Chlorination in the Clearwell is the final step of PWSA's water treatment process
Pittsburgh, PA - At the June Board of Directors Meeting, the Pittsburgh Water and Sewer Authority (PWSA) approved a $1.6 million contract to Brown and Caldwell, an engineering firm focused on infrastructure improvements, for the design of a Clearwell Bypass. Other contracts awarded to Brown and Caldwell include the rehabilitation of the Aspinwall and Bruecken Pump Stations totaling approximately $4.4 million for design and engineering services.
Reconstructing the Clearwell will refurbish a facility that is more than a century old and serves the entire PWSA distribution system. This project is part of the 2020-2024 Capital Improvement Program. Its rehabilitation will strengthen and add redundancy to our water system. It is an essential project to provide safe and reliable water service for current and future generations of Pittsburgh.
We are completing this work in tandem with several other projects critical to the future of our drinking water system. Other projects include the rehabilitation of large diameter water mains and upgrades to water storage facilities.
What is a Clearwell
A Clearwell is a water storage structure where the final step of the water treatment process – disinfection – occurs. In the Clearwell, the water is first dosed with chlorine and allowed sufficient "contact time" to ensure that the chlorine effectively kills any bacteria or pathogens before consumption. The PWSA Clearwell is a single structure that cannot be partitioned to make incremental repairs, nor is it easily bypassed; it must be completely isolated and shut down for rehabilitation. To prepare for this, the PWSA engineering and construction team has spent several years devising a bypass strategy to treat drinking water and maintain consistent service for all customers.
The Plan to Bypass the Clearwell
While serving PWSA as Director of Engineering, recently retired Executive Director Robert Weimar, developed the solution to bypass the Clearwell and send treated drinking water to other parts of the distribution system – giving us the necessary space to work on the existing facility.
Using this plan, we will send water from the Water Treatment Plant directly to the Lanpher Reservoir in Shaler Township and the Highland II Reservoir in Highland Park. These reservoirs are large enough to use as temporary clearwells, where water will be chlorinated, achieve the necessary contact time, and sent out into the distribution system. By rerouting water to these reservoirs, we can safely accomplish the work at the Clearwell. When complete, the future Clearwell will have multiple cells to allow for future maintenance and repair without having to redirect the path of water.
Preparing the water system for this change is no easy feat. Several projects must first take place to adjust the treatment process and reroute the path of water through our service area. These capital projects include rehabilitating the Aspinwall and Bruecken Pump Stations, replacing reservoir liners and cover systems, updating electrical and backup power systems, restoring pump stations, and repairing or replacing various large-diameter water mains throughout the system.
Brown and Caldwell’s design work 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. Their design work will continue through 2021 and construction is anticipated to begin in 2022.
“We’ve worked closely with our state regulators to determine which water distribution projects are most crucial to providing reliable water service to our customers” said PWSA Executive Director, Will Pickering. “Over the next few years, we will invest approximately $312 million to meet our goals and improve our water infrastructure for future generations.”
Some necessary projects for the implementation of the Clearwell have already begun, including design on the Lanpher Rising Main Project and the rehab of the Highland Park Rising Main and Pump Station. As design work proceeds, project updates will be found in the Projects and Maintenance section of our website.
“Beginning the design of the Clearwell has been several years in the making,” stated Barry King, Director of Engineering. “This is a once-in-a-generation project that will modernize our water distribution system and provide customers with more secure and reliable water services.”
