The return of freshwater flows from the Kaituna River into Te Awa o Ngātoroirangi/Maketū Estuary has been celebrated with a gathering this morning.

Tangata whenua, Maketū schoolchildren, and other locals gathered with contracting staff, Bay of Plenty Regional Council and Western Bay of Plenty District Council representatives.

Aerial of completed Kaituna River re-diversion works - looking downstream along the new channel towards new culverts (right) and Te Tumu Cut (left). Photo / Supplied
Aerial of completed Kaituna River re-diversion works - looking downstream along the new channel towards new culverts (right) and Te Tumu Cut (left). Photo / Supplied

Bay of Plenty Regional Council deputy chairwoman Jane Nees acknowledged the efforts of tangata whenua, regional council staff, J Swap Contractors Ltd, Western Bay of Plenty District Council, and the many passionate locals who had been involved in the project since the council first began exploring design options in 2013.

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"Healthy waterways and environments are the foundation of a thriving community. This project has taken hard work, investment and collaboration from many local people and landowners over many years. It's a great example of what can be achieved when everyone works together," Nees said.

"Today marks a turning point for estuary health but it doesn't stop here. We've got more work to do, and many other projects already under way, to keep improving water quality and wildlife habitat throughout the Kaituna catchment."

Bay of Plenty Regional Council Kaituna Catchments manager Pim De Monchy said the local community had been calling for freshwater flows to be restored to the estuary since the 1970s.

"There had been a noticeable decline in estuary health since the Kaituna River was diverted out to sea at Te Tumu Cut in 1956 by the Crown and Regional River Board for land drainage purposes. The estuary had silted up, become choked with algae, and birds and fish had lost their breeding and feeding grounds.

School children line the bank to get a glimpse of the waka. Photo / Samantha Motion
School children line the bank to get a glimpse of the waka. Photo / Samantha Motion

"Through this project, up to 20 per cent (600,000m3) of the Kaituna River's flows will now be returned to the estuary on every tidal cycle, while maintaining existing levels of flood protection and boat access through the Te Tumu Cut."

Bay of Plenty Regional Council had invested $16.6m (including design, consultation, consenting and land acquisition costs) to complete the project.

Contractors began construction work in June 2018 and had now completed it, on budget and five months ahead of schedule. Ford's Cut Channel had been widened, moved and upgraded stop banks, and a new 60-metre wide, 1km channel had been installed to carry freshwater from the Kaituna River into the Maketū Estuary via 12 large culverts, fitted with automatic gates, under the Ford Road bridge.

The contractors installed a new salinity block downstream of the new channel, to reduce saltwater intrusion into the upper estuary, and upgraded the Ford Road boat ramp facilities.

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They also re-contoured low-lying paddocks beside the upper estuary, to create 20ha of estuarine wetland. Volunteers have helped to plant the new wetland called Te Pā Ika with 65,000 native plants.

De Monchy said since 1956 it had taken 15 tidal cycles to flush the estuary with river water, but it would now take only two and a half tidal cycles when all 12 of the new culverts were open.

"For the first year of operation, we'll be allowing the estuary to adapt gradually by opening just nine culverts on each incoming tide, and monitoring that closely before we open all 12.

"The increased flushing and improved salinity balance that the restored river flow will bring, along with the 20 hectares of wetland we've re-created, will help the estuary to recover and become healthier for fish and wildlife to live in, and people to enjoy."

Construction facts and figures:

Construction work on the Kaituna River re-diversion and Te Awa o Ngātoroirangi/Maketu Estuary enhancement project has involved:

• About 50,000 person hours by J Swap Ltd staff and contractors.

• The use of 25 different excavators, trucks and other heavy machines.

• Planting of 65,000 wetland plants with help from community volunteers.

• Laying of 800m of new electrical cable and 404.1m3 of concrete.

• 110,000 tonnes of gravel, sand, rocks and clay brought to site through 2704 truck movements.

• 152,660m3 of earth dug out to create new river channel.

• Installation of 12 new 2.5m x 2.5m concrete culverts and automatic flow control gates.