Canal not at risk, claims council

CLARE County Council has quashed hopes that the proposed €120 million motorway crossing South-East Clare may be scuppered because of the alleged risk it poses to the Headrace Canal.
A concerned Clonlara resident believes the latest revelation contained in the Draft Supplementary Constraints Study for Phase Two of the Northern Distributor Road may scupper the controversial Emerging Preferred Route, which splits Parteen village and crosses a flood plain on the outskirts of Clonlara.
In response to the route options public consultation process, the ESB highlighted the hydro-geological sensitivity of the area immediately south of the Headrace Canal, in the vicinity of the most northerly route options.
The Headrace Canal is formed by Category A earthen embankment dams. According to the Draft Supplementary Constraints Study published last week, this categorisation is one where a breach of the structure could lead to loss of life downstream.
“This constraint had previously been recognised as a restriction on the construction of routes that cross the Headrace but had not previously been understood to constrain route options south of the canal.
“Further clarifications received from the ESB have advised that over the years, incidents have occurred relating to drainage, mainly minor in nature, that were deemed to have a connection to the Headrace canal.
“These incidents were detected by the ESB as part of its routine monitoring of the Headrace and were dealt with without any adverse impact on the Headrace. However, these incidents indicate that route options to the north traverse ground with very poor drainage qualities.
“Excavation and construction work on the scale required to deliver these routes could alter the groundwater flow patterns in the area, with potential adverse consequences for the stability of the Headrace,” the study stated.
It concluded that the contents of the January 2011 Draft Constraints Study and the latest Draft Supplementary Constraints information, together with any extra information gathered during the ongoing public consultation process, will be compiled into the formal report on the route selection once this process is complete.
The resident, who did not wish to be named, described this section of the report as “alarming”. He claimed this revelation presents serious question marks about the threat posed by the Emerging Preferred Route, which crosses into Bishop Murphy Park near Parteen south of the Headrace Canal and Ardnacrusha Power Generating Station.
Urging the project engineers Roughan and O’Donovan or Clare County Council to address this issue, the resident said it now appears as if this latest report totally undermines the Emerging Preferred Route Corridor (ePRC).
However, senior engineer, Tom Tiernan stated the resident has misinterpreted the situation in the context of the Headrace Canal.
“The location of the ePRC has been defined and has taken full account of all of the identified constraints, including the Headrace Canal and all of the concerns articulated by the ESB in relation to same. This is why the more northerly options closer to the canal have been ruled out.
“The ePRC, which is presently the subject of a public consultation process, is located appropriately distant from the Headrace Canal. The ePRC is located to the north of Bishop Murphy Park and does not cross into the park, as claimed by the resident,” he said.
The Headrace Canal has one existing crossing, the Blackwater Bridge, located along the regional road linking Parteen with Ardnacrusha, which is heavily trafficked. The study area included areas north of the Headrace to examine a potential additional crossing as part of the Limerick Northern Distributor Road.
The Headrace Canal at Ardnacrusha is 13 kilometres long and connects Parteen Weir to the concrete dam and power station at Ardnacrusha. Over the entire length of the Headrace Canal within the study area, embankments constructed on each side of the canal act as impoundment dams, impounding the water in the canal.
In the Draft Constraints Report published in January 2011, the engineers acknowledged the Ardnacrusha Power Station and Headrace Canal upstream are key elements of the strategic national infrastructure.
“These structures are vital for power generation for the Mid-West Region and the State. In addition, the Headrace Canal diverts water to the Lower Shannon, thus alleviating flooding in areas such as Castleconnell, Montpelier, Springfield and Mountshannon between Parteen Weir and Limerick City.
“A breach of the Headrace dams would require the Ardnacrusha Power Station to be shut down, preventing the generation of power and would require the diversion of 450m3 of water from the Headrace Canal to the River Shannon, resulting in a significant flooding event downstream of Parteen Weir.
“It is evident that any potential crossing of the Headrace Canal would be required to be a significant single span bridge to sufficiently clear both the canal and the associated Category A dams.
“Notwithstanding the additional cost of such a structure, the risk of an object falling onto the impoundment dams during construction and causing a breach can’t be discounted,” the study stated.