DENVER -- An incoming winter storm is good and bad news for sewage cleanup near Denver International Airport.

One million gallons of raw sewage leaked from DIA Wednesday, into a creek that flows downstream to Barr Lake. To put that into perspective, Thunder Bay, the big wave pool at Water World holds 1.1 million gallons of water.

Two man-made dirt dams have been built to prevent contaminated water from flowing to Barr Lake. One dam is on DIA property at 112th Avenue and Quency Street. The second dam is near E-470 and 120th Avenue.

According to DIA spokesperson Jeff Green, three water samples came back negative for fecal bacteria. The water samples were taken Wednesday from three locations:

Between DIA and the 112th Avenue/Quency Street dam

Between the 112th Avenue/Quency Street dam and the E-470/120th Avenue dam

Between the E-470/120th Avenue dam and Barr Lake

"The primary concern is direct, physical contact with that water, and luckily it's in an area where there's not much risk of that at this point," said Tony Butts, Tri-County Health Department director of environmental health. "The more diluted it is, the less impact it has, but it just gets spread over a larger area."

The winter storm could both help and hurt containment of any bacteria.

"Certainly the more water you have in that drainage, the harder it's going to be to contain," said Butts in reference to the predicted snow storm.

"The first dam was set up (at E-470/120th Avenue) to prevent anything from flowing toward Barr Lake, the second dam is set up (at 112th Avenue/Quency Street) to prevent anything more from flowing off airport property with the snow that's coming," said Green.

The contaminated water flowed into Third Creek through DIA downstream toward Barr Lake, north of the airport. Barr Lake isn't used for drinking water, so there's not a concern for what comes out of the tap. Tri-County Health didn't notice any major environmental impact in preliminary tests Wednesday.

"If it's too concentrated it reduces the oxygen level in the creek, kills off the aquatic life, or creates some odors and things like that, so that's one of the things we were looking for (Wednesday) that we did not see," said Butts.

Test results from Barr Lake are expected Friday.

DIA is also investigating how the leak went undetected for 12 hours.

"We found that the speaker for the audible alarm had been turned down. Don't know why that would have been done," said Green. "Certainly we'd like to know who did it so we can correct it, but I think more importantly we're going to put some changes in place, certainly a speaker that can't be turned off or turned down at all."

According to Green, the airport's maintenance control center has a visual and audible alarm for leaks similar to what occurred Wednesday.

"It's both a visual and an audible alarm system that rings in the airport's maintenance control center. The reason for the redundancy is there are a lot of screens in the maintenance control center and they're not always watched on a regular basis," said Green. "We don't want that to be the only cue, which is why we have the audible backup, and unfortunately it failed for no good reason. It's embarrassing."

Green told 7News the control center is monitored 24 hours a day, seven days a week, with several people who watch the train system and call for janitorial services.

"Was there someone physically in that room that missed seeing the alarm or was there no one in that room?" asked 7News reporter Marshall Zelinger.

"No, there were folks in that room, there's always folks in that room 24-7," said Green.