Lake Oswego sewers overflowed 75,000 gallons of untreated sewage to Tryon Creek Tuesday, damaging a local business and again subjecting the city to fines for violating the federal Clean Water Act.

Lake Oswego is still negotiating sanctions for sewage overflows to Oswego Lake last winter.

The city's aging sewers generally show signs of strain in wet weather but this time Elizabeth Papadopoulos, head of maintenance for the city of Lake Oswego, said problems stemmed from unbolted manhole covers in a Foothills pipe and not from mostly capacity issues in the system. Capacity issues caused overflows in heavy rain on the west end of town in January.

Papadopoulos said a city contractor left manhole covers unbolted on an aerial pipe in Foothills after recently being hired to clean it. Increased pressure in the pipe during heavy rain ultimately caused the overflow, which was discovered by employees at Toklat Originals at about 10 a.m. Tuesday.

Papadopoulos said Toklat, which sells equestrian equipment, suffered some effects from the leaks and will require cleaning. Toklat officials could not be reached for comment.

It took city maintenance workers until about 4 p.m. to control the problem. They spent most of the day manufacturing parts to bolt the manhole covers onto the pipes.

'If you think of it as a hose under pressure, if you tighten all the holes but one, that will blow,' Papadopoulos said.

She said crews secured each of the covers on the aerial pipe, which leads from the underside of State Street to the Tryon Creek Wastewater Treatment Plant on the bank of the Willamette River.

As overflow raged, crews diverted spills from the Toklat area to a detention pond in Foothills. The pond eventually flooded, spilling sewage to Tryon Creek. Papadopoulos said the flows stopped when rain slowed in mid-afternoon Tuesday. She added crews plan a clean-up of the pond in the coming days or weeks.

The city contractor responsible for cleaning the pipe may ultimately be held accountable for fines from the Oregon Department of Environmental Quality and be asked to pay for damages and clean-up at Toklat, Papadopoulos said.

'We will pick up the cost for cleaning and if it turns out another party is responsible, we will pass those costs along,' she said.

The city of Lake Oswego is currently negotiating sanctions for sewage overflows from December 2005 and January 2006. City sewers overflowed 97,000 gallons of untreated waste into streets in heavy rains at that time, which eventually flushed into the west end of the Oswego Lake.

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