Hundred of tonnes of sludge are to be removed from a lake bed in a bid to restore a 19th Century park.
The work at Penllergare Valley Woods, near Swansea, gets under way on Monday.
John Dillwyn Llewelyn, a 19th Century horticulturist and early photographer, developed the woods on his estate.
The work at the Upper Lake will cost £455,190 and is expected to be completed by September. The silt will be reused on pastureland and the lake allowed to refill.
It is part of the Penllergare Trust's project which has seen the lake's waterfall repaired and a lakeside ornamental walkway built.
Project director Philip James said: "The lake project is the centre piece of our programme to restore the character and key features of the romantic landscape created by the Dillwyn Llewelyn family back in the 19th Century."
The sludge removal has been funded by the Heritage Lottery Fund (HLF) and Veolia Environmental Trust.
Located north of Swansea, the woods were once a famous gentry estate and home to philanthropist Llewelyn.
For almost 50 years, according to the HLF, it was "neglected, vandalised and threatened by development".
But the Penllergare Trust was formed in 2000 as an independent charity to restore and regenerate the area.
The trust is supported by volunteers, as well as the Friends of Penllergare, with 180 members.