Three more booms will be used to contain a large diesel spill in the Makotuku stream.
Since Wednesday, 15,000 litres of diesel have leaked from the Turoa Ski Field in Tongariro National Park into the stream - the primary tributary for Raetihi's water supply.
The town's water supply has been shut off as a result, causing major problems for residents who are having to collect fresh water from a tanker at the Seddon St Four Square.
The water supply is expected to remain shut off for at least 10 days. A boom was installed on Thursday for the initial clean-up job.
Horizons Regional Council incident controller Craig Grant said two teams were to carry out tests of all waterways in the catchment Friday.