Top notch techniques used in restoration and investigation work:

Ancient Sigiriya going high-tech

by Sajitha PREMATUNGE

Minister of Environment and Natural Resources, Patali Champika Ranawaka

"Sigiriya", what comes to mind, World Heritage site, ancient rock fortress, 5th Century A.D. frescoes or major tourist attraction? But did the word "high-tech" ever cross your mind? Well, the restoration work in Sigiriya is sure going high-tech.

The Geological Survey and Mines Bureau (GSMB), which used to be considered as a government authority handing out permits for mining has been the silent force behind making Sigiriya a safer place, for its invaluable archaeological treasures as well as travellers. The initial restoration project in Sigiriya has been a result of a request made by Prof. Shiran Deraniyagala over ten years ago. Special attention has been paid to possible threat to historical monuments and safety of visitors due to potential unfavourable geological anomalies in the detailed investigation and restoration projects on the Sigiriya rock fortress which in total costs Rs. 50 million conducted by the GSMB, under the Ministry of Environment and Natural Resources, on request of Central Cultural Fund (CCF).

A project which comprised four stages has been completed and another JICA funded project has just commenced. It was evident that the restoration process was going as planned, on schedule. A dilapidated metal bridge that was constructed in 1930s has been replaced with a stainless steel bridge. "It has been burnt to prevent glare", said R. Madanagala, Senior Technical Officer, GSMB. Under the new JICA project access to fresco pockets is being widened, fractured and partly loose rock slabs have been removed or split, widening the flights of stairs, etc."

GSMB officials explained that only the least invasive methods are used in the restoration process. Earlier iron wedges were used to hold nails in place, but iron is subject to decay.

Now making use of more scientific methods, stainless steel nails driven into the rock surface are held in place by special glue. "No drilling machines are used and even the level of vibration is measured, to minimize the effects to the rock", explained Prof. D.M.D.O.K. Dissanayake, Director, GSMB. Geophysics is playing a major role in the restoration and investigation work at the Sigiriya rock fortress, conducted by the GSMB. Earlier attempts at detecting buried archaeological sites have not been successful because the methods used were low tech, explained Nalin de Silva, GSMB Geophysicist. The new ones month pilot project, which will cost the GSMB Rs. 88,000, will make use of a new technique called Ground Penetrating Radar.

This Resistivity Imaging System will send an electric surge of up to 100 k Ohm into the ground using two electrodes; Nalin De Silva explained the procedure. "One salient feature when studying the patterns of the archaeological discoveries made is that the ancient structures on either side of the main path leading to the rock fortress makes a mirror image", which means that the buildings on either side are similar.

This makes pinpointing ancient structures all the more easier. Nalin de Silva pointed out that the Sigiriya Rock itself is not an independent boulder and that this method can also be used to detect how deep the bedrock which Sigiriya belongs to lies.

The information collected by the high-tech Resistivity Imaging System is then converted to a 3D program. "This is the first time we have ever been able to observe any information in 3D", said Nalin de Silva. He further explained that they hope to scan 16 12X12m squares. This site is very near surface, around 2 to 3 m.

Nalin de Silva explained that these high-tech methods have shed much needed light on the Sigiriya excavation process.

"Geophysics has been used to assist excavation in countries like Cambodia and Egypt", he said. "A preliminary survey is important in any well planned excavation." He assured that this new method of exploration in a non invasive method.

The information collected will be handed over to the Archaeological Department, revealed Prof. D.M.D.O.K. Dissanayake. "Earlier archaeologists just excavated till they found something, this method is much less invasive. In fact this technique has already been used to identify and pinpoint the location of the prehistoric burial grounds near Sigiriya and proved so promising that it will be used in many archaeological projects to come".

Minister of Environment and Natural Resources, Patali Champika Ranawaka pointed out that the Ministry of Cultural Affairs and the Archaeology Department has the fullest cooporetion of the GSMB and Ministry of Environment in the investigation and restoration process of such an archaeological and engineering marvel. "Caves containing frescoes that were earlier inaccessible will be accessible to the public at the end of the restoration process in five months", said the Minister. "The observation space in the fresco pocket was very limited and the platform has been corroded", said Prof. D.M.D.O.K. Dissanayake. As a result only a limited area was open to the public.

The Minister pointed out that significant discoveries have been made by GSMB engineers during the restoration process, such as the discovery of frescoes and graffiti on the opposite side of the Mirror Wall.

"A grave threat to the Mirror Wall posed by the unstable rocks above has already been eliminated by our engineers", explained the Minister.

"Scientific methods such as the Ground Penetrating Radar eliminate the need for haphazard excavation", he explained. "We can pinpoint the exact location that needs to be excavated." Consequently, this is a non-invasive method imposing least disturbance on the sensitive and priceless archaeological site. "We plan to use the same method in other archaeological sites in the country, such as Anuradhapura", he explained that scientifically sound methods were used and the investigation and said that it was a matter of pride that the restoration process was conducted with the help of national expertise and engineers.