A sewage leak that is the result of a century-old sewage line improperly connected to a storm drain that runs under Mechanic Street in the South End of Rockland was discovered on Wednesday.

The city will begin digging up the area on Monday, August 4, to correct the problem so that the sewage line directs flow to the city wastewater treatment plant, not into the harbor.

The lines should be rerouted by the end of the first week in August, said Terry Pinto, Rockland's wastewater treatment manager.

This is the first source of fecal pollution identified by the city, and relatively easy to fix, but Pinto said it is not the only source in the South End and is unlikely to be the primary problem.

In June, state tests revealed extremely high E. Coli bacteria counts in the salt water at the outlet of storm drains that flow into the harbor at Snow Marine Park and the adjacent area. The discovery shifted the focus of the city-wide survey of the sewer and storm drain system, which was already underway, to that vicinity.

Dye tests and a survey of the lines with the city's sewer robot showed that sewage from the Sail Power and Steam Museum and two houses directly across the entrance from Snow Marine Park, where the railroad tracks cross, were piped into the storm drain that dumps directly into the harbor off the point. The sewer line is at least a century old, according to Pinto. The storm drain was probably installed in the mid-twentieth century.

The storm drain connects much of the south end and Pinto suspects another source of pollution in the South Street and Suffolk Street area of the South End.

A separate storm drain discharges water from Snow Marine Park itself, an area that used to be part of the harbor and was created by fill. Popular for use as a dog park, it is an unsuitable site for that use, said Pinto, largely because it is a damp area where dog feces and the bacteria they carry do not easily disperse and instead spread into the damp ground.

Some residents have disputed that the high E. Coli counts, which indicate that an area is a perfect breeding ground for disease-causing orangisms that pose a public health hazard to humans and pets, are a result of dog feces.

Results of the lab tests on the water taken from the outlet of the storm drains are due back by August 6, said Pinto and should reveal whether the fecal contamination is caused by humans or dogs.

Dog feces have almost twice the bacteria count as human feces, according to Pinto.

On Wednesday evening, one dog was roaming in the park with a man, even though the area is closed to pets and humans, both of whom are susceptible to diseases carried by feces.

The city will continue dye testing house by house, as necessary, and begin city-wide smoke testing of the storm water system to look for sewage leaks on August 4.