Contributed by Matt Ebbert, Senior Geologist, PPM Consultants
Environmental regulations serve an important purpose: protecting human health and the environment from harmful exposures. However, in many cases, regulatory agencies have moved beyond site-specific, risk-based decision making and instead require remediation simply because a chemical is detected above an increasingly conservative screening level or because default exposure assumptions are applied without considering actual site conditions. This approach can result in enormous expenditures with little or no corresponding environmental benefit.
The presence of a constituent in soil or groundwater should trigger the right questions:
- Is there a complete exposure pathway?
- Who are the receptors?
- Is groundwater being used, or reasonably likely to be used, as drinking water?
- Is the plume stable, shrinking, or migrating?
Those questions are often more important than the detection itself.
Groundwater contamination is a prime example. At many industrial sites, responsible parties are required to spend hundreds of thousands or even millions of dollars treating groundwater that poses little or no realistic risk to human receptors or ecological systems. In some cases, regulators mandate remediation of groundwater containing metals such as chromium, iron, or magnesium even when the groundwater is not used for drinking water, does not discharge to sensitive surface waters, and presents no vapor intrusion, inhalation, or direct-contact exposure pathway.
In our experience, the issue is rarely as simple as “detected equals dangerous” or “above a screening level equals active remediation.” Screening levels are useful tools, but they should not replace a site-specific understanding of actual risk. Even when regulators apply risk-based cleanup standards, the assumptions used to calculate those standards are often highly conservative. Many risk models assume that an individual resides at a property for decades, consumes contaminated groundwater every day, and is exposed continuously throughout that period. Residential exposure scenarios commonly assume a 70-year lifetime and daily groundwater ingestion rates that may bear little resemblance to actual site conditions. Cancer risk calculations are frequently based on an incremental lifetime cancer risk of one in one million (1 x 10⁻⁶) or one in one hundred thousand (1 x 10⁻5) and reflect a highly protective regulatory approach. That conservative approach is appropriate in many circumstances, especially when site information is limited or when sensitive receptors may be present. The concern arises when conservative default assumptions are carried forward after site data show that the assumed exposure scenario does not match actual property use, groundwater use, receptor locations, or hydrogeologic conditions. EPA’s Regional Screening Levels are useful risk-based screening tools, but EPA cautions that RSLs are not cleanup standards and should not automatically be used as cleanup levels. ASTM’s Standard Guide for Risk-Based Corrective Action also recognizes that corrective action decisions should account for the characteristics and risks of the specific site.
The issue is not whether contamination should be addressed when it threatens public health. Few would argue against cleaning up groundwater that impacts drinking water supplies or creates significant exposure pathways. The problem arises when remediation is required solely because analytical results exceed a regulatory threshold derived from conservative assumptions, regardless of whether an actual exposure pathway exists. This is where a well-developed conceptual site model becomes critical. A consultant’s job is not just to identify a problem, but to help the client and regulator understand what the data mean for the decision in front of them. The source, affected media, groundwater flow direction, receptor locations, land use, vapor intrusion potential, and future property use all matter. PPM’s article on Environmental Geology and the Surprises Beneath the Surface makes a similar point: site decisions are only as good as the understanding of what is happening beneath the surface.
For example, iron and magnesium are naturally occurring elements and are commonly consumed as dietary supplements. Yet facilities can face substantial remediation obligations when these constituents are detected at elevated concentrations in groundwater, even when no human or ecological receptors are affected. Similarly, low concentrations of petroleum constituents may trigger long-term monitoring and treatment programs despite presenting negligible risk under actual site conditions. That does not mean these constituents should be dismissed without evaluation. It means they should be evaluated in context. Background conditions, geochemistry, plume behavior, exposure pathways, and actual receptor risk should guide the response.
The consequence is that limited environmental resources are diverted away from sites that present genuine threats. Companies and property owners spend significant sums on treatment systems, monitoring wells, and reporting requirements that may achieve little measurable environmental improvement. Additionally, state regulatory agencies that are already burdened with heavy workloads must devote valuable staff time to reviewing and managing these sites. Those resources could instead be directed toward contaminated drinking water supplies, aging infrastructure, or sites with demonstrable risks to human health and the environment. Unnecessary remediation can also affect redevelopment, financing, transactions, and facility operations. A site that remains open for years because cleanup goals are disconnected from actual exposure risk may create business uncertainty without providing a meaningful environmental benefit. PPM has discussed this same practical concern in the context of UST risk-based closure, where better risk-based oversight can help move appropriate sites toward closure without weakening environmental protection.
Environmental regulation is most effective when it is grounded in sound science, realistic exposure assumptions, and actual risk. Contamination alone does not equal danger. Remediation should be required when contaminants create a credible threat to people or the environment—not simply because modern analytical methods can detect them or because highly conservative models predict a theoretical risk that may never occur. The same principle applies when evaluating vapor intrusion and redevelopment risk. Where a vapor pathway is present, the issue should be evaluated early and carefully. Where the pathway is incomplete, the remedy should reflect that reality. PPM’s article on vapor intrusion risk highlights why pathway evaluation, timing, and conceptual site models matter for redevelopment and due diligence projects.
Before committing to active remediation, owners, operators, lenders, developers, and attorneys should ask several practical questions:
- Is there a complete exposure pathway?
- Who are the current and reasonably anticipated future receptors?
- Is groundwater used, or reasonably expected to be used, as drinking water?
- Is the plume stable, shrinking, or migrating?
- Are vapor intrusion, surface water, utility corridor, or direct-contact pathways present?
- Would active remediation create a measurable reduction in risk?
These questions do not weaken environmental protection. They strengthen it by making sure cleanup decisions are tied to actual site conditions and meaningful outcomes. That is also the practical question raised by PPM’s discussion of what “clean enough” means in environmental compliance: cleanup decisions should be defensible, protective, and connected to how the property is used.
At PPM Consultants, we help clients develop technically sound, risk-based remediation strategies that protect human health and the environment while avoiding unnecessary expenditures. By working collaboratively with regulators and stakeholders, we strive to ensure that cleanup decisions are based on actual site conditions, realistic exposure scenarios, and meaningful environmental outcomes. Please reach out to me at 205-919-0169 if you would like to discuss one of your ongoing remediation projects.
PPM’s risk-based remediation and corrective action support can include soil and groundwater assessment, soil and groundwater remediation, risk assessments, vapor intrusion assessment and remediation, corrective action planning, regulatory coordination, and closure strategy development. Our goal is to help clients spend cleanup dollars where they make the greatest difference.
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