MEXICO – Current and future development in the Dixfield, Mexico and Rumford area could be jeopardized if the three towns don’t work together to correct discharge flow-rate violations into the Androscoggin River from the public sewer system.

That’s what Mexico selectmen learned at Wednesday night’s board meeting from Town Manager John Madigan and a draft of the Rumford-Mexico Sewerage District’s proposed decade-long plan to find and remedy the problems.

“At times of high water, our treatment plant has had excessive discharges four to five times a year into the river, so, the solution they’ve come up with is a 10-year plan to take care of excess groundwater that’s been getting into the system,” Madigan told Selectmen George Byam, Reggie Arsenault, Richie Philbrick and Peter Merrill on Wednesday night.

After a short discussion, selectmen unanimously agreed to implement the infiltration and inflow management plan prepared for the district and the three towns by Main-Land Development Consultants Inc. of Livermore Falls. Rumford and Dixfield selectmen have yet to review and vote on the document, their town managers said Friday afternoon.

Additionally, on Monday, Dec. 18, in Augusta, environmental, enforcement and compliance officials with the Maine Department of Environmental Protection’s Bureau of Land and Water Quality will meet with RMSD officials to review the proposed plan, DEP compliance staff supervisor Sterling Pierce said Friday afternoon by phone in Augusta. It’s DEP’s first look at it.

According to a Nov. 22 letter to Madigan from Main-Land engineer Robert L. Berry III, the plan is being driven by the problems that DEP is requiring the district and towns to fix before it’ll approve Rumford developer Lem Cissel’s 306-unit subdivision on more than 400 acres along Isthmus Road near Black Mountain in Rumford.

“In effect, this could stifle some types of development in all the communities that discharge to RMSD,” Berry stated.

On Nov. 1, Rumford planners approved Cissel’s project, which will tie into the public sewer system.

The discharge culprit, Berry added, is infiltration and/or inflow of “clean” water into the sanitary sewer collection system.

Infiltration is the process of groundwater entering the sanitary sewer conveyance system in an unintended manner. Inflow is the process of intentional or negligent introduction of surface storm-water runoff and groundwater into the sewer system.

The treatment plant is licensed by the state to process a monthly average of 2.65 million gallons per day. But, during times of heavy rains and snow melt, the plant receives more wastewater than it is licensed to process – up to 5 or 6 million gallons per day, the plan states. During dry periods, it operates at about half capacity.

This means, Madigan said, that “clean” water is entering municipal sewer systems and is being processed by the plant unnecessarily, increasing handling costs, reducing discharge water quality, taxing sewer transport piping, and could potentially cause smaller lines laden with water to back up into basements and streets.

To prevent the treatment plant from exceeding its capacity in wet weather, the plan’s goal is to remove 80 percent of current infiltration and inflow within the next 10 years.

In each town, the first step is to map sewer systems, then identify problem areas, suggest corrections and pursue ordinance changes or new ordinances, all of which could be costly.

The end result, the plan states, is the towns will be required to either upgrade the treatment plant and sewage collection system to handle higher flows, or reduce the amount of infiltration and inflow entering the collection system.

“The former solution treats the symptom, the latter solves the problem. Conventional wisdom favors the latter,” the document states.