Blackwater CSO Tunnel excavation completed in Lynchburg
(UI) — Lynchburg, Va., has completed excavation of the 4,744-ft Blackwater Combined Sewer Overflow (CSO) Tunnel, marking a major construction milestone on the city's largest capital improvement project and the final phase of its decades-long CSO control program.
Crews completed the final drill-and-blast excavation on July 11, finishing the tunnel approximately 100 feet below Blackwater Creek. The underground tunnel extends from the project's construction site at the base of 7th Street in downtown Lynchburg to the CSO 52 site near Hollins Mill Dam. Tunnel excavation began in March 2025.
With excavation complete, contractor Atkinson Construction and engineering firm Stantec will begin installing the tunnel's interior lining, creating storage capacity for up to 4.7 million gallons of combined stormwater and wastewater during heavy rainfall events. Construction also continues on associated surface infrastructure, including a diversion structure at the CSO 52 site and a pump station at the 7th Street portal.
The Blackwater CSO Tunnel is the capstone project in Lynchburg's 45-year combined sewer overflow program. Once completed, the project is expected to reduce combined sewer overflows into local waterways by approximately 98% compared with conditions before the city's long-term CSO improvement program began. The project is scheduled for completion in summer 2027.
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