Coromandel could be in a hole lot of trouble with another chunk of a key highway disappearing down a hillside.

State Highway 25 between Whangamatā and Hikuai is open for essential travel only and later today will close completely for patch up work.

The bite out of the road is now almost touching the centre line with earth beneath the remaining seal clearly dropping away and the highway down to one lane.

Yesterday maintenance workers had to cut into the bank to give some extra room on the shoulder of the road and allow for one way traffic.

The peninsula's other main access road State Highway 25A already has a massive canyon in it and residents are nervous another lifeline road could go.

Thames Coromandel emergency management boss Garry Towler talks to Lisa Owen.