Wednesday, March 20, 2013

Indecent Haste that Ignored Tunnel Project’s Viability Within a Risk-based Framework

PENANG Chief Minister Lim Guan Eng has refuted claims that the tender and subsequent award for the tunnel project was not a “rush job”. Let’s see if this is true or not.
The proposed tunnel is a technically-challenging project but it has not been through the required public selection processes for consultants and bidders, environmental studies, public hearings, design completion and independent reviews.
It does not have a detailed, bottom-up cost estimate.
It does not even spell out the number of lanes that the tunnel will have.
If this is not a rush job, why did the state government bulldoze through the award of the letter of intent?
Underground construction presents unique risks that are not typically encountered on other types of heavy civil construction.
It is industry practice to evaluate any tunnel project’s viability within a risk-based framework. This has not been done for the tunnel and it is not accounted for in the tender process.
Until today, there is no effort to carry out additional subsurface exploration and testing or revisit designs, construction sequences, and associated costs and schedules to mitigate the risks reflected in the anticipated subsurface conditions.
Nor is there any effort to identify other elements, including agency, owner/operator or local requirements, which could cause major scope increases during final design or construction
Without a preliminary engineering study, there is insufficient information to complete a level of tunnel design that can be used to conclude the selection of a tunnel boring machine (TBM) and arrive at a credible estimate of the TBM advance rate.
One of the largest cost factors associated with tunnel construction is determining what kind of geological conditions exist between the portals or shafts of a tunnel.
Modern geotechnical engineers utilise a variety of imaging technologies and boring samples to determine rock type and groundwater penetration.
These technologies can provide an acceptable level of confidence in the type of rock that needs to be bored through.
The major geological and geotechnical factors that pose a high level of uncertainty to the current design and estimates of schedule and costs were totally ignored by the Lim administration throughout the tender process.
The developer is also obligated to provide safety equipment and high levels of insurance.
Construction safety costs must consider proper ventilation, which is necessary to provide for the health of workers during construction. These costs can be very high which often result in construction management companies making the bare minimum investment in such safety requirements.
Since there is no preliminary engineering study, no normal operation ventilation analysis has been performed.
This would normally be expected in order to give confidence in the sizing of ventilation system components, particularly the ventilation shafts.
In the absence of this analysis, ventilation shaft sizes remain unconfirmed.
An increase in shaft size will have significant cost implications.
Additionally, there are costs associated with providing for the safety of people using a tunnel after construction.
All transportation tunnels require more portals and ventilation shafts than may be necessary during the construction phase.
One of the largest safety costs is associated with preventing and suppressing tunnel fires.
Protecting against fire involves detection and communication systems to determine the source of a fire.
Tunnel fires and smoke can spread rapidly, which necessitates fire suppression and ventilation systems.
In addition, there is a need for a means of egress and regular intervals to allow for the swift exit of individuals using the tunnel in question.
Lastly, there is a cost associated with protecting structural elements from fire so that the tunnel will not immediately collapse in the event of a fire.
There have been cases of unexpected water penetration which have drastically increased the price of tunnelling and severely reduced the profit for the contractor.
One such case was during the construction of the Burnley tunnel, part of Melbourne’s CityLink project.
The Burnley tunnel passes deep beneath the Yarra River, and consequentially resulted in very high water pressure surrounding the tunnel.
As a result of unforeseen conditions in the design stage, some of the 1.8m thick concrete floor panels or inverts were lifted out of place by the water pressure, causing the contractor to lose US$154mil (RM477mil) in damages (Samuel, 2007).
Problems like the Burnley tunnel cause contractors to place higher percentage contingencies into the bid price than any other infrastructure projects.
This variance in the type of substrate present in different countries has a profound effect on the cost of tunnelling.
In the case of cost overruns, what should we do? Abandon the project? Bail out the developer at our expenses? Or do we just allow the developer to build a sub-standard tunnel and ignore safety requirement in order to prevent cost overruns?
Lim needs to clarify how he going to handle issues of cost overruns and safety if he insists that the tunnel project should proceed as planned.

No comments:

Post a Comment