The survey work will start this month with an intention to offer additional geophysical data to ensure the seabed is clear of obstructions, such as unexploded ordnance from the Second World War, before construction begins.
The company will use three vessels for the work.The 41m Fugro Helmert will survey at the main wind farm site.
The 24 RV Discovery will operate on both wind farm site and export cable route, while the 12m Fugro Valkyrie which will survey the near shore works on export cable route.
Dong said that it will appoint another contractor at a later stage to undertake a detailed survey with a remotely operated vehicle to check for and, if required, deal with any debris or ordnance found.
Dong Energy Walney Extension programme director Andrew Cotterell said: "Carrying out geophysical surveys is an important step before we can safely begin offshore construction."
"We are delighted to be working with an experienced UK contractor on this phase of our programme."
Expected to become operational in 2018, the project is said to surpass the current biggest offshore wind farm in the world, 630MW London Array offshore wind farm.
The clean energy generated at Walney Extension will be enough to power over 460,000 UK homes.
Image: Fugro Helmert conducting survey. Photo: courtesy of DONG Energy.
