The SR 520 Legislative Workgroup considered the following westside design options:

Westside
cost estimate
Full corridor
cost estimate
Option A+
Option A+


Recommended option
$2.027B to $2.127B $4.531B to $4.631B
Option A
Option A



$2.022B to $2.298B $4.526B to $4.802B
Option K
Option K



$4.070B to $4.168B $6.574B to $6.672B
Option L
Option L



$2.562B to $2.642B $5.066B to $5.146B
Option M
Option M



$3.358B $5.862 B

The upcoming SR 520, I-5 to Medina: Bridge Replacement and HOV Project Supplemental Draft Environmental Impact Statement (SDEIS) analyzes three westside design options, A, K and L, each with sub-options.

The Option A+ recommendation is comprised of Option A with specific sub-options and is covered in the SDEIS.

While Option M also includes a tunnel underneath the Montlake Cut, it would require a different construction method than Option K, and is not covered in the SDEIS.