BUTLER TWP — Heavy rains late last month pushed the Butler Area Sewer Authority’s storage tanks past their limits.

Back-to-back nights of storms beginning June 23 resulted in about 1.5 million gallons of overflow pouring from the three sets of tanks.

“It was not a very good two or three days,” said John Schon, the operations manager for BASA.

Schon discussed the overflows Tuesday at BASA’s monthly board meeting.

While having enough untreated sewage to fill more than two Olympic-sized swimming pools pour directly into creeks and streams is not ideal, it was much better than what had happened in the past.

Schon said before the construction of the tanks, which were finished last summer, all excess flow drained into the waterways.

However, the tanks did collect 22 million gallons during the two days of storms, which is a positive mark for the system, he said.

The authority’s pumping system averaged 12 to 18 overflows per year before the addition of the tanks. Last year, the tanks were activated six times.

However, the Monroe Street tanks had three overflows due to mechanical issues with its pump stations. BASA found the pump stations were not working efficiently, causing delays in the rate the sewage was processed.

Schon said repairs are under way, and the station already appears to be operating better, but he added the pump station was still unable to keep up with the heavy flow on those two days.

BASA spent more than $40 million building the tanks to comply with requirements of the state Department of Environmental Protection.

DEP in October 2006 issued an order to BASA and its municipalities mandating the authority eliminate sewage overflows into creeks and streams.

The order was lifted in November 2013 following the building of the tanks.

Schon said more than 6 inches of rain fell in 36 hours at the end of June. Much of that came the night of June 23, when 3.5 inches of rain fell in a span of less than three hours.

The burst of rain caused havoc at BASA’s two Deshon tanks, which are along Sawmill Run Road.

Schon said the more than 4 million gallon tanks are on a hillside, just below where Butler Township stores salt. The rush of water from the storm ran down the hill, passing through the barriers in place, and flooded the electrical transmitter for the pumps.

The piping carrying the wiring in the transmitter filled with water, causing the system to shut down.

Without electric, the three pumps that send excess flow into the tanks did not work, causing sewage to overflow directly from the pumps.

Schon said about 300,000 gallons of overflow ran into Sullivan Run June 24, despite one of the tanks being about half empty.

But the authority’s other two sets of tanks faired well during the first storm.

“They worked as they were supposed to during the storm,” Schon said.

Trouble began when another storm hit the following night.

BASA was unable to bleed the sewage stored in the tanks back into its system on June 24 due to the high amount of water still pumping through it.

When the other storm hit that next night, the excess sewage quickly filled what little space was left in the tanks.

The Monroe Street storage tanks had the largest overflow, with about 842,000 gallons of sewage running into the Connoquenessing Creek.

The pair of tanks each hold 1 million gallons.

While the Monroe tanks have had issues in their short life, BASA’s Central Storage tanks at the end of Negley Avenue overflowed for the first time that night.

Each of the three 3.47 million gallon tanks filled up, resulting in about 435,000 gallons of sewage to overflow into Sullivan Run.

“It was very unusual,” said Schon. “It was the first time the tanks were ever full.”

Schon said the authority is inspecting each of the tanks and pumps to see what, if anything, can be done to improve the system.

But he noted heavy rains will always pose as a threat to any sewage system.

“You are always fighting the laws of probability,” he said. “The capabilities of rainfall is infinite.”

Schon said the authority will continue to monitor its Monroe tanks in particular. He said if they continue to have overflow issues, the authority may have to consider adding a third tank.

“We don’t want to have to do that,” he said.