Ninyo & Moore Geotechnical and Environmental Sciences Consultants.

Ninyo & Moore provides geotechnical engineering, engineering geology, geophysics, hydrogeology, soil and materials testing, and environmental services.
3202 East Harbour Drive Phoenix, AZ
Phone: 602.243.1600

La Pata Avenue Gap Closure and Camino Del Rio Extension

La Pata Avenue Gap Closure and Camino Del Rio Extension


Orange County, CA

Scope of Work:

  • Geotechnical Observation and Testing of Compacted Fill
  • Geologic Observation and Mapping of Remedial Grading Bottoms and Buttress Backcuts
  • Slope Instrumentation and Monitoring

Ninyo & Moore provided geotechnical consulting services during construction of the La Pata Avenue Gap Closure and Camino Del Rio Extension Project in Orange County, California. This project, which provides an essential link in the local roadway network, involved widening of 1.8 miles of La Pata Avenue in San Juan Capistrano, constructing 2 miles of new roadway to connect La Pata Avenue to Avenida La Pata in San Clemente, connecting Avenida La Pata to Camino Del Rio via 0.4 mile of new roadway, and construction of two bridges and two long-span structural plate steel undercrossings. The project was awarded Project of the Year by the Orange County branch of the American Society of Civil Engineers, earned Engineering Project Achievement award from OCEC, earned the #2 award in Roads & Bridges magazine’s 2016 Top 10 Roads list, and was awarded the Design Quality Partner Award by the Southern California Chapter of the Construction Management Association.

Project Challenge: The project included construction of soil buttresses to stabilize slopes along the roadway alignment that descend from San Diego Gas & Electric (SDG&E) and Southern California Edison (SCE) transmission lines due to out-of-lope bedding conditions. Grading included the construction of temporary backcuts adjacent to SDG&E and SCE metal lattice towers and double wood pole structures. Slope monitoring during construction was recommended in the Geotechnical Design Reports prepared for the project along with a sequenced grading approach to limit the heights, lateral extents, and duration of exposure of the backcuts.

Innovative Solution: Our services included the design and implementation of a slope monitoring plan to monitor the stability of temporary remedial grading cuts adjacent to SDG&E and SCE transmission lines. The plan included the design and installation of thirteen continuously monitored in-place inclinometer and tilt meter systems that were solar powered and transmitted data via cellular modem to a web-based monitoring service. The plan established automatic alert levels based on ground or tower/pole movement and recommendations for actions. Our services included review and maintenance of the monitoring system and implementation of actions following automatic alarms.

Services: Prior to construction, we provided review of third-party review comments regarding the geotechnical design reports and preparation of comment response letters. During construction, our services included observation and compaction testing during 12 million cubic yards of mass grading that involved removal of landslides and construction of buttresses. We performed geologic mapping of remedial grading bottoms and temporary backcuts for buttresses, observed canyon subdrain and buttress backdrain construction, performed in-grading exploratory borings to evaluate removal of landslide deposits, and prepared geologic cross sections for slope stability analyses to evaluate adequacy of buttresses and preparation of revised buttress configurations. We also performed settlement analyses of deep fill, and we prepared geotechnical field memoranda and as-graded reports. Our as-graded reports included preparation of geotechnical maps documenting the geologic structure exposed during grading, the locations of buttress keyways and subdrains, and maps showing the locations of our field density tests.