epa vapor intrusion update · epa vapor intrusion update. ... (e.g., geology, biology, physics) or...

by

Ben Bentkowski, P.G.Scientific Support Section, R4 Superfund

Presented April 29, 2016

Southeastern States Vapor Intrusion Symposium

March 2016 1

EPA Vapor Intrusion Update

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

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


5/3/2016 4Conceptual Model of Soil Vapor Intrusion Pathway

SOURCE: Illangasekare et al. [2014], SERDP Project ER-1687 Report Figure 1-1

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replace EPA’s 2002 draft guidance.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.


Technical Guide For Addressing Petroleum Vapor Intrusion At Leaking Underground Storage Tank Sites

EPA 510-R-15-001

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 non-residential settings (e.g., commercial and industrial).

6

OSWER Technical Guide For Assessing And Mitigating The Vapor Intrusion Pathway From Subsurface Vapor Sources To Indoor Air

OSWER Publication 9200.2-154

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

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

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)

9OSWER VI Guide

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

10OSWER VI Guide

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?

11OSWER VI Guide

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)

12OSWER VI Guide

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


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?


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


Vapor Intrusion Screening Level

Calculator -- VISL

• https:///.epa.gov/vaporintrusion/vapor-

intrusion-screening -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

VISL Calculator


Q&A

May 2016 OSWER VI Guide: Indoor Air Treatment 18

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

19

Example of Indoor Sources of Vapors

Image Source: EPA Region 9

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}

20OSWER VI Guide

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

21OSWER VI Guide

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

22OSWER VI Guide

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)

23OSWER VI Guide

Categories of Lines of Evidence

Some Categories of Evidence for Vapor IntrusionSource: Figure 2-3 of the OSWER VI Guide (Some Factors That Affect Vapor Intrusion)

24

Greater

Vapor

Intrusion

Potential

Less

Vapor

Intrusion

Potential

Vadose

Zone

Geology

Building

Found-

ation

Vadose

Zone

Hydrology

Vertically

Fractured or

Coarse-

Grained,

Vertically

Uniform

Media

Horizontal

and

Laterally

Extensive

Fine-

Grained

Layers

Low

Moisture

Content in

Vadose

Zone,

Shallow

Water

Table,

Large

Water Table

Fluctuations

High

Moisture

Content in

Vadose

Zone, Deep

Water Table,

Thick

Capillary

Fringe

Cracked

Slab,

Partial

Slabs,

Sumps or

Drains

Intact ,

Extensive,

and

Thicker

Slab

High Source

Conc.,

Highly

Volatile

Chemicals

Low Source

Conc., Less

Volatile

Chemicals

Vapor

Source

Vadose

Zone Bio-

chemistry

Unfavorable

for

Complete

Degradation

or Non-

Degradable

Chemicals

Favorable

for

Complete

Degradation

and

Degradable

Chemicals

See

Sections 2.1

and 6.3.1

See

Sections 2.2

and 6.3.2

See

Sections 2.2

and 6.3.2

See Sections

2.1, 2.2 and

6.3.2

See

Sections

2.3, 6.3.3,

and 6.4.1

Lines of Evidence: Definition (continued)

Multiple Lines of Evidence (continued)

• 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

Image Source: Physics Stack Exchange

[http://physics.stackexchange.com]

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)

26OSWER VI Guide

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

27OSWER VI Guide

Human Health Risk Assessment: Key

Recommendations {§7.4} (continued)

• Consider the potential for adverse (non-

cancer) 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 28OSWER VI Guide

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 non-

carcinogens. Generally, if chemical concentrations are above

an RSL, the EPA considers further investigation to determine

the full nature and extent of any contamination.

• http://www.epa.gov/risk/regional-screening-table

April 2016 U.S. Environmental Protection Agency 29

http://www.epa.gov/risk/regional-screening-table

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.

• http://www.epa.gov/risk/regional-removal-management-levels-chemicals-rmls


http://www.epa.gov/risk/regional-removal-management-levels-chemicals-rmls

RSLs & RMLs for TCE and PCE

Contaminant Residential

RSL

Residential

RML

Commercial

RSL

Commercial

RML

PCE 11 ug/m3 126 ug/m3 47 ug/m3 540 ug/m3

TCE 0.48 ug/m3 6.3 ug/m3 3 ug/m3 26 ug/m3

TCE

(sensitive sub-

population)1

0.48 ug/m3 2.1 ug/m3 3 ug/m3 8.8 ug/m3


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.


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 33OSWER VI Guide

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


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


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


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

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



Former Macon Naval Ordnance Plant (N/2)

Google

Earth Pro

2016


Former MNOP

1998 TCE

Concentrations

Highest at

Waste Water

Plant and

Plating Bldg

Note the ND

near the

Textbond Bldg

Plating BldgWW

Plant

5/3/2016


770

µg/L

79 ug/L

90 µg/L

210 µg/L

27,000 µg/L

Former

MNOP

Groundwater

analytical

results for

TCE 2014

Ran the

results

through the

VISL

Proceeded

promptly to

plan VI

investigation

Subslab

6,800 µg/m3

Indoor

230 µg/m3

Subslab

89 µg/m3

Subslab

33 µg/m3

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/m3 April 20 2015

• 35 µg/m3 April 21 2015


Resample at Textbond Break Room December 2015

Will continue to stay in

touch with Textbond

as the work

progresses on this

site.

August 2015 TAGA sampling showed

detections around base of woman’s toilet –

on second day of testing.

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

Former MNOP Unit 6 Bldg


Large warehouse – site of former

plating operations

TAGA - elevated detections in

floor cracks, bathroom and this

small lab

Unit 6 Sampling with Summa Canisters

Follow up to TAGA Screening


Mitigation Options


• Seal cracks

• Increase HVAC

exchange rate

• Move laboratory

• Adjust work

schedules

• Install temporary air

filtration unit

Unit 6 Sample Results

After Filtration Unit Installed


Sampled two sequential days March 24 & 25, 2016

24th – normal work day- large bay doors open

25th – Good Friday, partial crew, large doors not open

Continue to work with business owner as PRP group is

formed

Assessing Protectiveness at Sites for Vapor Intrusion

Supplement to the “Comprehensive Five-Year

Review Guidance”

OSWER Directive 9200.2-84

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.


Guidance for Evaluating Completion of

Groundwater Restoration Remedial

Actions (November 2013, OSWER 9355.0-129)

• 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 95th percentile is below the remedial goal

• CERCLA sites and authority


Q&A

May 2016 OSWER VI Guide: Indoor Air Treatment 51

epa vapor intrusion update · epa vapor intrusion update. ... (e.g., geology, biology, physics) or...

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