Sealing Water Ingress at Melchsee-Frutt – Switzerland

Persistent Leakage in Alpine Hydropower Galleries

Melchsee-Frutt is a high-altitude hydropower facility embedded in the Swiss Alps, supplying renewable energy across the region. Over years of operation, chronic water ingress developed in:

• Construction joints of the surge chamber
• Interfaces between tunnels and galleries
• Micro-cracking due to freeze-thaw cycling and movement of the rock mass

These leaks were causing:

• Continuous water pooling in maintenance galleries
• Increased corrosion risks for steel reinforcements
• Progressive weakening of aging concrete structures
• Difficulty accessing infiltration zones due to confined spaces and elevation

Traditional cement grouts were ineffective in saturated, moving cracks exposed to seasonal temperature variations.

EURAS® Gel Type B – Elastic Sealing for Dynamic Alpine Conditions

After a technical review, EURAS® Gel Type B was chosen for its unique combination of:

• Hydroscopic expansion, displacing active water even under pressure
• Compatibility with wet, aging concrete and prior sealing attempts
• Elasticity and adhesion, accommodating movement from thermal shifts and settlement

Given the confined galleries and high-altitude logistics, the work required:

1. Detailed mapping of infiltration pathways using endoscopy and moisture sensors
2. Drilling of injection ports along identified joints and cracks
3. High-pressure injection up to 160 bar for deep cavity saturation
4. Continuous monitoring of flow reduction and gel return to confirm coverage
5. Post-injection inspection and verification of watertightness

Despite weather constraints and elevation, the work was completed without disrupting plant operations.