The Greensferry Sewer Separation project was constructed to meet the obligations of federal consent decrees to eliminate combined sewer overflows (CSOs) in the City of Atlanta. A key component of the city’s CSO Remediation Program, the project developed 60,000 lf of separated sewer that includes a 1,200-ft-long mined tunnel section. Schnabel provided tunnel engineering services to the HDR-led team during its design.

Tunnel planning and design were complicated by the presence of a city park, two active subway lines, an urban landfill, and an abandoned storm sewer, each located along the alignment. Our work included site reconnaissance of the proposed route; researching historical geotechnical information, borings, and MARTA construction drawings; developing tunnel and shaft designs; and preparing associated plans, specifications, and the project Geotechnical Baseline Report.

During construction, we provided construction management services including the review of contractor submittals and value engineering proposals. Our involvement in the value engineering effort increased the city’s savings from $440,000 to more than $2 million.