Several hundred gardaí were set to work through the night on Tuesday to create a secure environment for Wednesday’s planned water charges protest outside Government Buildings in Dublin city centre.
Senior gardaí are anticipating a crowd of up to 30,000.
Thousands of crowd control barriers will be erected, with the controlled environment they create set to be heavily policed from the early hours.
While trouble is not expected at the main event on Merrion Square in the south inner city, contingency plans have been made in the event small groups of militant protesters seek to “take on” gardaí after the main rally.
“We feel the main protest will be family friendly and there will be a good atmosphere where efforts to start trouble won’t be tolerated by the main crowd,” said one security source.
“The key thing will be to monitor if there is some kind of breakaway protest that might turn ugly a bit later.”
The Socialist Party is joining the event and plans to continue a smaller We Won't Pay protest outside the Dáil into the evening.
Some senior Garda sources believe those intent on trouble may be inclined to hijack such an event.
The Right2Water main protest will run from 1pm, with a stage assembled at the junction of Merrion Square west and south from which speakers, including politicians and union leaders, will address the crowds.
A number of personalities are due to appear, including singers Sinead O'Connor and Damien Dempsey, comic duo the Rubber Bandits and British entertainer Russell Brand.
A team of up to 500 gardaí will be on standby.
Garda sources stressed the operation would be centred on crowd control and “keeping people safe and the traffic moving through the city”.
The Garda helicopter will monitor the build-up and movement of the crowd from the air while a team of uniformed high-visibility gardaí will patrol the protest at street level.
Graduated levels of security will become more evident if they are needed through the afternoon.
Senior sources stressed that the policing operation will maintain tight control of the streets, but would only become more intense if the need arose.
The Garda’s Public Order Unit will be on standby in vehicles parked alongside streets close to the main event, as will the Garda’s Dog Unit.
The National Surveillance Unit will also be present to photograph and film any violent protesters.
Senior gardaí have been in constant contact with the organisers of the main event to agree crowd control, road closure and traffic management measures.
Dedicated parking is also being provided by the Garda for any coaches bringing people to the venue from around the country.
Some of those travelling by train from outside Dublin are set to march in groups from Connolly and Heuston stations.
Some local groups who have been active in blocking the installation of water meters in parts of Dublin are set to walk from those suburbs to the city centre.