SENNETT — As one of 600 municipalities with a combined sewer system in New York, the city of Auburn is required to submit reports through the NY-Alert system in the event of any overflow discharge.
At a meeting of the Cayuga County Water Quality Management Agency Thursday, Auburn Municipal Utilities Director Seth Jensen provided an explanation of combined sewer overflows.
Under the 2013 Sewage Pollution Right to Know Act, municipalities with publicly-owned treatment works or publicly-owned sewer systems must report any untreated or partially treated discharges to the state within two hours and to the public in four through the NY-Alert system.
"If a drop from the sanitary system makes it out of the pipes and into the environment, we note it," Jensen said.
Combined sewers collect stormwater runoff, domestic sewage and industrial wastewater in the same system and transport it to a wastewater treatment facility, according to the state Department of Environmental Conservation.
During wet weather events like significant rainfall or snow melt, such sewers are designed and permitted to overflow into a waterbody. In Auburn's case, the system flows into the Owasco River.
In Auburn, which has more than 100 miles of sanitary sewers and 65 miles of stormwater sewer in the 16-square-mile city, approximately 85 percent of the system is separated, while the remainder is combined, according to Jensen.
A 6.5 million gallon storage and release facility that activates during peak flows helps ward against overflow events, which the city is able to monitor for using a Supervisory Control and Data Acquisition system.
When an overflow discharge does occur, rather than simply flowing into the river, the water is partially treated by one of four high-rate treatment facilities throughout the city.
Each of the facilities partially treats the water in a process that includes the use of what's called a swirl converter. Water flows into into a rounded structure that forces floating materials, including grease and oils from restaurants, to the bottom while smaller solids are caught by a collector.
The facilities are only allowed four discharges per year under the permit issued by the DEC. If the city separated more of the system — which a 1993 DEC consent order stopped it from doing — that could mean stormwater runoff would go untreated.
In the currently separated sections, stormwater flows in specific catch basins within the city.
Separating the parts of the system which are still combined would come at a significant cost, according to Jensen. Just the planning for such a move would likely be approximately $2 million, while actual implementation could run as much as $20 to $30 million.
In the meantime, Jensen said the utilities department is constantly identifying funding to enable them to strategically "pick away" at areas. For example, the city recently applied for a grant to combine a current project mapping the system with an engineering study that would allow points of inflow and infiltration to be identified and repaired, reducing the likelihood of overflows.