The contaminated well on Mesquite Flat Street is about a half-mile west of the pile of wood chips, brush, dirt and logs that's been burning since Christmas. It's southwest of two wells that were previously contaminated for a short time by ashy residues, officials said.

Even though another sampling of the well shortly after noon on Friday showed no contamination, the pollution detected earlier in the day was enough to trigger a clause in the agreement between the San Antonio Water System and the Texas Commission on Environmental Quality that no more water will be used on the pile itself.

The water that was being used on the pile — and that may have contaminated the aquifer — was being used to cool the equipment and operators working on the pile, which reached temperatures as high as 1,600 degrees.

That equipment is not necessary now that they're working with a cooler part of the fire, said Andy Saenz, communications director for the state environmental agency. The temperature at the hottest part is about 500 degrees now, he said.

Greg Flores, spokesman for SAWS, said the smoky water was discovered as part of stepped-up monitoring activities agreed upon by the two agencies in an effort to protect the drinking water supply for 1.7 million people in the region.

Saenz said firefighters have made "tremendous progress" since resuming operations on Feb. 12. TCEQ seized control of the pile and hired contractors to extinguish the blaze on Jan. 9.

"The latest estimate we have is that we are between 60 percent and 70 percent extinguished, so we are right on track if not maybe a little bit ahead of schedule to put this thing out," he said, adding that the schedule calls for having it doused by March 5.

"We've knocked the top off the fire," he said. "We've used bulldozers to change the mound itself. The hottest part of the fire has already been pushed into the sluice. Now we're just pushing the hot stuff down into the quench pit."

Fire contractors constructed a clay-lined sluice adjacent to the 700-foot-long pile that slopes to a clay-lined quench pit. The impermeable clay is an effort to keep the dirty water from leaking down into the aquifer.

After Friday's discovery of the contaminated well and two meetings between officials, an amended agreement was signed by the heads of the two agencies that requires the state agency to keep the water level in the quench pit no higher than 5 feet.

"We've just taken extra precautions in this agreement to make sure that the integrity of these pits is maintained," said Flores of SAWS.

Although the quench pit was filled to 5 feet high and tested for leakage before firefighting efforts resumed, the addition of debris and water since then has pushed the level to between 8 feet and 9 feet, sparking fears that the pit could be leaking at the higher levels.

The fire contractors will treat the excess water in the pit, reusing some to douse burning material in the sluice, but sending most to a nearby SAWS sanitary sewer line, Saenz said.

The state agency will pick up the costs of sending the tainted firefighting water to the sewer plant, Flores said.

Firefighting efforts had stopped after the well contamination on Jan. 17 while fire contractors came up with another plan, but the SAWS board voted to withhold its water unless the state agreed to certain conditions to protect the aquifer.

One of those conditions was that all strategies that relied on putting water directly on the pile would be abandoned if fire residues were detected in nearby wells.

SAWS officials said they'll continue to provide water to keep the quench pit at the 5-foot level to make up for losses from evaporation and water sent to the sanitary sewer lines.