City officials are baffled by a mysterious sewage leak into the Town Branch of Elkhorn Creek.
Officials learned about the spill -- which is entering a section of Town Branch along Manchester Street -- last Tuesday, but they have been unable to isolate its source, said Charlie Martin, director of the city's Division of Water and Air Quality.
The city has dumped hundreds of gallons of dye into the sewage system, snaked TV cameras through the sewer pipes and blown smoke into the pipes to try to find the leak.
Nothing has worked, and the sewage is continuing to flow into the creek.
The mysterious sewage leak is the second spill into the Town Branch in the last month. Unlike last month's spill, fish in the Town Branch have not been affected and there should not be any major environmental harm because of the latest leak, Martin said. "Sampling indicated the stream was still healthy," he said.
In the meantime, the city has set up an aeration area downstream from where the sewage is entering Town Branch. Aerating the water helps reduce the level of bacteria in the stream, Martin said. The city began aerating last week, after the spill was reported.
City workers have determined the leak is not coming from the public sewer system, Martin said. Since the spill was discovered, between four and 10 employees have worked full time trying to discover the source, said Rod Chervus, the collection and conveyance manager in the Division of Water and Air Quality.
The next step in finding the source of the leak is to test the individual sewage lines of private businesses and residences and to work with geologists who are familiar with the area.
The sewage appears to be traveling underground, and groundwater can travel through cracks, Martin said.
The sewage could be coming from "upstream in a pocket or cave, and with our drought, it's coming out now," Chervus said.
If the source of the sewage is found to be underground, the city could drill a hole and pump the sewage out of it into the sanitary sewer system before it reaches the Town Branch, Martin said.