Rotary drum soil blending for source zone remediation: Various application scenarios

Mechanical blending of contaminated soil with amendments has recently reemerged as an important treatment technology. From its original application using large‐diameter augers in the early 1990s to the current use of rotary drum blenders, soil blending is being used as an alternative to other remediation technologies like amendment injection and soil vapor and groundwater extraction. Shallow (approximately 10 m below ground surface [bgs] or less) soil blending also offers an alternative to excavation and disposal. Soil blending has been used to remediate a site with various contaminants including, but not limited to, chlorinated solvents, petroleum, and metals. The types of soils susceptible to soil blending vary from sands and gravels to silts and clays to fractured rock and combinations of all of these. The types of amendments blended include oxidants, reducing agents, biological enhancements, and stabilizing amendments. Soil blending systems deliver the power to the mixing head to adequately mix the soil and amendment to enhance remediation effectiveness. Since long‐term contamination is often a result of heterogeneously distributed residual contaminant in localized source zones that are difficult to access, the typical aim of soil blending is to homogenize the soil while effectively distributing amendment to these zones made accessible by blending. By effectively homogenizing the soil, however, soil blending will increase the void ratio and disrupt the shear strength and bearing capacity of the soil so an important component of a soil blending technology is proper recovery of these geotechnical parameters. This can be achieved by using well‐known soil improvement techniques such as amending all or a portion of the blended area with Portland cement or lime. Several case studies of soil blending treatments of different contaminants and amendments in various soil types are provided.     

Circumpolar terrestrial arthropod monitoring: A review of ongoing activities,opportunities and challenges,with a focus on spiders

The terrestrial chapter of the Circumpolar Biodiversity Monitoring Programme (CBMP) has the potential to bring international multi-taxon, long-term monitoring together, but detailed fundamental species information for Arctic arthropods lags far behind that for vertebrates and plants. In this paper, we demonstrate this major challenge to the CBMP by focussing on spiders (Order: Araneae) as an example group. We collate available circumpolar data on the distribution of spiders and highlight the current monitoring opportunities and identify the key knowledge gaps to address before monitoring can become efficient. We found spider data to be more complete than data for other taxa, but still variable in quality and availability between Arctic regions, highlighting the need for greater international co-operation for baseline studies and data sharing. There is also a dearth of long-term datasets for spiders and other arthropod groups from which to assess status and trends of biodiversity. Therefore, baseline studies should be conducted at all monitoring stations and we make recommendations for the development of the CBMP in relation to terrestrial arthropods more generally.     

Robust detection protocols for uncertain introductions of invasive species

Two important features of real-world port inspections of shipping containers for invasive species are the general absence of underlying economic considerations and the climate of severe uncertainty that surrounds the likelihood of invasive species introductions. In this article we propose and illustrate a method for determining inspection protocols that address both of these issues. We seek inspection protocols that are robust in the sense that they maximize the range of uncertainty over which the expected loss from the introduction of an invasive species plus the costs of inspections do not exceed some critical value. These inspection strategies are practical and provide ready alternatives to existing protocols.     

Removal of trihalomethane precursors by reverse osmosis

The effect of pre- and postchlorination on reducing trihalomethane (THM) precursors by reverse osmosis (RO) was investigated. Prechlorination of the feedwater, in contrast to postchlorination of the permeate, resulted in improved reduction of maximum total THM potential (MTP) due to adsorption. No significant difference in permeate MTP concentration occurred between the prechlorinated feed and the postchlorinated permeate. Recirculating permeate water through the RO unit was successful in restoringv flux rates and resuspending the precipitate that accumulated on the RO membranes. The small loss in free chlorine residual indicated prechlorination may be economically attractive in controlling biological fouling of cellulose acetate membranes. Reverse osmosis was not reliable in removing THM precursors and failed to produce a permeate with MTP concentration less than the maximum contaminant level of 0.10 mg/L.     

SENSITIVITY ANALYSIS: A NECESSITY IN WATER PLANNING1

ABSTRACT In water planning activities, major emphasis has been placed on the development of procedures for devising “optimum plans.” These plans are defined as those which meet prespecified demands for water at “minimum cost.” However, all plans are developed subject to postulated conditions regarding the state of the physical system and of nature. Because planning takes place in a dynamic and uncertain environment in which postulated conditions are known to change, it is imperative that the planner be apprised in the planning phase of the effect of changes which can occur. Using “this information, a planner can temper his judgment with a knowledge of the effect of the uncertainty resulting from changes in the system state variables. This paper presents results of the use of a computer simulation and optimization model to quantify possible variations in system response which could occur as a result of uncertainty in the postulated physical and economic conditions under which the proposed water development system was to perform. The possible effects of these variable responses on planning decision-making is discussed.     

BENEFITS OF POLLUTION CONTROL ON MASSACHUSETTS’ HOUSATONIC RIVER: A HEDONIC PRICING APPROACH1

ABSTRACT: This paper illustrates one mode of analysis for estimating the benefits of water pollution control projects. Results indicate regional benefits associated with an abatement program instituted for point source pollution along the Housatonic River during the 1960's were substantial. Studies of this kind can aid regulatory and recreation resource administrators in devising and evaluating environmental programs.     

Dioxins and polychlorinated biphenyls (PCDD/Fs and PCBs) in food from farms close to foot and mouth disease animal pyres

To control the outbreak of foot and mouth disease, which occurred in the UK in early 2001, a large number of farm animals were slaughtered. Where it was not possible to render or landfill the carcasses, they were destroyed by burning on open pyres, with wood, coal and other materials. Uncontrolled combustion such as this is known to produce small quantities of dioxins and an investigation was made into whether, as a result of the burning, there was an elevation in the concentrations of these compounds in food produced in the areas close to the pyres. With few exceptions, concentrations of PCDD/Fs and PCBs were within the expected ranges as predicted by reference data. No accumulation over time was evident from a repeat milk sampling exercise. Where elevated concentrations of PCDD/Fs and PCBs were found in chickens and eggs, they were in samples not destined for the food chain. Elevated levels in some samples of milk from Dumfries and Galloway were not found in earlier or later samples and may have been found as a result of a temporary feeding regime. Elevated concentrations in lamb from Carmarthenshire were from very young animals which would not have entered the food chain. There was no evidence of any significant increase in dietary exposure to PCDD/Fs and PCBs as a result of the FMD pyres.     

EIA in a risk society

Environmental Impact Assessment (EIA) was developed and introduced in the 1960s during a time that was dominated by three key societal influences. These were the growth of modern environmental concern, the drive for more rational, scientific and objective environmental decision making and a desire for more public involvement in environmental decision making. The legitimacy of EIA, as a tool to aid decision making, lies in its ability to meet the requirements of all three demands, the chief among these being its ability to be a systematic scientific and rational approach to decision making. Yet today we live in a society that no longer accepts the rationalist model as either possible or desirable. The deference to ‘the expert’ and our trust in science and technology has steadily declined during the period of EIAs development and widespread use. Today, EIA still depends for its legitimacy on its claim to provide a systematic and scientific approach to assessments, while society has moved on. This paper examines this growing divergence and argues that it is time for a major re‐evaluation of the role of EIA in environmental decision making.     

DECISION ANALYSIS FOR THE RIVER WALK EXPANSION IN SAN ANTONIO,TEXAS1

ABSTRACT: The San Antonio River Walk is considered a unique tourist attraction as well as an urban rejuvenation catalyst for San Antonio, Texas. This utilization of the mile-long horseshoe bend in the downtown area of San Antonio is as successful and imaginative as can be found in the United States. Testimony is very strong from San Antonio voters and outside visitors of the great social and economic value of the River Walk. This overwhelming success has led to plans for expansion of the present River Walk. The River Walk expansion decision should not be evaluated merely on a benefit-cost ratio. It has become the recommendation of the Water Resources Council that intangible attributes such as recreational values and social impacts should be considered as well as tangible attributes such as cost. This prevailing attitude has highlighted the application of decision analysis techniques with multiattribute utility ratings. Decision analysis is a systematic solution procedure which can be used to crystallize a complicated decision problem into manageable subproblems by ranking the decision alternatives in accordance with cardinal utility values attached to their consequences. Recent advances in multiattribute utility theory allow a decision maker to weigh utility assessment over tangible and intangible attributes according to their relative importance. This insures that the intangible attributes will receive due consideration in the final decision-making.