The two combined to dump raw sewage into Stoney Creek.
As a result, Naugle said, the creek was contaminated from the bridge to Darby Creek.
On Monday, the borough received a call about suspicious-looking water near the bridge.
Although the problem is under the county's jurisdiction, Ridley Park has built a damming wall around the manhole.
The health officer has posted notices near the site, and residents of apartments nearby have been notified.
The state Department of Environmental Resources will inspect the area to treat contaminated water, Naugle said.
The borough received good news last week when PennDot announced plans to begin construction on the Ridley Avenue and Lake project within four years.
In addition, the Swarthmore Avenue bridge will be closed for two years while it is rebuilt. Swarthmore Avenue is the main road connecting MacDade Boulevard and Chester Pike.
Council President Bruce M. Gordon said the Lake Task Force was a strong factor in making state legislators aware of the Ridley Lake area. The task force produced videos about Ridley Park, and wrote to PennDot officials and politicians to urge action.
"Unbelievable" and "devastating" were two adjectives Gordon used to describe the likely effects on traffic in the borough when construction is under way.