The U.S. Army Corps of Engineers might eliminate a planned detention basin in the upper Palolo Valley, part of the agency’s Ala Wai canal flood control project, to avoid condemning four private homes there.
“If we can impact the timing (of flood waters) by doing something elsewhere in the Palolo Valley … then let’s do it,” Jeff Herzog, the corps’ project manager, told construction industry, nonprofit and academia professionals Monday at the Honolulu Country Club.
In neighboring Manoa Valley, where the project has faced especially strong community resistance, the need for the detention basins is certain, Herzog said. In Palolo Valley, however, it’s “not so black and white — and that’s why we are looking at that right now.”
The corps’ flood control project has already cleared the feasibility phase, leaving its design about one-third complete and its details subject to change.
So far, it calls for permanent easements onto 37 or so private properties. The four parcels in Palolo are the only ones that would be entirely condemned for the project, Herzog said Monday.
His comments came during the corps’ “industry day” — a daylong briefing by construction and engineering officials on the $345 million project that aims to prevent severe flood damage to Waikiki in a major storm.
The corps has faced widespread criticism that it hasn’t sufficiently reached out to the community on its plans to build a network of 10 debris and detention basins, some of them concrete-reinforced, in the Ala Wai watershed area and in the Manoa, Palolo and Makiki valleys.
A wall of varying heights would be built along the Ala Wai canal, along with at least one pumping station.
“They should’ve had this a long time ago,” Ala Wai Watershed Association Executive Director Karen Ah Mai said afterward.
She and other local advocates have described the flood-control project’s scope as short-sighted since it no longer includes watershed restoration as one of its key goals. That objective was removed in 2012 when the corps said it couldn’t find sufficient benefits on a national level to justify including restoration.
Nonetheless, Herzog told the gathering Monday that the corps wants “to engineer with nature as much as we can” for the Ala Wai flood project.
“I’m not interested in your concrete structures, I’m interested in your innovative, green infrastructure moving forward where we can. Clearly, there will be some concrete that’s necessary,” Herzog told industry professionals.
“We’re not afraid of concrete; we just think there’s something better out there,” he added.
Still, Ah Mai said during the meeting that she hoped the corps could engineer a design that’s even less intrusive to homes and the surrounding environment — one that avoids having to create detention basins to help hold back flood waters in the upper watershed.
With the flood project entering the design phase, the corps has been working since November to refine its data on how flooding would impact the watershed, Herzog said. Under optimal conditions, construction could start as early as 2021 and wrap in 2024, he added.