In terms of what it can do for a densely populated and underserved Honolulu community, the redevelopment of what’s called Kapalama Kai may be the most important project now starting to appear on the horizon, thanks to Kamehameha Schools.

Kamehameha Schools’ mission is to advance the education of Native Hawaiian students, financed through revenues from its property, and its development program is key. It is the state’s largest private landowner and here is turning its attention to the district that also houses its flagship school campus.

The 104 acres comprise a largely industrial zone that should become more homelike to thousands of current or future area residents. Both the developer and the city must move to capitalize on one of the best opportunities for narrowing the affordable-housing gap.

Conceptual plans for the sprawling complex — which would accommodate 4,000-5,000 housing units, 150,000 square feet of retail space and 6 acres of open space — were unveiled at a recent Hawaii Society of Business Professionals meeting. Kamehameha Schools officials there said first-phase construction of three residential towers and a retail marketplace on 16 acres could begin in five to seven years.

That means housing advocates and the current residents and business tenants themselves soon must be engaged in planning, even though developers say that is at the early stages.

From the business perspective, Kamehameha Schools needs to hear what companies need if many of them still will have a home in the area, as the community surely hopes that they will. Some, such as the tenants of Kapalama Shopping Center, have become long-term neighborhood fixtures.

Officials have said the trust intends to maintain about half the acreage in industrial use, including new development, allowing room for the new high-rise towers, retail and open space. Some increased density may enable more of the local businesses to remain.

In exchange for any density allowances, the city should ensure that the affordability of the units being built is maximized.

What would make this project more workable in an urban zone already heavy with traffic is its alignment with the city’s rail project. The future rail stop will be located adjacent to Kapalama Canal, easily accessible to the area’s residents and shoppers, as well as to the students at Honolulu Community College.

Reducing the number of cars, including those used by the students and those living onsite, will be essential. The rail can provide needed transportation service, so that parking capacity provided by developers — generally one of the most costly construction elements of a new project — can be reduced.

In return, as many units as possible that are priced within reach of residents earning below the area median income (AMI) — ideally in the 60-80% AMI range — should be required.

This has been one of the chief selling points for the rail project from the start. Transit-oriented development, or TOD, has been touted as one of the goals of city policymakers.

So far, the promise has not been fulfilled in adequate measure. Development activity to date has occurred along the rail route on the downtown side, in Kakaako and on the approach to the planned Ala Moana terminus. There, much of the inventory has been aimed at higher-income buyers as opposed to renters.

Kapalama Kai, by comparison, is where the vision seems more closely to match the need for affordable rentals and units for sale, where real gains could be made toward shrinking the island’s housing deficit. So much hope is riding on the city, rail officials and Kamehameha Schools getting the formula right.