A field inland from the White Cliffs of Dover, a totem of English identity, is one of four sites the U.K. has earmarked for conversion into lorry parks for customs checks after Brexit, according to a person familiar with the plans.

The site next to the White Cliffs Business Park, less than a 10-minute drive from the coast, will have capacity for 1,200 trucks, said the person, who asked not to be identified because the plans aren’t complete.

In addition to the Dover site, ministers are looking at using Manston Airport near Ramsgate, which has capacity for 5,800 trucks, and a site at Waterbrook Park in Ashford, with space for about 950 lorries. Work started last week on another facility in the same town.

The sites are needed because at the end of the year Britain will reintroduce customs controls on goods moving to and from the European Union for the first time in 30 years. The checks will be necessary even if the two sides reach a free trade agreement.

Because Britain is leaving the EU’s customs union, freight traveling to the continent will require customs declarations, and the U.K. is building IT systems and facilities to check trucks have the right paperwork before reaching ports. Cabinet Office Minister Michael Gove said last month the government is seeking to buy five sites in Kent for customs checks.

About 10,000 lorries use the Dover-Calais crossing every day, making it a key trade artery between the U.K. and the EU, its largest partner for imports and exports.

The Department for Transport said it is looking at a range of sites where vehicles will be able to stop temporarily to have paperwork checked.

“Preparations for the end of the transition period are well underway to ensure the free flow of freight across our borders,” the department said in a statement. “This includes exploring options for permanent facilities to complete new border processes, as well as contingency plans in place to minimize any potential short-term disruption.”