More than three years after a huge mulch fire threatened to pollute San Antonio's water supply, the Edwards Aquifer Authority is considering new rules for the storage of chemicals above the aquifer's recharge zone.

The December 2006 mulch fire in Helotes tainted wells with ash runoff and made aquifer managers realize the water supply was vulnerable to similar threats.

“Some of the wells were like you had washed out your barbecue pit,” said John Hoyt, the assistant general manager at the Edwards Aquifer Authority.

Fortunately, the runoff was not toxic, but the authority is concerned the next major fire will not be of decomposing brush, but at a warehouse full of pesticides and solvents like those stored and sold at major retail stores.

If one of those buildings were to start burning and then become doused by firefighters, the runoff could carry those toxic chemicals directly into the aquifer.

The authority has identified 28 businesses in the aquifer recharge zone that could be affected by the new rules. They include big-box stores, quarries, paint companies and county and city buildings, any place that stores large quantities of motor oil, antifreeze, pesticides and other potentially hazardous chemicals.

Starting this week, the authority will host a series of public meetings to gather input on new rules designed to protect the aquifer by requiring all property owners storing more than 10,000 pounds or 1,000 gallons of “regulated substances” to notify the authority of where the material is, what the plan is if the material is threatened by a fire, and where the containment equipment and safety equipment is kept.

“It's basically anything you can't drink,” Hoyt said of the materials the authority wants to know about.

The information will be stored in an online database so firefighters responding to a call will know how to best address the situation.

In some cases, the information may tell the firefighters to simply let the fire burn itself out.

In November, a fire destroyed the 180,000-square-foot warehouse at the Border Recycling Center outside Uvalde. Fueled by a lot of plastic, old computers and piles of unidentified materials, the fire emitted a plume of black smoke that could be seen 80 miles away in downtown San Antonio.

The Uvalde Fire Department decided to let the fire burn out on its own.

Fewer than 100 yards from the building was a well, and the local ranchers were very sensitive to any contaminants getting into the groundwater, Fire Chief Gene Ayala said.

For four days a gentle wind spread the smoke across South Texas as the fire consumed the building and the crews kept watch.

“No matter what, you are still going to have contamination whether it is air quality or water quality,” Ayala said.

In that case, it was better to choose air pollution over water pollution.

Every fire is different, and the new rules will give firefighters more information on which to base their decision, explained EAA spokesman Roland Ruiz.

“Of course, if that had been in the middle of town, we would have been forced to get it out,” Ayala said.