A duck-killing parasite is leading the National Park Service to drain and clean the Lincoln Memorial Reflecting Pool on the National Mall in Washington, D.C.

Crews plan to start draining the pool on Sunday and begin cleaning it on Tuesday. By June 19, the pool should be full again.

In late May, approximately 80 ducklings were found dead in the Reflecting Pool. Wildlife biologists with the U.S. Geological Survey’s National Wildlife Health Center believe the cause of death was high levels of parasites that develop and grow in snails that live in the pool, a Park Service release said. Chemical treatments alone are not sufficient to reduce the parasite and snail population, so the pool must be drained and cleaned.

Humans who come into contact with the parasite could develop “swimmer’s itch” (cercarial dermatitis), an allergic reaction in the form of a skin rash; it is not contagious and rarely requires medical treatment. The risk of contracting it at the Lincoln Memorial Reflecting Pool is extremely low, as it is only contracted by sustained contact with affected water, such as swimming or wading, the Park Service said.

It will take approximately two days for the Reflecting Pool to fully drain. Crews are to begin cleaning the pool bottom on Tuesday, utilizing skid steers, pumper and water trucks, and a sprayer. The cleaning should be complete in time for refilling to begin on Friday, June 16. After the cleaning and treatment are complete, the Park Service will continue to monitor the water quality of the pool.