Providing water for a mine

Summary

A preliminary hazard and operability (HAZOP) study of a mine expansion project identified potentially major risks associated with a large water pipeline near a village. A simple scenario-based risk assessment, conducted quickly by a small team, generated a range of improvement options for pipeline design and construction.

Simple approaches can generate excellent results when used appropriately. It is important not to short-cut the risk management process by eliminating any of the steps, but the steps themselves can be tailored according to the project’s scope and need.

Background

The project

As a result of a major expansion project, a mine in an arid, mountainous region required additional water for processing. Process water was to be generated from seawater by a desalination plant on the coast and then pumped to the mine through a large pipeline that would be buried for most of its length. The water quality would be suitable for industrial purposes, but not for domestic consumption nor for agricultural use.

The landform, the presence of a village near the desalination plant and the difficulty of obtaining additional rights-of-way restricted the possible pipeline route. The first section of the pipeline had to cross the back of a hill behind the village. This section was quite long, so it would contain a large volume of water, and because it extended into the hills to a much higher elevation the water would be at very high pressure near the village.

The initial HAZOPs

We conducted two hazard and operability (HAZOP) studies for the expansion project: a Preliminary HAZOP at the preliminary design stage and a full HAZOP when the majority of the final process design work had been completed. The objectives of the HAZOPs were to:

Examine the design systematically to identify the potential hazards to people, plant assets, operations and the environment
Assess the hazards, and the proposed methods of control, and agree appropriate actions and responsibilities to enable the risks to be reduced or eliminated
Assess the operability of the proposed plant and agree appropriate improvement actions
Document the study results in the form of a hazard study register and task plan for ongoing management.

The Preliminary HAZOP identified and recorded a large number of matters the project would need to address, including many associated with the desalination plant, pumping and the water pipeline. Of particular relevance for this case study, it identified that an accident resulting from damage to the pipeline in the neighbourhood of the village posed a significant risk. As a consequence, a formal risk assessment of this aspect of the pipeline was requested.

The requirement

A major failure of the pipeline above the village could result in a disaster, with water and mud running through the village, potentially killing people, destroying homes and damaging farmland. The Preliminary HAZOP identified that pipeline failure could arise from natural causes such as earthquake, or more likely from human intervention.

The risk assessment only considered the section of pipeline in the neighbourhood of the village.

The objectives of the assessment were to:

Understand the risks associated with different kinds of pipeline damage, their likely causes and consequences
Assess the level of risk
Develop risk treatment actions appropriate to the level of risk.

Risk assessment for the village area

Approach

The approach to risk assessment was discussed and agreed with the client’s team. In particular, options of analysing risks qualitatively or quantitatively were discussed, but the team considered that quantitative estimates could only be guesses, and poor ones at that. They concluded that a quantitative analysis would be difficult, it would not be possible to support the data on which it would be based, and therefore a qualitative approach was preferred.

The agreed approach involved the following steps:

Describe plausible scenarios that might lead to pipeline damage
Analyse the consequences and likelihood of each scenario to provide a qualitative estimate of the level of risk
Based on the scenario and the level of risk, develop appropriate treatment actions.

Scenario analysis

Four scenarios in which the pipeline might be damaged were developed. They were discussed individually and relevant influencing factors were noted. The consequences and likelihoods of the scenarios were analysed, using the company’s agreed risk management framework, and the level of risk was derived for each scenario.

The scenarios and the assessments are summarised in Table 1 to Table 4.

Table 1: Scenario 1, Natural disaster
Description	A landslip or earthquake breaks the pipeline across its full diameter. A large volume of water is released, generating a mudslide that impacts on the village and kills many people, destroys many homes, damages farmland and receives national press and possibly international press coverage.
Contributing factors	Earthquakes do occur in the region, but they are generally not large enough to cause faulting and shear forces capable of breaking a pipeline. A major earthquake sufficiently large to break the pipeline would cause widespread damage, of which the pipeline rupture would only be a part.
Consequences	This scenario has the potential to cause ‘catastrophic’ consequences (multiple fatalities and large scale damage).
Likelihood	This would be very rare, a less than 1 per 1,000-year event.
Level of risk	Medium

Table 2: Scenario 2, Accidental damage
Description	Digging in the vicinity of the pipe damages the pipe and makes a hole. A large volume of water is released, generating a mudslide that impacts on the village and kills many people, destroys many homes, damages farmland and receives national press and possibly international press coverage.
Contributing factors	There is no known ownership of excavating equipment in the village, and the only excavators belong to contractors in the nearby town, most of whom have a working relationship with the company and are therefore likely to know of the line. There will be a maintenance access road beside the pipeline. The road will be used regularly for inspections. There will be signage along the route indicating the pipeline location. The villagers do and will know of the existence of the line. The local council has a strict permitting system for the kind of work that might dig into the line. The permitting process would involve consideration of the pipeline. A second pipeline may be installed in the future. This would most likely run in the same right-of-way. It is conceivable that the installation contractor for the new line could accidentally dig into the operating water line.
Consequences	is scenario has the potential, in the worst case, to cause ‘catastrophic’ consequences.
Likelihood	Unlikely
Level of risk	High
Note	An event that results in lower consequences could also occur, but this would be ‘unlikely’ and would rate as a Medium risk.

Table 3: Scenario 3, Wilful damage
Description	Someone purposefully attempts to tap into the pipe to obtain water in the mistaken belief that it is potable or suitable for crops. This creates a hole in the pipeline (estimate 25 to 50 mm hole near the top of the pipe) and, due to the very high water pressure, the death of the person tapping into the pipe. The leak would have to continue for an hour or more to cause any flooding damage, but it would be very obvious (a fountain) and other people would be able to avoid it.
Contributing factors	It is very unlikely that anyone would attempt to tap into the pipe in the open above the village. Illegal tapping would be more likely in the valley, where it could be concealed, and therefore there would be a lower chance of significant impacts on the village.
Consequences	This scenario has the potential to cause ‘major’ consequences (single fatality and significant damage).
Likelihood	Possible
Level of risk	High

Table 4: Scenario 4, Poor installation
Description	The pipe fails due to poor installation and testing. The worst-case outcome would be a full-diameter failure when the pipe is fully pressurised and filled with water, causing a water flood and mudslide into the village with the potential for multiple fatalities.
Contributing factors	Construction processes, pipeline installation and testing procedures may be poor, without oversight or precautions.
Consequences	This scenario has the potential to cause ‘catastrophic’ consequences (multiple fatalities and large-scale damage).
Likelihood	Unlikely
Level of risk	High

Treatment options

Analysing the four scenarios generated a set of 25 treatment options, categorised as options to:

Reduce the likelihood of the cause of the risk, or to avoid it altogether
Reduce the extent of the adverse consequences if a pipeline failure did occur.

The advantages and disadvantages of each option were considered, and the options were classified as those that the project would:

Adopt, the advantages clearly outweigh the disadvantages (17 options)
Review, the advantages seem to outweigh the disadvantages but more work must be done to confirm this, and, where significant additional capital might be needed, to confirm this would be feasible for the company (3 options)
Discard, the option is clearly not worthwhile (5 options).

The 17 actions to be adopted immediately addressed prevention, protection and consequence reduction including:

Thicker walled pipe
Concrete slab over the top of the line combined with burying the line more deeply than initially planned
Warning signs and buried warning tape
Regularly patrolled route with security gate access control
Leak detection with shutdown interlocks and backflow prevention
Community communications to ensure the villagers were fully aware of the risks.

The effects of implementing the agreed ‘Adopt’ options, and both the ‘Adopt’ and ‘Review’ options, on the level of risk associated with each scenario are summarised in Table 5, recognising that some options are relevant for more than one scenario.

Table 5: Levels of risk
Scenario	Initial	‘Adopt’	‘Adopt’ and ‘Review’
1 Natural disaster	Medium	Medium	Low
2 Accidental damage	High	Low	Low
3 Wilful damage	High	Medium	Low
4 Poor installation	High	Low	Low

The intent of some of the options and their implications for design and construction of the pipeline are illustrated in Figure 1.

Figure 1: Suggested pipeline design improvements

Lessons

The HAZOP process

Hazard and operability (HAZOP) studies form an important part of design and design assurance processes for major changes to plant, equipment and procedures. A HAZOP is a formal, structured and facilitated process; it is intended to be detailed and comprehensive.

In this case the Preliminary HAZOP highlighted pipeline damage as a hazard with potentially severe consequences. It was not feasible, nor desirable, to try to develop treatments during the HAZOP workshop – the causes and consequences of pipeline damage were too complex for that – but it did flag that the pipeline in the neighbourhood of the village needed to be examined in more detail.

Potentially severe impacts on the community prompted senior managers to make a rapid decision to extend the time core members of the team were together to complete a targeted risk assessment. The continuous presence of the same team meant that the risk assessment was conducted while the hazards were fresh in everyone’s minds, and the treatments were seen as part of the overall design confirmation and improvement process of which the HAZOP was a core part.

Having the same team and facilitator also made the process more efficient. They had all become used to communicating with one another and working well together, and there was no ‘ramp up’ or mobilisation effort required. Debates still took place, but reaching a common understanding and agreeing on the best ways forward was relatively easy because team processes and relationships had been established. The risk assessment was completed very quickly.

Risk assessment process

This case illustrates the level of detailed insight that can be generated by a focused team in a short period, using a structured approach that covers all the main steps of the risk management process but in an abbreviated form. This laid the foundation for enhanced communication within the team through the remainder of the project.

The scenarios identified four different ways in which the pipeline could be damaged, and expanded on the associated causes and consequences. This helped to structure the team’s thinking about treatment options, and ultimately to select a set of worthwhile options.

The assessment was simple to understand and the results were acceptable to the organisation so that there were no barriers to adopting the recommended treatments. There was no need for quantitative analysis, as the outcomes from the qualitative approach were quite sufficient for making the necessary decisions about the pipeline, its design and its route.

One of the options flagged for review pending further investigation, using horizontal drilling through the hill to avoid the risk altogether, had not been considered previously by the project, and more detailed analysis of this option was planned.

Notes

A version of this case study appeared in our book:

Cooper, DF, PM Bosnich, SJ Grey, G Purdy, GA Raymond, PR Walker and MJ Wood (2014) Project Risk Management Guidelines: Managing Risk with ISO 31000 and IEC 62198. John Wiley and Sons, Chichester. ISBN 978 1 118 82031 5.

We were prompted to return to the case by an editorial by Noel Dyson in the December 2019 issue of Australia’s Mining Monthly that said:

There is already a lot of work being done to reduce the amount of water being used in mining. What is becoming clear is that there needs to be more. There have been big advances in countries such as Chile, where access to water is an even bigger issue than it is in Australia … We certainly need to do something because it is becoming easier for authorities to say no to new mining projects based on where their water comes from.

Client:: International mining company
Sector:: Mining and minerals processing; Water
Services included:: Technical risk analysis and hazard studies; Project risk management