See inside one of the city’s largest sewer pipes as MSD repair enters final phase
The final phase of repairing a large, 84-inch diameter sewer line, which is more than 20-feet below Main Street, is nearing a conclusion. MSD contractors are completing installation of the corrosion-resistant PVC panels, which mold to the unique shape of pipe to form a new pipe inside of the old pipe. Additionally, crews are pumping a special concrete mix into the small space between the PVC panels and the old pipe. This process bonds the new pipe and the old pipe to form a stronger structure. The pipe repair will be complete, and wastewater flow restored to the pipe by December 10. The pipe carries 40 percent of the community’s wastewater to MSD’s Morris Forman Water Quality Treatment Center for proper treatment and release to the Ohio River.
Crews will begin removing the “pump-around” on December 12. This process will continue through December 21.
“We appreciate the patience of the business and tourism entities located in this vibrant corridor of our community during this emergency repair of this pipe, which is vital for the health and safety of our community.” — MSD Executive Director Tony Parrott.
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ADDITIONAL WORK IN THE AREA
MSD is making new connections from existing sewer lines on Fifth, Sixth and Seventh streets to the large Main Street pipe. These connections will drastically reduce combined sewer overflows into the Ohio River.
ROADWAY CLOSURES AND OPENINGS
• Fifth Street – OPEN
• Sixth Street – TEMPORARILY OPEN
• Seventh Street – TEMPORARILY OPEN
Fourth Street and River Road (closure)
• December 5-21: Fourth Street at River Road and one eastbound lane of River Road (between Fourth and Sixth streets) close for the restoration of a water line and removal of the temporary pump station and diversion structure
Main Street (opening)
• December 6: Main Street south-side parking lanes OPEN between Fourth and Seventh streets
Sixth and Seventh streets (closure)
• December 14-16: Sixth and Seventh streets at River Road, closed Friday evening through Sunday night, for removal of the “pump-around” pipe
Eighth Street (closure)
• Week of December 17: Eighth Street at the Science Center parking lot entrance closed during overnight hours for removal of “pump-around” pipe
Fourth Street (opening)
• December 21: Fourth Street at Main Street and River Road, open for traffic
MSD commissioned an inspection of the concrete Ohio River Interceptor — an 84-inch sewer pipe — in November 2017 and used technology that allowed engineers to analyze the pipe without having to empty it. The resulting March 2018 report, revealed that some of the concrete and rebar support systems have worn away between Fourth and Seventh streets.
MSD closed the southside parking lane on Main Street between Fourth and Seventh streets in April to ensure public safety from the threat of a potential cave-in of the pipe. Work then began with a team of consultants to develop a plan to repair this vital infrastructure with the least disruption to this vibrant area of our community.
The $20 million repair project requires a “pump-around” to remove wastewater flow from the damaged section of pipe so that workers can go underground and make repairs from within the 7-foot tall pipe. Workers enter the pipe through existing hatches in the pavement at Fourth and Main streets.
Constructing the pump-around required seven weeks of basically building a temporary sewer system on the surface with four parallel pipes, which total three linear miles. Wastewater pumped out of the damaged pipe is temporarily re-routed west along River Road to Ninth Street where it re-enters the large sewer pipe and continues its path to MSD’s Morris Forman Water Quality Treatment Center for treatment and release to the Ohio River.
Inspection reveals structural failure compounded by heavy rains
On August 19, a routine in-pipe camera inspection revealed that the potential cave-in had become a reality. Contractors discovered a 5- by 2-feet section of the Main Street pipe had collapsed just west of Fourth Street. Further inspections revealed a large void, or empty space, under the pavement just west of Fourth Street. The void was 40-50 feet across in both directions, and 25 feet deep at the worst spot. The void left the roadway unsupported in the area with a gas and water line suspended in the void.
Heavy rains in August compounded the problem by washing the loose sandy soil through into the pipe the hole in the side of the pipe. The force of the water carried this soil downstream in the pipe. The area received more than 4 inches of rain from August 1 through 26, when filling of the void began. Crews worked 24/7 to slowly fill the void with a light-weight grout, making sure the suspended gas and water lines were protected. Surveys show the pavement rose 1.5 to 1.75 inches after the void was filled, as compared to surveys before the void was filled.
Traffic was reduced to only one lane on the north side of Main Street midway between Third and Fourth streets to ensure public safety. An early inspection of the pipe from June 21 shows a deteriorated pipe with exposed rebar, but no cave-in.
The repair to the pipe will be complete by December 10. The dismantling of the pump-around system is scheduled for completion by December 21. Crews will return after the first of the year to restore sites at River Road and Fourth and Seventh streets.