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Hawai‘i Groundwater and Geothermal Resources Center

Collection Manager: Nicole Lautze
Digitization Coordinator: Alice Kim
Digitization Assistants: Honour Booth and David Perreira


Recent Submissions

Now showing 1 - 5 of 16
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    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.
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    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."
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    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.
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    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.
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    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.