Our work began with a data room that contained over 10,000 documents and, since we worked during the summer months, many of the key people involved in the project were on holiday during our mandate. Despite these challenges, we managed to conduct 20 interviews and review 2,000 letters. Our main task was to explain forty claims, which totalled nearly CAD 200m, and determine why each had arisen. An example of one of the claims was that a corridor should have been 3 metres instead of 9 metres. We had to investigate and explain why this difference had occurred. Given the scale of the CAD 2bn PPP project, understanding the project governance and process was a challenge in itself. We not only had to describe but also provide an opinion on whether the cost overrun prevention measures were sufficient and properly applied. Understanding each claim was also a challenge, as each was very specific and complex, involving highly technical construction aspects that were discussed in various pieces of correspondence between the construction company and the representatives of the public body.