While opponents of a proposed oil well in St. Tammany Parish made their arguments Tuesday before an official of the state’s Department of Natural Resources, several blocks away, a lawsuit seeking to halt the plan, filed Monday by the St. Tammany Parish Council, was winding its way through the East Baton Rouge Parish Clerk of Court’s Office.

The suit names James Welsh, the state’s commissioner of conservation, as a defendant and asks a state judge to issue an injunction preventing the DNR from issuing a permit that would allow the operator to dig a well and extract oil by hydraulic fracturing, or fracking.

The suit argues that the parish’s zoning laws prohibit drilling a well at the proposed site, and it points to a recent legislative auditor’s report that said the DNR was negligent in overseeing many of Louisiana’s abandoned and inoperative wells.

The proposed well location — in the southeast part of a 960-acre tract north of Interstate 12 and bisected by La. 1088 — is zoned A-3, a designation that requires a “single-family residential environment on moderate-sized lots,” according to the council’s suit. Activities on the land are limited to dwellings and certain “cultural, education, religion and public uses,” the suit says.

The case has been assigned to 19th Judicial District Judge William Morvant.

On Tuesday morning, several opponents of the proposed well made impassioned pleas before Todd Keating, director of the DNR’s engineering division, at a “unitization” hearing, a proceeding to determine whether the proposed tract of land is sufficiently large for Helis Oil & Gas to harvest minerals from it.

Helis was represented at the hearing by Rick Revels, who noted that the proposal has generated considerable public interest and urged Keating to consider only testimony and comments relevant to unitization. Revels then called geologist Bill Dale, who testified that Helis’ proposed unit is similar in size to parcels in Washington, Tangipahoa and St. Helena parishes where fracking is occurring.

Keating, who was sitting in for Welsh, opened the floor to public questions and comments. Several people questioned whether the well could be guaranteed to remain safe and whether additional wells would be proposed for the site. Dale said he could not answer either question. Several times, Keating instructed speakers to restrict their questions to the scope of Dale’s testimony.

Dale acknowledged that the well planned for St. Tammany is about 40 miles from the nearest similar well, but he said the plan for it is consistent with other such plans.

Helis’ proposed well is at the far southeastern end of the Tuscaloosa Marine Shale, a rock formation that stretches like a belt across Louisiana’s midsection and also includes parts of southern Mississippi and eastern Texas. Recently, drilling activity in the shale has picked up, and estimates indicate the formation could hold as much as 7 billion barrels of oil.

The oil would be extracted through a process known as fracking, in which water, sand and chemicals are injected at high pressure into the formation to create cracks from which oil and natural gas can be pumped to the surface. Fracking is controversial in other parts of the country, where it has been blamed for a host of environmental and human health concerns. Some communities either are attempting or have attempted to ban the practice — efforts that have met with varying levels of success.

In St. Tammany Parish, the activist group Concerned Citizens of St. Tammany has enlisted the help of environmental lawyers and vowed to fight the proposed well all the way to the U.S. Supreme Court.

Other groups are working on similar plans, including the town of Abita Springs. Lisa Jordan, an attorney from the Tulane Environmental Law Center who said she represented Abita Springs, questioned Revels on Tuesday about the type of public notices issued for the hearing.

When Revels admitted he couldn’t say where the notices had been posted, Jordan said the “unit order” Helis is seeking should be withheld until it can prove it properly informed the public. Jordan also entered into the record a copy of a resolution opposing fracking that was unanimously passed by Abita’s town council.

Speakers repeatedly referenced the Southern Hills aquifer system, from which St. Tammany draws its drinking water, and said drilling through the aquifer, which Helis would have to do to get to the oil 12,600 feet down, could endanger the water supply for the parish’s 200,000-plus residents.

“Has Helis put any plan in place if there is an effect to the aquifer? What is the contingency plan?” asked Rick Franzo, the president of Concerned Citizens of St. Tammany.

Revels conceded that it was a legitimate question but suggested Franzo direct it at Helis. He said the question was outside the scope of Dale’s testimony and the unitization hearing.

Franzo was not satisfied.

“I think these are good questions to be asked by DNR,” Franzo said. “I want to know what they are going to do to solve our water problem.”

At the end of the hearing, Revels renewed his objection to what he called comments beyond the scope of the hearing and again said the well would be similar to dozens of others in other parishes.

“The only thing I see unusual about the proposal is that it happens to be in St. Tammany,” he said. He added that Helis has expressed a willingness to work with parish officials to “address all legitimate concerns.”

No decision was announced at the end of the hearing, and Keating said the period for the public to submit written comments would remain open until June 24. It takes typically between 30 and 60 days to issue a ruling either approving or denying a unit, according to DNR spokesman Patrick Courreges.

Helis also has applied for a wetlands permit from the U.S. Army Corps of Engineers. That permit is currently under consideration.

Follow Faimon A. Roberts III on Twitter, @faimon.