How Citadel EHS Secured Rare NFA Letters for VOC Sites in California: A Practical Path to Closure11/24/2025
Brownfield Braintrust Podcast
California regulators have dramatically reduced the number of No Further Action letters issued for contaminated properties over the past several years. Closures for sites impacted by chlorinated solvents such as PCE, TCE, and benzene have become increasingly difficult, especially under the updated 2023 CalEPA vapor intrusion guidance. In this new episode of the Brownfield Braintrust podcast, Matt Winefield talks with Greg McIver of Citadel EHS, one of the few consultants in California that has successfully obtained No Further Action letters for VOC sites in 2024 and 2025. Their discussion provides rare insight into what still works, what regulators expect, and how a property can realistically move toward closure today. This blog post summarizes the key lessons and case studies from their conversation and includes the embedded episode so readers can listen in full.
Why California Closures Have Declined
Winefield & Associates reviewed statewide NFA data earlier this year and found a 50 percent reduction in closures between 2017 and 2023. Vapor intrusion concerns, expanded screening requirements, and stricter risk evaluations have contributed to this decline. Regulators now require more data, more lines of evidence, and more certainty before approving closure, which prolongs investigation/remediation timelines and increases costs. Many owners and brokers underestimate the effort required to reach closure under today’s rules. This episode explains how closure is still possible when the process is managed strategically from the start. Who Citadel EHS Is and Why Their Success Matters Citadel EHS is a leading environmental consulting firm in California with expertise in vapor intrusion, chlorinated solvent remediation, toxicology, sub slab depressurization, and remedial design. Greg McIver, Principal Scientist and Co Practice Lead, brings 25 years of experience managing complex VOC sites. Citadel received multiple No Further Action letters for VOC impacted properties in 2024 and 2025. These recent closures provide a practical roadmap for others navigating the same challenges. The Most Important Factor: Stakeholder Buy In Greg explains that successful closures start with coordinated involvement from: • The regulatory agency • The environmental consultant • The property owner or developer • The legal and technical team when needed Instead of working in isolation and submitting reports at the end, Citadel collaborates closely with regulators from the outset. They confirm data gaps, agree on next steps, and shape the conceptual site model with the case manager involved. This approach reduces surprises and builds a shared understanding of the path to closure. Using the Low Threat Closure Framework for Solvent Sites Citadel uses the San Francisco Bay Regional Water Board’s 2009 Low Threat Closure Criteria for chlorinated solvents as an internal guide. Even when a regional board does not formally adopt this guidance, the structure helps consultants prepare a logical, evidence-based closure argument. Key criteria include: • Source removal • Delineation of soil vapor and groundwater impacts • Evaluation of sewer pathways • Demonstration of long-term protectiveness • Assurance that groundwater concentrations will reach water quality objectives • Documentation of multiple lines of evidence for vapor intrusion This consistent framework is one of the strongest tools for navigating closure under today’s standards. Case Study 1: Dry Cleaner Site in San Mateo County Citadel obtained a No Further Action letter for this site in October 2025. The property had legacy PCE releases from a former dry cleaning operation. Key achievements include: • Groundwater PCE concentrations decreased to 32.9 micrograms per liter • Soil vapor concentrations decreased from 1950 to 612 micrograms per cubic meter • Indoor air remained below commercial screening levels • Contaminated soil and sewer line impacts were excavated • Zero valent iron was injected to accelerate attenuation • No post NFA long term indoor air monitoring was required • A commercial use land use covenant was recorded This case demonstrated that closure is possible even with soil vapor concentrations above screening values, provided indoor air risk is sufficiently controlled. Case Study 2: Central Valley Dry Cleaner with High VOC Impacts A second No Further Action letter was issued by the Central Valley Regional Water Board in October 2025. This property had two former dry cleaners and much higher chlorinated solvent concentrations than Case Study 1. Key results: • Historical groundwater PCE reached 8,000 micrograms per liter • The highest well PCE concentration at closure measured 88.3 micrograms per liter • All other wells were below the 5 micrograms per liter drinking water standard • Soil vapor dropped from 900,000 to 1.77 micrograms per cubic meter • Vapor extraction, injections, and groundwater treatment had been used previously • Citadel shut down treatment systems that were no longer effective • Multiple lines of evidence supported continued natural attenuation • Post closure groundwater trending was the only requirement This case shows how strategic reassessment and focused sampling can replace years of unnecessary treatment system operations. What These Closures Tell Us About Costs Many brokers and property owners assume a dry cleaner cleanup costs in the neighborhood of $100,000 (“Just dig it out of there.”). The real numbers are far more daunting. VOC sites regularly require: • Several hundred thousand dollars when limited excavation or injections are enough • More than one million dollars when vapor extraction or groundwater treatment is involved • Higher budgets when two or more operators contributed to a comingled release Accurate cost modeling helps reduce uncertainty during brownfield transactions. Citadel uses expected, optimistic, and pessimistic cost scenarios to help clients make informed decisions. Major Lessons from Citadel’s Closure Strategy The episode highlights several takeaways for anyone evaluating or remediating VOC sites: • Collaborative regulators make closure achievable when engaged early • A complete conceptual site model prevents expensive surprises • The low threat closure framework remains one of the best planning tools • Treatment systems should be shut down when they no longer remove mass • Multiple lines of evidence are essential for demonstrating protectiveness • Thorough groundwater data reduces risk premiums for buyers and sellers • Closure is possible even with residual VOCs when indoor air is safe These lessons reflect what is working now across California. Listen to the Full Conversation The full discussion between Matt Winefield and Greg McIver offers detailed explanations, regulatory insights, and a rare look at recent NFA letters for VOC impacted sites. About Citadel EHS Citadel EHS is a market-leading environmental consulting firm specializing in vapor intrusion, toxicology, site assessment, remedial design, and environmental health and safety solutions. Greg McIver Principal Scientist & Practice Leader, Engineering & Environmental Sciences Email: [email protected] Website: https://citadelehs.com LinkedIn: Greg McIver
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