The dam, an earth or rockfill dam on rock foundation of 15 or 27 m height is 288 km northeast of the capital Colombo. It was built in 614 by King Agbo II and 1869 and restored in 1952. He was 2500 m long and the storage space was 135 million cubic meters. The dam served agriculture for irrigation.
On the morning of 20 April 1986, the dam broke near the overflow on the left slope, 50 m from a construction site, on which was built a lead-in for a pump for water supply and therefore sheet piles were rammed. In addition to these vibrations there was a lively site traffic of heavy 30-ton truck over the dam. It is believed that these causes have led to the seepage of water ( Piping ). Another reason was probably that the dam foundation was drained for the construction work, which may have led to strong seepage.
Other sources say that the dam had been sabotaged by the Tamil terrorists.
The number of deaths is given completely different with 14 dead 25 missing, 30, 68, 82, 100, 127 or 178 deaths, the number of homeless with 9500-18000. 200 to 400 homes were destroyed and 450 houses damaged. Wells were contaminated, disease broke out and farmland were destroyed.