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Complex, Emergency Pump Station Repair Yields Unique Rehab Solutions
“The interior forms were set and the 10-foot lift of concrete was poured pushing the Danby panels tight against the forms and integrating them into the wall,” he continued. “This was repeated in 10-foot lifts until the entire structure was complete. Danby panels were installed for the floor and locked in with high-strength flowable grout.”
Rehab needs grow
During the temporary bypassing, it was discovered that there was extreme deterioration of two junction boxes, a sluice gate operating room over the wet well, and two 84-inch diameter concrete connecting pipes.
The project was expanded to repair and line all of these structures with Danby PVC lining.
After the full flow bypass system was installed and operational in November 2011, Boyer crews were able to enter the wet well, clean it and make the repairs to the piping, valves and pumps to get the pump station totally operational. Once these critical functions were restored the rehabilitation of the deteriorated structures and pipes could begin.
“Before the liner could be installed, surfaces were cleaned and a 10,000 psi water blaster was used to remove any loose or deleterious material,” said Boyer. “Personnel entered the 45-foot-deep structure through the influent line. Hydraulic cement and Avanti chemical grout injection were used at joints to control ground water infiltration.”
A removable cofferdam was placed in the diversion chamber to raise the flow level so that three 75-horsepower submersible bypass pumps could operate. The Boyer-designed, proprietary arched coffer dam required no cast-in-place hardware to function in the diversion chamber. A unique feature, added Boyer, is its ability to by-pass the flow over the top without any human action preventing costly sewer over flows.
“Workers were now able to access the connecting sewers, junction boxes and wet well through the dry side of the cofferdam,” Boyer continued. “The bypass pumps could handle the peak dry weather flow and small rain events. When a major storm occurred, crews were evacuated and the flow allowed to top over the cofferdam and flow into the wet well where the now-refurbished main pumps could be activated. Whenever this occurred, major re-cleaning was required.”