SH73 Route Security Strategic Study Project Summary

Transcription

1 November 2009 SH73 Route Security Strategic Study Project Summary Managing Route Security from Springfield to Aickens

2 STATE HIGHWAY 73 SPRINGFIELD TO AICKENS ROUTE SECURITY STRATEGY CONSULTATION 1. Introduction State Highway 73 is a Regional State Highway in the National State Highway Strategy, and provides often the primary inter-regional link between Canterbury and the West Coast. SH73 provides community linkage from the towns and villages located within the section of highway covered by this study (Springfield, Castle Hill, Cass, Arthur s Pass and Otira) to Christchurch City, Hokitika and Greymouth. SH73 provides access from Canterbury to many recreational activities used by both domestic and international visitors, including skifields during the winter season. The route is recognised as being vital to the economic wellbeing of the West Coast, with increasing numbers of heavy vehicle movements and significant numbers of tourists travelling in campervans, buses or rental cars. Route security is crucial, as severance, depending on location, can result in significant detours. The alternative route from Christchurch to Greymouth via SH7 is considerably longer than SH73, taking around an additional one and a half hours. The most significant threat to the route is slope instability, more specifically rock fall, landslides, debris flows, rock avalanches and frittering (weathering). Additional threats to the route include flooding and river erosion of embankments. This strategic study has identified, investigated and prioritised areas of SH73 subject to route security issues, including threats from rock falls, slope instability, river erosion and flooding. The speed and severity of these hazards require particular expertise to assess the likely damage both to roads and the safety of users, and to consider the optimum period for timely intervention with capital improvements, or if ongoing maintenance is the most viable solution. 2. Purpose of this Document This document is designed to inform you of the Agency s proposed management of the section of SH 73 between Springfield and Aickens for the foreseeable future. The Agency is keen to receive your comments on its proposed Strategy before it is formally adopted. Your comments are important and necessary to ensure the Agency has addressed areas that cause greatest concern to the highway s stakeholders and is your opportunity to raise any further issues. 3. Purpose of the Study The SH 73 Study aims to identify, investigate and prioritise route security and road user safety issues along the highway from Springfield (Canterbury) to Aickens (West Coast), including risks from rock falls, slope instability (including debris flows), civil structures (excluding bridges), river erosion and flooding. The output of this study will be a recommended Strategy and Implementation Plan that will detail a practical and affordable management regime of the highway that will range from continuing current practice to investigating and developing new projects as they are required. Project Number NZTA Page 2 November 2009

3 4. Stakeholder Consultation An initial consultation exercise was completed in January 2009, inviting Stakeholders to provide insight of areas or specific sites where they believed hazards pose a significant risk to the highway and its users. The particular issues of concern within the feedback is summarised as follows: Localised flooding, erosion and washouts occurring in storm events; Snow and ice as a major hazard during winter, including clearance, tree-fall from snow, treatment of road surface for ice, warning signage and blockages caused by stuck vehicles. Rockfall hazards; Dropouts, landslides and slumping Narrow road corridor between Klondyke and Arthurs Pass; Extended closure of SH73 is considered a major impact to West Coast from reduced tourist numbers, inconvenience and cost of increased travel distances. 5. Investigation of Issues At-risk sites have been identified through document and report review, consultation, preliminary risk assessments and a drive-over exercise. In total, twenty five sites have been recognised as potentially problematic, comprising rock fall, landslide, flooding, coastal erosion and debris flow hazards. The sites are shown on the map presented as Figure 1. Each of the sites has been assessed in terms of its geological stability and/or environmental setting and their contributions to route security with an attempt to prioritise sites in terms of seriousness and urgency. The following ten sites are considered the most problematic: Porter s Pass (rock fall, landslide, debris flow, underslips) West of Paddy s (rock fall) Paddy s Bend (rock fall, landslide) White s Bridge (rock fall, landslide) Waimakariri Bluffs and Cornishman s The Deviation (rock fall, underslips, flow) Rise (rock fall, landslide, underslips) Otira Gorge (debris flow, landslide, rock fall, underslips) Bealey Spur (rock fall, landslide, underslip) Otira A, B and C (rock fall, rock flow) Craigieburn Cutting (rock fall, landslide) The issues experienced at these sites are typical for their general area. Consequently, this Study has developed a Corridor Management Strategy approach over an individual site approach, which is considered a more cost effective solution to reducing natural hazard risk along the route. Project Number NZTA Page 3 November 2009

4 NZ Transport Agency Project Number NZTA Page 4 November 2009

5 6. Proposed Corridor Management Plan The section of SH73 covered by this Study has been subdivided into six continuous sub-sections, as shown in Figure 1 and described in Table 1. The table also summarises the typical issues and Management Strategy to be adopted for each section. The proposed Corridor Management Plan has been developed to manage risk along SH73 within the constrained funding that is available and is based on the DNA principle of Detect, Notification, and Action. Detect and Identify risks to road users, route security and the environment through monitoring and surveillance by the Network Consultant and Contractor. Notify risks to NZTA State Highway Manager and affected Stakeholders as appropriate. Action Plan development including emergency response plans, investigation of highest risk sites, exposure and hazard reduction plans. See Figure 2 for the process to be adopted for determining appropriate action. Figure 2: Investigate, Design and Construct Process Route Security Site Normal Activity Unexpected Activity Monitor and Record Activity Small Event Activate Emergency Plan (Warnings, Road Closures, Detours etc.) Major Event Annually Review Monitoring Data. Review Risk Profile Remedial Work Under Network Operations Low Cost Option Undertake Initial Road Opening/ Clearing Where Possible Investigate Remedial Options Low or High Cost Higher Cost Options Secure Emergency Funds for Permanent Repair Submit to RLTP Submit to NLTP Implement Urgent Hazard Reduction Works Prepare Plans for Remedial Works Implement Preplanned Remedial Work New Emergency Work Normal Project Development Project Number NZTA Page 5 November 2009

6 Some of the ways in which hazard and exposure can be reduced comprise the following: Increase driver awareness e.g. through signage. Install more warning signs e.g. No Stopping, Rock Fall. Develop early warning systems for drivers and have response plans in place for the various hazard scenarios, including road closures and diversions when warranted. Close off rest areas or lay-bys in areas of increased exposure. Consider traffic management systems to remove road users from areas of greatest risk. Where physical works are needed to reduce the hazard, this could be in the form of: Improve drainage (rainfall and high ground water most common cause of instability). Preventative maintenance to protect the road (engineered solution such as rockfall netting). Realignment of the road away from the hazard. Porter s Pass Paddy s Bend Waimakariri Bluffs & Cornishman s Rise Otira Gorge Sites Identified as Potentially At-Risk During the SH 73 Strategic Study Otira A, B and C West of Paddy s White s Bridge The Deviation Project Number NZTA Page 6 November 2009

7 Table 1: Summary of Corridor Management Section Length Name RP Description (km) Springfield to 52.86/12.80 Kowai 16 Porters Pass to 76/5.77 Environment Identified Sites Typical Issue(s) Typical Management 5.3km West of Springfield monitoring Upper river valley. Over steepened valley Riverbank and 1km East of Kowai Bluffs Underslip sides. Highway follows Kowai river and embankment then rises to a high point at Porter s Kowai Bluffs inspections Pass. Predominantly farmland, with The Deviation, flow, underslip General and routine elevated areas supporting alpine flora. maintenance of catch Porters Pass, flow, underslip ditches Castle Hill Basin Porters Pass to Cornishman s Rise 76/5.77 to 121/ Alpine basin with several river crossings. Generally flatter terrain with some steep cut embankments present. Alpine vegetation, pasture and bush. Craigieburn Cutting Craigieburn Stream Flock Hill Lake Pearson, landslide River scour below road Rockfall, slumping Localised flooding monitoring Riverbank inspections Traffic management Flood monitoring and response management Waimakariri Cornishman s Rise to Bealey Bridge 121/2.50 to 136/ Road is formed on a steep hill slope overlooking and adjacent to the Waimakariri River. A number of large cuttings are present, with slopes below the road also being steep. Some bush, otherwise alpine vegetation and wilding trees. Cornishman s Rise & Waimakariri Bluffs Paddy s Bend West of Paddy s 350m East of the Poplars Bealey Spur Waimakariri Bridge to Klondyke Corner (southern) Rockfall, underslips Rockfall Rockfall, underslips Localised flooding Rockfall, colluvial instability Flooding, scour of road embankments Rockfall monitoring Riverbank and embankment inspections Flood monitoring and response management Traffic management Bealey Bealey Bridge to Arthur s Pass 136/0.00 to 145/ Road passes over Waimakariri River and is then undulates across steep, hill slopes that overlook the Bealey River. Sub alpine to alpine. Generally native bush covered slopes. Waimakariri Bridge to Klondyke Corner (northern) Public Shelter Mingha Bluff to Rough Ck Flooding, scour of road embankments Rockfall Rockfall, underslips, soil slippage monitoring Riverbank inspections Traffic management Flood monitoring and response management Arthur s Pass to McGrath s Corner and vegetation instability McGrath s Corner, landslide Otira Arthur s Pass to Aickens 145/1.06 to 159/ Steep alpine slopes generally descending to a broader, more gently sloping river valley. Some narrow and very winding sections of road. Dense temperate rainforest on slopes White s Bridge Pegleg Hill Otira Gorge Otira A, B and C Below Starvation Point & Windy Point, debris flow Debris flow, rock fall monitoring Flood and storm management Traffic management Pavement monitoring Wallace Point & Yorkeys Point, debris flow, landslide Big Slip Bridge to Aickens Debris flow Project Number NZTA Page 7 November 2009

8 SH 6 Route Security Strategic Study Project Summary 7. Your Views and Feedback We welcome your comments about the draft strategy before it is finalised in late December Please submit your feedback to GHD (see contact details below) by Friday 4 th December When commenting please provide: Your name; Organisation if appropriate; Daytime and mobile telephone numbers; and address. For further information please contact the Consultant Project Co-ordinator in the first instance, or the Transportation Planning Manager (NZTA). Consultant Project Co-ordinator: Mary O Callahan, GHD Ltd Level 4, 148 Victoria Street PO Box Christchurch 8013 T: F: E: mary.ocallahan@ghd.com Transportation Planning Manager: Michael Blyleven, NZTA NZTA Christchurch Regional Office Level 7, Pacific Brands House 123 Victoria Street PO Box 1479 Christchurch Mail Centre Christchurch 8140 T: F: E: michael.blyleven@nzta.govt.nz Project Number NZTA Page 8 November 2009