Inside CalEPA’s 2025 Vapor Intrusion Workshop: 10 Big Insights

CalEPA spearheaded a virtual vapor intrusion workshop on July 24, 2025.  There were about 300 attendees, and the workshop took place over three hours.  The four workshop PowerPoint presentations are linked here, and 10-point summary of the workshop is provided below:
 

1. Strong multi-agency collaboration – The CalEPA Vapor Intrusion Workgroup, active since 2014, continues to align State Water Board, DTSC, OEHA, and other agencies on policy, training, and technical guidance.
2. Updated guidance & training – The Supplemental Vapor Intrusion Guidance (Feb 2023) was rolled out alongside internal staff training and public video resources, with a focus on consistency and transparency.
3. Path to closure strategies – Early scoping meetings, robust conceptual site models, and timely responses to agency comments were highlighted as key to overcoming project delays.
4. California-specific data development – A major effort is underway to build a state-specific vapor intrusion attenuation factor dataset, informed by consultant, regulator, and public input.
5. Partner panel insights – Developers, advocates, and academics called for earlier regulator involvement, interim remedies, mitigation cost guidance, and more predictable permitting timelines.
6. Equity and climate considerations – Panelists stressed balancing environmental protection with housing equity and climate goals to avoid pushing development into unsafe or high-carbon areas.
7. Community-level solutions – Experts urged a shift from building-by-building fixes to broader, community-scale strategies, factoring in social dynamics that affect data collection and trust.
8. Consistent breakout session themes – Participants prioritized clearer conceptual site model expectations, more plain-language outreach in multiple languages, funding for community engagement, and consistent attenuation factor use.
9. Technical and procedural needs – There were calls for improved data accuracy, updated databases, consistent long-term monitoring approaches, and alignment between DTSC and Water Board screening levels.
10. Commitment to ongoing dialogue – Agencies pledged continued flexibility, recurring technical sessions, and integration of stakeholder feedback to improve vapor intrusion assessment and mitigation across California.

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2025-7-24 CalEPA VI Workshop Introduction.pdf
2025-7-24 CalEPA VI Workshop-Path to Closure.pdf
2025-7-24 CalEPA VI Workshop-VI Attenuation Factor Database.pdf
2025-7-24 CalEPA VI Workshop-VI Partner Panel Presentations.pdf

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About Matt Winefield
Matt  Winefield is an environmental engineer–turned–brownfield investor and the founder of Winefield & Associates. For 30‑plus years he has transformed contaminated, blighted sites into profitable infill assets through cost‑conscious remediation, creative agency negotiations, and third‑party cost‑recovery strategies. Matt partners with investors who see hidden value where others see risk. 

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