The site was designed in January and February 1943 by engineers from the Peenemünde research facility and the Organisation Todt.
On 25 March 1943 the construction plans were presented to Hitler, who immediately gave the go-ahead for the project to begin.
The construction firm Holzman & Polanski was awarded the contract and 6,000 workers from Building Battalion 434 started construction that same month using plans by Franz Xaver Dorsch, Construction Director at the Organisation Todt.
It was envisaged that the structure would be ready by the end of July 1943, though not its wiring and plant, and it was intended that it would be fully operational by 1 November 1943.

The workforce consisted of a mixture of German specialists and forcibly conscripted Frenchmen from the Service du Travail Obligatoire (STO).
They were supplemented by Belgian, Dutch, French, Polish, Czech and Soviet prisoners of war and civilian conscripts, who were used as slave labour.
The labour force also included many French political prisoners and Spanish Republicans who had fled to France after General Franco's victory in the Spanish Civil War but had then been interned by the invading Germans.
The non-German workers lived in two camps officially known as Organisation Todt Watten Zwangsarbeitslager 62 (Forced Labour Camp 62) about 2 kilometres (1.2 mi) distant from the site, near the village of Éperlecques.

The camps were guarded by the French civil police with the assistance of Belgian and Dutch Nazis and Russian POWs who had volunteered for guard duty.
Although escape attempts were punished by immediate execution, there were up to three escapes daily with external assistance.
The commandant of the camp is said to have complained that it would have been easier to "guard a sack of fleas".
Over 35,000 foreign workers passed through the camps during the period in which they were operational.

The labourers worked in 12-hour shifts of 3,000–4,000 men, with three 20-minute breaks during each shift.
The work continued around the clock, seven days a week, under giant floodlights during the night.
The living and working conditions were extremely harsh, especially for the political prisoners and the eastern Europeans, who were given especially punitive treatment due to their status as the most expendable members of the workforce.
For the non-German workers, falling ill or being unable to work through injury was the equivalent of a death sentence, as they would either be left to die or be transported back to the concentration camps from which they had been brought.
A German commission that inspected the labour camps in the area in late 1943 commented: "The Eastern [European] worker is very tough.
He works at his job until he falls flat on his face in the mire, and all that is left for the doctor to do is to issue the death certificate."

A large supply dump was established at Watten next to the River Aa.
This site was eventually used to store material required for all the V-weapon sites in the Saint-Omer area.
Building materials were brought there by barges and trains where they were unloaded onto a Decauville narrow-gauge railway for transportation to the construction site, where concrete mixers operated day and night.
A 90 kV power line running to a transformer at Holque north of Watten provided electricity.
An old quarry at Wizernes codenamed Schotterwerk Nordwest (Gravel Quarry Northwest), some 12 kilometres (7.5 mi) south of Watten, was also converted into a storage dump to supply the Watten facility.
The site was designed in January and February 1943 by engineers from the Peenemünde research facility and the Organisation Todt. On 25 March 1943 the construction plans were presented to Hitler, who immediately gave the go-ahead for the project to begin. The construction firm Holzman & Polanski was awarded the contract and 6,000 workers from Building Battalion 434 started construction that same month using plans by Franz Xaver Dorsch, Construction Director at the Organisation Todt. It was envisaged that the structure would be ready by the end of July 1943, though not its wiring and plant, and it was intended that it would be fully operational by 1 November 1943.
The workforce consisted of a mixture of German specialists and forcibly conscripted Frenchmen from the Service du Travail Obligatoire (STO). They were supplemented by Belgian, Dutch, French, Polish, Czech and Soviet prisoners of war and civilian conscripts, who were used as slave labour. The labour force also included many French political prisoners and Spanish Republicans who had fled to France after General Franco's victory in the Spanish Civil War but had then been interned by the invading Germans. The non-German workers lived in two camps officially known as Organisation Todt Watten Zwangsarbeitslager 62 (Forced Labour Camp 62) about 2 kilometres (1.2 mi) distant from the site, near the village of Éperlecques.
The camps were guarded by the French civil police with the assistance of Belgian and Dutch Nazis and Russian POWs who had volunteered for guard duty. Although escape attempts were punished by immediate execution, there were up to three escapes daily with external assistance. The commandant of the camp is said to have complained that it would have been easier to "guard a sack of fleas". Over 35,000 foreign workers passed through the camps during the period in which they were operational.
The labourers worked in 12-hour shifts of 3,000–4,000 men, with three 20-minute breaks during each shift. The work continued around the clock, seven days a week, under giant floodlights during the night. The living and working conditions were extremely harsh, especially for the political prisoners and the eastern Europeans, who were given especially punitive treatment due to their status as the most expendable members of the workforce. For the non-German workers, falling ill or being unable to work through injury was the equivalent of a death sentence, as they would either be left to die or be transported back to the concentration camps from which they had been brought. A German commission that inspected the labour camps in the area in late 1943 commented: "The Eastern [European] worker is very tough. He works at his job until he falls flat on his face in the mire, and all that is left for the doctor to do is to issue the death certificate."
A large supply dump was established at Watten next to the River Aa. This site was eventually used to store material required for all the V-weapon sites in the Saint-Omer area. Building materials were brought there by barges and trains where they were unloaded onto a Decauville narrow-gauge railway for transportation to the construction site, where concrete mixers operated day and night. A 90 kV power line running to a transformer at Holque north of Watten provided electricity. An old quarry at Wizernes codenamed Schotterwerk Nordwest (Gravel Quarry Northwest), some 12 kilometres (7.5 mi) south of Watten, was also converted into a storage dump to supply the Watten facility.
Blockhaus d'Éperlecques