A geohydrologic investigation of Honolulu's basal waters based on isotopic and chemical analyses of water samples

Typescript.Thesis (Ph. D.)--University of Hawaii at Manoa, 1974.Bibliography: leaves 156-160.x, 160 leaves ill., mapsBasal groundwaters in the Honolulu area were studied by a combination of three methods: radiocarbon age dating, tritium tracing, and examination of chemical data. Basic data used in this effort consisted of isotopic and chemical data on water samples. Isotope data included radiocarbon, carbon 13, and tritium; chemical data were primarily chloride, bicarbonate and silica. Water samples were mostly from groundwater sources in the Honolulu area, Pearl Harbor area, and Windward Oahu. Method of collection as well as procedures and equipment used for the analyses were described. The main objective of the study was the determination of basal water radiocarbon ages; how they were obtained and how they related to other parameters such as tritium, chloride, location or depth of sampling. A general objective was to show that studies such as this one, based largely on isotopic analysis of water samples, can yield hydrologic and geohydrologic information that enhances the understanding of the dynamics of groundwater systems in general and that of basal groundwater systems in particular. Radiocarbon ages obtained refer to the average time basal water samples resided in the basal aquifers, i.e. the time elapsed between recharge and sampling. Age calculations were based on differences in radiocarbon activity between basal water samples on the one hand and the activity of a recharge reference on the other, this difference being due to loss of radiocarbon through radioactive decay. Radiocarbon activity of the recharge reference was obtained from radiocarbon data on dike waters, high level perched waters and others. Processes such as carbonate dissolution, carbonate exchange and salt water intermixing were examined in some detail because, if they occur, they alter the relative or absolute content of aqueous radiocarbon, thus resulting in false ages. On the basis of theoretical considerations and experimental data it was shown that the effects of such nonradiogenic processes in principle can be detected and adjusted for with the aid of carbon 13 data. No such adjustment was applied in calculating the majority of basal water radiocarbon ages because respective carbon 13 data and recharge reference carbon 13 data had distributions that largely overlapped each other. Averages of radiocarbon ages for Isopiestic Areas 1 ~o 3, called geochemical mean residence times, ranged between 270 and 550 years, whereas displacement mean residence times calculated from geologic and hydrologic data ranged between 30 and 40 years. On the basis of this and other observations, a hypothesis was advanced that old water from pre-development bottom storage is still being flushed out of some systems. In accordance with this hypothesis, it was concluded that during the period of study old stored water was discharged by several sources in Isopiestic Areas 1, 2, 3, and 4 and, in particular, by sources in Areas 3 and 4. The amount of old stored water in the discharge from Kalihi Shaft varied as a function of time, a feature attributed to variations in pumping rate

WRRCTR No.129 Underground Residence Times and Chemical Quality of Basal Groundwater in Pearl Harbor and Honolulu Aquifers, O'ahu, Hawai'i

Information on the large-scale movement and origin of groundwater in southern Oahu was obtained by examining the natural isotopic and chemical composition of water samples. Six basal groundwater systems (Pearl Harbor, Moanalua, Kalihi, Beretania, Moiliili, and Waialae) were studied and are discussed in this report. The experimental data base comprises the analyses of 84 groundwater samples, 2 surface water samples, and 49 rain-water samples for the following parameters, radiocarbon (l4C), carbon 13 (13C), tritium (3H), major ions, nitrate, silica, and pH. These data were supplemented with isotope and chemical data obtained in previous studies and selected data from the literature. Carbon isotope data, radiocarbon and carbon 13, on basal groundwater samples were evaluated with respect to "recharge reference" values. The latter were established on the basis of isotope analyses of water samples obtained from inland sources, such as tunnels tapping high-level dike compartments or wells located close to the mountains. Tritium data on basal groundwater samples were evaluated with respect to values for local rainfall and the recharge reference. Radiocarbon dating was used as an index of age to identify those groundwaters whose underground transit or residence times are in excess of about 200 years. Radiocarbon and tritium were used to identify young water, less than 20 yr old, through the detection of artificially high radiocarbon and tritium activities resulting from atmospheric testing of nuclear weapons during the past two decades. Underground residence times of basal waters in the Kalihi, Beretania, and Moiliili systems are quite long compared to the residence times of the other systems. Rain water infiltration in regions of high elevations located far inland is a definite source for most of the recharge to these systems. Basal water in the Waialae system has a short residence time compared to the other Honolulu systems. Moanalua basal waters were not uniform in their isotopic and chemical characteristics and indicated very long as well as very short residence times. Basal water in the western, inland portion of the Pearl Harbor system is similar in underground residence time to that in the Kalihi, Beretania, and Moiliili systems but water in the eastern and seaward portions is characterized by short residence times and, in many cases, the presence of young water. Many regions in this basal water system and, in part1cular, the eastern part, show the presence of transition-zone water, return irrigation water, and caprock-type water, either singularly or in some combination. Simple mixing models utilizing several suitable chemical parameters made it possible to determine the possible origins of water present in the discharge of a selected source or the presence of a particular type of water in the discharge of several sources located within a few miles of each other.Board of Water Supply, C&C of Honolulu; Oahu Sugar Co., Ltd.; Naval Facilities Engineering Command, U.S. Navy; and the Div. of Water and Land Development, State of Hawaii Grant/Contract No. 14-31-0001-381

WRRCTR No. 53 Tritium and Radiocarbon in Hawaiian Natural Waters: Part I

A field investigation was undertaken to establish the present tritium and radiocarbon activity levels of natural waters found in various parts of the island of Oahu. The instrumentation required for the radiocarbon analysis was assembled and workable procedures were developed. Monthly rainwater samples obtained from rain gages on the Koolau Range contained seasonally fluctuating tritium concentrations which are well in excess of the natural abundance level. Excess concentrations were also found for the tritium and radiocarbon content of surface waters from three separate sources. These excess concentrations are the result of fallout from atmospheric nuclear explosions. Samples from nine tunnels, which tap various Koolau dike compartments, contained tritium activities ranging from the current rainwater levels down to the pre-nuclear explosion levels. Most samples showed radiocarbon activities comparable to pre-explosion atmospheric C02 levels. Two samples, however, showed excess radiocarbon. Samples from wells and shafts tapping basal water in the Honolulu area generally showed little or no tritium and their radiocarbon concentrations were lower than those of the dike-water samples. Makiki, Booth, and Roseapple Springs, which discharge perched water, exhibited tritium levels slightly in excess of the contemporary rain water levels. Nuclear explosion radiocarbon was present at Makiki Spring whereas it was absent at Booth Spring. Correlations between radiocarbon and chloride content were found for samples from Central Oahu and the Pearl Harbor area. The magnitude of both constituents were moreover a function of the distance between the sample source and Pearl Harbor. Three multiple depth samples from well T-133 at Ewa Beach showed very low radiocarbon content. These results can be evidences of radioactive decay of the radiocarbon thus indicating very long residence times of these waters. Exchange reactions between the water-carbonates and the radiocarbon-free aquifer carbonates can lead to the same results however. The discovery of a linear relationship between the radiocarbon activity and chloride contents of these samples indicates that chemical exchange reactions have taken place.OWRR Project No. B-016-HI, Grant Agreement No. 14-31-0001-3271 The programs and activities described herein were supported in part by funds provided by the United States Department of the Interior as authorized under the Water Resources Act of 1964, Public Law 88-379

WRRCTR No. 65 Tritium Measurement of Natural Waters on Oahu, Hawaii: A Preliminary Interpretation (Sampling Perio: July 1969 to June 1970)

Water samples collected from various surface and sub-surface sources on the island of Oahu were analyzed for tritium levels. Tritium activity levels in twenty-five monthly rainwater samples show a seasonal dependence with a maximum in the summer (18.5 to 23 TU) and a minimum in the winter (12 TU). Samples from two surface-water reservoirs had activities of 13.2 and 19.7 TU reflecting contemporary rainwater which is their major source of recharge. Four streams in the Pearl Harbor area showed "rainwater" tritium levels when sampled at high flow. At low flow, two of the streams had low tritium levels indicating ground-water discharge into the stream, while the tritium activity of the other two streams was conparable to rainwater. Tritium activity higher than that of contemporary rainwater (22-38 TU) was exhibited by samples from two springs which discharge perched water, while samples from three wells and two shafts in the Honolulu area showed very little or no tritium activity. Multiple-depth samples obtained from wells in the Pearl Harbor area showed correlations between tritium activities, depths of sampling, and chloride concentrations.OWRR Project No. A-021-HI , Grant Agreement No. 14-31-0001-3011 The programs and activities described herein were supported in part by funds provided by the United States Department of the Interior as authorized under the Water Resources Act of 1964, Public Law 88-379

WRRCTR No.34 Some Measurements of the Tritium Content in the Natural Waters of Southern Oahu, Hawaii

An analysis was made of the tritium content of samples from various sources of surface and subsurface waters of the island of Oahu. Twenty rainwater samples collected from various rain gages located on the Koolau Range over a period of four months showed an activity between 16.3 and 28.2 tritium units. Samples from four streams in the Pearl Harbor area ranged from 14.5 to 21.3 tritium units, while samples from two springs and five wells in this same area all showed an activity below 5 tritium units. The instrumentation consisted of an electrolysis enrichment apparatus, a vacuum distillation unit and a liquid scintillation counter. A detailed description is given of the various parts of the electrolysis apparatus and the vacuum distillation unit. Both the enrichment and counting procedures are reviewed as well as the calibration of these systems.U.S. Department of the Interior Grant/Contract No. 14-01-0001-1630; A-016-H

Environmental baseline study for geothermal development in Puna, Hawaii

With illustrations.The Hawaii Geothermal Project, a coordinated research effort of the University of Hawaii funded by the County and State of Hawaii, as well as ERDA, was initiated in mid-1973 in order to identify and help develop geothermal energy on the Big Island of Hawaii. To develop a geothermal resource, a number of stages preliminary to production are required: exploration and selection of a site for drilling; exploratory drilling; testing to determine critical characteristics of the well or wells; and -- optionally -- operating a model plant to test output potential. By the spring of 1974 Phase I of the Project had been completed, when a site for an exploratory well was located and permission for drilling was obtained from the private corporation owning the site. After the competitive bidding process was completed, a drilling contract was awarded in November, 1975 and actual drilling began in December of last year. The drilling was completed late in April, 1976, when a depth of approximately 6,400 feet had been penetrated -- approximately 6,000 feet below sea level. A slotted liner for the bottom portion of the well was installed in June, 1976. The well flashed spontaneously on 3 July and was blown to rid it of drilling debris on 22 July 1976, after which testing of its physical properties was begun. From the beginning of the Hawaii Geothermal Project, it has been recognized that the successive steps of geothermal development starting with drilling must be carefully scrutinized to ascertain in a timely way if there would be any adverse effects on the environment and local ecosystems, and, should they occur, that it was necessary to identify and recommend measures to minimize such impacts. For this reason, in the summer of 1975, once the drill site had been selected and long before the drilling began, baseline data were collected on critical aspects of environmental conditions as they existed before any significant disturbance by the Project. These included ground water supply, air, soil and the flora, as well as the archaeology of the area surrounding the drill site. In February, 1976 the area was studied to see if it provided a habitat for birds which are endemic, or otherwise of special interest. Generally, the area examined for environmental impact lies within a circle having a radius of approximately a half mile from the center of the four-acre drill site. However, the testing of ground water included sampling wells and a spring more than a mile from the site. Additional tests of the water and air were conducted at the site in June, 1976, after the drilling was completed but before the well was blown to free it of debris accumulated during drilling. The results of that testing, along with results obtained before the drilling began, are summarized in this assessment statement. The results of the pre-drilling studies were such as to enable the University of Hawaii, under the regulations of the Hawaii Environmental Quality Commission, to issue a negative declaration concerning the exploratory hole -- i.e. that the drilling of the well seemed to pose no significant threat to the environment in the vicinity of the well site in Puna, Hawaii. It is hoped and intended that the environmental data established by this study will serve as baselines from which to measure changes which may be associated with geothermal development, not only in the area immediately neighboring the present drill site, but, with appropriate adjustments, for development which may occur elsewhere in the Puna District. How transferable the baselines may be to other areas, say other districts of the Island of Hawaii or to other islands within this archipelago, is a question which must be examined in context as further geothermal exploration is undertaken.U.S. Energy Research & Development AdministrationState of HawaiiCounty of Hawai