The facility, which will provide coronavirus patients with acute medical care, will cost around £14.4 million.
Chief Minister John Le Fondré said: 'We expect the number of cases to grow slowly over time and then to escalate, and the Jersey Nightingale Hospital will provide the extra in-patient care capacity we will need as our curve gets steeper and the number of Islanders needing medical support in hospital increases.
'Health and Community Services are recruiting and upskilling staff in preparation for the increase in demand and this field hospital is the other vital element. It is a significant investment, but it is necessary if we are to cope with the extra demand. We cannot allow Islanders to die because we wouldn’t spend the money that would save their lives.'
Senior clinicians from Jersey General Hospital are working with UK’s National Clinical Lead on how to most effectively use the facility once it is operational.
Site preparation was due to begin on Thursday and the building will be 150-metres by 30-metres and provide enough space for six wards, each with 30 bed as well as areas for patient admissions and discharge, staff changing and rest, X-ray, equipment storage, laundry and a morgue.
Senator Le Fondré added: 'Our objective is to increase capacity and support staffing and additional beds while using the current workforce resources available in Jersey. By having beds set out in rows in the Nightingale configuration, we are enabling our staff to work most efficiently, and will be in the best position we can be to meet increased demand.
'Millbrook was identified as the most suitable site after a review of 16 sites against criteria including available space, topography, accessibility and access to infrastructure. I want to place on record my thanks to the family of the late Lord Trent for their support and willingness to allow the site to be used for the Jersey Nightingale Hospital.'
Millbrook was selected over People’s Park, Lower Victoria Park, Les Jardin Car Park and FB Playing Fields because of its access to electricity and drainage and its accessibility.
Senator Le Fondré added: 'Although we continue to pull out all the stops, we do need Islanders to play their part. We can all make a difference by complying with the government’s instructions and staying at home.
'The need to establish this new hospital underlines the serious nature of the Covid-19 pandemic, but it shows how seriously it is being responded to, and I hope that Islanders are reassured by the swiftness of this action.'