Reason 9 to stop the FLE: Safety and construction concerns

Riverstone Holdings Ltd commissioned, paid for, and submitted a number of reports as part of its concession application, including an engineering report by the consultancy Opus, and a hydrology report by the research agency NIWA.

Dr Christoph Zink has produced a PhD thesis on the geology of the Te Anau and Waiau basins and has given his support and time voluntarily to the Save Fiordland campaign to study the reports commissioned by Riverstone Holdings Ltd. He believes these reports raise a number of serious concerns, outlined below.

1. Inadequate information

Dr Zink is concerned that the level of investigation undertaken by Riverstone Holdings is inadequate to reassure the Department of Conservation and the public that a safe monorail could be constructed and operated along the route proposed within normal boundaries of quality engineering and maintenance requirements.

The Opus report for Riverstone Holdings says it conducted a survey of the conservation land that the monorail would be built upon (using techniques such as “RT Differential, RTK and post processing”) but that some sections of the conservation land were not surveyed because “time did not permit the entire section to be surveyed because of the limited working day available due to weather conditions such as fog. Sections not surveyed include: the section from 17.5 to 25.5km, a section of the Kiwiburn saddle where reception was very limited, and a section around 27km where reception was very limited.”

2. Instability of the terrain in an earthquake zone

The monorail would run across forested slopes and river beds through an earthquake zone.

The Opus report mentions seismic concerns due to concealed seismic fault traces. It says these traces are not considered to be “active” but  “the effect of these faults has not been investigated in detail.”

The report adds that “a preliminary seismic assessment indicates that ground shaking associated with these faults will be less severe than that of the alpine fault which is approximately 70km distant.” However, Dr Zink is worried this statement offers no reassurance and downplays a great risk.

His concerns are shared by Dr. Ian Turnbull, author and field geologist of almost all relevant geological maps in the wider region. Dr Turnbull says: “Nowhere in any of the documents I have read is there any serious discussion of seismotectonic hazard, or of associated hazards such as ground shaking amplification or liquefaction. For a major engineering project in the Te Anau basin, close to the Alpine Fault and surrounded by active fault traces, and in the light of recent events in Christchurch, this omission is both surprising and worrying.”

Dr Zink draws attention to the Opus report, which says that the ability of the monorail to be built avoiding areas of instability is “by no means completely resolved at this stage”.

The Opus report mentions specific areas of concern. For example: “There is a significant area of instability on the true right bank of the Upukerora near Takaro Lodge (at 26km). This is the end of a spur which shows signs of long term and recent instability. This area has been avoided by climbing above the end of the spur on ground which is unaffected by any existing or predicted effect of instability.”

Going above a slip of uncertain size in unstable geology seems risky, says Dr Zink.

The NIWA report adds: The area of instability on the true right bank of the Upukerora River (Figure 11) has potential to jeopardise the monorail infrastructure and needs more detailed investigation.

As well as suggesting climbing above the instability, the report suggests an alternative would be “traversing the area of instability and/or perhaps spanning the worst areas with a longer span structure. This last option would require deeper, larger piles due to lateral loading and/or more costly superstructure, and geotechnical investigations to establish depth of and rate of movement of unstable material and establish if is there is bedrock to found on/into.”

Crossing over to the true left of the river has been suggested by NIWA and also by Opus, but not discussed further. The proposed and extensive 300m wide corridor at this section of the track does not provide for the possibility of crossing the river to the true left. 

3. Big trees tend to fall over

The dense forest that the monorail would pass through includes many mature beech and other trees of great height. These frequently fall over in high winds and snowy conditions and therefore would present a very real and major threat to a train unless the forest is entirely cleared either side of the monorail to a width greater than the height of the tallest trees.

The report by Opus references this problem and explains that, unless this clearance takes place, there would inevitably be a need for intense, detailed management of tree health.

It states: “There has been a large amount of tree fall at the site, a significant amount of this seems to have occurred recently. It appears to have been caused by a combination of wet ground, snow and wind. The risk of a Beech Tree falling onto the monorail beam needs to be managed, and a number of measures can be considered such as:

·        Providing a realistic tree clearance width including "at risk" trees beyond the minimum clearance width.

·        Establishing a process for identification, assessment and management of falling risk trees.

·        Developing contingency plans, such as beam repair or replacement.

·        Operational systems, for example remote detection and/or visual checking of the route on a daily basis.”

The Opus report says: “Tree clearance will be required on the monorail alignment to provide a safe operating envelope for the trains. This is expected to be a width between trees of 4-6m. It is expected that trees will need to be assessed beyond this envelope and some, for example those in poor condition, rotten or leaning, will need to be removed.”

It is worth noting that it is not always possible to judge whether a tree will fall or not. Trees fall for all sorts of reasons, including for reasons to do with climactic uncertainties, such as lightening and snowfall, and it is also not always possible to easily judge the health or age of a tree and its likelihood of falling, and to do so would be enormously time consuming and not practical over many kilometres. Cutting a corridor into a mature forest will channel winds and take away support, greatly increasing the risk of further windfall, says Dr Zink.

4. River channels tend to migrate

One of the problems faced in such an area of wilderness is river flow. As the NIWA report says: “The active nature of each of the Mararoa, Kiwi Burn, Whitestone and Upukerora Rivers has been highlighted within this report. Field investigations revealed abandoned channels, overflow channels, and active bank erosion in the Mararoa, Kiwi Burn, Whitestone and Upukerora Rivers. The 1974 aerial photographs support the fact that these channels are all subject to lateral migration. Therefore, it cannot be assumed that any of these rivers will hold their current course during the life of the monorail. It should be noted that the risk of scour to monorail piles and foundations therefore extends beyond the bed of the existing river channels across the river floodplains.

“Our understanding is that the height of the monorail above the ground would typically be around 1 – 2 m, with a maximum of 6 m. The height of the monorail at the river crossings will need to be such that it allows for the design flood level (design flood is currently unknown) as well as additional clearance for flood debris, which may include very large trees. If debris collects on the upstream side of the monorail, this will increase the likelihood of bed scour and bank erosion, and may affect the integrity of the monorail infrastructure. The height of the monorail should also allow for aggradation of the channel bed associated with gravel bar formation (both associated with downstream and lateral bar migration). At this stage it is uncertain whether the planned monorail height will allow sufficient clearance.”

To counter this, says Dr Zink, Riverstone Holdings Ltd would need to construct bigger, higher piles across the width of a valley floor; even more of an eyesore and major construction project. Dr Zink is also concerned that the fluvial sediments that the high piles are proposed to be anchored in are prone to liquefaction in case of earthquakes.

5. Environment management plans have not been made available as part of the concession application

Dr Zink is concerned at the size of the construction project, and the fact that environment management plans have not been produced relating to how the project would be managed sensitively to protect the environment.

The Opus report says: “An overall construction environment management plan will be developed for the project. A key component of this plan will be management of erosion and sediment.”

It also says: “Construction techniques will be developed to minimise disturbance to the river bed and ensure materials, spoil and concrete is carefully contained and removed off site upon completion of concreting. This methodology will be developed and become part of a construction environment management plan.” 

But no such plan is available for study. The report says: “More consideration of the best approach to backfilling, rehabilitation and restoration is required including inputs from specialists.”

Dr Zink is worried that the Department of Conservation would be put in a position of having to police the production and implementation of such an environment management plan, at great cost to DOC and taking up staff resources that should be invested elsewhere, in conservation matters rather than construction projects.

6. It’s not even clear where the monorail would go

Zink is concerned that the Department of Conservation is intending to grant a concession to a company that hasn’t even finalised where its monorail would go. The Opus report says the monorail route is “indicative” and “approximate” only, and that “further work is required to fit a three dimensional monorail alignment to the ground”.

It adds: “This can be done when a more detailed ground model is a vailable. We note that the monorail will have geometric constraints such as: minimum radii for curves and maximum grade. Due to the constraints of the monorail and the topography of the route, the monorail alignment will have some scope to be adjusted to avoid features such as large trees, banks, bluffs, creeks. However due to the form of construction, the monorail beam could span some of these features.

The report says: “Further work will be required as the monorail proposal develops.” It says that key aspects include:  “Geotechnical investigation, especially in the areas of more difficult topography; an environment management plan including further development of erosion and sediment control measures; development of monorail operational requirements.”

Dr Zink is concerned that this work has not been completed prior to the monorail’s consideration by the Department of Conservation.