Did lawmakers mean to have the final say in 2006 when they mandated that Public Service of New Hampshire install a scrubber to remove mercury from the smokestack at its Bow plant? That was the crux of oral arguments made before the state Supreme Court yesterday.

In the two years that followed the bill's passage, the estimated cost of the project jumped from $250 million to $457 million. A group of environmental organizations, commercial ratepayers and PSNH competitors wanted the Public Utilities Commission last summer to review whether the project was still in the public interest and said the law allowed for such a review.