The section of a concrete pillar known as a tetrapod fell during demolition activities. The Washington State Department of Transportation said a gas line may have been pierced, too, but that was under investigation.
South Tacoma Way will remain closed through Monday morning, WSDOT said.
Tacoma Water advised people who live and work in the area between South M and Pine streets and South 56th and Center streets should not drink their water if it looks dirty, and should call (253) 502-8384 to report it.
Several businesses in the area do not have water service, Tacoma Water said. Tacoma Water will continue to assess the damage and fix the main as soon as possible, but must wait for removal of the portion of SR 16 and repair of other damage.
View pictures of the site. Tacoma Water Main Break on South Tacoma Way Photos.