After decades of controversy, reams of studies and millions of taxpayer dollars — with billions more ahead to be spent — Honolulu’s rail system faces its last three known hurdles, thrown up by a federal judge last month. The obstacles: the vetting of a rail tunnel under Beretania Street, the project’s impact on humble Mother Waldron Park in Kakaako, and a cultural review of rail’s effect on Chinatown.

Meanwhile, trenching continues in earnest along the rail’s downtown route for Native Hawaiian remains, or iwi, a condition of an earlier, separate ruling by the Hawaii Supreme Court.

Despite all the lingering legal conditions, city officials express confidence that actual construction on the 20-mile rail system from East Kapolei to Ala Moana Center will proceed without delay.

"You can talk to anybody in public transportation, road, bridge construction anywhere in the country, and I assure you that there are environmental hurdles and challenges, legal hurdles and challenges to almost every significant project," said Daniel Grabauskas, executive director of the Honolulu Authority for Rapid Transportation. "I would have to say that I have never heard of a significant works project that didn’t have legal and environmental hurdles and challenges that have had to be addressed."

Work on the project in central Honolulu is not planned until June 2014, so federal Judge A. Wallace Tashima’s ruling — requiring the studies on the Beretania tunnel and on Mother Waldron Park be added to the rail’s final environmental impact statement (EIS) — will not result in delay, said Grabauskas. He expects these additions to be completed by the end of this year.

"We had not even anticipated doing construction in the city center area until the middle of 2014, so there’s no impact right now to our construction schedule, for instance in the downtown area," said Grabauskas, former head of the Massachusetts Bay Transportation Authority before being selected last March to run Honolulu’s rail project.

But longtime rail opponent Cliff Slater, who is part of the group that filed the federal lawsuit, is not about to concede, preparing to appeal any order by Tashima to lift the freeze on construction. An appeal could include rulings already made by Tashima in favor of the city.

Slater and fellow plaintiffs, including former Gov. Ben Cayetano, challenged the rail project in 57 areas and prevailed in three: that the EIS was insufficient in rejecting a possible rail route that includes a tunnel below Beretania Street; addressing effects at Mother Waldron Park; and making a "traditional and cultural review" of the effects on Chinatown.

The judge essentially ruled that the city must "do a better job of explaining" why it should construct the rail line on a route that, in certain areas, may be protected against transportation projects, said city Deputy Corporation Counsel Gary Takeuchi.

City officials "did do what they thought needed to be done in terms of analyzing these various impacts," Takeuchi said, "but in these three instances the court has ruled that more (explanation) is necessary."

In 2006, long before Grabauskas arrived in Honolulu, the city rejected the possibility of tunneling the rail beneath King Street, estimating that it would cost $650 million and be difficult to structure through the soil. Although a tunnel under Beretania Street was not mentioned as an alternative, the city estimated in court that a tunnel at Beretania would be about the same price.

Slater argues that the city neglected to seriously consider why digging the tunnel below Beretania should be considered.

"They should be able to provide that," he said. "They can’t just say it. The language of the (environmental) statute is that you rigorously explore the alternative.

"King Street, as you might imagine, is full of all different kinds of utilities, old ones and new ones," he said. "You get up to Beretania, and it’s a lot more sparse up there, I’m led to believe. The utilities and everything that’s underground are a lot more sparse up in Beretania than they are on King Street. And because of where King Street is, you’d have a lot more expense on King Street than you would on Beretania."

The alignment of the rail was chosen along Halekauwila Street, closer to King Street, in 2007, and is in the direction of Ala Moana.

That shouldn’t matter, Slater suggested, pointing out that the rail line initially was to stretch from Kapolei to the University of Hawaii at Manoa, "and the project neither goes to UH nor to Kapolei." A leg from Ala Moana to UH-Manoa was dropped from the project.

Plaintiffs in the lawsuit against the rail project cited a 1966 federal transportation law aimed at protecting public parks from harm by transportation projects. Mother Waldron Park, which is eligible for listing in the National Register of Historic Places, is a city park bounded by Pohukaina, Coral, Halekauwila and Cooke streets.

According to the Historic Hawaii Foundation, Mother Waldron Park was listed on the Hawaii Register of Historic Places on June 9, 1988, as an element of the thematic group "City & County of Honolulu Art Deco Parks."

This park — along with Ala Moana Park, Ala Wai Park Clubhouse, Haleiwa Beach Park and Kawananakoa Playground — are on Hawaii’s historic register because of its association with the playground movement, both nationally and locally.

It also is considered historic for its architectural and landscape design by Harry Sims Bent, the foundation said: "One of Bent’s best playground designs and a good example of Art Deco/Art Moderne styles in hardscape."

The park, originally built in 1937, includes a historic one-story comfort station, two basketball courts, a volleyball court and open field.

"That is a public park," Slater said. "A lot of people use it. It has some historical structures in it."

What disruption would the rail cause to the park? "Noise, for one thing," Salter said. "The visual."

Grabauskas responded that "a significant amount of development" is planned close to Mother Waldron Park. A rental apartment tower perhaps as high as 650 feet, the tallest on Oahu, is being proposed across the street from the park by the Hawaii Community Development Authority.

In addition, Grabauskas said, "The train will run elevated. It will be electric. We will have sound barriers along the entire alignment that will further minimize and direct noise up rather and not out." The impact, he added, will be "very minimal."

Grabauskas is confident that the rail project is in no danger in court.

"My own experience with extending rail lines, or alterations of everything from bus routes to construc- tion of new stations, or reconstruction of old stations even, that we’ve had legal and environmental challenges," he said. "The reason that the law is there is to afford people who have concerns and opportunity to voice those concerns and make sure we do it right.

"We feel pretty good," Grabauskas said.