The U.S. Geological Survey, in cooperation with the U.S. Air Force Civil Engineer Center, collected borehole geophysical data and completed simple aquifer tests to estimate the thickness and hydraulic properties of surficial deposits. The purpose of data collection was to create generalized contour maps of the elevation of the top of the Pierre Shale and the thickness of overlying surficial deposits within and near Ellsworth Air Force Base (study area). Natural gamma and electromagnetic induction data were collected to refine or determine surficial deposit thickness at selected wells. Additionally, data from previous geophysical studies and driller logs were compiled and combined with results from natural gamma and electromagnetic induction data to provide a more spatially complete image of the subsurface. Borehole nuclear magnetic resonance (bNMR) data were collected to estimate hydraulic conductivity and water content of surficial deposits overlying Pierre Shale. Simple aquifer tests using water slugs (slug tests) were completed to estimate hydraulic conductivity of surficial deposits, and results were compared to hydraulic conductivity estimates from bNMR data. All data used to construct maps and estimate hydraulic properties are provided in an accompanying U.S. Geological Survey data release (available at
Generalized contour maps were constructed using results from 26 borehole geophysical logs, 35 geophysical transects from previous studies, and 304 wells with driller logs. The elevation of the top of the Pierre Shale generally followed land-surface topography, sloping from high elevations in the north to lower elevations in the south. Topographic highs of Pierre Shale, where present, could act as groundwater divides that potentially affect groundwater flow direction. Surficial deposit thickness varied spatially and ranged from 0 to 86 feet. Surficial deposits generally were thickest in higher elevation areas near ephemeral streams in the northern part of the study area. Hydraulic conductivity estimated from bNMR results using two analytical methods ranged from 0.1 to 2,314 feet per day, whereas hydraulic conductivity estimated from slug tests ranged from 0.001 to 193 feet per day. Hydraulic conductivity estimates from slug tests were plotted with surficial deposit thickness contours instead of bNMR estimates because bNMR estimates were determined to overestimate hydraulic conductivity. Hydraulic conductivity values generally were greater in the southwestern part of study area than the northeastern part.
Medler, C.J., Eldridge, W.G., Anderson, T.M., and Phillips, S.N., 2022, Datasets used to create maps of Pierre Shale elevation and surficial deposit thickness within and near Ellsworth Air Force Base, South Dakota, 2021: U.S. Geological Survey data release,
Medler, C.J., Tatge, W.S., and Bender, D.A., 2021, Electrical resistivity tomography (ERT) and horizontal-to-vertical spectral ratio (HVSR) data collected within and near Ellsworth Air Force Base, South Dakota, from 2014 to 2019: U.S. Geological Survey data release,
U.S. Geological Survey, 2022a, USGS water data for the Nation: U.S. Geological Survey National Water Information System database,
For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit
For an overview of USGS information products, including maps, imagery, and publications, visit
Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.
The authors thank the U.S. Air Force Civil Engineer Center for funding assistance and Ellsworth Air Force Base, the South Dakota Ellsworth Development Authority, and private landowners for providing access to field sites and wells.
This work was supported in part by the U.S. Geological Survey Water Mission Area Hydrogeophysics Branch. The authors also thank Carole Johnson (Observing Systems Division, Hydrologic Remote Sensing Branch) and Randall Bayless (Ohio-Kentucky-Indiana Water Science Center) for guidance and expertise for geophysical data collection. Additionally, the authors thank the U.S. Geological Survey reviewers for their careful analysis and comments.
Multiply | By | To obtain |
Length | ||
---|---|---|
inch (in.) | 2.54 | centimeter (cm) |
inch (in.) | 25.4 | millimeter (mm) |
foot (ft) | 0.3048 | meter (m) |
mile (mi) | 1.609 | kilometer (km) |
Area | ||
acre | 0.004047 | square kilometer (km2) |
Flow rate | ||
foot per minute (ft/min) | 0.3048 | meter per minute (m/min) |
foot per day (ft/d) | 0.3048 | meter per day (m/d) |
Hydraulic conductivity | ||
foot per day (ft/d) | 0.3048 | meter per day (m/d) |
Multiply | By | To obtain |
Length | ||
---|---|---|
meter (m) | 3.281 | foot (ft) |
meter (m) | 1.094 | yard (yd) |
Volume | ||
liter (L) | 33.81402 | ounce, fluid (fl. oz) |
liter (L) | 2.113 | pint (pt) |
liter (L) | 1.057 | quart (qt) |
liter (L) | 0.2642 | gallon (gal) |
liter (L) | 61.02 | cubic inch (in3) |
Flow rate | ||
meter per day (m/d) | 3.281 | foot per day (ft/d) |
Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88).
Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).
Elevation, as used in this report, refers to distance above the vertical datum.
Electrical conductivity is given in millisiemens per meter (mS/m).
Frequency is given in kilohertz (kHz).
borehole nuclear magnetic resonance
colloidal borescope flowmeter
Ellsworth Air Force Base
electromagnetic induction
Kansas Geological Survey
light detection and ranging
Mount Sopris Instruments
Schlumberger-Doll research
sum of echoes
transverse relaxation time
U.S. Geological Survey
Ellsworth Air Force Base (EAFB; study area) is 6 miles east of Rapid City, South Dakota, next to the town of Box Elder, and includes about 4,860 acres of land (
Figure 1. Map showing
The direction and magnitude of groundwater flow through surficial deposits are necessary data for tracking and (or) intercepting contaminant migration within and near EAFB. Surficial deposits in the study area are defined as any unconsolidated deposits overlying the Cretaceous Pierre Shale and are primarily Quaternary alluvial and terrace deposits consisting of a mixture of clay, silt, sand, and gravel (
The U.S. Geological Survey (USGS), in cooperation with the U.S. Air Force Civil Engineer Center, collected borehole geophysical data and completed simple aquifer tests to estimate the thickness and hydraulic properties of surficial deposits. Contour maps of the elevation of the top of the Pierre Shale and thickness of overlying surficial deposits with hydraulic properties were created for the study area (
The purpose of this report is to provide maps of the elevation of the top of the Pierre Shale (sheet 1; available for download at
Generalized contour maps of Pierre Shale elevation and surficial deposit thickness were constructed using data from borehole geophysical logs, published geophysical surveys, and driller logs. Borehole geophysical techniques included natural gamma, EMI, and bNMR (
Table 1. Observation wells within and near Ellsworth Air Force Base, South Dakota, where borehole geophysical data and aquifer tests were completed from July 2020 to August 2021 with site information, including latitude, longitude, elevation, and measuring point height.
[USGS, U.S. Geological Survey; NAVD 88, North American Vertical Datum of 1988; MP, measuring point; LS, land surface; EMI, electromagnetic induction; bNMR, borehole nuclear magnetic resonance; CBFM, colloidal borescope flowmeter; x, denotes method used; --, no data or not applicable]
Well name1 | USGS site number2 | Latitude, in decimal degrees | Longitude, in decimal degrees | Elevation, in feet above NAVD 88 | MP height, in feet above LS | Borehole geophysical method | Slug test | |||
Natural gamma | EMI | bNMR | CBFM ( |
|||||||
MW020402 | 440731103055401 | 44.12552 | −103.09949 | 3,133.60 | 2.82 | x | x | x | x | x |
MW050201 | 440730103053301 | 44.12516 | −103.09311 | 3,131.99 | 2.72 | x | x | x | -- | x |
MW060105 | 440752103055214 | 44.12969 | −103.09905 | 3,165.29 | 2.72 | x | x | x | -- | x |
MW060403 | 440737103061103 | 44.12848 | −103.10541 | 3,150.52 | 2.67 | x | x | x | x | x |
MW080101 | 440752103055217 | 44.12944 | −103.09889 | 3,153.44 | 2.82 | x | x | x | -- | x |
MW080102 | 440752103055218 | 44.13003 | −103.09922 | 3,171.59 | 2.99 | x | x | x | -- | x |
MW080103 | 440752103055202 | 44.12990 | −103.09926 | 3,166.50 | 2.66 | x | x | x | -- | x |
MW080401 | 440743103061701 | 44.12859 | −103.10489 | 3,153.94 | 2.75 | x | x | x | x | x |
MW080402 | 440738103061101 | 44.12739 | −103.10226 | 3,146.00 | 2.75 | x | x | x | x | x |
MW101102 | 440811103050701 | 44.13649 | −103.08532 | 3,179.46 | 2.92 | x | x | x | -- | x |
MW10BG501 | 440904103035901 | 44.15116 | −103.06690 | 3,181.33 | 2.87 | x | x | x | x | x |
MW10OB03 | 440909103033901 | 44.15256 | −103.06071 | 3,181.99 | 2.92 | x | x | x | x | x |
MW112303 | 440809103050601 | 44.13588 | −103.08492 | 3,178.77 | 2.59 | x | x | x | -- | x |
MW12BG501 | 440909103035801 | 44.15258 | −103.06625 | 3,185.66 | 2.62 | x | x | x | -- | x |
MW12BG502 | 440911103035801 | 44.15299 | −103.06619 | 3,186.88 | 2.62 | x | x | x | x | x |
MW12BG503 | 440913103035801 | 44.15358 | −103.06619 | 3,191.99 | 2.67 | x | x | x | x | x |
MW170102 | 440809103055701 | 44.13583 | −103.09917 | 3,194.32 | 2.43 | x | x | x | x | x |
MW170109 | 440752103055901 | 44.13111 | −103.09972 | 3,189.99 | 2.17 | x | x | x | -- | x |
MW170118 | 440720103054501 | 44.12124 | −103.09618 | 3,123.00 | 2.07 | x | x | x | -- | -- |
MW170119 | 440705103055001 | 44.11821 | −103.09739 | 3,068.01 | 1.97 | x | x | x | x | x |
MW18PFC0401 | 440844103054101 | 44.14557 | −103.09467 | 3,212.00 | 0.30 | -- | -- | -- | -- | x |
MW18PFC1003 | 440756103044101 | 44.13166 | −103.07733 | 3,113.79 | 0.00 | -- | -- | -- | -- | x |
MW201603 | 440747103043801 | 44.12995 | −103.07713 | 3,118.66 | −0.20 | -- | -- | -- | -- | x |
MW930209 | 440738103060001 | 44.12716 | −103.10006 | 3,147.57 | 2.99 | x | x | -- | -- | x |
MW930210 | 440741103062001 | 44.12812 | −103.10563 | 3,147.44 | 2.88 | x | x | -- | -- | x |
MW930213 | 440738103052001 | 44.12722 | −103.08894 | 3,115.19 | 2.68 | x | x | -- | -- | x |
MW930412 | 440800103064102 | 44.13285 | −103.11114 | 3,202.66 | 2.79 | x | x | -- | x | x |
MW930420 | 440754103063601 | 44.13166 | −103.10986 | 3,190.04 | 2.06 | x | x | -- | x | x |
MW930421 | 440752103062802 | 44.13254 | −103.10988 | 3,200.23 | 2.70 | x | x | -- | x | x |
MW930422 | 440741103062001 | 44.12812 | −103.10563 | 3,147.44 | 2.88 | x | x | -- | -- | -- |
MW930426 | 440752103062804 | 44.13065 | −103.10829 | 3,178.54 | 2.42 | x | x | -- | x | x |
MW940203 | 440731103053001 | 44.12533 | −103.09176 | 3,135.38 | 2.61 | x | x | -- | x | x |
MW950101 | 440743103055701 | 44.12873 | −103.09912 | 3,160.41 | 2.48 | x | -- | -- | -- | x |
MW960102 | 440751103055902 | 44.13083 | −103.09972 | 3,175.98 | 2.82 | x | x | x | -- | x |
MW960404 | 440745103062401 | 44.12906 | −103.10665 | 3,154.30 | 2.92 | x | x | x | x | x |
MW970202 | 440732103054800 | 44.12561 | −103.09669 | 3,125.17 | 2.53 | x | x | x | -- | x |
MW970401 | 440737103055204 | 44.12554 | −103.10084 | 3,134.02 | 2.59 | x | x | x | x | x |
MW97BG0502 | 440904103040001 | 44.15115 | −103.06658 | 3,179.46 | 2.71 | x | x | x | x | x |
MW97BG0503 | 440909103040001 | 44.15260 | −103.06656 | 3,185.10 | 2.49 | x | x | x | x | x |
MW98BG501 | 440909103041100 | 44.15261 | −103.06968 | 3,193.86 | 2.79 | x | x | x | x | x |
MW98BG502 | 440911103035901 | 44.15319 | −103.06632 | 3,188.89 | 3.18 | x | -- | -- | x | x |
MW99BG0501 | 440913103035802 | 44.15369 | −103.06616 | 3,191.99 | 3.54 | x | x | x | x | x |
P39402vp60w | 440727103054601 | 44.12424 | −103.09610 | 3,117.14 | −0.35 | -- | -- | -- | -- | x |
PE–58ER | 440606102570001 | 44.10178 | −102.94989 | 2,930.68 | 2.53 | x | x | x | -- | -- |
PZ980404 | 440733103060302 | 44.12582 | −103.10095 | 3,134.35 | 2.79 | x | x | x | -- | x |
PZ99BG0501 | 440909103040101 | 44.15258 | −103.06687 | 3,186.65 | 2.92 | x | x | x | x | x |
PZ99BG0502 | 440907103040101 | 44.15185 | −103.06701 | 3,183.01 | 3.21 | x | x | x | x | x |
SVE0101 | 440751103055904 | 44.13083 | −103.09972 | 3,189.96 | 2.92 | x | x | x | -- | -- |
SVE0106 | 440751103055901 | 44.13083 | −103.09972 | 3,182.19 | 3.00 | x | x | x | -- | -- |
Well names from the
Well number in the U.S. Geological Survey National Water Information System database (
Borehole geophysical techniques used in this study included natural gamma, EMI, and bNMR. Borehole geophysical data were collected at 45 wells in the study area from September 2020 to August 2021. Wells chosen for borehole geophysical logging were selected based on location, access, well-construction materials, and the condition of the well casing and screen. Wells were selected to cover as much of the study area as possible but were restricted to wells belonging only to EAFB or the State of South Dakota. Well-construction materials were examined from driller logs (
Methods for each borehole geophysical method, including physics, instruments, and analysis, are described in the following sections. Additional background information for geophysical methods is provided by
Natural gamma logging measures the total amount of gamma radiation emitted by materials surrounding a borehole (
Gamma tools are calibrated by manufacturers to American Petroleum Institute units; however, tool calibration drifts over time and the data collected in American Petroleum Institute units may not be accurate (
Field procedures used for natural gamma log data collection in the “down” and “up” directions using the MSI 2PGA–1000 tool are described in this section. Before the gamma tool was inserted in a well, the depth to water and depth to bottom of the well were measured using an electric water-level tape using procedures described in
Natural gamma log data were collected at 45 wells in September 2020 and from July to August 2021. Natural gamma log data were processed using MSI WellCAD software (
EMI logging measures the bulk electrical conductivity (in millisiemens per meter) of materials and fluids in materials surrounding a borehole (
The MSI 2PIA–1000 tool was calibrated before each measurement following procedures provided by the manufacturer. First, the tool was powered on and lowered into the borehole until it was either fully or partially submerged in the borehole fluids for 15–20 minutes to stabilize and equilibrate the internal temperature of the tool. Second, the tool was removed from the borehole and calibrated using two-point calibration with a free-air value of zero and (or) a calibration ring with the dial set at 465 or 2,060 millisiemens per meter based on the expected range of electrical conductivity values at each site. The two-point calibration involved holding the tool vertically in the air either with or without the calibration ring and was completed as quickly as possible to avoid major thermal changes. At some wells, the two-point calibration could not be completed because of tool malfunctions and was instead operated at “full scale” using manufacturer settings. EMI logs collected when operating at “full scale” were evaluated at three wells using two EMI tools—one calibrated and the other at “full scale.” The EMI logs from the calibrated and “full scale” tools were nearly identical and indicated minor variations. The tool was submerged for 15–20 minutes in the borehole fluid when the “full scale” settings were used to minimize thermal effects on data collection.
EMI log data were collected at 43 wells from July to August 2021. EMI log data were processed using MSI WellCAD software (
The bNMR logging estimates the water content, pore-size distribution, and hydraulic conductivity of materials in the saturated zone surrounding a borehole. Either a Javelin JP–175 or JP–238 logging tool, both manufactured by Vista Clara, Inc. (
The bNMR data were collected at 34 wells from July to August 2021 using Javelin JP–175 or JP–238 tools. The diameter of the drilled borehole and the screened interval were reviewed in driller logs for each well, if available, before data collection to ensure the measurement zone of the tool was outside of the drilled hole and in surficial deposits overlying the Pierre Shale. Measurements in packing material within the drilled hole and the Pierre Shale were not the focus of this study and were removed where possible when collecting bNMR data; however, in some cases, bNMR data were collected within the disturbed zone of the borehole and (or) in wells screened entirely in the Pierre Shale. Additionally, bNMR data were not collected in the unsaturated zone of each well because hydraulic conductivity and pore-size distribution can be estimated only in the saturated zone.
At each site, the water level and total depth of each well were measured using an electric water-level tape. Next, the tool was connected to a winch system that recorded the depth and speed at which the tool moves in the well. Additionally, a laptop was connected to the winch system to monitor data collection. The tool then was inserted in the well and referenced to the top of casing (either above or below land surface). The bNMR data were collected in the up direction at 1.6-ft intervals in the saturated zone of the well starting from the bottom of the well. Dual-frequency measurements were made at center frequencies of about 300 and 250 kilohertz. Additionally, two relaxation times were used for both tools: a full relaxation time of 4 seconds and a shorter “burst-mode” relaxation time of 1 second. Measurements were stacked 30 times for the full relaxation time and 180 times for the burst-mode relaxation time.
The bNMR data were processed using the manufacturer-supplied software, VC_Javelin_Processor, version 4.1.1. In postprocessing, the full and burst-mode measurements for each frequency were combined for each 1.6-ft depth increment. An impulse noise filter was used to remove noisy
Hydraulic conductivity estimates from bNMR data were calculated using default parameters in VC_Javelin_Processor software (version 4.1.1) with two equations: (1) the Schlumberger-Doll research (SDR) equation ( is the SDR hydraulic conductivity, in meters per day; is an empirically derived constant that was set to the default parameter of 8,900; is total porosity; is an empirically derived constant that is generally about 1 for unconsolidated sands ( is the mean log is an empirically derived constant fixed at 2 ( is the SOE hydraulic conductivity, in meters per day; is an empirically derived constant set to 4,200; and is the measured sum of echoes (
Previous geophysical surveys and wells with driller logs containing lithologic information were used to construct generalized maps of the elevation of the top of the Pierre Shale (sheet 1) and thickness of surficial deposits (sheet 2) in the study area.
In addition to geophysical surveys, wells with driller logs containing lithologic information also were used to construct sheets 1 and 2. Driller logs were obtained from the
Surficial deposit thickness derived from geophysical logs identifying the top of the Pierre Shale in
Table 2. Thickness of surficial deposits from driller logs and (or) delineated using borehole geophysical logs for 45 wells in the study area.
[URL, Uniform Resource Locator]
Well name1 | Depth to top of Pierre Shale from driller logs, in feet below land surface2 | Depth to top of Pierre Shale from geophysical logs, in feet below land surface3 | Driller log URL from |
MW020402 | 23 | 22 | |
MW050201 | 28 | -- | |
MW060105 | 14 | 17 | |
MW060403 | 26 | -- | |
MW080101 | 13 | -- | Not available online. |
MW080102 | 11.5 | 11.5 | |
MW080103 | 14 | 13 | |
MW080401 | 27.5 | 29 | |
MW080402 | 29 | 28 | |
MW101102 | 13 | -- | |
MW10BG501 | 28 | -- | |
MW10OB03 | 35 | -- | |
MW112303 | 12 | -- | |
MW12BG501 | 36 | -- | Not available online. |
MW12BG502 | 34 | 34 | Not available online. |
MW12BG503 | 40 | 38 | Not available online. |
MW170102 | -- | -- | |
MW170109 | -- | 16 | |
MW170118 | -- | 17 | |
MW170119 | -- | 14 | |
MW930209 | -- | 31 | No lithologic information available |
MW930210 | -- | 33.5 | |
MW930213 | 8.4 | 16 | |
MW930412 | 25 | -- | |
MW930420 | -- | 31 | No lithologic information available. |
MW930421 | 15 | -- | |
MW930422 | -- | -- | No lithologic information available. |
MW930426 | 22 | -- | |
MW940203 | 26 | -- | |
MW950101 | -- | 15.5 | |
MW960102 | 8.5 | 8.5 | |
MW960404 | 24 | 24 | |
MW970202 | 20 | 16 | |
MW970401 | 21 | 19.5 | |
MW97BG0502 | -- | 17.5 | No lithologic information available. |
MW97BG0503 | 33 | -- | |
MW98BG501 | -- | 22.5 | No lithologic information available. |
MW98BG502 | -- | -- | No lithologic information available. |
MW99BG0501 | -- | -- | No lithologic information available. |
PE–58ER | 23.5 | 23.5 | Not available online. |
PZ980404 | -- | 21 | No lithologic information available. |
PZ99BG0501 | 24 | -- | No lithologic information available. |
PZ99BG0502 | -- | 14 | No lithologic information available. |
SVE0101 | 20 | 19 | |
SVE0106 | 6 | -- |
Well names from the
Rows containing “--” indicate the Pierre Shale was not penetrated or could not be differentiated from overlying surficial deposits.
Rows containing “--” indicate natural gamma and electrical resistivity patterns consistent with the Pierre Shale were not observed on composite geophysical logs.
Slug tests were completed from July 10, 2020, to September 3, 2020, at 44 wells (
Data collected for slug test analysis included well-construction information, general aquifer characteristics, and water-level changes recorded during each test. Driller logs, when available (
Water levels were measured before slug testing with a calibrated electric water-level tape (
Water slugs were used rather than solid slugs to prevent cross contamination between wells. The water slug also ensured a rapid head displacement in the well during the slug test. One to three slug test trials were completed at each well with differing volumes of water for each trial; the first trial used 0.5 liter (L) of water, the second trial used 1.0 L, and the third trial used 1.5 L. Water-level response during slug testing was variable among the wells; some tests recovered in less than 1 minute but other tests did not fully recover within 60 minutes. If water-level recovery times exceeded 20 minutes, only one trial was completed. Water-level displacement was calculated by subtracting the barometrically corrected water level from a reference (static) water level. The reference (static) water level was equal to the median of 30 consecutive seconds of stable barometrically corrected water-level data recorded by the transducer before or after the slug test.
Sampling intervals for some slug test trials were edited to ensure an appropriate and manageable number of data points for analysis because some slug test trials recorded as many as 60 minutes (more than 3,000 data points) of water-level data. Editing the sampling interval also reduced “noisy” data caused by spurious water-level data points. Python programming language (
Water-level changes for each slug test trial were analyzed with AQTESOLV Pro, version 4.50.002 (
AQTESOLV uses curve fitting to provide an estimate of hydraulic conductivity and specific storage. The curve-fitting algorithm creates a best-fit curve by varying the estimated hydraulic conductivity and other hydrogeologic parameters until a theoretical curve best fits the measured time and water-level observations (
Geophysical logging and slug test results were used to estimate the thickness and hydraulic properties of surficial deposits in the study area. Thickness of surficial deposits was delineated using a combination of natural gamma logs, EMI logs, and lithologic information from driller logs. Hydraulic conductivity and water content estimates were calculated from bNMR data collected at 30 wells. Slug tests provided estimates of hydraulic conductivity at 44 wells completed in the surficial deposits and the Pierre Shale. Hydraulic conductivity estimates from bNMR data and slug tests were compared and evaluated spatially to highlight relatively higher conductivity values that indicate areas of preferential groundwater flow.
Composite geophysical logs were constructed for 34 of the 45 total wells where natural gamma, EMI, and bNMR data were collected together (
Borehole geophysical logs for well PE–58ER, including natural gamma, electromagnetic induction, and borehole nuclear magnetic resonance logs with well-construction and lithology information from the accompanying driller log. Borehole nuclear magnetic resonance data provided measurements of water content and estimates of hydraulic conductivity. The amplitude color plot shows the distribution of the transverse relaxation time (
Figure 2. Borehole geophysical logs for well PE–58ER, including natural gamma, electromagnetic induction, and borehole nuclear magnetic resonance logs with well-construction and lithology information from the accompanying driller log.
Surficial deposit thickness could not be determined from borehole geophysical logs for 19 of 45 wells (
Reported thickness of surficial deposits from driller logs was compared to thickness estimates from borehole geophysical logs for 15 wells (
Surficial deposit thickness from borehole geophysical logs in
The elevation of the top of the Pierre Shale generally followed land-surface topography, sloping from high elevations in the north to lower elevations in the south (sheet 1). Topographic highs of Pierre Shale, where present, could act as groundwater divides that potentially affect groundwater flow direction. Surficial deposit thickness varied throughout the study area and ranged from 0 to 86 ft. The thickness of the surficial deposits generally was less than 20 ft in areas where the surficial deposits are incised by ephemeral stream valleys (sheet 2). Thicknesses likely are exaggerated in areas with roads or infrastructure that artificially increased the land-surface elevation. Surficial deposits generally were thickest in higher elevation areas near ephemeral streams in the northern part of the study area (sheet 2).
Hydraulic conductivity and water content were estimated from bNMR logs for 30 of the 34 wells with composite geophysical logs (
Table 3. Hydraulic conductivity and water content estimates computed using the Schlumberger-Doll research and sum of echoes equations on borehole nuclear magnetic resonance data for 34 wells in the study area.
[SDR, Schlumberger-Doll research; SOE, sum of echoes; --, no data or not applicable]
Well name | Number of measurements | Hydraulic conductivity from SDR equation, in feet per day | Hydraulic conductivity from SOE equation, in feet per day | Mean total water content | Mean mobile water content | Mean immobile water content (combined clay and capillary water content) | ||
Mean | Median | Mean | Median | |||||
Wells screened in surficial deposits | ||||||||
---|---|---|---|---|---|---|---|---|
MW020402 | 5 | 959 | 859 | 523 | 525 | 0.37 | 0.32 | 0.05 |
MW050201 | 1 | 1,253 | -- | 528 | -- | 0.33 | 0.28 | 0.04 |
MW060403 | 1 | 10 | 10 | 47 | -- | 0.46 | 0.22 | 0.24 |
MW080103 | 7 | 378 | 332 | 227 | 211 | 0.31 | 0.29 | 0.02 |
MW080401 | 3 | 163 | 49 | 192 | 147 | 0.37 | 0.26 | 0.11 |
MW080402 | 3 | 397 | 249 | 325 | 272 | 0.41 | 0.32 | 0.08 |
MW101102 | 5 | 177 | 111 | 169 | 176 | 0.31 | 0.23 | 0.08 |
MW10BG501 | 7 | 6 | 3 | 35 | 34 | 0.33 | 0.09 | 0.24 |
MW10OB03 | 7 | 1 | 1 | 12 | 11 | 0.30 | 0.04 | 0.26 |
MW112303 | 3 | 3 | 1 | 20 | 7 | 0.33 | 0.07 | 0.26 |
MW12BG501 | 8 | 2 | 1 | 10 | 9 | 0.30 | 0.05 | 0.25 |
MW12BG502 | 6 | 6 | 4 | 31 | 27 | 0.33 | 0.13 | 0.20 |
MW12BG503 | 9 | 60 | 24 | 83 | 84 | 0.31 | 0.23 | 0.09 |
MW170102 | -- | -- | -- | -- | -- | -- | -- | -- |
MW170109 | 1 | 26 | -- | 60 | -- | 0.36 | 0.28 | 0.08 |
MW170118 | -- | -- | -- | -- | -- | -- | -- | -- |
MW170119 | 5 | 153 | 79 | 235 | 232 | 0.34 | 0.24 | 0.10 |
MW960102 | 3 | 172 | 154 | 213 | 237 | 0.33 | 0.27 | 0.06 |
MW960404 | 1 | 610 | -- | 447 | -- | 0.35 | 0.30 | 0.05 |
MW970202 | 6 | 772 | 787 | 378 | 370 | 0.33 | 0.28 | 0.05 |
MW970401 | 2 | 87 | 87 | 106 | 106 | 0.31 | 0.18 | 0.13 |
MW97BG0502 | 5 | 1 | 1 | 4 | 2 | 0.29 | 0.02 | 0.26 |
MW97BG0503 | 7 | 16 | 9 | 78 | 67 | 0.33 | 0.13 | 0.20 |
MW98BG501 | 2 | 27 | 27 | 67 | 67 | 0.25 | 0.15 | 0.10 |
MW99BG0501 | 1 | 129 | -- | 155 | -- | 0.29 | 0.21 | 0.08 |
PE–58ER | 9 | 39 | 18 | 78 | 62 | 0.30 | 0.13 | 0.18 |
PZ99BG0501 | -- | -- | -- | -- | -- | -- | -- | -- |
PZ99BG0502 | 1 | 12 | -- | 43 | -- | 0.27 | 0.11 | 0.15 |
SVE0101 | 5 | 552 | 481 | 280 | 327 | 0.32 | 0.31 | 0.01 |
SVE0106 | 6 | 1,313 | 1,488 | 500 | 522 | 0.34 | 0.31 | 0.03 |
Wells screened entirely or partially in Pierre Shale | ||||||||
MW060105 | 7 | 297 | 296 | 167 | 135 | 0.30 | 0.28 | 0.02 |
MW080101 | 6 | 46 | 38 | 69 | 93 | 0.27 | 0.16 | 0.11 |
MW080102 | 8 | 103 | 58 | 97 | 82 | 0.29 | 0.24 | 0.05 |
PZ980404 | 4 | -- | -- | 579 | 550 | -- | -- | -- |
An example of bNMR results for well PE–58ER is shown in
Hydraulic conductivity estimates for all bNMR measurements ranged from 0.1 to 2,314 feet per day (ft/d) for
Comparison of hydraulic conductivity estimates from
The bNMR tool also measured water content, including the mobile and immobile fractions, of the unsaturated and saturated zones surrounding boreholes. The mean total water content across the 30 sites in
Hydraulic conductivity estimates from slug tests are listed in
Table 4. Hydraulic conductivity estimates from slug tests for 44 wells in the study area.
[--, no data or not applicable]
Well name | Hydraulic conductivity for water slug test trial, in feet per day | |||
1a | 2b | 3c | Mean | |
Wells screened in surficial deposits | ||||
---|---|---|---|---|
MW020402 | 14 | 30 | 32 | 25 |
MW050201 | 4 | 23 | -- | 14 |
MW060403 | 47 | 42 | -- | 44 |
MW080103 | 1.0 | 0.1 | -- | 0.6 |
MW080401 | 4 | 3 | -- | 3 |
MW080402 | 112 | 156 | -- | 134 |
MW101102 | 1.1 | 0.9 | 0.9 | 1.0 |
MW10BG501 | 66 | 54 | -- | 60 |
MW10OB03 | 2.3 | 1.7 | -- | 2.0 |
MW112303 | 9.1 | 1.8 | 3.0 | 4.6 |
MW12BG501 | 6.3 | 4.9 | -- | 5.6 |
MW12BG502 | 14 | 5 | -- | 9 |
MW12BG503 | 0.001 | 0.001 | -- | 0.001 |
MW170102 | 0.1 | -- | -- | 0.1 |
MW170109 | 0.003 | -- | -- | 0.003 |
MW170119 | 34 | 33 | -- | 33 |
MW201603 | 36 | -- | -- | 36 |
MW930209 | 129 | 80 | -- | 104 |
MW930210 | 12 | 19 | 29 | 20 |
MW930213 | 14 | 15 | 14 | 14 |
MW930412 | 2 | 2 | 2 | 2 |
MW930420 | 4 | 3 | -- | 3 |
MW930421 | 4 | 2 | -- | 3 |
MW940203 | 13 | 9 | -- | 11 |
MW950101 | 1.9 | 1.8 | 1.9 | 1.9 |
MW960102 | 4.4 | 7.1 | -- | 5.8 |
MW960404 | 78 | 32 | -- | 55 |
MW970202 | 28 | 32 | 45 | 35 |
MW970401 | 12 | 6 | -- | 9 |
MW97BG0502 | 37 | 30 | -- | 34 |
MW97BG0503 | 9 | 55 | -- | 32 |
MW98BG501 | 3 | 39 | 78 | 40 |
MW98BG502 | 50 | 1 | 193 | 82 |
MW99BG0501 | 7 | -- | -- | 7 |
P39402VP60W | 2 | 0.3 | -- | 1 |
PZ99BG0501 | 52 | 46 | 35 | 45 |
PZ99BG0502 | 1.3 | 1.3 | -- | 1.3 |
Wells screened entirely or partially in Pierre Shale | ||||
MW060105 | 0.04 | -- | -- | 0.04 |
MW080101 | 0.05 | -- | -- | 0.05 |
MW080102 | 0.9 | 0.8 | -- | 0.9 |
MW18PFC0401 | 0.2 | -- | -- | 0.2 |
MW18PFC1003 | 0.2 | -- | -- | 0.2 |
MW930426 | 0.09 | -- | -- | 0.09 |
PZ980404 | 0.06 | 0.07 | -- | 0.06 |
The first trial used 0.5 liter for the water slug test.
The second trial used 1.0 liter for the water slug test.
The third trial used 1.5 liters for the water slug test.
Mean hydraulic conductivity estimates from slug tests were plotted spatially with contours of surficial deposit thickness for spatial evaluation (sheet 2). Slug test hydraulic conductivity estimates generally were greater in the southwestern part of the study area than the northeastern part. The northeastern part of the study area is close to infrastructure (
Mean hydraulic conductivity estimates for 28 wells with results from bNMR logging and slug tests were compared (
Mean hydraulic conductivity estimates from borehole nuclear magnetic resonance logging (Schlumberger-Doll research equation and sum of echoes equation) and slug test results for 28 wells.
Figure 3. Graph showing mean hydraulic conductivity estimates from borehole nuclear magnetic resonance logging and slug test results for 28 wells.
The largest differences in mean hydraulic conductivity between SDR and SOE estimates and slug test estimates were from wells MW12BG503 and MW170109 (
Mean hydraulic conductivity differences between bNMR and slug tests were attributed to differences in data collection methodology and parameters used in analysis. The bNMR logging estimated hydraulic conductivity of material at a specific radius surrounding wells and at several depth intervals, which were combined to compute a mean hydraulic conductivity of the well profile. The bNMR logging also does not consider the well screen for calculation of hydraulic conductivity. Slug testing estimates hydraulic conductivity by evaluating the water column response to increases or decreases in hydraulic head from insertion or removal of a slug, and the condition of the well screen affects the results. Therefore, hydraulic conductivity estimates calculated from bNMR data may have evaluated a different part of the aquifer near the wells than the slug tests. Additionally, well-screen conditions, such as sediments trapped in the screen, may have affected slug test results and contributed to differences in estimated mean hydraulic conductivity. The parameters used to calculate hydraulic conductivity also may have contributed to overestimation of hydraulic conductivity for bNMR data, which was observed in previous studies (
The U.S. Geological Survey, in cooperation with the U.S. Air Force Civil Engineer Center, collected borehole geophysical data and completed simple aquifer tests to estimate the thickness and hydraulic properties of surficial deposits. Contour maps of the elevation of the top of the Pierre Shale and thickness of overlying surficial deposits were created for areas within and near Ellsworth Air Force Base (study area). Borehole geophysical data were collected at 46 wells, and logging methods included natural gamma, electromagnetic induction, colloidal borescope flowmeter, and borehole nuclear magnetic resonance (bNMR). Borehole geophysical data were combined with well-construction and lithologic information from driller logs to aid interpretation of the thickness of surficial deposits. Natural gamma and electromagnetic induction data were used to estimate thickness of surficial deposits, whereas colloidal borescope flowmeter and bNMR data were used to estimate hydrologic properties of surficial deposits. Hydrologic properties also were estimated analytically using water-level changes from slug tests. All data used to construct maps and estimate hydraulic properties are provided in an accompanying U.S. Geological Survey data release (available at
Surficial deposit thickness was successfully delineated for 26 of 45 wells using geophysical logs. Surficial deposit thickness could not be determined from borehole geophysical logs for 19 of 45 wells because either the well did not penetrate the Pierre Shale or lithologic similarities between surficial deposits and the Pierre Shale prevented contact delineation. Lithologic information from driller logs, if available, was used to determine surficial deposit thickness for wells lacking natural gamma and electrical resistivity trends consistent with the Pierre Shale. Reported thickness of surficial deposits from driller logs was compared to thickness estimates from geophysical logs for 15 of those 26 wells. The absolute difference between reported thicknesses from driller logs and thicknesses delineated using geophysical logs ranged from 0 to 7.6 feet (ft), and differences were less than or equal to 2 ft for 12 of the 15 wells.
Surficial deposit thickness from the 26 borehole geophysical logs was combined with thicknesses from 35 geophysical transects and 304 wells with driller logs to construct generalized contour maps of the elevation of the top of the Pierre Shale and thickness of surficial deposits in the study area. In total, 35 geophysical transects and 330 wells were used to construct the two contour maps. The elevation of the top of the Pierre Shale generally followed land-surface topography, sloping from high elevations in the north to lower elevations in the south. Topographic highs of Pierre Shale, where present, could act as groundwater divides that potentially affect groundwater flow direction. Surficial deposit thickness varied throughout the study area and ranged from 0 to 86 ft. Surficial deposits generally were thickest in higher elevation areas near ephemeral streams in the northern part of the study area.
Hydraulic conductivity and water content were estimated from bNMR results for 30 of the 34 wells. Hydraulic conductivity estimates for all bNMR measurements ranged from 0.1 to 2,314 feet per day (ft/d) and 0.1 to 874 ft/d for
Slug tests were completed at 44 wells to estimate hydraulic properties of surficial deposits and the Pierre Shale. Hydraulic conductivity estimates from slug tests for wells completed in surficial deposits ranged from 0.001 to 193 ft/d, and mean and median hydraulic conductivity estimates were 25 and 9 ft/d, respectively. The mean hydraulic conductivity for an individual well ranged from 0.001 ft/d at MW12BG503 to 134 ft/d at MW080402. Hydraulic conductivity estimates for wells screened entirely or partially in the Pierre Shale ranged from 0.04 ft/d at MW060105 to 0.9 ft/d at MW080102, and mean and median hydraulic conductivity estimates were 0.3 and 0.09 ft/d, respectively. The range of hydraulic conductivity estimates for surficial deposits was generally within the range of hydraulic conductivity values representative of silty sand to gravel. Hydraulic conductivity estimates for the Pierre Shale generally were within the range of estimates for shale or silt.
This study tested the utility of colloidal borescope flowmeter (CBFM) logging for determining the horizontal flow direction and velocity of groundwater in the study area. The CBFM logging was not part of the scope of the project, but the methods and results of data collection are included in this appendix to provide insight on CBFM logging within and near Ellsworth Air Force Base in South Dakota. The CBFM data from this test are provided in the data release accompanying this pamphlet (
CBFM data were collected using a tool manufactured by AquaVISION Environmental LLC of Palisade, Colorado (
Field procedures outlined in
CBFM data were collected at 24 wells from November to December 2020. CBFM data were analyzed using Python programming language (
The direction of horizontal groundwater flow and horizontal groundwater flow velocity were estimated from CBFM results for 13 of the 24 wells. Of the 24 wells, 11 produced erroneous groundwater direction and velocity results that could not be used to interpret groundwater flow direction. The horizontal groundwater flow direction estimated at the 13 wells deviated from the general direction of groundwater flow approximating the bedrock elevation contours in sheet 2. This deviation was attributed to the CBFM tool being placed below the flowing interval of the well during dry conditions in winter months (November and December) when either groundwater levels were low or the surficial aquifer was dry. During dry conditions, groundwater may not have been flowing through the screened interval of the wellbore or the flowing interval likely was reduced to the bottom part of the aquifer that may not have been measured by the tool. The effects of tool placement outside the flowing interval of the wellbore likely also affected estimates of horizontal groundwater flow velocity for the 13 wells. The horizontal flow velocities ranged from 3.9 to 137.5 ft/d, and mean and median velocities were 48.2 and 25.8 ft/d, respectively. The CBFM tool measures horizontal groundwater flow velocity through the wellbore, and several studies (
Director, USGS Dakota Water Science Center
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