After a trip that has lasted nearly four years, Seattle's boring machine Bertha, which is digging the new Highway 99 tunnel to replace the Alaskan Way Viaduct, is expected to reach the end of its journey Tuesday.

WSDOT said the cutter head was about 30 feet from reaching the disassembly pit. Tunneling was expected to resume at 8 a.m. It's expected to arrive at the wall sometime in the late morning or early afternoon. A WSDOT spokesperson says the arrival will not be dramatic -- appearing as more of a puff of smoke as it reaches the 5-foot thick wall. It could take several hours before the cutter head emerges.

The pit is located just east of Aurora Avenue and north of the Battery Street Tunnel. That's where the big machine will be taken apart.

Although digging will be finished, it will be nearly two more years before the tunnel opens to traffic. The double-decker lanes and other infrastructure still need to be added.

The drill began overheating in late 2013, prompting long delays as it was repaired. Litigation is underway to determine who will pay for close to $500 million in cost overruns. But there have been no major stoppages since digging resumed in December of 2015.

The Associated Press contributed to this report.