As part of the plan, the municipalities would tell the department how many connections they anticipate needing during the time the plan is being implemented.
That corrective plan of action likely will be improvements to the treatment system, Rundquist said. Planning for a new treatment plant that meets Chesapeake Bay requirements and has expanded capacity already is under way, but the project is about five years down the road, he said.
The system serving the borough and townships has a permitted average daily flow of 6.8 million gallons, but can treat a maximum of 17 million gallons per day, Rundquist said. The daily flow usually is between 4.5 million and 5 million gallons, he said.
During periods of heavy precipitation, however, infiltration into the system can cause the flow into the treatment plant to surge, Rundquist said. In 2006, that happened from June 26 to 28, when heavy rains caused flooding, he said.
This year, the 17-million-gallon maximum was exceeded on March 2 and April 15, Rundquist said. The overflow results in heavily diluted sewage bypassing the plant, he said.
Despite heavy rains in recent days, Rundquist said the treatment plant has been running at about 7.5 million gallons per day, well below its maximum capacity.
"We don't overflow every time it rains," Rundquist said. Any time the system does overload, it is documented and the DEP is notified, he said.
Infiltration of storm water into the system can come from several sources, including cracked sewer lines, manholes or people diverting water from roof drains or sump pumps into the sewer system, Rundquist said. The system has hundreds of miles of lines, with some made of terra cotta and dating back to the early 20th century.
"I've never worked in a treatment plant that doesn't have larger flows when it rains," Rundquist said. Unlike combined storm sewer and sanitary sewer systems, which are designed to bypass the treatment plant when flows exceed capacity, Chambersburg's treatment plant is for sanitary sewer only, he said.
In some heavy rains, however, the end result is the same, Rundquist said. The sewage lines can deliver more water to the plant than it is designed to handle.