The Seattle Times announced that Bertha made a foot-and-a-half of progress yesterday. More drilling is expected today. At this rate, the tunnel is expected to be completed around April 2018. After that, work will be done to connect the entrance ramps, etc. so traffic won't actually use the tunnel until at least mid-year 2018.
Originally, that date was supposed to be right around now- the end of 2016 or very early 2016.