A 41-foot-high art installation that the city of San Francisco planned to unveil as part of its new $6 billion Transbay Transit Center has been canceled and its lead artist released from his contract.

The San Francisco Arts Commission (SFAC) and Transbay Joint Powers Authority (TJPA) hired artist Tim Hawkinson to create the installation using materials salvaged from the old Transbay Terminal. It was to be one of five major public art installations planned for the new center.

The art installation was originally budgeted at $1.67 million. But the TJPA and SFAC decided to cancel the project after they realized that the actual cost of completing the artwork would come in around $3.7 million. They also said the project would be overdue and it wouldn’t debut until after the transit center opened.

In a statement released Wednesday, the TJPA said the sculpture “has proven to be a particularly complex engineering task.” The statement cited “the nature of the materials, the sculpture’s size, and its location” as reasons for the cancellation.

In a statement sent to KQED, SFAC spokeswoman Kate Patterson cited many of the same reasons. Patterson also said she hopes SFAC will get to work with the artist again. “Tim Hawkinson is a brilliant artist,” Patterson said.