ARNOLD AIR FORCE BASE, Tenn. -- Arnold Engineering Development Complex Commander Col. Jeffrey Geraghty took time April 22 during a virtual town hall to explain a key tool used in determining the who, what, when and how members of Team AEDC will return to the installation, both in the short term for operationally-urgent testing, and in the long term for a greater return to operations.
The Air Force Test Center, which AEDC is part of, uses a risk assessment matrix with the level of risk, ranging from high to negligible, determined by crossing the probability of a mishap occurring and the severity of a mishap.
The five probability categories are frequent, probable, occasional, remote and improbable. Each is assigned based upon a quantified likelihood of occurrence, with improbable being less than one in one million and frequent being greater than one in 10.
The four severity categories are catastrophic, critical, marginal and negligible.
“The ones (categories) that we’re specifically looking at for this COVID-19 crisis in terms of severity are loss of life (catastrophic) and lengthy hospital stays (critical),” Geraghty said. “Those are the two main ones that we’re really protecting against and taking care of priority number one – protecting the health of the workforce. We are making sure that we are not taking more risk of loss of life or more risk of a lengthy hospital stay than is acceptable.”
Geraghty stated a high or medium risk of loss of life is not acceptable to him, nor is a high risk of a lengthy hospital stay.
“We consider taking a medium risk of a lengthy hospital stay, unmitigated, if we can drive that unmitigated risk down,” he said.
Risks with catastrophic or critical severity are only considered a low risk if the probability of occurrence is improbable, or less than one in one million likelihood. A risk with a critical severity would be a medium risk if the probability was remote or occasional, or likelihood of occurrence between less than one in 100 but greater than one in one million.
“As we started to look at how to protect the health of workforce early in this problem more than a month ago, there are very few levers that we can use to make sure that we protect the health of the workforce; and the most powerful one we had is just keeping everyone at home and that’s the same thing that the governor did,” Geraghty said. “Just reducing the amount of human interactions is the most powerful way to get that order-of-magnitude change for the risk of death.”
Mitigation efforts to reduce the risk of hospitalization and allow team members to return to work is a focus of AEDC leadership for moving forward.
“As you might know from the Tennessee Department of Health, the hospitalization rate here in the state of Tennessee for those with the disease is about 14 percent,” Geraghty said. “So, clearly, trying to drive that risk down to somewhere closer to one in a million is not terribly easy to do, but that’s why we have so many risk mitigations in place, to make sure that we’re taking care of priority number one.”
Concerning reopening Arnold Air Force Base, headquarters of AEDC, Geraghty stated it would be a phased reopening, referencing the guidelines published by the White House.
He also shared a chart showing a rolling 14-day average of new cases comparing Tennessee and the Republic of Korea. Geraghty has been looking at the country’s response and that of a U.S. Air Force base in the country.
“This is what we’re looking for to start to reopen, is this rapid decrease,” he said while pointing to a steep section of the line representing data for the Republic of Korea.
“Here in Tennessee, we have not suffered the amount of new cases per day as they have, thankfully, in part because we have seven times fewer people, but you can see we’re also not entering that nice steep decline,” he said. “We’re kind of flattening out in our new cases per day, and we have a few blips where we add a lot of cases per day, but I would really like to see a good sharp decline in the Tennessee numbers.”
Geraghty also spoke about the infection rate per 10,000 people, noting the importance of infection rate when making calculations to assess risk.
“How many people around you, in your communities, are infected with this disease?” he said. “In Tennessee we’re climbing through 10 people per 10,000, so about 1 in every 1,000 people has the infection.”
AEDC numbers for infection rate roughly mirror that of the community rate for Tennessee.
“This number of infections only reflects that about 1 percent of the population has been tested, so there’s still so many unknowns with this disease,” Geraghty said. “And these numbers might not reflect the actual reality.
“Quite frankly, here at AEDC we do not do a test (ground flight testing) that is so important that anyone from AEDC needs to die or have a member of their family die because we came to base and did the test.”