Tom Nance Water Resource Engineering

Permanent URI for this collection

https://hdl.handle.net/10125/61934

This digital collection results from a collaboration between these organizations in the University of Hawaii at Manoa:

The following people made this project happen:

Renowned hydrogeophysicist Tom Nance lent his invaluable reports, datasets, and maps for digital dissemination.
WRRC faculty and HGGRC director Dr. Nicole Lautze led this project -- overseeing the digitization, metadata generation, and posting of these files.
Digitization Coordinator Alice Kim created the metadata.
Research assistants David Perreira and Honour Booth scanned the reports.
Library programmer Daniel Ishimitsu set up the collection onto ScholarSpace, the University’s digital repository, and will maintain it.

The National Science Foundation via the Ike Wai -- Epscor project (award #1557349), Tom Nance Water Resource Engineering, and Hawai‘i Groundwater and Geothermal Resources Center sponsored this digitization project.

Hawai‘i Groundwater and Geothermal Resources Center https://www.higp.hawaii.edu/hggrc/

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Now showing 1 - 10 of 57

Geophysical test surveys with FDEM methods, Ewa Marina, Oahu, Hawaii

(Blackhawk Geosciences, Inc., 1990-05-30) Nance, Tom

This report contains the results of a geophysical test survey conducted on May 22, 1990, for Haseko (Hawaii) Inc. near Ewa Marina on the Island of Oahu, Hawaii. The test data were acquired on two lines. The objective of the survey was to determine the lateral boundary between saline saturated and fresh/brackish water saturated limestones. Due to the large change in electrical resistivity between saline saturated and fresh/brackish water saturated limestones, a method which is sensitive to the ground resistivity (or its inverse, conductivity) was chosen for the test. The geophysical method utilized was frequency domain electromagnetic (FDEM) measurements with the Geonics EM-34. The EM-34 is a rapid and inexpensive method which is highly sensitive to lateral changes in resistivity. Data coverage in the study area was somewhat limited to existing roads, due to the thick vegetation, and time constraints.
Time domain electromagnetic surveys for assisting in determining the groundwater resources at the Pearl Harbor Well Field, Island of Oahu

(Blackhawk Geosciences, Inc., 2011-08) Nance, Tom

"This report contains the procedures and results of surface Time Domain Electromagnetic (TDEM) geophysical surveys performed for groundwater resource evaluation in Central Oahu near Kunia and Waipio Acres, Oahu. The property included land owned by the State of Hawaii Department of Land and Natural Resources (DLNR), Waikele Farms, Inc. (WFI) and Honbushin International Center (HIC). Zapata Incorporated (ZAPATA) performed the surveys for Belt Collins Hawaii Ltd. (BCH) and Tom Nance Water Resource Engineering (TNWRE) from July 13 through July 16, 2011. The main objective of the TDEM surveys was to identify basal or high-level groundwater at the sounding sites to refine the boundary between the two. The surveys were conducted at five TDEM sounding sites to help determine the location for future groundwater wells. TDEM is a geophysical method that determines from the surface the geoelectric section (resistivity layering) of the subsurface. From the geoelectric section, information about geology and water quality can be inferred. This is possible because the electrical resistivity of the earth depends on lithology, porosity, degree of saturation, and concentration of dissolved solids in the groundwater. Geophysical surveys, combined with other hydrogeologic information, are used to provide optimum locations for water well placement and well completion depths."
Time domain electromagnetic surveys at the Lihi Lani project site, Pupukea, Koolauloa District, Oahu, Hawaii

(Blackhawk Geosciences, Inc., 1992-07-15) Nance, Tom

This report contains the resUlts of time domain electromagnetic (IDEM) surveys conducted at the Lihi Lani Project Site, Pupukea, Koolauloa District, on the Island of Oahu, Hawaii. The survey was performed by Blackhawk Geosciences, Inc. (BGI) for Kuilima Development Company during June 1992. The overall objective of the survey was to assist in defining potential fresh water resources at the project site. The two major factors which influence the location and availability of fresh ground water in this geologic setting are (i) the elevation of the fresh water - salt walter interface for basal ground water occurrences, and (ii) the location and attitude of potential ground water damming structures (e.g., dikes) and aquitards. Thus, the specific objectives of this survey were to • map the fresh water - salt water interface underlying the survey area, and • identify and map geologic structures or lithologic units which may affect ground water distribution. In TDEM surveys, the electrical resistivity of the subsurface is measured. Previous TDEM surveys on the Hawaiian Islands have shown large resistivity contrasts to occur between volcanics saturated with fresh water and saline water. In most cases, also significant resistivity contrasts exist between geologic structures and between weathered and unweathered volcanics.
Geophysical surveys for ground water evaluation, central aquifer and west beach areas, Oahu, Hawaii

(Blackhawk Geosciences, Inc., 1990-04-10) Nance, Tom

In the Central Aquifer area the TDEM soundings taken near wells at the 400-ft elevation show good agreement with borehole data in depth to the unconformity between the Koolau and Wainae flows and in the depth to fresh-brackish water. TDEM soundings taken at other locations failed to detect the unconformity. However, data density across much of the Central Aquifer area was inadequate to properly define the existence of the unconformity. The low data density was mainly due to property access restrictions imposed during the field survey. TDEM soundings taken at the West Beach area show excellent agreement with water well data in the area, and indicate that a hydrologic barrier (possibly a dike) exists in the vicinity of soundings WB2W and WB4W. In the Central Aquifer area additional TDEM soundings would be helpful to better define the orientation of the unconformity between the Koolau and Waianae flows detected on Line lN. Additional data between Lines lN and 2N and east of Kunia Road would also help to define the position of the fresh water head in this area.
Geophysical surveys for ground water investigations, Central Oahu, Hawaii

(Blackhawk Geosciences, Inc., 1990-09-11) Nance, Tom

Time domain electromagnetic (TDEM) soundings were used to assist in the ground water evaluation of the Central Oahu area on the island of Oahu, Hawaii. The results of the TDEM survey show: (1) The unconformity between the Waianae and Koolau lava flows was detected and mapped on four TDEM survey lines from line 3N toward the south and not detected north of line 3N. Good agreement was observed about the presence, depth of occurrence, and thickness of the unconformity mapped in a borehole and interpreted from TDEM soundings. From TDEM measurements along lines on both sides of the unconformity no consistent influence of the unconformity on fresh water head could be observed. (2) The elevation of the fresh-salt water interface was mapped throughout the survey area. Over most of the survey area the elevation of the salt water interface ranges from -600 ft to -900 ft below msl. This range is consistent with observations of fresh water head in wells, although locally some differences between TDEM interpretations and heads observed in wells occur. An important conclusion from the TDEM survey is that large fresh water resources exist uniformly throughout the survey area with heads above 15 ft.
Geophysical survey with FDEM methods, Ewa Marina, Campbell Industrial Park and Barbers Point Harbor, Oahu, Hawaii

(Blackhawk Geosciences, Inc., 1990-08-08) Nance, Tom

A geophysical survey was conducted in three areas in the vicinity of the Barbers Point Naval Air Station on Oahu, Hawaii. The areas are designated as Ewa Marina, Campbell Industrial Park, and Barbers Point Harbor. The objective of the survey was to infer from the geophysical data information about the thickness of a brackish water lens floating on saline water in the limestone aquifer of this region. A geophysical method was employed that allows relatively quick areal coverage for determining lateral variation in the thickness of the brackish water lens. To also derive from the survey information about the thickness of the brackish water lens, the geophysical data was correlated to salinity observations in boreholes placed in the three survey areas. The results of the survey are given as profiles of the thickness of the brackish water lens along lines generally perpendicular to the shore. The profiles are mainly characterized by a rapid increase in the thickness of the brackish water lens in the first 150 ft from the shore. The thickness of the brackish water lens varies from about 100 ft in the Ewa Marina area to less than 50 ft in the Barbers Point Harbor area.
Geophysical survey for ground water evaluation, West Beach Estates area, Oahu, Hawaii

(Blackhawk Geosciences, Inc., 1990-09-10) Nance, Tom

TDEM soundings were conducted in the West Beach Area along four lines during March and July 1990, to attempt to map a postulated hydrologic barrier inferred from prior drilling results. Heads calculated from the TDEM data, using the Ghyben Herzberg relation along line lN, show good agreement with measured heads in nearby boreholes. The likely location of the hydrologic barrier has been delineated on three of the survey lines (lS, lN, 2N) and the position of the barrier. On line .2S the barrier was not detected, mainly because measurements could not be made far enough to the east to intercept the expected position of the barrier. The location of the hydrologic barrier is inferred from (i) an increase in the resistivity of the lower layer (possibly due to dolomitization or other lithologic change), and (ii) a rapid change in depth to the salt water saturated zone east of the barrier. This rapid change in depth to salt water was detected on three lines. Accuracy in determining depth to the salt water saturated zone is expected to be about ± 5% of the total depth. If it is important to determine the course of the hydrologic barrier further to the south then additional soundings on the east side of line 2S would be necessary, and an additional line parallel and south of line 2S would further assist in locating its position.
Time domain electromagnetic surveys for assisting in determining the groundwater resources on Kawela Plantation property, Island of Molokai

(Blackhawk Geosciences, Inc., 2006-01) Nance, Tom

"This report contains the results of surface Time Domain Electromagnetic (TDEM) geophysical surveys performed for groundwater resource evaluation at the Kawela Plantation Property located approximately two miles east of the town of Kaunakakai on the Island of Molokai. Blackhawk a Division of ZAPATA ENGINEERING (Blackhawk) conducted the surveys from January 13 through 16, 2006 for Kawela Plantation Homeowners Association (Kawela) of Kaunakakai, Hawaii and Tom Nance Water Resources Engineering (TNWRE) of Honolulu, Hawaii. TDEM is a geophysical method that determines from the surface the geoelectric section (resistivity layering) of the subsurface. From the geoelectric section, information about geology and water quality can be inferred. This is possible because the electrical resistivity of the earth depends on lithology, porosity, the degree of saturation, and concentration of dissolved solids in the groundwater. The main objective of the TDEM surveys on Molokai was to explore for possible basal groundwater occurrences at the survey areas. The TDEM surveys were conducted along the approximate 525 ft (160 m) elevation level on Kawela Plantation Properties I, II and III located above the town of Kawela, Hawaii. Geophysical surveys, combined with other hydrogeologic information, are used to provide optimum locations for well placement and well completion depths."
Geophysical surveys for assisting in determining the groundwater resources, Puu O Hoku Ranch site, Island of Molokai, Hawaii

(Blackhawk Geosciences, Inc., 1999-01-12) Nance, Tom

This report contains the procedures and results of surface geophysical surveys conducted to assist in determining the groundwater resources on property owned by Puu o Hoku Ranch, Ltd., Island of Molokai, Hawaii. The geophysical method employed during this survey was Time-Domain Electromagnetic (TDEM) soundings. The surveys were performed by Blackhawk Geometries (Blackhawk) for Puu o Hoku Ranch, Ltd. during December 5 to December 8, 1998. Survey oversite was provided by Tom Nance of Tom Nance Water Resource Engineering (TNWRE). The TDEM soundings for this survey were positioned on the ranch property above and below the main water tank, and on pasture land located below the ranch buildings. The Puu o Hoku Ranch of Molokai is located on the eastern portion of the island. The ranch property lies on the eastern dipping flank of the East Molokai Volcano. The main geologic feature on this portion of the Island of Molokai is the eastward trending rift zone, which is suggested by Fiske and Jackson (1972) to extend away from the caldera complex of the East Molokai Volcano toward the coastline to the mouth of Halawa Valley. A mapped volcanic cone near Koalii (Stearns and Macdonald, 1947) is also located in the study area. The main objective of the geophysical survey was to assist in characterizing the hydrologic regime at the Puu o Hoku Ranch site for a proposed groundwater well. Groundwater resources can occur on the Island of Molokai basically in two modes: • In a basal mode, where a lens-shaped body of fresh water floats on saline water, and • In a high-level mode, where the groundwater occurrence is controlled by subsurface damming structures. The surficial volcanic rocks in an island setting are generally highly permeable, and this allows rainwater to infiltrate directly downward through the island mass. The basal groundwater lens extends from the outer edges of subsurface structures (i.e., impervious dikes) to a discharge area near the shoreline. The subsurface structures can impede the flow of groundwater from the interior of the island toward the sea and result in fresh water-filled compartments that can extend above and below sea level. These types of occurrences are referred to as high-level ground water on the Hawaiian Islands. At the Puu o Hoku Ranch study area, groundwater was expected to occur mainly as a basal fresh-brackish water lens. Previous TDEM surveys on the Hawaiian Islands have reliably mapped the boundary between fresh water in the basal mode and high-level water occurrences. Geophysical surveys, combined with other hydrogeologic information, are used to provide optimum locations for well placement and completion depths.
Geophysical surveys performed on the Island of Molokai, Hawaii : final report

(Blackhawk Geosciences, Inc., 1995-12-18) Nance, Tom

The TDEM geophysical technique was effective at mapping the fresh/saline groundwater interface in the Kawela Plantation area of Molokai. Soundings were made along two survey lines which extended from an elevation of approximately 1,300 ft (400 m) ASL to 2,700 ft (820 m) ASL. Below approximately 2,100 ft (640 m) ASL, the fresh/saline water interface was mapped in both lines. In Line 2, a significant thickening of the basal groundwater lens occurs between soundings made at elevations of 1,470 ft (450 m) ASL and 2,100 ft (650 m) ASL. It is likely that a change in horizontal hydrologic permeability, possibly caused by a leaky volcanic dike, is present in the area between the lines. Above approximately 2,100 ft (640 m) ASL, the TDEM soundings do not map the saline/fresh groundwater interface. The- depth of exploration for these soundings indicates that the interface has to be below an elevation of approximately 750 ft below sea level. Although it is probable that volcanic dike damming structures occur either at the higher elevation soundings or immediately down slope from them, it is unknown if high-level groundwater is present at these sites.

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