Heavy rainfall triggered a landslide on Lucas Valley Road, located in Marin County, that damaged a large section of the critical two-way corridor. As part of an existing on-call geotechnical contract, Kleinfelder was tasked to develop a study of the site’s geologic conditions and rapidly design a retaining wall that would safely restore the busy roadway that had limited alternative routes.
The elevated water of the adjacent creek removed the roadway’s lateral support from one side, damaging 200 feet of the structure. To provide emergency assessments, design, and construction materials testing and oversight to the heavily damaged and critical roadway, Kleinfelder responded immediately by mobilizing a multi-disciplinary team of engineers, geologists, and construction professionals, across several offices.
Kleinfelder geologists determined the character of the landslide which provided fellow Kleinfelder geotechnical engineers the information needed to establish the right drilling program. The program identified the geotechnical parameters of the landslide material and the underlying stable bedrock which were relayed to Kleinfelder structural engineers that calculated the required slope stability for the retaining wall design. The engineers provided the County with two types of retaining walls: beam and wood lagging and concrete wall with tiebacks, with the County selecting the latter option. Kleinfelder construction specialists provided inspection and materials testing during the emergency construction to verify compliance with the project design. Kleinfelder’s constant consultation to the County and the contractor accelerated the pace of the roadway’s restoration.
The rapid assembly and coordination of Kleinfelder’s in-house, multi-disciplinary specialists, allowed the roadway’s high-quality repair to occur within two months. This extremely quick turnaround was also a result of Kleinfelder’s experience with numerous similar roadway/landslide/retaining wall projects, the firm’s working relationship/experience with the County, and the County’s motivation to fully reopen the road using a force account for construction.
Location:
Nicasio, California
Owner:
County of Marin Department of Public Works
