The Superfund Remedial Action Decision Process: A Review of Fifty Records of Decision

Abstract

Although the Superfund remedial action decision process is a complex process involving a variety of technical, political, and public health issues, the primary goal of remedial action is the protection of public health. We performed an in-depth analysis of 50 post-SARA Records of Decision in order to characterize the role of risk assessment in the decision-making process and determine whether decisions are being made in an effective and environmentally protective manner. Our findings indicate that the majority of decisions to remediate Superfund sites are based on the existence of contamination per se and not on actual public health risk. Although hypothetical risk is an essential consideration, this gray area is not well-defined in the current decision-making process.

The lack of assessment of the degree of risk reduction associated with the remedial alternatives evaluated and the lack of support indicating the effectiveness of the remedial alternatives selected also constitute major weaknesses in the majority of decisions. These inadequacies undermine rationales regarding the protectiveness and cost-effectiveness of the remedial alternatives selected. The fact that objectives beyond addressing public health risk are often unclear in the decision-making process also weakens rationales for costeffectiveness.     

Indoor Ozone Exposures

Indoor and outdoor ozone concentrations were measured from late May through October at three office buildings with very different ventilation rates. The indoor values closely tracked the outdoor values, and, depending on the ventilation rate, were 20 to 80 percent of those outdoors. The Indoor/outdoor data are adequately described with a mass balance model. The model can also be coupled with reported air exchange rates to estimate indoor/outdoor ratios for other structures. The results from this and previous studies indicate that Indoor concentrations are frequently a significant fraction of outdoor values. These observations, and the fact that most people spend greater than 90 percent of their time indoors, indicate that indoor ozone exposure (concentration × time) is greater than outdoor exposure for many people. Relatively Inexpensive strategies exist to reduce indoor ozone levels, and these could be implemented to reduce the public’s total ozone exposure.     

Spatial Variation in Acidic Sulfate and Ammonia Concentrations within Metropolitan Philadelphia

Abstract

Acidic sulfate concentrations were measured in metropolitan Philadelphia during the summers of 1992 and 1993, as part of a continuing effort to characterize particle concentrations in urban environments. Sampling was performed simultaneously at eight sites located within and around metropolitan Philadelphia. Sites were selected based on their population density and on their distance and direction from the city center. Air pollution sampling was conducted every other day during the summer of 1992 and every day during the summer of 1993. All samples were collected for 24-h periods beginning at 9 a.m. (EDT). All acidic sulfate and ammonia samples were collected using modified Harvard-EPA Annular Denuder Systems (HEADS).

In this paper, we examine the spatial variation in acidic sulfate and ammonia concentrations within the metropolitan Philadelphia area. We also identify factors that may influence their variation and develop models to predict their concentrations. Outdoor sulfate (SO₄ ^2?) concentrations were uniform within metropolitan Philadelphia; however, aerosol strong acidity (H⁺) concentrations varied spatially. This variation generally was independent of wind direction, but was related to local factors, such as the NH₃ concentration, population density, and distance from the center of the city. Physico-chemical models, which were developed using data collected during the summer of 1992, were excellent predictors of 24-h and mean summertime H⁺ concentrations measured during the summer of 1993. Models accounted for 78% of the variation in 24-h H⁺ levels. Results suggest that a single stationary ambient (SAM) monitor would be sufficient to estimate SO₄ ^2? exposures for populations living in Philadelphia. For H⁺, however, multiple monitoring sites or models should be used to determine the outdoor H+ exposures of populations living in urban environments, although a single SAM site may provide an excellent index of H⁺ variation over time.     

Hydrocarbon Measurements During the 1992 Southern Oxidants Study Atlanta Intensive: Protocol and Quality Assurance

Abstract

A major component of the Southern Oxidants Study (SOS) 1992 Atlanta Intensive was the measurement of atmospheric nonmethane hydrocarbons. Ambient air samples were collected and analyzed by a network of strategically located automated gas chromatography (GC) systems (field systems). In addition, an extensive canister sampling network was deployed. Combined, more than 3000 chromatograms were recorded. The SOS science team targeted for quantitative analysis 56 compounds which may be substantial contributors to ozone formation or used as air mass tracers. A quality assurance program was instituted to ensure that good measurements were being made throughout the network for each target compound. Common, high-quality standards were used throughout the network. The performance of individual field systems was evaluated during the intensive through the analysis of challenge mixtures. This methodology helped to identify and correct analytical problems as they arose.     

Unsteady Tall Stack Dispersion of Chimney Emissions and its Application to Varying Wind Directions

A procedure for calculating the concentration at any point and time under varying emissions and mean wind conditions is developed based on exact integration of the governing conservation equation. The procedure is simple, easy to use and has no numerical instability difficulties. Application of the procedure shows the fast achievement of steady state concentration under steady chimney emissions and mean wind conditions. It is also suggested that the procedure be used to calculate the correction factor to the time-averaged concentrations determined by conventional computer or physical modelling for constant wind condition to account for the actual fluctuating mean wind direction condition. If the wind databank does not contain detailed minute-to-minute data for exact calculation of the correction factor, the sinusoidal wind assumption should give good approximation without adversely affecting the margin of safety for environmental protection. It is also suggested that the meteorological data bank should contain information on hourly amplitude and standard deviations of wind directions if storage is insufficient to store minute-to-minute wind data.     

Solvent Extraction Processes: A Survey of Systems in the SITE Program

Solvent extraction of contaminated soils, sludges and sediments has been successfully completed at a number of Superfund sites. Each commercialized process uses a unique operating system to extract organic contaminants from solids. These operating systems may be classified by the properties of the solvents each utilizes: (1) standard solvents, (2) near-critical fluids/liquified gases, and (3) critical solution temperature solvents. Pretreatment and post-treatment requirements vary depending upon the operating systems of the solvent extraction system. Future demonstrations of these technologies by the U.S. EPA’s Superfund Innovative Technology Evaluation Program will provide additional information regarding the efficacy of these processes.     

Ozone Control Strategies Based on the Ratio of Volatile Organic Compounds to Nitrogen Oxides

The 1990 Clean Air Act Amendments require states with O₃ nonattainment areas to adopt regulations to enforce reasonable available control technologies (RACT) for NO_X stationary sources by November 1992. However, if the states can demonstrate that such measures will have an adverse effect on air quality, NO_X requirements may be waived. To assist the states in making this decision, the U.S. EPA is attempting to develop guidelines for the states to use in deciding whether NO_X reductions will have a positive or negative impact on O3 air quality. Although NO_X is a precursor of O₃, at low VOC/NO_X ratios, the reduction of NO_X can result in increased peak O₃. EPA is examining existing information on VOC/NO_X ratios to develop “rules of thumb” to guide the states in their decision-making process. An examination of 6 a.m. to 9 a.m. VOC/NO_X ratios at a number of sites in the eastern U.S. indicates that the ratio is highly variable from day-to-day and there is no apparent relationship between ratios measured at different sites within the same area. In addition, statistical analysis failed to identify significant relationships between the 6 a.m. to 9 a.m. VOC/NO_X ratio and the maximum 1-hr. O₃ within a given area. Since we know from smog chamber and modeling studies that such a relationship exists, this further invalidates the assumption that a ratio measured at a single site is representative of the ratio for the entire region. Based on this Information, we conclude that having the 6 a.m. to 9 a.m. ambient VOC/NO_X ratio for a given area is insufficient information, by itself, to decide whether a VOC-alone, a NO_x-alone, or a combined VOC-NO_X reduction strategy is a viable or optimum O₃-reduction strategy.     

The Potential of Pulse-Jet Baghouses for Utility Boilers. Part 2: Performance of Pulse-Jet Fabric Filter Pilot Plants

Pulse-jet fabric filters (PJFFs) are widely used in U.S. industrial boiler applications and in utility and industrial boilers abroad. Their small size and reduced cost relative to more conventional reverse-gas baghouses makes the use of PJFFs appear to be an attractive particulate control option for utility boilers. This paper (Part 2 of a three-part series) summarizes the results of pilot PJFF studies sponsored by the Electric Power Research Institute at different utility sites in the United States. The purpose of these tests is to evaluate PJFF performance for U.S. fossil-fuel-fired applications. These data are also used to corroborate the results of a recent worldwide survey of PJFF user experience, as described in Part 1 of this series. Part 3 will provide a cost comparison of PJFFs to other particulate control options such as electrostatic precipitators and reverse-gas baghouses.     

Controlled Enrichment System for Experimental Fumigation of Plants in the Field with Sulfur Dioxide

A prototype Free-Air Controlled Enrichment (FACE) system was developed at Brookhaven National "Laboratory (BNL) for the experimental control of gas concentrations in an open field, without any form of enclosure. This FACE system consists of a toroidal plenum chamber, 15 m in diameter, with a series of 32 vertical vent pipes from which the release of a test gas can be controlled. Data on gas concentration at the center of the array and wind velocity are fed to a microprocessor where a proportional, integrative, differential (PID) algorithm is used to regulate a mass-flow controller. Data on wind direction are used to control the opening and closing of the vertical vent pipes to maintain an upwind release. In 72 hours of continuous operation during which wind velocity varied between 0.3 to 8 m sec^-1, the FACE prototype maintained 1 -min averaged concentrations within twenty percent of the 40 ppb set point 94 percent of the time.