The Environment Agency said in one incident an underground pipeline at the company’s clay production plant near Goonamarris failed on 15 September 2021.
Clay was released on the surrounding land and also entered the Gwindra Stream, which flows into the River Fal.
It said Imerys estimated that an equivalent weight of clay lost was 87.8 dry tonnes.
Officials added that an investigation found that the pipe fracture was likely caused by damage from machinery and subsequent sampling suggested impacts were still present two months after the incident.
It said a second clay discharge took place at the stream in December 2022.
Other incidents included the failure of a buried pipeline joint causing a clay discharge into a stream, and a leaking joint at its Maclarens tank site caused clay to flow into the River Fal, the agency added.