MEMPHIS, Tenn. — The Shelby County Health Department has released the report filed following a burn-off at the Valero refinery.

The incident happened on July 25. The Shelby County Health Department said that an unplanned MLGW power outage triggered Valero’s flare system. The health department says Valero “released excessive confined gas to reduce pressure on the refinery system, increasing flames and smoke.”

According to the report from Valero, the power outage caused all of the boilers that supply steam to the flares to shut down. Valero says that there wasn’t enough steam to mitigate smoke from the refinery flares.

Valero says the flares emitted sulfur dioxide into the air. Valero also says that because the power outage shut down the systems used to remove hydrogen sulfide from the fuel system, sulfur dioxide was also emitted from heater combustion.

Valero’s report says that the refinery’s sulfur plants also shut down due to the power outage, contributing to the sulfur dioxide emissions.

Valero says that 941 pounds of sulfur dioxide was released, exceeding the 500-pound reportable quantity.

According to Valero’s report, the units affected by the power outage were “secured to a safe posture” until they could be safely restarted. Valero says the initial flaring ended when the units “depressured” to a safe level.

According to the United States Environmental Protection Agency (EPA), sulfur dioxide can affect both the environment and people’s health.

The EPA says that short-term exposure to sulfur dioxide can “harm the respiratory system and make breathing difficult,” and that those with asthma, especially children, can be sensitive to the effects of sulfur dioxide.

The EPA says that at high concentrations, sulfur dioxide can harm trees and plants and can even contribute to acid rain.

Valero’s report states that there is “no known or anticipated acute or chronic health risk” associated with July’s burn-off.

The Shelby County Health Department says it is reviewing Valero’s report and may investigate further if necessary.