With no mention of what is controversial

I looked it up further, seems this is a tradition they celebrate for what they call Twelfth of July Marches, the night before, on the eleventh, Orange Order parades commemorate the 1690 Battle of the Boyne by lighting massive bonfires throughout the city, with upwards of 80 to 100 bonfires being built and burned. Over the decades though the population has grown around the area's these bonfires are traditionally built making it a fire hazard to nearby homes, as shown in this picture below...

The other problem is building them in parking lots, heat of that magnitude can literally melt a tar surface. The council tried to deal with it by ordering the dismantling of some of the locations but some of the bonfires are built by paramilitary organizations. The council told those hired to remove the materials they couldn't guarantee their safety while dismantling the structures so the people hired backed out after threats from these organizations. That's why they went to offering incentives to those who would follow safety guidelines and not burn materials that were hazardous.