In January 1986, Chevron Resources and Yankee-Caithness began exploratory drilling of geothermal wells in the Steamboat Hills, about 2km southwest of the Main Terrace [BLM 1987]. Until May 1986, one of these wells, designated 28-32, was observed to be venting steam under considerable pressure. At times, the noise from this well could be heard on the Main Terrace, despite the distance. The effect of this activity on the thermal activity was devastating. Nearly every flowing spring ceased, and most non-flowing springs dropped anywhere from a few centimeters to over two meters. The springs that seemed to be least affected were #8 and #10.
After this venting ended, some springs immediately began to recover. By early September 1986, no specific effects could be found. That autumn saw the reactivation of #40 and #23n after several years of dormancy. The flowing springs (e.g. #2, #23, #19n, #34) reestablished their algae mats.