>>1344234Inb4 LNPshill blames the unions again.
Basically the budget blew out because of expanding the scope of the project, but also some unforeseen issues as well. The construction works of State Library station basically had to be redesigned due to technical challenges, there were adverse geological conditions, and more utility services had to be relocated, 93 utilities instead of the planned 86.
There were also things brought forward in the project timeline into the early works rather than main works phase. These included non-critical "Network enhancement projects" like traffic light timings, road diversions and the like around the main disruptions. The start of tunnelling works was also brought forward so that the project overall is running ahead of schedule - 2024 instead of 2025.
The total cost of the revised, larger early works phase has therefore cost $150m over budget to a total of $625m, but is currently covered with contingency funds. However as the Auditor-General states, this poses a risk of running out of contingency money in the later stages of the project.
tl;dr there was stuff that had to be unfucked, there was stuff that was done earlier than planned, but at the moment the project is mostly still on track.
Link to the report - part 4 has the info about additional works done:
https://www.audit.vic.gov.au/report/melbourne-metro-tunnel-project-phase-1-early-works 
