Complex, Emergency Pump Station Repair Yields Unique Rehab Solutions

By Jeff Griffin, Senior Editor | May 2012, Vol. 67 No. 5
Clean-up of upper chamber.

Because of the level of deterioration, Boyer said rebar was installed to replace the steel loss from the original host structures and pipe.

First in U.S.

“The Danby system,” Spero explained, “normally is spiral wound from coils for lining circular, elliptical, or arch pipes. Panels are used for more unusual non-circular shapes. The system can be adapted to line just about any shape. Although it has been used overseas to line chambers and manholes, this is the first major use of the panels installed vertically in the U.S. Because the Danby material is rigid PVC, it is ideally suited to resist the high groundwater pressures encountered on this project.”

One junction box was circular, 20-feet in diameter, 20-feet high of cast-in-place concrete with a concrete slab on top with a 9-by-9-foot square opening. On top of that, was a 9-by-9-foot precast concrete box 25-feet high with a concrete slab top at grade. Its walls were described as almost completely corroded.

Grouting the first lift of the south 84-inch pipe section.

“The ground level top slab was removed for access,” Boyer said. “It was decided to make the rehabbed structure an 8-by-8-foot box for its entire 45-foot depth. Eight-foot wide by 10-foot high Danby panels were assembled above ground by connecting eight 12-inch wide by 10-feet long vertical panels, lowering those into position, and connecting them with 90-degree PVC corner strips. Ten-foot high modular concrete forms were set against the Danby panels and concrete poured from above. This process was repeated for the entire 45-foot-deep structure. The half pipe invert of the chamber and the spring line shelves were also lined with PVC.”

The other junction chamber was a below ground structure and not directly connected to the surface, Spero said. The 13-by-15-foot chamber had only the upper 12-feet lined with Danby panels since that was the only part that was ever above the water level and the only portion that had corrosion.

“The support beams and ceiling of the chamber were also Danby lined,” he added. “PVC panels were individually installed, fitted and field trimmed where required. High-strength, 6,000 psi grout was pumped to this location to lock the panels in place and rehabilitate the structure. Grout was introduced from the top of the forms which were supported by scaffolds and shoring and internally braced.”

A 15-by-27-foot, 12-foot-high sluice gate operating room was above the wet well and connected by two square openings.