Geology topics

Jackson N. Mitchell

Publications and source records attributed to Jackson N. Mitchell.

7 recordsLinked to original sources

USGS2024

Groundwater and surface-water interactions in the Lower Duwamish Waterway, Seattle, Washington

The U.S. Geological Survey (USGS), in cooperation with the Washington State Department of Ecology (Ecology), conducted a study to describe the current understanding of the regional groundwater system of the lower Duwamish River valley and groundwater and surface-water interactions in the lower Duwamish Waterway. The lower Duwamish Waterway is the final 5-mile (mi) reach of the Duwamish River before it empties into Elliott Bay in Puget Sound near Seattle, Washington. A nearshore site (hereinafter referred to as “Nearshore Site” to distinguish the particular site from general discussions of nearshore areas) along the western shoreline of the Duwamish River, about 1.5 mi upstream from the river mouth, was selected for focused groundwater data collection by USGS. Data loggers were deployed in seven groundwater wells and one stilling well in the Duwamish River to measure specific conductance, temperature, and depth at 15-minute intervals for a period of about 2 years. At the Nearshore Site during 2020–22, water levels in the shallow wells were 3–8 feet (ft) higher than water levels in the deep wells, providing evidence for a low-permeability layer between the shallow and deep aquifers in this area. The shallow wells had a pronounced seasonal variability, with high water levels in winter and low water levels in summer. Data from the deep wells showed far less seasonal variability, with slight increases in winter and a near-constant water level from spring to autumn. The deep wells had a strong hydraulic connection to the Duwamish River, as evidenced by the synchronous water-level variability during the tidal cycle, whereas the shallow wells had minimal to no tidal response. The potentiometric maps developed for the Nearshore Site and surrounding areas indicate large differences in groundwater-flow directions for the shallow and deep aquifers at low and high tides. For the shallow aquifer, flow is toward the lower Duwamish Waterway near the Nearshore Site, regardless of the tidal condition. For the deep aquifer, a potentiometric trough forms parallel to the shoreline during high tide, indicating that groundwater flow converges from the uplands to the west and the Duwamish River to the east. The geometry of the potentiometric surfaces between the nearshore-most well and the shoreline is complex and is further confounded by intermittent shoreline armoring and other buried infrastructure, which could serve as either a barrier or a conduit to flow. Groundwater and surface-water interactions in the lower Duwamish Waterway are inherently complex as a result of three overarching factors. First, water levels in the lower reaches of the Duwamish River vary daily by 11–16 ft because of tides from Puget Sound, which create large swings in the hydraulic gradient in the nearshore groundwater system. Second, the density and chemical composition of water in the Duwamish River change daily with the tides and seasonally, which constrains how river water entering the nearshore sediments interacts with discharging groundwater. Third, the nearshore subsurface and shoreline conditions are heterogenous because of extensive shoreline armoring over the past century, which governs the flow of groundwater and infiltrating river water. These unique features of groundwater and surface-water interactions in the lower Duwamish Waterway thus govern the transport of terrestrial contaminants to the lower Duwamish Waterway. Furthermore, the heterogenous aquifer properties in the lower Duwamish Waterway contribute to spatially and temporally dynamic contaminant-transport processes.

Washington↗

USGS2023

Magnitude and frequency of floods on Kauaʻi, Oʻahu, Molokaʻi, Maui, and Hawaiʻi, State of Hawaiʻi, based on data through water year 2020

Accurate estimates of flood magnitude and frequency are needed to (1) optimize the design and location of infrastructure, including dams, culverts, bridges, industrial buildings, and highways, and (2) inform flood-zoning and flood-insurance studies. The U.S. Geological Survey (USGS), in cooperation with the State of Hawaiʻi Department of Transportation, estimated flood magnitudes for the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities (AEP) for unregulated streamgages in Kauaʻi, Oʻahu, Molokaʻi, Maui, and Hawaiʻi, State of Hawaiʻi, using data through water year 2020. Regression equations were developed to estimate flood magnitude and associated frequency at ungaged streams. This study improves upon a previous USGS flood-frequency report (Oki and others, 2010) by including more peak-flow data, implementing new statistical methods in flood-frequency analysis, and using updated techniques to estimate the regional-skewness coefficient (regional skew). Flood magnitude and frequency at 238 streamgages were estimated—following national guidelines established in Bulletin 17C (England and others, 2019)—by fitting annual peak-flow data to the Log-Pearson Type III distribution using the expected moments algorithm and the PeakFQ flood-frequency software. Potentially influential low outliers in the data were identified and removed using the Multiple Grubbs-Beck Test. An updated regional skew for Hawaiʻi was estimated using the Bayesian weighted least squares/Bayesian generalized least squares method. The updated regional skew employs a constant model for the five islands in the study area and has a value of −0.157 (mean square error of 0.212). Multiple linear regression techniques were used to develop regression equations that relate basin and climatic characteristics to peak flows at streamgages. The regression equations can be applied to estimate flood magnitude and frequency at ungaged sites. The study area was split into 10 regions—2 regions per island, generally following a leeward/windward division—containing from 9 to 49 streamgages each. The final regression equations for each region were determined with generalized least-squares analysis using the USGS weighted-multiple-linear regression (WREG) program. The standard error of prediction at the 1-percent AEP for the regression equations ranged from 18 to 164 percent; the pseudo coefficient of determination (pseudo-R2) at the 1-percent AEP ranged from 46 to 100 percent. The regression equations performed well for all regions except leeward Molokaʻi and southern Island of Hawaiʻi; for all other regions, the pseudo-R2 values ranged from about 75 to 100 percent. Compared to the regression equations developed by Oki and others (2010), the regression equations in this study generally showed modest improvements, although the magnitude of differences varied for each region. Peak-flow estimates at the 238 streamgages included in this study are improved by weighting the at-site statistics computed with PeakFQ and the predicted flows based on the regression equations. Results of this study—including the final peak-flow estimates at streamgages and the regional regression equations—are implemented in the USGS StreamStats web application (U.S. Geological Survey, 2023, StreamStats: https://streamstats.usgs.gov/ss/ ). StreamStats provides a consistent approach for obtaining peak-flow estimates at streamgages and for applying the regional regression equations for estimating peak flows at ungaged locations.

Hawaii↗

USGS2022

Groundwater-level monitoring from January 17 to March 3, 2022, Hālawa area, O‘ahu, Hawai‘i

A reported fuel release in November 2021 at the Red Hill Bulk Fuel Storage Facility within the naval reservation at Red Hill led to the shutdown of several production wells in the Hālawa area, O‘ahu, Hawai‘i. Red Hill Shaft—one of the high-capacity production wells that shut down—was reactivated on January 29, 2022. Submersible pressure transducers were deployed at 20 wells in the Hālawa area to measure groundwater levels and evaluate the regional groundwater-level response to the resumption of groundwater withdrawals from Red Hill Shaft. Groundwater levels measured in wells from January 17 to March 3, 2022, ranged between 16 and 20 feet at all sites and generally between 17 and 19 feet at most sites. Average groundwater-level decreases measured in wells 10 days after the January 29, 2022, resumption of withdrawal from Red Hill Shaft ranged from about 0.1 to 0.4 foot. In general, greatest decreases in groundwater levels occurred in wells closest to Red Hill Shaft. The groundwater-level data contain uncertainty because of several potential sources of error associated with (1) the accuracy of the measuring tapes and submersible pressure transducers used, (2) the accuracy of the measuring-point altitude at the top of each well, (3) the stability of the submersible pressure transducers’ suspension depth in each well, (4) well plumbness and alignment, and (5) human error. Because of the potential sources of error, comparability of groundwater-level data may be affected. Some sources of uncertainty, including the accuracy of measuring-point altitudes, can be addressed and lead to improved accuracy and comparability of groundwater levels. Data collected for this study are available in the U.S. Geological Survey National Water Information System database.

Hawaii↗

USGS2022

January 18, 2022, Red Hill synoptic groundwater-level survey, Hālawa area, O‘ahu, Hawai‘i

On January 18, 2022, groundwater levels were measured in selected wells in the Hālawa area, O‘ahu, Hawai‘i, constituting a synoptic groundwater-level survey (shortened herein to “synoptic survey”) of the area. Groundwater levels were measured mainly from 9:00 a.m. to 12:00 p.m. (times listed in Hawai‘i standard time) and provide a snapshot of groundwater levels during the survey period. Following a reported fuel release that affected groundwater quality in the Red Hill area, several production wells were shut down in the weeks prior to the synoptic survey. These wells include the Red Hill Shaft (shut down on November 28, 2021) and the Hālawa Shaft (shut down on December 3, 2021, except for weekly, short-duration operations for water-quality sampling). Groundwater levels measured in wells during the synoptic survey ranged from 16.81 to 20.19 feet above mean sea level. The groundwater levels measured on January 18, 2022, were about 0.3 to 0.6 feet higher than those measured at common sites during a synoptic groundwater-level survey on December 23, 2021. The groundwater levels collected during the multiagency synoptic survey contain uncertainty because of several potential sources of error associated with (1) the accuracy of the measuring tapes used, (2) the accuracy of the measuring-point altitude at the top of each well, (3) well plumbness and alignment, (4) human error, and (5) changing conditions during the survey period. Because of these potential sources of error, comparability of groundwater-level measurements may be affected. Some of the sources of uncertainty can be addressed and lead to improved accuracy and comparability of the groundwater levels. For example, uncertainty associated with the measuring-point altitudes can be addressed by resurveying measuring-point altitudes to a common vertical datum using consistent surveying methods.

Hawaii↗

USGS2022

December 23, 2021, Red Hill synoptic groundwater-level survey, Hālawa area, O‘ahu, Hawai‘i

On December 23, 2021, groundwater levels were measured in selected wells in the Hālawa area, O‘ahu, Hawai‘i, constituting a synoptic groundwater-level survey (shortened herein to “synoptic survey”) of the area. Groundwater levels were measured mainly from 9:00 a.m. to 12:00 p.m. (times listed in Hawai‘i standard time) and provide a snapshot of groundwater levels during the survey period. Following a reported fuel release that affected groundwater quality in the Red Hill area, several production wells were shut down in the weeks prior to the synoptic survey. These wells include the Red Hill Shaft (shut down on November 28, 2021) and the Hālawa Shaft (shut down on December 3, 2021, except for weekly, short-duration operations for water-quality sampling). Groundwater levels measured in wells during the synoptic survey ranged from 16.34 to 19.77 feet above mean sea level. The groundwater levels collected during the multiagency synoptic survey contain uncertainty because of several potential sources of error associated with (1) the accuracy of the measuring tapes used, (2) the accuracy of the measuring-point altitude at the top of each well, (3) well plumbness and alignment, (4) human error, and (5) changing conditions during the survey period. Because of these potential sources of error, comparability of groundwater-level measurements may be affected. Some of the sources of uncertainty can be addressed and lead to improved accuracy and comparability of the groundwater levels. For example, uncertainty associated with the measuring-point altitudes can be addressed by resurveying measuring-point altitudes to a common vertical datum using consistent surveying methods.

Hawaii↗

USGS2021

Groundwater conditions and trends, 2009–19, Saipan, Commonwealth of the Northern Mariana Islands

Groundwater is the primary source of municipal water for Saipan. Nearly all groundwater for the municipal water supply is withdrawn from a freshwater-lens system with a limited amount of freshwater that is susceptible to saltwater intrusion. The status of Saipan’s groundwater resources has not been thoroughly assessed since 2003. The U.S. Geological Survey—in cooperation with the Office of Grants Management, Commonwealth of the Northern Mariana Islands, and in collaboration with the Commonwealth Utilities Corporation—assessed the status and characteristics of Saipan’s groundwater resources by (1) evaluating groundwater withdrawals from municipal production wells during 2014–19, (2) evaluating chloride concentrations of municipal groundwater withdrawals during 2009–19, and (3) collecting salinity profiles at selected groundwater-monitoring wells during 2018–19. At the time of preparation of this report (2019), the periods of groundwater-withdrawal and chloride-concentration data represent the only periods of data available since 2003. During 2014–19, groundwater for the municipal water supply was withdrawn from about 143 production wells. Most of the wells are drilled into limestone formations in the southern plateau and the Kagman Peninsula and generally have withdrawal rates of about 40–60 gallons per minute. Records of monthly groundwater withdrawals from municipal production wells were available for May 2014–March 2019; during that period, monthly withdrawals ranged from 5.7 to 12.8 million gallons per day (Mgal/d) and averaged 9.3 Mgal/d, although records were unavailable for 9 months (May 2015–January 2016). Private wells, mainly located on the western coastal plain, currently are permitted to withdraw a total of about 7 Mgal/d of groundwater. Actual groundwater withdrawals from private wells, however, are uncertain because withdrawal records for private wells are not available. The Commonwealth Utilities Corporation measured the chloride concentration of groundwater pumped from each of its production wells about twice a year from 2009–19; during this period, 146 production wells were active and sampled. Only 32 of the 146 (22 percent) municipal production wells had median chloride concentrations less than or equal to 250 milligrams per liter (mg/L), the secondary drinking water standard set by the U.S. Environmental Protection Agency. Eighty-one wells (55 percent) pumped water with median chloride concentrations above 500 mg/L. The Mann-Kendall test was used to determine if chloride concentrations of groundwater withdrawals at 146 municipal production wells had statistically significant trends during December 2009–February 2019. Trends were considered statistically significant for probability values (p-values) less than or equal to 0.05. Test results indicate an upward trend at 9 wells, a downward trend at 52 wells, and no trend at 85 wells. Salinity profiles were measured in 12 selected monitor wells during July–August 2018 and were measured in six of the twelve selected monitor wells during March 2019. The salinity profiles were used to estimate the thickness of the freshwater lens at 10 monitor wells; freshwater-lens thickness was greatest (46 ft) in a monitor well in the Dan Dan well field near the northern part of the southern plateau. Freshwater-lens-thickness estimates elsewhere were (1) between 0 and 28 ft for the remaining monitor wells on the southern plateau, (2) between 19 and 21 ft for monitor wells on the Kagman Peninsula, (3) 2 ft for a monitor well in the Sablan Quarry well field on west-central Saipan, and (4) 8 ft for a monitor well in the Marpi Quarry well field on northern Saipan.

Commonwealth of the Norhtern Marianas Islands, Sai↗

USGS2018

Groundwater-level, groundwater-temperature, and barometric-pressure data, July 2017 to February 2018, Hālawa Area, Oʻahu, Hawaiʻi

The Red Hill Bulk Fuel Storage Facility, operated by the U.S. Navy and located in the Hālawa area, Oʻahu, Hawaiʻi, includes 20 underground storage tanks that can hold a total of 250 million gallons of fuel. In January 2014, the U.S. Navy notified the Hawaiʻi Department of Health and U.S. Environmental Protection Agency of release of an estimated 27,000 gallons of fuel from the Red Hill Bulk Fuel Storage Facility. In response to past and potential future fuel releases, data are needed to evaluate groundwater flow in the surrounding area. During July 2017–February 2018, the U.S. Geological Survey collected groundwater-level data at 24 sites near the Red Hill Bulk Fuel Storage Facility. At 14 of the 24 sites, groundwater-temperature data were also collected, and at 6 of the 24 sites, barometric-pressure data were collected. During the data-collection period, a regional aquifer test was conducted in coordination with the operators of three production wells in the area. The recorded water-level changes in response to planned withdrawal changes during December 2017–February 2018 can be used to improve understanding of the groundwater-flow system. The scope of this report is limited to a non-interpretive presentation of the data and a brief discussion of the factors affecting the water-level data.

Hawai'i↗