https://www.siliconvalley.com/2022/01/27/cause-of-hayward-power-plant-explosion-determined/

HAYWARD — Last year’s explosion at a power plant that started a fire and sent debris flying hundreds of feet was caused by too much water under pressure and high temperatures, combined with power plant operators not detecting the problem in time, investigators have determined.

The accumulation of water was the result of a gearbox failure that led to a valve not closing as it should, according to a letter from Calpine Corporation of Houston, which operates the site.