Gladstone Road Bridge Cycleway/Walkway

Concept Options Report

Prepared for: Tairāwhiti Roads

Prepared by: Cheng Liu

November 7, 2017

Revision Description Author Quality Check Independent Review

1 For Client Review

Cheng Liu 19/9/17 Nigel Beatson 19/9/17 Rob Partridge 19/9/17

2 Update for Option 6

Cheng Liu 07/11/17 Nigel Beatson 07/11/17 Rob Partridge 07/11/17

Sign-off Sheet

This document entitled ‘Gladstone Road Bridge Cycleway/Walkway’ was prepared by MWH, now part of Stantec for the account of Tairāwhiti Roads. Any reliance on this document by any third party is strictly prohibited. The material in it reflects the professional judgment of MWH, now part of Stantec in light of the scope, schedule and other limitations stated in the document and in the contract between MWH, now part of Stantec and the Client. The opinions in the document are based on conditions and information existing at the time the document was published and do not take into account any subsequent changes. In preparing the document, MWH, now part of Stantec did not verify information supplied to it by others. Any use which a third party makes of this document is the responsibility of such third party. Such third party agrees that MWH, now part of Stantec shall not be responsible for costs or damages of any kind, if any, suffered by it or any other third party as a result of decisions made or actions taken based on this document.

Prepared by

Cheng Liu

Check by

Nigel Beatson

Reviewed by

Rob Partridge

Approved by

Rob Partridge

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Executive Summary As part of the Urban Cycleway Programme (UCP) the NZ Transport Agency and Tairawhiti roads are proposing to provide a new cycleway/walkway on the Gladstone Road Bridge. The purpose of this document is to report on the concept options that have been considered for the new cycleway/walkway on Gladstone Road Bridge to ultimately enable the selection of a preferred option.

Gladstone Road Bridge is the one of the main road bridges running through Gisborne connecting the eastern and western parts of the city. There is a narrow existing cycle lane and a raised concrete footpath that is approximately 1.5m wide of either side of the bridge. The original bridge was built in 1923/24.

As part of the Detailed Business Case (DBC), completed in December 2016, and recent consultation meetings a number of factors/issues were identified that need to be considered as part of the concept option development. These include:

• The Heritage Status of the Gladstone Road Bridge (Historic Place Category 2) • Accumulation of debris underneath bridge during periods of flooding • Age, design and remaining life of the bridge • Existing services and utilities attached to bridge and on the eastern shore • Consenting and permit requirements • Delivery timeframe • Provision of space for all potential users of the new path • Safety in Design (SiD)

Six concept options have been developed for widening on the downstream side of the bridge (due to the need to connect with the inner harbour walking and cycling linkages). The table below sets out the key details of the concept options along with a preference based on the advantages and disadvantages identified in the report which respond to the key considerations identified above. It should be noted that at this stage no detailed analysis has been undertaken.

Option Description Existing

Balustrade

Obtaining Consent

Est Cost ($M) Construction

Est Time Construction

Preference

1 New 2.4m wide concrete deck (Keep existing external beam)

Remove* Relatively

Easy 0.9 - 1.1 6 months Less Preferred

2 New 3m wide timber deck Remove Relatively

Easy 0.9 – 1.1 6 months

Not

recommended

3 Widened section bolted to pier (concrete or timber)

Keep Medium 1.2 – 1.4 6-8 months Not

recommended

4 New timber deck with balustrade (2 separate sections)

Keep Relatively

Easy 0.9 – 1.1 6 months

Not

recommended

5 Pier extension at downstream with widened deck

Remove or

Keep Difficult 1.6 – 2.0 10 months

Not

recommended

6 New 3~4m wide concrete deck (Replace existing external beam)

Remove * Medium 1.2 – 1.5 6-8 months Preferred

*Possibility of reusing/keeping a section of the existing balustrade

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The preferred option, based on consideration of the identified factors and constraints, is Option 6:

- Remove the existing footpath and external beam, install a new concrete external beam on top of the existing pier. Install a new 3~4m wide concrete slab that is supported by the first two external beams and cantilevers out.

This option allows for a new external beam which can accommodate a longer cantilever, providing more flexibility for a wider and more usable path. The bridge appearance and cornice can be replicated and some of the existing balustrade may be able to be reused. This option is supported by Heritage New Zealand.

Option 6 will require careful management of demolition and relocation of some services, which increases costs and timeframe, however it provides the best outcome without works within the waterway (which would require significant consenting).

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1 Introduction

As part of the Urban Cycleway Programme (UCP) the NZ Transport Agency and Tairawhiti roads are proposing to provide a new cycleway/walkway on the Gladstone Road Bridge. This is a key component of the cycleway network set out in the Detailed Business Case (DBC) completed in December 2016. The purpose of this document is to report on the concept options that have been considered for the new cycleway/walkway on Gladstone Road Bridge to ultimately enable the selection of a preferred option. All options considered involve widening on the downstream side of the bridge (due to the need to connect with the inner harbour walking and cycling linkages).

Gladstone Road Bridge is the one of the main road bridges running through Gisborne connecting the eastern and western parts of the city. The original bridge was built in 1923/24. It is a two lane, 110m long bridge consisting of eight spans. Each span consists of a concrete deck supported on eight concrete beams. The concrete beams are founded on concrete piers and abutments.

There is a narrow existing cycle lane along either side of the bridge. The cycle lanes are marked but unprotected from motor vehicles on the bridge. Beyond each cycle lane is a raised concrete footpath that is approximately 1.5m wide. The bridge has heritage status (Historic Place Category 2).

Figure 1: Aerial View of Gladstone Road Bridge

Downstream Side

N

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2 Key Considerations As part of the DBC and recent consultation meetings a number of factors/issues were identified that need to be considered as part of the concept options development. The items identified below are by no means exhaustive and other considerations may come up through further investigation and consultation.

1. Heritage Status

The Heritage Status of the Gladstone Road Bridge has been assessed and classed to be “Historic Place Category 2”. Retention of various heritage features of the bridge, including the balustrades, needs to be considered.

2. Flood Debris

In times of flood, debris can get caught around the bridge (particularly on the upstream side). In 2015, during a major flood in the Gisborne region, a large amount of debris was caught under the bridge (refer Figure 2). Options that have the potential to further collect or restrict debris would not be desirable.

Figure 2: Debris being cleared from underneath the bridge during the 2015 Gisborne flood

3. Age, design and remaining life of the Bridge

As identified earlier the bridge was built in 1923/24 and the existing superstructure of the bridge was designed with the current footpath layout. Any widening will cause additional loads on the existing beams and there will be a limit on the amount of additional loading and widening possible (depending on the option). Confirmation of the extent of widening possible for each option hasn’t been confirmed at this stage, however an indication of likely restrictions have been identified.

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In 2013 Holmes Consulting Group estimated the bridge has a remaining life of only 25 years due to the high levels of chlorides found in the concrete when testing the beams and deck. The widened section of the bridge, regardless of the choice of material, will be designed to have a minimum life of 50 years as required by the NZTA Bridge Manual. This will result in the original bridge requiring replacement much sooner than the widened section and hence the whole of life cost of the widening is a factor.

4. Services

There are a number of existing services under the bridge including power, water and wastewater. Most of these are located between the 1st and 2nd external beam, under the footpaths, on both sides of the bridge (although the majority are on the upstream side). There is also a service building on the eastern shore near the abutment.

5. Consenting

Any widening option that involves work which alters or needs construction within the waterway will require more permits, consents and waterway assessments compared to options that require work on the bridge superstructure only. In addition, any structural features that fall below the underside of the existing beams will reduce the existing waterway area and may also need more consents. Obtaining consents takes time and can increase the cost to the project.

6. UCP Funding Expenditure

NZTA requires a portion of the funding for UCP to be spent by June 2018. The quicker construction can get underway the sooner this portion of money can be spent.

7. Recreational Use

With the increased use of the area through the Inner Harbour and cycleway projects any additional path on the bridge could become an attraction for other recreational users such as tourists, fishermen and bridge jumpers. These users present a potential hazard for pedestrians and cyclists by obstructing the flow. Consideration of all potential users on the path in a safe manor will be important.

8. Safety in Design

Safety in Design (or SiD) is an important consideration for all projects and hence all options that are being considered for the Gladstone Road Bridge widening. SiD essentially responds to safety during construction, operation and maintenance.

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3 Risks and Assumptions At this stage of developing concept options the reader should be aware of the following:

• A recent site inspection has shown that the existing bridge is in deteriorating condition. Some repairs may be required to the existing components to enable the widening options to be constructed.

• Only preliminary analyses have been undertaken to determine the capacity of the existing structure to carry the additional loads of the widening options. The extent of widening shown for each option is an estimate at this stage.

• Due to the age of the bridge and the close proximity to the marine environment, previous testing has identified high levels of chlorides in the concrete. A previous report undertaken by Holmes Consulting has estimated that ongoing repairs to the bridge will eventually become uneconomic and they estimate the existing bridge has a remaining life of 25 years.

• Holmes Consulting have also identified this bridge as likely having a low seismic capacity due to the relatively short piles which are in ground that is relatively soft and may liquefy during an earthquake. They estimate the bridge only has the ability to resist a 1 in 100 year earthquake.

• All options will result in traffic disruption during construction, however with careful planning and construction methodology this can be minimised.

4 Widening Options As part of this concept exercise six options have been developed for the downstream side of Gladstone Road Bridge. These options are:

1. A new 2.4m wide concrete deck (keep the existing external beam) 2. A new 3m wide timber deck 3. A widened section bolted to pier (concrete or timber) 4. A new timber deck with balustrade (two separate sections) 5. A pier extension downstream with widened deck 6. A new 3~4m wide concrete deck (Replace the existing external beam)

The following has been provided for each option as part of this report:

1. A sketch cross-section 2. A high level rough order construction cost estimate 3. An estimated construction time 4. An indication as to how easy it will be to obtain consents 5. Advantages and disadvantages of each option which respond to the key considerations identified in

Section 2.

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4.1 Option 1 – New 2.4m wide concrete deck (Keep existing external beam) This option involves a new concrete overlay on the existing footpath and a cantilevered concrete widening

Est Construction Cost $0.9 – 1.1 Million Est Time to Construct 6 months

Obtaining Consent Relatively Easy

Advantages Disadvantages

Structurally more simplistic and therefore easier to construct (shorter timeframe)

Capacity of existing outer beam limits path width to 2.4m providing a poor level of service

Cornice and face of bridge maintained and cornice could be replicated at edge of widened deck

Path vs road level is high creating a more confined look on the road corridor

Possibility of pre-casting parts of new concrete deck (Safety in Design)

Existing balustrade will have to be removed first to install new deck although there is a possibility of retaining a section of the original balustrade after the new deck has been installed

New structure is all concrete which could more easily match the appearance of the existing bridge

Potential to incorporate F-Shape vehicle barrier Easier tie-in at abutments

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4.2 Option 2 – New 3m wide timber deck This option involves a timber overlay on the existing footpath and widened timber section supported on new steelwork.

Est Construction Cost $0.9 – 1.1 Million Est Time to Construct 6 months

Obtaining Consent Relatively Easy

Advantages Disadvantages

Timber deck construction is more light weight Existing balustrade will have to be removed although there may be a possibility of retaining a section of the original balustrade after the new deck has been installed

Timber deck could fit well with the “boardwalk look” Heritage value of face and cornice degraded – This is not supported by Heritage NZ

More sustainable option as the timber deck can be reused (Note limited remaining life of existing bridge)

Timber and steel will need to be treated for being in a marine environment

An anti-slip surface will need to be installed Extent of widening is limited to the capacity of the existing

structure More work required under structure (Safety in Design)

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4.3 Option 3 – Widened section bolted to pier (concrete or timber) This option involves a timber overlay on the existing footpath with an independent timber widening supported on steel spanning between the piers.

Est Construction Cost $1.2 – 1.4 Million Est Time to Construct 6-8 months

Obtaining Consent More Difficult

Advantages Disadvantages

Existing balustrade is kept Debris getting caught around the steel frames bolted to the piers and impact of these on the waterway area under the bridge.

The widened section is independent from the existing beams, and therefore does not transfer any additional load onto the existing bridge superstructure

Heritage value of face and cornice degraded and poor aesthetics from underneath the bridge – This is not supported by Heritage NZ

Two separate 1.5m paths creates a poor level, particularly for cyclists and a ‘caged’ feel.

Extent of widening is limited by the capacity of the cantilevered steel beams and the connection of these to the existing piers.

More work required under structure (Safety in Design)

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4.4 Option 4 – New timber deck with balustrade (two separate sections) This option involves a timber overlay on the existing footpath and a timber widening supported on new steelwork.

Est Construction Cost $0.9 – 1.1 Million Est Time to Construct 6 months

Obtaining Consent Relatively Easy

Advantages Disadvantages

Existing balustrade is kept Heritage value of face and cornice degraded – This is not supported by Heritage NZ

Timber deck could fit well with the “boardwalk look” Two separate 1.5m paths creates a poor level, particularly for cyclists and a ‘caged’ feel.

More sustainable option as the timber deck can be reused. (Note limited remaining life of existing bridge)

Timber and steel will need to be treated for being in a marine environment

An anti-slip surface will need to be installed Extent of widening is limited to the capacity of the existing

structure More work required under structure (Safety in Design)

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4.5 Option 5 – Pier extension at downstream with widened deck This option involves widening the pier and piling into the river with a concrete deck overlay

Est Construction Cost $1.6 – 2.0 Million Est Time to Construct 10 months

Obtaining Consent Difficult

Advantages Disadvantages

Possibility of keeping the existing balustrade Long timeframe for construction Additional beam takes off load from existing beam High cost Additional pier/pile increases seismic capacity of bridge Widening the pier involves driving piles in the river bed

and working in the river itself which may have more consenting requirements. These consents may be difficult to obtain.

The new deck could potentially be designed to take vehicle load, as there is more substructure support from the additional pile

Has a higher level of safety risk for workers (Safety in Design)

No limit to the extent of widening Overdesigning the extension when the existing bridge has a limited remaining life

Can match existing appearance of bridge

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4.6 Option 6 – New 3~4m wide concrete deck (Replace existing external beam) This option involves removal of the existing footpath and external beam. A new concrete external beam will be installed on top of the existing pier. A new 3~4m wide slab will be supported on the first two external beams and cantilevers out.

Est Construction Cost $1.2 – 1.5 Million Est Time to Construct 6-8 months

Obtaining Consent Medium

Advantages Disadvantages

The new external beam can be designed to have a higher capacity to accommodate for a longer cantilever providing a path 3~4m wide (improved level of service and better for recreational use)

More complication demolition phase of construction which increases cost and time (Higher level of risk – SiD)

Cornice and face of bridge can be replicated A number of consents required.

Possibility of pre-casting parts of new concrete deck (Safety in Design)

A need to relocate power and protect gas.

New structure is all concrete which could more easily match the appearance of the existing bridge

Overdesigning the extension when the existing bridge has a limited remaining life.

Can have barrier kerb or F-Shape vehicle barrier Existing balustrade will have to be removed first to install new deck although there is a possibility of retaining a section of the original balustrade after the new deck has been installed.

Easier tie-in at abutments Supported by Heritage NZ

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5 Summary Six concept options have been developed for widening on the downstream side of the Gladstone Road Bridge to accommodate a cycleway/walkway. The table below summarises the key elements of each option including an estimate of construction cost and time, the ease of obtaining consents and whether or not the balustrade can be retained. In addition a preference has been based on the advantages and disadvantages identified in the report which respond to the key considerations identified in Section 2.

Option Description Existing

Balustrade

Obtaining Consent

Est Cost ($M) Construction

Est Time Construction

Preference

1 New 2.4m wide concrete deck (Keep existing external beam)

Remove* Relatively

Easy 0.9 - 1.1 6 months Less preferred

2 New 3m wide timber deck Remove Relatively

Easy 0.9 – 1.1 6 months

Not

recommended

3 Widened section bolted to pier (concrete or timber)

Keep Medium 1.2 – 1.4 6-8 months Not

recommended

4 New timber deck with balustrade (2 separate sections)

Keep Relatively

Easy 0.9 – 1.1 6 months

Not

recommended

5 Pier extension at downstream with widened deck

Remove or

Keep Difficult 1.6 – 2.0 10 months

Not

recommended

6 New 3~4m wide concrete deck (Replace existing external beam)

Remove* Medium 1.2 – 1.5 6-8 months Preferred

*Possibility of reusing/keeping a section of the existing balustrade

The preferred option, based on consideration of the identified factors and constraints, is Option 6:

- Remove the existing footpath and external beam, install a new concrete external beam on top of the existing pier. Install a new 3~4m wide concrete slab that is supported by the first two external beams and cantilevers out.

This option allows for a new external beam which can accommodate a longer cantilever, providing more flexibility for a wider and more usable path. The bridge appearance and cornice can be replicated and some of the existing balustrade may be able to be reused. This option is supported by Heritage New Zealand. Option 6 will require careful management of demolition and relocation of some services, which increases costs and timeframe, however it provides the best outcome without works within the waterway (which would require significant consenting).

The next steps will be to:

1. Confirm the preferred option with key stakeholders.

2. Estimate cost of construction for the preferred option with detailed breakdown.

3. Complete preliminary design, followed by detailed design and preparation of contract documents.