* Volunteers, soldiers build sandbag defences
* Serbia braced for fresh flood wave
* At least 37 killed in Serbia, Bosnia, Croatia
By Fedja Grulovic
OBRENOVAC, Serbia, May 19 (Reuters) - Soldiers and energy workers stacked thousands of sandbags overnight to protect Serbia’s biggest power plant from flood waters expected to keep rising after the heaviest rains in the Balkans in more than a century killed dozens of people.
In neighbouring Bosnia, state radio reported that the swollen River Sava, which has wreaked havoc in Serbia, Bosnia and Croatia, had again overwhelmed flood defences late on Sunday and flooded parts of the northern town of Orasje.
Waters receded in other parts of Bosnia, leaving behind scenes of devastation - mud, debris and dead animals. Another 1,000 people were evacuated from the border town of Bijeljina, threatened by flood waters from the Sava and the River Drina, and 5,000 from the northern town of Odzak, reports said.
In Serbia, a wall of sandbags several kilometres long was built around the Nikola Tesla power plant in the flood-hit town of Obrenovac, 30 km (18 miles) southwest of the capital, Belgrade. It covers roughly half of Serbia’s electricity needs.
A Reuters cameraman saw another 10 trucks stacked with sandbags standing by. Authorities in Belgrade said emergency services and volunteers had filled 60,000 bags and dispatched them to the power plant.
A union spokeswoman at Serbia’s EPS power utility said some employees had worked three days with barely a break because their relief team could not reach the plant.
“The plant should be safe now,” Djina Trisovic told Reuters. “We’ve done all we could. Now it’s in the hands of God.”
Parts of the plant were already shut down as a precaution, and it would have to be powered down completely if the waters breached the defences.
Serbia is bracing for another flood wave from the Sava, swollen by the heaviest rains since records began 120 years ago.
At least 37 people have drowned or been killed by landslides mainly in Serbia and Bosnia, as waters submerged towns and swept away roads and bridges. Tens of thousands of people have been displaced and swathes of agricultural land devastated.
Aca Markovic, head of the Executive Board of Serbia’s EPS power utility, told Reuters that the situation was under control at the Kostolac coal-fired power plant east of Belgrade, which currently supplies Serbia with 20 percent of its electricity.
There was still concern over the Kolubara coal mine that supplies the Nikola Tesla plant.
At Kostolac, volunteers joined plant workers, police and the army in building flood defences and digging up roads to divert waters from the swollen River Mlava.
“New sandbag barriers have been put up as a precaution in Kostolac and all water has been diverted into an old riverbed of the Mlava,” an EPS spokeswoman told Reuters.
Additional reporting by Ivana Sekularac and Matt Robinson in Belgrade, Daria Sito-Sucic and Maja Zuvela in Sarajevo; Writing by Matt Robinson; Editing by John Stonestreet