Mount Maunganui-based HEB Construction won the contract to build 49 metres of tidal stairs, a 27m pier and 24m floating pontoon. The contract was worth $2.8 million.
Mr Sedcole said he was speaking from experience, having kayaked that stretch of water a fair bit.
"I have grandchildren and it scares me that one could go in there."
Mr Sedcole said he had decided to "rattle a few cages" after seeing his concerns echoed by letters to the editor and online responses to Bay of Plenty Times stories.
It was not dangerous at high tide, but everything changed three hours later when the tide was running, he said.
"There will be a 5-second opportunity to get out, or else they will be gone."
He was not persuaded by the safety features being built into the project and said it could be a case of a person dying before concerns were properly addressed.
Mr Sedcole said the running tide was so strong that Maori paddlers launching a waka nearly lost the boat. Conditions were exacerbated by the running tide being choked between the railway bridge and the Harbour Bridge, caused by the fingers of land to reduce the lengths of the bridges.
An added danger for a child was the wake from a passing boat. It could easily take the depth of water from knee high to waist high, depending on the slope of the hull and speed, he said.
Council general manager of city transformation Jaine Lovell-Gadd said there were already boat ramps along The Strand area, a commercial fishing pier, three pontoons, a promenade walkway and a boardwalk.
All of them were unfenced and accessible by the public. They were used and enjoyed in a range of ways including swimming and jumping in the water, fishing, and a range of vessel-related uses.
"Council appreciates that there is a very strong current in parts of the Tauranga Harbour. In particular, this includes the deep areas of the shipping channel, and the centre of the harbour channels. The deepest point at the pontoon location will be about 2.5m at low tide and 4.5m at high tide. The bottom of the tidal stairs will be about 0.2m under water during a low tide and 2m under water during a high tide.
"A hydrological study of the water flows past the site has been completed by the University of Waikato. This study shows that the maximum tidal flow is 1.8km/h, which is the equivalent of a light current in diving terms and is about half the speed of walking," she said.
"A large number of safety features are being incorporated into these facilities. In fact, the safety features to be provided are generally at a higher level of protection than often seen at similar facilities in other city centres in New Zealand."
Safety features would include fully fencing the pier with pool gates at the end and information signs about the risks associated with water and the water flows. Ladders from the water to the pontoon would be provided to enable people to return to the pontoon. There would be a handrail and rescue equipment on both the tidal stairs and the pier, and the geometry of the tidal steps would allow wide-stepped platforms.
A row of seats would provide a physical barrier between the walkway path and the tidal stairs. The tidal stairs would be set back into the waterfront to create a semi-enclosed harbour space reducing exposure to waves and current. There would also be an anti-slip treatment on the tidal stairs.
"It will take longer to climb down the new tidal stairs than it would to fall from the current 1:1 slope rock wall and for this reason the stairs are considered to be safer than the current rock wall environment," Ms Lovell-Gadd said.
Tidal steps safety features
- Signs about risks and water flows.
- Navigation signs for boats
- Anti-slip treatment and regular cleaning of stairs
- Handrail and rescue equipment on the pier
- Ladders from water to pontoon
- Lighting at night
- Child safety gate to the jump platform and pontoon
Source: Tauranga City Council
