Mt. Lebanon continues to address overflow in sanitary sewers
For obvious reasons, the attitude of most people toward sanitary sewers is out of sight, out of mind.
The exception is when the bill arrives, especially when it turns out to be more costly than before.
As Allegheny County Sanitary Authority customers recently learned through letters they received, they can expect rate increases of 7% in each of the next three years, attributable to the $2 billion in improvements that ALCOSAN plans to implement.
The work to be done is outlined in what’s called a modified consent decree, which basically represents an agreement that ALCOSAN hammered out with various regulatory agencies on the federal, state and county levels. The revised version of the original 2008 decree continues the authority’s efforts toward achieving compliance with the federal Clean Water Act, which governs water pollution, during periods of wet weather.
According to ALCOSAN, implementing the plan would “significantly reduce the overflows of diluted, untreated wastewater into the region’s rivers,” partly through expanding the capacity of the authority’s treatment plant and upgrading conveyance systems.
Tying into the ALCOSAN infrastructure are local sanitary systems, some of which are operating under their own consent decrees. Mt. Lebanon is among them, and the municipality for many years has undertaken projects to mitigate the amount of excess flow.
“Those have been more of getting the systems back in line, just doing good operation and maintenance on things,” Dan Deiseroth, consulting municipal engineer and president of Gateway Engineers, said during a recent Mt. Lebanon Commission discussion session.
Now comes a new phase of the ongoing efforts.
“We’re on the verge of the next consent order, which we expect will be really the big consent order that’s going to cost the most money,” Deiseroth told commissioners. “And it’s going to be the one where we’re going to be required to do a lot of work to take out infiltration and inflow into our systems.”
The two key sources of overflow are defined with subtle differences. Infiltration is groundwater that enters a sewer system through defective pipes, pipe joints, connections or manholes, while inflow emanates from such sources as drains, catch basins and surface runoff.
Either way, Deiseroth and his staff members expect regulators to place a maximum on the flow through Mt. Lebanon’s sanitary system – they anticipate an initial standard of 4,000 gallons per day per inch of diameter per mile of pipe – as it makes its way toward the ALCOSAN system.
To put that somewhat in perspective, Gateway project manager Dennis Flynn said he has been reviewing flow-monitoring data and determined that out of nine points of contact between Mt. Lebanon’s and ALCOSAN’s systems, four measured flow at above the 4,000 mark.
Mt. Lebanon also has 21 points of contact with neighboring municipalities’ systems, and among those, the flow in 11 exceeded the anticipated standard.
“Our next step is to evaluate these systems and try to break that down to a more manageable area, so we can try to pinpoint and identify where this additional infiltration and inflow is making its way into the (Mt. Lebanon) system,” Flynn told commissioners. “If you really pinpoint those areas and focus your repairs or your future work on those areas, you can really benefit, essentially get more bang for your buck for the projects that we perform down the road.”
To address the issue further, commissioners also have discussed the possibility of adopting an ordinance to require testing in some form of sewer laterals, pipes that connect residences and business to the main line, for infiltration. Laterals generally are the responsibility of property owners.
“I think we’re going to have to come back to that conversation at some point,” Commissioner Craig Grella said, “just by nature of doing what we need to do to protect the municipality from this new consent order.”
Regarding the next agreement, Deiseroth addressed some priorities for Mt. Lebanon.
“No. 1, we want to make sure that we get as much credit as possible, because not all of the communities in Allegheny County have done the same amount of work,” he said about local improvements. “That, we think, is very important.”