Rehab Of A 100-Year Old Brick Storm Sewer

U-TECH
By Datta Shirodkar, Boyer Inc. and Michael Spero, P.E., Danby LLC | July 2010 Vol. 65 No. 7

After the river backwater and pipe base flow were under control and the ventilation system established, cleaning of the sewer was accomplished. The debris in the pipe was mostly sand and silt with an occasional brick or chunk of concrete dislodged during the installation of a lateral pipe. About half the debris was removed manually using wheelbarrows. The remaining debris was removed using a jet rodder and vactor truck. In preparation for the lining, the walls of the sewer were cleaned using a high pressure water blast of 6,000 psi. This removed any dirt, oil, grease, loose mortar, concrete, aggregates, laitance or other contaminants. What remained was a clean, competent brick and concrete sewer. There were eight abandoned services and one groundwater leak that were also plugged.

Twice during the cleaning operation there were rain storms. Crews and equipment had to be quickly removed from the sewer and the downstream plug deflated. These events stopped the sewer cleaning for six days.

Liner installation
As can be seen in the drawings, the three inches of grout in the annular space will result in a liner ID of 84 inches. In order to maintain the three-inch minimum grout thickness, steel spacers (bolsters) were mounted on the pipe wall. The liner is fed into the pipe through the manhole, then pulled into position. The panels are spiral wound by connecting the adjacent panels with a joiner strip. The joiner strip is installed using a pneumatic palm hammer. The end of the next coil is connected to the previous one with an “H” strip splice. A steel buoyancy restraint angle is anchored at the bottom of the liner. Grout bulkheads are placed about every 400 feet using hydraulic cement.

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During the liner installation, there were several times when storms necessitated evacuating the sewer and delayed the completion of the lining by almost two weeks.