Purity: Wudu in Shrine Courtyards Built on Graveyards
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 274:
If a pool or a stream is built in the courtyard of the shrine (ḥaram) of one of the Infallible Imams (ʿA) or one of the children of the Infallible Imams (ʿA), and that courtyard had previously been a graveyard, in the event that one does not know that the ground of the courtyard was a charitable endowment for the graveyard, there is no problem in performing wuḍūʾ with the water from that pool or stream.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)