One of the goals of the Oahu rail system is to support the construction of more affordable housing along its route.

A down side is that the developers often want higher density in order for the complex to pencil out and remain within reach of lower-income residents. That means buildings that rise beyond the usual height limits, raising objections from community members.

A textbook case illustrating all of this ultimately will land in front of Honolulu City Council members, who get the final word on the proposed Keawalau at Waipahu.

Council members need to give it due consideration, as it would help offset Oahu’s serious shortage in affordable housing inventory.

A team of developers — led by Highridge Costa, a California-based firm with expertise in affordable housing projects — want to build about 400 rental units near the intersection of Farrington Highway and Hikimoe St, where an American Savings Bank building now stands.

An additional 130 units would be reserved for seniors and would fit within the 60-foot height limit.

However, the larger portion would encompass retail and commercial uses, including the bank branch, in the base, with the residential units rising 200 feet (20 floors), more than triple the height limit.

It’s the height that seems to be a dealbreaker for some members of the Waipahu Neighborhood Board.

The board members are not without justification for their argument. For example, they point to the transit- oriented development (TOD) plan the Council adopted for Waipahu in 2014, with community input.

In most transit-oriented development plans, developers are given some leeway in height and density for projects with community benefits, such as affordable housing. That’s not promised in Waipahu’s plan, though: The aim was to preserve the “Old Waipahu Town” character. The landmark for the former sugar plantation town is the iconic smokestack of the old Oahu Sugar Co. refinery, which highrises could overwhelm.

Nonetheless, the community should reflect on what is being offered, and how it can benefit. Seven years have elapsed since that plan was adopted, and the need for housing has grown ever more acute. The median price of a single-family home on Oahu is nearing $1 million, while the latest Census figures put the island’s population at 1 million and growing. New affordable housing, if properly designed and strictly bounded by rail-station proximity, can provide economic vitality without violating the intent of Waipahu’s TOD plans.

At Keawalau, the range for monthly rents would top out at $1,269 for a studio to $1,885 for three-bedroom units, prices calculated if apartments were available today. Affordability, linked to local household income, would extend for 60 years.

The income for a qualifying tenant would be capped at 60% of the annual median household income for Honolulu: $50,760 for a single person, $58,020 for a couple and $72,480 for a family of four.

This is important on two fronts. The term of affordability is reasonably long, allowing time for children to grow up in these households. And the inclusion of three-bedroom units is an accommodation at least for an average household size that exceeds what is offered in many other rental projects.

The community could insist on a higher proportion of larger unit sizes and assurance that traffic impact would be manageable — an obvious stipulation, as the whole point of TOD is to encourage rail use over cars.

And residents could advocate for some compromise on height and viewplanes, to reduce the visual impact. But if there is no accommodation for some density along the already urbanized corridor, it’s hard to see how TOD on the 20-mile spine of the transit line will ever yield the housing that Oahu desperately needs.