SUDBURY -- A Sudbury construction company is suing the Ontario government, arguing the contract it signed to expand part of Highway 69 incorrectly estimated the amount of rock that would be leftover at the end of the project.

The $20 million suit centres on whether the province incorrectly estimated the amount of rock, as Bot Construction claims, or whether the excess rock is a result of the way it was blasted, as the Ontario government claims.

Lawyers for the company argue the excess rock is a result of a design error, as well as errors estimating the extent to which crushed and broken rock takes up more volume than rock sitting in the bank.

Bot argues that its bid for the work was much lower than it should have been because of the errors. It said the amount of rock it had to deal with was "approximately 26 times more than was estimated."

"The plaintiffs’ position is that this case is fundamentally about whether two pieces of information provided by the defendant to bidders on the contract were incorrect and if so, was the price the plaintiffs’ bid for the contract artificially deflated by its reliance on that incorrect information," said a court transcript of the latest hearing on the case, released May 31.

In response, lawyers from the province said Bot is responsible for the excess rock because "of the way it conducted the work on the project."

"The defendant asserts that the source of the additional rock is the drilling and blasting techniques employed by the plaintiffs and its subcontractors," the transcript said.

"Specifically, one source of additional rock would be over-blasting by the plaintiffs: blasting beyond the design lines of the contract, also referred to as 'overbreak.' While over-blasting is permitted, disposal of any additional rock generated by over-blasting would be the responsibility of the plaintiffs."

The province argued that Bot should have to provide extensive documentation on their blasting techniques to determine whether that was the cause of the excess rock.

But Bot argued their case is based on arguments the information provided the province in the contract was incorrect, leading the company to bid too low. Specific blasting techniques, they argue, aren't relevant.

While largely finding for Bot, the judge in the case said the company had to say whether an expert report they had prepared would allow them to answer how much they would have bid on the contract at the time, if the alleged design errors had not been made.

"If the report did provide them with sufficient information/data to answer how they would have bid but for the design error, they must also answer that question," the judge ruled.

"If they do not have the data/ information to respond, they are not required to do so, because that would impose an undue burden of work."

Read the full transcript here.