New Ross Bypass Paper-10-04-2018-MURPHY
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ENGINEERS IRELAND N25 NEW ROSS BYPASS N25 NEW ROSS BYPASS JOHN T. MURPHY, B.E., C.Eng., F.IEI., H.Dip.M.M., FConsEI. Project Director, Mott MacDonald Ireland JOE SHINKWIN, B.E., C.Eng., M.IEI., Dip. Mech. Eng. Project Manager, Mott MacDonald Ireland BAIRBRE MOYNIHAN, B.E., C.Eng., M.IEI. Project Engineer, Mott MacDonald Ireland Presented to a meeting of the Cork Region of Engineers Ireland 10th April 2018 SYNOPSIS The N25 New Ross Bypass PPP Scheme involves the construction of approximately 15km of National Route comprising approximately 14km of Dual Carriageway and approximately 1.2km of Single Carriageway and associated works. It also includes an extrados bridge crossing of the River Barrow which will include two main 230m spans and a total length of approx. 900m with a clearance of 36m above high water. This paper describes the development of the current route for the N25 New Ross Bypass including the various phases of route selection and follows the project through the statutory processes. The paper also describes the selection of the chosen bridge type for the River Barrow Crossing. Finally, the paper will outline the tender process and will briefly describe the construction contract and some of the progress to date. 1 MURPHY, SHINKWIN and MOYNIHAN INTRODUCTION Initially, a comprehensive examination FIRST PHASE ROUTE of the constraints in the area was SELECTION The need for a second river crossing undertaken to allow the feasibility and providing a bypass of New Ross has route selection process to begin. The Constraints Study was published in been recognised for a number of years Subsequently, in keeping with “National February 2001. After the constraints and has been identified in the Wexford, Roads Project Management Guidelines had been identified, the first phase of Kilkenny, and New Ross Development March 2000”, a Constraints Report was the Route Selection was undertaken. A Plans. The importance of the N25 Cork prepared gathering together all of the variety of alternative corridors were to Rosslare route has been emphasised known constraints. The Constraints selected for consideration having regard in the National Roads Needs Study, Study identified the following main to traffic performance, road network published in 1998 by the National considerations: connectivity, topography, alignment Roads Authority (NRA now Transport The River Barrow was used in design, constraints identified in the Infrastructure Ireland (TII)), and the connection with both commercial Constraints Study and feedback from National Development Plans (NDP) shipping and recreational/pleasure Public Consultation. 2000-2006 and 2007-2013, as well as craft. The Port of New Ross had the Infrastructure Investment Priorities stated that a second river crossing The principal objective of the Study was 2010-2016, published by the should not interfere with the to identify the best overall solution to the Department of Finance in July 2010. navigation of the River Barrow. different needs of local traffic and The N25 connects Cork at one end to Candidate Special Areas of people in New Ross, and those of long- Rosslare Europort at the other end, Conservation, Proposed National distance high-speed National Primary passing through New Ross. Heritage Areas and rare plant Road traffic. It was thus necessary to test each logical combination of species were identified in the study corridors. In the end 46 alternative road This paper describes the development area. networks (comprising various of the current route for the N25 New A large number of archaeological combinations of twelve different route Ross Bypass including the various sites had been identified in the study corridors; Routes A to L) were tested phases of route selection and follows area with a potential for further sites and evaluated. These are illustrated in the project through the statutory of archaeological or historic value on Figure 1. processes. The bypass includes an detailed inspection. iconic extrados structure crossing the The landscape rises on either side of A new crossing of the River Barrow River Barrow and the paper describes the river with hills and tributary and/or the River Nore in the New Ross the selection of the chosen bridge type valleys forming an undulating area together with a bypass of the town for the River Barrow Bridge. It also countryside. Visual constraints would impose costs on, and produce deals with some of the other structures identified include the scenic river benefits for the community at large. among the other 46 structures on the valley, ridgelines, steep hill sides Such a scheme would be justified if the bypass Finally, the paper will outline the and areas of woodland. The benefits that it produced exceeded their tender process and will briefly describe Wexford Development Plan associated costs and did so by more the construction contract and some of identified views from N30 and N25 to than would be the case for any the progress to date. be preserved or improved. alternative investment of the same funds. The existing N25 route at New Ross The constraints identified assisted in the passes right through the town, crossing development of potential route corridors. The benefits that could arise from a new the River Barrow over O’Hanrahan Issues identified in potential corridors river crossing include: Bridge and travelling along the quays. were examined in further detail at route The N30 to Enniscorthy joins the N25 at selection phase. (i) travel cost savings enjoyed by motor vehicles and their occupants, New Ross and also passes through the town via an inner relief road. These are key commercial and tourist routes. In the event that O’Hanrahan Bridge had to close to traffic, this strategic link would be severely affected forcing traffic to divert through Thomastown, utilising the R700 and the restricted bridge at Ferry Bridge (Mount Garrett Bridge). Delays on both the N25 and N30 routes are common. On the N25 in particular, at peak times queues of several kilometres and delays of up to half an hour are a regular occurrence and the delays can be greater. The existing traffic volumes as well as anticipated growth in traffic indicated that a new bypass and crossing of the river was needed. CONSTRAINTS STUDY In March 1999, Mott MacDonald (formerly Ewbank Preece OhEocha) were appointed by Wexford County Council to determine the need for and location of a Second River Crossing & Bypass of New Ross. Fig 1: Combinations of 12 corridors used to establish 46 Alternative Routes. 2 N25 NEW ROSS BYPASS (ii) increased travel opportunities The existing situation showed evidence Options which included a junction with arising from improvement of the of significant problems relating to the the R733 showed better benefits and local road network, N25 traffic through New Ross – in internal rate of return than those (iii) stimulation of the local economy by particular, on both sides of the bridge without a connection. They also increasing its potential to attract and on the quays. While significant provided for better connectivity to New commerce, trade and industry to problems repeatedly existed at Peak Ross and its ports. the area, Hours, the hourly average traffic outputs Of those remaining options with an (iv) positive environmental impacts of also revealed underlying problems. In upstream crossing, i.e. Corridors D, E, the crossing particular, O'Hanrahan Bridge, the Quay F, & G, Corridor D was preferred and (v) Benefits to town in terms of and Bridge Street were virtually at was retained for further consideration. pedestrianisation capacity and North Street had reached Corridors E, F & G had practical, (vi) collision reduction/ savings its maximum working capacity. The traffic/connectivity, and environmental model indicated average hourly traffic difficulties and did not offer a viable The costs that might be associated with speeds of less than 15kph (10mph) on solution to the needs of New Ross and these benefits include: O'Hanrahan Bridge, which indicated the National Primary Route Network. (vii) the capital, land, and property very low speeds during peak hours. Of the remaining options with a acquisition costs of the crossing crossing at Corridor D, the and its associated roadworks, The mathematical model of traffic combination of D with L was preferred (viii) the annual operating and behaviour was used to produce and was retained for further maintenance costs of the crossing, forecasts of New Ross area traffic consideration. Options combining (ix) costs associated with the protection conditions that might be associated with Corridor D with crossings at A, B and of river navigation, each of forty six road networks made up C (i.e. multiple river crossings) all had (x) negative environmental impacts of of various combinations of the route high cost and lower internal rate of the crossing and approach roads. corridors shown in Figure 1. For each return. These were eliminated. network, separate predictions were Of the remaining options, those with a Evaluation Methodology made for a typical hour, for each of the crossing at corridor B were eliminated years 2010 & 2020. These predictions due to difficulties with vertical The 46 scheme options were assessed enabled assessments to be made of the alignment (steep gradients on eastern in terms of their environmental impacts economic benefit, and the traffic and side of the river) and environmental and also having regard to their residual congestion implications of each issues including general fit with the performance in terms of traffic, alternative network. landscape (particularly on the western effectiveness as a bypass, and side of the river). economic performance. A variety of Following the evaluations described crossing types were also considered as above the 46 different options were The options remaining at that stage, appropriate at each river crossing carefully examined with a view to therefore, were as shown in Figure 2. location including high level bridges, eliminating the less favourable options.