Tempe Police Department

The train bridge over Tempe Town Lake caught fire and partially collapsed after a freight train partially derailed on Wednesday, July 29, 2020.

The chemical released in the train derailment on the Salt River Union Pacific Bridge in Tempe may not have long-term environmental impacts.

The challenge is to keep it out of Tempe Town Lake. 

Cyclohexanone is a combustible liquid frequently used as a solvent. It becomes more volatile at high temperatures.

At 111 degrees, for example, a small amount of vapors from the chemical can ignite with a single spark.

But it is not carcinogenic, and it breaks down quickly. 

"It’s readily biodegradable, which is good," said Kiril Hristovski is an engineering professor at Arizona State University. "That means that the microorganisms that live in the soil, can utilize it rapidly as a food source, so they can degrade it."

The chemical also evaporates quickly at high temperatures.

That means about 75% of the spill could be gone within a month. 

“Another thing about Arizona, is that we have in the summer, high temperatures, and these are causing rapid evaporation of these types of materials,” Hristovski said. 

But it is toxic in the water. The Arizona Department of Environmental Quality and Union Pacific are monitoring the site.

→ 2 Union Pacific Contractors Injured By Chemical From Tempe Train Cars