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Core photos, Hole 1 (PTA-2), Humu‘ula Groundwater Research Project

Item Summary

Title:Core photos, Hole 1 (PTA-2), Humu‘ula Groundwater Research Project
Authors:Thomas, Donald M.
Lautze, Nicole C.
Haskins, Eric
Keywords:core logging
core samples
Hawaii--Mauna Kea
Hawaii--Mauna Loa (Hawaii Island)
Humuʻula Groundwater Research Project
show 5 moreGroundwater
drill cores
well logging
Groundwater flow
Water table
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LC Subject Headings:Drill cores -- Hawaii -- Mauna Kea
Drill cores -- Hawaii -- Mauna Loa
Volcanism -- Hawaii -- Mauna Kea
Volcanism -- Hawaii -- Mauna Loa
Hawaii -- Mauna Kea
show 1 moreHawaii -- Mauna Loa
show less
Date Issued:2016
Publisher:University of Hawaii at Manoa
Hawaii Groundwater and Geothermal Resources Center
Humu‘ula Groundwater Research Project
Citation:Hawaii Groundwater and Geothermal Resources Center:
Abstract:Also known as “PTA” or “Saddle Road Project,” the Humuʻula Groundwater Research Project (HGRP) aimed to research the groundwater resources in the Hawaiʻi Island ‘Saddle’ region between Mauna Loa and Mauna Kea volcanoes by drilling two test holes on Army Garrison Hawaii land. Results include the discovery of: i) groundwater at a much shallower depth than expected, ii) a dike-impounded aquifer, and iii) a potential geothermal reservoir.

By using the diamond wireline core drilling technology, we collected a continuous sequence of rock core. We documented our progress in a blog and made a complete stratigraphic record of the region. This continuous stratigraphic sequence contained subaerial shield-stage and post-shield-stage lava rock and ash samples from the Mauna Kea Volcano, documenting the area’s environmental, geologic, hydrologic, and thermal history.
Description:The site of the first hole was based on results of a geophysical (Magnetotelluric or MT) survey. We drilled into the area where the measured subsurface resistivity is consistent with highest level water saturation – on the southern edge of the Pohakuloa Training Area cantonment. During the drilling, we encountered the following:
- ~215 meters (700’) below the ground surface — The initial stable saturated zone.
- ~215 meters (700’) – 345 meters (830’) — A perching layer of clay-rich ash. Water levels began to drop.
- 345 meters (830’) – ~550 meters (1,800’) — Dry rock.
- ~550 meters (1,800’) — A second saturated interval.
- ~550 meters (1,800’) – 1,763 meters (5,780’) — Water levels in the borehole remained stable. This deeper water is likely the regional water table for this area.
- ~1,000 m and beyond — The borehole temperatures showed significant increases.
Intervals of intruded dike rocks indicate a dike-impounded aquifer. Along with the unexpected presence of high-elevation water, the borehole temperatures significantly increased below depths of ~1,000 m, suggestive of a previously unknown geothermal reservoir in the Saddle region.
Pages/Duration:1,058 pages
Rights:CC0 1.0 Universal
Appears in Collections: The Geothermal Collection

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