WASHINGTON – The U.S. Supreme Court on Monday declined to consider an appeal by the former owner of the closed HoltraChem plant in Orrington over a court-ordered study of mercury levels in the Penobscot River.

Mallinckrodt Inc., a St. Louis-based company which is part of Tyco International, in August asked the nation’s high court to review a ruling issued last year by the 1st Circuit Court of Appeals in Boston.

The Supreme Court each year agrees to hear only about 150 of the 6,000 cases that seek a review.

The Maine People’s Alliance and the Natural Resources Defense Council sued Mallinckrodt in 2000 in U.S. District Court in Bangor. The two sides have been battling since then over the company’s liability for mercury found downstream from the facility.

Mallinckrodt owned and operated the former chlorine and chemical manufacturing facility from 1967 to 1982.

MPA and NRDC representatives applauded the announcement that the court would not hear the appeal in a press release issued Monday. A spokeswoman for Mallinckrodt expressed disappointment in a similar release.

“This secures the legal victory and ensures that the court-ordered mercury study will be completed,” Adam Goode, environmental organizer for MPA, said. “The legal part of the order has been finished. The downriver study will go until completion and this decision secures the opportunity for having a full remediation plan if indicated in the study.”

In its brief to the high court, Mallinckrodt had argued that the circuit court’s decision improperly broadened judicial power and the role of private citizens to enforce federal environmental laws, giving private citizens an enforcement authority equal to that of the executive branch.

Unless corrected, Mallinckrodt maintained, the appellate court’s decision would allow citizens to second-guess EPA’s policy and enforcement choices, intruding upon the autonomy of the executive branch and injuring the economy.

“Congress properly recognized that government agencies don’t always protect public health and the environment from hazardous wastes,” Nancy Marks, a litigator for NRDC, said Monday. “That’s why they empowered the federal courts to hear these citizen suits. This is precisely the way the law was intended to work.”

Despite the company’s legal appeals, Mallinckrodt already has allocated more than $2.5 million to the river study, estimated to cost about $4 million. That figure, however, does not include the potentially enormous cleanup costs Mallinckrodt might face for downstream contamination.

“We are disappointed with the decision issued today by the Supreme Court,” JoAnna Schooler of Mallinckrodt said, “but must respect their decision to decline review of the case. We will continue our remediation work on the site and separately consider the issues surrounding the river study.”

The cleanup of the 12-acre HoltraChem site is not related to the legal battle in federal court. A dismantling and remediation plan, scheduled to begin this month, includes the removal of seven buildings and 20 tanks. The final phase of the cleanup is scheduled to be completed in August 2008, according to a company press release.

“This matter before the Supreme Court is distinct from the ongoing projects that we are currently funding at the former HoltraChem manufacturing plant in Orrington,” Schooler said. “Mallinckrodt has been actively engaged in a sustained, multiyear investigation and cleanup and will continue with the current dismantling and demolition activities. This lawsuit concerns complicated issues surrounding a separate study of the Penobscot River.”