Field Trip to Nevada Test Site

Home , Pahute Mesa, Yucca Flat

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* FIELD TRIP TO NEVADA TEST SITE

This field guide has been prepared for use during the trip from

Las Vegas to the Nevada Test Site and the tour of the NTS. A brief

discussion of major geologic structures between Las Vegas and Mercury

is followed by a general discussion of the geology and hydrology of

NTS. The remainder of the field guide covers geologic and hydrologic

features of interest at the NTS.

Most of the brief writeups are synthesized from selected published t 'Ip reports, administrative reports and from other unpublished data. 1 I'

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Las Vegas to Mercury

The Las Vegas Valley shear zone is expressed topographically by * -- the trough which extends parallel to U.S. Highway 95 from Las Vegas to Mercury, Nevada, a distance of about 55 miles. The amount and

a direction of movement along this shear zone is estimated from

S.-. * structural and stratigraphic evidence to be on the order of 15 to

40 miles; the movement is right lateral. The evidence for the

movement is based upon the sharp bending of fold axes, traces of thrust faults, topographic trends, and facies boundaries in the

vicinity of the shear zone. Most of the displacement on the Las

Vegas shear zone may be taken up by structural bending in the Specter Range area at the north end of the shear zone. The move-

ment may have taken place as early as the Jurassic and have been completed by early or middle Miocene time. Major ranges north and northeast of the Las Vegas Valley shear zone are the Las Vegas Range, Sheep Range, Desert Range, Pintwater .: Range and Spotted Range. These ranges trend in a north-south

direction, and in the vicinity of the shear zone bend sharply to

the southwest. The Spring Mountains and Specter Range, southwest

of the shear zone, strike to the northwest. The major ranges north and northeast of the shear zone consist of the typical thick miogeosynclinal section of eastern Nevada, whereas ridges on the southwest of the shear zone consist of a much thinner section containing several different facies.

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tfbd taTP Of SOuthmbtOI Nevada study area an~dthe Nevada Ttst Site I ] Volcanic Rocks. UPaleozoic Rocks `&-T-1hrust Pault .=-Las Vegas Shear toni I l. " : I ** *~- ~ - . ;e 114AMfiik& r- 2 ' * "';N. Mik- .I I

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'30~~. PI11, Nevada Test Site

The Nevada Test Site is the principal testing area for nuclear explosions. Since its inception in 1951 through 1969 there were

375 announced nuclear tests. Of these, 84 were in the atmosphere and 291 were underground. All but four of the atmospheric detonations

occurred prior to the 1958 moratorium. Since 1962, the United States has conducted all of its nuclear detonations underground. The NTS

encompasses 1,350 square miles in the southern part of the Basin

and Range province about 70 miles northwest of Las Vegas. It is in a belt of late Mesozoic thrust faults along the eastern side of the Cordilleran miogeosyncline. The eastern part of the Test Site area

is characterized by the parallel Cenozoic topographic and structural

elements generally associated with the Basin and Range province. The western part of the area was the locus of intense late Miocene

and early Pliocene volcanism whose topographic and structural effects in part mask the more typical Basin and Range geologic features. The Quaternary basin-filling deposits and some of the Tertiary volcanic rocks of Yucca Flat and nearby areas are the principal media used for underground testing. Most nuclear detonations are made at Yucca Flat in the volcanic tuff that Hi , the carbonate aquifer. Ground water in the tuff

beneath Yucca Flat is semi-perched and is slowly draining into the carbonate aquifer. The movement of ground water in the tuff is

4 controlled by interstitial permeability. The ground water velocity

through the tuff aquitard is less than 1 foot per year. The maximum I161

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t A Water-level contours Nevada Test Site and vicinity. vertical velocity, based on a permeability of 0.005 gallons per day

per square foot and an effective porosity of 30 percent, is 2 x 10~

feet per year. The permeability and porosity values were obtained

from laboratory analyses of cores of zeolitized tuff. A carbon-14 date of water from the valley-fill aquifer in Frenchman Flat suggests

that the age of the ground water in the tuff is probably in the range

of several tens of thousands of years. The quantity of water moving through the lower carbonate aquifer

beneath Yucca Flat probably is less than 350 acre-feet per year. ._k

.A- N. Estimated velocity ranges from 7.3 to 730 feet per year. Carbon-14

analyses of water from the carbonate aquifer beneath Yucca Flat indicate that the lower velocity is more accurate. Within the

Nevada Test Site, water moves south and southwestward in the carbonate

aquifer beneath Yucca and Frenchman Flats, through Mercury Valley, to discharge areas in east-central Amargosa Desert. The hydraulic

gradient varies from 0.3 to 5.9 feet per mile. Interbasin movement through the carbonate rocks is significantly controlled by geologic PZ-. ~structure. In the vicinity of major structures, the lower carbonate * 1 1$ ~~aquifer is compartmentalized either through its juxtaposition against

riEthelower or upper Paleozoic clastic aquitards along major normal

or thrust faults, by the occurrence of the lower clastic aquitard in

structurally high position along major anticlines or by gouge developed

along major strike-slip faults. The water levels in the lower carbonate

S -- oaquifer on opposite sides of such structures differ as much as 500 feet

in a single valley and as much as 2,000 feet between valleys, although -I

-~~~~ ,~~~~~ ~1971 (Datium la BO bovel) Contour na p of Tertiary water kvels Yucc Faot, Nevada Test Site the hydraulic gradient within each aquifer compartment or block is only a few feet per mile.. Ground water studies on and near NTS show that major faults, such as Yucca Fault, the Las Vegas shear

zone south of NTS, and a major fault near the western boundary of

NTS at Pahute Mesa, commonly are barriers rather than conduits, for normal ground water flow. If one applies the unlikely assumption

that the maximum flow rate exists over the whole region, at least 145 years will pass before ground water which may contain tritium

could move offsite. Considering that most explosions occur in the volcanic tuff section, that tritium must first percolate downward through the tuff aquitard to enter the carbonate aquifer, and that 4;'' the lower velocity in the carbonate aquifer appears to be more valid, the most probable time required for this water to leave government-

controlled lands is thousands of years. Ground water beneath Pahute Mesa, in the northwestern part of NTS, moves generally southward toward the Amargosa Desert through Oasis Valley, Crater Flat, and western Jackass Flats. The quantity of water moving beneath Pahute Mesa is estimated at 8,000 acre-feet

per year. The magnitude of effective fracture porosity in the

heterogeneous volcanic rocks is difficult to estimate. Hence, velocities were computed using effective porosities ranging from 0.5 to 20 percent. The estimated velocities beneath the mesa range

from 7 to 250 feet per year. Low permeability blocks between fractures probably result in velocities that vary as much as 2 or 3 orders of

magnitude over short distances. A median velocity of 10 percent porosity probably is the most acceptable value, assuming that the most ground water movement occurs along interconnected fractures and some through interstices. Computations using this value of

porosity would yield velocities of approximately 15 feet per year.

For detonations of larger yields at Pahute Mesa, some water could travel to the boundary of NTS in about 20 years if a maximum

rate of travel is assumed everywhere. However, it would require a century or more before the ground water could move off the contiguous

government-controlled land of the Nellis Air Force Range. At the

more probable ground water velocities for the area, no water from

-Pahute Mesa tests could leave government-controlled land for thousands of years.

A continuous program of spring and well water sampling comprising about 100 water use points off the NTS has detected no radioactivity

I. in above background concentrations. The present water supply for all

uses at the ETS is provided by several wells, which are monitored . continuously. The closest well is 1,600 feet from the nearest under-

ground test location.

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Weftff-IIY eoldm afti tte l11IIof tb* hyra.IIO barrier at Pihe. Oh"u, !, .. %. ~. I "a"s Tedt i".. Frenchman Flat

Several air-burst tests were conducted in the area prior to

the moratorium on nuclear testing in 1958. The north end of the

valley is now being developed as a test area for underground

explosions. The valley is underlain by playa deposits and alluvium,

probably about 5,000 feet deep in the center of the basin. Tertiary

volcanic deposits are thick in the northern part of the valley,

V4 which marked the edge of the Tertiary volcanic basin, and are

virtually absent on the south side.

The Ranger Mountains on the east are composed of Ordovician

limestone, quartzite and dolomites. Low hills west of Frenchman

Flat are composed of volcanic rocks.

Water supply for Mercury is obtained from Army Well 1--located 6e>

on Highway 95 east of the junction to Jackass Flats--and from Wells

Water from Army Well 1 is pumped 4W. 5A, 5B, and 5C at Frenchman Flat. from Paleozoic carbonate aquifers; water from the wells in Frenchman

Flat is obtained from valley fill and volcanic rocks. Water from

wells in Frenchman Flat is of the sodium potassium bicarbonate type;

calcium magnesium bicarbonate water is obtained from the Paleozoic

carbonate aquifers in Army Well 1.

The altitude of land surface at Well 5B is 3,092 feet; static

water level is at a depth of 683 feet below land surface. The specific

capacity of the well, while pumping at a rate of 260 gpm, is about

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; ~~~3.5 gpm per ft. The well is cased to total depth of 900 feet with

12-inch OD casing from 0-460 feet and 10-inch OD casing from 460 feet - ~~to the total depth of 900 feet. The casing is perforated from

'* ~~700-900 feet. Water from the three wells in Frenchman Flat is

.> ~~lifted 700 feet vertically over Checkpoint Pass to Mercury via a If ~~system of pumping stations.

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The campsite west of the Mercury highway is the control point for all tests in Yucca and Frenchman Flats. The elevation of Yucca

Pass is 4,065+ feet. The hills west of the pass consist of Cambrian dolomite and limestone; east of the pass is the C. P. Hogback made of welded ash-flow tuff and vitric nonwelded tuff.

Yucca Flat

This area has been used extensively by the Los Alamos Scientific

Laboratory and the Lawrence Radiation Laboratory for underground testing of nuclear devices.

Mine Mountain, west of the Flat,consists of ridges of Ordovician quartzites and carbonates, and Devonian carbonates. Other Paleozoic rocks are exposed in this area which is complicated by major thrust faulting. Hills and ridges east of Yucca Flat consist of Paleozic carbonates and quartzites and Tertiary volcanics. The maximum thickness of alluvium and volcanic tuff overlying Paleozoic rocks is about 5,000 feet.

Major supply wells for CP-1 and area 3 compound, north of CP-1, are located in the southern part of Yucca Flat. Wells C and C-1, at the south end of Yucca Lake, were drilled to depths of 1,620 and

1,650 feet. Water is produced from the Paleozoic carbonate aquifer; specific capacity of Well C while pumping at a rate of 212 gpm is in excess of 200 gpm per ft. Elevation of the well is 3,921 and depth to water below land surface is 1,541 feet. ' 1, .. I I ..-. 1. .. -f - . .. I., #I., , , , . -.I . . '. ... , , . , ; ., - , ,, ,, -- , , . 'j, : I - " , - ;. 1 ,- , k '- , '., , . 17.7N ..1, I '.4. , .,o,- .. I . - , -, , :,, .4 - ..., - ; --, -- -, - - #I . 111 "I .. . I . I . I . 1 4 , . ., 11I :, '.. . I . , -, . ,1;4 , ,- . % , . - I .": V , . - .. .. I %, . .1

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"Bilbv Site

The Bilby event was a nuclear detonation in September 1963,

in the U3cn emplacement hole, Area 3, Yucca Flat, Nevada Test Site.

The working point was 2,340 feet below land surface in volcanic

tuff. The reported yield was approximately 200 kilotons. The sink

resulted from collapse of the land surface over the site of the

explosion; it is about 1,800 feet in diameter and 80 feet deep.

.- Water levels in wells surrounding the emplacement hole rose

sharply within seconds after the detonation. The water level in

the rubble chimney was later found to be depressed.

Hydrologic data collected during the Bilby event indicated

rapid transmission of hydraulic pressure not only in the detonating

medium, but also in the underlying Paleozoic carbonate rocks. This

rapid transmission of hydraulic pressure and the suspected proximity

of the working point to the carbonate basement rocks suggested the

possibility of nuclear contamination of the Paleozoic aquifer.

The Bilby offset well U3cn-5, located about 400 feet from

ground zero, was a multipurpose hole drilled to determine: 1) the

depth of Paleozoic rocks at the Bilby site; 2) the possibility of injection

of radionuclides from the dynamic phase of the event into the Paleozoic

rocks beneath the site; 3) the distribution and the amount of radio-

nuclides in the tuff and the alluvial deposits; 4) the permeability

of the tuff in the zone surrounding the rubble chimney; 5) the lithology

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If and the fracture pattern, particularly those fractures resulting from the event; 6) the extent of the alluvial disturbance below the depression floor; and 7) the possibility of hydraulic coupling between the tuff and the Paleozoic aquifers by measuring the radioactivity of the water in the Paleozoic aquifers by extended pumping of U3cn-5 after the water level returned to a higher level in the tuffs than the Paleozoics. The well was drilled to a total depth of 3,026 feet and cased in stages to a depth of 2,832 feet. The lower 194 feet, Paleozoic dolomite and orthoquartzite, is uncased; water level is 1,625 feet below land surface. Borehole geophysical logs and core samples indicated that the radiation at a depth between 2,200 to 2,335 feet was above background level. Examination of the cores in this interval revealed the occurrence of radionuclides in pre-existing joints. There was no indication that the Bilby event created new fractures in this radioactive interval. The well was pumped on a nearly continuous basis for 2k years beginning on March 6, 1967 and ending September 22, 1969. During this period, numerous drawdown tests and some recovery tests were made.

Water samples were collected daily with an automatic sampling device; recorders were used to measure temperature and conductivity. No contamination of water in the Paleozoics was found during the pumping.

Intermittent pumping of the hole will be continued for an indefinite period. (- " :.' AC, ::,_ , %%- _ " - C V.", , '5 C-_'_ 'A'-,.-k - a , 01_ a 0, C A -k 9 -;'

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Pore pressure response to the Bilby event, Sept., 1963. Sedan Crater

The Sedan event was a nuclear cratering experiment in July /

1962 in the alluvium of north Yucca Flat. The device was detonated at a depth of 635 feet below land surface in a drill hole that penetrated 730 feet of alluvium. The explosion produced a crater approximately 1,216 feet in diameter and 323 feet deep. Ejected material fell within a radius of 3,700 to 5,800 feet from ground zero. Yucca Fault which may be seen west of the Sedan crater extends the length of Yucca Valley--some 20 miles. The fault probably dips

steeply to the east and the east side is downthrown. Vertical displacement of the alluvium in Yucca Flat during Holocene time is estimated to be as much as 100 feet. As the result of contained nuclear explosions in Yucca Valley, openings with horizontal as well as vertical displacement have occurred along Yucca Fault.

Some of the openings were as wide as 0.25 foot vertically and

0.10 foot horizontally. - -°U ?A Vv-"OuM

Area 12 Camp (_4 -Aok A

Area 12 camp contains housing facilities and basic services to sustain the tunnel mining operations that are centered principally in the Rainier Mesa area. 4n

e- -c S _ C.A)C.° The Stockade Wash Road, from Area 12 to Pahute Mesa crosses

the Eleana Range which consists of quartzites and argillites of

Carboniferous age; Paleozoic carbonates are in fault contact with

*.gF the Eleana Formation west of the road. Southwest of the outcrops 4 r. of Paleozoic age, the road traverses ash-fall and ash-flow volcanic

4.... rocks of Tertiary age to Pahute Mesa. V.

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GENERALIZED SUBSURFACE GEOLOGY OF PAHUTE MESA AND VICINITY

HORIZONTAL SCALE:r APPROXIMATELYI MILES VERTICAL ICALE: 1' APPROXIMATELY 5000 FEET

HOLMES I*ARVER INC. AMPTYD FROM U.S WOLBICAL UvaVEK NIUFLCATPOMUloAND ooAsLE NAPS by KIa YLE

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S.. Pabute Mesa * V i 4 A deep structural depression, the Silent Canyon caldera,

underlies the eastern part of Pahute Mesa. The caldera is elliptical

I in plan and measures about 11 by 14 miles; the greater axis trernd *D. in a north-northeast direction. Exploratory drilling revealed a

Tertiary volcanic section of ash-flowr and ash-fall tuffs anal rhyolitic

4 lava floss which attained thicknesses in excess of 13,686 feet. if Hydraulic tests unde in deep drill holes indicated that these volcanic

rocks were capable of transmitting water, and that measureable

t permeability occurred at depths greater than 3,500 feet below the

top of the saturated zone.

i. - Most movement of ground water beneath the mesa occurs through

interconnecting fault and joint systems. Fractures are more colrion .4 in rhyolitic lava flows and in densely welded ash-flowu tuffs, and

C. these fractures have a greater tendency to remain open than do those

in ash-fall and nonwelded ash-flow tuffs. The yield of water to wells

from intervals of ash-fall and nonwelded ash-flow tuffs, particularly

those that are zeolitized or argillized, is low. Hence, these rocks

are considered the best media for mining of underground chambers in A the saturated zone.

In the Silent Canyon caldera depth to water ranges from about

1,952 feet (altitude 4,164 feet) in the western part to 2,350 feet

) (altitude 4,685 feet) in the eastern part. In the extreme northwestern

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part of the ITCVr'Oc T(~jt Site, outside the caldera, the depth to

water is aboutd -50 feet (altitude 4',700 fedt). Stable and decliniug

hercl poteati.aif. oightw: in all. but onc of the hol~es drilled in the

eaIstoz2Ji pz!rt7 O. ibI: r~eLarea; variable bea-ds with increasing heads

*1 to totkal drillnd dcpth occur in holes drilled in the w~estern part.

JTraitmissi. vitics, based on pumping tests, range fromt 1,400 to more 4- tban 100,000 gallons per dlay par foot. The greatest transmissivities 4- occur in holes drille d along the eastern margin -of the caldera. where

the' prin~cipal rockr type in the saturated zone is rbyolite. Wate-r

derived froim drill, holes t at Pahute Mesa is-sodium potassium type. The-sc chaniical constituents comprised in excess of 90 percent of

the total cations in more than half the sample-s that were analyzed.

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I 550.000 g 550,000 - I 570.000 a *60.000 a s0ooo F 6S0. EXPLANATION I1630 k 6o.6-O I 14415 1 zE

s- as -I NOCK TYPES WITH RESISTIVITIES I 2 LESS THAN 2tS OHMS -U PER U OR Ie- PICH NORMAL CURVE OF I I- ELECTRIC LO'.

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ROCK TYPES WITH RESITIVITIES N 550,000 I 1I~:I__ I .. - -REATER THAN 22l OHMS- U2 PER M ON 15S-INCH NORMAL CURVE OF ELECTRIC LOS

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SECORDARY PAVED ROAD

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a 610.000 a 550*O00 NEVADA STATE COORDINATES

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NEVADA TEaT SITE DOUNDARY

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RESISTNITY OF ROCKS IN UPPER 2000 FEET OF SATURATED ZONE - PAHUTE MESA. . . 4 1-- - COA - , -,t -

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Head changes with depth in exploratory test holes, Pohule Mesa, Nevada Test Site .

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Water chemistry map, Pohute Mesa, Nevada Test Site. a i , I'..

4) -4o I2 1 1 If 1 0.00 - .02 4J4 *-I -, % .1 -4 P~d 0.03 - .U4)- - rT_ 11, M .3 *1 4 0.05 - .09

'CO N-4 Ze litized edde tuf "4 0.10 -

C'. 9 ~4 0 5 10 15 20 25 30 35 40 45 50 Number of tests

%4 a. 0.00 - .02 & & & 2 s £ A1.a0 t -4. -4 0.03 - .04 A 1, V co I 0.05 - .09 Weddd tu f - S.

V4 0.10 - .5 …- as C:

0 5 10 15 20 25 30 35 40 45 50 Number of tests

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-4 1.4. 0.03 - U .314 0.05 - .09 twuusa& & I v.. I I I I r.-. 4 .. -r. * -rn, -4 0.10 - .5 * 6) RI~yol ite, riyolii~teI Jzeccil. an4 vi tiroph~re~~~~~~IJ 0 5 10 15 20 25 30 35 40 45 50

'S. * Number of tests 14

1 C..-9 Figure T.--Relative specific capacity (150-to 200-foot intervals) of the major rock . types wiwthin the saturated zone, Pahute Mesa, Nevada Test Site. - U.9b K - bet±LSinLk*

An intermediate yield undergroiind nuclear explosion at the U19b

site, Pahute Mesa, Nevada Tebt Site, produced widespread fractures and

hV *~a shallow sink. Most of the fractures within a 2,000-foot radius of

ground zero are closely spaced and reflect a polygonal preexplosion

- : joint pattern in the underlying volcanic rocks. Farther from ground

zero, particularly to the west, linear fracture zones trend north-

northeast to nofth and lie along or parallel to preexplosion faults

>; : in the area. Many fracture zoned have vertical displacement across

them. The largest displacement, 2 feet, east side relatively down, occurs

along a zone 1,800 feet north-northwest of ground zero. A few trees

-were felled otut to a distance of at least 3,300 feet from ground zero.

Elevation at the U19b site is approximately 6,800 feet. The

1' static water level in the emplacement hole was 2,117 feet, and the

test device was emplaced at a depth of 2,874 feet.

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.t.... t.s Cecologic effects ,rroduced 'A-vundergrounid explosion at the lrl9b site 4 -;

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. . I .9' U20g (Greeley) Sink

The Greeley event with a device of intern2diate yield was

detonated Deceimber 20, 1966, in the U20g drill hole at PFthute Mesa.

The nuclear device, detonated at a depth of 3,990 feet below land

,V surface caused fracturing in rocks and spalling of rock from cliffs

as far as 4 3.5 and 8 miles, respectively, frorn the detonation point.

Most of the fractures that developed beyond a radius of 2,500 feet

from ground zero were controlled by north-trending preexplosion natural S. fractures. Access to within 2,000 feet of ground zero was riot permitted i after the explosion because of occasional seismic. activity-be low ground zero, which was indicative of possible cavity collapse. The collapse

sink was first reported about 9 months after the event.

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ta Buckboard Mesa

Buckboard Mesa near the head of Fortymile Canyon is capped by a 4z. Quaternary flog of basalt underlain by a sequence of alluvium and 5. welded and nomi elded tuffs. The basalt varies in thickness from

50 to more than 200 feet; the source of the flow was apparcntly a

* small volcanic cone near the north end of the mesa. A Thirteen high explosive (1,000 - 40,000 lbs) cratering experiments

were conducted by the Sandia Corporation on Buckboard Mesa. The water

'5$ level beneath the. mesa. is about 775 feet below land surface. * t. .p.

q. Timber Mountain Caldera

1. I Timber Mountain caldera is the largest, and is topographically

the best expressed, of the calderas now known in the southwestern

I f Nevada volcanic field. The caldera, which is about 20 miles in

diameter, is defined by a wall and rim that are preserved around / nearly 2700 of its circumference; a ring-fracture zone, and a central

'S structural dome. The caldera was formed during or immediately after

eruption of most of the Rainier Mesa Member of the Timber Mountain Tuff.

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10 0 20 MILES 1t I I I I I 4 I *5 - Figure 3.- Index map of the Timber Mountain caldera complex and adjacent region, showing the location of major volcanic centers

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OBJECTIVES OF HYDRAULIC TESTING AT AEC TEST SITES 1958-1971

YEARS PRIMARY CONSIDERATIONS DATA REQUIRED

1958-1963 SAFETY--Transport of radionuclides Study of regional ground-water (Nevada Test Site off test sites--contamination. systems--recharge/discharge areas, and adjacent areas) ENGINEERING SUPPORT--Depth to velocities, water quality. water principally in carbonate aquifer and development of water supply.

1963-1971 SAFETY--Rate of rubble chimney As above but with more detail on (All test sites) infill, dispersion and transport of hydraulic conductivities, heads with radionuclides off test sites--con- depth, velocities, storage coefficients, tamination. and water sample analyses of specific ENGINEERING SUPPORT--Selection intervals. of intervals suitable for. mining of chambers at depths greater than 5,000 feet below saturated zone, relation of nuclear explosions to aquifers and short and long term changes in water levels, evaluation of water supply. DEVELOPMENT OF HYDRAULIC TESTING PROCEDURES AT AEC TEST SITES 1958-1971

YEAR(S) METHODS * DATA OBTAINED 1958-1961 Rotary drilling with mud as circula- Heads, transmissivity, water samples (Nevada Test Site ting medium or cable tool drilling. for chemical and radiochemical and adjacent areas) Basic geophysical logs. Bailing and analyses. pumping tests.

1962-1963 Rotary drilling with mud as circula- Heads, transmissivity, water samples (Nevada Test Site ting medium. Basic geophysical for chemical and radiochemical and adjacent areas) logs. Bailing tests, pumping tests, analyses. Heads from pressure data Halliburton drill-stem tests. accurate to +20 feet at depths of 1, 750 feet below land surface. 1963-1967 Rotary drilling with air-mist, water, Heads, water yields of specific (All test sites) detergent--organic foam or mud intervals, estimated transmissivity, often used in unsaturated zone, and cross-flow in borehole, relative in zones of loss of circulation. specific capacity, water samples for Complete suite of geophysical logs. chemical and radiochemical analyses. Pumping tests, radioactive tracer tests, spinner tests, injection and swabbing tests using single or straddle inflatable packers. 1967-1971 As above with some experimental As above, however, more sophisticated (All test sites) work in reverse circulation and interpretive methods permit cal- vacuum drilling methods. culation of transmissivity, storage coefficient and velocity of ground- water movement in selected intervals. a - 'Tr f.

STANDARD SEQUENCE OF HYDRAULIC TESTING

1. Case and cement hole through unsaturated zone with 13-3/8-inch casing. 2. Drill 8-5/8- or 9-5/8-Inch hole to total projected depth if possible using air mist, water, and detergent. 3. Run geophysical logs including electric, caliper, temperature, 3-dimensional velocity, continuous velocity, density, gamma- neutron, epithermal neutron, fluid density, radioactive tracer (static), borehole televiewer.

4. Run pumping test of entire open hole for 12 to 24 hours to determine capacity of well. Measure drawdown and when well stabilizes run temperature log and radioactive tracer log while pumping to determine water yielding zones. Collect water samples and measure recovery. 5. Based on study of geophysical logs determine spacing between inflatable straddle packers and run consecutive series injection and swabbing tests down borehole. Collect water san'ples at end of each swabbing test. w OPDAGN 'AlunlOO GA '041S

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