SACRAMENTO, Calif. -- Two environmental groups sued Lake Tahoe regulators Friday over rules allowing new pier construction and other shoreline development.

The suit filed in U.S. District Court in Sacramento alleges that the Tahoe Regional Planning Agency violated environmental laws when its governing board approved a new development plan last month.

The plan will allow up to 138 new piers around the lake, 1,862 buoys, 6 new boat ramps and 235 boat slips -- reversing a more than two-decade-old moratorium on most new pier construction.

"Those structures will introduce more motorized boating on the lake and that will result in more pollution in the lake," said Wendy Park, an attorney at Earthjustice. "Lake Tahoe is a national treasure and (the agency) is under obligation to protect the lake from environmental harm."

Earthjustice sued on behalf of the League to Save Lake Tahoe and the Sierra Club. They say the agency failed to evaluate the impacts of additional boats on the lake.

Agency spokesman Dennis Oliver said the agency lawyers were reviewing the lawsuit and could not immediately comment.

The Tahoe Regional Planning Agency, which is charged with improving the clarity of Lake Tahoe, has spent the past 20 years trying to craft shoreline rules governing development.

When regulators approved the rules at their Oct. 22 meeting, they said their plan wouldn't impede efforts to clean up Lake Tahoe. However, several members said they expected lawsuits.

The plan calls for the agency to adopt a "blue boating" program to address boat pollution and invasive species transported by pleasure boats. That program is expected to go before the board in March.

Environmental groups say the agency violated environmental laws by approving a development plan without first evaluating how it will offset additional boat pollution. Boat exhaust spews carbon monoxide, nitrogen oxides, particulate matter and other pollutants blamed for contributing to clouding Lake Tahoe and dirty air.

In 1968, the lake was clear to an average depth of 102.4 feet. Scientists say the waters of Lake Tahoe were clear to an average depth of 70.2 feet in 2007.