Danish developer Dong Energy handed the Scottish-based subsea specialist the contract to clear and prepare the seabed for the installation of 35 array cables in August.
ESS' Scar seabed plough cleared approximately 50,000 boulders and other obstructions along the cable routes. The plough was deployed from ESS' Havila Jupiter vessel.
It took 72 days to complete and was finished on time, ESS said.
Westermost Rough is located eight kilometres off England's northeast coast and will use 35 Siemens 6MW turbines. Commissioning is due to take place in 2015.