Complex Leak Sealing at ČHE Avče Pumped-Storage Plant – Slovenia

Infiltration at the Surge Chamber–Tunnel Connection

ČHE Avče is Slovenia’s first pumped-storage power plant, a strategic facility providing grid balancing and peak electricity production. Over time, persistent water ingress developed at critical interfaces between the surge chamber and the connecting tunnels, as well as around construction joints.

Key challenges included:

• High moisture saturation of the concrete lining,
• Active leaks under fluctuating reservoir pressure,
• Complex geometry making conventional sealing difficult,
• The need to maintain continuous readiness for energy dispatch.

Traditional approaches such as cement-based grouting were ineffective in achieving lasting watertightness, and the client required a flexible, adaptive sealing system compatible with dynamic water loads.

EURAS® Gel Type B – Adaptive Waterproofing for Critical Interfaces

After technical evaluation, EURAS® Gel Type B was selected to solve the issue due to:

• Exceptional hydroscopic behavior, actively displacing water from cracks,
• Ability to penetrate deep capillaries and micro-fissures without shrinking,
• High elasticity ensuring performance under structural movement,
• Compatibility with moist concrete and prior bituminous coatings,
• Proven durability against chemical attack and freeze-thaw cycles.

The EURAS team executed a targeted intervention that included:

1. Mapping infiltration zones and drilling injection ports around the perimeter of the chamber–tunnel transition,
2. Sequential high-pressure injection of EURAS Gel under pressures up to 160 bar to ensure deep fill and adhesion,
3. Real-time monitoring of flow reduction and gel return to confirm saturation,
4. Post-injection performance verification tests to ensure full watertightness.

Despite the complexity, the work was conducted without interrupting plant readiness.

• Complete sealing of all active and latent leaks at the chamber–tunnel interface,
• Restoration of structural protection against water ingress,
• No operational impact during or after the intervention,
• Long-term resistance to pressure cycles and aggressive water chemistry.