Roughan & O’Donovan N14 / N15 to A5 Link Consulting Engineers Environmental Impact Statement – Volume 1 Chapter 3 Description of the Scheme Ref: 10.152 July 2011 Roughan & O‟Donovan N14/N15 to A5 Link Consulting Engineers Environmental Impact Statement – Volume 1 Chapter 3 Description of the Proposed Development 3.1 General Description The proposed cross border scheme will link County Donegal with County Tyrone across the River Finn at a point to the immediate south west of Lifford in the Republic of Ireland and Strabane in Northern Ireland (refer Figure 2.1, Volume 2). The Scheme involves the design of a road linking the proposed A5 Western Transport Corridor (A5 WTC) in County Tyrone to the existing N15 in County Donegal. The distance between the junction on the A5 WTC and the proposed N14/N15 junction is approximately 500m. In the longer term the scheme will facilitate connection to the proposed N14 Letterkenny to Lifford/Strabane and N15 Lifford to Stranorlar Schemes in County Donegal which are currently unprogrammed. The Scheme includes a significant structure crossing the River Finn candidate Special Area of Conservation and the associated floodplain, as shown in Plate 3.1, below. The proposed structure is detailed at Section 3.3 below and shown on Figures 3.5 to 3.7, Volume 2. The River Finn and the floodplains within County Donegal are designated as the River Finn candidate Special Area of Conservation. In County Tyrone the River Finn is also designated and lies within the River Foyle and Tributaries Special Area of Conservation (refer to Chapter 7, Section 7.2 for further details). Plate 3.1: Looking South from Donegal to Tyrone Ref: 10.152 July 2011 Page 3/1 Roughan & O‟Donovan N14/N15 to A5 Link Consulting Engineers Environmental Impact Statement – Volume 1 Plate 3.2: Looking North from Tyrone to Donegal 3.2 Scheme Layout 3.2.1 General Route Alignment The proposed N14 / N15 to A5 Link will provide a new Type 2 Dual Carriageway connecting the existing N15 at Lifford in County Donegal with the proposed A5 Western Transport Corridor (A5 WTC) at Strabane in County Tyrone. The proposed road alignment is shown on Figures 3.1 and 3.2 (aerial), Volume 2. The southern element of the scheme, in County Tyrone, will tie in to the roundabout to be provided as Junction 7 of the A5 WTC (refer Plate 3.3). At the northern end of the scheme an at-grade roundabout will be constructed to allow the scheme to tie-in to the existing N15. The alignment, as designed, allows for the future connection, in the form of a further at grade roundabout, to the proposed N14 Letterkenny / Lifford and N15 Lifford / Stranorlar upgrade schemes. The geometric standards used in the design of the road follow the requirements of the National Road Authority‟s Design Manual for Roads and Bridges (NRA DMRB) and the Highway Agency‟s Design Manual for Roads and Bridges (UK DMRB). 3.2.2 Road Cross Section The traffic modelling analysis (refer Chapter 5 and Tables 5.1 to 5.3) indicates that the proposed link road will have an Annual Average Daily Traffic (AADT) range in the design year of 14,100 to 16,400, indicating that a Type 2 Dual Carriageway is appropriate (refer Section 6, Table 4 of NRA TD9/07). Ref: 10.152 July 2011 Page 3/2 Roughan & O‟Donovan N14/N15 to A5 Link Consulting Engineers Environmental Impact Statement – Volume 1 TD27 (NRA DMRB) identifies the cross section required for a Type 2 Dual Carriageway. As such, the following minimum cross-sections are proposed for the Link project: Bridge Cross-Section: 2 x 7.0m carriageways 14.0 2 x 1.5m hardstand 3.0 2 x 0.5m hard strips 1.0 1 x1.5m median 1.5 Total Width: 19.5m The cross section is proposed for the full length of the bridge. Bridge Approach Cross Section 2 x 7.0m carriageways 14.0 2 x 0.5m hard strips (included in verge width) 2 x 3.5m wide verges (including 2.0m hard standing) 7.0 1 x1.5m median 1.5 Total Width 22.5m The proposed cross sections are shown on Figure 3.4, Volume 2. N15 Connections For the existing N15 carriageway connections, the current carriageway widths have been maintained i.e. on the northern approach a reduced single carriageway is to be maintained, whilst on the southern approach the widened carriageway with median hatching has been extended. 3.2.3 Junction Strategy Connection to A5 Western Transport Corridor (A5 WTC) Scheme The tie in to the A5 WTC has been defined by the Road Service and is to be located at Junction 7 (Refer Plate 3.3, below). The proposed roundabout will be constructed as part of the A5 scheme but will leave a leg off the roundabout to accommodate the proposed N14 / N15 to A5 Link. Ref: 10.152 July 2011 Page 3/3 Roughan & O‟Donovan N14/N15 to A5 Link Consulting Engineers Environmental Impact Statement – Volume 1 A5 Junction 7 Plate 3.3: Connection to A5 WTC (Extract from A5 Western Transport Corridor Exhibition Material) Plate 3.4: Typical A5 Cross Section (Extract from A5 Western Transport Corridor Exhibition Material) The roundabout proposed has an ICD (Inscribed Circle Diameter) of 70m, with the road entries being a typical dual carriageway, as illustrated above. The Roads Service Northern Ireland completed a Public Consultation exercise for the A5 WTC (the „Publication of Draft Orders and Environmental Statement‟ Exhibition) and the scheme was published in November 2010. The publication of the scheme has confirmed the approximate location of this link to the public. In terms of construction programme, it is likely that the A5 WTC Contract will require construction of the roundabout in the first instance, which will then facilitate the subsequent construction of the bridge abutment and structure. The A5 roundabout may need to be revisited to carry out finishing works at a later date. Connection to Existing N15 Road Network Traffic analysis has shown that a roundabout with an ICD of 55m is appropriate to provide sufficient capacity for existing and future traffic (refer to Chapter 5). Direct Accesses to/from the Existing N15 No new accesses will be allowed to/from the Link Road and current accesses on the N15 will either be maintained or repositioned (refer Figure 3.1, Volume 2). Ref: 10.152 July 2011 Page 3/4 Roughan & O‟Donovan N14/N15 to A5 Link Consulting Engineers Environmental Impact Statement – Volume 1 3.2.4 Proposed Design Speed The proposed design speed for the link shall be 50kph. The proposed roundabouts at either end of the scheme shall have a design speed of 50kph and consequently, for consistency it is proposed that the Link should also have a design speed of 50kph. This is justified as the length of the link is short and speeds are likely to be low due to the proximity of the roundabouts. 3.2.5 Segregation Barrier For a Type 2 Dual Carriageway, TD10/07 (Para 2.9) states that “in all cases the full pavement construction shall be continued through the central reserve and a segregating barrier shall be provided”. However, following discussions with An Garda Siochana, the need to facilitate a turning around facility prior to the international border was identified. Consequently, a departure from standard was granted to remove the need for a segregation barrier across the Link. As stated previously, the capacity of the Link Road required is that of a Type 2 Dual Carriageway with a design speed of 50kph. As such there is only limited benefit in providing a segregating barrier in the median, the function of which is to prevent head on collisions on high speed roads. 3.2.6 Enforcement Areas Consultations have been held with both the PSNI and the An Garda Siochana regarding the scheme. Although no additional facilities were required by the PSNI, An Garda Siochana require an enforcement area on both sides of the approach to the bridge from the N15 (refer Figure 3.1, Volume 2). 3.2.7 Accessibility for Pedestrians and Cyclists Currently there are limited facilities for pedestrians in the area of the bridge crossing and no facilities for cyclists. The current facilities on the Donegal side includes footpaths on either side of the existing N15 at the Carricknaslate/Coneyburrow estate. Refer to Plate 3.5 below. Plate 3.5: Existing Footpath at N15 Tie-in Ref: 10.152 July 2011 Page 3/5 Roughan & O‟Donovan N14/N15 to A5 Link Consulting Engineers Environmental Impact Statement – Volume 1 It is noted that the existing footpath terminates at the estate and does not continue southwards along the existing N15 to where the bridge crossing is proposed. On the Tyrone side of the river, no pedestrian facilities are being provided along the A5 WTC at this location. Due to the speed of the road such facilities will not be provided. Furthermore, overall demand is likely to be low as there are few local “destinations” which could generate pedestrian activity and in addition it is noted that there are plans for pedestrian facility enhancements within Lifford which will be the focus for such activity. Although no facilities are to be provided during the opening year, it may be necessary to allow for facilities in the future. To allow for potential future pedestrian usage, it is proposed to future-proof the bridge and allow for a suitable landtake within the CPO. Consequently the design allows for the safety barrier setback to be increased to 2m allowing for a 2m footway/cycleway in front of the barrier.