Introduction Drill ing operations Lithologic sampling and well logging Lithology Hydrologic properties of sidewall core samples Geophysical well logs Hydrologic testing and water sampling Drill ing fluid Water levels Pumping tests Radioactive-tracer borehole flow and temperature survey Injection tests Chemical analysis of watei Selected references ILLUSTRATIONS Page Figure 1. Map showing location of test well USW H-4 and nearby geographic features in southern Nevada 2 2. Chart showing generalized vertical distribution of out-ofgage hole 13 3-26. Graphs showing: 3. Drilling-fluid use 20 4. Water-level drawdown versus time for pumping test 2, depth interval from 519 to 1,219 meters-23 5. Water-level drawdown versus time for pumping test 3, depth interval from 519 to 1,219 meters 23 6. Water-level recovery versus time for pumping test 2, depth interval from 519 to 1,219 meters 24 7. Water-level recovery versus time for pumping test 3, depth interval from 519 to 1,219 meters 24 8. Semi logarithmic graph of water-level drawdown versus time for pumping test 6, depth interval from 519 to 1,219 meters-25 9. Logarithmic graph of water-level drawdown versus time for pumping test 6, depth interval from 519 to 1,219 meters 25 10. Water-level recovery versus time for pumping test 6, depth interval from 519 to 1,219 meters 26 11. Borehole-flow and temperature survey for test well USW H-4 showing percent of pumping rate produced for intervals from 555 to 1,219 meters GEOHYDROLOGIC AND DRILL-HOLE DATA FOR TEST WELL USW H-4,

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This report presents data collected to determine the hydraulic characteristics of rocks penetrated in test well UE-25b#l. This well is one of a series of test wells drilled in and near the southwestern part of the Nevada Test Site in a program conducted in cooperation with the U.S. Department of Energy. These investigations are part of the Nevada Nuclear Waste Storage Investigations to identify suitable sites for storage of high-level radioactive wastes. Data on drilling operations, lithology, core analyses, borehole geophysics, hydrologic monitoring, hydraulic testing, and groundwater chemistry for test well UE-25b#l are contained in this report.

The Green River-Moab area encompasses about 7,800 square kilometers or about 25 percent of the Paradox basin. The entire Paradox basin is a part of the Colorado Plateaus that is underlain by a thick sequence of evaporite (salt) beds of Pennsylvanian age. The rock units that underlie the area have been grouped into hydrogeologic units based on their water-transmitting ability. Confining beds consist of evaporite beds of mostly salt, and overlying and underlying thick sequences of rocks with minimal permeability; above and below these confining beds are aquifers. The upper Mesozoic sandstone aquifer, probably is the most permeable hydrogeologic unit of the area and is the subject of this investigation. The principal component of groundwater outflow from this aquifer probably is subsurface flow to regional streams (the Green and Colorado Rivers) and is about 100 million cubic meters per year. All other components of outflow are relatively small. The average annual recharge to the aquifer is about 130 million cubic meters, of which about 20 million cubic meters is from local precipitation. For the lower aquifer, all recharge and discharge probably is by subsurface flow and was not estimated.The aquifers are generally isolated from the evaporite beds by the bounding confining beds; as a result, most ground water has little if any contact with the evaporites. Brines are present in the confining beds, but solution of beds o£ salt probably is very slow in most parts of the area. No brine discharges' have been identified.

Test hole USW UZ-6, located 1. 8 kilometers west of the Nevada Test Site on a major north-trending ridge at Yucca Mountain, was dry drilled in Tertiary tuff to a depth of 575 meters. The area near this site is being considered by the U.S. Department of Energy for potential construction of a high-level, radioactive-waste repository. completed in the unsaturated zone as part of the U.S. Geological Survey's Yucca Mountain Project to characterize the potential repository site. pertaining to borehole drilling and construction, lithology of geologic units penetrated, and laboratory analyses for hydrologic characteristics of samples of drill-bit cuttings are included in this report. Test hole USW UZ-6 is one of seven test holes Data Test hole USW UZ-6 penetrated an estimated 77 percent of the unsaturated zone present at the drilling site. encountered while drilling. selected intervals for determining lithology, water content, and water potential of the geologic units penetrated. No saturated perched water zones were Samples of drill-bit cuttings were collected at The water content in the samples collected is related to the degree of welding of the rock units; densely welded tuff is relatively dry; nonwelded and bedded tuff is relatively moist. Average values of gravimetric water content for the driest zones of the densely welded sections of the Miocene Tiva Canyon Member and the Topopah Spring Member of the Paintbrush Tuff were 0.024 and 0.020 gram per gram, respectively; the average values of water potential were-7,500 and-16,000 kilopascals, respectively. Average values of gravimetric water content for the nonwelded tuff of the Tiva Canyon Member and the bedded tuff unit of the Paintbrush Tuff were 0.107 and 0.121 gram per gram, respectively; average values of water potential were-270 and-74 kilopascals, respectively.