ASCE Los Angeles Section

Intersection of I-15 and I-215 San Bernardino County

The proposed Devore Interchange Improvement project limits extend along I-15 from approximately 0.8 miles south of the Glen Helen Parkway Undercrossing to 1.4 miles north of the Kenwood Avenue Undercrossing, and along I-215 from 1.2 miles south of the Devore Road Overcrossing to the I-15 junction.  The project goals are to reduce existing operational deficiencies at the I-15/I-215 interchange, facilitate efficient goods movement through the I-15/I-215 interchange, reduce existing and forecast traffic congestion, reduce freeway traffic diversions to local streets, and upgrade the I-15/I-215 interchange to modern standards where feasible. Travel through this interchange is one of the main corridors for freight trucks, recreation automobiles and commuters. This corridor is known to be one of the major passages to popular destinations such as Las Vegas and Colorado River for the California natives.

The geotechnical design of foundations for bridges, retaining walls, embankments for this project are all considered to be non-standard due to high seismic area. Caltrans standard design for retaining walls and embankments is limited to 0.2g whereas the elements for this project had to be designed for 0.4g of horizontal acceleration. Caltrans does not have set guidelines or procedures on how to design geotechnical elements such as ground anchors, soil nails or MSE wall reinforcement for high seismic regions. Vague guidelines are available in AASHTO or FHWA.  Geotechnical design recommendations that are acceptable by Caltrans and reasonable for the contractor to build within available budget (due to limitations of a design build bid) was challenging but was achieved.

Working with Caltrans Design oversight personnel from various offices such as Caltrans headquarters (Sacramento), Diamond bar and San Diego was challenging. Some of the design guidelines and approval for design guidance generation or deviation from existing guidelines needed approval from headquarters. For this project, several deviations and guidance was needed from headquarters and working through it for approval generated special relationships with personnel in Caltrans. This project won the “Partnering Success in Motion” Gold Award (highest award for jobs over $50 million dollars) from California Department of Transportation (Caltrans).

The project is funded by 20% Federal funds, 24% local (SANBAG Measure I funds) and 56% State (Caltrans) funds.

This project is considered one of the biggest challenges in terms of geotechnical design due to the site being located within 1 kilometer of San Andreas Fault (the biggest fault within California) with a magnitude of 7.9 and capable of generating peak ground accelerations as high as 1.2g.  Designing soil nails, ground anchors and MSE wall straps for high accelerations and keeping the lengths reasonable for construction was a challenge.

The proposed project limits extend along I-15 from approximately 0.8 miles south of the Glen Helen Parkway Undercrossing to 1.4 miles north of the Kenwood Avenue Undercrossing, and along I-215 from 1.2 miles south of the Devore Road Overcrossing to the I-15 junction.  The project goals are to reduce existing operational deficiencies at the I-15/I-215 interchange, facilitate efficient goods movement through the I-15/I-215 interchange, reduce existing and forecast traffic congestion, reduce freeway traffic diversions to local streets, and upgrade the I-15/I-215 interchange to modern standards where feasible. The proposed design build project will construct, 8 new bridges, widening of 10 existing bridges, traffic design, geotechnical investigations, 31 non-standard retaining walls design, utility relocations, and drainage and water quality design, addition of new and auxiliary lanes to and from the interchange, rehabilitating some of existing roadway with white topping, for the project. The project includes a complete reconfiguration of the interchange to provide route continuity and truck bypass lanes for I-15 traffic.  The project will reconstruct approximately 6 miles of existing freeway and will reconnect the original “Route 66” highway which was severed during the original construction in the 1960’s.  The project site is located within 1 kilometer of San Andreas Fault (the biggest fault within California) with a magnitude of 7.9 and capable of generating peak ground accelerations as high as 1.2g. Due to the site being in high seismic region, all the bridges, retaining walls and slope embankments within this project are considered special design. AECOM (Formerly URS) services included a geotechnical investigation that involved drilling almost 175 borings with a total footage of 8,200 feet for bridges, retaining walls, pavements and miscellaneous structures. AECOM (Formerly URS) also had to prepare 12 Preliminary Foundation Reports and Final Foundation Reports for the special design retaining walls of various types consisting of 8 mechanically stabilized earth (MSE) walls, 5 Type 1 walls, 13 Soil Nail walls and 3 Ground Anchor/Soil Nail combination walls, and 3 Materials Report for pavement design within various segments of the project. Due to very dense sandy gravelly material encountered through the entire project site, most of the bridge foundations utilized large diameter cast-in-drilled-hole (CIDH) piles that ranged from 3ft to 12 feet in diameter.

AECOM (Formerly URS)/Atkinson team was selected with highest technical score based on the qualification/technical innovations provided in the proposal as well as the lowest bid price. San Bernardino Associated Governments (SANBAG), in cooperation with California Department of Transportation (Caltrans), has proposed improvements to the Interstate 15 (I-15) and Interstate 215 (I-215) interchange near the unincorporated community of Devore in southwestern San Bernardino County.