When thinking of projects that tunnels are used for, infrastructure and utility inevitably cover the balance of the industry. Such hugely expensive projects require justification in terms of the necessity of their existence. Traversing extreme geography by old routes is dangerous and inefficient – so a tunnel is built. An increasing inner city population results in large demands and limited means to provide and remove – therefore a tunnel is built. Out of sight, out of mind and, crucially, out of the way.

When a tunnel does not service any immediate requirements of the populace or increase the revenues of the client, the discerning tunneller knows that the project must be special.

The Tata Institute for Fundamental Research (TIFR) finally on 18 October 2010 had a site request cleared by the Indian Ministry of Environment and Forests for the pet project it has been nursing for years: the India-based Neutrino Observatory.

Requirements of the lab
The project, currently undergoing feasibility investigation, calls for construction of the largest cavern laboratory ever constructed in India. It must be located under a mountain of hard, dense rock with a minimum rock cover of 1000m on all sides to eliminate interference from cosmic radiation. The rock must also be stable to ensure the safety of the structure.

A 2km tunnel, with a maximum overburden of 1300m, will provide the only access to the lab. The initial reaches being excavated by cut and cover until more stable rock is reached. Blasting will be used to excavate the remainder of the tunnel and cavern. Although it is anticipated that vibration will be minimal due to the sturdy rock at the site, progress on the early sections of the tunnel will be slow due to the two blast daily limit. Once an acceptable depth has been reached, blasting will begin in earnest.

There must be provision for a good quality road enabling easy access to the site as well as a supply of water to cool the massive magnetic detectors used in the neutrino experiments.

A reliable 3MW source of electricity is also required for the lab to function, though diesel generators could be activated in emergencies. Living quarters for a permanent research staff of up to 30 scientists and engineers must also be provided.

The lab will be located in the Bodi West Hills, near Madurai in the Theni District of Tamil Nadu, India. This region was chosen for the characteristics of its rock, landscape and fairly remote location.

Rock at the Bodi West Hills site, as with southern Indian mountains in general, is highly dense and compact. Gneiss and some schists can be found although the majority is hard charnockite. The geology is also stable, unlike the metamorphic, sedimentary rock of the Himalayas in the north. These factors make it perfect for the INO.

The previously proposed location was Singara near Masinagudi, also in Tamil Nadu. This was the preferred site, however the project moved when the Singara area was declared a tiger sanctuary and the Ministry of Environment and Forests refused permission for the start of works.

Engineering and environmental challenges
An environmentalist hand can be felt throughout the plan for this project. The rejection of the first site then the conditional approval of the second – trees cannot be cut and there is to be no damage to the forest cover or noise disruption of any kind – shows a clear weighting given to the environmental interest side of the project. This provides a challenge. Other environmental issues faced by the project include the lack of an electric fence to keep animals out, heavy noise restrictions and muck disposal.

The estimated total generated muck for all underground operations is around 224,000 cubic metres. Dust will be minimal, estimated at around 10 per cent of total muck, owing to the hard nature of the rock. Topsoil removed during the cut and cover phase will be reused for backfilling and greening the dump yard. Rock debris will be processed and used to produce about 80 per cent of the sand needed for the entire project. Some 20 percent of the rock debris will be used for concrete lining and shotcreting the tunnel and cavern, as well as building construction.

Wind presents a particular obstacle to surface works at the portal. The region experiences very strong wind for six months of the year. Dry masonry walls are required to protect the muck store yard and avoid contamination of nearby water. Metal or fabric wind sheets will also be used as protective fences.

The construction force of around 100 people will be required to undergo environmental guidelines training.

Learning from experience
The Tamil Nadu Electricity Board (TNEB) announced that it has been given a consultancy role for the project owing to past tunnelling experience in the region, such as work done on the Pykara Dam. For fear of putting bias on the future tendering process, the client, TIFR, refused to confirm this appointment, or indeed anything regarding the construction process.

There are four main neutrino observatories in existence today. These are: Sudbury Neutrino Observatory in Canada, Kamioka in Japan (now the larger ‘Super- K’), Gran Sasso Mountains in Italy and the Nova site at the Soudan Mine in the USA.

Although this is the first purpose-built neutrino observatory in India, the nation does have a history in this field. The Kolar Gold Field mine experiments of the sixties saw the first detection of atmospheric neutrinos some 2km below the surface. This has inspired the conception of the INO and also perhaps the Aristotle quotation that is so frequency paraphrased in INO documentation: ‘The search for truth is in one way hard and in another way easy, for it is evident that no one can master it fully or miss it wholly. But each adds a little to our knowledge of nature, and from all the facts assembled there arises a certain grandeur’.

Need for the lab
The INO hopes to determine the mass of neutrinos as well as the mass order they are ranked by. As they are the most numerous particles with mass in the universe, this is of great importance for getting a clear understanding of reality. Despite the neutrino observatories already available to scientists, this is still unknown and TIFR scientists believe that only the INO (or perhaps the Nova site in the USA) stands a chance of answering this in the next 10 years. This is because the INO can distinguish between neutrino forms.

A neutrino observatory in India is particularly desirable as it is close to the Earth’s equator, meaning that any night time observations will be of neutrinos that have passed through the Earth’s core. This could reveal help with the tomography of the Earth, as no other particle can equal the neutrino’s ability to penetrate matter.

Long-term goals include working in tandem with other observatories and even yet-to-be-built neutrino factories.

Unlocking the secrets of neutrinos will hopefully lead us closer to understanding the fusion furnaces that nourish the stars. It will also shed light on the origins of the universe.


The new INO site at Bodi West Hills near Madura Location of the India based Neutrino Observatory relative to Madurai Madurai, the nearest city to the INO in Tamil Nadu, India The ‘Super-K’ detector in Japan Scientists building INO particle detector