The Honolulu Authority for Rapid Transportation has taken steps forward and steps back in its halting progress in developing the state’s largest public works project. That’s been more or less par for the course for the controversial $6.57 billion rail project that will link East Kapolei with Ala Moana Center.

There was some good news with the bids for the next set of station contracts coming in within budget targets, which indicates the strategy of repackaging the work into smaller increments was the right move.

The extension of the rail tax also seems less in doubt, following action on Wednesday by the Honolulu City Council’s Budget Committee.

However, there’s also reason for added concern.

It’s unclear exactly how many steps back are involved in the latest wrinkle: the complication of power lines along a stretch of busy Dillingham Boulevard.

That’s another warning sign that HART needs to better anticipate the cost-containment challenges ahead as the project chugs toward town, through some potential landmines.

One of them came to light this week in a story by Honolulu Star-Advertiser writer Kevin Dayton about the latest report from consultant Jacobs Engineering Group Inc. Jacobs was hired by the federal government as an external monitor, producing monthly Project Management Oversight Contractor (PMOC) reports.

The September 2015 report identified a number of concerns, but the highlight — what it ominously defined as “HART’s most significant risk to the project” — is the cost of moving the rail through a 2-mile corridor along Dillingham, where some power lines likely will have to be buried.

There’s been some preparation for this, but it does seem to be coming late in the planning process, and with much of the detail still in question.

HART in December estimated that an additional $50 million was needed for work to relocate utility lines on the 4-mile-long City Center portion of the project, and to resolve problems of siting the rail guideway near Hawaiian Electric Co’s high-voltage lines.

The issue of placing utility lines underground in some sections has come up, and only in October, HART announced it would allot another $70 million to replace and relocate power lines and other utilities on the alignment, with the lion’s share going to the undergrounding project.

Jacobs’ experts rightly argue that HART should not rely on projections from HECO’s consultant and recommend that the rail authority “prepare an independent cost estimate for all additional HECO-related costs, given their potential order of magnitude.”

It plainly makes sense to reduce uncertainty in a project in which that element can cause further delay and costs. At Honolulu Hale, where legislation affecting project financing has bogged down, the Council Budget Committee this week finally moved closer to a key decision, the five-year extension of the 0.5 percent general excise tax surcharge.

The panel may have felt pressure that Mayor Kirk Caldwell brought to bear, having met with Federal Transit Administration officials who signaled that further delay could imperil the project. The committee has moved a draft of the measure, Bill 23, that caps the amount of tax for the rail project at $910 million, which was the shortfall Caldwell and HART officials had presented to state lawmakers as the basis for the extension.

Council Chairman Ernie Martin has favored redirecting any excess tax revenue above that ceiling to other city projects, but that would require an additional authorization from the Legislature, which set up the surcharge exclusively for transportation projects.

When the bill comes up for a final vote early next year, it should be a “clean” extension that requires no further wrangling at the Capitol.

There are better ways for the Council to lean on HART for cost-containment.

One would be to require more-detailed accounting from HART on disclosures such as payments to subcontractors.

Another would be on how well the rail agency navigates building a rail line through high-power electrical lines on Dillingham.