Workers were repairing a leaking sewer line Monday at a creek where sewage might have been running into the water for a month or more.
After a report of leaking sewage in early July, a city crew found no sewage flowing and drew up a plan to check the sewer line with a camera, said Mark York, a spokesman for the city's Division of Water Quality.
That work hadn't been done when the spill was spotted again Sunday.
"Had it been a visible overflow like it was today, we would have responded last month like we did today," York said.
Ken Cooke, an officer in a citizens' group called Friends of Wolf Run, reported the sewer leaks both times. He said the city's sanitary sewer workers usually respond to problems within 24 hours.
The leak is where an 8-inch sewer line crosses Vaughns Branch, a tributary of Wolf Run Creek.
The line is small and serves about 50 residences and a retirement home, York said.
Last week, two groups doing water sampling along the creek found dead crayfish.
First, a volunteer collecting water samples for the Kentucky River Watershed Watch program spotted dead crayfish on Vaughns Branch on Thursday morning.
Then, on Thursday afternoon, a group of girls from the neighborhood who were taking samples as part of the STARS program found dead crayfish in Wolf Run.
Darcy Everett, a program manager with Bluegrass PRIDE, was with the latter group.
"We had gone out Tuesday to check it out in advance, and they were running all over the place," Everett said of the crayfish. When they went back Thursday, they saw about 30 dead crayfish, she said.
Cooke, a retired state Division of Water employee, first thought the crawfish were being killed by low levels of dissolved oxygen in the water, which is common when algae grows in very hot weather. Vegetation along a creek provides shade to cool the water and filters runoff.
Cooke said he now thinks it could have been "a one-two punch" of sewage and weather conditions that did in the crayfish.
The biological material in sewage would be enough to reduce oxygen levels, Cooke said. There also could have been chemicals such as ammonia in the sewage that would be fatal to aquatic life.
The city hired a contractor to repair the sewer line, York said.
Dams were built in the creek above and below where the sewage was leaking, and water was routed around the area. The sewage was being pumped into a nearby manhole that went to a larger sewer line.
There also were people picking up any "debris" from the leak downstream.
A video camera will be sent through the line to find the problem. The solution might be to put a new liner inside the leaking pipe.
York said he did not know how long the repair would take.