Construction work on the Southern Pipline will now continue after an assessment came back giving the all clear.

On Thursday morning mud used for drilling seeped through loose ground and reached the low tide harbour surface on the Memorial Park side.

Construction workers were forced to stop work and pump the excess mud out of the harbour.

'The drill hit softer material than they first anticipated and some of the drilling mud seeped to the surface. Clean up started immediately and has had no lasting impact on the site," says Project manager Steve Wiggill.

A team of drilling experts, including an independent international expert in the USA, review the project's progress on a daily basis, and drilling was put on hold until their assessment.

He says most of the mud was collected and removed offsite, but some had washed into the harbour.