Phillips Petroleum Co. drilled 8 temperature-gradient drill holes in 1981 in an area of the western Virginia Range about 7 km east of Steamboat Hot Springs (SMU; Sass and others, 1999). The drill holes are centered on an area about 1 km northwest of Castle Peak (GeothermEx, 2004). The holes have a maximum reported temperature of 29.4ºC in wells as deep as 275 m. Location: 39.42ºN, 119.66ºW.