A stubborn fire continues to smolder at an agricultural waste processing center putting up a plume of smoke that can be seen from miles away.
The fire has burned piles of almond hulls since Saturday and was thought to be under control until it sent embers down wind and started a 10 acre grass fire.
The old Holly Sugar plant, which is now a storage facility for trucks and equipment, barely escaped damage.
Almond hulls are the fuzzy outer coating of almond shells and can ignite spontaneously through a chemical reaction when exposed to too much moisture.
It is primarily used to feed dairy cows.
But when they burn, they are difficult to put out because the can smolder deep within 15 to 20 high piles of hulls.
"Try to spread it out ... try to get into the piles … it's tough, we don't want to use a lot of water, it takes a lot of time and a lot of effort … they don't go out very quick," said Tracy Fire Division Chief Pat Vargas.
Crews used bulldozers and front loaders to move piles of hulls and tanker trucks sprayed smoldering piles of fuel with water.
An air-quality alert has been issued.
A few miles downwind at Banta Elementary School, outdoor activities were curtailed and indoor activities expanded. Kids with a history of asthma and respiratory issues were sent to the office for evaluation.
The added smoke from the grass fire made things worse.
"It’s already bad enough with all the pollution and everything, and all the smoke that's there, it's really scary,” said Fatima Batres whose daughter attends kindergarten.
The air-quality alert stretches to Lathrop, Manteca and Modesto.
The air quality depends heavily on the direction of the wind and how long the stubborn fire continues to burn. Fire officials say it could be several days or longer before the fire is totally extinguished.