Two tunnel options were mapped and considered in the Final EIS.  They were not incorporated into the plan because of the added cost.  From the EIH: "A Downtown tunnel would increase the cost by an extraordinary magnitude and including Dillingham Blvd. would increase the cost to more than $1 billion, which would not be prudent because of its extraordinary cost."  The irony, of course, is that the estimate has already gone up by nearly $5 billion.