Draft Report Volume 1. January 5, 2009

Transcription

1 Investigation and Validation of Multiple Lines of Evidence to Assess Vapor Intrusion for US Air Force School of Aerospace Medicine (USAFSAM/OE) at Brooks City-Base, TX Draft Report Volume 1 January 5, 2009 Submitted to: Department of the Air Force USAFSAM/OE Attention: Mr. Steven Strausbauch (COR) 2513 Kennedy Circle Brooks City-Base, TX Prepared by: Tetra Tech, Inc Mount Diablo Blvd # 300 Lafayette, CA Tetra Tech, Inc. 301 Mentor Dr., Suite A Santa Barbara, CA 93110

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3 TABLE OF CONTENTS 1 INTRODUCTION SITE BACKGROUND INFORMATION AND SUMMARY OF PREVIOUS FIELD STUDIES Site Background Information Previous Field Studies Preliminary Field Sampling for MLE Investigation Chemicals of Potential Concern Identified at the Site MULTIPLE LINES OF EVIDENCE FIELD INVESTIGATION Building Description and Indoor Volume Estimates Sampling Program Design and Execution First Sampling Event Soil Vapor Probe Installations Soil, Groundwater, and Soil Vapor Probe Sampling Indoor and Outdoor Air Sampling, Air Exchange Rate, and Differential Pressure Monitoring Second Sampling Event Analytical Data results Meteorology during Sampling Periods Pressure Differential Between Sub-Slab and Indoor Environment Soil Physical Properties Groundwater Sample Results Soil Vapor Sample Results Indoor and Outdoor Air Data QA/QC Considerations ANALYSIS OF DATA Air Exchange Rate Analysis Comparisons of Data Between Event #1 (11 13 June 2008) and Event #2 (26 28 June 2008) Comparison of Sub-slab and Near-slab Data Comparison of Soil Vapor Concentrations with Vapor Concentrations in Equilibrium with Dissolved Groundwater Concentrations Vinyl Chloride (VC) and cis-1, 2-DCE in groundwater, in soil vapor, and in indoor air Tetra Tech, Inc. i

4 5 VAPOR INTRUSION MODELING RESULTS Background and Approach Model Results: Event #1 (HVAC on) Modeling Results for Event #2 (HVAC off) Steady-state Model Comparisons Using All Source Term Options STUDY CONCLUSIONS REFERENCES ii Tetra Tech, Inc.

5 LIST OF FIGURES Figure 2-1 Location of Building 1381 at Cape Canaveral AFS Figure 2-2 TCE DNAPL groundwater plume at Building 1381 in Figure 2-3 Shallow groundwater contours and flow direction Figure 2-4 Trichloroethene in indoor air and sub-slab samples from Building Figure 3-1 Building 1381 floor plan Figure 3-2 Photograph showing the north-west facing front of Building 1381 with the slotted doors of the HVAC room in the foreground Figure 3-3 Photograph showing the large main room inside Building 1381 with HVAC ducting covered by paneling in the upper left corner and a network of black metal plates covering concrete trenches for sub-floor cables and piping Figure 3-4 Photograph showing an uncovered concrete trench housing sub-floor cables and piping. The thickness of the concrete slab directly underlying these trenches is unknown Figure 3-5 Location map showing sample points for groundwater, near-slab soil gas, sub-slab soil gas, and indoor and outdoor air, as well as locations for the helium tanks and differential pressure monitor Figure 3-6 Plot of maximum and minimum differential pressure, measured every 15 minutes Figure 4-1 Analysis of Air Exchange Rate at CCAFS Using Instantaneously Released He and Method # Figure 4-2 Analysis of Air Exchange Rate at CCAFS Using Instantaneously Released He as a tracer and method # Figure 4-3 Comparison of soil gas TCE and cis-1, 2-DCE concentrations for sampling Period #1 with HVAC on, with sampling results for Period #2 with HVAC off Figure 4-4 Comparison of Soil Gas Concentration for TCE and cis-1, 2-DCE during two events Figure 4-5 Indoor air concentrations of TCE and cis-1, 2-DCE Figure 4-6 Comparison of indoor vapor concentrations for TCE and cis-1, 2-DCE during two events Figure 4-7 Correlation of attenuation coefficients between event #1 and event # Figure 4-8 Comparison of VOC concentration in indoor air for TCE, cis-1, 2-DCE, Freon 113, and Vinyl chloride during two events Figure 4-9 Comparison of near-slab and closest sub-slab TCE and cis-1, 2-DCE soil gas concentrations using data from both sampling events Figure 4-10 Comparison of soil gas TCE concentrations with concentrations in equilibrium with dissolved groundwater concentrations Figure 4-11 Vinyl Chloride and cis-1, 2-DCE concentrations in groundwater, soil gas, and in indoor air on June 12, Tetra Tech, Inc. iii

6 Figure 5-1 Predicted and observed TCE concentrations for Event #1, both indoor and directly beneath the slab Figure 5-2 Time Evolution Of Subsurface TCE Concentrations For Several Months Following The Beginning Of Deep Soil Contamination For Event # Figure 5-3 Predicted and observed attenuation factors with confidences limits for Event # Figure 5-4 Monte Carlo Generated traces of predicted concentrations for Event # Figure 5-5 Monte Carlo generated traces of attenuation factors for Event # iv Tetra Tech, Inc.

7 LIST OF TABLES Figure 2-1 Location of Building 1381 at Cape Canaveral AFS. Source: Google Earth Pro (2008) Figure 2-2 TCE (µg/l) DNAPL groundwater plume at Building 1381 in 2005, prior to recent remediation. Source: Tetra Tech (2007) Figure 2-3 Shallow groundwater contours and flow direction (October 2005). Source: Tetra Tech (2007) Figure 2-4 Trichloroethene (µg/m 3 ) in indoor air and sub-slab samples from Building Indoor air collected by Tetra Tech (highest concentrations shown in January 2008; complete results in Table 2-3). Sub-slab samples collected by BEM in 2004 (2004a,b; complete results in Table 2-2). Modified from BEM (2004b) Figure 3-1 Building 1381 floor plan Figure 3-2 Photograph showing the north-west facing front of Building 1381 with the slotted doors of the HVAC room in the foreground Figure 3-3 Photograph showing the large main room inside Building 1381 with HVAC ducting covered by paneling in the upper left corner and a network of black metal plates covering concrete trenches for sub-floor cables and piping Figure 3-4 Photograph showing an uncovered concrete trench housing sub-floor cables and piping. The thickness of the concrete slab directly underlying these trenches is unknown Figure 3-5 Location map showing sample points for groundwater (6 points), near-slab soil gas (6 points), sub-slab soil gas (9 points), and indoor and outdoor air (9 points), as well as locations for the helium tanks and differential pressure monitor Figure 3-6 Plot of maximum and minimum differential pressure, measured every 15 minutes Figure 4-1 Analysis of Air Exchange Rate (AER) at CCAFS Using Instantaneously Released He and Method #1. The individual red and green symbols denote the concentration data collected during the two sampling events. The solid and dashed lines denote the least-squares best-fit line. The two red lines and the two green lines reflect uncertainties in the initial helium concentrations Figure 4-2 Analysis of Air Exchange Rate (AER) at CCAFS Using Instantaneously Released He as a tracer and method #2. Method #2 does not use the initial calculated helium concentrations Figure 4-3 Comparison of soil gas TCE and cis-1, 2-DCE concentrations for sampling Period #1 (June 12, 2008) with HVAC on, with sampling results for Period #2 (June 27, 2008) with HVAC off. (All soil gas samples were taken at 8 feet (2.5 m) below grade) Figure 4-4 Comparison of Soil Gas Concentration for TCE and cis-1, 2-DCE during two events (6/12/08 and 6/27/08) Figure 4-5 Indoor air concentrations of TCE (panel (a)) and cis-1, 2-DCE (panel (b)) Tetra Tech, Inc. v

8 Figure 4-6 Comparison of indoor vapor concentrations for TCE and cis-1, 2-DCE during two events (6/12/08 and 6/27/08) Figure 4-7 Correlation of attenuation coefficients (defined as ratio of indoor air concentrations to sub-slab concentrations) between event #1 and event # Figure 4-8 Comparison of VOC concentration in indoor air for TCE, cis-1, 2-DCE, Freon 113, and Vinyl chloride during two events (6/12/08 and 6/27/08) Figure 4-9 Comparison of near-slab and closest sub-slab TCE and cis-1, 2-DCE soil gas concentrations using data from both sampling events (6/12/08 and 6/27/2008) Figure 4-10 Comparison of soil gas TCE concentrations with concentrations in equilibrium with dissolved groundwater concentrations (June 12, 2008) Figure 4-11 Vinyl Chloride and cis-1, 2-DCE concentrations in groundwater, soil gas, and in indoor air on June 12, Figure 5-1 Predicted and observed TCE concentrations for Event #1 (HVAC on), both indoor and directly beneath the slab Figure 5-2 Time Evolution Of Subsurface TCE Concentrations For Several Months Following The Beginning Of Deep Soil Contamination For Event #1 (Note: The Begin Date Is Arbitrary And Intended Only To Illustrate The Evolution Of The Soil Gas Profile Over Time ) Figure 5-3 Predicted and observed attenuation factors with confidences limits for Event # Figure 5-4 Monte Carlo Generated traces of predicted concentrations for Event # Figure 5-5 Monte Carlo generated traces of attenuation factors for Event # Table 2-1 Indoor air sample analytes and detection limits from BEM in Table 2-2 Sub-slab soil gas sample results from Building 1381 collected in Table 2-3 Indoor air sampling analytical results Table 2-4 Summary of VOCs detected during previous site investigations Table 2-5 Chemicals of Potential Concern Table 3-1 Summary table of indoor volumes for Building Table 3-2 Summary of Field Activities in Support of First Sampling Event Table 3-3 Summary of Field Activities in Support of Second Sampling Event Table 3-4 Soil boring logs Table 3-5 Groundwater data Table 3-6 Soil vapor concentrations collected on 6/12/ Table 3-7 Soil vapor concentrations collected on 6/27/ Table 3-8 Indoor air vapor concentrations for 6/12/ Table 3-9 Indoor air vapor concentrations for 6/26/ Table 3-10 Comparison of indoor vapor concentrations using methods TO-15 & TO-17 on 6/12/ Table 3-11 Comparison of indoor vapor concentrations using methods TO-15 & TO-17 on 6/26/ vi Tetra Tech, Inc.

9 Table 3-12 Helium release rate data on 6/12/ Table 3-13 Helium release rate data on 6/26/ Table 5-1 ViM and J&E Comparison Table 5-2 TCE data collected at CCAFS June Table 5-3 Summary of all model predictions for two scenarios: HVAC-on and HVAC-off Tetra Tech, Inc. vii

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11 1 INTRODUCTION Tetra Tech, Inc. (Tetra Tech) has been contracted by the United States Air Force (USAF), HSW/PKAH to conduct an investigation of multiple lines of evidence (MLE) used in assessing risk associated with the vapor intrusion (VI) pathway. To that end, research is being conducted at up to four Air Force installations where VI is suspected: 1) Cape Canaveral Air Force Station (CCAFS), 2) Travis Air Force Base (AFB), 3) Ellsworth AFB, and 4) former Kelly AFB. The purpose of the investigation is to evaluate a variety of parameters related to VI in order to develop a better understanding of the processes that lead to a complete VI pathway, and ultimately, to develop tools for use by the Air Force in assessing VI at other installations. Tetra Tech conducted a preliminary site visit to CCAFS and Patrick AFB in December 2007 to identify buildings considered likely to be subject to VI. Data provided by AFSPC 45 CES/CEVR were reviewed to identify suitable buildings located over shallow groundwater volatile organic compound (VOC) plumes. Criteria used to select candidate buildings were: Moderate size (i.e. less than 10,000 square feet) Slab-on-grade construction Closed interior space Limited occupancy (to avoid impacting mission operations) Location over a shallow groundwater VOC source Availability for conducting experiments Building 1381 was identified as the best candidate building at CCAFS based on these criteria, and in January and February 2008, air samples were collected from the building to verify the presence of VOCs. The results of this preliminary sampling indicated the presence of VOCs in the indoor air, and the building was selected for the comprehensive investigation discussed in this report. Tetra Tech, Inc. 1-1

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13 2 SITE BACKGROUND INFORMATION AND SUMMARY OF PREVIOUS FIELD STUDIES 2.1 Site Background Information Building 1381 is located on Armory Road, in a relatively remote area of Cape Canaveral Air Force Station (CCAFS), Florida, approximately one mile south of the intersection of Central Control Road and Armory Road and approximately 0.3 miles to the southwest of the nearest building (Figure 2-1). The building is surrounded by forested lands. Figure 2-1 Location of Building 1381 at Cape Canaveral AFS. Source: Google Earth Pro (2008). From its construction in 1958 through 1968, Building 1381 was operated as the Guidance Azimuth Transfer Building. From 1968 until 1977, it served as the In-Place Precision Cleaning Lab for Pan Am World Services (Pan Am). During Pan Am s operations, the building housed Tetra Tech, Inc. 2-1

14 acid and solvent dip tanks that were used for cleaning metal components. Trichloroethene (TCE) was used on-site during cleaning operations. Stainless steel acid dip tanks containing Fozdip acid, oil, and water were used on site to clean galvanized steel pipes (Tetra Tech 2007). A concrete pad containing three dip tanks was located to the south-east of Building Generally, the waste TCE was drummed and taken to Space Launch Complex (SLC) 15 for disposal. However, during the 1960s and 1970s, tanker trucks reportedly also dumped solvents in the woods surrounding Building Hereinafter, Building 1381 and the immediately surrounding areas are referred to as the Site. From 1977 to approximately 2006, the Site served as an Ordnance Support Facility for the U.S. Coast Guard. The U.S. Coast Guard moved out of Building 1381 in There are currently no activities at the Site that have the potential to release chlorinated solvents. A Non-Aqueous Phase Liquid (NAPL) chlorinated solvent groundwater plume was located to the south-east of Building 1381, centered near the area of the former solvent dip tanks (Tetra Tech 2007) (Figure 2-2). TCE was detected at concentrations greater than 10 milligrams per liter (mg/l) in this area. Although the NAPL plume did not extend beneath Building 1381, groundwater in the area flows from the source area towards the building (Figure 2-3). A major remediation effort was conducted at the Site in 2006, and much of groundwater contamination was removed; however, a low concentration VOC plume still exists beneath the building. Figure 2-2 shows isoconcentration contours for the groundwater plume prior to the remediation effort. Figure 2-2 TCE (µg/l) DNAPL groundwater plume at Building 1381 in 2005, prior to recent remediation. Source: Tetra Tech (2007). 2-2 Tetra Tech, Inc.

15 Figure 2-3 Shallow groundwater contours and flow direction (October 2005). Source: Tetra Tech (2007). 2.2 Previous Field Studies In 2004, BEM Systems (BEM 2004a) collected two indoor air samples from Building 1381 (the precise locations of the indoor samples are not known). The samples were collected over a 90 minute period and were analyzed using the National Institute for Occupational Safety & Health (NIOSH) Method 1022 for VOCs and NIOSH Method 1007 for vinyl chloride. The report (BEM 2004a) did not state whether the Heating, Ventilation, and Air Conditioning (HVAC) system was on or off during sampling. No VOCs were detected in the indoor air samples. The chemicals analyzed and the corresponding detection limits are provided in Table 2-1. Table 2-1 Indoor air sample analytes and detection limits from BEM in 2004 (2004a). Chemical Detection limit (µg/m 3 ) cis-1,2-dichloroethene trans-1,2-dichloroethene tetrachloroethane trichloroethene vinyl chloride 0.14 Sub-slab soil gas samples were collected from six locations beneath Building 1381 (slab1 through slab6) and from one location beneath a cement apron to the south of the building (slab7) (Figure 2-4). The samples were analyzed by an on-site mobile laboratory using U.S. Environmental Protection Agency (EPA) Method 8260 for VOCs (BEM 2004a, b). Relatively Tetra Tech, Inc. 2-3

16 high concentrations of TCE were found in sub-slab soil gas. The sampling locations are shown in Figure 2-4; the results are shown in Table 2-2. Figure 2-4 Trichloroethene (µg/m 3 ) in indoor air and sub-slab samples from Building Indoor air collected by Tetra Tech (highest concentrations shown in January 2008; complete results in Table 2-3). Sub-slab samples collected by BEM in 2004 (2004a,b; complete results in Table 2-2). Modified from BEM (2004b). Table 2-2 Sub-slab soil gas sample results from Building 1381 collected in Concentration (µg/m 3 ) Chemical Slab1 Slab2 Slab3 Slab4 Slab5 Slab6 Slab7 BTEX (except m,p-xylene) <200 <200 <200 <200 <200 <200 <200 1,1-dichloroethane <200 <200 <200 <200 <200 <200 <200 cis-1,2-dichloroethene <200 <200 <200 <200 <200 <200 <200 trans-1,2-dichloroethne <200 <200 <200 <200 <200 <200 <200 Freon 113 3, , ,000 64,000 11,000 17,000 tetrachloroethene <200 <200 <200 <200 <200 <200 <200 1,1,1-trichloroethene <200 <200 <200 <200 <200 <200 <200 trichloroethene 740 <200 < ,000 vinyl chloride <200 <200 <200 <200 <200 <200 <200 m,p-xylene 210 <200 <200 <200 <200 <200 <200 Notes: < indicates chemical was not detected above the DL (given to the right of the < symbol). 2.3 Preliminary Field Sampling for MLE Investigation Because BEM (2004a) did not detect any VOCs in indoor air, Tetra Tech conducted preliminary indoor air sampling under conditions more favorable to VI (i.e. with the HVAC system turned off) to verify the presence of VOCs in the indoor air before proceeding with a comprehensive investigation. The HVAC system was turned off and the doors were shut on Friday, 28 December 2007, and the building was left undisturbed for 1 week. On Friday, 4 January 2008 (7 days after turning off the HVAC system), two 6-liter SUMMA canisters and two TO-17 badges were placed in Building 1381 for 24 hours. A flow controller was attached to the SUMMA canisters so that indoor air sampling was integrated over 24 hours. The two indoor air sampling 2-4 Tetra Tech, Inc.

17 locations are shown in Figure 2-4. The samples were retrieved on 5 January 2008 and sent to Air Toxics, Inc. (Air Toxics), located in Folsom (CA) for analysis via EPA methods TO-15 and TO-17. After sampling was complete, the HVAC system was turned back on. Approximately one month later (13 February 2008), another indoor air sample was collected. However, due to the cool/cold weather at the time, the HVAC system may not have been active much (if any) of the time. The analytical results from both rounds of indoor air sampling are shown in the Table 2-3. Table 2-3 Indoor air sampling analytical results (units: µg/m 3 ) HVAC off HVAC on Chemical TO-15 TO-17 TO-15 TO-17 TO-15 TO-17 1,1-dichloroethene <0.012 < <0.71 <0.068 <0.36 cis-1,2-dichloroethene trans-1,2-dichloroethene <0.25 <0.60 <0.2 <0.60 <0.68 <0.039 Freon tetrachloroethene J J J trichloroethene vinyl chloride < < Notes: < indicates chemical was not detected above the MDL (given to the right of the < symbol). 2.4 Chemicals of Potential Concern Identified at the Site A number of VOCs have been detected during past site investigations in groundwater and subslab soil gas at Building 1381 (BEM 2004a, b, 2006, Tetra Tech 2007) and in indoor air during January and February 2008 (Table 2-3). The VOCs that have been detected are shown in Table 2-4. Table 2-4 Summary of VOCs detected during previous site investigations. Groundwater Sub-slab soil gas Indoor air acetone 1,1 dichloroethane 1,1-dichloroethane 1,1-dichloroethane cis-1,2-dichloroethene cis-1,2-dichloroethene trans-1,2-dichloroethene freon 113 (1,1,2-trichloro-1,2,2-trifluoroethane freon 113 tetrachloroethene tetrachloroethene trichloroethene trichloroethene trichloroethene vinyl chloride Vinyl chloride m,p-xylene The concentrations of acetone and m,p-xylene that were previously detected at the Site are generally low. Further, acetone is a common laboratory contaminant and xylenes are likely to be present in both indoor and outdoor air from sources unrelated to the past activities at Building 1381; e.g., car exhaust. Therefore, the VOCs shown in Table 2-5 were selected from the list of previously detected chemicals as chemicals of potential concern (COPCs) and all samples collected at the Site in support of the current field studies were analyzed for these COPCs. Tetra Tech, Inc. 2-5

18 Table 2-5 Chemicals of Potential Concern Chemicals of Potential Concern 1,1-dichloroethane 1,1-dichloroethene cis-1,2-dichloroethene trans-1,2-dichloroethene freon 113 tetrachloroethene trichloroethene vinyl chloride 2-6 Tetra Tech, Inc.

19 3 MULTIPLE LINES OF EVIDENCE FIELD INVESTIGATION The MLE field investigation was conducted during two mobilizations in June A variety of parameters were measured during the field investigation to develop a comprehensive understanding of the processes occurring at the Site. The following sections detail the field activities. 3.1 Building Description and Indoor Volume Estimates Building 1381 is a single story slab-on-grade structure. The structural integrity of the back portion of the building has been jeopardized. Cracks in the building appear to be widening, which may cause an increased flow rate into the building. An HVAC system located in a room in the northern corner of the building services the entire building (Figure 3-1). The HVAC room has no internal connections to the rest of the building (i.e., doors or passageways), other than the HVAC ducting. While the intake for the HVAC system is located within the building (i.e., design specifications are for 100% re-circulated air), the room containing the HVAC system does have vents on the two front doors and another fanned vent on the side of the building. Figure 3-1 Building 1381 floor plan. Figure 3-2 through Figure 3-4 are photographs of the outside and inside of Building The HVAC room has an uncovered concrete floor. The two other north-west facing rooms (front) are carpeted, while the remaining rooms in the middle and rear of the building have linoleum floors. The large center room with linoleum floors has sub-floor piping set into concrete trenches. These trenches and the floor of the HVAC room are the only parts of the building where the slab foundation is uncovered. Tetra Tech, Inc. 3-1

20 Figure 3-2 Photograph showing the north-west facing front of Building 1381 with the slotted doors of the HVAC room in the foreground. Figure 3-3 Photograph showing the large main room inside Building 1381 with HVAC ducting covered by paneling in the upper left corner and a network of black metal plates covering concrete trenches for sub-floor cables and piping. 3-2 Tetra Tech, Inc.

21 Figure 3-4 Photograph showing an uncovered concrete trench housing sub-floor cables and piping. The thickness of the concrete slab directly underlying these trenches is unknown. During June 2008, detailed measurements were taken of each room in order to assess the indoor volume of Building Indoor volume estimates are presented in Table 3-1. Each room contained various amounts of furniture and equipment that filled space, and the large center room contains HVAC ducting (Figure 3-3) and concrete trenches containing sub-floor utility lines creating void spaces that may or may not be considered part of the indoor volume of the room. Therefore, the volume estimates presented in Table 3-1 are considered to have a margin of error of ±10 percent. Tetra Tech, Inc. 3-3

22 Table 3-1 Summary table of indoor volumes for Building Room containing Length (in) Width (in) Height (in) Volume (ft 3 ) Revised Volumes (ft 3 ) 1381-SS-1 (HVAC) ,180 5, SS ,747 5, SS ,553 3,553 Bathroom SS ,610 1, SS ,596 10, SS ,010 3, SS ,883 1,883 Total Volume with HVAC Room 32,819 32,218 Total Volume without HVAC Room 27,639 27, Sampling Program Design and Execution Field activities in support of the current investigation were divided into two sampling events separated by a 13-day interval. During the first event, sampling was conducted with Building 1381 operating under normal conditions, i.e., with the HVAC system turned on. During the second sampling event, all sampling activities were repeated with the HVAC system off. Soil and groundwater samples were only collected during the first sampling round, while installing the outdoor soil vapor probes. The HVAC system was turned off on June 16, three days after the first sampling event and had been turned off for 10 days prior to the second sampling event. 3.3 First Sampling Event The first sampling event was conducted from 11 through 13 June Field activities included the installation of nine sub-slab soil vapor probes inside the building, installation of six soil vapor probes around the outside of the building, collection of soil and groundwater samples from the outdoor vapor probe borings, collection and on-site analysis of soil vapor samples by an onsite mobile laboratory, deployment of SUMMA canisters and co-located TO17 badges, and installation of a differential pressure monitor to measure the sub-slab vapor pressure relative to indoor air. In addition, a known quantity of helium was released into the building, and periodic indoor air samples were collected for off-site helium analysis in order to develop an estimate of the building air exchange rate (AER). A summary of field activities including dates is provided in Table Tetra Tech, Inc.

23 Table 3-2 Summary of Field Activities in Support of First Sampling Event 11 June 2008 Nine indoor sub-slab soil vapor probes installed Six outdoor near-slab soil vapor probes installed at 8 feet below ground surface (bgs) Four soil samples collected for chemical and physical testing at offsite lab Six groundwater samples collected for chemical analysis at offsite lab 12 June 2008 All soil vapor probes sampled with on-site analysis performed by a mobile laboratory Nine SUMMA canisters deployed (seven indoors and two outdoor) Nine TO17 badges co-located with SUMMA canisters deployed Air exchange rate investigation initiated via instantaneous release of approximately 220 ft 3 of helium gas at STP into building and subsequent periodic sampling of indoor air Differential pressure monitor set up and installation for continuous monitoring of sub-slab to indoor air pressure differential 13 June 2008 SUMMA canisters and TO17 badges collected and sent to offsite laboratory for analysis Site cleaned up and logistical preparations made for second round of field activities Sampling locations are shown on Figure 3-5. The prefix 1381 has been deleted from all sample location IDs on Figure 3-5 for visual clarity; the prefix has, however, been retained in text and tables for the presentation and discussion of results in following sections. Additionally, all indoor air sampling locations were co-located with the numerically associated sub-slab soil gas sampling points. For this reason, there are no indoor air sampling location IDs ending in -4 or -6. Tetra Tech, Inc. 3-5

24 Figure 3-5 Location map showing sample points for groundwater (6 points), near-slab soil gas (6 points), sub-slab soil gas (9 points), and indoor and outdoor air (9 points), as well as locations for the helium tanks and differential pressure monitor Soil Vapor Probe Installations Nine sub-slab soil vapor probes (1381-SS-1 through 1381-SS-9) were installed directly beneath the slab inside Building 1381 (Figure 3-5). Soil vapor probes consisting of 1.5-inch gas permeable filters attached to inch outer diameter Nylaflow tubing terminated by 3-way valves were installed in holes drilled through the building slab using a rotohammer drill with a inch diameter drill bit and penetrating the sub-slab material just enough to accommodate the filters (approximately 1 to 2 inches). Prior to installation, the holes were cleaned with a damp towel to ensure a good seal. Sand to 1 inch above the filters and hydrated granular bentonite to approximately 1 inch below the surface completed the installations. Cement caps were not installed, because these probes are not permanent and the 1-inch depression at the surface was designed to accommodate the tubing during periods of sampling inactivity, when foot traffic 3-6 Tetra Tech, Inc.

25 through the building may cause damage to exposed sampling points. The tubing extends approximately 8 inches above the surface from each location. Six near-slab soil vapor probes (1381-SG-1 through 1381-SG-6) were installed peripherally outside Building 1381 (Figure 3-5). These were constructed in the same manner as the indoor soil vapor probes, but extend to a depth of 8 feet below ground surface (bgs), directly above the capillary fringe. A direct-push Geoprobe system was used to hydraulically drive 2.25-inch diameter rods containing 2-inch Macro-Core acetate sampling sleeves to groundwater. Soils were logged by sampling the hand auger bucket used to clear each location to 5 feet bgs and by inspecting the acetate sleeves, which retrieved samples from 5 to 10 feet bgs. Boring logs describing soils and soil vapor probe construction diagrams are provided in Appendix A. The probes were installed after grab groundwater samples had been collected from each location. The borings generally collapsed to between 10 and 8.5 feet bgs upon retrieval of the groundwater sampler. After backfilling the boring as necessary to approximately 8 feet bgs, the filters were lowered to 8 feet bgs and sand was then poured into the hole to approximately 2 to 3 inches above the filter. Then, a 1-foot granular bentonite dry pack was poured into the hole and topped with bentonite chips to grade. The bentonite chips were repeatedly hydrated during several lifts to ensure a proper seal. All soil vapor probes were installed through the open boring, with the exception of 1381-SG-3; this boring location collapsed completely upon retrieval of the rods and the probe was therefore installed through the rods after re-drilling the location. The tubing extends above surface approximately 1 foot from each location Soil, Groundwater, and Soil Vapor Probe Sampling During installation of the near-slab soil vapor probes, four in-tact soil samples from the 7 to 8 feet bgs intervals were collected from locations 1381-SG-2, 1381-SG-4, 1381-SG-5, and SG-6 for physical parameters testing. In each case an approximately 1-foot section of the acetate sampling sleeve was carefully cut and capped at either end, minimizing disturbance to the soil sample within. Analytical results for soil samples are presented in Section and discussed in Section 4.0. In addition, a total of six grab groundwater samples were collected from locations 1381-SG-1 through 1381-SG-6 immediately prior to installation of the soil vapor probes. Groundwater around the building generally occurred at 9.5 to 10 feet bgs. At each location, a 1-inch diameter stainless steel groundwater sampler was driven to 14 feet bgs with the rods, which were then retracted, exposing a 4-foot screen to groundwater. Each groundwater sample was therefore collected from the 10 to 14 feet bgs interval. A ball check valve attached to tubing was lowered through the rods and bounced up and down until groundwater filled the tube. Samples were collected after turbidity had visually gone down. Analytical results for groundwater sampling are presented in Section and discussed in Section 4.0. On 12 June 2008, after the newly installed soil vapor probes had set for 24 hours, each soil vapor probe was sampled using a 60-milliliter (ml) syringe. In each case, three system volumes were purged prior to filling a 1L Tedlar bag with 180 ml of soil gas. Thus, approximately 4.5 ml from the sub-slab soil vapor probes and 27 ml from the near-slab probes were purged prior to sampling each location. Purging and sampling with the same syringe at each location was accomplished via use of a 3-way valve, minimizing the potential for outside contamination. Samples were collected from locations 1381-SG-1 through 1381-SG-6 and 1381-SS-1 through Tetra Tech, Inc. 3-7

26 1381-SS-9 throughout the day and hand delivered to an onsite mobile laboratory operated by KB Labs, Inc., which ran one analysis every 20 to 30 minutes. This real-time approach allowed the field crew to make critical decisions based on analytical results. Analytical results for soil gas samples are presented in Section and discussed in Section Indoor and Outdoor Air Sampling, Air Exchange Rate, and Differential Pressure Monitoring In order to estimate the indoor-outdoor air exchange rate, approximately 222 cubic feet (ft 3 ) of helium gas from two point sources were released into the building on 11 June The sources were two 111 ft 3 cylinders, which were placed in the two largest rooms of the building (Figure 3-5). The valves were fully opened simultaneously by the field crew and the tanks allowed to empty into the building. Each cylinder emptied in approximately 1 minute. Indoor air samples integrated throughout each room of the building were subsequently obtained with a syringe and Tedlar bag at 15, 30, and 60 minutes after the initial release, and again at 2, 4, and 6 hours. Each Tedlar bag was filled approximately ¾ full, labeled, and sent to Air Toxics for analysis. Analytical results are presented in Section and discussed in Section 4.0. On 11 June 2008, during installation of the soil vapor probes, a differential pressure monitor was installed in the center of the building (Figure 3-5). One end of a 3/8-inch diameter tube (without a filter) was installed as a soil gas probe directly beneath the slab, while the other end was attached to an Omniguard 4 Differential Pressure Monitor. The device was set to begin monitoring the pressure differential on 11 June 2008 and continuously through the second sampling round ending on 27 June Results are presented in Section and discussed in Section 4.0. On 12 June 2008, seven SUMMA canisters were deployed inside the building and two outside (Figure 3-5). Passive dosimeters (SKC diffusive samplers) co-located with each SUMMA canister were deployed one hour later. The canisters were placed near the soil gas sampling points and at elevated locations where possible (e.g., on tables), in order to obtain samples more representative of the breathing zone. Samples from indoor locations 1 through 3, 5, and 7 through 9 were collected with SUMMA canisters and co-located passive dosimeters (Figure 3-5). A duplicate sample was not obtained, because one of the SUMMA canisters arrived from the laboratory with a compromised vacuum. It was therefore agreed to eliminate the duplicate indoor air sample after the issue was discussed with USAFSAM personnel. The SUMMA canister from indoor location 1 arrived with a marginally acceptable initial vacuum (24 in Hg). In addition, SUMMA canisters 1381-SM-ODN and 1381-SM-2 filled prematurely; therefore, all three canisters had to be closed prior to completing the 24-hour sampling period. All other SUMMA canisters were closed on 13 June 2008, after sampling for a 24-hour period. All canisters and passive dosimeters were collected on 13 June 2008 and sent to Air Toxics for offsite analysis. Analytical results are presented in Section and discussed in Section Second Sampling Event The second sampling event was conducted on 26 and 27 June 2008 after the HVAC system had been off and the building closed for 10 days. Field activities included collection of soil vapor samples from the interior sub-slab probes and the exterior near-slab probes, collection of indoor air samples using Summa canisters and TO17 badges, and a repeat of the air exchange measurements by releasing helium into the building and collecting periodic indoor air samples. 3-8 Tetra Tech, Inc.

27 Table 3-3 Summary of Field Activities in Support of Second Sampling Event 26 June 2008 Nine SUMMA canisters deployed (seven indoors and two outdoor) Nine TO17 badges co-located with SUMMA canisters deployed Air exchange rate investigation conducted via instantaneous release of approximately 220 ft 3 of helium gas into building and subsequent periodic sampling of indoor air 27 June 2008 All soil vapor probes sampled with on-site analysis performed by a mobile laboratory SUMMA canisters and TO17 badges collected and sent to offsite laboratory for analysis Retrieval and data download from the differential pressure monitor Site cleaned up The sampling locations for the second round were the same as the first, as shown on Figure 3-5, and all soil vapor and indoor/outdoor air sample collection procedures were the identical to those used during the first sampling round, with the following exceptions: Due to the anticipated lower air exchange rate with the HVAC system turned off, air samples for helium were collected at 15, 30 and 60 minutes, and 2, 4, 6, 8, 10, and 24.5 hours after release of the helium. A second type of passive dosimeter (the Radiello badge) was deployed at five of the sampling locations: Nos. 2, 3, 5, 8, and 9. All of the SUMMA canisters had sufficient vacuum, therefore, a duplicate sample was collected at location No. 1, and all of them filled at an appropriate rate and were therefore deployed for 24 hours. The SUMMA canisters and diffusion samplers (both SKC and Radiello) were deployed simultaneously, rather than with 1 hour of separation. 3.5 Analytical Data results Meteorology during Sampling Periods During the first sampling event, the days were clear with temperatures ranging in the mid to high 80s, accompanied by high humidity. There was only a slight breeze and no rain. During the second sampling event, temperatures ranged in the high 70s and low 80s, and scattered thunderstorms occurred throughout the sampling period Pressure Differential Between Sub-Slab and Indoor Environment The Omniguard 4 differential pressure monitor installed near soil vapor probe 1381-SS-5 recorded minimum and maximum pressure differentials during every successive 15 minute time interval from 11 June 2008 through 27 June Figure 3-6 illustrates the results in graphical form. Shortly after installation of the monitor, field staff monitoring the readings noted that the pressure differential changed from negative to positive within seconds to minutes in a periodic fashion. Therefore, in order to record the true temporal changes in differential pressure, the unit would ideally have to record the instantaneous differential every few seconds, which was not an option given the logistical constraints of the project. However, the maximum and minimum pressure differentials recorded every 15 minutes do show a notable pattern. Tetra Tech, Inc. 3-9

28 Differential Pressure Measurements Tt On-site Tt On-site 20 HVAC turned off (approx) 15 Differential Pressure (Pa) Back doors open Hi Lo Date Figure 3-6 Plot of maximum and minimum differential pressure, measured every 15 minutes Soil Physical Properties Off-site laboratory analysis for soil physical properties was performed by Keantan Laboratories, located in Diamond Bar, California. Soil samples SG2-7, SG4-7, SG5-7, and SG6-7 were analyzed for moisture content, dry density, total organic carbon (TOC), total porosity, effective permeability, and air conductivity. Analytical test results are presented in Table 3-4 and discussed in Section 4.0. Boring logs describing soil lithology at sample depth are provided in Appendix A. The laboratory report for these analyses is provided as Appendix B Tetra Tech, Inc.

29 Moisture Content (%) Table 3-4 Soil boring logs Dry Density (pcf) Total Porosity (%) Effective Permeability (millidarcy) Air Conductivity (cm/second) Sample ID Collection Date USCS Classification TOC (%) SG Jun-08 SW-SP E-05 SG Jun-08 SW-SP E-05 SG Jun-08 SW-SP E-05 SG Jun-08 SW-SP E-05 Definitions: cm centimeter pcf pounds per cubic foot SP poorly graded sand SW well graded sand TOC total organic carbon USCS Universal Soil Classification System Note: 1 Samples contain shell fragments Groundwater Sample Results Off-site laboratory analysis for groundwater samples collected during installation of the nearslab soil vapor probes was performed by Southeast Accutest Laboratories, located in Orlando, Florida. Samples CC1381SG1-GW through CC1381SG6-GW were analyzed for VOCs by U.S. Environmental Protection Agency (EPA) method SW8260B. Analytical test results are presented in Table 3-5 and discussed in Section 4.0. The laboratory report for these analyses is provided as Appendix C. The highest concentrations of TCE and its degradation products cis-1,2- dichloroethene (DCE), 1,1-dichloroethane (DCA) and vinyl chloride were detected in the groundwater sample from location 1381-SG-6, at the northern corner of Building 1381 (Figure 3-5). The most abundant compound detected in the samples was cis-1,2-dce, followed by vinyl chloride. TCE, trans-1,2-dce, 1,1-DCA were detected in most of the samples. Tetra Tech, Inc. 3-11

30 Table 3-5 Groundwater data (µg/l) Sampling Location CC1381-SG-1 CC1381-SG-2 CC1381-SG-3 CC1381-SG-4 CC1381-SG-5 CC1381-SG-6 Sample ID CC1381SG1-GW CC1381SG2-GW CC1381SG3-GW CC1381SG4-GW a CC1381SG5-GW CC1381SG6-GW a Collection Date 11-Jun Jun Jun Jun Jun Jun-08 VOCs MDL RL TCE ND 12.0 J 7.3 J 0.52 J cis-1,2-dce ,050 a,b 2,400 b 3,080 b 0.6 J 3.2 8,340 trans-1,2-dce ND 10.2 J 14.8 J ND trans-1,3-dcp ND ND ND 4.5 ND ND 1,1-DCA J 13.0 J ,1-DCE J ND ND ND ND ND Benzene ND ND ND ND Chloroethane ND ND 10.0 J 0.99 J 6.0 ND Chloroform ND ND ND ND 0.68 J ND Ethylbenzene ND ND ND 0.89 J 0.61 J ND Toluene ND ND ND ND Methyl chloride ND ND ND ND 0.67 J ND Methylene chloride c J 28.0 c J 24.8 c J ND ND 119 c JB Vinyl chloride , , ,490 Xylene (total) ND ND ND 2.0 J ND ND All other analytes N/A N/A ND ND ND ND ND ND Data Validity Qualifiers: J The result is greater than or equal to the MDL but less than the RL. B Indicates analyte found in associated method blank Definition(s): a Sample was not preserved to a ph<2; reported results are considered minimum values. b- Result is from run #2 c suspected laboratory contaminant DCE dichloroethene EPA Environmental Protection Agency MDL method detection limit µg/l micrograms per Liter N/A not applicable ND Not detected; result is less than the MDL. PCE tetrachloroethene RL reporting limit TCE trichloroethene VOC volatile organic compound Soil Vapor Sample Results On-site laboratory analysis for soil gas samples collected during the first and second sampling events was performed by KB Laboratories, based in Gainesville, Florida. All samples were analyzed for vinyl chloride, Freon 113, 1,1-DCE, cis-1,2-dce, trans-1,2-dce, 1,1-DCA, TCE, and tetrachloroethene (PCE) by EPA method SW8260. Near-slab samples SG-1 through SG-6 and duplicate sample SG-Dup, as well as sub-slab samples SS-1 through SS-9 were collected during the first sampling event. Near-slab samples SG-1B through SG-6B, as well as sub-slab samples SS-1B through SS-9B and duplicate sample SS-DUPB associated with sampling location 1381-SS-3 were collected during the second sampling round. In addition, a field blank sample was collected during each sampling round. Analytical results are presented in Table 3-6 (first sampling event, HVAC on) and Table 3-7 (second sampling event, HVAC off) and are discussed in Section 4.0. The laboratory report for both sampling events is provided as Appendix D. TCE was consistently detected in all of the soil vapor samples, and cis-1,2-dce was detected in most Tetra Tech, Inc.

31 Table 3-6 Soil vapor concentrations on 6/12/2008 (µg/l) Sample ID SS-1 SS-2 SS-3 SS-4 SS-5 SS-6 SS-7 SS-8 SS-9 Collection Date 6/12/2008 6/12/2008 6/12/2008 6/12/2008 6/12/2008 6/12/2008 6/12/2008 6/12/2008 6/12/2008 Volume, ml 100,10 100, Vinyl Chloride <0.10 <0.10 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 Freon <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 1,1-Dichloroethene <0.10 <0.10 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 trans-1,2-dichloroethene <0.10 <0.10 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 1,1-Dichloroethane < <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 cis-1,2-dichloroethene < <1.0 <1.0 <1.0 Trichloroethene Tetrachloroethene 0.11 <0.10 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 Sample ID SG-1 SG-2 SG-3 SG-4 SG-Dup 1 SG5 SG-6 Collection Date 6/12/2008 6/12/2008 6/12/2008 6/12/2008 6/12/2008 6/12/2008 6/12/2008 Volume, ml Vinyl Chloride <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 Freon <1.0 <1.0 <1.0 <1.0 <1.0 1,1-Dichloroethene <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 trans-1,2-dichloroethene <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 1,1-Dichloroethane <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 cis-1,2-dichloroethene <1.0 <1.0 <1.0 <1.0 <1.0 Trichloroethene Tetrachloroethene <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 Definitions: HVAC heating, ventilation, and air conditioning µg/l micrograms per liter ml milliliter Note: 1 Associated with SG-4 Table 3-7 Soil vapor concentrations on 6/27/2008 (µg/l) Sample ID SS-1B SS-2B SS-3B SS-DUPB 1 SS-4B SS-5B SS-6B SS-7B SS-8B SS-9B Collection Date 6/27/2008 6/27/2008 6/27/2008 6/27/2008 6/27/2008 6/27/2008 6/27/2008 6/27/2008 6/27/2008 6/27/2008 Volume, ml Vinyl Chloride <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 Freon 113 < <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 1,1-Dichloroethene <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 trans-1,2-dichloroethene <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 1,1-Dichloroethane <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 cis-1,2-dichloroethene < <1.0 <1.0 <1.0 Trichloroethene Tetrachloroethene <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 Sample ID SS-1B SS-2B SS-3B SS-4B SS-5B SS-6B Analysis Date 6/27/2008 6/27/2008 6/27/2008 6/27/2008 6/27/2008 6/27/2008 Volume, ml Vinyl Chloride <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 Freon <1.0 <1.0 <1.0 <1.0 1,1-Dichloroethene <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 trans-1,2-dichloroethene <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 1,1-Dichloroethane <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 cis-1,2-dichloroethene <1.0 <1.0 <1.0 <1.0 Trichloroethene Tetrachloroethene <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 Definitions: HVAC heating, ventilation, and air conditioning µg/l micrograms per liter ml milliliter Note: 1 Associated with SS-3B Indoor and Outdoor Air Data Off-site laboratory analysis for indoor and outdoor air samples collected during the first and second sampling event was performed by Air Toxics Ltd., located in Folsom, California. During the first sampling event, samples 1381-SM-1 through 1381-SM-3, 1381-SM-5, 1381-SM-7 through 1381-SM-9, 1381-SM-ODN, and 1381-SM-ODS, collected with SUMMA canisters, were analyzed using EPA method TO-15 in selected ion monitoring (SIM) mode. Samples Tetra Tech, Inc. 3-13

32 SK-1 through 1381-SK-3, 1381-SK-5, 1381-SK-7 through 1381-SK-9, 1381-SK-ODN, and 1381-SK-ODS, collected with passive diffusion badges, were analyzed using EPA method TO-17. The badges were co-located with SUMMA canisters to assess the comparability of results obtained via the two methods. Analytical data results are presented in Table 3-8 and Table 3-9 (TO-15 data with HVAC on and off, respectively) and results from the two methods are compared in Table 3-10 and Table During the second sampling event, the same sample IDs were used, appended with a B. In addition, duplicate samples 1381-SM-DUP B and 1381-SK- DUP B were collected from indoor sampling location 2 (Figure 3-5). Laboratory data reports for both sampling events are provided in Appendix E. Table 3-8 Indoor air vapor concentrations for 6/12/2008 (µg/m 3 ) Sample ID 1381-SM SM SM SM SM SM SM SM-ODN 1381-SM-ODS Collection Date 12-Jun Jun Jun Jun Jun Jun Jun Jun Jun-08 MDL 1 RL 1 PCE J J TCE cis-1,2-dce trans-1,2-dce 0.40 ND ND ND ND ND ND ND ND ND 1,1-DCE ND ND ND ND ND ND ND ND ND Freon J ND ND ND ND 4.5 J ND 0.39 J 0.55 J Vinyl chloride J ND ND ND ND ND J ND ND All other analytes N/A N/A ND ND ND ND ND ND ND ND ND Data Validity Qualifiers: J The analyte was positively identified and the result is usable; however, the analyte concentration is an estimated value. Definition(s): DCE dichloroethene EPA Environmental Protection Agency µg/m 3 micrograms per cubic meter MDL method detection limit NA not analyzed N/A not applicable ND Not detected PCE tetrachloroethene RL reporting limit TCE trichloroethene VOC volatile organic compound Table 3-9 Indoor air vapor concentrations for 6/26/2008 (µg/m 3 ) Sample ID 1381-SM-1B 1381-SM-2B 1381-SM-DupB 1381-SM-3B 1381-SM-5B 1381-SM-7B 1381-SM-8B 1381-SM-9B 1381-SM-ODNB 1381-SM-ODSB Collection Date 26-Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun-08 MDL 1 RL 1 PCE TCE cis-1,2-dce J J trans-1,2-dce J 0.11 J 0.10 J J 0.11 J 0.12 J 0.11 J J ND J 1,1-DCE ND ND ND 1,2-DCA ND J 0.12 J 0.12 J 0.11 J J J Freon J J 0.62 J Vinyl chloride ND ND ND All other analytes N/A N/A ND ND ND ND ND ND ND ND ND ND Data Validity Qualifiers: J The analyte was positively identified and the result is usable; however, the analyte concentration is an estimated value. Definition(s): DCE dichloroethene EPA Environmental Protection Agency µg/m 3 micrograms per cubic meter MDL method detection limit NA not analyzed N/A not applicable ND Not detected; result is less than the MDL. PCE tetrachloroethene RL reporting limit TCE trichloroethene VOC volatile organic compound 3-14 Tetra Tech, Inc.

33 Table 3-10 Comparison of indoor vapor concentrations using methods TO-15 & TO-17 on 6/12/2008 (µg/m 3 ) Sample Location Sample Collection Period (hours) Collection Date TO-15 TO-17 PCE TCE cis-1,2-dce trans-1,2-dce 1,1-DCE Method: TO-15 TO-17 TO-15 TO-17 TO-15 TO-17 TO-15 TO-17 TO-15 TO-17 MDL: RL: RPD RPD RPD RPD Jun % % % ND ND NA ND ND NA Jun % % % ND ND NA ND ND NA Jun % % % ND ND NA ND ND NA Jun % % % ND ND NA ND ND NA Jun % % % ND ND NA ND ND NA Jun % % % ND ND NA ND ND NA Jun % % % ND ND NA ND ND NA 1381-ODN 12-Jun J ND NA % 0.20 ND NA ND ND NA ND ND NA 1381-ODS 12-Jun J ND NA % 0.14 ND NA ND ND NA ND ND NA Data Validity Qualifiers: J The analyte was positively identified and the result is usable; however, the analyte concentration is an estimated value. Definition(s): DCE dichloroethene EPA Environmental Protection Agency µg/m 3 micrograms per cubic meter MDL method detection limit NA not applicable ND Not detected; result is less than the MDL. PCE tetrachloroethene RL reporting limit TCE trichloroethene VOC volatile organic compound RPD Table 3-11 Comparison of indoor vapor concentrations using methods TO-15 & TO-17 on 6/26/2008 (µg/m 3 ) Sample Location Sample Collection Period (hours) Collection Date TO-15 TO-17 PCE TCE cis-1,2-dce trans-1,2-dce 1,1-DCE Method: TO-15 TO-17 TO-15 TO-17 TO-15 TO-17 TO-15 TO-17 TO-15 TO-17 MDL: RL: RPD RPD RPD RPD B 26-Jun ND NA % % J ND NA ND ND B 26-Jun % % % 0.11 J ND NA ND 1381-DupB 26-Jun % % % 0.10 J ND NA ND B 26-Jun % % % J ND NA ND B 26-Jun % % % 0.11 J ND NA 0.10 ND B 26-Jun % % % 0.1 J ND NA 0.10 ND B 26-Jun % % % 0.11 J ND NA 0.11 ND B 26-Jun % % % J ND NA ND 1381-ODSB 26-Jun ND NA % 0.04 J ND NA J ND NA ND ND Sample Location Sample Collection Period (hours) Collection Date TO-15 TO-17 PCE TCE Method: TO-15 TO-17 TO-15 TO-17 MDL: RL: RPD B 26-Jun % % B 26-Jun % % B 26-Jun % % B 26-Jun % % B 26-Jun % % Data Validity Qualifiers: J The analyte was positively identified and the result is usable; however, the analyte concentration is an estimated value. Definition(s): DCE dichloroethene EPA Environmental Protection Agency µg/m 3 micrograms per cubic meter MDL method detection limit NA not applicable ND Not detected; result is less than the MDL. PCE tetrachloroethene RD Leeder Consulting, Radiello passive sampler RL reporting limit SKC SKC Gulf Coast, Inc., ULTRA passive sampler TCE trichloroethene VOC volatile organic compound RPD Off-site laboratory analysis for indoor air in support of the air exchange rate investigations undertaken during the first and second sampling events was performed by Air Toxics Ltd. All samples were analyzed for helium (He) in air by modified ASTM Method D Analytical data are presented in Table 3-12 (first sampling event) and Table 3-13 (second sampling event) and are discussed in Section 4.0. Laboratory reports are provided in Appendix E. Table 3-12 Helium release rate data on 6/12/2008 (%) Sample ID Collection Date Collection Time Time After He Release (min) RL Result He Jun He Jun He Jun He Jun He Jun He Jun Definitions: HVAC heating, ventilation, and air conditioning RL reporting limit Tetra Tech, Inc. 3-15

34 Table 3-13 Helium release rate data on 6/26/2008 Sample ID Collection Date Collection Time Time After He Release (min) RL Result He Jun ND He Jun He Jun He Jun He Jun He Jun He Jun He Jun He Jun He Jun , Definitions: HVAC heating, ventilation, and air conditioning RL reporting limit QA/QC Considerations All on-site and off-site laboratory analyses and data validation were performed in accordance with Appendix F. Several data quality discrepancies were encountered. During the first sampling event SUMMA canisters 1381-SM-2 and 1381-SM-ODN filled faster than anticipated and had to be closed prematurely. The samples collected with these two SUMMA canisters therefore are not integrated over a 24-hour period. A third SUMMA canister arrived on site with a marginal starting vacuum and was therefore not used. As a result, the SUMMA canister intended for the duplicate air sample was used for that location, and no duplicate was collected. The groundwater sample results from locations 1381-SG-1, 1381-SG-4, and SG-6 were flagged by the laboratory as estimated because the samples had not been preserved at a ph below 2. The samples were collected in pre-preserved volatile organic analysis (VOA) vials provided by the laboratory, and the field crew took care to prevent overflowing of the sample containers; therefore, flawed field procedures are not suspected. Rather, it appears that the groundwater is buffered, probably due to the high carbonate content of the formation, and the volume of acid provided was insufficient to lower the ph below 2. However, the hold time for samples collected in unpreserved VOAs is seven days, and these samples were analyzed within eight days of being collected, only slightly outside holding time; therefore, this issue is considered negligible. TCE was detected in the field blank collected for the mobile lab during the first sampling round (Appendix D). However, the concentration detected in the field blank (0.98 µg/l) is only a fraction of the concentrations detected in the environmental samples, and so the impact on data quality, if any, is considered insignificant. Furthermore, during the second mobilization, when exactly the same sampling procedures and equipment were used, the field blank results were non-detect for all compounds. During the second sampling event, a SUMMA canister fell over during an overnight thunderstorm and the attached TO-17 badge was discovered the next morning in a puddle. The analysis for outdoor air sample 1381-SK-ODN was therefore cancelled Tetra Tech, Inc.

35 These discrepancies are considered minor and do not significantly impact the data quality or interpretations presented in this report. Tetra Tech, Inc. 3-17

36

37 4 ANALYSIS OF DATA 4.1 Air Exchange Rate Analysis Air exchange rates were experimentally determined by instantaneously releasing a known mass of helium into Building 1381, and periodically collecting samples of air containing helium in the building at times subsequent to the release. The theoretical basis for each of two methods used is presented in Appendix I. The results are presented graphically in Figure 4-1 (method #1) and Figure 4-2 (method #2). Figure 4-1 Analysis of Air Exchange Rate (AER) at CCAFS Using Instantaneously Released He and Method #1. The individual red and green symbols denote the concentration data collected during the two sampling events. The solid and dashed lines denote the least-squares best-fit line. The two red lines and the two green lines reflect uncertainties in the initial helium concentrations. Method #1 requires an estimate of the initial He mass released while method #2 does not require that information. Method #2 was developed because the information available to estimate the initial He mass released was somewhat uncertain. Note that the first three data points collected during the June 27 event were not used in the analysis. It appeared that the He was not wellmixed within the building for approximately the first hour after the initial release. The method assumes He levels are well-mixed. Tetra Tech, Inc. 4-1

38 Figure 4-2 Analysis of Air Exchange Rate (AER) at CCAFS Using Instantaneously Released He as a tracer and method #2. Method #2 does not use the initial calculated helium concentrations. As shown in the figures, helium concentrations decreased much faster during the first test (June 13, 2008) when the HVAC was on than during the second test when the HVAC was off (June 27, 2008). The calculated air exchange rates are: When the HVAC was on: 7.8/day to 10.0/day When the HVAC was off: 2.2/day to 3/day The air exchange rate information is used subsequently in simulating soil vapor intrusion. 4.2 Comparisons of Data Between Event #1 (11 13 June 2008) and Event #2 (26 28 June 2008) During Event #1 the HVAC was on, but prior to and during Event #2 the HVAC was intentionally turned off. In this section, the data analysis focuses on the two chemicals (TCE and cis-1, 2-DCE) that were typically above detection limits in groundwater, soil gas, and indoor air. Some limited analysis is provided for the remaining chemicals, as well. The analysis begins with soil gas results for TCE and cis-1, 2-DCE (Figure 4-3). Panel (a) in the figure shows TCE results for the two events while panel (b) shows cis-1, 2-DCE results for the two events. Both TCE and cis-1, 2-DCE concentrations vary spatially, with concentrations lower near the southeast facing wall and higher near the northwest facing wall. 4-2 Tetra Tech, Inc.

39 Figure 4-3 Comparison of soil gas TCE and cis-1, 2-DCE concentrations for sampling Period #1 (June 12, 2008) with HVAC on, with sampling results for Period #2 (June 27, 2008) with HVAC off. (All soil gas samples were taken at 8 feet (2.5 m) below grade). Tetra Tech, Inc. 4-3

40 The soil gas concentrations are correlated between the two events for both TCE and cis-1, 2- DCE, as shown in Figure 4-4. When the data are compared against the 1:1 line of perfect correlation, a small bias toward higher soil gas concentrations during Event #1 for both TCE and cis-1, 2-DCE is evident. The reason for this (slight) bias is not known, but could be associated with increased soil moisture from thunderstorms that occurred prior to Event #2, or variability in analytical instrument calibration. Figure 4-4 Comparison of Soil Gas Concentration for TCE and cis-1, 2-DCE during two events (6/12/08 and 6/27/08) Indoor air concentrations for TCE and cis-1, 2-DCE are shown in Figure 4-5 for the two events. The indoor air vapor concentrations are much more uniformly distributed spatially than soil vapor, since mixing of indoor air between the various compartments reduces differences. There is no pronounced spatial trend from the southeast to the northwest as was noted for soil gas concentrations. However, there is a clear bias toward higher concentrations during Event #2, as shown in Figure 4-6. One likely reason for higher indoor vapor concentrations is the lower air exchange rate associated with the HVAC being off during Event #2, in spite of slightly lower soil gas concentrations during Event #2. The results from location SM-8 during Event #1 were anomalously high relative to the other Event #1 concentrations, and were in fact higher than the Event #2 concentrations. The reason for these anomalous concentrations is not known. 4-4 Tetra Tech, Inc.

41 Figure 4-5 Indoor air concentrations of TCE (panel (a)) and cis-1, 2-DCE (panel (b)) Tetra Tech, Inc. 4-5

42 Figure 4-6 Comparison of indoor vapor concentrations for TCE and cis-1, 2-DCE during two events (6/12/08 and 6/27/08) Attenuation coefficients (ratio of indoor vapor concentrations to sub-slab soil gas concentrations) are shown in Figure 4-7) for cis-1, 2-DCE and TCE. Estimates are made by location within the building, even with the knowledge that indoor vapor concentrations are affected by neighboring concentrations. A building-wide average attenuation coefficient is also calculated. The attenuation coefficients are typically larger (i.e. less attenuation) for Event #2 (HVAC off). 4-6 Tetra Tech, Inc.

43 Figure 4-7 Correlation of attenuation coefficients (defined as ratio of indoor air concentrations to sub-slab concentrations) between event #1 and event #2 To compare correlations in indoor vapor concentrations for TCE and cis-1, 2-DCE with other detected chemicals, Figure 4-8 was developed. In addition to TCE and cis-1, 2-DCE, PCE, Freon 113, and vinyl chloride indoor vapor concentrations were plotted. Correlations between events are evident for all the chemicals. Tetra Tech, Inc. 4-7

44 Figure 4-8 Comparison of VOC concentration in indoor air for TCE, cis-1, 2-DCE, Freon 113, and Vinyl chloride during two events (6/12/08 and 6/27/08) 4.3 Comparison of Sub-slab and Near-slab Data Figure 4-9 shows a comparison of sub-slab and near-slab soil gas concentrations for TCE and cis-1, 2-DCE. Pairs of closest sub-slab and near-slab data points were generated by inspection. As indicated by the figure, a correlation exists between the sub-slab and near-slab data for both sampling events and both chemicals. Data points for the two events are highlighted to illustrate that the correlations are similar between the two events. The correlations appear to be best at those locations where the near-slab samples were taken though 6 8 of asphalt or concrete. Figure 3-5 shown earlier indicates the surface cover (asphalt, no asphalt, concrete) associated with each near-slab location. 4-8 Tetra Tech, Inc.

45 Figure 4-9 Comparison of near-slab and closest sub-slab TCE and cis-1, 2-DCE soil gas concentrations using data from both sampling events (6/12/08 and 6/27/2008) Tetra Tech, Inc. 4-9

46 4.4 Comparison of Soil Vapor Concentrations with Vapor Concentrations in Equilibrium with Dissolved Groundwater Concentrations Since deep soil vapor samples were collected just above the groundwater where dissolved phase concentrations in the groundwater were also taken, it is worthwhile to compare the measured soil vapor concentrations with those theoretically generated by the groundwater dissolved concentrations. This comparison is made in Figure 4-10 for TCE. For each of the six SG locations, the ground water concentration, soil vapor concentration, and hypothetical vapor concentration in equilibrium with the dissolved groundwater concentration are shown. At nearly all locations, the actual TCE soil vapor levels far exceed those consistent with dissolved groundwater levels (based on using Henry s Law to estimate the vapor phase concentrations). This implies that there may be a source or sources of VOCs in soil gas other than, or in addition to, the groundwater sampled at the SG locations. Conversely, the cis-1,2-dce concentrations measured in the soil vapor were below the equilibrium concentrations expected based on Henry s law. Figure 4-10 Comparison of soil gas TCE concentrations with concentrations in equilibrium with dissolved groundwater concentrations (June 12, 2008) 4-10 Tetra Tech, Inc.

47 Historically there have been very high TCE levels (up to 10,000 µg/l) in the groundwater near Building However, a recent remediation program has substantially lowered the concentrations present. 4.5 Vinyl Chloride (VC) and cis-1, 2-DCE in groundwater, in soil vapor, and in indoor air VC was consistently detected in groundwater samples at the SG locations, and concentrations ranged between 1.1 to 2,490 µg/l (Figure 4-11). VC is very volatile, and such high concentrations in the ground water would be expected to generate vapor phase concentrations as high as 3,000 µg/l, based on Henry s Law constant of 1.21 (dimensionless) at 29 C. However, as shown in Figure 4-12, soil vapor concentrations and indoor air concentrations were typically below detection limits. One plausible explanation that would explain these data is if VC, while present in the groundwater, was not in contact with the water table. The same general behavior is observed for cis-1,2-dce as for vinyl chloride (see Figure 4-11 (b)). Since cis-1,2-dce has a Henry s Law constant of about 0.20 (dimensionless), it would be expected that soil vapor could be as high as 1,920 µg/l if the plume were in contact with the water table. Actual soil vapor concentrations were nearly always below 10 µg/l, and indoor air concentrations were orders of magnitude below those values. Indoor vapor data collected on the site during the January 2008 preliminary investigation were consistent with the present results (Table 2-3), indicating that the present results are not anomalous. Tetra Tech, Inc. 4-11

48 Figure 4-11 Vinyl Chloride and cis-1, 2-DCE concentrations in groundwater, soil gas, and in indoor air on June 12, Tetra Tech, Inc.

49 5 VAPOR INTRUSION MODELING RESULTS 5.1 Background and Approach Vapor intrusion into Building 1381 was simulated using two modeling approaches: the J&E Model (Johnson & Ettinger, 1991) and ViM (Mills et al, 2007). Detailed descriptions of each model can be found in these two references. A summary is shown in Table 5-1. The J&E model is the simpler of the two models and assumes a steady-state source term. ViM allows for a timevariable source term. Another difference in the two models is that ViM has the option of using a Monte Carlo analysis. This feature can be used to create a confidence interval about the predicted results, assuming a range of input data can be reasonably specified. This feature is used in the modeling predictions that follow. Table 5-1 ViM and J&E Comparison Capability ViM J&E/EPA Basements, slab-on-grade Crawl space Multiple compartments Outdoor air intrusion Non-steady conditions Lifetime exposure Monte Carlo: Uncertainty Analysis Chemical Processes: biodecay, adsorption Sensitivity Analysis Simulations have been completed for TCE for both Event #1 and Event #2 to illustrate the predicted impact of the differing air exchange rates and source term concentrations between the two events. Since ViM can simulate five different building configurations (such as one-story buildings with crawl spaces or one-story buildings with slab-on-grade foundations), the appropriate building type for Building 1381 was selected (one-story slab-on-grade). Both ViM and the J&E models were run with alternative source term configurations. This was done to examine how source term differences could propagate into differing predictions of indoor air concentrations. The source terms were generated as follows: Three alternative source configurations were developed based on: groundwater data sub-slab soil gas data near-slab soil gas data Four alternative metrics were used for each source term: arithmetic mean spatially weighted mean UCL 95 Maximum Tetra Tech, Inc. 5-1

50 Data used by the two models were the same when possible. Examples of the datasets are shown in Appendices G and H. An overview of the TCE data collected at the site is shown in Table 5-2. Also shown near the bottom of the table (shaded in gray) are source term concentrations generated using the four different approaches. Table 5-2 TCE data collected at CCAFS June Four alternative source term calculations are made. All combinations generated are modeled. Soil Gas, µg/m 3 Indoor air, µg/m 3 Eqilibrium Groundwater Outdoor air, µg/m 3 soil gas HVAC HVAC HVAC on HVAC off µg/m 3 µg/m 3 Location/surface cover on off SS-1/ slab 55,300-45, SS-2/slab 140, , SS-3/slab 58,300-47, SS-4/slab 26,500-22, SS-5/slab 68,800-54, SS-6/slab 77,000-58, SS-7/slab 14,500-15, SS-8/slab 7,500-6, SS-9/slab 14,300-13, SG-1/asphalt - 163, , ND ND SG-2/asphalt - 78,500-64, ,000 6,000 SG-3/soil - 17,600-12, ,300 3,650 SG-4concrete - 7,100-5, SG-5/soil - 5,500-4, , SG-6/soil - 10,600-10, ,000 30,500 ODN ODS Source Term Approach Maximum, µg/m 3 140, , , , ,000 30,500 Arithmetic mean, µg/m 3 51,356 47,050 41,470 36, ,700 6,830 Spatially Weighted 3 mean, µg/m 58,079 51,320 46,573 39, ,269 UCL , ,749 61, , ,311 ND = Not detected 5.2 Model Results: Event #1 (HVAC on) The first set of results is shown in Figure 5-1, and includes both predicted and sampled TCE concentrations in the indoor air, and predicted and sampled TCE concentrations just beneath the slab. ViM model predictions correspond to the 50 th percentile values along with the 5 th and 95 th percentile confidence limits. At the beginning of the simulation ViM uses an initial condition that assumes the vapor intrusion process is just beginning. This accounts for the evolving TCE concentrations shown on the left side of the figure. The initial time chosen to begin the ViM simulation (2006) was far enough in the past that the full effects of vapor intrusions were manifested during the June 2008 field events. The plume evolution illustrates that there is a lag between the time when the source beneath the building begins and when the full effects of the source are manifested in indoor air. For this application of ViM, the transit time period is between 3 to 6 months. 5-2 Tetra Tech, Inc.

51 Figure 5-1 Predicted and observed TCE concentrations for Event #1 (HVAC on), both indoor and directly beneath the slab The observed indoor air data in Figure 5-1 are the indoor air concentrations sampled at the seven locations shown previously in Figure 4-5(a) using method TO-15. Six of the seven concentrations are very comparable to each other, and are between the 5 th percentile and 50 th percentile ViM predictions. The J&E predicted value lies just below the observed data. During the course of applying the J&E model, it was found that the diffusion coefficient through foundation cracks was defaulted to the effective diffusion coefficient through the soil column, and J&E predicted concentrations were several times lower than ViM predictions. The default value in ViM is the air diffusion coefficient. When the J&E model was changed to be consistent with ViM, the predictions matched better, as will be shown subsequently. One concentration (at SS-8) was much higher than the remaining concentrations, and lies outside of the 95 th percentile confidence limit. The cause of this higher concentration is not known. However, the concentrations at SS-8 using TO-15 and TO-17 methods differ significantly: Concentration at SS-8 using TO-15: 93 µg/m 3 Concentration at SS-8 using TO-17: 19 µg/m 3 Tetra Tech, Inc. 5-3

52 A re-check of the laboratory data did not reveal any sources of error. Several additional points should be made about the results in Figure 5-1: Once the ViM model predictions reach steady-state, they approach the observed data The ViM model also simulates and displays the soil vapor concentrations directly beneath the slab (using measured deep soil vapor as the source term), but the J&E model does not The ViM model accounts for the effects of the ambient air concentrations (0.03 µg/m 3 ). However, for this setting, the ambient concentrations are low relative to soil TCE vapor concentrations, and are inconsequential. Figure 5-2 illustrates the evolution of the soil vapor profile beneath the building over the three months assumed beginning on January 2, The three curves represent a time span of three months. The deep soil vapors require a little over a month to reach the slab elevation but at low concentrations, and over three months to attain a steady profile. Figure 5-2 Time Evolution Of Subsurface TCE Concentrations For Several Months Following The Beginning Of Deep Soil Contamination For Event #1 (Note: The Begin Date Is Arbitrary And Intended Only To Illustrate The Evolution Of The Soil Gas Profile Over Time ) Attenuation factors both predicted by ViM and J&E and calculated from the observed data are shown in Figure 5-3. Note that the subslab attenuation factors (defined as the vapor phase concentration just beneath the slab to the deep vapor phase concentration just above groundwater) approach 1.0 (no attenuation) as steady-state conditions are approached. 5-4 Tetra Tech, Inc.

53 Figure 5-3 Predicted and observed attenuation factors with confidences limits for Event #1 The predicted indoor air attenuation factors range from about 10-4 to 10-3 once steady conditions are attained. However, during the transient period, attenuation factors are much less, since indoor vapor concentrations are low during this period. This result shows that using attenuation factors based on data collected during a highly transient period could be misleading. The 5% and 95% attenuation factor range from draft EPA guidance (EPA 2008) are also shown in the figure. They range over two orders of magnitude, and encompass both the modeled results and calculated results. 5.3 Modeling Results for Event #2 (HVAC off) For Event #2 (with lower air exchange rates), TCE was again simulated by the ViM and J&E models. The results are shown in Figure 5-4 and Figure 5-5. In these two figures, each of the 100 individual model traces generated through the Monte Carlo approach are shown, rather than the confidence intervals. As shown in Figure 5-4, all but one of the observed data points lie within the traces generated by ViM. The J&E prediction is slightly higher than the lower trace. In Figure 5-5, attenuation coefficients predicted by ViM and J&E are shown, along with those attenuation factors shown previously in Section 5.2. Each of the 100 Monte Carlo traces is shown. The calculated attenuation coefficients span a range of nearly two orders of magnitude, while the ViM-predicted attenuation coefficients span a range closer to one order of magnitude. Tetra Tech, Inc. 5-5

54 Figure 5-4 Monte Carlo Generated traces of predicted concentrations for Event #2 Figure 5-5 Monte Carlo generated traces of attenuation factors for Event #2 5-6 Tetra Tech, Inc.