PITTSBURGH (KDKA) — Every time it rains, our old sewage system gets overloaded, and a combined overflow of raw sewage and rain water pours into our rivers and streams. A total of 10 billion gallons a year.

Cities around the country with the same problem are building huge tunnels, like the one running for miles under Washington DC, which is designed to capture the foul water before it pollutes their rivers.

Like DC, Pittsburgh and Allegheny County are under a federal order to fix our sewage systems, but Mayor Bill Peduto hates the idea of building tunnels, calling them the biggest septic tank in the world.

“What we’re looking at is the most expensive, most archaic way of being able to solve a problem,” said Mayor Peduto.

Any solution will cost billions, but the city and Allegheny County want to start with doubling the capacity of the ALCOSAN treatment plant on the Ohio River at a cost of $1 billion.

Then, they want to develop so-called green solutions — things like rain barrels and rain gardens and green roofs that capture and soak up the rain water before it gets into the system.

To that end, Mayor Peduto and Allegheny County Executive Rich Fitzgerald have sent a letter to the federal Environmental Protection Agency asking for another decade before building any tunnel.

It reads in part: “It is essential that our region receive a 10-year window to properly evaluate the combined efforts of plant expansion and source reduction.”

“You build a system that is about a sponge, not about a funnel. And that is the way it’s being done all throughout the world,” Mayor Peduto said.

The EPA said Wednesday it’s preparing a response to the request. But the city and county are already three years behind schedule in submitting a plan to the EPA, and the agency is growing impatient.

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Still, Mayor Peduto says the city and county will hold firm in building as few tunnels as possible.

“Because if we just tie up our riverfronts, putting these wells in and these pipes in for the next 20 years, we’re not going to see economic development and growth occur,” Mayor Peduto said. “We’re going to hold everything back because somebody in some office just wanted to get a file off their desk.”

Eventually, some length of tunnel will be required, but when they will be built and how long they will be remain open questions.