The largest chemical spill in recent memory in this area pulled together officials from seven organizations Wednesday morning.

At about 7 a.m., near mile marker 114 on southbound Interstate 35, a motorist phoned the Story County Sheriff’s Office because something appeared to be leaking out of the back of a semitrailer the caller was following.

The semitrailer was driven by David Lee Allen of Little Rock, Ark., said Capt. Gary Foster of the Story County Sheriff’s Department.

Allen was stopped by county police officers who noticed the chemical identification on the trailer. The two officers, Sgt. Dave Lekwa and Deputy Jim Atkinson, and Allen were taken to Mary Greeley Medical Center after experiencing some respiratory problems, Foster said. They were examined and released Wednesday morning.

I-35 was closed from E29 to Highway 30 at about 8 a.m. after officials determined that several chemicals, including hexane, sulfuric acid, toluene and zepaoume were being transported in Allen’s semi and were potentially involved in the hazardous spill.

The section remained closed until 11:30 a.m.

HazMat crews from Des Moines and Ames, as well as Nevada and Ames Fire Departments, the Iowa State Patrol, Department of Transportation and the Department of Natural Resources responded to the scene.

It was determined that only one 55-gallon drum of zepaoume was leaking because it had fallen from a pallet in the truck, Foster said.

Zepaoume is an industrial- grade soap, said Capt. Bob Cox of the Des Moines Fire Department, who worked on the HazMat crew. Cox said zepaoume is used in cleaning aluminum products like air conditioners, he said. It is corrosive because it contains hydrochloric acid.

Within the truck and on the roadway, HazMat respondents used absorbent material to clean up the spill.

“The pure form [of zepaoume] is pretty bad,” Cox said, but the drum in the truck was filled with a diluted form of the chemical.

The contents of the semi were transported to another truck and relocated offsite for investigation and cleaning.

“I don’t believe there will be a significant impact on the environment, but the [Department of Transportation] is doing all the clean-up necessary,” Foster said.

Cox said if more of the zepaoume had spilled, there could have been an environmental impact. This spill, he said, was a best-case scenario.

The truck was transporting both acids and bases, Cox said. A mix of the chemicals would have produced large amounts of heat.

“If two barrels had broken we could have had a pretty violent reaction,” Cox said.

There was no damage to the vehicle driving behind the semi; it only needed to be washed with water to further dilute the zepaoume, Cox said. The driver of the vehicle reported no injuries.

Cox said this type of spill is “pretty rare.” He said Des Moines HazMat crews typically respond to 150 smaller incidents of various kinds each year.

Foster said it is unlikely that Allen, 53, will be charged with a crime.