Infiltration and Inflow 101 – What residents need to know.

What: I&I stands for “Inflow and Infiltration”. In laymans terms this means an unwanted intrusion of “clear water” (stormwater or groundwater) into a sewer system. This can happen in a number of ways and often results in “sewage system overflows” (overflows).

Inflow and Infiltration sources

Inflow and Infiltration sources – Points where clearwater intrudes into sewer systems.

Why is this a problem: Sanitary sewer systems are designed to carry wastewater from toilets, dishwashers, sinks, or showers in homes or businesses to treatment locations.

Unwanted I&I that comes with an aging system adds unwanted clear water to sewers increasing the volume load.  This creates a strain. Clear water belongs in storm-water sewers or on the surface of the ground, not in the sanitary lines. An excess of I&I (additional clearwater volume) can lead to overflows during major storm events.

Overflows are a serious problem since it means untreated sewage is discharged from the system into the environment prior to reaching treatment facilities. This is why the EPA is very concerned. Note: This isn’t a Lower Mac or even Lehigh Valley specific issue. But a problem with aging sewer systems everywhere.

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Why does Lower Mac have to be concerned right now? (and really almost every single valley municipality) Because of concerns about outflows in 2009, the EPA issued an “Administrative Order” to all the municipalities served by the regional sewer system in our area. The Lehigh County Authority provides that system to residents in Lower Mac.

Here is a very good overview from Pat Lester formally of the Morning Call:
Lehigh Towns could face EPA fines over missed deadlines for sewer work

The order requires municipalities to make significant and costly improvements to sewers to eliminate overflows.  EPA has demanded outflows be eliminated by 2014. That has not happened. As of right now LCA and certain LCA municipalities have requested an extension.

How big is the issue?
Lower Macungie Township has 121.86 plus miles of gravity fed sanitary sewers. The total mandated costs to eliminate I&I issues (the major cause of outflow) will be in total astronomical.

We have been paying for awhile now. And we will continue for the foreseeable future. For at least the next 5 years the township has budgeted 250,000 dollars a year to address the issue. Costs will continue to soar.

To date we have been able to pay for scheduled work without substantial sewer rate increases. This year Commissioners rejected a proposal to increase rates by 10%. To be frank the increase really could have been justified. And further to be 100% honest it’s going to be continuously tougher to avoid moving forward. There were some one time circumstances this year that allowed us to avoid rate increase this year.

Relationship to development:
A question needs to be asked. As clearwater is removed from sewer systems will capacity be increased? If so will this lead to sprawling outward pressure? Next, if so does LCA have it’s sites set on Berks County?

How about further up the South Mountain in Lower Mac? It’s my understanding that at times municipalities have paid for required I&I work with new connection fees. At some point we need a sustainable system. Sewer expansion is the number one driver of costly sprawl.

Basically, should a strategy involve – 1. Remediating outflows by addressing capacity issues. 2.  Paying for those repairs in part with new hookups. 3. With new hookups we create more capacity issues. And 4. Repeat… One can easily see the potential problem here.

I&I is just one part of the strategy.
Granted a huge part. And one mandated that we (Lower Mac) fix on our 120+ mile system. But LCA is also looking at other options to also address treatment issues. One possibility is spray irrigation. Another is expansion of Klines Island. These would be costs LCA passes onto township ratepayers. *UPDATE 10/28 I’ve found out that spray irrigation has been ruled out and that expansion of Klines island is most likely. Also to clarify Klines island or potential spray irrigation relates to treatment issues not conveyance. I&I is a conveyance issue.

Bottom line is this federally mandated remediation is going to be astronomically expensive. Much of the scope of the problem and cost to fix remains unclear. While Lower Macungie has been doing a very good job staying ahead of the issue, alot of what’s to come also depends on what  how our neighbors respond and how LCA handles treatment issues.

Another item looming with potentially large impacts is Pennsylvania Ms4 program. It is another important area that we as a community need to become more familiar with. Staff has already been doing an excellent job in preparing. I think now the local legislators myself included need to do a better job understanding. This will be the subject of another blogpost within the next 2 weeks.