(CNN) The National Park Service will drain the Lincoln Memorial Reflecting Pool this weekend after approximately 80 ducklings were found dead, including 53 in one day.

The culprit is a parasite that grows in snails that live in the pool, said park service spokesman Mike Litterst.

The federal agency says chemical treatments alone aren't sufficient to fully reduce the parasite and snail population. So the pool must be drained and cleaned.

The cleanup begins Sunday. It will take about two days to fully drain the water. On Tuesday, crews will begin cleaning the interior.

Humans who come in contact with the parasite could develop cercarial dermatitis , better known as "swimmer's itch." It's not contagious and rarely requires medical treatment, but it's uncomfortable.

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