Darien sewer system needs repair
"The original sanitary sewer (system) is at the end of its life," said Greg Epping, superintendent of public works.
Engineering firm Crispell Snyder recommended the village repair the cracked and leaking sewer mains and associated manholes at a cost of about $120,000. Replacement of the oldest sewer mains would cost $1.4 million.
The discussion goes back to 2006, when the Walworth County Metropolitan Sewerage District (WalCoMet) decided too much rainwater and groundwater were getting into sanitary sewer pipes and being treated as sewage.
WalCoMet recommended that communities seal their systems to reduce:
-- Inflow—storm water entering the sanitary sewer system through manholes or from sump pumps connected to basement floor drains.
-- Infiltration—groundwater entering the system through cracks or leaks in the sewer pipes or manholes.
Epping said significant rain events last summer, record snowfall last winter and significant rain again this summer tested the capacity of the wastewater treatment plant.
Darien is in a low-lying area, worsening the village's inflow and infiltration problems.
"Any crack, any hole, any loose pipe joint, (water) seeps into the pipes and goes to our lift station, and we pump it to WalCoMet, and we have to pay for it to be treated," Epping said. "We're paying to treat clean water."
While the recent dry weather has "disguised the problem," he said, it's not going away.
WalCoMet asked the municipalities in its service area to identify inflow and infiltration problems by Sept. 30.
Epping said he popped open manhole covers in the wee hours of the morning, when residents were sleeping and not using sanitary sewer system, and noticed much more water running through pipes than would be expected.
"We found trouble spots," Epping said.
In mid-August, technicians ran cameras through Darien's sanitary sewer system to search for defects.
The oldest sewer mains, installed in 1970, are made of clay and are in the worst shape, he said. Those pipes are leaking and could be responsible for a large portion of the infiltration into the system, he said.
"After 50 years, they start failing," Epping said, "and we're approaching that right now."
The next-oldest mains are concrete and are in poor condition, too, he said. Those pipes are cracked in some places.
The newest mains are plastic and don't present any concerns, he said.
WalCoMet told municipalities in its service area to come up with a plan to reduce inflow and infiltration by March 2010. The district expects repairs or replacements completed by the end of 2013.
Epping said the tentative plan is to repair the clay and concrete sewer mains and seal any associated manholes.
"For immediate relief, we know we have to fix that area," he said. "But the question comes up: If we fix the mains, we still have to fix the laterals."
Sewer laterals, the pipes that run from the road right-of-way to property owners' homes, also could be cracked or leaking. Replacing laterals would cost an average of $5,000 each, and property owners would have to pay that bill.
"What the engineers are telling me is … fixing the mains only stops 40 percent of the infiltration," Epping said. "Then if we fix the laterals … it's another 40 percent.
"To really fix the problem over there, I think you have to do both.
The village board met Sept. 23 to discuss the situation, but the board hasn't yet given the public works department the go-ahead.
"It's definitely something we have to address," Epping said. "We know it. We need to deal with it. But it's going to be difficult."
Last updated: 10:45 pm Thursday, December 13, 2012