Methane in monitoring wells at AltEn not cause for concern - Lincoln Journal Star

Methane in monitoring wells at AltEn not cause for concern

Efforts to clean up solid and liquid waste contaminated by pesticides are ongoing at a former ethanol plant near Mead, but potentially unsafe levels of methane detected inside groundwater monitoring wells have forced contractors to take added safety precautions.

Samples taken from five of 11 monitoring wells surrounding AltEn’s lagoon system showed concentrations of methane between 5% and 18%, levels where the gas could potentially ignite and burn, environmental contractor NewFields told the Nebraska Department of Environment and Energy on July 7.

Methane was detected above 18% — in excess of the explosive limit — in three other wells, where the concentration would be too high to ignite but could still pose a health risk to contractors on site, while three other wells showed no or minimal levels of the gas, according to the report.

Bill Butler, a senior engineer and partner at NewFields, said the concentrations of methane inside the well casings — a 2-inch-wide PVC pipe that reaches into the water table — were discovered during routine sampling activities at AltEn.

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A wastewater lagoon of contaminated water and seed is photographed in April by a drone over the site of the former AltEn Plant where cleanup is underway.

“Based on that, we checked in other wells and found (methane) in a few other wells,” Butler said. “But it was just in the wells. We didn’t find it in any of the ambient air monitoring or in different parts of the site.”

Butler said the elevated levels of methane do not pose any health or safety risks to the community of Mead a little more than a mile to the north of AltEn, and won’t disrupt any cleanup activities at the site.

“We don’t have any concerns at this point of any large plume of methane gas migrating either above or below ground, but we’re going to continue monitoring,” he said.

NewFields does plan to enact some additional safety procedures, which Butler likened to urging motorists to not smoke a cigarette while they fill up their gas tanks.

According to the memo sent to the state environmental department, NewFields plans to cap and lock the monitoring wells, create a buffer zone for vehicles to prevent any inadvertent ignitions and conduct wider routine air testing in buildings on site.

The methane gas is believed to have formed by the decomposition of organic matter in AltEn’s three wastewater ponds, which were the subject of a February 2021 order from the Department of Environment and Energy that eventually led to the plant’s closure.

Unlike other ethanol plants, AltEn used seeds coated in pesticides to produce biofuel, which left behind solid and liquid waste heavily contaminated by neonicotinoids and fungicides that have been detected in soil, surface and groundwater, as well as insects and other wildlife in the area.

After AltEn completed its state-ordered shutdown, a coalition of six seed companies that formerly used the plant to discard of their unused seeds assumed responsibility for cleaning up the site.

In a November 2021 report, the AltEn Facility Response Group said it found the facility in a “dire” state of repair, and said the lagoon system was overfilled and in danger of failing.
The site of the former AltEn Plant near Mead is photographed by a drone over the site on April 27.

Several tears in the lagoon liners were noted in a separate report filed the same month, when decaying organic matter had leaked into the ground below and begun a buildup of methane gas.

The “whales” or gas bubbles created by the methane at that time threatened to damage the embankment of the holding pond, which could have allowed contaminated wastewater to run uncontrolled away from the property.

NewFields, along with Clean Harbors and Tetra Tech, conducted an operation to depressurize the largest gas bubble by perforating the liner and directing the gas through a filtration system.

Butler said NewFields, which was hired by the AltEn Facility Response Group, will continue to manage any off-gassing of methane that builds up on the property.

“If we see anything, we’ll communicate that to NDEE and the public,” he said.

NewFields recently completed an effort to remove 1,500 tons of rubbish and other materials from AltEn’s site and transport it to a landfill. Butler said a total 150 truckloads of material were carried out of the facility.

A pilot program to study methods for removing 115,000 tons of pesticide-contaminated wet distiller’s grains, a solid byproduct of AltEn’s ethanol production, is still being planned and is expected to begin later this year.

Meanwhile, the Department of Environment and Energy last month signed off on a plan from Entact, an environmental cleanup contractor, to build a new temporary wastewater treatment plant on the site.

The new treatment facility, which will be able to run 24 hours a day, is expected to be up and running in mid-August, according to a permit application with the state.

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Reach the writer at 402-473-7120 or cdunker@journalstar.com.

On Twitter @ChrisDunkerLJS