For more than 80 years the gypsum mines have been a feature of the landscape and economy of south Monaghan, and residents have learned to live with the drawbacks in return for having a company regarded as a good employer in their midst. But since subsidence took their GAA grounds and closed their road, they are asking if the good employer is also being a good neighbour. Caroline O’Doherty reports
Home time at Drumgossatt National School sees a small surge of activity at McGrane’s Country Store.
In a scene that has been repeated for generations, children potter in to see what the loose change in their pockets will buy. How much is a jelly snake? How many foam teeth for 50 cent?
The school, the church that sits beside it, and the small grocery shop opposite form the hub of this rural south Monaghan village.
Crucial to them all is a narrow bumpy road, the LP4900, that leads many of the scattered neighbours in the townlands of Magheracloone and Knocknacran to this central point.
Close to the far end of the road, lies Magheracloone GAA grounds, where early on Monday morning last September 24, dramatic crevices and sinkholes appeared in the pitches which lie above the old Drumgossatt gypsum mine, while cracks running from ground to ceiling split the walls in the GAA clubhouse and the adjacent community centre.
Thirty-six hours earlier, several hundred people, mainly children, had been on the grounds for an inter-club blitz, so the timing of the collapse was fortunate.
The LP4900 and a stretch of the busy R179, the road between Carrickmacross and Kingscourt, which it intersects, were closed for eight weeks, causing hardship for several businesses. There was huge relief when they reopened and even more so when, a week before Christmas, two consultants’ reports declared them stable.
Then two days later another sinkhole appeared, this time in a field beside the LP4900, which has been closed ever since. Monaghan County Council says it will remain so until “mid-March at the earliest”.
Shop-owner Michael McGrane is measured in his comments. He wants a fix for this problem, not a fight, but his frustration is obvious.
“This is normally the main road into the parish. People can get here but they’ve to go a long way round and out on to the main road. They have to, to get to the school and the church.
Geraldine Ward has the advantage of being able to walk the short distance from her house to the shop but she too is feeling somewhat marooned.
Now a spokesperson for local residents, she admits she hid in her garage the first time the media turned up at her gate. Living right at the edge of the exclusion zone set up when the cracks and sinkholes appeared, hers was the last accessible house before emergency barriers blocked any further progress on the road.
But Geraldine wasn’t keen on publicity. “The irony is, I hid in the garage for safety but I’ve seen maps that show the old mine comes up to the garage, so I don’t know how safe I was.”
She laughs, but it’s gallows humour. “We get plenty of jokes. We’ve made a few ourselves. But after four months of this, my sense of humour is wearing a bit thin.”
It should be pointed out that she doesn’t know for sure if an old mine tunnel like the ones that run under the GAA grounds also encroaches on her garage.
Gyproc, the current mine operators, have assured her otherwise and invited residents to inspect maps at their offices.
As of last week, the company has also undertaken to produce a fresh set of maps — a clear outline of the mine boundaries within three weeks and a detailed chart of the underground tunnels in about 12 weeks.
But there’s a niggling doubt in her mind that will take convincing evidence to dispel.
“There’s been mining since the 1930s. They didn’t have the technology they have today. They have hand-drawn maps. I don’t believe every tunnel is recorded or recorded accurately. How could it be?” she says.
Gyproc, formerly known as Gypsum Industries, and in more recent years part of the global Saint-Gobain group, has two current gypsum mines — the Knocknacran opencast pit and the adjacent Drummond underground mine.
About a third of the Knocknacran pit lies above their old Drumgossatt underground mine and excavations in parts have gone deep enough to expose Drumgossatt tunnels.
The rest of Drumgossatt has grassland above it, used for farming, some homes, and the GAA and community centre.
Drumgossatt was mined by the ‘pillar and room’ method. It’s like a giant potato waffle in reverse.
The potato is the tunnelled out gypsum, the ‘rooms’, and the square holes are the ‘pillars’ of gypsum left behind.
The method has the disadvantage of requiring much of the gypsum to be left behind as pillars, but the advantage is that it provides natural support for the mine.
Mining at Drumgossatt ended in 1989 but the mine wasn’t closed.
It has been used since for storing water pumped out of Knocknacran and Drummond.
Under licensing conditions imposed by the Environmental Protection Agency, Gyproc has to be careful how much water it releases into the nearby Bursk River because it risks contaminating it with sulphate if river levels are too low. So the company stores it in Drumgossatt and waits until the river is full-flowing.
“As part of normal mining operations, we have historically and regularly stored naturally-occurring mine water in Drumgossatt mine,” the company says.
But in June last year, “a unique and complex set of circumstances”, as SRK, investigating consultants employed by Gyproc, would later describe it, began to arise.
Miners in the Drummond Mine “intersected a fault” — a large crack in the rock — and water flowed in from a natural underground reservoir at a “more accelerated rate than normal”.
Gyproc had to take swift action and started pumping the water into a part of Drumgossatt “previously unused for water storage”.
Over the next three months, the water destabilised some pillars — unusually “slender” pillars not much in use in the rest of the mine, although the company hasn’t quantified “slender” — and they collapsed, causing a domino effect on other pillars, leading to the subsidence above.
There are things we don’t know yet, pending ongoing investigations, such as how the mining at Drummond came to hit such an extensive body of underground water, apparently without warning.
And there are things proving difficult to find out, such as why Drumgossatt, a mine known to have subsidence problems in places, was allowed to continue in use for regular and, as it turned out, emergency, water storage for 30 years after mining finished there, without frequent subsidence monitoring.
It should also be noted that rock blasting takes place, as permitted, at Knocknacran, beside and above Drumgossatt, and still the monitoring at Drumgossatt was infrequent. Surface measurements were taken twice a year and underground inspections were carried out up to the early 2000s but since 2005, there has been too much water in the mine to access it for underground inspections and surface monitoring still continued only twice a year.
There was a three-month potential window of warning between the water inflow at Drummond and the collapse at Drumgossatt, but with monitoring taking place only every six months, it is unclear if there were signs of movement during that window. Gyproc says it only monitored twice a year because that’s what the Department of Marine and Natural Resources (now Communications, Climate Action and the Environment) deemed necessary.
When asked if, in retrospect, that was sufficient, it said: “Gyproc prioritises safety in all its activity and conducts all monitoring in line with the requirements set by and agreed with the relevant licensing authority.
“Gyproc supports this active monitoring regime and it would be inappropriate of Gyproc to comment on questions regarding the efficacy of a monitoring regime that is set by our licensing authority.”
The department said the twice-yearly monitoring was recommended on foot of consultants’ surveys in the mid-1990s and early 2000s. When asked if, in retrospect, it considered this was sufficient, it said: “The trend from the subsidence monitoring over the years indicated that conditions had stabilised.”
Local Sinn Féin councillor Colm Carthy says a much closer eye should have been kept on the mine.
Fianna Fáil councillor Padraig McNally is also unimpressed. “The mine needs to be pumped out completely and a full inspection carried out so that we know exactly what state it’s in. Nothing beats the human eye. They’re drilling boreholes and sending down probes. To me, that’s like sending a stick with a camera on it up into your attic to have a look around instead of going up there and looking for yourself.”
In relation to the water inflow at Drummond, the company says: “Gyproc has undertaken a significant engineering project over the last number of months to successfully install bulkheads in the underground mine workings.
“These bulkheads allow Gyproc to control the rate at which the inflow water enters the mine.”
In relation to the water in Drumgossatt, investigations and assessments are still ongoing to work out the best way to remedy the situation.
In relation to the local community, Gyproc has apologised for what happened. As of last week, it is part of a forum comprising local residents and representatives from the county council and other state agencies, that is to meet regularly to review progress.
Gyproc’s managing director Brian Dolan has said the company “will not be found wanting”.
The GAA club and community centre are to be rehomed at Gyproc’s expense but that was in train anyway because the company has wanted the land for some time, to enable it go back in and take out the remainder of the Drumgossatt gypsum by opencast mining. That would secure the company’s presence, and the 200-plus jobs in the mines and associated processing plant, for possibly decades more to come.
Damian Martin was brought up to believe that was a good thing. His home, and the house next door which belonged to his parents and where his mother lived until her death last June, are across the road from the GAA club.
Since last September, he, his wife and three children have been living in a rented house in Carrickmacross supplied by Gyproc, but he has to return daily because his cabinet-making workshop is beside his home, for which he has now been denied insurance cover.
“We don’t know what’s going to happen in a few months’ time but long-term, this is going to affect the young generation of this area. The houses we’d planned to leave them won’t be worth anything and the community we’d built for them mightn’t even be here.”
Gerry Collins’ father, Eugene, was unusual among his generation in that he took on the company.
Gerry has an old newspaper cutting that shows how, in 1970, he went to court to sue Gyproc for nuisance caused by dust and traffic on his land, and for subsidence.
He was awarded £51 for nuisance but the judge told him to take the subsidence matter up with the Mining Board.
“He was bought out in the end and there’s a sinkhole by the old property now,” says Gerry. “There’s an awful feeling of history repeating itself.”
Subsidence has long been recognised as a hazard with respect to the gypsum mines.
The Environmental Impact Statement (EIS) that accompanied the 2007 Gypsum Industries (now Gyproc) planning application to extend the Knocknacran opencast pit, which had been operating since 1984, contained the following observation: “A portion of the road leading to Drumgoosat village is located directly above mine workings. A short stretch (+/-140m) of this road is experiencing subsidence. In 1997, the Department of Civil, Structural & Environmental Engineering of Trinity College Dublin were commissioned to investigate this subsidence.
“The report concluded that the subsidence was found to be caused by stiff gypsum pillars punching through a weak mudstone floor.”
The Trinity report also said the pillars were intact and sudden collapse was unlikely to occur, but it concluded “settlement” of the road could be as much as 1.2 metres. The EIS stated that up to March 2006, it was 0.88 metres.
Subsidence had also been on the company’s mind when it sought permission to begin underground mining at Drummond.
One of the technical reports it commissioned in 1999 — well in advance of the planning application submitted in 2003 — stated: “More quantitative data is needed for the mudstone in close proximity to the gypsum seam.
That report, from Golder Associates, referenced a site visit in February 1999 and noted: “There is evidence of some heave and pillar damage at some distance from the main subsidence area.”
It continued: “The main floor heave and pillar failure in Drumgoosat is associated with excavation close to the base of the lower seam and subsequent failure of the mudstone below.”
Mudstone, as its name suggests, is a rock formed mainly from clay and mud that can present stability issues.
Monaghan County Council sought more information from the company and another report, prepared by Rock Mechanics Technology Ltd, was submitted that detailed the monitoring and measuring instrumentation that could be used “to minimise the subsidence risk associated with this mine”.
A green, amber and red alert system was proposed.
Green would cover the detection of movement of up to 5mm, which would require no action.
Amber would denote movement of 5-10mm and require increased monitoring, on-site inspections, assessments of the integrity of the pillars, roof and floor beams, possibly probe drilling, and the installation of localised support and additional instrumentation.
Red would signal movement in excess of 10mm which would require access to be restricted, additional support installed or the area closed, pillar and roadway support design to be assessed and pillars, roof beams, floor beams, stress and rock displacement all to be measured and monitored.
A further report, a Comparative Analysis of Drumgoosat and Drummond Mines was also submitted, which referred to sinkholes in the north and eastern part of Drumgoosat.
It noted that excavation of the Knocknacran opencast pit had exposed an “undulating surface” to the rock beneath and “cavities” within it.
“These features were not recognised in the early days of mining at Drumgoosat. Consequently and coupled with the lack of rigorous roof beam monitoring, an occasional breakthrough of the lower seam roof resulted,” it said.
It added: “The mining plan for Drummond recognises both of these facts and adequate steps have been built into the mine design to avoid similar situations occurring.”
One of the challenges of working with gypsum is that it dissolves in water, although only until the water becomes saturated with it. That happens at a concentration of about 2.4 grammes of gypsum per litre of water.
After that, the science tells us, the water won’t take in any more so as long as any body of water coming into contact with gypsum is stable rather than flowing, it shouldn’t cause significant erosion.
Numerous dam operators have learned that the hard way. Vast amounts of water constantly moving over bedrock containing gypsum has caused stability issues or collapses in more than 20 dams worldwide and there is remedial work taking place currently to try to save the Mosul Dam in Iraq.
The trouble with mining is that you’re likely to hit water in aquifers if you go underground.
The standard approach is to pump the water out so that the excavations can take place safely and efficiently.
But water finds its level so when you pump out some, more will take its place and maybe the fresh inflow of water hasn’t sat in a seam of gypsum and isn’t saturated and it may dissolve some of the material being mined as it goes, or some of the material being left behind to provide natural ‘pillars’ to support the mine structure.
When Gypsum Industries set about planning for the opencast mine at Knocknacran in the early 1980s, however, they had other water-related issues to worry about.
Opencast mining also has to deal with inflows of water — from underground, from rainfall, and from the water it uses itself to dampen down dust — and that water has to be discharged as wastewater in an environmentally responsible manner.
The plan was to discharge into the nearby Bursk River, but the wastewater from Knocknacran would contain sulphate which can reduce water quality and damage fish so it could only be released into the river if river levels were high enough to dilute it.
In dry spells, when the river was low, the mine would have to hold back some of its wastewater.
“Excess effluent will be stored in the holding lagoons (capacity 5000 cubic metres). Anything in excess of this will be pumped to a deep level isolated section of Drumgoosat mine,” the company submitted.
Drumgossat was on the wane at this stage — it would shut for mining purposes in 1989 — but it would remain an essential part of the water management system for the new mine at Knocknacran and for Drummond to follow.
The plans for Drummond, submitted in 2003, examined two options for when excavation would cease there — in five to 10 years from now.
The cavities left behind will naturally fill with water and one option considered was to keep pumping it out indefinitely.
The post-closure report submitted warned: “If the mining void at Drummond is kept pumped indefinitely, it is possible that water that is unsaturated with respect to gypsum may enter the mine.
“This unsaturated water could then attack the mine support system. Eventually localised failure of the mine support system could occur, leading to surface subsidence.
“It is recommended that flooding of the proposed Drummond mine, following completion of mining operations, is the most suitable closure mechanism to ensure long-term surface stability.”
Flooding would also bring challenges. The mine would have to be securely sealed and it was estimated it would take 3.6 billion litres of water to fill it. It would fill quickly at the start but the rate would slow so that it would be 90% flooded within 11 years, but take 30 years to fill completely.
During this process, some of the remaining gypsum would dissolve.
In a worst-case scenario, it was estimated 8,700 tonnes of gypsum from the pillars, floor, and walls would dissolve but given the total surface area of the mine, that would translate into just 1mm of gypsum being removed from all exposed surfaces.
The report stated: “Pillar size may be affected during the flooding process in two ways. Incoming water could dissolve minimal amounts of gypsum from the surface of the pillars.
So sealing and flooding was seen as the safer option for Drummond. Drumgossat, excavated the same way as Drummond, was not sealed and flooded.
For 30 years post-closure, it has been used as part of the water management system of the other mines, including last summer when it was used to hold the sudden inflow that occurred when excavations at the Drummond mine hit a fault in the rock and unleashed a torrent of water from an adjacent underground reservoir.
Drummond couldn’t hold the water — it would have endangered the whole excavation.
It couldn’t release the water to the Bursk — it was the driest summer in decades and the river levels were too low to deal with high concentrations of sulphate.
So the water was diverted to Drumgossat where it destabilised some pillars which collapsed, causing a domino effect on other pillars which also collapsed, causing the subsidence above.
Investigations by SRK, consultants commissioned by Gyproc, concluded the water affected weakness in the pillars and the mudstone floor.
Wardell Armstrong, commissioned by the department to review SRK’s work, did not consider the mudstone floor the problem — only the water entering cracks and fissures in the pillars.
But both agreed it was the water and inherent weakness in the mine structure that caused the problem.
Drumgossat seems to have coped adequately with its role as support act for the other mines for many years up to last summer, but the fact that knowledge existed about subsidence there, and the challenging relationship between gypsum and water, raises questions as to whether it should have been expected to.
In mid-November 1965, an anxious call was received by Monaghan County Council from the manager of Gypsum Industries, as Gyproc was then called.
He had a problem. He was about to start the construction of a large leaching plant to serve the mines. The plans were drawn, the materials ordered, the contracts signed, and future production commitments depended on it. But he didn’t have planning permission. He hadn’t even applied.
The official who took the call wrote a note of their conversation and forwarded it to the county engineer. Their exchange remains in the council’s planning files.
“The job is rushed, as the programme requires them to meet an operating date of the 16th of May 1966. They have purchased the land required in Drumgossat. They have placed the order for the contract. They have not sought town planning permission. He inquired did we consider it necessary,” he wrote.
The official told the engineer he advised that permission was necessary, but “in view of the size of the project, you might be prepared to take an immediate personal interest in it, with a view to expediting the permission”.
That was on November 19. The engineer would return a note, stating that discussions took place between the plant manager, the county manager, and himself on November 22. A site visit took place in mid-December and permission was granted on January 17.
Given the statutory notice period required for objections and the Christmas shutdown, that does sound like expedited permission.
Some context is necessary. Ireland’s planning system, as we know it today — with requirements for formal applications for permission, supporting documents, objections and appeals — had only come into effect a year earlier, so was probably still bedding-in.
But the incident underlines a feature of mining in Ireland that has legacy effects to this day. Much of it began in the absence of planning and regulatory oversight, so even though it may continue to have an impact on communities today, applying current standards retrospectively is problematic.
Gyproc’s first significant underground mine was at Drumgill, near Carrickmacross, and it was worked from 1947-1989. A second underground mine, at Cormey, north of Drumgill, was opened in 1952 and worked until 1961. Drumgossatt, a little further north again, opened in 1958 and closed for extraction purposes in 1989.
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Drumgill, Cormey, and Drumgossatt all opened without planning permission and ceased operating without the kind of post-closure supervision that was built into the planning for the current excavations at the open-cast pit at Knocknacran and underground mine at Drummond.
When the Drumgossatt collapse caused the subsidence last September, Monaghan County Council, the Environmental Protection Agency (EPA), the Health and Safety Authority (HSA), and the Department of Communications, Climate Action, and the Environment all assessed the situation.
But without a planning history, the county council is limited in what it can do, and the EPA only came into existence in 1993, after mining ceased at Drumgossat.
Even now, its role in mining is focused on issuing licences for emissions and pollution control, and while that is connected to the overall operation of a mine, the agency is not an overarching watchdog.
It said it was assisting the county council and Department by “providing supporting information in relation to the licenced activities, such as the associated emissions, hydrogeological assessments, and monitoring data of the local catchment area”.
However, it stressed: “Mining activities at the Drumgossatt mine ceased in 1989, prior to licensing of the activities by the EPA. As the disused mine at Drumgossatt does not fall under the remit of the EPA licence, it is not monitored by the EPA.”
The HSA was established in 1989, the same year Drumgossat closed for mining. The HSA said: “The HSA has a very limited role in the investigation of the subsidence incidents at the Drumgossat mine, as it is not a working mine.”
It continued: “Access to the Drumgossat mine has not been possible since 2005 and no inspections have been carried out by the HSA since its closure.”
It got involved in the current incident only in relation to the safety of miners at Drummond mine, where the sudden inflow of water that caused the Drumgossatt collapse originated and where works were being carried out to reduce and cap that inflow.
The department has a stated policy “to maximise the contribution of the mining sector to the economy, with due regard to its social and environmental impact”.
Gyproc is working under a 30-year State lease, which expires in 2032 and under the terms of which it must pay the Department €36,666 in rent annually, plus €0.785 in royalties for every tonne of material produced.
The amounts received from individual companies are not disclosed, but the Drummond mine alone was expected to yield 300,000 to 500,000 tonnes of gypsum a year.
The department, which has a dedicated Exploration and Mining Division (it inspects working mines twice a year) was asked about its role in monitoring Drumgossatt mine.
It said: “The department has consistently monitored Drumgoosat mine and Drummond mine, for subsidence, since 1998 and 2005, respectively.
This twice-yearly monitoring arrangement was put in place after the department contracted external consultants to independently review the subsidence risk from the mine.
The consultants carried out their first round of work in 1998-99, producing a report that recommended “detailed underground inspections and a programme of periodic measurement of surface levelling points and surface inspections in those areas of the mine lying below public roads and buildings”.
They carried out this work between 2001 and 2005, after which Gyproc continued twice-yearly, surface-only subsidence monitoring (increased since last September), sending the data to the department.
The consultants’ reports are not being made public by the department, because they contain “data relating to private land and property”.
The consultants who prepared them were SRK, whom Gyproc has employed to investigate the current subsidence.
SRK’s initial investigation report, which has not been made public, was reviewed by consultants employed by the department. Their review was made public and it agreed with SRK’s findings.
The department’s consultants were Wardell Armstrong, a company involved in the Drummond mine design plans for Gyproc.
There is no suggestion that the consultants are anything but professional, but there is a perception, locally, that there is a lack of detached oversight of the mining operations.
That was not helped when SRK declared the mine workings under two roads, the LP4900 and R179 (which had been temporarily closed), to be stable and Wardell Armstrong agreed, only for a new hole to appear beside the LP4900 a few days after these findings were published. The road was closed again and remains closed.
Gyproc acknowledges calls locally for an independent inquiry into the incident and the safety of the mines generally — or, as the company says it would be, “an additional independent inquiry” — and says it would fully cooperate, but Minister of State for Natural Resources, Sean Canney, has so far ruled that out.
He is likely to face further calls, however. Locals say they understand fully that the Drumgossatt mine harks back to a less regulated time, but they say that should not stop modern-day standards of scrutiny being applied.