A week after displaying modest plans for revamping small buildings in a block next to Ala Moana Boulevard, the Hawaii Community Development Authority sprang a decision allowing a spectacular condominium skyscraper nearby on state land in the heart of Kakaako. Gov. Neil Abercrombie supports the project — a bold one with many points to recommend it — but extensive hearings are necessary to review what would be the tallest building in Hawaii, far above the height limit.

At first envisioning a Kakaako featuring towers with rooftop parks and elevated passageways, HCDA revised its plans in recent years to comprise low-rise buildings along Ala Moana and high-rises included at suitable locations. The vision set forth this past week is a surprising version, featuring a 650-foot tower for market-rate condominiums named 690 Pohukaina, the street makai. The tower would surpass the 438-foot First Hawaiian Bank tower downtown, and bust the area’s 400-foot height restriction — but the HCDA has the authority to exempt a building from that limit. Whether it should, in order to create a signature landmark to entice developers and potential buyers, is a question that requires more vetting.

Announcement of this public-private project comes only a week after Kamehameha Schools revealed plans for a $30 million renovation on the 29 acres it owns in Kakaako in a block surrounded by Coral, Keawe and Auahi streets and Ala Moana, including 54 rental loft apartments and up to 30 shops, restaurants and pubs.

The $500 million state plan, tentatively approved by HCDA on Wednesday, includes the tall tower with 500 condo units, a smaller building with 300 units of affordable condos and a third building with 204 units of affordable rental housing, plus significant office space for commercial businesses. The proposed development is kittycorner from the two 400-foot tall Waterfront Towers erected along South Street nearly 20 years ago.

Abercrombie noted that "the key to ending urban sprawl, ending arguments about where we’re going to build, is to have urban density in the urban core that makes sense in community terms. And Kakaako is the ideal laboratory for the project." Its placement near the planned rail line’s Kakaako station would enhance building of the urban core.

HCDA’s jigsaw plan is aimed at achieving that result — and the eye toward building a mix of affordable housing is needed. Executive Director Anthony Ching says Kakaako’s population is expected to more than triple to 30,000 in the next 20 years. He says large buildings will play an important role, applied in large, single-owner plots, such as the 690 Pohukaina, while smaller lots will be used for modest projects, such as the Kamehameha Schools project nearby.

Where a large building is suited, Ching said the "skinny side" will be positioned from makai to mauka, limiting the scenic disruption. Of the 16 parcels that may be suited for buildings 400 feet tall or more, he expects four more will be put to the test in Kakaako in the next two decades.

The development authority had been quiet about the project before giving its tentative approval this week. The notion of planting skyscrapers in Kakaako is likely to face opposition — and we question this 650-foot height — but residents need to confront the value of fill-in building in an already-zoned urban core, especially on underutilized sites for housing. Extensive, transparent hearings must be held by the HCDA before deciding on final approval of this project, or a modified version of it.