The head of Baton Rouge’s regional road planning agency urged Ascension Parish leaders Tuesday to get behind a new Interstate 10 interchange at La. 74 that could be built as part of long-range “mega projects” being mulled by state highway officials.

Though the future interchange at La. 74 would run past a former Superfund site, Jamie Setze, executive director of the Capital Region Planning Commission, said the interchange is the one that state Department of Transportation and Development officials now support.

He said the interchange would be built as part a $200 million project to widen I-10 between Highland Road in Baton Rouge and La. 74 north of Gonzales. That highway project is furthest along, Setze said, of two Baton Rouge mega projects on the state’s “A” priority list. The “A” list is the one most likely to be funded.

Setze warned that disputes over new interchanges could lead to delays in interstate highway projects and can send federal and state officials looking elsewhere to spend scarce funding.

“I don’t want to see the one mega project ‘A’ in the Baton Rouge area get held up because we don’t agree on the location to do that,” Setze told the Ascension Parish Council Transportation Committee.

The funding would come from state vehicle sales taxes that are supposed to be set aside, under 2009 legislation, in the state highway trust fund, Setze said. The money hasn’t yet flowed into the fund because the trigger in the law has not yet kicked in; but whenever it does, the shift would generate $350 million to $400 million per year.

New interchanges on I-10 in Ascension have been a topic of discussion for years as growing loads of commuters on the north end of the parish and industrial traffic on the south end pile onto the existing interchanges.

But settling on a location has been tough for various generations of parish leaders as wetlands, key property lost to development, funding issues and public opposition to some locations have all posed roadblocks through the years.

Meanwhile, Ascension voters watched as the state widened I-12 in equally fast-growing Livingston Parish and built a new interchange at Juban Road.

Setze’s claim that DOTD officials are behind an La. 74 interchange conflicted with what the agency’s spokesperson said Tuesday hours before the council meeting.

Indira Parrales, DOTD spokeswoman, said engineers told her none of three mega projects on the proposed widening of I-10 between Highland Road and La. 22 in Sorrento anticipate new interchanges or turning existing highway overpasses into new interchanges.

But Setze told the council committee later Tuesday that he had planned to push the committee to support a new interchange connecting I-10 with Airline Highway north of La. 42 and with Bluff Road, west of I-10. But he changed his opinion after DOTD officials told him the agency supported an La. 74 interchange. One reason DOTD officials are interested is that La. 74 already has an I-10 overpass, Setze said.

Setze, who later Tuesday disputed what the DOTD spokeswoman had said, noted the interchange is in the state’s draft long-range master plan, which is set to be finished at the end of this year. He said that interchange was not put in the consultant contract for the projects but the contract could be amended to add the interchange.

Before the council, Setze also aired his initial worries about the former Superfund site. Setze said he checked with federal highway officials whether the La. 74 interchange has a “fatal flaw” but was surprised to learn the interchange did not.

A 2009 DOTD feasibility study of the La. 74 intersection done by Volkert Inc. notes the former Dutchtown Treatment Plant Superfund site is in the intersection’s northwest quadrant. The site was home to an oil refinery and reclamation facility from 1965 to 1982. The remediation was finished in 1999, the Volkert report says.

The report says each corner of the intersection would require relocations, including parts of the Lakeside Oaks Apartment complex and the large Twin Lakes Mobile Home and RV Park.

But Volkert’s study lays out two suitable interchange configurations that would avoid the former Superfund site. The report says DOTD would need to coordinate with the state Department of Environmental Quality and U.S. Environmental Protection Agency before it started buying property.

Another concern for Setze, he said, is that La. 74 interchange would be 1.1 miles from the La. 73/I-10 interchange, a distance that is just above the one-mile minimum that highway planners use between two interchanges.

Ascension Parish President Tommy Martinez said he had been “dead set” on an interchange at Cornerview Road and I-10, which is south of La. 74, but changed his view after meeting Friday with the parish legislative delegation and officials with the parish’s industrial plants. He said the consensus was for an La. 74 interchange.

“And we’re all going to support a Highway 74 interchange as far as I’m concerned,” Martinez said.

Members of the parish road committee generally supported the idea of backing one interchange but some also struck a note of caution about getting behind La. 74 without further assurances from DOTD and federal highway officials in light of the former Superfund site.

Councilwoman Teri Casso, who represents part of the La. 73 corridor in Dutchtown, urged Setze to get a more definitive determination of the interchange’s suitability upfront.

She questioned what would happened several years down the road if the Superfund site suddenly becomes a problem and the parish has to switch interchange locations.

Setze said that would create delays and suggested he and parish officials meet with DOTD’s chief designer and federal highway officials about La. 74.

Follow David J. Mitchell on Twitter, @NewsieDave.