Lava Hot Springs Rock Fall Mitigation

Stabilizing a slope above a historic Idaho attraction


Lava Hot Springs, Idaho

Lava Hot Springs is a popular tourist attraction nestled among the rocky slopes of Southwest Idaho’s wilderness. The state’s Lava Hot Springs Foundation has maintained a series of geothermal pools just off Highway 30 for more than a century, but eventually the facility had to contend with a far less profitable geologic feature—falling rocks.

Two of the hot springs’ pools are almost directly beneath a steep slope of exposed rocky outcrops. Over the years, sections of the facility have been closed due to rockfall risks. The area was within Idaho Transportation Department (ITD) right-of-way, so the agency hired GeoEngineers to assess the slope and design stabilization plans. GeoEngineers immediately began working to stabilize the slope and lower the risk of future rockfalls.


A GeoEngineers subconsultant used a small unmanned aerial vehicle to image and survey the slope in detail. Geologist and WTS member Rachel Hunt and her GeoEngineers colleagues used these images as a reference to develop rock fall stabilization plans, specifications, and engineer’s cost estimate.

The team had to carefully consider additional factors in the stabilization design because of the proximity to the Hot Springs facility, ultimately recommending different approaches for different regions of the slope. The final design included a mix of rock dowels, vegetated steel wire mesh and sculpted and stained shotcrete (sprayed concrete) to secure it.


To meet an initially aggressive construction timeline, GeoEngineers had to complete all field work and deliver design packages before October 2020. The team was up to the challenge, completing work in less than five weeks. With construction complete, visitors to Lava Hot Springs can now safely relax in the shadow of a newly stabilized and secured slope.

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