As it's a $375 million project, the park board's attitude is that the extra cost, and the rolling disruption to its neighbours, is a small price to pay to protect the park from being violated.
It's hard to believe Sir John Logan Campbell, who gave the park and adjacent endowment land to the public just over 100 years ago, would have agreed with the trustees' action.
Dubbed the Father of Auckland, he was all for progress, and among his battles was the fight to get a water reservoir established on the slopes of One Tree Hill.
Five water supply reservoirs are housed in Cornwall Park (three) or on the adjoining One Tree Hill Domain.
The oldest was opened by Sir John himself in February 1902. This iron-roofed reservoir - surely a heritage structure now - was designed to supply water from the Onehunga springs, but was subsequently linked to first the Waitakere Ranges dams and later to the Hunua Ranges.
At the 1902 ceremony at the Onehunga Borough's new waterworks pumping station, Sir John had the honour of starting the machinery to begin pumping water up to the One Tree Hill holding reservoir, sited at the same height as an existing Mt Eden reservoir, to allow for future linkage. An 8 inch (20cm) main fed water along Manukau Rd to Newmarket, Remuera and Ellerslie.
Sir John was reported in the Auckland Star as saying "for 42 years he had been patiently waiting for that day".
He said he'd first called for such infrastructure at a public meeting in November 1859, at a time when Auckland "was destitute of any water supply, except what was caught from roofs, or worse, from insanitary wells."
He'd told that meeting, "that time had come when we must rectify the crying evil we were labouring under."
He told his 1902 audience, to much applause, of his hope that "our wealthier colonists would be donors of what would enable people to listen to the sweet music of rippling waters flowing from the fountains of their erection in Cornwall Park."
Evidence here, that Sir John had battled for half a century to ensure Auckland had a decent water supply, and of his joy that the "great reservoir" sited on his property was an integral part of it. Unlike the present day trustees of his dream, Sir John embraced the chance to be part of guaranteeing Aucklanders a healthy supply of fresh water.
Park director Michael Ayrton said the board had to be conscious of the "huge spiritual significance to local iwi," of the park.
He also said the existing reservoir and the interconnecting pipe network were "significant restraints around what we can do," and that "we didn't want another corridor through the park that would restrict future development".
Apparently the trustees were also concerned that if they gave way to the waterpipe, they'd be inundated with power lines, telephone cables and the like.
This is reasoning the Father of Auckland would, I suspect, have found unfathomable and against everything he believed in.