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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Transition and Transfer of Remediated FUSRAP Sites from USACE to US DOE for Long-Term Surveillance and Maintenance - 16209

The US Department of Energy (DOE) expects to receive the transfer of 10 FUSRAP Sites from the US Army Corps of Engineers (USACE) over the next 10 years; however, the timing of the transfers is highly dependent upon federal funding of the ongoing remedial actions. When remediation for each site is complete and the 2-year operations and maintenance period has concluded, each site will transfer from USACE to DOE for long-term surveillance and maintenance (LTS and M). US DOE's Office of Legacy Management (LM) will accept program responsibility for these sites and conduct LTS and M activities required to maintain protectiveness, preserve site-specific knowledge, and retain the cleanup and stewardship records while keeping stakeholders informed. Since the last FUSRAP site transfer occurred in 2007, LM in coordination with USACE intends to establish a transition process to promote the seamless transfer of sites from the time when the first record of decision is signed to the completion of FUSRAP activities. The approach to transfer active FUSRAP sites to completed sites status has been historically outlined in foundational documents such as the 1999 Memorandum of Understanding and supporting letters of agreement between the two agencies. As more complex FUSRAP sites are completed, this transition process will provide a model between the two agencies to communicate future long-term care liabilities. Ultimately, the FUSRAP transition process is structured to acquire and preserve site knowledge and information necessary for protecting the environment and public health. As of 2015, LM has transitioned and accepted programmatic responsibility for over 90 sites. From LM's perspective, successful transition of any site includes understanding the long-term environmental liabilities. LM uses site transition framework requirements from past transitions to develop site-specific transition plans. Site-specific transition plans are developed by LM in coordination with USACE and executed during the 2-year operations and maintenance period. An integrated project team of subject matter experts is assembled to address the conditions of the transitioning site; acquire a site records collection; evaluate site operations and final site conditions and associated risks; identify and contact stakeholders; and document the basis for site LTS and M requirements. While the majority of the transition activities are completed by LM, close coordination between US DOE LM and USACE throughout this process is essential for an effective and seamless transfer to assure that there is no lapse in site protectiveness. (authors)

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DOE OSTI2016

Waste Management 2016 300-296 Soil Remediation Project. Developing Innovative Solutions to Overcome Design Challenges - 16229

The 324 Building is a non-reactor, Hazard Category 2, Nuclear Facility located in the 300 Area of the U.S. Department of Energy (DOE) Hanford Site, located near Richland, Washington. The building is undergoing deactivation, decommissioning, decontamination, and demolition by Washington Closure Hanford (WCH) under the River Corridor Closure Contract. During the Cold War Era, the facility was used for chemical and radionuclide processing associated with nuclear weapons production. Historical records indicate that in October 1986, approximately 516 L of a concentrated liquid waste stream containing cesium-137 and strontium-90 was spilled onto the floor of B-Cell. B-Cell is located in the Radiochemical Engineering Complex (REC) of the 324 Building. It is estimated that this spill contained approximately 1.3 million curies of radioactivity. Some fraction of the spill was recovered; however, an unknown quantity was released into the soil beneath the 324 Building through an undetected breach in the B-Cell floor sump. Unknown quantities of water were used after the spill to wash items contained in B-Cell. When B-Cell was taken out of service, wastes being removed from B-Cell were placed in Grout Containers (GCs) and stabilized using a particulate grout. In the course of grouting activities, grout was spilled on the floor of B-Cell, eventually filling the sump. The primary scope of this project is to design, test, and implement a process capable of removing and isolating contaminated soil below B-Cell. This remediation effort has been divided into two removal zones identified as the primary and secondary removal zones. Based on current assumptions and estimates, the primary phase of this cleanup effort will remove roughly 156.45 m{sup 3} of highly contaminated materials. B-Cell debris, particulate grout, and the floor slab and liner comprise about 21.24 m{sup 3} of the total. The remaining 135.21 m3 will be contaminated soil. All of this material must be disposed of within the existing 324 Facility or packaged for disposal at the Hanford site. The objective of this project is to remove the B-Cell floor and highly contaminated underlying soils from beneath B-Cell using remote equipment to reduce the radiation levels and allow open-air excavation for the remaining contaminated soil. The challenges and subsequent technological solutions encountered from the Conceptual Design phase to the 100% Design Issued For Fabrication/Issued For Construction (IFF/IFC) consisted in part of the following: Design an efficient remote cleanup strategy for highly contaminated Low Level Waste (LLW) given the unknowns. Maintain contamination control down to 18 feet below B-Cell in a highly radioactive environment (12,870 R/Hr Cs-137 and Sr-90). Perform facility upgrades to enable remediation process implementation while maintaining integrity of pre-existing facility structure and license. Designing first-of-a-kind remote equipment for use in high radiation areas. Developing first-of-a-kind operations sequences for remote equipment while minimizing usage of original facility equipment (i.e. cranes, manipulators, etc.). Conducting time-motion studies of operations sequences to maximize efficiency while keeping dose As Low As Reasonably Achievable (ALARA) in a high dose environment. Construction of a full scale mockup to conduct performance testing in a clean environment and train the work force to operate the equipment. Overcoming scope, budget and schedule constraints associated with a fast-track DOE project. (authors)

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DOE OSTI2016

Survey and Remediation Project at the DOE Bannister Site - 16280

The Department of Energy Kansas City office has operated the Bannister site with a variety of contractors since the late 1940's. This facility has had a number of missions, some of which included using natural and depleted uranium. In order to prepare for the demolition of the site, ANTECH was contracted to perform radiometric surveys of the areas where these uranium operations took place. In the process of performing these surveys, areas with low levels of fixed radioactive contamination were identified; ANTECH then remediated these areas using a variety of techniques. In all areas surveyed, the only radioactive contaminant of interest was uranium and members of its decay chain. In no cases were other radionuclides found. The detection equipment used for the surveys included a Ludlum model 239- 1F Floor Monitor, a Ludlum 2360 Alpha Beta Data Logger Scaler/Ratemeter, and an ORTEC IDM-200-V High Purity Germanium Detector. The Ludlum instruments were used for bulk surveys and the ORTEC instrument was used to determine an accurate radioactive background spectra and subsequent spectra for areas where radioactive contamination was identified. Contamination was located on concrete floors and columns, cinder block walls, steel beams, inside ductwork and in floor drain piping. After these areas were identified, a number of methods were used to remove the contamination for disposal including scabbling, core drilling and wholesale removal. Extensive use of Pentek scabbling equipment on the concrete sections proved to be very effective at removing the contaminated layer. Upon completion, the waste materials were consolidated and packaged in a strong tight sea land container and shipped to the Energy Solutions waste facility in Utah. The completed work at the Bannister site serves as an example and demonstration of an effective and comprehensive decommissioning project. It involved the integration of a variety of decommissioning activities all executed and managed by a single contractor. These included radiometric measurement surveying using a variety of detection technologies to identify and locate uranium contamination, decontamination and removal of low level radioactive waste including some deconstruction activities and finally the management of low level radioactive waste including packaging, consignment and shipping of waste to a remediation site. The effective and efficient identification and removal of radioactive contamination at the Bannister site has contributed to the overall goal of returning the site to unrestricted use. (authors)

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DOE OSTI2016

The Little Engine That Could: No Project is too Small for Sustainable Remediation Moab Uranium Mill Tailings Removal Project - 16427

Executive Order 13693, 'Planning for Federal Sustainability in the Next Decade', mandates the reduction of energy use and cost and greenhouse gas emissions, and the search for renewable or alternative energy solutions. DOE EM manages the Moab Uranium Mill Tailings Remedial Action Project in Utah that involves relocating a 16-million-ton uranium mill tailings pile and associated contaminated materials at the former Atlas mill site to a permanent disposal cell constructed near Crescent Junction, Utah, predominantly by rail. Project personnel strive to support the Executive Order in making preparations for the impacts of climate change. Meeting the goals of the Executive Order in light of the remote location and limited resources of the Project sites often requires an innovative approach and perseverance. The Moab Project is a 'Small Site' within EM and has a comparatively short-term completion date. As a result, large-scale sustainability projects, such as retrofits or remodels, do not offer a cost benefit over this period. Instead, less dramatic process changes are achievable. The Project purchases renewable wind energy through the local power provider to reduce Scope 2 (purchased electricity) greenhouse gas emissions. Toward its ambitious goal of achieving zero landfill waste, the Project has diverted over 50 percent of its nonhazardous solid waste from the local landfill through composting and recycling efforts. In particular, electronics must meet various sustainable criteria prior to purchase, and be recycled through donations and certified recyclers, diverting it from the waste stream. The Project has received multiple Green Buy Awards from DOE by reaching leadership goals for purchasing energy-efficient, water-efficient, bio-based, and recycled-content products. In fiscal year 2014, in response to President Obama's June 2014 memorandum, 'Sustainable Practices for Designed Landscapes and Supporting Pollinators on Federal Landscapes', the Project decided to take a proactive approach and work with a local pollinator group, hosting two beehives in a revegetation area on the Moab site. An increase in plant growth and blossoming plants in the revegetation area has been observed and is believed to be related to the added pollinators. The Project has previously seeded disturbed areas mainly with native drought-resistant species to reduce water usage. Storm water collected in sediment basins at the Crescent Junction site is used for dust control and compaction of mill tailings in the disposal cell. The Project worked with the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service to gain support for re-contouring a remediated area adjacent to the Colorado River, which borders the Moab site on the east, to allow the area to flood at a lower river stage. This re-contouring promotes more varied vegetation growth and river water that tops the west bank brings soil nutrients to inundated areas of the site. Ponded floodwater has been pumped into revegetation plots for irrigation, reducing freshwater usage. Innovation in sustainable practices comes in many different fashions. The Moab Project demonstrates that no project is too small to implement sustainable practices. (authors)

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DOE OSTI2016

Scientific Investigations on the Chemical Reactivity of Los Alamos Remediated Nitrate Salt Wastes - 16540

The February 14, 2014 release of radioactivity at the Waste Isolation Pilot Plant (WIPP) was the result of runaway thermal reactions that occurred in a TRU waste drum containing nitrate salts remediated using an organic absorbent. Experimental and modeling studies performed at LANL indicate that mixtures of metal nitrate salts (oxidizer) with sWheat Scoop{sup R} organic kitty litter (fuel) create the potential for exothermic chemical reactions. The use of sWheat{sup R} absorbent in the processing of nitrate salt wastes can be pinpointed as the critical processing decision that led to the failure of the breached drum in the WIPP repository. The most plausible scenario is that a production of heat, either from low-level chemical reactions or the growth of natural microbes, in concert with mixed metal nitrate salts, bismuth lined glovebox gloves and/or lead nitrates when combined with the sWheat{sup R} organic kitty litter, generated a series of exothermic reactions that heated and pressurized the drum resulting in the venting of high-temperature gases and radioactive material into the room. Observations and modeling studies indicate that the probability of thermal runaway in another drum has decreased with time since the WIPP event. However, the complexity of the mixtures, ambiguity in procedures such as those used for neutralization, the heterogeneity of the drum contents, and the difficulty of sampling leads to an irreducible level of uncertainty that mandates the exercise of caution in managing RNS wastes. The situation also requires that this waste stream continue to be stored in a temperature-controlled environment and monitored until the waste can be remediated to remove the hazard permanently. We recommend that proposals to treat nitrate salts with organic absorbents of any kind be accompanied by experimental studies to confirm that similarly sensitive mixtures are not inadvertently created over the range of conditions (mixture quantities, moisture content, etc.) anticipated during processing and storage. (authors)

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DOE OSTI2018

Remediation of D-Area Ash Units, Savannah River Site - 18151

At the Savannah River Site (SRS), under the tri-party Federal Facility Agreement (FFA) between the United States Department of Energy (US DOE), United States Environmental Protection Agency (US EPA), and South Carolina Department of Health and Environmental Control (SCDHEC), agreement was reached to remediate two ash basins, one coal pile runoff basin and one ash landfill as Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Removal Actions within a schedule of five years (2014 - 2019). These removal actions complete the remediation of these basins and the ash landfill which originated from nearly 60 years of powerhouse operations and cover a total area of nearly 40.5 hectares (100 acres). Utilizing proven as well as state of the art technologies and methods, the completed actions culminate in two protective multi-layer cover systems and the conversion of the coal pile runoff basin to an ecological diverse storm water retention basin. Completion of these removal actions has been determined to provide protection of future industrial workers and ecological receptors as well as prevent migration of mobile contaminants found in coal residues (e.g., arsenic) from powerhouse operations, achieving all applicable or relevant and appropriate requirements. (authors)

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DOE OSTI2018

Exploiting Knowledge of Technetium in the Subsurface to Develop Remediation Strategies - 18223

Technetium-99 (Tc) contamination remains a major environmental problem at legacy nuclear reprocessing sites, such as the Hanford Site in south-central Washington State, where the total inventory of released Tc is estimated at 700 curies (Ci). The environmental risk associated with Tc is due to its long half-life (213,000 years) and the high mobility of the oxidized anionic pertechnetate species (Tc(VII)O{sub 4}{sup -}). Thus, there is a critical need to resolve scientific and technical issues underpinning the ability to safely, cost-effectively, and efficiently remediate Tc-contaminated vadose zone sediments and groundwater. Developing enhanced attenuation strategies for released Tc that reduce contaminant migration, while mitigating risk to human health and the environment, requires characterization of any retardation processes and Tc mass flux. The current conceptual model for Tc transport in the vadose zone assumes that Tc is predominantly present in its oxidized form as TcO{sub 4}{sup -}, which is highly soluble and mobile. However, under certain conditions, Tc can become entrained in solid phases. Tc-containing mineral phases from sediment cores extracted from various Hanford waste disposal sites were characterized to determine Tc present in vadose zone sediments as (i) TcO{sub 4} - that remains in water films associated with fine-grained sediments; (ii) Tc co-precipitated with other lanthanides in phosphate mineral phases; and (iii) Tc present as TcO{sub 2}.nH{sub 2}O in localized reducing zones. These results will be used to develop improved long-term Tc remediation strategies that are most likely to succeed during field application, through stimulation of conditions that enhance Tc attenuation. (authors)

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DOE OSTI2018

Technical Advances for Sustainable Remediation: In Situ Monitoring and Climate Resiliency - 18436

Recent advances in sustainable remediation techniques show promise as solutions for contaminant removal in soil and groundwater media. Although passive remediation (or natural attenuation) has gained momentum as an acceptable technique, there are still challenges in regulatory frameworks as well as in public acceptance. Leaving contaminants in subsurface requires increased burden of proof to show that plumes are stable and residual contaminants do not pose a significant health risk. Climate changes and frequent extreme climate events contribute another level of complexity and make it difficult to demonstrate system stability and predict future plume conditions. In this study, we show two coupled approaches to tackle this challenge: (1) in situ groundwater monitoring based on advanced sensor and data analytics technologies (i.e., Big Data), and (2) state-of-art modeling for optimizing monitoring and site closure strategies. In the new monitoring approach, in situ sensors are used to continuously measure the key variables that control contaminant plume mobility and its spatial and temporal distribution (such as pH, redox potential, electrical conductivity, and groundwater level). Coupled with a limited number of groundwater sampling, the data analytics methods - data mining and machine learning - allow us to estimate contaminant concentrations, and also to detect any significant changes associated with the plume mobility. In parallel, the state-of-art numerical flow and reactive transport model - ASCEM software under DOE Office of Environmental Management - provides a physical and mechanistic understanding of the system behavior, and predicts the long-term plume migration for optimizing the monitoring and closure strategies. In particular, we focus on the effects of extreme precipitation or drought on the site closure as well as monitoring strategies. We demonstrate this approach at the Savannah River Site (SRS) F-Area, where groundwater is contaminated by various radionuclides, including uranium, tritium and technetium. (authors)

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DOE OSTI2018

3-D Radiation Mapping and Data Fusion for Environmental Remediation and Cleanup - 18449

Recent developments in radiation detection and imaging in combination with the enormous advances in computer vision and data processing enable new and improved means in the assessment of radiological contamination relevant for environmental remediation. We have developed a new concept called 3-D Scene Data Fusion (SDF) that allows us to map scenes in three dimensions and fuse this scene data with nuclear radiation data in near real time while the instrument is freely moving through the scene. This new technology provides more accurate radio-isotopic mapping at higher speed than currently possible. SDF is designed to be independent of the deployment platform and can be implemented with gamma-ray imaging and non-imaging instruments. We have demonstrated this concept in a large range of configurations on unmanned aerial and ground-based systems, in hand-portable configurations or mounted on cars or manned helicopters. While it can be utilized in a wide range of applications, this paper focuses on the mapping of radiological and nuclear materials in the context of environmental remediation and clean-up specifically in urban environments. We show results from measurements in the evacuated areas in the Fukushima Prefecture to demonstrate the new concept in the mapping of contamination and hot spots and the verification of decontamination activities in urban environments. (authors)

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DOE OSTI2018

Use of Physics Based Management Optimization for Groundwater Remedy Design - 18671

Numerical modeling coupled with formal mathematical optimization techniques was used to design a groundwater remedy strategy to address a carbon tetrachloride (CCl{sub 4}) plume covering several square miles. The optimization approach, methodology, and project costs are described. The site consists of a large grain elevator in Nebraska. CCl{sub 4} was used as a fumigant and subsequently impacted soils and groundwater. Remedy design focused on the more diffuse plume, which extended approximately 4.5 miles down gradient of the source area. An eleven-layer model was developed and calibrated to observed groundwater conditions. This model was linked with formal optimization techniques to identify the best design capable of meeting client specified requirements and well location limitations. The planned system included requirements on the location of extraction and injection wells, total system flow rate, number of management periods, and specific constraints limiting further plume expansion. A separate trinitrotoluene (TNT) contaminant plume from a third party was located vertically above the leading edge of the CCl{sub 4} plume within the same aquifer. A further constraint imposed was that the design could not affect or cause additional migration of the TNT plume. Optimal system design was determined using HydroGeoLogic's Physics Based Management Optimization (PBMO{sup TM}) system. Over 38,000 candidate solutions consisting of different combinations of pumping and injection wells locations and rates, were evaluated through flow modeling coupled with either particle tracking or fully convective-dispersive transport simulations to determine the optimal design. Planning for installation of the optimal design is underway. Simulations were completed on a distributed computing platform consisting of 3 Quad Core PCs. Flow and particle tracking simulations required less than 2 minutes per simulation. Coupled flow and transport simulation run times were generally between 30-40 minutes per simulation. The total costs for developing the groundwater flow model and completing the subsequent optimal design were approximately $400,000. (authors)

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DOE OSTI2018

Chromium Plume at LANL - From Conceptual Site Model to Development of Complex Remediation Strategies - 18682

A hexavalent chromium plume is present in deep groundwater beneath Los Alamos National Laboratory (LANL or the Laboratory). The plume originated from releases of potassium dichromate from cooling towers from 1956 - 1972. Estimates are that up to 72,000 kg of chromium was released during that period. Data from surface water-balance studies, core-hole and groundwater characterization, geomorphic investigations and geology and geophysics provide the basis for an evolved conceptual model that chromium initially traveled rapidly via an effluent-supported stream for several kilometers, then infiltrated through a stratigraphically complex 275-300 meters thick vadose zone and eventually into a deep (regional) aquifer that is the water supply for the Laboratory and surrounding municipality. The travel time from the release point to the regional aquifer is estimated at 5-10 years based on modeling and contaminant tracers. Monitoring data from two-screen wells and piezometers within the regional aquifer, and data derived from stratified sampling conducted during sonic coring and from analysis of sonic core indicate that the chromium contamination occurs within the upper 23 meters of the highly stratified regional aquifer. Different geologic units at the water table and structural dip of depositional bedding appear to have little effect on chromium migration and plume shape and thickness which instead appear to be a manifestation of multiple breakthrough locations, interconnectedness of preferential hydraulic strata, and a negligible vertical gradient. Recent monitoring data indicate that the down-gradient plume edge (as defined by the New Mexico groundwater standard of 50 μg/L) may be advancing near the Laboratory's boundary with a neighboring Indian reservation. The Laboratory is addressing the increasing concentrations with a regulatory-driven interim measure that uses hydraulic control to manage plume migration. The interim measure involves limited-duration (2-3 years) pumping, treatment, and injection to rapidly establish and maintain the 50 μg/L plume edge within the Laboratory boundary while a final remediation strategy is developed and approved by the State regulator. A final remediation strategy will depend heavily on the ability to cost-effectively access the deep aquifer. (authors)

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DOE OSTI2019

Using Superfund Guidance and Tools for the Remediation of Uranium Mine sites - 19056

The Environmental Protection Agency (EPA) Office of Superfund Remediation and Technology Innovation (OSRTI) has primary responsibility for implementing the long-term (non-emergency) portion of a key U.S. law regulating cleanup of contaminated sites: the Comprehensive Environmental Response, Compensation and Liability Act, CERCLA, nicknamed 'Superfund.' The purpose of the Superfund program is to protect human health and the environment over the long term from releases or potential releases of hazardous substances from abandoned or uncontrolled hazardous waste sites. The focus of this paper is on the guidance and tools for addressing radioactively contaminated sites by the Superfund program that are most important when remediating uranium mine sites. This presentation will also discuss some of the key features of these tools that may have more utility at a uranium mine site. (authors)

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DOE OSTI2019

Evaluating Environmental Remediation Performance at Radwaste Sites Using Multiple, Censored Regression Analysis - 19348

Located on the U.S. Department of Energy's Hanford Site in Richland,Washington, the 300 Area's remediation performance monitoring requires assessment of concentration trends and calculation of means and lower and upper confidence limits on the mean. The performance monitoring wells for uranium are located within 400 m of the Columbia River and groundwater elevations and uranium concentrations are influenced by groundwater-surface water interactions. A multiple regression approach was used to assess trends because multiple covariates can be used to account for the observed fluctuations in groundwater elevation and concentration. Incorporation of covariates accounting for these groundwater-surface water interactions (i.e., river stage) reduces the random error in the trend estimation and improves the estimates of remediation performance metrics (i.e., mean and confidence limits on the mean) over traditional, non-parametric methods. (authors)

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DOE OSTI2020

Characterisation of Specimens from a Former Soviet Thorium Processing Facility to Support Site Remediation

The former Prydniprovski Chemical Plant (PChP) is a large ex-soviet nuclear materials processing site of roughly 260 hectares, located in central Ukraine. PcHP was in operation between 1948 and 1991 for the purposes of processing uranium and thorium ore into ore concentrate. During its operational lifetime, tens of millions of tonnes of radioactive waste was generated on the site. A consequence of these activities, coupled with the mismanagement of the resulting radioactive materials and by-products, is that approximately 45% of the southern part of the site has become radioactively contaminated. This area comprises some 100-200 buildings and structures, many of which are in a state of disrepair and dereliction. Around 20 of these buildings are heavily radioactively contaminated, with radiation levels from a few μSv/hr to a maximum of 4 mSv/hr reported. The European Commission is currently working with the Ukraine Ministry of Energy and Coal Use and the Nuclear Regulator to improve radiological safety and security at the site. In order for these remediation works to proceed, the site management needs to characterise the radioactive materials that are held there. As part of this activity, the team from the University of Bristol have undertaken a survey of one of the most heavily contaminated buildings, collecting a selection of in situ material samples. A suite of complimentary materials characterisation techniques (e.g. X-ray Fluorescence, Raman Spectroscopy, etc) have been deployed in order to determine the radionuclides and composition of the compounds present. Characterisation of these samples will allow the operators of the chemical plant to go forward with remediation works within the building.

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DOE OSTI2020

Excavation Volume Growth Factors at Environmental Remediation Sites - 20318

The U.S. Army Corps of Engineers (USACE) manages numerous environmental remediation projects in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act, otherwise known as CERCLA. These include projects for the Formerly Utilized Sites Remedial Action Program (FUSRAP). Utilizing the CERCLA framework to address these projects requires detailed cost estimates and a significant portion of costs are associated with the volume of material to be excavated and that material's final disposition. Accordingly, understanding the expected volumes and uncertainty associated with those volumes is vital to project cost estimating. These estimates are completed at various stages of the CERCLA process, thus the project team has varying degrees of information available from which to develop these estimates depending on how far along the project is. Understanding the factors contributing to volume growth (increase in volume of material from that originally estimated) is a crucial element to determining volume and cost uncertainty. This paper presents a case study of a FUSRAP site which involves excavation and offsite disposal of contaminated soils from complex commercial, industrial, and residential properties. Original volume estimates were compared to post excavation volumes on a property by property basis. Reasons for differences are determined along with magnitude of impacts to cost estimating. For both residential and commercial property types, volume estimating factors, uncertainty considerations, and methods to account for each are discussed with emphasis on volume growth considerations. Cost estimating model input considerations are discussed with specific emphasis on accounting for volume uncertainty at the Feasibility Study (FS) phase of CERCLA. Underestimating or overestimating costs at the FS phase has repercussions under CERCLA that may impact project close out or completion schedule. Discussions presented will be helpful to both reviewers and preparers of cost estimates involving excavations. Additionally, project planners may be able to use the information to plan for volume growth contingencies. (authors)

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DOE OSTI2020

Novel Remediation of Mercury-Contaminated Sediments Using Manganese Oxide and Activated Carbon Amendments - 20394

Mercury contamination in sediments poses a challenging remediation problem because of its ability to biogeochemically cycle and biomagnify in the food chain as methylmercury from low resident sediment and porewater concentrations. One mitigation approach is to lower the overall rate of net methylmercury production by creating conditions unfavorable for sulfate and iron reduction or methanogenesis, the primary pathways for methylation of inorganic mercury. Manganese oxides and other redox-active amendments are a promising and novel in situ amendment technology aimed at reducing net methylation of mercury though control of redox conditions in mercury-contaminated sediment-water systems. This paper reviews the thermodynamic and kinetic framework for this remediation technology, presents experimental and spectroscopic data illustrating the approach using solid manganese oxides, and discusses potential advantages, disadvantages, and applications. (authors)

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DOE OSTI2020

Applications of Hyporheic Zone Sampling for Assessing VOC Plume Engineered Remediation and Natural Attenuation Effectiveness - 20414

Determining the efficacy of engineered remedial actions and/or natural attenuation as an acceptable EPA Record of Decision (ROD) must address long-term temporal and spatial variability. Since final plume downslope destinations are aquifers and related surface streams and rivers, hyporheic zone sampling is essential. Comprehensive hyporheic sampling documents plume groundwater remediation prior to upwelling into stream benthic strata and natural attenuation within this dynamic zone itself. Our intensive sampling of the Savannah River Site (SRS) Chemical, Metals, and Pesticides (CMP) Pits VOC plume-fringe from 2005 to 2018 documented PCE natural attenuation and effectiveness of In Situ Thermal Treatment (ISTT). Most plume hyporheic upwelling was delimited to a 20 m inflow reach along Pen Branch. Our study utilized corroborative sampling methodologies: ambient hole-water grab samples: passive diffusion bags (PDB); and hole-core sediment samples to confirm station to station spatial and temporal trends. VOC hot spot detections were confirmed from both groundwater and soil core samples. VOC pathways through the Pen Branch hyporheic zone were assessed at hole-installation using sequential soil samples from augered cores and grab-samples of hole-bottom water. Longer term, composite water samples were collected from PDBs deployed for a minimum two-week equilibration period. Soil samples were collected from the 15 and 65 cm core levels in December 2017 and June 2018 at six stations. Additional core depths of 40 and 85 cm were sampled in June 2018 at the highest VOC station (5DB80). All samples were analyzed in an EPA certified lab by purge and trap GC-MS. Effectiveness of previous ISTT and soil vapor extraction (SVE) for this CMP Pits PCE plume, was clearly documented by significant downward trends in VOC at hyporheic zone stations prior to December 2015. Achieving final stage conversions of PCE daughter products to ethene and CO{sub 2} may be limited depending upon suitable interactions between hyporheic zone sediment morphology, hydrology, and redox conditions. Because declines in VOC daughter products at our hyporheic stations may also be caused by physical actions of dilution and dispersion rather than true biochemical dechlorination, full quantification of natural attenuation requires the use of compound-specific isotope ratio analysis (CSIA) and microbial 16S rRNA with qPCR. To assist these next-phase efforts, a natural attenuation index (NAI) was used to help produce quicker, more cost-effective decision making for locating CSIA and microbial sampling efforts. The NAI used natural logarithm transformed GC-MS results for station VOC degradation compounds versus VOC parent compounds. Wide differences were observed between stations. (authors)

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DOE OSTI2020

The Challenges of Air Monitoring at a Soil Remediation Project in a Suburban Setting - 20448

Air monitoring during soil excavation at a chemically and radiologically impacted site in a suburban setting presents unique challenges. Site activities were conducted in a manner that minimized the release of airborne particulates of concern, principally radionuclides of concern (ROC). Dust and air monitoring were performed to ensure the public was not being exposed to the soil contaminants. The project team collected representative air and dust data while being mindful to not impose on the lives of residents in the area. Due to the close proximity to the public, there was a high level of oversight from the client and regulatory agencies. The challenges involved with air sampling at this soil remediation site located in a suburban setting included the number of contaminants, the ranges of risks and hazards presented by the contaminants and the method of remediation, the concerns of the regulators and the public, and the perception of risk from the public. (authors)

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