Mystic — The Stonington Water Pollution Control Authority has told home and business owners that they must disconnect their sump pumps from the Mystic sewer system by Sept. 30 or face fines of up to $100 a day.

Because the aging Mystic sewer plant is almost at capacity resulting in a moratorium on any hookups for new development, the town will undertake a study this fall to determine and eliminate any illegal discharges into the system.

While the typical home may generate a few hundred gallons of water a day, even a small half-horsepower sump pump can generate up to 4,000 gallons an hour. Property owners still would be able to discharge water out of their homes but not into the sewer system.

In a letter to Mystic sewer customers, WPCA Director Doug Nettleton wrote that the WPCA is looking for assistance from customers to help solve the capacity problem.

He wrote that as the Mystic plant moves ever closer to full capacity, the WPCA is being forced to examine and eliminate private inflow into the sewer system from sump pumps in order to comply with its state and federal environmental permits. Exceeding the plant’s capacity could cause mechanical breakdowns, result in partially treated water being discharged into the Mystic River and expose the town to state and federal fines for violating the discharge limits of its permits.

The town also has appropriated money for upgrades to send some of the sewage from the Mystic plant to the underused borough plant, which will allow hookups from new development in Mystic.

Nettleton wrote that, unfortunately, one of the reasons the Mystic facility is quickly approaching capacity is that it receives substantial sump pump discharges especially during wet weather. Many areas of downtown Mystic flood in heavy rains and high tides send water into basements.

“This additional water, which doesn’t require any treatment at all, must nevertheless be treated once it enters the sewer system and becomes mixed with sewage. I believe most people are unaware of the high amount of water these sump pumps add to the flows to the treatment facility, and thereby increase costs,” he wrote.

The WPCA has set up an amnesty program for those who contact the authority with information about their sump pump by Sept. 30. The authority has said it will then work with property owners on potential options for sump pump discharge with the goal of permanently removing the discharge from the sewer system.

If no option is available and the pumping must continue, property owners eventually may be charged for the flow into the plant.

The letter states that information property owners provide about their sump pumps will help the authority develop a database about how much flow is entering the system.

Underlined and in bold letters is a warning that anyone who does not take advantage of the amnesty program and is subsequently found to have an illegal connection will be ordered to remove it. “No options for its continued use will be offered or assistance will be provided. You will also be liable for the fine of $100/day from the date of notification until such time it is permanently removed from the system,” it states.

The letter further advises property owners that the infiltration study the town will conduct this coming fall and next spring “will more than likely identify these illegal connections.”

For those who don’t know if their sump pump is connected to the sewer system or are unable to provide the requested information, they can contact the WPCA office at (860) 535-5065 and authority staff will come to the propery and make the determination.

Not everyone is happy with the letter.

Health in Harmomy owner Shelley Raineau, whose said she does not know if her sump pump, which she said is used only a few times a year, is connected to the system, criticized the town for its approach to the problem.

She said the town has only given people a few weeks to comply and has threatened them with fines.

“I think it could have been handled more professionally," she said about the letter, adding other business owners feel the same way.

She said the town should be offering options and costs for alternative ways to discharge the water. In the case of her Broadway property, she said there is no place to discharge the water.

First Selectman Rob Simmons said he has not received any complaints about the letter, and that property owners are being given an opportunity and assistance to comply.

He commended the Whaler’s Inn, which he called “a publicly spirited business,” for telling the town it is discharging into the system and asking for help to rectify the problem.

“I give them credit for that,” he said.

j.wojtas@theday.com