The boat launch at City Beach in Whitefish will close  Saturday, April 4 to install a trench gate intended to protect water quality and public health.

The trench gate will intercept water coming off boats exiting the lake and  treat the water. The launch will remain closed through April 17 during installation.

When watercraft exit the lake, it’s common for the boats to drain on the boat ramp. The drain water currently flows directly into the lake.

The project is in response to a study conducted by the Whitefish Lake Institute that showed elevated levels of gasoline in the water between the boat ramp and the public swimming area.

Mike Koopal, executive director of the institute said the study found high concentrations of BTEX or benzene, toluene, ethyl-benzene and xylene at the location.

“We know that BTEX can cause a myriad of health issues and we want to keep the water clean for the kids swimming at City Beach,” Koopal said. “Boaters are pulling their transom plugs to drain their boats and petroleum products are draining directly to the lake with bilge water.”

An added benefit is that the trench gate will intercept water from boaters with ballast tanks that sometimes drain their tanks prior to launching. These boats have a potential for housing aquatic invasive species and transfer them to the lake, Koopal noted.

Maria Butts, city parks and recreation director, said the construction timeframe is designed to have minimal impact on the 2015 boating season.

“Now all people need to do is drive over the trench gate before they pull their transom plug,” she said. “There will be education signs, but boaters will not be inconvenienced.”