Downtown Rail Extension (DTX) — San Francisco, CA

We have served as the GEC for the TJPA’s DTX project from 2005 to 2026, preparing the final environmental impact statement, environmental impact report, and the conceptual and preliminary design. We also delivered several innovative designs that reduced cost and overall risk to the client, as well as the final design and construction documents for the Downtown Rail Extension.

It also improves service for travelers on the state’s future high-speed rail system. The scope of work includes track and systems to accommodate both Caltrain and California High-Speed Rail operations. It also includes station infrastructure, U-wall structures, cut-and-cover tunnels, a mined tunnel, roadway improvements, and utility relocations. Parsons has coordinated this work with multiple agency stakeholders and third parties.

Key Features Of The DTX Extension

• 2.2-Mile Extension
• Cut-And-Cover Tunnel
• Mined Tunnel
• New Fourth & Townsend Underground Station
• Salesforce Transit Center Station Fit-Out
• Emergency Exit And Ventilation Structures
• Utility Relocation
• Building Demolition
• Rail Systems And Trackwork
• Railyard Reconfiguration
• BART/Muni Pedestrian Connector

Our History With The DTX

2005-2008: Early Concept Development And Environmental Phase

From 2005 to 2008, our team prepared conceptual engineering (15%) plans and reports. These efforts refined the project definition that came out of the prior environmental phase. The team also established the configuration footprint and helped the client clarify the long-term vision. This early work laid the foundation for later design decisions and cost estimates.

2008-2011: Advancing To Preliminary Engineering And Consensus Alignment

Building on the approved conceptual plans, the Parsons team prepared 30% preliminary engineering plans and reports from 2008 to 2011. This work involved extensive coordination with Caltrain. After voter approval of California’s high-speed rail program, the team began coordination with CHSRA environmental planners. Parsons updated the design to accommodate new high-speed rail rolling stock and operational requirements. The team helped secure a consensus alignment signed off by the TJPA, Caltrain, CHSRA, and FRA. This agreement allowed completion of preliminary engineering plans and development of defensible cost estimates.

2011-2016: Coordination With Operators And City Agencies

From 2011 to 2016, the Parsons team supported the TJPA in coordinating with the train operators and FRA. The work included East Bay connection studies, support for design variances, planning of train operations, and refinement of track alignments. The team also worked with the City of San Francisco to refine the position of the Fourth & Townsend Underground Station. In addition, the team supported early studies of a future southern tunnel extension along Pennsylvania Avenue.

Parsons worked closely with the Salesforce Transit Center and station design team, Pelli-Clarke-Pelli Architects, who held a separate design contract. The team ensured that the train box shell in the Transit Center design met all spatial, track, and platform requirements for multiple operators. Furthermore, the design tied seamlessly into the overall DTX design led by Parsons.

2016-2018: Environmental Updates And Tunnel Construction Options

From 2016 to 2018, Parsons completed partial updates to the preliminary engineering design. These updates supported the TJPA’s supplementary environmental study for the alignment and other changes that had accumulated since the 2004 environmental approval. In response to City concerns over cut-and-cover construction, the team evaluated multiple tunneling methods. The analysis included Sequential Excavation Method and Tunnel Boring Machine options. The goal was to identify the best approach for the soil conditions, lower project risk, reduce cost, and shorten the construction schedule.

We also prepared conceptual designs for the underground BART/Muni Pedestrian Connector tunnel. This tunnel will link the Transit Center and the BART Embarcadero Station beneath Beale Street. To support TJPA coordination with adjacent property owners, the team prepared preliminary underpinning plans. These plans helped minimize impacts to nearby structures. Construction cost estimates were also updated with review by MTC.

2018-2020: Tunnel Options And East Bay Connection Studies

From 2018 to 2020, Parsons updated preliminary engineering plans to include deferred scope. The team also incorporated the TBM plus SEM tunnel option into the design. During this period, Parsons updated the conceptual study of the future DTX connection to the East Bay. This work took place in coordination with the BART/Capitol Corridor New Transbay Rail Crossing team. Together, the teams explored how the DTX could integrate with a larger regional rail vision.

2020-Present: Phase 2 GEC Role And Design Progression

In 2020, TJPA again selected us to serve as the Phase 2 GEC for design, procurement, and engineering support services. This award followed the successful delivery of the initial contract. Under the Phase 2 contract, Parsons built on past work and advanced all preliminary designs to a 30 percent completion level. The team achieved this milestone in 2022. Since then, Parsons has developed contract document packages for multiple construction packages defined by the TJPA. The firm advanced the final design and construction documents for all enabling works packages, including utility relocation, railyard site clearing, and building demolition, to a 60% design level.

Meeting An Aggressive Design Schedule

The plan allowed rapid response to task orders as funding became available. The team also initiated a formal over-the-shoulder review process. Under this process, the program manager reviewed “pens-down” documents before any internal QA/QC. This early review helped identify major issues that could slow the overall review. As a result, the team has maintained the overall design schedule.

Design Innovations And Project Optimization

Even under the tight schedule, we developed several design innovations that reduce project cost, schedule, and risk. The team created a two-track alignment that meets all operational requirements of the prior three-track concept. This change significantly reduced tunnel width and the project right-of-way needs. Parsons also optimized the Third And Townsend ventilation structure configuration. The new configuration cut its footprint to about half of the originally allocated right-of-way, a major saving in downtown San Francisco.

Working with multiple telecom owners, we developed a scheme to relocate all fiber lines along Townsend Street into a single combined trench. This approach reduced cost, risk, and potential schedule delays. It also supported efficient construction of the Fourth And Townsend Street Station. Finally, in close collaboration with Caltrain, Parsons developed and optimized a preliminary engineering design for a multi-stage reconfiguration of the track and rail systems within the existing railyard. These complex modifications enable construction of the DTX tunnel in a confined space while still minimizing impacts to Caltrain service.

Our Scope

• Conceptual Design
• Preliminary Design
• Final (60%) Design
• As-Needed Engineering Services
• Project Management

Learn More About Our Rail Expertise

Fully optimizing our rail and transit systems is more important than ever. The challenges we face require a visionary approach to modernize transportation systems, enhancing both freight and passenger rail networks to reduce our dependence on personal vehicles, and improve our ability to move both people and goods within and between regions, and increase overall efficiency. Learn more about our full range of rail and transit services.