Unexpected Playa Geohazards Create Issues for Solar Facility-Paper

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A 100 MW solar facility built on the edge of a dry lakebed in the western United States experienced repeated ground fissures after significant rainfall. Conventional geotechnical investigations before construction found no fissures or unusual hazards, but the studies focused mainly on shallow soils.<br /><br />The first fissures appeared in 2016 and were filled with controlled low-strength material. In 2017, a larger fissure extending about 1,200 feet developed, with depths up to 11 feet; repairs later used epoxy-based urethane foam. A third event in 2022 was substantially more severe, extending about 2,500 feet and reaching depths exceeding 20 feet, with some reported fissure depths near 30 feet. It damaged access routes, solar panels, and support structures.<br /><br />Investigations after the 2022 event included geophysical surveys, soil testing, historical imagery review, and hydrologic modeling. Surveys identified deep, low-velocity subsurface zones, including beyond visible fissures. Laboratory tests showed that site soils were moderately to highly dispersive. Field observations and modeling suggested that concentrated stormwater run-on, including water from an off-site retention area, contributed to subsurface erosion or “piping.” The events appear unrelated to seismic activity.<br /><br />Repairs used sand-cement slurry in deeper, narrow sections and granular backfill near the surface. Drainage channels and berms were also designed to divert runoff away from the affected area. Further assessment may determine whether deeper ground improvement is needed.<br /><br />The case highlights that dry lakebed settings can present hazards beyond flooding. For projects in playas or other settings with potentially unusual subsurface conditions, deeper investigations and geophysical studies may be warranted in addition to standard shallow geotechnical assessments.

Keywords

solar facility

dry lakebed

ground fissures

playa soils

geotechnical investigation

subsurface erosion

piping

dispersive soils

stormwater run-on

geophysical surveys