sh73 route security strategic study project summary · sh73 route security strategic study project...

November 2009

Managing Route Security from Springfield to Aickens

SH73 Route Security Strategic StudyProject Summary

NZ Transport AgencySH 73 Route Security Strategic Study – Project Summary

Project Number NZTA 62095 November 2009

STATE HIGHWAY 73SPRINGFIELD 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 theprimary inter-regional link between Canterbury and the West Coast. SH73 provides community linkage fromthe 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 fromCanterbury to many recreational activities used by both domestic and international visitors, including skifieldsduring 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 incampervans, buses or rental cars.

Route security is crucial, as severance, depending on location, can result in significant detours. The alternativeroute from Christchurch to Greymouth via SH7 is considerably longer than SH73, taking around an additionalone 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 erosionof 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 thesehazards require particular expertise to assess the likely damage both to roads and the safety of users, and toconsider the optimum period for timely intervention with capital improvements, or if ongoing maintenance isthe 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 73between Springfield and Aickens for the foreseeable future. The Agency is keen to receive your comments onits proposed Strategy before it is formally adopted. Your comments are important and necessary to ensure theAgency has addressed areas that cause greatest concern to the highway’s stakeholders and is your opportunityto 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 thehighway 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 thisstudy will be a recommended Strategy and Implementation Plan that will detail a practical and affordablemanagement regime of the highway that will range from continuing current practice to investigating anddeveloping new projects as they are required.



4. Stakeholder Consultation

An initial consultation exercise was completed in January 2009, inviting Stakeholders to provide insight ofareas or specific sites where they believed hazards pose a significant risk to the highway and its users. Theparticular 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 ofroad 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 riskassessments and a drive-over exercise. In total, twenty five sites have been recognised as potentiallyproblematic, comprising rock fall, landslide, flooding, coastal erosion and debris flow hazards. The sites areshown 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 theircontributions to route security with an attempt to prioritise sites in terms of seriousness and urgency. Thefollowing 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’sRise (rock fall, landslide, underslips)

The Deviation (rock fall, underslips, flow)

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 hasdeveloped a ‘Corridor Management Strategy’ approach over an individual site approach, which is considered amore cost effective solution to reducing natural hazard risk along the route.



6. Proposed Corridor Management Plan

The section of SH73 covered by this Study has been subdivided into six continuous sub-sections, as shown inFigure 1 and described in Table 1. The table also summarises the typical issues and Management Strategy tobe adopted for each section.

The proposed Corridor Management Plan has been developed to manage risk along SH73 within theconstrained 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 andsurveillance 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 determiningappropriate action.

Figure 2: Investigate, Design and Construct Process

Route Security Site

Normal Activity

Monitor andRecord Activity

Annually ReviewMonitoring Data.

Review RiskProfile

InvestigateRemedial Options

Submit to RLTP

Submit to NLTP

UnexpectedActivity

ActivateEmergency Plan

(Warnings, RoadClosures, Detours

etc.)

Remedial Work UnderNetwork Operations Undertake Initial

Road Opening/Clearing Where

Possible

SecureEmergency Funds

for PermanentRepair

New EmergencyWork

Implement Pre-planned Remedial

Work

ImplementUrgent Hazard

ReductionWorks

Prepare Plansfor Remedial

Works

Low or HighCost

Small Event Major Event

Low Cost Option

Higher Cost Options

Normal ProjectDevelopment



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 hazardscenarios, 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



Table 1: Summary of Corridor Management

NameSectionDescription

RPLength(km)

Environment Identified Sites Typical Issue(s) Typical Management

5.3km West of Springfield Rock fall

1km East of Kowai Bluffs Underslip

Kowai Bluffs Rock fall

The Deviation Rock fall, flow, underslip

KowaiSpringfield toPorters Pass

52.86/12.80to 76/5.77

16

Upper river valley. Over steepened valleysides. Highway follows Kowai river andthen rises to a high point at Porter’sPass. Predominantly farmland, withelevated areas supporting alpine flora.

Porters Pass Rock fall, flow, underslip

Rock fall monitoringRiverbank andembankmentinspectionsGeneral and routinemaintenance of catchditches

Craigieburn Cutting Rock fall, landslide

Craigieburn Stream River scour below road

Flock Hill Rockfall, slumping

Castle HillBasin

Porters Pass toCornishman’sRise

76/5.77 to121/2.50

42

Alpine basin with several river crossings.Generally flatter terrain with some steepcut embankments present. Alpinevegetation, pasture and bush.

Lake Pearson Localised flooding

Rock fall monitoringRiverbank inspectionsTraffic managementFlood monitoring andresponse management

Cornishman’s Rise & WaimakaririBluffs

Rockfall, underslips

Paddy’s Bend RockfallWest of Paddy’s Rockfall, underslips350m East of the Poplars Localised floodingBealey Spur Rockfall, colluvial instability

WaimakaririCornishman’sRise to BealeyBridge

121/2.50 to136/0.00

13

Road is formed on a steep hill slopeoverlooking and adjacent to theWaimakariri River. A number of largecuttings are present, with slopes belowthe road also being steep. Some bush,otherwise alpine vegetation and wildingtrees. Waimakariri Bridge to Klondyke

Corner (southern)Flooding, scour of roadembankments

Rockfall monitoringRiverbank andembankmentinspectionsFlood monitoring andresponse managementTraffic management

Waimakariri Bridge to KlondykeCorner (northern)

Flooding, scour of roadembankments

Public Shelter RockfallBealeyBealey Bridge toArthur’s Pass

136/0.00 to145/1.06

10

Road passes over Waimakariri River andis then undulates across steep, hillslopes that overlook the Bealey River.Sub alpine to alpine. Generally nativebush covered slopes. Mingha Bluff to Rough Ck Rockfall, underslips, soil slippage

Rock fall monitoringRiverbank inspectionsTraffic managementFlood monitoring andresponse management

Arthur’s Pass to McGrath’s Corner Rock fall and vegetation instabilityMcGrath’s Corner Rock fall, landslideWhite’s Bridge Rock fallPegleg Hill Rock fallOtira Gorge Rock fall, debris flowOtira A, B and C Rock fallBelow Starvation Point & WindyPoint

Debris flow, rock fall

Wallace Point & Yorkeys Point Rock fall, debris flow, landslide

OtiraArthur’s Pass toAickens

145/1.06 to159/11.28

24

Steep alpine slopes generally descendingto a broader, more gently sloping rivervalley. Some narrow and very windingsections of road. Dense temperaterainforest on slopes

Big Slip Bridge to Aickens Debris flow

Rock fall monitoringFlood and stormmanagementTraffic managementPavement monitoring



7. Your Views and Feedback

We welcome your comments about the draft strategy before it is finalised in late December 2009. Pleasesubmit your feedback to GHD (see contact details below) by Friday 4th December 2009.

When commenting please provide:

Your name;

Organisation if appropriate;

Daytime and mobile telephone numbers; and

Email address.

For further information please contact the Consultant Project Co-ordinator in the first instance, or theTransportation Planning Manager (NZTA).

Consultant Project Co-ordinator:

Mary O’Callahan, GHD Ltd

Level 4, 148 Victoria StreetPO Box 13-468

Christchurch 8013

T: +64 3 364 5503F: +64 3 377 8575

E: [email protected]

Transportation Planning Manager:

Michael Blyleven, NZTA

NZTA Christchurch Regional OfficeLevel 7, Pacific Brands House

123 Victoria StreetPO Box 1479

Christchurch Mail CentreChristchurch 8140

T: +64 3 963 3218F: +64 3 365 6576

E: [email protected]

sh73 route security strategic study project summary · sh73 route security strategic study project...

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