At recently as 2012, Sound Transit had less than one billion dollars of debt. That increased to $4.6 billion by the end of 2017. The ST3 program will push it much higher, peaking at a projected $17.6 billion in 2035. That path puts Sound Transit close to legal limits as major ST3 projects are delivered. After 2035, as most major projects are completed, the outstanding debt could be reduced.