In compliance with federal mandates regulating pollutants found in storm- water runoff, Mercer County will apply to the state Department of Environmental Protection for a permit to discharge storm water and asking to be exempted from the regulations.

County commissioners approved the action Thursday.

The state has had storm-water regulations since 1978, and with the passage of the federal Clean Water Act of 1999, DEP fell back on the older plan for meeting certain federal requirements.

Mercer County bridge engineer Mark Miller said previous water-control regulations focused on limiting pollution from industrial sites, municipal wastewater-treatment plants and other easily identified points.

The federal government is now interested in storm water because gas, oil, road salt, lawn chemicals and garbage that wash from roads, driveways and lawns may be polluting waterways, Miller said.

Governments ordered to comply with the new regulations must obtain a state permit to discharge storm water into natural water systems, Miller said.

To obtain a permit, the county and municipalities must submit a notice of intent, Miller said.

Miller said the county has also applied for a waiver so it will not have to regulate and test its storm-water runoff.

Miller said the financial effects on the county have not been calculated in case the waiver isn't granted.

The permits require testing at four places at each runoff site. The tests look for numerous pollutants and bacteria and has varying criteria that must be met, including public education about water-runoff issues.

The county maintains 21 bridges in the areas that are being targeted for regulation, Miller said.

Municipalities in urbanized areas must apply for the permits. That means Sharpsville, Sharon, Hermitage and Farrell are required to seek state permits to discharge storm water, similar to those they already have for sanitary sewer water discharges. The Shenango Valley is considered urbanized because it is attached to Youngstown in a Metropolitan Statistical Area, a Census Bureau distinction.

Wheatland, West Middlesex and Shenango and South Pymatuning townships may apply for waivers that would allow them to duck the regulations.