SPOKANE, Wash. (AP) -- An explosion that blew a hole in a sewage tank dumped up to 200,000 gallons of sludge and wastewater into the Spokane River and a parking lot, authorities said. One worker was missing and presumed dead and three others were injured.
The four sewage treatment plant workers had gone to check on an unusual pressure buildup in the tank and were either on or near it at the time of the explosion Monday afternoon, Fire Chief Bobby Williams said. The cause of the pressure buildup and explosion was under investigation.
A search of the river and its banks was called off Monday evening, with authorities reluctantly concluding the missing man was most likely in the sewage tank at the Wastewater Treatment Plant northwest of the city.
``Our hope would be that the individual would not be in the tank, but it's looking like that's the most likely probability,'' Williams said.
The man's name was not released. Crews were draining the tank, a process that could take as long as 40 hours.
One worker suffered breathing problems and was airlifted to a hospital. A second was taken to another hospital for evaluation with minor injuries and a third had minor injuries but did not require treatment. Officials did not release the men's names.
The explosion blew a ``relatively small hole'' near the top of the tank, Williams said. That loosened the tank's lid, which then fell into the tank, causing some of the contents to splash out.
As much as 200,000 gallons of sludge and wastewater spilled onto the parking lot, the river bank and into the river, Williams said.
Health officials issued a warning for people living downstream to avoid withdrawing drinking water from the river, or using it to irrigate crops or for livestock use, for at least three days.
Washington Department of Ecology spokeswoman Jani Gilbert said there are no municipal drinking water withdrawal points downstream from the plant. City employees will be testing the river water for bacterial contamination, she said.
