Vapor intrusion: 2019 changes to cleanup levels and screening levels

If you’re evaluating vapor intrusion at your contaminated cleanup site, you can still use the October 2009 Draft: Guidance for evaluating soil vapor intrusion in Washington State: Investigation and remedial action but Table B-1 in Appendix B of the 2009 guidance is out of date and should not be used.

Since 2016, we've issued four vapor intrusion implementation memos that supersede or supplement parts of the 2009 guidance:

  1. Memo No. 14: Updated process for initially assessing the potential for petroleum vapor intrusion (2016)
  2. Memo No. 18: Petroleum vapor intrusion (PVI): Updated screening levels, cleanup levels and assessing PVI threats to future buildings (2018)
  3. Memo No. 21: Frequently asked questions (FAQs) regarding vapor intrusion (VI) and Ecology's 2009 draft VI guidance (2018)
  4. Memo No. 22: Vapor intrusion (VI) investigations and short-term trichloroethene (TCE) toxicity (October 2019)

In 2019, we updated the toxicity values for calculating indoor air cleanup levels, based on recent toxicological information. You'll find these changes in the 2019 update of Cleanup Levels and Risk Calculation (CLARC). Read about all of CLARC's changes in Latest news.