Grindley worked at the New Zealand Geological Survey. He spent time on the West Coast, where he assisted Harold Wellman, and also worked on the displacement of the Alpine Fault. After working in south Wales and Canada for a year in the early 1950s, Grindley worked on the geological mapping of New Zealand, and was site geologist at Wairakei. He also worked on geothermal power projects overseas, including in Mexico and the Philippines. He was also involved in geothermal monitoring of Mount Ruapehu and the monitoring of rifting in the Taupo Volcanic Zone.