Tetra Tech aims to PlumeStop airport PFAS

Tetra Tech vice president Ron Myrick, whose firm has been handling testing and mitigation of per- and polyfluoroalkyl substances (PFAS) around the Martha’s Vineyard Airport area, notified the Martha’s Vineyard Airport Commission during a Thursday meeting about plans to use a remediation pilot program of “targeted PlumeStop application to assess mitigating further migration of PFAS” off the airport.

PFAS describes a family of long-lasting chemicals that break down very slowly, which is also why they are nicknamed “forever chemicals.” Extended periods of exposure to PFAS or high concentrations of the chemicals are toxic, and can affect developing fetuses, thyroid, liver, kidneys, hormone levels, and the immune system. The chemicals have also been known to create a cancer risk. Tetra Tech completed the first stage of PFAS investigations in 2019.

“We’re closing in on four and a half years,” Myrick said.

Commission chair Bob Rosenbaum said the investigation began to “ensure all of the properties that have been affected by any potential use of the aircraft firefighting foam (Aqueous Film Forming Foam, or AFFF)” would be addressed. He said the airport stopped using the foam once they became aware of the issue. Myrick said “testing of AFFF hasn’t occurred on the airport in nearly four years, or at least to the environment.” However, PFAS traveling via groundwater is still a concern, which is where remediation “at the source” comes into play.

“Everything we’ve been doing so far has been what is going into people’s homes. If it’s above the standard, we’ve been treating it with a charcoal filter, it’s called activated carbon,” Myrick said. “But, the idea is let’s try to potentially close the gate at an appropriate spot so that the time it takes for whatever was discharged at the airport, the time that it takes to start seeing clean water down at the private wells south of the airport is shorter.”

To “close the gate,” Myrick introduced PlumeStop, an activated carbon substance made by the company Regenesis.

“It’s ground up to the consistency probably smaller than coffee in your coffee cup,” Myrick said. “So, instead of a particulate size [that’s] granular like coarse sand, it’s ground to such a fine consistency that it’s almost liquid.”

According to the audio of a video presentation Myrick played for the commission, applying PlumeStop “directly into the subsurface effectively converts the polluted aquifer itself into a purifying filter.” Myrick said the plan is to apply this technology in an area south of the wastewater treatment plant, which is near locations AFFF testing or usage occurred in the past. However, the application of this pilot program could extend to other areas to “mitigate [PFAS] migration off-site.”

“What we’ve learned is the migration is following preferred pathways. They aren’t changing significantly over time,” Myrick said. “So, we would not be putting a permeating wall across this entire one thousand feet or so. We would be targeting certain areas to inject this solution in … making this, essentially, a wall.”

The pilot program is expected to cost $185,000. Myrick said in the proposal that was approved in fiscal year 2023, there were also “some additional tests to refine this design.” These include FluxTracer tests, which gives “direct data on the amount of PFAS and the velocity of this flow,” and soil leachability tests, which helps understand how much PFAS will “leach out” of different types of soil and sand. Myrick said once all of the data is in, a final design and proposal for the PlumeStop use can be made by the end of August and presented to the Martha’s Vineyard Commission in September.

“If approved, we expect to be able to implement this in the fall,” Myrick said. “The benefit is an immediate one.”

Commission vice chair Don Ogilvie asked how long it would take, in the scenario the PlumeStop usage was successful, to before monitoring the wells south of the airport is unnecessary.

“It’s a long time,” Myrick said. The area that is being monitored is about a mile and groundwater moves slowly. So, if the calculation is done with the groundwater’s speed as “200 feet per year,” it would still generally be around 26 years of monitoring, according to Myrick. However, the “bulk of the problem” is in the first quarter-mile near the airport, so homes further down may be cleared up faster.

Rosenbaum wanted to know why the PFAS has not migrated elsewhere at this point.

“Given the fact that we haven’t discharged any firefighting foam in … four years?” Rosenbaum asked.

“That’s the complexity that we just did the calculations for. Groundwater moves at a certain rate and PFAS moves at a slower rate, and different PFAS move at different speeds,” Myrick replied.

Commissioner Richard Knabel pointed out that the Environmental Protection Agency (EPA) had released an advisory that “anything above a non-detect level is not really acceptable because there’s no safe limit for PFAS in drinking water.” The limit in Massachusetts for PFAS in drinking water is 20 parts per million. “Is this a conflict with what we have to do?” Knabel asked.

“You’ve hit on a very challenging issue that all states are dealing with and all practitioners in this business, and all of us in the world,” Myrick said. He continued by saying the EPA’s standards are “not achievable” and everyone is drinking higher than the set limits. “What they put out there, in my opinion, is not scientific based on the practicality of what you can do in the world. We live in a world with PFAS. So, to eliminate it completely from our world, we’re [70] years past that. We needed to not make these chemicals … in 1950. Because we made them and used them in such amounts over the last 70 years, it’s everywhere. It’s in Antarctica. You’re not going to find a place on this planet that has non-detect [levels]. That’s why they put a very challenging number for us as environmental professionals to explain … especially as the labs get better. They can’t get close to detecting the concentrations that EPA put out there as not acceptable.”

Meanwhile, the commission unanimously approved several projects for the airport. An amendment was made to the owner’s project manager agreement with Weston & Sampson to allow reflect the additional tasks (e.g. added design phase work, design adjustments, etc.) work the firm took on in managing the wastewater treatment facility, which would increase the cost by $95,000 to the “total $215,600 for the construction phase of their service.” A work order for McFarland Johnson to do construction work on the wastewater treatment facility, costing $1.55 million, was approved. Martha’s Vineyard Airport director Geoff Freeman was given authorization to continue to prepare a request for proposal for an airfield paint job, which is estimated to cost $330,000. This project is to meet Federal Aviation Administration (FAA) requirements about markings and Freeman said it must be done by November.