A fire station access roadway developed cracking from subsurface voids caused by storm drain seam gaps that washed out soil during heavy rain, threatening daily emergency operations and pavement integrity. Geotech specialists from Helicon were brought in to assess the situation.
Initial Assessment
CCTV and probing identified voids up to several inches beneath the asphalt and open joints along the drain, allowing soil migration. Excavation replacement was rejected due to weeks-long closure risk, higher cost, and potential future seam misalignment, making trenchless permeation grouting the viable path.
Proposed Solution
AP Fill 700 was chosen for hydrophobic, single‑component injection with very low viscosity, and adjustable cure, enabling soil permeation, joint sealing, and formation of a water‑tight bearing layer for traffic.
Procedures
- Map defects and mark the injection grid along the pipe and pavement.
- Drill ports; set packers to target joints and halo around pipe.
- Inject AP Fill 700 to refusal, prioritizing seam sealing.
- Permeate surrounding soils to fill voids and densify subgrade.
- Monitor pressures/returns; adjust set times for water presence.
- Verify with sounding/CCTV and traffic proof-load.
Results
- Restored structural support and sealed joints with zero operational downtime.
- Completion in days vs weeks.
- Approximately 95% cost savings compared to full excavation and pipe replacement.
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