Passive Groundwater Sampling and Regulatory Compliance: What You Need to Know
A significant consideration when evaluating passive sampling on your projects centers around the regulatory approval process. Everyone we talk to wants to know if regulators will approve passive sampling. What do regulators require when considering passive sampling? And how do various jurisdictions vary?
In the 25+ years since the USGS first introduced passive groundwater sampling, thousands of projects across the United States have transitioned to passive sampling. Each year, many projects are approved to transition to passive sampling by regional and state regulators across numerous different agencies. However, there are many individual people who oversee monitoring plans, each with their own background and experience, and some of these regulators may be unfamiliar with passive sampling and hesitant to change sampling methods without more information. We’ll explore the various Federal and State regulations with regards to passive sampling acceptance and provide tips on how to pursue regulatory approval for your sites.
· Federal Regulations Governing Groundwater Sampling
· State Regulations and Passive Sampling Acceptance
· What You Should Consider First
· How To Approach Regulatory Approval
Federal Regulations Governing Groundwater Sampling
At the Federal level, there are three main considerations.
Federally Mandated MCL’s
The EPA determines the baseline for Maximum Contaminant Levels (MCLs) to regulate the presence of a variety of contaminants. These standards are designed to protect public health by setting the highest permissible concentration of a contaminant in water delivered to users.
MCLs are determined based on potential health risks, the feasibility of detection and removal, and cost considerations.
It's important to note that while MCLs apply to public water systems, they also serve as critical benchmarks in groundwater sampling, especially when assessing potential impacts on drinking water sources.
There may be specific monitoring program guidelines for different industries, for example:
Solid Waste: Title 40 of the Code of Federal Regulations (CFR) Part 258, Subpart E outlines the specific contaminants and MCL’s that Municipal Solid Waste Landfills must sample.
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA/Superfund)
CERCLA is the EPA’s federal program for cleaning up abandoned contaminated sites.
Groundwater monitoring at contaminated sites must provide defensible, representative data. Sampling methods on Superfund sites are generally decided by a combination of EPA oversight, combined with local state agency guidelines.
Passive groundwater samplers have been approved for use on Superfund sites in every region of the EPA, but approval often depends on an individual’s discretion.
Ultimately, approval is case-dependent and may require validation when proposed for use on a site with regulators that are not familiar with passive sampling. Sampling plans are often approved by regulators without exposure to passive sampling after validation testing of the passive method against the traditional sampling method.
In 2024, two PFAS, PFOA and PFOS, were added to the list of CERCLA hazardous substances. This, combined with increased emphasis on sustainability in sampling technology, bodes well for increased acceptance of passive sampling.
Resource Conservation and Recovery Act (RCRA)
At the heart of RCRA’s groundwater requirements is a commitment to early detection and long-term oversight—mandating facilities to implement EPA-approved sampling methodologies to assess contamination risks accurately.
Like the Superfund Program, passive groundwater samplers have been approved for use on RCRA sites in every region of the EPA. With no explicit approval under EPA’s SW-846 method compendium, passive sampling requires regulator buy-in before it can be incorporated into compliance programs. This buy in may be at the regulatory agency’s discretion, so if there is familiarity and a positive history with passive sampling, there may be little to no additional validation needed. However, some individuals and agencies may require site-specific validation, especially when they have not been exposed to passive sampling.
The key challenge is proving data equivalency—demonstrating that passive samplers provide results comparable to traditional techniques while maintaining regulatory defensibility. Sampling plans are often approved by regulators without exposure to passive sampling after validation testing of the passive method against the traditional sampling method.
State-Level Regulations and Passive Sampling Acceptance
Many contaminated sites fall outside of federal programs and many states have additional requirements for specific industries or sources of contamination
States have the authority to be stricter on MCL’s and can require more frequent monitoring than is laid out in federal regulations. The good news is that passive samplers are used on groundwater monitoring programs in every state in the US.
Many state regulators are familiar with passive sampling and may approve passive sampling on a case-by-case basis, but others may require comparison to traditional methods such as low-flow before approval.
Examples of State Regulatory Approaches
While acceptance of passive samplers on monitoring projects almost always comes down to the individual regulator and agency that oversees a site, some states have included it in their sampling plan. The below list is not exhaustive, so contact EON for questions regarding how your state regulators approach passive sampling.
New Jersey
Passive Samplers are included in New Jersey DEP’s Field Sampling Procedures Manual and are an established sampling method throughout the state.
California
California actively integrates passive sampling into state programs, including water quality monitoring and Superfund compliance, with documented pilot studies and white papers supporting its use. The regional water boards throughout the state operate on a case-by-case basis, generally dependent on a regulator’s familiarity.
Kansas
Kansas actively integrates and recommends passive samplers, specifically the HydraSleeve, into monitoring programs.
The Kansas DHE - Solid Waste Permits Section conducted a study of HydraSleeves used for sampling at landfill groundwater monitoring programs. The study concluded that HydraSleeves produced accurate results and should be approved for sampling.
What To Consider Before Using Passive Sampling
Before deciding to pursue regulatory approval for passive sampling on a site, make sure you’ve done the due diligence to ensure it’s a viable site. When introducing a new sampling method, it is helpful to list the project objectives and decision criteria. Here are some diagnostic questions to ask yourself, and EON’s team of experts can help every step of the way:
· Is this a site assessment that requires sampling for a large list of contaminants at low lab reporting limits?
· Do my monitoring wells provide enough representative water column to support my volume requirements?
· Is it a long-term monitoring project with the focus on whether Maximum Reporting Limits (MCLs) are exceeded?
· Is this an active remediation site looking at the remediation efficiency?
· Perhaps this is a site working toward eventual closure and contaminant concentration trends?
· Are there contaminants requiring special sampling efforts?
How to Approach Regulatory Approval at Federal, State, and Local Levels
If the site is a good candidate for passive sampling, it’s time to discuss passive sampling with your regulator before transitioning your sampling plan.
First, identify whether passive sampling is already accepted at similar project sites (e.g., RCRA sites, Superfund projects).
Next, engage with regulators to understand their stance on passive methods. They may or may not be aware of passive sampling as an accepted method. This understanding will help you develop an approach that matches their point of view.
Provide your regulators with scientific literature and case studies supporting passive sampling’s effectiveness compared to their accepted methods. Case studies or comparisons from similar projects can show where passive sampling was proposed, tested, and used for similar applications.
Your regulator may require that you conduct a side-by-side comparison with a currently accepted method. We’ve helped dozens of companies successfully conduct these comparisons and gain regulator approval.
We can help you throughout this process. Book a call and we’ll explain how.
Future Trends in Passive Sampling Regulation
· EPA is researching passive methods for future SW-846 inclusion.
· There is growing state-level acceptance in sustainability-focused programs.
· PFAS and other emerging contaminants may drive increased passive sampling adoption.
Need help navigating passive sampling regulations? Contact our team for expert guidance on regulatory compliance and passive groundwater sampling solutions.
The Complete Guide to Passive Diffusion Samplers
This month, we look at Passive Diffusion Bags (PDBs) and take a deeper dive into how they work, when to use them, and what you need to know before choosing them for your projects.
Passive diffusion bags (PDBs) have become an industry standard. As pioneers in this technology, EON Products offers a comprehensive line of PDBs designed to meet diverse monitoring needs while maximizing efficiency and data quality.
Understanding Your Options
EON's passive sampling technology comes in three specialized varieties:
The Equilibrator™ (Standard PDB)
· Specifically designed for VOC sampling
· Perfect for sites where VOCs are the primary contaminants of concern
· Ideal for monitoring chlorinated solvents (including PCE, TCE, and DCE) and BTEX compounds
· Available pre-filled with deionized water or field-fillable
Dual Membrane PDB™ (DMPDB)
· Enhanced capability to sample nearly any dissolved compound
· Suitable for metals, SVOCs, and emerging contaminants like 1,4-dioxane
· It uses two semi-permeable membranes of different porosity
· Maintains the simplicity of passive sampling while expanding applications
DMPDB for PFAS
· Specially designed with HDPE materials for PFAS sampling
· Ensures no cross-contamination from sampling materials
· Provides representative samples of these emerging contaminants
How the Technology Works
These innovative samplers operate on a straightforward scientific principle: molecular diffusion. Once deployed in a monitoring well, contaminants naturally move from areas of higher concentration to lower concentration through the sampler's membrane pores. After a 2-3 week equilibration period, the sampler provides a time-weighted average of groundwater conditions.
Regulatory Acceptance
PDBs have gained widespread regulatory acceptance, supported by extensive research from organizations including the USGS, EPA, and Interstate Technology & Regulatory Council (ITRC). This documented history of successful use provides confidence in data quality and regulatory compliance.
Practical Benefits for Your Team
For Project Managers:
· Significant cost savings through reduced field time and equipment needs
· Regulatory acceptance backed by USGS, EPA, and ITRC documentation
· Consistent, reliable data quality for confident decision-making
· Simplified planning and scheduling of sampling events
For Field Technicians:
· No purging or parameter stabilization required
· Minimal equipment to transport and maintain
· Simple deployment and retrieval process
· Reduced physical demands compared to traditional sampling methods
Making the Right Choice
When selecting a passive sampler, consider the following:
1. Target contaminants (VOCs only vs. broader range of compounds)
2. Required sample volume (typically up to 1L per sampler)
3. Well specifications (diameter, screen length)
4. Sampling frequency and program duration
With over two decades of proven performance in the field, EON's passive diffusion samplers offer a scientifically sound approach to groundwater monitoring that saves time and resources without compromising data quality.
Ready to optimize your groundwater monitoring program? Contact our team to determine which passive sampling solution best fits your project requirements.
Customer Success Stories
Ryan Nanny's team from Arcadis implemented passive sampling on an oil & gas site in New Mexico and achieved striking results.
The change resulted in annual cost savings of $15,000 - $20,000 and reduced the number of days for the sampling event from 20 down to 8 (60%). In addition to the cost and time savings Ryan said the change eliminated IDW, made the process easier, safer, and improved data quality due to lower turbidity among other factors.
Ryan also gave a great shout-out to the service levels our team strives to fulfill:
“The sales team at EON are the nicest and most helpful supplier I have ever worked with."
If you're ready to find out how passive sampling can benefit your project, schedule a free consultation with one of our experts.