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Vapor Intrusion Investigations and Short-term TCE Toxicity

Implementation Memo No. 22

NEBC Remediation ConferenceOctober 3, 2019

Tacoma Convention Center

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Goals of the Presentation

1. Brief Summary of Ecology’s VI Guidance Documents

2. Background on Short-term TCE Risks

3. Overview of Implementation Memo No. 22

4. Supporting Documents

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What VI Guidance is Available?

Ecology’s VI guidance was released in October 2009.

Numerous portions of this document need updating.

We anticipate releasing an updated version of the guidance for public review and comment by fall 2020.

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What VI Guidance is Available? (cont.)

1. Implementation Memo 14 (March 2016) – Updated Process for Initially Assessing the Potential for Petroleum Vapor Intrusion.

2. Implementation Memo 18 (January 2018) – Petroleum Vapor Intrusion (PVI): Updated Screening Levels, Cleanup Levels, and Assessing PVI Threats to future buildings.

3. Implementation Memo 21 (November 2018) – Frequently Asked Questions (FAQ’s) Regarding Vapor Intrusion (VI) and Ecology’s 2009 Draft VI Guidance.

4. Implementation Memo 22 (October 2019) – Vapor Intrusion (VI) Investigations and Short-term Trichloroethene (TCE) Toxicity.

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Short-term TCE VI Risks

The inhalation RfC developed as part of EPA’s 2011 TCE toxicity assessment was partially based on developmental effects early in pregnancy.

Regions 9 and 10 have issued memos with “do not exceed” TCE air concentrations protective of short-term fetal exposures.

These memos are on Ecology’s VI web page.

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• The Region 10 memo indicates that exposures as short as 3 weeks can potentially result in fetal heart defects.

• This is a much shorter exposure timeframe than the chronic based exposures used for calculating Method B and C indoor air cleanup levels.

Short-term TCE VI Risks

Exposures [ATSDR]

acute(< 2 weeks)

intermediate duration(> 2 weeks to < 1 yr)

chronic(> 1 yr)

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Major Components of Implementation Memo No. 22

Action Levels and Screening Levels

Site Investigation/Indoor Air Sampling

Responding to Exceedances

Public Involvement

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Short-term TCE Action Levels and Screening Levels

Indoor Air Action Levels (g/m3) GW SL (ug/L)

Sub-slab soil gas SL(g/m3)

Residential 2.0 8 67

Commercial/Industrial Workers

7.5 31 250

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How the Short-term TCE Residential AL’s and SL’s Compare to Ecology Method B levels

Indoor Air Levels (g/m3) GW SL (g/L)Sub-slab soil gas SL

(g/m3)

EPA Residential Levels 2.0 8 67

Ecology Method B CUL’s/SL’s

0.37 1.6 12.3

How Does I.M. No. 22 Change the VI Evaluation Process?

In general, the guidance anticipates that the initial steps for evaluating the VI pathway will be similar to other non-petroleum VOC’s.

The major difference is: • Once it is determined that VI has the potential to cause

exceedances of the short-term action levels, additional data gathering and/or response actions should be conducted quickly.

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Data Collection and Evaluation

The first steps will typically include:

1. Is TCE in groundwater, soil or soil gas?

2. Do the concentrations exceed screening levels?

3. Are there buildings present within 100 feet of screening level exceedances or are there potential preferential pathways for buildings farther away?

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TCE Source 12MW 1: [TCE] = 10 µg/lExample #1

MW 2: [TCE] = 5 µg/l

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TCE Source 13“exterior” soil gas samplesExample #1

MW 1: [TCE] = 10 µg/l

TCE Source 14MW 1: [TCE] = 75 µg/lExample #2

MW 2: [TCE] = 40 µg/l

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Indoor Air Sampling Considerations

When indoor air sampling will be implemented:1. Inform building owners of the steps necessary.2. Schedule and perform a building visit to discuss timing and access. 3. Select sampling locations and gather building information that will help when

developing the sampling plan.4. Don’t wait for more VI-conducive weather conditions to perform the sampling.

The guidance recommends that for at least the first sampling event to request lab data within 3 business days.

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slab-on-grade

indoor air, ambient air, and sub-slab VIsampling

indoor air:• 24-hr samples• 3-wk passive sample

sub-slab soil gas samples

ambient air: 24-hr sample

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Addressing Exceedances

If VI is resulting in TCE concentrations that exceed the short-term action levels, prompt action is needed. This could include any or some combination of the following actions:

1. Increase building pressure/ventilation2. Seal conduit entry points3. Use temporary indoor air treatment units4. Temporarily relocate occupants5. Install mitigation systems such as sub-slab depressurization.

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TCE Fact Sheet This fact sheet will be released at the same

time as Implementation Memo No. 22.

It provides information on what TCE is, how it can get into homes or other buildings and the potential health risks of breathing TCE.

It was developed in cooperation with the Department of Health and is intended for the general public interested in information about potential exposures to TCE from VI.

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Requests for Evaluation of the VI Pathway from TCE

When Ecology initially becomes aware of sites with exceedances of the screening levels, we send a letter that requests:

1. Submitting any data not already provided within 30 days and2. Completing a VI investigation within 60 days to determine whether any

further actions are necessary to address short-term TCE risks.

These requests will primarily be sent to independent sites or those early in evaluation process (Initial Investigations or Phase 2’s).

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Summary

There are a number of documents that provide updated information on vapor intrusion.

Implementation Memo No. 22 and a fact sheet on TCE will be released in the Site Register next week.

Consider requesting assistance from the State Health Department when building occupants or other interested parties have questions on the potential health effects of TCE.

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Questions?

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