Casella Waste Systems is closing its Hawk Ridge Compost Facility in Unity Township after Maine regulators discovered high levels of forever chemicals on the site and indications that the contamination may have spread to the land around it.
The Maine Department of Environmental Protection asked the company in February 2024 to test more and remediate contamination. Casella declined, citing uncertain future regulations and high costs of remediation as reasons to close in letters between it and the DEP obtained by the Bangor Daily News.
For almost four decades, Hawk Ridge, the state’s largest composting facility, has accepted millions of gallons of sewage sludge and turned it into compost used in Maine and beyond. The test results and Casella’s response show the pervasive nature of the chemicals and the difficulty in crafting Maine’s pioneering effort to regulate them.
Maine banned the spreading of sludge and sludge-based compost under a 2022 law. But companies have been allowed to import sludge from elsewhere to make the compost here even though it contains high levels of per- and polyfluoroalkyl substances known as PFAS, which are linked to several health conditions including cancers.
Hawk Ridge’s case highlights the challenges the state faces in containing the damage from chemicals that are pervasive nationally. The state began focusing on PFAS levels in 2019, when the owner of Stoneridge Farm in Arundel reported very high levels of the chemicals at his dairy farm.
Maine subsequently focused testing on the sludge, typically from municipal waste plants, that was spread for decades on farmland and seeped into many private wells. Only several years later did it start looking closely at compost made from sludge, which scientists said also contains high levels of PFAS.
Casella submitted its closure proposal to the DEP in late August. It includes no longer accepting sludge as of Sept. 1 and removing all materials from the site, cleaning it and closing by June 30, 2026. Casella would pay for the closure, a DEP spokesperson said.
“Although the facility has played a critical role for decades in the recycling of biosolids into useable products, the current regulatory environment no longer supports these efforts and Casella has deemed that the continued operation of the Hawk Ridge Facility is not sustainable,” Samuel Nicolai, vice president of engineering and compliance at Casella, told the DEP in a June 30 letter.
Neither the state nor the company had publicly acknowledged the closure plans before the BDN requested a set of documents from the state that included the letter. A Casella spokesperson cited the Maine law as the reason for the company closing Hawk Ridge.
The DEP licensed the site in 1989 to turn sludge waste into compost. Hawk Ridge had been accepting sludge from Maine, Massachusetts and other locations and processing it into compost. Some of the compost was sold in Maine until passage of the 2022 law that made the state the first in the nation to ban the spread of both sludge and sludge-derived compost on land.
Other states are following, with 12 introducing bills as of this year, according to SaferStates. Massachusetts, which is considering such a move, has been providing 95 percent of the sludge to Hawk Ridge and using 64 percent of the compost made there, according to a January 2025 report by the Massachusetts regulators. If the bill passes, Casella would also be facing a loss of sales to Massachusetts.
Sewage sludge, which state and local governments heralded as a cheap fertilizer for decades, is a problem both here and across the country. It has contaminated nearly 70 million acres of U.S. farmland, according to the Environmental Working Group.
Hauling sludge from Massachusetts to Maine, which forbids its use, is especially frustrating to Adam Nordell, the campaign manager for Maine farmland contamination at the advocacy group Defend Our Health. Nordell owned Songbird Organic Farm in Unity, which had to halt sales in 2022 after PFAS was found in the soil and water there from earlier sludge applications.
“I’m glad that central Maine isn’t going to be New England’s toilet any more,” Nordell said. “But what is Casella’s commitment to cleaning up a place that they have so thoroughly polluted?”
Laura Orlando, a senior scientist at Just Zero, a waste reduction advocacy group, said calling the product “compost” is a misnomer, meant to disguise a toxic product as something that is eco-friendly.
“But the state is learning just how contaminated this compost facility is, and I think the state can pat itself on the back for taking action to end land application of sludge or sludge-derived products,” she said.
Hawk Ridge has accepted 1.5 million cubic yards of sewage sludge, 240,000 cubic yards of papermill sludge and 130,000 cubic yards of feedstocks for processing since it began in 1989, according to a February 2024 letter from the DEP to Casella. It has produced more than 2 million cubic yards of finished compost. A cubic yard equals 202 gallons or almost 14 standard-sized bags of mulch from a home gardening shop. Casella’s compost is sold mostly in bulk now to commercial buyers.
Sludge-based compost was not routinely tested for PFAS in Maine until 2019. The state had assigned a level of 2,500 parts per trillion for a PFAS chemical known as PFOA, and 5,200 parts per trillion for another known as PFOS. The recent test levels at Hawk Ridge were vastly higher than those past standards.
The DEP said in the February 2024 letter that one pond containing water from sludge processing measured 15,200 parts per trillion to 49,900 parts per trillion over the past two years for the six most commonly measured forever chemicals. Tests of the finished compost were 54,448 parts per trillion for all six of those.
The pond was dredged — meaning water was pumped out onto the ground — six times in the facility’s history, according to the DEP. The agency asked Casella in February for additional testing, a written plan to monitor off-site PFAS impacts to water quality and a plan including potential corrective actions for the contamination. Casella reported back with several remediation possibilities, saying it is not clear how the current cleanup technology will work long term.
In its proposed closure process, Casella said it would remove the primary processing materials and waste and clean the area by Dec. 31 of this year. The company still has 52,740 cubic yards of compost at the facility. The state and Casella still are working out the details of the cleanup and closure.
The main processing building and paved surfaces are to be swept and powerwashed and stormwater drains are to be redirected or capped by June 30, 2026. Casella said it does not plan to disassemble or remove buildings or other structures. The company said it may still use the site for equipment storage and other non-regulated activities.
Lori Valigra reports on the environment for the BDN’s Maine Focus investigative team. Reach her at lvaligra@bangordailynews.com. Support for this reporting is provided by the Unity Foundation, a fund at the Maine Community Foundation and donations by BDN readers.