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.

A photo shows an empty “room” with gleaming white walls and ceiling, perhaps part of a new laboratory facility? Perhaps a dust-free space in a manufacturing plant? Or will it be an environmentally-controlled storage area?

None of the above.

The photo is of a recently rehabilitated, badly deteriorated sluice gate operating chamber above a wet well at an influent pump station in the city of Houston’s Almeda Sims Wastewater Treatment Plant, and it is 34 feet below ground. The treatment plant is 39-years- old, normally treats 20 million gallons per day (MGD) and can flow as high as 80 MGD in extreme wet weather.

“The plant is old and had a major piping failure which flooded a dry well and shut down more than half the plant,” said Mark Boyer, president, Boyer, Inc., the prime contractor for the project.

Boyer was called in to make repairs under an emergency contract to get the station back in operation. A temporary flow bypass was set up so that initial repairs could be made to the pumps and controls to get at least part of the pump station back in operation. While making the initial repairs, it was discovered extensive work was necessary that would require long-term bypassing of the influent pump station. Without it, there was no way to clean the wet well and repair or replace piping, valves and refurbish the pumps.

Bypass pit design.

Boyer developed a design/build plan to create a permanent means to bypass the pump station for current and future repairs, and scheduled maintenance. The proposal called for constructing a diversion structure over the existing 84-inch influent tunnel and lining it entirely with Danby PVC grout-in-place pipe liner, to make it corrosion resistant. Normally used for man-entry installation in pipes of diameters of 36 inches and greater, Danby LLC President Mike Spero said the combination of the ribbed profile of the rigid PVC liner and the highly fluid nature of the grout combined to produce a highly integrated structure with the PVC liner "tied" to the original pipe through the grout which, in addition, provides some direct repair of the old pipe.

“The result,” he said, “is a structural rehabilitation of the pipe and a lining that will prevent corrosion.”

Spero said the 20-foot diameter by 50-foot deep diversion structure was constructed by installing 60-foot deep auger cast secant piles, constructing concrete ring beams as the interior was excavated, pouring a bottom slab, then placing rebar and installing the Danby PVC vertical panels.