GENEVA – Neighborhoods on Geneva’s east side had sewer backups after the seven-inch rain deluge in May because of lift station issues, a partial obstruction in the sanitary sewer, leaking joints, 21 lateral service lines that were not emptying properly – and way too much rain, Public Works Director Richard Babica said.
Speaking at the Sept. 21 City Council meeting, Babica said the total estimated cost to address the issues is nearly $2.2 million:
• $1.2 million to correct sanitary sewer lateral connections including air testing and grouting.
• $405,000 to install overhead sewer backflow systems to 27 identified properties.
• $554,650 for sanitary system repairs that includes grouting and lining and repairs on 144 manholes.
Water and Wastewater Superintendent Bob VanGyseghem said the department can “shift some money around” to get $500,000 to do the system repairs, but that would be all for the current year.
The additional approximately $1.6 million would have to be considered in the city’s next budgeting process, Babica said.
'The tipping point'
Babica laid out the findings in the 46-page engineering study from Deuchler Engineering Corporation, leading to the cost estimates to deal with it.
“It was a sequence of bad events that just finally created a cascade of failure,” Babica said.
“If you remember before we had that seven-inch rain event back in May, we had a very wet spring. We had one of the wettest springs on record,” Babica said. “The system was handling itself right up until we had that heavy heavy rain."
With the ground super-saturated already from the wet spring, it could not take on any more water, Babica said.
“And then we had a massive downpour within that 48-hour period. And the ground just could not take any more water. So wherever it could find a void or an opening, it was just dumping water into it left and right,” Babica said. “That really was the tipping point. It was the straw that broke the camel’s back.”
The typical flow from Crissey Avenue is 3.1 million to 3.5 million gallons a day.
“During that rain event, we pegged over 19 million gallons,” Babica said. “We were performing what we called a bypass – treating effluent with chlorine and pushing it through the system. We could not treat it fast enough.”
The Deuchler report showed that the sanitary flows from a manhole in the 800 block of Manchester Course carries all the effluent from north of Manchester east, including most of the effluent off Geneva Drive, Division Street, the Chesapeake area and Westfield Course, Babica said.
A typical daily dry weather flow is 0.06 million gallons a day. What came through after the May rainfall increased to 1.15 million gallons a day, Babica said.
“That’s a 19-fold increase of effluent through that manhole,” Babica said. “And obviously, that is not because people were home for the covid. We had a situation and we have been investigating that ever since.”
The Deuchler also found that infiltration and inflow warrant upstream rehabilitation of both the sanitary system, the lift station, and private sanitary service lateral lines, Babica said.
Inflow is water other than sanitary flow, which comes from improper connections – sump pumps, drain tiles and downspouts. Infiltration is groundwater that comes through the joints of the sanitary sewer, he said.
Another area of concern is the Parker Court lift station that serves that area to the west of Geneva East.
Lift stations move wastewater from lower elevations to higher elevations.
The study suggests that they redesign the flow path of how that sanitary lift station enters the main channel, Babica said because the Parker Court lift station creates a hydraulic bubble which prevents any additional flow from getting through the system until that is transmitted
Old sewer pipes
The study reviewed more than 27,000 linear feet of sanitary transmission main within the Geneva East area and found the majority of areas for concern were within 11,500 feet of vitrified clay pipe and ductile iron pipe.
Vitrified clay pipe is made from a blend of clay and shale that has been subjected to high temperature which creates in a hard ceramic. Ductile iron pipe is a type of cast iron that is used in water transmission. Pipes made of polyvinyl chloride colloquial – known as PVC – are more commonly used these days.
The study called for air tests to look for leaks in the joints, then inject chemical grout into those joints, Babica said.
“They’re also recommending a … cured-in-place pipe for root intrusions where joints have separated enough to allow for tree roots to get in,” Babica said. “Wherever there’s a loose joint or where there’s tree roots, it allows for infiltration to get into the system. And that is what we’re trying to eliminate.”
Lateral service lines
The infrastructure of that subdivision is about 35 years old, he said.
The city will be contacting residents in that area whose sanitary service laterals – that is, the pipe that connects a home's or business’s plumbing to the city's sanitary sewer system – are not as watertight as they should be, he said.
“Deuchler is recommending that these sanitary service laterals be air tested and grouted, much the same as sanitary mains,” Babica said. “Because the concerns that we have identified in the sanitary mains cannot possibly account for the 19-fold increase in inflow.”
Because the lateral connections are on private property, the city would need construction easements from every property in order to proceed, he said.
Deuchler identified 21 of these lateral connections as flat – that is, they already have effluent inside of them and never truly empty, Babica said.
Deuchler recommends that the city install and coordinate with those 21 property owners – as well as the six who had sewer backups – to install an overhead or backflow prevention device of their choice, he said.
“They’re also encouraging us to continue with our sump pump inspections throughout the subdivision," Babica said. "Because again, a 19-fold increase is very hard to quantify as to where that came from.”