Problem: A Maryland housing complex under construction was experiencing significant issues with unstable soils and recurring sinkhole activity along a 150-foot stretch of sanitary sewer. Ground Penetrating Radar (GPR) and CCTV inspections revealed that bellies had formed in the pipe due to poor soil compaction, necessitating excavation and soil recompaction. This was the third time the soil line required replacement due to unfavorable soil conditions, posing a substantial delay risk for the construction project.
Solution: USG devised a comprehensive solution to stabilize and compact the soils while ensuring the safety of all personnel involved. A 10-foot-deep trench was excavated in 30-foot increments. High-density structural polyurethanes were injected at 5-foot intervals, reaching depths of up to 25 feet below the pipe, to densify and stabilize the underlying soils.
The injections were carefully coordinated with the trench shoring process to maintain safety and structural integrity. Following the polyurethane injection, an infrastructure team realigned the sewer pipes to correct any existing bellies and ensure proper alignment.
Results: The project was completed efficiently, preventing further delays in the construction of the residential complex. The fully stabilized base provided by the polyurethane injections is expected to prevent future soil settlement, thereby mitigating the risk of recurring sinkhole activity. The USG team expedited the repair process by eliminating the need for additional heavy machinery and fill material, resulting in significant time and cost savings. The customer was fully satisfied with the outcome, and the project successfully avoided potential ordinance issues with the local government, ensuring a smooth continuation of the construction project.
