How Do You Protect Dam Infrastructure from Seasonal Icefall?
- Geovert
- Jul 15
- 4 min read
Project Overview
At Yellowtail Dam, Montana, Geovert was engaged to develop and implement comprehensive icefall and rockfall protection systems while maintaining uninterrupted power generation. This Design and Construct project, executed under the Northern Colorado USBR service contract, required a balance of expertise, safety considerations and operational continuity at a vital infrastructure facility.
The scope encompassed multiple protection elements across both abutments and the powerhouse area, with particular emphasis on icefall mitigation systems designed to address the unique seasonal challenges present at the site. Our mandate included not only addressing immediate hazards but installing barrier systems that would provide long-term protection against both rockfall and seasonal icefall events.
The Challenge
Icefall presents a significant seasonal hazard at Yellowtail Dam. Leakage through the dam occurs primarily during winter months along the lift lines, at various locations across the downstream face. As ice buildup from this leakage thaws, it breaks off in large pieces that slide down the downstream face of the dam and break into smaller pieces along the way, posing ongoing risk to personnel and property at the site, particularly in the vicinity of the power plant.
Alongside the icefall challenge, constant weathering of the abutments downstream of the dam causes rockfall to be a constant occurrence that has the potential to block access, damage property, disrupt communications and injure personnel. The existing protection had become compromised - the original rockfall barrier installed near the base of the right abutment groin during dam construction had been damaged by rockfall, and the area behind it had filled with fallen debris, rendering it ineffective. Most critically, a large rock formation (referred to as the "hoodoo pinnacle") was precariously poised above the powerplant service road, requiring immediate removal with careful handling to protect the adjacent roadway infrastructure.
The project's remote location created substantial logistical complexities. Access constraints around the dam structure required systematic solutions for equipment deployment and material handling, particularly when working on the steep abutments and near critical operational areas. Environmental protection requirements mandated that no scaling or block removal debris could enter the river system, necessitating comprehensive containment methods through custom-designed PMSB barriers during scaling operations.
The powerhouse protection elements presented critical timing constraints, with ice deflector structure installation requiring execution within an extremely tight power shutdown window to prevent any disruption to regional energy supply. This demanded careful planning and coordination to complete the structural work within the limited timeframe available.
Technical Solution
Following data collection and site assessment, we implemented the following protection systems:
Scaling and Block Removal
Systematic removal of loose rock from both abutments was executed to prevent river contamination. PMSB barriers provided complete debris containment during operations. The challenging "hoodoo pinnacle" removal required methods to protect adjacent roadway infrastructure.
Right Abutment Protection
We engineered and installed a modified a Geobrugg GBE500 rockfall barrier with increased energy absorption capacity for areas where analysis indicated potential for larger rockfall events while maintaining structural integrity. This system replaced the original damaged barrier and cleared the debris-filled area behind it to restore effective protection.
Icefall Protection Systems
The downstream protection strategy comprised two complementary barrier systems designed for optimal energy attenuation to address the seasonal icefall from leakage along the dam's lift lines:
Right Abutment Groin:
Custom-designed icefall attenuator utilising Geobrugg Rocco Mesh with Deltax backing technology. This configuration effectively attenuates the kinetic energy of falling ice before reaching the powerplant parking area through graduated energy dissipation mechanisms. The Rocco Mesh system provides flexible energy absorption while the Deltax backing enhances overall barrier performance under dynamic loading conditions.
Powerplant Transformer Deck:
An engineered deflector structure at the west end utilising Geobrugg Tecco G65/4 mesh technology. This high-tensile system redirects ice trajectory away from critical equipment and personnel areas without requiring extensive infrastructure modifications. The Tecco G65/4 configuration provides superior strength-to-weight ratios essential for effective icefall deflection from ice breaking off the downstream face of the dam.
Left Abutment Stabilisation:
Rock bolt pattern installation across the left abutment was tailored to the specific geological conditions. Installation locations were determined through detailed structural analysis to maximise effectiveness while minimising unnecessary intervention.
Implementation Excellence
The project execution demanded exceptional coordination across multiple disciplines and technical applications.
Access solutions included rope access techniques that allowed our teams to reach areas inaccessible by conventional means, complemented by strategic use of elevated work platforms and crane support where site conditions permitted. This integrated approach to access management ensured work could progress efficiently across multiple areas simultaneously.
The installation sequence was carefully orchestrated to align with operational requirements, with critical components scheduled during planned facility downtime. This approach allowed us to complete the most sensitive work - particularly the barrier installations around the powerhouse - without impacting energy generation capacity.
During the project, we conducted a comprehensive rope access rescue exercise from the dam wall, further enhancing our team's emergency response capabilities in this challenging environment. This exercise reinforced safety protocols specific to the unique site conditions at Yellowtail Dam, ensuring preparedness for any contingency.
Outcomes and Benefits
The completed icefall and rockfall protection systems now provide comprehensive security for both infrastructure and personnel at this facility. The barrier technologies deliver proven energy attenuation performance, with the power generating capability now operating with significantly reduced risk from both rockfall and icefall events, ensuring operational continuity even during seasonal weather extremes.
The icefall attenuator systems demonstrate measurable effectiveness in energy dissipation, with the Rocco Mesh and Deltax backing combination providing graduated kinetic energy reduction that protects critical infrastructure areas. The Tecco G65/4 deflector structures successfully redirect ice trajectory patterns away from sensitive equipment zones.
Perhaps most significantly, the entire implementation was accomplished without disruption to power generation operations, maintaining this essential service while enhancing the long-term safety and reliability of the facility through proven barrier technology applications. This outcome represents the ultimate measure of success for critical infrastructure protection projects of this nature.
This case study describes work performed by Geovert. The project integrated design, construction, rope access, drilling, grouting, scaling, block removal and barrier installation services to deliver icefall and rockfall protection for critical infrastructure.
