The BBC's Stephen Chittenden, at Stansted, said protesters had brought concrete blocks and 6ft-high securityfencing with them and erected a "stockade" about 50m (164 ft) from the runway.
Agreements would also have to be reached with the Department for Transport on securityfencing, airline operators on hangars and the fire service on what facilities it would require to keep costs down.
Councillor Charles Yarwood, portfolio holder for assets, said a developer would be required to relocate the allotments and ensure the new site provided improvements such as water supply throughout the site, increased and improved car parking, and securityfencing.