ALBERT

Notes: A method for determining a spatially distributed set of ground-water withdrawals that maintains a regionally “optimized” potentiometric surface is presented. A goal-programing approach, in its quadratic form, is used to minimize the sum of squares of differences between the optimized surface and a “target” potentiometric surface. Constraints on withdrawals and recharge, imposed through a two-dimensional ground-water flow equation, and bounds on drawdowns assure that the withdrawal strategy developed is realistic and physically feasible. Application is demonstrated using data from the Grand Prairie region of Arkansas.

Notes: Relatively little work has been done using streamflow data as a means of estimating hydrologic parameters such as transmissivity and storativity. An approach to this problem utilizing the physical insight offered by electric analog modeling techniques has been developed with streamflow data from two small drainage basins in northwest Virginia. Streamflow modeling has produced regional estimates of the ratio of transmissivity to storativity, and results from each region indicate this ratio to be larger than expected. This discrepancy is resolved by assuming that the drainage basins contain only a small percentage of permeable rock, and this assumption suggests a further use of the model to estimate the percent of permeable rock in a watershed. The analog approach presented here shows potential for further development using digital computer methods.

Notes: Influences of limestone on physical and chemical characteristics of Abrams Creek in Cades Cove, Great Smoky Mountains National Park, were investigated from February to July 1977. Infiltration of stream water into subsurface permeable limestone conduits caused reduced and intermittent surface flow within the middle reach of the Cove. At the downstream (west) edge of the Cove, inflowing waters characteristically warmed the stream in winter and cooled it in summer and increased stream conductivity, total hardness, and pH. Management activities in the Cove did not appear to appreciably affect the chemistry of the aquatic system downstream relative to the large effects of limestone substrate.

Notes: In situ water-quality measurements, with respect to various ion and dissolved solids concentrations, have been closely approximated using open-hole borehole geophysical logs. Analyses have shown good correlation between water resistivity (Rw, as determined from the logs) and dominant ion concentrations sampled from a wide range of water quality in Tertiary carbonate and granular formations.Rw can be accurately determined by cross-plotting saturated formation resistivity (Ro), obtained from normal or lateral resistivity logs, against formation bulk porosity from neutron, density, or acoustic velocity logs. Plotting these data on Hingle Resistivity-Porosity Cross Plot (RPCP) paper with the proper matrix cementation factor (m, commonly 1.4 for unconsolidated sands or 1.6 for noncompacted Tertiary carbonates), will yield a graphical solution for Rw based upon the relationship Rw=φm Ro. The graphical technique also provides information concerning water-quality variations with depth, true matric resistivity, location of confining beds, and vertical changes in formation porosity.Once Rw has been determined, other ion concentrations can be estimated based upon chemical analyses of water samples from adjacent wells tapping a similar type water mass (i.e., calcium-bicarbonate, sodium-chloride water, etc.). Total dissolved solids (TDS), chloride, sulfate, potassium, sodium, magnesium, and hardness (as CaCO3) concentrations have consistently shown a high correlation with Rw.

Notes: A model to solve the inverse problem in ground water has been developed. The model consists of an unconstrained multivariable optimization algorithm and a ground-water simulation model. The optimization algorithm is a modified version of Newton's second derivative method. It is a ground-water-specific algorithm and was found to be more efficient than other more general unconstrained optimization algorithms requiring first- and/or second-order derivatives and those requiring no derivatives. The groundwater simulation model is based on a finite-difference technique but it can be replaced easily by a finite-element model. The results of an application of this model to a real aquifer are discussed in a companion paper titled “Inverse Problem in Ground Water: Model Application.”

Notes: Field studies along the southeastern shore of Trout Lake, Wisconsin, documented the presence of downward hydraulic gradients in a known discharge area as well as an anomalous distribution of seepage to the lakebed which deviates significantly from the generally accepted dogma that ground-water seepage rates decrease exponentially with distance from shore. A numerical ground-water model facilitated identification of the hydrologic control, namely the presence of a unit of high hydraulic conductivity, that accounts for the anomalous data, and is important for understanding the dynamics of the flow system. Field data including seepage measurements, visual inspection of lakebed materials and springs, and information obtained during drilling, indicate that a lens of coarse-grained material intersects the lake. However, the significance of the coarsegrained material was not fully appreciated until a ground-water model was used to simulate the flow system. The model indicated that the presence of the coarse-grained lens has a marked effect on the flow pattern in the nearshore area causing downward hydraulic gradients which divert ground water into the lens and cause the occurrence of a localized high-seepage area offshore where the lens intersects the lake. The numerical model predicts the anomalous seepage distribution noted in the field and the downward hydraulic gradients demonstrating that numerical models are practical tools for interpreting field data and for use in hypothesis testing.

Notes: A parameter identification (PI) procedure is developed and implemented with the United States Geological Survey's Method of Characteristics (USGS-MOC) model. The PI procedure can be used to estimate selected model parameters from limited observations by quadratic programming. The code combining the PI procedure and the USGS-MOC model has been tested by two numerical examples from a hypothetical aquifer. The test results show that the proposed algorithm can identify transmissivity and dispersivity accurately under ideal situations. The effects of using a simple characterization of the aquifer on parameter estimation and model are shown. Because of the improved efficiency in model calibration, extended application to field conditions is encouraged. However, it is cautioned that the interested users should be aware of the difficulties in field applications of PI, and it is recommended that sound engineering and scientific judgements are always needed in the use of the proposed, or any other PI method.

Notes: This paper illustrates several interesting effects of aquifer stratification on the results of two-well tracer tests by means of a simplified computer model. In the model, it is assumed that the aquifer is horizontal, confined, of constant thickness and porosity, and perfectly stratified in the vicinity of the test wells. The nonuniform advection pattern is taken into account in detail by the model, but the local hydrodynamic dispersion is completely neglected. This simplified model has been verified in part by comparisons with available analytical solutions valid for homogeneous aquifers and in part by comparisons with the results of a two-well field experiment of Pickens and Grisak (1981a) which was performed in a locally stratified aquifer. The applications of the model to several field situations with assumed values of the relevant parameters show that the concentration versus time breakthrough curve measured at the withdrawal well during a standard two-well test would be very sensitive to variations of the hydraulic conductivity in the vertical. Without the use of supplementary observation wells with isolated multilevel sampling points, the standard test would give little useful information about the hydraulic and dispersive characteristics of an aquifer. Factors such as the length of the tracer injection period, the use of recirculation and the physical size of the experiment all have a strong effect on the breakthrough curve measured at the withdrawal well, making the interpretation of field results difficult unless aquifer stratification is measured and properly taken into account.

Notes: Proper design, construction, testing and maintenance of Class 1 (hazardous waste) injection wells can guarantee that all waste is delivered to the injection zone. To assess the effects of waste injection, analytical models were developed which predict waste movement and pressure increases within the injection zone, and describe upward permeation through confining layers.A basic plume model was used to track waste from several injection wells with varied injection history at DuPont's Victoria Texas site. To determine the maxi-mum distance that any portion of the waste might travel, special purpose models were employed to account for (1) density differences between the waste and the native formation brine, and (2) layered permeability variation within the injection zone. The results were generalized to a “multiplying factor concept,” which facilitates development of a worst-case scenario.A pressure distribution model based on the Theis (1935) equation for radial flow was applied to the Victoria site, with modifications to account for multiple wells, injection history and geological complexities.Permeation into an intact confining layer was investigated by a new technique based on the Hantush and Jacob (1955) “leaky aquifer” theory. The model defines the maximum permeation distance, taking into account post-injection pressure decay.Defects within confining layers, such as faults, fractures and abandoned wells, have been considered. Studies to evaluate their detailed characteristics are continuing. Initial results indicate that faults and fractures are not likely to provide conductive pathways in Gulf Coast settings, and site-specific evaluations are required to assess the impact of abandoned wells.

Notes: In 1984, the Illinois Department of Energy and Natural Resources was required to assess the regulations and practices of the Illinois Underground Injection Control (UIC) program as it relates to Class I hazardous waste disposal wells. Nine injection wells, including two standbys (one inactive), are currently in operation at seven sites in the state. These wells range in depth from 1540 to 5524 feet (470 to 1683m; most inject wastes into porous carbonate formations (two wells inject into a thick sandstone). In 1984, approximately 300 million gallons (1.1 billion liters) of industrial wastes were disposed of in these wells. Acids were the most common waste disposed of, although water made up 70 to 95 percent of the wastes by volume. Illinois has been granted primacy in operating this program.The geologic environment, consisting of the unit accepting the waste and confining units lying above and below, has the capacity to accept the waste, to retain it, and to protect all underground sources of drinking water (USDW) from contamination by its injection. The geology of Illinois is relatively simple and includes disposal zones and associated confining units suitable for deep-well injection across the central two-thirds of the state.The regulatory structure for Class I injection wells is generally adequate in concept and scope to ensure containment of injected wastes and to safeguard underground sources of drinking water in Illinois. There is a need to update and strengthen selected portions of the regulatory practices in the areas of waste sampling protocol, chemical analysis of collected waste samples, and evaluation of injection well testing and monitoring data.A number of technologies exist that can treat and dispose of most hazardous and non-hazardous waste streams. Each of these technologies has associated with it economic, environmental and societal impacts.

Notes: A method for removing dissolved contaminants from ground water by emplacing electrodes in the aquifer has been tested using laboratory columns of pure quartz silty sand saturated with solutions of CuSO4 and copper-contaminated synthetic ground water. In the Soviet Union a similar method is commonly used in searching for hidden deposits of metallic minerals. In the Soviet method, electrodes are emplaced in the ground and ions of the metals being sought are caused to migrate along an imposed voltage gradient; the ions are collected for analysis in acid-filled ceramic cylinders which surround the cathodes.In this study, quick-freezing was used to obtain the distribution of ions within the columns as a function of time and space. With voltages up to 2.5 V and cur-rents of a few tens of microamps, more than 50 percent of the dissolved copper was removed from the interstitial fluid in the porous columns in a period of five days. Current efficiencies ranged from more than 80 percent to less than 5 percent, depending on such factors as length of time of electrolysis, pH, concentration of Cu, and presence of other ions. The efficiency and economics of the technique of electromigration should be evaluated in additional laboratory studies and in the field, but in theory the method should be useful for removing any charged species in ground water, including some organics.

Notes: Ground water scientists engaged in assessment of contaminant occurrence and migration are faced with a number of practical problems. These problems include, but are not limited to, escalating drilling costs, labor costs for proper sampling of monitoring wells, collection of ground water samples that are representative of aquifer conditions and accurate delineation of hydrogeologic regimes and the areal and vertical distribution of ground water contaminants.In response to these problems, a number of ground water sampling devices have been developed. One device is a gas-driven ground water sampler developed for multilevel installation. Use of these samplers have been shown to decrease project costs and allow easy collection of high quality samples. However, the currently available samplers are relatively expensive, some of them operate on a closed check valve system, which does not allow determination of piezometric heads in aquifers with fluctuating water tables and they are not adaptable to design changes in the field necessitated by site-specific hydrogeologic conditions.GHR Engineering Associates Inc. has designed an effective gas-driven sampler, which accomplishes the same objectives as the commercially available models, but is on the average, one-tenth the cost of currently available samplers. It offers the advantages of being more cost-effective than commercially available models, has an open check valve system to allow measurements of water table fluctuation and is easily adaptable in the field to meet site-specific hydrogeologic conditions.

Notes: Three monitoring wells were installed in borings that were constructed using water-based drilling fluids containing either (1) guar bean, (2) guar bean with breakdown additive, or (3) bentonite. These fluids were selected to observe their effect on the chemistry of subsequent water samples collected from the wells. The wells were installed to depths of 66 feet, 100.5 feet and 103 feet, respectively, in fine-to-medium sand and gravel outwash deposits near Antigo, Wisconsin. Drilling fluids were necessary to maintain an open borehole during well construction through strata containing cobbles and boulders.The bentonite and guar drilling fluids caused temporarily elevated concentrations of chemical oxygen demand (COD) in ground water samples collected from the monitoring wells. Using standard development, purging and sampling procedures, elevated COD concentrations persisted for about 50 days for the well bored with the guar-with-additive fluid, 140 days for the bentonite well and 320 days for the guar well. Unfiltered ground water samples for all wells had greater concentrations of COD than samples filtered through a 0.45 micron filter. Sulfate concentrations also decreased with time in the guar-with-additive well and bentonite well, but not in the guar well.The elevated COD concentrations are attributed to the large concentrations of oxidizable carbon present in the guar bean drilling fluid and in the organic polymers present in the bentonite drilling fluid. Well development and purging procedures, including borehole flushing, surging, bailing and/or chemically induced viscosity breakdown of the guar mud decreased the time before background conditions were achieved. Future research should evaluate the physical and geochemical interaction of different drilling fluid compositions with a variety of geologic matrices and drilling, well development and well purging techniques.

Notes: A shallow seismic refraction survey was conducted as part of a geologic and hydrologic investigation of an area adjacent to a proposed coal strip mine in southeastern Illinois. Data obtained from the survey were used to estimate the thickness and geometry of litho-logic units within approximately 40 feet of the surface in unconsolidated material overlying bedrock. Data from a nearby ground water monitoring well and several shallow geologic cores obtained in the survey area indicated the presence of a silt-clay unit roughly 10 feet beneath the surface. This unit strongly inhibits the vertical movement of ground water, resulting in a perched water table.The refraction survey revealed that the morphology of the top of this silt-clay layer is dominated by a narrow, sinuous channel criss-crossing the survey region with an overall downward trend in elevation from the mine site to a small creek roughly 0.25 miles away. Detailed knowledge of the location of this channel was used to identify optimal sites for shallow ground water monitoring stations. The method proved to be a relatively rapid and cost-efficient means of obtaining detailed information concerning the thickness and geometry of the near-surface unconsolidated materials.

Notes: Using the most comprehensive inhalation study available, (Wagner, et al., 1974), the dose-response effects of the four major types of asbestos fibers (amosite, anthophyllite, crocidolite, and chrysotile: Canadian, Rhodesian) for lung cancer have been determined. From linear regression analysis of the animal data and five human epidemiology studies giving a wide range of risk estimates, slopes of the curves have been determined and lifetime risk estimates made. Projected risks for rats are presented with and without surface area (s.a.) conversion factors. On the basis of cumulative exposure, the geometric mean of the point estimates for the human studies (0.0146) is quite close to the geometric mean of the animal data (0.0179 without s.a.; 0.0122 with s.a. calculations). These values also match quite well if one of the studies (McDonald, et al.) is eliminated (geometric mean = 0.031) due to qualitatively different exposure considerations (mining and milling vs. industrial environments). Animal risks based on a concentration per day basis (assuming an average 70-year lifespan for humans) are below the lowest human estimate but within 5–6 fold (less) of the projected risk from nonsmoking asbestos workers (2.2time10-3) using the Hammond et al. study.

Notes: The Color Additives Scientific Review Panel considered whether there was information sufficient to perform a carcinogenic risk assessment on the colors D&C Red No. 19 (R-19), D&C Red No. 37 (R-37), D&C Orange No. 17 (O-17), D&C Red No. 9 (R-9), D&C Red No. 8 (R-8) and FD&C Red No. 3 (R-3) and to evaluate the assessments sent to FDA as part of the petitions for use of the colors for drug and external uses by the Cosmetic, Toiletry and Fragrance Association (CTFA). There is a lack of human data concerning the colors for making a human health assessment, so the assessments are based upon the extrapolation of animal data. The risk assessments are determined for exposure to single chemicals. Excluded from consideration are possible effects from exposure to multiple chemicals, such as cocarcinogenesis, promotion, synergism, antagonism, etc. In the light of recent efforts in establishing a consensus in risk assessment, the Panel has determined that the CTFA assessments for R-10, O-17, and R-9 are consistent with present acceptable usages, although it questions some of the assumptions used in the assessments. The Panel identified a number of general assumptions made, and discusses their validity, their impact on total uncertainty, and the potential options to address the gaps in understanding that necessitate the assumption. The Panel also derived revised risk estimates using more “reasonable” assumptions than “worst-case” situations, for 90th percentile and average exposure. For those assumptions that are easily quantifiable, the Panel's estimates are less than an order of magnitude lower than the CTFA risk estimates, indicating that the underestimates and overestimates of the CTFA risk estimates tend to balance each other. The impact of most of the assumptions is not quantifiable. The assessment for R-3 is complicated by the fact that there is no good skin penetrance study for this color. It was assumed that the penetrance is similar to that of another water-soluble xanthene color, R-19. It is expected that the absorption of the color is not likely to exceed that of the smaller molecule, R-19. Therefore, the risk estimates are similar to the CTFA estimates, but with different reasoning. The estimates for R-8 and R-37 are different from the others in that there is a lack of any exposure or toxicological information on these colors. The toxicological properties were considered to be similar to the chemically related colors R-9 and R-19, respectively. The risk calculated for these dyes is actually a unit risk (i.e., a risk based on particular unit exposure). The unit exposure used is the exposure estimated from the chemically related color, which, from the production values for the dyes, is likely to have much higher usage. Exposure to all of these colors from external and drug uses is quite low, especially as a result of exposure through skin. Therefore, the risk estimates are low. It is cautioned that usage information is based on a recent survey, and changes in usage will alter the risk estimate.

Notes: The comparison and ranking of risks is very important for safety and cost-benefit analysis. Most formats present risks in the form of probability distribution. Different ranking criteria for probability distributions are considered. It is demonstrated that significantly overlapping distributions lead to ambiguous results. For this reason, criteria of insignificant overlapping distributions are proposed. The first criterion uses the information theory approach; and the second criterion uses the statistical tests approach. Both approaches can be applied to decision theory to avoid questionable decisions based on statistically insignificant differences between two risks.

Notes: Book reviewed in this article:Paolo F. Ricci and Michael D. Rowe, (eds.Saul I. GassJane Ives, (ed.)Robert W. Cates, Christoph Hohenemser, and Jeanne X. Kasperson, (eds.)

Notes: This paper explores reasons for difficulties in communicating risks among analysts, the laypublic, media, and regulators. Formulating risk communication problems as decisions involving objectives and alternatives helps to identify strategies for overcoming these difficulties. Several strategies are suggested to achieve risk communication objectives like improving public knowledge about risks and risk management, encouraging risk reduction behavior, understanding public values and concerns, and increasing trust and credibility.

Notes: A de minimis risk management strategy sets a threshold so that risks below the specified level are defined as trivial and exempted from further consideration. The intended purpose is to help avoid inappropriate and wasteful concern with insignificant low-level risks. In most instances a de minimis strategy is likely to have beneficial or innocuous effects, but under certain circumstances large differences may develop between nominal and actual de minimis levels. The potential for such discrepancies illustrates why de minimis (and all other risk management) strategies should be evaluated on the basis of the portfolio of risks that would accumulate from applying such strategies over time, rather than on the apparent reasonableness of any single instance of application.

Notes: Determining the fate of an oil spill on soil is often the first step in analyzing the risks of human exposure to hazardous viscous liquids such as PCBs. The special surface properties of rigidity and porosity are not among the boundary conditions in previous analyses of spills on water. The present work solves the expressions of mass and momentum conservation using a perturbation approach. Using the example of an Aroclor 1254 spill to illustrate the approach, we find that the radius at the halt of spreading is roughly proportional to spill volume for large spills. Spreading halts when the infiltration equals the spill volume. The radial distribution of infiltration decreases gradually from its central maximum, but falls suddenly to zero approaching the outer edge. Sample results are plotted for Aroclor 1254 spills from 4 to 21 liters in volume.

Notes: Consequence models for the risk assessment of man-made or natural disasters do not ordinarily take into account time-of-day variations in the size of the exposed population. Residential census population statistics are used instead. This paper proposes and illustrates a methodology for using metropolitan travel survey data to estimate the variations in question. Variations are computed from the Washington, D.C. area sample survey statistics on the number of trips taken in and out of different census tracts throughout each workday. Four principal patterns of population variation are identified, corresponding to four types of land use: (a) commercial, (b) residential, (c) shopping/entertainment, and (d) mixed use. Some general implications for consequence analysis are discussed.

Notes: The objective of this paper is to develop the ex ante perspective for benefit analysis with natural hazards. It defines an ex ante evaluation of the economic benefits that arise from policies designed to reduce either the risk of or the detrimental effects associated with a natural hazard. In the process the paper compares the ex ante and ex post perspectives and discusses the prospects for implementing the framework by measuring the valuation concepts that are developed.

Notes: At the request of Congress, a Working Group of the National Institutes of Health prepared radioepidemiologic tables which estimate the likelihood that cancer victims previously exposed to a dose of radiation developed their cancer as a result of this exposure. The ultimate purpose of the tables is to provide a scientific basis for determining compensation for such victims, and their use would represent a marked departure from the current tort system for deciding compensation. The preparation of radioepidemiologic tables requires extensive mathematical modeling because matters such as sex, size of dose, age at exposure, type of cancer, and age at diagnosis must be taken into account. The limited data require many assumptions about the quantitative relationship between radiation dose and the age-specific incidence rate of cancer. After partitioning a population into reference sets based on age at exposure, size of dose, type of cancer, etc., an assigned share is computed for each reference set and then assigned to all of its members. The assigned share represents the fraction of the cancer cases in the reference set that are attributed to the radiation dose. Because the population can be partitioned in many ways, each individual's assigned share depends on the partition used and will change with different partitions. Options for modeling and limitations in epidemiologic data lead to considerable uncertainties in estimates of assigned shares that have been scientifically evaluated for the Working Group's tables. In contest, the uncertainties associated with the current approach for determining the likelihood that a claimant's cancer was caused by radiation have not been appraised, but are likely to be even greater than those associated with the Working Group's tables. One issue is how to use such tables to compensate victims. Some among many possibilities are: (i) to use them together with a compensation formula to determine the fraction of a standard award to be given; (ii) to use them as a starting value for the fraction, to be modified by an authority on the basis of additional information supplied by the claimant and defendant; and (iii) to use them as input to the present compensation system.

Notes: We consider animal bioassay experiments with variable dosing regimens in which groups of animals are dosed beginning at different ages and for varying durations. Two response models are discussed and then applied to data from an experiment on vinyl chloride exposure of F-344 rats, B6C3F1 and Swiss CD-1 mice, and Syrian Golden hamsters. The multistage model of Armitage and Doll,(1) as extended by Whittemore,(2) Day and Brown,(3) and Crump and Howe,(4) is used to estimate the dose effect on the ordered stages of tumor development. The data for all endpoints and species/strains examined consistently indicate a predominant effect on the first stage, suggesting that vinyl chloride is primarily a tumor initiator. This is consistent with evidence from two-stage experiments on this chemical.5 The second response model, new to this article, adjusts for survival nonparametrically. It is used to test for an age difference in susceptibility, to evaluate alternative exposure durations, and to compare the effectiveness of alternative dosing regimens for detecting carcinogenicity.

Notes: Methods are needed to improve the ability of biomonitoring and epidemiological studies to identify potential carcinogenic hazards and to quantify human risk. The limitations of pharmacokinetic models can be mitigated by the direct measurement of molecular markers of biologically effective dose of carcinogen. Parallel animal and human studies are recommended as a means of validating these markers.

Notes: Three methods for making a consumer product safety decision were evaluated on scales relating to their perceived acceptability, logical soundness, completeness, and sensitivity to moral and ethical concerns. Two of the methods were formalized techniques: cost-benefit analysis and risk analysis. The third method involved abiding by standard industry practices. Other factors in the decision-making context were also varied. The results indicated that formalized techniques were preferred over the standard practices method. Within the formalized methods, cost-benefit analysis was judged less acceptable than a comparable method that did not involve making explicit value tradeoffs. All methods were judged more acceptable when they led to improved product safety. Knowledge of consequences did not exert direct effect on judgments, though it did interact significantly with other variables. The results are discussed in terms of judgmental processes that people apply when evaluating decision methods.

Notes: Every source of liquid pollutants lies somewhere on a watershed. Leachwaters derived from water percolating through solid waste deposits and liquid effluents from industry are diluted on their way down the river until they interact with man or particular environmental systems. This environmental dilution of potentially toxic effluents has to be estimated in assessing health and environmental risks. The problem for the risk assessor is to find an appropriate mathematical model. In this paper, the recent mathematical theory of fractal objects is used to demonstrate that, within certain limits, rivers of all lengths and their river basins are self-similar. Simple general relations exist, therefore, between the length and drainage area of rivers both large and small. These relations and a few additional assumptions are then used to derive an improved set of models for estimating environmental dilution of some pollutants.

Notes: This is a report on the Environmental Protection Agency's (EPA's) efforts to communicate with the public about the risks of ethylene dibromide (EDB), what the agency said it was doing about these risks and what information the public actually received through television and newspapers. Although special in many ways, the EDB case illustrates the problems that regulatory agencies have when they must take regulatory action and assure the public that the risks in question are being dealt with adequately. It also illustrates issues that the press faces. Above all, it illustrates the barriers to communication presented by the different perspectives of regulatory agencies and individuals and the types of information they each are most interested in.

Notes: The risk homeostasis theory posits, in essence, that a control mechanism analogous to the thermal homeostatic system in warm-blooded animals tends to keep risk per unit time constant, and, as a consequence, the number of traffic accidents per unit time of driving also tends to remain constant, essentially independent of changes in the traffic safety system. It is the purpose of the present research to examine the validity of this claim using a wide variety of traffic accident data. All the data examined are found to be incompatible with the risk homeostasis theory. The only specific field accident data offered in the literature to support the risk homeostasis theory are found to, in fact, refute the theory. The accident data provide evidence that a rich variety of user responses occur. While it is possible for users to collectively respond in such a way that safety benefits are completely cancelled, such a response is not particularly common; it is certainly not universally occurring, as suggested by the risk homeostasis theory. It is concluded that the risk homeostasis theory should be rejected because there is no convincing evidence supporting it and much evidence refuting it.

Notes: A quick and summary comment is made on a paper by Evans,(1) who set out to “definitively answer” the question “whether there is any validity” in risk homeostasis theory (RHT), and who arrives at the conclusion that the “theory should be rejected” because the data “provide the clearest evidence refuting the theory.” It will be argued here that the seven cases Evans puts forward against RHT do not justify such a rather boldly-worded conclusion. On the contrary, the data presented by Evans can be seen to be either not inconsistent with RHT (Case 1), in error (Case 2), or fail to take account of relevant economic changes (Case 3) and of pertinent exposure variables (Case 5), incomplete or the product of guesswork (Case 4), irrelevant (Case 6), nonrepresentative (Case 7) and in all cases open to alternative interpretations that do not conflict with the theory under debate. Moreover, Evans’reasoning seems to betray not only careless reading of what RHT does in fact say, but also a fundamental misunderstanding of the notion of target risk in particular. Refuting a “refutation” does not, of course, imply that RHT is valid, or valid at least within as yet to be defined limits. Attempts to address the validity question should preferably take the form of well-controlled field experiments, instead of retrospective analyses of multünterpretable archival data that can be debated ad infinitum.

Notes: PRINCIPLES OF HEALTH RISK ASSESSMENTPaolo F. Ricci, Prentice-Hall, 1985, $50.00. RISK THEORY: THE STOCHASTIC BASIS OF INSURANCE Third Edition, R. E. Beard, T. Pentikainen, and E. Pesonen, Metheun, Inc., 1984, $24.00 pb, $49.95 hb. TOXICITY TESTING: NEW APPROACHES AND APPLICATIONS IN HUMAN RISK ASSESSMENT Li et al, (eds.) Raven Press, 1985, $47.00 TOXICOLOGICAL RISK ASSESSMENT Clayson et al, (eds.), CRC Press, 1985, $82.00.

Notes: This paper is primarily concerned with environmental risks arising from utilizing modern technology. Our attention focuses on the interface between policy decisions and regulatory measures. The interface involves not only science and technology but also politics and social values, and perceptions which are deeply rooted in the industrial countries. A case of setting air quality standards and regulatory practices in Japan is studied on the basis of scientific and technological knowledge, economic cost, and subjective judgment of what constitutes an acceptable level of risk or health hazard.

Notes: This study examined factors affecting risk estimates and tolerance among persons directly exposed to environmental health risks. Data were gathered from questionnaires distributed at public hearings regarding proposed air pollution standards for an arsenic emitting copper smelter located in Tacoma, Washington. Approximately 80% of the area residents who attended the hearings completed the questionnaires, and the responses of 347 subjects were analyzed. Results indicated that informal risk estimates and risk tolerance were closely associated with judged benefits of the hazard source, acceptance or denial of vulnerability, judgments of exposure voluntariness, and environmental attitudes. Neither factual knowledge of formal risk estimates and proposed standards nor residential distance from the smelter was found to be closely related to risk tolerance or informal risk estimates. Implications of the results are discussed in relation to past and future studies of reactions to risk, and in relation to risk management policy and practice.

Notes: A risk assessment comparing the acute effects of mineral oil and PCB-askarel dielectric fluids in two transformer sites was performed. The first site has the installation characteristics for a PCB-askarel-filled transformer with sprinkler fire protection. A risk comparison is made between two types of transformers (PCB-askarel-filled and mineral oil-filled) for this site. The second site (a vault) has the installation characteristics for a mineral oil-filled transformer, and a risk comparison is made in a fashion similar to the first site. Risk is expressed in terms of frequencies of one or more acute injuries or fatalities per transformer year.

Notes: Book Reviewed in this article:RISK AND REASON. RISK ASSESSMENT IN RELATION TO ENVIRONMENTAL MUTAGENS AND CARCINOGENS P. Oftedal and A. Brogger, (eds.)THE MONITORING OF OCCUPATIONAL GENOTOXICANTS M. Sorsa and H. Norppa, (eds.)RISK. MAN-MADE HAZARDS TO MAN M. G. Cooper, (ed.)READ THE LABEL: REDUCING RISK BY PROVIDING INFORMATION S. G. HaddenMETHODS FOR ESTIMATING RISK OF CHEMICAL INJURY: HUMAN AND NONHUMAN BIOTA AND ECOSYSTEMS V. B. Houk et al., (eds.)TOXIC TERROR E. M. WhelanELEMENTS OF TOXICOLOGY AND CHEMICAL RISK ASSESSMENT ENVIRON Corporation

Notes: POSSM, the PCB On-Site Spill Model, is a contaminant transport model developed to predict environmental concentrations associated with a chemical spill. The model predicts daily changes in chemical concentrations on a spill site (e.g., in soil and on vegetation) and losses of chemical due to volatilization, surface runoff/soil erosion, and leaching to groundwater. Spill areas consisting of soil/vegetation and/or an impervious surface (e.g., asphalt and concrete) can be analyzed, as can different spill cleanup practices. POSSM is used to analyze exposure levels associated with a hypothetical capacitor spill. While the model was developed for PCB spills, it is generally applicable to a number of organic compounds.

Notes: The risk of oil spills is a major environmental issue in the siting of proposed coastal refineries, oil terminals, deepwater ports, and in the leasing of offshore lands for oil exploration and development. As with any kind of risk, oil spill risk assessment is inherently judgmental and no analytic method can eliminate the need for judgment. This paper compares representative examples of oil spill risk assessments with regard to decisions about data, variables, functional relations, and uncertainty. The comparison emphasizes the judgmental basis of analytic methods.

Notes: A general discussion of knowledge dependence in risk calculations shows that the assumption of independence underlying standard Monte Carlo simulation in uncertainty analysis is frequently violated. A model is presented for performing Monte Carlo simulation when the variabilities of the component failure probabilities are either negatively or positively coupled. The model is applied to examples in human reliability analysis and the results are compared to the results of Sandia Laboratories as published in the Peer Review Study and to recalculations using more recent methods of uncertainty analysis.

Notes: Book Reviewed in this article:THE LANGUAGE OF RISK D. NelkinRISK AND FREEDOM: THE RECORD OF ROAD SAFETY REGULATION J. G. U. AdamsRISK ANALYSIS AND THE SCIENTIFIC METHOD K. S. Shrader-FrechetteENVIRONMENTAL IMPACT ASSESSMENT, TECHNOLOGY ASSESSMENT, AND RISK ANALYSIS V. T. Covello et al., (eds.)

Notes: Under the assumption of multistage carcinogenesis, a multiplicative carcinogenic effect would be produced by the action of different carcinogens in a mixture on different stages of the carcinogenic process. An additive effect would be produced by the effect of different carcinogens on the same stage. A mathematical argument for these hypotheses is presented here.

Notes: In the long run, molecular epidemiological techniques (1) can provide important insights for understanding a wide variety of important issues in current risk assessment and (2) are applicable across a broad spectrum of adverse effects in addition to carcinogenesis. Unfortunately, current risk assessment practices make very little use of the kind of detailed mechanistic information that molecular epidemiology can provide. Eventually, there is reason to hope that the availability of mechanistic insights provided in part by molecular epidemiology can produce some of the “essential tension” required to reform paradigms for the formulation of quantitative risk assessment models in general.

Notes: An attempt is made to analyze in quantitative terms the uncertainties in multiple regression estimates of the effects of air pollution on death rates. A range of factors—statistical fluctuations in numbers of deaths, differences in local age distribution, differences in smoking habits, errors in estimated pollution levels, migration, and variability of the characterization of socioeconomic effects—are assessed as potential sources of error. Both the precision and the robustness of the regression calculation are shown to be poor. Examples and illustrative calculations are given based on a study of U. K. death rates around the 1971 Census.

Notes: The Southern California Edison Company (SCE) has instituted a series of control strategies designed to minimize human exposure to polychlorinated biphenyls (PCBs) in electrical equipment used on its system. This paper describes a method of analyzing PCB risks using conservative estimates of human intake of PCBs originating from accidental spills from electrical equipment. The PCB releases from the Edison system were determined. The fate of these releases in soil, air, and water was analyzed to determine how much material reaches human receptors. The air and water pathways were determined to be the most likely candidates for the exposure and risk considerations. PCB intake via ingestion of soil at the spill site was neglected as an exposure pathway. Equipment spills without controls resulted in at the most 2 ng/day human intake of PCBs via the water exposure pathway. This was determined to be negligible in comparison with intake rates used in conjunction with the setting of food tolerance levels based on fish being the main dietary pathway of human exposure. The inhalation exposure of the hundred or so persons in the immediate vicinity of a spill was determined to equal the PCB intakes of the fish-eating subpopulation analyzed by the Food and Drug Administration for 2 ppm tolerance standard in the case of no controls or cleanup. Current cleanup procedures assure that even the persons in the immediate area are well below the intake of the subjects in the fish contamination analysis. All exposures were well below a “virtual safe dose” level estimated in the fish tolerance study.

Notes: Estimating the potential health risk encountered by workers due to their exposure to various chemicals is enormously complex, since many chemicals be involved and each may have multiple toxic effects. As an aid to this estimation process, a computer program, or model, which computes index numbers expressing the relative health risk of occupational groups due to their potential chemical exposures was developed at the National Institute for Occupational Safety and Health (NIOSH). This model considers an inventory of the chemicals to which specific occupational groups are potentially exposed, the published information regarding the toxic effects of each chemical, and the conditions of occupational exposure. The system then develops indices of potential occupational group health risk by considering weighted combinations of eight distinct health effects. No direct comparison with external occupational risk indices is currently possible, but internal testing of the model reveals no obvious inconsistencies.

Notes: We emphasize the distinction between two forms of uncertainty that arise in risk and reliability analyses: (1) that due to the randomness inherent in the system under investigation and (2) that due to the vagueness inherent in the assessor's perception and judgement of that system. It is proposed that whereas the probabilistic approach to the former variety of uncertainty is an appropriate one, the same may not be true of the latter. Through seeking to quantify the imprecision that characterizes our linguistic description of perception and comprehension, fuzzy set theory provides a formal framework for the representation of vagueness. In connection with the second form of uncertainty, fuzzy sets and the associated theory of “possibility” are considered as a basis upon which to model the imprecision and vagueness attached to the expert judgement of event likelihood (e.g. component failure). It is noted that from the perspective of the technical complexity of propagation, the possibilistic treatment of uncertainty compares favorably with the more familiar Bayesian approach.

Notes: A model is developed for the detection time of fires in nuclear power plants, which differentiates between competing modes of detection and between different initial fire severities. Our state-of-knowledge uncertainties in the values of the model parameters are assessed from industry experience using Bayesian methods. Because the available data are sparse, we propose means to interpret imprecise forms of evidence to the develop quantitative information, which can be used in a statistical analysis; the intent is to maximize our use of all available information. Sensitivity analyses are performed to indicate the importance of structural and distributional assumptions made in the study. The methods used to treat imprecise evidence can be applied to a wide variety of problems. The specific equations developed in this analysis are useful in general situations, where the random quantity of interest is the minimum of a set of random variables (e.g., in “competing risks” models). The computational results indicate that the competing modes formulation can lead to distributions different from those obtained via analytically simpler models, which treat each mode independently of the others.

Notes: The objective of informing and educating the public about risk issues seems easy to attain in principle, but, in practice, may be difficult to accomplish. This paper attempts to illustrate why this is so. To be effective, risk communicators must recognize and overcome a number of obstacles that have their roots in the limitations of scientific risk assessment and the idiosyncrasies of the human mind. Doing an adequate job of communicating means finding comprehensible ways of presenting complex technical material that is clouded by uncertainty and inherently difficult to understand. The problems may not be insurmountable, however, if designers of risk information programs are sensitive to the difficulties.

Notes: A method is developed for estimating a probability distribution using estimates of its percentiles provided by experts. The analyst's judgment concerning the credibility of these expert opinions is quantified in the likelihood function of Bayes’Theorem. The model considers explicitly the random variability of each expert estimate, the dependencies among the estimates of each expert, the dependencies among experts, and potential systematic biases. The relation between the results of the formal methods of this paper and methods used in practice is explored. A series of sensitivity studies provides insights into the significance of the parameters of the model. The methodology is applied to the problem of estimation of seismic fragility curves (i.e., the conditional probability of equipment failure given a seismically induced stress).

Notes: The methodology and results reported in this paper are based on an analysis of a hypothetical accident occurring in a two unit power plant with shared systems (i.e., the diesel generator, the emergency service water, and the residual heat removal service water systems). The accident postulated is a loss of coolant accident (LOCA) in one out of two nuclear units in conjunction with a loss of offsite power (LOOP) and a failure of one out of four diesel generators to start. To analyze the intersystem effects, we needed to develop and apply a new methodology, intersystem common cause analysis (ICCA). The ICCA methodology revealed problems which were not identified by the traditional intrasystem failure modes and effects analysis (FMEA) performed earlier by the design teams. The first potential problem arises if one unit experiences a LOCA and diesel generator failure while one loop of its residual heat removal system is in the suppression pool cooling mode (SPCM); in this event, it is likely that minimum emergency core cooling system (ECCS) requirements will not be met. The second potential problem arises if a diesel generator fails while both units are simultaneously subjected to a controlled forced shutdown (a LOCA need not be postulated for either unit); in this event, it is likely that one unit will be required to use a heat removal path identified as off-normal in the final safety analysis report (FSAR) for the two unit plant. These and other potential concerns identified through application of the ICCA presented here were resolved early in the design phase.

Notes: New societal obligations for communicating risk information are emerging in a variety of contexts. This article draws upon the lengthy societal experience with citizen participation programs to identify how risk communication efforts may be effectively structured and implemented. Six major propositions address such themes as means/ends differences in expectations, the timing of the program, the role of credibility and trust, the need for technical and analytical resources, differing thresholds of public involvement, and limitations upon current understandings. Key conclusions for the design of risk communication programs are set forth.

Notes: Extensive carcinogenesis data compiled by Gold et al.(1) for 770 compounds tested in 2944 chronic bioassays in animals provided an opportunity to compare cancer rates across animal species for a wide variety of compounds administered by various routes of exposure. The comparisons in this paper are restricted to the most frequently tested species: rats, mice, and hamsters. When sufficient experimental data exist, Gold et al.1’ provide estimates of the TD50 (the chronic dose rate expressed in mg/kg body weight/day which halves the actuarially adjusted percentage of tumor-free animals at the end of a standard lifetime experiment). Since the current practice generally is to base risk assessments upon the data set producing the highest cancer risk, the ratio of the minimum TD50's provides a measure of the relative potency between two species for each compound administered to animals by the same route. The geometric means of the ratios of minimum TD50's for rats: mice are 1/2.2 and 1/1.3 for diet and gavage, respectively. A mean ratio for rats: mice of 1/1.48 is obtained for compounds administered in the diet when the tumor site is the liver for both species. In general the minimum TD50 is lowest for the rat and highest for the hamster. Although limited data are available for inhalation studies, this route of administration resulted in the poorest agreement between rats and mice. In general, comparisons of minimum TD50's across the three rodent species are generally within a factor of 100 for a wide variety of compounds.

Notes: Estimating the potential health risk encountered by workers due to their exposure to various chemicals is enormously complex, since many chemicals may be involved and each may have multiple toxic effects. As an aid to this estimation process, a computer program, or model, which computes index numbers expressing the relative health risk of occupational groups due to their potential chemical exposures was developed at the National Institute for Occupational Safety and Health (NIOSH). This model considers an inventory of the chemicals to which specific occupational groups are potentially exposed, the published information regarding the toxic effects of each chemical, and the conditions of occupational exposure. The system then develops indices of potential occupational group health risk by considering weighted combinations of eight distinct health effects. No direct comparison with external occupational risk indices is currently possible, but internal testing of the model reveals no obvious inconsistencies.

Notes: This paper introduces stochastic dominance as a technique to reduce the set of possible actions that a decision maker must consider in a decision problem under risk. The procedure usually does not choose an optimal action, but instead eliminates certain actions as unacceptable. Very little need be known about the decision maker's utility function. Two possible applications are presented: (1) upgrading buildings to better withstand an earthquake; and (2) choosing a site for a LNG facility.

Notes: A simple relationship is formulated that helps to discriminate between acceptable and unacceptable individual lifetime risks (RL) to populations that are exposed to chemical carcinogens. The relationship is an empirical one and is developed using objective risk data as well as subjective risk levels that have found substantial acceptance among those concerned with carcinogenic risk assessment issues. The expression sets acceptable levels of lifetime carcinogenic risk and is a function of the total population exposed to the carcinogen. Its use in risk assessment and risk management provides guidance in distinguishing those carcinogens that should be regulated because of the health hazard they pose from those whose regulation may not be needed.

Notes: Brackish-water contamination of the Patuxent aquifer has been a serious water-quality problem in Baltimore, Maryland, since the early 1900's. The Patuxent aquifer presently contains a circular plume of brackish-water contamination that is about 5 miles in diameter. This plume is centered on the Patapsco River estuary and is characterized by chloride concentrations that range up to 5,000 milligrams per liter. Borehole data demonstrate that the Arundel Clay Formation, which overlies the Patuxent and functions as a confining bed, has been breached by Pleistocene river channels in the Baltimore area. These erosional channels, which have been subsequently filled with relatively permeable sediments, provide conduits for brackish water to seep from the Patapsco River into the Patuxent aquifer when aquifer water levels arc lower than river water levels.A two-dimensional areal solute-transport model of the Patuxent aquifer was used to estimate the future movement of the brackish-water plume based on alternative strategies of aquifer use. Model simulations suggest that the plume will not spread rapidly if present pumping patterns are continued. Furthermore, sharply curtailing pumpage in the Baltimore area will probably not reduce the size of the plume, although this strategy may slightly decrease the spreading rate. While the plume is presently remaining nearly stationary, new pumping centers southeast of Baltimore could cause brackish water to migrate in that direction, significantly increasing the size of the plume.

Notes: This paper examines two eases of surface-water/ ground-water interrelationships, one in Beaufort County, North Carolina and one in Ramona, California. In each case the author has to make a differential diagnosis between alternate solutions rendered by hydrologic methods.In the first ease, the author proves that the pumping and subsequent wastage to the ocean of 65 mgd in order to operate the Texas Gulf Sulphur phosphate mine, in all likelihood poses no threat to the environment.In the second case, the author has attempted to obtain, by means of the theory of ground-water flow, an estimate of the physiographic volume of the Santa Maria creek ground-water basin in Ramona. He has submitted the outcome of his calculations to the test of compatibility with the results of an actual pumping test, and with pumping records made available by the Ramona Municipal Water District. The outcome shows a water storage capacity of the order of 4,600 AF for the entire basin.In order to correlate recharge of the basin directly with the precipitation on the basin, a hydrograph analysis has been done for the 20 largest runoff-producing months of the streamflow records 1965–1982. From this study it follows that the average (annual) recharge to the basin is of the order of 1,340 AF/yr and that the physiographic volume, as derived previously, is amply adequate to absorb this recharge.

Notes: A radial injection tracer experiment was conducted in Scarborough, Ontario, as part of a program to evaluate the feasibility of using a confined aquifer, underlying the Canada Centre building site for the storage of chilled and/or heated water for a seasonal thermal energy storage system. Water was injected into the aquifer for five hours before a salt solution was added as a tracer. This tracer was injected into the aquifer over a period of four hours at a rate of 22.7 1/s. Injection of the water into the aquifer continued for an additional 1 5 hours following injection of the salt solution. Samples were collected from a monitoring well located 6.54 meters from the injection well. A sampling device was installed prior to the injection experiment to permit the collection of water samples at different elevations within the screened portion of the monitoring well. The samples which were collected at five different elevations at various times, both during and following the salt injection, were analyzed for specific conductance and chloride concentration. The data suggest that the aquifer is inhomogeneous and that the ratio of the hydraulic conductivity to porosity increases from the lowest sampling port to the highest sampling port near the top of the aquifer. A linear relationship was obtained between the time of arrival of the tracer and the apparent resistivity of the formation. This linear relationship was used to calibrate the apparent resistivity log of the injection well to provide a continuous characterization of the vertical variation in the hydraulic conductivity/porosity ratio across the full thickness of the aquifer. Data analysis also suggests that the dispcrsivity parameter varies linearly with the time of arrival of the tracer. The combination of geophysical logs with tracer experiments may permit detailed characterization of the hydraulic properties of aquifers.

Notes: The transient movement of contaminant under pumpage and recharge conditions in steady ground-water flow in a vertical cross section of a confined aquifer is simulated using a finite-element numerical model based on Galerkin technique. Various factors like time step, space increment, and boundary condition affecting the accuracy of the numerical solution are considered in validating results of the numerical model with results of an analytical solution. The solution with the application problem illustrates the effectiveness of subsequent operation of pumpage on the movement of contaminant downstream of the point of injection.

Notes: Mapping of ground-water spatial data is an important part of any geohydrologic investigation. There are three main classes of interpolators used for such mappings. The first group include simple estimators which are commonly used in practice. The second group are least-squares estimators which are basically fitting processes. The last category are Gauss-Markov estimators, such as kriging, which beside being exact interpolators, produce measures for the accuracy of the estimated field. These estimators are compared theoretically and numerically. These studies show that kriging yields relatively robust estimates. However, its suggested statistical inference method may not always produce robust estimates of the covariance function parameters. Simple estimators produce unstable results, while least-squares methods ignore local variations by fitting a single polynomial function over the whole field. For this study, water-table data from northwest Kansas are used.

Notes: Findings from a detailed hydrogeologic study of a Micronesian atoll island are combined with published descriptions of the hydrogeology of other atoll islands. The purpose is to propose a conceptual model which describes how the occurrence and flow of ground water in atoll islands are related to the underlying geologic framework. The study island is Deke, a small, uninhabited island on Pingelap Atoll in the Eastern Caroline Islands.Integrated studies on Deke of surface geology and physiography, water levels and their variation, surface geophysics (seismic refraction and resistivity), and subsurface core samples indicate a hydrogeologic system that is more complex than would ordinarily be expected for a small and, at first glance, uncomplicated island. Of utmost importance to the occurrence and flow of ground water is the fact that the island straddles the lagoonward edge of the very firmly indurated reef-flat plate. This plate is a hard, impermeable substrate beneath the northern portion (ocean side) of the island, occurs at sea level, and is underlain by unconsolidated or loosely cemented sediments. Study results indicate that this reef-flat plate acts as a confining bed along the ocean side of the lens; elsewhere the lens is unconfined, receives recharge directly, and forms a thicker fresh-water nucleus.The conceptual model of atoll-island hydrogeology involves a dual aquifer system: (1) an aquifer of mostly unconsolidated Holocene sediments resting on (2) a once emergent and now very permeable Pleistocene limestone platform. The Holocene aquifer, which is where the island lens occurs, is heterogeneous with respect to its hydraulic properties and is confined in part of the island and unconfined elsewhere, with the location of the two regions depending on where the island sits relative to the pinchout of the reef-flat plate. In the unconfined region, there is a hydrologically-important central depression, where low lying sediments are enclosed by ocean-derived washover fans and a lagoon-bordering dune. This area is a likely ground-water sink due to direct evapotranspiration during the dry season. Accordingly, the model includes two flow patterns: a wet-season pattern radiating outward from the unconfined lagoon-side of the island, and a dry-season pattern that includes a superimposed area of centripetal flow at the central depression.

Notes: A method has been developed by which the slope between any two successive data points on a time-drawdown plot can be used for determining aquifer parameters in nonleaky and leaky aquifers. The method yields values of transmissivity and storage coefficient which are in good agreement with the results of the classically known techniques. The method of slope analysis offers several advantages in its use. These advantages include the following: Changes in values for the aquifer parameters that might occur during a pumping test can be identified. Confidence limits can be calculated for average values of aquifer parameters. The method yields meaningful aquifer parameter estimates even for short duration pumping tests. Subjective interpretation of the data is minimized.

Notes: The equation for two-dimensional, vertically averaged steady-state flow to a finite-length line sink, a semiempirical expression for the radius of influence, and the theory of superposition are used to predict the impacts of excavations on ground-water flow patterns. The algorithm provides a rapid method for estimating the inflow to mine pits, and the impact of mines on the potentiometric surface. An accurate expression for the radius of influence is developed by comparison with analytical and finite-difference model solutions. The algorithm is an accurate estimate of drawdowns at longer times, when the steady-state approximation is appropriate.

Notes: Ground water from deep wells was sampled for the presence of heterotrophic bacteria. Over 500 bacteria were isolated from well-water samples on a low-nutrient medium (R2A). Gram-negative, rod-shaped, nonmotile bacteria predominated, and Acinetobacter spp. comprised 54% of the total number of isolates. Selected isolates were inoculated into unamended and carbon-enriched well water, and growth was measured by acridine orange direct count (AODC). Carbon sources included glucose, acetate, pyruvate, and succinate in 100 μg carbon/liter and 1,000 μg carbon/liter concentrations. The isolates grew in unamended filtered well water within 24 hours, and growth of an Acinetobacter sp. was further stimulated (greater than two orders of magnitude within five days) in the carbon-enriched well water.

Notes: The disappearance of aldicarb [2–methyl–2(methylthio) propionaldehyde 0-(methylcarbamoyl) oxime] and its two toxic degradation products, aldicarb sulfoxide and aldicarb sulfone, were measured in laboratory studies using ground waters and subsoils collected from citrus groves in Indian River County, Florida, and incubated under controlled conditions which best represented the in situ environment. The half-life times for the disappearance of aldicarb and its two oxidized sulfur derivatives in ground-water-saturated subsoils ranged from 10–26 days. Based on the degradation rates found in this study, hydrologic parameters obtained for Indian River County subsoils, and amounts of total toxic residue reported entering Florida ground waters, it was estimated that toxic residues in aldicarb-contaminated ground waters in Indian River County would migrate only short distances (0.3–5.2 m) before conversion of toxic residues to nontoxic residues was complete.

Notes: Oil and gas exploration and engineering studies in water-covered areas routinely use continuous seismic profiling techniques to obtain subsurface geologic information. Such profiling also can be used effectively in hydrologic studies to define the geologic framework of aquifer systems, to locate hydrologic boundaries, and in some places, to interpret the lithologic character of aquifers and confining beds.High-resolution continuous seismic profiling, through the use of nonexplosive sound sources, can be used to produce continuous records that require little data processing before hydrogeologic interpretation. High-resolution tuned transducer, minisparker, Uniboom, and small airgun systems operating from small boats in shallow water are capable of transmitting energy that can penetrate up to a hundred meters of earth materials. The resulting analog records of the reflected seismic signal closely resemble geologic sections.Surveys on the Housatonic River in Connecticut and Massachusetts, and on the Connecticut River, in water from 1 to 10 meters deep, have defined the bedrock surface beneath 60 meters of stratified drift. Seismic-reflection profiling also was used to determine the extent and thickness of recent lake-bottom deposits in two Connecticut lakes.Surveys along 90 kilometers of river channels in the Sarasota-port Charlotte, Florida, area defined in detail the stratigrapahy and continuity of the shallow aquifers.

Notes: A major vertical fracture in a permeable rock mass may act as an extended well and can provide water through pumping cither directly from the fracture itself or if the fracture width is not enough to install pumps, from an abstraction well drilled in the fracture. In such a case the ground-water flow is not radial but linear toward the fracture and the flow lines are perpendicular to the fracture axis.A mathematical description of ground-water flow toward vertical fractures is presented. The cases considered are: (1) an infinitesimally small fracture width corresponding to a planar source or sink, and (2) a finite width fracture in which the effects of ground-water storage in the fracture are taken into account. The necessary type curves are presented for the main and observation wells. It is observed that the type curve in the linear flow pattern case is extremely different from the radial flow solution especially for long times. In addition, recovery type curves are also given. The application of the method is presented for some available data in the literature.

Notes: Abstract. The San Luis Drain (SLD) has enabled us to learn quickly the facts and effects of irrigating only 8,000 acres of seleniferous soils: the dissolving and organic uptake of selenium, its dissemination from ponds, entry into food chains, and accumulation in a wide variety of biota and detritus. If deprived access to SLD, the Westlands Water District (WWD) could direct their toxic wastes down natural slopes by trickling or sumps and drain ditches, but this means toward the Mendota Pool and the Main Canal and Outside Canal which carry water for irrigation and domestic wells; that is more ominous to Merced County than the SLD ever was.The WWD needs detailed testing and mapping of its irrigable lands to discriminate the areas of seleniferous soils from those which are safe for irrigation. In the meantime, in irrigated lands above the Delta-Mendota Canal, all sumps and drains should be monitored for selenium in toxic concentrations, and irrigation should cease in the areas producing the excessive selenium. Monitors along the Outside and Main Canals (below drainage from known seleniferous areas) might be needed for preservation of good quality, perhaps by dilution with CVP water.

Notes: Abstract. WATIN is a FORTRAN 77 program for creating and modifying input files of analytical data for WATEQF, the aqueous geochemical speciation/saturation model. WATIN uses menus to display information about the data file and to accept new information from the user. In addition to providing basic editing functions, WATIN provides default values for WATEQF parameters and checks for errors and inconsistencies in the data file. WATIN simplifies and streamlines access to WATEQF for both researchers and students, and along with WATEQF, can be an important part of a geochemical data analysis system.