REMEDIAL INVESTIGATION REPORT Art Brass Plating

Transcription

1 REMEDIAL INVESTIGATION REPORT Art Brass Plating Prepared for: Art Brass Plating, Inc. Project No C September 27, 2012 Agency Review Draft

2 REMEDIAL INVESTIGATION REPORT Art Brass Plating Prepared for: Art Brass Plating, Inc. Project No C September 27, 2012 Agency Review Draft Aspect Consulting, LLC Dana Cannon, LHG Senior Project Hydrogeologist Doug Hillman, LHG Principal Hydrogeologist V:\ Art Brass Plating\RI Report\Sept 27 Agency Review Draft\RI Report_AgencyDraft docx e a r t h + w a t e r Aspect Consulting, LLC 401 2nd Avenue S. Suite 201 Seattle, WA

3 Contents Executive Summary... ES-1 ABP Facility and the RI Study Area... ES-1 Mapped Extent of Solvent and Metals Impacts... ES-1 Interim Cleanup Action at the ABP Facility... ES-2 Human Health Currently Protected... ES-3 Recommended Next Steps... ES-3 1 Introduction Purpose and Objectives Site Background and Study Area Report Organization Facility Background Facility Location and Description Facility Operations Past and Current Land Use Environmental Setting Topography and Surface Water Features Vegetation Climate Hydrogeologic Conditions Geology Groundwater Summary of Completed Investigations Pre-RI Investigations Soil and Groundwater Sampling (PSI, 1999) Preliminary Site Investigation (Aspect, 2005a) Follow-up Site Investigation (Aspect, 2005b) Data Gaps Investigation (Aspect, 2006a) SVE and Air Sparging Pilot Test (Aspect, 2007) Downgradient Groundwater Investigation (Aspect, 2008) Soil Sampling during Interim Action Implementation (Aspect, 2008) RI Investigations Groundwater Monitoring Well Installations Groundwater Monitoring Groundwater Sampling with Probes Porewater Sampling Soil Sampling Indoor Air and Soil Vapor Sampling Data Quality Assessment and Usability PROJECT NO C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT i

4 5 Environmental Regulations and Potential Cleanup Levels Potential Applicable Regulatory Requirements Potentially Applicable Federal Requirements Potentially Applicable State and Local Requirements Potential Exposure Pathways Screening Levels Groundwater Potability Analysis Interim Actions Vapor Intrusion Mitigation Program Source Control Nature and Extent of Contamination Chemicals of Concern Soil Quality Chlorinated Solvents Metals Groundwater Quality Chlorinated Solvents Metals ,4-Dioxane Sediment Porewater Quality Soil Vapor and Indoor Air Quality Fate and Transport of COCs Chlorinated COCs Attenuation/Transport Evaluation Metal COCs Conceptual Site Model and Exposure Pathway Assessment Summary of Contaminant Source and Extent Pathways of Exposure Soil Groundwater Air Sediment/Surface Water Conclusions and Recommendations References Limitations ii AGENCY REVIEW DRAFT PROJECT NO C SEPTEMBER 27, 2012

5 List of Tables 1 Aquifer Hydraulic Conductivity Estimates from Slug Tests 2 Well Completion Summary 3 Summary of Monitoring Objectives for Individual Wells 4 Summary of Chemical Analyses Completed to Date for Groundwater Monitoring 5 Summary of Data Gaps 6 Summary of Potential Exposure Pathways 7 Soil Screening Levels 8 Groundwater and Surface Water Screening Levels 9 Indoor Air and Groundwater IPIMALs for Residential and Commercial Scenarios 10 BIOCHLOR Model Inputs 11 Summary of Literature Biodegradation Rate Half Lives 12 Summary of BIOCHLOR Model Results 13 Evaluation of Potential Exposure Pathways List of Figures 1 Vicinity map 2 Facility Map 3 Historical and Present Commercial/Industrial Land Use 4A 4B 4C Exploration Locations Area-wide Exploration Locations Art Brass Plating Facility Detail Exploration Locations Duwamish Shoreline 5 Cross Section A-A 6 Cross Sections B-B, C-C, D-D, E-E 7 Site Stratigraphy and Sampling Intervals 8 Groundwater Elevations, August 2012 Water Table Interval 9 Groundwater Elevations, August 2012 Shallow Interval 10 Groundwater Elevations, August 2012 Intermediate Interval 11 TCE Data in Vadose Zone Soil PROJECT NO C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT iii

6 12 TCE Data in Saturated Soil 13 Nickel Data in Vadose Zone Soil 14 Nickel Data in Saturated Soil 15 Plume Delineation: Trichloroethene (TCE) 16 Plume Delineation: Tetrachloroethene (PCE) 17 Plume Delineation: cis-1,2-dichloroethene (DCE) 18 Plume Delineation: Vinyl Chloride 19 Plume Delineation: Total Chlorinated Ethenes 20 Seasonal Groundwater Quality: Tetrachloroethene (PCE) Water Table Interval 21 Seasonal Groundwater Quality: Tetrachloroethene (PCE) Shallow Interval 22 Seasonal Groundwater Quality: Tetrachloroethene (PCE) Intermediate Interval 23 Seasonal Groundwater Quality: Trichloroethene (TCE) Water Table Interval 24 Seasonal Groundwater Quality: Trichloroethene (TCE) Shallow Interval 25 Seasonal Groundwater Quality: Trichloroethene (TCE) Intermediate Interval 26 Seasonal Groundwater Quality: cis-1,2-dichloroethene (DCE) Water Table Interval 27 Seasonal Groundwater Quality: cis-1,2-dichloroethene (DCE) Shallow Interval 28 Seasonal Groundwater Quality: cis-1,2-dichloroethene (DCE) Intermediate Interval 29 Seasonal Groundwater Quality: Vinyl Chloride Water Table Interval 30 Seasonal Groundwater Quality: Vinyl Chloride Shallow Interval 31 Seasonal Groundwater Quality: Vinyl Chloride Intermediate Interval 32 Nature and Extent of Dissolved Cadmium in Groundwater 33 Nature and Extent of Dissolved Copper in Groundwater 34 Nature and Extent of Dissolved Nickel in Groundwater 35 Nature and Extent of Dissolved Zinc in Groundwater 36 Groundwater ph 37 Subsurface Utilities with Sewer Camera Survey Observations iv AGENCY REVIEW DRAFT PROJECT NO C SEPTEMBER 27, 2012

7 38 Nature and Extent of Total Iron in Groundwater 39 Nature and Extent of Total Manganese in Groundwater 40 Nature and Extent of Total Arsenic in Groundwater 41 Nature and Extent of Total Barium in Groundwater 42 Nature and Extent of 1,4-Dioxane in Groundwater 43 Porewater Salinity 44 Trichloroethene (TCE) in Porewater 45 Cis-Dichloroethene (cis-dce) in Porewater 46 Vinyl Chloride in Porewater 47 Buildings Where ABP is Responsible for Interim VI Activities 48 Modeled Concentrations Near the Waterway, Base Case Model Parameters 49 Modeled Concentrations Near the Waterway, Velocity x2 Case 50 Modeled Concentrations Near the Waterway, Velocity x2, Revised Half Life Case 51 Modeled Concentrations Near the Waterway, Velocity x2, Incr. Conc., Rev. Half Life Case 52 Modeled Concentrations Near the Waterway, Velocity x10, Revised Half Life Case 53 Areas Exceeding Screening Levels for Potential Exposure Pathways PROJECT NO C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT v

8 List of Appendices A B C D E F G H I J K Boring Logs Data Tables Facility Background Hydraulic Studies Vapor Intrusion Assessment Interim Measures Evaluation Mann-Kendall Trend Tests and Plots BIOCHLOR Modeling Results Geochemical Modeling Results Duwamish Waterway Porewater Risk Assessment Anchor QEA Data Usability with Lab and Data Validation Reports on CD vi AGENCY REVIEW DRAFT PROJECT NO C SEPTEMBER 27, 2012

9 Executive Summary The purpose of this Art Brass Plating (ABP) Remedial Investigation report (RI) is to present sufficient information to characterize site conditions attributed to releases of chemicals from the ABP Facility, to assess area conditions that could affect ABP s selection of a remedy, and to evaluate the effectiveness of interim remediation actions. Information collected for the RI will enable ABP to prepare a feasibility study and select a remedy to address contamination. Aspect Consulting, LLC prepared this RI on behalf of ABP and in accordance with the Washington State Department of Ecology (Ecology) Agreed Order No. DE5296. ABP Facility and the RI Study Area The ABP Facility (Facility) is the property located at rd Avenue South (the northwest corner of South Findlay Street and 3rd Avenue South). The RI Study Area (Study Area) extends from the ABP Facility to the Duwamish Waterway (Waterway), a distance of about 2,200 feet towards the west-southwest. The Study Area is a subset of a broader area that includes soil and groundwater contaminated by historical releases at several facilities: Philip Services Corporation located at 734 South Lucile Street; Capital Industries located at rd Avenue South; and Blaser Die Casting located at rd Avenue South. Since 1983, the Facility has been operated exclusively for metal plating and related work (e.g., metal polishing and powder coating). Metal plating has included nickel, chrome, brass (an alloy of copper and zinc), copper, and gold. The chlorinated solvent trichloroethene (TCE) was formerly used at the Facility for vapor degreasing from approximately 1983 to February Environmental investigations confirm the likely release of chlorinated solvents and plating metals from the Facility to soil and groundwater. The investigation data show the downgradient migration of TCE and its degradation products cis-dce and vinyl chloride via groundwater flow. These data also indicate the historical release of plating solutions resulting in depressed ph and elevated concentrations of cadmium, copper, nickel, and zinc in soil and groundwater beneath, and in close proximity to, the Facility. Mapped Extent of Solvent and Metals Impacts Screening levels protective of human health and environmental exposures are used in this RI to evaluate the investigation data and map the extent of impacts. The screening levels are based on protection against direct contact (soil, groundwater), consumption of organisms (surface water), ecological receptors (surface water), and vapor inhalation (air, soil/dust). Chlorinated Solvents The primary chemical of concern in the Study Area is the chlorinated solvent TCE. However, under certain conditions observed in the Study Area, TCE undergoes reductive dechlorination and forms less chlorinated ethenes: dichloroethenes (cis-dce, 1,1-DCE, trans-dce) and vinyl chloride. The highest concentrations of TCE in soil have been PROJECT NO C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT ES-1

10 detected beneath the western portion of the Facility and at depths close to the water table. TCE appears to have migrated downward but has not been detected in soils at depths greater than 20 feet beneath the Facility. The groundwater TCE plume migrates slightly downward and towards the southwest, consistent with the vertical and horizontal groundwater gradients in this area, until around 1st Avenue South where it reaches its maximum depth (approximately 75 feet). West of 1st Avenue South, the plume migrates upward to the southwest (consistent with the upward gradients observed in this area) and extends to the Waterway. Vinyl chloride concentrations exceeding the screening levels for protection of human health via fish consumption are located throughout the plume, including wells located adjacent to the Waterway. Because TCE, cis-dce, and vinyl chloride contamination in groundwater extends to the Waterway, sediment porewater within the potential groundwater discharge zone was characterized to evaluate potential impacts to surface water. Vinyl chloride was detected in sediment porewater exceeding screening levels based on protection of human health via consumption of surface water organisms. Currently, recreational uses in the area are limited due to the industrial nature of this area of the Waterway and subsistence shellfish harvesting activities are limited due to limited available populations. Metals In addition to chlorinated solvents, data indicate the likely historical release of plating solutions at the Facility. These past releases result in depressed ph and elevated concentrations of copper, nickel, and zinc in soil and groundwater beneath the Facility. The highest concentrations in soil and groundwater have been detected beneath and downgradient of the former plating area located in the southwest corner of the Facility. In contrast with the chlorinated solvents, the extent of plating metals impacts appears limited to a distance of approximately 400 feet downgradient of the Facility. Interim Cleanup Action at the ABP Facility Interim cleanup actions at the Facility and in the likely source areas are underway and have significantly reduced chlorinated COC concentrations. Since starting the interim action in 2008, the TCE concentrations in groundwater have decreased by over 90 percent near the Facility and declining trends are now observable at wells located more than 100 feet downgradient. The interim cleanup action consists of an air sparging/soil vapor extraction system capable of removing volatile organic compounds (including chlorinated solvents) from both soil and groundwater. With groundwater quality conditions improving at the Facility, the highest concentrations of TCE are now detected mid-plume (which is around 1st Avenue South). Using reasonably conservative fate and transport parameters, modeling predicts that groundwater concentrations near the Waterway will not increase over time. However, given the uncertainty in model inputs, it is also conceivable that concentrations could increase over time, and neither potential future outcome can be rejected. Continued monitoring is warranted to empirically evaluate trends. ES-2 AGENCY REVIEW DRAFT PROJECT NO C SEPTEMBER 27, 2012

11 Human Health Currently Protected Based on existing data, most of the potential human health and environmental exposure pathways are not complete. The exposure pathways that are potentially complete are currently mitigated as follows: Vapor migration from groundwater to indoor air is mitigated by monitoring and/or sub-slab depressurization/sve systems within areas of vadose-zone soil and water table groundwater contamination. Downgradient property owners have been cooperative in providing access for vapor intrusion monitoring and mitigation; Impermeable covers (asphalt and concrete) prevent contact with contaminated soil; and Utility companies have been contacted to inform them of areas of shallow groundwater contamination to protect against potential exposure to underground workers. Recommended Next Steps The RI provides sufficient technical information to delineate the nature and extent of contamination associated with the ABP Facility. These data should be used to prepare a Feasibility Study (FS) that develops remedial action objectives and evaluates a range of potential alternatives to achieve these objectives. Based on this alternatives evaluation, a Cleanup Action Plan (CAP) detailing the selected remedy should be developed. Quarterly groundwater monitoring should continue during FS/CAP preparation, but an analysis of the monitoring data may warrant a reduction in sampling frequency beginning in spring PROJECT NO C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT ES-3

12 1 Introduction 1.1 Purpose and Objectives The Art Brass Plating (ABP) Remedial Investigation report (RI) has been prepared in accordance with the Agreed Order between Department of Ecology (Ecology) and Art Brass Plating, Inc dated January 8, 2008 (Agreed Order No. DE5296). The purpose of the RI is to collect sufficient information to characterize site conditions attributed to releases of chemicals from the ABP Facility; characterize area conditions that affect ABP s selection of a remedy; and evaluate the effectiveness of interim remediation actions. This data includes the distribution of contaminants at the site and the associated potential threat to human health and the environment. Information collected for the RI will enable ABP to prepare a feasibility study and select a remedy to address contamination under a subsequent Agreed Order. The RI Work Plan (Aspect, 2008) summarized data available at that time and identified data needed to complete site characterization for the RI. The RI Work Plan was approved by Ecology on October 17, From October 2008 through the present, Aspect Consulting, LLC (Aspect) has been implementing the RI Work Plan. In addition to the data needs identified in the RI Work Plan, additional data needs have been identified and the data collected in accordance with Ecology-approved work plans. This report presents the data collected throughout the RI period and discusses all relevant data collected to date. 1.2 Site Background and Study Area To complete the RI, ABP has conducted investigations in the area of the ABP Facility extending to the Duwamish Waterway (Waterway). The ABP Facility (Facility) is the property located at rd Avenue South (the northwest corner of South Findlay Street and 3rd Avenue South) as illustrated on Figure 1. Figure 1 also shows the ABP Study Area (Study Area). The Study Area was originally confined to the area east of East Marginal Way South in the RI Work Plan, but the boundaries were extended to the Waterway based on data collected during the RI. The Study Area is a subset of a broader area that includes soil and groundwater contaminated by historical releases at several facilities. As part of their own remedial investigation, Philip Services Corporation (PSC) has conducted groundwater investigations throughout the Georgetown neighborhood (PSC, 2003). Chlorinated solvent releases from the PSC Georgetown facility have migrated downgradient of their facility located at 734 South Lucile Street and may impact groundwater in the area west of 4th Avenue. Based on the PSC s area-wide groundwater investigations, other potential sources of solvent contamination were identified west of Fourth Ave South including the ABP Facility, Capital Industries (Capital) located at rd Avenue South, and Blaser Die Casting (Blaser) located at rd Avenue South. Ecology concluded there were significant releases associated with these facilities and as a result, required separate agreed orders. Ecology has named ABP, Capital, Blaser, and PSC as PLPs for PROJECT NO C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT 1

13 groundwater contamination west of 4th Avenue South. In this report, ABP, Blaser, Capitol, and PSC are collectively referred to as the West of Fourth (W4) Group. Capital and Blaser have conducted similar RI activities at the same time as ABP. During the course of the RI, investigation activities and data sharing were coordinated among ABP, Blaser, Capitol, and PSC. Data collected by the W4 Group relevant to the ABP RI, including area groundwater chemistry, plume delineation, and hydrogeologic characterizations, has been included in this report and referred to as area-wide data. The Study Area illustrated on Figure 1 is based on data collected by ABP and others in the W4 group. Figures and text in Section 7 will provide additional details about the available data. 1.3 Report Organization This RI includes 10 sections and 8 appendices. The main text is organized as follows: Section 1 The Introduction presents information regarding the objectives and approaches for the ABP RI; Section 2 The Facility Background section provides information about the facility location and history, and past and current land use; Section 3 The Environmental Setting section summarizes environmental information relevant to the ABP RI including topography and surface water features, vegetation, climate, and hydrogeology; Section 4 A Summary of Completed Investigations describes the purpose and scope of each investigation conducted in the area of the Facility; Section 5 Environmental Regulations and Potential Screening Levels are identified for the purposes of comparing chemical concentrations and identifying potential exposure pathways; Section 6 Interim Actions summarizes interim remedial measures, including vapor intrusion mitigation and source control that have been implemented to date; Section 7 The Nature and Extent of Contamination describes the distribution of chemicals in environmental media within the Study Area; Section 8 The Fate and Transport of COCs (chemicals of concern) describes the mechanisms of contaminant transport through groundwater, and the potential future migration of chemicals in the Study Area; Section 9 The Conceptual Site Model Summary and Exposure Pathway Assessment evaluates potential exposure pathways resulting from COC occurrences; Section 10 Conclusions of the RI are summarized and recommendations for future actions are provided; and References are provided at the end of the main report text. The RI includes multiple appendices to support the analyses and discussions in the main body of the text. These appendices include: 2 AGENCY REVIEW DRAFT PROJECT NO C SEPTEMBER 27, 2012

14 Appendix A Boring Logs; Appendix B Data Tables grouped by analyte group and sampling interval; Appendix C Facility Background; Appendix D Hydraulic Studies; Appendix E Vapor Intrusion Assessment; Appendix F Interim Measures Evaluation; Appendix G Mann-Kendall Trend Tests and Plots; Appendix H BIOCHLOR Modeling Results; Appendix I Geochemical Modeling Results; Appendix J Duwamish Waterway Porewater Risk Assessment Anchor QEA; and Appendix K Data Usability with Lab and Data Validation Reports on CD. 2 Facility Background 2.1 Facility Location and Description The ABP Facility is located at rd Avenue South in the Georgetown neighborhood in Seattle, Washington, as shown on Figure 1. The Facility and surrounding area are generally flat, with a gradual slope to the west. The Facility surface is completely covered with either buildings or pavement. According to King County assessor records, the Facility covers 20,000 square feet. The property is owned by Dean Allstrom. 2.2 Facility Operations Based on a review of historical records, including Sanborn Fire Insurance Maps and city directories, the property now occupied by the Facility was used as a residence or undeveloped prior to Addresses of residences located on the property, as identified on City of Seattle sewer cards, were rd Avenue South, 306 South Findlay Street, and 318-1/2 South Findlay Street. The site was purchased by the current property owner in 1983 and has been used for metal finishing since that time. The current property owner, Dean Allstrom, owned and operated Art Brass Plating, Inc. between 1983 and Since 2001, Mike Merryfield has owned and operated Art Brass Plating, Inc., which leases the property. A facility map showing locations of various operations is provided on Figure 2. The existing ABP building was constructed in three phases: the westernmost building was constructed in 1983, the easternmost building in 1987, and the central portion in Site process areas have slowly expanded to the current layout since metal finishing operations began in A more detailed discussion of the building expansion and use PROJECT NO C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT 3

15 is provided in Appendix C, which is a reproduction of an earlier submittal to Ecology dated June 6, Since 1983, the Facility has been operated exclusively for metal plating and related work (e.g., metal polishing and powder coating). Metal plating has included nickel, chrome, brass (an alloy of copper and zinc), copper, and gold. A former plating area in the southwest corner of the Facility was closed in 1999 and is currently used for storage. Plating operations currently take place in the central portion of the Facility within a secondary containment area. Plating bath schematics of the former and current plating lines are provided in Appendix C. For dangerous waste reporting, ABP is classified by Ecology as a Large Quantity Generator and submits dangerous waste reports and Toxic Release Inventory reports that detail chemical and waste volumes used. Following on-site treatment, aqueous wastes are discharged to King County sanitary sewer under a King County Industrial Waste Permit. Trichloroethene (TCE) was formerly used at the Facility for vapor degreasing from approximately 1983 to February Since 1983, the vapor degreaser has been located at its current location just south of the polishing area, labeled Former TCE Degreaser No. 1 on Figure 2. A second vapor degreaser, located in what is now the Time-Saver Room, was temporarily used between 1988 and 1993, labeled Former TCE Degreaser No. 2 on Figure Past and Current Land Use The Facility is located within the Georgetown neighborhood that has a long history of mixed industrial, commercial, and residential land use. While industrial is the predominant land use in the area, commercial and residential uses are present, and the mixed-use pattern is anticipated to remain in the long-term. Land use surrounding the Facility includes a residence to the north, an autobody shop and restaurant to the east, a plastics fabricator and warehouse to the south, and a supplier of point-of-use sales equipment to the west. During the RI, Aspect conducted a historical review of properties adjacent to and downgradient of the Facility. The purpose of the research was to identify potential sources of chlorinated solvent contamination. Historical sources that were consulted included Polk City Directories, Sanborn Fire Insurance Maps, and building records at the City of Seattle Department of Planning and Development. Figure 3 provides a summary of some of the historical and present commercial/industrial land use activities adjacent to and downgradient of the Facility. 3 Environmental Setting 3.1 Topography and Surface Water Features The Facility is located within the floor of the north-south-trending Duwamish River Valley, where the land surface is relatively level. The valley floor is approximately 6,000 feet wide in this area, and bounded to the east and west by steeply sloped uplands that 4 AGENCY REVIEW DRAFT PROJECT NO C SEPTEMBER 27, 2012

16 rise to elevations of 300 to 500 feet above mean sea level. The ground surface elevation of the Facility is approximately 15 feet mean sea level. The Lower Duwamish Waterway is located approximately 2,200 feet west-southwest of the Facility. No other surface water bodies are known to be present in the area. The Lower Duwamish Waterway was dredged and straightened in the early 1900s. Prior to that time, the Duwamish River meandered as it flowed north through the Duwamish River Valley toward Elliott Bay. The abandoned meanders reportedly were filled with dredged material during the waterway straightening project. 3.2 Vegetation Vegetation in the area is generally sparse, which is consistent with the predominantly industrial setting. The area is typical of urban, developed land, with vegetation limited to landscaped planting areas, street-side trees, and plantings on the dispersed residential properties. 3.3 Climate The climate is characterized by mild temperatures and a rainy season, with considerable cloudiness during the winter months. The following description is excerpted from the PSC (2003) RI Report. Average winter daytime temperatures are in the 40s (degrees Fahrenheit) and nighttime readings in the 30s. During the summer, daytime temperatures are usually in the 70s, with nighttime lows in the 50s. The middle of the dry season occurs in July or early August, with July being the driest month of the year. The rainy season extends from October to March, with December normally the wettest month. However, precipitation is rather evenly distributed throughout the winter and early spring months. More than 75 percent of the yearly precipitation falls during the rainy season. At the King County Airport (located approximately 2 miles south), an average annual precipitation of inches is reported (PSC, 2003). 3.4 Hydrogeologic Conditions The hydrogeology provides a framework for understanding the subsurface conditions and groundwater flow system in the Study Area, which is entirely located in the Duwamish River Valley. This section provides a description of the local hydrogeology based on area borings and an area-wide interpretive report called the Duwamish Basin Groundwater Pathways Study (Booth and Herman, 1998). Boring locations are presented on Figures 4A (Area-wide), 4B (Facility), and 4C (Duwamish Shoreline) Geology The hydrogeologic units encountered in borings completed in the vicinity of ABP include a Younger Alluvium and Older Alluvium. The upper portion of the Younger Alluvium has been modified and is referred to as the Fill Unit. A description of these units is provided below. Figures 5 and 6 provide geologic cross sections: one along the approximate centerline of the plume oriented northeast-southwest (Figure 5, A-A ) and four others that are drawn PROJECT NO C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT 5

17 perpendicular to the plume and oriented northwest-southeast (Figure 6, B-B, C-C, D-D and E-E ). Cross section locations are shown on Figure 6. Fill Unit The Fill unit consists of heterogeneous layers of gravelly sand, silt, and silty sand with scattered bits of inert debris such as glass shards or brick fragments. This unit extends up to a depth of 8 feet. In some cases, the boundary between the Fill Unit and the Younger Alluvium is difficult to distinguish. Therefore, in most discussions and figures these units are grouped together. Younger Alluvium The Younger Alluvium (Qyal) represents channel and overbank/floodplain deposits from the Duwamish River (Booth and Herman, 1998). Based on borings in the vicinity of the Facility, the Younger Alluvium consists of two subunits, a sandy silt or silty sand unit overlying slightly silty fine-medium sand unit. Scattered bits of wood and organic debris are also present. This unit is typically found within a few feet above or below the current sea level and extends to a depth of approximately 25 to 30 feet beneath the Facility. West of the Facility, starting near 2nd Avenue South, the Younger Alluvium extends to a depth of approximately 55 feet. The upper sandy silt/silty sand unit typically extends to a depth of 8 to 12 feet and includes a 4- to 6-foot thick silt unit beneath the Facility and adjacent right-of-ways. The sand in the underlying slightly silty sand unit has a characteristic salt and pepper appearance. This lower portion of the Qyal also includes silt stringers that range up to a few inches thick. Older Alluvium The Older Alluvium (Qoal) represents materials deposited in an estuarine and deltaic environment. Based on borings in the vicinity of the Facility, the Older Alluvium consists of interbedded sequences of silty fine sand and sandy silt. While not observed in ABP borings, this unit can also contain discontinuous gravel lenses and locally abundant shells and some wood (Booth and Herman, 1998). A silt aquitard, likely a subunit of the Older Alluvium, and bedrock have been identified in deeper borings east of 4th Avenue (PSC, 2003). These additional units were not encountered in the borings located in the Study Area, where the deepest borings were completed to a depth of 74 feet. Based on a review of the Duwamish Valley cross sections available in Booth and Herman (1998), it is expected that the silt aquitard and bedrock are present at a depth greater than 150 feet Groundwater Groundwater in the Study Area is encountered at a depth of 4 to 10 feet below grade. Groundwater flow is towards the Waterway, which is west-southwest of the Facility. Appendix D provides a summary of the groundwater hydraulic characterization studies that have been completed during the RI, including slug tests, tidal studies and water level measurements. This section summarizes the conclusions of these studies. Please refer to the appendix for details. 6 AGENCY REVIEW DRAFT PROJECT NO C SEPTEMBER 27, 2012

18 Groundwater Sampling Intervals The lithologic units discussed above correspond to the hydrogeologic units encountered in the Study Area. However, PSC (2003) adopted a standardized nomenclature for groundwater monitoring and sampling intervals that does directly correspond to the lithologic units. For consistency, this convention has been maintained in describing groundwater conditions within the Study Area. These sampling intervals are illustrated on Figure 7 and are described below: Water Table Interval. This interval includes monitoring wells screened above 20 feet below ground surface (bgs) and reconnaissance groundwater samples collected above 20 feet bgs. Shallow Interval. This interval includes monitoring wells screened below 20 feet and above 40 feet bgs, and reconnaissance groundwater samples collected between 21 feet and 40 feet bgs. Intermediate Interval. This interval includes monitoring wells and reconnaissance groundwater samples screened below 40 feet bgs Aquifer Characteristics The discussion below provides a characterization of aquifer characteristics based on the data collected during the RI. Methodologies and data analysis techniques are reviewed in Appendix D. Groundwater Flow Direction and Gradients The W4 Group completed multiple coordinated water level measurements during the RI. The events completed between May 2010 and August 2012 represent the most comprehensive data set for the W4 Group. Groundwater elevations were contoured for these events and are provided in Appendix D. Little seasonal variability in flow direction was observed. The August 2012 groundwater elevations with contours are provided in Figures 8, 9, and 10 for the Water Table, Shallow, and Intermediate Intervals, respectively. Some localized and anomalous high water levels have been noted at the Water Table Interval in wells MW-16 and PSC-CG-143-WT. Groundwater mounding at PSC-CG- 143-WT is sporadically observed and the cause has not been determined. Groundwater mounding at MW-16 has been observed during winter months and may be related to recharge from a leaking combined sewer. A sewer survey identified potential leaking joints in the Findlay Street sewer upgradient of MW-16 (see Section 7.3.2). In addition to the two anomalous readings noted at the Water Table Interval, the remaining anomalous reading was from October 2010 in well MW The October 2010 reading is likely a field error since all other water levels from this well were consistent with readings from surrounding wells. Findings from the May 2010 through August 2012 events indicate the following: Water Table Interval. The approximate direction of groundwater flow was southwest. The gradient for the Water Table Interval ranges from to feet per foot; PROJECT NO C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT 7

19 Shallow Interval. The approximate direction of groundwater flow is westsouthwest. The gradient for the Shallow Interval ranges from to feet per foot; and Intermediate Interval. The approximate direction of groundwater flow is westsouthwest. The gradient for the Intermediate Interval ranges from to feet per foot. Vertical gradient between the Water Table and Shallow Intervals are typically downward. Vertical gradients between the Shallow and Intermediate Intervals fluctuate between upward and downward except in the well clusters close to the Waterway, west of East Marginal Way. Upward gradient were typical in these well pairs. Hydraulic Conductivity Measurements Hydraulic conductivity measurements are based on slug tests completed at multiple wells for each sampling interval. Hydraulic conductivities estimated using slug test results are generally biased low compared to those hydraulic conductivity values calculated from pumping tests. Estimated hydraulic conductivities at each well location are summarized in Table 1. The following provides a summary of the data: Water Table Interval. Based on data from 6 wells, the geometric mean is cm/sec; Shallow Interval. Based on data from 8 wells, the geometric mean is 0.03 cm/sec; and Intermediate Interval. Based on data from 8 wells, the geometric mean is cm/sec. The hydraulic conductivity values measured in the Shallow and Intermediate Intervals by ABP are consistent with those values from the other W4 Group. It should be noted that the hydraulic conductivity values measured at the Water Table Interval were an order of magnitude lower compared to the geometric mean of the entire W4 Group data set for Water Table Interval slug test (0.022 cm/sec). Water Table Interval wells MW-8, MW- 10, MW-11, and MW-13, which are part of the ABP slug test data set, have a four- to sixfoot thick silt layer within the screened intervals, which would result in lower hydraulic conductivity measurements Groundwater Flow and Tidal Variability ABP has completed four tidal studies during the following periods: May/June 2010, October 2010, January 2011, and August Appendix D provides a summary of the analyses that were completed on the tidal data. A discussion of some of the results is provided below. Groundwater from upland areas generally flows toward the Waterway. Water levels in the Waterway are influenced by river flow and tidal effects from Puget Sound. The typical tidal range in Seattle s Elliott Bay is approximately 11 feet, based on the difference between mean higher high water (MHHW) and mean lower low water (MLLW) ( Monitoring wells completed near the waterway in the Shallow and Intermediate Intervals (MW-22-30/-50, MW-23-30/-50 and, PSC-CG ) had a tidal range of 6 to 8 feet. Monitoring wells in the same interval 8 AGENCY REVIEW DRAFT PROJECT NO C SEPTEMBER 27, 2012

20 but 300 feet from the Waterway (MW-24-30/-50) had a recorded tidal range of approximately 3 feet. Tidal influences on water levels diminish to 0.5 feet or less east of East Marginal Way, approximately 800 feet east of the Waterway. High tides result in localized groundwater flow gradient reversal, although the timeaveraged net groundwater flow direction is still toward the Waterway (Booth and Herman, 1998). The occurrence of localized and transient flow reversals is consistent with site characterization data collected at other similar sites in the Waterway, and with the ABP RI data. For the four RI tidal studies completed, the magnitude and direction of the gradient were calculated using a solution to the three-point problem using a threewell configuration: MW-23-30, PSC-CG , and MW Gradients ranged between and feet per foot with groundwater flows to the southwest and feet per foot or less with groundwater flows to the northeast. In the two nearshore well clusters (MW-22-30/-50 and MW-2-30/-50), the tidallyaveraged vertical gradients were slightly upward: at MW-22 and at MW- 23. This slightly upward gradient is consistent with the regional flow path of groundwater discharge from adjacent uplands into the Waterway. The relatively dense saline water wedge that occurs in and below the Waterway results in an upward gradient of groundwater discharge into the river. In the Waterway, fresh surface water moving downstream overlies this tidally oscillating saltwater wedge. These conditions result in the occurrence of saline water in the groundwater zone beneath the channel. Less dense, low salinity groundwater does not readily mix or migrate into these deeper saline zones. As a result, fresh groundwater migrating beneath upland areas discharges upward primarily into shallower areas of the Waterway when it meets the saline groundwater wedge located directly beneath the channel. The size and shape of the saltwater wedge within this section of the Waterway is dependent upon local groundwater flux, aquifer permeability, and seasonal upstream river flows and stages Geochemical Conditions During the RI, select groundwater samples were analyzed for nitrate, sulfate, ferrous iron, and methane. With the field parameters, these data provide an understanding of the oxidation-reduction potential (redox) conditions in groundwater. Reducing conditions have been documented by PSC as ubiquitous in groundwater in the Georgetown area (PSC, 2003). The likely reason for widespread reducing conditions is the presence of naturally occurring organic materials in the Younger and Older Alluvial deposits. These organics act as a food source (electron donor) for indigenous microbial consumption. Anthropogenic releases of chemicals that can be used as a microbial food source (e.g., petroleum or non-chlorinated solvents) can locally exacerbate area-wide reducing conditions. The remediation system at the Facility, which includes air sparging of the shallow aquifer, has resulted in localized oxidized redox conditions at the water table. The RI data indicate that as redox conditions became oxidized, methane concentrations decreased and sulfate concentrations increased. Conditions remain reducing in the Shallow and Intermediate Intervals and in the Water Table Interval away from the air sparging area. This is evidenced by low dissolved oxygen and Eh, elevated ferrous iron, and moderate sulfate concentrations. The presence PROJECT NO C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT 9

21 and persistence of methane indicates some localized areas of methanogenesis; however, the continued presence of sulfate suggests methanogenesis does not occur everywhere in the Study Area. 4 Summary of Completed Investigations This section provides a discussion of the environmental investigations completed by ABP. The first part details the investigations completed prior to finalizing the RI Work Plan (Aspect, 2008). This is followed by a summary of the site characterization completed during the RI. 4.1 Pre-RI Investigations ABP conducted several subsurface and indoor air investigations at and around the Facility between 1999 and 2008, prior to the RI. The reports for each investigation are compiled in Volume II and Appendix B of the Draft Interim Cleanup Action Plan (Aspect, 2007). The purpose and scope of these investigations are summarized below; the exploration locations are depicted on Figure 4. Boring and well construction logs are provided in Appendix A Soil and Groundwater Sampling (PSI, 1999) In March 1999, PSI conducted a subsurface investigation to evaluate whether plating solution releases from ABP operations had impacted soil or groundwater at the Facility. Work included the following: Advancing 2 direct-push borings to a depth of 9 feet at the southwestern (downgradient) corner of the Facility; Collecting continuous soil samples and 1 groundwater grab sample from the Water Table Interval, from each boring; and Submitting 2 soil and 2 grab groundwater samples for analysis for cyanide, chromium, copper, lead, nickel, and zinc. This investigation did not identify any constituents in soil or groundwater above Model Toxics Control Act (MTCA) Method A cleanup levels, except for a slight exceedance of chromium in groundwater. There were reported detections of chromium, copper, nickel, and zinc in groundwater exceeding the proposed cleanup levels. One soil sample exceeded the proposed cleanup level for protection of groundwater for zinc Preliminary Site Investigation (Aspect, 2005a) In June 2005, Aspect conducted a subsurface investigation to evaluate whether TCE detected in groundwater at PSC explorations 217F and N15 may have originated from the Facility. Work included the following: Reviewing operations at the Facility and identifying potential areas where TCE was used or handled; Reviewing historical records to identify potential background sources of TCE; 10 AGENCY REVIEW DRAFT PROJECT NO C SEPTEMBER 27, 2012

22 Advancing 12 direct-push soil borings in and around the Facility to depths from 12 to 16 feet bgs; Collecting continuous soil samples and 1 grab groundwater sample from the Water Table Interval, from each boring; Collecting soil gas samples from the 1- to 4-foot bgs depth interval at 3 borings located inside the building at the Facility; Submitting 18 soil and 12 groundwater samples for analysis for volatile organic compounds (VOCs) by EPA Method 8260; and Submitting 3 soil gas samples for analysis for VOCs by EPA Method TO-15. This work confirmed the probable release of TCE from the two vapor degreasers located on the Facility. Elevated concentrations of TCE were detected in soil and grab groundwater samples collected in close proximity to each degreaser and extending to the downgradient property line Follow-up Site Investigation (Aspect, 2005b) In October 2005, based on the results of the Preliminary Site Investigation, Aspect conducted a follow-up investigation to characterize local hydrogeology and identify vertical and horizontal boundaries of the contamination plume. Work included the following: Installing monitoring wells MW-1 through MW-4 adjacent to and downgradient of two vapor degreasers that formerly used TCE. Monitoring wells were screened across the Water Table Interval to a depth of 14 feet bgs; Surveying monitoring well top-of-casing elevations into the PSC well network, measurement of water levels, and estimation of local groundwater flow direction; Advancing 7 direct-push borings downgradient of the Facility to depths from 11 to 15 feet bgs; Advancing 2 direct-push borings downgradient of the former TCE-using degreasers to depths between 42 and 45 feet bgs; Collecting continuous soil samples from each soil boring; Collecting 1 grab groundwater sample from the Water Table Interval of each shallow boring, and collecting 3 grab groundwater samples at approximately 15- foot intervals from each of the two deep borings; Collecting 1 groundwater sample from each of the fur monitoring wells; Submitting 13 groundwater samples for analysis for VOCs by EPA Method 8260 and total suspended solids by EPA Method 160.2; and Submitting 6 soil samples from the two deep borings for analysis for VOCs by EPA Method Monitoring wells installed at the Facility were used to investigate and confirm the prior analytical results for probe-based sampling. Two deeper probe explorations located in the downgradient right-of-way were used to evaluate the vertical extent of impacts. No PROJECT NO C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT 11

23 VOCs were detected in groundwater collected from depths of approximately 40 feet bgs in either location. Neighborhood-area probe-collected groundwater samples also were used to bound the extent of TCE migration at the Water Table Interval, with nondetectable results to the west at 2nd Avenue South and to the south at Orcas Street when coupled with PSC-collected data Data Gaps Investigation (Aspect, 2006a) In June 2006, Aspect conducted a data gaps investigation to define the vertical and horizontal extent of soil and groundwater contamination at the Facility. Work included the following: Installing 3 monitoring wells, screened across the Water Table Interval to a depth of 14 feet bgs, to provide permanent monitoring points downgradient of the former TCE storage area (MW-5), upgradient of the Facility (MW-6), and between the two degreasers (PMW-1); Installing air sparging wells AS-1 and AS-2 adjacent to the former degreasers, screened from 25 to 28 feet bgs at the base of the shallow sand unit, to vertically delineate contamination in potential source areas, and to provide points to pilot test air sparging; Advancing direct-push borings SP-14 to SP-17 to depths from 12 to 20 feet bgs; Collecting continuous soil samples at each boring and monitoring well location; Collecting 1 grab groundwater sample from the Water Table Interval of each direct-push boring; Collecting groundwater samples from the five new monitoring and air sparging wells; Submitting 9 groundwater samples for analysis for VOCs by EPA Method 8260; and Submitting 19 soil samples from the two deep borings for analysis for VOCs by EPA Method Interpretation of the data collected by this investigation refined the understanding of the distribution of TCE-impacted soil and groundwater on the Facility, enabling more focused source-control remediation efforts. The data also indicated a potential historical release of TCE in the former solvent storage area near the northwestern corner of the Facility building. Two air sparging wells were installed in close proximity to the degreasers. Groundwater samples collected from each well yielded non-detectable TCE results at a depth of 30 feet SVE and Air Sparging Pilot Test (Aspect, 2007) In August 2006, Aspect conducted a pilot test for soil vapor extraction and air sparging to evaluate the potential applicability of these technologies for source control of VOCs, and to determine design parameters. Work included the following: Applying SVE at existing monitoring wells MW-1, MW-2, and MW-5 for 1 to 5.5 hours each; 12 AGENCY REVIEW DRAFT PROJECT NO C SEPTEMBER 27, 2012

24 Applying air sparging at existing air sparging wells AS-1 and AS-2 for 1.5 to 2 hours each; and Monitoring of performance parameters, including pressure/vacuum at active and surrounding wells, dissolved oxygen at surrounding monitoring wells, air injection and extraction flow rates, and VOC concentrations in off-gas. On the basis of the pilot test results, Aspect concluded that SVE and air sparging are viable technologies for interim source control remediation, and the results have provided further site-specific performance data for system design Downgradient Groundwater Investigation (Aspect, 2008) In 2008, Aspect completed five geoprobe borings southwest of the Facility to provide additional lateral and vertical definition of the contaminant plume. Work included the following: Advancing direct-push borings SPO-10 through SPO-14 to a depth of 70 feet bgs. Collecting 1 grab groundwater sample from the Water Table Interval of borings SPO-11, SPO-13, and SPO-14. Collecting 2 grab groundwater samples from the Shallow Interval from borings SPO-11, SPO-13, and SPO-14. Collecting 3 grab groundwater samples from the Intermediate Interval from borings SPO-11, SPO-13, and SPO-14 and two grab groundwater samples from SPO-10 and SPO-12. Submitting 22 groundwater samples for analysis for chlorinated VOCs by EPA Method Submitting 1 groundwater sample from SPO-13 for analysis of total and dissolved iron and manganese by EPA Method 6010B and 1,4-dioxane by EPA Method Results from these investigations were incorporated into the RI Work Plan and used to guide additional RI investigations Soil Sampling during Interim Action Implementation (Aspect, 2008) In 2008, Aspect conducted soil sampling during implementation of the interim action. Thirteen soil samples were collected for analysis of chlorinated VOCs by EPA Method 8260B, and two soil samples were also analyzed for 1,4-dioxane by EPA Method The samples analyzed for TCE were collected from shallow soils at air sparging wells along the underground piping alignment to characterize soil removed from trenching for disposal. The samples submitted for dioxane analysis were collected from boring AS-25 at 6 feet bgs and from the pipe trench near MW-1 at a depth of 2 feet. The sample from the trench was also analyzed for TCE. Soil sampling data collected during implementation of the interim action have been incorporated into this RI Report. PROJECT NO C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT 13