ALBERT

Notes: Ground-water flow models developed for the flow systems around Bass Lake and Nepco Lake, Wisconsin, show that models can be useful tools for estimating lake seepage rates. A two-dimensional profile model for Bass Lake illustrates that the ratio of horizontal to vertical hydraulic conductivity of the aquifer around the lake is related to both the magnitude of vertical hydraulic gradients near the lake and the distribution of seepage from the lake as a function of distance from shore. The model also shows that it is important to know the vertical hydraulic conductivity of littoral lake-bed sediments to estimate lake seepage rates.A three-dimensional model constructed for an unusual ground-water flow system around Nepco Lake provides a more realistic simulation of the flow system than does a comparable two-dimensional model. Both models were useful for identifying additional data that could be used to quantify the ground-water portion of the lake's water budget more accurately. It is suggested that a combination of two-and/or three-dimensional models could be used to estimate seepage rates at many lakes for which sufficient data exist.

Notes: A digital model of a buried channel aquifer contaminated by hydrocarbons is used to evaluate development alternatives. The response to ground-water pumping is critical because the hydrocarbons cause taste and odor problems. The source of contamination is an abandoned pit used to dispose of coal tar residues from an old coal-gas plant. The hydrocarbon residues overflowed the pit, migrated a short distance and seeped into flood plain soils. The downward movement of the hydrocarbons stopped at the water table but some dissolved into the ground water. Three general approaches taken to evaluate management alternatives include: (1) regulation of pumping of the city wells and of drawdown, and recovery periods are considered and the model stressed with various pumping rates and times; (2) construction of a pumping trough barrier is considered and a hypothetical control well is simulated; (3) new well field developments in various locations are considered. Results suggest that there is no way to prevent movement of contaminants to the well field. The only feasible solution is the removal of coal tar residues from the source area and construction of a pumping trough barrier.

Notes: Increased attention is being directed toward the investigation of tight zones in relation to the storage and disposal of hazardous wastes. Shut-in tests, slug tests, and pressure-slug tests are being used at the proposed Waste Isolation Pilot Plant site, located in southeastern New Mexico, to evaluate the fluid-transmitting properties of several zones above the proposed repository zone. Apparatus used to conduct these tests includes a pressure-transducer system connected to a recording device at the land surface. All three testing methods were used in various combinations to obtain values for the hydraulic properties of the test zones. Multiple testing on the same zone produced similar results. Transmissivities determined by these tests range from 0.00001 to 10 feet squared per day (.000001 to 1 meter squared per day).

Notes: Organic solvents, including 1,1,1-trichloroethane at concentrations up to 40,000 ppb, were detected in the Old Bridge aquifer under an industrial plant in South Brunswick Township, New Jersey. A hydrogeologic investigation defined the ground-water flow system and a plume of contamination which extended, at a concentration of at least 100 ppb, for a distance of about 1000 feet down-gradient of the plant. A contamination abatement system was designed and installed to prevent this plume from reaching a municipal well located about 2500 feet from the site. The system includes seven extraction wells and a water treatment facility. The locations of the extraction wells and their combined pumping rate were determined in part by a computer simulation of the aquifer, which was subsequently checked by a 20-day pumping test of the system. The on-site treatment facility uses two cooling towers in series to air-strip the volatile organics, and two infiltration ponds to return the treated water to the aquifer. The abatement system has been operating for about 10 months. Ground-water monitoring results show that the plume is now significantly smaller and less concentrated than before the abatement system was installed. It is projected that in several years the aquifer will be largely decontaminated.

Notes: Pumpage from shallow aquifers, primarily dolomite bedrock, in northeastern Illinois has exceeded estimates of ground-water recharge in extensive areas creating concern that ground-water recharge estimates are too low. Pumpage increased 92 percent during the period 1966-1978 and was 61.7 million gallons per day (2.33 × 108 liters/day) during 1978. During the period 1966-1979 water level declines exceeded 30 feet (9.14 meters) in some areas. Based on a ground-water budget study, it was determined that recharge estimates were in the right order of magnitude and pumpage in excess of recharge was balanced by water taken out of storage from the shallow aquifers. A specific yield of 0.017 was determined for the dolomite bedrock aquifer based on the ground-water budget study.

Notes: Thirty-three wells and two springs yielding high chloride water from granitic rocks define a northwesttrending lineament, which extends for 60 miles (100 km) along the western Sierra Nevada foothills of Fresno and Madera Counties. Geochemical evidence indicates that many of the constituents in this water are marine connate in origin. However, the connate water has been strongly diluted with meteoric water. The connate water is believed to have been derived from Paleozoic and early Mesozoic marine clastic rocks (now metamorphosed) in the Sierra Nevada. The lineament marks the location where marine connate water has migrated upward from these rocks along an eastward-dipping fault zone. A capping of granitic rocks has enhanced the persistence of this connate water for millions of years. The lineament may be structurally related to the Oakhurst-Fine Gold fault zone, which it parallels for approximately 15 miles (25 km). There is a remarkable correlation in the Oakhurst area between wells yielding high-chloride water and fracture trends determined from aerial photographs. High chloride ground water is present only in topographically low areas, where little flushing by meteoric water has been possible.

Notes: This is the second of two articles on calculator programs for inverse solutions of the Theis equation.Newton's method is used to develop an iteration formula for the determination of transmissivity and storage coefficient values from a combined Theissian expression that incorporates the information contained in two independent aquifer test data point sets.The algorithm is used in a polynomial-based program for Hewlett Packard HP 67/97 calculators that is designed to process data corresponding to the full practical range of Theis well function arguments and to accept measurements from one or two observation wells, or from entirely different tests of a given aquifer. Program modifications providing for series-based well function calculations are appended, and example calculations are shown.

Notes: The major water-bearing units in the Houston district are the Chicot and Evangeline aquifer systems. Both systems consist of discontinuous layers of unconsolidated sand (aquifers) separated by clay layers.Extensive pumping has caused large declines of potentiometric surfaces in and around Houston. The declines have caused both the compaction of clay layers, which has resulted in land-surface subsidence, and the movement of salt water towards Houston.During the early 1960's, an electric analog model of the district was made. The model simulated water-level declines; but more importantly, the model indicated that the available data and conceptual model of the hydrologic system, consisting of two aquifers, were not totally adequate to allow simulation of the ground-water systems.During the early 1970's, a second electric analog was built. The second model used new data and a conceptual model consisting of two aquifer systems simulated water-level declines quite accurately, but the model was unable to accurately simulate the spatial distribution of water yielded from clay storage.A digital model was then developed during 1979 to simulate the hydrology of the district. The digital model used five layers and accurately simulated the hydraulic heads in both aquifer systems and land-surface subsidence.

Notes: Marquardt algorithm has been used for estimating aquifer parameters from pump test data in nonleaky and leaky aquifers. It emerges from the study that in spite of poor initial estimates, the convergence is quick; and the residual square error, for the difference between the observed drawdowns and those calculated from parameters estimated using Marquardt algorithm and the known methods, is minimum in the case of Marquardt estimates.

Notes: The geochemistry of a very permeable ground-water system containing calcium sulfate was studied to determine the present rate of dissolution. An estimate was made of the chemical composition of water recharging the system and the difference between that estimate and the composition of the ground water in the system was used to determine the minimum amount of calcium sulfate being dissolved under existing hydrologic conditions. This result was used, with published data on rates of calcium-sulfate dissolution, to determine the effective surface area involved in solution processes. Results indicate that flow in this system is through large solution openings, which are growing larger at a rate of a few tens of millimeters per year.

Notes: Due to inexperience on the part of those assigned to purchase computer facilities for water resource tasks, a poor or unacceptable choice of equipment is often made. The political realities of introducing new computing equipment into a firm which has several departments which will vie for the use of that equipment must be faced.The size, complexity, and capabilities of the machine to be purchased as well as the software and personnel involved must be considered carefully in relation to the specific tasks at hand. The bidding process, demonstrations, and reference materials offer some assistance in deciding among the often confusing array of systems available on the market.

Notes: Enjebi Island on Enewetak Atoll has been the site of extensive hydrological, geological and geophysical studies. Tidal lag, tidal efficiency and water levels have been measured in 24 wells ranging in depth from one m to 90 m (3–290 ft). Hydraulic conductivity has been measured both on laboratory samples and by aquifer testing in the field. Theoretical ground-water tidal responses have been calculated using a model based on horizontal propagation of tidal signals. Comparison of field observations and model results indicates that the observed results are not consistent with horizontal tidal propagation and that the hydraulics of the system are probably controlled by vertical coupling between the unconsolidated surface aquifer and an underlying aquifer of more permeable limestone. Results from other islands of Enewetak, Bikini and Kwajelein Atolls are comparable, and suggest that vertical transport between layered aquifers is an important feature of atoll ground-water hydrology at least throughout the northern Marshall Islands.

Notes: In an investigation of the hydrogeology of bedrock valley fills in northeastern Wisconsin, it was determined that the yield and spatial distribution of glacial aquifers are controlled by bedrock topography and glacial geology. Lithologic control for identification and classification of aquifer units was obtained from several hundred drillers' logs calibrated by auger borings and interviews. Transmissivities of drift aquifers calculated from specific capacity tests using Jacob's equation agree well with estimates made from lithologic logs. Seismic refraction and gravity surveys were coupled with well log data to derive a bedrock elevation map. Vertical variability maps calculated from the lithologic logs show that bedrock topography strongly influences the distribution and character of glacial units, and clearly delineate the two glacial aquifer types present, valley and morainal units. Morainal units parallel the Late Wisconsin end moraine trends, while valley units are perpendicular to the moraines. The morainal units are small ice-contact features such as kames, fans, and deltas. The valley units are stream deposits and may have been deposited subglacially. Valley aquifers are the most productive units. Using lithologic and geophysical data, and statistical analysis, a predictive depositional model can be proposed. This conceptual model allows knowledge of bedrock topography to be coupled with glacial geology to predict the spatial distribution of glacial aquifers.

Notes: An exact expression is derived for the optimal spacing between interfering wells in a rectangular well field in an ideal confined aquifer. A simple, practical method for determining the optimal spacing is presented. The optimal spacing is shown to be substantially different from the spacing determined by use of the Theis formulation. The economic savings resulting from use of the revised approach are evaluated and found to be considerable, especially when the number of wells is large and the transmissivity of the aquifer low.

Notes: Abstract. A hydrologic test system has been designed to measure the intrinsic permeabilities of individual fractures in crystalline rock. This report contains the design schematics and specifications necessary to build and/or modify this test system for other similar field applications. This system is used to conduct constant pressure/declining flow rate and pressure pulse hydraulic tests. The system is composed of four distinct units: (1) The Packer System, (2) Injection System, (3) Collection System, and (4) Electronic Data Acquisition System. The apparatus is built in modules so it can be easily transported and reassembled. It is also designed to operate over a wide range of pressures (0–300 psig) and flow rates (0.2–1.0 gal/min). This system has proved extremely effective and versatile in its use at the Climax Facility, Nevada Test Site.

Notes: Field and laboratory analyses of pH, alkalinity, and specific conductance from water samples collected from the Columbia aquifer on the Delmarva Peninsula in eastern Maryland were compared to determine if laboratory analyses could be used for making regional water-quality interpretations.On the basis of 170 field pH and specific conductance measurements, 165 laboratory pH and specific conductance measurements, and 86 field and 135 laboratory alkalinity measurements, a significant difference at the 0.1-percent level was found between laboratory and field analyses of pH and specific conductance. No significant difference was found between laboratory and field analyses of alkalinity. In most samples, laboratory pH was greater than field pH, laboratory specific conductance was less than field specific conductance, and laboratory alkalinity was equally likely to be less than, the same as, or greater than field alkalinity.Kruskal-Wallis tests of field and laboratory data grouped by north-south and east-west coordinates and by land use indicate that the difference between field and laboratory values is usually not enough to affect the outcome of the statistical tests. Thus, laboratory measurements of these constituents may be adequate for making certain regional water-quality interpretations, although they may result in errors if used for geochemical interpretations.

Notes: Preliminary vadose zone nitrate extraction experiments have revealed the extractant (2N KCl) volume affects the determination of nitrate and its nitrogen isotope ratio.In five cores, extractable NO3-N concentrations increased an average of 1.7 times after the soil-to-extractant ratio was increased from 1:1 to 1:10. An increased extractant volume resulted in a large positive shift of stable nitrogen values (δ15N), which averaged +6.2%.An underestimation of available NO3-N for leaching and transport through the vadose zone and a biased source interpretation from the δ15N values probably would occur if a procedure which leads to incomplete extraction of nitrate is used.

Notes: Currently, one of the most popular methods of containing contaminated ground water is through use of subsurface impermeable barriers. These barriers can take one of three forms: slurry walls, grout curtains, or steel sheet piles. Successful operation of these barrier systems is dependent upon three basic criteria. First, the barrier must be truly impermeable and remain so over time even upon exposure to the contaminated ground water. Second, there must exist an underlying impermeable formation, at a reasonable depth, to which the barrier can be connected. Third, an adequate connection between the barrier and the underlying formation must be assured.This paper presents the results of the analysis of the movement of contaminated ground water under or through an imperfect barrier. The first phase of the analysis consists of the development of an analytical solution for the flow of ground water under a barrier and a simple numerical integration technique for developing concentration breakthrough curves. This simple solution algorithm was applied to the cases of variable recharge rates and lengths, variable depths of penetration of the barrier, and anisotropic soils. The second phase of the analysis involves applying a numerical solute transport model to analyze the performance of a barrier with and without the effects of hydrodynamic dispersion, and in the presence of a layered soil, and finally the performance of a fully penetrating but partially permeable barrier.

Notes: Hydrogeologic and ground water quality data obtained from a gas-driven multilevel sampler system and a polyvinyl chloride (PVC) monitoring well nest with the same aquifer communication intervals are compared. All monitoring points are in close proximity to each other.The study was conducted at an eight-acre uncontrolled hazardous waste site. The site is located in an alluvial valley composed of approximately 40 feet of alluvium overlying shale bedrock. The ground water at the site is contaminated with various organic constituents.A ground water monitoring network consisting of 26 conventional monitoring wells, nine observation well points, and six multilevel gas-driven samplers was established to characterize the hydrogeologic regime and define the vertical and horizontal extent of contamination in the vicinity of the abandoned chemical plant. As part of this study, a multilevel monitoring system was installed adjacent to a well nest. The communication zones of the multilevel samplers were placed at the same elevation as the sand packs of the well nest. The multilevel sampler system and well nest are located in a contaminated area directly downgradient of the site. A comparison of the vertical head distribution and ground water quality was performed between the well nest and the multilevel sampling system.The gas-driven multilevel sampling system consists of three gas-driven samplers that monitor separate intervals in the unconsolidated materials. The well nest, composed of two PVC monitoring wells in separate boreholes, has the same communication interval as the other two gas-driven samplers.Hydraulic head information for each multilevel sampler was obtained using capillary tubing. This was compared with heads obtained from the well nest utilizing an electric water level indicator.Chemical analyses from the PVC and multilevel sampler wells were performed and compared with one another. The analyses included organic acids, base neutrals, pesticides, PCBs, metals, volatile organics, TOX, TOC, CN, pH and specific conductance.

Notes: A total of four vertical electrical soundings were conducted in a layered andesitic rock aquifer known in places to yield ground water with total dissolved solids (TDS) in excess of 2,000 milligrams per liter (mg/L). The objective of the soundings was to locate zones of moderate to high permeability but with acceptable chemical quality.The resistivity of a geologic unit is a function that includes the quantity of total dissolved solids in the interstitial water and the distribution of the water within the unit. Thus, the resistivity of most granular soils and rocks is controlled more by porosity, water content and water quality than by the conductivity of the matrix materials.The electrical data delimited a drill site where it was believed that ground water of acceptable chemical quality could be expected. Completion and test pumping of two exploration wells confirmed the electrical sounding results.The first test well drilled prior to the survey yielded only small amounts of ground water with total dissolved solids in excess of 2,000 mg/L. The second exploration well drilled at the site as a result of the electrical study yielded in excess of 100 gallons per minute of ground water with total dissolved solids of 830 mg/L.

Notes: An advanced two-way radio link (transceiver units) and data logging system have provided a powerful means of real-time series data collection and analysis. The application of this telemetry system to surface tiltmeter surveys provides significant cost savings for testing and analysis of deep, large-scale horizontal anisotropic permeability and heterogeneity determinations.The determination of horizontal anisotropic properties requires one pumping well and eight to 10 tiltmeter monitoring stations. The validity of the depth of the test may reach 4,000 feet below land surface. With the addition of one partially penetrating observation well, the entire three-dimensional anisotropic permeability can be determined. With the addition of a fully penetrating well, the storage coefficient can be determined as well as leakage property (including vertical permeability of the confining layers). An example test case was analyzed for horizontal anisotropic permeability with remarkable success despite relatively unfavorable detection conditions.A thorough understanding of the geology overlying the aquifer system must be made in order to assess the applicability of the surface tiltmeter survey to large-scale horizontal anisotropic permeability determinations.

Notes: This paper describes a new system for ground water monitoring, “the BAT System,” which includes the following functions: (a) sampling of ground water in most types of soils, (b) measurement of pore water pressure, and (c) in situ measurement of hydraulic conductivity. The system can also be used for tracer tests. The system utilizes a permanently installed filter tip attached to a steel or PVC pipe. Installation is normally performed by pushing the tip down to the desired depth. The filter tip can also be buried beneath a landfill. The primary feature of the new system is that the filter tip contains a self-sealing quick coupling unit, which makes it possible to temporarily connect the filter tip to adapters for various functions, e.g. water sampling and for measurement of pore pressure and hydraulic conductivity. The new technique makes sampling of both pressurized water and gas possible. Samples are obtained directly in hermetically sealed, pre-sterilized sample cylinders. Sampling of ground water and measurement of pore pressure can be repeated over a long period of time with undiminished accuracy. This technique is also well-adapted for taking water samples from different strata in a soil profile, in both the saturated and unsaturated zones. Actual installations range from 0.5 to 60m depth.

Notes: State-of-the-art analytical techniques are capable of detecting contamination In the part per billion (ppb) range or lower. At these levels, a truly representative ground water sample Is essential to precisely evaluate ground water quality. The design specifications of a ground water monitoring system are critical in ensuring the collection of representative samples, particularly throughout the long-term monitoring period.The potential interfaces from commonly used synthetic well casings require a thorough assessment of site, hydrogeology and the geochemical properties of ground water. Once designed, the monitoring system must be installed following guidelines that ensure adequate seals to prevent contaminant migration during the installation process or at some time in the future. Additionally, maintaining the system so the wells are in hydraulic connection with the monitored zone as well as periodically Inspecting the physical integrity of the system can prolong the usefulness of the wells for ground water quality. When ground water quality data become suspect due to potential interferences from existing monitoring wells, an appropriate abandonment technique must be employed to adequately remove or destroy the well while completely sealing the borehole.The results of an inspection of a monitoring system comprised of six 4-inch diameter PVC monitoring wells at a hazardous well facility Indicated that the wells were improperly installed and in some cases provided a pathway for contamination. Subsequent down hole television inspections confirmed inaccuracies between construction logs and the existing system as well as identified defects in casing materials. An abandonment program was designed which destroyed the well casings in place while simultaneously providing a competent seal of the re-drilled borehole.

Notes: Transmissivity can be estimated by several well documented methods employing data from rising water level slug tests in wells. A very simple and relatively inexpensive system can be constructed to lower the water level in a well. Compressed air is injected through a sealed device called a well head manifold, which screws onto the casing top and contains an air pressure gauge, an air entry valve, a quick release valve and a multi-channel water level indicator or a pressure transducer. Either of the latter is lowered into the well prior to pressurization.Compressed air is injected into the casing at a low rate through the manifold, depressing the water level a desired amount. After stabilization, the quick release valve is opened and the air pressure inside the casing is reduced to atmospheric pressure instantaneously; the water level then starts to rise. Successive elevations of the rising water level are determined with the indicator or transducer and their elapsed times from valve opening are recorded. Plots of water level recovery vs. time can then be used to estimate transmissivity by the published methods of Cooper, Bredehoeft and Papadopulos (1967), Ferris and Knowles (1954) and Hvorslev(1951).All of the items used for construction, with the exception of the quick release valve, can be bought off the shelf. The valve can be easily constructed in a machine shop. The total cost of the device, exclusive of the transducer, should be less than $500.

Notes: Ground water flow in karst terranes generally occurs in the solution channels of carbonate aquifers. A hydrogeologist may utilize borehole geophysical methods to identify these solution channels in aquifers. Two specific methods that are applicable in karst terrains are:1. Natural gamma ray logging2. Borehole caliper logging.Gamma ray logging can detect the presence of inter-bedded strata in the main limestone unit, such as shale, which emit high levels of gamma radiation. Gamma ray logging can also detect clay deposits in solution channels that may act to restrict the flow of ground water. The areal extent of these rock strata or clay-filled solution channels can be determined when gamma ray logs are conducted at several borehole locations across the site of investigation.Borehole caliper logging can be employed to determine the presences of solution channels within the aquifer when penetrated by a borehole. In addition, since shale layers and clay filling are less resistant than the surrounding limestone, the caliper log may detect both the presence and the thickness of shale or clay layers in the aquifer.Gamma ray logs can be used in conjunction with caliper logs to provide data on the stratigraphic location and thickness of solution channels and clay and shale layers within a limestone aquifer. This information is valuable to the hydrogeologist performing investigations at sites located in limestone terranes because ground water flow preferentially occurs along solution channels.

Notes: Column leaching experiments show that fly ash Interlayered with sulfide-rich tailings can reduce the vertical permeability of tailings by at least three orders of magnitude. Chemical reactions between the fluid, alkaline fly ash from Western coal and pyritic tailings result in a one to three order of magnitude reduction in the dissolved metals content of the effluent solution. Metal precipitation, which produces the dissolved metals reduction, is a significant element in the permeability reduction. The combined factors reduce the metals flux from the tailings by four to six orders of magnitude. We believe that tailings ponds with fly ash layers as amendments can greatiy reduce ground water contamination from pyritic tailings. In addition, concentrated application of fly ash layers near the end of mining should act to restrict infiltration and access of oxygen, thereby enhancing reclamation. Similar results maybe obtainable using other amendments with lower base capacity (lime, crushed limestone, trona).

Notes: This article describes a computer automated, hydrologic analysis system designed to allow the collection of high quality, long-term pumping test data. The instrument solves two of the major problems encountered in the field during aquifer tests: insufficient data, particularly during the early part of a test when drawdown is rapid; and high labor costs associated with long-term monitoring.To illustrate the system's application, results are presented from the test of a highly transmissive aquifer. The aquifer's drawdown response was rapid; thus the time-drawdown curve was essentially flat after the first two minutes of the test, and correspondingly rapid data acquisition was essential for a unique solution of the aquifer's three-dimensional hydraulic conductivities.

Notes: Traditional monitoring methods using chemical analysis of ground water samples to detect pollutant migration are being superseded or used in conjunction with innovative approaches. A need to detect pollutants before they reach the water table has drawn interest to vadose (unsaturated) zone monitoring and brought together hydrogeologists, soil scientists and agricultural engineers who have been working on this subject for years.Recent studies have identified over 50 different types of vadose zone monitoring devices and methods that have optimum utility in varying hydrogeologic settings. In general, measurements made in the vadose zone are trying to define storage, transmission of liquid waste in terms of flux and velocity, and pollutant mobility.Criteria for the selection of alternative vadose zone monitoring methods are important for the development of site-specific systems. These criteria include: type of site; applicability to new, active, and abandoned sites; power requirements; depth limitations; multiple use capability; type of data collection system; reliability and life expectancy; degree of operational complexity; direct versus indirect methods; applicability to alternate media; effect on flow regime; and effect of hazardous waste on sampling or measurements. Application of the selection criteria is discussed in Everett et al. (1982a).

Notes: In recent years we have seen major advances in the variety and quality of ground water sampling instrumentation, in almost every case involving increases in sensitivity of one or more orders of magnitude. Software number-crunching ability brings us the capability of running sophisticated mathematical and statistical programs, while modern analytical chemistry routinely makes determinations of metals, organics and radioactive elements accurate in the parts per billion range.The construction of sample points rarely supports these levels of precision. The well is the basic sampling machine for the ground water industry and its ability to produce a truly representative sample underpins all data and conclusions. Regardless of the type of instrumentation employed, a sample point that cannot be shown to be truly representative and that fails to provide a series of reliable samples over the long term–let us say 25 years minimum–is a negative investment.In the authors’professional sampling work, it has been observed that, wherever it is possible to improve the quality of the ground water sample point, a reduction in the measured level of pollutant elements in the sample is found and the confidence level improves. Volatile organic values are the sole exception to this observed reduction in concentration, the reason being that sample point and method improvements capture the fully representative water sample, thus reducing volatile losses.It is not possible to address all hydrogeologic environments and sampling methods in this review. Instead, features were selected that had been found to be important in commercial, high-precision, water quality sampling in Western U.S. environments. In this area, water movement is slow and little or no exchange of water occurs between wells and the surrounding aquifer without artificial stimulation. Water quality stabilization requires multiple casing volume evacuations in wells ranging to 1,000 feet deep. High-volume pumping or mechanized bailing is an economic requirement. Dedicated installations cannot supply the volume of water required for comprehensive analytical programs.It is the nature of these sources, as well as practical recommendations for corrective action, that will be addressed in this article.Any attempted improvement in utilization of data by mathematical processing or statistical treatment will be inadequate because:〈list xml:id="l1" style="custom"〉• Samplings are infrequent and often accumulate at rates of only two or four sample suites per year. Seasonal variations may obscure evidence of passage of a low-intensity pollution front and some years may elapse before the true situation becomes apparent from statistical analyses. By such time, the problem pollutant may have escaped from the treatment area.• Powerful biases occur due to the failure of the sample point to eliminate false contributions to the sample from sources other than the natural environment or a pollution source, most frequently originating in casing materials and annular seal leakage.

Notes: A quantitative approach to risk management for accidents in light water nuclear power reactors is proposed to serve as one focus for discussion. In this proposal risk management is divided into two major tasks: the predominantly social and political task of setting the safety goals and the technical task of estimating the risks and deciding whether the safety goals have been met. The proposed safety goals include limits on the following: risk to the individual of early death or delayed cancer death; overall societal risk of early or delayed death; and the frequency of core melt accidents as well as the frequency of containment failure, given a core melt. Also included are a small element of risk aversion and an “as low as reasonably achievable” (ALARA) approach with a cost-effectviness criterion which includes both economic and health effects.

Notes: This paper develops a descriptive framework for siting large scale technological facilities such as liquefied natural gas (LNG) terminals, and suggests ways of using analyses to improve the process. A key feature of these problems is that they involve relatively new technologies where there has not been a long history with which to construct a statistical data base. Hence the interested parties will each have different estimates of the probabilities and losses associated with events that affect the environment or safety of the population. The decision-making process can be characterized as a sequence of decisions, subject to change over time, which are influenced by exogenous factors and new legislation. Each of the separate decisions involves an input phase and an interaction phase. The input phase specifies the relevant alternatives and attributes associated with a particular decision. The interaction phase focuses on the nature of the conflicts between the different parties in evaluating the alternatives. Conflicts are often difficult to resolve because each stakeholder in the process has his own objectives, a limited information base shaped by these objectives and scarce computational resources. We illustrate the above descriptive framework through a case study of the LNG siting process in California. The paper then explores possible ways of improving the input and interaction phases through more structured analyses. Specific attention is given to the role of decision analysis, the analytic hierarchy process, examining assumptions, and the use of interactive computer models for scenario generation. The paper concludes by suggesting future research needs on designing policy instruments for helping to reconcile conflicts between the vying interest parties. Promising areas for more problem-focused research include the role of insurance and compensation schemes.

Notes: The purpose of this paper is to provide the main results of a study concerning the risk of chlorine transport by train in France. The specific problem of chlorine transport is presented in the framework of a general model for assessing the risk in the transport of dangerous materials. The probability of accidents followed with a chlorine release involving fatalities are put in perspective with other risks having potential health effects on the public. Two types of application of the model are envisaged in relation to the management of risk: the selection of protective measures through a cost-effectiveness approach and the use of the model for a better planning of decisions in an accident situation.

Notes: In recent years, benefit-cost analysis has been increasingly applied to large societal decision problems (such as developing a fast breeder energy economy) which involve both risks to society and analysis of very long-term consequences possibly extending over many human generations. This paper examines the philosophical underpinnings of the technique which is a special case of utilitarianism, and compares implications of the technique to those arising from alternative ethical systems in analyzing questions of public safety. Ethical systems which emphasize the good of the whole, such as utilitarianism, are shown to differ sharply in decision outcomes from those which emphasize the rights of the individual, such as libertarianism. It is suggested that benefit-cost analysis should be broadened to include alternative weightings of benefits and costs consistent with a variety of ethical views.

Notes: A cancer risk assessment methodology based upon the Armitage–Doll multistage model of cancer is applied to animal bioassay data. The method utilizes the exact time-dependent dose pattern used in a bioassay rather than some single measure of dose such as average dose rate or cumulative dose. The methodology can be used to predict risks from arbitrary exposure patterns including, for example, intermittent exposure and short-term exposure occurring at an arbitrary age. The methodology is illustrated by applying it to a National Cancer Institute bioassay of ethylene dibromide in which dose rates were modified several times during the course of the experiment.

Notes: Several recent nuclear power plant probabilistic risk assessments (PRAs) have utilized broadened Reactor Safety Study (RSS) component failure rate population variability curves to compensate for such things as expert “overvaluation bias” in the estimates upon which the curves are based.A simple two-components of variation empirical Bayes model is proposed for use in estimating the between-expert variability curve in the presence of such biases. Under certain conditions this curve is a population variability curve. Comparisons are made with the existing method.The popular procedure appears to be generally much more conservative than the empirical Bayes method in removing such biases. In one case the broadened curve based on the popular method is more than two orders of magnitude broader than the empirical Bayes curve. In another case it is found that the maximum justifiable degree of broadening of the RSS curve is to increase α from 5% to 12%, which is significantly less than the 20% value recommended in the popular approach.

Notes: A study of driver behavior before and after a mandatory seat belt use law in Newfoundland found that the benefits of such legislation are not reduced by riskier driving, as has been suggested by some theorists. On average, belt use in Newfoundland increased from 16% of drivers before the law to 77% after the law. At the same time, the quality of driving changed very little when compared to control groups of Nova Scotia drivers, who were not subject to the law and whose belt use rates did not change. In only one situation did Newfoundland drivers differ from the control group in Nova Scotia: after the belt law, drivers in Newfoundland became relatively more cautious (slower) in their speeds on four-lane expressways. These data confirm the results of earlier less controlled studies that also found no changes in driving behavior following nonvoluntary changes in occupant protection. Since the “risk-compensation” hypothesis predicts such changes, it seems to have no merit in explaining changes in fatalities and injuries after occupant protection legislation.

Notes: The benefits and costs of automobile safety policies are compared using a methodology which explicitly quantifies the uncertainties. The policies addressed include both voluntary and compulsory manual belt usage, nondetachable passive (automatic) seat belts, and air bags. Estimates of the effectiveness and usage rates of these alternatives were obtained in the form of subjective probability distributions from eight experts. Their opinions were combined using equal weighting. The direct economic costs of the technologies were also estimated probabilistically. The number of lives saved and the net benefits of the policies were calculated probabilistically for a range of values of lifesaving. Probabilistic computations and sensitivity analysis were performed by the Demos modelling system using Monte Carlo simulation. The results are highly uncertain and quite sensitive to the value of lifesaving. Nevertheless, they imply that repeal of the passive-restraint standard is defensible according to the net-benefit criterion only if a relatively low value is assigned to lifesaving. The degree of uncertainty emphasizes the potential value of demonstration programs to obtain better information.

Notes: This paper examines taxonomies for classifying risks and conflicts about risky technologies. First, we describe six levels of conflict that represent various “ shades of gray” between purely factual and purely value laden conflicts in technology disputes. Subsequently, we survey several recent taxonomies of risks and hazards that were at least partly intended to clarify the nature of the public conflicts about technologies and their risks. After pointing out that non-risk features frequently shape technology debates, we develop a taxonomy of the disputes themselves, based on a collection of 162 cases. Our taxonomy of technological controversies is related to the recent risk taxonomies and to the different levels of conflict. It turns out that the different technological disputes create quite different levels of conflict ranging from mainly factual (consumer products, drugs) to extremely value laden (nuclear power, genetic engineering). Depending on the type of controversy and level of conflict we suggest alternative conflict management strategies.

Notes: Scientists disagree in their risk analyses because they use intuitive judgments to generalize results from the laboratory to circumstances not yet studied. If this assertion is correct, techniques intended to reduce intuitive judgments and increase analytical cognition should reduce scientific dispute. The results of a test case involving allegedly high risk and sharp dispute among scientists are described.

Notes: Probabilistic risk assessment (PRA) is a relatively new tool in the nuclear industry. The Reactor Safety Study started the present trend of conducting PRAs for nuclear power plants when it was published in 1975. Now, nine years later, those in the industry currently using PRA techniques are frequently asked the same question: Why should the nuclear utility industry, with so many accepted analytical tools already available, invest the time and manpower to develop a new technique with so many uncertainties?

Notes: The historical basis and more recent activities and products of probabilistic risk analysis (PRA) in the Atomic Energy Commission and Nuclear Regulatory Commission (NRC) are reviewed. Current NRC program activities and objectives are described. The author's opinions on the best uses of PRA are presented.

Notes: There are many uncertainties in a probabilistic risk analysis (PRA). We identify the different types of uncertainties and describe their implications. We then summarize the uncertainty analyses which have performed in current PRAs and characterize results which have been obtained. We draw conclusions regarding interpretations of uncertainties, areas having largest uncertainties, and needs which exist in uncertainty analysis. We finally characterize the robustness of various utilizations of PRA results.

Notes: Data on the effects of human exposure to carcinogens are limited, so that estimation of the risks of carcinogens must be obtained indirectly. Current risk estimates are generally based on lifetime animal bioassays which are expensive and which take more than two years to complete. We here show how data on acute toxicity can be used to make a preliminary estimate of carcinogenic risk and give an idea of the uncertainty in that risk estimate. The estimates obtained are biased upwards, and so are useful for setting interim standards and determining whether further study is worthwhile. A general scheme which incorporates the use of such estimates is outlined, and it is shown by example how adoption of the procedures suggested could have prevented regulatory hiatus in the past.

Notes: An early attempt to measure risk was the 1738 paper of Bernoulli in which he describes the well-known Saint Petersburg paradox. Subsequent writers have considered this game to draw conclusions about the nature of risk or to test newly devised risk models. We analyze the paradox, evaluate various theories which have been advanced to resolve it, and briefly examine the implications of these theories on the wider area of risk analysis.

Notes: If the point of view is adopted that in calculations of real-world phenomena we almost invariably have significant uncertainty in the numerical values of our parameters, then, in these calculations, numerical quantities should be replaced by probability distributions and mathematical operations between these quantities should be replaced by analogous operations between probability distributions. Also, practical calculations one way or another always require discretization or truncation. Combining these two thoughts leads to a numerical approach to probabilistic calculations having great simplicity, power, and elegance. The philosophy and technique of this approach is described, some pitfalls are pointed out, and an application to seismic risk assessment is outlined.

Notes: A method is presented for projecting mortality rates for certain causes on the basis of observed rates during past years. This method arose from a study of trends in age-specific mortality rates for respiratory cancers, and for heuristic purposes it is shown how the method can be developed from certain theories of cancer induction. However, the method is applicable in the more common situation in which the underlying physical processes cannot be modeled with any confidence but the mortality rates are approximable over short time intervals by functions of the form a exp (bt), where b may vary in a continuous, predictable fashion as the time interval is varied. It appears from applications to historical data that this projection method is in some cases a substantial improvement over conventional curve-fitting methods and often uncovers trends which are not apparent from observed data.

Notes: This paper estimates the number of workers in the United States who were occupationally exposed to asbestos during and after World War II and assesses the impact of this exposure on overall cancer mortality. The results suggest that over half of the estimated 7–8 million potentially exposed workers employed between 1940 and 1970 may still be alive and at risk of dying from some form of asbestos-related cancer. While the maximum number of excess cancer deaths associated with this occupational exposure is likely to occur sometime in this decade, such deaths will continue to be seen for many years thereafter. At their peak, these deaths may account for an estimated 3% of the annual cancer death toll, with an associated range of 1.4–4.4%.

Notes: A comparison of the costs and benefits of 57 lifesaving programs reveals striking disparities across agencies and programs in cost/life saved and even greater disparities in cost/life-year saved. Within a broad range the monetary value assigned to the benefits of averting a death usually does not alter the policy implications of the analyses. The findings suggest that despite the substantial disagreements and uncertainties in the theory and practice of valuing lives, careful quantitative analysis can be helpful in setting health, safety, and environmental priorities.

Notes: Criteria are proposed for both an acceptable upper bound of nuclear power plant risk and a lower bound as a design target. Recognizing that the public risk associated with a power plant can be estimated only by probabilistic analysis of the design features, the spread between the lower design target and the upper bound provides a margin for uncertainty in th probabilistic estimate. The combination of a low probabilistic design target and this margin provides a reasonable expectation that the overall performance will be in the domain of an acceptable risk level. Because the exposure to potential risk is chiefly in the locality of the nuclear station, it is also proposed that compensatory benefits should be provided locally and that these be included as a cost of operation. It is suggested that the upper bound be set at a risk level equivalent to those risks of routine living which are normally accepted, i.e., about 10-4 deaths per year per person (100 deaths/yr/million). The proposed lower design target is 10-8 (0.1 deaths/yr/million), about one-hundredth of the minimal risk from the natural hazards all people are exposed to.