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In Louisville's Aging Sewer System, Collapses Are Frequent

A 102-inch sewer pipe, installed in 1948, collapsed Aug. 30, causing sections of roadway at the intersection of Main and Hancock streets to cave in.
A 102-inch sewer pipe, installed in 1948, collapsed Aug. 30, causing sections of roadway at the intersection of Main and Hancock streets to cave in.

In August, a sewer collapse in downtown Louisville stopped traffic on parts of Main Street and drew weeks of media coverage. The collapse ended up costing the Metropolitan Sewer District about $3 million in repairs. But it was only one of nearly 400 cave-ins in the county so far this year; in the past, there have been as many as 843 similar incidents annually.

Jefferson County has two distinct systems: a combined sewer system in the older parts of the city (largely inside the Watterson Expressway) and a sanitary sewer system. The combined sewer system uses one pipe for both wastewater and storm water; the sanitary sewer system uses one pipe for wastewater and a separate one for storm water.

Last year, there was one cave-in for every four miles of infrastructure within MSD’s combined sewer system. There was one cave-in for every eight miles of infrastructure in the larger sanitary sewer system.

MSD Regulatory and Compliance Manager Dan French said the data doesn’t surprise him.

“We treat everything we can, but those pipes in those older developments inside the city are so large that we know during a rain event we’re not going to be able to treat everything,” French said. “A lot of these systems, the infrastructure is old, it wasn’t put in properly in the first place, so it causes a lot of problems.”

For every year since at least 2008, there have been several hundred more cave-ins in the sanitary sewer than in the combined system. French said one reason is the sheer number of miles of infrastructure in the sanitary system. But another reason is in these areas — largely suburban and rural — there’s less concrete to keep cave-ins from showing.

He said in other areas, the infrastructure is just poor and aging. Some of that infrastructure in the combined sewer system was built using brick in the late 1800s and is still in use. Rain plays a role, too.

But collapses have decreased since peaking in 2011. MSD responded to 600 cave-ins last year, and French said the number of cave-in calls this year also seems lower than usual. He attributed that low number to Louisville’s dryer weather season.

Even so, MSD still has outstanding infrastructure problems to address. Officials published a 20 year, $4.3 billion Critical Repair and Reinvestment Planearlier this year, and have requested two significant rate hikes to fund the plan.

In both 2016 and 2017, MSD sought Metro Council approval for 20 percent rate hikes, which officials estimated would have increased the average ratepayer’s bill by about $11. But neither cleared the Metro Council, and MSD settled for smaller increases.

“A lot of people don’t think about the sewers and the pipes that are underground that are running under their feet and how they actually work,” French said.

Of that larger $4.3 billion plan, MSD officials estimate they’ll need $496 million to upgrade existing sewers and facilities to cut down on the number of yearly system cave-ins. They plan to discuss sewer rate hikes with the Metro Council again next year.