Given the increasing seismic and volcanic activity, Johnston and the other volcanologists working for the USGS in its Vancouver branch prepared to observe any impending eruption. Geologist Don Swanson and others placed reflectors on and around the growing domes, and established the Coldwater I and II observation posts to use laser ranging to measure how the distances to these reflectors changed over time as the domes deformed. Coldwater II, where Johnston died, was located just north of the mountain. To the astonishment of the USGS geologists, the bulge was growing at a rate of 5 to 8 feet (1.5 to 2.4 meters) per day.