EPA Vapor Intrusion Update

Transcription

1 EPA Vapor Intrusion Update by Ben Bentkowski, P.G. Scientific Support Section, R4 Superfund Presented April 29, 2016 Southeastern States Vapor Intrusion Symposium March

2 What is Vapor Intrusion? A potential human exposure pathway -- a way that people may come into contact with hazardous vapors while performing their day-to-day indoor activities. Can occur in a broad range of land use settings (e.g., residential, commercial, institutional, industrial) Can arise from a broad range of hazardous substances, contaminants, and pollutants Can pose health or safety threats U.S. Environmental Protection Agency 2

3 What is Vapor Intrusion? (continued) Exposure pathway entails five elements Subsurface vapor source Vapor migration route(s) into and through the vadose zone Susceptibility of building to gas entry Vapor presence in building Exposure to occupants U.S. Environmental Protection Agency 3

4 5/3/2016 Conceptual Model of Soil Vapor Intrusion Pathway 4 SOURCE: Illangasekare et al. [2014], SERDP Project ER-1687 Report Figure 1-1

5 Overview of EPA VI Guidance EPA s vapor intrusion guidance is comprised of two guides, published in June 2015, which supersede and replace EPA s 2002 draft guidance. Guide for petroleum releases from underground storage tanks sites. Guide for all other sites within EPA s jurisdiction. U.S. Environmental Protection Agency 5

6 Technical Guide For Addressing Petroleum Vapor Intrusion At Leaking Underground Storage Tank Sites EPA 510-R June 2015 This document is intended for use at any site subject to petroleum contamination from underground storage tanks where vapor intrusion may be of potential concern ( OUST PVI Guide ). It is applicable to both residential and nonresidential settings (e.g., commercial and industrial). 6

7 OSWER Technical Guide For Assessing And Mitigating The Vapor Intrusion Pathway From Subsurface Vapor Sources To Indoor Air OSWER Publication June 2015 This document is intended for use at any site being evaluated pursuant to CERCLA or the corrective action provisions of RCRA, where vapor intrusion may be of potential concern ( OSWER VI Guide ). It is also intended for use by EPA s brownfield grantees, where vapor intrusion may be of potential concern. It is applicable to both residential and non-residential settings (e.g., commercial and industrial). 7

8 Organization of OSWER VI Guide Executive summary identifies key recommendations Glossary identifies key terms Major sections devoted to Preliminary analysis (initial site assessment) Site investigation Community involvement and risk communication Response actions (remediation, mitigation, ICs) OSWER VI Guide 8

9 Scope of OSWER VI Guide { 1.3} Considers full range of vapor-forming chemicals at pertinent sites Chlorinated solvents (e.g., PCE, TCE) Petroleum hydrocarbons such as benzene, trimethylbenzenes Hydrophobic compounds that also meet the volatility and toxicity criteria (e.g., some PCBs, some pesticides) OSWER VI Guide 9

10 Vapor Intrusion Investigations: Key Planning Recommendations { 6.2} (continued) Use the initial conceptual site model (CSM) to guide the investigation and its phasing Generally proceed in a stepwise fashion Initially, develop a basic understanding of the site Subsequently, fill gaps in CSM understanding and attempt to reconcile data inconsistencies Gather information necessary to evaluate the various options for managing risk OSWER VI Guide 10

11 Conceptual Site Models: Key Recommendations { 5.4, 7.1, & 7.2} (continued) At the outset, at a minimum include and evaluate available information about The potential nature and location(s) of the subsurface source(s) of vapor-forming chemicals Type(s) and form(s) Composition and potential degradability due to natural processes The use, occupancy, and basic construction of existing, nearby buildings Does this preliminary information indicate a completed pathway? OSWER VI Guide 11

12 Conceptual Site Models: Key Recommendations (continued) Also consider the presence of preferential migration routes and significant openings that could facilitate vapor migration to greater distances and at higher concentrations than otherwise expected Naturally occurring (e.g., fractures and macropores) Anthropogenic (e.g., sewers, utility vaults, drains) OSWER VI Guide 12

13 VI Assessment or VI Investigation Assessment is desktop study with available data and reasonable assumptions Investigation when you have a likely completed pathway, especially if you have TCE and an occupied building U.S. Environmental Protection Agency 13

14 When do you need to do a VI Assessment? Evaluate if you have a completed pathway Subsurface vapor source Vapor migration route(s) into and through the vadose zone Susceptibility of building to gas entry Vapor presence in building Exposure to occupants Do you have VOC present in the soils and/or the shallow groundwater? U.S. Environmental Protection Agency 14

15 When do you need to do a VI Assessment? (continued) Run the available data through the Vapor Intrusion Screening Level (VISL) Calculator If the cumulative risk is >10-6 and/or the Hazard Index is >1.0, begin to plan a VI assessment - unless it is TCE - then PROMPTLY contact your HH Risk Assessor. If the cumulative risk is >10-4 and/or the Hazard Index is >3.0, prompt action is recommended U.S. Environmental Protection Agency 15

16 Vapor Intrusion Screening Level Calculator -- VISL -levels Excel spreadsheet and Users Guide Make sure you are using a current version as sometimes the risk factors are updated. 5/3/2016 U.S. Environmental Protection Agency 16

17 VISL Calculator 5/3/2016 U.S. Environmental Protection Agency 17

18 Q&A May 2016 OSWER VI Guide: Indoor Air Treatment 18

19 Vapor Intrusion Investigations: Key Sampling Recommendations Anticipate that indoor air can have vapors from sources other than vapor intrusion and the subject site { 2.7 and 6.3.5} When sampling indoor air { 6.4.1}, attempt to remove and document indoor vapor sources before sampling Example of Indoor Sources of Vapors Image Source: EPA Region 9 19

20 How is Background Considered? Recommended methods are described to account for background contributions to indoor air concentrations { 6.3.5} If background vapor sources are found to be primarily responsible for indoor air concentrations, then response actions for vapor intrusion would generally not be warranted for current conditions { 7.4.2} OSWER VI Guide 20

21 What Are Some Implications of Background? (continued) Identify and remove indoor sources to extent possible during an interior investigation Generally limit chemical analyses of subslab soil gas and indoor and outdoor air to those vapor-forming chemicals known or reasonably expected to be present in the subsurface environment { 6.4 and 6.3.5} Additional lines of evidence also useful Collect metrological data during the sampling OSWER VI Guide 21

22 Multiple Lines of Evidence: Key Recommendation Generally assess the vapor intrusion pathway by collecting, weighing, and evaluating multiple lines of evidence, particularly when no-further-action decisions are to be supported OSWER VI Guide 22

23 Lines of Evidence: Definition (continued) Facts or other information, which are useful for forming a conclusion or judgment May be categorized into scientific realms (e.g., geology, biology, physics) or investigatory objectives (e.g., characterize vapor migration routes) OSWER VI Guide 23

24 Lines of Evidence: Definition (continued) Greater Vapor Intrusion Potential Less Vapor Intrusion Potential Vapor Vadose Zone Vadose Zone Building Found- Source Categories Geologyof Hydrology Lines chemistry of Evidence ation High Source Conc., Highly Volatile Chemicals See Sections 2.1 and Low Source Conc., Less Volatile Chemicals Vertically Fractured or Coarse- Grained, Vertically Uniform Media See Sections 2.2 and Horizontal and Laterally Extensive Fine- Grained Layers Low Moisture Content in Vadose Zone, Shallow Water Table, Large Water Table Fluctuations See Sections 2.1, 2.2 and High Moisture Content in Vadose Zone, Deep Water Table, Thick Capillary Fringe Vadose Zone Bio- Unfavorable for Complete Degradation or Non- Degradable Chemicals See Sections 2.2 and Favorable for Complete Degradation and Degradable Chemicals Cracked Slab, Partial Slabs, Sumps or Drains See Sections 2.3, 6.3.3, and Intact, Extensive, and Thicker Slab Some Categories of Evidence for Vapor Intrusion Source: Figure 2-3 of the OSWER VI Guide (Some Factors That Affect Vapor Intrusion) 24

25 Multiple Lines of Evidence (continued) Image Source: Physics Stack Exchange [ EPA recommends the appropriate use and evaluation ( weighing ) of multiple lines of evidence for determining, for example whether the vapor intrusion pathway is complete or not, whether any elevated levels of contaminants in indoor air are likely caused by subsurface vapor intrusion versus an indoor source or an ambient (outdoor) air source. 25

26 Multiple Lines of Evidence Example Collect complementary data to be weighed when sampling indoor air { 6.4.1}, Subsurface vapor strength (e.g., subslab soil gas) Building conditions (e.g., differential pressure across building foundation; occupancy and compartmentalization; presence of sumps and floor drains or seeping groundwater) Building operations (e.g., ventilation, heating, and cooling; exhaust fans; indoor air treatment units) OSWER VI Guide 26

27 Multiple Lines of Evidence (continued) Characterizing groundwater as a vapor source { 6.3.1) Collect soil gas samples immediately above the groundwater table Compare the measured soil gas concentrations to concentrations predicted by chemical equilibrium between the aqueous/dissolved and soil gas phases A significant divergence between the two concentration estimates may identify site-specific conditions important to incorporate into the conceptual site model OSWER VI Guide 27

28 Human Health Risk Assessment: Key Recommendations { 7.4} (continued) Consider the potential for adverse (noncancer) health effects from short-duration inhalation exposures (i.e., acute, short-term, or subchronic exposure durations), as well as longer term inhalation exposure (i.e., chronic exposure) conditions. April 2016 OSWER VI Guide 28

29 Evaluation of the Data Regional Screening Levels (RSLs) RSLs are values used by the EPA to determine whether a chemical should be considered for further monitoring or investigation. They are conservative (protective) risk-based values calculated at a 10-6 risk level for carcinogens (1 excess cancer per 1,000,000 people) or a Hazard Quotient of 1 for noncarcinogens. Generally, if chemical concentrations are above an RSL, the EPA considers further investigation to determine the full nature and extent of any contamination. April 2016 U.S. Environmental Protection Agency 29

30 Evaluation of the Data Removal Management Levels (RMLs) RMLs are values used by the EPA to identify areas, contaminants, and conditions where an action may be necessary to protect human health and/or the environment. The RMLs are risk-based values calculated at a 10-4 risk level for carcinogens (1 excess cancer per 10,000 people) or a Hazard Quotient of 3 for non-carcinogens. These actions, determined on a site-specific basis, can vary depending on the contaminant and the concentration and could include such actions as interim measures to lessen exposure or active mitigation/treatment. Generally, if chemical concentrations are above an RML, the EPA considers appropriate exposure or treatment actions. Exceedance of an RML by itself does not imply that adverse health effects will occur. April 2016 U.S. Environmental Protection Agency 30

31 RSLs & RMLs for TCE and PCE Contaminant Residential Residential Commercial Commercial RSL RML RSL RML PCE 11 ug/m ug/m 3 47 ug/m ug/m 3 TCE 0.48 ug/m ug/m 3 3 ug/m 3 26 ug/m 3 TCE (sensitive subpopulation) ug/m ug/m 3 3 ug/m ug/m 3 April 2016 U.S. Environmental Protection Agency 31

32 Sensitive Sub-Population Region 4 s Scientific Support Section (SSS) recommends a chemical specific RML for TCE in residential air of 2.1 ug/m3 (HQ of 1) and 8.8 ug/m3 (HQ of 1) for commercial/industrial air with sensitive sub-populations (i.e., women of child bearing age) present. These concentrations are expected to be protective for potential non-cancer health effects, including developmental effects. April 2016 U.S. Environmental Protection Agency 32

33 Potential Response Actions: Options for Prompt Action Notification and risk communication to building occupants and owners Reduce mass flux into buildings, for example by Sealing major openings for soil gas entry Over-pressurizing non-residential buildings Operating vapor traps for pipe gas entry Reduce indoor air concentrations, for example by increasing building ventilation or treating indoor air Avoid exposure by temporary relocation May 2016 OSWER VI Guide 33

34 Introduction to Indoor Air Treatment Refers to interim measures that reduce vapor concentrations in the building by treating air directly, as opposed to blocking soil gas or conduit gas entry Indoor air treatment has promise as a response action for vapor intrusion, but the literature on its efficacy is currently limited May 2016 OSWER VI Guide 34

35 I(A). Introduction to Indoor Air Treatment (continued) What do we know? Available options include Various operating principles (e.g., adsorption, oxidation) Various implementation formats (e.g., in-duct vs. portable devices) Economic analyses suggest that adsorption-based approaches will be most cost-effective, particularly those involving activated carbon May 2016 OSWER VI Guide 35

36 I(A). Introduction to Indoor Air Treatment (continued) How does it compare to other mitigation methods, considering selection criteria? Potentially quicker deployment, compared to sub-slab depressurization (e.g., design, construction, permitting) Avoids loss of conditioned air (e.g., heat, humidity), which will accompany ventilation and sub-slab depressurization Less disruptive than re-location/evacuation Operating noise may be bothersome to building occupants Continuity of operations can be interrupted by occupants, as with most other options May 2016 OSWER VI Guide 36

37 Former Macon Naval Ordnance Plant Multiple operations through its history Electroplating by the Navy during WWII TCE metal cleaning Waste piped to waste water treatment plant with ponds No VOCs in current operations 5/3/2016 U.S. Environmental Protection Agency 37

38 Former MNOP Feb 1988 EPIC Operations in transition West Process Area plating Treatment Area WW Plant and Ponds NB new building now Textbond was ammo storage bunkers 5/3/2016 U.S. Environmental Protection Agency 38

39 Google Earth Pro 2016 Former Macon Naval Ordnance Plant (N/2) 5/3/2016 U.S. Environmental Protection Agency 39

40 WW Plant Plating Bldg Former MNOP 1998 TCE Concentrations Highest at Waste Water Plant and Plating Bldg Note the ND near the Textbond Bldg 5/3/2016 U.S. Environmental Protection Agency 40

41 90 µg/l Former MNOP 770 µg/l Groundwater analytical results for TCE ug/l 27,000 µg/l 210 µg/l Ran the results through the VISL Proceeded promptly to plan VI investigation 5/3/2016 U.S. Environmental Protection Agency 41

42 Subslab 6,800 µg/m 3 Indoor 230 µg/m3 Subslab 33 µg/m 3 Subslab 89 µg/m 3 NOTE: NO TCE detected in Ambient Air samples map symbol yellow circles Other air data in tan boxes. Former MNOP Fairly substantial TCE conc. around the Line 7 Building. All the other indoor air samples either ND or lower than the risk range. Risk evaluation for Break Room even with shortened duration showed unacceptable risk Adjusted the air exchange rate on the HVAC system Verified use and duration of Break Room Resampled 7 µg/m 3 April µg/m 3 April

43 August 2015 TAGA sampling showed detections around base of woman s toilet on second day of testing. Resample at Textbond Break Room December 2015 Will continue to stay in touch with Textbond as the work progresses on this site. 5/3/2016 U.S. Environmental Protection Agency 43

44 Planned TAGA Screening Investigation Given the size of the TCE plume, planned to use TAGA for rapid screening of many buildings. Other Buildings to be scanned as necessary 5/3/2016 U.S. Environmental Protection Agency 44

45 Former MNOP Unit 6 Bldg Large warehouse site of former plating operations TAGA - elevated detections in floor cracks, bathroom and this small lab 5/3/2016 U.S. Environmental Protection Agency 45

46 Unit 6 Sampling with Summa Canisters Follow up to TAGA Screening 5/3/2016 U.S. Environmental Protection Agency 46

47 Mitigation Options Seal cracks Increase HVAC exchange rate Move laboratory Adjust work schedules Install temporary air filtration unit 5/3/2016 U.S. Environmental Protection Agency 47

48 Unit 6 Sample Results After Filtration Unit Installed Sampled two sequential days March 24 & 25, th normal work day- large bay doors open 25 th Good Friday, partial crew, large doors not open Continue to work with business owner as PRP group is formed 5/3/2016 U.S. Environmental Protection Agency 48

49 Assessing Protectiveness at Sites for Vapor Intrusion Supplement to the Comprehensive Five-Year Review Guidance OSWER Directive For sites at which a vapor intrusion remedy has not been selected or implemented, but new information raises the potential for a complete vapor intrusion pathway, the five-year review process may offer an appropriate opportunity to: identify issues, review data, make recommendations, and develop a protectiveness determination for vapor intrusion. U.S. Environmental Protection Agency 49

50 Guidance for Evaluating Completion of Groundwater Restoration Remedial Actions (November 2013, OSWER ) Recommends evaluating contaminant of concern (COC) concentration levels on a well-by-well basis There is Policy, Guidance, Spreadsheet and Users Guide to help in the evaluations Eight samples once you meet the remedial goal for which the 95 th percentile is below the remedial goal CERCLA sites and authority 5/3/2016 U.S. Environmental Protection Agency 50

51 Q&A May 2016 OSWER VI Guide: Indoor Air Treatment 51