Risk Assessment Report Update Area Groundwater Investigation Sweet Home, Oregon. Prepared for Oregon Department of Environmental Quality

Transcription

1 Risk Assessment Report Update Area Groundwater Investigation Sweet Home, Oregon Prepared for Oregon Department of Environmental Quality August 31, /Task 4 Task Order:

2 Risk Assessment Report Update Area Groundwater Investigation Sweet Home, Oregon Prepared for Department of Environmental Quality August 31, /Task 4 Task Order Prepared by Hart Crowser, Inc. Troy Fowler Task Order Manager Richard D. Ernst, RG Program Manager 8910 SW Gemini Drive Beaverton, OR Fax Tel

3 CONTENTS Page 1.0 INTRODUCTION AND PURPOSE BACKGROUND Study Area Description Previous Investigations SUMMARY OF ANALYTICAL RESULTS Potential Contaminants of Interest Groundwater Sampling Domestic Wells Groundwater Sampling Monitoring Wells Presence and Extent of Chlorinated Hydrocarbons Identification of Compounds of Potential Concern DOMESTIC WATER WELL SURVEY UPDATED HUMAN HEALTH RISK ASSESSMENT Exposure Assessment Toxicity Assessment Risk-Based Concentrations Risk Characterization Uncertainty Risk Contours LEVEL 1 ECOLOGICAL RISK ASSESSMENT Sensitive Environments Threatened and Endangered Species Site Visit Summary Exposure Pathways SUMMARY AND CONCLUSIONS RECOMMENDATIONS LIMITATIONS REFERENCES 29 Hart Crowser /Task 4 August 31, 2009 Page i

4 CONTENTS (Continued) TABLES 1 Summary of Domestic Well Sampling Results 2 Summary of Groundwater Monitoring Well Sampling Results 3 Statistical Summary of Domestic Well Sampling Results 4 Statistical Summary of Groundwater Monitoring Well Sampling Results 5 Risk Screening of Domestic Well Sampling Results 6 Risk Screening of Monitoring Well Sampling Results 7 Summary of Wells Exceeding RBCs 8 Exposure Point Calculation of Domestic Well Sampling Results 9 Exposure Point Calculation of Monitoring Well Sampling Results 10 Human Health Toxicity assessment 11 Exposure Dose Equations and Exposure Factors Values; Groundwater Ingestion 12 Exposure Dose Equations and Exposure Factors Values; Dermal Contact with Groundwater 13 Exposure Dose Equations and Exposure Factors Values; Inhalation of Volatiles 14 Residential Risk Estimates from Domestic Well Sampling Results 15 Residential Risk Estimates from Monitoring Well Sampling Results 16 Occupational Worker Risk Estimates from Domestic Well Sampling Results 17 Occupational Worker Risk Estimates from Monitoring Well Sampling Results 18 Excavation Worker Risk Estimates from Domestic Well Sampling Results 19 Excavation Worker Risk Estimates from Monitoring Well Sampling Results 20 Human Health Risk Assessment Uncertainty Evaluation FIGURES 1 Site Location Map 2 Site Plan and Groundwater Monitoring Well Locations 3 Site Plan with Domestic Well Locations 4 Estimated Extent of VOCs in Groundwater October Human Health Conceptual Site Model 6 Cumulative Residential Risk from Groundwater Exposure Pathways Hart Crowser /Task 4 August 31, 2009 Page ii

5 CONTENTS (Continued) APPENDIX A MANN-KENDALL STATISTICAL ANALYSIS AND LINEAR REGRESSIONS APPENDIX B ESTIMATE OF PCE AND TCE EXPOSURE FOR OUTDOOR WATER USER APPENDIX C LEVEL I SCOPING ECOLOGICAL RISK ASSESSMENT SUPPORTING INFORMATION Hart Crowser /Task 4 August 31, 2009 Page iii

6 RISK ASSESSMENT REPORT UPDATE AREA GROUNDWATER INVESTIGATION SWEET HOME, OREGON 1.0 INTRODUCTION AND PURPOSE This report presents the results of an updated Human Health Risk Assessment (HHRA) based on groundwater data collected as part of the Areawide Site Investigation (Hart Crowser, 2009) in the Midway area of the city of Sweet Home. The project site is shown on Figure 1. Figure 2 shows the location of the groundwater monitoring wells, and Figure 3 shows the location of domestic wells that have been sampled as part of the areawide site investigation. The concentrations and estimated extent of chlorinated volatile organic compounds (cvocs) in groundwater at this site (as of October 2008) are shown on Figure 4. The purpose of this HHRA is to incorporate recent groundwater data, revised chemical exposure factors, and additional statistical analysis to evaluate potential risks and hazards to human health. Initial analysis was completed in 2003 and included flux chamber sampling which is no longer relied on for risk assessment purposes (Hart Crowser, 2003). Based on a groundwater beneficial use survey completed for the study area, complete pathways are inhalation of cvocs from shallow groundwater and direct contact and ingestion from outdoor use. No potential exposure pathways to ecological receptors were identified by a Level 1 - Scoping Ecological Risk Assessment (ERA) that was completed as part of the Phase II Site Investigation Report (Hart Crowser, 2000). This Scoping ERA is included in this report in its entirety (Appendix C). Carcinogenic risks attributable to complete exposure pathways were calculated for various people groups. As presented in this report, risks to occupational and excavation workers were minimal, typically represented by one or two well locations. Several domestic wells were identified that may pose risks above the Oregon Department of Environmental Quality (DEQ) standards. Based on these exceedences, we prepared a cumulative residential carcinogenic risk contour map of the Midway area (Figure 6). Calculations are presented in Tables 14 through 19. This report was prepared for the DEQ under Task 4 of Task Order Hart Crowser Page /Task 4 August 31, 2009

7 2.0 BACKGROUND 2.1 Study Area Description 2.2 Previous Investigations The city of Sweet Home is located in Linn County, Oregon, southeast of Lebanon, along Highway 20. The study area is located in an area midway between downtown Sweet Home and Foster, which was annexed by Sweet Home in 1977 (Township 13 South, Range 1 East, Sections 27, 28, 33, and 34). The location of the study area (locally known as Midway) is shown on Figure 1. The population of Sweet Home is about 8,300. The study area is currently limited by 40th Avenue to the west, 49th Avenue to the east, Long Street to the south, and the South Santiam River to the north. City water is currently available to all of the residents in the study area. Previous work in this area included connecting residences with domestic wells impacted by cvocs to the municipal water supply. Other residences, outside of the contaminant plume, may continue to use their domestic water wells for potable use. Many residents with city water available also continue to use existing domestic wells (primarily for irrigation and other non-potable uses). The domestic wells draw water from two water-bearing zones. The majority of the wells are completed in a shallow, regional alluvial aquifer at depths of 30 to 60 feet. Several wells penetrate deeper into the bedrock unit underlying the shallow gravel aquifer to depths of 100 to 600 feet below ground surface (bgs). Previous investigations have occurred in the Midway area of Sweet Home between 1992 and This work included the installation and routine sampling of 20 groundwater monitoring wells, and connection of impacted residences and businesses to the municipal water supply. Tetrachloroethene (PCE), trichloroethene (TCE), and 1,1,1-trichloroethane (TCA) were identified as compounds of interest (COIs) in the shallow groundwater based on the results of the historical investigations. In 1998, Hart Crowser collected water samples from the private wells of selected houses throughout the study area (including all houses within the area known to be impacted by cvocs, but also including a representative collection of wells outside of the known plume area). Since the conclusion of the Phase II Site Investigation (May 2000), groundwater samples have been collected quarterly from all monitoring wells through December 2000, semi-annually through June 2002, annually through October 2006, and most recently in October Three monitoring wells installed during 2004 (MW-18, MW-19, and MW-20) were sampled twice during 2004 and then joined the same schedule as the other 17 monitoring wells. Samples from selected domestic groundwater wells have been collected semi-annually through Hart Crowser Page /Task 4 August 31, 2009

8 September 2000 and are now sampled to coincide with the sampling of the monitoring wells. However, because some wells were not functional or not accessible during planned monitoring events, not all wells were sampled during each event. In March 2002, a soil vapor survey was completed on the Ridgeway Logging property (Ridgeway) located within the Midway area of Sweet Home to assess for the potential existence of source areas (Figure 2). In 2003, Hart Crowser performed an area-wide human health risk assessment for the Sweet Home area. The risk assessment determined that two compounds, PCE and TCE, exceeded remedial action objectives for groundwater at the Ridgeway site. Hart Crowser performed an Interim Removal Action Measure (IRAM) at the Ridgeway site, which included implementation of a pilot study to assess delivery alternatives for treatment solutions and to obtain pertinent hydrogeologic parameters. This was later followed by the full-scale injection of emulsified oil and a microbial consortium during 2004 to enhance biodegradation of contaminants in groundwater at the site. Additional information about these investigations is included in the Site Investigation Report (Hart Crowser, 1999), the Phase II Site Investigation Report, (Hart Crowser, 2000), Interim Final Risk Assessment Report (Hart Crowser, 2003), and the Groundwater Monitoring Data Report (Hart Crowser, 2009). 3.0 SUMMARY OF ANALYTICAL RESULTS This section summarizes the groundwater analytical data collected at the study area through October Potential Contaminants of Interest Based on sampling and analysis activities conducted to date, potential COIs in groundwater in the study area consist of VOCs. Specifically, the target chemicals of concern include PCE, TCE, cis-1,2-dichloroethene (cdce), 1,1-dichloroethene (1,1-DCE), TCA, and 1,1-dichloroethane (DCA). Gasoline constituents, including benzene, ethylbenzene, toluene, xylene, (BTEX) and methyl-tert-butylether (MTBE) have been detected in a limited number of wells near a gasoline service station and are being investigated under a separate regulatory program. 3.2 Groundwater Sampling Domestic Wells The routine domestic well sampling program includes up to 63 domestic wells. These wells have been sampled semi-annually through September 2000 and are Hart Crowser Page /Task 4 August 31, 2009

9 now sampled to coincide with the sampling of the groundwater monitoring wells. The results of the domestic well sampling events are provided in Table 1 of this report. During the October 2008 sampling event, samples were collected from 16 domestic wells to evaluate groundwater VOC trends in key wells and to confirm plume delineation. Sampling was scheduled for 33 domestic wells of interest but several of the selected wells were not functional, not accessible at the time of the sampling, or outside taps had been plumbed to municipal water. Many of the unsampled wells have been allowed to become dysfunctional following the connection of the residence or business to the city water supply. Future domestic well sampling events will continue to attempt collection of water samples from these wells, if still active. Samples from 9 of the 16 sampled domestic wells had detectable concentrations of VOCs for the October 2008 sampling event. Detected compounds from the October 2008 sampling event include: PCE was detected in 9 wells, ranging from 1.85 micrograms per liter (μg/l) in well 21 to 11.7 μg/l in well 22; and TCE in 4 wells, ranging from 0.57 μg/l (well 31) to 1.99 μg/l (well 22). There were no detections of DCE, TCA, DCA, cdce, or vinyl chloride (VC) in any sampled domestic well. Samples collected from three residences (wells 1, 51, and 53) reflected municipal tap water, as evidenced by low conductivity, high ORP, and elevated concentrations of chloroform and bromodichloromethane. Chloroform concentrations ranged from 28.7 μg/l to 37.4 μg/l. All of these samples were collected from hose bibs on the front of the house due to no homeowner present. Additional details of the domestic well sampling program are provided in previous site documents (Hart Crowser, 1999, 2000, 2002, and 2009). The domestic groundwater data used in the risk screening and to calculate estimated carcinogenic risks are presented in Table Groundwater Sampling Monitoring Wells The routine groundwater monitoring well sampling program previously included up to 20 wells. Monitoring well MW-16 was decommissioned during early 2008 and was not available for sampling during October Monitoring wells MW-1 through MW-17 have been sampled quarterly through December 2000, semi-annually during 2001, annually through 2006, and again during 2008 (with the exception of MW-16). Three wells installed during 2004 (MW-18, MW-19, and MW-20) were sampled twice during 2004 and then joined the same schedule as the other monitoring wells. Hart Crowser Page /Task 4 August 31, 2009

10 Nine of the 16 groundwater monitoring wells contained cvocs during the October 2008 sampling event, including MW-2 through MW-5, MW-13, MW-14, MW-17, MW-19 and MW-20. PCE concentrations in these wells ranged from 0.66 μg/l (MW-3) to 407 μg/l (MW-2). MW-5 and MW-14 had detectable TCE, at 2.17 μg/l and 1.35 ug/l respectively. MW-5 also contained detectable cdce and VC at 3.57 μg/l and 2.38 μg/l, respectively. TCA, DCA, and DCE were detected in only one well (MW-3) at concentrations of 8.11 μg/l, 2.46 μg/l, and 19.7 μg/l, respectively. Additional details of the groundwater monitoring well sampling program are provided in previous site documents (Hart Crowser, 1999, 2000, 2002, 2009). The groundwater monitoring well data used in the risk screening and to calculate estimated carcinogenic risks are presented in Table Presence and Extent of Chlorinated Hydrocarbons The extent of VOCs in site groundwater (using data from both the groundwater monitoring wells and the domestic supply wells) is shown on Figure 4. These data show the highest relative concentrations of PCE are in the vicinity of the Ridgeway site and the former Hi-Tech Muffler Shop (with the highest relative concentrations of PCE consistently found on the north side of Highway 20, near the Hi-Tech site). The only detected concentrations of TCA and DCA were found in domestic well 48 and monitoring well MW-3 (west of the USDA Forest Service Sweet Home Work Center). The extent of VOCs in groundwater is similar to that observed during previous assessment work. Based on the chemicals identified at the site and the degradation pathways for those chemicals, at least two parent chemicals are present: PCE and TCA. As shown on Figure 4, the largest plume of chlorinated hydrocarbons is associated with PCE and its breakdown products, TCE and cdce. A second, smaller plume is associated with TCA and its breakdown products, DCA and 1,1-DCE, and is present in the west-central portion of the larger PCE plume. 3.5 Identification of Compounds of Potential Concern COIs are defined as compounds detected at the site, and contaminants of potential concern (COPCs) are those COIs that exceed the risk-based screening levels as discussed below and are carried forward in the HHRA. Based on sampling and analysis activities conducted to date, potential COIs in the groundwater in the study area consist of VOC compounds. Specifically, the COIs include PCE, TCE, cdce, 1,1-DCE, TCA, DCA, and MTBE. Statistical summary tables of detected compounds in domestic wells and monitoring wells Hart Crowser Page /Task 4 August 31, 2009

11 are presented in Tables 3 and 4, respectively. One monitoring well (MW-11) has also exhibited elevated concentrations of petroleum hydrocarbons (BTEX). This monitoring well was located adjacent to a gasoline station and this issue is being investigated under a separate regulatory program. BTEX was not detected in any of the domestic water well samples (Hart Crowser, 2009). In accordance with DEQ human health risk assessment guidance (DEQ, 2000), COPCs were identified following the steps presented in Section of the guidance. As recommended in Section 2.3.2(1), COIs detected at a historical frequency of less than five percent were screened from consideration as COPCs. These included: Domestic Wells: TCA; 1,1-DCA; 1,1-DCE, and MTBE. Monitoring Wells: MTBE. COIs detected at greater than five percent frequency are presented in Tables 5 and 6. To provide an updated assessment of current risk, recent groundwater data for these COIs were compared against applicable risk-based concentrations (RBCs) for potentially complete exposure pathways to groundwater: inhalation of cvocs that have migrated from groundwater to indoor or outdoor air and dermal contact with groundwater. If the maximum concentration from any well during the last four sampling events did not exceed an RBC, then the COI was further screened out as a COPC of current risk (DEQ, 2008). Maximum groundwater concentrations during the last four sampling events and RBCs are presented in Tables 5 and 6. The following compounds were screened out based on the criteria of evaluating current risk: Domestic Wells: cdce. Monitoring Wells: TCA; 1,1-DCA; and 1,1-DCE. As a result of this focused evaluation and screening criteria, the following compounds were identified as current COPCs for evaluation in this HHRA: Domestic Wells: PCE and TCE. Monitoring Wells: PCE and TCE. 4.0 DOMESTIC WATER WELL SURVEY From April 30, 1998, to May 4, 1998, Hart Crowser conducted a door-to-door survey of all houses/buildings within the defined study area to identify users of private water wells for their potable water supply. During the study period, users Hart Crowser Page /Task 4 August 31, 2009

12 (homeowners, tenants, or building owners) were questioned about the source of their potable water and their willingness to participate in the sampling program. If a home/building was unoccupied at the time of the survey call, we left a simple questionnaire along with a stamped, self-addressed envelope to be completed and returned. During the survey, 237 homes/buildings were visited, 192 of which responded to the survey (45 owners/residents did not respond to the survey), and 121 of which had private water wells within the study area (shown on Figure 3). Of those that knew how deep their well was (66 out of 121), 68 percent of the wells are extracting from the shallow aquifer. It is not expected that these are indicative of all water wells in the study area. However, with the addition of two resident responses in November 1998, we believe that we have identified all of the domestic wells affected by the known VOC plumes. City water is currently available to all of the residents in the study area. Previous work in this area included connecting residences with domestic wells impacted by the chlorinated hydrocarbons to the municipal water supply. Many residents that do have city water available are also continuing to use existing domestic wells (primarily for irrigation and other non-potable uses). 5.0 UPDATED HUMAN HEALTH RISK ASSESSMENT This section describes the scope, focus, and approach of the updated HHRA. This risk assessment conforms to the protocol for performing risk assessments under OAR and DEQ s Guidance for Conduct of Deterministic Human Health Risk Assessments (DEQ, 1998). Other guidance was used as appropriate and where indicated. The HHRA evaluates the probability and magnitude of adverse impacts on human health associated with actual or potential exposure to site-related COPCs. Deterministic human health risk assessments for both existing and reasonably likely future exposure scenarios were performed. In accordance with EPA and DEQ guidance, the risk assessment consists of the following four phases: Exposure Assessment, Toxicity Assessment, Risk Characterization, and Uncertainty Analysis. In the exposure assessment, potentially exposed populations and potentially complete exposure pathways (shown in the human health conceptual site model [CSM], Figure 5) were identified based on current and future land use scenarios. Exposure point concentrations (EPC) and reasonable maximum exposure (RME) intake rates were calculated for each complete exposure pathway based on the use of exposure factors that reflect site-specific conditions. In the toxicity assessment, quantitative toxicity information was collected, and appropriate, current toxicity values were determined for use in quantifying Hart Crowser Page /Task 4 August 31, 2009

13 5.1 Exposure Assessment carcinogenic and non-carcinogenic risks associated with exposure to site-related chemicals. In the risk characterization phase, the intake rates calculated in the exposure assessment and the toxicity assessment results were combined to calculate RBCs based on each potential receptor and exposure pathway. The EPC calculated in the exposure assessment were then divided by the RBCs to estimate the potential cancer risks and non-cancer hazard quotients at the site. In the uncertainty section, the uncertainty associated with the exposure assessment, toxicity assessment, and risk characterization sections are discussed. The objectives of an exposure assessment are to: Identify potentially exposed populations; Identify potentially complete exposure pathways; and Measure or estimate the magnitude, duration, and frequency of exposure for each receptor (or receptor group) Conceptual Site Model A human health conceptual site model (CSM) was developed for the study area. The human health CSM is based on an evaluation of existing data and the current conditions at the study area. This CSM provides the framework for selecting potential exposure pathways to be considered in the risk assessment. To be considered complete, an exposure pathway must have: (1) an identified source of COPCs; (2) a release/transport mechanism from the source; and (3) a receptor to whom contact can occur. At the study area, VOCs (PCE and TCA and their breakdown products) have been detected in shallow monitoring and domestic wells. Potential receptors to these COPCs are identified on Figure 5. Potential receptors were identified based on current land and water uses within the locality of the facility (LOF). Identification of receptors is discussed in greater detail below. Potentially complete exposure pathways are shown as a checkbox in the exposure pathway model on Figure 5. This model will serve as the basis for the HHRA. Potentially Exposed Populations (Receptors). The study area is located in an area of mixed residential and commercial uses (Hart Crowser, 2000). City water is currently available to all of the residents in the study area. Previous work in this area included connecting residences with domestic wells impacted by the chlorinated hydrocarbons to the municipal water supply. Based on these study area characteristics, the potentially exposed populations identified at this site are Hart Crowser Page /Task 4 August 31, 2009

14 residents, occupational (retail) workers, and excavation workers. Because there were no COIs detected in any of the soil samples collected from this study area, no soil exposure pathways are considered complete. Potentially Complete Exposure Routes. Exposure pathways identified for risk screening are presented in the human health CSM (Figure 5). Based on available information, the exposure pathways to be evaluated for current and future receptors in the human health risk screening are: Residents: Indoor air inhalation, outdoor air inhalation, and outdoor water users exposure pathways (ingestion, dermal contact, and inhalation). The outdoor water user exposure pathways include adults exposed to groundwater while irrigating and children exposed to groundwater swimming in child-size swimming pools. The indoor air and outdoor air inhalation pathways are based on the migration of VOCs from groundwater (in situ) to indoor and outdoor air, respectively. The outdoor water user inhalation pathway is based on the volatilization of groundwater (ex situ) during irrigating and swimming; Occupational Workers: Indoor air inhalation and outdoor air inhalation. The indoor air and outdoor air inhalation pathways are based on the migration of VOCs from groundwater (in situ) to indoor and outdoor air, respectively; and Excavation Workers: Outdoor air inhalation and dermal contact with groundwater. The outdoor air inhalation pathway is based on volatilization of VOCs from groundwater that has been exposed during excavation activities. The dermal contact pathway assumes excavation workers would come into contact with groundwater during excavation activities Determining Representative Exposure Point Concentrations Due to natural attenuation, plume migration, and/or remedial actions conducted at the Ridgeway site during 2004, groundwater data was initially evaluated by comparing the last four sampling events against the lowest potentially applicable RBC at each monitoring location. Any monitoring location that exceeded any potentially applicable RBC during the last four events was used to evaluate current risk through EPC calculation methods described below Development of Exposure Point Concentrations EPCs represent the chemical concentrations in groundwater that either the receptor will potentially contact during the exposure period or are available for volatilization to indoor and outdoor air. The EPCs for the site s COPCs were Hart Crowser Page /Task 4 August 31, 2009

15 derived from groundwater sampling data and calculated for monitoring locations that had a least one COPC exceed any RBC during the last four sampling events. The following methodology was used to develop a representative EPC: For each monitoring point containing a COPC above the lowest potentially applicable RBC, the entire data set was evaluated using the Mann-Kendall statistical method to determine if groundwater concentrations reflected an increasing, decreasing, or stable/no trend with 95 percent certainty. Where COPCs were not detected in groundwater, half of the detection limit was used for Mann-Kendall analysis. Results from this analysis are presented in Table 7. For wells showing increasing or decreasing COPC concentration trends using Mann-Kendall analysis of all available data, the maximum concentration over the last four sampling events was used as a conservative measure of the EPC to reflect current risk. For wells showing stable or no COPC concentration trend, all available data were analyzed using EPA s ProUCL version (EPA, 2009a) software to develop a recommended analysis method and calculate the 90 percent upper confidence limit (UCL) on the arithmetic mean concentration under the following conditions: If a COPC had 5 or more valid detections and up to one non-detectable value, the EPC was based on the UCL calculation using software recommendations; If a COPC had more than one non-detectable concentration, then EPC was calculated using the software option to calculate a UCL with non-detects; and If the COPC has 4 or fewer valid observations, the maximum concentration was used as EPC. Of the 22 domestic wells and 8 monitoring wells that exceeded at least one RBC during the last four sampling events, three wells indicated statistically significant decreasing trends. These locations include Well 32, MW-2, and MW-5. All three of these wells are near the Ridgeway portion of the groundwater plume. The remaining wells did not indicate a 95 percent statistically certain concentration trend. However, many of these wells did indicate some degree of increasing or decreasing trend using linear regression methods, as discussed in Section and presented in Appendix A. The absence of statistically certain trends using Mann-Kendall could be attributed to either concentration instability or a small concentration data set. Domestic wells 11, 25, 29, 33, 56 and monitoring wells MW-18, MW-19, and MW-20 had fewer than 10 distinct data points but the most recent water quality results exceeded one or more RBCs. Hart Crowser Page /Task 4 August 31, 2009

16 5.2 Toxicity Assessment Groundwater EPCs for each individual domestic and monitoring well which exceeded at least one RBC during the last four sampling events are presented in Tables 8 and 9, respectively. If a COPC was not detected during the last four sampling events, then no EPC was calculated. The objectives of the toxicity assessment are to evaluate the inherent toxicity of the compounds under investigation and to identify and select toxicological measures for use in evaluating the significance of the exposure. These toxicological measures or criteria were used in conjunction with standard and site-specific intake rates for chemicals of concern in the risk characterization process of the human health risk assessment. Standard DEQ human health risk assessment toxicity databases were used to derive health-based toxicity criteria for most COIs (DEQ, 2008). The exception was DCA, which used new toxicology data based on EPA PRGs expected to be incorporated into DEQ s standard toxicity database (EPA, 2009b) Types of Toxicity Values for Quantifying Risks Toxicity and risk assessments vary for different chemicals depending upon whether non-carcinogenic or carcinogenic responses (i.e., endpoints) are used to assess potential risks. These criteria, in turn, are based on the endpoints observed from laboratory or epidemiological studies with the chemicals. Some chemicals of concern may result in both non-carcinogenic and carcinogenic effects, although in many cases the EPA has published toxicity criteria for only the most sensitive type of toxic effect supporting the most restrictive toxicological criteria. The toxicity criteria used in this HHRA are presented in Table 10. Reference Doses (RfDs). Reference doses are used to quantitatively evaluate non-carcinogenic toxicity of a specific chemical. Reference doses are established at levels associated with no adverse effect the "no observed adverse effect level" (NOAEL). In general, the RfD is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. RfDs are developed from an analysis of the available toxicological literature from which a critical study is selected. The selection of a critical study is made by professional judgment and considers factors such as the quality of the study, the relevance of the study to human exposures, and other factors. Good quality Hart Crowser Page /Task 4 August 31, 2009

17 human toxicological data are preferred to animal studies. If human data are not available, the study on the most sensitive species is selected as the critical study. Similarly, the toxic effect manifested at the lowest exposure level is (generally) selected as the critical effect. Cancer Slope Factors (SFs). The toxicity of potential human carcinogens is evaluated differently. It is assumed for carcinogens that no threshold concentrations exist below which adverse effects may not occur. Probabilistic methods based on chemical-specific dose-response curves are used to establish slope factors, which are then used to quantify potential risks from exposure to carcinogens. Dose-response curves are generated in laboratory studies using high chemical concentrations. The dose-response curve is fitted to a linearized multistage model that extrapolates the slope of the curve from high experimental concentrations to low concentrations at which people are typically exposed. The final slope factor (SF) is based on the 95 percent UCL of the extrapolated slope of the dose-response curve. Because of the non-threshold assumption and the UCL statistical procedure, the use of published slope factors provides a conservative upper-bound estimate of potential risks associated with exposure. 5.3 Risk-Based Concentrations The human health CSM identified potentially exposed populations and potentially complete exposure pathways present at the study area (Section and Figure 5). As shown in Figure 5, each potential receptor at this site may be exposed to groundwater contaminants via volatilization from groundwater to indoor or outdoor air. DEQ s Risk-Based Decision Making guidance (RBDM; DEQ, 2008) and associated spreadsheet model provide equations for calculating RBCs associated with the potentially complete exposure pathways evaluated in this risk assessment with the exception of the residential outdoor water user exposure pathways. Site-specific residential outdoor water user RBCs were calculated using methodology described below. The RBCs used in this risk assessment were calculated based on a cancer risk of 1 x 10-6, and, therefore, acceptable groundwater concentrations for the exposure pathways were considered in the RBC. The RBCs are used in Section 5.4 (Risk Characterization) to estimate potential carcinogenic risks and noncarcinogenic hazards. The RBCs used in this risk assessment are presented in Tables 5 and DEQ and Site-Specific RBCs The following DEQ RBDM groundwater RBCs were used in this risk assessment (DEQ 2008). Hart Crowser Page /Task 4 August 31, 2009

18 Volatilization to Outdoor Air Residential Inhalation of compounds volatilizing from groundwater to outdoor air for residents. Volatilization to Outdoor Air Occupational Inhalation of compounds volatilizing from groundwater to outdoor air for commercial workers. Vapor Intrusion into Buildings Residential Inhalation of compounds volatilizing from groundwater to indoor air for residents. Vapor Intrusion into Buildings Occupational Inhalation of compounds volatilizing from groundwater to indoor air for commercial workers. Excavation Worker Dermal contact with groundwater and inhalation of compounds volatilizing from groundwater to outdoor air for excavation/utility workers. The site-specific residential outdoor water user groundwater RBC includes groundwater ingestion, dermal contact with groundwater, and inhalation of compounds volatilizing from groundwater to outdoor air for residential outdoor water users Exposure Factors DEQ s RBDM spreadsheet, updated in October 2008, presents generic RBCs for each of the above bulleted pathways based on the toxicity factors for each COPC that are combined with variables that describe the exposed population (e.g., contact rate, exposure frequency and duration, body weight). Exposure assumptions are presented in DEQ s RBDM guidance (DEQ, 2003) and are not discussed in detail here. As part of this risk assessment, a site-specific RBC for residential outdoor water user scenario was calculated based on exposure factors as described below. These calculations are presented in Appendix B. General Exposure Factors. The residential outdoor water user exposure frequencies for adults and children are assumed to be 60 and 36 days/year, respectively. The adult exposure frequency is based on 3 days/week for 20 weeks, and the child exposure frequency is based on best professional judgment. Incidental Groundwater Ingestion. Residential outdoor water users were assumed to ingest water during irrigation (adults) and swimming (children) activities. The RME site-specific groundwater ingestion rates used in this HHRA are 50 ml/day for adults and 100 ml/day for children. These ingestion rates are based on best professional judgment and on EPA s surface water ingestion rate during swimming of 50 ml/hour (EPA, 1997). The ingestion rates include incidental groundwater ingestion during irrigation and swimming and drinking Hart Crowser Page /Task 4 August 31, 2009

19 groundwater directly from a garden hose. Exposure parameters for this exposure pathway are presented in Table 11. Dermal Contact with Groundwater. This risk assessment also assumes residential outdoor water users are or will be exposed to groundwater COPCs via the dermal contact pathway. The RME skin surface area assumptions used in this HHRA are 1,840 cm 2 for adults and 6,600 cm 2 for children. The adult value represents the mean surface area of hands and feet (average of adult males and females), while the child value represents the median whole body surface area of a 3- to 4-year old boy. This exposure pathway assumes a child will be exposed to groundwater in a wading pool for 1 hour/day. The wading pool was assumed to be 1.52 meters wide, filled with 20 cm of water. An average wind speed of 3.2 meters per second was used for volatilization purposes and is based on National Climatic Data Center average wind speed through 2002 for nearby Eugene, Oregon. The Interim Final HHRA (Hart Crowser, 2003) calculated that dermal COPCs exposure would be reduced by approximately 60 percent due to volatilization during pool filling and as a result of splashing. The result of the modeling, PCE and TCE calculations include dermal correction factors of 0.6 for the children only. For example, based on the dermal correction factor of 0.6, a PCE groundwater concentration of 50 μg/l would be used to evaluate the groundwater ingestion and inhalation of volatiles exposure pathways, and a concentration of 30 μg/l would be used to evaluate the dermal contact with groundwater pathway. Exposure parameters for this exposure pathway are presented in Table Risk Characterization Air Inhalation. Inhalation rates for the residential outdoor water users were based on DEQ default adult and child inhalation rates of 20 m 3 /day and 8.3 m 3 /day, respectively. The inhalation rates were modified to account for the limited exposure of 1 hour/day assumed for this exposure scenario. Exposure parameters for this exposure pathway are presented in Table 13. Risk characterization is the process of comparing the chemical intake by a receptor to the toxicity of the chemical. This comparison is expressed either as a hazard index (non-carcinogens) or an excess lifetime risk of cancer (carcinogens). These two methods for completing the risk characterization are described in Section Section summarizes the results of the risk characterization. RBCs were was used to evaluate the residential and commercial worker inhalation of volatiles that have migrated from groundwater in situ to outdoor Hart Crowser Page /Task 4 August 31, 2009

20 and indoor air; residential outdoor water user exposure to groundwater via ingestion, dermal contact, and inhalation of volatiles; and excavation worker exposure to groundwater via dermal contact and inhalation of volatiles Methods Used to Quantify Risks As discussed in Section 5.2.1, non-carcinogenic chemical effects are quantitatively evaluated using an RfD, while carcinogenic chemical effects are evaluated using an SF. Non-Carcinogenic Effects. For each non-carcinogen, the EPC is divided by the non-carcinogenic RBC to compute a hazard quotient (HQ) as follows: where: Hazard Quotient = EPC/RBC EPC = Exposure point concentration in μg/l. RBC = Risk-based concentration in μg/l. The RBCs are calculated based on a Hazard Quotient of 1. Carcinogenic Effects. For each carcinogen, the EPC is divided by the carcinogenic RBC, and is then multiplied by the acceptable risk level of 1 x 10-6 to compute the risk estimate as follows: where: Risk = (EPC/RBC) x (1 x 10-6 ) EPC = Exposure point concentration in μg/l. RBC = Risk-based concentration in μg/l. These PRGs are calculated based on a cancer risk level of 1 x Cumulative Hazard and Risk Estimates. For simultaneous exposure to multiple chemicals with similar toxic effects or target organs, a Hazard Index (HI) is calculated as the sum of chemical-specific HQs. A toxic effect is considered possible if the HI or HQ exceeds 1 (OAR ). For simultaneous exposure to multiple chemicals, individual risk estimates are summed to provide pathway, media, and receptor total risk estimates. Combining potential cancer risks as a result of exposure to multiple chemicals through multiple exposure pathways assumes the following: Hart Crowser Page /Task 4 August 31, 2009

21 Exposure to all COPCs will result in the same effect (cancer); and Each COPC exerts its effect independently (i.e., there is no synergism or antagonism). OAR considers 1 x 10-6 and 1 x 10-5 to be acceptable risk levels for individual and multiple carcinogens, respectively Human Health Risk Estimates Risk estimates for each receptor are discussed in this section and are presented in Tables 14 through 19. Hazard estimates are not presented in the risk characterization text or tables. Because PCE and TCE are both carcinogenic, and the carcinogenic risks for these two compounds will exceed DEQ acceptable levels before the hazard estimates will, there is no value in providing the hazard estimates for each domestic and monitoring well. The residential hazard estimate based on the Ridgeway domestic well, which has the highest PCE and TCE EPCs, was calculated to be 1.0, which is acceptable under DEQ regulations. Therefore, the hazard estimates for all other wells and receptors is less than the DEQ acceptable level of Residents Risks to residential receptors were evaluated for the following exposure pathways: indoor air inhalation, outdoor air inhalation, and the outdoor water user exposure pathways (ingestion, dermal contact, and inhalation during irrigation and swimming in child-size pools). The outdoor air inhalation pathway was not included in the residential risk estimates discussed below and in Tables 14 and 15 because the indoor air inhalation pathway risks are more than an order of magnitude higher than outdoor air. Both residential pathways use the same exposure assumptions but different dispersion models (DEQ 2003). As a result, relying on residential indoor vapor intrusion exposure for risk purposes is the most conservative since a resident cannot be simultaneously exposed to both indoor and outdoor air and apportioning exposure time would only serve to decrease calculated risk. Of note however, the PCE EPC exceeded the outdoor air RBC in four domestic wells (wells 11, 12, 25, 29) and three monitoring wells (MW-2, MW-5, and MW-20). The cumulative outdoor air risk estimates for PCE and TCE was exceeded in domestic well 29. Domestic Wells (Table 14). The residential cumulative risk estimates for the domestic wells exceeding at least one RBC range from 1 x 10-6 to 3 x The OAR acceptable level of 1 x 10-5 for cumulative carcinogenic risk was exceeded at domestic wells 11, 12, 25, 29, 31, 46, and 56. Ridgeway well 29 Hart Crowser Page /Task 4 August 31, 2009

22 contained the highest cumulative residential risk estimate of 3 x Of these wells exceeding the cumulative risk, wells 11, 25, 29, 46 have not been sampled since Therefore, their respective risk estimates reflecting current likely risk is uncertain. As indicated in Table 14, PCE risk estimates exceed the DEQ acceptable risk level for individual COPCs of 1 x 10-6 for all evaluated domestic wells except wells 9, 51, and 143. Because PCE was most likely to trigger risk screening, based on the EPC calculation criteria, most wells for which calculations were performed were most likely to exceed the PCE RBC for at least one pathway. TCE risk estimates exceed the DEQ acceptable risk level for individual COPCs of 1 x 10-6 for wells 1, 12, and 29. Well 29 has not been sampled since Therefore its risk estimate reflecting current likely risk is uncertain. Monitoring Wells (Table 15). The residential cumulative risk estimates for the monitoring wells range from 5 x 10-6 to 1 x The OAR acceptable level of 1 x 10-5 for cumulative carcinogenic risk was exceeded at MW-2, MW-5, MW-13, MW-19, and MW-20. As indicated in Table 15, PCE risk estimates exceed the DEQ acceptable risk level for individual COPCs of 1 x 10-6 for all evaluated monitoring wells. Because PCE was most likely to trigger risk screening, based on the EPC calculation criteria, wells for which calculations were performed were most likely to exceed the PCE RBC for any given pathway. All PCE data is considered current and reliable. TCE risk estimates exceed the DEQ acceptable risk level for individual COPCs of 1 x 10-6 for monitoring wells MW-5. All TCE data is considered current and reliable Occupational Workers Risks to occupational workers were evaluated for indoor air and outdoor air inhalation exposure pathways. The indoor air inhalation pathway risk estimates are presented in Tables 16 and 17. As discussed for the residents exposure, an occupational worker cannot be simultaneously exposed to both indoor and outdoor air. Since indoor air RBCs are significantly lower than outdoor air, the more conservative indoor air exposure pathway was used for individual COPC and cumulative risk calculations to occupational workers. Domestic Wells (Table 16). The occupational worker cumulative risk estimates for the domestic wells range from 7 x to 2 x The OAR Hart Crowser Page /Task 4 August 31, 2009

23 acceptable level of 1 x 10-5 for cumulative carcinogenic risk was not exceeded at any of the domestic wells. As indicated in Table 16, PCE risk estimates did not exceed the DEQ acceptable risk level for individual COPCs of 1 x 10-6 for any domestic wells. TCE risk estimates exceed the DEQ acceptable risk level for individual COPCs of 1 x 10-6 for well 29. Well 29 has not been sampled since Monitoring Wells (Table 17). The occupational worker cumulative risk estimates for the monitoring wells range from 1 x 10-8 to 2 x The OAR acceptable level of 1 x 10-5 for cumulative carcinogenic risk was not exceeded at any of the monitoring wells. PCE and TCE risk estimates did not exceed the DEQ acceptable risk level for individual COPCs of 1 x 10-6 in any monitoring wells Excavation Workers Risks to excavation workers were evaluated for the following exposure pathways: outdoor air inhalation and dermal contact with groundwater (Tables 18 and 19). Domestic Wells (Table 18). The occupational worker cumulative risk estimates for the domestic wells range from 4 x 10-9 to 6 x The OAR acceptable level of 1 x 10-5 for cumulative carcinogenic risk was not exceeded at any of the domestic wells. As indicated in Table 18, PCE risk estimates exceed the DEQ acceptable risk level for individual COPCs of 1 x 10-6 for wells 11 and 29. Both wells 11 and 29 have not been sampled since Therefore their respective risk estimates reflecting current likely risk is uncertain. TCE risk estimates did not exceed the DEQ acceptable risk level for individual COPCs of 1 x 10-6 for any domestic wells. Monitoring Wells (Table 19). The occupational worker cumulative risk estimates for the monitoring wells range from 2 x 10-6 to 6 x The OAR acceptable level of 1 x 10-5 for cumulative carcinogenic risk was not exceeded at any of the monitoring wells. PCE risk estimates exceeded the DEQ acceptable risk level for individual COPCs of 1 x 10-6 in monitoring well MW-2. TCE risk estimates did not exceed the DEQ acceptable risk level for individual COPCs of 1 x 10-6 for any monitoring wells. All data is considered current and reliable. Hart Crowser Page /Task 4 August 31, 2009

24 5.5 Uncertainty It is important to fully specify the assumptions and uncertainties inherent in the risk assessment to place the risk estimates in proper perspective. For this risk assessment, the general sources of uncertainty that are addressed include: Data collection and evaluation; Exposure assessment; Toxicity assessment; and Risk characterization Data Collection and Evaluation Groundwater data were collected from domestic and monitoring wells in the Sweet Home Area. Risks were estimated at each well individually based on PCE and TCE EPC concentrations that were calculated using either the maximum of the last four events (based on Mann-Kendall trend) or the entire groundwater data set from selected domestic and monitoring wells. Data sets ranged from 4 to 20 rounds of groundwater monitoring data. Monitoring well data were collected from 1997 or 1998 through October 2008, while many of the domestic wells have not been sampled since Table 20 presents a human health risk assessment uncertainty evaluation that focused on PCE and TCE risk estimates greater than 1 x 10-6, UCL EPC reliability, and whether the EPCs likely overestimate current PCE and TCE groundwater concentrations. Many of the EPCs are based on UCL calculations that used small sample sizes of less than ten distinct data points, relied on old groundwater data, heavily biased based on a single analytical result, or resulted in values significantly above recent groundwater analytical results. Groundwater data is considered old when the most recent analytical results are greater than 5 years old. Even though Mann- Kendall analysis did not indicate a groundwater concentration trend with 95 percent certainty, several monitoring locations have shown significant concentration declines over the last several monitoring events. Since sampling frequency has decreased over time, this recent data is under-weighted in the UCL calculation and Mann-Kendall analysis. These four factors can significantly impact the assessment accuracy of current risk. The uncertainty evaluation yielded the following results: Small data sets Domestic wells 11, 25, 29, 33, 46, 45 and monitoring wells MW-18, MW-19, and MW-20; Old data sets Domestic wells 1, 11, 25, 29, 33, 46, and 56; Hart Crowser Page /Task 4 August 31, 2009

25 Biased based on one analytical result Domestic wells 17, 46, and 143; and EPC significantly above recent results Domestic wells 12, 25, 31, 33, and 51 and monitoring wells MW-4 and MW Exposure Assessment The exposure estimation methods are subject to varying degrees of uncertainty. The degree of uncertainty generally depends on the amount of site-specific data available. The following sources of uncertainty have been identified. Exposure Scenario Identification. This HHRA assumes receptors are limited to residents, commercial workers, and excavation workers. If this assumption is incorrect, future risks and hazards could be under- or overestimated. Exposure Parameters and Assumptions. The standard and site-specific exposure assumptions may or may not be representative of the actual exposure conditions and could under- or overestimate future risks and hazards. The outdoor water user exposure pathway assumptions were based primarily on best professional judgment. Adult and child exposure frequencies were set at 60 and 36 days per year, respectively. The exposure time associated with the outdoor water user pathways was assumed to be 1 hour per day. Additionally, groundwater ingestion rates assumed that adults drink the groundwater from a garden hose during irrigation and children ingest the water while playing in the swimming pool. The intent of these exposure assumptions was to represent reasonable maximum exposure to groundwater at this site. Assumption of Steady-State Conditions. The inherent assumption is that future COPC concentrations are the same as current concentrations. In general, this assumption overestimates COPC concentrations and resulting exposure intakes. As stated in Section 5.5.1, many of the domestic well EPCs were based on maximum detected concentrations that were collected up to 10 years ago or that recent detections were significantly below historic concentrations. Several wells indicate declining groundwater concentrations through linear regression but statistically stable concentrations when analyzed through Mann-Kendall. Consistent monitoring frequency would improve statistical weighting of concentration changes in some wells. Linear regression trends for wells considered stable/no trend by Mann-Kendal suggest potential long-term PCE concentrations changes are summarized below: Increasing PCE regressions domestic wells 1, 7, 9, 11, 17, 22, 36, 56, and 143 and monitoring wells MW-13 and MW-20; and Hart Crowser Page /Task 4 August 31, 2009

26 Decreasing PCE regressions domestic wells 6, 12, 13, 20, 21, 25, 29, 31, 33, and 51 and monitoring wells MW-4, MW-14, MW-18, and MW-19. When combined with the Mann-Kendall analysis, these regressions suggest that concentration near the Ridgeway site are in long-term decline while concentrations north of the site are increasing. Modeling Procedures. DEQ s RBDM guidance and resulting RBCs estimate the volatilization from groundwater to indoor and outdoor air. The assumptions used in these models introduce uncertainty in that they may not reflect actual conditions. There is significant uncertainty associated with the volatilization model used to estimate indoor and outdoor air concentrations based on soil and groundwater concentrations. Areas of uncertainty include, but are not limited to: COPC Concentration: The model assumes the COPC EPCs represent current conditions. Because some COPC concentrations are based on the maximum detected concentration or are biased based on a limited data set, this is likely to significantly overestimate the amount of contamination present. Building Parameters: The RBDM guidance uses various building parameter assumptions as a basis for the indoor air concentrations such as building volume to area ratio (essentially the height of the building), building air exchange rate (the amount of times the air in the building is replace per second), the foundation crack thickness, and the foundation crack fraction (that is, the fraction of the building floor that contains cracks). Many of these assumptions have a linear effect on the model output (that is, if the air exchange rate is doubled, the indoor air concentration would drop in half). The model also assumes there is no vapor barrier under the foundation and that the building is not under positive pressure. DEQ s default building parameters were used in this HHRA. COPC-Specific Parameters: The RBDM guidance uses various chemical parameters such as diffusion coefficients, Log K oc or Log K d, Henry s Law Constant, vapor pressure, and solubility. These values can vary considerably in the literature. Default chemical parameters included in the RBDM model were used. These COPC-specific parameters can have a significant effect on the results, and, therefore, the degree that the parameters used represent actual conditions at the site may lead to an overestimation or underestimation of actual air concentrations. Depth to Groundwater: The RBDM guidance assumes a depth to groundwater of 9.8 feet when modeling vapor phase transport to outdoor air or to the soil directly under a building. Groundwater levels across the site Hart Crowser Page /Task 4 August 31, 2009

27 5.6 Risk Contours ranged from approximately 9 to 27 feet below ground surface during October Historically, groundwater elevations are also shown to fluctuate between 3 and 21 feet in any given shallow monitoring well Toxicity Assessment Whether verified by consensus among EPA scientists or not, uncertainty is present in the derivation of toxicity factors, and several assumptions are necessary. The primary uncertainty associated with the toxicity assessment is the provisional nature of the PCE and TCE toxicity factors. Only the PCE oral RfD is available on EPA s IRIS database. The provisional toxicity values for DCA were recently updated by EPA s National Center for Environmental Assessment (NCEA). These provisional values are available in the EPA Region 9 PRG tables (EPA, 2009b). Based on discussions with DEQ toxicologists, the DCA provisional values from the April 2009 PRG tables were used to calculate applicable RBCs for this constituent. Values from the October 2008 DEQ RBDM guidance were used for all other constituents in this risk assessment. The rationale behind this decision to use different sources for the DCA versus other toxicity factors is that the DCA toxicity factors are likely to be incorporated in the DEQ RBDM guidance tables Risk Characterization This HHRA used EPA s standard algorithms to calculate chemical intakes and associated health risks and hazards. There are certain assumptions inherent in the use of these equations that add uncertainty. For example, calculations of carcinogenic risks and non-carcinogenic risk assume the additivity of toxic effects. This assumption adds uncertainty to the assessment and may result in an overestimation or underestimation of the potential risks, depending on whether synergistic or antagonistic conditions apply. Exposure pathway risks are combined assuming that a single receptor may be exposed to contamination through a selected number of pathways concurrently. This is a conservative estimate that may overestimate risks and hazards. Additionally, the standard algorithms used do not consider certain factors, such as absorption or matrix effects. In cases where these processes are important, the risk estimates may overestimate or underestimate the potential human risks at this site. To further evaluate the results of the risk assessment, the cumulative potential carcinogenic risks for residents were calculated from the domestic well and groundwater monitoring well data. The data used to produce the risk contours are presented in Tables 14 and 15 of this report. Only the risks to residential Hart Crowser Page /Task 4 August 31, 2009

28 receptors were contoured, as this receptor population represents the maximally exposed population present within the LOF. Residential risk contours are presented on Figure 6. The risk contours show there are two areas within the Sweet Home Areawide LOF that exceed the DEQ cumulative carcinogenic acceptable risk level of 1 x As shown on Figure 6, the two areas of higher relative risk are: (1) associated with the detected levels of COPCs in near the Ridgeway and Hi-Tech Muffler Shop sites (wells 11, 12, 25, 29, MW-2, MW-19, and MW-20) and (2) associated with detected levels of COPCs in wells 1, 31, 56, and MW-4. The risk estimates for individual COPCs associated with either of these domestic or groundwater monitoring wells are presented in Tables 14 and 15. In addition, there were individual domestic and monitoring wells for which estimated risks for individual COPC exceeded the DEQ acceptable risk level of 1 x These domestic wells and monitoring wells are all scattered within the 1 x 10-6 contour line on Figure 6. Risk estimates exceed the DEQ acceptable risk level for individual COPCs in the following domestic wells listed below by COPC: PCE: 1 (Allen; 1 x 10-5 ), 6 (Garcia; 7 x 10-6 ), 7 (Groshong; 3 x 10-6 ), 11 (Webb; 9 x 10-5 ), 12 (Funk; 3 x 10-5 ), 13 (Krangness; 5 x 10-6 ), 17 (Lewis; 3 x 10-6 ), 20 (Mckinnion; 6 x 10-6 ), 21 (Mennonite; 2 x 10-6 ), 22 (Miller; 6 x 10-6 ), 25 (ODF; 3 x 10-5 ), 29 (Ridgeway; 3 x 10-4 ), 31 (Seward; 2 x 10-5 ), 32 (Sorrel; 1 x 10-5 ), 33 (Kunzman; 8 x 10-6 ), 36 (Brooks; 4 x 10-6 ), 45 (Wagon I; 2 x 10-6 ), 46 (Wagon II; 2 x 10-5 ), and 56 (USFS; 2 x 10-5 ); and TCE: 1 (Allen; 2 x 10-6 ), 12 (Funk; 6 x 10-6 ), and 29 (Ridgeway; 4 x 10-5 ). Risk estimates exceed the DEQ acceptable risk level for individual COPCs in the following monitoring wells listed below by COPC: PCE: MW-2 (1 x 10-4 ), MW-4 (1 x 10-5 ), MW-5 (3 x 10-5 ), MW-13 (2 x 10-5 ), MW-14 (9 x 10-6 ), MW-18 (4 x 10-6 ), MW-19 (2 x 10-5 ), and MW-20 (3 x 10-5 ); and TCE: MW-5 (2 x 10-6 ). 6.0 LEVEL 1 ECOLOGICAL RISK ASSESSMENT A Level 1 Scoping Ecological Risk Assessment (ERA) was completed as part of Hart Crowser s Phase II Site Investigation Report (Hart Crowser, 2000). The Scoping ERA was completed to provide a qualitative determination of whether Hart Crowser Page /Task 4 August 31, 2009

29 6.1 Sensitive Environments there are any reasons to believe ecological receptors and/or exposure pathways are present or potentially present in the study area. The results of the scoping ERA are duplicated from Hart Crowser (2000) and are presented below. A sensitive environment is defined by OAR as follows: an area of particular environmental value where a hazardous substance could pose a greater threat than in other non-sensitive areas. Sensitive environments include but are not limited to: critical habitat for federally endangered or threatened species; National Park, Monument, National Marine Sanctuary, National Recreational Area, National Wildlife Refuge, National Forest Campgrounds, recreational areas, game management areas, wildlife management areas, designated federal Wilderness Areas, wetlands (freshwater, estuarine, or coastal), wild and scenic rivers, state parks, state wildlife refuges, habitat designated for state endangered species, fishery resources, state designated natural areas, county or municipal parks, and other significant open spaces and natural resources protected under Goal 5 of Oregon s Statewide Planning Goals. Based on this definition, there are no sensitive environments located within the LOF. A wetland and the South Santiam River are located north of the site. 6.2 Threatened and Endangered Species Threatened and endangered (T&E) species were not observed on this site during the ecological scoping visit. The Oregon Natural Heritage Program (ONHP), which monitors threatened and endangered plants and wildlife, conducted a data search of T&E species within a 2-mile radius of the site. A letter from the ONHP is included in Appendix C. Eight (8) records of observations of state or federal T&E species were noted within a 2-mile radius of the site and are summarized below. Rana pretiosa (Oregon spotted frog) reported in Sweet Home; the year of last observation was Coccyzus americanus (yellow-billed cuckoo) reported in Sweet Home; the year of last observation was Canis lupus (gray wolf) reported in Foster; the year of last observation was Clemmys marmorata marmorata (northwestern pond turtle) reported in Foster Dam Pond, adjacent to Santiam River; the year of last observation was Hart Crowser Page /Task 4 August 31, 2009

30 6.3 Site Visit Summary Clemmys marmorata marmorata (northwestern pond turtle) reported 1 mile east of foster, South Santiam River at bridge; the year of last observation was Clemmys marmorata marmorata (northwestern pond turtle) reported at Foster Quarry Road; the year of last observation was Oncorhynchus mykiss pop 20 (Upper Willamette River steelhead) the presence of steelhead is considered undocumented but as having the potential of being present. Oncorhynchus tshawytscha pop 16 (chinook salmon Upper Willamette River ESU) - the presence of chinook is considered undocumented but as having the potential of being present. The South Santiam River (which has the potential for the presence of steelhead and chinook salmon) is outside the LOF. This section describes the results of Hart Crowser s April 11, 2000, site visit to assess whether ecological receptors and/or exposure pathways are present or potentially present at or in the study area. The discussion of ecological features present at the facility is based on our on-site observations. Photographs taken during the site visit are presented in Appendix C Observed Impacts Impacts to the site and surrounding properties attributable to contaminated environmental media were not observed. The contamination is currently limited to the shallow groundwater aquifer, and samples of surface water in the direction of groundwater flow have not indicated any migration of contaminants from groundwater to surface water features Ecological Features Ecological features were assessed by evaluating the habitat within the LOF. Appendix C presents the checklists used in this evaluation. The LOF at this site includes two distinct areas. To the south of Highway 20, the land use is characterized by residential and commercial development and use. To the north of Highway 20, the LOF has more undeveloped areas characterized by open space and thickets. Further to the north are a wetland and the South Santiam River. This area also contains several residential developments and a commercial/industrial area with an associated log pond. Hart Crowser Page /Task 4 August 31, 2009

31 6.4 Exposure Pathways Grasses, ornamental trees, and shrubs characterize vegetation present in the area south of Highway 20. Much of the open space present is landscaped and actively maintained. Species of vegetation observed included: bitter cherry (Prunus emarginata), black cottonwood (Populus trichocarpa), vine maple (Acer circinatum), cypress (Cupressus spp.), Colorado blue spruce (Picea pungensis), English yew (Taxus baccattas), crab apple (Pyrus spp.), dogwood (Cornus spp.), and holly (Ilex spp.). Several species of birds were observed that are common in residential areas, including American robin (Turdus migratorius), and common raven (Corvus corax), and no undomesticated mammals were observed in this area during the site visit. On the north side of Highway 20, the vegetation cover types are a mixture of deciduous and coniferous trees. Observed trees included: red alder (Alnus rubra), Douglas fir (Pseudotsuga manziesii), western hemlock (Tsuga heterophylla), western red cedar (Thuja plicata) and lodgepole pine (Pinus contorta). Additionally, the understory vegetation included dense cover of poison oak (Rhus diversiloba), thistle (Cirsium sp. and Carduus sp.), and blackberry (Bubus sp.). Bird species observed included: chestnut-backed chickadee (Parus rufescens), northern flicker (Colaptes auratus), American robin (Turdus migratorius), and common raven (Corvus corax). Other ecological features included unvegetated areas being developed for residential purposes, revegetated sapling stands at various stages of maturity, and a log pond within an active unvegetated industrial area Ecologically Important Species and Habitats Ecologically important species, as defined by DEQ guidance, include T&E species, species that are recreational and/or commercial resources, local vertebrate species, and invertebrate species that serve as potential food sources for higher organisms and perform critical ecological functions. No ecologically important terrestrial species were observed on or adjacent to the site. However, the open fields and thickets to the north of Highway 20 likely support small mammal and invertebrate species that serve as food sources for other organisms. Their associated habitats would also be present in these open areas and thickets. A general evaluation of potential receptor-pathway interactions is provided in the checklists presented in Appendix C. As summarized in these checklists, the only ecologically important species or habitats present in the LOF are in the areas north of Highway 20. At the present time, the contamination at this site is limited to chlorinated hydrocarbons present in the shallow groundwater aquifer. Hart Crowser Page /Task 4 August 31, 2009

32 There are no complete exposure pathways currently present in the LOF to ecological receptors identified during this Level 1 Scoping ERA. No additional ecological risk assessment activities are warranted at this time. 7.0 SUMMARY AND CONCLUSIONS An updated HHRA and a Scoping ERA have been completed for this site. A human health CSM was developed for the Sweet Home Areawide site based on available information and the beneficial water use survey completed at the study area. Human receptor populations identified for the study area were residents, commercial workers, and utility/excavation workers. Potentially complete exposure pathways from groundwater were identified and presented on Figure 5. A screening of analytical data was conducted, and PCE and TCE were identified as COPCs for this human health risk assessment. A human health risk assessment was completed and the results presented in Tables 14 through 19 and Section 5.4 of this report. Based on the estimated cumulative risk levels, risk contours were developed for the Sweet Home Areawide study area based on EPCs developed for each domestic and groundwater monitoring well for the groundwater to indoor air volatilization pathway and outdoor use pathway for residents. There were exceedances of individual carcinogenic and cumulative carcinogenic acceptable risk levels found. The wells associated with the calculated unacceptable risks are presented in Tables 14 through 19. There were two general areas of the study area where exceedences of cumulative carcinogenic acceptable human health risk levels were observed. As shown on Figure 6, the two areas of higher relative risk are: (1) associated with the detected levels of COPCs in near the Ridgeway and Hi- Tech Muffler Shop sites (wells 11, 12, 25, 29, MW-2, MW-19, and MW-20) and (2) associated with detected levels of COPCs in wells 1, 31, 56, and MW-4. In addition, the domestic wells and monitoring wells with estimated unacceptable carcinogenic risks to residents for individual COPCs are all scattered within the 1 x 10-6 contour line on Figure 6. These wells are listed in Section 5.6. A Scoping ERA was conducted to provide a qualitative determination of whether there is reason to believe ecological receptors and/or exposure pathways are present or potentially present at or in the LOF. The site visit and historical research did not identify any ecologically important species or habitats present at this site. In addition, there were no complete exposure pathways identified to aquatic species or to terrestrial species via exposure to surface water or Hart Crowser Page /Task 4 August 31, 2009

33 groundwater. Therefore, it is concluded that further ERA activities (e.g., Level 2 Risk-Based Screening) are not warranted at this site. 8.0 RECOMMENDATIONS Based on the results of this updated HHRA, several recommendations are made. These include continued annual monitoring of water quality, installation of additional monitoring wells to assist in the on-going assessment of plume location, and additional remediation efforts. In areas of unacceptable cumulative risk (1 x 10-5 ), continued annual monitoring is recommended to assist in developing a more reliable statistical trend of current conditions. This trend will improve statistical certainty of whether contamination continues to attenuate and determine how rapidly the plume may be migrating to the north. While Mann-Kendall indicates that concentrations are statistically decreasing in only 3 locations, linear regression suggests that overall PCE groundwater concentration declines may actually be occurring at 17 monitoring locations currently exceeding one or more RBCs. Linear regressions also suggest that long-term PCE groundwater concentration trends may be increasing at 11 locations, including north of the Ridgeway site and in the vicinity of 45 th Avenue and US Highway 20. As some wells have become inaccessible or decommissioned, the installation of up to four additional shallow monitoring wells is recommended. These monitoring wells would be located in key areas of concern to improve the accuracy of conceptual shallow plume distribution and to assist in on-going risk evaluation. Specific locations of interest include: Replace decommissioned monitoring well MW-16 to monitor possible northerly plume migration; Northeast of the intersection of 46 th Avenue and US Highway 20 to improve delineation near a residential area and provide current water quality data between domestic wells 11 and 25, which could not be sampled since 1998; Southwest corner of 45 th Avenue and US Highway 20 to improve delineation near a residential area and provide current water quality data downgradient of domestic well 1, which could not be sampled since 2003; and Approximately 400 feet west-southwest of MW-13 along Osage Street to confirm western and northern plume delineation and residential risk north of US Highway 20 between 44th Avenue and 45th Avenue. Hart Crowser Page /Task 4 August 31, 2009

34 Additional remediation efforts are recommended for the core plume area downgradient of the former Ridgeway site. Linear regression suggests that PCE concentrations in MW-2 and MW-13 are increasing. To minimize remediation costs, a low-maintenance bioremediation approach may be a viable option. This could include push probe slug injections of a long-lasting bioremediation substrate in several lines, perpendicular to groundwater flow. This could significantly reduce residual PCE mass by stimulating processes including reductive dechlorination. Generation of methane in a typically oxidative aquifer can also stimulate certain co-metabolic degradation pathways downgradient of the actual injection locations. These efforts would compliment bioremediation already performed on the Ridgeway site. 9.0 LIMITATIONS Hart Crowser performed this work in accordance with generally accepted professional practices related to the nature of the work accomplished, in the same or similar localities, at the time the services were performed. This report is for the specific application to the referenced project and for the exclusive use of the DEQ. No other warranty, express or implied, is made REFERENCES DEQ, Guidance for Use of Probabilistic Analysis in Human Health Risk Assessments. Interim Final. Updated November DEQ, Risk-Based Decision Making for the Remediation of Petroleum- Contaminated Sites. September 22, DEQ, Risk-Based Concentration Table. Updated October 3, EPA, Exposure Factors Handbook; Volume III Activity Factors. Chapter 17, Residential Building Characteristics. EPA/600/P-95/002Fc. EPA, 2009a. Statistical Software ProUCL 4.0 for Environmental Applications for Data Sets with and without Nondetect Observations. Downloaded April EPA, 2009b. EPA Region 9, Preliminary Remediation Goals (PRGs). Updated April Hart Crowser Page /Task 4 August 31, 2009

35 Hart Crowser, Site Investigation Report, Areawide Groundwater Investigation, Sweet Home, Oregon. January 13, Hart Crowser, Phase II Site Investigation Report, Areawide Groundwater Investigation, Sweet Home, Oregon. May 22, Hart Crowser, Groundwater Monitoring Data Report, Areawide Groundwater Investigation, Sweet Home, Oregon. August 6, Hart Crowser, Interim Final Risk Assessment Report, Areawide Groundwater Investigation, Sweet Home, Oregon. February 17, Hart Crowser, Groundwater Monitoring Data Report, Areawide Groundwater Investigation, Sweet Home, Oregon. August 26, Hart Crowser Page /Task 4 August 31, 2009

36 Table 1 - Summary of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Well 1 - Allen 2 - Archey 3 - Dunn 4 - Eads Sheet 1 of 14 Analytical Results in µg/l Date cis-1,2-1,1,1- Chloro- Total Sampled PCE TCE DCE TCA 1,1-DCA 1,1-DCE form MTBE VOCs 10-Aug < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Nov-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug < < < < < < < Mar < < < < < Sep < < < < < Mar < < < < < Sep < < < < < Jun < < < < < Jun < < < < < Jun < 1.0 < < 1.0 < Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < < Oct-08 < 0.5 < 0.5 < 0.5 < 1.0 < 0.5 < < Dec-94 < 0.5 < 0.5 < < 0.5 < Jan-97 < 0.5 < 0.5 < 0.5 < < 0.5 < Jul-97 < 0.5 < 0.5 < < 0.5 < Feb-98 < 0.5 < 0.5 < 0.5 < < 0.5 < Aug-98 NS NS NS NS NS NS NS NS NS 22-Mar-99 < < < < < < < Jun-01 < < < < < < < Dec-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 10-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 27-Aug-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 15-Mar-00 < < < < < < < < ND 20-Sep-00 < < < < < < < < ND 14-Jun-01 < < < < < < < < ND 5-Jun-02 < < < < < < < < ND 25-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 18-Jun-92 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 31-Jul-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 11-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 26-Aug-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 16-Mar-00 < < < < < < < < ND 10-Oct-00 < < < < < < < < ND 14-Jun-01 < < < < < < < < ND 6-Jun-02 < < < < < < < < ND 26-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 11-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 30-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND 12-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND Please refer to notes on the last page of this table.

37 Table 1 - Summary of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Well 5 - Evans Analytical Results in µg/l Date cis-1,2-1,1,1- Chloro- Total Sampled PCE TCE DCE TCA 1,1-DCA 1,1-DCE form MTBE VOCs 10-Aug-92 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 6-Jan-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 31-Jul-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 10-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 26-Aug-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 16-Mar-00 < < < < < < < < ND 20-Sep-00 < < < < < < < < ND 13-Jun-01 < < < < < < < < ND 5-Jun-02 < < < < < < < < ND 12-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 31-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < < Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 6 - Garcia 3-Nov-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 9-Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug * < < < < < Sep < < < < < < Mar < < < < < < Sep < < < < < < Jun < < < < < < < Jun < < < < < < Aug < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct < 0.5 < 1.0 < 1.0 < 0.5 < 0.5 < 0.5 < Groshong 10-Aug-92 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 6-Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 10-Feb-98 < < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug < < < < < < < Mar < < < < < < < Sep < < < < < < < Apr < < < < < < < Sep < < < < < < < Jun < < < < < < < Jun < < < < < < Jun < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct < 0.5 < 1.0 < 0.5 < 0.5 < 0.5 < Please refer to notes on the last page of this table. Sheet 2 of 14

38 Table 1 - Summary of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Well 8 - Hale 9 - Hampton 10 - Hilltop 11 - Webb Analytical Results in µg/l Date cis-1,2-1,1,1- Chloro- Total Sampled PCE TCE DCE TCA 1,1-DCA 1,1-DCE form MTBE VOCs 8-Mar-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 6-Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug < < < < < < < Mar < < < < < < < Sep < < < < < < < Mar < < < < < < < Sep-00 < < < < < < < < ND 14-Jun-01 < < < < < < < < ND 6-Jun < < < < < < < Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 11-Aug < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 6-Oct < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 < 0.5 < Aug-92 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 13-May-96 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 10-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 26-Aug-98 < < < < < < < Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 10-Oct-00 < < < < < < < < ND 14-Jun-01 < < < < < < < < ND 6-Jun-02 < < < < < < < < ND 10-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 29-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND 11-Oct < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct-08 < 0.5 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 < 0.5 < 1.0 ND 30-Jul-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 10-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 26-Aug-98 < < < < < < < < ND 25-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 16-Mar-00 < < < < < < < < ND 20-Sep-00 < < < < < < < < ND 12-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 20-Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug < 2.50 < 2.50 < 2.50 < 2.50 < 2.50 < Well decommissioned Please refer to notes on the last page of this table. Sheet 3 of 14

39 Table 1 - Summary of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Well 12 - Funk Analytical Results in µg/l Date cis-1,2-1,1,1- Chloro- Total Sampled PCE TCE DCE TCA 1,1-DCA 1,1-DCE form MTBE VOCs 3-Nov < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < Jan < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < Aug * < 2.50 < 2.50 < 2.50 < 2.50 < Mar < < < < < Sep < < < < < Mar < < < < < Sep < < < < < Jun < < < < < < Jun < < < < < Jun < 1.0 < < 1.0 < Aug < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Kragness 20-Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug < < < < < < Mar < < < < < < Sep < < < < < < Mar < < < < < < Sep < < < < < < < Jun < < < < < < Jun < < < < < < Jun < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Lanz 27-Mar-96 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 31-Jul-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 27-Aug-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 16-Mar-00 < < < < < < < < ND 20-Sep-00 < < < < < < < < ND 5-Jun-02 < < < < < < < < ND 31-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND 10-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 15 - Lee 8-Mar-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 31-Jul-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 11-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 26-Aug-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 15-Mar-00 < < < < < < < < ND 30-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND Please refer to notes on the last page of this table. Sheet 4 of 14

40 Table 1 - Summary of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Well 17 - Lewis Analytical Results in µg/l Date cis-1,2-1,1,1- Chloro- Total Sampled PCE TCE DCE TCA 1,1-DCA 1,1-DCE form MTBE VOCs 20-Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug-98 < < < < < < Mar-99 < < < < < < < < ND 29-Sep < < < < < < Mar-00 < < < < < < < < ND 21-Sep < < < < < < < Jun < < < < < < < Jun-02 < < < < < < < < ND 24-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 10-Aug < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 < 0.5 < Lundquist 20-Dec-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 31-Jul-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 27-Aug-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 15-Mar-00 < < < < < < < < ND 19-Jun-01 < < < < < < < < ND 6-Jun /ND** 0.71/ND** < < < < < < ND 24-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND Well Decommissioned 20 - Mckinnon 10-Aug-92 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 19-Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug < < < < < < Mar < < < < < < Sep < < < < < < Mar < < < < < < Sep < < < < < < Jun < < < < < < Jun < < < < < < Jun < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < Mennonite 18-Jun-92 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 3-Nov < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug-98 < < * < < < < < Please refer to notes on the last page of this table. Sheet 5 of 14

41 Table 1 - Summary of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Analytical Results in µg/l Date cis-1,2-1,1,1- Chloro- Total Well Sampled PCE TCE DCE TCA 1,1-DCA 1,1-DCE form MTBE VOCs 21 - Mennonite 10-Sep < < < < < (continued) 22-Mar < < < < < < Sep < < < < < < Mar < < < < < < Sep-00 < < < < < < < Jun < < < < < < Jun < < < < < < Jun < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Sep < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Miller 10-Aug < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug < < < < < < Mar < < < < < < < Sep < < < < < < Mar < < < < < < < Sep < < < < < < Jun < < < < < < < Jun < < < < < < Jun < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < Oct < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct < 0.5 < 1.0 < 0.5 < 0.5 < 0.5 < Moore 19-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 10-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 26-Aug-98 < 1.00 < 1.00 < 1.00 < 1.00 < 1.00 < 1.00 < 1.00 < 1.00 ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 16-Mar-00 < < < < < < < < ND 20-Sep-00 < < < < < < < < ND 13-Jun-01 < < < < < < < < ND 6-Jun-02 < < < < < < < < ND 31-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND 13-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 24 - Mountain View 10-Aug-92 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 27-Mar-96 < < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 11-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 26-Aug-98 < < < < < < < < ND 25-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 20-Sep-00 < < < < < < < < ND 5-Jun-02 < < < < < < < < ND Please refer to notes on the last page of this table. Sheet 6 of 14

42 Table 1 - Summary of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Well 25 - ODF Analytical Results in µg/l Date cis-1,2-1,1,1- Chloro- Total Sampled PCE TCE DCE TCA 1,1-DCA 1,1-DCE form MTBE VOCs 8-Mar < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug < < < < < < Pointer 10-Aug-92 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 3-Nov-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 30-Jul-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 10-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 26-Aug-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 27 - Reagan 30-Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug * < < < < < Sep < < < < < < < Sep < < < < < < < Jun < < < < < < < Jun-02 < < < < < < < < ND 25-Jun < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 29-Aug < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 < 0.5 < Rice 20-Dec-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 19-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 31-Jul-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 10-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 26-Aug-98 < < < < < < < < ND 25-Mar < < < < < < < Sep-99 < < < < < < < < ND 16-Mar < < < < < < < Sep-00 < < < < < < < < ND 13-Jun-01 < < < < < < < < ND 6-Jun-02 < < < < < < < < ND 25-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 12-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 30-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND 12-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 2-Oct-08 < 0.5 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 < 0.5 < 1.0 ND 29 - Ridgeway 24-Jan < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 1, Dec < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 1, Feb < 0.5 < 0.5 < 0.5 < 0.5 < Sep < 2.50 < 2.50 < 2.50 < 2.50 < Please refer to notes on the last page of this table. Sheet 7 of 14

43 Table 1 - Summary of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Well 30 - Rodriguez Analytical Results in µg/l Date cis-1,2-1,1,1- Chloro- Total Sampled PCE TCE DCE TCA 1,1-DCA 1,1-DCE form MTBE VOCs 20-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 31-Jul-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 11-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 26-Aug-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 15-Mar-00 < < < < < < < < ND 20-Sep-00 < < < < < < < < ND 14-Jun-01 < < < < < < < < ND 5-Jun-02 < < < < < < < < ND 26-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 12-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 30-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND 10-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 31 - Seward 20-Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jan < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug < 1.00 < 1.00 < 1.00 < 1.00 < 1.00 < Mar < < < < < < Sep < < < < < < Mar < < < < < < Sep < < < < < < Jun < < < < < < < Jun < < < < < < Jun < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < Oct < 0.5 < 1.0 < 0.5 < B < Sorrel 20-Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug * < < < < < Mar < < < < < < Sep < < < < < Mar < < < < < < Mar < < < < < < Sep < < < < < < Jun < < < < < < Jun < < < < < < Jun < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < Oct < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct < 0.5 < 1.0 < 0.5 < 0.5 < 0.5 < Please refer to notes on the last page of this table. Sheet 8 of 14

44 Table 1 - Summary of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Well 33 - Kunzman Analytical Results in µg/l Date cis-1,2-1,1,1- Chloro- Total Sampled PCE TCE DCE TCA 1,1-DCA 1,1-DCE form MTBE VOCs 18-Jun < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Nov < < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug * 0.32* < < < < < Sheet 9 of Taylor 10-Aug-92 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 1-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 11-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 27-Aug-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 15-Mar-00 < < < < < < < < ND 35 - West 24-Jan-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 27-Aug < < < < < < < Mar < < < < < Sep < < < < < < < Mar < < < < < < < Sep < < < < < < < Jun < < < < < < < Jun-02 < < < < < < < < ND 25-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 10-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 29-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND 12-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 2-Oct-08 < 0.5 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 < 0.5 < 1.0 ND 36 - Brooks 10-Aug-92 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 3-Nov < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Dec < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jan < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Jul < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Aug < < < < < < Mar < < < < < < < ** 29-Sep < < < < < < Jun < < < < < < Jun < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Martin 31-Jul-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 43 - Nelson 20-Dec < 0.5 < 0.5 < < 0.5 < Please refer to notes on the last page of this table.

45 Table 1 - Summary of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Sheet 10 of 14 Analytical Results in µg/l Date cis-1,2-1,1,1- Chloro- Total Well 45 - Wagon Wheel I Sampled PCE TCE DCE TCA 1,1-DCA 1,1-DCE form MTBE VOCs 18-Jun < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Nov-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 19-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 46 - Wagon Wheel II 18-Jun < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Dec-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < < Wilmot 49 - Keenon 50 - Louie 18-Jun-92 < 0.5 < 0.5 < < 0.5 < Nov-94 < 0.5 < 0.5 < < 0.5 < Dec-94 < 0.5 < 0.5 < < 0.5 < Aug-98 < < < < Sep-98 < < < < Jun-02 < < < < Jun-03 < 1.0 < 1.0 < < 1.0 < Sep-04 < 1.0 < 1.0 < < 1.0 < Aug-05 < 1.0 < 1.0 < < 1.0 < Aug-92 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < < Aug-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 16-Mar-00 < < < < < < < < ND 10-Oct-00 < < < < < < < < ND 13-Jun-01 < < < < < < < < ND 6-Jun-02 < < < < < < < < ND 26-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 11-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 2-Oct-08 < 0.5 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 < 0.5 < 1.0 ND 27-Aug < < < < < < < Mar < < < < < < < Sep < < < < < < < Oct-00 < < < < < < < < ND 14-Jun-01 < < < < < < < < ND 6-Jun < < < < < < < Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 11-Aug < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND Well Decommissioned 51 - Martinez 26-Aug < < < < < < < Mar < < < < < Sep < < < < < < Mar < < < < < < < Sep < < < < < < < Jun < < < < < < < Jun-02 < < < < < < < < ND 25-Jun < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Aug < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < Oct-08 < 0.5 < 0.5 < 0.5 < 1.0 < 0.5 < < Please refer to notes on the last page of this table.

46 Table 1 - Summary of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Well 52 - Myers Sheet 11 of 14 Analytical Results in µg/l Date cis-1,2-1,1,1- Chloro- Total Sampled PCE TCE DCE TCA 1,1-DCA 1,1-DCE form MTBE VOCs 26-Aug-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 20-Sep-00 < < < < < < < < ND 14-Jun-01 < < < < < < < < ND 6-Jun-02 < < < < < < < < ND 26-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 11-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 30-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND 12-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 53 - Rietz 10-Aug-92 < 0.5 < 0.5 < < 0.5 < 0.5 < 0.5 < Aug-98 < < < < * < < Mar-99 < < < < < Sep-99 < < < < < < Mar-00 < < < < < < < Sep-00 < < < < < < < < ND 14-Jun-01 < < < < < < < < ND 5-Jun-02 < < < < < < < < ND 26-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 11-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 30-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND 13-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 6-Oct-08 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < < Sweet Home RV 1-Jun-96 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 10-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 26-Aug-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 16-Mar-00 < < < < < < < < ND 20-Sep-00 < < < < < < < < ND 13-Jun-01 < < < < < < < < ND 6-Jun-02 < < < < < < < < ND 25-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 11-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 30-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND 12-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 2-Oct-08 < 0.5 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 < 0.5 < 1.0 ND 55 - Walker 26-Aug * < < < < < < Mar-99 < < < < < < < < ** 29-Sep-99 < < < < < < < < ND 15-Mar-00 < < < < < < < < ND 20-Sep-00 < < < < < < < < ND 14-Jun-01 < < < < < < < < ND 5-Jun-02 < < < < < < < < ND 26-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 11-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 2-Oct-08 < 0.5 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 < 0.5 < 1.0 ND Please refer to notes on the last page of this table.

47 Table 1 - Summary of Domestic Well Sampling Results Sheet 12 of 14 Sweet Home Areawide Risk Assessment Sweet Home, Oregon Analytical Results in µg/l Date cis-1,2-1,1,1- Chloro- Total Well Sampled PCE TCE DCE TCA 1,1-DCA 1,1-DCE form MTBE VOCs 56 - USFS Work Center 15-Sep < < < < < Mar-99 < < < < < < < < ND 29-Sep < < < < < < Sep < < < < < Jun < < < < < < Jun < < < < < < Jun < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Well Decommissioned 64 - Hudson 18-Jun < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < Mason 20-Dec-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 73 - Whitfield 10-Aug-92 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 76 - Leonard 15-Sep-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 16-Mar-00 < < < < < < < < ND 20-Sep-00 < < < < < < < Jun-02 < < < < < < < < ND 78 - King 27-Aug-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 16-Mar-00 < < < < < < < < ND 20-Sep-00 < < < < < < < < ND 13-Jun-01 < < < < < < < < ND 31-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND 96 - Pace 20-Oct-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 11-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 15-Sep-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < Stevens 8-Sep-98 < < < < < < < < ND 22-Mar-99 < < < < < < < < ND 29-Sep-99 < < < < < < < < ND 16-Mar-00 < < < < < < < < ND 20-Sep-00 < < < < < < < < ND 14-Jun-01 < < < < < < < < ND 5-Jun-02 < < < < < < < < ND 26-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 12-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 30-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND 10-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND Please refer to notes on the last page of this table.

48 Table 1 - Summary of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Well Underwood Sheet 13 of 14 Analytical Results in µg/l Date cis-1,2-1,1,1- Chloro- Total Sampled PCE TCE DCE TCA 1,1-DCA 1,1-DCE form MTBE VOCs 6-Jan-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND E. Allen 8-Mar-95 < 0.5 < 0.5 < < < 0.5 < Lucky 6-Nov-98 < < < < < < < 5.00 < ND 29-Sep-99 < < < < < < < 5.00 < ND Richter 10-Aug-92 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 6-Nov-98 < < < < < < < 5.00 < ND 29-Sep-99 < < < < < < < Sep-00 < < < < < < < Jun-01 < < < < < < < 5.00 < ND 26-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 31-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 12-Oct < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Nov * < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < Oct-08 < 0.5 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 < 0.5 < 1.0 ND Noble 20-Dec-94 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND 20-Dec-95 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 2.0 ND Lacey 16-Dec-99 < < < < < < < 5.00 < ND 16-Mar-00 < < < < < < < 5.00 < ND 12-Jun-01 < < < < < < < 5.00 < ND 26-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 11-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 31-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND 10-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND Brown 16-Dec-99 < < < < < < < 5.00 < ND 16-Mar-00 < < < < < < < 5.00 < ND 20-Sep-00 < < < < < < < 5.00 < ND 12-Jun-01 < < < < < < < 5.00 < ND 6-Jun-02 < < < < < < < 5.00 < ND 26-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 11-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 31-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 2.0 ND 10-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND R. Stock 16-Dec-99 < < < < < < < 5.00 < ND 16-Mar-00 < < < < < < < 5.00 < ND 20-Sep-00 < < < < < < < 5.00 < ND 12-Jun-01 < < < < < < < 5.00 < ND 6-Jun-02 < < < < < < < 5.00 < ND 26-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 11-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 31-Aug-05 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < *** Please refer to notes on the last page of this table.

49 Table 1 - Summary of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Well Hufford Palmer Rivers Sheet 14 of 14 Analytical Results in µg/l Date cis-1,2-1,1,1- Chloro- Total Sampled PCE TCE DCE TCA 1,1-DCA 1,1-DCE form MTBE VOCs 16-Dec-99 < < < < < < 5.00 < Mar-00 < < < < < < 5.00 < Sep-00 < < < < < < < 5.00 < ND 26-Jun-03 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 11-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 11-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND 11-Aug-04 < 1.0 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 < 1.0 < 2.0 ND Notes: Shading represents detected concentrations of VOCs. Only compounds detected more than once are shown. PCE = Tetrachloroethene. TCE = Trichloroethene. TCA = Trichloroethane. DCA = Dichloroethane. DCE = Dichloroethene. MTBE = Methyl-tert-butyl-ether. VOCs = Volatile organic compounds. * Estimated Concentration, below Method Reporting Limit. ** Methylene chloride detected in sample (confirmed). *** Vinyl chloride detected in associated trip blank at the same concentration. As such, this result is suspect. ND = Not Detected. NS = Not Sampled. NA = Not Analyzed. B = Estimated quantitation, analyte detected at higher concentrations in an associated quality control blank.

50 Table 2 - Summary of Groundwater Monitoring Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Analytical Results in µg/l Sample 1,1,1- Total Well Date PCE TCE TCA 1,1-DCA 1,1-DCE VOCs MW-1 17-Jul-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 ND 15-Oct-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 ND 19-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 ND 8-Sep < < < < Dec-98 < < < < < ND 23-Mar-99 < < < < < ND 16-Jun-99 < < < < < ND 29-Sep-99 NS NS NS NS NS NS 2-Dec-99 NS NS NS NS NS NS 29-Mar-00 < < < < < ND 19-Jun-00 < < < < < ND 19-Sep-00 < < < < < ND 13-Dec-00 < < < < < ND 12-Jun-01 < < < < < ND 28-Dec-01 < < < < < ND 4-Jun-02 < < < < < ND 23-Jun-03 < 1.00 < 1.00 < 1.00 < 1.00 < 1.00 ND 10-Aug-04 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 30-Aug-05 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 9-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 1-Oct-08 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 ND MW-2 17-Jul < 0.5 < 0.5 < Oct < 0.5 < 0.5 < Feb < 0.5 < 0.5 < Sep < < < Dec < 2.50 < 2.50 < Mar < < < Jun < 5.00 < 5.00 < 5.00 < Sep < 5.00 < 5.00 < 5.00 < Dec < 5.00 < 5.00 < Mar-00 1, < 5.00 < 5.00 < , Jun < 5.00 < 5.00 < Sep < < < Dec < 5.00 < 5.00 < 5.00 < Jun < 5.00 < 5.00 < Dec < 2.50 < 2.50 < Jun < 2.50 < 2.50 < Jun < 5.00 < 5.00 < 5.00 < Aug < 1.0 < 1.5 < Aug < 1.0 < 1.5 < Oct < 1.0 < 1.0 < Oct < 5.0 < 10 < 5.0 < MW-3 17-Jul-97 < 0.5 < Oct-97 < 0.5 < Feb-98 < 0.5 < Sep-98 < < Dec-98 < < Please refer to notes on the last page of this table. Sheet 1 of 8

51 Table 2 - Summary of Groundwater Monitoring Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Analytical Results in µg/l Sample 1,1,1- Total Well Date PCE TCE TCA 1,1-DCA 1,1-DCE VOCs MW-3 23-Mar < (cont.) 15-Jun-99 < < Sep-99 NS NS NS NS NS NS 2-Dec-99 NS NS NS NS NS NS 29-Mar < Jun < Sep < Dec < Jun < Dec B < Jun < Jun < Aug < Aug-05 <1.0 < Oct-06 <1.0 < Oct < MW-4 17-Jul < 0.5 < 0.5 < Oct < 0.5 < 0.5 < Feb < 0.5 < 0.5 < 0.5 < Sep < < < Dec < < < Mar < < < < Jun < < < Sep < < < Dec < < < Mar < < < Jun < < < Sep < < < Dec < < < Jun < < < Dec < < < Jun < < < Jun < 1.00 < 1.00 < Aug < 1.0 < 1.0 < 1.5 < Aug < 1.0 < 1.0 < 1.5 < Oct < 1.0 < 1.0 < 1.0 < Oct < 0.5 < 1.0 < 0.5 < MW-5 17-Jul < 0.5 < 0.5 < Oct < 0.5 < 0.5 < 0.5 < Feb < 0.5 < 0.5 < Sep < < < Dec < < < Mar < < < ** 16-Jun < < < Sep < < < Dec < < < Please refer to notes on the last page of this table. Sheet 2 of 8

52 Table 2 - Summary of Groundwater Monitoring Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Analytical Results in µg/l Sample 1,1,1- Total Well Date PCE TCE TCA 1,1-DCA 1,1-DCE VOCs MW-5 30-Mar < < < (cont.) 19-Jun < < < Sep < < < Dec-00 NS NS NS NS NS NS 12-Jun < < < Dec < < < Jun < < < Jun < 1.00 < 1.00 < Aug < 1.0 < 1.0 < 1.5 < Aug < 1.0 < 1.5 < Oct < 1.0 < 1.0 < Oct < 1.0 < 0.5 < MW-6 17-Jul-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 ND 14-Oct-97 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 ND 20-Feb-98 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 ND 10-Sep < < < < Dec-98 < < < < < ND 24-Mar-99 < < < < < ND 15-Jun-99 < < < < < ND 29-Sep-99 < < < < < ND 2-Dec-99 < < < < < ND 30-Mar-00 < < < < < ND 19-Jun-00 < < < < < ND 19-Sep-00 < < < < < ND 14-Dec-00 < < < < < ND 13-Jun-01 < < < < < ND 28-Dec-01 < < < < < ND 4-Jun-02 < < < < < ND 27-Jun-03 < 1.00 < 1.00 < 1.00 < 1.00 < 1.00 ND 10-Aug-04 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 30-Aug-05 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 9-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 1-Oct-08 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 ND MW-7 23-Sep-98 < < < < < ND 7-Dec-98 < < < < < ND 23-Mar-99 < < < < < ND 16-Jun-99 < < < < < ND 29-Sep-99 < < < < < ND 2-Dec-99 < < < < < ND 29-Mar-00 < < < < < ND 19-Jun-00 < < < < < ND 18-Sep-00 < < < < < ND 13-Dec-00 < < < < < ND 12-Jun-01 < < < < < ND 28-Dec-01 < < < < < ND Please refer to notes on the last page of this table. Sheet 3 of 8

53 Table 2 - Summary of Groundwater Monitoring Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Analytical Results in µg/l Sample 1,1,1- Total Well Date PCE TCE TCA 1,1-DCA 1,1-DCE VOCs MW-7 4-Jun-02 < < < < < ND (cont.) 23-Jun-03 < 1.00 < 1.00 < 1.00 < 1.00 < 1.00 ND 10-Aug-04 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 29-Aug-05 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 9-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 1-Oct-08 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 ND MW-8 23-Sep-98 < < < < < ND 7-Dec-98 < < < < < ND 23-Mar-99 < < < < < ND 16-Jun-99 < < < < < ND 29-Sep-99 < < < < < ND 2-Dec-99 < < < < < ND 29-Mar-00 < < < < < ND 19-Jun-00 < < < < < ND 18-Sep-00 < < < < < ND 13-Dec-00 < < < < < ND 12-Jun-01 < < < < < ND 28-Dec-01 < < < < < ND 4-Jun-02 < < < < < ND 23-Jun-03 < 1.00 < 1.00 < 1.00 < 1.00 < 1.00 ND 10-Aug-04 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 29-Aug-05 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 9-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 1-Oct-08 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 ND MW-9 23-Sep-98 < < < < < ND 7-Dec-98 < < < < < ND 24-Mar-99 < < < < < ND 16-Jun-99 < < < < < ND 29-Sep-99 < < < < < ND 2-Dec-99 < < < < < ND 30-Mar-00 < < < < < ND 19-Jun-00 < < < < < ND 19-Sep-00 < < < < < ND 14-Dec-00 < < < < < ND 13-Jun-01 < < < < < ND 28-Dec-01 < < < < < ND 4-Jun-02 < < < < < ND 24-Jun-03 < 1.00 < 1.00 < 1.00 < 1.00 < 1.00 ND 10-Aug-04 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 30-Aug-05 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 9-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 1-Oct-08 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 ND MW Sep-98 < < < < < ND 7-Dec-98 < < < < < ND 24-Mar-99 < < < < < ND 15-Jun-99 < < < < < ND Please refer to notes on the last page of this table. Sheet 4 of 8

54 Table 2 - Summary of Groundwater Monitoring Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Analytical Results in µg/l Sample 1,1,1- Total Well Date PCE TCE TCA 1,1-DCA 1,1-DCE VOCs MW Sep-99 < < < < < ND (cont.) 2-Dec-99 < < < < < ND 30-Mar-00 < < < < < ND 19-Jun-00 < < < < < ND 18-Sep-00 < < < < < ND 14-Dec-00 < < < < < ND 13-Jun-01 < < < < < ND 28-Dec B < < < < Jun-02 < < < < < ND 23-Jun-03 < 1.00 < 1.00 < 1.00 < 1.00 < 1.00 ND 10-Aug-04 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 29-Aug-05 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 9-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 1-Oct-08 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 ND MW Sep-98 < 5.00 < 5.00 < 5.00 < 5.00 < * 7-Dec < 5.00 < 5.00 < 5.00 < * 23-Mar-99 < < < < < * 15-Jun-99 < < < < < * 29-Sep-99 < < < < < * 2-Dec-99 < < < < < * 29-Mar-00 < < < < < * 19-Jun-00 < < < < < * 18-Sep-00 < < < < < * 13-Dec-00 < < < < < * 12-Jun-01 < < < < < * 28-Dec-01 < < < < < * 4-Jun-02 < < < < < * 23-Jun-03 < 1.00 < 1.00 < 1.00 < 1.00 < * 10-Aug-04 < 1.0 < 1.0 < 1.0 < 1.5 < * 29-Aug-05 < 1.0 < 1.0 < 1.0 < 1.5 < * 9-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < * MW Sep-98 < < < < < ND 7-Dec-98 < < < < < ND 23-Mar-99 < < < < < ND 15-Jun-99 < < < < < ND 29-Sep-99 < < < < < ND 2-Dec-99 < < < < < ND 29-Mar-00 < < < < < ND 19-Jun-00 < < < < < ND 18-Sep-00 < < < < < ND 13-Dec-00 < < < < < ND 12-Jun-01 < < < < < ND 28-Dec-01 < < < < < ND 4-Jun-02 < < < < < ND 23-Jun-03 < 1.00 < 1.00 < 1.00 < 1.00 < 1.00 ND 10-Aug-04 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 29-Aug-05 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 9-Oct-06 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND Please refer to notes on the last page of this table. Sheet 5 of 8

55 Table 2 - Summary of Groundwater Monitoring Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Analytical Results in µg/l Sample 1,1,1- Total Well Date PCE TCE TCA 1,1-DCA 1,1-DCE VOCs MW Sep < < < < Dec < < < < Mar < < < < Jun < < < < Sep < < < < Dec < < < < Mar < < < < Jun < < < < Sep < < < < Dec < < < < Jun < < < < Dec < < < < Jun < < < < Jun < 1.00 < 1.00 < 1.00 < Aug < 1.0 < 1.0 < 1.5 < Aug < 1.0 < 1.0 < 1.5 < Oct < 1.0 < 1.0 < 1.5 < *** 2-Oct < 0.5 < 1.0 < 0.5 < MW Sep < < < < Dec < < < Mar < < < Jun < < < Sep < < < Dec < < < Mar < < < Jun < < < Sep < < < Dec < < < Jun < < < Dec < < < Jun < < < Jun < 1.00 < 1.00 < Aug < 1.0 < 1.5 < Aug < 1.0 < 1.5 < Oct < 1.0 < 1.0 < Oct < 1.0 < 0.5 < MW Sep < < < < Dec < < < < Mar < < < < Jun < < < < Sep-99 < < < < < ND 2-Dec-99 < < < < < ND 29-Mar-00 < < < < < ND 19-Jun-00 < < < < < ND 19-Sep-00 < < < < < ND 13-Dec-00 < < < < < ND 12-Jun-01 < < < < < ND 28-Dec-01 < < < < < ND Please refer to notes on the last page of this table. Sheet 6 of 8

56 Table 2 - Summary of Groundwater Monitoring Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Analytical Results in µg/l Sample 1,1,1- Total Well Date PCE TCE TCA 1,1-DCA 1,1-DCE VOCs MW-15 4-Jun-02 < < < < < ND (cont.) 23-Jun-03 < 1.00 < 1.00 < 1.00 < 1.00 < 1.00 ND 10-Aug-04 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 30-Aug-05 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 9-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 1-Oct-08 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 ND MW Jan-00 < < < < < ND 30-Mar-00 < < < < < ND 21-Jun-00 < < < < < ND 19-Sep-00 < < < < < ND 15-Dec-00 < < < < < ND 13-Jun-01 < < < < < ND 28-Dec-01 < < < < < ND 4-Jun-02 < < < < < ND 24-Jun-03 < 1.00 < 1.00 < 1.00 < 1.00 < 1.00 ND 10-Aug-04 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 30-Aug-05 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 9-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 1-Oct-08 Well has been decommissioned. MW Jan-00 < < < < < ND 30-Mar-00 < < < < < ND 21-Jun-00 < < < < < ND 19-Sep-00 < < < < < ND 15-Dec-00 < < < < < ND 13-Jun-01 < < < < < ND 28-Dec-01 < < < < < ND 4-Jun-02 < < < < < ND 24-Jun < 1.00 < 1.00 < 1.00 < Aug-04 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 30-Aug-05 < 1.0 < 1.0 < 1.0 < 1.5 < 1.0 ND 9-Oct-06 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 ND 1-Oct < 0.5 < 1.0 < 0.5 < MW Feb < 1.0 < 1.0 < Jul < 1.0 < 1.0 < Aug <1 <1 < Oct < 1.0 < 1.0 < MW Feb < 1.0 < 1.0 < 1.0 < Jul < 1.0 < 1.0 < Aug <1 <1 < Oct < 1.0 < 1.0 < 1.0 < Oct < 0.5 < 1.0 < 0.5 < MW Feb < 1.0 < 1.0 < 1.0 < Jul < 1.0 < 1.0 < Aug <1 <1 <1 < Oct < 1.0 < 1.0 < Oct < 1.0 < 2.0 < 1.0 < Please refer to notes on the last page of this table. Sheet 7 of 8

57 Table 2 - Summary of Groundwater Monitoring Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Sheet 8 of 8 Notes: Shading represents detected concentrations of listed analyte. Only primary contaminants of concern are shown. PCE = Tetrachloroethene. TCE = Trichloroethene. TCA = Trichloroethane. DCA = Dichloroethane. DCE = Dichloroethene. VOCs = Volatile organic compounds. * = Detected VOCs include gasoline components. ** = Detected VOCs include Methylene Chloride. *** = Detected VOCs include Naphthalene. = Detected VOCs include cis-1,2-dichloroethene. = Detected VOCs include MTBE. = Detected VOCs include cis-1,2-dichloroethene and Acetone. = Detected VOCs include 1,1,2-Trichloroethane. = Detected VOCs include cis-1,2-dichloroethene and 4-Methyl-2-Pentanone. = Detected VOCs include cis-1,2-dichloroethene and Vinyl Chloride. B = Detected concentration has been flagged as an blank detection based on QA/QC review.

58 Table 3 - Statistical Summary of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Detection Historical Maximum Last 4 Sampling Events Maximum Analyte Frequency Concentration Sample ID Date Concentration Sample ID Date Volatiles in µg/l 1,1,1-trichloroethane 20 / Wilmot 6/18/ Wilmot 9/15/2004 1,1-dichloroethane 19 / Wilmot 6/18/ Wilmot 6/25/2003 1,1-dichloroethene 22 / Wilmot 9/8/ Wilmot 9/15/2004 cis -1,2-dichloroethene 32 / Allen 9/20/ Funk 6/25/2003 Methyl-tert-butyl-ether 5 / Hampton 8/26/1998 ND NA NA Tetrachloroethene 258 / 613 1,110 Ridgeway 12/20/ Webb 8/26/1998 Trichloroethene 159 / Ridgeway 12/20/ Funk 6/25/2003 Notes: ND = Not detected. NA = Not applicable.

59 Table 4 - Statistical Summary of Groundwater Monitoring Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Detection Historical Maximum Last 4 Sampling Events Maximum Analyte Frequency Concentration Sample ID Date Concentration Sample ID Date Volatiles in µg/l 1,1,1-trichloroethane 19 / MW-3 6/19/ MW-3 10/10/2006 1,1-dichloroethane 19 / MW-3 9/10/ MW-3 10/10/2006 1,1-dichloroethene 19 / MW-3 10/10/ MW-3 10/10/2006 Tetrachloroethene 134 / 321 1,420 MW-2 3/30/ MW-2 10/10/2006 Trichloroethene 74 / MW-4 12/7/ MW-2 10/10/2006

60 Table 5 - Risk Screening of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Historical Detection Frequency Maximum Detected During Last 4 Events Groundwater RBC Volatilization Outdoor Air Residential Groundwater RBC Volatilization Outdoor Air Occupational Groundwater RBC Vapor Intrusion into Buildings Residential Groundwater RBC Vapor Intrusion into Buildings Occupational Groundwater RBC Outdoor Water User Scenario Groundwater RBC Excavation Worker Analyte Volatiles in µg/l Cis-1,2-dichloroethene 32 / ,000 1,600,000 34, , ,600 Tetrachloroethene 258 / ,500 8, , Trichloroethene 159 / Notes: 1. Shaded boxes indicates Maximum Detected During Last 4 Events exceeds the lowest potentially Risk-Based Concentration (RBC) for the analy 2. Refer to Section 5.0 for description of Screening Levels 3. Compounds detected at greater than 5 percent Historical Detection Frequency are considered Contaminants of Potential Conce

61 Table 6 - Risk Screening of Monitoring Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Detection Frequency Detected Maximum Last 4 Events Groundwater RBC Volatilization Outdoor Air Residential Groundwater RBC Volatilization Outdoor Air Occupational Groundwater RBC Vapor Intrusion into Buildings Residential Groundwater RBC Vapor Intrusion into Buildings Occupational Groundwater RBC Outdoor Water User Scenario Groundwater RBC Excavation Worker Analyte Volatiles in µg/l 1,1,1-trichloroethane 19 / > 100,000,000 > 100,000,000 > 100,000,000 > 100,000, ,000,000 1,1-dichloroethane 19 / ,000 70, , ,800 1,1-dichloroethene 19 / ,000 2,200,000 27, , ,000 Tetrachloroethene 134 / ,500 8, , Trichloroethene 74 / Notes: 1. Shaded boxes indicates Maximum Detected During Last 4 Events exceeds the lowest potentially Risk-Based Concentration (RBC) for the analyte. 2. Refer to Section 5.0 for description of Screening Levels. 3. Compounds detected at greater than 5 percent Historical Detection Frequency are considered Contaminants of Potential Concern.

62 Table 7 - Summary of Wells Exceeding RBCs Sweet Home Areawide Risk Assessment Sweet Home, Oregon Sheet 1 of 2 Well No Analyte Last 4 Event Maximum Detect Mann- Kendall Analysis 90% UCL in µg/l Analysis Comments Domestic Wells 1 PCE 52.0 Stable 38.8 TCE PCE 22 Stable 30.2 TCE PCE 11.2 Stable 10.3 TCE PCE 21 Stable 0.95 Only one detection 11 PCE 401 NA 377 Not sampled since August 1998 TCE PCE 50.5 Stable 140 TCE PCE 24 Stable 20.2 TCE PCE 48 Stable PCE 19 Stable 23.6 TCE PCE 9.8 Stable PCE 37.5 Stable 25.1 TCE PCE 80 NA 111 Not sampled since August 1998 TCE PCE 1,110 NA 1,110 Not sampled since September 1998 TCE PCE 37 Stable 75.8 TCE PCE 50 Decreasing 47.1 TCE PCE 9.02 NA 31.9 Not sampled since August 1998 TCE PCE 15.0 Stable 10.6 TCE PCE 10 Stable 10 Not sampled since December 1995 TCE PCE 67 Stable 67 Not sampled since December 1994 TCE PCE 6.09 Stable PCE 79.7 NA 41.5 Well decommissioned, last sample June 2003 TCE PCE 11 Stable 5.98 One detection above reporting limit Monitoring Wells MW-2 PCE 560 Decreasing 843 TCE 6.4 Stable 3.9 MW-4 PCE 4.9 Stable 51 Please refer to notes on the last page of this table.

63 Table 7 - Summary of Wells Exceeding RBCs Sweet Home Areawide Risk Assessment Sweet Home, Oregon Well No Analyte Last 4 Event Maximum Detect Mann- Kendall Analysis 90% UCL in µg/l Analysis Comments Monitoring Wells (continued) MW-5 PCE 75 Decreasing 130 TCE 8.3 Stable 7.2 MW-13 PCE 69 Stable 62.4 MW-14 PCE 21 Stable 36.8 TCE MW-18 PCE 18 NA 18 Small data set TCE MW-19 PCE 61 NA 66 Small data set TCE MW-20 PCE 180 NA 130 Small data set TCE Sheet 2 of 2 Notes: PCE = Tetrachloroethene. TCE = Trichloroethene. µg/l = microgram per liter. NA = Mann-Kendall analysis not performed due to small (less than 10) data set. Shading indicates Mann-Kendall concentration trend in the 95 percent upper confidence limit.

64 Table 8 - Exposure Point Calculation of Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon SQL Range Detect Range Date of Last 4 Event Well Detection in µg/l in µg/l Historic Maximum 90 % UCL RME EPC No. Name Analyte Frequency (Min-Max) (Min-Max) Maximum Detect Distribution in µg/l in µg/l 1 Allen Tetrachloroethene 13 / /11/ Nonparametric Trichloroethene 9 / /25/ Nonparametric Garcia Tetrachloroethene 13 / /27/ Nonparametric Trichloroethene 10 / /27/ Nonparametric Groshong Tetrachloroethene 14 / /25/ Nonparametric Trichloroethene 4 / /10/ Nonparametric Hampton Tetrachloroethene 1 / /11/ Normal Trichloroethene 0 / Webb Tetrachloroethene 6/ /19/ Normal Trichloroethene 6/ /26/ Normal Funk Tetrachloroethene 16 / /31/ Normal Trichloroethene 15 / /10/ Normal Kragness Tetrachloroethene 15 / /27/ Normal Trichloroethene 14 / /12/ Normal Lewis Tetrachloroethene 12 / /11/ Nonparametric Trichloroethene 1 / /26/ Mckinnon Tetrachloroethene 13 / /15/ Normal Trichloroethene 13 / /29/ Normal Mennonite Tetrachloroethene 17 / /15/ Nonparametric Trichloroethene 11 / /22/ Miller Tetrachloroethene 17 / /20/ Gamma Trichloroethene 9 / /25/ Nonparametric ODF Tetrachloroethene 6/ /19/ Normal Trichloroethene 6/ /19/ Normal Ridgeway Tetrachloroethene 4/ ,110 12/20/1995 1,110 Maximum 1,110 1,110 Trichloroethene 4/ /20/ Maximum Seward Tetrachloroethene 15 / /15/ Normal Trichloroethene 15 / /15/ Gamma Sorrel Tetrachloroethene 18 / /6/ Normal Trichloroethene 18 / /20/ Normal Kunzman Tetrachloroethene 8/ /3/ Normal Trichloroethene 3/ /20/ Nonparametric Brooks Tetrachloroethene 11 / /20/ Normal Trichloroethene 7 / /20/ Nonparametric Wagon I Tetrachloroethene 1/ /18/ Maximum Trichloroethene 1/ /18/ Maximum Wagon II Tetrachloroethene 1/ /18/ Maximum Trichloroethene 1/ /18/ Maximum Martinez Tetrachloroethene 8 / /25/ Nonparametric Trichloroethene 1 / /25/ USFS Tetrachloroethene 6 / /21/ Normal Trichloroethene 6 / /21/ Gamma Richter Tetrachloroethene 2 / /12/ Nonparametric Trichloroethene 0 / Acronyms and Abbreviations: EPC = Exposure point concentration. -- = Not applicable. SQL = Standard quantification limit. UCL = Upper confidence limit on the mean. RME = Reasonable maximum exposure. Notes: Wells not listed above have never contained detectable tetrachloroethene or trichloroethene Bold indicates a groundwater concentration exceeding at least Risk-Based Concentration

65 Table 9 - Exposure Point Calculation of Monitoring Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon SQL Range Detect Range Date of Last 4 Event Detection in µg/l in µg/l Historic Maximum 90 % UCL RME EPC Well Analyte Frequency (Min-Max) (Min-Max) Maximum Detect Distribution in µg/l in µg/l MW-2 Tetrachloroethene 21 / ,420 3/30/ Normal Trichloroethene 16 / /10/ Lognormal MW-4 Tetrachloroethene 21 / /7/ Lognormal Trichloroethene 15 / /7/ MW-5 Tetrachloroethene 20 / /2/ Normal Trichloroethene 18 / /2/ Nonparametric MW-13 Tetrachloroethene 18 / /4/ Normal Trichloroethene 0 / MW-14 Tetrachloroethene 18 / /2/ Normal Trichloroethene 18 / /2/ Normal MW-18 Tetrachloroethene 4 / /23/ Maximum Trichloroethene 4 / /30/ Maximum MW-19 Tetrachloroethene 5 / /23/ Normal Trichloroethene 2 / /19/ Nonparametric MW-20 Tetrachloroethene 5 / /10/ Normal Trichloroethene 2 / /10/ Maximum Acronyms and Abbreviations: EPC = Exposure point concentration. -- = Not applicable. SQL = Standard quantification limit. UCL = Upper confidence limit on the mean. RME = Reasonable maximum exposure. Notes: MW-8, MW-9, MW-12, and MW-16 have never contained detectable contaminants of potential concern. Bold indicates a groundwater concentration exceeding at least Risk-Based Concentration \Tables 1-20 (values)-table 9 - MW Stats

66 Table 10 - Human Health Toxicity Assessment Sweet Home Areawide Risk Assessment Sweet Home, Oregon Noncarcinogenic Toxicity Factors Compound of Oral RfD in mg/kgday Potential Concern Inhalation RfD in mg/kg-day Volatile Organic Compounds 1,1-Dichloroethane 2.0E E-01 1,1-Dichloroethene 5.0E E-02 1,1,1-Trichloroethane 2.8E E-01 cis-1,2-dichloroethene 1.0E E-02 Tetrachloroethene 1.0E E-01 Trichloroethene 3.0E E-02 Carcinogenic Toxicity Factors Compound of Oral CSF in Potential Concern (mg/kg-day) -1 Inhalation CSF in (mg/kg-day) -1 Volatile Organic Compounds 1,1-Dichloroethane 5.7E E-03 Tetrachloroethene 5.4E E-02 Trichloroethene 4.0E E-01 Notes: All toxicological data, except 1,1-dichloroethane, per DEQ Risk-Based Concentrations for Individual Chemicals, revised August 16, 2006 ( 1,1-dichloroethane data per EPA Region 9 Preliminary Remediation Goals, April 2009 ( RfD = Reference Dose. CSF = Carcinogenic Slope Factor.

67 Table 11 - Exposure Dose Equations and Exposure Factor Values Groundwater Ingestion Sweet Home Areawide Risk Assessment Sweet Home, Oregon LADD a (mg/kg-d) = C water x IRW x EF x ED BW x At carc ADD b (mg/kg-d) = C water x IRW x EF x ED BW x At non EXPOSURE FACTOR (units) RME Value C water = Chemical concentration in water (mg/l) UCL 90 c IRW = Groundwater Ingestion Rate (L/d) Outdoor Water User Adult Outdoor Water User Child EF = Exposure frequency (days/year) Outdoor Water User Adult Outdoor Water User Child ED = Exposure duration (year) Outdoor Water User Adult Outdoor Water User Child BW = Body weight (kg) Adult Child 0.1 e 0.05 e 60 f 36 f 24 d 6 d 70 d 15 d AT carc = Averaging time for carcinogens (days) 25,550 d AT non = Averaging time for noncarcinogens (days) ED (years) x 365 days/year Notes: (a) Lifetime average daily dose, the intake value used to evaluate potential carcinogenic effects. For the residential evaluation, the adult and child intakes will be combined as recommended in Appendix A, Section A.0 of DEQ guidance (1998). (b) Average daily dose, the intake value used to evaluate potential noncarcinogenic effects. (c) An upper one-sided 90 percent confidence limit of the mean or the maximum concentration (whichever is lower) used for the RME case. (d) DEQ (1998). (e) These ingestion rates are based on best professional judgment and on EPA s surface water ingestion rate during swimming of 50 ml/hour (EPA 1989). (f) The adult exposure frequency is based on 3 days/week for 20 weeks and the child exposure frequency is based on best professional judgment. RME = Reasonable maximum exposure.

68 Table 12 - Exposure Dose Equations and Exposure Factor Values Dermal Contact with Groundwater Sweet Home Areawide Risk Assessment Sweet Home, Oregon LADD a (mg/kg-d) = DA water x SA x EF evd x EF dy x ED x DCF BW x At carc ADD b (mg/kg-d) = DA water x SA x EF evd x EF dy x ED x DCF BW x At non Exposure Factor (units) RME Value DA water = Dose absorbed per unit area per event (mg/cm 2 /event) See note c SA = Skin surface area (cm 2 ) Outdoor Water User Adult Outdoor Water User Child 6,600 e 1,840 e EF evd = Exposure frequency (events/day) Outdoor Water User Adult Outdoor Water User Child EF dy = Exposure frequency (days/year) Outdoor Water User Adult Outdoor Water User Child ED = Exposure duration (years) Outdoor Water User Adult Outdoor Water User Child DCF = Dermal correction factor (unitless) Outdoor Water User Adult Outdoor Water User Child BW = Body weight (kg) Adult Child 1 d 1 d 60 f 36 f 24 d 6 d 1 g 0.6 g 70 d 15 d AT carc = Averaging time for carcinogens (days) 25,550 d AT non = Averaging time for noncarcinogens (days) ED (years) x 365 days/year d Notes: (a) Lifetime absorbed daily dose, intake value used to evaluate potential carcinogenic effects. (b) Absorbed daily dose, intake value used to evaluate potential noncarcinogenic effects. (c) DA water will be calculated using the equations presented in Appendix A, Section A.7 of DEQ guidance (1998). The RME exposure time per event (t event ) for outdoor water users will be 1 hour. The RME exposure point concentrations (EPC) will be the UCL 90. If the UCL 90 exceeds the maximum concentration, the maximum will be use as the EPC. (d) DEQ (2003). (e) The adult value represents the mean surface area of hands and feet (average of adult males and females), while the child value represents the median whole body surface area of a 3- to 4-year old boy. (f) The adult exposure frequency is based on 3 days/week for 20 weeks and the child exposure frequency is based on best professional judgment. (g) The derivation of the DCF is discussed in Appendix ZZ. RME = Reasonable maximum exposure.

69 Table 13 - Exposure Dose Equations and Exposure Factor Values Inhalation of Volatiles Sweet Home Areawide Risk Assessment Sweet Home, Oregon LADD a (mg/kg-d) = C air x IR x EF x ED BW x At carc ADD b (mg/kg-d) = C air x IR x EF x ED BW x At non Exposure Factor (units) RME Value C air d = Chemical concentration in air (mg/m 3 ) UCL 90 c IR = Inhalation rate (m 3 /day) Outdoor Water User Adult Outdoor Water User Child EF = Exposure frequency (days/year) Outdoor Water User Adult Outdoor Water User Child ED = Exposure duration (years) Outdoor Water User Adult Outdoor Water User Child BW = Body weight (kg) Adult Child 0.83 e 0.35 e 60 f 36 f 24 e 6 e 70 e 15 e AT carc = Averaging time for carcinogens (days) 25,550 e At non = Averaging time for noncarcinogens (days) ED (years) x 365 days/year Notes: (a) Lifetime average daily dose, intake value used to evaluate potential carcinogenic effects. For the residential evaluation, the adult and child intakes will be combined as recommended in Appendix A, Section A.0 of DEQ guidance (2003). (b) Average daily dose, intake value used to evaluate potential noncarcinogenic effects. (c) Upper one-sided 90 percent confidence limit of the mean or the maximum concentration (whichever is lower) was used for the RME case. (d) C air was derived from groundwater concentrations using a volatilization factor of 3.73E-04 L/m 3, which was calculated using the VF model presented in the Eugene Yard Off-Property Preliminary Risk Evaluations. (e) DEQ (2003) standard inhalation rate adjusted based on 1 hour/day exposure. (f) The adult exposure frequency is based on 3 days/week for 20 weeks and the child exposure frequency is based on best professional judgment. RME = Reasonable maximum exposure.

70 Table 14 - Residential Risk Estimates from Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Indoor Air Inhalation Pathway a Swimming Pool/Irrigation Pathways b PCE TCE Well PCE Risk TCE Risk PCE Risk TCE Risk Total Risk Total Risk Cumulative No. Name in µg/l Estimate in µg/l Estimate in µg/l Estimate in µg/l Estimate Estimate Estimate Risk 1 Allen E E E E-07 1E-05 2E-06 1E-05 6 Garcia E E E E-07 7E-06 5E-07 8E-06 7 Groshong E E E E-08 3E-06 3E-07 3E-06 9 Hampton E E-07 2E-07 2E Webb 377 5E E E E-07 9E-05 8E-07 9E Funk 140 2E E E E-06 3E-05 6E-06 4E Kragness E E E E-08 5E-06 3E-07 5E Lewis E E-06 3E-06 3E Mckinnon E E E E-07 6E-06 3E-07 6E Mennonite E E-06 2E-06 2E Miller E E E E-07 6E-06 4E-07 7E ODF 111 1E E E E-07 3E-05 7E-07 3E Ridgeway 1,110 1E E-05 1,110 3E E-05 3E-04 4E-05 3E Seward E E E E-07 2E-05 1E-06 2E Sorrel 50 6E E E E-07 1E-05 9E-07 1E Kunzman E E E E-08 8E-06 1E-07 8E Brooks E E E E-08 4E-06 2E-07 4E Wagon I 10 1E E E E-08 2E-06 2E-07 3E Wagon II 67 9E E E E-07 2E-05 6E-07 2E Martinez E E-06 1E-06 1E USFS E E E E-07 2E-05 1E-06 2E Richter E E-06 1E-06 1E-06 Notes: (a) Risk-based concentrations (RBCs): PCE = 78 µg/l; TCE = 6.6 µg/l. (b) Risk-based concentrations (RBCs): PCE = 4.3 µg/l; TCE = 13 µg/l. = Risk not calculated due to constituent not detected during last 4 sampling events. PCE = Tetrachloroethene. TCE = Trichloroethene. Shading indicates exceedence of DEQ acceptable risk levels.

71 Table 15 - Residential Risk Estimates from Monitoring Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Indoor Air Inhalation Pathway a Swimming Pool/Irrigation Pathways b PCE TCE PCE Risk TCE Risk PCE Risk TCE Risk Total Risk Total Risk Cumulative Well in µg/l Estimate in µg/l Estimate in µg/l Estimate in µg/l Estimate Estimate Estimate Risk MW E E E E-07 1E-04 9E-07 1E-04 MW E E-05 1E-05 1E-05 MW E E E E-07 3E-05 2E-06 3E-05 MW E E-05 2E-05 2E-05 MW E E E E-07 9E-06 4E-07 9E-06 MW E E E E-07 4E-06 7E-07 5E-06 MW E E E E-08 2E-05 3E-07 2E-05 MW E E E E-08 3E-05 2E-07 3E-05 Notes: (a) Risk-based concentrations (RBCs): PCE = 78 µg/l; TCE = 6.6 µg/l. (b) Risk-based concentrations (RBCs): PCE = 4.3 µg/l; TCE = 13 µg/l. = Risk not calculated due to constituent not detected during last 4 sampling events. PCE = Tetrachloroethene. TCE = Trichloroethene. Shading indicates exceedence of DEQ acceptable risk levels.

72 Table 16 - Occupational Worker Risk Estimates from Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Indoor Air Inhalation Pathway a Well PCE Risk TCE Risk Cumulative No. Name in µg/l Estimate in µg/l Estimate Risk 1 Allen E E-08 9E-08 6 Garcia E E-08 4E-08 7 Groshong E E-08 2E-08 9 Hampton E-10 7E Webb 377 3E E-08 3E Funk 140 1E E-07 3E Kragness E E-08 3E Lewis E-08 1E Mckinnon E E-08 3E Mennonite E-09 7E Miller E E-08 4E ODF 111 9E E-08 1E Ridgeway 1,110 9E E-06 2E Seward E E-08 1E Sorrel 50 4E E-08 7E Kunzman E E-09 3E Brooks E E-09 2E Wagon I 10 8E E-09 2E Wagon II 67 5E E-08 7E Martinez E-09 5E USFS E E-08 1E Richter E-09 5E-09 Notes: (a) Risk-based concentrations (RBCs): PCE = 1,300 µg/l; TCE = 110 µg/l. = Risk not calculated due to constituent not detected during last 4 sampling events. PCE = Tetrachloroethene. TCE = Trichloroethene. Shading indicates exceedence of DEQ acceptable risk levels.

73 Table 17 - Occupational Worker Risk Estimates from Monitoring Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Indoor Air Inhalation Pathway a PCE Risk TCE Risk Cumulative Well in µg/l Estimate in µg/l Estimate Risk MW E E-08 5E-07 MW E-08 4E-08 MW E E-08 2E-07 MW E-08 5E-08 MW E E-08 5E-08 MW E E-08 4E-08 MW E E-08 6E-08 MW E E-09 1E-07 Notes: (a) Risk-based concentrations (RBCs): PCE = 1,300 µg/l; TCE = 110 µg/l. = Risk not calculated due to constituent not detected during last 4 sampling events. PCE = Tetrachloroethene. TCE = Trichloroethene.

74 Table 18 - Excavation Worker Risk Estimates from Domestic Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Outdoor Air Inhalation/Dermal Contact Pathways a Well PCE Risk TCE Risk Cumulative No. Name in µg/l Estimate in µg/l Estimate Risk 1 Allen E E-08 2E-07 6 Garcia E E-08 1E-07 7 Groshong E E-08 5E-08 9 Hampton E-09 4E Webb 377 2E E-08 2E Funk 140 6E E-07 8E Kragness E E-09 9E Lewis E-08 5E Mckinnon E E-08 1E Mennonite E-08 4E Miller E E-08 1E ODF 111 5E E-08 5E Ridgeway 1,110 5E E-06 6E Seward E E-08 4E Sorrel 50 2E E-08 2E Kunzman E E-09 1E Brooks E E Wagon I 10 4E E-09 5E Wagon II 67 3E E-08 3E Martinez E-08 3E USFS E E-08 4E Richter E-08 2E-08 Notes: (a) Risk-based concentrations (RBCs): PCE = 240 µg/l; TCE = 130 µg/l. PCE = Tetrachloroethene. TCE = Trichloroethene. Shading indicates exceedence of DEQ acceptable risk levels.

75 Table 19 - Excavation Worker Risk Estimates from Monitoring Well Sampling Results Sweet Home Areawide Risk Assessment Sweet Home, Oregon Outdoor Air Inhalation/Dermal Contact Pathways a PCE Risk TCE Risk Cumulative Well in µg/l Estimate in µg/l Estimate Risk MW E E-08 2E-06 MW E-07 2E-07 MW E E-08 6E-07 MW E-07 3E-07 MW E E-08 2E-07 MW E E-08 1E-07 MW E E-09 3E-07 MW E E-09 5E-07 Notes: (a) Risk-based concentrations (RBCs): PCE = 240 µg/l; TCE = 130 µg/l. U = Not detected at the indicated method reporting limits (MRL). PCE = Tetrachloroethene. TCE = Trichloroethene. Shading indicates exceedence of DEQ acceptable risk levels.

76 Sheet 1 of 2 Table 20 - Human Health Risk Assessment Uncertainty Evaluation Sweet Home Areawide Risk Assessment Sweet Home, Oregon Wells Domestic Wells Residential Risk Comment Residential Risk Comment No. Name 1 Allen 1.E-05 No samples since June E-06 No samples since June 2003 No Unknown 11 Webb 9.E-05 Small sample size (6); no samples since August No Unknown 12 Funk 3.E Lewis 3.E ODF 3.E Ridgeway 3.E Seward 4.E Sorrel 1.E Kunzman 8.E-06 PCE EPC Based on Maximum Concentration? Do EPCs Overestimate Current PCE and TCE Concentrations? PCE concentration in last six sampling events less than one-half of EPC 6.E-06 TCE concentration in seven of last eight sampling events less than one-half of EPC No Likely EPC biased based on one sampling event (2006) No Likely Small sample size (6); no samples since August 1998; PCE concentration in last three events less than one-half EPC No Likely Small sample size (4); no samples since Small sample size (4); no samples since September September 1998; PCE concentration in last 1998; TCE concentration in last two sampling events two sampling events less than one-half of 4.E-05 less than one-half of EPC Yes Likely PCE concentration in last five sampling events less than one-half of EPC No Yes Mann-Kendall decreasing trend; EPC based on maximum of last 4 events and is greater than UCL Yes Likely Small sample size (8); no samples since August 1998; last four events less than onehalf EPC No Likely 46 Wagon II 2.E-06 Small sample size (1); no samples since 1992; only PCE detection was in June Yes Likely 51 Martinez 1.E-06 PCE concentration in last eight sampling events an order of magnitude below EPC Yes Yes 56 USFS 2.E-05 Small sample size (7); no samples since June 2003; PCE concentration in last two events less than one-half EPC Yes Likely 143 Richter 1.E-06 Only one unqualified PCE detection since Yes Likely Please refer to notes on the last page of this table. TCE

77 Sheet 2 of 2 Table 20 - Human Health Risk Assessment Uncertainty Evaluation Sweet Home Areawide Risk Assessment Sweet Home, Oregon Wells Residential Risk PCE Comment Residential Risk TCE Comment EPC Based on Maximum Concentration? Do EPCs Overestimate Current PCE and TCE Concentrations? Monitoring Wells MW-2 MW-4 MW-5 MW-18 MW-19 MW-20 1.E-04 Mann-Kendall decreasing trend; EPC based on maximum of last 4 events Yes No 1.E-05 PCE concentrations in last six sampling events less than one-half of EPC No Yes 3.E-06 Mann-Kendall decreasing trend; EPC based on maximum of last 4 events Yes No 4.E-06 Small sample size (4); EPC based on maximum Yes Unknown 2.E-05 Small sample size (5) No Likely 3.E-05 Small sample size (5) No Unknown Notes: TCE = Trichloroethene. PCE - Tetrachloroethene. EPC - Exposure Point Concentration. UCL = 90% Upper Confidence Limit on the Arithmetic Mean.

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84 APPENDIX A MANN-KENDALL STATISTICAL ANALYSIS AND LINEAR REGRESSIONS Hart Crowser /Task 4 August 31, 2009

85 MW-2 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -102 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Sample Z Trend Decreasing Mann-Kendall "S" 1600 (# plus - # minus) Event Number Concentration (ug/l)

86 MW-2 Mann-Kendall Analysis Contaminant: TCE Mann-Kendall "S" Event Number "S" Value 60 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Sample Z Trend Stable/No Trend Mann-Kendall "S" 7 (# plus - # minus) 60 Concentration (ug/l) Event Number

87 MW-4 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -73 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Sample Z Trend Stable/No Trend Mann-Kendall "S" 200 (# plus - # minus) -73 Concentration (ug/l) Event Number

88 MW-5 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -94 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Sample Z Trend Decreasing 250 Mann-Kendall "S" -94 (# plus - # minus) 200 Concentration (ug/l) Event Number

89 MW-5 Mann-Kendall Analysis Contaminant: TCE Mann-Kendall "S" Event Number "S" Value 30 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Sample Z Trend Stable/No Trend 16 Mann-Kendall "S" (# plus - # minus) Event Number Concentration (ug/l)

90 MW-13 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value 45 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Sample Z Mann-Kendall "S" 45 (# plus - # minus) Trend Stable/No Trend 100 Concentration (ug/l) Event Number

91 MW-14 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -55 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Sample Z Mann-Kendall "S" -55 (# plus - # minus) Trend Stable/No Trend Concentration (ug/l) Event Number

92 MW-18 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -4 # Quarters Concentration Sum Variance of "S" Number of tied groups # 2 times 0 Mann-Kendall "S" # 3 times 0 (# plus - # minus) -4 # 4 times 0 # 5 times 0 # 6 times # 8 times 0 0 # 7 times # 9 times # 10 times 0 10 Variance V(S) Trend Evaluation 0 Z 95% Sample Z Concentration (ug/l) Event Number Trend Stable/No Trend

93 MW-19 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -8 # Quarters Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times 0 Mann-Kendall "S" # 4 times 0 (# plus - # minus) -8 # 5 times 0 # 6 times 0 # 7 times 0 # 8 times # 9 times 0 80 # 10 times 0 60 Variance V(S) Trend Evaluation 20 Concentration (ug/l) Z 95% Sample Z Trend Stable/No Trend Event Number

94 MW-20 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value 6 # Quarters Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times 0 Mann-Kendall "S" # 4 times 0 (# plus - # minus) 6 # 5 times 0 # 6 times 0 # 7 times 0 # 8 times 0 # 9 times 0 # 10 times Variance V(S) 2562 Trend Evaluation Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Event Number

95 Well 1 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value 15 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) 2562 Mann-Kendall "S" (# plus - # minus) 15 Trend Evaluation 70 Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Quarters (1/4 Years)

96 Well 1 Mann-Kendall Analysis Contaminant: TCE Mann-Kendall "S" Event Number "S" Value 53 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Mann-Kendall "S" 25 (# plus - # minus) 53 Trend Evaluation 20 Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Event Number

97 Well 6 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -2 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Event Number Mann-Kendall "S" -2 (# plus - # minus)

98 Well 7 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value 77 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Sample Z Mann-Kendall "S" (# plus - # minus) Trend Stable/No Trend 25 Concentration (ug/l) Event Number

99 Well 9 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value 26 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Mann-Kendall "S" Variance V(S) (# plus - # minus) 26 Trend Evaluation Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Event Number

100 Well 11 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value 5 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times 0 Mann-Kendall "S" # 5 times 0 (# plus - # minus) 5 # 6 times 0 # 7 times 0 # 8 times 0 # 9 times 0 # 10 times Variance V(S) Trend Evaluation Z 95% Sample Z Trend Stable/No Trend Event Number Concentration (ug/l)

101 Well 12 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -52 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation 350 Mann-Kendall "S" -52 Z 95% Sample Z 300 (# plus - # minus) Trend Stable/No Trend Concentration (ug/l) Event Number

102 Well 12 Mann-Kendall Analysis Contaminant: TCE Mann-Kendall "S" Event Number "S" Value -40 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation 60 Mann-Kendall "S" -40 Z 95% Sample Z (# plus - # minus) Trend Stable/No Trend 30 Concentration (ug/l) Event Number

103 Well 13 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -37 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation 30 Mann-Kendall "S" (# plus - # minus) -37 Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Event Number

104 Well 17 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value 33 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation Mann-Kendall "S" Z 95% Sample Z (# plus - # minus) Trend Stable/No Trend Concentration (ug/l) Event Number

105 Well 20 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -30 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Mann-Kendall "S" -30 Trend Evaluation 30 (# plus - # minus) Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Event Number

106 Well 21 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -6 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Sample Z Trend Stable/No Trend 20 Mann-Kendall "S" -6 (# plus - # minus) Concentration (ug/l) Event Number

107 Well 22 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value 38 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation Mann-Kendall "S" Z 95% Sample Z (# plus - # minus) Trend Stable/No Trend Concentration (ug/l) Event Number

108 Well 25 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -9 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times 0 Mann-Kendall "S" # 5 times 0 (# plus - # minus) -9 # 6 times 0 # 7 times 0 # 8 times 0 # 9 times 0 # 10 times Variance V(S) Trend Evaluation Z 95% Sample Z Trend Stable/No Trend Event Number Concentration (ug/l)

109 Well 29 Mann-Kendall Analysis Contaminant: PCE PCE 7 Yea Mann-Kendall "S" Event Number "S" Value -4 # Quarters Concentration Sum Variance of "S" Number of tied groups # 2 times 0 Mann-Kendall "S" # 3 times 0 (# plus - # minus) -4 # 4 times 0 # 5 times 0 # 6 times 0 # 7 times 0 # 8 times 0 # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Event Number

110 Well 29 Mann-Kendall Analysis Contaminant: TCE TCE 7 Year Mann-Kendall "S" Event Number "S" Value -4 # Quarters Concentration Sum Variance of "S" Number of tied groups # 2 times 0 Mann-Kendall "S" # 3 times 0 (# plus - # minus) -4 # 4 times 0 # 5 times 0 # 6 times 0 # 7 times 0 # 8 times 0 # 9 times 0 # 10 times Variance V(S) 2562 Trend Evaluation Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Event Number

111 Well 31 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -43 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation 180 Mann-Kendall "S" (# plus - # minus) Z 95% Sample Z Trend Stable/No Trend Event Number Concentration (ug/l)

112 Well 32 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -91 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Sample Z Mann-Kendall "S" (# plus - # minus) Trend Decreasing 60 Concentration (ug/l) Event Number

113 Well 32 Mann-Kendall Analysis Contaminant: TCE Mann-Kendall "S" Event Number "S" Value -102 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Sample Z Mann-Kendall "S" (# plus - # minus) Trend Decreasing 6 Concentration (ug/l) Event Number

114 Well 33 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -14 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times 0 Mann-Kendall "S" # 7 times 0 (# plus - # minus) -14 # 8 times 0 # 9 times 0 70 # 10 times 0 60 Variance V(S) Trend Evaluation Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Event Number

115 Well 36 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value 6 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times # 9 times # 10 times 0 Mann-Kendall "S" 6 Variance V(S) 2562 (# plus - # minus) Trend Evaluation Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Event Number

116 Well 51 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value -20 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times 0 Mann-Kendall "S" # 9 times 0 (# plus - # minus) -20 # 10 times 0 Variance V(S) 2562 Trend Evaluation Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Event Number

117 Well 56 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value 1 Event # Concentration Sum Variance of "S" * Number of tied groups # 2 times # 3 times # 4 times # 5 times 0 Mann-Kendall "S" # 6 times 0 (# plus - # minus) 1 # 7 times 0 # 8 times 0 # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Event Number

118 Well 56 Mann-Kendall Analysis Contaminant: TCE Mann-Kendall "S" Event Number "S" Value 7 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times 0 Mann-Kendall "S" # 6 times 0 (# plus - # minus) 7 # 7 times 0 # 8 times 0 # 9 times # 10 times Variance V(S) Trend Evaluation Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Event Number

119 Well 143 Mann-Kendall Analysis Contaminant: PCE Mann-Kendall "S" Event Number "S" Value 19 Event # Concentration Sum Variance of "S" Number of tied groups # 2 times # 3 times # 4 times # 5 times # 6 times # 7 times # 8 times 0 Mann-Kendall "S" # 9 times 0 (# plus - # minus) 19 # 10 times 0 Variance V(S) Trend Evaluation Z 95% Trend Sample Z Stable/No Trend Concentration (ug/l) Event Number

120 APPENDIX B ESTIMATE OF PCE AND TCE EXPOSURE FOR OUTDOOR WATER USER Hart Crowser /Task 4 August 31, 2009

121 MEMORANDUM DATE: November 22, 2002 TO: FROM: RE: Neil Morton, Hart Crowser Jeremy Porter, Hart Crowser Estimate of PCE and TCE Exposure in a Child-Size Swimming Pool This memo explains the assumptions behind the calculation of the average PCE and TCE concentration in a child-size swimming pool filled with water containing the two compounds. Calculations are attached. The given conditions are as follows: Pool Diameter: 5 feet Pool Height: 12 inches Water Height: 8 inches Starting PCE Concentration: 50 μg/l Starting TCE Concentration: 15 μg/l Note that the starting PCE and TCE concentrations were set at the Outdoor Water User RBC for PCE and TCE, respectively. The relevant chemical properties of PCE and TCE are as follows: Diffusivity of PCE in air = cm 2 /s Diffusivity of TCE in air = cm 2 /s Henry s Law Constant for PCE = (dimensionless) Henry s Law Constant for TCE = (dimensionless) We assume that the layer of air between the top of the water and the top of the pool (4 inches) is stagnant, mass loss from the pool is controlled by the rate of diffusion through this air layer. The rate of diffusion through this layer (according to Fick s law) is proportional to the difference in concentration in the air at the water surface (calculated using Henry s Law Constant, assuming equilibrium portioning between the air and water at the interface) and the concentration in the air above the top of the pool (assumed to be zero, taking the

122 Hart Crowser November 22, 2002 Page 2 air above the pool to be well mixed via wind and the atmosphere to be an effectively infinite volume). This is a conservative assumption, as any advection between the tops of the pool and the water would increase the mass flux of PCE and TCE from the pool. We also assume that the water in the pool is well mixed, through a combination of advective mixing while being filled, disturbance by any pool inhabitants, and convection arising from temperature differences. Therefore, the entire pool is estimated to contain the same concentration of PCE and TCE at any time, and the concentrations of PCE and TCE in the air at the water-air interface is proportional to the average PCE and TCE concentrations in the pool. We calculated the average concentration in the pool by assuming the pool takes 10 minutes to fill (losses during the fill period are estimated assuming an average depth of water in the pool of 4 inches) and then recalculating for each minute a rate of PCE and TCE mass loss and the resulting new concentrations in the pool. The average concentration for the onehour period is then calculated by averaging the concentrations calculated for each minute. As shown in the attached calculations, a dermal correction factor (DCF) of 0.6 was derived for this exposure pathway. The DCF was only applied to the child receptors and was used to reduce the PCE and TCE EPCs for the dermal contact with groundwater pathway. Attachment: Calculations - PCE Loss from Kiddie Pool

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126 Hart Crowser /Task 4 August 31, 2009 APPENDIX C LEVEL I SCOPING ECOLOGICAL RISK ASSESSMENT SUPPORTING INFORMATION

127 Hart Crowser /Task 4 Photograph 1 - Residential area off of 44th Avenue, looking southwest. Photograph 2 - Trailer park off of 44th Avenue, looking southwest. Page C-1

128 Hart Crowser /Task 4 Photograph 3 - New residential development, off of 44th Avenue, looking southwest. Photograph 4 - Drainage ditch, 44th Avenue, looking north. Page C-2

129 Hart Crowser /Task 4 Photograph 5 - Open space, east of 47th Avenue, looking southwest. Photograph 6 - Commercial space, east side of 47th Avenue, looking southwest. Page C-3

130 Hart Crowser /Task 4 Photograph 7 - New construction, off of 47th Avenue, looking southwest. Photograph 8 - Surface run off creek/ditch, north of Highway 20 at 45th Avenue, looking north. Page C-4

131 Hart Crowser /Task 4 Photograph 9 - Blackberry thicket, north of Highway 20, looking north. Photograph 10 - Open field, north of Highway 20, looking east. Page C-5

132 Hart Crowser /Task 4 Photograph 11 - Log pond, looking northeast. Photograph 12 - MW-16, looking southwest. Page C-6