The term brownout took on a literal meaning Tuesday night, when a malfunctioning town sewer system, caused by a temporary loss of electricity, left the basement of a waterfront Edgartown restaurant flooded with sludge.

The Atlantic restaurant remained closed yesterday while cleanup continued but the owners expected to be ready to reopen on Monday.

Diners had already cleared out of the Atlantic on lower Main street by the time town health agent Matt Poole arrived at the stinky scene at 5:30 p.m. on Tuesday. A brownout, which causes a partial loss of electrical power, had cut off power to the downtown sewer pump station, causing a sewage backup in the restaurant basement.

“There was about three inches, plus or minus, of wastewater that had backed up into the basement at the Atlantic. Perhaps more,” said Mr. Poole Wednesday.

He said the malfunction can be traced back to a sewer pump station, located in the grassy island across from Dock Street Diner on lower Main street. “[Sewage] all collects at this low point. Then a pump, powered by electricity, pushes it back up to the plant. But without enough electricity, the pump wouldn’t push [the sewage], and it all flowed down the hill,” said Mr. Poole.

Eli Levy, an operating partner of the Atlantic with owner Gerret C. Conover, said yesterday that when the pump malfunctions, it’s meant to trigger an alarm. But because of the brownout, it didn’t. He said that the blame lies with the town wastewater department.

But Edgartown wastewater facility manager Joe Alosso said that the department had no control over the event. Because of the excessive heat and jump in the use of air conditioning units, NStar Electric could not support its normal amount of voltage. This caused the pump station on lower Main street to fail. Normally when NStar sees a similar voltage drop, they warn the wastewater officials, who then turn on backup generators. This time, they didn’t, Mr. Alosso said.

“Had we been notified that there was going to be a voltage drop, we could have made modifications and this never would have happened,” said Mr. Alosso. “There was nothing we could do to avoid it.”

“We’re working very, very closely with town officials and the health department,” said Mr. Levy of the cleanup effort. He expects it to run through the weekend, and the owners hope to reopen the Atlantic by Monday. In the meantime, Mr. Alosso said the sewer system has been back up and running since later Tuesday night, with no additional problems. But there is still a lot of cleaning up to do.

“We are disposing of all our food, liquor, beer and wine inventory,” said Mr. Levy.

“They are removing the entire contents of the basement. Everything,” said Mr. Poole. “All partitions, shelving; everything they’ve built in down there to store their inventory is going to be removed.”

Mr. Poole said that the sewage collected in the basement because it marks the lowest point among the surrounding buildings on lower Main street. There has also been some leakage to surrounding areas, including into the harbor. But the health agent said the sewage does not pose a risk to the town, and that the same conditions could easily be caused by a heavy rainstorm.

“It’s a significant cleanup effort. But beyond that, there’s no immediate health risks or anything like that,” said Mr. Poole.

In the aftermath of the flooding this week, the restaurant was surrounded by pump trucks designed to vacuum the wastewater out of the basement and enormous dumpsters for the ruined inventory. And while Mr. Poole said he was told that the restaurant hoped to cut the cleanup time enough to reopen for the weekend, it is not likely to happen. “I’ll be surprised if they make it. I think it’s just ending up being a slower job than they anticipated. They knew it was a big job, but I think they were thinking that if they put enough people on it they could get it done quickly. But it looks like reality is setting in,” Mr. Poole said. “I wouldn’t expect it to go much beyond a long week. But in July, to a merchant, that’s a long time. Hopefully everyone is insured.”

Mr. Levy said that, in closing at the height of the summer season, he anticipates a significant loss in revenue for the owners. And the situation is compounded by the fact that the restaurant will have to restock its entire inventory before reopening. But he said safety for their patrons is the top priority. “We’re not taking any chances,” Mr. Levy said.

There have been no formal discussions yet about liability for the malfunction, but Mr. Levy said he expects there will be a future conversation between Mr. Conover and Wastewater Department representatives. “I’m sure there’s going to be some negotiation and discussion about that,” he said.

Mr. Alosso said that he’s already asked the Atlantic owners to put together a list of items lost to the flooding. He said he expects NStar to be held responsible for their replacement. “The powers that be will battle it out from there,” he said.

But for now, everyone is taking it one step at a time, and focusing on the task at hand. “We have had great support from everybody in the community. Everyone tried to help,” said Mr. Levy of the aftermath and cleanup effort. “That was very, very nice on the community’s part.”