Legal proceedings will begin on Tuesday to remove travellers encamped on Penwortham Holme playing fields.
The group of around 30 families pitched their caravans on the fields off Leyland Road, late on Monday, June 27.
Officers from South Ribble Council and police were sent to survey the site, which also includes dozens of cars and animals. They were given no indication of when the families intended to move on.
In order to facilitate an eviction, the council will attend a County Court possession hearing at noon on Tuesday, to prove that the land is theirs.
When that is established, there will be an immediate application for a warrant of possession on the land.
That means that shortly afterwards - possibly by Wednesday - bayliffs will be instructed to serve notice for the families to leave the site.
The Penwortham Holme site has been used several times by traveller families in recent years.
The most recent time was in August 2015, when a group of around 10 families pitched up on the land. Legal proceedings also had to be engaged to remove them at that time.