The quarry landfill in Rockland. Credit: Stephen Betts / BDN

ROCKLAND, Maine — A century ago, it seemed like a good idea. Quarries that dotted the landscape were being retired and there was a need for more landfills for waste. But decades later, the problematic nature of the rocky areas would become clear.

In the midcoast region for more than a century, a limestone deposit between Thomaston and Rockport was quarried for the stone’s use in cement and other products. The industry was an economic driver for the region, but it largely fizzled out by the early to mid-20th century as the deposit depleted.

Left behind were the empty quarries that were beginning to fill with water.

“Trash disposal has been a problem since humans have urbanized themselves. The old solution has been ‘let’s bury it, find a hole in the ground and bury it.’ So those quarries were dug as deep as they were going to get and they were there,” said John Peckenham, an associate research scientist at the University of Maine’s Senator George J. Mitchell Center for Sustainability Solutions.

Quarry landfills opened in Rockland, Rockport and at least one other Maine town. It’s unclear exactly how many were once in operation in the state, but today just two remain.

In Rockland, a quarry landfill owned by the city is nearly at capacity and will be capped soon. In neighboring Rockport, a quarry landfill operated by Mid-Coast Solid Waste Corporation remains and is years away from closure. Both have been in use since at least the 1930s.

However, with these quarries containing both trash and water, what once seemed like a good solution has become a challenging operational and environmental problem.

“You can say the Rockland landfill to anyone, at any level of the [Maine Department of Environmental Protection], and they immediately know everything about it. It’s the Jessie James of landfills. Everybody knows about it,” said Chris Donlin, the interim director of public works for the city of Rockland.

Since quarries over time fill with water, the disposal of waste into them has been prohibited in Maine for decades. But the Rockland and Rockport facilities were grandfathered in and can continue to operate as long as the facilities comply with operational rules by the DEP that are aimed at mitigating environmental risks, such as the contamination of groundwater.

Very few quarry landfills are known to have existed in Maine, according to DEP spokesperson David Madore. Rockland had a second one, for instance, but that’s been long closed. And a quarry landfill was also operated in Monson.

But in the century since their creation, the understanding of waste management practices and their impacts on the environment have improved.

Environmental experts now know that the presence of water in quarries ― or any landfill ―  is problematic for trash disposal. It creates leachate, which is water that has come in contact with waste, and also makes compaction difficult and leads to problems with settling.  

“Everything that’s in there is a really thick soup. There is a lot of water in there and the stuff is almost quite literally floating,” Peckenham said.

Modern landfills that collect municipal solid waste are built with liner systems, according to Peckenham, to prevent leachate from leaking out and contaminating groundwater. Those liners didn’t exist in the quarry landfills. Peckenham said the bedrock walls of the quarries might actually cause the leachate to leak more slowly than it would other types of old, unlined landfills.

In recent decades, only construction and demolition debris have been collected in the Rockport and Rockland landfills. This type of debris is relatively inert ― meaning it breaks down slowly or not at all ― and can be collected in an unlined landfill under state rules, according to Madore.

To mitigate the risk of groundwater contamination, the DEP requires Rockland and the Mid-Coast Solid Waste Corp. to pump out enough leachate on a daily basis to keep the water level in the quarries below surrounding groundwater levels. The contaminated water is sent to a wastewater facility for treatment. The facilities also have to monitor groundwater near the quarries for signs of contamination.

Even when Rockland closes its quarry landfill, this pumping and monitoring will likely continue, according to the DEP.

These types of landfills will also continue to settle after they are capped so the cover system could settle and require maintenance. Unlike other more stable landfills, it is unlikely the quarries can ever be repurposed for a different land use in the future, according to Peckenham.

Rockland will stop accepting demolition debris at the end of the year and is working with state officials on a plan for final closure of the landfill by 2024.

In Rockport, current estimates predict that the landfill will be full in six years, according to Mid-Coast Solid Waste Corp. Facility Manager Michael Martunas. The facility’s original agreement with the DEP included dates for closure, Martunas said. But he is currently working with the department to come up with a new document that will “define the life of the landfill” based on how full it is, in accordance with DEP requirements, rather than a specific date.

But even after the landfills are closed, the legacy of what once seemed like a good idea will remain.

“We were the ‘Lime City’ in the 1880s and now we have the proof of it,” Donlin said.