.: 09151Date: 02/08/2016

NAPHTHALENE SOURCE AREA GROUNDWATER

CONCENTRATIONSFormer Koppers Facility

Wauna, Oregon

y = ‐0.003x + 103.2R² = 0.62

y = ‐0.003x + 121R² = 0.99

y = 8E+06e‐3E‐04x

Concen

tration (m

Source zone Release Period

Naphthalene Solubility Limit (31 mg/L)

PNW‐05 Pre‐wall Obs

Installation Barrier Wall Ramp Up

PNW‐05 Post‐Wall Obs

Linear (PNW‐05 Pre‐wall Obs)

Linear (PNW‐05 Post‐Wall Obs)

Expon. (Forecasted Source Term)

*Wauna - Date: 2002 Model OutputNotes:1. Model results presented for 2002.2. Model ran from 1954-2002, or 48 years.

1954–2002 NAPHTHALENE TRANSPORT MODEL

CALIBRATIONFormer Koppers Facility

Wauna, Oregon

acilit

ATT-02 NAPHTHALENE TREND PLOT

Naphthalene

(µg/L)

ATT‐02

Southern Aeration Trench Shutdown

Simulation vs Observation Statistics:Residual Mean ‐20Absolute Residual Mean 232Residual Std. Deviation 359Sum of Squares 1550509RMS Error 359Min. Residual ‐607Max. Residual 805Number of Observations 12Range in Observations 5740Scaled Residual Std. Deviation 6.3%Scaled Absolute Residual Mean 4.0%Scaled RMS Error 6.3%Scaled Residual Mean ‐0.0034Correlation Coefficient 97.5%

acilit

SIMULATED VS. OBSERVED NAPHTHALENE

CONCENTRATIONS 2002Former Koppers Facility

Wauna, Oregon

PMW‐09

PMW‐08

PMW‐13

PMW‐06

PMW‐02

PMW‐01

PMW‐05

PMW‐10PMW‐070

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000

Simulated

Naphtha

centratio

n (μg/L)

Observed Concentration (μg/L)

*Wauna - Date: 2016.0 Model Time 1825.0 Days

SIMULATED 2015 NAPTHALENE DISTRIBUTION

Simulation vs Observation Statistics:Residual Mean 2Absolute Residual Mean 198Residual Std. Deviation 471Sum of Squares 46785625RMS Error 470Min. Residual 2673Max. Residual 2446Number of Observations 212Range in Observations 13000Scaled Residual Std. Deviation 3.6%Scaled Absolute Residual Mean 1.5%Scaled RMS Error 3.6%Scaled Residual Mean 0.00013Linear Correlation Coefficient 98.0%

acilit

SIMULATED VS. OBSERVED NAPHTHALENE

CONCENTRATIONS 2005–2015Former Koppers Facility

Wauna, Oregon

0.00E+00

2.00E+03

4.00E+03

6.00E+03

8.00E+03

1.00E+04

1.20E+04

1.40E+04

0 2000 4000 6000 8000 10000 12000 14000

Simulated

centratio

n (ug/L)

Observed Concentration (ug/L)

acilit

GROUNDWATER NAPHTHALENE CALIBRATION SUMMARY

ATT-05 & ATT-06Former Koppers Facility

Wauna, Oregon

Figure 11By: CDH

Project No.: 09151

Date: 02/09/2016

Napthalen

tration (μg/L)

Figure 11a: ATT‐05 Groundwater Naphthalene Calibration

Groundwater Field Data

Groundwater ModelSimulationBarrier Wall Contruction

Southern Aeration TrenchShutdown

Napthalen

tration (μg/L)

Figure 11b:ATT‐06 Groundwater Naphthalene Calibration

Groundwater Field Data

Groundwater ModelSimulationBarrier Wall Contruction

Southern Aeration TrenchShutdown

acilit

GROUNDWATER NAPHTHALENE CALIBTRATION SUMMARY

ATT-02, ATT-03, AND ATT-04Former Koppers Facility

Wauna, Oregon

Figure 12By: CDH

Project No.: 09151

Date: 02/09/2016

0100200300400500600700800900

Napthalen

tration (μg/L)

Figure 12a: ATT‐02 Groundwater Naphthalene Calibration

Groundwater FieldData

Groundwater ModelSimulation

Barrier WallContruction

Napthalen

tration (μg/L)

Figure 12b: ATT‐03 Groundwater Naphthalene CalibrationGroundwater FieldDataGroundwater ModelSimulationBarrier WallContructionSouthern AerationTrench Shutdown

Napthalen

tration (μg/L)

Figure 12c: ATT‐04 Groundwater Naphthalene Calibration

Groundwater FieldDataGroundwater ModelSimulationBarrier WallContruction

acilit

HISTORICAL NAPHTHALENE FLOW PATH MODEL SIMULATION

Figure 13By: CDH

Project No.: 09151

Date: 02/09/2016

Napthalen

tration (μg/L)

Figure 13a: Southern Groundwater Flow Path

ATT‐05

ATT‐07

ATT‐02

Napthalen

tration (μg/L)

Figure 13b: Northern Groundwater Flow Path

ATT‐06

ATT‐08

ATT‐03

acilit

NAPHTHALENE FLOW PATH PREDICTIONS

Figure 14By: CDH

Project No.: 09151

Date: 02/09/2016

Napthalen

tration (ug/L)

Figure 14a: Sourthern Groundwater Flow Path

ATT‐05ATT‐07ATT‐02ATT‐11ATT‐12SLV

Napthalen

tration (ug/L)

ATT‐06

ATT‐08

ATT‐03

ATT‐04

PMW‐07

acilit

POINT OF COMPLIANCE PREDICTIONS-NAPHTHALENE

Figure 15By: CDH

Project No.: 09151

Date: 02/09/2016

700Napthalen

tration (ug/L)

ATT‐04

PMW‐07

ATT‐12

ETHYLBENZENE AND DIBENZOFURAN

CONCENTRATION UPGRADIENT OF AERATION TRENCHFormer Koppers Facility

Wauna, Oregon

Figure 16By: CDH

Project No.: 09151

Date: 02/09/2016

Concen

tration (μ

Figure 16a: Ethylbenzene Upgradient of Trench

ATT‐05

ATT‐06

ATT‐10

Concen

tration (μ

Figure 16b:Dibenzofuran Upgradient of Trench

ATT‐05

ATT‐06

ATT‐10

acilit

FLOURENE AND PHENANTHRENE

CONCENTRATION UPGRADIENT OF AERATION TRENCHFormer Koppers Facility

Wauna, Oregon

Figure 17By: CDH

Project No.: 09151

Date: 02/09/2016

Concen

tration (μ

Figure 17a:Fluorene Upgradient of Trench

ATT‐05ATT‐06ATT‐10

Concen

tration (μ

Figure 17b:Phenanthrene Upgradient of Trench

ATT‐05ATT‐06ATT‐10SLV

acilit

ETHYLBENZENE FLOW PATH PREDICTIONS

Figure 19By: CDH

Project No.: 09151

Date: 02/09/2016

dwater Con

centratio

dwater Con

centratio

n (μg/L)

ATT‐06

ATT‐08ATT‐03ATT‐04

PMW‐07SLV

acilit

DIBENZOFURAN FLOW PATH PREDICTIONS

Figure 20By: CDH

Project No.: 09151

Date: 02/09/2016

18Groun

dwater Con

centratio

n (μg/L)

ATT‐05

ATT‐07

ATT‐02

ATT‐11

ATT‐12

dwater Con

centratio

n (μg/L)

ATT‐06ATT‐08ATT‐03ATT‐04PMW‐07SLV

acilit

FLUORENE FLOW PATH PREDICTIONS

Figure 21By: CDH

Project No.: 09151

Date: 02/09/2016

30.0Groun

dwater Con

centratio

dwater Con

centratio

n (μg/L)

ATT‐06

ATT‐08

ATT‐03

ATT‐04

PMW‐07

acilit

PHENANTHRENE FLOW PATH PREDICTIONS

Figure 22By: CDH

Project No.: 09151

Date: 02/09/2016

7Groun

dwater Con

centratio

n (μg/L)

ATT‐05

ATT‐07

ATT‐02

ATT‐11

ATT‐12

dwater Con

centratio

n (μg/L)

ATT‐06

ATT‐08

ATT‐03

ATT‐04

PMW‐07

APPENDIX A

Western Discharge Area Trend Plots

Values plotted for nondetections are half of detection limit. The highest concentration value of the primary and duplicate samples are plotted.

Jan-05 Jan-06 Jan-07 Jan-08 Jan-09 Jan-10 Jan-11 Jan-12 Jan-13 Jan-14 Jan-15 Jan-16

L)Figure A1: Western Interior Wells ATT-05, ATT-06, & ATT-10

ATT-05

ATT-06

ATT-10

Level II SLV

Aeration Shutdown, S. Trench

WESTERN INTERIOR WELLS ATT-05, ATT-06, & ATT-10

Figure A1By: Project No.:91510120 Date: 01/13/16

P:\9151 - Wauna Facility\Wauna Final Remedy O&M\MNA Demonstration\2015 MNA Report\Appendix A - Western Discharge Area Trend Plots\Figure A1

WESTERN INTERIOR WELLS ATT-01 & ATT-02

Figure A2: Western Exterior Wells ATT-01 & ATT-02

ATT-01

ATT-02

Level II SLV

Aeration Shutdown, S. Trench

WESTERN INTERIOR WELLS ATT-03, ATT-04, & ATT-11

Figure A3: Western Exterior Wells ATT-03, ATT-04, & ATT-11

ATT-03

ATT-04

ATT-11

Level II SLV = 620 µg/L

INTERIOR WELL ATT-05Former Koppers Facility

Wauna, Oregon

Figure A4: Interior Well ATT-05

Ethylbenzene

Dibenzofuran

Fluorene

Phenanthrene

Wauna, Oregon

Ethylbenzene 2-Methylphenol Benzoic acid

Dibenzofuran Fluorene Pentachlorophenol

Phenanthrene Fluoranthene bis(2-ethylhexyl) Phthalate

Wauna, Oregon

Ethylbenzene

Fluorene

Phenanthrene

Dibenzofuran

Wauna, Oregon

Figure A7: Exterior Well ATT-02

Ethylbenzene

Dibenzofuran

Fluorene

PhenanthreneAeration Shutdown, S. Trench

APPENDIX B

Supplemental RI Soil Boring Data

Appendix B

Wauna, Oregon

Station ID Depth

B-1 7.5 470

B-1 10 0.1 U

B-10 7.5 53

B-10 2.5 320

B-11 7.5 123

B-11 FD 2.5 0.10 U

B-12 2.5 0.10 U

B-12 10 147

B-13 2.5 0.10 U

B-13 7.5 --

B-14 2.5 0.10 U

B-15 2.5 0.10 U

B-16 2.5 0.10 U

B-14 7.5 --

B-15 7.5 --

B-16 10 144

B-17 7.5 --

B-17 2.5 0.10 U

B-2 2.5 --

B-2 5 260

B-2 10 0.1 U

B-20 2.5 0.1 U

B-20 7.5 0.66

B-21 2.5 --

B-21 12.5 219

B-22 12.5 145

B-23 12.5 8.5

B-3 2.5 0.1 U

B-3 10 340

B-3 12.5 0.1 U

B-4 FD 2.5 0.2 U

B-4 2.5 0.2 U

B-4 FD 7.5 --

B-4 7.5 390

B-4 10 25

B-5 2.5 31

B-5 5 4.6

B-5 10 8.5

Naphthalene

K:\13000\13200\13236\SEA MNA Report\Tables - Figures - Appendices\Appendix B Supplemental RI Soil Boring Data

March 2016

Appendix B

Wauna, Oregon

Station ID Depth Naphthalene

B-6 2.5 0.1 U

B-6 10 0.1 U

B-7 2.5 1.1

B-7 FD 2.5 --

B-7 7.5 220

B-8 2.5 10.9

B-8 10 26

B-9 2.5 0.1 U

B-9 5 14

B-9 10 4.6

EPA-D1 -- 0.8 U

EPA-D4 -- 0.025 NJ

EPA-DC1 -- 0.7 U

SS-01 FD 0.5 0.85 U

SS-01 0.5 0.87 U

SS-02 0.5 0.8 U

SS-03 0.5 0.82 U

SS-04 0.5 0.8 U

SS-05 0.5 0.73 U

SS-06 0 0.035 U

PMW-05 -- 115,000

Notes:

Results reported in milligrams per kilogram.

Depth measured in feet below ground surface.

Abbreviations:

-- = not analyzed

FD = field duplicate

March 2016

Appendix B

Wauna, Oregon

Station ID Depth

B-1 7.5 470

B-1 10 0.1 U

B-10 7.5 53

B-10 2.5 320

B-11 7.5 123

B-11 FD 2.5 0.10 U

B-12 2.5 0.10 U

B-12 10 147

B-13 2.5 0.10 U

B-13 7.5 --

B-14 2.5 0.10 U

B-15 2.5 0.10 U

B-16 2.5 0.10 U

B-14 7.5 --

B-15 7.5 --

B-16 10 144

B-17 7.5 --

B-17 2.5 0.10 U

B-2 2.5 --

B-2 5 260

B-2 10 0.1 U

B-20 2.5 0.1 U

B-20 7.5 0.66

B-21 2.5 --

B-21 12.5 219

B-22 12.5 145

B-23 12.5 8.5

B-3 2.5 0.1 U

B-3 10 340

B-3 12.5 0.1 U

B-4 FD 2.5 0.2 U

B-4 2.5 0.2 U

B-4 FD 7.5 --

B-4 7.5 390

B-4 10 25

B-5 2.5 31

B-5 5 4.6

B-5 10 8.5

Naphthalene

March 2016

Appendix B

Wauna, Oregon

B-6 2.5 0.1 U

B-6 10 0.1 U

B-7 2.5 1.1

B-7 FD 2.5 --

B-7 7.5 220

B-8 2.5 10.9

B-8 10 26

B-9 2.5 0.1 U

B-9 5 14

B-9 10 4.6

EPA-D1 -- 0.8 U

EPA-D4 -- 0.025 NJ

EPA-DC1 -- 0.7 U

SS-01 FD 0.5 0.85 U

SS-01 0.5 0.87 U

SS-02 0.5 0.8 U

SS-03 0.5 0.82 U

SS-04 0.5 0.8 U

SS-05 0.5 0.73 U

SS-06 0 0.035 U

PMW-05 -- 115,000

Notes:

Abbreviations:

-- = not analyzed

March 2016

Appendix B

Wauna, Oregon

Station ID Depth

B-1 7.5 470

B-1 10 0.1 U

B-10 7.5 53

B-10 2.5 320

B-11 7.5 123

B-11 FD 2.5 0.10 U

B-12 2.5 0.10 U

B-12 10 147

B-13 2.5 0.10 U

B-13 7.5 --

B-14 2.5 0.10 U

B-15 2.5 0.10 U

B-16 2.5 0.10 U

B-14 7.5 --

B-15 7.5 --

B-16 10 144

B-17 7.5 --

B-17 2.5 0.10 U

B-2 2.5 --

B-2 5 260

B-2 10 0.1 U

B-20 2.5 0.1 U

B-20 7.5 0.66

B-21 2.5 --

B-21 12.5 219

B-22 12.5 145

B-23 12.5 8.5

B-3 2.5 0.1 U

B-3 10 340

B-3 12.5 0.1 U

B-4 FD 2.5 0.2 U

B-4 2.5 0.2 U

B-4 FD 7.5 --

B-4 7.5 390

B-4 10 25

B-5 2.5 31

B-5 5 4.6

B-5 10 8.5

Naphthalene

March 2016

Appendix B

Wauna, Oregon

B-6 2.5 0.1 U

B-6 10 0.1 U

B-7 2.5 1.1

B-7 FD 2.5 --

B-7 7.5 220

B-8 2.5 10.9

B-8 10 26

B-9 2.5 0.1 U

B-9 5 14

B-9 10 4.6

EPA-D1 -- 0.8 U

EPA-D4 -- 0.025 NJ

EPA-DC1 -- 0.7 U

SS-01 FD 0.5 0.85 U

SS-01 0.5 0.87 U

SS-02 0.5 0.8 U

SS-03 0.5 0.82 U

SS-04 0.5 0.8 U

SS-05 0.5 0.73 U

SS-06 0 0.035 U

PMW-05 -- 115,000

Notes:

Abbreviations:

-- = not analyzed

March 2016

MONITORED NATURAL ATTENUATION DEMONSTRATION

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