The five-year contracts for Eneco's 129MW Luchterduinen and Princess Amalia offshore projects, and the under-construction 144MW Westermeerwind nearshore site – all in the Netherlands – have been sold to the Dutch subsidiary of German operations firm Deutsche Windtechnik.
Ballast Nedam's deal for the 288MW Butendiek offshore project in the German North Sea is the fourth contract in the deal.
The transaction also includes two members of staff, Dutch firm Ballast Nedam said.
The move follows the sale of its offshore construction divisions at the end of 2014. The company said it wishes to concentrate on its activities in the housing and mobility sectors.
In October 2014, Ballast Nedam said it was selling its offshore unit, including heavy lifting vessel Svanen, in a bid to improve its financial position. However, at the time, the group's inspection and maintenance operations were unaffected.
The offshore division was sold to Van Oord in November 2014.
Deutsche Windtechnik currently holds servicing contracts with eight offshore wind projects in Germany. These include EnBW Baltic 1, WPD's Nordergrunde site, and Nordsee Ost.