A proposal to build South Africa’s and Africa’s first underground science laboratory has now moved into the project stage, with the launch of the Paarl Africa Underground Laboratory (PAUL), following a recent science symposium on the concept.

Although South African scientists have set up temporary underground labs before, this will be the first permanent such facility in the country and continent, and only the second in the southern hemisphere.

The symposium was sponsored by the Department of Science and Innovation (DSI) and supported by Stellenbosch University and the University of the Western Cape, as well as by France’s National Institute of Nuclear and Particle Physics and Italy’s National Institute for Nuclear Physics.

The DSI has provided seed funding for the project. The concept is PAUL would have a volume of some 10 000 m3, and be located 800 m underground, beneath the Du Toits Kloof mountains, near Paarl, in the Western Cape.

Investigations into the creation of a permanent underground lab in the country started in 2011. Originally, the focus was on South Africa’s very deep gold mines. It had been in a temporary lab, set up in one of these mines, some 3 000 m below the surface of the East Rand (that part of the Witwatersrand east of Johannesburg), that, back in 1965, South African physicist Friedel Sellschop and American physicist (and 1995 Nobel Physics Prize winner) Frederick Reines made the first ever observation of a naturally occurring neutrino (an elementary particle).

Recently, however, the investigation changed its focus to the Western Cape and specifically to the Huguenot tunnel. This is a 4 km road tunnel under the Du Toits Kloof mountains, linking the towns of Paarl and Worcester. It is the longest such tunnel in South Africa, and managed by the South African National Roads Agency Limited (Sanral).

The opportunity has been created by Sanral’s plan to upgrade the North Bore tunnel, hitherto used as a service tunnel, to become a traffic tunnel, to relieve the pressure on the current sole traffic tunnel, known as the South Bore tunnel. An engineering feasibility study will be done on the viability of including the creation of the underground laboratory, as part of Sanral’s upgrade programme.

Underground labs were created to detect rare particles, by using the thick rock layers above them to screen out unwanted background phenomena, such as cosmic ray showers. Only by screening out this “noise” can these rare or difficult- to-detect particles be observed. Already in 2015, the scientific suitability of the Huguenot tunnel site, for an underground lab, was established by a study by Stellenbosch University and iThemba LABS (Laboratories for Accelerator Based Sciences) radiation research groups.