This is the third phase of construction at the one million sq ft industrial and logistics site formerly known as Burton Gateway.
The new speculative unit will include a 50-metre deep yard, 10 dock levellers (including two euro-docks) and grade A office space.
Completion is expected in September 2019.
St Modwen Park Burton, alongside the A38 in east Staffordshire, is already one of the largest warehouse developments in the Midlands, with more than 200,000 sq ft of space.
St Modwen senior construction manager Steven Smith said: “We are pleased to have instructed GMI Construction Group on this latest phase. GMI is a well-respected construction company and we have great confidence in the team’s ability to deliver this quality unit.”