The Billings city water audit continues to move forward, with leaders saying Monday the company hired to complete that audit, SL Circo, is on track to finish by Jan. 31.The Minnesota-based firm is working on two phases of the project, starting with a data analysis of 37,000 files.The analysis includes looking at residents' bills for the two cycles before the software conversion and comparing those with two billing periods after the conversion.The company has told the city it is about 45% done with the first part of the audit.After that, the city is swapping out meters that have been randomly selected for testing.City Administrator Chris Kukulski said at the Monday Billings City Council meeting that all of those meters are now out and waiting to be shipped to a third party for testing.The city ordered the audit in late October after residents experienced unexplained high water bills for months following a change in billing software by the Public Works Department.Related: City of Billings begins replacing water meters for third-party testingWhat to know about the Billings utilities bill delayBillings rate payers boiling over high water bills