SERDP researchers are working to collect, analyze, and translate data that will help us safely and successfully remediate underwater sites impacted by munitions and unexploded ordnance.
By Laura Mack
Munitions and unexploded ordnance (UXO) remain in rivers, lakes, and oceans from past military operations, and the Department of Defense has been working to safely remove these hazards. An accurate depiction of the seabed floor is essential for locating UXO and can be revealed using diverse technologies and research. Dr. Nina Stark, faculty in the geotechnical engineering program at Virginia Tech, is contributing critical information about seabed properties that are key to successful UXO remediation through her SERDP project.
“If you’re trying to investigate the site and find UXO, you will use acoustic methods, magnetic methods, etc. There’s a broad spectrum. But since UXOs are interacting with the seabed, that means the seabed has quite some relevance,” Dr. Stark explained.
UXOs will sit, sink, or roll on the seabed. Dr. Stark and her team are focusing on geomechanical properties of the seabed, which encompass how the seabed responds to different interactions or loads. The team is collecting data with portable free fall penetrometers (PFFP) and building a tool for users to interpret the information for remediation at underwater UXO sites.
Historically, seabed characterization has been very limited. Researchers have mostly relied upon simple qualitative descriptions, identifying the environment as sand, gravel, or mud. However, seabed conditions are typically more complex than that. If researchers misidentify the material, the UXO could become more deeply buried, thereby creating a higher risk of non-detection and greater challenges in safely remediating the site.
“You could have the same material – take mud for example. That mud could be soft, hard, or stiff, and that will determine if this UXO would sink in or not,” Dr. Stark explained. “A good example is a tidal flat or marsh. You might have locations where the ground looks the same, but in one spot you will be able to walk over it and the other spot you’re sinking knee-deep into the mud.”
Researchers have traditionally gained information about seabed properties using large seabed cone penetrometers. However, that method is not ideal for delicate habitats like UXO sites. A PFFP is shaped like a small torpedo and can be easily deployed from any vessel. PFFPs are commonly used to gather more information about the underwater environment, but their basic dataset is not immediately relevant for UXO remediation. The data would need to be sent back to experts to analyze it for specific applications. Dr. Stark wants to streamline this process so the Department of Defense can deploy this technology and quickly receive the properties needed to navigate the environment for UXO.
“We focused on translating [the data] into properties that allow us to predict: will this munition sink into the seabed? Will it scour, or will it roll around? Will a sonar be able to penetrate to a certain depth, or will the seabed practically disguise it?” said Dr. Stark.
Her team is also looking at the activity of small creatures in the seabed that can impact geomechanical properties. Though also limited in the past, this data could provide more answers for determining the exact location of UXO.
“If you could identify that a certain critter weakens the seabed at a certain time of the year, then that could explain why you have a UXO moving or sinking deeper into an area than you did at another time,” Dr. Stark said. With a better understanding of the species local to UXO sites and their patterns of behavior, researchers have better odds of predicting how UXO remediation efforts will play out.
The team conducted field experiments at three sites across different seasons to gather data with PFFPs and determine active species, population sizes, and the types of seabed activities (loosening up the soil, compacting the soil, etc.).
The final main component of the team’s project is developing a probabilistic framework to share the level of uncertainty regarding its predictions for how the seabed will interact with the UXO. This way, researchers can decide if they accept the amount of risk, or if they would prefer to collect more data before they try to remediate the site. Building this type of framework requires a big data set. In their first year, the team mostly focused on assembling a database to begin testing out the probabilistic framework.
Dr. Stark’s research is strengthening other munitions projects in real-time. Her team has assisted several SERDP performers to gather measurements at their sites to characterize the seabed. This past fall, the team visited Sequim Bay, a large site where many teams are testing, demonstrating, and validating munitions response technologies.
“A project might be testing some new sonars [to survey the site for UXO] and see that the response is better in one area than the other. Our data can assist explaining that and then take action to improve the method further,” Dr. Stark added.
Towards the end of the project, the team will determine how their data can be directly implemented into the Underwater Munitions Expert System (UNMES). Developed under another SERDP project, this computer tool also uses a probabilistic framework to predict patterns of UXO burial, migration, and exposure so that researchers can better plan and execute remediation efforts. Ideally, this system could serve as an even larger database that stores and analyzes environmental conditions gained from many different field research efforts.
This past December, Dr. Stark and her team received the 2022 SERDP Project of the Year award for collecting data that has already benefited other projects in the short-term and analyzing it to advance future remediation efforts. Dr. Stark added that the munitions response program with SERDP and ESTCP is unique in the strategic collaboration across projects, which has been key to her project’s value.
“It’s exciting to communicate with other performers. A lot of ideas come from this communication,” Dr. Stark concluded. “The concept that the data is immediately being used, that there’s an interest and people are coming to me and asking me to collect the data – that contribution is extremely rewarding.”
About SERDP & ESTCP
The Strategic Environmental Research and Development Program (SERDP) and the Environmental Security Technology Certification Program (ESTCP) harness the latest science and technology to improve the Department of Defense’s environmental performance, reduce costs, and enhance and sustain mission capabilities. The programs respond to energy and environmental technology requirements across the military services. SERDP and ESTCP are independent DoD programs managed jointly to coordinate the full spectrum of research and development efforts, from the laboratory to field demonstration and validation. For more information, visit https://www.serdp-estcp.org. Follow us on Twitter, Facebook, and LinkedIn.