A very challenging project. Exposed conditions and divers working at depths greater than -30m. The sewer outfall was ca. 1km offshore of which the first 150m was buried in a trench. After the pipeline emerged from the trench we had to cover every metre of the pileline with concrete mattresses. In addition to the normal challenges of excavating the trench in the sea we encountered rock unexpectedly necessitating the use of our jack up barge and an excavator with an underwater hammer breaker.