This story has been updated.

FORT PIERRE, S.D. (KELO) — An outside consultant said Wednesday he doesn’t recommend that Navigator look at placing an odorant in the carbon dioxide that would flow through the pipeline the company wants to build and run in South Dakota.

The South Dakota Public Utilities Commission is trying to decide whether to grant a permit to the project that would remove CO2 from ethanol plants at Aurora, Chancellor and Hudson. As part of reaching that decision, the commission’s staff contracted with William Byrd, a pipeline engineer from Houston, Texas, to review whether Navigator’s proposal follows federal pipeline regulations and whether it meets state requirements for transmission projects.

Byrd took the witness chair Wednesday morning on day six of the two-week permit hearing. He didn’t support Navigator’s inquiry into possibly adding an odorant to the CO2 in its transmission line. Navigator is considering an odorant as a way to further alert the public and first responders in case of a disruption.

Byrd acknowledged that an odor is added to natural gas, but he said that step occurs as the natural gas transfers from the main transmission pipeline to the distribution system carrying the gas to its final customers.

One of the reasons why Byrd wouldn’t recommend adding an odorant in a CO2 transmission line was that the smell can fade.

“You have to re-inject and re-inject and re-inject,” Byrd said in response to a question from commissioner Gary Hanson.

While Navigator hasn’t publicly disclosed what odorant is under consideration, Byrd said an odorant can be corrosive to the pipe. He said a major leak could be detected on a transmission line without odorant.

Hanson, who said earlier in the week that his primary concern on the project is safety, suggested Wednesday that adding odorant was similar to putting chlorine in water as a disinfectant.

Byrd replied that he didn’t think it would really be a help.

Hanson responded, “It would be beneficial to citizens to have that aroma to know that something is wrong.” The commissioner added that “it would just seem intuitively it would be beneficial” because condensed CO2, which is heavier than air, hangs close to the ground.

“From a practical standpoint, I still don’t see much value in it,” Byrd replied. He said a leak is not a quiet event. “You literally get sonic booms. You have shock waves beyond this system as the CO2 is getting released.” He added, “I just don’t think it’s the right tool for finding a CO2 leak.”

Hanson replied, “I appreciate your thoughts. They’re valid.”

Brian Jorde, an Omaha lawyer representing landowners who oppose the project, said an odorant could become a regulation of the federal agency that oversees pipelines. Byrd acknowledged that was a possibility.

However, Byrd said there were other signs, such as water vapor in the air condensing if a CO2 line ruptured. “You see evidence of the CO2,” he said

Jorde suggested that all pipelines would sound like an explosion during a rupture. Byrd said an oil pipeline wouldn’t, because there isn’t an explosion, but he agreed that a ruptured CO2 line and a ruptured natural-gas line could sound similar.

Byrd said federal pipeline regulations require an ongoing public-awareness program. “That’s not a once-and-done deal. That’s an every-year deal,” he said. He added there’s also an effectiveness requirement where the company has to prove that it communicated with the public. 

The hearing resumes at 8 a.m. CT Thursday.