Upload
others
View
1
Download
0
Embed Size (px)
Citation preview
• Surface geophysical methodso Frequency-domain electromagneticso Time-domain electromagneticso Capacitively coupled electromagneticso Direct-current resistivityo Magnetic resonance soundingso Ground-penetrating radarThe geophysical workgroup actively participates and col-
laborates with local, State, national, and international members of the environmental geophysical community. In addition, it regularly contributes to the knowledge base through presenta-tions and publications.
Example Applications of Geophysical TechniquesGeophysical project activities of the TXWSC have steadily
increased over the past 10 years. All projects mentioned below (fig. 1) have a substantial geophysical component. Each of the projects listed was published during 2005–10. This is not a complete list of projects, but it highlights examples of several geophysical techniques and their applications.
U.S. Department of the InteriorU.S. Geological Survey
Fact Sheet 2011–3037 May 2011
Enhancement of USGS Scientific Investigations in Texas by Using Geophysical Techniques, 2005–10
Printed on recycled paper
IntroductionGeophysical techniques are an increasingly important
tool for scientific investigations, environmental planning, and resource management. During 2005–10 the U.S. Geological Survey (USGS) Texas Water Science Center (TXWSC) greatly expanded its capabilities of using surface and borehole geophys-ical techniques to gain insights into how groundwater systems work and the occurrence and distribution of certain contami-nants. Geophysical techniques provide a relatively quick and inexpensive means to characterize the subsurface hydrology and lithology.
Surface and borehole geophysical methods are used to measure the physical properties of the subsurface, such as elec-trical conductivity or resistivity, dielectric permittivity, magnetic permeability, density, and acoustic velocity. Geophysical mea-surements can be influenced by chemical and physical proper-ties of soils, rocks, and pore fluids. Interpretations from these measurements can be used to image the distribution of physical properties in the subsurface. Surface and borehole geophysical methods and their application to groundwater and environmen-tal investigations are described in detail in Zohdy and others (1974), Keys (1990), and U.S. Army Corps of Engineers (1995).
This report describes the technical capabilities and proj-ect activities of the TXWSC geophysical workgroup during 2005–10. After a brief summary of the geophysical workgroup’s capabilities, the details of project activities are described. Proj-ects are grouped by the primary techniques used and include overviews, project images, and Internet links to additional project material and related publications.
Geophysical Workgroup Skills and Capabilities The TXWSC geophysical workgroup consists of geophysi-
cists and hydrologists who specialize in surface and borehole geophysical techniques. The workgroup collaborates with resi-dent natural resource scientists on a diverse range of projects. There is emphasis on technical training to keep skills current with advances in software and technology. The workgroup’s technical capabilities include but are not limited to the following:• Borehole logging techniques
o Natural gammao Electromagnetic inductiono Long and short normal resistivityo Heat pulse and electromagnetic flow metero Neutron densityo Acoustic and optical televiewero Fluid resistivity/conductivityo Full wave sonic
In cooperation with the Barton Springs/Edwards Aquifer Conservation District
Geophysical Delineation of the Freshwater/Saline-Water Transition Zone in the Barton Springs Segment of the Edwards Aquifer, Travis and Hays Counties, Texas, September 2006
SScciieennttiiffiicc IInnvveessttiiggaattiioonnss RReeppoorrtt 22000077––55224444
UU..SS.. DDeeppaarrttmmeenntt ooff tthhee IInntteerriioorrUU..SS.. GGeeoollooggiiccaall SSuurrvveeyy
In cooperation with the Texas Water Development Board
Application of Surface Geophysical Methods, With Emphasis on Magnetic Resonance Soundings, to Characterize the Hydrostratigraphy of the Brazos River Alluvium Aquifer, College Station, Texas, July 2006— A Pilot Study
Scientific Investigations Report 2007–5203
U.S. Department of the Interior U.S. Geological Survey
U.S. Department of the InteriorU.S. Geological Survey
Scientific Investigations Report 2008–5181
In cooperation with the San Antonio Water System
An Integrated Hydrogeologic and Geophysical Investigation to Characterize the Hydrostratigraphy of the Edwards Aquifer in an Area of Northeastern Bexar County, Texas
U.S. Department of the Interior U.S. Geological Survey
Scientific Investigations Report 2007–5143
In cooperation with the U.S. Section, International Boundary and Water Commission
Geophysical Analysis of the Salmon Peak Formation Near Amistad Reservoir Dam, Val Verde County, Texas, and Coahuila, Mexico, March 2006, to Aid in Piezometer Placement
U.S. Department of the InteriorU.S. Geological Survey
Open-File Report 2009–1017
In cooperation with the U.S. Department of Energy/National Nuclear Security Administration and Babcock & Wilcox Technical Services Pantex, LLC
Analysis of Vertical Flow During Ambient and Pumped Conditions in Four Monitoring Wells at the Pantex Plant, Carson County, Texas, July–September 2008
U.S. Department of the InteriorU.S. Geological Survey
Scientific Investigations Report 2010–5122
In cooperation with the San Antonio Water System
Lithologic and Physicochemical Properties and Hydraulics of Flow in and near the Freshwater/Saline-Water Transition Zone, San Antonio Segment of the Edwards Aquifer, South-Central Texas, Based on Water-Level and Borehole Geophysical Log Data, 1999–2007
500
600
700
800
900
1,000
GeorgetownFormation
Pers
on F
orm
atio
nKa
iner
For
mat
ion
Cyclic andmarine
members
Leached andcollapsedmembers
Regionaldense member
Grainstonemember
Kirschbergevaporitemember
Dolomiticmember
Basal nodularmember
Glen RoseLimestone
Figure 1. Map showing the cover page of each report presented in this report. Lines point to approximate location of each study.
Surface Geophysical Techniques
Direct Current Resistivity
Geophysical Analysis of the Salmon Peak Formation near Amistad Reservoir Dam, Val Verde County, Texas, and Coahuila, Mexico, March 2006, to Aid in Piezometer Placement
In 1995 the Mexico Section of the International Boundary and Water Commission (IBWC) completed a study (including surface geophysics, borehole geophysics, and installation of piezometers) of subsurface conditions of the western embankment (Coahuila, Mexico) of Amistad Reservoir Dam. Technical advisors recommended that one line of similarly constructed piezometers be installed on the eastern embankment of the dam for comparison of water levels (potentiometric head) on both the western and eastern embank-ments of the dam. To provide technical assistance for the horizontal and vertical placement of piezometers on the eastern embankment of Amistad Reservoir Dam, the USGS, in coop-eration with the U.S. Section of the IBWC, conducted a study along both the western and eastern embankments of Amistad Reservoir Dam. The study involved an integrated approach using surface and borehole geophysical methods. In the western embankment investigation, geological and geophysical charac-teristics that indicate relatively large water-yielding properties of the Salmon Peak Formation were identified. The direct-current (DC) resistivity method was selected as the surface geophysical reconnaissance technique to correlate relatively large water-yielding properties of the Salmon Peak Formation, identified from analysis of borehole geophysical logs, with variations in subsurface resistivity. The correlation of surface geophysical DC resistivity, historical lithologic data, and general trend of documented sinkholes along the eastern end of the eastern embankment profile was used to justify further exploration (drilling of piezometers). The spatial location of the piezometers and screened intervals were selected to best match the locations of the screened intervals of the western embank-ment piezometers. • USGS Scientific Investigations Report 2007–5143: http://
pubs.usgs.gov/sir/2007/5143/
Capacitively Coupled Resistivity
Two-Dimensional Resistivity Investigation Along West Fork Trinity River, Naval Air Station-Joint Reserve Base Carswell Field, Fort Worth, Texas, October 2004
The USGS, in cooperation with the Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) at Fort Worth, Tex., conducted a 2D resistivity investigation at a site to characterize the
distribution of subsurface resistivity. Contaminants, primar-ily volatile organic compounds and metals, have entered the groundwater flow system through leakage from waste-disposal sites and manufacturing processes. The Goodland Limestone and the underlying Walnut Formation form a confining unit that underlies the alluvial aquifer. The bedrock confining unit is the zone of interest because of the potential for contaminated groundwater to enter the river through saturated bedrock. The study involved a capacitively coupled resistivity survey and inverse modeling to obtain true or actual resistivity from appar-ent resistivity. • USGS Data Series Report 178–06: http://pubs.usgs.gov/
ds/ds178/
Magnetic Resonance Soundings
Application of Surface Geophysical Methods, With Emphasis on Magnetic Resonance Soundings, to Characterize the Hydrostratigraphy of the Brazos River Alluvium Aquifer, College Station, Texas, July 2006—A Pilot Study
The USGS, in cooperation with the Texas Water Development Board, used
surface geophysical methods in a pilot study to characterize the hydrostratigraphic properties of the Brazos River alluvium aqui-fer at the Texas A&M University Brazos River Hydrologic Field Research Site near College Station, Texas, and determine the effectiveness of the methods to aid in generating an improved groundwater-availability model. Three noninvasive surface geophysical methods were used to characterize the electrical stratigraphy and hydraulic properties and to interpret the hydro-stratigraphy of the Brazos River alluvium aquifer. Two methods, time-domain electromagnetic (TDEM) soundings and two-dimensional direct-current (2D–DC) resistivity imaging, were used to define the lateral and vertical extent of the near-surface hydrogeologic zones. Magnetic resonance sounding (MRS), a recently developed geophysical method, was used to derive esti-mates of the hydrologic properties including percentage water content and hydraulic conductivity. Results from the geophysics study demonstrated the usefulness of combined TDEM, 2D–DC resistivity, and MRS methods to reduce the need for additional boreholes in areas with data gaps and to provide more accurate information for groundwater availability models.• USGS Scientific Investigations Report 2007–5203: http://
pubs.usgs.gov/sir/2007/5203/
Time-Domain Electromagnetics
Geophysical Delineation of the Freshwater/Saline-Water Transition Zone in the Barton Springs Segment of the Edwards Aquifer, Travis and Hays Counties, Texas, September 2006
The USGS, in cooperation with the Barton Springs/Edwards Aquifer Conservation District, conducted a pilot geophysical study to use TDEM sound-
Lake Worth
West Fork
Tri nity R iver
and 3 ea
0.5 MILE0 0.25
EXPLANATION
NAS–JRB boundary
Boundary of resistivityinvestigation site
Concentration of TCE, in micrograms per liter
5 to 50
50.1 to 500
500.1 to 1,000
1,000.1 to 5,000
5,000.1 to 15,000
More than 15,000.1
Base map USGS Digital Orthophoto Quarter Quadrangle - 2002 State Plane Coordinate System, North Central Zone, NAD 83
32o46'
97o25'
32o47'
97o24'
MWA2-4MWB2-4MWC3-4
45
50
55
60
65
70
35
40
45
50
55
60
65
70
25
30
35
40
45
50
55
60
65
70
50 100 150 200 250 300 350 400 450 500 550
DISTANCE, IN METERS
BRA09BRA100
BRA110BRA160BRA170
BRA180BRA60
BRA70BRA80
BRA90BRA01
BRA05BRA40
BRA50
DC resistivity profile
MWA2-4MWB2-4
MWC3-4
746,700 746,800 746,900 747,000 747,100 747,200
3,38
2,80
0
3,382,900
EASTING, IN METERS
NO
RTH
ING
, IN
ME
TER
S
BRA05BRA09BRA100
BRA110BRA160
BRA170BRA40
BRA50
BRA60
BRA70
BRA80
BRA90BRA180
BRA01
lessthan 10 20 32 54 89
greaterthan 175
Direct-current resistivity, in ohm-metersClay
Sand and gravel
Water level
Direct-current resistivity profile
Time-domain electromagnetic soundingand identifier
EXPLANATION
Time-domain electromagneticlayered-earth model sounding
BRA170
MWC3-4
Lithology
Monitoring well and identifier Shale
)D()C()B(
ALT
ITU
DE
, IN
ME
TER
S A
BO
VE
NAV
D 8
8
APPROXIMATE LAND SURFACE
500 ft
200
500 ft
240
500 ft
245
500 ft
247
500 ft
250
500 ft
260
ALLT
ITU
DE,
INFE
ETAB
OVE
NG
VD29
A
B
-100
0
100
200
300
400
500
600
700
0 50 100150200250
0 50 100 0 50 0 50 100 0 50 0 50
EXPLANATIONTaylor Group
Austin Group
Eagle Ford Group
Buda Limestone
Del Rio Clay
Georgetown Formation
Edwards Group
Regional dense member TDEM apparent resistivity,in ohm-meters
Edw
ards
aqui
fer
Upp
erco
nfin
ing
unit
TDEM soundingand identifier
1,000 0 1,000 FEET
-100
0
100
200
300
400
500
600
700
Top of Edwards aquifer
Approximate land-surface elevation
ALTI
TUD
E,IN
FEET
ABO
VEN
GVD
29
200
240
245
247
250
260
C6 20 43 66 89 113 145
Resistivity, in ohm-meters
200
0 46 325 641 925 1,202 1,583 2,081
Dissolved solids concentration,in milligrams per liter
200
240245
250260
247
DC resistivity profile
Spring
2
Spring
3
GG15
GG17
200 m
200 m
W EA70E
A70W
A72E
A72W
A74E
A74W
A76E
A76W
A80E
A80W
LA-6
LA-7
LA-8L
LA-10
LA-11
LA-12L
LA-14
LA-15
LA-16L
Profile 1
Profile 2
240
250
260
270
280
290
300
310
320
330
340
DISTANCE, IN METERS
ELE
VA
TIO
N, I
N M
ETE
RS
AB
OV
E N
AV
D 8
8
less than75 166 256
greater than365
RESISTIVITY,IN OHM-METERS
0 100 200 300 400 500 600 700 800 900 1,000 1,100 1,200 1,300 1,400
Base from U.S. Department of Agriculture National Agricultural Imagery Digital Ortho Photo ImageUniversal Transverse Mercator projection, Zone 14North American Datum of 1983
Direct-current resistivity profile
Top of zone of weathered features in limestoneTop of limestoneArgillaceous fossiliferous zone
Section trace line
EXPLANATION
Selected core hole and identifier
Piezometer and identifier—Underlined identifier indicates logged well
Spring and identifier
Sinkhole and identifier
.
A
B
feet or meter
F other3servZM
latitude 29 40 58.4
deltat matrix
44
mud tem
pN
Ares m
ud filtrate
elev kbN
Alog m
eas fromLSD
sys version3.59T
temp gradient
0m
ud resN
A
file type id
township
NA
time circ stopped
NA
eng units or cps E
recorded byTH
OM
AS
field office TWSC - AUSTIN
depth driller320 field
CSSA
rangeN
A
mean surface tem
p
casing typeSTEEL
casing bottom45
tool serial num
deltat fluid
longitude -098 38 18.8
fluid viscosity
SERVICE COMPANY USGS
bit size6.125
01.
tni
elp
mas
gol
Uno
itce
rid
gol
elect cutoff9999
elev perm datum
1179
countyB
EXA
R
truck cal num.599
mud sam
ple sourceN
A
temp m
ud cake
LOC
ATIO
N
casing diameter
10.
drl meas from
NA
permanent datum
LSD
Nam
e Prn AP
UN
IQU
E WELL ID
neutron matrix
DO
LOM
ITE
fluid typeH
2O
fluid ph
company
CSSA
- U.S. G
EOLO
GIC
AL SU
RV
EY
elev dfN
A
stateTX
PRO
VIN
CE
temp m
ud filtrate
file type ORIGINAL
sys serial1
remarks1
AM
BIEN
T
other1servZE
log bottom 328.60
time
12:13:
sectionN
A
density matrix
2.85
logging unit302
remarks2
WL = 156.46
casing thick0 elev gl
1179
log top 2.90
well
I10-4
DA
TE02/17/11
other2servZI
mag declination
0
res mud cake
NA
fluid density
Depth
1ft:120ft
GAM(NAT)
0 150CPS
RES(FL)
0 35OHM-MSP
75 175MV
RES(16N)
1 1000OHM-MRES(64N)
1 1000OHM-M
TEMP
68 73DEG F
LATERAL
1 1000OHM-M
DEL TEMP
-1 1DEG FCALIPER
0 10INCHCCL
60000 63000CPS
IND. Res
1 1000OHM-MAP-COND
0510 MMHO/M
SP COND
300 350US/CMTool.Image-NM
°0°0 180°90° 270°
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
310
320
Depth
1ft:120ft
GAM(NAT)
0 150CPS
RES(FL)
0 35OHM-M
SP
75 175MVRES(16N)
1 1000OHM-M
RES(64N)
1 1000OHM-MTEMP
68 73DEG F
LATERAL
1 1000OHM-MDEL TEMP
-1 1DEG F
CALIPER
0 10INCH
CCL
60000 63000CPS
IND. Res
1 1000OHM-M
AP-COND
0510 MMHO/M
SP COND
300 350US/CM
Tool.Image-NM
°0°0 180°90° 270°
NORTH SOUTH
NNN
27 103 206 308 411 513 616 718 821 923
RESISTIVITY, IN OHM-METERS
EXPLANATION
Time-domain electromagnetic sounding site and identi�er
Site–12
Fault projection (Stein and Ozuna, 1995)
Interpreted fault location fromgeophysical data
Indicates change in location of fault, basedon interpretation of geophysical data
Interpreted karst feature fromgeophysical data
K
Geologic unit (hydrostratigraphic zone) (table 1)Kkd (VII)
Site–12 Site–13
Kkd (VII)
Kkd (VII)
Bat Cave fault(Stein and Ozuna, 1995)
Kkd (VII)
Bat Cave faultinterpreted from
surface geophysics
Kplc (III)
Kplc (III) Kprd (IV)
Bat Cave fault(Stein and Ozuna, 1995)
Bat Cave faultinterpreted from
surface geophysics
KK
ALT
ITU
DE,
IN M
ETER
SA
BOVE
NAV
D 8
8
245255265275285295305315325
CAPACITIVELYCOUPLEDSURVEY
CAPACITIVELYCOUPLEDSURVEY
Site–13
Site–12
LINE
Bat Cave fault(George, 1952; Stein and Ozuna, 1995)
Unnamed fault
Geologic units, hydrostratigraphic zones, and fault locations interpretedfrom geophysical data and hydrogeologic mapping for this report
125 0 125 METERS
Vertical scale greatly exaggerated
Altitude of log datum (ft above NAVDof 1988) 3539.11Casing depth (ft) 613
Log datum LSD
Well name PTX06–1044County Carson
Borehole bit size (in) 7.865Borehole depth (ft) 622
Casing diam. (in) 4
Latitude N35 deg. 19' 44"Date of log 7/25,8/11,9/24/08
Site ID 351944101324201Owner Pantex
State TexasLongitude W101 deg. 32' 42"
Depth ConstructionEMFM Amb Before
-5 5Gal/Min
Neutron
0 50CPS
Natural Gamma
0 150CPS
RES(FL) Amb Before
15 20OHM-MEMFM Pu Before
-5 5Gal/Min
WL Depth Before
0Ft005 54WL Depth After
0Ft005 54Trans. Before
0.5 500Ft^2/D
TEMP Amb. Before
63 73DEG FTEMP Pu Before
63 73DEG F
RES(FL) Pu Before
15 20OHM-MEMFM Amb After
-5 5Gal/MinTrans. After
0.5 500Ft^2/DStatic WL
0 1
EMFM Pu After
-5 5gpm
TEMP Amb After
63 73DEG F
RES(FL) Amb. After
15 20OHM-MRES(FL) Pu After
15 20OHM-M
400
450
500
550
600
473
482
481
481
481
473
9/24/08
34 Lithologic and Physicochemical Properties and Hydraulics of Flow, Freshwater/Saline-Water Transiti on Zone
Estimated �ow less than0.1 gallon per minute (gpm)
1
Corrected �owstation 05/19/2005
Corrected �owstation 06/20/2006
Corrected �owstation 09/14/2006
gpm
gpm
gpm
Zone of in�ow or out�ow
Depth
1 in
ch:1
00 fe
et
Acoustic televiewer
0° 0°180°90° 270°
1000 cps
GAM(NAT)
122 inch
CALIPER
-1
1-1
1-1Corrected �owstation 11/06/2007
gpm 1-1
Stratigraphic unit
24.2 29.2
COND 05/19/2005
TEMP 06/20/2006
TEMP 09/13/2006
23 28
COND 09/13/2006
10000 35000COND 11/06/2007
7000 32000
TEMP 11/06/2007
25 30
deg C
deg C
deg C
deg C
10000 35000µS/cm
µS/cm
µS/cm
Gen
eral
ized
cal
iper
pro
�le
Conductance (COND), inmicrosiemens
per centimeter (µS/cm)Temperature (TEMP), indegrees Celsius (deg C)Natural gamma (GAM(NAT)), in
counts per second (cps)
TEMP 05/19/2005
23.8 28.8µS/cmµS/cm
COND 06/20/2006
10000 35000
23.7 28.7
COND 11/08/2002
deg C25000 50000µS/cm
TEMP 11/08/2002
µS/cmµS/cmµS/cm
600
700
800
900
Note: “Corrected” indicates that EM �owmeter data sets were corrected by zeroing out values measured in intervalswhere no �ow was expected, such as in the casing, and by subtracting those values from �owmeter measurements madein open borehole; this adjustment allowed for more consistent �owmeter data sets and well hydraulic interpretations.
GeorgetownFormation
Pers
on F
orm
atio
nKa
iner
For
mat
ion
Cyclic andmarine members
Leached andcollapsedmembersRegional
dense member
Grainstonemember
Kirschbergevaporitemember
Dolomiticmember
Basal nodularmember
570
575
580
585
590
595
600
JAN
FEB
MA
RA
PRM
AY
JUN
EJU
LYA
UG
SEP
OCT
NO
VD
ECJA
NFE
BM
AR
APR
MA
YJU
NE
JULY
AU
GSE
PO
CTN
OV
DEC
JAN
FEB
MA
RA
PRM
AY
JUN
EJU
LYA
UG
SEP
OCT
NO
VD
EC
700260025002
ALT
ITU
DE,
IN F
EET
ABO
VE N
ORT
H A
MER
ICA
N V
ERTI
CAL
DA
TUM
OF
1988
EXPLANATION
Geophysical data collected May 2005
Geophysical data collected June 2006
Geophysical data collected September 2006
Geophysical data collected November 2007
Daily mean equivalent freshwater head, in feet above North AmericanVertical Datum of 1988.Water-level data providedby the San Antonio WaterSystem
DATE
Figure 8. Daily mean equivalent freshwater head and borehole geophysical data in Kyle 4 well (LR–67–02–105), San Antonio segment of the Edwards aquifer, south-central Texas, 2005–07.
ing to delineate the freshwater/saline-water transition zone of the Edwards aquifer in Travis and Hays Counties, Tex.. There was uncertainty regarding the application of TDEM sounding for this purpose because of the depth of the aquifer (200–500 feet to the top of the aquifer) and the relatively low-resistivity clayey units in the upper confining unit. Twenty-five TDEM soundings were made along four 2- to 3-mile-long profiles in a study area overlying the transition zone. The soundings yielded measurements of subsurface electrical resistivity, the variations in which were correlated with hydrogeologic and stratigraphic units, and then with dissolved-solids concentrations in the aquifer. On the basis of reasonably close matches between the inferred locations of the freshwater/saline-water transition zone from resistivities and from dissolved-solids concentrations in three of the four profiles, TDEM sounding appears to be a suit-able tool for delineating the transition zone.• USGS Scientific Investigations Report 2007–5244: http://
pubs.usgs.gov/sir/2007/5244/
Frequency-Domain Electromagnetic Profiling
An Integrated Hydrogeologic and Geophysical Investigation to Characterize the Hydrostratigraphy of the Edwards Aquifer in an Area of Northeastern Bexar County, Texas
The USGS, in cooperation with the San Antonio Water System, did a hydrogeologic and geophysical investigation to characterize the hydrostratigraphy (hydrostratigraphic zones) and karst features (features such as sinkholes and caves) of the Edwards aquifer in a 6.2-square-mile area undergoing urban development. Existing hydrostrati-graphic information, enhanced by local-scale geologic mapping in the area, and surface geophysics were used to associate ranges of electrical resistivities, obtained from capacitively coupled resistivity surveys, frequency-domain electromagnetic (FDEM) surveys, TDEM soundings, and 2D-DC resistivity surveys, with each of seven hydrostratigraphic zones of the Edwards aquifer. The principal finding of this investigation is the relation between electrical resistivity and the contacts between the hydrostratigraphic zones of the Edwards aquifer and the underlying Trinity aquifer in the area. • USGS Scientific Investigations Report 2008–5181: http://
pubs.usgs.gov/sir/2008/5181/
Borehole Geophysical Techniques
Analysis of Vertical Flow During Ambient and Pumped Conditions in Four Monitoring Wells at the Pantex Plant, Carson County, Texas, July–September 2008
The USGS, in cooperation with B&W Pantex, made a series of flowme-ter measurements and collected other borehole geophysical logs during July–September 2008 to analyze vertical flow
in screened intervals of four selected monitoring wells at the Pantex Plant. Hydraulic properties (transmissivity values) of the section of the High Plains (Ogallala) aquifer penetrated by the wells also were computed. Geophysical data were col-lected under ambient and pumped flow conditions in the four monitoring wells. Unusually large drawdowns occurred at two monitoring wells while the wells were pumped at relatively low rates. A decision was made to redevelop those wells, and logs were run again after redevelopment in the two monitoring wells. • USGS Open-File Report 2009–1017: http://pubs.usgs.
gov/of/2009/1017/
Lithologic and Physicochemical Properties and Hydraulics of Flow in and near the Freshwater/Saline-Water Transition Zone, San Antonio Segment of the Edwards Aquifer, South-Central Texas, Based on Water Level and Borehole Geophysical Log Data, 1999–2007
The freshwater zone of the Edwards aquifer in south-central Texas is bounded
to the south and southeast by a zone of transition from fresh-water to saline water (hereinafter, the transition zone). The boundary between the two zones is the freshwater/saline-water interface (hereinafter, the interface), defined as 1,000-mil-ligrams per liter of dissolved solids. This report presents the findings of a study, done by the USGS in cooperation with the San Antonio Water System, to obtain lithologic properties and physicochemical properties and to analyze the hydraulics of flow in and near the transition zone of the Edwards aquifer on the basis of water level and borehole geophysical log data collected from 15 monitoring wells in four transects during 1999–2007. A hydraulic connection between the transition zone and the freshwater zone is indicated by similar patterns in the hydrographs of the 15 transect monitoring wells in and near the transition zone and three county index wells in the fresh-water zone during 1999–2007. The data for this report support, in part, a conceptualization of regional flow in and near the transition zone in which water enters the transition zone from the freshwater zone in the western part of the Edwards aquifer, flows toward the northeast, and discharges to the freshwater zone in the eastern part of the aquifer. The data for this report support the hypothesis that the interface is likely to remain laterally and vertically stable over time. • USGS Scientific Investigations Report 2010–5122: http://
pubs.usgs.gov/sir/2010/5122
References Cited
Keys, W.S., 1990, Borehole geophysics applied to ground water investigations: U.S. Geological Survey Techniques of Water-Resources Investigations, book 2, chap. E2, 150 p.
U.S. Army Corps of Engineers, 1995, Geophysical exploration for engineering and environmental investigations: Engineer-ing Manual 1110-1-1802, chap. 4, 57 p.
Zohdy, A.A.R., Eaton, G.P., and Mabey, D.R., 1974, Application of surface geophysics to ground-water investigations: U.S. Geological Survey Techniques of Water-Resources Investiga-tions, book 2, chap. D1, 116 p.
Geophysical Workgroup Contact InformationGregory P. Stanton Jason D. PayneGroundwater Specialist Geophysicist1505 Ferguson Lane 944 Arroyo StreetAustin, Tx 78754 San Angelo, Tx 76903512-927-3558 325-944-4600 x-28
Andrew P. Teeple Jonathan V. ThomasHydrologist Geophysicist944 Arroyo Street 2775 Alta Mesa Blvd.San Angelo, Tx 76903 Fort Worth, Tx 76133325-944-4600 x-17 817-263-9545 x-228
Publishing support provided byLafayette Publishing Service Center
For additional information, contact DirectorUSGS Texas Water Science Centerhttp://tx.usgs.gov/ [email protected]
Time-domain electromagnetic sounding layout and operation
Transmitter loop
Protem-47 transmitter
Eddy currents
Receiver loopReceiver