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July 22, 2020

Alexandria’s Current Combined Sewer System at a Glance

Like many older cities in the United States, Alexandria is facing a century-old problem. Every year, millions of gallons of sewage mixed with rainwater overflow into its waterways.

Called “combined sewage,” this discharge flows out of the city’s combined sewer system, which was built in the early 19th century.

In such a system, there is only one pipe to transport both sewage and rainwater to AlexRenew’s Wastewater Resource Recovery Facility for treatment. The capacity of this pipe is exceeded nearly every time it rains in the city, causing overflow events.

Currently, these events occur at four “outfalls” across the city and impact the health of local waterways like Hunting Creek, Hooffs Run, and the Potomac River.

In April 2017, the Virginia General Assembly passed a new law requiring the remediation of these outfalls by July 1, 2025. In response to the law, Alexandria Renew Enterprises (AlexRenew), with support from the City of Alexandria, developed the RiverRenew Program to meet the strict regulatory requirements and aggressive timeline.

RiverRenew includes the construction of a tunnel system, sewer infrastructure and improvements to AlexRenew’s wastewater treatment plant. Learn more about the largest infrastructure project in Alexandria’s history in this animated video.

Map of Alexandria's Existing Outfalls
Click the image to view larger version.