California Department of Transportation



Office of Geotechnical Design South 1

The Office of Geotechnical Design South (OGDS) provides expert Soils and Foundations recommendations for structures and roadways throughout portions of the Southern Region of California. The Service Area for OGDS is comprised of Districts 7 and 12.

John Ehsan
Phone: (916) 227-4575
Fax: (916) 227-0395


Branch A

David Jang

(916) 227-5722

Branch C

Ted Liu

(213) 620-2136

Branch D

Shiva Karimi

(213) 620-2146


Engineering Geology

Gustavo Ortega

(213) 620-2179

Earthquake Engineering

Mohammed Islam

(916) 227-0993

Geotechnical Liason

Fariborz Gahvari

(949) 724-2837

District 12 Oversight

Sharid Amiri

(949) 724-2599


Plantable Geosynthetic Reinforced (PGR) Wall
San Diego, I-5/I-805 Interchange

The Plantable Geosynthetic Reinforced Wall (PGR Wall) was designed and constructed for the widening of Interstate 5 north of San Diego, California. The wall is facing an environmentally sensitive estuary that connects to the Pacific Ocean. The size of the wall, approximately 1.2-km (0.75-mi) long with a maximum height of 22-m (71-ft) and an average height of 16-m (52-ft), makes it visually prominent in the surrounding area.
Plantable Geosynthetic Reinforced (PGR) Wall  San Diego, I-5/I-805 Interchange

In addition to the sheer size of the wall, the project faced many environmental mandates and design challenges. Most importantly, the wall face was required to provide planting space to sustain native vegetation and to blend into the surrounding environment with natural looking contours. Complex horizontal and vertical curvatures to form these contours, steep batter, and the necessity of providing terraces for maintenance access necessitated designing a wall face that could follow a continuously changing surface using simple and easily buildable structural elements. In addition, the wall spans over two subsurface canyons filled with 25-m (80 -ft) of thick interfingering clayey to sandy alluvial deposits and a high groundwater table. These conditions created design challenges for global and seismic stability and the total and differential settlement of the wall facing system.
Plantable Geosynthetic Reinforced (PGR) Wall  San Diego, I-5/I-805 Interchange

The PGR Wall was developed and patented by a team at Caltrans to address these mandates and challenges. It is a unique combination of modular precast facing elements with geosynthetic soil reinforcement to create a relatively light and open wall face considering the height of the wall. The modular and self-aligning design of the wall face allows it conform to a wide range of geometries using only two basic precast elements (repeated more than 16,000 times) with speed and precision. The modular design also allows the wall to be flexible enough to accommodate the large differential settlements expected in the area.
Plantable Geosynthetic Reinforced (PGR) Wall  San Diego, I-5/I-805 Interchange


The subject slope site is located near the intersection of Nohl Canyon Road and Santiago Boulevard in the City of Anaheim. The approximately 1500 feet long northern section of the slope has experienced a number of landslides since it was originally cut in 1959-60 when grading for 55 Freeway was undertaken. The slope ascends southeast above the 55 Freeway and Santiago Boulevard at a gradient of about 1:1.5 (V: H), and has a complex topography and subsurface conditions with height ranging from about 85 to 100 feet. Residential developments of Circle Haven Road and Maple Tree Drive are located above the slope. The original grading for the residential development was undertaken in 1963

Major landslides involving approximately 300 to 400 feet wide sections of the slope occurred in 1996, 1998 and 2005. These slides affected areas above and outside the State R/W and a number of residential lots and structures. The Office of Geotechnical Design-South 1 (OGDS-1) has been supporting District 12 to address various issues arising from these landslides including remediation, ROW, legal, maintenance and continuous monitoring of the conditions of the slopes. The OGDS-1 has conducted slope stability investigations and recommended remedial measures for each of these highly complex landslides. Construction to stabilize the 2005 landslides and additional work on the remainder of the slope is on-going.

2004/2005 Storm Damage Remediation
07-VEN-150 PM 28.83

In January 2005 and during a major storm in southland, sliding occurred on the embankment slope of VEN 150 PM 28.83 after the Santa Paula Creek washed out the slope toe. Soil underneath the northbound lane was also part of the slide leaving the roadway pavement completely unsupported. Furthermore, intense rainfall flooded and backed up the surface drains on the uphill side of the roadway and caused excess rainfall to flow over the top of the asphalt pavement.
2004/2005 Storm Damage Remediation
07-VEN-150 PM 28.83

Subsurface conditions determined from drilled boreholes revealed 5 feet of roadway fill overlying hard siltstone/shale bedrock. Furthermore, the slide material on the slope face was determined to be only a few feet thick. Based on the results of subsurface investigation in the slide area, design recommendations for a soldier pile wall were provided to District 7 Project Development. A soldier pile wall to be constructed from roadway was considered the most feasible option due to the steepness of the slope and inaccessibility of the bottom of the slope embankment.
2004/2005 Storm Damage Remediation
07-VEN-150 PM 28.83

The wall was constructed through a Director’s Order for an emergency contract. The entire project from the initial site investigation by GDS-1 to completion of construction lasted approximately four months.
2004/2005 Storm Damage Remediation
07-VEN-150 PM 28.83