Casa Del Valle Landslide – El Sobrante, CA
Construction Observation and Testing Services
AKA performed geotechnical consultation services for the repair of a landslide at the Casa Del Valle Development in El Sobrante. This landslide impacted the access road for the development as well as adjacent properties. The initial phase of the work involved consultation on geotechnical aspects associated with the landsliding, reviewing existing information from other consultants, and identifying the likely causes of the landslide. AKA then worked with the design/build team consultant to develop recommendations and design details for an appropriate landslide repair scheme. AKA also monitored the geotechnical aspects during grading operations including the removal of the slide and reconstruction of the slope, drainage installation, and construction of a new keystone wall.
La Conchita Slope Stabilization – Ventura, CA
Geotechnical Engineering Assessment
AKA conducted a geotechnical engineering assessment for the State of California Governor’s Office of Emergency Services (OES) relating to slope instability at the town of La Conchita. AKA lead a multi-disciplinary project team that included specialists in geotechnical engineering, engineering geology, seismology, risk assessment, and cost estimating. The scope of our initial assessments included compiling and reviewing available subsurface information from previous test borings, monitoring wells, and other geotechnical data sources as well as historic aerial photography and new topographic data obtained using aerial laser scanning methods. Based on these data sets, preliminary conceptual designs were developed and analyzed to evaluate feasibility, risks, and costs. The results of our initial study included a suite of conceptual risk management options and geotechnical mitigation approaches that were submitted to the Governor for action. Once a preferred concept is selected and funded, it will be fully investigated, designed, and constructed in two follow-on project phases.
Blakemont Landslide – El Cerrito, CA
Preliminary Geologic and Geotechnical Study
AKA has extensive data and specialized expertise pertaining to urban landslides, particularly the series of large active and potentially active landslides that exist on the western flank of the Berkeley Hills. The active Blakemont landslide straddles the border between El Cerrito and Kensington and is about 3,000 feet long and 700 feet wide. Most residences located over the landslide have experienced damage due to landslide movements. AKA conducted a preliminary study for the Blakemont Property Owners Association to delineate a proposed boundary for a planned Geologic Hazard Abatement District (GHAD) and develop conceptual approaches and cost estimates for landslide mitigation. The scope of our study entailed reviewing historic aerial photography and existing geologic/geotechnical reports, mapping surface conditions, and investigating subsurface conditions with deep borings, exploratory trenches, and inclinometers. The results of our preliminary study indicate that the active portion of the landslide is relatively shallow, averaging less than about 25 feet thick, and that lowering groundwater levels could stop or significantly reduce future landslide movement under static (non-earthquake) conditions. Based on this finding, AKA developed a detailed and constructible conceptual mitigation design utilizing deep subdrains coupled with surface drainage improvements to permanently lower groundwater to a level that would result in acceptable stability.
Portola Middle School – El Cerrito, CA
Landslide Hazard Assessment
AKA has been providing ongoing geotechnical engineering services to the West Contra Costa County Unified School District in support of $1 billion dollars worth of new bond measure construction. The modernization of Portola Middle School would have involved several new school buildings as well as major structural upgrades to the existing school buildings. In an initial geologic hazard screening study, AKA found that the existing school buildings were located on the toe of a large urban landslide. Subsequent detailed investigations and analysis by AKA confirmed that the school is underlain by the landslide, which is seismically unstable. After achieving concurrence from the California Geological Survey that a seismically-induced landslide hazard exists for the school, we worked closely with the District to develop conceptual mitigation options, evaluate mitigation feasibility from technical, economic, legal and public relations perspectives, explore alternative school development and funding options, and probabilistically evaluate landslide-related risks. Through these analyses it was determined that safety concerns associated with the landslide could not be readily mitigated and that future school development would need to occur at an alternate nearby site.
Vista Del Monte Apartments – San Francisco, CA
Multi-Phase Geotechnical Investigation Study
Construction Observation and Testing Services
AKA conducted a multi-phase geotechnical investigation study for the repair of a landslide at the Vista Del Monte apartment complex in San Francisco. The first phase of our work was performed in response to emergency requests from the property owner and the City and County of San Francisco after concerns were raised about landslide movements affecting the existing apartment complex. AKA provided on-the-spot recommendations for temporary measures to increase stability and helped to identify a quality specialty contractor to perform the work. AKA then conducted a geotechnical investigation study to evaluate the nature of the landsliding and to develop recommendations for permanent repairs. An initial phase of the repairs was implemented on a fast-track basis in order to assure the safety of the apartment complex. A second phase of the work was performed the following year to complete the repair and to create two downslope buildable lots at the landslide location. AKA provided comprehensive geotechnical engineering services during the investigation, design, permitting, and construction phases of the project, and also consulted on the geotechnical aspects of various legal issues associated with the landsliding.