The Mansion House Hotel has paid fines totaling $21,400 to the town of Tisbury for illegally discharging groundwater into the aging municipal sewer system over more than half a year.

The charge represents $100 a day for 214 days, according to a letter to the hotel from town administrator John (Jay) Grande dated Oct. 29, 2021.

A copy of the hotel’s check, dated the same day, was provided to the Gazette by Mr. Grande along with his letter, which warns the Mansion House that similar violations will cost the hotel at least five times as much in daily fees.

“[A]ny future discharge of stormwater or wastewater into the municipal wastewater system from your premises will be assessed at a higher rate per day,” Mr. Grande wrote.

“I have been advised by our wastewater superintendent [Jared Meader] that the rate will be a minimum of $500 a day.”

The illegal discharge was discovered in May 2020 by former wastewater superintendent David Thompson, who saw the hotel’s pumping hours at the treatment plant as unusually high given that the Mansion House was closed due to the pandemic.

With an approved wastewater flow of 11,000 gallons a day, the hotel is already one of the largest users of the town’s small treatment plant, which has exceeded its capacity on multiple occasions over the past few years.

After an investigation, Mr. Thompson found that 12,000 to 15,000 gallons of groundwater — which is illegal to discharge — were being pumped into the town’s sewer system through a sump pump in the hotel’s laundry area.

Mansion House owner Josh Goldstein said a pit liner for laundry graywater had cracked, allowing the groundwater to enter the system unbeknownst to hotel staff.

No fine was imposed and the Mansion House was allowed to reconnect the pump to the sewer system by Memorial Day weekend. Mr. Thompson’s employment was terminated by the town a few weeks later.

Superintendent Jared Meader was hired in October 2020. In December of that year, the hotel completed a new leaching field.

Covid-19 shutdowns, delayed meetings and turnover on the select board and wastewater board all contributed to the slow pace of resolving the Mansion House matter, Mr. Grande told the Gazette last year.