Blackwater CSO Tunnel Excavation Reaches Major Milestone Beneath Lynchburg

LYNCHBURG, Va. — Crews have completed excavation of the underground Blackwater Combined Sewer Overflow (CSO) Tunnel, marking a major milestone in what city officials describe as the largest capital improvement project in Lynchburg's history.

The final drill-and-blast took place Saturday, July 11, breaking through the last section of the 4,744-foot tunnel located approximately 100 feet beneath Blackwater Creek.

The tunnel now stretches from the construction site at the base of Seventh Street in downtown Lynchburg to the CSO 52 site along the Point of Honor Trail near Hollins Mill Dam. Excavation began in March 2025.

Once completed, the tunnel will be capable of storing up to 4.7 million gallons of combined stormwater and wastewater during heavy rain events. By temporarily holding the excess flow, the system will dramatically reduce the amount of untreated water entering Lynchburg's rivers and streams.

According to the city, the Blackwater CSO Tunnel serves as the capstone project of Lynchburg's 45-year Combined Sewer Overflow improvement program. When the entire program is complete, combined sewer overflows into local waterways will have been reduced by approximately 98% compared with conditions before the program began.

With excavation finished, contractors will now begin installing the tunnel's permanent concrete lining. Construction also continues on above-ground facilities, including a diversion structure near the Point of Honor Trail and a pump station at the Seventh Street site.

The Blackwater CSO Tunnel project is expected to be completed in the summer of 2027.

Why it matters

Many of Lynchburg's oldest neighborhoods were built with combined sewer systems that carry both stormwater and wastewater in the same pipes. During periods of heavy rainfall, those systems can exceed capacity, causing untreated water to overflow into local waterways. The new tunnel is designed to capture that excess flow and hold it until it can be treated, significantly improving water quality throughout the Blackwater Creek and James River watershed.