Highland II reservoir normally holds 125 million gallons of treated drinking water. On Friday, the Pittsburgh Water & Sewer Authority was showcasing the work underway in the drained reservoir. That work is the first step in a five-year, nearly $500 million modernization.Watch the report from Highland Park: Click the video above.The more than $27 million job of replacing the Highland II reservoir's liner and cover is the biggest project of its type underway in the U.S. right now. It sets the stage for that reservoir temporarily being the place where Pittsburgh water is disinfected."We need to replace that cover and liner to make sure that no contaminants or things from the atmosphere enter that reservoir again, ensuring treated high-quality drinking water is coming out of this reservoir," said Will Pickering, CEO of the Pittsburgh Water & Sewer Authority. "More importantly, this reservoir, temporarily, is going to serve as our primary disinfection point for all of our treated drinking water as we make repairs to a century-old facility at the Aspinwall water treatment plant."It will stand in while a century-old underground storage tank called the Clearwell will be replaced. Right now, the Clearwell is PWSA's only disinfection storage facility."If you were to go there today, it just kind of seems like a football field. But underneath it is a single concrete cell that was built about 100 years ago. We recognize that's too long for a hundred-year-old facility that is the final step in our drinking water treatment process to be in place," Pickering said.He led a tour showcasing this first phase of its multi-year "Water Reliability Plan" on Friday."We have a number of projects going on over four to five years. We're investing nearly $500 million in our system to make sure that we're adding another century of life, and have additional resiliency and safe and clean, reliable water for all of our customers here in Pittsburgh," Pickering said.The tour also included a visit to the area where the Highland Reservoir pump station will be replaced by a new, larger pump station to assure a more resilient system. The intention is to minimize the public impact of shifting use of resources while the plan is implemented."That's been a lot of the focus of our work, is working through all of those outages to make sure so that nobody realizes everything that we're doing," said Sarah Bolenbaugh, PWSA senior group manager for water.State and federal low-interest financing will help control project costs and PWSA is also seeking federal infrastructure grants."We take every dollar that we get from ratepayers and we put it back into our system. And what we're looking to do is to not have to ask our ratepayers for as much. So we want to use the fee or best case scenario, grants, to fund this work," Pickering said. "There will, unfortunately, be rate increases. But what PWSA has spent a lot of time doing within the last few years is building programs for customers to get help, for those who can't afford the rate increases."