California Department of Transportation

 

 

Office of Geotechnical Design West

The Office of Geotechnical Design West (OGDW) provides expert Soils and Foundations recommendations for structures and roadways throughout the Western Service Region of California. The Service Area for OGDW is corresponds to District 4 and the State Toll Bridge Program.

OFFICE CHIEF
Tim Pokrywka
Phone: (510) 286-4840
Fax: (510) 286-4839
E-mail: Tim.Pokrywka@dot.ca.gov

BRANCH CHIEFS

Geology

Chris Risden

(510) 622-8757

Chris.Risden@dot.ca.gov

Sonoma, Contra Costa,
Santa Clara
, Napa, Solano

Hooshmand Nikoui

(510) 286-4811

Hooshmand.Nikoui@dot.ca.gov

Alameda, San Francisco,
San Mateo
, Marin

Mahmood Momenzadeh

(510) 286-5732

Mahmood.Momenzadeh@dot.ca.gov

Geotechnical Support

Tom Whitman

(510) 286-4848

Thomas.Whitman@dot.ca.gov


SENIOR SPECIALISTS

Geotechnical Liason

John O'Leary

(916) 227-7085

John.O'Leary@dot.ca.gov

Toll Bridge Support

Bob Price

(916) 227-7091

Robert.Price@dot.ca.gov

Earthquake Engineering

Hossain Salimi

(916) 227-7147

Hossain.Salimi@dot.ca.gov

SAMPLE CURRENT PROJECTS

Devil's Slide Tunnel

Construction has recently begun on the twin-bore Devil’s Slide Tunnel on Route 1 just south of the town of Pacifica. The Office of Geotechnical Design West (OGDW) has been involved for several years in the design process, including conducting oversight and review of consultant designs, designing multiple walls in conjunction with Structures Design, conducting extensive stability analyses and design for the disposal site embankment, and design and inspection of rockfall protection measures above the portals. OGDW has developed a close working relationship with District 4 Design Staff as well as District and Structures Construction groups.

In addition, OGDW is taking the lead on monitoring groundwater elevations at several wetlands critical to the adjacent Shamrock Ranch property. Three piezometers and one weir were installed and are monitored monthly. This system provides water to Shamrock Ranch on a year-round basis. Similar work was done by OGDW staff to aid in the design of the post-construction wetland mitigation site south of the tunnel site.

During the Spring of 2006, chaos enveloped the Devil’s Slide Tunnel construction site, as multiple slides and rockfall closed Route 1. The largest slide was the reactivation of the 1995 Devil’s Slide that closed Route 1 for six months. OGDW staff worked closely with District Design and Construction to quickly develop a repair strategy. Deep tie-backs were installed across 4 rows, two above, and two below the roadway. Rock bolts were drilled to 20’ both above and below the horizontal rows of tie-backs to increase the bearing capacity of the surrounding rock. OGDW staff also worked with District Maintenance staff to scale a 300’ slope to prevent further rockfall. Additional work by OGDW during the 2006 Devil’s Slide event included designing a rip-rap/geogrid combination slide repair and a soldier pile/tie-back wall.

Devil’s slide tunnel construction

Devil’s slide tunnel construction

Devil’s slide tunnel construction

Devil’s slide tunnel construction

Devil’s slide tunnel construction

Devil’s slide tunnel construction

Devil’s slide tunnel construction

Doyle Drive Replacement Project

The project proposes to replace a 1.5 miles long section of Route 101, from Golden Gate Bridge Toll Plaza to Lombard Street, within the City of San Francisco known as “Doyle Drive.” Doyle Drive winds along the northern edge of San Francisco and connects the San Francisco peninsula to the Golden Gate Bridge and the North Bay. It is located within the Presidio of San Francisco and provides access to historic and cultural landmarks including the Golden Gate National Recreation Area, the Presidio, the Golden Gate Bridge and the Palace of Fine Arts.

Doyle Drive was originally constructed in 1936 with narrow lanes, no median, and no shoulders and it is approaching the end of its useful life. Due to its importance within the regional transportation system, seismic, structural, and traffic safety improvements are needed along Doyle Drive. The project proposes to replace the existing high viaduct structure, construct new cut and cover tunnels, construct a new cause-way, modify the Route 101/Route 1 interchange, and replace existing at-grade roadway. The project is estimated to cost $810 million and it will be completed in 2012.

The geotechnical investigation for the Doyle Drive replacement project will be performed by the partnership of Caltrans Geotechnical Services and ARUP consulting engineers. The investigation will involve drilling of 88 borings to a maximum depth of 147 feet and 26 Cone Penetration Tests (CPT) soundings to maximum depth of 98 feet. Piezometers will be installed in 12 of the borings. Geophysical testing and insitu testing including packer tests, suspension velocity test, and vane shear tests will also be performed.

Doyle Drive Replacement Project

San Francisco - Oakland Bay Bridge
04-ALA,SFO-80

The San Francisco-Oakland Bay Bridge (SFOBB) carries 280,000 vehicles of traffic per day across San Francisco Bay. During the 1989 Loma Prieta earthquake, the east span of the bridge suffered considerable damage, including the collapse of one section of the upper deck. A series of subsequent studies determined that the existing structure did not meet present-day seismic safety standards for the region, and it would be more cost-effective to replace the east span of the bridge than it would be to retrofit it.

The proposed new bridge will be constructed along a parallel alignment to the north of the existing bridge. The new bridge will be approximately 3.8 kilometers (2.3 miles) long and include a 565-meter-long, single-tower, self-anchored suspension cable, “ signature span” and a 2.1-kilometer-long “Skyway” structure. The geology of the bridge was extensively mapped by Geotechnical Services through drilling explorations conducted from barges. The majority of the new bridge foundations will be founded on large 1.8 to 2.5-meter diameter, approximately 60- to 100-meter long pile foundations. The ability to install the mammoth piles, designed to hold compression loads up to 140MN, was confirmed through an on-site pile installation demonstration project.

As of Summer 2007,  the "Skyway" and "Main Tower"  foundations have been completed.  The majority of the Skyway piles were driven into the Lower Alameda Formation.  Skyway Piers E-3 through E-5 and SAS Pier E-2 piles were driven to refusal on the Franciscan Formation bedrock.  The SAS Tower shafts were socketed 30 meters into the Franciscan Formation bedrock.  Foundation work is on-going on YBI ( South/South Detour and YBI Structures) and many have been completed. The YBI foundations are supported on various footings: spread footings with tiedowns; driven H and pipe piles; and CIDH piles.    Foundation work for Westbound Oakland Touchdown is expected to commence Fall/Winter 07/08 and will consist of driven pipe piles.

SFO-Oakland Bay Bridge 04-ALA, SFO-80 Project

SFO-Oakland Bay Bridge 04-ALA, SFO-80 Project

SFO-Oakland Bay Bridge 04-ALA, SFO-80 Project

SFO-Oakland Bay Bridge 04-ALA, SFO-80 Project

SFO-Oakland Bay Bridge 04-ALA, SFO-80 Project

SFO-Oakland Bay Bridge 04-ALA, SFO-80 Project

SFO-Oakland Bay Bridge 04-ALA, SFO-80 Project

SFO-Oakland Bay Bridge 04-ALA, SFO-80 Project

SFO-Oakland Bay Bridge 04-ALA, SFO-80 Project

SFO-Oakland Bay Bridge 04-ALA, SFO-80 Project

Landslide Repair on Sonoma Coast on Highway 1

The Office of Geotechnical Design West was contacted to provide Geotechnical expertise for a major landslide on the Sonoma County Coast along Highway 1 at Post Mile 30.3 (KP 48.8). Significant landslide movements had compromised the existing tieback wall at Shotgun Curve, located near Timber Gulch. The Geologists and Engineers of Geotechnical Design West worked in conjunction with Structures Design staff to design a permanent geotechnical solution.

A very complex landslide history and the close proximity of the San Andreas Fault (0.3 km west of project) made this a challenging project. The roadway will be moved approximately 30 meters inland behind the head scarp of the landslide. In order to accomplish this, the construction of a 20-meter high soil nail wall and the excavation of approximately 45,000 cubic meters of material were required. In addition, a new tieback wall is being constructed on the outside shoulder of the new highway alignment to prevent the current landslide scarp from encroaching on the new roadway.

I-80 Carquinez Bridge Replacement Project
04-CC, SOL, KP 0.7/1.8

The ambitious construction of the New Carquinez 1-kilometer long suspension bridge to replace the existing 1927 westbound steel truss bridge is currently under way. To facilitate the roadway widening for the bridge approaches, a series of temporary and long-term retaining walls required design and construction, with heights up to 25 m. Geotechnical Design West performed field investigations, type selection studies, geotechnical studies, groundwater monitoring, plans and specifications generation, and construction support throughout the project.

A number of standard soil nail and soldier pile walls were developed on north approach. In addition, The north anchorage excavation, as seen in the photo, was developed up to 25 m depth below the adjacent high voltage PG&E towers. This wall incorporated a combination of very high capacity post-tensioned strands and standard soil nails. The geology of the sites is very complex and consists of very weak and steep adversely bedded rock. A water-bearing fault, which crosses the NE corner of the site, also imposed a considerable challenge during the construction of the excavation shoring for the bridge north anchorage.

The bridge south approach project included development of the New Crockett Interchange and widening of the westbound I-80 up to Cumming Skyway. A number of standard, soil nail and soldier pile tieback walls were developed for the Interchange and the south approach roadway widening. Of a particular interest was a 21-m short-term and 18 m permanent tieback wall aligned along Wanda Street in Crockett, as seen in the photo. The primary purpose of this wall is to provide stability during construction for the residential covered hills overlooking the strait. The wall also serves to control the creep in the weak and weathered rocks and to allow construction of 6-lane on- and off-ramps structures. Geotechnical Design West performed complete soil-structure interaction analyses for the stability and deformation of this wall to confirm the design. The presence of the nearby Franklin Thrust Fault, swelling and slaking soft rock, and a congested project site have made this project both unique and challenging.