Cedar Rapids takes flood repairs underground with massive sewer project

So much damage from the city's historic 2008 flood and so much of the rebuilding after it have been so easy to see.

There's more than meets the eye.

This summer the city is embarking on the start of some $70 million in work to repair or replace parts of about 84 miles of sanitary sewer - about 13 percent of the city's total of 660 miles. Add another $8.9 million in work to replace the century-old, brick storm sewer underneath 10 blocks of E Avenue NW, and the cost of the post-flood sewer work will total nearly the amount spent to buy out about 1,200 flood-damaged properties in the city. Like the $80 million that has gone to buyouts, nearly all of the sewer repair and replacement work is being paid for with federal disaster dollars with the help of state dollars.

Yes, the toilet still flushes, and for now, what is flushed is getting where it is supposed to go, report Dave Wallace and Joe Mailander, project engineers in the city's Public Works Department.

Without the sewer fixes, though, there would be no long-term guarantees. For now, too, the damaged sanitary sewer lines are letting in too much groundwater, which increases the amount of liquid that the city's Water Pollution Control plant must take on and treat.

Wallace credits the Federal Emergency Management Agency for alerting the city to the prospect that the 2008 flood may have damaged the city's sanitary sewer system more significantly than the city realized.

“Obviously, we had never been through a disaster like that, so we never anticipated that amount of damage,” Wallace says.

But problems, he says, were quickly apparent. Twenty to 30 collapsed sewer lines required immediate intervention after the flood. In other places, sink holes appeared and flood debris ended up in sewer lines. Most telling, the amount of liquid arriving via the sanitary sewers at the treatment plant had increased by 35 percent, proof that the sewer lines were comprised and groundwater was getting into them, Wallace says.

Then the city turned to its sewer-line video-monitoring cameras, which showed joint separations and sections of sewer lines that had moved up or down.

Wallace says the city needed to prove the extent of damage, but the cost would have been too high to televise and document every sanitary sewer line in the city's flooded neighborhoods. So instead, he says the city televised 10 percent of the sanitary sewers in and near the city's flooded areas and extrapolated from that evidence the overall level of damage.

FEMA's first expert initially agreed to the sewer work, but FEMA sent in a second expert in 2011 because of the extent and expense of the damage. A second FEMA expert had different opinions than the city over the extent of flood damage at the city's Water Pollution Control treatment plant, a judgment that the city is now appealing. But the second FEMA expert agreed on the extent of the damage to the sanitary sewer lines.

Wallace says the city benefitted from its now 13-year-old program of annual sewer-line repair and replacement and its sewer-line camera program that began about 30 years ago. The camera evidence showed the quality of the sewer lines before the flood and afterward, he says.

“It showed we hadn't been neglecting our sewers,” Wallace says. “It showed we weren't looking for a cash cow to fix them.”

The city's Mailander reports that sanitary-sewer work will commence at a variety of locations in the city's northwest quadrant on June 25 and in the southwest quadrant on July 9 with much of the work in those quadrants and the other two to follow in 2013 and 2014. Much of the sanitary sewer is made of clay pipe with rope dipped in tar and jammed between the sections to seal the joints, Mailander says. It will be replaced with plastic pipe.

Wallace says sanitary sewer lines, unlike water lines, are not pressurized and, as a result, were more susceptible to damage from the flood. He says sanitary sewer lines were compromised by the internal pressure of flood water flowing into them and the weight of 10 feet of saturated soil and 10 feet of flood water on top of them.

“It wrecked havoc on 50-to-100-year-old pipes not designed to be under pressure,” Wallace says.

Mailander reports that 70 percent of the damaged sanitary sewer lines will be relined to fix them while 30 percent will require excavation and replacement. Much of the work will be in smaller sections with work involving longer sections will come near the end of the project, he adds.

Overall, about $61.45 million of the sanitary sewer work will be paid for by the Federal Emergency Management Agency and some state dollars.

In addition, the city has secured $7.4 million from the U.S. Housing and Urban Development's Community Development Block Grant program to replace the major sanitary sewer line that runs through the former Sinclair plant site and under the Cedar River to connect to the trunk sewer line that passes by the Mount Trashmore landfill on its way the city's wastewater treatment plant.

“Since it's such a big pipe, it would be catastrophic if it fails,” Wallace says.

Another high-profile sanitary sewer replacement project is on Second Street SE from Fifth Avenue SE to the former Sinclair site beyond 12th Avenue SE, a $3.4-million, FEMA-funded project which recently closed down the busy intersection at Eighth Avenue SE for a few days. FEMA has declared this sewer line a historic one, and so it employs a historian to document the work now going to replace it. The work will continue in 2013.

The city also is using $8.9-million in federal Community Development Block Grant funds to replace the collapsed brick arch storm sewer on E Avenue NW from Third Street to 13th Street NW. Work on the 100-plus-year old storm sewer will start this year and be mostly complete in 2013.