GROUND AND SURFACE WATER QUALITY IMPACTS OF NORTH CAROLINA SANITARY LANDFILLS1

ABSTRACT: Ground and surface water quality monitoring data from 71 municipal sanitary landfills in North Carolina were analyzed to determine the nature and extent of current contamination problems and identify any common characteristics associated with this contamination. A total of 322 surface and 411 ground water quality records were analyzed using the SAS data system. Almost all the landfill records included inorganic and heavy metal analyses while approximately half of the records also included organic analyses by CC/MS. Our analysis indicates that landfills are having measurable impacts on ground and surface water quality, but these impacts may not be as severe as is commonly assumed. Statistically significant increases were detected in the average concentrations in ground water and downstream surface water samples when compared to upstream surface water samples. The largest percentage increases were observed for zinc, turbidity, total organic carbon, conductivity, total dissolved solids, and lead. Violations of ground water quality standards for heavy metals and hazardous organic compounds were detected at 53 percent of the landfills where adequate data existed. The moat common heavy metal violations were for lead (18 percent), chromium (18 percent), zinc (6 percent), cadmium (6 percent), and arsenic (6 percent) (percentage of landfills violating shown in parenthesis). The organic compounds that appear to pose the greatest threat to ground water are the chlorinated solvents (8 percent), petroleum derived hydrocarbons (8 percent), and pesticides (5 percent). A comparison of monitoring data from sanitary landfills and secondary wastewater treatment plants suggests that the concentrations of heavy metal and organic pollutants discharged to surface waters from these two sources are similar.     

Occurrence of Volatile Organic Compounds in Aquifers of the United States1

Abstract: Samples of ambient ground water were collected during 1985‐2002 from 3,498 wells in 98 aquifer studies throughout the United States. None of the sampled wells were selected because of prior knowledge of nearby contamination. Most of these samples were analyzed for 55 volatile organic compounds (VOCs) to characterize their national occurrence. Volatile organic compounds were found in samples collected from 90 of the 98 aquifer studies. Occurrence frequencies of one or more VOCs for the 98 aquifer studies ranged from 0 to about 77% at an assessment level of 0.2 microgram per liter (μg/l). The aquifer studies with the largest occurrence frequencies were in southern Florida, southern New York, southern California, New Jersey, and Nevada. Trihalomethanes and solvents were the most frequently occurring VOC groups. Of the 55 VOCs included in this assessment, 42 occurred in at least one sample at an assessment level of 0.2 μg/l. Chloroform, perchloroethene, and methyl tert‐butyl ether were the most frequently occurring VOCs. Many factors, such as the hydrogeology of the aquifer, use of VOCs, land use, and the transport and fate properties of VOCs, affect the occurrence of VOCs in ground water.     

MEASURING ECONOMIC LOSSES FROM GROUND WATER CONTAMINATION: AN INVESTIGATION OF HOUSEHOLD AVOIDANCE COSTS1

ABSTRACT: Economic losses from ground water contamination were estimated in a central Pennsylvania community. The averting expenditures method was applied via a mail survey of households in which water contained the unregulated volatile organic chemical, perchloroethylene (PCE). Expenditures were estimated at $148,900 (1987 dollars) over the six-month contamination period or approximately $252 per household annually. These costs underestimate the lower bound measure of welfare losses to households from ground water contamination. An upper bound measure of welfare losses was estimated at $383 per household annually. These estimates do not represent the full economic losses resulting from ground water contamination since the study did not address municipal-level and business avoidance costs and losses from actual health effects, increased fear and anxiety, ecological damages, and nonuser ground water benefits. The results expand the existing empirical base of information about municipal-level responses and economic losses from ground water contamination to include household-level impacts. The findings indicate that households undertake substantial averting actions in response to ground water contamination and that such actions can have significant economic consequences. The extent and magnitude of avoidance costs documented suggests that policy-makers should give greater attention to this category of economic losses.     

A CLOSED SYSTEM SAMPLE TRANSFER DEVICE FOR VOLATILE ORGANIC COMPOUNI)S1

ABSTRACT: A sample transfer device was designed to provide a closed loop sampling system between a ground water sampling pump and a 40 ml volatile organic compound (VOC) vial. The same attachment can also be used with a bailer. The unit is constructed of a poly-tetrafluoroethylene (PTFE) body into which two stainless steel needles are press fitted. The needles puncture the Teflon septum of a vial; fluid flows through the longer needle into the vial and exits the vial from the shorter needle. The device eliminates sample transfer bias associated with head space, visible gas bubbles, and atmospheric contamination. Field sampling designed to determine differences in trichloroethylene (TCE) concentrations presumedly due to the device were statistically significant in one case, and insignificant in the second.     

THE EFFECT OF RESIDENTIAL DEVELOPMENT ON GROUND‐WATER QUALITY NEAR DETROIT,MICHIGAN1

ABSTRACT: Two water‐quality studies were done on the outskirts of the Detroit metropolitan area to determine how recent residential development has affected ground‐water quality. Pairs of monitor and domestic wells were sampled in areas where residential land use overlies glacial outwash deposits. Young, shallow waters had significantly higher median concentrations of nitrate, chloride, and dissolved solids than older, deeper waters. Analysis of chloride/bromide ratios indicates that elevated salinities are due to human activities rather than natural factors, such as upward migration of brine. Trace concentrations of volatile organic compounds were detected in samples from 97 percent of the monitor wells. Pesticides were detected infrequently even though they are routinely applied to lawns and roadways in the study area. The greatest influence on ground‐water quality appears to be from septic‐system effluent (domestic sewage, household solvents, water‐softener backwash) and infiltration of storm‐water runoff from paved surfaces (road salt, fuel residue). No health‐related drinking‐water standards were exceeded in samples from domestic wells. However, the effects of human activities are apparent in 76 percent of young waters, and at depths far below 25 feet, which is the current minimum well‐depth requirement.     

WATER QUALITY IN SHALLOW ALLUVIAL AQUIFERS,UPPER COLORADO RIVER BASIN,COLORADO, 19971

ABSTRACT: Shallow ground water in areas of increasing urban development within the Upper Colorado River Basin was sampled for inorganic and organic constituents to characterize water‐quality conditions and to identify potential anthropogenic effects resulting from development. In 1997, 25 shallow monitoring wells were installed and sampled in five areas of urban development in Eagle, Grand, Gunnison, and Summit Counties, Colorado. The results of this study indicate that the shallow ground water in the study area is suitable for most uses. Nonparametric statistical methods showed that constituents and parameters measured in the shallow wells were often significantly different between the five developing urban areas. Radon concentrations exceeded the proposed USEPA maximum contaminant level at all sites. The presence of nutrients, pesticides, and volatile organic compounds indicate anthropogenic activities are affecting the shallow ground‐water quality in the study area. Nitrate as N concentrations greater than 2.0 mg/L were observed in ground water recharged between the 1980s and 1990s. Low concentrations of methylene blue active substances were detected at a few sites. Total coliform bacteria were detected at ten sites; however, E. coli was not detected. Continued monitoring is needed to assess the effects of increasing urban development on the shallow ground‐water quality in the study area.     

THE BISCAYNE AQUIFER CONTAMINATION: CLEANUP AND PREVENTION1

ABSTRACT: The Biscayne Aquifer is the sole source of drinking water for approximately three million residents of southeast Florida. Nine hazardous waste sites on the EPA National Priority List overlie this aquifer. Extensive investigation of an 80 square-mile area in metropolitan Miami detected low to moderate levels of toxic contaminants in the ground water, with volatile organic chemicals the most prevalent. The Centers for Disease Control concluded that contamination of the aquifer within the study area poses a serious potential threat to public health. Recommendations for source control and cleanup have been partially carried out. The top few feet of soil at the Miami Drum site have been excavated and relocated; ground water encountered during excavation has been withdrawn and treated, and the Northwest 58th Street Landfill has been closed. Recovery and treatment of ground water from the contaminated area was the recommended cleanup measure and has been approved by EPA and state and local agencies. A preventive action program for the Biscayne Aquifer region was also recommended for implementation by local agencies. This program consists of regulations, waste management practices, construction and treatment guidelines, and public information activities and materials. Implementing this program will help keep the Biscayne Aquifer water drinkable far into the future.     

WATER QUALITY BENEATH URBAN RUNOFF WATER MANAGEMENT BASINS1

ABSTRACT: The chemical impact of urban runoff water on water quality beneath five retention/recharge basins was investigated as part of the US EPA's Nationwide Urban Runoff Program in Fresno, California. Soil water percolating through alluvium soils and the ground water at the top of the water table were sampled with ceramic/Teflon vacuum water extractors at depths up to 26 m during the two-year investigation. Inorganic and organic pollutants are present in the runoff water delivered to the basins. No significant contamination of percolating soil water or ground water underlying any of the five retention/recharge basins has occurred for constituents monitored in the study. The oldest basins was constructed in 1962. The concentration of selected trace elements in the ground water samples was similar to the levels reported in the regional ground water. None of the pesticides or other organic priority pollutants, for which water samples were analyzed, was s̊ detected except diazinon which was found in trace amounts (0.3 μg/L or less) in only three soil water samples. These results are important to the continued conservation of storm water and the development of a best management practice for storm-water management using retention/recharge basins in a semi-arid climate.     

CHALLENGES IN GROUND WATER REMEDIATION: DENSE NONAQUEOUS PHASE LIQUIDS1

ABSTRACT: Dense nonaqueous phase liquid (DNAPL) contaminated ground water has proven to be exceptionally difficult to remediate for both physical and chemical reasons. Since DNAPL's are denser than water, their movement is not governed by the direction of ground water flow as is generally the case for other ground water contaminants. Additionally, DNAPLs' interactions with aquifer solids through processes such as sorption tend to make the pollution linger or sometimes apparently disappear, only to return later. Unfortunately, pump-and-treat systems, the traditional way ground water contamination is addressed, have not been effective in cleaning DNAPL contaminated water. Other remediation technologies continue to be developed to address these problems. Policy changes will also be necessary to effectively address the difficulties associated with ground water remediation.     

EVALUATING THE EFFECTIVENESS OF A FIXED WELLHEAD DELINEATION: REGIONAL CASE STUDY 1

The 1996 Safe Drinking Water Act amendments mandated that every state must determine the hydrogeologic origin of each public drinking water system and assess the degree to which each system may be adversely affected by potential sources of contamination. Wisconsin delineated and assessed one specific class of systems, transient noncommunity drinking water wells, with the least stringent standards of all governed system types. This study evaluates the effectiveness of Wisconsin's arbitrarily fixed radius approach used in determining susceptibility to potential contamination from 1,872 transient noncommunity ground water wells. Nearly 28 percent of the wells with contaminated water did not have any recorded potential sources of contamination within the delineation radii. Additionally, regression models derived from potential contaminant inventories within the delineation radii could not accurately predict actual incidences of water contamination. Differences between observed and expected frequencies of contamination further suggest that some transient noncommunity systems should probably be delineated with larger and more sophisticated methods that would account for varying geology and contaminant susceptibility. The majority of contamination cases without recorded potential sources of contamination within the delineation radii were in a karst area. Subsequently, the arbitrarily fixed radius delineation method should not be used in areas with karst aquifers.     

IRRIGATION METHODS AND TRANSPORT OF IMAZAMETHABENZ‐METHYL TO GROUND WATER: GREENFIELDS BENCH,MONTANA1

ABSTRACT: A series of gravel terraces support a shallow aquifer that is the sole source of drinking water for three public water supplies and more than 400 private wells on the Greenfields Bench in west‐central Montana. Farming practices on the Greenfields Bench include irrigation of malting barley and the yearly application of herbicides for the control of weeds. The most commonly used herbicide (imazamethabenz‐methyl, U.S. trade name Assert®) has been found in the ground water on the Greenfields Bench. An experiment was conducted in 2000 and 2001 to characterize the transport of Assert and its acid metabolite to ground water under three irrigation methods: flood, wheel line sprinkler, and center pivot sprinkler. Results show that Assert concentrations in ground water are controlled by hydraulic loading rates of each irrigation method, Assert persistence in soil, hydraulic characteristics of the aquifer, and adsorption/desorption of Assert onto clay particles and organic matter.     

APPLICATION OF ENHANCED ANNEALING TO GROUND WATER REMEDIATION DESIGN1

ABSTRACT: A methodology for ground water remediation design has been developed that interfaces ground water simulation models with an enhanced annealing optimizer. The ground water flow and transport simulators provide the ability to consider site‐specific contamination and geohydrologic conditions directly in the assessment of alternative remediation system designs. The optimizer facilitates analysis of tradeoffs between technical, environmental, regulatory, and financial risks for alternative design and operation scenarios. A ground water management model using an optimization method referred to as “enhanced annealing” (simulated annealing enhanced to include “directional search” and “memory” mechanisms) has been developed and successfully applied to an actual restoration problem. The demonstration site is the contaminated unconfined aquifer referred to as N‐Springs located at Han‐ford, Washington. Results of the demonstration show the potential for improving groundwater restoration system performance while reducing overall system cost.     

RECYCLING INPUT DATA DURING ANALYTIC ELEMENT MODELING NEAR INDIANAPOLIS,INDIANA1

ABSTRACT: Overlapping and adjacent ground water investigations are common in areas where aquifers are threatened by industrial development. In the Indianapolis area in Marion County, Indiana, a patchwork of ground water flow models have been used during the past 20 years to evaluate ground water resources and to determine the effects of local contamination. In every case these ground water models were constructed from scratch. Site specific finite difference grids or finite element meshes inhibit the direct reuse of input data when the area of interest shifts. Because the aquifer is not discretized into a grid or mesh with analytic element models, there are unique opportunities for direct reuse of model input data. In two applications of this principle we illustrate how the newly emerging analytic element method allows a fairly straightforward reuse of model input data from previous models in the same general area. In analytic element models of Central Indiana, streams and their tributaries are represented in different resolutions. Input data items of several modeling studies are stored and cataloged on disk in such a manner that they can be selectively retrieved by a data management program PREPRO. In this manner, a new ground water model can be set up quickly with input data which have been previously defined and tested during model calibration.     

ATRAZINE AND METOLACHLOR OCCURRENCE IN SHALLOW GROUND WATER OF THE UNITED STATES, 1993 TO 1995: RELATIONS TO EXPLANATORY FACTORS1

ABSTRACT: Since 1991, the U.S. Geological Survey has been conducting the National Water Quality Assessment (NAWQA) Program to determine the quality of the Nation's water resources. In an effort to obtain a better understanding of why pesticides are found in shallow ground water on a national scale, a set of factors likely to affect the fate and transport of two herbicides in the subsurface were examined. Atrazine and metolachlor were selected for this discussion because they were among the most frequently detected pesticides in ground water during the first phase of the NAWQA Program (1993 to 1995), and each was the most frequently detected compound in its chemical class (triazines and acetanilides, respectively). The factors that most strongly correlated with the frequencies of atrazine detection in shallow ground‐water networks were those that provided either: (1) an indication of the potential susceptibility of ground water to atrazine contamination, or (2) an indication of relative ground‐water age. The factors most closely related to the frequencies of metolachlor detection in ground water, however, were those that estimated or indicated the intensity of the agricultural use of metolachlor. This difference is probably the result of detailed use estimates for these compounds being available only for agricultural settings. While atrazine use is relatively extensive in nonagricultural settings, in addition to its widespread agricultural use, metolachlor is used almost exclusively for agricultural purposes. As a result, estimates of agricultural applications provide a less reliable indication of total chemical use for atrazine than for metolachlor. A multivariate analysis demonstrated that the factors of interest explained about 50 percent of the variance in atrazine and metolachlor detection frequencies among the NAWQA land‐use studies examined. The inclusion of other factors related to pesticide fate and transport in ground water, or improvements in the quality and accuracy of the data employed for the factors examined, may help explain more of the remaining variance in the frequencies of atrazine and metolachlor detection.     

油气田挥发性有机物管控源项及排放系数研究

对美国油气田挥发性有机物(VOCs)管控要求、排放系数、可行技术及相关治理费用进行梳理总结,为我国油气田VOCs排放标准、排污许可申请技术规范、污染源核算技术指南等制定以及油气田企业VOCs治理提供借鉴。美国新建污染源控制标准主要对油气田油气井完井、储存、气动阀、气动泵、压缩机、设备泄漏、无组织逸散等VOCs污染源提出管控要求。参照我国当前石油化学工业VOCs管控理念,可将上述污染源归为设备和管道组件密封点、物料转移和输送、工艺无组织、储存4个源项进行管控。     

VOLATILE ORGANIC COMPOUNDS IN GROUND WATER FROM RURAL PRIVATE WELLS, 1986 TO 19991

ABSTRACT: The U.S. Geological Survey (USGS) collected or compiled data on volatile organic compounds (VOCs) in samples of untreated ground water from 1,926 rural private wells during 1986 to 1999. At least one VOC was detected in 12 percent of samples from rural private wells. Individual VOCs were not commonly detected with the seven most frequently detected compounds found in only 1 to 5 percent of samples at or above a concentration of 0.2 microgram per liter (μg/l). An assessment level of 0.2 μg/l was selected so that comparisons of detection frequencies between VOCs could be made. The seven most frequently detected VOCs were: trichloromethane, methyl tert‐butyl ether, tetrachloroethene, dichlorodifluoromethane, methylbenzene, 1,1,1‐trichloroethane, and 1,2‐dibromo‐3‐chloropropane. Solvents and trihalomethanes were the most frequently detected VOC groups in private wells. The distributions of detections of gasoline oxygenates and fumigants seemed to be related to the use patterns of compounds in these groups. Mixtures were a common mode of occurrence of VOCs with one‐quarter of all samples with detections including two or more VOCs. The concentrations of most detected VOCs were relatively small and only 1.4 percent of samples had one or more VOC concentrations that exceeded a federally established drinking water standard or health criterion.     

IDENTIFYING DISCHARGE ZONES OF ARSENIC IN THE GOOSE RIVER BASIN,MAINE1

ABSTRACT: Water balance modeling and the analysis of stable water isotopes in ground water were conducted to aid the location of ground water discharge areas within the Goose River basin, in mid‐coastal Maine. Previous investigations of drinking water from wells in the fractured crystalline bedrock encountered persistent elevated total arsenic. Such contamination may be related to discharging ground water from fractured zones in the basin. Modeled discharge rates greater than +10 cm/yr and ¹⁸O values lighter than‐9.5 per mil VSMOW may indicate recent recharge is mixing with deeper ground water and is focused along some fractured zones in arsenic bearing crystalline rocks.     

GROUND WATER MONITORING FOR TEMIK (ALDICARB) IN FLORIDA1

ABSTRACT: Over 700 community drinking water supplies were sampled for the pesticide Temik (aldicarb and its oxidative metabolites aldicarb sulfoxide and aldicarb sulfone) in Florida. All community supply wells sampled for Temik were located in counties where Temik was reported to have been used and approximately one-half of the wells were located in counties where ground water was determined to be highly susceptible to contamination by Temik. Susceptibility was determined using ranking criteria that incorporated ground water recharge characteristics, water use, and Temik use patterns. Temik was not detected in any of the community supply wells sampled during the study. However, Temik was detected in shallow, private wells, as was the pesticide ethylene dibromide in counties with ground water characterized as highly susceptible to contamination.     

INTERACTIONS BETWEEN GROUND WATER AND SURFACE WATER IN THE SUWANNEE RIVER BASIN,FLORIDA1

ABSTRACT: Ground water and surface water constitute a single dynamic system in most parts of the Suwannee River basin due to the presence of karst features that facilitate the interaction between the surface and subsurface. Low radon-222 concentrations (below background levels) and enriched amounts of oxygen-18 and deuterium in ground water indicate mixing with surface water in parts of the basin. Comparison of surface water and regional ground water flow patterns indicate that boundaries for ground water basins typically do not coincide with surface water drainage subbasins. There are several areas in the basin where ground water flow that originates outside of the Suwannee River basin crosses surface water basin boundaries during both low-flow and high-flow conditions. In a study area adjacent to the Suwannee River that consists predominantly of agricultural land use, 18 wells tapping the Upper Floridan aquifer and 7 springs were sampled three times during 1990 through 1994 for major dissolved inorganic constituents, trace elements, and nutrients. During a period of above normal rainfall that resulted in high river stage and high ground water levels in 1991, the combination of increased amounts of dissolved organic carbon and decreased levels of dissolved oxygen in ground water created conditions favorable for the natural reduction of nitrate by denitrification reactions in the aquifer. As a result, less nitrate was discharged by ground water to the Suwannee River.     

ENHANCEMENTS OF NONPOINT SOURCE MONITORING OF VOLATILE ORGANIC COMPOUNDS IN GROUND WATER1

ABSTRACT: The U.S. Geological Survey (USGS) has compiled a national retrospective data set of analyses of volatile organic compounds (VOCs) in ground water of the United States. The data are from Federal, State, and local nonpoint‐source monitoring programs, collected between 1985–95. This data set is being used to augment data collected by the USGS National Water‐Quality Assessment (NAWQA) Program to ascertain the occurrence of VOCs in ground water nationwide. Eleven attributes of the retrospective data set were evaluated to determine the suitability of the data to augment NAWQA data in answering occurrence questions of varying complexity. These 11 attributes are the VOC analyte list and the associated reporting levels for each VOC, well type, well‐casing material, type of openings in the interval (screened interval or open hole), well depth, depth to the top and bottom of the open interval(s), depth to water level in the well, aquifer type (confined or unconfined), and aquifer lithology. VOCs frequently analyzed included solvents, industrial reagents, and refrigerants, but other VOCs of current interest were not frequently analyzed. About 70 percent of the sampled wells have the type of well documented in the data set, and about 74 percent have well depth documented. However, the data set generally lacks documentation of other characteristics, such as well‐casing material, information about the screened or open interval(s), depth to water level in the well, and aquifer type and lithology. For example, only about 20 percent of the wells include information on depth to water level in the well and only about 14 percent of the wells include information about aquifer type. The three most important enhancements to VOC data collected in nonpoint‐source monitoring programs for use in a national assessment of VOC occurrence in ground water would be an expanded VOC analyte list, recording the reporting level for each analyte for every analysis, and recording key ancillary information about each well. These enhancements would greatly increase the usefulness of VOC data in addressing complex occurrence questions, such as those that seek to explain the reasons for VOC occurrence and nonoccurrence in ground water of the United States.