Observational Methods and Construction Adaptivity for Earth Retention Systems in Talus Slope Conditions - A Case Study, Breckenridge, Colorado-PPT Presentation

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The Goldrush Project in Breckenridge, Colorado, was developed to create employee and affordable housing, preserve existing parking during construction, and expand skier parking. The steep, high-elevation site presented significant challenges, including a short construction season, limited geotechnical information, restricted access for investigation, and a high-visibility location requiring an attractive finish.<br /><br />The site lies on a talus-covered slope over glacio-fluvial deposits and the Niobrara Formation. Ground conditions included silty clayey gravel, cobbles, and boulders, with groundwater reported 18–26 feet below the surface. Although 12 exploratory borings were completed, none were located on the hillside where the retaining system was built. A preconstruction soil-nail testing program found an ultimate adhesion of 40 psi in the southern area, while testing in the talus-covered middle area was inconclusive because drilling and grouting returns were absent.<br /><br />Because conditions varied along the wall, the design integrated three retention systems: soil-nail walls where excavations could remain stable, cantilever soldier-pile walls where talus prevented reliable soil-nail bonding or property limits ruled out tiebacks, and soldier-beam-and-tieback walls where excavation stability and available tieback space allowed. Design included permanent stability checks, proof testing, and reinforcement for the wall facings.<br /><br />Construction methods included hollow-core-bar drilling and grouting for soil nails, as well as large-diameter cased drilling for soldier piles to maintain borehole stability in difficult ground. The project achieved its parking and housing objectives while adapting to changing subsurface conditions.<br /><br />Key lessons emphasized the importance of thorough site investigation, flexible design, and ongoing field verification. Different ground conditions may require multiple retention solutions within a single project.

Keywords

Goldrush Project

Breckenridge Colorado

employee housing

affordable housing

skier parking

soil-nail walls

soldier-pile walls

tieback walls

retaining systems

geotechnical investigation