Crews searching for buried explosives at a Formerly Used Defense Site (FUDS) in northwest Washington D.C.’s Spring Valley neighborhood are using the latest in advanced technology to reduce unnecessary impacts to private property and to improve efficiency.
Historically, crews doing this sort of work end up digging hundreds if not thousands of pieces of scrap metal and other items referred to as cultural debris, rather than buried munitions. These “false digs” are pretty common at FUDS across the country — and Spring Valley is no exception.
During World War I, the Spring Valley site was known as the American University Experiment Station (AUES) and was the site of America’s initial research into chemical warfare. Part of that included storing, testing and firing explosive rounds in an area that has since developed into a community of more than 1,000 private homes.
This is why crews are using the latest technology to reduce the amount of false digs.
“It’s been over 100 years since the Army finished its research and training in what is now the Spring Valley Formerly Used Defense Site, and that’s a lot of time for all kinds of metallic objects to have shown up and become buried in addition to any munition items that may remain from past military use,” said U.S. Army Corps of Engineers Project Manager Alex Zahl. “Our teams in the field now are using the latest in geophysical mapping technology to classify subsurface metallic anomalies to say ‘yes, that’s a munitions item’ or ‘no, that’s construction debris or a horseshoe.’”
The process, known as Advanced Geophysical Classification, or AGC, was recently accredited by the Department of Defense and the EPA to be deployed during munitions investigations. While the geophysical principle involved is not necessarily new, the use of the newly developed smaller equipment and the AGC process provides clear improvements for a site like Spring Valley. Previously, the technology has been larger and less maneuverable, and primarily used at FUDS with more open space.
With advancements in the technology and the equipment getting smaller, Baltimore District collaborated with Naval Research Laboratories and to conduct a pilot study at three Spring Valley properties to determine how this technology might work in a residential setting. This meant not only working with different topography and surfaces like decks and driveways, but also addressing greater signal interference from things like buried utilities and foundations.
While the U.S. Army Corps of Engineers has worked to address immediate hazards in Spring Valley over the past several years, the recently completed Spring Valley Site-Wide Decision Document identifies 92 private properties and 12 government-owned parcels where further investigation to remove potentially buried explosive hazards is recommended based on historical research and site investigation.
With the pilot study proving the new technology could be effective in a neighborhood setting before that larger Site-Wide effort began, the team was able to incorporate the AGC technology going forward.
“We were lucky enough that as this technology was coming on the market, we were planning to conduct our investigation into these properties to remove any potential buried munitions,” said Zahl.
AGC involves state-of-the-art electromagnetic survey tools that not only locate buried metallic objects, but also identify which anomalies are buried intact munitions.
These tools create an electromagnetic pulse over an anomaly and listen for the items’ ‘decay curve,’ which is based on things like the size, shape and thickness of the buried item. Different items have unique decay curves. AGC files contain an extensive library of all the standard ordnance used by the Department of Defense, and specialty devices developed at the AUES were added prior to work in Spring Valley.
The decay curves of detected buried metallic anomalies are compared with the files in the AGC library to identify the anomalies and help determine whether they are likely to be a munition item or cultural debris.
There are many benefits to reducing the amount of false digs when doing munitions cleanups.
It reduces the impacts to private properties, where crews are only able to work with the permission of homeowners.
It also reduces the amount of restoration needed since every hole dug in a yard, patio, or driveway has to be restored whether munitions items were discovered or not. These restoration efforts take time and can be costly.
Reducing the amount of digs also saves time, which in turn can save money.
“While we’re able to save time and money by conducting fewer digs, we will not compromise safety and are still digging if there’s uncertainty,” said Zahl. “We’re doing a lot fewer false digs while still addressing the potential hazards we’re here to address.”
The U.S. Army Corps of Engineers expects to be done with this munitions investigation in 2020, pending permission from the property owners.