Fairfax County, is one of Virginia’s largest counties located just south of Washington, D.C. across the Potomac River, it has one of the nation’s largest sanitary sewer systems—collecting and cleaning up to 161 million gallons of wastewater per day for about 340,000 residential and business connections. The county’s wastewater collection and conveyance system covers nearly 234 square miles.
About 20 years ago, the county installed dual 36-inch prestressed concrete cylinder pipe (PCCP) sanitary force mains. At that time, they only put one of these lines in service and kept the second line capped and flooded for future use. Due to current capacity concerns, Fairfax County needed to reinstate the second 36-inch line. After inspecting the line, it was discovered that areas of the pipe had degraded over time and it was currently unsuitable for until first addressing these issues. It was decided a combination of dig-and-replace and cured-in-place-pipe (CIPP) rehabilitation was the best means of repair. Taking into consideration the internal pressures and the location of the line, the county and its engineers determined which sections would be repaired and which would be rehabilitated.
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