A wealthy Wall Street executive and his wife are facing a fine of as much as $157,500 for filling 1.5 acres of wetland when expanding the airstrip at their sprawling estate on the western shore of Moosehead Lake.

Robert Greenhill, former president of Morgan Stanley and former chairman and CEO of Smith Barney, and his wife Gayle Greenhill own more than 3,200 acres of land on the western shore of the lake. Their vacation home, which was built under a climate-controlled dome, is one of the more elaborate examples of so-called kingdom estates getting carved out the commercial forest of northern Maine.

The U.S. Environmental Protection Agency said in a news release issued today that the couple filled wetlands while expanding an airstrip for their private jet and digging a rock quarry sometime between 2001 and 2005. The damage is a violation of the federal Clean Water Act and wetland protection rules, EPA says.

The couple also got in trouble with federal regulators in 1997 when they created a trout pond on the property and disturbed about a half-acre of wetland without first seeking a Clean Water Act permit.

Wetlands serve as wildlife habitat, groundwater discharge and recharge areas, sediment and toxin removal and flood water storage. The wetlands disturbed by the Greenhills were part of larger forested complex and adjacent to two tributaries that flow into Moosehead Lake, according to the EPA.

The Greenhills are already restoring about one acre of the filled wetlands, and are creating new wetlands on another half acre, the agency said.

The final size of the fine has yet to be decided. But it may not hurt as much as the last mishap that got Robert Greenhill into the news.

Greenhill’s 604-horsepower Porsche Carrera GT – a rare auto with a $440,000 sticker price – was crumpled last November in New York City, according to this New York Post article.

Greenhill had taken the car in for some work, and the owner of an auto body shop was driving it when he swerved to avoid a truck, lost control and wrapped the silver sports car around a telephone poll. Not a pretty picture.