Bertrand van Ee, to be chairman of the merged group.

Netherlands-based DHV n.l., Amersfoort, and Royal Haskoning group have agreed to merge, forming one of the world’s largest independent design firms, with combined annual sales of $940 million.

The new group’s main activities will be in the maritime, water and delta sectors, in addition to aviation and transportation.

To be named Royal Haskoning DHV, the firm will be based in Amersfoort and will chaired by Bertrand van Ee, who holds the same position in DHV. Erik Oostwegel, Royal Haskoning’s chairman, will be deputy chairman.

The new company will have some 8,000 staff in more than 100 offices spread across 35 countries in Europe, South Africa, Middle East and Asia.

The deal is due to close this summer.

DHV last year ranked No. 59 on ENR's Top 150 Global Design Firms list, reporting annual revenue in 2010 of $625.2 million. Royal Haskoning was not ranked last year but ranked No. 65 in 2010, reporting annual revenue in 2009 of $505.9 million.