Location: Lexington, NC Overview: Project Gemini used Low-Density Cellular Concrete to address settlement issues along a sanitary sewer alignment caused by poor subsurface conditions. LDCC was selected as an engineered fill solution to stabilize the pipe and prevent future deflection where traditional remediation methods had proven unsuccessful. Challenge: A 120-linear-foot section of 6-inch SDR 26 sanitary sewer pipe exhibited sagging due to silty soils, partially weathered rock near the pipe invert, and groundwater levels at or above the invert elevation. These conditions reduced the shear strength of the supporting soils, creating a soft and compressible subgrade. After two unsuccessful remediation attempts, the geotechnical engineer evaluated three corrective options: over-excavation, aggregate piers, or cellular concrete fill. Further evaluation suggested that vibratory loading from structural fill placed above the pipe may have contributed to the settlement, increasing the risk of continued deflection if traditional backfill methods were used again. Solution: Low-Density Cellular Concrete (LDCC) was selected due to its lightweight properties, uniform load distribution, and elimination of compaction- induced vibration. RyanGeo placed LDCC above the pipe for the first 7 feet of backfill, reducing mechanical influence on the pipe while providing consistent support. A total of 250 cubic yards of 30 pcf LDCC was placed in two 3.5-foot lifts over two days, stabilizing the alignment and preserving pipe geometry. Results: • Pipe Length Stabilized: 120 linear feet of 6" SDR 26 sanitary sewer • Material Placed: 250 cubic yards of 30 pcf LDCC • Placement Configuration: Two 3.5-foot lifts over two days • Key Benefit: Reduced settlement risk and eliminated vibration-induced pipe deflection