Signs warning of pollution in Columbia's signature rivers were removed Monday as bacteria levels returned to normal, nearly a week after the remnants of Tropical Storm Ida sent raw and partially treated sewage spilling out of area wastewater systems.
But at the same time that state regulators pronounced the Saluda, Congaree and Broad rivers safe for kayaking, fishing or swimming, new details - and criticism - emerged about efforts last week to protect water quality after the tropical storm.
For 15 hours Wednesday and Thursday, oxygen in the Saluda River plummeted to levels considered dangerously low for fish and aquatic life, federal river data show. While state agencies didn't get any reports of fish kills, a water-quality advocate laid blame for the low oxygen levels on power company SCE&G.
The company, which manages the dam at Lake Murray, released oxygen-starved water from the bottom of the lake after Ida's rains swelled the reservoir, said Alan Mehrzad, the riverkeeper for the Saluda, Broad and Congaree rivers.
If SCE&G had released oxygen-rich water from the top of the lake into the Saluda, there would have been plenty of oxygen in the river and fish would have been better protected, he said.
Mehrzad said Columbia-area officials should redouble their efforts to upgrade sewer systems that are prone to fail during heavy rains - and the Department of Health and Environmental Control should crack down on SCE&G. The release of water so low in oxygen violated state water-quality standards for the Saluda, he said.
"It is worthy of a fine," Mehrzad said. "They violated the law, and DHEC is the one, the protector of our water."
SCE&G spokesman Robert Yanity said the problem could not be avoided. The company's hydroelectric plant is not equipped to keep oxygen levels high if it is inundated with excess water, like Columbia had last week.
"We do take our role as a steward for the environment seriously," Yanity said. "We did our best, as soon as we could, to get the oxygen levels back up to where they need to be."
Mehrzad said the power company could have released some surface water through a spillway, rather than all of it from the bottom of the lake through its hydro plant. But Yanity said use of the spillway is reserved only for extreme emergencies.
DHEC is investigating SCE&G's release of water, agency spokesman Thom Berry said.
Meanwhile, some of the trash that had piled up for months in the Broad River at Riverfront Park apparently was flushed into the Columbia Canal because of the heavy rains Nov. 10 and 11, a city parks official said Monday.
The disappearance of some trash reduces the eyesore at the park's north end but means the city will have to clean up any floating garbage at the bottom of the canal. The old canal supplies drinking water for Columbia, but trash isn't affecting the quality of water supplied to customers, Columbia public utilities director John Dooley said.
Yanity said the power company still plans to clean up any remaining trash at the top of the canal along its dam and lock.
Last week's storm, which took a toll on much of the East Coast, dumped more than 3 inches of rain on Columbia and higher amounts north of the city. In Little Mountain, for instance, nearly 4.7 inches fell in a 48-hour period ending Thursday night. That caused rivers to swell and prompted flood warnings in some places.
The rains overwhelmed some area sewer plants, causing partially treated sewage to be released into rivers. Pipes and pump stations also failed, sending sewage running into waterways.
Water-quality tests taken Wednesday through Friday initially found high levels of bacteria at treatment plants run by the city of Columbia and Alpine Utilities. (Alpine experienced a sewer spill in July 2008 that prompted an outcry from river enthusiasts.)
Bacteria levels were 40 times the standard considered safe for swimming in South Carolina on Wednesday at Alpine's plant and Thursday at Columbia's. But those levels had dropped well below the safe swimming standard at both spots by Friday, according to DHEC.
On Monday, agency officials took down eight temporary warning signs along the Saluda, Congaree and Broad rivers, Berry said. But agency officials cautioned heavy rains could again threaten water quality.
"Streams and rivers in metropolitan areas are susceptible due to their location near sewer collection systems and wastewater treatment plants," said Harry Mathis, director of DHEC's regional office, which includes Columbia. "Contaminants such as fecal coliform bacteria can be washed into surface waters during and after a rainfall. So anyone using a river or stream for recreational purposes should be aware of the potential for this to occur."
Riverkeeper Mehrzad said last week's rains underscore the need to protect the waterways that meander through South Carolina's capital city. The Saluda, Broad and Congaree Rivers - which link together in Columbia - are resources that draw an increasing level of interest from the public, he said.
"You are only going to see more and more people out there recreating" in the future, Mehrzad said. "There is a public feeling that this is a resource we should be protecting, and we have that ability to manage it better than we are doing."'