Oahu homeowners should be allowed to construct second dwellings on their lots to bolster the number of rental units affordable to local tenants, which is the intent behind a bill awaiting full City Council approval. The Honolulu Department of Planning and Permitting, though, must ensure Bill 20’s passage won’t lead to a proliferation of illegal vacation units. The last thing Oahu needs is one more unenforceable law on the books or one with gaping loopholes.

Bill 20, which would allow accessory dwelling units, is expected to go to the full City Council on Sept. 2. If approved, the measure heads to the mayor’s office for consideration, where a favorable reception is likely. Under the bill, the ADUs would be no larger than 800 square feet and each unit would have to include at least one off-street parking space, except when it is within a half-mile of a rail station.

Opponents maintain that ADUs subvert existing planning guidelines and overburden roads, water and sewer lines and other infrastructure. They also worry that ADUs would make it easy for people to set up illegal transient vacation or bed-and-breakfast units, which bring higher rental income.

Rightly so, the latest version of the measure adds new components aimed at ensuring ADUs don’t become vacation units or B&Bs. Advertising an ADU as a B&B or vacation unit would be grounds for revoking an ADU permit. The minimum rental or lease period must be six months. Plus, a written rental agreement would be required.

Such safeguards are needed to stress the affordable-homes intent of Bill 20 — but the Department of Planning and Permitting, as the city’s enforcement arm policing ADUs, would need to be vigilant from the start to ensure ADU compliance.

City Planning and Permitting Director George Atta said Thursday the administration supports the additional enforcement conditions. But supporting the enforcement conditions is one thing; actively enforcing them is another.

Creation of ADUs is one of three major components of a housing crisis action plan pitched by Mayor Kirk Caldwell last year. And given the current homeless crisis, particularly visible in Honolulu’s urban core, it’s imperative that more affordable rental units are built on Oahu.

Government leaders need to think beyond homeless shelters, and this is a positive step in this direction.

One major supporter of Bill 20 is the Sovereign Councils of Hawaiian Homelands Assembly, which believes the bill will ultimately help Native Hawaiians. A significant number of Native Hawaiians make up the homeless population in Kakaako and ADUs could be established in nearby neighborhoods like Papakolea, Kalawahine and Kewalo; the goal would be to build 500 ADUs throughout the homesteading community, a representative said. If such progress can indeed be made, it would be significant headway in getting local families off the streets and stabilized into rental units.

The Hawaii Appleseed Center for Law and Economic Justice also testified in support of the bill. In urging the City Council’s approval, Jenny Lee, Hawaii Appleseed public policy director, said, “ … this is a chance for the Council to do something right away to increase our inventory of rental housing.”

She’s right. There is a real sense of urgency in getting Bill 20 passed and it is evident along the streets in Kakaako where families find shelter in reinforced tents that line the sidewalks. We are in the midst of a housing and homeless crisis, and this is one way to chip away at the encampment edges.