End‐state land uses,sustainably protective systems,and risk management: A challenge for remediation and multigenerational stewardship

This article discusses creating a sustainably protective engineered and human management system in perpetuity for sites with long‐lived radiological and chemical hazards. This is essential at this time because the federal government is evaluating its property as assets and attempting to reduce its holdings, while seeking to assure that health and ecosystems are not put at risk. To assist those who have a stake in the remediation, management, and stewardship of these and analogous privately owned sites, this article discusses current end‐state planning by reviewing the federal government's accelerated efforts to reduce its footprint and how those efforts relate to sustainability. The article also provides a list of questions organized around six elements of risk management and primary, secondary, and tertiary disease and injury prevention. Throughout the article, the U.S. Department of Energy (DOE) is used as an example of an organization that seeks to reduce its footprint, manage its budget, and be a steward of the sites that it is responsible for. However, the approach and questions are appropriate for land controlled by the Department of Defense (DOD), the General Services Administration (GSA), and other public and private owners of sites with residual contamination. © 2005 Wiley Periodicals, Inc.     

Leaching of inorganic contaminants from cement-based waste materials as a result of carbonation during intermittent wetting

Characterization of the leaching behavior of wastes is a crucial step in the environmental assessment for reuse or disposal scenarios. The release of inorganic contaminants from waste materials is typically evaluated by tank leaching of continuously water-saturated material. However, materials, in many field or management scenarios, experience cyclic wetting and drying under varied environmental conditions (i.e. variable relative humidity, atmospheric CO2 or CO2 from biologic activities). During periods of storage in an unsaturated environment, many processes may occur that can influence the release potential and release rate of inorganic constituents. The research presented here was carried out to examine how the phenomena of carbonation during drying influence the release of inorganic contaminants from Portland cement-based materials during cyclic wetting and storage. Batch equilibrium leaching tests were used to determine constituent solubility as a function of pH. Dynamic leaching tests on monolithic material were carried out to determine the rate of constituent release as a function of leaching time and intermittent storage conditions. This paper presents the results observed for three typical waste constituents, arsenic, cadmium and lead.     

Evaluation of air permeability in layered unsaturated materials

Field estimation of air permeability is important in the design and operation of soil-vapor extraction systems. Previous models have examined airflow in homogenous soils, incorporating leakage through a low-permeability cap either as a correction to the airflow equation or as a boundary condition. The dual leakage model solution developed here improves upon the previous efforts by adding a leaky lower boundary condition, allowing for the examination of airflow in heterogeneous layered soils. The dual leakage model is applied to the evaluation of pump tests at a pilot soil-vapor extraction system at the Savannah River Site in South Carolina. A thick, low-permeability, stiff clay layer divides the stratigraphy at the site into two units for evaluation. A modified version of the previous model, using the water table as the impermeable lower boundary, is used to evaluate the permeability of the low-permeability stiff clay layer (3.2 x 10(-10) cm(2)) and permeable sand (7.2 x 10(-7) cm(2)) beneath it. The stiff clay permeability estimate is used in the evaluation of the shallow unit. Permeability estimates of the shallow sand (3.8 x 10(-7) cm(2)) and kaolin cap (1.5 x 10(-9)cm(2)) were obtained with the dual leakage model. The shallow unit was evaluated using the previous model for comparison. The effects of anisotropy were investigated with a series of model simulations based on the shallow unit solution. The anisotropy sensitivity analysis suggests that increased anisotropy ratio or decreased axial permeability has a significant impact on the velocity profile at the lower boundary, especially at high values of the anisotropy ratio. This result may increase estimates of SVE removal rates for contaminants located at the interface of the lower boundary, typical of chlorinated solvent contamination.     

Development and application of a methodology for determining background groundwater quality at the Savannah River Site

A statistical methodology formulated for defining background or baseline levels of constituents of concern in groundwater is presented. The methodology was developed for the case where prior delineation of unimpacted areas is not possible because of site history and a large set of groundwater monitoring measurements exists. Consideration was given to spatial and temporal trends, outliers, and final segregation of wells into impacted or unimpacted categories to develop probability distributions and summary statistics for each constituent evaluated. The formulated approaches were applied to groundwater monitoring data for the U.S. Department of Energy Savannah River Site facility, and results for four representative constituents (aluminum, arsenic, mercury, and tritium) are discussed.     

Pore structure of soot deposits from several combustion sources

Soot was harvested from five combustion sources: a dodecane flame, marine and bus diesel engines, a wood stove, and an oil furnace. The soots ranged from 20% to 90% carbon by weight and molar C/H ratios from 1 to 7, the latter suggesting a highly condensed aromatic structure. Total surface areas (by nitrogen adsorption using the Brunauer Emmett Teller, BET method) ranged from 1 to 85 m2 g(-1). Comparison of the surface area and meso-pore (pores 2-50 nm) surface area predicted by density functional theory (DFT) suggested that the soot was highly porous. Total meso-pore volume and surface area ranged from 0.004-0.08 cm3 g(-1) and from 0.33-6.9 m2 g(-1) respectively, accounting for up 33% of the BET surface area. The micro-pore volume (pores <2 nm) calculated from CO2 adsorption data (by DFT) ranged from 0.0009 to 0.013 cm3 g(-1) and micro-pore surface area was 3.1-41 m2 g(-1), accounting for 10-20% of the total intra-particle (meso-plus micro-pores) pore volume and 70-90% of the total intra-particle surface area. Higher pore volume and surface area values were computed using the Dubinin Radushkevich plot technique; ranging from 0.004-0.04 cm3 g(-1) to 11-102 m2 g(-1) for micro-pore volume and surface area, respectively. Comparison of the C/H ratio and the micro-pore structure showed a strong correlation, suggesting a relationship between the condensation of the skeletal structure and micro-porosity of the soot. These data contradict literature reports that soot particles are non-porous and are consistent with recent literature reports that soil organic matter has large micro-pore surface areas.     

Comparison of LLW Disposal Facilities at Major Department of Energy Sites

Near surface disposal facility design and management are examined and compared using a systems approach that defines facility performance as a function of three components (or subsystems): the disposal facility design (cover systems and bottom liners); the properties of the waste (waste composition, waste form and waste package); and the site‐specific environmental features (climate, geology, and hydrology). We report an evaluation of five DOE near surface disposal facility case studies, selected to provide a “representative” sample that included disposal sites with a range of waste and environmental characteristics across the DOE. The facilities selected were the Savannah River E‐Area Engineered Trenches, Hanford Integrated Disposal Facility, Idaho Radioactive Waste Management Complex, Oak Ridge Environmental Management Waste Management Facility, and Nevada National Security Site Area 5. ©2015 Wiley Periodicals, Inc.     

A biomonitoring plan for assessing potential radionuclide exposure using Amchitka Island in the Aleutian chain of Alaska as a case study

With the ending of the Cold War, the US and other nations were faced with a legacy of nuclear wastes. For some sites where hazardous nuclear wastes will remain in place, methods must be developed to protect human health and the environment. Biomonitoring is one method of assessing the status and trends of potential radionuclide exposure from nuclear waste sites, and of providing the public with early warning of any potential harmful exposure. Amchitka Island (51 degrees N lat, 179 degrees E long) was the site of three underground nuclear tests from 1965 to 1971. Following a substantive study of radionuclide levels in biota from the marine environment around Amchitka and a reference site, we developed a suite of bioindicators (with suggested isotopes) that can serve as a model for other sites contaminated with radionuclides. Although the species selection was site-specific, the methods can provide a framework for other sites. We selected bioindicators using five criteria: (1) occurrence at all three test shots (and reference site), (2) receptor groups (subsistence foods, commercial species, and food chain nodes), (3) species groups (plants, invertebrates, fish, and birds), (4) trophic levels, and (5) an accumulator of one or several radionuclides. Our major objective was to identify bioindicators that could serve for both human health and the ecosystem, and were abundant enough to collect adjacent to the three test sites and at the reference site. Site-specific information on both biota availability and isotope levels was essential in the final selection of bioindicators. Actinides bioaccumulated in algae and invertebrates, while radiocesium accumulated in higher trophic level birds and fish. Thus, unlike biomonitoring schemes developed for heavy metals or other contaminants, top-level predators are not sufficient to evaluate potential radionuclide exposure at Amchitka. The process described in this paper resulted in the selection of Fucus, Alaria fistulosa, blue mussel (Mytilus trossulus), dolly varden (Salvelinus malma), black rockfish (Sebastes melanops), Pacific cod (Gadus macrocephalus), Pacific halibut (Hippoglossus stenolepis), and glaucous-winged gull (Larus glaucescens) as bioindicators. This combination of species included mainly subsistence foods, commercial fish, and nodes on different food chains.     

Scientific research, stakeholders, and policy: continuing dialogue during research on radionuclides on Amchitka Island, Alaska

It is increasingly clear that a wide range of stakeholders should be included in the problem formulation phase of research aimed at solving environmental problems; indeed the inclusion of stakeholders at this stage has been formalized as an integral part of ecological risk assessment. In this paper, we advocate the additional inclusion of stakeholders in the refinement of research methods and protocols and in the execution of the research, rather than just at the final communication and reporting phase. We use a large study of potential radionuclide levels in marine biota around Amchitka Island as a case study. Amchitka Island, in the Aleutian Island Chain of Alaska, was the site of three underground nuclear tests (1965-1971). The overall objective of the biological component of the study was to collect a range of marine biota for radionuclide analysis that could provide data for assessing current food safety and provide a baseline for developing a plan to monitor human and ecosystem health in perpetuity. Stakeholders, including regulators (State of Alaska), resource trustees (US Fish and Wildlife Service, State of Alaska), representatives of the Aleut and Pribilof Island communities, the Department of Energy (DOE), and others, were essential for plan development. While these stakeholders were included in the initial problem formulation and approved science plan, we also included them in the refinement of protocols, selection of bioindicators, selection of a reference site, choice of methods of collection, and in the execution of the study itself. Meetings with stakeholders resulted in adding (or deleting) bioindicator species and tissues, prioritizing target species, refining sampling methods, and recruiting collection personnel. Some species were added because they were important subsistence foods for the Aleuts, and others were added because they were ecological equivalents to replace species deleted because of low population numbers. Two major refinements that changed the research thrust were (1) the inclusion of Aleut hunters and fishers on the biological expedition itself to ensure that subsistence foods and methods were represented, and (2) the addition of a fisheries biologist on a NOAA research trawler to allow sampling of commercial fishes. Although the original research design called for the collection of biota by Aleut subsistence fishermen, and by a commercial fishing boat, the research was modified with continued stakeholder input to actually include Aleuts and a fisheries biologist on the expeditions to ensure their representation. The inclusion of stakeholders during the development of protocols and the research itself improved the overall quality of the investigation, while making it more relevant to the interested and affected parties. Final responsibility for the design and execution of the research and radionuclide analysis rested with the researchers, but the process of stakeholder inclusion made the research more valuable as a source of credible information and for public policy decisions.     

Multi-regime transport model for leaching behavior of heterogeneous porous materials

Utilization of secondary materials in civil engineering applications (e.g. as substitutes for natural aggregates or binder constituents) requires assessment of the physical and environment properties of the product. Environmental assessment often necessitates evaluation of the potential for constituent release through leaching. Currently most leaching models used to estimate long-term field performance assume that the species of concern is uniformly dispersed in a homogeneous porous material. However, waste materials are often comprised of distinct components such as coarse or fine aggregates in a cement concrete or waste encapsulated in a stabilized matrix. The specific objectives of the research presented here were to (1) develop a one-dimensional, multi-regime transport model (i.e. MRT model) to describe the release of species from heterogeneous porous materials and, (2) evaluate simple limit cases using the model for species when release is not dependent on pH. Two different idealized model systems were considered: (1) a porous material contaminated with the species of interest and containing inert aggregates and, (2) a porous material containing the contaminant of interest only in the aggregates. The effect of three factors on constituent release were examined: (1) volume fraction of material occupied by the aggregates compared to a homogeneous porous material, (2) aggregate size and, (3) differences in mass transfer rates between the binder and the aggregates. Simulation results confirmed that assuming homogeneous materials to evaluate the release of contaminants from porous waste materials may result in erroneous long-term field performance assessment.     

Application of a Proposed Generic LLW Waste Package Analysis With Changing Infiltration in a Humid Environment

Corrosion of carbon steel boxes filled with low‐level radioactive waste and buried within a near surface disposal facility in a humid environment was evaluated using an integrated systems approach framework. The time to hydraulic failure from initial burial to development of holes through the wall of a given waste package from pitting corrosion was calculated for four corrosion scenarios under two different corrosion cases. The two corrosion cases chosen were a constant rate of corrosion and a slowing rate of corrosion. Corrosion rates were estimated for carbon steel buried in soil from several historical studies and related to the corrosivity and aeration profile of the soil. The scenarios were chosen to represent a range of possible conditions at current and future U.S. Department of Energy disposal facilities. For each scenario, once the time to hydraulic failure had been estimated, the amount of liquid present in each waste package at the time of failure was calculated as an estimate of leachate available for subsurface transport. The Savannah River E‐Area Engineered Trench was used as a basis for the hypothetical disposal facility. © 2016 Wiley Periodicals, Inc.