TransAlta operates the Keephills powerplant in Alberta. KAL stores fly and bottom ash previously produced at the plant between 1980-2021. KAL is impounded by eight zoned-earthfill dykes constructed in 1981/1982 and raised several times between 1990-2008, with portions on soft Lacustrine clay, to a maximum height between 11 m and 17 m and 3H:1V slopes with toe berms. The last two dyke raises were conducted using upstream and downstreamraise methods for the six ash-impounding and two water-impounding dykes, respectively. Foundation failures occurred during construction at Dyke 7 in 1981 and Dyke 6 in 2008. After 2008, toe berms were constructed to achieve a FOS of 1.3 and a performance monitoring program (SIs and piezometers) was initiated. TransAlta also started to place ash above crest elevation at several dykes. By late 2018, ash water levels were above dyke crest elevations and water levels used in toe berm design. Foundation movement rates varied with a maximum of 0.1 mm/day. In spring 2019, the downstream slope of Dyke 7 deformed and cracked. A toe berm was constructed to maintain safe containment. During construction, short-term SI movements up to 0.3 mm/day were triggered along the 1981 foundation failure plane. Stabilization efforts started after the 2019 failure focused on ditching and ash water-level drawdown. Between 2021-2025, ash water levels were lowered below the first upstream dyke raise and SI movements varied between 0.001-0.01 mm/day. By late 2024, FOS varied from 1.3 to over 1.5 for both shallow-fill and deep-downstream foundation dyke failures.