Arapuni Dam is a hydro dam and power station on the Waikato River, near Arapuni in South Waikato. It was the first government-built high dam on the Waikato River, and it began operating in 1929. The site is a listed historic heritage item. Mercury runs it as part of the Waikato Hydro System, which the company says provides about 10% of New Zealand's electricity. The station's eight turbines have an installed capacity of 196 MW.
We hear that Arapuni Road across the dam has been closed since Tuesday 1 September 2026, and the closure is expected to last 24 to 36 months. A one-lane detour runs along Powerhouse Road, controlled by traffic lights. Drivers should allow about 20 extra minutes at peak morning and afternoon times, and about 10 extra minutes off-peak. The detour is open to cars, light vehicles, motorcycles, school buses, emergency services and rigid trucks up to 8 metres long. Freight and long-distance heavy vehicles are asked to use state highway routes. The western end of the swing bridge is closed, and Waikato River Trail users can still use Powerhouse Road.