The cathedral complex on the Rock of Cashel is one of Ireland's most important early mediaeval monuments and one of its components is Cormac's Chapel, situated on the south-east side of the main cathedral. It is not only one of the most significant early Romanesque buildings in the country, but it also contains fragments of an immensely important scheme of wall paintings that are practically unique in Ireland.
In recent years it became apparent that there was a significant problem at Cormac's Chapel. Despite a long programme of conservation treatment, the paintings continued to suffer deterioration as a result of the severely adverse environmental conditions in the building. As a result, a project was begun in 2001 to investigate and control the environmental conditions causing damage to the chapel and, in particular, the mediaeval wall paintings. The results of the initial study showed that the moisture levels in the building fabric and internal microclimate were extremely high as a result of rainwater penetration through the fabric and uncontrolled ventilation with external air. In short, the building was suffering from extreme damp penetration brought about by failure of the roof and the roof drainage system. Enclosure tests involving a reduction in the external ventilation demonstrated that the internal microclimate could effectively be stabilised, but because of the residual water in the building fabric the relative humidity remains extremely high, resulting in significant condensation and large levels of microbiological growth. This is reflected in green algal growth on the internal walls.
The results of all of the technical investigations demonstrated that while some of the conservation approaches had value, overall, the underlying causes of deterioration of the wall paintings were associated with both liquid water and water vapour and this needed to be tackled at source with a comprehensive building fabric intervention. The most serious damage was associated with liquid water, largely due to the failure to effectively remove rainwater from the chapel, with the result that a significant volume of water penetrated the building structure. This is primarily due to the complex design of the building and lack of any systematic rainwater disposal system. The condition of the building fabric, although structurally stable, was found to be extremely vulnerable to penetration of dispersed rainwater.
Roofed and enclosed scaffolding was erected over Cormac's Chapel in January 2010 in order to allow the building structure to dry and provide access to the roof and protection during the repair work. This was a highly complex operation, not only for structural reasons but also because of the very large volumes of rainwater that needed to be removed from the structure. Careful records of rainwater volumes have been kept by the Rock of Cashel works team throughout the project. In 2012, for example, it amounted to 126,750 litres, and in 2013, 113,200 litres. This provided confirmation of the very high volume of rainfall to which the chapel was subject, in addition to the complexities of successfully removing such a large volume of water from the building structure in the future.
In the period since the cover was erected on the building, extensive and continuous monitoring has taken place. In essence, this reveals that the building is drying out well but extremely slowly. There was an initial sharp decrease in most areas in the first six months and then a slower decrease in subsequent years. However, some areas of the croft appeared to have dried less well.
Artificial conservation ventilation undertaken during this period also showed a more significant effect on the internal micro-climate, causing a slow but cumulative reduction in air moisture content. However, this process is highly sensitive as any too-rapid change in micro-climatic conditions would potentially be very damaging to the paintings and the entire building must be monitored on an ongoing basis.
In tandem with the environmental monitoring, the OPW National Monuments Service is currently carrying out consolidation and repair of the sandstone roof. This entails removing the cement bedding mortar and the careful repair and replacement, where necessary, of damaged roof stones. The long-term rainwater disposal system is also being fashioned as part of the work. This will allow the removal of liquid water from the roof of the chapel safely for the future. Due to the complexity of the project, the OPW envisages that the scaffolding will remain in place for approximately the next 18 to 24 months.
In conclusion, I would like to make a few specific points in response to the Deputy's comments. The project could not, as the Deputy states, have run over its time-frame by four years since no definitive projection of project duration was ever made and even the speculation that did exist said that the work would take an absolute minimum of five years from its start on site in 2010. Second, the work at Cormac's Chapel is clearly at the forefront of conservation practice in Ireland. Lessons are being learned on this project which will serve to protect monuments all over the country in the future. This project is not, however, one that can be precisely planned to every last degree. As it is so novel and because the building is reacting so slowly to the ministrations of the technical team, it would have been impossible to speculate definitively in 2010 how long this project would take. Equally, I should reflect that if there is the slightest suspicion that we could damage the monument or these paintings in any way by rushing the project to its conclusion, we should exercise caution and not take that risk.
I also point out that, notwithstanding the fact that the presence of the scaffold on the Rock of Cashel is visually intrusive, it has not adversely impacted on visitor numbers. Visitor numbers have increased from 204,270 in 2010 to 272,503 last year. Additionally, the OPW guide management on site reports that it is not experiencing high levels of complaints in respect of the issue and indeed many visitors express keen interest in it and an appreciation of the effort being made by the Irish State to safeguard its heritage.