Residents weigh in on underwater neutrino detector

REGIONAL— Impact to water quality and the fishery on Lake Vermilion appeared to be the main concern for the dozen or so area residents who sat in on Monday’s Fermilab webinar on the pending installation of new underwater neutrino detectors in Big Bay.
The installation could get underway as early as next week and is expected to be completed by late November should all go according to plan, which includes the lake remaining ice-free.
Fermilab has contracted with Veit and Co., a full-service contractor with experience in marine operations, to do the installation of the ten detectors, known as muon underwater monitors or MUMs. They plan to use a connected assemblage of barges with a rectangular center opening through which the MUMs and their concrete anchors will be lowered. Veit is also the current contractor on the water and sewer installation at the Tower Harbor.
Monday’s webinar outlined in general terms the intent of the neutrino research and the timeline, and took questions from a handful of local residents.
Much of the information provided has already been reported by the Timberjay, but Fermilab’s Jen Raaf, who led the presentation on the physics behind the project, noted that the location of the deployment had shifted several hundred yards to the east after it became apparent that the lake sediment at the original site lacked the necessary stability to hold the four ten-ton concrete anchors that will be used to maintain each of the MUMs in place.
Raaf did address many of the concerns that local residents had initially raised, suggesting that the detectors would generate noise and require electrical upgrades. Raaf confirmed that the electrical draw would be minor, about 3,000 watts, roughly the draw of two hand-held hair dryers. Fermilab officials confirmed the MUMs themselves are silent and the onshore metal shed that’s connected to the detectors has no noise-making devices other than a window air conditioner.
Most of the questions centered on the impact of the MUMs deployment on water quality. “My overriding concern is the condition of the lake bottom,” said Frank Williams, who had the most questions of all those in attendance. “All of my neighbors with whom I have spoken all share the same concern, water quality, water quality, water quality,” he said.
He said he was most concerned about the large-scale disturbance of lake sediments caused by the deployment and removal of the large concrete anchors that will hold the MUMs in place. He noted that Vermilion is listed as impaired for mercury levels and that much of the methyl mercury that is of greatest concern is located within the sediments, which could exacerbate the mercury situation if disturbed.
Fermilab’s Bill Pellico, who is overseeing much of the project’s engineering, said the anchors will be lowered and eventually raised very slowly in order to minimize sediment disturbance.
Williams asked whether Fermilab had assessed the sediment to determine what kinds of potential toxins could be stirred up. “Do we know what’s down there?”
The Fermilab officials didn’t have a definitive answer, but said they would follow up on the question. Williams noted that cores were taken at the deployment site and asked for a copy of the findings.
The timing of the removal of the detectors also raised concerns. Mike Indihar questioned when or if the anchors will be removed and when the MUMs themselves would be removed from the lake and he challenged Fermilab officials when they indicated the removal would be done in late summer or fall of next year. Indihar argued they should be removed earlier in the season, but spokesperson Rae Moss said their timeline was based on recommendations from the DNR and a request from the managers of the McKinley Park Campground, which will serve as the landing for both deployment and removal of the MUMs. Campground officials had asked for that work to be delayed until after the primary camping season.
Williams asked why the DNR permit extended until 2030 if the project would wrap up next year. Raaf said the experiment will be done in February of 2027, which is when the NuMi neutrino beam at Fermilab will be turned off permanently. That beam is directed at the site of the former MINOS detector, which had operated for several years at the 27th level of the Soudan Mine, and the existence of that beam is the reason for locating the new experiment in Lake Vermilion.
Moss noted that area communities have long been a partner in the ongoing research into neutrinos and other high-energy physics research and that Fermilab was thankful for the widespread support for their efforts.