Indonesian engineers have started inserting 2,000 chained-together concrete balls into a mud volcano in East Java that has discharged hot, toxic sludge almost without letup since May in hopes of repeating the apparent success of an earlier insertion. The flow was halted for about 30 minutes March 19 after nearly 1,500 30-cm-dia balls linked with chains were dropped into the crater earlier this month. Scientists are unsure whether to credit the countermeasures or an interior collapse of the funnel spewing the mud for the obstruction of the flow. The mud flow erupted during drilling of a natural-gas well in Sidoarjo near Surabaya, Indonesia's second largest city.

The National Mudflow Mitigation Team, supported by an Insertion Monitoring and Evaluation Supervision team from Indonesia's Bandung Institute of Technology (ITB), devised the scheme to form concrete balls in chained groups of four and drop them into the crater. The first group consisted of 374 chain-groups at a cost of $329,000. The cost of the second chain-group is $55,000.

According to news reports, the ITB team chose the approach after rejecting the more common approach of drilling relief wells. The team leader, Bagus Endar Bachtiar Nurhandoko, says he is satisfied it is successful because there have been no more discharge points or eruptions. The flow-rate is decreasing but is still an estimated 160,000 cu meters per day, according to news reports.

The national team plans to construct a 1.5-km canal to divert the mud into the Porong River at a cost of $13.8 million. The flow has engulfed eight villages to the rooftops, permanently displacing more than 15,000 people, and is threatening a highway and railway.

Indonesia's energy ministry reportedly has estimated liability for the damage at $826 billion. Jakarta-based Prakarsa Group has said it will bear the cost, according to news reports.