In July 2020, the City of Carlsbad retained ESi to investigate a landslide on city property that threatened to destabilize several upslope residential properties. When the landslide accelerated after heavy rainfall in 2024, the city requested ESi develop a scope of repair for an earthwork contractor to conduct the emergency repair work and for ESi to provide technical engineering support to the city during the emergency repair work.
Our Approach
ESi assigned two experts to the matter with backgrounds in engineering geology and geotechnical engineering. Landslide characteristics were investigated by means of borings, inclinometers (which yield the depth and rate of sliding), and piezometers (which measure groundwater depth). ESi also investigated factors such as rainfall and water usage at nearby residences. Strength parameters of soil and bedrock materials were derived from samples recovered from the borings. ESi used data from the borings to develop geologic cross sections, perform slope stability analyses, and prepare slope repair recommendations.
The subject hillside had experienced a creeping (slow, intermittent) type of movement since early 2020. ESi attributed this initial movement to a malfunctioning sprinkler system on an upslope property, which contributed large volumes of water to the slope during the late autumn months preceding the landslide. This creeping movement accelerated following episodes of heavy rainfall in early 2023, then became rapid after additional heavy rainfall in early 2024. During a site visit on February 13, 2024, ESi observed a significantly enlarged landslide scarp, reaching heights of approximately 10 feet. The accelerated movement led to the declaration of a local emergency by the City of Carlsbad on February 14, 2024.
The city’s declaration triggered efforts to arrest the ongoing movement. ESi was hired by the city to execute an emergency design and oversee construction of a slope repair to restore the slope and the affected residental properties to their original configuration.
By March 1, 2024, ESi had prepared the emergency repair scope and design, and the city engaged an earthwork contractor to commence the emergency repair work. The plan initially entailed the construction of a row of shear pins, 28 in total, 40 feet in depth, spaced 10 feet center-to-center to arrest the movement. This was followed by the installation of a second row of shear pins higher on the slope, also 28 in total, 50 feet in depth, and similarly spaced to afford permanent stability at a factor of safety exceeding 1.5. Finally, the upper, disrupted part of the slope was regraded and replaced with geogrid-reinforced engineered fill.
Services Utilized
Expertise Utilized
The Outcome
The construction and repair commenced under ESi supervision in late March 2024 and was completed by July 2024. The repair returned the slope to its original condition, at a factor of safety that exceeded statutory requirements. The San Diego section of the American Society of Civil Engineers (ASCE) recognized ESi and the City of Carlsbad with an “Outstanding Geotechnical Project in 2024” award for this work in a well-attended ceremony in 2025
