Kamehameha Highway near Punaluu Beach Park is being contra-flowed as Board of Water Supply crews repair a broken 30-inch water main.
The Kahuku-bound lane of the highway is closed while the main is repaired.
Motorists are asked to avoid the area, if possible.
The Board of Water Supply says repairs and the lane closure are likely to last into the evening.
No customers are without water at this time.