Existing DSTT Can Accommodate Light Rail Commuters

 Several posts on this blog have questioned the need for a 2^nd Seattle Transit Tunnel.  Still, the March 23^rd Sound Transit Board meeting continued to insist the 2nd tunnel was needed,  That the North of CID station at Pioneer Square was the “preferred alternative”, for access.  However, they directed Sound Transit spend an additional 2 months considering the 4^th Ave CID station location.

This post opines a competent Sound Transit would quickly recognize the existing DSTT has the capacity to accommodate all those needing to go beyond existing CID station from the south and beyond existing Westlake station from the north.

 

 A 2004 PSRC study, funded by Sound Transit, concluded the DSTT could accommodate fifteen 4-car light rail trains an hour. Each 74-seat, light rail car could accommodate 148 sitting and standing riders, so capacity was limited to 8880 riders per hour in each direction.  

 

The “Voter approved” extensions do nothing to increase that capacity.  Thus, the existing DSTT can already accommodate all the capacity of the light rail spine into Seattle.  The 2^nd tunnel was included in the ST3 vote to accommodate the West Seattle and Ballard Links.  

 

The West Seattle link is scheduled for service in 2030 because it isn’t routed through the 2^nd tunnel.  That when completed it will share the light rail capacity with Line 1 Link from  the SODO station into Seattle.  Rather than increase transit capacity into Seattle, the link will reduce Line 1 Link capacity to SeaTac and beyond.   

 

However the  Line 1 Link will already have lost half of the DSTT capacity when East Link begins service in 2025.    Thus, if half of that limited capacity is diverted to West Seattle, SeaTac and beyond could lose up to 75% of its current capacity until the 2nd tunnel is routed to SODO. 

The  2nd tunnel and Ballard Link, scheduled for service in 2035, does add light rail capacity into Seattle.  However, most of the riders will chose to egress and access at the new Westlake station rather than continue in tunnel to Pioneer Sq station.  The Ballard Link could be terminated at existing Westlake Station rather than routed through 2nd tunnel.

 

Prior to the 2016 vote, Sound Transit used an ST3 map of the Ballard-to-tunnel-to West Seattle that included the following projected costs.

 

The 5.4 Mile Ballard-to-Tunnel Link would cost $2,383-$2,550 (2014$M) 

The 1.7 Mile 2^nd tunnel would cost $1,638-$1,752 (2014 $M)   The 4.7 Mile Tunnel-to-West Seattle Link would cost $1,431-$1,531 (2014 $M) Thus, what voters were told the tunnel would coast, was $5,452-$5,833 (2014 $M).  

 

The Sound Transit Expansion Committee was told at the March 9^th meeting the Ballard through 2^nd tunnel and West Seattle Link would cost $12B, more than twice what voters were told.  The Board’s decision to continue to study the 4^th Ave CID station was widely applauded during the April 27^th Board meeting.  Yet the board refuses to appease their concerns by considering using  existing CID station and DSTT

 

The bottom line is the existing DSTT can accommodate all the light rail spine train capacity into Seattle.  Sound Transit plan to to share part of that capacity with West Seattle link does nothing to increase that capacity.  The existing DSTT can easily accommodate Ballard Link needing to go beyond existing Westlake station. 

Sound Transit Board needs to recognize the existing DSTT has the capacity needed to accommodate all those wishing to go beyond existing CID and Westlake stations.  Saving billions and years of delay and disruption required for 2nd tunnel.