Land Movement Update, Dewatering Wells Update

In May, the RPV city council approved the installation of two hydraugers in the Portuguese Bend landslide complex as an emergency measure to remove water underground that is contributing to accelerated movement. Borehole samples revealed a deeper slide plane that is moving at a much faster rate than the shallow slide plane. This discovery meant the city’s project team had to change its landslide remediation strategy to prioritize the deeper slip plane over the shallow plane targeted by the horizontal hydraugers. 

In August, the city council authorized city staff to proceed with a pilot program drilling deep vertical dewatering wells at the toe of the Portuguese Bend landslide to provide immediate relief from water pressure. 

Over the past week, the first two wells were installed along the shoreline between the South Bay Archery Club and the Portuguese Bend Beach Club. Both wells, energized using generators, are now operational and pumping a combined approximately 200 gallons of water per minute. Three more deep dewatering wells are anticipated to be installed and operational by the end of next week. Underground instruments are being installed and GPS surveys are being taken to measure the effectiveness. While these wells will be sheared over time at the deep slip plane, city staff anticipates they can be re-drilled quickly and efficiently until movement slows to the point that they will last longer. 

For updates on the dewatering wells, please read the City Manager’s Weekly Administrative Report and watch the Oct. 1 city council meeting, where city staff is scheduled to provide an update.