Project phases: from plans to construction

From idea to operation, it takes a lot of work to bring a complex transit project into service.

Project phases

System expansion project phases: voter approval, planning, design, construction, start of service


Planning: 4 - 5 years

Alternatives development: 1 - 1 1/2 years

  • Starting with the representative project from the voter-approved system plan, Sound Transit develops alternatives for study and review, including route and station locations.
  • Community members, stakeholders, commuters, elected officials and partner agency staff provide comments on alternatives, helping to screen for reasonable alternatives to carry forward.
  • Based on input and analysis, the Sound Transit Board identifies a preferred alternative in addition to other alternative(s) to be studied during environmental review.

Environmental review and preliminary design: 3 - 3 1/2 years

As required by state and federal law, Sound Transit then studies potential environmental impacts of the alternatives. This results in the publishing of an Environmental Impact Statement (EIS).

  • Sound Transit obtains data through field work that may include observing and counting traffic, studying natural resources and land use, and monitoring noise.
  • Sound Transit publishes a Draft EIS, followed by a public comment period. The agency responds to those comments in the Final EIS.
  • Sound Transit completes preliminary design work.
  • Based on environmental studies, public input and other data, the Sound Transit Board selects the project to be built, including route and station locations.
  • For projects with federal involvement that require an EIS such as funding or certain approvals, the lead federal agency issues an environmental decision document called a Record of Decision (ROD).

Less complex projects, such as construction of a parking garage, are more streamlined and follow a shortened environmental process that does not require the identification of alternatives.

Final design: 2 - 3 years

  • With public input, architects and engineers define what the facilities will look like and how they will operate as well as technical specifications for the stations and tracks.
  • Field work includes testing soil conditions and ground water levels, surveying, and locating utilities.
  • Project teams gather public input at design milestones, typically at 30 percent, 60 percent and 90 percent design completion.
  • Through a public process, Sound Transit selects artists for permanent art installations.
  • Sound Transit obtains private property and easements. This may include relocating businesses and/or residents.
  • Sound Transit acquired permits from local jurisdictions, including land use approvals, noise variances, storm water discharge and wetland impacts. A light rail project requires separate permits from each jurisdiction through which it travels.

Some contracts are issued as "design-build," which means that a single contractor is responsible for both final design and construction. Under these contracts, design and construction often overlaps rather than being sequential.

Construction: 5-plus years

Construction schedules vary widely from project to project depending on complexity. Some of the factors that can influence schedule and budget:

  • Highly technical project elements, such as tunneling or water crossings.
  • Type of development surrounding project. Noise, time and other constraints to build in dense residential and business settings exceed those for building close to interstate highways.
  • External factors such as labor disputes, material shortages, unforeseen site conditions and weather.
  • Property acquisitions and relocations.

Testing and pre-operations: 6 months to a year prior to service

Before the project opens for riders, the testing phase includes a safety certification process including:

  • Simulations to assure that communications, safety, emergency and other systems are operational. The agency checks intersection signals, crossing gates and pedestrian signals.
  • Trains begin running without passengers to help pedestrians, bikers and drivers learn how to travel safely with trains.