The LUST community has made tremendous strides in cleaning up releases from UST systems, with more than 500,000 cleanups completed and thousands more completed each year. Due to advances in science and cleanup technologies, we’ve increased our understanding and our ability to clean up LUST releases. However, we still have nearly 60,000 confirmed releases to address, and more than 4,000 new releases are reported each year. We regularly hear about innovative approaches and emerging technologies to address this backlog of LUST sites. With than in mind, I want to share some recent work EPA completed regarding high-resolution site characterization (HRSC).
There are many types of HRSC for use in a wide variety of contaminants and geologic settings. EPA describes HRSC as strategies and techniques that use scale-appropriate measurements and sample density to define contaminant distributions, and the physical context in which they reside, with greater certainty, supporting faster and more effective site cleanup. In other words, more data is better. We decided to study the applicability of HRSC to LUST sites, focusing on driven probe, direct sensing investigations, which have been the most widely used HRSC techniques used with UST releases.
EPA has been encouraging the use of HRSC at large, complex RCRA and Superfund sites to help focus site investigations and improve cleanups. HRSC techniques identify the contaminant mass in soil and groundwater, including Light Non-Aqueous Phase Liquid (LNAPL). HRSC provides a detailed geologic profile of soil zones that are storing and transmitting contaminants. In contrast, HRSC use at LUST sites has not been widespread. A few states are using HRSC at some of their UST release investigations, but most petroleum UST release sites continue to be assessed using traditional monitoring well investigation techniques. Our study examined the potential utility, benefits, and cost impacts of using HRSC at various types of LUST sites.
ITRC’s guides for LNAPL (LNAPL-3), petroleum vapor intrusion, advanced site characterization, and fractured
high-resolution technologies and sampling approaches in detail.
In 2022, EPA worked with its economics consultant, Industrial Economics, Inc., on a study called High Resolution Site Characterization (HRSC) at Petroleum Underground Storage Tank Release Sites – Applicability, Benefits, and Costs. The study goals were to:
1) Quantify the costs and benefits of HRSC investigations and their impacts on overall project costs and time at petroleum UST release sites,
2) Identify situations where HRSC is likely to provide a benefit in site characterization compared to the use of only traditional, non-HRSC methods at petroleum UST release sites, and
3) Identify barriers to more widespread use of HRSC.
The study results indicate that in comparison to traditional boring and monitoring well investigations at petroleum UST release sites, HRSC provides the following benefits:
Experts interviewed as part of the EPA 2022 study concluded that average costs of HRSC investigations at typical petroleum UST release sites are $36,679 for a 3-day investigation, and $49,550 for a 5-day investigation.
For three common petroleum UST release scenarios the expert panel concluded HRSC could save on average 9% to 19% in project costs — HRSC would sometimes add 20% to overall project costs on the typical UST release, and on other sites save 40%. On average HRSC would save 9% on overall project costs at typical UST releases. The experts concluded that HRSC would always save costs when investigating catastrophic releases and stalled remediation projects.
The experts in the study agreed that HRSC also saves time in the remedial process. Three experts analyzed three UST release scenarios, with and without HRSC and concluded that HRSC can save 3.3 years of a typical 10-year remediation project, 3.7 years off catastrophic release cleanups, which typically take 9 years to complete, and 8.5 years off 33-year timeframe for sites that are not progressing to their cleanup goals.
States, consultants, and practitioners identified many situations where HRSC was useful in developing the conceptual site model when collecting additional information was necessary. The study participants evaluated 15 different LUST site scenarios. All scenarios had at least one person support HRSC use and there was near unanimous support for using HRSC in 8 of the 15 scenarios.
*Scenarios with near unanimous support for using HRSC.
Despite potential benefits, barriers to HRSC use at LUST sites remain. In the study, experts identified a couple of technical barriers. There was widespread recognition that HRSC would not be used at sites where there were no significant data gaps – such as a “straightforward” UST closure where only limited contamination was identified and cleaned up during the excavation work. Also, uncooperative consolidated geology is a fundamental barrier to the use of direct sensing HRSC tools.
Beyond those two technical barriers, administrative and economic barriers remain that prevent wider HRSC use and application. LUST site practitioners and experts identified a number of barriers to wider use of HRSC to investigate UST releases, but there was little agreement on which barriers were most important. HRSC practitioners rated the lack of state fund reimbursement schedules for HRSC as a reason for not using HRSC, while state regulators pointed to the providers not proposing HRSC investigations as a significant barrier. Other barriers included the lack of guidance on when to use HRSC on petroleum UST release sites and on how to incorporate HRSC data into corrective action decisions. Some barriers seem to be “chicken or egg” situations. Overcoming these barriers to reap the many benefits of HRSC at LUST sites will require creativity and collective effort.
The results of our HRSC study can help inform site owners and other stakeholders on the best use cases for HRSC in site cleanups, including where it is most cost effective, and where it may inform selection of effective remediation techniques. This study points to an opportunity to improve environmental protection and to save time and money by expanding HRSC use at petroleum UST release sites. We’re going to work with our partners to spread the word about the benefits of HRSC at LUST sites. In addition, we plan to develop guidance for use of HRSC at federal-lead LUST cleanups in Indian Country.
Below you will find an article from our state partners in Michigan regarding use of HRSC at a LUST cleanup site. Have you also used HRSC in your state or at your LUST site? If so, I ask you to share your experiences with others. In particular, you may wish to contact EPA staff in your region, or Alex Wardle or Tom Schruben at our headquarters office.