Archive for Wednesday, May 9, 2007

Runoff overwhelms treatment plant’s pump

May 9, 2007

When one of the three effluent pumps at the Tonganoxie Sewage Treatment Plant fails, the city can be assured that the two remaining pumps are more than enough to cover the city's sewage needs.

When two pumps fail, the remaining pump can still pump the 450,000 gallons a day needed to meet city's requirement under normal weather conditions.

Drop in several hundred-thousand gallons of stormwater and you have the makings of a big wet problem.

"It's not rare to lose one pump; it's rare to lose two," said Lloyd Wisdom, plant operator at the treatment facility. "When you lose two-thirds of your pumps you better hope nothing goes wrong."

This weekend brought substantial rain to the area, flooding surrounding waterways including Tonganoxie Creek, which is the draining site for the treatment plant, and flooding the area surrounding treatment plant.

The wet weather came at a very inopportune time for the city, which recently had sent two of its water treatment pumps to the shop for repairs. The remaining pump wasn't able to keep up with the extra inflow of water from the weekend.

"Most of the issues aren't wastewater issues, it's stormwater issues," Wisdom said.

Under normal conditions stormwater is diverted right into creeks and does not pass through the treatment plant.

But the system isn't perfect and when too much stormwater enters the treatment plant it begins to overflow into two large ditches that are remnants of the former treatment plant. This allows the pumps ample time to catch up with a large inflow of water, but the ditches were only meant to hold roughly 400,000 gallons of water before they start to overflow back into the system.

When treated water cannot be released it starts to cause a backup on the back-end of the treatment process, which slows down the entire process.

"It completely backs up the whole system and when it stops that's when the manholes lids start popping.

Wisdom said that he and other plant operators decided about noon Monday that the remaining pump wouldn't be able to get the system back to normal, so they contacted Meadows Construction in Tonganoxie. The city rented a 1,000-gallon-per-minute water pump from the company to help ease the problem.

By 4 p.m. Monday the pumps already had moved more than 672,000 gallons of water through the treatment plant. That is on top of the 808,000 gallons of water that already were moved since Sunday morning.

Tonganoxie Mayor Mike Vestal said the timing for the pump failures couldn't have been any worse.

"If the effluent pumps had been working, we probably would have been OK," he said. "We are very fortunate that it's not worse than it already is."

Vestal said the problem comes with the cracks in pipes that are supposed to drain storm water. The city has budgeted money each year for repairs, but it can take a long time.

"Some of the pipes are really old. You can't repair them all at once because that would be millions," he said.

For now the creek levels have dropped more than five feet and the water backup seems to be under control.

Kathy Bard, assistant city administrator, said the city was no longer satisfied with the two existing pumps. She said city officials would request that the city council not spend the $4,500 needed to repair the failed pumps, but to instead use that money toward buying a new $7,500 pump from a different manufacturer.

Bard said the new pumps were "better quality pumps in our opinion."

She also mentioned that the backup did not affect the city's drinking water.

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