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137 records · Page 8Linked to original sources
USGS1998

Hydrogeology and simulation of ground-water flow in the Paluxy aquifer in the vicinity of Landfills 1 and 3, U.S. Air Force Plant 4, Fort Worth, Texas

Ground-water contamination of the surficial terrace alluvial aquifer has occurred at U.S. Air Force Plant 4, a government-owned, contractor-operated facility, northwest of Fort Worth, Texas. A poorly constructed monitoring well, P–22M, open to the underlying middle zone of the Paluxy aquifer was installed at landfill 3, October 1987, allowing leakage of contaminated ground water to reach the Paluxy aquifer. This well was plugged and abandoned in November 1995. Additionally, volatile organic compounds have been detected in fractures in the Goodland-Walnut confining unit, the hydrogeologic unit separating the terrace alluvial aquifer from the underlying Paluxy aquifer, beneath the western part of landfill 1. Volatile organic compounds in concentrations near the analytical detection limit were detected in the upper Paluxy prior to the drilling of well P–22M. The ground-water-flow simulation model described in this report was developed to examine the best logistically feasible location to install recovery wells to capture the low concentration (less than 100 micrograms per liter) trichloroethylene plume beneath landfills 1 and 3 (west Paluxy plume). Once the recovery wells were installed (1996), the simulation model was recalibrated with new data. This report documents the capture area of the installed recovery wells. Four geologic units are pertinent to this site-specific model. From oldest to youngest, these are the Glen Rose Formation, Paluxy Formation, Walnut Formation, and Goodland Limestone. The Glen Rose Formation is relatively impermeable in the study area and forms the confining unit underlying the Paluxy Formation. The Paluxy Formation forms the Paluxy aquifer, which is a public drinking water supply for the City of White Settlement. The Walnut Formation and Goodland Limestone form the Goodland-Walnut confining unit overlying the Paluxy aquifer. Near landfill 3, gamma-ray logs indicate three distinct zones of the Paluxy Formation; upper, middle, and lower. The formation is about 170-feet thick near landfill 3, and each zone is about 57-feet thick. Two steady-state simulations using the computer program MODFLOW were analyzed using the particle-tracking computer program, MODPATH. One simulation is the calibration simulation using Paluxy aquifer water-level data for May 1993. The second simulation includes the installed recovery wells. A variably spaced grid was designed for the model. The smallest grid cells, 25 by 25 feet, are in the vicinity of landfills 1 and 3. The largest cells, 4,864.5 by 1,441.5 feet, are at the northwestern corner of the model grid near the Parker-Tarrant County line. The modeling was accomplished with three layers representing the upper, middle, and lower zones of the Paluxy aquifer. Particles, which represent contaminant molecules moving in solution with the ground water, were tracked from well P–22M and an area below landfill 1, at the top of the upper zone of the Paluxy aquifer, for 9 years (forward tracking). The forward tracking estimates where contaminants might move by advection from 1987 to 1996. Analysis of backward tracking from the new recovery wells indicates that the simulated contributing area to the recovery wells intercepts the contaminant plume, minimizing off-site migration of the west Paluxy plume. To determine the effectiveness of the recovery wells, monitoring wells southeast of Building 14 have been installed (1996–97) for sampling.

Texas↗
USGS2025

Inundation processes, barrier island breaching, and structure impacts during Hurricane Michael (2018)

We demonstrate the increased ability to forecast hurricane impacts with a coupled numerical modeling system by simulating ocean waves, water levels, currents, sediment transport, and structural damage to predict inundation, coastal morphological change, and residential building impacts. The Coupled-Ocean-Atmosphere-Waves-Sediment-Transport (COAWST) modeling system is applied to simulate Hurricane Michael (category 5, 2018) that made landfall near Tyndall Air Force Base, FL, in the northern Gulf of America, causing severe devastation and flooding. Atmospheric forcings from the Coupled Ocean/Atmosphere Mesoscale Prediction System for Tropical Cyclones (COAMPS-TC) are used to drive the ocean and wave models on a series of nested grids. Results identify that coastal inundation at Mexico Beach is due to surge from winds and waves, supplemented by pulses of infragravity wave motions that propagate landward into the inundation region. Seed lines observed on interior building walls also demonstrate variable changes in water level. In addition, a machine learning model was applied to hindcast structure damages, caused mostly by waves and winds, with a 72% accuracy estimate of substantial damage in proximity of landfall. The storm also created a breach across Cape San Blas, the adjacent barrier spit, due to large surge and low dune elevations. Dune locations with vegetated land cover are shown to reduce wave-energy dissipation and reduce erosion, whereas locations without land cover had increased breaching potential. The breach occurred during the maximum ocean-side water level, and the delayed high water on the bay side allowed a pressure gradient to drive flow seaward and promote breach development.

Florida↗
USGS2005

Analysis of borehole-radar reflection data from Machiasport, Maine, December 2003

In December 2003, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, collected borehole-radar reflection logs in two boreholes in Machiasport, Maine. These bedrock boreholes were drilled as part of a hydrogeologic investigation of the area surrounding the former Air Force Radar Tracking Station site on Howard Mountain near Bucks Harbor. The boreholes, MW09 and MW10, are located approximately 50 meters (m) from, and at the site of, respectively, the locations of former buildings where trichloroethylene was used as part of defense-site operations. These areas are thought to be potential source areas for contamination that has been detected in downgradient bedrock wells. This investigation focused on testing borehole-radar methods at this site. Single-hole radar-reflection surveys were used to identify the depth, orientation, and spatial continuity of reflectors that intersect and surround the boreholes. In addition, the methods were used to (1) identify the radial depth of penetration of the radar waves in the electrically resistive bimodal volcanic formation at the site, (2) provide information for locating additional boreholes at the site, and (3) test the potential applications of borehole-radar methods for further aquifer characterization and (or) evaluation of source-area remediation efforts. Borehole-radar reflection logging uses a pair of downhole transmitting and receiving antennas to record the reflected wave amplitude and transit time of high-frequency electromagnetic waves. For this investigation, 60- and 100-megahertz antennas were used. The electromagnetic waves emitted by the transmitter penetrate into the formation surrounding the borehole and are reflected off of a material with different electromagnetic properties, such as a fracture or change in rock type. Single-hole directional radar surveys indicate the bedrock surrounding these boreholes is highly fractured, because several reflectors were identified in the radar-reflection data. There are several steeply dipping reflectors with orientations similar to the fracture patterns observed with borehole imaging techniques and in outcrops. The radar-reflection data showed that the vitrophyre in borehole MW09 was more highly fractured than the underlying gabbroic unit. The velocities of radar waves in the bedrock surrounding the boreholes were determined using single-hole vertical radar profiling. Velocities of 114 and 125 meters per microsecond were used to determine the distance to reflectors, the radial depth of penetration, and the dip of reflectors. The bimodal volcanic units appear to be ideal for radar-wave propagation. For the radar surveys collected at this site, radar reflections were detected up to 40 m into the rock from the borehole. These results indicate that boreholes could conservatively be spaced about 15-20 m apart for hole-to-hole radar methods to be effective for imaging between the boreholes and monitoring remediation. Integrated analysis of drilling and borehole-geophysical logs indicates the vitrophyric formation is more fractured than the more mafic gabbroic units in these boreholes. There does not, however, appear to be a quantifiable difference in the radar-wave penetration in these two rock units.

Maine↗
USGS2007

Correlations between Cassini VIMS spectra and RADAR SAR images: Implications for Titan's surface composition and the character of the Huygens Probe Landing Site

Titan's vast equatorial fields of RADAR-dark longitudinal dunes seen in Cassini RADAR synthetic aperture images correlate with one of two dark surface units discriminated as “brown” and “blue” in Visible and Infrared Mapping Spectrometer (VIMS) color composites of short-wavelength infrared spectral cubes (RGB as 2.0, 1.6, 1.3 μm). In such composites bluer materials exhibit higher reflectance at 1.3 μm and lower at 1.6 and 2.0 μm. The dark brown unit is highly correlated with the RADAR-dark dunes. The dark brown unit shows less evidence of water ice suggesting that the saltating grains of the dunes are largely composed of hydrocarbons and/or nitriles. In general, the bright units also show less evidence of absorption due to water ice and are inferred to consist of deposits of bright fine precipitating tholin aerosol dust. Some set of chemical/mechanical processes may be converting the bright fine-grained aerosol deposits into the dark saltating hydrocarbon and/or nitrile grains. Alternatively the dark dune materials may be derived from a different type of air aerosol photochemical product than are the bright materials. In our model, both the bright aerosol and dark hydrocarbon dune deposits mantle the VIMS dark blue water ice-rich substrate. We postulate that the bright mantles are effectively invisible (transparent) in RADAR synthetic aperture radar (SAR) images leading to lack of correlation in the RADAR images with optically bright mantling units. RADAR images mostly show only dark dunes and the water ice substrate that varies in roughness, fracturing, and porosity. If the rate of deposition of bright aerosol is 0.001–0.01 μm/yr, the surface would be coated (to optical instruments) in hundreds-to-thousands of years unless cleansing processes are active. The dark dunes must be mobile on this very short timescale to prevent the accumulation of bright coatings. Huygens landed in a region of the VIMS bright and dark blue materials and about 30 km south of the nearest occurrence of dunes visible in the RADAR SAR images. Fluvial/pluvial processes, every few centuries or millennia, must be cleansing the dark floors of the incised channels and scouring the dark plains at the Huygens landing site both imaged by Descent Imager/Spectral Radiometer (DISR).

Planetary and Space Science↗
USGS2014

Groundwater-flow and land-subsidence model of Antelope Valley, California

Antelope Valley, California, is a topographically closed basin in the western part of the Mojave Desert, about 50 miles northeast of Los Angeles. The Antelope Valley groundwater basin is about 940 square miles and is separated from the northern part of Antelope Valley by faults and low-lying hills. Prior to 1972, groundwater provided more than 90 percent of the total water supply in the valley; since 1972, it has provided between 50 and 90 percent. Most groundwater pumping in the valley occurs in the Antelope Valley groundwater basin, which includes the rapidly growing cities of Lancaster and Palmdale. Groundwater-level declines of more than 270 feet in some parts of the groundwater basin have resulted in an increase in pumping lifts, reduced well efficiency, and land subsidence of more than 6 feet in some areas. Future urban growth and limits on the supply of imported water may increase reliance on groundwater. In 2011, the Los Angeles County Superior Court of California ruled that the Antelope Valley groundwater basin is in overdraft—groundwater extractions are in excess of the Court-defined safe yield of the groundwater basin. The Court determined that the safe yield of the adjudicated area of the basin was 110,000 acre-feet per year (acre-ft/yr). Natural recharge is an important component of total groundwater recharge in Antelope Valley; however, the exact quantity and distribution of natural recharge, primarily in the form of mountain-front recharge, is uncertain, with total estimates ranging from 30,000 to 160,000 acre-ft/yr. Technical experts, retained by parties to the adjudication, used 60,000 acre-ft/yr to estimate the sustainable yield of the basin, and this value was used in this study. In order to better understand the uncertainty associated with natural recharge and to provide a tool to aid in groundwater management, a numerical model of groundwater flow and land subsidence in the Antelope Valley groundwater basin was developed using old and new geohydrologic information. The groundwater-flow system consists of three aquifers: the upper, middle, and lower aquifers. The three aquifers, which were identified on the basis of the hydrologic properties, age, and depth of the unconsolidated deposits, consist of gravel, sand, silt, and clay alluvial deposits and clay and silty clay lacustrine deposits. Prior to groundwater development in the valley, recharge was primarily the infiltration of runoff from the surrounding mountains. Groundwater flowed from the recharge areas to discharge areas around the playas where it discharged from the aquifer system as either evapotranspiration or from springs. Partial barriers to horizontal groundwater flow, such as faults, have been identified in the groundwater basin. Water-level declines owing to groundwater development have eliminated the natural sources of discharge, and pumping for agricultural and urban uses have become the primary source of discharge from the groundwater system. Infiltration of return flow from agricultural irrigation has become an important source of recharge to the aquifer system. The groundwater-flow model of the basin was discretized horizontally into a grid of 130 rows and 118 columns of square cells 1 kilometer (0.621 mile) on a side, and vertically into four layers representing the upper (two layers), middle (one layer), and lower (one layer) aquifers. Faults that were thought to act as horizontal-flow barriers were simulated in the model. The model was calibrated to simulate steady-state conditions, represented by 1915 water levels and transient-state conditions during 1915–95, by using water-level and subsidence data. Initial estimates of the aquifer-system properties and stresses were obtained from a previously published numerical model of the Antelope Valley groundwater basin; estimates also were obtained from recently collected hydrologic data and from results of simulations of groundwater-flow and land-subsidence models of the Edwards Air Force Base area. Some of these initial estimates were modified during model calibration. Groundwater pumpage for agriculture was estimated on the basis of irrigated crop acreage and crop consumptive-use data. Pumpage for public supply, which is metered, was compiled and entered into a database used for this study. Estimated annual agricultural pumpage peaked at 395,000 acre-feet (acre-ft) in 1951 and then declined because of declining agricultural production. Recharge from irrigation return flows was assumed to be 30 percent of agricultural pumpage; delays associated with return flow moving through the unsaturated zone were also simulated. The annual quantity of mountain-front recharge initially was based on estimates from previous studies. The model was calibrated using the PEST software suite; prior information from the area was incorporated through the use of Tikhonov regularization. During model calibration, the estimated mountain-front recharge was reduced from the previous estimate of 30,300 acre-ft/yr to 29,150 acre-ft/yr. Results of the simulations using the calibrated model indicate that simulated groundwater pumpage exceeded recharge in most years, resulting in an estimated cumulative depletion in groundwater storage of 8,700,000 acre-ft during the transient-simulation period (1915–2005). About 15,000,000 acre-ft of cumulative groundwater pumpage was simulated during the transient-simulation period (1915–2005), reaching a maximum rate of about 400,000 acre-ft/yr in 1951. Groundwater pumpage resulted in simulated hydraulic heads declining by more than 150 feet (ft) compared to 1915 conditions in agricultural areas. The decline in hydraulic head in the groundwater basin is the result of this depletion of groundwater storage. In turn, the simulated decline in hydraulic head in the groundwater basin has resulted in the decrease in natural discharge from the basin and has caused compaction of aquitards, resulting in land subsidence. The areal distribution of total simulated land subsidence for 2005, after about 90 years of groundwater development, indicates that land subsidence occurred throughout almost the entire Lancaster subbasin, with a maximum of about 9.4 ft in the central and eastern parts of the subbasin. An important objective of this study was to systematically address the uncertainty in estimates of natural recharge and related aquifer parameters by using the groundwater-flow and land-subsidence model with observational data and expert knowledge. After the model was calibrated to the observations and a reasonable parameter set obtained, the parameter null space—parameter values that do not appreciably affect the model calibration but may have importance for prediction—was identified. The effect of parameter uncertainty on the estimation of mountain-front recharge was addressed using the Null-Space Monte Carlo method. The Pareto trade-off method of visualizing uncertainty was also used to portray the reasonableness of larger natural-recharge rates. Results indicate that the total mountain-front recharge likely ranges between 28,000 and 44,000 acre-ft/yr, which is appreciably less than published estimates of 60,000 acre-ft/yr. Additionally, expected errors associated with agricultural pumpage estimates used in this study were found to have relatively little effect on the estimates of mountain-front recharge, reflecting the difficulty in increasing recharge through manipulation of other components of the water budget. The calibrated model was used to simulate the response of the aquifer to potential future pumping scenarios: (1) no change in the distribution of pumpage, or status quo; (2) redistribution of pumpage; and (3) artificial recharge. All three of these scenarios specify a total pumpage throughout the Antelope Valley of 110,000 acre-ft/yr according to the safe yield value ruled by the Los Angeles County Superior Court of California. This reduction in groundwater pumpage is assumed uniform throughout the basin, based on a 10-percent reduction of the total pumpage in 2005 to achieve the 110,000 acre-ft/yr level. The calibrated Antelope Valley groundwater-flow and land-subsidence model was used to simulate the hydrologic effects of the three groundwater-management scenarios during a 50-year period by using the reduced, temporally constant, pumpage distribution. Results from the first scenario indicated that the total drawdown observed since predevelopment would continue, with values exceeding 325 ft near Palmdale; consequently, land subsidence would also continue, with additional subsidence (since 2005) exceeding 3 ft in the central part of the Lancaster subbasin. The second scenario evaluated redistributing pumpage from areas in the Lancaster subbasin where simulated hydraulic-head declines were the greatest to areas where declines were smallest. Neither a formal optimization algorithm nor water-rights allocations were considered when redistributing the pumpage. Results indicated that hydraulic heads near Palmdale, where the pumpage was reduced, would recover by about 200 ft compared to 2005 conditions, with only 30 ft of additional drawdown in the northwestern part of the Lancaster subbasin, where the pumpage was increased. The magnitude of the simulated additional land subsidence decreased slightly compared to the first, status quo, scenario but land subsidence continued to be simulated throughout most of the northern part of the Lancaster subbasin. The third scenario consisted of two artificial-recharge simulations along the Upper Amargosa Creek channel and at a site located north of Antelope Buttes. Results indicate that applying artificial recharge at these sites would yield continued drawdowns and associated land subsidence. However, the magnitudes of drawdown and subsidence would be smaller than those simulated in the status quo scenario, indicating that artificial-recharge operations in the Antelope Valley could be expected to reduce the magnitude and extent of continued water-level declines and associated land subsidence.

California↗
USGS2021

Assessment of runoff volume reduction associated with soil amendments added to portions of highway median-strip catchments in Ohio, 2018–20

The U.S. Geological Survey installed 10 rain gages and 12 calibrated H-flumes to measure rainfall and runoff volumes at 10 locations in Ohio Department of Transportation highway median-strip catchments. Data were collected to facilitate comparisons of rainfall and runoff volumes at study sites before and after stormwater best management practices (BMPs) were installed and between sites with different BMPs. The BMP treatments comprised removing the top layer of the existing soil, rototilling the remaining soil to a 6-inch depth, mixing the soils with one of two soil amendments (compost with sand or shale) at one of two thicknesses (4 inches or 6 inches), topping with a compost blanket, seeding, and installing erosion control matting. The overall treatment used at a given study site is referred to as “BMP.” At two locations where soil amendments were installed, a second “control” site was installed to measure runoff from an adjacent catchment in the same median strip where no soil amendment was installed. This no-treatment option (no soil amendment) was considered its own class of BMP. Rainfall and runoff data were collected during periods when air temperatures were above freezing (including all months except January, February, and parts of December and March) from 2018 to 2020. The data collection period for each study site was divided into “pre-BMP” and “post-BMP” periods. Equipment to measure rainfall and runoff was installed and data were collected from April to December 2018 before installation of soil amendments (the pre-BMP period). The post-BMP period started between April and May of 2019 at the first measured rainfall after soil amendments were installed. Rainfall and runoff monitoring continued through September 2020. For control sites, the post-BMP periods were assigned to start with the first measured rainfall in the 2019 data collection season. A rainfall-runoff “event” was defined as beginning at the time of the first measured rainfall and ending when rainfall and runoff (if any) ceased and remained ceased for at least 3 hours. A value referred to as “event runoff percentage,” defined as the total volume of runoff during an event expressed as a percentage of the total volume of rainfall falling over the catchment, was computed for each event. The distribution of rainfall totals associated with events was similar between the pre-BMP and post-BMP periods; however, there were appreciable between-site differences in the distribution of event runoff percentages during the pre-BMP and post-BMP periods. Empirical distribution function (EDF) tests were performed with and without data from events that resulted in no runoff to determine whether the distribution of event runoff percentages changed from the pre-BMP period to the post-BMP period. The null hypothesis that the EDFs of event runoff percentages were equal in the pre-BMP and post-BMP periods was rejected ( α =0.05) in at least one of the two tests for four sites (one site with a shale amendment and three sites with sand amendments). Mean event runoff percentages at each of those four sites decreased from the pre-BMP period to the post-BMP period. The null hypothesis that the EDFs of event runoff percentages were equal was not rejected for the other six sites’ draining catchments with soil amendments or the two control sites. EDF tests performed on event rainfall totals indicated no statistically significant changes between the pre-BMP and post-BMP period distributions for any of the sites. Double-mass analyses of cumulative runoff were performed for two pairs of closely spaced sites (each pair located in a common median strip): one site in each pair drained a catchment where soil amendments were installed, and the other (a control) drained a catchment without soil amendments. Those double-mass analyses indicated a small reduction in runoff from the pre-BMP to post-BMP period at the site whose catchment received the sand and compost amendment, but no perceptible reduction in runoff at the site whose catchment received the shale and compost amendment. Regression analyses indicated that (a) three rainfall factors (event rainfall totals, total rainfall for the previous 7 days, and a cross product of the factors) and the intercept term were the four most important factors explaining event runoff percentages, (b) the effect of amendment type on event runoff percentage was small in comparison to the rainfall and intercept terms, (c) event runoff percentages tended to be lower for sites with shale amendments than sites with sand amendments; however, event runoff percentages tended to be lower for control sites than for sites with shale or sand amendments, and (d) event runoff percentages increased with increasing amendment thickness. The counterintuitive results that event runoff percentages increased with increasing amendment thickness and that control sites tended to have lower event runoff percentages than sites draining soil-amended catchments likely reflects unmeasured factors that existed at the sites before BMPs were installed rather than the effect of the BMP treatments. Although not definitive, some support for the conclusion that the sand amendment was generally more effective at reducing runoff than the shale amendment was provided by results from the EDF tests, double-mass analyses, and runoff statistics.

Ohio↗
USGS2013

Potential reductions of street solids and phosphorus in urban watersheds from street cleaning, Cambridge, Massachusetts, 2009-11

Material accumulating and washing off urban street surfaces and ultimately into stormwater drainage systems represents a substantial nonpoint source of solids, phosphorus, and other constituent loading to waterways in urban areas. Cost and lack of usable space limit the type and number of structural stormwater source controls available to municipalities and other public managers. Non-structural source controls such as street cleaning are commonly used by cities and towns for construction, maintenance and aesthetics, and may reduce contaminant loading to waterways. Effectiveness of street cleaning is highly variable and potential improvements to water quality are not fully understood. In 2009, the U.S. Geological Survey, in cooperation with the Massachusetts Department of Environmental Protection, the U.S. Environmental Protection Agency, and the city of Cambridge, Massachusetts, and initiated a study to better understand the physical and chemical nature of the organic and inorganic solid material on street surfaces, evaluate the performance of a street cleaner at removing street solids, and make use of the Source Loading and Management Model (SLAMM) to estimate potential reductions in solid and phosphorus loading to the lower Charles River from various street-cleaning technologies and frequencies. Average yield of material on streets collected between May and December 2010, was determined to be about 740 pounds per curb-mile on streets in multifamily land use and about 522 pounds per curb-mile on commercial land-use streets. At the end-of-winter in March 2011, about 2,609 and 4,788 pounds per curb-mile on average were collected from streets in multifamily and commercial land-use types, respectively. About 86 percent of the total street-solid yield from multifamily and commercial land-use streets was greater than or equal to 0.125 millimeters in diameter (or very fine sand). Observations of street-solid distribution across the entire street width indicated that as much as 96 percent of total solids resided within 9 feet of the curb. Median accumulation rates of street solids and median washoff of street solids after rainstorms on multifamily and commercial land-use streets were also similar at about 33 and 22 pounds per curb-mile per day, and 35 and 40 percent, respectively. Results indicate that solids on the streets tested in Cambridge, Mass., can recover to pre-rainstorm yields within 1 to 3 days after washoff. The finer grain-size fractions tended to be more readily washed from the roadway surfaces during rainstorms. Street solids in the coarsest grain-size fraction on multifamily streets indicated an average net increase following rainstorms and are likely attributed to debris run-on from trees, lawns, and other plantings commonly found in residential areas. In seven experiments between May and December 2010, the median removal efficiency of solids from street surfaces following a single pass by a regenerative-air street cleaner was about 82 percent on study sites in the multifamily land-use streets and about 78 percent on the commercial land-use streets. Median street-solid removal efficiency increased with increasing grain size. This type of regenerative-air street cleaner left a median residual street-solid load on the street surface of about 100 pounds per curb-mile. Median concentrations of organic carbon and total phosphorus (P) on multifamily streets were about 35 and 29 percent greater, respectively, than those found on commercial streets. The median total mass of organic carbon and total P in street solids on multifamily streets was 68 and 75 percent greater, respectively, than those found on commercial streets. More than 87 percent of the mass of total P was determined to be in solids greater than or equal to 0.125 millimeters in diameter for both land-use types. The median total accumulation rate for total P on multifamily streets was about 5 times greater than on commercial streets. Total P accumulation in the medium grain-size fraction was nearly the same for streets within both land-use types at 0.004 pounds per curb-mile per day. Accumulation rates within the coarsest and finest grain-size fractions on multifamily streets were about 11 and 82 times greater than those on the commercial streets. Median washoff of total P was 58 and 48 percent from streets in multifamily and commercial land-use types, respectively, and generally increased with decreasing grain size. Total P median reductions resulting from a single pass of a regenerative-air street cleaner on streets in multifamily and commercial land-use types were about 82 and 62 percent, respectively, and were similar in terms of grain size between both land-use types. A Source Loading and Management Model for Microsoft Windows (WinSLAMM) was applied to a 21.8 acre subcatchment in Cambridge, Mass. The subcatchment area consists of mostly commercial and multifamily land-use types to evaluate the potential reductions of total and particulate solids, and P attributed to street cleaning. Rainwater runoff from rooftops represented between 20 and 50 percent of the total basin runoff. Street surfaces only accounted for about 20 percent of the total basin runoff. Monthly applications of mechanical-brush and vacuum-assisted street cleaners within the subcatchment as defined by SLAMM for areas with long-term (24-hour) on-street parking and monthly parking controls using five average climatic years resulted in total solid reductions of about 3 and 5 percent, respectively. Simulating the regenerative-air street cleaner tested as part of this study resulted in total solid reductions of about 16 percent. Increasing street cleaning frequency to three times weekly increased total solids removal for mechanical-brush, vacuum-assisted, and regenerative-air street cleaners to about 6, 14, and 19 percent, respectively. Monthly applications of mechanical-brush, vacuum-assisted, and regenerative-air street cleaners within the subcatchment resulted in total P reductions of about 1, 3, and 8 percent, respectively. A street cleaning frequency of three times each week for each of the three street-cleaner types increased total P removal to about 3, 7, and 9 percent, respectively.

Massachusetts↗
USGS2014

High-resolution delineation of chlorinated volatile organic compounds in a dipping, fractured mudstone: depth- and strata-dependent spatial variability from rock-core sampling

Synthesis of rock-core sampling and chlorinated volatile organic compound (CVOC) analysis at five coreholes, with hydraulic and water-quality monitoring and a detailed hydrogeologic framework, was used to characterize the fine-scale distribution of CVOCs in dipping, fractured mudstones of the Lockatong Formation of Triassic age, of the Newark Basin in West Trenton, New Jersey. From these results, a refined conceptual model for more than 55 years of migration of CVOCs and depth- and strata-dependent rock-matrix contamination was developed. Industrial use of trichloroethene (TCE) at the former Naval Air Warfare Center (NAWC) from 1953 to 1995 resulted in dense non-aqueous phase liquid (DNAPL) TCE and dissolved TCE and related breakdown products, including other CVOCs, in underlying mudstones. Shallow highly weathered and fractured strata overlie unweathered, gently dipping, fractured strata that become progressively less fractured with depth. The unweathered lithology includes black highly fractured (fissile) carbon-rich strata, gray mildly fractured thinly layered (laminated) strata, and light-gray weakly fractured massive strata. CVOC concentrations in water samples pumped from the shallow weathered and highly fractured strata remain elevated near residual DNAPL TCE, but dilution by uncontaminated recharge, and other natural and engineered attenuation processes, have substantially reduced concentrations along flow paths removed from sources and residual DNAPL. CVOCs also were detected in most rock-core samples in source areas in shallow wells. In many locations, lower aqueous concentrations, compared to rock core concentrations, suggest that CVOCs are presently back-diffusing from the rock matrix. Below the weathered and highly fractured strata, and to depths of at least 50 meters (m), groundwater flow and contaminant transport is primarily in bedding-plane-oriented fractures in thin fissile high-carbon strata, and in fractured, laminated strata of the gently dipping mudstones. Despite more than 18 years of pump and treat (P&T) remediation, and natural attenuation processes, CVOC concentrations in aqueous samples pumped from these deeper strata remain elevated in isolated intervals. DNAPL was detected in one borehole during coring at a depth of 27 m. In contrast to core samples from the weathered zone, concentrations in core samples from deeper unweathered and unfractured strata are typically below detection. However, high CVOC concentrations were found in isolated samples from fissile black carbon-rich strata and fractured gray laminated strata. Aqueous-phase concentrations were correspondingly high in samples pumped from these strata via short-interval wells or packer-isolated zones in long boreholes. A refined conceptual site model considers that prior to P&T remediation groundwater flow was primarily subhorizontal in the higher-permeability near surface strata, and the bulk of contaminant mass was shallow. CVOCs diffused into these fractured and weathered mudstones. DNAPL and high concentrations of CVOCs migrated slowly down in deeper unweathered strata, primarily along isolated dipping bedding-plane fractures. After P&T began in 1995, using wells open to both shallow and deep strata, downward transport of dissolved CVOCs accelerated. Diffusion of TCE and other CVOCs from deeper fractures penetrated only a few centimeters into the unweathered rock matrix, likely due to sorption of CVOCs on rock organic carbon. Remediation in the deep, unweathered strata may benefit from the relatively limited migration of CVOCs into the rock matrix. Synthesis of rock core sampling from closely spaced boreholes with geophysical logging and hydraulic testing improves understanding of the controls on CVOC delineation and informs remediation design and monitoring.

New Jersey, New York, Pennsylvania↗
USGS2015

Spatial and temporal migration of a landfill leachate plume in alluvium

Leachate from unlined or leaky landfills can create groundwater contaminant plumes that last decades to centuries. Understanding the dynamics of leachate movement in space and time is essential for monitoring, planning and management, and assessment of risk to groundwater and surface-water resources. Over a 23.4-year period (1986–2010), the spatial extent of the Norman Landfill leachate plume increased at a rate of 7800 m 2 /year and expanded by 878 %, from an area of 20,800 m 2 in 1986 to 203,400 m 2 in 2010. A linear plume velocity of 40.2 m/year was calculated that compared favorably to a groundwater-seepage velocity of 55.2 m/year. Plume-scale hydraulic conductivity values representative of actual hydrogeological conditions in the alluvium ranged from 7.0 × 10 −5 to 7.5 × 10 −4 m/s, with a median of 2.0 × 10 −4 m/s. Analyses of field-measured and calculated plume-scale hydraulic conductivity distributions indicate that the upper percentiles of field-measured values should be considered to assess rates of plume-scale migration, spreading, and biodegradation. A pattern of increasing Cl − concentrations during dry periods and decreasing Cl − concentrations during wet periods was observed in groundwater beneath the landfill. The opposite occurred in groundwater downgradient from the landfill; that is, Cl − concentrations in groundwater downgradient from the landfill decreased during dry periods and increased during wet periods. This pattern of changing Cl − concentrations in response to wet and dry periods indicates that the landfill retains or absorbs leachate during dry periods and produces lower concentrated leachate downgradient. During wet periods, the landfill receives more recharge which dilutes leachate in the landfill but increases leachate migration from the landfill and produces a more concentrated contaminant plume. This approach of quantifying plume expansion, migration, and concentration during variable hydrologic conditions provides increased understanding of plume behavior and migration potential and may be applied at less monitored landfill sites to evaluate potential risks of contamination to downgradient receptors.

Water, Air, & Soil Pollution↗
USGS2019

National assessment of shoreline change — Historical shoreline change along the north coast of Alaska, Icy Cape to Cape Prince of Wales

Beach erosion is a persistent problem along most open-ocean shores of the United States. Along the Arctic coast of Alaska, coastal erosion is widespread and threatens communities, defense and energy-related infrastructure, and coastal habitat. As coastal populations continue to expand and infrastructure and habitat are increasingly threatened by erosion, there is increased demand for accurate information regarding past and present trends and rates of shoreline movement. Shoreline change was evaluated by comparing three to four historical shoreline positions derived from 1950s-era topographic surveys and black and white aerial photography, 1980s-era color-infrared Alaska High-Altitude Aerial Photography, 2003 natural color aerial photography, and 2010s-era natural color aerial photography. Long-term (1950s–2010s) and short-term (1980s–2010s) shoreline change rates were calculated using linear-regression and end-point methods, respectively, at transects spaced approximately every 50 meters along both the mainland and barrier island coasts. Shoreline change rates calculated on more than 24,000 individual transects indicate that between 1948 and 2016 the northern coast of Alaska between Icy Cape and Cape Prince of Wales was slightly erosional, with 68 percent of the total transects showing shoreline retreat over the long term and 63 percent over the short term. However, only 9 percent of the total transects showed shoreline retreat greater than 1 meter per year (m/yr) over the long and short term, respectively. Mean rates of shoreline change of −0.2±0.1 and −0.2±0.3 m/yr, were calculated for the long and short term, respectively. Many rates measured were near the limit of our shoreline change uncertainty estimates. Erosion and accretion rates on individual transects ranged from −8.3 to +9.6 m/yr over the long term and −16.0 to +20.0 m/yr over the short-term analysis periods. The highest rates of erosion and accretion were associated with the formation and migration of inlets along barrier island coasts. The highest erosional rates of change were measured in the southern part of the study area between Sullivan Lake and Cape Prince of Wales. The highest accretional rates of change were measured in the northern part of the study area on the open-ocean coast of barrier islands fronting Kasegaluk Lagoon. Open-ocean exposed shorelines compose 85 percent of all transects and 70 percent were erosional over the long term. Sheltered mainland-lagoon shorelines compose 15 percent of all transects in the study area and 58 percent were erosional over the long term. Although mean shoreline change rates were quite low along all coasts, exposed shorelines retreated at twice the rate (−0.2±0.1 m/yr) of sheltered shorelines (−0.1±0.1 m/yr). Barrier shoreline transects (includes barrier islands, spits, and beaches) compose 49 percent of the total transects and 56 percent of all exposed shoreline transects. Mean shoreline change rates on exposed barrier shorelines were only slightly greater than exposed mainland shorelines (−0.3±0.1 and −0.2±0.1 m/yr, respectively). Mean shoreline change rates on sheltered barrier shorelines were similar to sheltered mainland shorelines (−0.1±0.3 m/yr). In contrast to the majority of the Nation’s shorelines, for all but three months of the year (July–September), the north coast of Alaska has historically been protected by landfast sea ice from processes such as waves, winds, and currents that typically drive coastal change on beaches in more temperate regions of the world. Projected and observed increases in periods of sea-ice-free conditions, as sea ice melts earlier and forms later in the year, particularly in the autumn, when large storms are more common in the Arctic, suggest that Arctic coasts will be more vulnerable to storm surge and wave energy, potentially resulting in accelerated shoreline erosion and terrestrial habitat loss in the future. Increases in air and sea water temperatures may also increase erosion of the ice-rich, coastal permafrost bluffs present along much of Alaska’s Arctic coast. More frequent shoreline change data collection and analysis in this rapidly changing environment should be considered in order to evaluate shoreline change trends in the future.

Alaska↗
USGS2015

Real-time validation of the Dst Predictor model

The Dst Predictor model, which has been running real-time in the Space Weather Analysis and Forecast System (SWAFS), provides 1-hour and 4-hour forecasts of the Dst index. This is useful for awareness of impending geomagnetic activity, as well as driving other real-time models that use Dst as an input. In this report, we examine the performance of this forecast model in detail. When validating indices it should be noted that performance is only with respect to a reference index as they are derived quantities assumed to reflect a state of the magnetosphere that cannot be directly measured. In this case U.S. Geological Survey (USGS) Definitive Dst is the reference index (Section 3). Whether or not the model better reflects the actual activity level is nearly impossible to discern and is outside the scope of this report. We evaluate the performance of the model by computing continuous predictant skill scores against USGS Definitive Dst values as “observations” (Section 4.2). The two sets of data are not well-correlated for both 1-hour and 4-hour forecasts. The Dst Predictor Prediction Efficiency for both the 1- and 4-hour forecasts suggests poor performance versus the climatological mean. However, the skill score against a nowcast persistence model is positive, suggesting value added by the Dst Predictor model. We further examine statistics for storm times (Section 4.3) with similar results: nowcast persistence performs worse than Dst Predictor. Dst Predictor is superior to the nowcast persistence model for the metric used in this study. We recommend continued use of the DstPredictor model for 1-and4-hour Dst predictions along with active study of other Dst forecast models that do not rely on nowcast inputs (Section 6). The lack of certified requirements makes further recommendations difficult. A study of how the error in Dst translates to error in models and a better understanding of operational needs for magnetic storm warning are needed to determine such requirements. Nowcast persistence is often hard to beat for short term forecasts and specification and Dst Predictor clearly performs well against that standard (with 1-hour and 4-hour skill-scores of 0.233 and 0.485 respectively), although poor in absolute terms (with1-hourand4-hour prediction efficiencies of-64.6and-43.1, respectively).

Air Force Research Laboratory Technical Report↗