How do you do maintenance on the portion of a water treatment system where all treated drinking water passes through? With a lot of planning! At the June Board of Directors Meeting, PWSA’s engineering and construction team approved a $1.6 million contract to Brown and Caldwell, an engineering and consulting firm focused on infrastructure improvement, for the design of a Clearwell Bypass and rehabilitation of the Aspinwall and Bruecken Pump Stations.
A Clearwell is a water storage structure where the final step of the water treatment process – disinfection – occurs. In the Clearwell, the water is dosed with chlorine to ensure any bacteria or viruses are killed before consumption. The water is then allowed sufficient “contact time” to ensure the chlorine does its job. Because the PWSA Clearwell is a single structure that cannot be sectioned off to make repairs in stages or easily bypassed, it will have to be physically isolated and shut down for ultimate replacement. This means treated water must travel to another location for completion of the disinfection process.
Over the years, we have considered several solutions that would allow for the safe replacement of the Clearwell while continuing to provide uninterrupted water service. The solution for this work will bypass the Clearwell by sending water from the Water Treatment Plant directly to the Lanpher Reservoir in Shaler Township and the Highland 2 Reservoir in Highland Park. These reservoirs are large enough to be used as temporary clearwells, where water will be chlorinated, achieve the necessary contact time, and sent out into the distribution system. This will allow the Clearwell to be replaced in its existing location. The restored Clearwell will have multiple cells to allow for future maintenance and repair.
“This strategy for replacing the Clearwell will have primary and secondary benefits,” said Sarah Bolenbaugh, Senior Group Manager for Water Programs. “We will be able to replace the Clearwell for the future which will ensure reliable water service. Also, the work that is necessary to prepare for taking the Clearwell offline will update aging infrastructure throughout the distribution system.”
This adjustment to the treatment process and the pathway of water through our service area will require the completion of several capital projects to prepare the pumping, storage, and transmission system for this change. PWSA will rehabilitate the Aspinwall and Bruecken Pump Stations, replace the reservoirs liner and cover systems, update electrical and backup power systems, as well as repair or replace various large-diameter water mains throughout the system. This work, and other large-scale water system improvements mandated by the Pennsylvania Department of Environmental Protection, is an investment of more than $312 million in Pittsburgh’s water future.
Design work on these projects will include analyses of pumps and pipe materials, locating underground infrastructure using sonar devices, and use of a remote-operated-vehicle to inspect the existing Clearwell pipes. We anticipate completing design in 2021 and beginning construction in 2022.