Hay fire spewing smoke into sky over Mesa

Posted: Updated:
By Catherine Holland By Catherine Holland
By Catherine Holland By Catherine Holland
By Catherine Holland By Catherine Holland
By Catherine Holland By Catherine Holland
By Catherine Holland By Catherine Holland

MESA, Ariz. -- A hay fire burning in southeast Mesa is spewing smoke into the air.

The fire started at about 3 a.m. at Superstition Farm, a working dairy farm on Hawes Road north of Elliot Road. The smoke plume was visible for miles.

Firefighters believe this is a case of spontaneous combustion.

Plant-cell respiration generates heat. If the hay bales are too moist, mesophilic (warm temperature) bacteria can grow, causing the interior temperature of a hay bale to reach between 130 and 140 degrees. Normally the bacteria dies and the interior temperature eventually stabilizes.

Sometimes, however, thermophilic (heat loving) bacteria comes into play, raising the interior temperature of the bales even more and damaging the hay itself. Once a bale's temperature hits 175 degrees, a fire is usually imminent.

The source of the heat is deep inside the haystacks, which makes hay fires very difficult to extinguish. Once the fire is out, there's a danger of flames sparking back up.

Hay fires can burn for anywhere from several hours to several days.

The Superstition Farm fire is not threatening any structures, so the plan is to let it burn itself out.

Fire crews from Mesa and Gilbert are at the farm to keep an eye on things and ensure that the fire does not spread. There is a neighborhood about 100 yards away, separated from the farm by empty desert.

Farm employees have been using tractors to move dry hay -- potential fuel for the fire -- to a safe location.

Hawes Road is closed between Peralta Avenue and Elliot Road. 3TV traffic reporter Gina Maravilla advised drivers to use Power Road or Loop 202 as alternates.

In addition to being a working farm, Superstition Farm offers school and family tours and hosts a weekly market.