JIM DENT CONSTRUCTION / SHOTCRETE CONSTRUCTION / BRITISH COLUMBIA
Project Overview
The Upper Ramona Tunnel Plug project was the final stage of a hydroelectric generating system designed to create 500 meters of hydraulic head pressure for power generation. Multicrete Systems Inc was contracted to construct a 25-meter-long shotcrete and cast-in-place concrete tunnel plug capable of withstanding high-water pressure while maintaining strict seepage control requirements.
Project Scope
The project involved designing and fabricating specialized low-profile equipment capable of accessing the remote tunnel location through an 800-meter-long mountain tunnel with limited clearance and a 10% uphill grade. Multicrete developed a modular concrete batching and pumping system that met both operational and mining safety requirements while achieving high-volume concrete placement rates underground.
Temperature control was critical throughout construction to prevent thermal cracking within the mass concrete structure. Concrete pours were completed in multiple stages with continuous temperature monitoring to ensure the hydrating concrete remained below specified limits.
Shotcrete Construction
Following the initial cast-in-place concrete lifts, shotcrete was applied throughout the tunnel plug to create a continuous water-tight seal. Shear keys and rubber water stops were installed between concrete lifts to control seepage at cold joints, while rebound material was removed during application to maintain proper bonding and sealing.
A SikaFuko post-grouting system was also installed to seal surrounding rock fissures and improve long-term water tightness of the tunnel plug structure.
Final Product
Once construction and post-grouting were completed, the shaft above the tunnel plug was flooded as part of the hydroelectric commissioning process. Final seepage through the tunnel plug measured only 5 L/s, exceeding the project requirement of 25 L/s and achieving an 80% reduction below the allowable seepage limit.
Project Highlights
- Constructed a 25-meter-long tunnel plug for a hydroelectric system generating 500 meters of head pressure
- Remote underground installation accessed through an 800-meter-long mountain tunnel with 10% grade
- Designed and deployed custom low-profile batching and pumping equipment for confined tunnel conditions
- Managed strict concrete temperature control to prevent thermal cracking in mass concrete pours
- Multi-stage cast-in-place concrete placement with embedded shear keys and water stops at lift joints
- Full-length shotcrete application to create a continuous water-tight tunnel seal
- Installed SikaFuko post-grouting system to seal surrounding rock fissures and improve long-term water tightness
- Achieved final seepage of 5 L/s, exceeding the 25 L/s performance requirement by a significant margin
- Successfully completed critical hydroelectric infrastructure under extreme logistical and environmental constraints
