Contributed by Trey Hess P.E., Director, Brownfields & Economic Development
It’s that time of year—when new year’s resolutions still linger and the urge to tidy up feels like turning a fresh page. As I was doing some spring cleaning in my office the other day, I came across the following memorandum tucked in a stack of old project files:
Memorandum
TO: Jerry Banks, Chief of the Groundwater Assessment and Remediation Division
FROM: Charles Chisolm, Chief of the Office of Pollution Control
SUBJECT: Consistent Cleanup Standards Between UST and State Uncontrolled Sites
DATE: December 28, 1994
Now that you have inherited this project, please advise of when it will be completed. Also, I will be pleased to help whenever I am needed.
[END OF MEMO]Historical Context and Programmatic Evolution
In the early years of the UST program in Mississippi, the focus was on preventing and remediating leaks of petroleum products that posed a threat to groundwater. The 18 mg/L Total BTEX threshold likely emerged during this time, influenced by operational needs and prevailing understandings of petroleum hydrocarbon behavior. Although no official documentation from the late 1980s or early 1990s defines how this value was derived, environmental professionals at the time leaned heavily on concepts such as effective solubility—the collective concentration of individual BTEX components in water when in contact with light non-aqueous phase liquids (LNAPL). This standard was likely considered a practical indicator that free-phase product may be present or that sufficient contaminant mass existed to warrant action.
On the other side of the agency, the Uncontrolled Sites Program had been treating all groundwater as a drinking water resource, with no mechanism for “Activity and Use Limitations” on that groundwater. Consequently, the Uncontrolled Sites Section (USS) was requiring cleanups to drinking water standards. In the case of benzene, that standard was 5 µg/L. To illustrate the disparity, consider a gas station on one side of the street with underground storage tanks (USTs) that could receive a “No Further Action” determination despite having 12,000 µg/L of benzene. Meanwhile, directly across the street, a site with an aboveground storage tank (AST) containing just 100 µg/L of benzene might be required to undergo extensive—and costly—remediation. Same agency, same gasoline, same site conditions, yet completely different cleanup standards. It’s hard to believe, but that’s how things were.
As Mississippi’s environmental programs matured, a growing recognition emerged around the limitations of one-size-fits-all standards. In 1998, the Mississippi Brownfields Voluntary Cleanup and Redevelopment Act was passed to encourage the cleanup and reuse of contaminated properties by offering liability protection and enabling risk-based corrective action—particularly through the use of institutional and engineering controls.
At that time, I was appointed the first Brownfield Section Chief for MDEQ; and in 2002, we promulgated regulations for the implementation of the Mississippi Brownfield Program. In 2005, under my direction as State Brownfield Coordinator, we launched an effort to implement a “One Cleanup Program.” This was a direct response to the mandate in Charles Chisolm’s 1994 memo and was designed to unify cleanup philosophies across the UST, Uncontrolled Sites, and Brownfield programs.
Recognizing the statutory authority needed to implement institutional and engineering controls across programs, we worked with the National Conference of Commissioners on Uniform State Laws (NCCUSL) on legislation. In 2008, the Mississippi Uniform Environmental Covenants Act (MUECA) was established. Based on the Uniform Environmental Covenants Act (UECA), it empowered MDEQ to implement institutional controls in the form of environmental covenants across all cleanup programs. Since that time, MUECA has been used at Brownfield Agreement Sites, Voluntary Evaluation Program (VEP) sites, Uncontrolled Sites, RCRA Corrective Action Sites, and even Superfund sites. This was one step closer to a true “One Cleanup Program” for MDEQ.
The Three-Tiered Brownfield Approach
Mississippi’s Brownfields Program embraces a three-tiered risk-based approach, accounting for site-specific conditions, future land use, and exposure pathways. The framework allows for institutional controls, such as environmental covenants, and engineering controls to manage residual risk at sites targeted for redevelopment.
Importantly, the Brownfields Program is forward-looking. It focuses on activity and use restrictions combined with risk-based cleanups that allow for planned future land uses. In contrast, the UST program’s issuance of a “No Further Action” (NFA) letter is typically based on current land use—usually an operating service station—and BTEX cleanup levels apply in the absence of sensitive receptors.
Why Risk-Based Integration Matters
During our Brownfield efforts, we worked closely with the Uncontrolled Sites Program to apply Brownfields Risk Evaluation Procedures across non-UST legacy sites. This cross-program consistency helped reinforce the importance of risk-based decision-making over blanket numeric standards. A notable case study was the Factory Stores of America site, where both Total BTEX and individual constituent concentrations were evaluated relative to specific receptors and redevelopment scenarios. It demonstrated that flexibility and protection of public health need not be mutually exclusive. Ultimately, the question was whether the UST Program would require delineation to below the 18 mg/L Total BTEX level or allow for a more tailored, risk-based approach.
Common Ground Among Programs
Despite differences in evaluation methods, all three programs—UST, Uncontrolled Sites, and Brownfields—require the removal of free product. This shared requirement underscores the importance of addressing contaminant mass regardless of site classification.
Only the Uncontrolled Sites and Brownfield Programs, however, have fully embraced institutional and engineering controls as tools for closure. These controls include groundwater use restrictions, capping through soil management plans, and—when appropriate—vapor mitigation systems. Together, they enable long-term stewardship and support safe reuse of sites, even where complete contaminant removal isn’t practical.
Navigating the Regulatory Landscape
Given the nuanced differences across programs, it’s essential that property owners, developers, and municipalities engage environmental consultants who understand both the technical and regulatory dynamics of MDEQ’s programs. Understanding the difference between a UST NFA and a Brownfield Agreement can be the key to ensuring a project’s success—or its delay.
Wrap-Up
The origin of Mississippi’s 18 mg/L Total BTEX cleanup standard can be reasonably attributed to a combination of scientific inference, administrative practicality, and evolving understandings from the late 1980s and early 1990s. While it likely reflected prevailing ideas such as effective solubility, it predates modern, risk-based regulatory frameworks and doesn’t fully align with today’s scientific understanding of exposure and public health.
EPA guidance on LNAPL behavior and BTEX solubility supports the theory that the 18 mg/L level may have been selected as a conservative marker for product presence. Yet, its continued use raises questions about whether legacy assumptions are sufficient for guiding cleanup decisions in today’s more sophisticated regulatory climate.
After following up with my team here at PPM which has been a leading assessment and remediation firm in Mississippi for over thirty years, I still couldn’t quite pinpoint the true origin of the 18 mg/L Total BTEX cleanup standard. That uncertainty made us reflect on whether it’s time to modernize this foundational value with current science, exposure modeling, and policy frameworks.
And while time marches on and environmental policy evolves, it’s hard not to smile thinking back on those “glory days” at MDEQ—when regulations were written on yellow legal pads, phones had cords, and Springsteen’s anthem reminded us that sometimes, the best stories are the ones we lived firsthand. Maybe that standard’s staying power is part of its mystery.