A 90-day delay caused by Irish Water during the construction of a major drainage improvement project cost a Mayo civil engineering company €3.6 million, it claimed in the Commercial Court.

Wills Bros, of Foxford, is suing the water company over the delay to the Balbriggan-Skerries network improvement scheme in north Co Dublin.

Wills won the tender for the scheme, which included design and construction of a storm-water pumping station for Skerries and surrounding areas. A contract was signed with Irish Water in August 2017.

Wills says it is not in dispute that a substantial delay has been caused to the project and that Irish Water is responsible for it.

The dispute between the parties now relates to the daily cost of the delay. Wills says it is €40,000 per day, or €3.6 million in total, while Irish Water says it is just €2,000 per day, or a total of €180,000.

Wills says the primary reason the delay costs are so high is the “specialised tunnelling aspect” of the project, which commonly requires round-the-clock specialist labour as well as the hiring of “particularly expensive imported machinery”.

It also says the €40,000 daily rate is “clearly demonstrable” from the contract documentation and equates to costs a company such as Wills might typically encounter in a delay caused by an employer.

The case was admitted to the fast-track Commercial Court this week by Mr Justice David Barniville on consent between the parties.

Irish Water said its consent was subject to disagreement as to whether the case met the €1 million threshold for admission to the commercial list.