Vapor Intrusion: How, Why, Where, When

Transcription

1 3/27/14 Vapor Intrusion: How, Why, Where, When Thomas McHugh GSI Environmental 1 Vapor Intrusion: Wazzat? BUILDING Effect on indoor air quality? GW source area Soil source area Vapors in subsurface Vapor intrusion is the movement of volatile chemicals into buildings from below ground. 2 MSECA Seminar: Wazzat? FEATURES Actual Size of Cookie! Great Snacks! Environmental Topic BASIC GAMEPLAN: Provide overview of vapor intrusion processes and investigation methods. 3 1

2 3/27/14 Vapor Intrusion Seminar Key Topics! Overview of Vapor Intrusion! Soil gas and subslab sampling! Indoor air sampling! Evaluation of petroleum vapor intrusion! Update on state and EPA guidance! Methods to distinguish between vapor intrusion and indoor sources of VOCs! Alternative Top Down approach to investigate vapor intrusion 4 Meet the Trainer Thomas McHugh, Ph.D.! GSI Environmental, Houston, Texas! PI for 3 DoD-funded vapor intrusion research projects! Author of several peer-reviewed publications on vapor intrusion! Modest and humble, despite having achieved greatness Before VI 5 Significance of VI Pathway Potential Sources Potential Exposure Evaluation of Threat! Regulatory guidance (often over conservative) indicates that groundwater containing low ppb of some VOCs could cause VI impact.! Exposure to indoor air far more common than direct exposure to groundwater.! Indoor air commonly impacted by indoor VOC sources, complicating evaluation of vapor intrusion. C ia Gas Increasing regulatory concern regarding VI impacts. However, regulatory guidance and investigation methods still evolving rapidly. 6 2

3 3/27/14 Vapor Intrusion Issues Corrective Action Re- Opener! Increased site assessment and remediation costs for many sites in corrective action process.! Some regulatory agencies requesting re-evaluation of closed sites. Litigation! Exposure via vapor intrusion claimed in many newer toxic tort cases. Impact of vapor intrusion issues potentially extends beyond normal corrective action process. 7 Vapor Intrusion: Outside the Building! Introduction! Conceptual Model for Vapor Intrusion 8 Conceptual Model for Vapor Intrusion: Basic Framework Air Exchange BUILDING 3 Building Attenuation Due to Exchange with Ambient Air Unsaturated Soil Affected Soil 2 Advection and Diffusion Through Unsaturated Soil and Building Foundation Groundwater -Bearing Unit Affected GW 1 Partitioning Between Source and Soil Vapor Conservative screening values for vapor intrusion based on sites without barriers to vapor intrusion. 9 3

4 3/27/14 Conceptual Model for Vapor Intrusion: Real Life Unsaturated Soil A A B B Building foundation: (A) Low permeability foundation without cracks or unsealed penetrations; (B) Positive building pressure Vadose Zone (A) High moisture content fine-grained soil layer (B) Aerobic Biodegradation Actual subsurface to indoor air attenuation factors vary by order of magnitude. Source Area Aquifer A B Groundwater Interface: (A) Clean water lens; (B) Saturated confining layer 10 Vapor Intrusion Screening: Two Scenarios 1 Idle Properties/ Real Estate Transaction! What: No known environmental releases! Why: Due diligence! How: ASTM E-2600, Assessment of Vapor Intrusion for Real Estate Transactions For Sale 2 Environmental Remediation Sites! What: Known subsurface sources of VOCs! Why: Evaluation of current or future buildings! How: Vapor Intrusion Screening Guidance: USEPA, state, ITRC, etc. SITE BUILDING Air Exchange sourc e area 11 Scenario 1, Real Estate Transaction: ASTM E-2600 What Evaluate potential vapor intrusion concern from potential on-site or off-site source based on information typically collected for Phase 1 audit. How 1) Identify and evaluate known and suspected sources of subsurface VOCs on and near target property. 2) Search distance based on type of COC & GW flow direction 3) Evaluate potential for vapor intrusion impact from each identified source. 4) If potential VI concern, consider Phase 2 investigation of potential sources 1/3 mi: other COCs Target Property 1/10th mile: petroleum 1 mi Upgradient: all COCs 12 4

5 3/27/14 Scenario 2, Env. Remediation Site / Known Release Screening Steps Field Measurements CHEMICAL CRITERIA Chemicals could cause VI impact based on volatility and toxicity DISTANCE CRITERIA SOIL/GW SCREENING SOIL GAS SCREENING Current or Soil/GW Soil gas future Yes concenreceptors Yes Yes concentrations > Yes tration within 100 ft > VI VI screening of edge of screening levels impacted area levels No No No No INDOOR AIR/ SUB-SLAB indoor air and/ or sub-slab concentrations weight-ofevidence indicate vapor intrusion impact NFA NFA NFA NFA NFA No Yes Mitigation POINT Step-wise VI investigation process. However, low screening values can make it difficult to exit early in process 13 Vapor Intrusion Screening: Distance Criteria 100 ft Target Building 100 ft No further evaluation if edge of impact* is: (1) more than 100 ft laterally removed from building OR (2) greater than 100 ft below the foundation or basement * = Use VI screening values to define edge of impact. 14 Soil Gas Sampling! Overview! Sample Point Installation! Sample Collection! Sample Analysis and Data Interpretation 15 5

6 3/27/14 Soil Gas Sampling: Overview When Assess need for soil gas data by building site conceptual model based on soil and GW data, building location/construction and understanding of preferential pathways How 1 Collect soil gas data 2 Compare to appropriate screening limits. 3 Site-specific modeling, if appropriate. Geoprobe Rig 4 Collect oxygen and CO 2 data with depth as evidence of bioattenuation. 16 Conceptual Model: Information Needs SITE INFORMATION NEEDED TO REFINE CONCEPTUAL MODEL AND INTERPERT VOC CONCENTRATION DATA: Building Conditions:! Foundation type! Basement?! Parking garage?! Sumps?! Elevator pit?! Other foundation penetrations? Subsurface Conditions:! Soil type! Depth to groundwater! Utility location and depth! Other preferential pathways Conceptual Site Model 17 Soil Gas Sampling: Two Scenarios Current Building Future Building Collect soil gas samples on at least two sides of small building or on source side of larger building. If possible <1.5 m from building & below solid cover Below depth of foundation, Min. total depth of 1.5 m Collect soil gas samples at depth to minimize difference between covered and uncovered location. Min. of: Depth just above source 7 to 8 m bgs Vertical profiles may be useful to evaluate attenuation. Future Building 18 6

7 3/27/14 Soil Gas Sampling! Overview! Sample Point Installation! Sample Collection! Sample Analysis and Data Interpretation 19 Soil Gas Sample Point: Installation Options Permanent! Sometimes required by regulatory guidance.! Preferred when multiple sample events may be required. Temporary! Used for one-time sampling.! Preferred when sample points cannot be left in place. 20 Sample Point Installation: Key Considerations, Temporary Geoprobe Other Options! Push hollow drive rod to desired depth! Pull back to create void! Seal surface! Collect sample! Fill hole! Use same construction methods as for permanent points, but without permanent surface completion! Remove hardware and fill hole after sampling Geoprobe Rig 21 7

8 3/27/14 Sample Point Installation: Key Considerations, Permanent Construction Details Multiple Depths (Nested Points)! Screen Length: 6 in (15 cm) or shorter! Tubing - diameter: 1/8-1/4 in ID ( cm) - inert material (e.g., nylon) - minimize total length! Use separate bore holes, if possible! Single borehole OK if borehole size and soil conditions adequate for proper sealing between depths NOTE: Typically wait 24 to 48 hrs after installation before collecting first sample. 22 Sample Point Installation: Hand Auguring 23 Sample Point Installation: Sample Point 24 8

9 3/27/14 Sample Point Installation: Adding Bentonite Seal 25 Sample Point Installation: Surface Completion 26 Sub-Slab Sample Points Example Construction Methods s Permanent Temporary Recessed Threaded Cap Cement Grout Brass or Stainless Steel Threaded Fitting or Compression Fitting Modeling clay or hydrated betonite Concrete Slab Brass or Stainless Steel Tubing Concrete Slab Course sand Sub-Slab Fill/Soil Sub-Slab Fill/Soil 27 9

10 3/27/14 Sub-slab Sample Points Permanent Temporary 28 Soil Gas Sampling! Overview! Sample Point Installation! Sample Collection! Sample Analysis and Data Interpretation 29 Soil Gas Sampling: Sample Container Options Off-Site Analysis Summa Canister:! Preferred! Limited availability outside U.S. On-Site Analysis Real-time decision making! Tedlar Bag Choose sample container based on type of analysis (on-site vs.off-site) and container availability

11 3/27/14 Soil Gas Sampling: Considerations Where Does Your Sample Come From? Goal: Minimize the flow of gas in subsurface due to sample collection Sample Volume: Preference is for smaller volume unless larger required by regulations (e.g., for Summa, use 1L, or smaller). Purge Volume: Purge 3x line volume prior to sample collection. Sample Rate: Use flow rate <200mL per typical regulatory guidance. Sample Canister (Off-site Analysis): Use Summa, if available. Summa susceptible to carry-over contamination if not properly cleaned. Use sorbent tube, if Summa not available. 31 Soil Gas Sample Collection: Scheme for Summa Canister 32 Soil Gas Sampling: Sample Collection Pressure gauge Flow controller Shallower Sample Point Deeper Sample Point 33 11

12 3/27/14 Soil Gas Sampling: Use of Leak Tracers Liquid Tracer Gas Tracer Spray on ground or apply to towel and place in enclosure or wrap around fittings. Examples: DFA, isopropyl alcohol, pentane High concentrations in samples may cause elevated detection limits for target analytes (Check w/ lab before using) Inject periodically or continuously into enclosure around fittings and sample point: Examples: Helium, SF 6 On-site analysis (helium) Potentially more quantitative DFA = 1,1-difluoroethane, SF 6 = sulfur hexafluoride 34 Soil Gas Sampling: Gas Phase Leak Tracer Leak Tracer Gas Sample Point Shroud Field Meter for Leak Tracer 35 Soil Gas Sampling: Field Screening VOCs Oxygen, CO 2 Helium! Why: Contaminant distribution.! How: FID or PID provides semi-quantitative measure of total VOCs.! Why: Aerobic and anaerobic biodegradation. Potential sample leaks.! How: Landfill gas meter.! Why: Real-time information on sample leakage.! How: Portable helium meter. Real time results allows user to address potential data quality issues or respond to unexpected findings during a single mobilization. FID = flame ionization detector, PID = photo ionization detector 36 12

13 3/27/14 Soil Gas Sample Collection by Sorbent Tube Field Screening Sorbent Sample Method! Use FID or PID to estimate sample concentration. Use result to determine appropriate sample volume for tube.! Select sorbent resistant to high moisture! Understand and apply proper sample procedures (e.g., per TO-17): - tubes in series to evaluate breakthrough - duplicate samples collected using different sample volumes Use of sorbent tubes for soil gas samples requires use of extra QA/QC procedures to ensure accurate results. SORBENT TUBES AND PUMPS FID = flame ionization detector, PID = photo ionization detector 37 Soil Gas Sampling: Summas vs Sorbent Tubes Summa Canisters Sorbent Tubes! Most accepted in U.S.! Simple to use! Less available outside U.S.! Canisters are re-used, subject to carry-over contamination! More available world wide! Better for SVOCs*! Use is more complex - pump calibration - backpressure - breakthrough of COC - selection of sorbent * = Analysis for SVOCs not typically required, but sometimes requested by regulators. 38 Summa vs Sorbent: Side-by-Side TCE PCE Results Comparison: TO-15 / TO-17 (ug/m 3 ) SG-02 SG-03 SG / / 149 <2.7 / < / ,200 / / 225 Careful sample collection results in agreement between Summa and sorbet tube results with about 2x. Reference: Odencrantz et al., 2008, Canister v. Sorbent Tubes: Vapor Intrusion Test Method Comparison, Proceedings of the Sixth International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Monterey, California, May

14 3/27/14 Soil Gas Sampling! Overview! Sample Point Installation! Sample Collection! Sample Analysis and Data Interpretation 40 Soil Gas Sampling: On-site Analysis What Mobile laboratory provides on-site analysis of gas samples by GC or GC-MS. (e.g., USEPA 8015, 8260, or TO-15). Quantitative results for individual VOCs. Why or Why Not! Real-time quantitative results! More flexibility for sample containers (e.g., syringe, glass bulb, tedlar)! Detection limits often 10x higher than fixed lab, but fine for most soil gas samples.! High mobilization cost, but cost-effective for large investigations (>30-50 samples)! Confirm regulatory acceptance Consider on-site analysis for larger investigation programs and for sites where rapid delineation is important. 41 Soil Gas Sampling: On-site Analysis Mobile Lab Real-time results Mobile GC Mass Spec 42 14

15 3/27/14 Soil Gas Sample Collection: Options for On-Site Analysis Why What Short holding time = more container options! 50 ml Syringe: - inexpensive and disposable - no carry-over issues - 30 minute holding time! Tedlar Bag: - $10/bag - 2 day holding time! Glass Bulb: - reuseable More options for sample container when samples are being analyzed on-site. 43 VOCs Oxygen, CO 2, Methane POINTS: Off-Site Analysis of Soil Gas Samples! Why: Risk assessment, contaminant distribution.! How: USEPA TO-15, TO-17 (sorbent tubes) or equivalent.! Request full analyte list unless site-specific consideration supports shorter list.! Why: Aerobic and anaerobic biodegradation. Potential sample leaks.! How: TO-3M (methane), EPA 3C (Oxygen), ASTM D-1946 (Oxygen, CO 2, Methane) or equivalent. Other options available. Confirm that analyte list includes all COCs. Confirm that method and laboratory can obtain required detection limits. 44 Soil Gas Sampling: Data Interpretation A - OK Data Quality Leak Tracer Conc.! Review sample procedures and lab QA results! Check units: ppbv ug/m 3! Use regulatory criteria for acceptable leakage, if applicable! For gas tracers, leakage rate estimated as C sample /C shroud! If leakage rate is > 10-20%, VOC results considered biased low Before conducting evaluation of vapor intrusion risk, confirm that data quality is suitable for purpose

16 3/27/14 Data Interpretation: Units Conversion Conversion: ppbv x MW ppbv to ug/m 3 ug/m 3 = 24.5 ug/m 3 = VOC concentration (ug/m 3 ) ppbv = VOC concentration (ppbv) MW = Molecular weight of VOC (g/mol) 24.5 = Constant for units conversion (at 25ºC) Make sure that analytical results and screening values are reported using same units. 46 Soil Gas Sampling: Data Interpretation Criteria! Compare results to applicable regulatory criteria! If no regulatory criteria, use J&E model to calculate site-specific criteria! Multiple samples events may be needed to evaluate temporal variability. Next Steps! No Exceedances = NFA! Exceedances: - Resample - Weight-of-evidence - Site-specific criteria - Indoor air and/or sub-slab evaluation Investigation Results NFA = No further action 47 16

17 Vapor Intrusion: Inside the Building! Introduction! Indoor Sampling: Indoor Sources! Indoor Sampling: Sampling Media! Indoor Sampling: Building Dynamics! Indoor Sampling Strategies! Indoor Sampling: Data Interpretation 1 Why Sample Indoor Air? Emergency Response Regulatory Driver Soil Gas Data! Complaints of petroleum odors! Other evidence of actual indoor impact! Request of regulatory project manager! Requirement of applicable regulatory document! Results of soil gas investigation indicates potential for vapor intrusion in building Indoor air data is often confusing. Consider alternatives before colleting indoor air samples. 2 Vapor Intrusion: Inside the Building! Introduction! Indoor Sampling: Indoor Sources! Indoor Sampling: Sampling Media! Indoor Sampling: Building Dynamics! Indoor Sampling Strategies! Indoor Sampling: Data Interpretation 3

18 Significance of Background Sources Source of Background Indoor Air Impacts Key Sources of VOCs in Indoor Air:! Ambient air! Vehicles, gasoline! Paints, adhesives! Cleaning agents! Insecticides! Tobacco smoke! Cosmetics, etc. REFERENCES:! USEPA, 1991, Building Air Quality Guide! OSHA, 1999, Tech Manual for Indoor Air Inv. 4 Significance of Background Sources Background Sources of Indoor Air Impacts Sources of VOCs in Indoor Air 5 Significance of Background Sources Background Sources of Indoor Air Impacts Sources of VOCs in Indoor Air 6

19 Significance of Background Sources Background Sources of Indoor Air Impacts Sources of VOCs in Indoor Air 7 But We Don t Use TOXIC Chemicals Anymore bulletin from vendor, October 2010: Technical Update Topics, trends, and news in the environmental industry TCE Contamination Affects Community's Water Wells The TCE, which was banned from public use in the 1970s, was detected at levels greater than the U.S. EPA's maximum contaminant level for public drinking water. Many people believe that TCE and other chlorinated solvents are no longer used in industrial operations or consumer products. 8 Regulator Perspective: Indoor Sources? Excepts from Comment Response Letter, January 2010: Regulatory PM was adamant that indoor sources were not an issue at the site. 9

20 Significance of Background Sources Examples of Indoor Sources: CVOCs Gun Cleaner: $19.95 >90% TCE Pepper Spray: $3.99 >90% TCE Hobby Glue: $4.95 >90% PCE Plastic Ornament: $4.95 1,2-DCA Chlorinated VOCs are legal and are still used in a wide variety of consumer products currently available for purchase. 10 Decision to Collect Indoor Air Samples Backgrd VOCs vs. USEPA Risk-Based Limits Range of Reported Background Concentration (ug/m 3 ) Avg. Ambient 2 BENZENE Avg. Indoor 1 Max. Indoor RISK LIMIT 3 Range of Reported Background Concentration (ug/m 3 ) TRICHLOROETHENE Avg. Ambient 2 Avg. Indoor 1 Max. Indoor AIR RISK LIMIT AIR RISK LIMIT AIR RISK LIMIT Average background indoor and outdoor air concentrations EXCEED risk-based limits for indoor air. 1) Range of values reported in the studies included in Indoor Air Quality Data Base for Organic Compounds, USEPA, ) 5th and 95th percentile concentrations in urban areas, National-Scale Air Toxics Assessment, USEPA, 1996 data. 3) USEPA Draft Vapor Intrusion Guidance, November Completing a Building Survey Identifying Potential Background Sources: Focus on Residential Common Sources of VOCs in Residential Indoor Air Ambient air Vehicles, gasoline, solvents Paints, adhesives Household cleaners Dry cleaned clothing: 1 suit ug/m 3 PCE Insecticides: naphthalene, p-dichlorobenzene Tobacco smoke: 435 ug benzene/cigarette New carpet: ug/m 3 VOCs Wood fires, cooking, scented candles Key Point: Homes have detectable levels of VOCs not associated with vapor intrusion. 12

21 Completing a Building Survey Identifying Potential Background Sources: Focus on Commercial Common Sources of VOCs in Commercial Indoor Air Vehicles, loading docks, fork-trucks Laboratories Commercial kitchens Janitorial supplies Copiers/printing operations/machinery Industrial equipment Supply warehouse Industrial processes, and neighboring industries Insecticides: naphthalene, p-dichlorobenzene Key Point: Consider sampling off-hours to avoid background VOCs from operational activities. 13 Completing a Building Survey Compiling a Product Inventory Do a complete building survey and product inventory Include all rooms, closets, attached garages Include sketches of each floor and photos Assess air flow List each item and its contents, photograph if possible 14 Completing a Building Survey Useful Tools: Building Survey Form Building Survey Includes: Occupant and Owner Information Building Characteristics Building Location Airflow Characteristics Basement and Construction Characteristics HVAC Considerations Potential Background Sources 15

22 Background VOCs Removing Background Sources Remove sources at least 24 hrs. before sampling No smoking If possible remove sources from attached garage and no car No new dry cleaning Resurvey to confirm removal before sampling Remember that attached garages are significant source of indoor air contamination In some cases, may need to ventilate the structure 16 Vapor Intrusion: Inside the Building! Introduction! Indoor Sampling: Indoor Sources! Indoor Sampling: Sampling Media! Indoor Sampling: Building Dynamics! Indoor Sampling Strategies! Indoor Sampling: Data Interpretation 17 Background VOCs Sampling Media Two primary types of sampling media for SVI in indoor air Summa canisters Sorbent tubes Summa canisters are preferred, but not available in all regions Summa Canister Summa canisters are straightforward to use Sorbent tubes require some additional preparation and analysis Both provide appropriate exposure assessment information when properly selected and used SORBENT TUBES AND PUMPS 18

23 Collection of Indoor Air Samples Considerations for Sampling Media Key considerations for Summa canisters (preferred method) Insure Summa is certified clean to the limit of detection for the method of analysis Use a calibrated flow regulator Verify initial vacuum in canister (-31 to -25 Hg) Periodically check remaining vacuum Record final vacuum Final vacuum should be between -1 and -10 Hg Consider validity of sample if outside this range Include contact information on un-manned samplers In some areas, may want to notify local emergency response personnel 19 Collection of Indoor Air Samples Considerations for Sampling Media Key considerations for sorbent tubes Select appropriate media for COCs Can consult published environmental and occupational methods (e.g. NIOSH, UK HSE, EPA Method TO-17) When in doubt, confirm with the lab Excerpt from TO-17 Appendix 1: 20 Collection of Indoor Air Samples Considerations for Sampling Media Key considerations for sorbent tubes (continued) Consider a pre-filter (e.g. Teflon) for dusty, industrial environments Need pre-screening to estimate VOC concentration Calculate appropriate pump rates, select appropriate sized tube - based on expected concentrations - methods will provide a minimum and maximum sampling rate Insure that you can evaluate breakthrough: - use sorbent tubes with a front and a back section, or - use two tubes in series Order extra tubes for calibration and blanks 21

24 Collection of Indoor Air Samples Considerations for Sampling Media Key considerations for sorbent tubes (continued) Position sorbent tubes vertically to avoid channeling Need to check pumps frequently, and have extras Insure adequate power sources, especially for sampling events over 8 hours Remember to pre- and post-calibrate pumps Consider sorbent tube storage Most tubes can be stored at room temperature before use Some sampling media/solvent combinations require storage at <4 C until analysis - may require expedited shipping on ice Remember, there is no sorbent tube method for methane 22 Vapor Intrusion: Inside the Building! Introduction! Indoor Sampling: Indoor Sources! Indoor Sampling: Sampling Media! Indoor Sampling: Building Dynamics! Indoor Sampling Strategies! Indoor Sampling: Data Interpretation 23 The Building Blocks of Building Science Understanding Vapor Intrusion Principles TRANSPORT DIRECTION Into Subsurface Into Building Why care about building pressure? TRANSPORT PROCESS Advection Diffusion High Pressure Low Pressure High Conc. Low Conc. Low Pressure High Pressure Low Conc. High Conc. SV infiltrates into buildings via 2 main processes: 1. Pressure driven advection 2. Concentration driven diffusion Advection usually dominates Residential structures are generally under net negative pressure, but net pressures may fluctuate several times in a day Commercial buildings are difficult to predict- depends on HVAC 1. COCs can migrate from subsurface to indoor air and from indoor air to subsurface 2. Can measure cross-foundation pressure using pressure transducer 24

25 The Building Blocks of Building Science Airflow Principles Airflow is always driven by pressure differences Both infiltration and COC movement within the structure is governed by pressure/airflow There are four main factors which modify infiltration of soil gas and act upon air movement in structures: Buoyancy effects (the stack effect) Mechanical effects Weather (primarily wind effects) Occupant activities 25 The Building Blocks of Building Science Airflow Drivers: Buoyancy Effects Pressures are generated by differences in air density with temperature. Hotter air rises within a structure, local areas of high and low pressure are created Drives infiltration on lower stories, exfiltration from higher stories Watch for the stack effect in: Tall buildings Cold climates Night vs. day Stack effects drive infiltration in lower portions of the building, including the foundation. 26 The Building Blocks of Building Science Airflow Drivers: Mechanical Effects Focus on Residential Mechanical equipment can create localized or building-wide pressure differences which drive air exchange rates In residential structures, look for: Kitchen, attic, and bathroom exhaust fans Forced air heating/cooling Furnaces Fan Exhaust Fan Stoves Bathroom Water heaters Other combustion appliances Living Area Clothes dryers Entry and Foyer Upper Floor Garage Door Garage Garage D When sampling: Generally, operate HVAC as typical for season Avoid operating exhaust systems when possible. 27

26 The Building Blocks of Building Science Airflow Drivers: Mechanical Effects Focus on Industrial/Commercial In commercial structures look for: Air handlers Commercial kitchen exhausts Laboratory hoods Local exhaust systems Welding/painting booths Elevators/stairwell ventilation Industrial furnaces Industrial processes A conceptual model of airflow in the structure may help sample location selection When Sampling: Consider sampling during off-hours Consider safety issues before altering ventilation 28 The Building Blocks of Building Science Airflow Drivers: Wind/Weather Effects Wind pressures act on all sides of a building in unequal measures. Higher pressures on some sides of the building than on other sides of the building. Pressure differences will drive infiltration and exfiltration of air through gaps and cracks in the building envelope Usually more prominent in commercial structures due to HVAC openings Changing weather conditions may cause fluctuations in SVI- always document weather. Wind pressure effects, indicated by arrows, can drive infiltration and direct airflow in structures 29 Vapor Intrusion: Inside the Building! Introduction! Indoor Sampling: Indoor Sources! Indoor Sampling: Sampling Media! Indoor Sampling: Building Dynamics! Indoor Sampling Strategies! Indoor Sampling: Data Interpretation 30

27 Collection of Indoor Air Samples Sampling Strategies Sample location considerations Recommend sampling in lowest level and consider sampling next highest level Investigate COC patterns Consider sampling near potential indoor sources or preferential pathways Attached garage, industrial source Basement sump, bathroom pipes Collect at least one outdoor sample Compare indoor and outdoor Consider collection subslab samples (concurrent with indoor air samples) Compare indoor and subslab or near-slab 31 Collection of Indoor Air Samples Sampling Strategies Placement of samplers Place at breathing-level height Avoid registers, drafts Remember to sample for appropriate length of time Typically 24 hours for residential NOTE: Typically 8-24 hours for occupational " Collect indoor and subslab samples concurrently " QA Samples: Collect greater of one duplicate per day or one per 20 samples. (Collect additional QA samples if required by regs.) Little value to collect multiple samples in a single building zone (e.g. same room), unless collecting QA duplicates. 32 Collection of Indoor Air Samples Analysis of Samples TO-15 (for summa canisters) and TO-17 (for sorbent tubes) are most widely used TO-3M for methane Both TO-15 and methane analysis can be completed from the same canister Insure that specific COC s designated by regulatory or other criteria are included Insure that the method provides detection limits adequate for regulatory standards Recognize that these analyses include various COC s not typically associated with subsurface sources 33

28 Vapor Intrusion: Inside the Building! Introduction! Indoor Sampling: Indoor Sources! Indoor Sampling: Sampling Media! Indoor Sampling: Building Dynamics! Indoor Sampling Strategies! Indoor Sampling: Data Interpretation 34 Interpretation of Results Interpretation Approaches Compare indoor air results with: Appropriate occupational or residential guidance values Outdoor Concentrations Collected outdoor samples Consider data from closest monitoring station Published indoor air background concentrations Sub-slab or near-slab data (if collected) Consider distribution of COCs in building More sophisticated analysis may be appropriate Slab attenuation factors/ratios of B/T/E/X in soil gas vs. indoor air Consider tracers (e.g. radon) Remember to Report analytical results in appropriate units. 35 Interpretation of Results When is Enough Enough? Scenario 1: Weight-of-evidence analysis indicates no SVI No additional sampling required Scenario 2: Results are inconclusive Consider re-sampling; keep in mind potential background source and seasonal variations If sampling was not conducted during the heating season, some regulators may require additional sampling If re-sampling, consider whether more sophisticated sampling/analytical approaches are warranted Chemical fingerprinting Use of tracer gases If additional sampling does not provide clarity, consider whether precautionary mitigation strategies are appropriate Scenario 3: Sampling indicates an issue Consider mitigation strategies 36

29 APPLICATION OF BIOVAPOR TO PETROLEUM VAPOR INTRUSION SITES API Training Program Overview of Petroleum VI! General VI Conceptual Model! Vadose Zone Attenuation of Petroleum Vapors! Oxygen Below Building Foundations! Framework for Evaluation of Petroleum VI Conceptual Model for Vapor Intrusion: Regulatory Framework Air Exchange BUILDING 3 Building Attenuation Due to Exchange with Ambient Air Unsaturated Soil Affected Soil 2 Advection and Diffusion Through Unsaturated Soil and Building Foundation Groundwater- Bearing Unit Affected GW 1 Partitioning Between Source and Soil Vapor Regulatory guidance focused on building impacts due to vapor migration. Indoor Air Concentration ( ug/m 3 ) Correlation Between Groundwater Concentration and Indoor Air?? Petroleum Hydrocarbons CORRELATION? NO (p = 0.11) Indoor Air Concentration ( ug/m 3 ) ?? IA Chlorinated Solvents GW CORRELATION? YES (p <0.001) GW Concentration (ug/l) GW Concentration (ug/l) Observable Relationship C ia vs. C gw?! Petroleum Hydrocarbons: No! Chlorinated Solvents: Yes - Direct C gw = COC conc. In groundwater; C ia = COC conc. In indoor air; (p = 0.11) = Probability = 11% that slope of best-fit line = 0 (I.e., no trend).

30 C o <C o min C o min C H max APPLICATION OF BIOVAPOR TO PETROLEUM VAPOR INTRUSION SITES API Training Program Overview of Petroleum VI! General VI Conceptual Model! Vadose Zone Attenuation of Petroleum Vapors! Oxygen Below Building Foundations! Framework for Evaluation of Petroleum VI Petroleum Biodegradation Conceptual Model C H min C o max Aerobic Biodegradation Possible C o >C o min δ L Oxygen No Aerobic Biodegradation Hydrocarbon Hydrocarbon Source Vapor Concentration Correlation between oxygen consumption and hydrocarbon attenuation. From Roggemans et al., 2001, Vadose Zone Natural Attenuation of Hydrocarbon Vapors: An Empirical Assessment of Soil Gas Vertical Profile Data, API s Soil and Groundwater Technical Task Force Bulletin No. 15. Petroleum Biodegradation: Real Site Data Diesel Release Site, North Dakota VOC Concentration vs. Depth Biogenic Gases vs. Depth

31 AF 1E-01 (excludes sub-slab) O2 & CO2 (% V/V) APPLICATION OF BIOVAPOR TO PETROLEUM VAPOR INTRUSION SITES API Training Program Petroleum Biodegradation: Real Site Data Oxygen Carbon Dioxide Benzene Beaufort, SC Beaufort, SC NJ-VW2 (Lahvis, et al., 1999) Oxygen Carbon Dioxide Benzene O2 & CO2 (% V/V) Coachella, CA Coachella, CA COA-2 (Ririe, et al 2002) AF 1E-04 O2 & CO2 (% V/V) OA <3.6E+00 Salina, UT Salina Cash Saver VMW-1 Utah DEQ, 7/ Free Product on GW 10 Benzene in GW 16,000 ug/l FP on GW E+00 1.E+02 1.E+04 1.E+06 1.E+08 Benzene (ug/m3) 15 1.E+00 1.E+02 1.E+04 1.E+06 1.E+08 Benzene (ug/m3) 20 1.E+00 1.E+02 1.E+04 1.E+06 1.E+08 Benzene (ug/m3) Ubiquitous vadose zone attenuation of petroleum hydrocarbons. Vadose zone profiles compiled by Robin Davis, UDEQ. Conceptual Model for Vapor Intrusion: Differences Between PVI and CVI From: Petroleum Hydrocarbons and Chlorinated Hydrocarbons Differ in Their Potential for Vapor Intrusion, September 2011, Conceptual Model for Vapor Intrusion: Differences Between PVI and CVI USEPA says that vapor intrusion risk is much lower at petroleum sites. From: Petroleum Hydrocarbons and Chlorinated Hydrocarbons Differ in Their Potential for Vapor Intrusion, September 2011,

32 APPLICATION OF BIOVAPOR TO PETROLEUM VAPOR INTRUSION SITES API Training Program Overview of Petroleum VI! General VI Conceptual Model! Vadose Zone Attenuation of Petroleum Vapors! Oxygen Below Building Foundations! Framework for Evaluation of Petroleum VI Oxygen Under Building Foundation Key Question! Is there enough oxygen below building foundations to support aerobic biodegradation? aerobic zone C t anaerobic zone C s Vapor Source Oxygen Under Foundation: Model Prediction Numerical model predicts oxygen shadow below building, but..! Very strong vapor source (200,000,000 ug/m 3 )! All flow into building is through perimeter crack! No advective flow below building Model may not account for key oxygen transport processes. From Abreu and Johnson, ES&T, 2006, Vol. 40, pp 2304 to 2315.

33 APPLICATION OF BIOVAPOR TO PETROLEUM VAPOR INTRUSION SITES API Training Program Aerobic Biodegradation: Oxygen Mass Balance Hydrocarbon + Oxygen bacteria Carbon dioxide + Water 1 kg C x H y + 3 kg O kg CO kg H 2 O Petroleum Hydrocarbons + Electrons & Carbon Energy New Cells Electrons Electron Acceptor (e.g., O 2 ) Aerobic Biodegradation: Oxygen Mass Balance! Atmospheric air (21% Oxygen) = 275 g/m 3 oxygen > Provides capacity to degrade 92 g/m 3 hydrocarbon vapors (= 92,000,000 ug/m 3 ) Even limited migration of oxygen into subsurface is sufficient to support aerobic biodegradation. Transport of Oxygen Under Foundation Wind Driven Advection Bi-Directional Flow Across Foundation +/- +/- Advection drives oxygen below building foundation.

34 APPLICATION OF BIOVAPOR TO PETROLEUM VAPOR INTRUSION SITES API Training Program Transport of Oxygen Under Foundation Conceptual Model Field Data 0.0 Wind Loading Wind-driving building ventilation Advection of subslab soil gas into bldg. Depth (m) isop CH 4 CO Upwind-downwind advection in soil gas Biodegradation Diffusion from deep sub-slab soil gas Subslab VOC source Depth (m) Concentration (g m -3 ) Conceptual model and field data indicate common presence of oxygen under building foundation. From Fisher et al., 1996 Environmental Science and Technology, Vol. 30 No. 10, p Soil Column Attenuation Transport of Oxygen Under Foundation Nitrogen Flooding Experiment: Purge sub-foundation soils with nitrogen gas and observe oxygen recovery Time = 0 Time > 0 Low Oxygen Oxygen Recovery Below Building N m % O 2 After Flood Injection wells % O 2 (shallow) garage concrete Data from Lundegard, Johnson, and Dahlen. Sub-slab Nitrogen Flood-Oxygen Re-entry Test. Soil Column Attenuation Transport of Oxygen Under Foundation Nitrogen Flooding Experiment: Purge sub-foundation soils with nitrogen gas and observe oxygen recovery Time = 0 Low Oxygen N garage 3 m concrete Time = 2 weeks High Oxygen N garage 3 m concrete Rapid recovery of oxygen below building foundation supports petroleum biodegradation. % O 2 After Flood Injection wells % O 2 (shallow) Data from Lundegard, Johnson, and Dahlen. Sub-slab Nitrogen Flood-Oxygen Re-entry Test.

35 APPLICATION OF BIOVAPOR TO PETROLEUM VAPOR INTRUSION SITES API Training Program Advective Transport Processes Gas flow from subsurface into Lower building pressure Flow in building EXAMPLES Residence in winter (chimney effect); bathroom, kitchen vents Low Pressure High Pressure Gas flow from building into subsurface Higher building pressure Flow out EXAMPLES Building HVAC designed to maintain positive pressure UPWARD TRANSPORT High Pressure Bi-directional flow between building and subsurface Variable building pressure Reversible flow EXAMPLES Barometric pumping; variable wind effects Low Pressure DOWNWARD TRANSPORT Pressure Gradient Measurements: School Building, Houston, Texas Differential Pressure (Pascals) 40 Pos. Pressure 30 (Flow out of Bldg) Neg. Pressure -30 (Flow into Bldg) -40 6:00 9:00 12:00 15:00 18:00 21:00 0:00 3:00 6:00 9:00 12:00 15:00 POINTS: Pressure gradient frequently switches between positive and negative within a single day. Continuous inward flow does not occur. Time (July 14-15, 2005) Advection Through Building Foundation: Field Evidence! VOCs from indoor air typically detected in sub-slab samples: - alpha pinene - limonene - p-dichlorobenzene INDOOR AIR S! Oxygen transported below foundation by same mechanism Reversing pressure gradient drives air (and VOCs and oxygen) through building foundation. BELOW SLAB S

36 APPLICATION OF BIOVAPOR TO PETROLEUM VAPOR INTRUSION SITES API Training Program Chatterton Research Site, British Columbia, Canada (Hers, et al 2000) Building Feet Below Grade 0 Fill, crust, sandy silt Fill, dredged river sand 5 SG-BC, 10/1/97 < % < % 55,000 6% 25,000, % 50,000, % SG-BR 5/14/97 10 % 80,000 8 % 3% 50,000,000 60,000,000 SG-BC Vapor sample point identifier Sub-Slab vapor sample point Sub-Surface vapor sample point 50,000,000 Benzene, ug/m3 1.0% Oxygen, % 10 Slide from Robin Davis, UDEQ LNAPL, benzene-rich 0 20 Feet, horizontal Hal s, Green River, Utah (Utah DEQ, 8/26/06) Feet Below Grade 0 Motel Office Basement Breezeway Café/Bar Basement VW % Asphalt VW-4 Clayey Silt VW % % , % Silt % 87 12,000 11% % 260,000 33,000, VW-7 Multi-depth vapor monitoring well Benzene in GW 1,000-5,000 ug/l LNAPL, gasoline 2.5% Sub-Surface vapor sample point 260, % Benzene, ug/m3 33,000,000 TPH-gro, ug/m3 Oxygen, % 0 20 Feet, horizontal Slide from Robin Davis, UDEQ Oxygen Under Building Foundation Summary! Wind and building pressure drive atmospheric air below building foundation! Even modest oxygen transport sufficient aerobic biodegradation

37 APPLICATION OF BIOVAPOR TO PETROLEUM VAPOR INTRUSION SITES API Training Program Overview of Petroleum VI! General VI Conceptual Model! Vadose Zone Attenuation of Petroleum Vapors! Oxygen Below Building Foundations! Framework for Evaluation of Petroleum VI Petroleum Vapor Intrusion: Field Experience 1 2 Sump draws NAPL or dissolved hydrocarbons into building. NAPL directly impacts building wall or floor. Unsaturated Soil NAPL Affected GW Groundwater -Bearing Unit BUILDING NAPL NAPL 3 Preferential pathway allows vapors to enter building. 4 Vapors from NAPL diffuse through vadose zone (large releases). For petroleum sites, vapor intrusion is generally associated with two factors acting together - shallow sources and preferential pathways. Framework for Evaluation of Petroleum Vapor Intrusion Sites: Based on Modeling and Empirical Data (McHugh et al. 1 ) 1 LNAPL or Dissolved Plume in Contact with Foundation: HIGHER RISK BUILDING Unsaturated Soil NAPL Affected GW GW-Bearing Unit Proposed Action: Test hydrocarbon concentrations inside structure. Mitigate as needed. 1) Adapted from McHugh, Davis, DeVaull, Hopkins, Menatti, and Peargin, Evaluation of Vapor Attenuation at Petroleum Hydrocarbon Sites: Considerations for Site Screening and Investigation, Soil and Sediment Contamination: An International Journal, November/December 2010, Vol. 19, No. 5.

38 APPLICATION OF BIOVAPOR TO PETROLEUM VAPOR INTRUSION SITES API Training Program Framework for Evaluation of Petroleum Vapor Intrusion Sites: Based on Modeling and Empirical Data (McHugh et al. 1 ) 2 LNAPL present 3 to 10 m (10 to 30 ft) below building foundation: MEDIUM RISK BUILDING Unsaturated Soil???? LNAPL 3 to 10 m (10 to 30 ft) Subsurface LNAPL: Vapor intrusion observed at a few large release sites (refineries) but not at UST sites. Groundwater -Bearing Unit Proposed Action: Test for hydrocarbons in shallow soil gas below or directly adjacent to building foundation. 1) Adapted from McHugh, Davis, DeVaull, Hopkins, Menatti, and Peargin, Evaluation of Vapor Attenuation at Petroleum Hydrocarbon Sites: Considerations for Site Screening and Investigation, Soil and Sediment Contamination: An International Journal, November/December 2010, Vol. 19, No. 5. Framework for Evaluation of Petroleum Vapor Intrusion Sites: Based on Modeling and Empirical Data (McHugh et al. 1 ) 3 LNAPL present >10 to 30 ft below building foundation: LOWER RISK BUILDING Unsaturated Soil Groundwater- Bearing Unit LNAPL >3 to 10 m (>10 to 30 ft) Proposed Action: Evaluate presence of preferential flow pathways or other site-specific risk factors. Testing for hydrocarbons in shallow soil gas below or directly adjacent to building foundation may be appropriate. 1) Adapted from McHugh, Davis, DeVaull, Hopkins, Menatti, and Peargin, Evaluation of Vapor Attenuation at Petroleum Hydrocarbon Sites: Considerations for Site Screening and Investigation, Soil and Sediment Contamination: An International Journal, November/December 2010, Vol. 19, No. 5. Framework for Evaluation of Petroleum Vapor Intrusion Sites: Based on Modeling and Empirical Data (McHugh et al. 1 ) 4 Dissolved hydrocarbon plume 5 to 10 ft below building: LOWER RISK BUILDING Unsaturated Soil >1.5 to 3 m (>5 to 10 ft) Affected GW Proposed Action: Evaluate presence of preferential flow pathways or other site-specific risk factors. 1) Adapted from McHugh, Davis, DeVaull, Hopkins, Menatti, and Peargin, Evaluation of Vapor Attenuation at Petroleum Hydrocarbon Sites: Considerations for Site Screening and Investigation, Soil and Sediment Contamination: An International Journal, November/December 2010, Vol. 19, No. 5.

39 APPLICATION OF BIOVAPOR TO PETROLEUM VAPOR INTRUSION SITES API Training Program PVI Screening Distances Dissolved Petroleum Hydrocarbons Free Phase LNAPL Depth California (Low Threat UST Closure Policy, Effective August 2012) 5 10 ft 30 ft New Jersey (VI Technical Guidance V3.1, March 2013) 5 10 ft 30 ft Maine DEP Draft (State of Maine VI Study, January 2012) 5 10 ft Vertical: 15 ft Lateral: 30 ft USEPA OUST (Draft PVI Guide for UST Sites, April 2013) 6 ft 15 ft Conceptual Model What is Clean Soil? Dirty Soil Soil impacted by mobile NAPL, residual NAPL, NAPL smear zone, or Groundwater fluctuation zone. O 2 HC Clean Soil Soil with low hydrocarbon concentrations (e.g., <100 mg/kg TPH). Watch-out Consider potential for shallow sources or other unexpected vadose zone impacts. Clean soil means low hydrocarbons, not zero hydrocarbons. BioVapor: 1-D VI Model w/ Bio! Conceptual Model

40 APPLICATION OF BIOVAPOR TO PETROLEUM VAPOR INTRUSION SITES API Training Program Conceptual Model What is BioVapor? 1-D Analytical Model Oxygen Mass Balance User- Friendly Version of Johnson & Ettinger vapor intrusion model modified to include aerobic biodegradation (DeVaull, 2007). Uses iterative calculation method to account for limited availability of oxygen in vadose zone. Simple interface intended to facilitate use by wide range of environmental professionals. SIMPLE MATH O 2 HC Easy-to-use vapor intrusion model that accounts for oxygen-limited aerobic vapor intrusion. Free download at: Conceptual Model BioVapor: Conceptual Model 3 Advection, diffusion, and dilution through building foundation C t aerobic zone 2 Diffusion & 1 st order biodegradation in aerobic zone Vapor Source C s anaerobic zone 1 Diffusion only in anaerobic zone Conceptual Model BioVapor: Oxygen Mass Balance Iterative Calculation Method Calculate oxygen demand: - depth of aerobic zone - HC vapor concentration - 1st order biodegradation?? anaerobic interface?? Vapor Source O 2 demand = supply? Yes Final Model Solution No Increase or decrease depth of aerobic zone Calculations are cheap & quick

41 APPLICATION OF BIOVAPOR TO PETROLEUM VAPOR INTRUSION SITES API Training Program Conceptual Model BioVapor: Intended Application Yes! Obtain improved understanding of petroleum vapor intrusion.! Calculate oxygen concentration/flux required to support aerobic biodegradation.! Identify important model input parameters and evaluate model sensitivity. Simplifying Assumptions " 1-D Model: Does not account for spatial variability " Steady State: Does not account for temporal variability " Single Source: Does not account for indoor sources and other background sources of petroleum VOCs BioVapor Model Gettin the Goods How Download at: (Registration information used so we can notify users of updates. No spam.) Who Roger Claff (202) Bruce Bauman (202)

42 Vapor Intrusion Guidance Summary of State Approaches to VI 2012/2013 Update Tom McHugh, Lila Beckley, Vivian Yates (GSI) Bart Eklund (URS) 1 Approach Vapor Intrusion Guidance Update of 2007 Survey Identified and reviewed available VI guidance documents Both draft and final documents Looked for areas of consensus and areas of divergence among states 2 States With VI Guidance Vapor Intrusion Guidance AK WA MT OR ID WY NV CO CA AZ HI MN ME SD WI VT NH MI IA NY MA NE PA IL IN OH CT RI MD KS MO WV KY VA NJ DE TN NC AL GA LA FL 44 States have issued draft or final guidance (as of December 2013) 3 1

43 Year Guidance was Issued Vapor Intrusion Guidance Number of Guidance Issued 39 new guides or updates since Vapor Intrusion Guidance Challenge for State Regulators Review and incorporate extensive VI-related literature Address concerns of various stakeholders 5 Results Vapor Intrusion Guidance Key Elements of Guidance Exclusion Distances Types of Screening Values Specific Numeric Screening Values Attenuation Coefficients (α values) Sampling Guidance 6 2

44 Exclusion Distance: 2012 Vapor Intrusion Guidance Petroleum VOCs Chlorinated VOCs 0 <30)ft 30,50)ft 100)ft 0 <100(ft 100(ft >100(ft 7 Types of Screening Levels: 2012 Vapor Intrusion Guidance Vapor Intrusion Guidance Screening Values Less consistency among states than in 2007 Survey Less reliance on soil data More reliance on shallow soil gas data than on deeper soil gas data Depending on State, values for <10 to >100 individual VOCs Very large differences in specific numeric values 9 3

45 Screening Levels: 2012 Vapor Intrusion Guidance 100 Indoor*Air:*Benzene* Concentration*(ug/m3) LA MN AK KS IN NJ VT DE ME NC OR CA 10 Screening Levels: 2012 Vapor Intrusion Guidance Shallow*Soil*Gas:*Benzene* Concentration*(ug/m3) MO CT HI NH MN AK WI NJ WA OH 11 Screening Levels: 2012 Vapor Intrusion Guidance Groundwater:*Benzene* Concentration*(ug/L) PA LA NH SD NE CT CO AK VT OH 12 4

46 Vapor Intrusion Guidance Selected 2012 Screening Values - Benzene Media Groundwater (µg/l) Soil Gas (µg/ m3) California New Jersey Mass. Range of Values NA 15 2,000 1,500x ,000x Indoor Air (µg/m3) x 13 Vapor Intrusion Guidance Selected 2012 Screening Values - TCE Media Groundwater (µg/l) Soil Gas (µg/ m3) California New Jersey Missouri Range of Values NA 1 1,600 33,000x ,000 2,500,000x Indoor Air (µg/m3) ,700x 14 Vapor Intrusion Guidance Selected Screening Values - PCE Media Groundwater (µg/l) Soil Gas (µg/ m3) California New Jersey Illinois Range of Values NA ,000x ,000 49,000x Indoor Air (µg/m3) NA 270x 15 5

47 Vapor Intrusion Guidance Sampling and Analysis Great variability from state to state on type and level-of-detail of sampling guidance Relatively little guidance in many cases for leak checks, quality control, and analysis 16 Sampling Requirements Vapor Intrusion Guidance Rounds of IA Sampling Sub-Slab Samples For a given building, most states require multiple rounds of testing and sub-slab samples from multiple locations. 17 Summary Vapor Intrusion Guidance Most states that have VI guidance follow a tiered evaluation approach There are significant differences from state to state in the degree of conservativeness used (e.g., screening levels) We offer no opinion as to which state is best or right in terms of technical issues except to caution that, contrary to public perception, a more conservative approach is not always better 18 6

48 Observations Vapor Intrusion Guidance It is hard to keep up with current VI policies: State vapor intrusion guidance is rapidly evolving. Some state policies are spread across multiple guidance documents. Many policies are inconsistent between states: Petroleum exclusion distances, screening concentrations, sampling requirements.! States may be challenged to keep up with emerging issues:! Spatial variability in soil gas! Temporal variability! How best to evaluate future use scenarios for undeveloped parcels! New investigation approaches, new sampling and analysis methods 19 For more information Vapor Intrusion Guidance Eklund, B., L. Beckley, V. Yates, and T. McHugh. Overview of State Approaches to Vapor Intrusion. Remediation. Vol. 22, Issue 4, pp7-20, Autumn (Fall) Q&A Opportunity Vapor Intrusion Guidance 21 7

49 3/27/14' USEPA&GUIDANCE! 2002 & &Dra0&VI&Guidance&issued& 2013 & &New&Dra0&Guidance&for&Public&Comment& && THE GOOD Comprehensive&discussion&of& principles,&tools& & Recognizes&the&difference&betw.& petroleum&and&nonkpetroleum& VOC&vapor&intrusion& USEPA&GUIDANCE:&&THE!BAD! Applicability&based&on&regulatory& program,&not&chemical& characterisocs/behaviour& & Lacks&clear&decision&logic& the'vapor'intrusion'site'where'all'available'informa;on'is'in'agreement'and' is'unambiguous&may&be&the&excepoon'rather'than'the'rule 'In'general,'when' lines'of'evidence'are'not'concordant'and'the'weight'of'evidence'does'not' support'a'confident'decision,'epa'recommends'collecong&a&new&line(s)&of& evidence'(e.g.,'indoor'air'data,'if'only'subsurface'data'have'been'collected'so' far),'an'addi;onal'round'of'sampling'data,'or'appropriately'adjus;ng'the'csm' to'bemer'represent'the'weight'of'the'available'evidence. ''''(USEPA'2013' draq,'sec;on'7.2)' 1' 2' USEPA&GUIDANCE:&&THE!UGLY! Lots&of&uncertainty&in&content,&Oming&of& final&guidance& & Some&jurisdicOons&are&implemenOng& anyway& & BUSINESS&DRIVERS:&&DUE!DILIGENCE! All&Appropriate&Inquiries &Rule& & WHO?! Innocent&landowners,&prospecOve&purchasers& WHAT?! Process&of&evaluaOng&a&property s&environmental& condioon&&&likelihood&of&environmental& contaminaoon& USEPA'Region'9'leMer'CA'Regional'Water'Quality'Control'Board,'3'Dec'2013'' HOW?! Follow&ASTM&E1527 &!! CERCLA&liability&is&limited&if&Phase&I&is&done&correctly&& 3' AAI'Rule'at'40'CFR'Part'312''' 4' ASTM&PHASE&I&GUIDANCE& Defines& good&commercial&and&customary&pracoce &for&esas& at&commercial&real&estate&properoes& Referenced&in& All&Appropriate&Inquiries &Rule 1& 2013&update&& ID!pot l!exposure!to!haz.!substances!or!petrol.!products!in!soil,!soil!vapor,! groundwater!and/or!surface!water!(3.2.2)! ID!movement!of!haz.!substances!or!petrol.!products!in!any!form!including! vapor!in!the!subsurface!(3.2.56)!!! New&ASTM&guidance&is&clear&that&vapors&and&vapor& migraoon&need&to&be&evaluated&in&a&phase&i&esa.& 1.''40'CFR'Part'312.'''USEPA'adopted'ASTM'E1527[13'in'final'AAI'rule,'12/30/2013.' 5' 1'

50 Vapor Intrusion: Advanced Methods Sept 2011 Stable Isotope Analysis to Distinguish Between Vapor Intrusion and Indoor Sources of VOCs Thomas E. McHugh, PhD., D.A.B.T Air Exchange SITE BUILDING source area 1 CSIA for Vapor Intrusion Significance of Background Sources Overview of Stable Isotope Analysis Use of CSIA for Vapor Intrusion Method Validation Field Application Air Exchange SITE BUILDING source area 2 TECHNOLOGY DESCRIPTION What are Stable Isotopes? p e - p e - n e p - n n Hydrogen, 1 H Deuterium, 2 H, D Tritium, 3 H, T Isotopes have the same number of protons identical atomic number Isotopes have different number of neutrons different atomic mass Stable isotopes do not undergo radioactive decay tritium is not a stable isotope 3 Part 2 CSIA.ppt 1 GSI Environmental Inc Norfolk, Suite 1000 Houston, Texas (713)

51 Vapor Intrusion: Advanced Methods Sept 2011 TECHNOLOGY DESCRIPTION Stable Isotope Fractionation Kinetic Effect: Biodegradation causes enrichment in PCE containing 13C Cl Cl C 12 C 12 Cl Cl Cl Cl C 12 Cl X C 13 Cl Biodegradation of PCE: 12 C Cl bond easier to break than 13 C Cl bond. Key Point: Differences in isotope ratios between samples can indicate different sources: indoor vs. subsurface. 4 CSIA for Vapor Intrusion Significance of Background Sources Overview of Stable Isotope Analysis Use of CSIA for Vapor Intrusion Method Validation Field Application Air Exchange SITE BUILDING source area 5 ISOTOPE RATIOS FOR INDOOR SOURCES Chlorine Ratio Indoor Sources Carbon Ratio 6 Part 2 CSIA.ppt 2 GSI Environmental Inc Norfolk, Suite 1000 Houston, Texas (713)

52 Vapor Intrusion: Advanced Methods Sept 2011 Advanced Methods Compound-Specific Stable Isotope Analysis, (C, Cl) CSIA: Fingerprinting method to distinguish between vapor intrusion and indoor sources Applicable to sites where biodegradation of subsurface VOCs has occurred, causing an isotope shift for subsurface source vs. indoor source. Range for indoor sources δ 37 Cl δ 13 C SOURCE EXAMPLE A: δ 13 C vs. δ 17 Cl Primary Source of Indoor PCE: Indoor Source Indoor Air Subsurface Source CSIA = Compound-Specific Stale Isotope Analysis 7 Advanced Methods Compound-Specific Stable Isotope Analysis, (C, Cl) CSIA: Fingerprinting method to distinguish between vapor intrusion and indoor sources Applicable to sites where biodegradation of subsurface VOCs has occurred, causing an isotope shift for subsurface source vs. indoor source. Range for indoor sources SOURCE EXAMPLE B: δ 37 Cl vs. δ 13 C Primary Source of Indoor PCE: Subsurface Source δ 37 Cl δ 13 C Indoor Air Subsurface Source CSIA = Compound-Specific Stale Isotope Analysis 8 CSIA Example Results: Indoor Air vs. Subsurface Vapor C 12 / C 13 Ratios 0 Residence 1: TCE Carbon Isotope Ratio ( ) FINDINGS: TCE in indoor air matches TCE in groundwater TCE is too heavy to be an indoor source Vapor intrusion is occurring -35 Range for Consumer Products Indoor Air Residence 1 Groundwater Near Residence 1 max min 9 Part 2 CSIA.ppt 3 GSI Environmental Inc Norfolk, Suite 1000 Houston, Texas (713)

53 Vapor Intrusion: Advanced Methods Sept 2011 CSIA Example Results: C 12 / C 13 and Cl 35 / Cl 37 Ratios FINDING: PCE in indoor air is from indoor source. (E6000 glue.) 10 CSIA for Vapor Intrusion Significance of Background Sources Overview of Stable Isotope Analysis Use of CSIA for Vapor Intrusion Method Validation Field Application Air Exchange SITE BUILDING source area 11 TECHNICAL CHALLENGE Challenge! Need ±100 ng of chemical to get accurate carbon stable isotope ratio measurement.! Need 100 L sample for 1 ug/m 3 conc. Really Big Summa RBS 12 Part 2 CSIA.ppt 4 GSI Environmental Inc Norfolk, Suite 1000 Houston, Texas (713)

54 Vapor Intrusion: Advanced Methods Sept 2011 TECHNICAL SOLUTION Air Sampling Pump Adsorbent Tubes Key Point: Active adsorbent tube sampling can be used to collect large volumes of indoor air or soil gas 13 METHOD VALIDATION: SORBENT TUBE SAMPLERS Complete adsorption Complete desorption Incomplete adsorption Incomplete desorption 14 METHOD VALIDATION: SORBENT TUBE SAMPLERS Complete adsorption Complete desorption Results from Laboratory Validation Study Incomplete adsorption Incomplete desorption Sorbent: Fractionation free performance from Carboxen 1016 Sampling Conditions: Validated for wide range of humidity, sample volume, sample mass, and non-target VOC mass Target VOCs: Validated for PCE, TCE, and benzene Paper on Laboratory Method Validation: Klisch, M., Kuder, T., Philp, R.P., McHugh, T.E., Validation of Adsorbents for Sample Preconcentration in Compound-Specific Isotope Analysis of Common Vapor Intrusion Pollutants, Journal of Chromatography A, Vol.1270, pp 20-27, Part 2 CSIA.ppt 5 GSI Environmental Inc Norfolk, Suite 1000 Houston, Texas (713)

55 Vapor Intrusion: Advanced Methods Sept 2011 METHOD VALIDATION: APPLICATION TO VAPOR INTRUSION SITE Site Sampling Program Results Five residences over chlorinated solvent plume with TCE or PCE detected in indoor air Near Hill AFB, Utah One indoor air sample from each residence One to four groundwater or soil gas samples from near-by sample points Confirmed Vapor Intrusion: Two residences Confirmed Indoor Sources: Two residences Not Conclusive: One residences Paper on Application of CSIA to Vapor Intrusion: McHugh et al., 2011 Env. Sci. Technol. Vol. 45(14) pp CSIA for Vapor Intrusion Significance of Background Sources Overview of Stable Isotope Analysis Use of CSIA for Vapor Intrusion Method Validation Field Application Air Exchange SITE BUILDING source area 17 CSIA FOR VI: FIELD APPLICATION Step 1A: Characterize Isotope Ratios for Subsurface Source. Groundwater OR Soil Gas Conduct CSIA on groundwater sample from existing monitoring well Conduct CSIA on soil gas sample <100 ug/m 3 = sorbent tube 100 to 500 ug/m 3 = 6L Summa > 500 ug/m 3 = 1L Summa Chlorine Ratio Indoor Sources Carbon Ratio? Can collect subsurface sample from existing sample point. 18 Part 2 CSIA.ppt 6 GSI Environmental Inc Norfolk, Suite 1000 Houston, Texas (713)

56 Vapor Intrusion: Advanced Methods Sept 2011 CSIA FOR VI: FIELD APPLICATION Step 1B: Compare Isotope Ratios for Subsurface Source to Measured Range for Indoor Sources Chlorine Ratio SS Chlorine Ratio SS Carbon Ratio Carbon Ratio Subsurface source NOT enriched in heavy isptopes: CSIA not likely to distinguish between indoor and subsurface sources. Subsurface source IS enriched in heavy isotopes: CSIA applicable to vapor intrusion. 19 CSIA FOR VI: FIELD APPLICATION Step 2: Collect indoor air samples for CSIA. Compare results to indoor source range and site-specific subsurface source. Range for indoor sources 20 CSIA for Vapor Intrusion Project Planning and Implementation Thomas McHugh, GSI Environmental Laboratory Analysis ($350-$800/sample) Tomasz Kuder, University of Oklahoma 21 Part 2 CSIA.ppt 7 GSI Environmental Inc Norfolk, Suite 1000 Houston, Texas (713)

57 Vapor Intrusion: Advanced Methods Sept 2011 ACKNOWLEDGEMENTS Work funded by: ESTCP Projects ER and ER AFCEE BAA Contract 09-C-8016 Hill AFB/BP America CSIA Proof of Concept Special Thanks to: Roger Lee, Sims & Associates Sam Brock & Erica Becvar, AFCEE Lisa Molofsky, Danny Bailey, Roberto Landazuri, GSI Env. Inc. Paul Johnson s Research Team, Arizona State University Beacon Environmental Part 2 CSIA.ppt 8 GSI Environmental Inc Norfolk, Suite 1000 Houston, Texas (713)

58 3/27/14 DEFINITIVE VAPOR INTRUSION INVESTIGATIONS USING ON-SITE GC/MS ANALYSIS Results from ER and ER Thomas McHugh, Ph.D. Lila Beckley, M.S. GSI Environmental Inc. Definitive Vapor Intrusion Investigations Using On-site GC/MS Analysis! INTRODUCTION Introduction! Indoor Focused Investigation Approach 2 Introduction Vapor Intrusion: Who cares? POINT Significant pathway: when VI occurs, it poses an actual, not hypothetical, exposure risk 3 1

59 3/27/14 Introduction Typical Sampling Program (Minimalist) Indoor Air Outdoor Air Sub-Slab Analyte List One sample from lowest level of building One sample from lowest occupied level One sample upwind of building(s) for each day of sampling One to three samples from below building (e.g., 6 in. below slab). Analyze solely for subsurface chemicals of concern Summa Canister Conventional program includes building survey and small no. of samples, with multiple lines of evidence evaluation. 4 Introduction Problems with Typical Program Most data collected are indirect measurements, not at POINT OF EXPOSURE Soil Gas Limited Indoor Air Challenges: Spatial variability/attenuation factors? Preferential pathways? Guidance varies, leading to confusion Sample at POE, but still have challenges: Indoor VOC sources? Spatial/temporal variability? Other Soil permeability Radon Multiple lines of evidence evaluations are NOT DEFINITIVE, often leading to: Collect more data. 5 Vapor Intrusion Processes Physical Barriers to Vapor Intrusion No Barrier Possible Barriers A B Building Foundation: (A) Low permeability foundation with no cracks or unsealed penetrations; (B) Positive building pressure Typical sampling program does little to identify physical features that could explain chemical results. Soil Source Area GW Aquifer Vapors A A B B Vadose Zone: (A) High moisture content or clay layer; (B) Aerobic biodegradation Groundwater interface: (A) Clean water lens (B) Clay layer 6 2

60 3/27/14 Definitive Vapor Intrusion Investigations Using On-site GC/MS Analysis! Introduction! Indoor Focused Investigation Approach 7 Approach Lab Validation Study Investigation Approach 1. Generic Screening 2. Screen Indoor Air 3. On-Site Analysis 4. Follow Up Target buildings of potential VI concern based on distance from source. Measure COC concentration INSIDE building (Summa, Passive Sorbent Sampler, or on-site GC/MS). If COC > Screening level, use HAPSITE to determine SOURCE of COCs. Mitigate VI? Use Passive Samplers (14-day) to address temporal variability Use LAB DATA for risk evaluation. Use HAPSITE to identify sources. 8 Approach 1. Generic VI Screening Target Building m Identify target buildings based on distance from subsurface source m Skip soil gas and subslab sampling: expensive and not definitive. Initial screening is based on results from generic site investigation. 9 3

61 3/27/14 Approach 2. Screen Indoor Air If indoor results are less than indoor air screening levels consider temporal variability. Sample with Summa or passive sorbent sampler or on-site analysis. C ia=? Directly measure COC concentration at point of exposure. No extrapolation. No arguments. 10 Investigation Approach Protocol 2. Screen Indoor Air: How? If COC Conc. BELOW Screening Level If COC Conc. ABOVE Screening Level Monitor, if needed to evaluate temporal variability - Cost effective options available No Further Action Use on-site analysis to identify source (indoor vs. VI) Don t panic can mobilize to site, determine source, and mitigate (if needed) in 2-4 days. Detections of COCs in indoor air are not a crisis if you have a plan. 11 Approach 3. On-site Analysis Area by Area Results 1.5X 0.2X 1X Prior Lab Sample > Screening Level triggered need for on-site testing GOAL: Find the source 12 4

62 3/27/14 Approach 3. On-site Analysis (con t) Room by Room Results - Upstairs 1.4X 1.5X 0.2X 1.6X 4X GOAL: Find the source 13 Investigation Approach Protocol 3. On-site Analysis (Final Step) INDOOR SOURCE PCE Ion Intensity (%) VAPOR ENTRY POINT TCE Survey Response 14 Protocol Building Pressure Control General Concept: 1) Use controlled NEGATIVE pressure to TURN ON vapor intrusion 2) Make it worse to address temporal variability 3) Evaluate potential for vapor intrusion using on-site analysis procedure NEGATIVE Pressure in Building = VI On POSITIVE Pressure in Building = VI Off 15 McHugh et al, 2012, Evaluation of Vapor Intrusion Using Controlled Building Pressure, Environ. Sci. Technol. 5

63 3/27/14 Building Pressure Control: Results at ASU Research House ASU RESEARCH HOUSE Radon Concentration (pci/l) Baseline Negative Positive Baseline Negative Positive Exterior 3 0 VI On VI Off VI On VI Off Control of building pressure controls vapor intrusion. POS NEG Building Pressure Control: Results at ASU Research House Baseline Negative Pressure (VI On ) Positive Pressure (VI Off ) Normalized Concentration Conc. in Outdoor Air Radon Chemicals in Subsurface Source Garage Source 1,1-DCE cis-1,2- DCE PCE TCE Benzene Ambient Source Toluene Indoor Source Vapor intrusion effects are maximized to get worsecase results for subsurface sources, reducing the need for multiple sampling events. SF6 Protocol Step-by-Step Process GOAL: Find the Source Project planning Instrument operation, calibration, QA/QC Building operating conditions Step-by-step sampling program (see flow chart) Data interpretation Comprehensive written protocol for application of on-site GC/MS analysis approach. 18 6

64 3/27/14 Approach HAPSITE Performance Assessment Precision Sensitivity Accuracy RPD typically <10% Chlorinated VOCs: 0.5 to 1 ug/m 3 BTEX: 1 to 5 ug/m 3 Typically within 2x accuracy (RPD<67%) POINTS: Met performance goals of ESTCP study. Lab results consistent with field experience: It works ESTCP Project ER Investigation Approach Protocol 4. Follow Up Mitigation Mitigate real vapor intrusion HAPSITE results may help with system design Monitoring May be required for sites that pass initial screening (e.g., temporal variability) Passive sorbent samplers - inexpensive - 14 day sample period Use low cost, long duration samplers to address regulatory concerns re: temporal variability. 20 7