The Dutch offshore contractor will design four suction buckets that will form the feet of the jacket foundations that will support the high-voltage transmission substations, which weigh around 2,500 tonnes each.
Substations for the 750MW Walney extension in the UK Irish Sea and the 258MW Burbo Bank Extension and the 590MW Race Bank, both in UK North Sea waters, are included in the deal.
Water depths at the sites vary from 11 to 29 metres. Installation of the first substation jacket is planned for 2016.
In January, Dong was awarded £6 million (EUR 7.3 million) by the UK's Carbon Trust to build a full-scale demonstration model of a suction bucket foundation for turbines. Earlier this month, SPT was also contracted to install this structure.
The performance and stability of the turbine foundation prototype will be tested at Dong's offshore wind farm Borkum Riffgrund 1 in the German North Sea, where the sandy soil conditions are suitable for testing the new concept.
Bucket foundations have been used by the oil and gas industry for more than 30 years for platforms installed in the North Sea.