N81 Tullow Footbridges & Associated Works
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N81 Tullow Footbridges & Associated Works Appropriate Assessment Screening Report Carlow County Council 10 April 2018 N81 Tullow Footbridges & Associated Works Appropriate Assessment Screening Report Notice This document and its contents have been prepared and are intended solely for Carlow County Council’s information and use in relation to N81 Tullow Footbridges and Associated Works project. Atkins Ireland assumes no responsibility to any other party in respect of or arising out of or in connection with this document and/or its contents. This document has 43 pages including the cover. Document history Job number: 5153094 Document ref: 5153094 DG36 Revision Purpose description Originated Checked Reviewed Authorised Date Rev 1.0 Appropriate Assessment POD POD NS MJ 10/04/18 Client signoff Client Carlow County Council Project N81 Tullow Footbridges & Associated Works Document title Appropriate Assessment Screening Report Job no. 5153094 Copy no. 1.0 Document 5153094DG36 reference Atkins Appropriate Assessment Screening Report | Version 1.0 | 10 April 2018 | 5153094 ii N81 Tullow Footbridges & Associated Works Appropriate Assessment Screening Report Table of contents Chapter Pages 1. Introduction 1 Background to the commission 1 Description of the Proposed Works 2 General Description of the Project Location 4 2. The Appropriate Assessment Process 9 The Stages in Appropriate Assessment 9 Objectives of Appropriate Assessment 10 3. Methods 11 Desk Study 11 Screening Process 11 Statement of Authority 13 4. Appropriate Assessment Screening 14 Identification of Natura 2000 Sites 14 Brief Description of Natura 2000 Sites 14 Conservation Objectives for the Natura 2000 sites 18 Features of Interest and Potential Threats to the Natura 2000 Sites 20 Likelihood of Potential Impacts on Natura 2000 Sites 23 Identification of potential impacts on Natura 2000 sites 23 Cumulative impacts 29 Likelihood of Significant Effects on Natura 2000 Sites 30 Consideration of Findings 30 5. Findings of No Significant Impacts 31 6. References 35 Appendices 37 Appendix A. Site Synopsis – Slaney River Valley SAC 38 Atkins Appropriate Assessment Screening Report | Version 1.0 | 10 April 2018 | 5153094 iii N81 Tullow Footbridges & Associated Works Appropriate Assessment Screening Report List of Tables Table 5.1 Natura 2000 sites features of interest and NPWS identified threats. Table 5.2 Potential for Impacts on Features of Interest of Slaney River Valley SAC (000781). List of Figure Figure 1.1 Site Location. Figure 5.1 Natura 2000 Sites. List of Plates Plate 1.1 N81 Slaney Bridge (downstream). Plate 1.2 View of left hand bank (upstream). Plate 1.3 View of left hand bank (downstream). Plate 1.4 View of right hand bank (upstream). Plate 1.5 View of right hand bank (downstream). Atkins Appropriate Assessment Screening Report | Version 1.0 | 10 April 2018 | 5153094 iv N81 Tullow Footbridges & Associated Works Appropriate Assessment Screening Report 1. Introduction 1.1. Atkins was commissioned by Carlow County Council (CCC) to examine a number of design options for footbridges adjacent to the existing N81 Slaney Bridge in Tullow, Co Carlow. The commission also includes design of a lighting system; the redesign of the junction of the N81 and R725 to improve turning movements for HGV vehicles turning northbound on the N81 from the R725. 1.2. Atkins ecology team has been tasked with preparation of the Appropriate Assessment Screening Report for the project. Background to the commission 1.3. The existing Slaney Bridge in Tullow is a four span masonry arch over the River Slaney, built circa 1855. The overall length of the bridge between abutments, is approximately 33.9 m. The overall width of the structure is 10.26 m. 1.4. It has been identified that both vehicular and pedestrian traffic safety is compromised during large HGV movements from the R725 northbound onto Slaney Bridge. During these movements, large HGV traffic is forced across into the opposing lane of the N81, in addition to mounting the nearside western footpath in order to complete the turning movement. With the aforementioned in mind it is considered that the existing 1.4 m pedestrian footpaths are inadequate and new footbridges on both sides of the structure are required. Various potential solutions were examined to alleviate existing conflicts in the traffic turning movements while facilitating the safe passage of pedestrians on the bridge. To facilitate safe pedestrian movement all options would require the construction of new footbridges on both sides of the existing bridge. 1.5. The protected status of Slaney Bridge required careful consideration of its interface with the proposed works. In consultation with conservation architects it was determined that the proposed works to the existing bridge would be kept to a minimum. Thomas Traynor Street between Hawkin’s Lane and Abbey Street would be widened by removing a section of the existing footpath and the two way traffic would be moved to the newly constructed southern kerb line to maximize the available space for traffic to carry out its required turning movements over Slaney Bridge. 1.6. Therefore, the aim of the proposed project is to alleviate vehicular congestion and provide safe pedestrian access across the N81. The proposed project does not aim to increase traffic volumes in the vicinity of the R418/ N81 junction and the Slaney Bridge. 1.7. Three options for the footbridges have been considered; these are as follows: - Option 1 consists of precast concrete bridges comprising pre-stressed slabs spanning between existing piers cutwaters and supported on in-situ concrete pad foundations incorporated into the cutwater and river walls. This option would include granite masonry cladding to the proposed footbridges facia to match the granite masonry façade of the existing bridge. Atkins Appropriate Assessment Screening Report | Version 1.0 | 10 April 2018 | 5153094 1 N81 Tullow Footbridges & Associated Works Appropriate Assessment Screening Report Option 2 consists of steel bridge decks with steel box sections spanning between the existing cutwaters and supported on circular steel sections at the cutwaters and on concrete pads on the river walls. The supports on the cutwaters are splayed outwardly (longitudinally) to minimise the deck span and therefore minimise the deck depth (this option is presented in the design drawings listed in paragraph 1.8). Option 3 is similar to Option 2 and comprises a steel bridge deck spanning between the existing cutwaters with simple vertical supports at the cutwaters. This option minimises steelwork fabrication, but requires deeper steel box sections. 1.8. All the above options include provisions for carrying multiple services under the footbridges. 1.9. The preferred design solution is Option 2; a full set of design drawings is included with the Part 8 planning application package. Key design drawings are listed below: - 5153094-HTR-DR-8101 Site Location Map / Plan 5153094-HTR-DR-8105 Proposed Bridge Site Layout Plan 5153094-HTR-DR-8107 Existing & Proposed Bridge Elevations (Sheet 1 of 2) 5153094-HTR-DR-8108 Existing & Proposed Bridge Elevations (Sheet 2 of 2) 5153094-HTR-DR-8109 Proposed Footbridges Typical Cross Sections 5153094-HTR-DR-8111 Photomontages of Proposed Footbridges 5153094-HTR-DR-8112 - 8114 Proposed Lighting Design (Sheets 1-3) Description of the Proposed Works 1.10. The proposed footbridges will be 2m wide and their vertical profile will, in so far as is possible, follow that of the existing masonry bridge. The footbridges will be constructed of profiled aluminium decking on a painted structural steel frame. The steel frame would span between the existing bridge pier cutwaters and the river walls. The footbridges will be anchored to the existing bridge at the piers. The new footbridge structures will be located on both sides of the existing masonry road bridge. 1.11. The archaeological and architectural heritage importance of the existing bridge (NIAH ref. no. 10400325) has been assessed as part of the design process and to support the application for Part 8 planning permission. 1.12. The junction of the N81 and R725 Thomas Traynor Street is currently geometrically inadequate to accommodate two way movements of HGV’s. This results in HGV’s frequently carrying out unsafe turning maneouvres while turning north onto N81 Slaney Bridge from R725 Thomas Traynor Street. The proposal to Atkins Appropriate Assessment Screening Report | Version 1.0 | 10 April 2018 | 5153094 2 N81 Tullow Footbridges & Associated Works Appropriate Assessment Screening Report provide footbridges and associated works will require the provision of appropriate signage, road markings and minor works to guide HGV traffic approaching the bridge along R725 Thomas Traynor Street and on to Slaney Bridge. 1.13. Site works associated with the design process included topographical surveys (completed in November & December 2016) and geotechnical and structural investigations (completed in August 2017). These works are required to inform the final design of the footbridges. The topographical surveys were carried out on foot and did not require any intrusive works on the river banks or within the river channel. 1.14. There shall be no large machinery, such as excavators or diggers, working in- stream at any time during the construction of the footbridges. Scaffolding will be required around the pier cutwaters to facilitate the installation of the footbridges and their supports on the cutwaters and river walls. The scaffolding will be manually erected by construction workers. The scaffolding will be placed on the existing concrete apron which extends underneath the bridge on both sides. The concrete apron extends 1.5-3.0m beyond the extent of the cutwaters and therefore provide sufficient room for access and erection of the scaffolding. The scaffolding will be 1.0 m wide and will not impact on the river bed as it will be wholly contained within the concrete apron. Thus, there shall be no in-stream works within the natural riverbed of the River Slaney. 1.15. Construction of the footbridges will be carried out from the scaffolding, existing bridge deck and from the river walls at either end of the bridge.