Michelle S. Boucher 1994 Water levels have been measured in the Yucca Mountain area, Nevada, since 1981 in order to gain a better understanding of the gound-water flow system in the area. Water level in wells J-11 and J-12 have been periodically measured using calibrated reeled steel tapes since 1989, however, calculation of water-level altitude was not possible prior to 1993 due to missing reference elevations. These elevations were determined in 1993 by the U.S. Geological Survey. During 1989-91, water-level altitudes for well J-11 ranged from 732.09 to 732.40 meters and the mean water-level altitude was 732.19 meters. During 1989-91, water-level altitudes for well J-12 ranged from 727.84 to 728.03 meters, and the mean water-level altitude was 727.95 meters. application/pdf 10.3133/ofr94303 en U.S. Geological Survey : USGS Earth Science Information Center, Open-File Reports Section [distributor], Water levels in wells J-11 and J-12, 1989-91, Yucca Mountain area, Nevada reports