Excessive air in the unloading system for a hydrated lime silo caused about 500 kilograms of fine, white powder to spill from a release spout and onto the ground at the Exshaw cement plant Monday (July 21) at about 10:30 a.m.
Plant spokesperson Michelle Gurney said Wednesday the hydrated lime, produced at the nearby Graymont plant, spilled while it was being unloaded.
“The hydrated lime was being offloaded and the level in the hydrated lime tank increased from 54 per cent to 100 per cent in just under a minute so it caused the silo to overfill and dust the immediate area,” she said.
“When the contractor was filling the bin, the hydrated lime became very fluffy, and staff there recognized there was too much air in the system, but the hydrated lime had already sloughed out of the overflow spout before they could completely shut it down.”
Gurney said the amount of lime that spilled is difficult to estimate, but she said Lafarge believes approximately 500 kg of hydrated lime poured from the silo.
She added heavy rain was falling at the time of the spill, which helped to knock down the amount of dust released.
“That definitely worked in our favour in terms of containing it,” she said. “Because of the rain, and of course going from observation, the rain knocked down a lot of that dust, but the wind was travelling northwest and we did see dust as far as the church and the parking lot near the plant site.”
The plant hosed the affected areas down with water, Gurney said.
Hydrated lime, used by the plant to absorb sulphur dioxide emissions, did travel further, spreading into the hamlet, according to residents who complained of headaches and sore throats following the spill.
However, Gurney said the plant received one call from an individual who found lime dust on his vehicle near the Heart Mountain Store.
That call came in on Monday at about 4 p.m. Gurney said the plant has not received any other calls, but encourages Exshaw residents who have been exposed to the hydrated lime dust to call her at 403-431-0759 or call the plant hotline at 403-673-5222. She also recommended calling Alberta Environment and Sustainable Resource Development and Alberta Health Link for information.
The plant did not initially release information about the spill, as staff believed it had been contained to the plant’s industrial lease.
“We knew it had happened, we were on standby to see what observations showed up, but of course we didn’t get any calls,” she said.
“We hadn’t heard from anybody else; we believed it was contained to the plant site given that there was such heavy rain.”
No Lafarge employees were adversely affected by the hydrated lime dust.
“Everybody was following their safety procedures; thankfully nobody on our site reported any skin contact, eye contact, inhalation or ingestion of this product,” she said.
According to a material safety data sheet provided to Lafarge by Graymont, acute or a single, large exposure to hydrated lime can cause severe irritation to skin, eyes and breathing passages, accompanied by coughing or sneezing.
Chronic or repeated or prolonged exposure to hydrated lime can cause desquamation (shedding of the skin) or respiratory disease.
