PITTSBURGH (KDKA/AP) – State environmental officials have granted a request to give the City of Pittsburgh and Allegheny County more time to include more “green” solutions to the region’s sewer system problems.

The antiquated sewers overflow during heavy rains because storm drains are tied to sewers in a way no longer permitted under environmental laws.

The cost to upgrade the system is at least $2 billion and as much as $3 billion.

The department said Monday that it will provide an 18-month extension to a March 30 deadline for a plan to fix the problem.

In a letter to the president and the Environmental Protection Agency obtained by KDKA, the mayor and County Executive Rich Fitzgerald asked for an additional year-and-a-half to revamp the plan, which they reject as being too grey – meaning too much concrete and steel.

They prefer green solutions like a water retention trench constructed recently in Schenley Park, which traps the water. That water is slowly absorbed into the ground and would slow the rampant runoff that overloads our combined storm and sanitary sewers.

The most hotly contested feature of the current plan is the planned construction of massive and lengthy tunnels, which can be 100 feet in diameter and stretch for miles.

On rainy days, those tunnels would fill with storm water and sewage and be held there until the weather changes. At that point, the Alcosan treatment plant would handle the waste. Then, the effluent would be pumped down to the plant.

The mayor hates the idea.

“You’re talking about building some of the largest septic tanks in the world. You’re basically building septic tanks the size of the Fort Pitt tunnels,” Peduto said.

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