Details of a new tunnel bypassing the Glen of the Downs in Co Wicklow have been released showing a 2km route under the western side of the Glen.
The new Purple Route would see traffic between Dublin and Wexford divert into the tunnel under some 20 local houses. The route corridor also passes below the Norman Downs village and fair green, the 15th-century St Mary’s Church, and a ninth-century ring fort overlooking the Glen itself.
At the northern end of the Glen the tunnel would emerge north of the local Red Lane, where it would rejoin the existing M11/N11.
Consultants Arup working with Transport Infrastructure Ireland’s regional roads office have come up with the design having discounted some earlier options, including two possible routes across Delgany Golf Club.
Details of the tunnel route were added to the project website last week under the heading Phase 2 short-listed corridors. Consideration of a tunnel was first mentioned in an update to the project website in December 2020, when the extent of difficulties with other route options became apparent.
Three options now remain on the project shortlist are:
– To widen the existing route along the Glen floor. This is considered controversial as it would require a further slice off the nature reserve, a Special Area of Conservation which is protected under EU law. Widening the route to a dual carriageway sparked a three-year protest by eco-campaigners some 20 years ago.
– A route high on the western side of the Glen known as the Cyan Route. This route is considered punitively expensive as it is 7.9km long. It contains a number of bends as it hugs the contours of Downshill. This route may also attract objections on heritage and environmental grounds given the presence of a pre-historic hillfort on Downshill.
– The tunnel route, while costly, would avoid much of the issues raised by other options.
A spokesman for the design team said the approach to the project was an incremental one. He said the first options would have been the simplest and most straightforward, and as each one was ruled out the more expensive and complex options were being investigated.
The tunnel option has already received a positive response from heritage enthusiasts. Founder of the website glenodownsheritage.com Jasime Fortune, who has researched and published much of the known history of the area said the tunnel was "the best outcome" in terms of reducing disruption to biodiversity and heritage.
Local TD Jennifer Whitmore who lives in Delgany said the community “has been very clear since the start of this process that they want the local, natural and cultural heritage of the area protected and this must be a key priority for the project”.
The Glen of the Downs section of the N11/M11 upgrade is part of a 22km upgrade of the N11/M11 corridor stretching from the M50 to Coynes Cross in Ashford.
The scheme traverses two local authority boundaries, Wicklow County Council and Dún Laoghaire-Rathdown County Council. Wicklow County Council is the lead authority and appointed consultants Arup in 2018.
However, as the area falls within the bounds of the Kildare National Roads Office, that office is responsible for the project management and delivery. Transport Infrastructure Ireland is the sanctioning authority.